U.S. patent application number 11/605584 was filed with the patent office on 2007-04-26 for method and apparatus for processing a wafer.
Invention is credited to ChristopherT Lane, Sasson R. Somekh, J Kelly Truman, Steven Verhaverbeke.
Application Number | 20070093071 11/605584 |
Document ID | / |
Family ID | 26923308 |
Filed Date | 2007-04-26 |
United States Patent
Application |
20070093071 |
Kind Code |
A1 |
Verhaverbeke; Steven ; et
al. |
April 26, 2007 |
Method and apparatus for processing a wafer
Abstract
A method of a single wafer wet/dry cleaning apparatus
comprising: a transfer chamber having a wafer handler contained
therein; a first single wafer wet cleaning chamber directly coupled
to the transfer chamber; and a first single wafer ashing chamber
directly coupled to the transfer chamber.
Inventors: |
Verhaverbeke; Steven; (San
Francisco, CA) ; Truman; J Kelly; (Morgan Hill,
CA) ; Lane; ChristopherT; (San Jose, CA) ;
Somekh; Sasson R.; (Los Altos Hills, CA) |
Correspondence
Address: |
APPLIED MATERIALS/BLAKELY
12400 Wilshire Boulevard
Seventh Floor
Los Angeles
CA
90025-1030
US
|
Family ID: |
26923308 |
Appl. No.: |
11/605584 |
Filed: |
November 27, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10229446 |
Aug 27, 2002 |
7159599 |
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11605584 |
Nov 27, 2006 |
|
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09945454 |
Aug 31, 2001 |
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10229446 |
Aug 27, 2002 |
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Current U.S.
Class: |
438/724 ;
430/269; 438/725; 438/906 |
Current CPC
Class: |
Y10S 414/141 20130101;
H01L 21/67173 20130101; Y10S 438/905 20130101; H01L 21/6719
20130101; Y10S 414/135 20130101; H01L 21/67161 20130101; G03F 7/16
20130101; H01L 21/67184 20130101; H01L 21/67207 20130101; H01L
21/67115 20130101 |
Class at
Publication: |
438/724 ;
438/725; 438/906; 430/269 |
International
Class: |
H01L 21/465 20060101
H01L021/465 |
Claims
1. A method of cleaning a residue or a photoresist layer from a
wafer comprising: transferring from a wafer cassette a wafer having
a residue thereon into a transfer chamber having robot contained
therein; transferring said wafer from said transfer chamber into an
ashing module coupled to said transfer chamber; ashing said wafer
in said ashing module to form an ashed wafer; transferring said
ashed wafer from said ashing module to said transfer chamber;
transferring said ashed wafer from said transfer chamber to a wet
processing module coupled to said transfer chamber; cleaning said
ashed wafer with a cleaning solution in said wet processing chamber
to form a cleaned and ashed wafer; transferring said cleaned and
ashed wafer from said cleaning module to said transfer chamber; and
removing said cleaned and ashed wafer from said transfer
chamber.
2. The method of claim 1 wherein said ashing comprises: exposing
said wafer to an energized cleaning gas; and before, during or
after exposing said wafer to said energized cleaning glass,
exposing the said wafer to an energized treating gas comprising a
halogen species and a hydrogen species.
3. The method of claim 2 wherein the cleaning gas comprises: a
stripping gas comprising one or more Of O.sub.2, N.sub.2, H.sub.2O,
NH.sub.3, CF.sub.4, C.sub.2F.sub.6, CHF.sub.3,
C.sub.3H.sub.2F.sub.6, C.sub.2H.sub.4F.sub.2, and CH.sub.3F
provided under process conditions selected to at least partially
remove said residue when said residue is remnant resist
material.
4. The method of claim 1 wherein said cleaning comprises:
transmitting sonic energy to a non-device side of said wafer while
flowing said cleaning solution onto said wafer device side.
5. The method of claim 2 wherein said cleaning comprises:
transmitting sonic energy to a non-device side of said wafer while
flowing said cleaning solution onto said wafer device side.
6. A method of processing a wafer comprising: transferring a wafer
from a wafer cassette into an atmospheric transfer chamber;
transferring said wafer from said atmospheric transfer chamber into
a load lock coupled to said atmospheric transfer chamber; reducing
the pressure in said load lock to a sub-atmospheric pressure;
transferring said wafer from said load lock into a sub-atmospheric
transfer chamber coupled to said load lock; transferring said wafer
from said sub-atmospheric transfer chamber into a sub-atmospheric
process chamber coupled to said sub-atmospheric transfer chamber;
processing said wafer in said sub-atmospheric process chamber to
produce a sub-atmospheric processed wafer; transferring said
sub-atmospheric processed wafer from said sub-atmospheric process
chamber to said sub-atmospheric transfer chamber; transferring said
sub-atmospheric processed wafer from said sub-atmospheric transfer
chamber into a load lock at said sub-atmospheric pressure; raising
the pressure in said load lock to atmospheric pressure;
transferring said sub-atmospheric processed wafer from said load
lock to said atmospheric transfer chamber; transferring said
sub-atmospheric processed wafer from said atmospheric transfer
chamber to an atmospheric process chamber coupled to said
atmospheric transfer chamber; processing said sub-atmospheric
processed wafer in said atmospheric process chamber to produce a
sub-atmospheric processed and a atmospheric processed wafer;
transferring said sub-atmospheric processed and said atmospheric
processed wafer from said atmospheric processing chamber to said
atmospheric transfer chamber; and removing said sub-atmospheric
processed and said atmospheric processed wafer from said
atmospheric transfer chamber.
7. The apparatus of claim 6 further comprising a CD measurement
tool coupled said sub-atmospheric transfer chamber.
8. A method of processing a wafer comprising: transferring a wafer
having a patterned photoresist layer formed on a thin film from a
wafer cassette into an atmospheric transfer chamber; transferring
said wafer from said atmospheric transfer chamber into a load lock
coupled to said atmospheric transfer chamber; reducing the pressure
in said load lock to a sub-atmospheric pressure; transferring said
wafer from said load lock into a sub-atmospheric transfer chamber
coupled to said load lock; transferring said wafer from said
sub-atmospheric transfer chamber into an etch chamber coupled to
said sub-atmospheric transfer chamber; etching said thin film in
alignment with said patterned photoresist layer in said etch
chamber at a sub-atmospheric pressure to form an etched wafer;
transferring said etched wafer from said etch chamber to said
sub-atmospheric transfer chamber; transferring said etched wafer
from said sub-atmospheric transfer chamber to an ashing chamber
coupled to said sub-atmospheric transfer chamber; ashing said
etched wafer in said ashing chamber to remove said patterned
photoresist layer; transferring said etched and ashed wafer from
said ashing chamber to said sub-atmospheric transfer chamber;
transferring said etched and ashed wafer from said sub-atmospheric
transfer chamber into a load lock at said sub-atmospheric pressure;
raising the pressure in said load lock to atmospheric pressure;
transferring said etched and ashed wafer from said load lock to
said atmospheric transfer chamber; transferring said etched and
ashed wafer from said atmospheric transfer chamber to a wet
cleaning chamber coupled to said atmospheric transfer chamber;
cleaning said etched and ashed wafer in said wet cleaning chamber
to produce an etched, ashed, and cleaned wafer; transferring said
etched, ashed, and cleaned wafer from said wet cleaning chamber to
said atmospheric transfer chamber; and removing said etched, ashed,
and cleaned processed wafer from said atmospheric transfer
chamber.
9. The method of claim 8 wherein said thin film comprises a metal
film.
10. The method of claim 8 wherein said thin film comprises a stack
of metal films.
11. The method of claim 10 wherein said stacked metal film
comprises an anti-reflective layer, a main conductive layer, and a
barrier layer.
12. The method of claim 8 wherein said thin film is a dielectric
film.
13. The method of claim 12 wherein said dielectric film is selected
from the group consisting of silicon dioxide, silicon oxynitride,
SiOF, BPSG, undoped silicon pass and organic dielectrics.
14. The method of claim 8 wherein said ashing comprises: exposing
said wafer to an energized cleaning gas; and before, during or
after exposing said wafer to said energized cleaning gas, exposing
said wafer to an energized treating gas comprising a halogen
species and a hydrogen species.
15. The method of claim 14 wherein said cleaning gas comprises: a
stripping gas comprising one or more of O2, N2, H2O, NH3, CF4,
C2F6, CHF3, C3H2F6, C2H4F2, and CHF3 provided under pressure
conditions selected to at least partially remove said residue when
said residue is remnant resist material.
16. The method of claim 8 wherein said cleaning comprises:
transmitting sonic energy to a nondevice side of said wafer while
flowing said cleaning solution on said wafer device side.
17. The method of claim 8 wherein said cleaning comprises:
transmitting sonic energy to a nondevice side of said wafer while
flowing said cleaning solution onto said device side.
18. The method of claim 8 further comprising: prior to transferring
said wafer from said atmospheric transfer chamber into said load
lock, transferring said wafer into a CD measurement tool, and
determining whether or not the CD measurements are in
compliance.
19. The method of claim 18 wherein if said CD measurements are not
in compliance transferring said wafer into a ashing chamber coupled
to said atmospheric transfer chamber, and removing said photoresist
mask in said ashing chamber.
20. The method of claim 8 further comprising the step of: prior to
etching said thin film in said etch chamber, trimming said
photoresist mask.
21. The method of claim 20 wherein said trim utilizes oxygen
plasma.
22. The method of claim 8 wherein after ashing said wafer,
passivating said substrate to a passivating gas which inactivates
corrosive etchant residue.
23. The method of claim 8 further comprising the step of: after
ashing said wafer in said ashing chamber, transferring said wafer
from said atmospheric transfer chamber into a CD measurement tool,
and checking the critical dimensions of said etched wafer.
24. The method of claim 8 wherein after wet cleaning said etched
and ashed wafer transferring said etched, ashed and cleaned wafer
into a critical dimension monitoring tool coupled to said
atmospheric transfer chamber and checking said critical dimensions
of said etched film.
25. The method of claim 8 wherein said thin film is a dielectric
film, and further comprising after transferring said etched, ashed
and cleaned wafer from said wet cleaning chamber to said
atmospheric transfer chamber; transferring said etched, ashed and
cleaned wafer from said atmospheric transfer chamber into a load
lock coupled to said atmospheric transfer chamber; reducing the
pressure of said load lock to a sub-atmospheric pressure;
transferring said wafer from said load lock into a sub-atmospheric
transfer chamber coupled to said load lock; transferring said wafer
from said sub-atmospheric transfer chamber into a metal deposition
chamber coupled to said sub-atmospheric transfer chamber;
depositing a metal film in said deposition chamber coupled to said
sub-atmospheric transfer chamber.
26. A method of forming a transistor comprising: transferring a
monocrystalline silicon substrate from a wafer cassette into an
atmospheric transfer chamber; transferring said a monocrystalline
silicon substrate from said atmospheric transfer chamber to a wet
cleaning chamber coupled to said atmospheric transfer chamber;
cleaning said monocrystalline silicon substrate with a cleaning
solution in said cleaning apparatus; transferring said cleaned
monocrystalline silicon substrate from said cleaning chamber to
said atmospheric process chamber; transferring said a
monocrystalline silicon substrate from said atmospheric transfer
chamber into a load lock coupled to said atmospheric transfer
chamber; reducing the pressure in said load lock to a
sub-atmospheric pressure; transferring said a monocrystalline
silicon substrate from said load lock into a sub-atmospheric
transfer chamber coupled to said load lock; transferring said wafer
from said sub-atmospheric transfer chamber into an oxidation
chamber coupled to said sub-atmospheric transfer chamber; oxidizing
the monocrystalline silicon substrate to a monocrystalline silicon
substrate to form a dielectric film on said monocrystalline silicon
substrate in said oxidation chamber; transferring said oxidized
monocrystalline silicon substrate from said oxidation chamber to
said sub-atmospheric transfer chamber; transferring said oxidized
wafer from sub-atmospheric transfer chamber to a polysilicon
deposition chamber coupled to said sub-atmospheric chamber;
depositing a polysilicon film on said dielectric film formed on
said monocrystalline silicon substrate in said polysilicon
deposition chamber; transferring said wafer with said deposited
polysilicon film from said polysilicon deposition chamber to said
sub-atmospheric transfer chamber; transferring said oxidized and
polysilicon deposited wafer from said sub-atmospheric transfer
chamber into a load lock at said sub-atmospheric pressure; raising
said pressure in said load lock to atmospheric pressure;
transferring said oxidized and polysilicon deposited wafer from
said load lock to said atmospheric transfer chamber; and removing
said oxidized and polysilicon deposited wafer from said atmospheric
transfer chamber.
27. A method of stripping a silicon nitride film from a wafer
comprising: transferring a wafer having a silicon nitride film
thereon into an atmospheric transfer chamber; transferring said
wafer from said atmospheric transfer chamber into a load lock
coupled to said atmospheric transfer chamber; reducing the pressure
in said load lock to a sub-atmospheric pressure; transferring said
wafer from said load lock into said sub-atmospheric transfer
chamber coupled to said load lock; transferring said wafer from
said sub-atmospheric transfer chamber into an etch module coupled
to said sub-atmospheric transfer chamber; etching said silicon
nitride film from said wafer in said etch module coupled to said
sub-atmospheric process chamber; transferring said silicon nitride
stripped wafer from said etch module to said sub-atmospheric
transfer chamber; transferring said silicon nitride etched wafer
from said sub-atmospheric transfer chamber into a load lock at said
sub-atmospheric pressure; raising the pressure in said load lock to
atmospheric pressure; transferring said silicon nitride etched
wafer from said load lock to said atmospheric transfer chamber;
transferring said silicon nitride etched wafer from said
atmospheric transfer chamber to a wet cleaning module coupled to
said atmospheric transfer chamber; and cleaning said silicon
nitride etched wafer in said wet cleaning chamber to produce a
silicon nitride etched and cleaned wafer.
28. The method of claim 27 wherein said wet cleaning comprises:
transmitting sonic energy to a nondevice side of said wafer while
flowing a solution on said wafer device side.
29. The method of claim 27 further comprising after cleaning said
wafer in said wet cleaning module, transferring said wafer to a
particle monitoring tool coupled to said atmospheric transfer
chamber, and checking said surface of said wafer for particles or
residue.
30. The method of claim 29 further comprising utilizing said
information from said particle monitoring tool to alter the silicon
nitride strip parameters and/or the wet cleaning parameters for
processing of subsequent wafers.
31. A method of photolithographic processing of a wafer comprising:
forming a photoresist film on a first side of a wafer having said
first side and a second side opposite said first side; cleaning
said wafer second side with a solution while said photoresist is on
said wafer first side; and exposing said photoresist film on said
wafer first side to radiation after cleaning said wafer second side
with said solution.
32. The method of claim 31 wherein said cleaning of said wafer
second side comprises: horizontally positioning said wafer second
side adjacent to and spaced-apart from a horizontal plate; and
providing said solution between said plate and said wafer second
side.
33. The method of claim 32 further comprising applying acoustic
energy to a second side of said plate while flowing said fluid
between said plate and said wafer second side.
34. The method of claim 33 wherein said acoustic energy is applied
in a direction normal to said wafer second side.
35. The method of claim 34 wherein said acoustic energy is applied
at a frequency of approximately 925 KHz.
36. The method of claim 31 wherein said wafer frontside is kept dry
while cleaning said wafer backside.
37. The method of claim 31 wherein said wafer first side has a
plurality of patterns formed thereon.
38. A method of photolithographically processing a wafer
comprising: placing a wafer into a transfer chamber; transferring
said wafer from said transfer chamber into a single wafer wet clean
module directly coupled to said transfer chamber; cleaning said
wafer backside in said single wafer cleaning module to produce a
backside cleaned wafer; transferring said backside cleaned wafer
from said single wafer clean module to said transfer chamber;
transferring said backside cleaned wafer from said transfer chamber
to a photoresist application module directly coupled to said
transfer chamber; applying photoresist to said wafer front side
opposite said backside in said photoresist application module to
produce a photoresist deposited wafer; transferring said
photoresist deposited wafer from said photoresist application
module to said transfer chamber; transferring said photoresist
deposited wafer from said transfer chamber to an exposure station
coupled directly to said transfer station; and exposing said
photoresist on said photoresist deposited wafer to radiation to
produce a radiation exposed photoresist film on said photoresist
deposited wafer.
39. The method of claim 38 wherein said cleaning of said wafer
backside comprises: horizontally positioning said wafer backside
adjacent to and spaced-apart from a horizontal plate; and flowing a
fluid between said horizontal plate and said wafer backside.
40. The method of claim 39 further comprising applying acoustic
energy to a second side of said horizontal plate while flowing said
fluid between said plate and said wafer backside.
41. The method of claim 40 wherein said acoustic energy is applied
in a direction normal to said wafer backside.
42. The method of claim 41 wherein said wafer frontside is kept dry
while cleaning said wafer backside.
43. The method of claim 41 further comprising: cleaning said wafer
frontside by flowing a second fluid onto said wafer front side
while providing said fluid between said plate and said wafer second
side.
44. The method of claim 39 further comprising filtering amine and
ammonia vapors from said transfer chamber.
45. A method of photolithographically processing a wafer
comprising: placing a wafer having a frontside opposite a backside
into a photoresist application tool and forming a photoresist film
on said frontside of said wafer; removing said wafer from said
photoresist application tool and placing said wafer into a backside
cleaning tool and cleaning the backside of said wafer without
exposing the wafer frontside to cleaning solutions or chemicals;
and removing said wafer from said backside cleaning tool and
placing said wafer into a exposure tool and exposing said
photoresist film to radiation in said exposure tool.
46. The method of claim 45 when the step of forming said
photoresist film on said wafer frontside includes baking said wafer
to remove moisture from said wafer, and spinning a photoresist film
on said wafer, and heating said wafer to remove solvents contained
within said photoresist film.
47. The method of claim 45 wherein said cleaning of said wafer
backside comprises: horizontally positioning said wafer backside
adjacent to and spaced-apart from a horizontal plate; and flowing a
fluid between said horizontal plate and said wafer backside.
48. The method of claim 47 further comprising applying acoustic
energy to a second side of said horizontal plate while flowing said
fluid between said plate and said wafer backside.
49. The method of claim 48 wherein said acoustic energy is applied
in a direction normal to said wafer backside.
50. The method of claim 45 further comprising after cleaning the
backside of said wafer, placing said wafer in a backside particle
inspection tool and inspecting said wafer backside for particles.
Description
[0001] This is a Division of application Ser. No. 10/229,446 filed
Aug. 27, 2002 which is a Continuation-in-Part of application Ser.
No. 09/945,454 filed Aug. 31, 2001.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to the field of semiconductor
processing and more specifically to a method and apparatus for
atmospheric and sub-atmospheric processing of a single wafer.
[0004] 2. Discussion of Related Art
[0005] In silicon wafer processing, a wafer undergoes a
predetermined sequence and steps to make an electronic circuit.
Some steps are carried out at an atmospheric pressure while other
steps are carried out at a sub-atmospheric pressure. Typically, a
wafer undergoes a process step in a process chamber. Process
chambers are loaded by a robot. Either a single robot, or more than
one robot, for loading a single process chamber or more than one
process chambers together with process chambers is called a tool or
platform. Different tools or platforms can contain different of
similar process chambers. All tools together contain the necessary
process chambers to complete an entire process sequence that is
necessary to fabricate an electronic circuit. Wafers are
transported from one tool to another tool in cassettes. In each
tool a robot takes the wafers out of the cassette and loads them
separately or in a batch into a process chamber or multiple process
chambers of that particular tool. After processing, the robot
returns the wafers to the same cassette or to a different cassette
and the entire cassette is then transported to the next tool in the
fab to perform the next process step.
[0006] In a number of instances, it is advantageous to combine
several different process chambers in one tool. In such a tool the
robot takes the wafers out of the wafer cassette and loads them
into the first process chamber. After the process is finished in
that process chamber, instead of returning the wafer to the
cassette the robot then loads the wafer into the next process
chamber to perform the next process step. After the next process
step, there can be another process step and so on until the wafer
has undergone all process steps that are available in that tool.
After the last process step of that tool, the wafers are then
finally returned to their wafer cassette and the cassette
transported to the next tool in the fab. Such a tool with one or
more different process chambers are presently referred to as
"cluster tools".
[0007] The advantages of a cluster tool include: reduced wafer
traveling distance, reduced footprint, reduced cycle time, and
improved yield. The reduced wafer traveling distance, reduced
footprint, and reduced cycle time are a result of the reduced
handling of the wafers. The improved yield is a result of the
reduced exposure of the wafer surface to the fab atmosphere. The
detrimental affect of the fab atmosphere exposure during transport
from one tool to another is dependent on the particular sequence of
process steps. Fab atmosphere exposure can be very detrimental to
electronic circuit yield between certain steps while it may not
affect whatsoever the yield between certain other steps.
[0008] The clustering of different process steps in one tool also
has some disadvantages. For example, if one process chamber is
inoperable due to a technical failure, the entire tool may not be
available and therefore technical failure in one process chamber
can have detrimental affect on the availability of the other
process chambers. Nevertheless, in certain occasions, the
advantages outlined above of clustering different sequential
process tools in one tool might be higher than the disadvantage of
lower availability or reliability. Therefore, there are a number of
instances where clustering of different process steps and different
process chambers around one or more robots in the single tool is
desirable. There are a number of examples where this has been done
and where commercial success is achieved proving the benefits of
such clustering. Most of the existing clustering tools have some
process benefit (i.e., reduced exposure to the fab environment
increases the yield).
[0009] One example of a cluster tool is a sub-atmospheric cluster
tool. In such a tool different sub-atmospheric process chambers are
provided around a sub-atmospheric wafer handler or robot. In this
case, the clustering provides a benefit that the process chambers
do not get exposed to the atmosphere and the wafers do not get
exposed to the atmosphere while being transferred from one chamber
to another chamber. This is especially useful in the sequence, such
as titanium nitride sputtering, aluminum sputtering, titanium
nitride sputtering which is generally used to form metal
interconnects of an integrated circuit. Another example of a
cluster tool is an atmospheric process cluster tool. For example, a
chemical mechanical polishing process chamber can be clustered with
a cleaning step such that the wafers are transported from the
chemical polishing process to the cleaning process while the wafers
are still in a wet condition. This avoids having to dry the wafers
between the two steps. Drying wafers between the two steps makes it
much more difficult to clean the wafers.
[0010] Thus, what is desired are novel cluster tool combinations as
well as cluster tools which utilizes both atmospheric and
sub-atmospheric process chambers.
SUMMARY OF THE INVENTION
[0011] A method of a single wafer wet/dry cleaning apparatus
comprising:
[0012] a transfer chamber having a wafer handler contained
therein;
[0013] a first single wafer wet cleaning chamber directly coupled
to the transfer chamber; and
[0014] a first single wafer ashing chamber directly coupled to the
transfer chamber.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is an overhead illustration of a atmospheric cluster
tool having a single wafer wet cleaning module, a single wafer
strip module, and a integrated process metrology tool each coupled
around an atmospheric transfer chamber having a robot contained
therein.
[0016] FIGS. 2A-2C is an illustration of a single wafer wet clean
module in accordance with an embodiment of the present
invention.
[0017] FIG. 3 is an illustration of a cross-sectional view of an
integrated particle monitoring tool in accordance with an
embodiment of the present invention.
[0018] FIG. 4 is an illustration of a cross-sectional view of a
single wafer stripping module in accordance with an embodiment of
the present invention.
[0019] FIG. 5A-5D illustrate a dry stripping and wet cleaning
process in accordance with an embodiment of the present
invention.
[0020] FIG. 6 is an illustration of a atmospheric/sub-atmospheric
process tool for the etching, stripping, cleaning and monitoring of
a wafer in accordance with an embodiment of the present
invention.
[0021] FIG. 7 is a block diagram of a review or monitoring tool
according to an embodiment of the present invention.
[0022] FIGS. 8A and 8B are flowcharts illustrating sequential steps
in monitoring methods according to embodiments of the present
invention.
[0023] FIG. 9 is a schematic sectional sideview of an etching
chamber.
[0024] FIGS. 10A-10E illustrate a method of etching conductive
features, and then stripping and cleaning a wafer in accordance
with an embodiment of the present invention.
[0025] FIGS. 11A-11F illustrate a damascene process in accordance
with an embodiment of the present invention.
[0026] FIG. 12 is an illustration of an atmospheric/sub-atmospheric
process tool which can be used to clean, grow a dielectric layer,
and deposit a silicon film on a wafer in accordance with an
embodiment of the present invention.
[0027] FIG. 13A illustrate a rapid thermal heating apparatus which
can grow a dielectric layer in accordance with an embodiment of the
present invention.
[0028] FIG. 13B illustrate the light source placement in the rapid
thermal heating apparatus of FIG. 13A.
[0029] FIG. 14A shows an illustration of a cross-sectional side
view a processing chamber comprising of a resistive heater in a
"wafer-process" position in accordance with an embodiment of the
invention through first cross-section and a second cross-section
each through one-half of the chamber.
[0030] FIG. 14B shows an illustration of a similar cross-sectional
side view as in FIG. 14A in a wafer separate position.
[0031] FIG. 14C shows an illustration of a similar cross-sectional
side view as in FIG. 14A in a wafer load position.
[0032] FIG. 15A-15E illustrate a method of depositing and forming a
dielectric film and a gate electrode in accordance with an
embodiment of the present invention.
[0033] FIG. 16A-16C illustrate a method of removing a silicon
nitride film in accordance with an embodiment of the present
invention.
[0034] FIG. 17A is a perspective view of high k dielectric
deposition module of the present invention.
[0035] FIG. 17B is a cross sectional view of the chamber of high k
dielectric deposition module.
[0036] FIG. 17C is a schematic view of a typical remote plasma
generator.
[0037] FIG. 18A is an overhead illustration of a photolithographic
tool in accordance with the present invention.
[0038] FIG. 18B is an overhead illustration of a photolithographic
tool in accordance with an embodiment of the present invention.
[0039] FIG. 18C is an overhead illustration of a photolithographic
process in accordance with an embodiment of the present
invention.
[0040] FIG. 18D is an overhead illustration of a photolithographic
apparatus in accordance with an embodiment of the present
invention.
[0041] FIG. 19-A-19G illustrates a method of cleaning a wafer,
forming a photoresist film on the wafer and exposing the
photoresist film in accordance with an embodiment of the present
invention.
[0042] FIG. 20A is an illustration of a computer/controller which
can be used in the tools of the present invention.
[0043] FIG. 20B is an illustration of a software program which can
be used to control the tools of the present invention.
DETAILED DESCRIPTION
I) Dry/Wet Processing Tool
[0044] FIG. 1 illustrates an apparatus or system 100 for the
stripping (ashing), wet cleaning and particle monitoring of a wafer
during the manufacture of a semiconductor integrated circuit. The
cleaning apparatus 100 includes a central transfer chamber 102
having a wafer handling device 104 contained therein. Directly
attached to transfer chamber 102 is a single wafer wet cleaning
module 200, a strip module 400, and an integrated process
monitoring tool 300, such as an integrated particle monitor. Wet
cleaning module 200, strip module 400, and integrated particle
monitor 300 are each connected to transfer chamber 102 through a
separately closable opening. In an embodiment of the present
invention, a second wet cleaning module 200B and/or a second strip
module 400B are also coupled to transfer chamber 102. In an
embodiment of the present invention, transfer chamber 102 is
maintained at substantially atmospheric pressure (i.e., atmospheric
transfer chamber) during operation. In an embodiment of the present
invention, the atmospheric transfer chamber 102 can be opened or
exposed to the atmosphere of a semiconductor fabrication "clean
room" in which it is located. In such a case, the transfer chamber
102 may contain an overhead filter, such as a hepafilter to provide
a high velocity flow of clean air or an inert ambient such as
N.sub.2, to prevent contaminants from finding their way into the
atmospheric transfer chamber. In other embodiments, the atmospheric
transfer chamber 102 is a closed system and may contain its own
ambient, of clean air or an inert ambient, such as nitrogen gas
(N.sub.2).
[0045] Transfer chamber 102 includes a wafer handling robot which
can transfer a wafer from one module to another. In an embodiment
of the present invention, the wafer handler is a single robot with
two wafer handling blades 114 and 116 which both rotate about a
single axis 119 coupled to the end of a single arm 120. Robot 104
can be said to be a dual blade single arm, single wrist robot.
Robot 104 moves on a track 122 along a single axis in transfer
chamber 102.
[0046] A system computer 124 is coupled to and controls each wet
clean module 200, strip module 400 and integrated particle
monitoring module 300 as well as the operation of transfer chamber
102 and robot 104. Computer 124 enables the feedback from one
module, such as the integrated particle monitoring module, to be
used to control the flow of a wafer through system 100 and/or to
control the process within a different module.
[0047] Also coupled to transfer chamber 102 is at least one wafer
input/output module 130 or pod for providing wafers to system 100
and for taking wafers away from system 100. In an embodiment of the
present invention, the wafer input/output module 106 is a front
opening unified pod (FOUP) which is a container having a slideable
and sealable door and which contains a cassette of between 13-25
horizontally spaced wafers. Transfer chamber 102 contains a
sealable access door 110 which slides vertically up and down to
enable access into and out of transfer chamber 102. In an
embodiment of the present invention, apparatus 100 includes two
FOUP's, 106 and 108 one for providing wafers into system 100 and
one for removing completed or processed wafers from system 100.
However, a wafer can be inputted and outputted from the same FOUP,
if desired. A second access door 112 is provided to accommodate a
second FOUP 108. Each access door can be attached to the counter
part door on each FOUP so that when the transfer chamber access
door 110 and 112 slides open, it opens the door of the FOUP to
provide access for the robot into the FOUP. The FOUP's can be
manually inserted onto apparatus 100 or a wafer stocking system
114, such as a Stocker, having multiple FOUP's in a rail system can
be used to load and remove FOUP's from apparatus 100.
A) Single Wafer Wet Cleaning Module
[0048] An example of a single wafer cleaning module 200 which can
be used as wet cleaning module 200 and 200B (if used) is
illustrated in FIGS. 2A-2C. FIGS. 2A-2C illustrate a single wafer
cleaning apparatus 200 which utilizes acoustic or sonic waves to
enhance a cleaning. Single wafer cleaning apparatus 200 shown in
FIG. 2A includes a plate 202 with a plurality of acoustic or sonic
transducers 204 located thereon. Plate 202 maybe made of aluminum
but can be formed of other materials such as but not limited to
stainless steel and sapphire. The plate is maybe coated with a
corrosion resistant fluoropolymer such as Halar or PFA. The
transducers 204 are attached to the bottom surface of plate 202 by
an epoxy 206. In an embodiment of the present invention the
transducers 204 cover substantially the entire bottom surface of
plate 202 as shown in FIG. 2b and cover at least 80% of plate 202.
The transducers 204 generate sonic waves in the frequency range
e.g. between 400 kHz and 8 MHz. In an embodiment of the present
invention the transducers 204 are piezoelectric devices. The
transducers 204 create acoustic or sonic waves in a direction
perpendicular to the surface of wafer 208.
[0049] A substrate or wafer 208 is held at distance of about 3 mm
above the top surface of plate 202. The wafer 208 is clamped by a
plurality of clamps 210 face up to a wafer support 212 which can
rotate wafer 208 about its central axis. The wafer support can
rotate or spin wafer 208 about its central axis at a rate between
0-6000 rpm. In apparatus 200 only wafer support 212 and wafer 208
are rotated during use whereas plate 202 remains in a fixed
position. Additionally, in apparatus 200 wafer 208 is placed face
up wherein the side of the wafer with patterns or features such as
transistors faces towards a nozzle 214 for spraying cleaning
chemicals or water thereon and the backside of the wafer faces
plate 202. Additionally, as shown in FIG. 2C the transducer covered
plate 202 has a substantially same shape as wafer 208 and covers
the entire surface area of wafer 208. Apparatus 200 can include a
sealable chamber 201 in which nozzle 214, wafer 208, and plate 202
are located as shown in FIG. 2A.
[0050] In an embodiment of the present invention, during use, DI
water (DI--H.sub.2O) is fed through a feed through channel 216 of
plate 202 and fills the gap between the backside of wafer 208 and
plate 202 to provide a water filled gap 218 through which acoustic
waves generated by transducers 204 can travel to substrate 208. In
an embodiment of the present invention DI water fed between wafer
208 and plate 202 is degassed so that cavitation is reduced in the
DI water filled gap 218 where the acoustic waves are strongest
thereby reducing potential damage to wafer 208. In an alternative
embodiment of the present invention, instead of flowing
DI--H.sub.2O through channel 216 during use, cleaning chemicals,
such as the cleaning solution of the present invention can be fed
through channel 216 to fill gap 218 to provide chemical cleaning of
the backside of wafer 208, if desired.
[0051] Additionally during use, cleaning chemicals and rinsing
water such as DI--H.sub.2O are fed through a nozzle 214 to generate
a spray 220 of droplets which form a liquid coating 222 on the top
surface of wafer 208 while wafer 208 is spun. In the present
embodiment the liquid coating 222 can be as thin as 100 micron. In
the present embodiment tanks 224 containing cleaning chemicals such
as diluted HF, de-ionized water (DI--H.sub.2O), and the cleaning
solution of the present embodiment are coupled to conduit 226 which
feeds nozzle 214. In an embodiment of the present invention the
diameter of conduit 226 has a reduced cross-sectional area or a
"Venturi" 228 in a line before spray nozzle 214 at which point a
gas such as H.sub.2 is dissolved in the cleaning solution as it
travels to nozzle 214. "Venturi" 228 enables a gas to be dissolved
into a fluid flow at gas pressure less than the pressure of the
liquid flowing through conduit 226. The Venturi 228 creates under
pressure locally because of the increase in flow rate at the
Venturi.
B) Integrated Particle Monitor
[0052] In an embodiment of the present invention, the integrated
process monitoring tool 110 is an integrated particle monitor (IPM)
300 such as shown in FIG. 3. An example of a suitable integrated
particle monitor (IPM) 300 is the IPM tool manufactured by Applied
Materials of Santa Clara, Calif. According to one embodiment of the
present invention, the integrated particle monitor 300 includes a
rotatable wafer support 302 for holding a wafer 301 and for
rotating a wafer on its central axis. A laser source 304 shines a
laser beam 306 on wafer 301 and the location of the reflected beam
308 is detected by one or more of a plurality of detectors 310.
Detection of the reflected beam 308 by one or more a detector 310
can be used as an indication of the presence of the particle at the
location. The detectors can take the form of "bright field"
detectors, "dark field" detectors or combination of "bright field"
and "dark field" detectors. The laser beam 306 can be scanned
across the radius of the wafer while the wafer is rotated in order
to monitor the entire wafer surface for particles. Computer 124
along with data processing software can be used to generate a
defect map of the entire wafer surface. Software can be used to
analyze the particle map, by for example, comparing to a blank
wafer or by comparing the particle map of one die on the wafer to
other dies on the same or different wafer. The software can be used
to classify defects as particles or microscratches. The data from
the integrated particle monitoring tool 300 can be used to
determine when downstream chambers have excurted from their process
base lines (i.e., chamber excursions). Similarly, the particle maps
can be sent to upstream chambers or modules in order to alter or
optimize or change the upstream process in view of the defect
map.
C) Strip or Dry Cleaning Module
[0053] A strip or dry cleaning module 400 in accordance with an
embodiment is illustrated in FIG. 4. In the cleaning chamber 400 of
the type illustrated in FIG. 4, an energized process gas comprising
cleaning gas is provided to clean the substrate 480 held on the
support 410 in a process zone 415. The support 410 supports the
substrate 480 in the process zone 415 and may optionally comprise
an electrostatic chuck 412. Within or below the support 410, a heat
source, such as infrared lamps 420, can be used to heat the
substrate 430. The process gas comprising cleaning gas may be
introduced through a gas distributor 422 into a remote plasma
generation zone 425 in a remote chamber 430. By "remote" it is
meant that the center of the remote chamber 430 is at a fixed
upstream distance from the center of a process zone 415 in the
cleaning chamber 108. In the remote chamber 430, the cleaning gas
is activated by coupling microwave or RF energy into the remote
chamber 430, to energize the cleaning gas and cause ionization or
dissociation of the cleaning gas components, prior to its
introduction through a diffuser 435, such as a showerhead diffuser,
into the process zone 415. Alternatively, the process gas may be
energized in the process zone 415. Spent cleaning gas and residue
may be exhausted from the cleaning chamber 108 through an exhaust
system 440 capable of achieving a low pressure in the cleaning
chamber. A throttle valve 425 in the exhaust 440 is used for
maintaining a chamber pressure from about 150 mTorr to about 3000
mTorr.
[0054] In the version illustrated in FIG. 4, the remote chamber 430
comprises a tube shaped cavity containing at least a portion of the
remote plasma zone 425. Flow of cleaning gas into the remote
chamber 430 is adjusted by a mass flow controller or gas valve 450.
The remote chamber 430 may comprise wall made of a dielectric
material such as quartz, aluminum oxide, or monocrystalline
sapphire that is substantially transparent to microwave and is
non-reactive to the cleaning gas. A microwave generator 455 is used
to couple microwave radiation to the remote plasma zone 425 of the
remote chamber 430. A suitable microwave generation 455 is an
"ASTEX" Microwave Plasma Generator commercially available from
Applied Science & Technology, Inc., Woburn, Mass. The microwave
generator assembly 455 may comprise a microwave applicator 460, a
microwave tuning assembly 465, and a magnetron microwave generator
470. The microwave generator may be operated at a power level of
about 200 to about 3000 Watts, and at a frequency of about 800 MHz
to about 3000 MHz. In one version, the remote plasma zone 425 is
sufficiently distant from the process zone 415 to allow
recombination of some of the dissociated or ionized gaseous
chemical species. The resultant reduced concentration of free
electrons and charged species in the activated cleaning gas
minimizes charge-up damage to the active devices on the substrate
480, and provides better control of the chemical reactivity of the
activated gas formed in the remote plasma zone 425. In one version,
the center of the remote plasma zone 425 is maintained at a
distance of at least about 50 cm from the center of the process
zone 415.
[0055] A cleaning process may be performed in the cleaning chamber
400 by exposing the substrate 480 to energized process gas
comprising cleaning gas to, for example, remove remnant resist
and/or to remove or inactivate etchant residue remaining on the
substrate after the substrate is etched. Remnant resist may be
removed from the substrate 480 in a stripping (or ashing) process
by exposing the substrate 480 to energized process gas comprising
stripping gas. Stripping gas may comprise, for example, one or more
of O.sub.2, N.sub.2, H.sub.2, H.sub.2O, NH.sub.3, CF.sub.4,
C.sub.2F.sub.6, CHF.sub.3, C.sub.3H.sub.2F.sub.6,
C.sub.2H.sub.4F.sub.2, or CH.sub.3F.
Method of Operating Wet/Dry Cleaning Tool 100
[0056] Wet/dry cleaning tool 100 is ideal for use in removing a
photoresist layer from a wafer as shown in FIGS. 5A-5D. In an
embodiment of the present invention, a patterned photoresist layer
502 is removed from a wafer 500 after an ion-implantation step 504.
The patterned photoresist layer as shown in FIG. 5a, forms a mask
which is used to mask an ion-implantation step which can be used to
form doped regions in a monocrystalline silicon substrate 508, such
as wells, source/drain regions, channel doping, and other well
known doped regions used to fabricate a semiconductor integrated
circuit. According to an embodiment of the present invention, a
cassette or FOUP of wafers 500 having a photoresist mask 502
thereon, are placed in a docking station in apparatus 100. An
access door 110 in docking station 131 slides down and pulls down
the door to FOUP 130. Robot 104 removes a wafer 500 from FOUP 130
and places the wafer into dry clean chamber 400. Clean chamber 108
is then sealed and pumped down to a pressure of between 150 mTorr
to 3000 mTorr.
[0057] A cleaning process is then performed in the cleaning chamber
400 by exposing the wafer 500 to energized process gas comprising
cleaning gas to, for example, remove photoresist mask 502 and/or to
remove or inactivate implant residue 512 remaining on the substrate
after the substrate is etched. Remnant resist 502 may be removed
from the substrate in a stripping (or ashing) process by exposing
the substrate to energized process gas comprising stripping gas.
Stripping gas may comprise, for example, one or more of O.sub.2,
N.sub.2, H.sub.2, H.sub.2O, NH.sub.3, CF.sub.4, C.sub.2F.sub.6,
CHF.sub.3, C.sub.3H.sub.2F.sub.6, C.sub.2H.sub.4F.sub.2, or
CH.sub.3F. In one version, a suitable stripping gas for stripping
polymeric resist material comprises (i) oxygen, and optionally (ii)
an oxygen activating gas or vapor, such as water vapor, nitrogen
gas, or fluorocarbon gas, the fluorocarbon gases including any of
those listed above. The oxygen activating gas increases the
concentration of oxygen radicals in the stripping gas. The
stripping gas composition may comprise oxygen and nitrogen in a
volumetric flow ratio of about 6:1 to about 200:1, and more likely
from about 10:1 to about 12:1. For a 5-liter process chamber 108, a
suitable gas flow rate comprises 3000 to 3500 sccm of O.sub.2 and
300 sccm of N.sub.2. In one version, a stripping gas comprises
about 35000 sccm O.sub.2, about 200 sccm N.sub.2 and optionally
about 300 sccm H.sub.2O, that is energized at a power level of
about 1400 watts and introduced into the cleaning chamber 108 at a
pressure of about 2 Torr for about 15 seconds. In one version, the
water vapor content in the stripping gas should be less than about
20% by volume of the combined oxygen and nitrogen gas content to
provide adequate stripping rates. A suitable ratio of the
volumetric water vapor flow V.sub.H2O to the combined volumetric
flow of oxygen and nitrogen (V.sub.O2+V.sub.N2) is from about 1:4
to about 1:40, and more likely about 1:10. When the remnant resist
comprises oxide hard mask, suitable stripping gases are gases
capable of stripping oxide, such as halogen containing gases,
including CF.sub.4, C.sub.2F.sub.6, CHF.sub.3,
C.sub.3H.sub.2F.sub.6, C.sub.2H.sub.4F.sub.2, and HF. The substrate
500 may be exposed to the stripping gas for a period of time of
from about 10 seconds to about 1000 seconds, and more likely for
about 45 seconds. A single stripping step may be performed or
multiple stripping steps may be performed, as discussed in U.S.
Pat. No. 5,545,289, which is incorporated herein by reference in
its entirety. After stripping or ashing in chamber 400, wafer 500
may still contain photoresist mask residue and/or implant residue
512 as shown in FIG. 5B.
[0058] In one version, the substrate may be heated during the
stripping and/or the passivation processes. For example, when
cleaning the substrate 500 in a cleaning chamber 400, such as the
cleaning chamber of FIG. 4, the lamps 420 may be used to heat the
substrate to a temperature of at least about 150.degree. C., and
more specifically to a temperature of at least about 250.degree. C.
Heating the substrate 500 improves the remnant resist removal rate
and may also improve the removal rate of some etchant residue, such
as Cl in the sidewall deposits 80, because the Cl can more readily
diffuse out of the sidewall deposits. The elevated temperature also
enhances the surface oxidation, when O.sub.2 containing strip
density is used, of the etched metal, making them less susceptible
to corrosion.
[0059] In one embodiment of the present invention, the wafer is
then transferred to the wet cleaning chamber 200 and is exposed to
a light clean consisting of only a Di water rinse. In another
embodiment of the present invention, the wafer is exposed to a Di
water rinse which has been ozonated. The ozonated water oxidizes
carbon left over from the ashing and insures its removal. In yet
another embodiment of the present invention, the wafer is exposed
to an ozonated water rinse and to cleaning chemicals comprising
NH.sub.4OH, H.sub.2O.sub.2, a surfactant and a chelating agent. In
yet another embodiment of the present invention, the wafer is
exposed to an ozonated Di water then HF then cleaning solutions
comprising NH.sub.4OH, H.sub.2O.sub.2, a surfactant and a chelating
agent. In yet another embodiment of the present invention, the
wafers are exposed to a mixture comprising sulfuric acid
(H.sub.2SO.sub.4) and hydrogen peroxide (H.sub.2O.sub.2) and then
exposed to a water rinse and dry. In yet another embodiment of the
present invention, the wafers are exposed to standard RCA cleaning
solutions of SC1 and SC2 and then exposed to a water rinse and dry.
While the wafers are being cleaned megasonic energy can be applied
to the wafer to enhance the cleaning. In an embodiment of the
present invention, megasonics is applied to the entire backside of
the wafer while cleaning. Not only can the cleaning solution being
applied to the device side of the wafer (frontside of the wafer)
but can also be applied to the backside of the wafer, if
desired.
[0060] After the wafer 500 has been sufficiently cleaned, as shown
in FIG. 5C, the door to the wet cleaning module 200 opens and the
robot 104 removes the wafer from the wet module 200. If process
metrology of the wafer 500 is desired, the door to the metrology
tool 300 is opened and the robot 104 transfers the wafer into the
process metrology tool 300. The door to the integrated particle
monitor 300 is then closed and the wafer 500 scanned, as shown in
FIG. 5D, to check for defects, such as scratches and particles.
Computer/controller 124 can generate a defect map of the defects
across the surface of wafer 500. Computer/controller 124 and data
process software can determine whether or not the wafer has been
sufficiently cleaned by the stripping chamber 400 and the wet
cleaning chambers 200 and can be used to determine which type of
defects have occurred. Depending upon the results of the metrology
scan, the wafer can be removed from the integrated particle monitor
tool 110 and can be either: (i) transferred back to the wet
cleaning module 200 for further wet cleaning, (ii) transferred back
to the dry clean module 400 for more stripping, (iii) can be
transferred back to both the dry clean module 400 and the wet
cleaning module 200 for further stripping and cleaning or (iv) can
be transferred back to the FOUP. The amount of and/or type of clean
or stripping necessary can be determined by the information
received from the integrated particle monitor tool 300. If the
wafer has been sufficiently stripped and cleaned, the wafer can be
removed from the integrated particle monitor by robot 104 and moved
through the transfer chamber 102 whereby the access door as well as
the door to the wafer cassette or FOUP which is to receive the
wafer is opened and the wafer placed therein. The wafer can be
placed into the same FOUP 130 in which the wafer started or can be
placed in a different FOUP 132, if desired.
[0061] In an embodiment of the present invention, the process time
in each module and the number of each module are chosen so that the
wafer flow is balanced for optimum use of each module. For example,
in an embodiment of the present invention, the process time used to
strip a wafer in cleaning module 400 is chosen to be substantially
similar to the process time used to wet clean a wafer in wet clean
module 200 and is about twice as long as the time necessary to
check a wafer for defects in module 300. Accordingly, apparatus 100
includes two wet clean modules 200 and 200B, and two strip modules
400 and 400B, and a single metrology tool 300. By providing two wet
cleaning tools 200 and 200B and two ashing tools 400 and 400B and a
single metrology tool 300, no module is left idle. For example, if
the wet cleaning time is chosen to be two minutes then the
stripping time is chosen to be two minutes, and the metrology tool
takes one minute then the wafer throughput of the modules is
balanced. By providing more modules for the processes which take
longer (e.g., to clean and strip) faster processing modules (e.g.,
metrology) do not sit idle while waiting for a wafer to complete
cleaning or stripping. In such a process, a wafer completes
processing (strips, cleans, and metrology) every 60 seconds
(apparatus 100 has a wafer through put of 60 seconds) as opposed to
every 120 seconds if the tool was unbalanced and only had one wet
clean or one strip module in apparatus 100. Preventing idle time of
the modules contained in apparatus 100 directly increases wafer
through put and reduces a cost of ownership of the apparatus.
II) Atmospheric and Sub-Atmospheric Process Tool
[0062] According to another embodiment of the present invention, a
process tool or apparatus having both atmospheric and
sub-atmospheric process chambers or modules is provided. According
to this embodiment of the present invention, the process tool
includes an atmospheric platform coupled via a load lock to a
sub-atmospheric platform. (A platform is a transfer chamber having
a robot contained therein and process modules attached thereto).
Attached to the sub-atmospheric transfer chamber are
sub-atmospheric process modules, such as but not limited to etch
modules, deposition chambers such as CVD chambers and sputter
chambers, oxidation chambers, and anneal chambers. Attached to the
atmospheric transfer chamber are atmospheric process modules, such
as wet cleaning tools, ashing (stripping) tools, and metrology
tools. The ashing (stripping) chambers can be connected to either
the atmospheric platform or the sub-atmospheric platform or both.
The atmospheric/sub-atmospheric tool utilizes a single wafer load
lock and generally two single wafer load locks coupled between the
atmospheric and sub-atmospheric platforms to enable transfer of
wafer between the atmospheric and sub-atmospheric transfer
chambers. In an embodiment of the present invention, wafers enter
the tool through the atmospheric transfer chamber and also exit the
tool through the atmospheric transfer chamber. Some of the benefits
of the atmospheric and sub-atmospheric process tool include the
fact that Queue time between two process steps can be reduced and
made consistent and independent of Queing or material logistic
issues. Additionally, the growth of silicon dioxide on silicon is
reduced due to reduced exposure (in time) to air. Particle and
contamination control can be improved through reduced exposure to
the fab environment. An atmospheric/sub-atmospheric process tool
can provide processing of a wafer in reduced cycle times and also
provides a reduced footprint of the tool. Additionally, an
atmospheric/sub-atmospheric process tool can reduce corrosion of,
for example metal lines, through reduced exposure to air.
Additionally, the amount of distance a wafer must travel is also
reduced thereby improving wafer throughput and contamination
control.
Etch/Strip Clean Process Tool
[0063] An example of an atmospheric/sub-atmospheric process
apparatus 600 in accordance with the present invention is
illustrated in FIG. 6. Shown in FIG. 6 is a process tool or system
600 which can be used to etch features, such as metal or
polysilicon lines, or opening in dielectric layers or silicon
substrates and can be used to strip or clean the photoresist layer
used to pattern the features. Etch/strip process tool 600 includes
an atmospheric platform 602 and a sub-atmospheric platform 604. The
sub-atmospheric platform 604 and the atmospheric platform 602 are
coupled together by a single wafer load lock 606 and generally by
two single wafer load locks 606 and 608. Atmospheric platform 602
includes a central atmospheric transfer chamber 610 having a wafer
handling device 612, such as a robot contained therein. Directly
attached to atmospheric transfer chamber 610 is a single wafer wet
cleaning module 200 and an integrated particle monitor 300 and a
critical dimension (CD) measuring tool 700. A strip or dry clean
module 400 can also be attached to atmospheric transfer chamber
610, if desired. Wet cleaning module 200, strip module 400,
integrated particle monitor 300, and critical dimension measuring
tool 700 are each connected to transfer chamber 610 through a
separately closable and sealable opening, such as a slit valve.
Transfer chamber 610 is maintained at substantially atmospheric
pressure during operation. In an embodiment of the present
invention, the atmospheric transfer chamber 610 can be opened or
exposed to the atmosphere of a semiconductor fabrication "clean
room" in which it is located. In such a case, the transfer chamber
610 may contain an overhead filter, such as a hepafilter to provide
a high velocity flow of clean air or an inert ambient such as
N.sub.2, to prevent contaminants from finding their way into the
atmospheric transfer chamber. In other embodiments, the atmospheric
transfer chamber 610 is a closed system and may contain its own
ambient, of clean air or an inert ambient, such as nitrogen gas
(N.sub.2).
[0064] Atmospheric transfer chamber 610 includes a wafer handling
robot 612 which can transfer a wafer from one module to another
module in atmospheric process tool 602. In an embodiment of the
present invention, the wafer handler 612 is a dual blade, single
arm, single wrist robot. The handling blades both rotate about a
single axis coupled to the end of a single arm as described
above.
[0065] Also coupled to atmospheric transfer chamber 610 is at least
one wafer input/output module 620 or pod for providing and taking
wafer to and from system 600. In an embodiment of the present
invention, the wafer input/output module is a front opening unified
pod (FOUP) which is a container having a sealable door and which
contains a cassette for between 13-25 horizontally spaced wafers.
In an embodiment of the present invention, apparatus 600 includes
two FOUPs 622 and 624, one for providing wafers into system 600 and
one for removing completed or processed wafers from system 600.
Atmospheric transfer chamber 610 contains a sealable access door
621 for allowing wafers to be transferred into and out of
atmospheric transfer chamber 610. There is an access door 621 for
each FOUP, and each assess door is attached to a counter part door
on each FOUP so that when transfer chamber access door 621 slides
open, it opens the door to the associated FOUP to provide access
for the robot 612 into the FOUP.
[0066] Coupled to the opposite sides of atmospheric transfer
chamber 610 then FOUP 622 and 624 is a single wafer load lock 606
and optionally second single wafer load lock 608. Single wafer load
locks 606 and 608 enable a wafer to be transferred from the
atmospheric conditions in transfer chamber 610 to the
sub-atmospheric transfer chamber 630 of platform 604 and allows
wafers to be transferred from the sub-atmospheric transfer chamber
630 to the atmospheric transfer chamber 610. A sealable door 605 is
located between atmospheric transfer chamber 610 and load lock 606
and a sealable door 607 is located between sub-atmospheric transfer
chamber 630 and load lock 606. Similarly, a sealable door 609 is
located between atmospheric transfer chamber 610 and load lock 608
and a sealable door 611 is located between sub-atmospheric transfer
chamber 630 and load lock 608. Coupled to each load locks 606 and
608 is a vacuum source which enables the pressure inside load locks
606 and 608 to be independently lowered. Additionally, also coupled
to each load lock 606 and 608 is a gas inlet for providing, for
example, air or an inert gas, such as N.sub.2, into a load lock to
enable the pressure within the load lock to be raised. In this way,
the pressure within the load locks 606 and 608 can be matched to
either the pressure within atmospheric transfer chamber 610 or the
pressure within sub-atmospheric transfer chamber 630.
[0067] Attached to the opposite ends of the single wafer load locks
606 and 608 is sub-atmospheric transfer 630 having a wafer handling
device 632, such as a robot contained therein. Sub-atmospheric
transfer chamber 630 is said to be a sub-atmospheric transfer
chamber because transfer chamber 630 is held at a pressure less
than atmospheric pressure and generally between 10.sup.-6-10 Torr
while in operation and passing wafers to the various
sub-atmospheric process modules coupled thereto. Directly attached
to sub-atmospheric transfer chamber 630 is a single wafer strip
module 400B and an etch module 900 optionally. Strip module 400B
and etch module 900 are connected to sub-atmospheric transfer
chamber 630 through separately closable openings. In an embodiment
of the present invention, a second strip module 400C and a second
etch 900B are also coupled to sub-atmospheric transfer chamber 630.
Although, load locks 606 and 608 are ideally low volume single
wafer load locks to enable fast wafer transfers between the
atmospheric transfer chamber and the sub-atmospheric transfer
chamber, load locks 606 and 608, however, can be larger multiple
wafer load locks which can hold multiple wafers at a single time,
if desired.
[0068] It is to be noted that the ashing or stripping processes
which occur in strip module 400 (as well as modules 400B and 400C)
typically occur at sub-atmospheric pressures. Accordingly, it is
advisable to place the stripping modules necessary for the process
onto sub-atmospheric transfer chamber because it simplifies and
reduces the pumping requirements in the stripping module. There
are, however, times when it maybe beneficial or necessary to
include a stripping module 400 on atmospheric transfer chamber 610.
For example, if all module location on the sub-atmospheric transfer
chamber are occupied by other modules one can place the stripping
module on the atmospheric transfer chamber 610. Additionally, some
integrated processes may require excessive wafer transfers between
sub-atmospheric chamber 630 and atmospheric transfer chamber 610
resulting in the over use of load lock 608 and 606 and possible
bottle neck at these locations. For example, in the case when a
wafer is given a quick wet clean to remove sidewall residue prior
to ashing or stripping, it may be desirable to provide a strip
module 400 on the atmospheric transfer chamber 610 so that the
wafer does not need to travel back through the load locks and into
the sub-atmospheric transfer chamber to the stripping module after
wet cleaning in a wet module 200 coupled to the atmospheric
transfer chamber. As such, although stripping module(s) 400 is
ideally coupled to sub-atmospheric transfer chamber 630, a strip
module 400 can be included on atmospheric transfer chamber 610 or
on both atmospheric transfer chamber 610 and on sub-atmospheric
transfer chamber 630, if desired.
[0069] Apparatus 600 also includes a system computer 124 which is
coupled to and controls each module coupled to the atmospheric
transfer chamber 610, controls each sub-atmospheric module coupled
to sub-atmospheric transfer chamber 630, controls load locks 606
and 608 as well as the operation of robots 612 and 632. Computer
124 enables the feedback from one module to be used to control the
flow of a wafer through system 600 and/or to control the processes
or operation of the other modules.
Critical Dimension (CD) Monitor
[0070] FIG. 7 illustrates a critical dimension monitoring tool or a
"metrology" tool 700 which can be used to measure, for example, the
width of photoresist feature formed on an incoming wafer.
[0071] The present invention can be implemented with a metrology
tool 700, such as shown in FIG. 7. Metrology tool 700 includes an
imager 710 and a computer/controller 124 to perform the analysis
disclosed herein electronically. Computer/Controller 124 typically
includes a process monitor 730 for displaying results of the
analyses of processor 720. Processor 720 can be in communication
with a memory device 740, such as a semiconductor memory, and a
computer software-implemented database system 750 known as a
"manufacturing execution system" (MES) conventionally used for
storage of process information. Processor 720 is also in
communication with a photo cell 760 and etcher 900. In an
embodiment of the present invention, the imager 710 can be an
optical CD tool (OCD), such as the Nano OCD 9000 available from
Nanometrics of Milpitas, Calif., or an optical imager as disclosed
in U.S. Pat. No. 5,963,329. Optical imager 710 can utilize
scatterometry or reflectometry techniques. The use of scatterometry
for inspection tools is disclosed in Raymond "Angle-resolved
scattermetry for semiconductor manufacturing", Microlithography
World, Winter 2000. The use of reflectometry for inspection is
taught in Lee, "Analysis of Reflectometry and Ellipsometry Data
from Patterned Structures", Characterization and Metrology for ULSI
Technology: 1998 International Conference, The American Institute
of Physics 1998.
[0072] Optical imager 710 can directly measure CD and profile of
certain patterns on photoresist layer, such as trenches and the
like using convention optical inspection techniques. For example, a
rigorous coupled wave analysis (RCWA) can be performed, wherein a
CD corresponding to a given waveform is derived by calculation,
such as by a processor in the optical inspection tool. RCWA is
discussed in Chateau, "Algorithm for the rigorous couple-wave
analysis of grating diffraction", Journal of the Optical Society of
America, Vol. 11, No. 4 (April 1994) and Moharam, "Stable
implementation of the rigorous couple-wave analysis for
surface-relief gratings: enhanced transmittance matrix approach",
Journal of the Optical Society of America, Vol. 12, No. 3 (May
1995).
[0073] In an embodiment imager 710 can be a CD SEM, such as the
Versa SEM.TM. available from Applied Materials of Santa Clara,
Calif.
[0074] FIG. 8A is a flow chart illustrating the major steps of
process control according to an embodiment of the present
invention, implemented in conjunction with inspecting a feature
(hereinafter called a "target feature") such as an etch mask formed
on a semiconductor wafer W at photo cell 760. At step 810, the
reference library is created, including reference CDs and waveforms
in the form of SEM or OCD waveforms, and stored locally in
inspection tool 700 or in MES 750. The stepper settings associated
with each of the reference waveforms and the appropriate etch
recipes are stored along with the waveforms. Profile images can
also be stored, if desired by the user. The reference library is
created only once for each layer to be inspected, such as when a
series of process steps, such as photo cell 760, creates a
"critical layer" that the user determines must be inspected. The
golden waveform; i.e., the waveform associated with the reference
feature exhibiting optimal CD and/or other characteristics, is
selected at step 820.
[0075] Computer/Controller 124 typically includes a processor 720,
such as a microprocessor, for processing information, and a monitor
730 for displaying or outputting information, and a input device
732, such as a keyboard or touch screen, and a memory, such as a
DRAM for steady information.
[0076] Wafer W, having features with unknown CD and other
characteristics, is brought to imager 710 from photo cell 760, the
target feature is imaged by imager 710 at step 830, and its
waveform is stored as a target waveform. At step 840, the target
waveform is compared to the stored golden waveform. If the target
waveform and golden waveform match within predetermined limits, the
CD of the target feature is reported to the user, as by a display
on monitor 730, along with a "matching score" indicating the amount
of deviation of the target waveform from the golden waveform (see
step 841). The results (i.e., the data) from the inspection are
then sent to MES 750, and the wafer W is sent to etcher 900 for
further processing.
[0077] If the target waveform does not match the golden waveform,
the target waveform is compared to each of the reference waveforms
in the library to identify the reference waveform most closely
matching the target waveform (see step 850). The reported stepper
settings are compared with those associated with the golden
waveform at step 860 to determine the different dEdF between the
settings which produced the golden waveform and those which produce
the target waveform; e.g., determine the difference between the
focus setting associated with the golden waveform and the focus
setting associated with the target waveform, and determine the
difference between the exposure setting associated with the golden
waveform and the exposure setting associated with the target
waveform. This information is then sent to photo cell 760, where it
is used to correct the stepper settings to minimize "drift" in the
stepper, which would cause CD variations in subsequently processed
wafers, by indicating the amount of adjustment to the stepper that
is required, as well as which particular adjustments (i.e., focus,
exposure, or both) should be made.
[0078] Next, dE and dF are compared to predetermined threshold
values at step 870. If dE and dF are not greater than the
predetermined threshold values, the CD and matching score of the
target feature are reported at step 871, the data from the
inspection is then sent to MES 750, and wafer W is sent to etcher
900. On the other hand, if dE and dF are greater than the
predetermined threshold values, the CD and matching score of the
target feature is reported at step 880, along with dE and dF and
the associated etch recipe, which is sent to etcher 900 to adjust
(or "update") the etch recipe to correct the CD deviation of the
finished features on wafer W. The etch recipes can typically adjust
the CD within a range of about 100% or less.
[0079] The feedback and feed-forward of steps 860 and 880 can be
done manually or automatically. In "manual mode", the user takes
the reported process correction information and implements it
manually at photo cell 760 and/or etcher 900. This allows expert
input from the user to decide the need for process adjustment. In
"automatic mode", the process correction information is
automatically fed to the stepper in photo cell 760 or to etcher 900
to effect the correction through recipe updating. This mode can be
implemented by a software interface allowing communication between
processor 720 and etcher 900, and between processor 720 and photo
cell 760. The predetermined threshold test of step 870 can be used
as a sensitivity filter to determine if updating is necessary. The
automatic mode is advantageous because it enables quick feedback
and consistency.
[0080] The above embodiment of the present invention has been
described relative to a "golden waveform" technique. However, it
should be realized by any SEM CD measurement technique capable of
correlating an FEM cell (or dF) to an etch recipe and to feature
profile and/or cross-section can be used to implement the present
invention. An example of such a technique is discussed in "An
Inverse Scattering Approach to SEM Line Width Measurements", Mark
P. Davidson and Andras E. Vladar, Proceedings of SPIE, Vol. 3677
(1999). In this technique, SEM waveforms are matched to a library
of Monte Carlo simulations to predict the sidewall shape and
dimensions of a feature (i.e., the feature profile).
[0081] Typically, the present methodology is carried out after a
lot of wafers, such as about 25 wafer, is processed by photo cell
760. A number of wafers W from the lot are selected to be
inspected, according to the user's preference. For example, when
manufacturing microprocessors, 1-3 wafers are typically selected
for inspection; however, when manufacturing memory devices such as
DRAMs, only one wafer is typically inspected per lot. A number of
sites on each selected wafer W are usually inspected by the present
methodology (i.e., to be target features at step 830), such as
about 9-17 sites per wafer W. If an OCD is used, each wafer maybe
inspected.
[0082] To determine the etch recipe to be implemented at step 880
when a number of target features from one or more wafers W in a lot
are inspected, the CDs of all the target features of the lot can be
averaged, and the etch recipe associated with the average CD used
to adjust the etch processing of the lot. To determine the stepper
focus and exposure information (dEdF) fed back to photo cell 760 at
step 860 to adjust the photolithographic processing of following
lots when a number of target features in a lot are inspected, the
user can employ previously gathered process information to decide
which sites on selected wafers W to inspect, and then decide which
inspected feature's information to use to adjust photo cell
760.
[0083] This is illustrated in FIG. 8B, which is a flow chart of an
embodiment of the invention. At step 890, the user maps field to
field CD variations across a number of wafers prior to inspection
using the present methodology. This is a standard process control
technique practiced by virtually all wafer fabricators. It
indicates which areas of the wafer typically have small CD
variations from the design value, and which areas of the wafer
typically have a large CD variation. For example, some wafer
processing equipment (e.g., photo cell 760) produces wafer having a
small CD variation in the center of the wafer and larger CD
variations at the periphery. Other equipment produces wafers having
large CD variations near the corner of the wafer and small CD
variations in a band surrounding the center. After mapping the CD
variations, the user identifies, at step 891, an area or areas of
the wafers that exhibit the worst CD variation.
[0084] Next, the user selects a threshold CD variation representing
the smallest CD deviation the user wishes to correct (see step
892). Target features are then inspected at step 893 using the
inventive methodology (e.g., steps 830 et seq. described above).
Target features are selected such that fields in the worst part of
the wafer, identified at step 891, are represented. If the field to
field variation of the inspected features is smaller than the
predetermined threshold (see step 894), dEdF associated with any
one of the target features can be fed back to photo cell 760 for
use in adjusting the processing of subsequent lots (step 895),
since they are relatively close to each other. On the other hand,
if the field to field variation of the inspected features is larger
than the threshold value selected in step 892, dEdF associated with
an inspected feature from the predetermined worst site from step
891 is fed back to photo cell 760 (see step 896). Thus, the worst
CD variation is corrected in subsequent lots.
[0085] At step 897, the CDs of the inspected features are averaged,
and at step 898, the etch recipe associated with the average CD is
fed forward to etcher 900 to adjust (or "update") the etch recipe
to correct the CD deviation of the features on the wafers in the
inspected lot. Thus, this embodiment of the present invention
allows the user to employ information, such as field to field CD
variation maps, that they gather as a matter of course
independently of implementing the present invention, to reduce lot
to lot variation with minimal added cost and inspection time.
Etch Module
[0086] An example of an etch module 900 which can be used in
accordance with the present invention, is illustrated in FIG. 9.
FIG. 9 illustrates an etch process module such as for example, a
DPS type Metal Etch Centura chamber, schematically illustrated in
FIG. 9 and from Applied Materials, Inc. in Santa Clara, Calif. The
particular embodiment of the etch module 900 shown herein is
provided only to illustrate the invention, and should not be used
to limit the scope of the invention. Etch module 900 includes a
chamber 910. A support 940 is potential within a process zone 945
in the chamber 910. A substrate 930 may be positioned on the
support 940 by the robotic arm. The substrate 930 may be held in
place during the etching process using a mechanical or
electrostatic chuck 950 with grooves 955 in which a coolant gas,
such as helium, is held to control the temperature of the substrate
930.
[0087] During processing of the substrate, the chamber 910 may be
maintained at a low pressure and process gas may be introduced into
the chamber 110 through a gas supply 960 having a gas source 962
and gas inlets 964 peripherally disposed about the substrate 930.
Alternatively, a showerhead gas distributor (not shown) may be
positioned above the substrate 930. The process gas may be
energized by a gas energizer that couples an energetic
electromagnetic field into the process zone 945, such as an
inductive, capacitive, or microwave field. In the version shown in
FIG. 9, an inductor coil 965 adjacent to the process chamber 910
forms an inductive electric field in the chamber 910 when powered
by a coil power supply 970 operating using, for example, an RF
voltage at a source power level that may be from about 200 Watts to
about 2000 Watts. Alternatively or additionally, a capacitive
electric field may be formed in the chamber 910. At least a portion
of the support 940 may be electrically conductive to serve as a
cathode electrode 975. The cathode electrode 975, in conjunction
with sidewalls of the chamber 910 which may be electrically
grounded to serve as an anode electrode 980, form process
electrodes in the process zone 945 that may capacitively couple to
energize the process gas. The cathode 975 may be powered by an
electrode power supply 985 operated using, for example, an RF
voltage at a power level of from about 10 Watts to about 1000
Watts. The capacitive electric field is substantially perpendicular
to the plane of the substrate 930, and may accelerate the plasma
species toward the substrate 930 to provide more vertically
oriented anisotropic etching of the substrate. The frequency of the
RF voltage applied to the process electrodes 975, 980, and/or the
inductor coil 965 is typically from about 50 KHz to about 60 MHz,
and more typically about 2.2 or 13.56 MHz. In one version, the
cathode 975 is also an electrode in a dielectric in the
electrostatic chuck 950.
[0088] The ceiling 990 of the process chamber 910 can be flat or
rectangular shaped, arcuate, conical, dome-shaped, or multi-radius
dome-shaped. In one version, the inductor coil 965 covers at least
a portion of the ceiling 990 of the process chamber 910 in the form
of a multi-radius dome-shaped inductor coil having a "flattened"
dome shape that provides more efficient use of plasma source power
and increased plasma ion flux uniformity directly over the
substrate 930 center.
[0089] When capacitively generated, the plasma formed in the
process zone 945 may also be enhanced using magnetically enhanced
reactors (not shown), in which a magnetic field generator, such as
a permanent magnet or electromagnetic coils, are used to apply a
magnetic field in the process zone 945 to increase the density and
uniformity of the plasma. The magnetic field may comprise a
rotating magnetic field with the axis of the field rotating
parallel to the plane of the substrate 930, as described in U.S.
Pat. No. 4,842,683, which is incorporated herein by reference in
its entirety.
[0090] Spent process gas and etchant residue are exhausted from the
process chamber 910 through an exhaust system 995 capable of
achieving a low pressure in the process chamber 910. A throttle
valve 200 is provided in the exhaust for controlling the pressure
in chamber 910. Also, an optical endpoint measurement system (not
shown) may be used to determine completion of the etching process
for a specific layer by measuring, for example, the change in light
emission of a particular wavelength corresponding to a detectable
gaseous species or by other interferometric techniques.
[0091] To perform an etching process in the process chamber 910, an
energized process gas comprising etchant gas may be provided in the
process zone 945. By "energized process gas" it is meant that the
process gas is activated or energized to form one or more
dissociated species, non-dissociated species, ionic species, and
neutral species. The etchant gas composition may be selected to
provide high etch rates, and highly selective etching of a
particular layer or layers that are being etched.
Method of Use of Etch/Strip Tool 600
[0092] An example of the use of etch/strip tool 600 is for the
patterning of a conductive film or stack of conductive films into
features used in an integrated circuit. An example of such a
process is illustrated in FIGS. 10A-10E. According to this
embodiment of the present invention, a wafer or substrate, such as
wafer 1000 as shown in FIG. 10A, is provided to apparatus 600 in a
FOUP 620. Wafer 1000 includes a blanket deposited conductive film
1002 formed across the surface of the wafer. The film 1002 can be
for example, but not limited to, a polysilicon film or a composite
polysilicon/silicide film stack used to form gate electrodes or
capacitor electrodes. In embodiments the conductive thin film 1002
can include a dielectric hard mask, such as silicon nitride or
silicon oxynitride film. The film can be a metal or metal alloy
film, such as aluminum, copper or tungsten or a stack of metal
films which include a main conductor 1001 and a barrier layer 1003
and an antireflective coating (ARC) 1005, such as titanium nitride
(TiN)/aluminum (Al)/titanium nitride (TiN) film stack used for the
formation of interconnects in an integrated circuit. Formed on
conductive film 1002 is a mask 1004, such as a well-known
photoresist mask, which has a patterned defined therein which is to
be formed in conductive film 1002. In order to process wafer 1000
in accordance with the present invention, the door to transfer
chamber 610 is opened as is the connected door on FOUP 622 and
wafer 1000 removed from FOUP 622 and brought into atmospheric
transfer chamber 610 by robot 612. Robot 612 then transfers the
wafer into CD module 700. In CD module 700 the critical dimensions
(CD) of the photoresist layer 1004 is measured at various location
across wafer 1000 as described with respect to CD measurement tool
700 described in FIG. 7. If the CD measurements taken of CD
measurement tool 700 are out of compliance, then wafer 1000 can be
removed from CD module 700 by robot 612 and removed from apparatus
600. Alternatively, if the CD measurements are out of compliance,
then wafer 1000 can be prepared for rework by removing wafer 1000
from CD module 700 and inserting it into strip chamber 400 whereby
the photoresist mask 904 is stripped as desired above. The stripped
wafer is then removed from strip module 400 and inserted it into
wet clean chamber 200 where wafer 1000 is wet cleaned as described.
Wafer 1000 can then be removed from clean module 200 and removed
from system 600 where it is now ready for application of a new
photoresist mask and patterning.
[0093] If the CD measurements of wafer 1000 are found to be in
compliance with desired results, then wafer 1000 is removed from CD
module 700 and brought into transfer chamber 610 by robot 612. The
pressure within load lock 606 is then brought to atmospheric
pressure and the door 605 between transfer chamber 610 and load
lock 606 opened and wafer placed into load lock 606 by robot 612.
The door between transfer chamber 610 and load lock 606 is then
closed and the pressure within load lock 606 reduced to the
pressure within sub-atmospheric transfer chamber 630.
[0094] Next, the door 607 between single wafer load lock 606 and
sub-atmospheric transfer chamber 630 is opened and robot 632
removes wafer 1000 from load lock 606 and brings it into transfer
chamber 632. Next, if desired, a photoresist trim, as shown in FIG.
10B can be applied to photoresist mask 904 to create a smaller
dimension photoresist mask 1006 then is possible by
photolithography alone. The photoresist trim can occur in either
the etch chambers 900 or 900B or the strip chamber 400B or 400C by
exposing the photoresist mask 1004 to thin oxygen plasma. The
photoresist trim step is optional.
[0095] Next, the door to etch chamber 900 is opened and wafer 1000
transferred from sub-atmospheric transfer chamber 630 into etch
chamber 900 and the door closed. Next, conductive film 1002 is
anisotropically etched in alignment with photoresist mask 1006 (or
1004) to pattern blanket deposited conductive film 1002 into
features 1008. The results of the CD measurements taken in CD
module 700 can be used to determine the etch parameters, such as
etch gas, time, pressure and power for the etch step.
[0096] When etching a metal-containing material, the etchant gases
may comprise one or more of halogen-containing gases, such as one
or more of Cl.sub.2, BCl.sub.3, CCl.sub.4, SiCl.sub.4, CF.sub.4,
NF.sub.3, SF.sub.6, HBr, BBr.sub.3, CHF.sub.3, C.sub.2F.sub.2, and
the like, and optionally, one or more additive gases, such as inert
or non-reactive gases, such as H.sub.2, N.sub.2, O.sub.2,
He--O.sub.2 and the like. In an exemplary process, the
anti-reflective material 1005 is etched by exposing the substrate
1000 to an energized process gas comprising etchant gas comprising,
for example, about 90 sccm Cl.sub.2 and about 30 sccm BCl.sub.3 at
a pressure of about 8 mTorr, a source power level of about 1600
Watts, a bias power level of about 145 Watts, a backside helium
pressure of about 4 Torr and a cathode temperature of about
50.degree. C. The main metal conductor 1001 may then be etched by
an energized process gas comprising etchant gas comprising, for
example, about 80 sccm Cl.sub.2, about 5 sccm BCl.sub.3, and about
10 sccm CHF.sub.3 at a pressure of about 14 mTorr, a source power
level of about 1600 Watts, a bias power level of about 150 Watts, a
backside helium pressure of about 8 Torr and a cathode temperature
of about 50.degree. C. Thereafter, the diffusion barrier layer
1003, and optionally a portion of the underlying oxide layer 1007,
may be etched by introducing an energized process gas comprising
etchant gas comprising, for example, about 30 sccm Cl.sub.2, about
5 sccm BCl.sub.2, and about 30 sccm N.sub.2, or Ar at a pressure of
about 10 mTorr, a source power level of about 1600 Watts, a bias
power level of about 125 Watts, a backside helium pressure of about
8 Torr and a cathode temperature of about 50.degree. C.
[0097] After conductive film 1002 has been etched, the pressure in
chamber 900 brought up to the pressure in sub-atmospheric transfer
chamber 630 and the door 637 between etch module 900 and
sub-atmospheric transfer chamber 630 is opened and wafer 1000
removed from etch module 900 and brought into sub-atmospheric
transfer chamber 630 by robot 632. Next, wafer 1000 is transferred
into strip module 400B and the door 633 between strip module 400B
and transfer chamber 630 sealed. Photoresist mask 1006 is then
stripped, as shown in FIG. 10D, in strip module 400B as described
above. If the conductive film is a silicon film, wafer 1000 can
first be placed into wet clean module 200 (before strip module 400)
and exposed to a quick diluted HF etch (100:1) to remove sputter
silicon from the sidewalls of the photoresist 1006 to enable better
stripping of photoresist 1006 in strip module 400.
[0098] The dry cleaning process may also comprise post-etch
passivation of the substrate 500, particularly when conductive
material has been etched in the etching process, to remove or
inactivate corrosive residue species on the substrate 500. To
passivate the substrate 500, energized process gas comprising
passivating gas may be provided in the process zone 415. The
passivating gas composition is selected to remove or inactivate
corrosive etchant residue, such as residue species 75 or to prevent
the formation of corrosive or contaminant materials on the etched
substrate. Passivating gas may comprise one or more of H.sub.2O,
NH.sub.3, H.sub.2O.sub.2, O.sub.2, N.sub.2, CF.sub.4,
C.sub.2F.sub.6, CHF.sub.3, H.sub.2, C.sub.3H.sub.2F.sub.6,
C.sub.2H.sub.4F.sub.2, or CH.sub.3F. In one version, any gas or
vapor containing hydrogen can serve as the passivating gas,
including hydrogen, water vapor, ammonia, methanol, hydrogen
sulfide, and mixtures thereof. In another version, the passivation
gases include (i) ammonia and oxygen, or (ii) water vapor, with
optional oxygen and nitrogen. When the passivation gas comprises
ammonia and oxygen, the volumetric flow ratio of ammonia to oxygen
is generally from about 1:1 to about 1:50, more typically from
about 1:5 to about 1:20, and most typically about 1:10. For a
5-liter capacity chamber 108, a gas flow comprises 300 sccm
NH.sub.3 and 3000 sccm O.sub.2. Alternatively, a passivating gas
comprising at least about 80 volume % H.sub.2, and typically about
100 volume % H.sub.2, can be used to passivate the etchant residue
75. In one version, a passivating gas comprises about 500 sccm
H.sub.2O energized at a power level of about 1400 watts and
introduced into the cleaning chamber 400 at a pressure of about 2
Torr for about 15 seconds. When a bubbler is used, an inert carrier
gas such as argon or helium can be passed through the bubbler to
transport water vapor to the vacuum chamber. Optionally, oxygen,
nitrogen or other additive can be added to the passivating gas to
enhance passivating. In this version, the passivating gas comprises
at least about 20 volume % H.sub.2O. The effect of the oxygen and
nitrogen addition depends on the ratio of the volumetric flow rate
of water vapor (VH.sub.2O) to the combined volumetric flow rates of
oxygen and nitrogen (VO.sub.2+VN.sub.2). A suitable volumetric
ratio of water vapor flow rate VH.sub.2O to combined volumetric
flow rates of oxygen and nitrogen (VO.sub.2+VN.sub.2) for use as a
passivating gas is at least about 1:2, more typically from about
1:2 to about 2:1, and most typically about 1:1. As with the
stripping process and as discussed in U.S. Pat. No. 5,545,289, the
passivating may be either a single step or multiple steps. In one
version, the substrate is exposed to the passivating gas for a
period of time of from about 10 seconds to about 100 seconds, and
more typically for about 45 seconds. In one version, a multi-cycle
passivation process, for example a three cycle process, has been
discovered to be particularly effective in preventing
corrosion.
[0099] Once photoresist layer 1006 has been sufficiently removed
from substrate 1000 and metal feature 1008 passivated (if desired),
the door 633 between strip module 400B and sub-atmospheric chamber
630 is opened and wafer 1000 is removed by robot 632. The pressure
within load lock 608 is then reduced or maintained at a
sub-atmospheric pressure similar to the sub-atmospheric pressure in
transfer chamber 630 and door 611 opened. Wafer 1000 is then
transferred into load lock 608 and door 611 sealed. The pressure
within load lock 608 is then brought up to atmospheric pressure by
inserting a gas, such as nitrogen into load lock 608. The door 609
is then opened and robot 612 removes wafer 1000 from load lock 608.
At this point, the wafer can be transferred into CD module 700 to
check the critical dimensions of the patterned features 1080 or can
be transferred into wet clean module 200 to remove any residual
contaminants or particles as shown in FIG. 10E. Wafer 1000 is then
subjected to a wet clean process in wet clean module 200. The wet
clean can vary from a light clean to an aggressive clean depending
upon requirements. After sufficient wet cleaning in module 200
transfer robot 612 removes wafer 1000 from clean module 200 and can
either (i) insert it into CD module 700 to check the critical
dimension or (ii) can insert it into integrated particle monitor
module 300 to determine the cleanliness of wafer 900. If wafer 900
is sufficiently clean then robot 612 removes wafer 900 from
integrated particle monitor 300 and transfers it into FOUP 622. If
however, wafer 1000 is not sufficiently cleaned of residue, then
wafer 1000 can be transferred into strip module 400 coupled to
atmospheric transfer chamber 610 and then into wet clean module 200
or alternatively only into wet clean module 200. Wafer 1000 can
then once again be inspected in integrated particle monitor 618 and
if sufficiently cleaned then removed by robot 612 into FOUP
622.
[0100] An example of another use of Etch/Strip tool 600 is in a
damascene or dual damascene process such as illustrated in FIGS.
11A-11F. A damascene or dual damascene process is used to form
conductive features, such as gate electrodes, capacitor electrodes,
interconnects, as well as vias, contacts and plugs in a dielectric
layer. In a damascene process, a wafer 1100 is provided which
contains a blanket deposited dielectric film 1104, such as but not
limited to silicon dioxide, silicon oxynitride, SiOF, BPSG, undoped
silicon glass or organic dielectric, and organic dielectrics and
can be formed by any well-known technique, such as but not limited
to chemical vapor deposition (CVD), high density plasma (HDP) CVD
and sputtering. Dielectric layer 1100 can be a single dielectric
film or can be a combination or stack of dielectric films. A mask
1102, such as a photoresist mask, is formed on dielectric film
1104. Mask 1102 is patterned with openings 1103 formed which
correspond to location where metal or conductive features are
desired in dielectric film 1004.
[0101] According to this embodiment of the present invention, a
wafer, such as wafer 1000, is provided to system 600 in a FOUP 620.
To begin processing the access door 621 between transfer chamber
612 and FOUP 622 is opened as it is corresponding door on FOUP 622.
Robot 612 removes wafer 1100 from FOUP 560 and brings it into
transfer chamber 610. Robot 612 then transfers wafer 1100 to CD
measurement module 700. The critical dimensions of photoresist mask
1102 is measured at various parts of the wafer to determine whether
or not the critical dimensions of the mask are within spec. If the
critical dimensions are outside of the specifications desired wafer
1100 is removed from CD measurement tool 700 by robot 612 and can
be either removed from tool 600 or can be placed in strip chamber
400 and then wet clean chamber 200 to remove photoresist mask 1102
so that wafer 1100 is ready for rework. If the critical dimensions
of photoresist mask 1102 are with specifications, then robot 612
removes wafer 1100 from CD module 700 and brings it into
atmospheric transfer chamber 612. The pressure (if not already at
atmospheric pressure) within load lock 606 is then brought up to
atmospheric pressure and the door 605 between load lock 606 and
atmospheric transfer chamber 610 opened and wafer 1100 transferred
into load lock 606 and the door 605 sealed. The pressure within
load lock 606 is then evacuated to a pressure substantially equal
to the pressure within sub-atmospheric transfer chamber 630. The
door 607 between load lock 606 and sub-atmospheric transfer chamber
630 is then opened and robot 632 removes wafer 1100 from load lock
606 and brings it into sub-atmospheric transfer chamber 630. Robot
632 then transfers wafer 1100 into etch module 636 and the door 637
between etch module 636 and sub-atmospheric transfer chamber 630
sealed.
[0102] Next, as shown in FIG. 11B, the dielectric layer 1104 is
etched, e.g., anisotropically etched, in alignment with mask 1102
to form a patterned dielectric layer 1106 having openings 1108
which correspond to locations where conductive features are
desired. Any well-known etch chemistry can be used to etch
dielectric film 1104. If dielectric film 1104 is a silicon dioxide
film that can be etched with an etch chemistry, such as but not
limited to CF.sub.4 or C.sub.2F.sub.6. Once dielectric layer 1104
has been sufficiently etched, the door 637 between etch chamber 900
and sub-atmospheric chamber 630 is opened and wafer 1100 removed by
robot 632. Robot 632 then transfers wafer 1100 into strip or dry
clean module 400B and the door between strip module 400B and
sub-atomospheric transfer chamber 630 sealed. The photoresist mask
is then stripped in strip module 400B as shown in FIG. 11C as
described above. Once the photoresist mask 1102 has been
sufficiently removed, the door between strip module 400 and
transfer chamber 610 opened and robot 612 removes wafer 1100 from
strip module 400 and brings it into atmospheric transfer chamber
610. After the photoresist strip in module 400, the photoresist
residue and/or etch residue 1110 may remain on wafer 1100.
[0103] Robot 632 then transfers wafer 1100 into load lock 608 and
door 611 between load lock 608 and sub-atmospheric transfer chamber
630 sealed. The pressure within load lock 608 is then raised to
atmospheric pressure by inserting a gas, such as nitrogen (N.sub.2)
therein. Once the chamber reaches atmospheric pressure, the door
609 between load lock 608 and atmospheric transfer chamber 610 is
opened and robot 612 removes wafer 1100 from load lock 608 and
brings it into atmospheric transfer chamber 610.
[0104] At this time, if desired, wafer 1100 can be inserted into
critical dimension monitoring tool 700 were the critical dimensions
of the patterned dielectric layer 1106 measured. To determine
whether or not the etch results are with specification, the CD
results can be used to optimize the etch parameters used in etch
module 900 for subsequently etched wafers.
[0105] Next, the wafer 1100, as shown in FIG. 11C, is transferred
into wet clean 200 and the door between wet clean module 200 and
atmospheric transfer chamber 610 sealed. Wafer 1100 is then
subjected to a wet clean in wet clean module 200 as described above
to remove residue 1110 as shown in FIG. 11D. Once a wafer has been
sufficiently wet cleaned as shown in FIG. 11D, wafer 1100 is
removed from clean module 614 by robot 612 and transferred into
integrated particle monitoring tool 618, wafer 1100 is then scanned
in integrated particle monitoring tool 300 to check the amount of
particles contained on wafer 1100 to determine if wafer 1100 has
been sufficiently cleaned. If wafer 1100 has not been sufficiently
cleaned, robot 612 removes wafer 1100 from integrated process
module 300 and transfers it into either strip chamber 400 or wet
clean 200 or to strip module 400 then wet clean module 200
depending upon the type and amount of residue detected in
integrated particle monitoring module 300. If wafer 1100 has been
sufficiently cleaned, wafer 1100 can then be removed from the
integrated process monitoring tool 300 and transferred into
atmospheric transfer chamber 610, wafer 1100 is then transferred by
robot 612 out of atmospheric transfer chamber 610 and placed into a
FOUP 622.
[0106] At this point, wafer 1100 can be transferred to a metal
deposition module chamber whereby a metal film 1112 or stack of
films is blanket deposited over wafer 1100 as shown in FIG. 11E.
Conductive film 1112 fills the openings 1108 formed in dielectric
layer 1106 and forms on top of dielectric layer 1106. Next, wafer
1100 is transferred to a planarization module, such as a chemical
mechanical planarization machine whereby the conductive film 1012
is planarized back to remove the conductive film from the top of
the dielectric film 1106 as shown in FIG. 11F. The end result of
the damascene process is the formation of conductive features 1114
in dielectric layer 1106 which are planar with dielectric layer
1106. At this time, damascene process in accordance with the
present invention is complete. In an alternative embodiment of the
damascene or dual damascene process, system 600 can be altered
whereby instead of a second etch chamber 900B, a metal chamber,
such as a chemical vapor deposition chamber or a sputtering chamber
is used therein. In this way, after wafer 1100 has been
sufficiently wet cleaned as shown in FIG. 11D and has passed
particle inspection in module 300, the wafer 1100 can be
transferred through load lock 606 back into sub-atmospheric
transfer chamber 630 and placed into the conductive film deposition
chamber were the film 1112 is deposited as shown in FIG. 11E. After
deposition of the film 1112 the wafer would be removed from the
deposition chamber brought into the sub-atmospheric transfer
chamber 632 transferred through load lock 608 into the atmospheric
transfer chamber 510 where the wafer would be removed into a FOUP
620. If desired, the wafer could be transferred to into the
integrated particle monitoring tool 618 to check for defects or
particles formed during the deposition process and then the wafer
removed from atmospheric transfer chamber 610. Alternatively, the
wafer 1100 could be subject to a dry clean in module 400 and/or a
wet clean in module 200 after film deposition, if desired.
[0107] Another use of etch strip tool 600 is for the stripping of a
silicon nitride film formed over a substrate and for the subsequent
cleaning of the wafer to remove nitride residues and particles.
Generally, silicon nitride films are removed with hot phosphoric
acid which has a slow etch rate and therefore requires a long
process time. As such, silicon nitride films are generally removed
in a batch type (35-50 wafers at a time) process. Etch/strip tool
600 can be used to strip silicon nitride films from a wafer in a
single wafer format and can do so without attacking or etching
existing oxide films and can strip silicon nitride films in a
economic cost effective amount of time.
[0108] In order to use tool 1600 to remove a silicon nitride film,
all that is required is at least one etch module 900 on
sub-atmospheric transfer chamber 630 and at least one wet clean
module 200 on atmospheric transfer chamber 610. In an embodiment of
the silicon nitride strip process of the present invention, tool
600 contains multiple etch modules 9000 on sub-atmospheric transfer
chamber 630 and multiple wet clean chambers 200 on atmospheric
transfer chamber 610. In an embodiment of the present invention,
the number of wet clean chambers 200 and etch modules 900 are
balanced with the desired process times for the nitride stripping
and cleaning process so the use of each module is maximized.
[0109] An example of the method of stripping a silicon nitride film
utilizing apparatus 600 in accordance with an embodiment of the
present invention is illustrated in FIG. 16A-16C. Shown in FIG.
16A, is a substrate or wafer 1600 having a silicon nitride film
1604. In a typical use, silicon nitride film 1604 forms an
oxidation resistant mask for the formation of shallow trench
isolation regions 1608 formed in the monocrystalline silicon
substrate 1602. (Typically a thin pad oxide 1606 is formed between
the silicon nitride mask 1604 and the monocrystalline silicon
substrate 1602). The mask 1604 is used to define locations where
trenches are etched in substrate 1602 for trench isolation regions
1608 to be formed. Additionally, silicon nitride mask 1604 provide
an oxidation resistant mask preventing the oxidation of underlying
silicon during the formation of a thin thermal oxide 1610 in the
trench isolation region 1608. Subsequently the trench is filled
with a deposited silicon dioxide film 1612 and polished back to be
planar with the top surface of nitride mask 1604 as shown in FIG.
16A. Nitride masks are also used in similar manner during the
formation of LOCOS (Local Oxidation of Silicon) isolation regions.
In both cases, after the formation of the isolation regions, it is
desirable to remove the nitride mask 1604 without etching or
affecting the integrity of the oxide isolation regions 1608.
[0110] Accordingly, a substrate or wafer having a nitride film,
such as substrate 1600 having a nitride film 1604 is brought to
apparatus 600 in a FOUP 622. In order to process the wafer 1600 in
accordance with the present invention, the door to transfer chamber
610 is opened, as is the connected door to FOUP 622 and wafer 1600
is removed from FOUP 622 and brought into atmospheric transfer
chamber 610 by robot 612. The door 605 between atmospheric transfer
chamber 610 and load lock 606 is then opened and robot 612
transfers wafer 1600 into load lock 606. The door 605 is sealed and
load lock 606 pumped down to the pressure within sub-atmospheric
transfer chamber 630. Once the pressure within sub-atmospheric
transfer chamber 630 is reached, door 607 opens and robot 632
removes wafer 1600 from load lock 606 and brings it into
sub-atmospheric transfer chamber 630. Wafer 1600 is then moved from
sub-atmospheric transfer chamber into an etch module 900 and the
door between the etch module and the sub-atmospheric transfer
chamber sealed and the etch chamber pumped down to the desired
process pressure.
[0111] Next, the silicon nitride film 1604 is stripped with a dry
plasma using a chemistry comprising, for example CF.sub.4 or
C.sub.2F.sub.6. The wafer is exposed to the stripping plasma in
module 900 until the silicon nitride mask 1604 has been
sufficiently removed. After removing silicon nitride film 1604,
silicon residue 1614 may be left on silicon monocrystalline
substrate 1602 (or pad oxide 1606 if used) as shown in FIG.
16B.
[0112] After stripping silicon nitride mask 1604, the pressure
within strip module 900 is brought to the pressure within
sub-atmospheric transfer chamber 630 and the door between strip
module 900 and sub-atmospheric transfer chamber 630 opened. Robot
632 then removes substrate 1600 from strip module 900 and places it
into one of the single wafer load locks 1606 or 1608. The pressure
within the load lock is then brought up to atmospheric pressure and
the door between the atmospheric transfer chamber and the load lock
opened and robot 612 removes the substrate 1600 from the load lock
and places it into wet clean module 200. In wet module 200 wafer
1600 is exposed to a wet cleaning process as described above. The
wet clean can vary from a light clean consisting of only DI water
rinse to a heavy clean utilizing cleaning solutions and etchants as
described above.
[0113] Once wafer 1600 has been sufficiently cleaned of particles
and residue 1614 the wafer is spun dried in module 200. Next, wafer
1600 is removed from clean module 200 by robot 612 and brought into
atmospheric transfer chamber 610. Robot 1612 can either i) bring
the wafer into FOUP 622 or 624 whereby processing is complete, or
can ii) bring wafer 1600 into integrated particle monitoring tool
300 where the surface is checked for particles and residue. If
substrate 1600 is placed into integrated particle monitoring tool
300 after monitoring the surface for contaminants depending upon
the results of the scan, the wafer is either moved into FOUP 622 or
is sent back to either wet clean chamber 200 or back into etch
module 900 or both for further processing. Additionally,
information gained from the surface monitoring can be used by
controller 124 to determine the process parameters for stripping
the silicon nitride 1604 on subsequent wafers and can be used to
determine cleaning parameters for cleaning subsequent wafer in wet
cleaning module 200. For example, if significant silicon nitride is
present during the scan in IPM module 300, the exposure time in
etch module 900 can be increased or the process chemistry altered
for subsequent wafers, or if particles are found a more aggressive
cleaning process can be used on subsequent wafers. The change in
process parameters would be determined by complex controller 124
from a stored look up table or formula which relates the process
parameters to the particle scan of wafer 1600. It is to be
appreciated that silicon nitride films used for other purposes than
for the formation of isolation regions can be stripped or removed
in a similar manner.
Integrated Clean/Gate Tool
[0114] FIG. 12 illustrates another atmospheric/sub-atmospheric
process tool 1200 in accordance with the present invention. Process
tool 1200 is an integrated clean/gate fabrication tool which can be
used to clean a wafer and then form a high quality gate dielectric
and a gate electrode on a silicon monocrystalline substrate or
epitaxial layer. In an embodiment of the present invention, the
process tool 1200 includes a module for forming a high dielectric
constant film, such as metal oxide dielectric, such as tantalum
pentaoxide or titanium oxides.
[0115] Integrated clean/gate tool 1200 includes an atmospheric
platform 1202 and a sub-atmospheric platform 1204. The
sub-atmospheric platform 1204 and the atmospheric platform 1202 are
coupled together by a single wafer load lock 1206 and preferably by
two single wafer load locks 1206 and 1208. Atmospheric platform
1202 includes a central atmospheric transfer chamber 1210 having a
wafer handling device 1212 contained therein. Directly attached to
atmospheric transfer chamber 1210 is a single wafer wet cleaning
module 200, an integrated particle monitoring tool 300 and an
integrated thickness monitoring tool 1290. Wet cleaning module 200,
integrated particle monitoring tool 300, and integrated thickness
monitoring tool 1290 are each connected to transfer chamber 102
through a separately closable opening or slit valve. Transfer
chamber 1210 is maintained at substantially atmospheric pressure
during operation. In an embodiment of the present invention, the
atmospheric transfer chamber 1210 can be opened or exposed to the
atmosphere of a semiconductor fabrication "clean room" in which it
is located. In such a case, the transfer chamber 1210 may contain
an overhead filter, such as a hepafilter to provide a high velocity
flow of clean air or an inert ambient such as N.sub.2, to prevent
contaminants from finding their way into the atmospheric transfer
chamber. In other embodiments, the atmospheric transfer chamber
1210 is a closed system and may contain its own ambient, of clean
air or an inert ambient, such as nitrogen gas (N.sub.2).
[0116] Atmospheric transfer chamber 1210 includes a wafer handling
robot 1212 which can transfer a wafer from one module to another
module in atmospheric process tool 1202. In an embodiment of the
present invention, the wafer handler 1212 is a dual blade, single
arm, and single wrist robot. The handling blades both rotate about
a single axis coupled to the end of the single arm.
[0117] Also coupled to atmospheric transfer chamber 1210 is at
least one wafer input/output module 1220 or pod for providing and
taking wafers to and from system 1200. In an embodiment of the
present invention, the wafer input/output module is a front opening
unified pod (FOUP) which contains a cassette of between 13-25
horizontally spaced wafers. In an embodiment of the present
invention, apparatus 1200 includes two FOUPs 1220 and 1222, one for
providing wafers into system 1200 and one for removing completed or
processed wafers from system 1200. Atmospheric transfer chamber
1210 contains sealable access doors 521 for allowing wafer to be
transferred into and out of atmospheric transfer chamber 1210.
There is an access door 1221 for each FOUP, and each access door is
attached to a counterpart door on each FOUP so that when the
transfer chamber access door 1221 slides open, it opens the door to
the FOUP to provide access for the robot 1212 into the FOUP.
[0118] Coupled to the opposite sides of atmospheric transfer
chamber 1210 then FOUP 1220 and 1222 is a single wafer load lock
1206 and typically a second single wafer load lock 1208. Single
wafer load locks 1206 and 1208 enable a wafer to be transferred
from the atmospheric conditions in transfer chamber 1210 to the
sub-atmospheric conditions of platform 1204 and allow wafer to be
transferred from sub-atmospheric platform 1204 to atmospheric
transfer chamber 1210. A sealable door 1205 is located between
single wafer load lock 1206 and atmospheric transfer chamber 1210.
A sealable door 1207 is located between sub-atmospheric transfer
chamber 1224 and load lock 1206. Similarly, a sealable door is
located between atmospheric transfer chamber 1210 and load lock
1208, and a sealable door 111 is located between load lock 1208 and
sub-atmospheric transfer chamber 1224. Coupled to each of the load
locks 1206 and 1108 is a vacuum source which enables the pressure
inside load locks 1206 and 1208 to be independently lowered.
Additionally, coupled to each load lock 1206 and 1208 is a gas
inlet for providing, for example, an inert gas into the load lock
to enable the pressure within the load lock to be raised to, for
example, to atmospheric pressure. In this way, the pressure within
the load lock 1206 and 1208 can be matched to either the pressure
within atmospheric transfer chamber 1210 or the pressure within
sub-atmospheric transfer chamber 1224. Although, load locks 1206
and 1208 are ideally low volume single wafer load locks to enable
fast wafer transfers between the atmospheric transfer chamber and
the sub-atmospheric transfer chamber, load locks 1206 and 1208,
however, can be larger multiple wafer load locks which can hold
multiple wafers at a single time, if desired.
[0119] Attached to the opposite ends of the single wafer load locks
1206 and 1208 is a sub-atmospheric transfer chamber 1224 having a
wafer handling device 1226 contained therein. Sub-atmospheric
transfer chamber 1224 is said to be sub-atmospheric transfer
chamber because transfer chamber 1224 is held at a pressure less
than atmospheric pressure and preferably between 10.sup.-3 to 50
Torr while in operation and while passing the wafers to the various
sub-atmospheric process modules coupled thereto.
[0120] Directly attached to sub-atmospheric transfer chamber 1224
is a single wafer thermal process chamber 1300 which can be used to
grow a silicon dioxide or silicon oxynitride or silicon nitride
dielectric film on wafer. Additionally, also directly attached to
sub-atmospheric transfer chamber 1224 is a polysilicon deposition
chamber 1400 which can be used to form a polysilicon film, for
example, a polysilicon gate electrode. In an embodiment of the
present invention, process tool 1200 includes a high k dielectric
film deposition module 1700 directly attached to sub-atmospheric
transfer chamber 1224 to enable the formation of a high dielectric
constant film, such as metal dielectrics, e.g. titanium oxides,
tantalum oxides, zirconium oxide, and hafnium oxides. Additionally,
in an embodiment of the present invention, apparatus 1200 includes
a second thermal process chamber 1300 in order to better balance
the wafer throughput of wafer through process tool 1100. Thermal
process tool 1300 and polysilicon deposition tool 1400 are
connected to sub-atmospheric transfer chamber 1224 through
separately closable and sealable openings.
[0121] Apparatus 1100 also includes a system computer or control
device 124 which is coupled and controls each module coupled to
atmospheric transfer chamber 1210 and controls each sub-atmospheric
module coupled to sub-atmospheric transfer chamber 1224, controls
load locks 1206 and 1208 as well as the operation of robots 1212
and 1226. Computer 124 enables a feedback from one module to be
used to control the flow of a wafer through system 1200 and/or to
control the process or operation of the other modules of system
1200.
Thermal Process Module
[0122] An example of a thermal process module which can be used as
thermal process modules 1300 or 1300B is illustrated in FIG. 13A-B.
FIG. 13A-B illustrates an insitu steam generation (ISSG) process
tool 1300 which can be used to grow an oxide film, such as a high
quality gate dielectric film. ISSG chamber 1300 can be adapted to
include nitrogen containing gas so that silicon nitride films or
silicon oxynitride films can also be formed.
[0123] Module 1300 as shown in FIG. 13A, includes an evacuated
process chamber 1313 enclosed by a sidewall 1314 and a bottom wall
1315. Sidewall 1314 and bottom wall 1315 are preferably made of
stainless steel. The upper portion of sidewall 1314 of chamber 1313
is sealed to window assembly 1317 by "O" rings 1316. A radiant
energy light pipe assembly 1318 is positioned over and coupled to
window assembly 1317. The radiant energy assembly 1318 includes a
plurality of tungsten halogen lamps 1319, for example Sylvania EYT
lamps, each mounted into a light pipe 1321 which can be a stainless
steel, brass, aluminum or other metal.
[0124] A substrate or wafer 1361 is supported on its edge in side
chamber 1313 by a support ring 1362 made up of silicon carbide.
Support ring 1362 is mounted on a rotatable quartz cylinder 1363.
By rotating quartz cylinder 1363 support ring 1362 and wafer 1361
can be caused to rotate. An additional silicon carbide adapter ring
can be used to allow wafers of different diameters to be processed
(e.g., 150 mm as well as 200 mm). The outside edge of support ring
1362 preferably extends less than two inches from the outside
diameter of wafer 1361. The volume of chamber 1313 is approximately
two liters.
[0125] The bottom wall 1315 of apparatus 1300 includes a gold
coated top surface 1311 for reflecting energy onto the backside of
wafer 1361. Additionally, rapid thermal heating apparatus 1300
includes a plurality of fiber optic probes 1370 positioned through
the bottom wall 1315 of apparatus 1300 in order to detect the
temperature of wafer 1361 at a plurality of locations across its
bottom surface. Reflections between the backside of the silicon
wafer 1361 and reflecting surface 1311 create a blackbody cavity
which makes temperature measurement independent of wafer backside
emissivity and thereby provides accurate temperature measurement
capability.
[0126] Rapid thermal heating apparatus 1300 includes a gas inlet
1369 formed through sidewall 1314 for injecting process gas into
chamber 1313 to allow various processing steps to be carried out in
chamber 1313. Coupled to gas inlet 1369 is a source, such as a
tank, of oxygen containing gas such as O.sub.2 and a source, such
as a tank, of hydrogen containing gas such as H.sub.2. In an
embodiment of the present invention, a nitrogen containing gas,
such as NH.sub.3, or N.sub.2O is produced to enable the formation
of silicon oxynitride films. Positioned on the opposite side of gas
inlet 1369, in sidewall 1314, is a gas outlet 1368. Gas outlet 1368
is coupled to a vacuum source, such as a pump, to exhaust process
gas from chamber 1313 and to reduce the pressure in chamber 1313.
The vacuum source maintains a desired pressure while process gas is
continually fed into the chamber during processing.
[0127] Lamps 1319 include a filament wound as a coil with its axis
parallel to that of the lamp envelope. Most of the light is emitted
perpendicular to the axis towards the wall of the surrounding light
pipe. The light pipe length is selected to at least be as long as
the associated lamp. It may be longer provided that the power
reaching the wafer is not substantially attenuated by increased
reflection. Light assembly 1318 preferably includes 187 lamps
positioned in a hexagonal array or in a "honeycomb shape" as
illustrated in FIG. 13B. Lamps 1319 are positioned to adequately
cover the entire surface area of wafer 1361 and support ring 1362.
Lamps 1319 are grouped in zones which can be independently
controlled to provide for extremely uniform heating of wafer 1361.
Heat pipes 1321 can be cooled by flowing a coolant, such as water,
between the various heat pipes. The radiant energy source 1318
comprising the plurality of light pipes 1321 and associated lamps
1319 allows the use of thin quartz windows to provide an optical
port for heating a substrate within the evacuative process
chamber.
[0128] Window assembly 1317 includes a plurality of short light
pipes 1341 which are brazed to upper/lower flange plates which have
their outer edges sealed to an outer wall 1344. A coolant, such as
water, can be injected into the space between light pipes 1341 to
serve to cool light pipes 1341 and flanges. Light pipes 1341
register with light pipes 1321 of the illuminator. The water cooled
flange with the light pipe pattern which registers with the lamp
housing is sandwiched between two quartz plates 1347 and 1348.
These plates are sealed to the flange with "O" rings 1349 and 1351
near the periphery of the flange. The upper and lower flange plates
include grooves which provide communication between the light
pipes. A vacuum can be produced in the plurality of light pipes
1341 by pumping through a tube 1353 connected to one of the light
pipes 1341 which in turn is connected to the rest of the pipes by a
very small recess or groove in the face of the flange. Thus, when
the sandwiched structure is placed on a vacuum chamber 1313 the
metal flange, which is typically stainless steel and which has
excellent mechanical strength, provides adequate structural
support. The lower quartz window 1348, the one actually sealing the
vacuum chamber 1313, experiences little or no pressure differential
because of the vacuum on each side and thus can be made very thin.
The adapter plate concept of window assembly 1317 allows quartz
windows to be easily changed for cleaning or analysis. In addition,
the vacuum between the quartz windows 1347 and 1348 of the window
assembly provides an extra level of protection against toxic gasses
escaping from the reaction chamber.
[0129] Rapid thermal heating apparatus 1300 is a single wafer
reaction chamber capable of ramping the temperature of a wafer 1361
or substrate at a rate of 25-100.degree. C./sec. Rapid thermal
heating apparatus 1300 is said to be a "cold wall" reaction chamber
because the temperature of the wafer during the oxidation process
is at least 400.degree. C. greater than the temperature of chamber
sidewalls 1314. Heating/cooling fluid can be circulated through
sidewalls 1314 and/or bottom wall 1315 to maintain walls at a
desired temperature. For a steam oxidation process utilizing the
insitu moisture generation of the present invention, chamber walls
1314 and 1315 are maintained at a temperature greater than room
temperature (23.degree. C.) in order to prevent condensation. Rapid
thermal heating apparatus 1300 is preferably configured as part of
a "cluster tool" which includes a load lock and a transfer chamber
with a robotic arm.
Chemical Vapor Deposition Module
[0130] FIGS. 14A-14C illustrates a low pressure chemical vapor
deposition (LPCVD) chamber 1400 which can be used as silicon
deposition module 1400 to deposit a doped or undoped
polycrystalline silicon film. The LPCVD chamber 1400 illustrated in
FIGS. 14A-14C is constructed of materials such that, in this
embodiment, a pressure of greater than or equal to 100 Torr can be
maintained. For the purpose of illustration, a chamber of
approximately in the range of 5-6 liters is described. FIG. 14A
illustrates the inside of process chamber body 1445 in a
"wafer-process" position. FIG. 14B shows the same view of the
chamber in a "wafer-separate" position. FIG. 14C shows the same
cross-sectional side view of the chamber in a "wafer-load"
position. In each case, a wafer 500 is indicated in dashed lines to
indicate its location in the chamber.
[0131] FIG. 14A-14C show chamber body 1445 that defines reaction
chamber 1490 in which the thermal decomposition of a process gas or
gases takes place to form a film on a wafer (e.g., a CVD reaction).
Chamber body 1445 is constructed, in one embodiment, of aluminum
and has passages 1455 for water to be pumped therethrough to cool
chamber 1445 (e.g., a "cold-wall" reaction chamber). Resident in
chamber 1490 is resistive heater 1480 including, in this view,
susceptor 1405 supported by shaft 1465. Susceptor 1405 has a
surface area sufficient to support a substrate such as a
semiconductor wafer 1400 (shown in dashed lines).
[0132] Process gas enters otherwise sealed chamber 1490 through gas
distribution port 1420 in a top surface of chamber lid 1430 of
chamber body 1445. The process gas then goes through blocker plate
1424 to distribute the gas about an area consistent with the
surface area of a wafer. Thereafter, the process gas is distributed
through perforated face plate 1425 located, in this view, above
resistive heater 1480 and coupled to chamber lid 1430 inside
chamber 1490. One objective of the combination of blocker plate
1424 with face plate 1425 in this embodiment is to create a uniform
distribution of process gas at the substrate, e.g., wafer.
[0133] A substrate 1408, such as a wafer, is placed in chamber 1490
on susceptor 1405 of heater 1480 through entry port 1440 in a side
portion of chamber body 1445. To accommodate a wafer for
processing, heater 1480 is lowered so that the surface of susceptor
1405 is below entry port 1440 as shown in FIG. 14C. By a robotic
transfer mechanism 1226, a wafer 1408 is loaded by way of, for
example, a transfer blade 1441 into chamber 1490 onto the superior
surface of susceptor. Once loaded, entry 1440 is sealed and heater
1480 is advanced in a superior (e.g., upward) direction toward face
plate 1425 by lifter assembly 1460 that is, for example, a stepper
motor. The advancement stops when the wafer 500 is a short distance
(e.g., 400-700 mils) from face plate 1425 (see FIG. 14A). In the
wafer-process position, chamber 1490 is effectively divided into
two zones, a first zone above the superior surface of susceptor
1405 and a second zone below the inferior surface of susceptor
1405. It is generally desirable to confine polysilicon film
formation to the first zone.
[0134] At this point, process gas controlled by a gas panel flows
into chamber 1490 through gas distribution port 1420, through
blocker plate 1424 and perforated face plate 1425. Process gas
thermally decomposes to form a film on the wafer. At the same time,
an inert bottom-purge gas, e.g., nitrogen, is introduced into the
second chamber zone to inhibit film formation in that zone. In a
pressure controlled system, the pressure in chamber 1490 is
established and maintained by a pressure regulator or regulators
coupled to chamber 1490. In one embodiment, for example, the
pressure is established and maintained by baretone pressure
regulator(s) coupled to chamber body 1445 as known in the art. In
this embodiment, the baretone pressure regulator(s) maintains
pressure at a level of equal to or greater than 150 Torr.
[0135] Residual process gas is pumped from chamber 1490 through
pumping plate 1485 to a collection vessel at a side of chamber body
1445 (vacuum pumpout 1431). Pumping plate 1485 creates two flow
regions resulting in a gas flow pattern that creates a uniform
silicon layer on a substrate.
[0136] Pump 1432 disposed exterior to apparatus provides vacuum
pressure within pumping channel 1440 (below channel 1440 in FIGS.
14A-14C) to draw both the process and purge gases out of the
chamber 1490 through vacuum pump-out 1431. The gas is discharged
from chamber 1490 along a discharge conduit 1433. The flow rate of
the discharge gas through channel 1440 is preferably controlled by
a throttle valve 1434 disposed along conduit 1433. The pressure
within processing chamber 1490 is monitored with sensors (not
shown) and controlled by varying the cross-sectional area of
conduit 1433 with throttle valve 1434. Preferably, a controller 124
receives signals from the sensors that indicate the chamber
pressure and adjusts throttle valve 1434 accordingly to maintain
the desired pressure within chamber 1490. A suitable throttle valve
for use with the present invention is described in U.S. Pat. No.
5,000,225 issued to Murdoch and assigned to Applied Materials,
Inc., the complete disclosure by which is incorporated herein by
reference.
[0137] Once wafer processing is complete, chamber 1390 may be
purged, for example, with an inert gas, such as nitrogen. After
processing and purging, heater 1480 is advanced in an inferior
direction (e.g., lowered) by lifter assembly 1460 to the position
shown in FIG. 14B. As heater 1480 is moved, lift pins 1495, having
an end extending through openings or throughbores in a surface of
susceptor 1405 and a second end extending in a cantilevered fashion
from an inferior (e.g., lower) surface of susceptor 1405, contact
lift plate 1475 positioned at the base of chamber 1490. As is
illustrated in FIG. 14B, in one embodiment, at the point, lift
plate 1475 remains at a wafer-process position (i.e., the same
position the plate was in FIG. 14A). As heater 1480 continues to
move in an inferior direction through the action of assembly 1460,
lift pins 1495 remain stationary and ultimately extend above the
susceptor or top surface of susceptor 1405 to separate a processed
wafer from the surface of susceptor 1405. The surface of susceptor
1405 is moved to a position below opening 1440.
[0138] Once a processed wafer is separated from the surface of
susceptor 1405, transfer blade 1441 of a robotic mechanism is
inserted through opening 1440 beneath the heads of lift pins 1495
and a wafer supported by the lift pins. Next, lifter assembly 1460
inferiorly moves (e.g., lowers) heater 1480 and lifts plate 1475 to
a "wafer load" position. By moving lift plates 1475 in an inferior
direction, lift pins 1495 are also moved in an inferior direction,
until the surface of the processed wafer contacts the transfer
blade. The processed wafer is then removed through entry port 1440
by, for example, a robotic transfer mechanism 1226 that removes the
wafer and transfers the wafer to the next processing step. A second
wafer may then be loaded into chamber 1490. The steps described
above are generally reversed to bring the wafer into a process
position. A detailed description of one suitable lifter assembly
1460 is described in U.S. Pat. No. 5,772,773, assigned to Applied
Materials, Inc. of Santa Clara, Calif.
[0139] In a high temperature operation, such as LPCVD processing to
form a polycrystalline silicon film, the heater temperature inside
chamber 1490 can be as high as 750.degree. C. or more. Accordingly,
the exposed components in chamber 1490 must be compatible with such
high temperature processing. Such materials should also be
compatible with the process gases and other chemicals, such as
cleaning chemicals (e.g., NF.sub.3) that may be introduced into
chamber 1490. Exposed surfaces of heater 1480 may be comprised of a
variety of materials provided that the materials are compatible
with the process. For example, susceptor 1405 and shaft 1465 of
heater 1480 may be comprised of similar aluminum nitride material.
Alternatively, the surface of susceptor 1405 may be comprised of
high thermally conductive aluminum nitride materials (on the order
of 95% purity with a thermal conductivity from 140 W/mK while shaft
1465 is comprised of a lower thermally conductive aluminum nitride.
Susceptor 1405 of heater 1480 is typically bonded to shaft 65
through diffusion bonding or brazing as such coupling will
similarly withstand the environment of chamber 1490.
[0140] FIG. 14A also shows a cross-section of a portion of heater
1480, including a cross-section of the body of susceptor 1405 and a
cross-section of shaft 1465. In this illustration, FIG. 14A shows
the body of susceptor 1405 having two heating elements formed
therein, first heating element 1450 and second heating element
1457. Each heating element (e.g., heating element 1450 and heating
element 1457) is made of a material with thermal expansion
properties similar to the material of the susceptor. A suitable
material includes molybdenum (Mo). Each heating element includes a
thin layer of molybdenum material in a coiled configuration.
[0141] In FIG. 14A, second heating element 1457 is formed in a
plane of the body of susceptor 1405 that is located inferior
(relative to the surface of susceptor in the figure) to first
heating element 1450. First heating element 1450 and second heating
element 1457 are separately coupled to power terminals. The power
terminals extend in an inferior direction as conductive leads
through a longitudinally extending opening through shaft 1465 to a
power source that supplies the requisite energy to heat the surface
of susceptor 1405. Extending through openings in chamber lid are
two pyrometers, first pyrometer 1410 and second pyrometer 1415.
Each pyrometer provides data about the temperature at the surface
of susceptor 1405 (or at the surface of a wafer on susceptor 1405).
Also of note in the cross-section of heater 1480 as shown in FIG.
14A is the presence of thermocouple 1470. Thermocouple 1470 extends
through the longitudinally extending opening through shaft 1465 to
a point just below the superior or top surface of susceptor
1405.
High K Dielectric Deposition Module
[0142] A high k dielectric deposition module 1700 which can be used
in the present invention is shown in FIG. 17A and includes a liquid
delivery system, chemical vapor deposition (CVD) chamber, exhaust
system and remote plasma generator which together comprises a
unique system especially useful in depositing thin metal-oxide
films as well as other films requiring vaporization of low
volatility precursor liquids. The system also provides for an
in-situ cleaning process for the removal of metal-oxide films
deposited on interior surfaces of a deposition chamber. The system
also has application in the use of fabricating metal-oxide
dielectrics useful in making ultra large scale integration (ULSI)
DRAM and other advanced feature electronic devices which require
the deposition of high dielectric constant materials. In general,
devices that can be made with the system of the present invention
are those devices characterized by having one or more layers of
insulating, dielectric or electrode material on a suitable
substrate such as silicon. One skilled in the art will appreciate
the ability to use alternative configuration and process details to
the disclosed specifics without departing from the scope of the
present invention. In other instances, well known semiconductor
processing equipment and methodology have not been described in
order not to unnecessarily obscure the present invention.
[0143] FIG. 17A is a perspective view of the high k deposition
module 1700 showing the relative positions of the main components
of the present invention. High k deposition module 1700 contains a
processing chamber 1702, a heat exhaust system 1704, a remote
plasma generator 1706 and a vapor delivery system 1708. Also shown
in FIG. 17A is a sub-atmospheric transfer chamber 1224. Processing
chamber 1702 is comprised of lid 1710 and chamber body 1712 and is
attached to central transfer chamber 1224. Gases supplied via
liquid delivery system 1708 are provided into a processing region
(not shown) within chamber 1708 via temperature controlled conduits
formed within inlet block 1714, mixing block 1716 and central block
1718. Cartridge style heaters 1720 are integrally formed into each
block and, in conjunction with individual thermocouples and
controllers, maintain temperature set points within the conduits.
For clarity, individual thermocouples and controllers have been
omitted. Not visible in FIG. 17A but an aspect of the module is
embedded lid heater located intregal to lid 1710 beneath heater
backing plate 1722.
[0144] Chamber 1702 processing by-products are exhausted via heated
exhaust system 1704 which is coupled to chamber 1702 via exhaust
port 1724. Also shown are isolation valve 1726, throttle valve
1728, chamber by-pass 1730, cold trap 1732 and cold trap isolation
valve 1734. For clarity, specific embodiments of vacuum pump and
wafer fabrication plant exhaust treatment systems are not shown. In
order to provide a clearer representation of the interrelationship
between and relative placement of each of the components of heated
exhaust system 1704, the jacket type heaters, thermocouples and
controllers used to maintain setpoint temperatures in exhaust port
1724, isolation valve 1726, throttle valve 1728, chamber by-pass
1730, and by-pass line 1736 have been omitted.
[0145] Activated species are generated by remote plasma generator
1706 and provided to a processing region within chamber 1702 via
conduits within activated species inlet block 1740, activated
species block 1742 and central block 1718. Other components of
remote plasma generator 1706 such as magnetron, auto tuner
controller 1746, and auto tuner 1748 are visible in FIG. 17A.
[0146] One of the main components of liquid delivery system 1708 is
liquid flow meter 1750 and vaporizer 1752. Three-way inlet valve
1754 allows either precursor 1756 or solvent 1758 into vapor
delivery system 1708. Heat exchangers 1760 and 1762 preheat carrier
gases and process gases respectively. Heated carrier gases travel
via a carrier gas supply line 1764 to vaporizer 1752 in order to
facilitate more complete vaporization within vaporizer 1752 as well
as carry vaporized liquids to chamber 1702. After vaporization in
vaporizer 1752, chamber by-pass valve 1766 allows vapor to be
ported either to processing region in chamber 1702 via outlet 1762
or to exhaust system 1704 via outlet 1768 which is coupled to
heated by-pass line 1736. A jacket style heater, thermocouple and
controller which maintain the temperature of chamber by-pass valve
1766 and vaporizer precursor line 1770 as well as the jacket style
heater, thermocouple and controller which maintain the temperature
of by-pass line 1736 have been omitted so as not to obscure the
components of liquid delivery system 1708 and their relationship to
chamber 1702 and heated exhaust system 1704.
[0147] The size and dimensions of the various components and the
placement of these components in relation to each other are
determined by the size of the substrate on which the processes of
the present invention are being formed. A preferred embodiment of
the invention will be described herein with reference to a high k
deposition module 1700 adapted to process circular substrate, such
as a silicon wafer, having a 200 mm diameter. Although described in
reference to a single substrate, one of ordinary skill in the art
of semiconductor processing will appreciate that the methods and
various embodiments of the present invention are adaptable to the
processing of multiple substrates within a single chamber 1702.
[0148] FIG. 17B is a cross sectional view of chamber assembly 1702
of processing system 1700 of FIG. 17A. Chamber body 1712 and heated
chamber lid 1710, which is hingedly connected to chamber body 1712,
together with O-ring 1770 form a temperature and pressure
controlled environment or processing region 1772 which enables
deposition processes and other operations to be performed within
processing region 1772. Chamber body 1712 and lid 1710 are
preferably made of a rigid material such as aluminum, various
nickel alloys or other materials having good thermal conductivity.
O-ring 1770 could be formed from Chemraz, Kalrez, Viton or other
suitable sealing material.
[0149] When lid 1710 is closed as shown in FIG. 17B, an annular
processing region 1772 is formed which is bounded by showerhead
1774, substrate support 1776 and the walls of chamber body 1712.
Substrate support 1776 (shown in the raised position for
processing) extends through the bottom of chamber body 1712.
Embedded within substrate support 1776 is a resistive heater which
receives power via resistive heating element electrical connector
1778. A thermocouple in thermal contact with substrate support 1776
senses the temperature of substrate support 1776 and is part of a
closed loop control circuit which allows precise temperature
control of heated substrate support 1776. Substrate support 1776
and substrate 1701 are parallel to showerhead 1774. Substrate 1701
is supported by the upper surface of support 1776 and is heated by
the resistive heaters within substrate support 1776 to processing
temperatures of, for example, between about 400.degree. C. and
500.degree. C. for Tantalum films formed using the methods and
apparatus of the present invention.
[0150] Processing chamber 1702 is coupled to sub-atmospheric
transfer chamber 1224 via opening 1780. A slit valve 1782 seals
processing region 1772 from sub-atmospheric transfer chamber 1224.
Substrate support 1776 may also move vertically into alignment with
opening 1780 which, when slit valve 1782 is open, allows substrates
to move between the processing region 1772 and sub-atmospheric
transfer chamber 1224. Substrate 1701 can be a substrate used in
the manufacture of semiconductor products such as silicon
substrates and gallium arsenide substrates and can be other
substrates used for other purposes such as substrates used in the
production of flat panel displays.
[0151] Pumping passage 1784 and outlet port 1786 formed within
chamber body 1712 for removing by products of processing operations
conducted within processing region 1772. Outlet port 1786 provides
fluid communication between components of heated exhaust system
1704 and processing region 1772.
[0152] Turning now to gas delivery features of chamber 1702, both
process gas/precursor mixture from liquid delivery system 1708, via
conduit 1788, and activated species from remote plasma generator
system 1706, via conduit 1790, flow through central conduit 1792 to
bore through 1794 formed in lid 1710. From there, gases and
activated species flow through blocker plate 1796 and showerhead
1774 into processing region 1772. A feature of showerhead 1774 of
the present invention is the plurality of apertures.
[0153] Process gas and vaporized precursors and mixtures thereof
are provided to central bore through 1794 via temperature
controlled conduits formed integral to heated feed through assembly
1798. Heated feed through assembly 1798 is comprised of central
block 1799, mixed deposition gas feed through block 1716 and inlet
and mixing block 1714. Although the embodiment represented in
chamber 1702 of FIG. 17B indicates a heated feed through assembly
1798 comprising three separate blocks 1718, 1716, and 1714, one of
ordinary skill will appreciate that the blocks can be combined such
as replacing inlet and mixing block 1714 and feed through block
1716 with a single block without departing from the spirit of the
present invention. Additionally, a plurality of cartridge heaters
1720 are disposed internal to each of the aforementioned blocks and
proximate to the conduits 1792, 1788, 1797, 1795, and 1793 which
maintain a setpoint in each conduit utilizing separate controllers
and thermocouples for the heater of a particular conduit. For
clarity, the separate thermocouples and controllers have been
omitted.
[0154] Lid 1710 is also provided with a cooling channel 1791 which
circulates cooling water within that of lid 1710 in proximity to
o-ring 1770. Cooling channel 1791 allows lid 1710 to maintain the
temperatures preferred for advantageous heating of showerhead 1774
while protecting o-ring 1770 from the high temperatures which
degrade the sealing qualities of o-ring 1770 thereby making o-ring
1770 more susceptible to attack by the reactive species generated
and supplied to processing region 1772 by remote plasma generator
1706.
[0155] Another feature of processing chamber 1702 of the present
invention also shown in FIG. 17B is embedded resistive heater 1789
within lid 1710. This feature of chamber assembly 1702 provides
elevated temperatures in lid 1710 in proximity to central bore
through 1794 and the area between the lower surface of the lid 1710
and showerhead upper surface 1787. The region between lid 1710 and
showerhead upper surface 1787 is referred to as the "gas box".
Formed within the top surface of lid 1710 is an annular groove
shaped according to the size and shape of embedded heater 1789 in
order to increase surface contact and heat transfer between
resistive heater 1789 and lid 1710. Without heater 1789, cooling
channel 1791 could continuously remove heat from lid 1710. As a
result, cooling channel 1791 also affects the temperature of
portions of lid 1710 in contact with precursor vapor, such as the
area surrounding central bore through 1794 and the gas box. While
cooler lid 1710 temperatures improve conditions for o-ring 1770,
cooler lid 1710 temperatures could result in undesired condensation
of precursor vapor. Thus, it is to be appreciated that resistive
heater 1789 is positioned to heat those portions of lid 1710 in
contact with the vaporized precursor flow such as the gas box and
the area surrounding central bore through 1794. As shown in FIG.
17B, for example, heater 1789 is located between cooling channel
1719 and central bore through 1794 while also positioned to provide
heating to the lid surface adjacent to blocker plate 1796.
Vapor Delivery System
[0156] Vapor delivery system 1708 provides a method and an
apparatus for supplying controlled, repeatable, vaporization of low
vapor pressure precursors for film deposition on a substrate 1701
located within processing region 1772. One method provides for the
direct injection of vaporized TAETO and TAT-DMAE. One of ordinary
skill will appreciate the specific features detailed below which
separately and when combined allow vapor delivery system 1708 to
vaporize and precisely control the delivery of liquid precursors
including those precursors having vapor pressures significantly
lower than precursors utilized in prior art vapor delivery system
or, specifically, precursors having vapor pressures below about 10
Torr at 1 atm and 100.degree. C. (FIG. 1).
[0157] The various components of vapor delivery system 1708 are
placed in close proximity to chamber 1702 in order to minimize the
length of temperature controlled vapor passageways between the
outlet of vaporizer 1752 and processing region 1772. Even though
practice in the semiconductor processing arts is to place vapor
systems remotely from processing chambers to either ensure
serviceability or reduce the amount of cleanroom space occupied by
a processing system, vapor delivery system 1708 of the present
invention utilizes an innovative compact design which allows all
system components--less bulk liquid precursor, carrier gas and
process gas supplies--to be located directly adjacent to chamber
1702 in close proximity to precursor and process gas chamber feed
throughs.
[0158] A low vapor pressure liquid precursor, such as TAT-DMAE or
TAETO, can be stored in bulk storage container 1756 located
remotely or on mainframe support in proximity to processing chamber
1702. Liquid precursor stored in tank 1756 is maintained under
pressure of an inert gas such as Helium at about 15 to 70 psig. The
gas pressure within tank 1756 provides sufficient pressure on the
liquid precursor such that liquid precursor flows to other vapor
delivery system components thus removing the need for a pump to
deliver the liquid precursor. The outlet of delivery tank 1756 is
provided with a shut-off valve (not shown) to isolate bulk tank
1756 for maintenance or replenishment of the liquid precursor. As a
result of the pressure head on tank 1756, liquid precursor from
tank 1756 is provided to liquid supply line and the precursor inlet
of precursor/solvent inlet valve 1754. When aligned for liquid
precursor, precursor/solvent valve 1754 provides liquid precursor
to precursor/solvent outlet and into precursor/solvent supply line
to liquid flow meter inlet. Liquid flow meter 1750 measures
precursor flow rate and provides via liquid flow meter outlet 511
liquid precursor to vaporize supply line 1763 and then to vaporized
inlet. Vaporizer 1752 in conjunction with a heated carrier gas
(described below) converts the liquid precursor into precursor
vapor. A carrier gas, such as nitrogen or helium, is supplied into
carrier gas heat exchanger inlet 1761 at a pressure of about 15
psi. Carrier gas heat exchanger 1760 is a gas to resistive heater
type heat exchanger like Model HX-01 commercially available from
Lintec. Carrier gas heat exchanger 1760 preheats the carrier gas to
a temperature such that the heated carrier gas stream entering
vaporizer 1752 does not interfere with the efficient vaporization
of the precursor liquid undergoing vaporization within vaporizer
1752. Heated carrier gas is provided to vaporizer 1752 via carrier
gas supply line 1764 and carrier gas inlet to vaporizer. The heated
carrier gas should not be heated uncontrollably since a carrier gas
heated above the decomposition temperature of the precursor
undergoing vaporization could result in precursor decomposition
within vaporizer 1752. Thus, carrier gas heat exchanger 1760 should
heat the carrier gas into a temperature range bounded by, at the
lower limit, the condensation temperature of the precursor and, at
the upper limit, the decomposition temperature of the precursor.
For a tantalum precursor such as TAT-DMAE for example, a
representative vaporization temperature is about 130.degree. C. and
a decomposition temperature is about 190.degree. C. A typical
carrier gas such as nitrogen could be provided to a vaporizer 1752,
which is vaporizing a tantalum precursor such as TAT-DMAE, at about
between 200 and 2000 standard cubic centimeters per minute (sccm)
and a temperature of about between 130.degree. C. and 160.degree.
C. These conditions result in a vaporized precursor flow rate in
the range of about 10-50 milligrams per minute. Carrier gas
temperature can also be such that the temperature of the carrier
gas entering vaporizer 1752 is at least as high if not higher than
the vaporization temperature of the precursor being vaporized in
vaporizer 1752. Of particular concern is the prevention of
precursor vapor condensation within the small diameter conduits
which exist within vaporizer 1752. As such, carrier gas
temperatures below vaporization conditions within vaporizer 1752
could sufficiently cool the vaporized precursor, result in
condensation and should therefore be avoided.
The Remote Plasma Generator
[0159] Another aspect of the processing apparatus 1760 of the
present invention is remote plasma apparatus 1706 shown FIG. 17C in
relation to central substrate transfer chamber 1224 and chamber
1702 and components of heated exhaust system 1705. Remote plasma
apparatus 1706 creates a plasma outside of or remote to processing
region 1772 for cleaning, deposition, annealing or other processes
within processing region 1772. One advantage of a remote plasma
generator 1706 is that the generated plasma or activated species
created by remote plasma generator 1706 may be used for cleaning or
process applications within the processing region without
subjecting internal chamber components such as substrate support
1776 or showerhead 1774 to plasma attack which usually results when
conventional RF energy is applied within process region 1772 to
create a plasma. Several components of remote plasma apparatus 1706
are visible in FIG. 17C such as magnetron 1744, auto tuner
controller 1746, isolator 1741, auto tuner 1748, adapter tube 1745
and adapter tube heat insulation disc 1747.
[0160] Magnetron assembly 1744 houses the magnetron tube, which
produces the microwave energy. The magnetron tube consists of a hot
filament cylindrical cathode surrounded by an anode with a van
array. This anode/cathode assembly produces a strong magnetic field
when it is supplied with DC power from a power supply. Electrons
coming into contact with this magnetic field follow a circular path
as they travel between the anode and the cathode. This circular
motion induces voltage resonance, or microwaves, between the anode
vanes. An antenna channels the microwaves from magnetron 1744 to
isolator 1741 and wave guide 1749. Isolator 1741 absorbs and
dissipates reflected power to prevent damage to magnetron 1744.
Wave guide 1749 channels microwave from isolator 1741 into auto
tuner 1748.
[0161] Auto tuner 1748 matches the impedance of magnetron 1744 and
microwave cavity 1743 to achieve the maximum degree of reflected
power by adjusting the vertical position of three tuning stubs
located inside wave guide 1749. Auto tuner 1748 also supplies a
feedback signal to the magnetron power supply in order to
continuously match the actual forward power to the setpoint. Auto
tuner controller 1746 controls the position of the tuning stubs
within wave guide 1749 to minimize reflected power. Auto tuner
controller 1746 also displays the position of the stubs as well as
forward and reflect power readings.
[0162] Microwave applicator cavity 1743 is where gas or gases
supplied via gas supply inlet 1739 are ionized. Gas supplied via
gas supply inlet 1739 enters a water cooled quartz or sapphire tube
within microwave applicator 1743, is subjected to microwaves and
ionizes producing activated species which can then be used in
cleaning and processing operations within processing region 1772.
One such cleaning gas is NF3 which can be used to supply activated
flourine for cleaning processing region 1772 when a substrate 1701
is not present in processing region 202. Activated species can also
be used to anneal or otherwise process semiconductor or other
materials present on a substrate 1701 positioned within processing
region 1772. An optical plasma sensor 1737 detects the existence of
plasma within cavity 1743. Activated species generated within
microwaves applicator cavity 1743 are supplied to activate species
chamber feed through 1735 via adapter tub 1745. Adapter tube 1745
is insulated from the elevated temperature of chamber body 1712 by
adapter tube isolation disc 1747.
[0163] From activated species chamber feed through 1739, the
activated species pass through lid bore-through and enter activated
species inlet block 1740 which, together with activated species
block 1742, provide an o-ring sealed, air tight conduit i.e.,
activated species conduit 1790, between lid bore-through and
central gas feed-through 1792 within central mixing block 1718.
Method of Using Clean/Gate Tool 1200
[0164] Clean/Gate Tool 1200 can be used to form a dielectric film
and electrode on a substrate. For example, as illustrated in FIGS.
15A-15D, the clean/gate tool 1200 can wet clean a substrate,
monitor the quality of the wet clean, grow a high quality gate
dielectric on the substrate, and then deposit a polysilicon gate
film on the dielectric and then measure the thickness of the
deposited gate film. A similar process can be used in Clean/Gate
Tool 1200 to form a capacitor dielectric and capacitor electrode on
a substrate.
[0165] According to an embodiment of the present invention, a
substrate or wafer, such as wafer 1500, shown in FIG. 15A is
brought to clean/gate tool 1200 in a FOUP 1220 which is loaded onto
Clean/Gate Tool 1200. Wafer 1500 will typically include a thin
sacrificial oxide or native oxide 1504 formed on a doped
monocrystalline silicon substrate 1502 (or a silicon epitaxial
film). Generally, contaminants, such as particles 1506, will be
present in and/or on sacrificial oxide 1504. First, access door
1121 is opened (as is the adjacent door on FOUP 1220). Robot 1212
then removes wafer 1500 from FOUP 1220 and brings it into
atmospheric transfer chamber 1210, and then inserts wafer 1500 into
clean module 200 where it is held by support 210.
[0166] Next, wafer 1500 is exposed to a wet etchant for a
sufficient period of time to etch or strip away all or a portion of
sacrificial oxide 1504. A sacrificial oxide film can be etched away
by exposing it to a dilute HF solution, such as a 500:1 to 10:1 DI
H.sub.2O:HF solution. The concentration and/or etch time will
typically depend upon the thickness of the sacrificial film and the
amount of the film to be removed.
[0167] Directly after etching sacrificial oxide 1504, wafer 1500 is
wet cleaned in module 200. Wafer 1500 can be cleaned in module 200
as described above. In an embodiment of the present invention,
wafer 1500 is cleaned with a single solution containing NH.sub.4OH,
H.sub.2O.sub.2, a chelating agent, and a surfactant. In another
embodiment of the present invention, wafer 1500 is cleaned by
standard RCA cleaning solutions (SC1 and SC2). After sufficient
cleaning, as shown in FIG. 15B, wafer 1500 is dried in module
200.
[0168] Wafer 1500 is then removed by robot 1212 from clean module
200 and brought into atmospheric transfer chamber 1210. The wafer
is then, if desired, transferred into either i) integrated particle
monitoring tool 300 or ii) into integrated thickness measuring
module 1290. Wafer 1500 can be brought into integrated thickness
monitoring module 1290 in order to measure the remaining thickness
of the sacrificial oxide 1504 to determine if either to much, to
little or the correct amount of film has been removed. If too
little film 1504 has been removed, wafer 1500 can be removed from
module 1600 and placed back into wet clean module 200 in order to
further etch the sacrificial film 1506. The amount of additional
etching required, as determined in thickness measuring module 1290,
can be used to determine or control the process parameters, such as
HF concentration, etch time and rotation rate, of the second
etching of sacrificial film 1506 to ensure that the required amount
of sacrificial oxide 1506 is removed. If too much film 1506 has
been removed, then wafer 1500 can be removed from module 1600 and
transferred out of Clean/Gate Tool 1200 through atmospheric
transfer chamber 1210 for further rework. If the correct amount of
film has been removed, then wafer 1500 can be removed from
integrated thickness module 1290 by robot 1212 and transferred into
integrated particle monitoring module 300, if desired.
[0169] In integrated particle monitoring tool 300, the surface of
wafer 1500, as shown in FIG. 15B, can be scanned and mapped to
determine if the surface has been sufficiently cleaned of
contaminants 1506. If the surface has not been sufficiently
cleaned, wafer 1500 can be removed from the integrated particle
monitoring module 300 and sent back to clean module 200 for further
cleaning. The amount and type of a second cleaning of wafer 1500
can be determined by the information received during the integrated
particle monitoring of wafer 1500.
[0170] If wafer 1500 has been sufficiently cleaned, then wafer 1500
is removed from the integrated particle monitoring tool 300 and
brought into the atmospheric transfer chamber 1210 to begin further
processing in the sub-atmospheric portion 1204 of Clean/Gate Tool
1200.
[0171] It is to be appreciated that a wafer can be brought into
either only integrated particle monitoring tool 300 and not
thickness monitoring tool 1700 or can be brought into only
thickness monitoring tool 1600 and not integrated particle
monitoring tool 300, if desired. Additionally, if desired, a wafer
can be brought into integrated particle monitoring 300 for process
prior to bringing it into integrated thickness monitoring tool 1600
for processing. Additionally, it is to be appreciated that every
wafer need not necessarily be measured for thickness and/or
particles. If desired, one can utilize spot checks, of for example
every ten wafers, to determine whether or not proper etching has
occurred and/or particles have been removed. In this case the
information from the integrated particle monitor tool and/or the
integrated thickness monitor tool 1700 can be used to adjust the
strip and cleaning recipe for the next 10 wafers.
[0172] After wafer 1500 has been sufficiently etched and cleaned,
as shown in FIG. 15B, door 1205 is opened and wafer 1500
transferred from atmospheric transfer chamber 1210 into load lock
1206 by robot 1212. Door 1205 is then sealed and load lock 1206
evacuated to the pressure within sub-atmospheric transfer chamber
1224. Next, door 1207 is opened and wafer handling device 1226
removes wafer 1500 from load lock 1206 and brings it into
sub-atmospheric transfer chamber 1224. Next, wafer 1500 is brought
into thermal oxidation chamber 1300 and placed on support 1362 by
wafer handling device 1226. Next, a silicon dioxide dielectric film
1508 is grown on monocrystalline silicon substrate 1502 as shown in
FIG. 15C. If desired, a nitrogen containing gas or a remotely
generated nitrogen plasma can be inserted into chamber 1313 during
film growth to form a silicon oxide containing nitrogen 1510 or a
silicon oxynitride film. It is to be appreciated that a silicon
oxynitride film has a higher dielectric constant than does a
silicon dioxide film.
[0173] In order to grow a dielectric film on wafer 1500, chamber
1313 is sealed and the pressure reduced to less than the
sub-atmospheric transfer chamber pressure of approximately 20 Torr.
Chamber 1313 is evacuated to a pressure to sufficiently remove the
nitrogen ambient, typically nitrogen, in chamber 1313. Chamber 13
is pumped down to a prereaction pressure less than the pressure at
which the insitu moisture generation is to occur, and is preferably
pumped down to a pressure of less than 1 torr.
[0174] Simultaneous with the prereaction pump down, power is
applied to lamps 1319 which in turn irradiate wafer 1500 and
silicon carbide support ring 1362 and thereby heat wafer 1500 and
support ring 1362 to a stabilization temperature. The stabilization
temperature of wafer 1500 is less than the temperature (reaction
temperature) required to initiate the reaction of the hydrogen
containing gas and oxygen containing gas to be utilized for the
insitu moisture generation. The stabilization temperature in the
preferred embodiment of the present invention is approximately
500.degree. C.
[0175] Once the stabilization temperature and the prereaction
pressure are reached, chamber 1313 is backfilled with the desired
mixture of process gas. The process gas includes a reactant gas
mixture comprising two reactant gasses: a hydrogen containing gas
and an oxygen containing gas, which can be reacted together to form
water vapor (H.sub.2O) at temperatures between 400-1250.degree. C.
The hydrogen containing gas, is preferably hydrogen gas (H.sub.2),
but may be other hydrogen containing gasses such as, but not
limited to, ammonia (NH.sub.3), deuterium (heavy hydrogen) and
hydrocarbons such as methane (CH.sub.4). The oxygen containing gas
is preferably oxygen gas (O.sub.2) but may be other types of oxygen
containing gases such as but not limited to nitrous oxide
(N.sub.2O). Other gasses, such as but not limited to nitrogen
(N.sub.2), may be included in the process gas mix if desired. The
oxygen containing gas and the hydrogen containing gas are
preferably mixed together in chamber 1313 to form the reactant gas
mixture.
[0176] In the present invention the partial pressure of the
reactant gas mixture (i.e., the combined partial pressure of the
hydrogen containing gas and the oxygen containing gas) is
controlled to ensure safe reaction conditions. According to the
present invention, chamber 1313 is backfilled with process gas such
that the partial pressure of the reactant gas mixture is less than
the partial pressure at which spontaneous combustion of the entire
volume of the desired concentration ratio of reactant gas will not
produce a detonation pressure wave of a predetermined amount. The
predetermined amount is the amount of pressure that chamber 1313
can reliably handle without failing.
[0177] According to the present invention, insitu moisture
generation is preferably carried out in a reaction chamber that can
reliably handle a detonation pressure wave of four atmospheres or
more without affecting its integrity. In such a case, reactant gas
concentrations and operating partial pressure preferably do not
provide a detonation wave greater than two atmospheres for the
spontaneous combustion of the entire volume of the chamber.
[0178] By controlling the chamber partial pressure of the reactant
gas mixture in the present invention any concentration ratio of
hydrogen containing gas and oxygen containing gas can be used
including hydrogen rich mixtures utilizing H2/O2 ratios greater
than 2:1, respectively, and oxygen rich mixtures using
H.sub.2/O.sub.2 ratios less than 0.5:1, respectively. For example,
any concentration ratio of O.sub.2 and H.sub.2 can be safely used
as long as the chamber partial pressure of the reactant gasses is
maintained at less than 150 Torr at process temperature. The
ability to use any concentration ratio of oxygen containing gas and
hydrogen containing gas enables one to produce an ambient with any
desired concentration ratio of H.sub.2/H.sub.2O or any
concentration ratio of O.sub.2/H.sub.2O desired. Whether the
ambient is oxygen rich or dilute steam or hydrogen rich or dilute
steam can greatly affect device electrical characteristics of the
deposited film 1510. The present invention enables a wide variety
of different steam ambients to be produced and therefore a wide
variety of different oxidation processes to be implemented.
[0179] In some oxidation processes, an ambient having a low steam
concentration with the balance O.sub.2 may be desired. Such an
ambient can be formed by utilizing a reactant gas mixture
comprising 10% H.sub.2 and 90% O.sub.2. In other processes, an
ambient of hydrogen rich steam (70-80% H.sub.2/30-20% H.sub.2O) may
be desired. A hydrogen rich, low steam concentration ambient can be
produced according to the present invention by utilizing a reactive
gas mix comprising between 5-20% O.sub.2 with the remainder H.sub.2
(95-80%). It is to be appreciated that in the present invention any
ratio of hydrogen containing gas and oxygen containing gas may be
utilized because the heated wafer provides a continual ignition
source to drive the reaction. Unlike pyrogenic torch methods, the
present invention is not restricted to specific gas ratios
necessary to keep a stable flame burning.
[0180] Next, power to lamps 1319 is increased so as to ramp up the
temperature of wafer 61 to process temperature. Wafer 61 is
preferably ramped from the stabilization temperature to process
temperature at a rate of between 10-100.degree. C./sec with
50.degree. C./sec being preferred. The preferred process
temperature of the present invention is between 600-1150.degree. C.
with 950.degree. C. being preferred. The process temperature must
be at least the reaction temperature (i.e., must be at least the
temperature at which the reaction between the oxygen containing gas
and the hydrogen containing gas can be initiated by wafer 1500)
which is typically at least 600.degree. C. It is to be noted that
the actual reaction temperature depends upon the partial pressure
of the reactant gas mixture as well as on the concentration ratio
of the reactant gas mixture, and can be between 400.degree. C. to
1250.degree. C.
[0181] As the temperature of wafer 1500 is ramped up to process
temperature, it passes through the reaction temperature and causes
the reaction of the hydrogen containing gas and the oxygen
containing gas to form moisture or steam (H.sub.2O). Since rapid
thermal heating apparatus 1300 is a "cold wall" reactor, the only
sufficiently hot surfaces in chamber 1313 to initiate the reaction
is the wafer 1500 and support ring 1362. As such, in the present
invention the moisture generating reaction occurs near, about 1 cm
from, the surface of wafer 1500. In the present invention the
moisture generating reaction is confined to within about two inches
of the wafer or about the amount at which support ring 1362 extends
past the outside edge of wafer 1500. Since it is the temperature of
the wafer (and support ring) which initiates or turns "on" the
moisture generation reaction, the reaction is said to be thermally
controlled by the temperature of wafer 1500 (and support ring
1362). Additionally, the vapor generation reaction of the present
invention is said to be "surface catalyzed" because the heated
surface of the wafer is necessary for the reaction to occur,
however, it is not consumed in the reaction which forms the water
vapor.
[0182] Next, once the desired process temperature has been reached,
the temperature of wafer 1500 is held constant for a sufficient
period of time to enable the water vapor generated from the
reaction of the hydrogen containing gas and the oxygen containing
gas to oxidize silicon surfaces or films to form SiO.sub.2. Wafer
1500 will typically be held at process temperature for between
30-120 seconds. Process time and temperature are generally dictated
by the thickness of the oxide film desired, the purpose of the
oxidation, and the type and concentrations of the process gasses.
FIG. 15C illustrates an oxide 1508 formed on wafer 1500 by
oxidation of silicon surfaces 1502 by water vapor (H.sub.2O)
generated by the insitu moisture generation process. It is to be
appreciated that the process temperature must be sufficient to
enable the reaction of the generated water vapor or steam with
silicon surfaces to form silicon dioxide.
[0183] Next, power to lamps 1319 is reduced or turned off to reduce
the temperature of wafer 1500. The temperature of wafer 1500
decreases (ramps down) as fast as it is able to cool down (at about
50.degree. C./sec.). Simultaneously, N2 purge gas is fed into the
chamber 1313. The moisture generation reaction ceases when wafer
1500 and support ring 1362 drop below the reaction temperature.
Again it is the wafer temperature (and support ring) which dictates
when the moisture reaction is turned "on" or "off".
[0184] Next, chamber 1313 is pumped down, preferably below 1 torr,
to ensure that no residual oxygen containing gas and hydrogen
containing gas are present in chamber 1313. The chamber is then
backfilled with N.sub.2 gas to the transfer pressure in
sub-atmospheric transfer chamber 1224, of approximately 20 torr and
wafer 1500 transferred out of chamber 1313 to complete the
process.
[0185] At times it may be desirable to utilize concentration ratios
of hydrogen containing gas and oxygen containing gas which will
produce an ambient with a large concentration of water vapor (e.g.,
>40% H.sub.2O). Such an ambient can be formed with a reactant
gas mixture, for example, comprising 40-80% H.sub.2/60-20% O.sub.2.
A gas mixture near the stoichiometric ratio may yield too much
combustible material to enable safe reaction conditions. In such a
situation, a low concentration gas mixture (e.g., less than 15%
O.sub.2 in H.sub.2) can be provided into the reaction chamber
during step 306, the wafer temperature raised to the reaction
temperature in step 308, and the reaction initiated with the lower
concentration ratio. Once the reaction has been initiated and the
existing reactant gas volume begins to deplete, the concentration
ratio can be increased to the desired level. In this way, the
amount of fuel available at the start of the reaction is kept small
and safe operating conditions assured.
[0186] In an embodiment of the present invention a relatively low,
reactive gas partial pressure is used for insitu steam generation
in order to obtain enhanced oxidation rates. It has been found that
providing a partial pressure of between 1 Torr to 50 Torr of
hydrogen gas (H.sub.2) and oxygen gas (O.sub.2) that an enhanced
oxide growth rate of silicon can be achieved. That is, for a given
set of process conditions (i.e., H.sub.2/O.sub.2 concentration
ratio, temperature, and flow rate) the oxidation rate of silicon is
actually higher for lower partial pressures (1-50 Torr) of H.sub.2
and O.sub.2 than for higher partial pressures (i.e., from 50 Torr
to 100 Torr).
[0187] After a sufficient dielectric film 1508 has been grown on
monocrystalline silicon substrate 1502, as shown in FIG. 15C, wafer
1500 is removed from thermal oxidation chamber 1300 by robot 1226.
In an embodiment of the present invention, wafer 1500 is
transferred by robot 1226 through sub-atmospheric transfer chamber
1224 and placed into high k dielectric module 1700 to deposit a
high k metal oxide dielectric film 1511 on silicon oxide film 1508
or a silicon oxide film containing nitrogen 1510. In an embodiment
of the present invention the dielectric film 1511 is a transition
metal dielectric film such as, but not limited to, tantalum
pentaoxide (Ta.sub.2O.sub.5) and titanium oxide (TiO.sub.2). In
another embodiment dielectric layer 1511 is a tantalum pentaoxide
film doped with titanium. Additionally dielectric layer 1511 can be
a composite dielectric film comprising a stack of different
dielectric films such as a
Ta.sub.2O.sub.5/TiO.sub.2/Ta.sub.2O.sub.5 stacked dielectric film.
Additionally, dielectric layer 208 can be a piezoelectric
dielectric such as Barium Strontium Titanate (BST) and Lead
Zirconium Titanate (PZT) or a ferroelectric.
[0188] In order to form a dielectric layer 1511 onto wafer 1500,
the substrate can be placed onto support 1776 in chamber 1702 of
high k module 1700. The wafer 1500 is then heated to a desired
deposition temperature while the pressure within the chamber is
pumped down (reduced) to a desired deposition pressure. Deposition
gases are then fed into the chamber and a dielectric layer formed
therefrom.
[0189] To blanket deposit a tantalum pentaoxide (Ta.sub.2O.sub.5)
dielectric film by thermal chemical vapor deposition a deposition
gas mix comprising, a source of tantalum, such as but not limited
to, TAETO [Ta (OC.sub.2H.sub.5).sub.5] and TAT-DMAE [Ta
(OC.sub.2H.sub.5).sub.4 (OCHCH.sub.2N(CH.sub.3).sub.2], and source
of oxygen such as O.sub.2 or N.sub.2O can be fed into a deposition
chamber while the substrate is heated to a deposition temperature
of between 300-500.degree. C. and the chamber maintained at a
deposition pressure of between 0.5-10 Torr. The flow of deposition
gas over the heated substrate results in thermal decomposition of
the metal organic Ta-containing precursor and subsequent deposition
of a tantalum pentaoxide film. In one embodiment TAETO or TAT-DMAE
is fed into the chamber at a rate of between 10-50 milligrams per
minute while O.sub.2 or N.sub.2O is fed into the chamber at a rate
of 0.3-1.0 SLM. TAETO and TAT-DMAE can be provided by direct liquid
injection or vaporized with a bubbler prior to entering the
deposition chamber. A carrier gas, such as N.sub.2, H.sub.2 and He,
at a rate of between 0.5-2.0 SLM can be used to transport the
vaporized TAETO or TAT-DMAE liquid into the deposition chamber
1702. Deposition is continued until a dielectric film 1511 of a
desired thickness is formed. A tantalum pentaoxide
(Ta.sub.2O.sub.5) dielectric film having a thickness between 50-200
.ANG. provides a suitable dielectric film.
[0190] It has been found that the use of nitrous oxide (N.sub.2O)
as the oxidizer (source of oxygen), as opposed to oxygen gas
O.sub.2 improves the electrical properties of the deposited
tantalum pentaoxide (Ta.sub.2O.sub.5) dielectric film during
deposition. The use of N.sub.2O, as opposed to O.sub.2, has been
found to reduce the leakage current and enhance the capacitance of
fabricated capacitors. The inclusion of N.sub.2O as an oxidizer
aids in the removal of carbon from the film during growth which
helps to improve the quality of the film.
[0191] In an embodiment of the present invention dielectric layer
1511 is a tantalum pentaoxide (Ta.sub.2O.sub.5) film doped with
titanium (Ti). A tantalum pentaoxide film doped with titanium can
be formed by thermal chemical vapor deposition by providing a
source of titanium, such as but not limited to TIPT
(C.sub.12H.sub.26O.sub.4Ti), into the process chamber while forming
a tantalum pentaoxide film as described above. TIPT diluted by
approximately 50% with a suitable solvent such as isopropyl alcohol
(EPA) can be fed into the process chamber by direct liquid
injection or through the use of a bubbler and carrier gas such as
N.sub.2. A TIPT diluted flow rate of between 5-20 mg/minute can be
used to produce a tantalum pentaoxide film having a titanium doping
density of between 5-20 atomic percent and a dielectric constant
between 20-40. The precise Ti doping density can be controlled by
varying the tantalum source flow rate relative to the titanium
source flow rate. It is to be appreciated that a tantalum
pentaoxide film doped with titanium atoms exhibits a higher
dielectric constant than an undoped tantalum pentaoxide film.
[0192] In another embodiment of the present invention dielectric
layer 1511 is a composite dielectric layer comprising a stack of
different dielectric materials such as a
Ta.sub.2O.sub.5/TiO.sub.2/Ta.sub.2O.sub.5 stack. A
Ta.sub.2O.sub.5/TiO.sub.2/Ta.sub.2O.sub.5 composite film can be
formed by first depositing a tantalum pentaoxide film as described
above. After depositing a tantalum pentaoxide film having a
thickness between 20-50 .ANG. the flow of the tantalum source is
stopped and replaced with a flow of a source of titanium, such as
TIPT, at a diluted flow rate of between 5-20 mg/min. After
depositing a titanium oxide film having a thickness of between
20-50 .ANG., the titanium source is replaced with the tantalum
source and the deposition continued to form a second tantalum
pentaoxide film having a thickness of between 20-50 .ANG.. By
sandwiching a higher dielectric constant titanium oxide (TiO.sub.2)
film between two tantalum pentaoxide (Ta.sub.2O.sub.5) films, the
dielectric constant of a composite stack is increased over that of
a homogeneous layer of tantalum pentaoxide (Ta.sub.2O.sub.5).
[0193] Next, dielectric film 1511 is annealed with remotely
generated active atomic species to form an annealed dielectric
layer 1511. Dielectric film 1511 can be annealed in chamber 1702
coupled to remote plasma generator 1706. Substrate 1500 is then
heated to an anneal temperature and exposed to active atomic
species generated by disassociating an anneal gas in application
cavity 1743. By generating the active atomic species in an
application cavity 1743 chamber remote from chamber 1702 (the
chamber in which the substrate is situated) a low temperature
anneal can be accomplished without exposing the substrate to the
harmful plasma used to form the active atomic species. With the
process and apparatus of the present invention anneal temperatures
of less than 400.degree. C. can be used. The use of remotely
generated active atomic species to anneal dielectric film 1511
enables anneal temperatures of less than or equal to the deposition
temperature of the dielectric film to be used.
[0194] In one embodiment of the present invention dielectric film
1511 is a transition metal dielectric and is annealed with reactive
oxygen atoms formed by remotely disassociating O.sub.2 gas.
Dielectric layer 1511 can be annealed in chamber 1702 with a
reactive oxygen atoms created by providing an anneal gas comprising
two SLM of O.sub.2 and one SLM of N2 into chamber application
cavity 1743, and applying a power between 500-1500 Watts to
magnetron 302 to generate microwaves which cause a plasma to ignite
from the anneal gas. Alternatively, reactive oxygen atoms can be
formed by flowing an anneal gas comprising two SLM of O.sub.2 and
three SLM of argon (Ar) into cavity 1743. While reactive oxygen
atoms are fed into anneal chamber 1702, substrate 200 is heated to
a temperature of approximately 300.degree. C. and chamber 1702
maintained at an anneal pressure of approximately 2 Torr, High K
Dielectric layer 1511 can be sufficiently annealed by exposing
substrate 200 to reactive oxygen atoms for between 30-120
seconds.
[0195] An inert gas, such as N.sub.2 or argon (Ar), is preferably
included in the anneal gas stream in order to help prevent
recombination of the active atomic species. It is to be noted that
as the active atomic species (e.g. reactive oxygen atoms) travel
from the application cavity 1743 to chamber 1702, they collide with
one another and recombine to form O.sub.2 molecules. By including
an inert gas, in the anneal gas mix, the inert gas does not
disassociate and so provides atoms which the active atomic species
can collide into without recombining. Additionally, in order to
help prevent recombination of the active atomic species, it is
advisable to keep the distance between application cavity 1743 and
chamber 1702 as short as possible.
[0196] Annealing a transition-metal dielectric film 1511 with
reactive oxygen atoms fills oxygen vacancies (satisfies sites) in
the dielectric film 1511 which greatly reduces the leakage of the
film. Additionally, annealing transition metal dielectric 1511
helps to remove carbon (C) in the film which can contribute to
leakage. Carbon can be incorporated into transition metal
dielectrics because the tantalum and titanium sources, TAT-DMAE,
TAETO, and TIPT are carbon containing compounds. The reactive
oxygen atoms remove carbon from the film by reacting with carbon
and forming carbon dioxide (CO.sub.2) vapor which can then be
exhausted out from the chamber. Next, a doped or undoped
polycrystalline silicon film or other gate material is deposited
onto the gate dielectric layer 1508 (or high k dielectric 1511, if
used), as shown in FIG. 15D.
[0197] In order to deposit a polysilicon film 1512 the desired
deposition pressure and temperature are obtained and stabilized in
chamber 1490. While achieving pressure and temperature
stabilization, a stabilization gas such as N.sub.2, He, Ar, H.sub.2
or combinations thereof are fed into chamber 1490. In a preferred
embodiment of the present invention the flow and concentration of
the dilution gas used in the subsequent polysilicon deposition is
used to achieve temperature and pressure stabilization. Using the
dilution gas for stabilization enables the dilution gas flow and
concentrations to stabilize prior to polysilicon deposition.
[0198] In an embodiment of the present invention the chamber is
evacuated to a pressure between 150-350 Torr with 200-275 Torr
being preferred and the heater temperature raised to between
700-740.degree. C. and preferably between 710-720.degree. C. while
the dilution gas is fed into chamber 1490 at a flow rate between
10-30 slm. According to the present invention the dilution gas
consist of H.sub.2 and an inert gas, such as but not limited to
nitrogen (N.sub.2), argon (Ar), and helium (He), and combinations
thereof. For the purpose of the present invention an inert gas is a
gas which is not consumed by or which does not interact with the
reaction used to deposit the polysilicon film and does not interact
with chamber components during polysilicon film deposition. In a
preferred embodiment of the present invention the inert gas
consists only of nitrogen (N.sub.2). In an embodiment of the
present invention H.sub.2 comprises more than 8% and less than 20%
by volume of the dilution gas mix with the dilution gas mix
preferably having between 10-15% H.sub.2 by volume.
[0199] In the present invention the dilution gas mix has a
sufficient H.sub.2/inert gas concentration ratio such that a
subsequently deposited polysilicon film is dominated by the
<111> crystal orientation as compared to the <220>
crystal orientation. Additionally, the dilution gas mix has a
sufficient H.sub.2/inert gas concentration ratio so that the
subsequently deposited polycrystalline silicon film has a random
grain structure with an average grain size between 50-500
.ANG..
[0200] In an embodiment of the present invention the dilution gas
mix is supplied into chamber 1490 in two separate components. A
first component of the dilution gas mix is fed through distribution
port 1420 in chamber lid 1430. The first component consist of all
the H.sub.2 used in the dilution gas mix and a portion (typically
about 2/3) of the inert gas used in the dilution gas mix. The
second component of the dilution gas mix is fed into the lower
portion of chamber 1490 beneath heater 1480 and consists of the
remaining portion (typically about 1/3) of the inert gas used in
the dilution gas mix. The purpose of providing some of the inert
gas through the bottom chamber portion is to help prevent the
polycrystalline silicon film from depositing on components in the
lower portion of the chamber. In the embodiment of the present
invention between 8-18 slm with about 9 slm being preferred of an
inert gas (preferably N.sub.2) is fed through the top distribution
plate 1420 while between 3-10 slm, with 4-6 slm being preferred, of
the inert gas (preferably N.sub.2) is fed into the bottom or lower
portion of chamber 1490. The desired percentage of H.sub.2 in the
dilution gas mix is mixed with the inert gas prior to entering
distribution port 1420.
[0201] Next, once the temperature, pressure, and gas flows have
been stabilized a process gas mix comprising a silicon source gas
and a dilution gas mix comprising H.sub.2 and an inert gas is fed
into chamber 1490 to deposit a polycrystalline silicon film 1512 on
substrate 1500 as shown in FIG. 15D. In the preferred embodiment of
the present invention the silicon source gas is silane (SiH.sub.4)
but can be other silicon source gases such as disilane
(Si.sub.2H.sub.6). According to the preferred embodiment of the
present invention between 50-150 sccm, with between 70-100 sccm
being preferred, of silane (SiH.sub.4) is added to the dilution gas
mix already flowing and stabilized during the temperature and
pressure stabilization step. In this way during the deposition of
polysilicon, a process gas mix comprising between 50-150 sccm of
silane (SiH.sub.4) and between 10-30 slm of dilution gas mix
comprising H.sub.2 and an inert gas is fed into the chamber while
the pressure in chamber 1490 is maintained between 150-350 Torr and
the temperature of susceptor 1405 is maintained between
700-740.degree. C. (It is to be appreciated that in the LPCVD
reactor 1400 the temperature of the substrate or wafer 1500 is
typically about 50.degree. (cooler than the measured temperature of
susceptor 1405). In the preferred embodiment of the present
invention the silicon source gas is added to the first component
(upper component) of the dilution gas mix and flows into chamber
1490 through inlet port 1420. If desired, a dopant gas source, such
as but not limited to diborane and phosphine can be included in the
process gas mix to insitu dope the polysilicon film.
[0202] The thermal energy from susceptor 1405 and wafer 1500 causes
the silicon source gas to thermally decompose and deposit a
polysilicon film on gate dielectric 1508 on silicon substrate 1502
as shown in FIG. 15D. In an embodiment of the present invention
only thermal energy is used to decompose the silicon source gas
without the aid of additional energy sources such as plasma or
photon enhancement.
[0203] As process gas mix is fed into chamber 1490, the silicon
source gas decomposes to provide silicon atoms which in turn form a
polycrystalline silicon film on insulating layer 1508. It is to be
appreciated that H.sub.2 is a reaction product of the decomposition
of silane (SiH.sub.4). By adding a suitable amount of H.sub.2 in
the process gas mix the decomposition of silane (SiH.sub.4) is
slowed which enables a polycrystalline silicon film 1512 to be
formed with small and random grains. In the present invention
H.sub.2 is used to manipulate the silicon resource reaction across
the wafer. By having H.sub.2 comprise between 8-20% of the dilution
gas mix random grains having an average grain size between 50-500
.ANG. can be formed. Additionally, by including a sufficient amount
of H.sub.2 in the dilution gas mix a polycrystalline silicon film
506 which is dominated by the <111> crystal orientation, as
opposed to the <220> crystal orientation is formed.
[0204] According to the present invention the deposition pressure,
temperature, and process gas flow rates and concentration are
chosen so that a polysilicon film is deposited at a rate between
1500-5000 .ANG. per minute with between 2000-300 .ANG. per minute
being preferred. The process gas mix is continually fed into
chamber 1490 until a polysilicon film 1512 of a desired thickness
is formed. For gate electrode applications a polysilicon film 1512
having a thickness between 500-2000 .ANG. has been found
suitable.
[0205] After completing the deposition polysilicon film 1512,
heater 1480 is lowered from the process position to the load
position and wafer 500 removed from chamber 1490 by robot 1226.
[0206] Door 1211 is then opened and then wafer 1500 placed into
load lock 1208 and door 1211 sealed. Next, the pressure within load
lock 1208 is raised to the pressure within atmospheric transfer
chamber 1210. The door 1209 is then opened and robot 1212 removes
wafer 1500 from load lock 1208. At this point, wafer 1500 can be i)
placed into integrated thickness monitoring tool 1700 to measure
the thickness of silicon film 1512; or ii) can be placed into wet
clean module 200 where it is exposed to a cleaning solution
comprising, for example, hydrofluoric acid in order to remove
contaminants from wafer 1500, or iii) can be removed from
atmospheric transfer chamber 1210 by robot 1212 and placed into
FOUP 1222. At this time a method of forming a gate dielectric film
1508 and a gate electrode film 1512 in Clean/Gate tool 1200 has
been described. Further processing can be used to etch a gate
electrode 1514 from film 1512 and to form source/drain regions 1516
as well as spacers 1518 in order to complete fabrication of a metal
oxide semiconductor device as shown in FIG. 15E.
Photolithography Process Tool
[0207] FIG. 18A illustrates a photolithography processing tool 1800
which can be used to clean a wafer, form a photoresist on the wafer
and then expose the wafer in a closed and controlled environment.
Photolithography process tool 1800 includes a single wafer wet
clean module, such as module 200 shown in FIG. 2A, a photoresist
track 1802 for applying, and exposing photoresist and a transfer
chamber 1804 having a wafer handling robot 1808 on a single linear
track 1806 contained therein. Wet clean station 200 and photoresist
track 1802 are each directly coupled to transfer chamber 1804 and
are each accessible by robot 1808. In an embodiment of the present
invention the photoresist track 1802 includes a bake station 1810
for removing water from a wafer to be photoresist coated, a
photoresist application station 1812, such as a spin station,
whereby a desired amount of photoresist is spun on a wafer, a soft
bake station 1814 which removes solvent from the deposited
photoresist material, and an exposure tool, such as a stepper,
where the deposited photoresist is exposed to radiation, such as
deep ultraviolet (DUV) radiation or extreme ultraviolet (EUV)
radiation through a mask used to define a pattern within the
photoresist layer.
[0208] Tool 1800 includes a filter 1820 coupled to transfer chamber
1804 for removing amine and ammonia vapor from tool 1800. In an
embodiment of the present invention, the ambient within tool 1800
is sufficiently void of amine and ammonia vapor so that they do not
affect the photoresist processing in tool 1800. Additionally, tool
1800 includes a computer/controller 124 which controls the
operation of robot 1808 as well as the various operations which
occur in clean module 200 and photoresist track 1802. Additionally,
photoresist tool 1800 can include a first FOUP 1822 coupled to a
first side of transfer chamber 1804 for providing wafers to tool
1800 through transfer chamber 1804. A second FOUP 1824 can be
included on the opposite end of transfer chamber 1806 the FOUP 1822
for removing completed wafers from photolithography process tool
1800.
[0209] In an embodiment of the present invention, as shown in FIG.
18B, a photolithography process tool 1850 optionally includes a
second wet clean chamber 200B positioned down stream of or after
the photoresist deposition module 1812 and positioned upstream or
before the exposure module 1816. In this way, the backside of the
wafer can be cleaned of particles after the photoresist has been
deposited (or spun) and before the photoresist has been
exposed.
Method of Operating Photolithography Process Tool
[0210] An example of the method of use of photolithography process
tool 1800 is illustrated in FIGS. 19A-19G. In an embodiment of the
present invention, a wafer 1900 is provided to photolithography
process tool 1800 in a FOUP 1822. Wafer 2000 has a frontside 1902
and a wafer backside 1904 opposite the wafer frontside. Generally
formed on the wafer frontside 1902 are plurality of small (less
then 0.25 um) device features 1906, such as thin film lines used to
form interconnects or electrodes. Wafer 1900 typically include a
plurality of particles 1908 undesirably formed on the frontside and
backside of the wafer 1900. In order to photolithographically
process wafer 1900, the door between transfer chamber 1804 and FOUP
1822 is opened and wafer handling device 1808 removes wafer 1900
from FOUP 1822 and brings it into transfer chamber 1804. Robot 1808
then transfers the wafer into wet clean module 200 where it is
horizontally positioned by wafer support 210 parallel to and over a
horizontally positioned plate 202 having a plurality of megasonic
transducers 204 formed on the backside of the plate. The wafer is
positioned so that the wafer backside 1904 is parallel to and
adjacent to and spaced-apart from megasonic plate 202. At this
time, the backside of the wafer is cleaned of particles 1908 by
flowing a fluid, such as DI water or a cleaning solution
comprising, for example, ammonia/peroxide/water. The cleaning
solution can include a chelating agent and/or surfactants. While
the liquid is flowing between the backside of the wafer 1904 and
plate 202, megasonic energy is applied by transducers 204 to
produce sonic waves in a direction perpendicular to the backside of
the wafer 1900. The wafer can be rotated by support 210 while
cleaning the wafer. In one embodiment of the present invention, no
fluid is provided onto the frontside 1902 of wafer 1900 while
cleaning the backside so that a liquid film 222 (shown in FIG. 2A)
is not formed on the wafer frontside. In this way, megasonic energy
is not able to transfer into a fluid on the frontside and fragile
device features 2006 formed on the wafer frontside are not
damaged.
[0211] However, in an alternative embodiment of the present
invention while cleaning the wafer backside, cleaning solution
and/or DI water can be provided onto the wafer frontside 1902 to
form a thin coat 222 (as shown in FIG. 2A) in order to clean the
wafer frontside. Once the wafer backside has been sufficiently
cleaned of particles 1908 as shown in FIG. 19B, the cleaning is
stopped and the wafer spun dry.
[0212] Next, robot 1808 removes the cleaned wafer 1900 from wet
clean module 200 and brings it into transfer chamber 1804 and then
slides down track 1806 to bake station 1810 where it places wafer
1902 into bake station 1810. While in bake station 1810 wafer 1900
is heated to a temperature of approximately 200.degree. C. in a
nitrogen ambient and at a reduced pressure in order to remove all
water vapor from wafer 1900 as shown in FIG. 19C. Bake station 1810
can include a horizontally positioned hot plate on which the
backside 1904 of wafer 1900 is situated. Next, after wafer 1902 has
been sufficiently baked to remove water residue, robot 1808 removes
the baked wafer 1902 from bake station 1810 and brings it into
transfer chamber 1804, slides down track 1806 to spin station 1812
and places wafer 1902 into spin station 1812. Spin station 1812
will typically include a rotatable plate on which the wafer is
situated and the nozzle placed above for depositing a photoresist
film thereon. Once in spin station 1812, a photoresist film 1910 is
formed on the wafer frontside 1902 as shown in FIG. 19D.
Photoresist material is an organic photo-sensitive material which
is sensitive to radiation at a certain frequency. Typically today,
photoresist films which are sensitive to deep UV (ultraviolet)
light are utilized. Additionally, if desired, adhesion promoter,
such as HMDS maybe deposited onto wafer frontside 1902 prior to
applying photoresist film 1910.
[0213] Next, after sufficient amount of photoresist 1910 has been
applied to the wafer frontside 1902, the wafer can optionally be
placed into a second wet clean chamber 200B in order to remove
particles 1908 which may have formed on the wafer backside during
the wafer coating process. In such a case, the wafer 1900 having a
photoresist film 1910 formed on the wafer frontside, is then held
by wafer support 210 horizontally above and parallel to a plate 206
as shown in FIG. 2A. The wafer backside 1904 is adjacent to the
plate 202. A fluid is then transported between the plate 1902 and
the wafer backside 1904 in order to remove particles 1908 which
develop during the photoresist deposition process. The cleaning
solution can include a chelating agent and/or surfactants. While
the liquid is flowing between the backside of the wafer 1904 and
plate 202, megasonic energy can be applied by transducers 204 to
produce sonic waves in a direction perpendicular to the backside of
the wafer 1900. The wafer can be rotated by support 210 while
cleaning the backside. During the backside cleaning of the wafer
with the photoresist materials 1910 on the frontside, no solution
is provided through nozzle 214 to the wafer frontside 1902. That
is, during the backside clean with a photoresist film on the
frontside the frontside is kept completely dry. It is to be
appreciated, that the photoresist film 1908 formed on the wafer
frontside is not to be exposed to cleaning solutions or DI water
during the wafer backside cleaning. In an embodiment of the present
invention, clean air or an inert gas, such as N.sub.2, can be blown
onto the top surface of wafer 1900 while the backside 1904 is
cleaned of particles to ensure that no backside cleaning solutions
travel around the edges of the wafer and wet or attack photoresist
film 1910 on the wafer frontside 1902. After all of the particles
1912 have been removed from the wafer backside 1904 as shown in
FIG. 19E, this optional cleaning step can be stopped. Next, the
robot 1808 removes wafer 1900 from wet clean station 1900B and
brings it into transfer chamber 1804. Robot 1808 then moves down
track 1806 to soft bake station 1814 and places wafer 1900 with
photoresist film 1910 into the soft bake station. (If backside
cleaning with photoresist film 1910 is not to be used, then the
wafer would be directly brought from the spin station into the soft
bake station 1814.) Once in soft bake station 1814 wafer 1900 is
heated to remove some of the solvents contained within photoresist
film 1910 as shown in FIG. 19F.
[0214] After the wafer 1900 has been sufficiently soft baked in
soft bake station 1814, wafer 1900 is removed from soft bake
station 1814 by robot 1808 and robot 1808 travels down track 1806
to exposure station 1816 and places wafer 1900 in exposure station
1816. In exposure station 1816 the photoresist film 1910 is exposed
to radiation, such as DUV radiation from a light source 1914 which
shines through a mask 1916 having a pattern formed therein as shown
in FIG. 19G. The mask 1916 blocks light from exposing some portions
of photoresist film 1910 and allows light to expose other portions
1920 of photoresist mask 1910. The light radiation alters the
chemical structure of the photoresist film to form light exposed
regions 1920 which can be selectively developed away with developer
from photoresist film 1910 which has not been exposed to light
(1918). In this way, a photoresist mask can be formed on substrate
1900. An excellent exposure can take place because backside
particles have been removed which could otherwise cause the image
to be out of focus. Once sufficiently exposed, the robot 1808
removes exposed wafer 1900 from exposure station 1816 and places it
in FOUP 1824.
[0215] Shown in FIG. 18C is a photolithography processing apparatus
in accordance with an embodiment of the present invention.
Photolithography processing apparatus 1880 includes a photoresist
application tool 1882, a single wafer backside cleaning tool 1884
and an exposure tool 1886. Single wafer backside cleaning tool 1884
is coupled between photoresist application tool 1882 and exposure
tool 1886. Single wafer backside cleaning tool 1884 can be said to
be a buffer station in that it is directly coupled between
photoresist application tool 1882 and exposure tool 1886. That is
backside cleaning tool 1884 is directly coupled, by for example
bolts, to the output of photoresist application tool 1882 and is
directly coupled, by for example bolts, to the input of exposure
tool 1886. In an embodiment photoresist application tool 1882,
backside clean tool 1884, and exposure tool 1886 each have their
own computer/controller for separately controlling each of their
operations.
[0216] The function of photoresist application tool 1882 is to form
a photoresist film (to subsequently be imaged) onto a wafer.
Photoresist application tool 1882 can be any well-known photoresist
application tool or track and in an embodiment it includes all
stations necessary for preparing a photoresist film for exposure in
exposure tool 1886 In an embodiment of the present invention,
photoresist application tool 1882 includes a bake station 1810, a
spin station 1812 and a soft bake station 1814 as described above.
Photoresist application tool 1882 has a wafer handling robot 1888
for transferring wafers between the various stations (e.g., between
bake station 1810, spin station 1812, and soft bake station 1814)
of photoresist application tool 1882. A wafer handling robot 1888
can be included within the photoresist application tool 1882 or can
be included in a separate transfer chamber which can access each of
the individual stations of the photoresist application tool 1882.
In an embodiment of the present invention, the wafer handler 1888
is a single wafer handling robot on a single linear track. In an
embodiment of the present invention, robot 1888 can take a wafer
from photoresist application module 1882 and insert it directly
into backside cleaning tool 1884.
[0217] Backside cleaning tool 1884 can be any suitable apparatus
which can clean and remove particles from the backside of a wafer
without exposing the frontside of the wafer, on which a photoresist
film is formed, to cleaning or wetting solutions. In an embodiment
of the present invention, the backside cleaning tool 1884 can be a
single wafer wet clean module, such as module 200, shown in FIG.
2A-2C. Other types of cleaning apparatuses, however, can be used as
long as they can clean the backside of the wafer without affecting
the frontside and a photoresist film formed thereon. For example,
backside cleaning tool can include a wafer support for holding or
rotating a wafer above a rotatable brush which is used for
dislodged particles from the wafer backside. In another embodiment
of the present invention, the backside cleaning tool can include an
air knife which utilizes air flow to create an air shear to remove
particles from the wafer backside while the wafer is rotated.
[0218] Exposure tool 1886 can be any well-known exposure tool, such
as a stepper, where photoresist material is exposed to radiation,
such as deep ultraviolet (DUV) radiation or extreme ultraviolet
(EUV) radiation through a mask used to define a pattern within the
photoresist film. Exposure tool 1886 contains a wafer handling
device 1890, such as a robot, which is able to receive a wafer from
backside cleaning tool 1884 and position the wafer within exposure
tool 1886. Robot 1890 can also remove the wafers from exposure tool
1886.
[0219] In a method of use of apparatus 1880, a wafer, such as wafer
1900 as shown in FIG. 19A is placed into photoresist application
tool 1882 where a photoresist film 1910 is formed on the wafer
frontside 1902. Ideally, wafer 1900 has been sufficiently cleaned
prior to placing into photoresist application tool 1882.
Photoresist film 1910 can be formed by any well-known technique or
series of steps, such as illustrated above. In an embodiment of the
present invention, photoresist film 1900 is formed utilizing a
pre-bake step such as set forth in FIG. 19C and accompanying
description, a photoresist spin step such as set forth in FIG. 19D
and accompanying description, and a soft bake step as set forth in
FIG. 19F and accompanying description. Robot 1888 moves a wafer
1900 between the various stations of the photoresist application
tool 1882.
[0220] Once a suitable photoresist film 1910 has been formed on the
frontside 1902 of wafer 1900, robot 1888 transfers wafer 1900 from
the photoresist application tool 1882 to the backside clean module
1884 where the backside 1904 of wafer 1900 is cleaned of particles.
In an embodiment of the present invention, the backside clean
occurs after the photoresist film 1910 has been formed and after
all necessary processes have occurred which are necessary prior to
the exposure of the photoresist 1910. In an embodiment of the
present invention, the backside clean occurs directly after a soft
bake step such as shown in FIG. 19F. In an embodiment of the
present invention, the backside cleaning occurs directly before or
immediately before placement in exposure tool 1886 and exposure
therein. In an embodiment of the present invention, the backside
cleaning occurs in a single wafer wet cleaning module 200 shown in
FIG. 2A-2C. In such a case, the wafer 1900 having a photoresist
film 1910 formed on the wafer frontside 1902 is then held by wafer
support 210 horizontally above and parallel to plate 202 as shown
in FIG. 2A. Wafer backside 1904 is adjacent to plate 202. A fluid
such as DI water or a cleaning solution comprising, for example
ammonia/peroxide/water, is then transported between plate 202 and
wafer backside 1904 in order to remove particles 1908 which develop
during the photoresist formation process. The cleaning solution can
include a chelating agent and/or surfactants. While the liquid is
flowing between the backside of the wafer 1904 and plate 202,
megasonic energy is applied by transducers 204 to produce sonic
waves in a direction perpendicular to the backside of the wafer
1900. The wafer can be rotated by support 210 while cleaning the
backside. During backside cleaning of the wafer with photoresist
materials 1910 on the frontside, no solution is provided through
nozzle 214 to the wafer frontside 1902. That is, during the
backside clean the photoresist film on the frontside is kept
completely dry. It is to be appreciated that the photoresist film
1910 formed on the wafer frontside is not to be exposed to cleaning
solution or DI water during the wafer backside cleaning. In an
embodiment of the present invention clean air or an inert gas, such
as N.sub.2, can be blown onto a top surface of wafer 1900 while the
backside 1904 is cleaned to insure that no backside cleaning
solution travels around the edges of the wafer and wets or attacks
the photoresist film 1910 on the wafer frontside 1902. The inert
gas can be blown onto the wafer frontside through nozzle 214 or a
separate nozzle can be provided.
[0221] After the backside of wafer 1900 has been sufficiently
cleaned, the wafer 1900 is removed from the backside cleaning
chamber 1884 by robot 1890 and is placed into exposure tool 1886.
In exposure tool 1886, the photoresist film 1910 is exposed to
radiation, such as DUV radiation from a light source 1940 which
shines through a mask 1916 having a pattern formed therein as shown
in FIG. 19G. The light radiation alters the chemical structure of
the photoresist film to form light exposed regions 1920 which can
be selectively developed away with a developer from photoresist
film 1910 which has not been exposed to light (1918). A high
quality exposure can take place because backside particles have
been removed which could otherwise cause the image to be out of
focus. Thus, a high quality photolithography processing apparatus
and method have been described.
[0222] FIG. 18D illustrates another embodiment of a
photolithography processing apparatus. Photolithography processing
apparatus 1892 includes a photoresist application tool or track
1882 as described above, a buffer station 1894 and an exposure tool
1886 as described above. Buffer station 1894 is located between
photoresist application tool 1882 and exposure tool 1886. Buffer
station 1894 includes a transfer chamber 1896 which has one side
directly coupled to the output of a photoresist application tool
1886 and a second side which is directly coupled to the input of
exposure tool 1886. Buffer station 1894 also includes a backside
cleaning tool 1884, as described above, which is directly coupled
to transfer chamber 1896 on a third side. In an embodiment of the
present invention, buffer tool 1894 includes a backside integrated
particle monitoring tool 1894 for inspecting the wafer backside for
particles. In an embodiment of the present invention, backside
integrated particle monitoring tool can include a light emitter for
shining light onto the backside of the wafer and collectors or
detectors for collecting the light scattered from the wafer
backside to inspect the wafer backside for particles. An example of
suitable backside particle monitoring tool is IPM tool 300 shown in
FIG. 3. IMP Tool 300, however, would be configured to scan the
wafer backside as opposed to the frontside as shown in FIG. 3.
Transfer chamber 1896 has a wafer handling robot 1899 contained
therein for handling a single wafer. Wafer handling robot 1899 can
receive a wafer from robot 1888, of photoresist application tool
1882 and robot 1899 can provide a wafer to robot 1890 of exposure
tool 1886. Additionally, robot 1899 can transfer a wafer into
backside cleaning tool 1884 and into backside particle monitoring
tool 1897, if used.
[0223] In a method of use, of photolithography apparatus 1892 shown
in FIG. 18D, a wafer is placed into photoresist application tool
1882 where it travels down the track and enters the various process
stations used to form a photoresist film on the wafer and to
prepare the photoresist film for exposure in tool 1886. Once a
suitable photoresist film has been formed on the wafer frontside,
the wafer is transferred by robot 1888 to robot 1899 where it is
brought into transfer chamber 1896. In an embodiment of the present
invention, robot 1899 transfers the wafer into backside cleaning
tool 1884 where the wafer backside is cleaned of particles as
discussed above. After a sufficient backside cleaning, the wafer is
removed from backside cleaning chamber 1884 by robot 1899 and
brought back into transfer chamber 1896. In an embodiment of the
present invention, where a backside particle monitoring tool 1897
is provided, after backside cleaning the wafer, the wafer can be
transferred by robot 1899 into backside integrated particle
monitoring tool 1897 where its backside is inspected for particles.
If the backside is suitably clean, the wafer can be removed by
robot 1899 from backside particle monitoring tool 1897 and brought
into transfer chamber 1896. Robot 1899 then transfers the wafer to
the robot 1890 of exposure tool 1886 which positions the wafer for
exposure as described above. In an embodiment of the present
invention, if the backside particle monitoring tool determines that
the backside is not sufficiently cleaned, the wafer can be
transferred back into backside cleaning module 1884 for additional
backside cleaning. After additional backside cleaning, the wafer
can be transferred back into backside particle monitoring tool 1897
and reinspected for particles.
[0224] In yet another embodiment of the present invention, after
the photoresist film has been formed and prepared in photoresist
application tool 1882, the wafer can be first transferred into
backside inspection tool 1894 to inspect for particles and then the
wafer transferred into backside cleaning tool 1884. In this way,
information regarding the backside particles can be used to
determine the type and amount of backside cleaning in backside
cleaning chamber 1884. After a sufficient backside cleaning in
backside cleaning apparatus 1884 the wafer can be transferred back
into backside particle monitoring tool 1897 and the wafer
reinspected prior to transferring the wafer into exposure tool
1886. Thus, a high quality photolithographic processing apparatus
has been described as well as its method of operation.
Computer/Controller
[0225] FIG. 20A illustrates a computer/controller 124 which can be
used to control the movement and processing of a wafer in a tool,
such as tool 100, 600, 1200 and 1800 in accordance with the present
invention. Computer/controller 124 includes a memory 740, such as a
hard drive or other type of memory, a processor 720 and an
input/output device, such as a CRT Monitor 730 and a keyboard 732.
The input/output device is used to interface between a user and
computer/controller 124. Processor 720 executes a system control
software program stored in computer readable medium, such as memory
740. Processor 720 executes the system control software and
provides and receives control signals for the tool which controls
the transfer of wafers through the tool and which provides the
specific control signals necessary to achieve the specific
processing parameters for each of the modules coupled to the tool,
such as process temperature, process gas/fluid flows and process
pressure, etc.
[0226] The process for processing a wafer in accordance with the
embodiment of the present invention can be implemented using a
computer program product which is stored in memory 740 and is
executed by processor 720. The computer program code can be written
in any conventional computer readable program language, such as
68000 Assembly Language, C, C++, Pascal, Fortran, or others.
Suitable program code is entered into a single file or multiple
files using conventional text editor and stored or embodied in a
computer usable medium, such as a memory system of the computer. If
the entered code text is in the high level language, a code is
compiled and the resultant compiler code is then linked with an
object code of precompiled windows library routines. To execute the
link compiled object code, the system user invokes the object code
causing the computer system to load the code in memory from which
the processor reads and executes the code to perform the task
identified in the program. Also stored in memory 740 are process
parameters, such as process gas/fluid flow rates and composition,
temperatures, pressures, and times necessary to carry out the
deposition of films, the etching of films, the wet cleaning of
wafers, the ashing of wafers, as well as the monitoring and
recording of metrology of the wafer, such as film thickness
uniformity and defects.
[0227] FIG. 20B illustrates an example of the hierarchy of the
system control computer program stored in memory 740. The system
control program includes a tool manager subroutine 2000. The tool
manager subroutine 2000 also controls the execution of various
chamber component subroutines which control the operation of the
chamber components necessary to carry out the selected process set
in the various chambers or modules of the tool. Examples of chamber
component subroutines are process gas/fluid control subroutine
2002, pressure control subroutine 2004, temperature control
subroutine 2008, and a wafer support subroutine 2010. Additionally,
the tool manager subroutine includes a wafer history subroutine
2012 and a wafer transfer subroutine 2014. Those having ordinary
skill in the art would readily recognize that other chamber control
subroutines can be included depending on what processes are desired
to be performed in the tool and process modules. In operation, the
tool manager subroutine 2000 selectively schedules or calls a
process component subroutines in accordance with the particular
process set being executed. Typically, the tool manager subroutine
2000 includes steps of monitoring the various chamber components,
determining which components need to be operated based on the
process parameters of the process set to be executed and causing
execution of a chamber component subroutine responsive to the
monitoring and determining step.
[0228] The process gas/fluid control subroutine 2002 has a program
code for controlling the reactive gas/fluid composition and flow
rates. The process gas/fluid control subroutine 2002 controls the
open/close position of the safety shut off valves, and also ramps
up and down the mass flow controllers to obtain the desired
gas/fluid flow rates. The process gas/fluid control subroutine 2002
is invoked by the tool manager subroutine 2000 as are all chamber
component subroutines and receives from the tool manager subroutine
process parameters related to the desired gas/fluid flow rates.
Typically, the process gas/fluid control subroutine 2002 operates
by opening the gas supply lines and repeatedly (i) reading the
necessary mass flow controllers, (ii) comparing the readings to the
desired flow rates received from the tool manager subroutine 2000
and (iii) adjusting the flow rates of the gas/fluid supply lines as
necessary. Furthermore, the process gas/fluid control subroutines
2002 includes steps for monitoring the gas/fluid flow rates for
unsafe rates, activating safety shut off valves when unsafe
conditions is detected.
[0229] The process control subroutine 2004 comprises program code
for controlling the pressure in the chamber of the various modules,
as well as the pressure within the sub-atmospheric transfer chamber
and load locks by regulating the size of the opening of the
throttle valves which are set to control the chamber pressure to
the desired level in relation to the total process gas flow, size
of the process chamber, and pumping set point pressure for the
exhaust system. When the pressure controls subroutine 2004 operates
to measure the pressure in a chamber by reading one or more
conventional pressure manometers connected to the chamber, compared
to measure values to the target pressure and adjust the throttle
valve according to the PID values obtained from the pressure table.
Alternatively, the pressure control subroutine 2004 can be written
to open or close the throttle valve to a particular opening size to
regulate the chamber to a desired pressure.
[0230] The temperature control subroutine 2008 comprises program
code for controlling the power provided to heaters or lamps which
are used to heat the substrate or wafer. The temperature control
subroutine 2008 is also invoked by the chamber manager subroutine
2000 and receives a target or set point temperature parameter. The
temperature control subroutine 2008 measures the temperature by
measuring voltage output of a temperature measurement device
directed at the susceptor or wafer and compares the measured
temperature to the set point temperature, and increases or
decreases power applied to the heater or lamps to obtain the set
point temperature.
[0231] The wafer support subroutine 2010 has a program code for
controlling the positioning and rotation rates of a wafer support
members, such as susceptors, during the processing of wafers and
during the loading and unloading of wafers into the module or
chamber. The wafer support subroutine controls the motors which
control the height position of the wafer support and the motors
which control the rotation rates of the wafer support.
[0232] The wafer history subroutine 2012 has program code for
storing and retrieving as well as analyzing the process history of
a wafer in the tool. Wafer history subroutine 2012 store data
detailing the processes that have occurred to a wafer processing in
the tool as well as metrology information on each wafer, such as
film thickness and uniformity maps as well as defect maps.
[0233] The wafer transfer subroutine 2014 comprises program code
for controlling the transfer of a wafer throughout the tool. Wafer
transfer subroutine 2014 determines which chamber or modules of the
tool a wafer is to be processed in as well as the order of the
processing. Wafer transfer subroutine 2014 can utilize information
from the wafer history subroutine to determine which processes a
wafer is to experience. For example, after a metrology scan to
determine the number or type of particles on a wafer, the wafer
transfer subroutine can be invoked to determine whether or not the
wafer should be further wet cleaned or ashed or be sent to the next
module in the process. The wafer subroutine can utilize wafer
metrology information to determine the subsequent processing of the
wafer.
[0234] Thus, novel atmospheric/sub-atmospheric process tools and
their methods of use have been described.
* * * * *