U.S. patent application number 11/825671 was filed with the patent office on 2008-01-24 for clean ignition system for wafer substrate processing.
This patent application is currently assigned to Accretech USA, Inc.. Invention is credited to Joel Brad Bailey, Paul F. Forderhase, Jean-Michel Claude Huret, Michael D. Robbins, Satish Sadam, Scott Allen Stratton.
Application Number | 20080017316 11/825671 |
Document ID | / |
Family ID | 46328969 |
Filed Date | 2008-01-24 |
United States Patent
Application |
20080017316 |
Kind Code |
A1 |
Bailey; Joel Brad ; et
al. |
January 24, 2008 |
Clean ignition system for wafer substrate processing
Abstract
An edge area of the substrate processing device is disclosed.
The edge area being processed is isolated from the remainder of the
substrate by directing a flow of an inert gas through a plenum near
the area to be processed thus forming a barrier while directing a
flow of reactive species at an angle relative to the top surface of
the substrate towards the substrate edge area thus processing the
substrate edge area. A flow of oxygen containing gas into the
processing chamber together with a negative exhaust pressure may
contribute to the biasing of reactive species and other gases away
from the non-processing areas of the substrate. A clean ignition
system is used to ignite the combustion flame.
Inventors: |
Bailey; Joel Brad; (Austin,
TX) ; Huret; Jean-Michel Claude; (Cedar Park, TX)
; Forderhase; Paul F.; (Austin, TX) ; Sadam;
Satish; (Round Rock, TX) ; Stratton; Scott Allen;
(Pflugerville, TX) ; Robbins; Michael D.; (Round
Rock, TX) |
Correspondence
Address: |
HARNESS, DICKEY & PIERCE, P.L.C.
P.O. BOX 828
BLOOMFIELD HILLS
MI
48303
US
|
Assignee: |
Accretech USA, Inc.
Bloomfield Hills
MI
|
Family ID: |
46328969 |
Appl. No.: |
11/825671 |
Filed: |
July 6, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11131611 |
May 18, 2005 |
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11825671 |
Jul 6, 2007 |
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10401074 |
Mar 27, 2003 |
6936546 |
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11131611 |
May 18, 2005 |
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11230261 |
Sep 19, 2005 |
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11825671 |
Jul 6, 2007 |
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11230263 |
Sep 19, 2005 |
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11825671 |
Jul 6, 2007 |
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11417297 |
May 2, 2006 |
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11825671 |
Jul 6, 2007 |
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60819521 |
Jul 7, 2006 |
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60376154 |
Apr 26, 2002 |
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Current U.S.
Class: |
156/345.29 ;
431/258 |
Current CPC
Class: |
H01L 21/681 20130101;
G01C 25/00 20130101; H01J 37/32366 20130101; H01L 21/31116
20130101; H01L 21/6708 20130101; H01L 21/67069 20130101; H01L
21/31612 20130101 |
Class at
Publication: |
156/345.29 ;
431/258 |
International
Class: |
C23F 1/00 20060101
C23F001/00; F23Q 7/22 20060101 F23Q007/22 |
Claims
1. A substrate processing apparatus for processing the substrate
with a combustion flame of hydrogen and a non-oxygen oxidizer,
comprising: a processing chamber for receiving the substrate and
for confining a clean environment for the combustion flame; a
processing nozzle assembly within the processing chamber for
directing the combustion flame onto the substrate; a source for
fuel and the oxidizer operationally attached to the processing
chamber; an igniter assembly having a ceramic hot body igniter
defining an interior cavity; a heating element disposed within the
interior cavity; a means for energizing the heating element; and an
igniter nozzle assembly operably coupled to a fuel source, said
igniter assembly configured to direct an initiation combustion
flame within a predetermined distance from the processing nozzle
assembly.
2. The substrate processing apparatus for processing the substrate
with a combustion flame of claim 1, wherein the hot body igniter
comprises a sapphire body.
3. The substrate processing apparatus for processing the substrate
with a combustion flame of claim 1, wherein the hot body igniter
comprises an optically clear ceramic.
4. The substrate processing apparatus for processing the substrate
with a combustion flame of claim 1, wherein the heater element is
electrically connected to a power source.
5. The substrate processing apparatus for processing the substrate
with a combustion flame of claim 1, further comprising a power
source configured to apply an electromagnetic wave to the heater
element.
6. The substrate processing apparatus for processing the substrate
with a combustion flame of claim 5, wherein the power source is one
of a laser or a laser diode.
7. The substrate processing apparatus for processing the substrate
with a combustion flame of claim 1, further comprising a power
source configured to apply an electromagnetic wave to the heater
element.
8. The substrate processing apparatus for processing the substrate
with a combustion flame of claim 1, wherein the processing chamber
maintains a substantially atmospheric pressure.
9. The substrate according to claim 1 wherein the ceramic has a
melting temperature greater than 3000.degree. k.
10. An igniter assembly comprising: a sapphire body; a heating
element thermally coupled to the sapphire body; a power source
configured to apply an electromagnetic wave to the heating element;
and an igniter nozzle assembly disposed adjacent to the sapphire
body, said nozzle assembly being coupled to a fuel source.
11. The igniter assembly according to claim 10 wherein the sapphire
body defines an interior chamber and wherein the heating element is
disposed within the chamber.
12. The igniter assembly according to claim 10 wherein the power
source is a laser diode.
13. The igniter assembly according to claim 12 wherein the power
source is a laser.
14. The igniter assembly according to claim 11 wherein the power
source is an electrical current supply.
15. The igniter assembly according to claim 10 wherein a power
source transmits photons at a predetermined frequency and the
sapphire body is transparent at the predetermined frequency.
16. The igniter assembly according to claim 10 wherein the igniter
nozzle defines a gas jet along a first line and wherein the
sapphire body is disposed a first predetermined distance from the
line.
17. The igniter assembly according to claim 16 further comprising
at least one process gas nozzle, said process gas nozzle is
disposed a second predetermined distance from the line.
18. The igniter assembly according to claim 19 further comprising
an air knife disposed between the igniter assembly and the process
gas nozzle.
19. A method for igniting a flame comprising: disposing a heating
element within an igniter assembly; energizing the heating element
so as to heat the igniter assembly to a predetermined ignition
temperature; passing a fuel past the ignition nozzle at a first
rate past the igniter assembly to ignite a flame; passing the flame
past a plurality of nozzles to ignite a plurality of processing
flames from the nozzles.
20. The method of igniting a flame according to claim 19 further
comprising passing an air dam in front of the first flame.
21. The method of ignition according to claim 19 further comprising
passing a non-flammable gas though the ignition nozzle at a second
predetermined rate.
22. The method of igniting a flame according to claim 21 wherein
the second predetermined rate is greater than the first
predetermined rate.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 60/819,521, filed on Jul. 7, 2006. This application
is a continuation-in-part of U.S. patent application Ser. No.
11/131,611, filed on May 18, 2005, which is a divisional
application of 10/401,074, filed on May 27, 2003, now U.S. Pat. No.
6,936,546, issued Aug. 30, 2005, which claims priority U.S.
Provisional Application 60/376,154, filed Apr. 26, 2002. This
application is also a continuation-in-part of U.S. patent
application Ser. No. 11/230,261, filed Sep. 19, 2005. This
application is also a continuation-in-part of U.S. patent
application Ser. No. 11/230,263, filed Sep. 19, 2005. This
application is also a continuation-in-part of U.S. patent
application Ser. No. 11/417,297, filed May 2, 2006. The disclosure
of the above applications is incorporated herein by reference.
FIELD
[0002] The present disclosure relates to a method and apparatus for
processing of a substrate. More particularly, a method and
apparatus for concentrically positioning a substrate relative to an
apparatus for processing the edge of the substrate is disclosed.
Furthermore, a seal arrangement for the alignment apparatus is also
provided. In addition, processes for dry etching of a substrate
with a combustion flame are disclosed.
BACKGROUND
[0003] The statements in this section merely provide background
information related to the present disclosure and may not
constitute prior art.
[0004] During the manufacture of integrated circuits, silicon
substrate wafers receive extensive processing including deposition
and etching of dielectrics, metals, and other materials. At varying
stages in the manufacturing process it is beneficial to "clean" the
edge area of the wafer to remove unwanted films and contaminants
including particles that develop as a result of the wafer
processing.
[0005] This includes films and contaminants that develop on a near
edge top surface (primary processed side), near edge back surface,
and edge (including, top bevel, crown and bottom bevel) of the
wafer (hereinafter "edge area" refers generally to the near edge
top surface, near edge bottom surface, and edge in combination or
individually). Removal of films and contaminants is desirable to
prevent the potential of particulate migration into the device
portion of the wafer. Potential contaminant particles are generated
during wafer handling, processing, and as a result of "pop-off"
effect due to film stress.
[0006] It is a challenge to process and thus remove edge area thin
films and contaminants in an efficient and cost effective manner
without affecting the remainder of the wafer that contains
in-process devices. This challenge is exacerbated by use of
chemistries and processes that may adversely impact the in-process
device portion of the wafer.
[0007] Many of the existing film removal techniques fail to
properly remove polymers, edge beads, dielectric or tantalum,
particularly from the edge area, as may be desired by the wafer
manufacturer. Specifically, it is desirable to maximize the usable
surface area of a wafer thus minimizing any unusable edge area with
the objective of maximizing die yield. Reduction in functional die
produced from the usable surface area is termed yield loss and is
generally undesirable and has a negative cost impact. Accordingly,
a need in the art exists for improved processing methods and
apparatus to remove various front side, back side and edge area
films and contaminants in a cost effective and efficient
manner.
SUMMARY
[0008] According to the teachings of the present invention, a
substrate processing apparatus for processing the substrate with a
combustion flame of hydrogen and a non-oxygen oxidizer, is
provided. The system has a processing chamber for receiving the
substrate and for confining a clean environment for the combustion
flame. A processing nozzle assembly is disposed within the
processing chamber for directing the combustion flame onto the
substrate. A source for fuel and the oxidizer operationally
attached to the processing chamber. An igniter assembly having a
ceramic hot body igniter defining an interior cavity is provided.
Disposed within the interior cavity is a heating element. An
igniter nozzle assembly operably coupled to a fuel source is
disposed within the chamber. The igniter assembly is configured to
direct an initiation combustion flame within a predetermined
distance from the processing nozzle assembly.
[0009] According to the teachings of another embodiment, a clean
igniter assembly is provided having a sapphire body. A heating
element is thermally coupled to the sapphire body. A power source
configured to apply an electromagnetic wave to the heating element.
An igniter nozzle assembly is disposed adjacent to the sapphire
body, the nozzle assembly being coupled to a fuel source.
[0010] According to the teachings of another embodiment, method for
igniting a flame is provided. The method includes disposing a
heating element within a ceramic igniter assembly. The heating
element is energized so as to heat the igniter assembly to a
predetermined ignition temperature. A fuel is passed through an
ignition nozzle at a first rate past the igniter assembly to ignite
a flame. The ignition flame is passed the flame past a plurality of
nozzles to ignite a plurality of processing flames from the
nozzles.
[0011] A substrate edge processing method is disclosed for
isolating for isolating and processing a portion of a substrate.
The portion to be processed extends from an edge of the substrate
radially across the top surface of the substrate to another part of
the edge of the substrate, thus isolating an edge area to be
processed. A pressure differential barrier is formed between the
portion of the substrate being processed and the remainder of the
substrate. A reactive species is directed towards the processed
portion of the substrate at an angle greater than parallel to the
top surface of the substrate and less than vertical to the top
surface of the substrate. A clean flame igniter is used to ignite
the nozzles.
[0012] In other embodiments, an edge area of the substrate to be
processed is isolated from the remainder of the substrate by
directing a flow of an inert gas through a plenum near the area to
be processed thus forming a barrier while directing a flow of
reactive species at an angle relative to the top surface of the
substrate towards the substrate edge area thus processing the
substrate edge area. A flow of oxygen containing gas into the
processing chamber together with a negative exhaust pressure may
contribute to the biasing of reactive species and other gases away
from the non-processing areas of the substrate.
[0013] The described method and apparatus allows for precise
processing of portions of the substrate particularly the substrate
edge area without allowing for encroachment in the excluded area.
Flow control as a part of the apparatus isolator structure in
combination with pressure differentials effectively limits movement
of reactive species into the area excluded. Using directed flow of
the reactive species to the edge area of the substrate allows for a
high etch rate and resulting overall significant improvement of
throughput of processed substrates. In sum, the system provides for
a clean, effective, and efficient method and apparatus for
processing the edge area of substrates in a manner that is highly
desired for achieving low contamination of the device portion of
the substrate.
[0014] Also disclosed is a multi-axis motion seal (i.e. labyrinth)
for sealing the processing chamber during processing of the wafer.
The seal functions in association with a wafer chuck. The seal and
processing chamber define a vacuum chamber connected to a vacuum
that is movable in cooperation with the alignment system.
[0015] In addition, processes for combustion flame based processing
of the wafer are disclosed. The disclosed chemistries react in a
combustion flame to produce a reactive species for processing the
wafer in a precise and efficient manner. A particle free igniter is
used to ignite the combustion flame.
[0016] In another embodiment, a system is provided for dielectric
film removal from near edge regions. These films are etched using
H.sub.2:NF.sub.3 dominant chemistries. Certain metal films can also
be removed. Examples include tungsten and tantalum. Many metal
oxide or nitride films can also be etched.
[0017] Further areas of applicability of the present invention will
become apparent from the detailed description provided hereinafter.
It should be understood that the detailed description and specific
examples, while indicating the preferred embodiment of the
invention, are intended for purposes of illustration only and are
not intended to limit the scope of the invention.
DRAWINGS
[0018] The drawings described herein are for illustration purposes
only and are not intended to limit the scope of the present
disclosure in any way.
[0019] FIGS. 1A-1C are cross-sectional schematics depicting a
system for concentric wafer process application;
[0020] FIG. 2 is a top schematic depicting exchange/centering and
processing positions of a wafer within a process chamber;
[0021] FIG. 3 is a side schematic depicting exchange/centering and
processing positions of a wafer within a process chamber;
[0022] FIG. 4A depicts a side sectional view of a labyrinth seal
assembly in relationship to a processing chamber and chuck
assembly;
[0023] FIG. 4B depicts a top sectional view of a labyrinth seal
assembly in relationship to a processing chamber and chuck
assembly;
[0024] FIG. 5 represents a side sectional view of the isolator
chamber shown in FIG. 1A;
[0025] FIG. 6A depicts a top view of a plurality of nozzle bodies
relative to an edge of a wafer;
[0026] FIGS. 6B through 6F represent side views depicting bevel
nozzles at a wafer bevel region;
[0027] FIGS. 7 through 8G represent cross-sectional views of pre
and post processed wafers;
[0028] FIGS. 9A-9C represent side views depicting alternate nozzle
configurations at a wafer bevel region;
[0029] FIG. 10 depicts a schematic view of a misaligned wafer at
two different rotational positions relative to an aligned position
within the exchange/centering apparatus;
[0030] FIGS. 11-12B detail an optical inspection system of the
present disclosure;
[0031] FIG. 13 represents an exploded cross sectional view of a
portion of the processing chamber and the isolator assembly shown
in FIG. 1;
[0032] FIGS. 14A and 14B are sectional views of the sealing
mechanism of the system shown in FIG. 3;
[0033] FIG. 15 represents a perspective sectional view of the
sealing mechanism shown in FIGS. 14A and 14B;
[0034] FIGS. 16A and 16B represent cross sectional views of the
system shown in FIG. 3;
[0035] FIGS. 17A-17C represent an exploded view of the isolator
assembly shown in FIG. 13;
[0036] FIGS. 18A and 18B represent perspective views of the nozzle
assembly of FIG. 17A;
[0037] FIGS. 19A and 19B represent a nozzle usable in the nozzle
assembly of FIGS. 18A and 18B;
[0038] FIGS. 20A and 20B represent an alternate nozzle usable in
the nozzle assembly of FIGS. 18A and 18B;
[0039] FIGS. 21A and 21B represent an alternate nozzle
assembly;
[0040] FIGS. 22a and 22b represent nozzle subplates as shown in
FIGS. 21A and 21B;
[0041] FIGS. 23A and 23B represent cross sectional views of an
alternate igniter assembly according to the present teachings;
[0042] FIGS. 24 through 25B represent top and side views of the
igniter and nozzle assemblies;
[0043] FIG. 26 represents a perspective view of an alternate clean
ignition assembly;
[0044] FIG. 27 represents a top view of a flame sense system for
use in the wafer processing system according to FIG. 1A; and
[0045] FIGS. 28 and 29 represent responses detected by the flame
sense system.
DETAILED DESCRIPTION
[0046] The following description is merely exemplary in nature and
is not intended to limit the present disclosure, application, or
uses.
[0047] FIGS. 1A and 1B represent a system level view of the
components and methods required to achieve concentric process
application utilizing a wafer processing system according to the
teachings herein. One example relates to selectively applying
chemistry to the near edge region of a wafer. Other possibly
applicable methods and apparatus are disclosed in U.S. patent
application Ser. Nos. 11/230,261 and 11/417,297 which are both
incorporated by reference.
[0048] Central to the present disclosure's near edge film removal
technology is the ability to apply reactive gas to a wafer in a
highly concentric and precise fashion. Process application is
typically sensitive to wafer or substrate eccentricity variation in
the range of 50 to 100 .mu.m. Multiple subsystems are required to
achieve this type of process application.
[0049] FIG. 1A shows a system level schematic view of the overall
system for concentric wafer process application. The process
chamber 22 contains the isolator 25 and diffuser 24 for controlled
application of reactive gas to the near edge wafer region. The
R-Z-.theta. or xyz-.theta. wafer movement alignment module or
system 27 is shown in the wafer load position where the laser
micrometer 15 measures the trajectory of the wafer edge during the
centering routine. Lift pins 16 are also shown.
[0050] The equipment front end module 17 contains a robot and the
pre-aligner station 19. Wafers are processed from a front opening
unified pod. The utility cabinet 20 contains control electronics,
computer(s), endpoint equipment, gas delivery equipment and other
facilities interconnects. Process gases 21 are connected to the
module and flow regulated by appropriate mass flow controllers
(MFC's) 52. Other facilities connections such as exhaust 56 and
cooling water 58 are also connected.
[0051] Referring generally to FIGS. 1A-9C, an embodiment of the
wafer edge area processing system 20 (the "system") of the
invention has a processing chamber 22 with an isolator 25 and wafer
alignment module 27 with associated wafer chuck 28 disposed
therein. A wafer 26 is retained on top of the wafer chuck 28 with
the wafer 26 having a top surface 30, bottom surface 32, and edge
area 33 (including edge and near edge as shown by lighter line
proximal to edge) that surrounds the radial perimeter of the wafer
26. The isolator 25 has an upper section 38 extending over a
portion of the top surface 30 of the wafer 26 and a lower section
39 extending over a portion of the bottom surface 32 of the wafer
26. The inside of the isolator 25 has a processing area for
processing the edge area 33 of the wafer 26. The processing area
leads into an exhaust plenum 41 connected to an exhaust system 56
for exhausting gases, process byproducts, and condensation.
[0052] Disposed within the upper section 38 of the isolator 25 are
a first nozzle 45 and a second nozzle 49. Both nozzles are
configured to emit a directed flow of reactive species towards the
edge area 33 of the wafer 26. First nozzle 45 is offset from an
axis perpendicular to a plane that is common with the top surface
30 of the wafer 26 (the "wafer plane"). First nozzle 45 is pointed
towards the top surface 30 at an angle of 80.degree.+/-5.degree.
relative to the wafer plane. Second nozzle 49 is offset by an angle
of 45.degree.+/-5.degree. to the wafer plane. Second nozzle 49 is
also offset by .about.15.degree. from a plane perpendicular to the
wafer plane that runs through the center of the isolator 25 and
center of the wafer 26.
[0053] First nozzle 45 is connected to a first channel 48 disposed
in the upper section 38. First channel 48 leads to a gas line 47.
Second nozzle 49 is connected to a second channel 53 disposed in
the upper section 38. Second channel 53 leads to the gas line 47.
First nozzle 45 and second nozzles 49 are connected via the gas
line 47 to a reactive gas species source. Optionally, the first and
second channels 48 and 53 can be coupled to sources having
differing chemistry.
[0054] First nozzle 45 is positioned for bevel and crown processing
at a distance of 0.1 to 0.5 mm from the edge of the wafer 26 and
1.3 to 1.8 mm distance from the top surface 30 of the wafer 26.
Second nozzle 49 is positioned 0.5 to 3.0 mm in from the edge of
the wafer 26 and 0.6 to 1.1 mm distance from the top surface 30 of
the wafer 26. Radial position of the nozzles and distance from the
wafer surface is dependent upon desired edge exclusion area and is
also process and film dependent.
[0055] Reactive gas species source either provides a reactive gas
species or component reactants for forming the reactive gas
species. Reactive gas species can be generated via near atmospheric
pressure techniques. This includes near atmospheric capacitively
coupled plasma source (i.e., APJET), as described in U.S. Pat. No.
5,961,772, incorporated herein by reference or inductively coupled
plasma discharge (i.e., ICP torch), as described in U.S. Pat. No.
6,660,177, incorporated herein by reference or combustion
flame.
[0056] Spontaneous etchants, for example F.sub.2, O.sub.3, or HF
can also be used. Advantageously, none of these reactive species
techniques produce ion bombardment characteristic of an ionic
plasma thus minimizing surface and device damage potential.
Further, although envisioned, none of these techniques requires a
vacuum chamber together with associated equipment.
[0057] An upper purge plenum 88 disposed in the upper section 38
extends at or near the edge of the top surface of the wafer 26,
above and across an area of the wafer to be processed to at or near
another edge of the top surface 30 of the wafer 26. The upper purge
plenum 88 is .about.3.0 mm wide and extends for a total path length
of .about.37.5 mm. The upper purge plenum 88 is part of a tuned
flow system which prevents reactive gas migration out of the
processing area.
[0058] The upper purge plenum 88 is connected to a first purge
channel 92 that is connected to a purge gas source 96 via a purge
gas line 94. The purge gas source 96 supplies an inert gas, for
example, argon that is fed via the first purge channel 92 into the
upper purge plenum 88. Alternatively, the upper purge plenum 88 can
provide CDA or oxygen containing gas, which augments the reaction
of the reactive gas.
[0059] The use of oxygen containing gas allows the reaction of
unreacted H.sub.2. This also compensates for extreme length
limitations and allows for a higher volume fraction of NF.sub.3.
The increased NF.sub.3 volume fraction leads to enhanced etched
rates as well as an enhancement of throughput. Although one purge
channel is seen disposed in the upper section 38 of the isolator
25, more than one channel may be present for directing a flow of
purge gas into the upper purge plenum 88. Purge channels have an
inside diameter of 2.00 mm. The flow of purge gas into the upper
purge plenum 88 creates a pressure differential in the area of the
top surface 30 surrounded by the upper purge plenum 88 resulting in
a barrier between the top surface 30 and the edge area 33 of the
wafer 26 being processed.
[0060] The upper purge plenum 88 is separated from the top surface
30 of the wafer 26 by an inside baffle 100. Inside baffle 100
follows along the inside perimeter of the upper purge plenum 88 and
is separated from the wafer 26 by a gap of 0.30 to 0.80 mm. An
outside baffle 104 follows along the outside perimeter of the upper
purge plenum 88 and is separated from the wafer 26 by a gap of 0.50
to 1.10 mm. As seen, outside baffle 104 is wider and closer to the
top surface 30 of the wafer 26 than the inside baffle 100. This
facilitates forming a pressure induced barrier around the
in-process portion of the wafer 26 by creating a pressure
differential biasing a flow of a purge gas in a direction across
inside baffle 100 into the processing area of the isolator 25.
[0061] A second purge channel 108 is disposed in the lower section
39 of the isolator 25. This is connected by the purge gas line 94
to the purge gas source 96. Second purge channel 108 is for feeding
purge gas to a lower purge plenum 114. Similarly to the upper purge
plenum 88, the lower purge plenum 114 extends from at or near the
edge area 33 of the wafer 26 below and across the bottom surface 32
to at or near another location of the edge of the wafer 26.
Similarly to the upper purge plenum 88, the lower purge plenum 114
is disposed between a lower inside baffle 112 and a lower outside
baffle 118. The lower purge plenum 114 together with the lower
inside baffle 112 and lower outside baffle 118 bias a flow of purge
gas in a direction across the lower inside baffle 112 and across
the bottom surface 32.
[0062] Wafer chuck 28 is movable in r-.theta.-z or xyz-.theta.
directions, using module 27, for positioning the wafer 26 and
rotating it within a slot of the isolator 25 defined between the
upper section 38 and lower section 39. Alternatively, the isolator
25 structure can also be moved in r with the chuck moving in
.theta. and z. Once in position the distance between each side of
the wafer 26 and the upper section 38 or lower section 39 is 0.30
to 0.80 mm. The slot open area without a wafer 26 is 124.20 to
216.20 mm.sup.2. The slot open area with a wafer 26 present is
55.20 to 147.20 mm.sup.2. The exhaust slot width is 93.0 mm.
[0063] A gas diffuser 24 extends into the processing chamber 22
providing a flow of inert or oxygen containing gas to the
processing chamber 22. The gas diffuser 24 is typically of the
shower head type design and is connected via a diffuser 24 gas line
148 to the purge gas source 96.
[0064] The exhaust plenum 41 together with the exhaust system 56
are an additional part of the tuned flow system which prevent
reactive gas migration out of the processing area. Exhaust system
56 creates a negative pressure in the exhaust plenum 41 that draws
active species gases together with the inert gas, processed
byproducts, and condensation away from the processing area and
prevents migration of these gases into the device area of the wafer
26.
[0065] A heater element 122 is connected by a heater line to a
heater power supply 126. The heater element 122 heats the isolator
25 and to a lesser extent, the wafer 26. Heating the isolator 25 is
desirable to prevent condensation of gases that can be corrosive to
the isolator 25 and potentially introduce contamination into the
processing area.
[0066] The nozzles of the edge area processing system 20, including
the first nozzle 45 and second nozzle 49 are made of sapphire.
Sapphire is advantageously non-reactive to the chemistries used in
substrate processing. This is desirable since the processing of
semiconductor substrates requires trace material contamination
analysis at the parts per million level with acceptable addition to
the substrate being less than approximately 10.sup.10
atoms/cm.sup.2. Further, particle additions to the substrate should
be zero for sizes greater than approximately 0.1 micron.
[0067] It is also, in many situations, desirable to achieve a
laminar gas flow from the nozzles. This requires setting the aspect
ratio of the nozzle at greater than or equal to 10.times. length to
diameter. With some reactive gases, aspect ratios of greater than
40:1 or preferably 80:1 are desirable. Nozzle inside diameters are
around 0.254 to 0.279 mm which requires a uniform smooth nozzle
bore length of approximately 2.50 mm.
[0068] The isolator 25 nozzles, including the first nozzle 45 and
second nozzle 49, while described as angled relative to the wafer
plane at .about.80 degrees and .about.45 degrees, respectively, can
advantageously be angled in a different direction relative to the
wafer plane in order to facilitate processing including etching or
deposition of a thin film.
[0069] In operation, a wafer 26 is centered on the wafer chuck 28
and then the wafer chuck 28 positions the wafer 26 in the slot of
the isolator 25 between the upper section 38 and the lower section
39 for processing. The movement system 27 rotates wafer chuck 28,
and thus the wafer 26.
[0070] Inert gas or CDA is allowed to flow into the upper purge
plenum 88 and lower purge plenum 114 from the purge gas source 96.
The inert gas or CDA flows into the upper purge plenum 88 and lower
purge plenum 114 at a rate of 100 sccm to 8,000 sccm. Inert gas or
CDA is also allowed to flow into the processing chamber 22 through
the gas diffuser 24. This gas flows into the processing chamber 22
at a rate of 500 sccm to 10,000 sccm.
[0071] The exhaust system 56 is activated to draw gases and process
byproducts including condensation through the exhaust plenum 41.
Next, reactive species 130 emit from first nozzle 45 and second
nozzle 49. The igniter power supply 126 energizes the clean igniter
system 78 and the first gas line 93 and second gas line 98 are
opened to allow a flow of hydrogen and nitrogen trifluoride gases
into the nozzle assembly 84 and through the four nozzles 84. The
gas mixture is frequently different during the ignition stage. The
igniter nozzle uses H.sub.2 and O.sub.2 only at higher total flow
rates than the processing nozzles 45, 49. Typically, the initiator
nozzle uses approximately 800 sccm H.sub.2 and 200 sccm. The
process nozzles typically ignite with a Lo NF.sub.3 fraction.
Typically about 20 sccm max. Reactive species (or gases in the case
of a combustion flame) flow through the nozzles at a rate of
between 200 and 800 sccm and preferably between 375 sccm to 475
sccm. The reactive species 130 impinge upon the edge area 33 of the
wafer 26 as the wafer 26 rotates. The reactive species 130 react
with a thin film or contaminant in the edge area 33 of the wafer 26
resulting in a reactant byproduct 66. Alternate nozzle
configurations are envisioned. For example, referring briefly to
FIGS. 9A-9C, the position of the first processing nozzle 45 and
second processing nozzle 42 includes the reactive species 130 to
"wrap around" the top bevel, crown, bottom bevel of the wafer
26.
[0072] Heater 122 is energized to heat the wafer top surface 30.
This optional step is intended to prevent vapor produced as a
byproduct of the chemical reaction, for example water vapor, from
condensing on the wafer top surface 30. Condensation can be
prevented by heating the wafer top surface 30 to a temperature at
or above the boiling point for the reactant byproducts, for example
heating the wafer top surface 30 above 100.degree. C. to prevent
the condensation of water. Alternatively, wafer 26 surface heating
can be supplied via a heated substrate holder 82 or via infrared
energy directed at the wafer perimeter, or via other heat sources
such as a flame.
[0073] The reactive species 130 are prevented from passing out of
the isolator 25 by the flow of inert gas working in concert with a
pressure differential drawing gases into the exhaust plenum 41 and
into the exhaust system 56. This inert gas forms a pressurized
barrier in the upper purge plenum 88 and lower purge plenum 114
surrounding the in-process edge area of the wafer. The inside
baffle member 61 in cooperation with the outside baffle member 63
biases the flow of insert gas towards the in-process area of the
wafer 26. Reactant byproducts formed as a result of the reactive
species 130 reacting with a thin film on the wafer 26 surface are
drawn away from the in-process area of the wafer 26 into the
exhaust plenum 41. Thus, advantageously, reactive species 130 and
reactive byproducts 142 are confined to the edge area of the wafer
26 and prevented from migration into other areas of the wafer 26
that may damage wafer component devices. In addition, the pressure
differential induced by the exhaust plenum 41 further biases gas
flow away from the central portion of the wafer 26.
[0074] As the wafer 26 rotates either the wafer chuck 28 translates
with respect to the nozzle assembly 84 and the combustion flame
across the wafer top surface 30. As a result a desired section of
the wafer top surface 30 is processed. Processing includes the
removal of a thin film, for example, silicon dioxide or tantalum as
described above in relation to the substrate processing method.
[0075] After the wafer is processed, the first gas controller 102
and second gas controller 106 are closed. Simultaneously, the
fourth gas controller 49 is opened to allow a flow of argon gas or
CDA into the edge-type nozzle assembly 84 and through the first and
second nozzles 45, 49 to "blow out" the combustion flame. The
controller 140 additionally allows blow off of the nozzles if EMO
or a power failure occurs. Additionally, the controller 52 can
extinguish the flames upon low gas delivery pressure, if the
enclosure is opened, or if there is a loss of control air. Also
coupled to the controllers are a plurality of H.sub.2 sensors which
will shut off the system or signal an alarm should the H.sub.2
level in the chamber 22 be above a predetermined level. The wafer
26 may be removed after the chamber 22 is evacuated of process
gases and byproducts.
[0076] Processing of the edge area 33 of the entire wafer may be
accomplished with a single rotation of the wafer 26. Alternatively,
more than one rotation may occur and more than one process may be
performed including deposition and etching. After the flow of
reactive species is stopped a flow of the inert gas continues until
the processing chamber 22 is sufficiently evacuated of other gases
and condensations. Then, the heater element 122 is turned off and
the flow of inert or CDA gas from the purge gas source 96 is
stopped and the wafer 26 is removed and replaced with another wafer
for processing.
[0077] The described system 20 and associated method for using the
system is suitable for etching of target thin films. This includes,
but is not necessarily limited to, tantalum and tantalum nitride;
inter-layer dielectrics; backside polymers; and photoresist edge
bead.
[0078] FIG. 2 represents a top view of the system shown in FIG. 1A.
Shown is the isolator 25 with associated nozzle assembly 84, Flame
sense system 212, and heater 122. Also shown is the movement system
27 with labyrinth seal 70 and measuring micrometer 15. The wafer 26
is moved from the installation position 134 to the processing
position 136 by translation of the chuck 28.
[0079] FIG. 3 shows exchange/centering 134 and processing 136
positions of the R-Z-.theta. stage. Relationship of the labyrinth
seal 70 to the process chamber 22 and chuck spindle 60 are also
shown. Vacuum for labyrinth seal 70 operation is supplied by a
vacuum pump 31 or other appropriate vacuum generator. Computer
control of the vacuum level can be integrated using a throttle
valve, electronic mass flow, or pressure controller in conjunction
with a venturi type vacuum generator. Vacuum for the wafer chuck
clamping force is also supplied by a vacuum pump 31. Pressure
differential was found to be the most critical parameter
determining function of the seal. Gap distance between 120 .mu.m
and 500 .mu.m between the sealing plate 74 and the bottom surface
76 of the process chamber 22 was also found to be important.
[0080] The translational `R-axis` gap and the `Z-.theta. axis` gap
are shown in FIG. 3. When operated using proper conditions, the
helium leak rate of the seal is <1.0.times.10.sup.-6 atm-cc/s.
This leak rate is equivalent to that of an o-ring sealed interface.
It must be noted that o-ring interfaces have been found to be
unacceptable inasmuch as they generate undesirable particulate. Gap
values in the range of 127 .mu.m to 508 .mu.m were tested and found
functional provided the proper pressure differential was
maintained. Mass flow magnitude increases dramatically with
increasing gap placing a practical upper limit of 254 .mu.m.
Machining tolerances set the practical lower gap limit at 127
.mu.m.
[0081] A minimum pressure differential between the seal exhaust
ports, and the process chamber 22 was found to be -2 water column
inches. Larger differential pressure values can be used and a
practical upper limit is not known. Pressure differential between
the process chamber and atmosphere should be at least -0.4 water
column inches. This results in a seal exhaust to atmosphere
pressure differential of at least -2.4 water column inches.
[0082] FIGS. 4A-4B show side and top views of the labyrinth seal 70
assembly in relationship to the chamber 22 and movement system 27.
Vacuum channel sealing the traverse (R-axis) motion is shown along
with the channel 79 sealing vertical (Z-axis) and rotary (O-axis)
motion components. Each vacuum channel is connected via tubing to
an independently controlled vacuum generator or pump. Note that the
labyrinth seal plate 74 is machined from 304 or 316 series
stainless steel. Corrosion resistance is enhanced by a post
machining metal finishing process consisting of electro-polishing
and passivation.
[0083] Referring again to FIGS. 1-9B, an embodiment of a substrate
processing method 10 of the invention employs a combustion flame 12
formed of an ignited combustion of gaseous reactants 14 including
hydrogen (H.sub.2) and nitrogen trifluoride (NF.sub.3, as a
non-oxygen "oxidizer") in an oxygen enhanced environment 13.
Although CDA is illustrated, other oxygen containing gases are
suitable. A mixture of gaseous reactants passes through a torch
nozzle 45 before igniting into combustion flame 12. Combustion
flame 12 impinges upon a substrate surface 18.
[0084] Gaseous reactants react in combustion flame to form gaseous
hydrogen fluoride (HF) (a reactive species) and gaseous nitrogen
(N.sub.2) effluents. The following chemical equation describes the
production of gaseous hydrogen fluoride and gaseous nitrogen from
gaseous reactants based on a stoichiometric mixture (a 3:2 molar
ratio):
3H.sub.2(gas)+2NF.sub.3(gas).fwdarw.6HF(gas)+N.sub.2(gas)
[0085] Advantageously, this reaction is performed substantially at
atmospheric pressure. This allows for use of viscous (rather than
molecular) flow properties to precisely treat portions of the
substrate surface 18 and minimize exposure of other substrate areas
to the reactive process. Although a 3:2 molar ratio is described
higher or lower ratios may be used depending on the desired
result.
[0086] Further, this reaction is not induced by an ion producing
field consistent with a plasma. It is believed that a plasma is a
collection of charged particles where the long-range
electromagnetic fields set up collectively by the charged particles
have an important effect on the particles' behavior. It is also
believed that the combustion flame 12 has substantially no ionic
species present. As a result, there is no risk of ionic damage to
the substrate.
[0087] Substantial heat is generated from the exothermic chemical
reaction of H.sub.2 and NF.sub.3. This effect allows a small volume
of highly reactive species in the form of HF to be generated due to
the amount of energy represented by the resultant temperature.
Elevated temperature in turn substantially increases reaction rates
which results in higher etch rates. The result is higher process
throughput.
[0088] A silicon dioxide thin film can be etched by the gaseous
hydrogen fluoride according to the following overall reaction:
4HF(gas)+SiO.sub.2(solid).fwdarw.SiF.sub.4(gas)+2H.sub.2O(gas)
[0089] Gaseous silicon tetrafluoride and water vapor leave the
surface of the silicon dioxide thin film. Advantageously, this
reaction provides for a change of silicon dioxide thin film from a
solid to a gas byproduct that can be easily evacuated.
[0090] Gaseous hydrogen fluoride will also etch a substrate surface
of silicon. Silicon etching follows the following overall reaction:
4HF(gas)+Si(solid).fwdarw.SiF.sub.4(gas)+2H.sub.2(gas) In this
reaction, gaseous silicon tetrafluoride and gaseous hydrogen leave
the silicon substrate surface. This reaction provides for a change
of silicon on the substrate surface from a solid to a gas byproduct
that can be evacuated.
[0091] Similarly, etching of a tantalum thin film follows the
following overall reaction:
10HF(gas)+2Ta(solid).fwdarw.2TaF.sub.5(gas)+5H.sub.2(gas) In this
reaction, gaseous tantalum pentafluoride and gaseous hydrogen leave
the tantalum substrate surface. This reaction provides for a change
of the tantalum on the substrate surface from a solid to a gas
byproduct that can be evacuated. For this reaction, preheating of
the wafer using an O.sub.2+H.sub.2 flame is desirable to prevent
the condensation of reaction products on the wafer.
[0092] Organic and polymer films can also be removed using the
above described chemistry however selectivity issues to Si and
SiO.sub.2 may in some instances make this less desirable. The above
chemistry for example can be used to etch SiO.sub.2 over Si where
etching of oxide is desirable but Si is not. Passivation of exposed
Si to the etch chemistry can be promoted by first exposing an etch
field to a hydrogen rich flame with oxygen. The etch field is then
exposed to the combustion flame of H.sub.2 and NF.sub.3 where the
oxide is etched.
[0093] Other desirable non-oxygen oxidizers for reaction with
hydrogen in a combustion flame for substrate etching include
fluoride (F.sub.2), chlorine (Cl.sub.2), and chlorine trifluoride
(ClF.sub.3). Hydrogen and fluoride react in a combustion flame as
follows: H.sub.2(gas)+F.sub.2(gas).fwdarw.2HF(gas) Similarly to the
combustion flame of H.sub.2 and NF.sub.3 the resulting HF reactive
species is a desirable etchant as described above.
[0094] Hydrogen and chlorine react in a combustion flame as
follows: H.sub.2(gas)+Cl.sub.2(gas).fwdarw.2HCl(gas)
[0095] Hydrogen and chlorine trifluoride react in a combustion
flame as follows:
4H.sub.2(gas)+2ClF.sub.3(gas).fwdarw.6HF(gas)+2HCl(gas)
[0096] In both the proceeding combustion flame reactions, the
resultant hydrogen chloride reactive species can be advantageously
used for etching when materials not readily etched by fluorine are
present in the film stack. This includes a film stack comprising
aluminum. Hydrogen chloride as a reactive species etches aluminum
as follows:
2Al(solid)+6HCl(gas).fwdarw.2AlCl.sub.3(gas)+3H.sub.2(gas)
[0097] Hydrogen chloride etches silicon as follows:
Si(solid)+4HCl(gas).fwdarw.SiCl.sub.4(gas)+2H.sub.2(gas)
[0098] Hydrogen chloride etches silicon oxide as follows:
SiO.sub.2(solid)+4HCl(gas).fwdarw.SiCl.sub.4(gas)+2H.sub.2O(vapor)
[0099] Chlorine trifluoride represents a hybrid etch chemistry
where both fluorine and chlorine based etchant reactive species are
produced. Often this compound is combined with another fluorine
containing gas (such as NF.sub.3 or CF.sub.4) or with Cl.sub.2 is
used in varying ratios when multiple materials are present in the
film stack, requiring both fluorine and chlorine based chemistry
for removal.
[0100] The chemical equations shown above are a simplified view of
the real reactions taking place within the combustion flame and on
the substrate surface. The reaction chemistries occurring are quite
complex resulting in intermediate and final reaction products.
[0101] A nozzle assembly 84 is held by a support member 46 over a
wafer 26 retained on the substrate holder 82. Four nozzles 45 are
disposed in the nozzle assembly 84. The nozzle assembly 84 is
maintained at a distance of .about.1.5 mm from the wafer top
surface 30 during processing.
[0102] A hydrogen gas source and nitrogen trifluoride gas source 55
are connected by a first gas line 48 and second gas line 53 through
a first gas controller 102 and second gas controller 106 to a
common mixing gas line 110 connected to the nozzle assembly 84 for
combining and mixing H.sub.2 and NF.sub.3. An exhaust scoop 116 is
adjacent to the substrate holder 82 for exhausting gases and
reactant byproducts. The exhaust scoop is connected by a plenum 67
to a blower device 124. The exhaust scoop 116 draws gases and
reactant byproducts out of the processing chamber 22 through the
blower device 124.
[0103] In one embodiment, an argon gas source 96 is connected by a
third gas line 132 through a third gas controller 49 to the
processing chamber 22. In another embodiment, a CDA (clean dry air)
or oxygen containing gas 72' is connected by the third gas line 132
through a third gas controller 49 to the process wafer. The argon
or CDA gas source 131 is also connected by a fourth gas line 134
through a fourth gas controller 49 to the common mixing gas line
110. An igniter assembly 78 positioned close to the nozzle assembly
84 is connected by wires 83 to an igniter power supply 126.
[0104] In operation, the robot unloads wafer from front opening
unified pod (FOUP) and places the wafer on a pre-aligner 19. Once
the pre-alignment routine is completed, the robot retrieves wafer
from pre-aligner and places it into the chamber 22 on lift pins 16.
Wafer chuck 28 moves up in z and lifts wafer 26 from lift pins 16
and rotates and positions the wafer edge to allow measurement using
laser micrometer 15. Wafer center offset direction and magnitude is
computed as described above. Wafer 26 is then rotated to align
offset direction with the `r` axis. The chuck 28 then descends in
`z` axis to return wafer to lift pins 16. The wafer movement system
27 moves chuck assembly increments in `r` by the offset magnitude
to center the chuck 28 with respect to the wafer 26. The movement
system 27 then elevates in `z` axis to lift wafer from lift pins
16. The chuck rotates and the edge position is re-measured to
validate centering. The wafer is then ready for concentric process
application as described above.
[0105] A heater 122 is positioned proximately to the area of the
wafer 26 to be processed. The heater 122 (shown in FIG. 5) is an
infrared (IR) or laser diode heater and is connected by a heater
wire 87 to an IR heater power source 125. In a preferred embodiment
the heater 122 is a fiber optic coupled laser diode array. A fiber
optic cable assembly can be used in place of the heater 122. The
fiber optic cable can deliver high power illumination originating
in a laser diode assembly located remotely. Such illumination can
perform heating of the wafer 26 such as discussed in United States
Patent Application Publication No. 2005/0189329, titled "Laser
Thermal Processing with Laser Diode Radiation" and incorporated
herein by reference.
[0106] FIGS. 6A through 6F represent the nozzle 45, 49 positioning
with respect the bevel edge of the wafer 26. By alternating the
angles of the nozzles, proper coverage of the edge for particular
region of the wafer edge can be accomplished. In this regard,
depending upon the defects or films to be removed, various nozzle
configurations are envisioned.
[0107] Referring to FIGS. 7 through 8G, a film such as deposited
through chemical vapor deposition (CVD) or physical vapor
deposition (PVD) extends as a thin film 129 over a wafer 26 such as
a wafer. The thin film 129 extends from the top surface of the
wafer 26 across a top bevel, crown and bottom bevel of the wafer
26. The above-described system 20 can be advantageously used to
process the thin film 129 on the wafer 26 resulting in a wafer 26
profile as shown in FIG. 8B.
[0108] Referring to FIGS. 7 and 8C, a full coverage thin film 128
extends from the top surface across the top bevel, crown and bottom
bevel and onto the bottom surface of the wafer 26. Thin films
having this profile can include for example thermal SiO.sub.2, and
Si.sub.3N.sub.4. Embodiments of the above-described system 20 can
be used to process the full coverage thin film 128 on the wafer 26
resulting in a wafer 26 profile as shown in FIG. 8D.
[0109] Referring to FIGS. 7 and 8E, a backside polymer thin film
130 extends from at or near the top bevel to across at least a
portion of the crown to the bottom bevel and onto the bottom
surface of the wafer 26. Embodiments of the above-described system
20 can be used to process the backside polymer thin film 130 on the
wafer 26 resulting in a wafer 26 profile as shown in FIG. 8F.
[0110] Now referring to FIGS. 9A-9C, an alternative embodiment edge
area processing system 20' (the "first alternative system") employ
alternate first and second nozzles 45, 49. In the alternate nozzle
configurations, the second nozzle "bends" the reaction gasses from
the first gas around the bevel edge.
[0111] FIG. 9A represents a 65.degree./140.degree. nozzle
configuration. This configuration allows the gases of the reaction
to be induced around the wafer 26 bevel. Each of the four nozzles
45,49 is constructed of sapphire with a bore diameter of 0.254 mm
and an aspect ratio of between 10:1 and 80:1 at the outlet end.
Each of the four nozzles 45,49 is press fitted into the nozzle
assembly 84. The nozzles are pressed into tightly toleranced bores
cut into the stainless steel nozzle assembly 84. Nozzle diameter is
1.577 mm, +0.003 mm, -0.000 mm. Bore diameter in the nozzle
assembly 84 for receiving the sapphire nozzle is 1.567 mm, +0.003
mm, -0.000 mm. This gives an interference fit in the range of 0.007
mm to 0.013 mm. Tolerance of this fit is important as interference
in this range allows a hermetic seal while only inducing elastic
deformation in the stainless steel nozzle assembly 84. This allows
a good seal without causing particulate generation during
processing. In this configuration, a spoiler jet 89 is used to
ensure the flame does not interact with the structure system 56.
Additionally, the lower moat 51 ensures reactants do not pass the
isolator so as to affect the back surface.
[0112] FIG. 9A shows that under some processing conditions, flame
outputs may impinge on portions of the exhaust or isolator
structures. Although moat 51 gasses generally can be used to
prevent reaction gasses from flowing upstream, under certain
processing conditions, the gasses may be forced toward the chuck
28. As seen in FIG. 9B, the use of a spoiler jet 89 can reduce or
eliminate the reaction gas impingement. Additionally, the gas flow
through the backside moat will eliminate the chance reaction
products will migrate into the wafer back surface.
[0113] Although NF.sub.3 is used in the above embodiments as the
non-oxygen oxidizer other non-oxygen oxidizers as previously
discussed are suitable for use in the preferred embodiments.
Further, additional embodiments for isolating and processing a
wafer according to the above-described method are disclosed in U.S.
patent application Ser. No. 11/230,263, filed on Sep. 19, 2005 and
titled "Method and Apparatus for Isolative Substrate Edge Area
Processing." The disclosure of this application is incorporated
herein by reference.
[0114] Removal of dielectric thin films such as silicon oxide from
substrates using H.sub.2 and NF.sub.3 gas mixtures is performed
with a hydrogen fraction in the range of 0.5 to 0.7. For example,
if the total flow is 800 sccm, H.sub.2 flow will be in the range of
400 sccm to 560 sccm with NF.sub.3 flow in the range of 400 sccm to
240 sccm. IR preheat is used in cases where ambient oxygen is
present to discourage combustion products from condensing on the
substrate.
[0115] Removal of tantalum from the near-edge region of the
substrate is carried out using an etch nozzle configuration similar
to that detailed for dielectric removal. Total gas flow per nozzle
is approximately 400 sccm with an H.sub.2 fraction in the range of
0.6 to 0.7. The primary tantalum etch product is TaF.sub.5 which
has a boiling point of .about.230.degree. C. Substrate surface
temperatures in the etch region must be kept about this temperature
to prevent condensation of the etch product. This is readily
achieved using an additional combustion flame nozzle (not shown)
positioned to impinge a flame on the substrate immediately prior to
the impingement of the etch flame. This pre-heat nozzle discharges
a flame of H.sub.2 and O.sub.2 preferably in the range of 0.5 to
0.8, H.sub.2 fraction at a total flow of .about.400 sccm for a
single nozzle.
[0116] A rate of etching of the edge portion of the wafer 26 can be
calculated based on consideration of exposure width, wafer
circumference and rotational speed. For example, consider a 200 mm
circumferential wafer with 2,000 .ANG. of SiO.sub.2 that is rotated
at 2 rpm and the SiO.sub.2 thin film on the edge area is completely
removed in one rotation. Assuming a conservative exposure width of
5 mm of the combustion flame effluent on the wafer edge (using a
0.256 mm nozzle bore) an exposure fraction can be calculated as 5
mm/(628 mm.times.2 rev/min)=0.004 min/rev. The etch rate can then
be approximated by dividing the 2,000 .ANG./rev removal by the
exposure fraction. That is 2,000 .ANG./rev/0.004 min/rev=500,000
.ANG./min SiO.sub.2 removal. If a smaller 2 mm exposure width is
assumed then the removal rate becomes 1,256,000 .ANG./min. Based on
these considerations and assumptions a poly-silicon thin film would
be etched at an approximate rate of 3.times.10.sup.6 .ANG./min; a
photoresist thin film would be etched at an approximate rate of
4.6.times.10.sup.6 .ANG./min; and a tantalum thin film would be
etched at an approximate rate of 1.times.10.sup.6 .ANG./min. This
is a significantly high rate of etching resulting in a high rate of
processing throughput of wafers.
[0117] One configuration is optimized for EBR from spin-on films on
the top surface and edge region of wafers. This configuration uses
reactive gas generated by a combustion flame of H.sub.2 and O.sub.2
to remove the resist. The present disclosure defines an optimized
process using a minor fraction of the non-oxygen oxidizer NF.sub.3
in the gas mixture for photoresist EBR. This addition increases the
combustion flame temperature and chemical reactivity. These
modifications to the combustion flame mixture substantially enhance
sharpness of the etch interface and increase slope of the
transition to full film thickness, both highly desirable
enhancements.
[0118] For spin on films with low or minimal etch rate in the
H.sub.2:O.sub.2 dominant chemistry such as organosilicates,
inorganic polymers, and spin on glass materials, increasing amounts
of fluorine containing gases such as NF.sub.3 can be added to
further increase etch rate. In this embodiment reactive gas
application to the near edge area of the wafer is achieved using
the invention disclosed in "Method and Apparatus for Isolative
Substrate Edge Area Processing," previously incorporated by
reference.
[0119] Undesirable dielectric films can be removed from the front
surface of in process semiconductor wafers. These films can also
flake and result in defects which cause yield loss. Concentric
process application is critical in these processes where reactive
gas application must be targeted to the edge region while not
affecting the device area of the wafer.
[0120] Tantalum removal is similar in configuration to the front
side dielectric removal module. Differences exist in the use of a
preheat nozzle to reach a higher surface temperature
(>230.degree. C. target) to prevent TaF.sub.5 condensation in
the etch region. Surface temperature pre-heat target for typical
film removal is .about.120.degree. C. and is primarily to prevent
condensation of water vapor byproduct from the combustion
reaction.
[0121] The in-situ wafer centering sequence typically takes 8 to 15
seconds. This overhead can be overlapped with gas flow
stabilization time or ignition sequence. Wafer `z` plane
displacement is measured during rotation and can be used to map out
`z` displacement due to wafer bow or warp.
[0122] Process operation and details for Ta and dielectrics is
discussed at length in the "Substrate Processing Method and
Apparatus Using a Combustion Flame" patent application, previously
incorporated by reference. This process operation can be applied to
backside polymer and edge bead removal.
[0123] Backside polymer removal according to the principles of the
present disclosure is accomplished by using four nozzles located in
the isolator structure. As shown in FIG. 9C, two nozzles are
positioned at 45 degrees and two are at 105.degree. relative to the
wafer surface. The 45.degree. nozzles are aimed at the back surface
while the 105.degree. nozzles are aimed at the bevel. In some
cases, 2.times.45 degree nozzles are directed at the back surface
along with 2.times.65 degree nozzles directed at the bottom bevel.
Using multiple nozzles in this fashion both increases throughput
and widens the process window. Nozzle angle relative to the wafer
surface is important as impingement angle affects flow attachment
to the surface and consequently degree of delivery of reactive
species to the surface. As previously mentioned, an optional
spoiler jet 89 can ensure the 105.degree. nozzle does not cause
degradation of the exhaust structure. It should also be noted that
in this configuration, gas from the moat 51 can be used to "spoil"
the flow of the flame to ensure it does not interfere with the
exhaust.
[0124] Typically, the thickest polymer is located on the bevel
region of the wafer. Consequently the NF.sub.3 fraction in the
105.degree. jets is higher than the 45.degree. jets aimed at the
thinner polymer on the back surface. Currently the method process
uses 210 sccm H.sub.2, 80 sccm O.sub.2, and 100 sccm NF.sub.3 in
each 105.degree. (high fraction) nozzle. Flows of 240 sccm H.sub.2,
120 sccm O.sub.2, and 20 sccm NF.sub.3 are used in each 45.degree.
(low fraction) nozzle. The nozzles are constructed from sapphire
with an ID of approximately 254 .mu.m and an aspect ratio of
greater than or equal to 10:1. Rotational speeds using during
process are typically in the 1 to 6 RPM range. Surface heating for
condensation prevention (>100.degree. C. target) is done using a
fiber coupled laser diode array.
[0125] Chemistry used for EBR depends on the film being removed.
For photoresist removal 240 sccm H.sub.2, 120 sccm O.sub.2, and 20
sccm NF.sub.3 performs well. Rotation rate to remove 15,000
Angstroms of resist is typically 1 to 3 RPM. Two nozzles are used
for the photoresist EBR process, one at 45.degree. and one at
65.degree.. In cases where minimum edge exclusion is desired
(.about.0.5 mm) only the 65.degree. jet is used. Films with low
removal rate, typically silicon containing films, require higher
NF.sub.3 fraction. The high fraction process used for backside
polymer is an example (25% NF.sub.3) although higher fractions can
be used, frequently without oxygen addition, to .about.50%.
[0126] Nozzle aiming for backside polymer removal is shown in FIG.
9C. Backside polymer removal approach differs from front side films
in that a sharp transition to full film thickness at the edge
exclusion boundary is not required. Multiple nozzles are used in a
partially overlapping fashion to increase the process window and
removal rate. Nozzles are angled at 45.degree. and 65.degree.
relative to the wafer surface. These angles were determined by a
combination of CFD modeling and experimental trials. Positioning of
the 65.degree. nozzles can be critical for flow attachment and
consequently efficient removal of material from the bevel region.
This angle can be optimized based on edge profile to maximize flow
attachment.
[0127] FIG. 10 shows a schematic view of the centering process. The
measurement window of the laser micrometer 15 is represented by a
rectangle 200. The edge location of a properly centered wafer or
circle of radius 150 mm is shown as 202. The target center position
of the wafer is (X.sub.c, Y.sub.c). A misaligned wafer is shown in
hidden line representation at two different angular positions. At a
first position identified as 204, the pre-centered wafer has been
rotated about the Z axis .theta.1 degrees. The center of the wafer
is identified at (X.sub.1, Y.sub.1). A second wafer position,
identified as 206, corresponds to the wafer being rotated an angle
of .theta.2 degrees. The center of the wafer is now at (X.sub.2,
Y.sub.2).
[0128] FIGS. 3 and 10 depict a "Z" axis, an "R" axis and .theta.
angles from a reference coordinate system having an origin at
(X.sub.c, Y.sub.c). The edge position measurement and offset
calculation includes the following: 1. R-Z-.theta. stage placed
with .theta. axis in known reference location; 2. Rotate .theta.
and measure radial position of wafer edge using laser micrometer
15; 3. Measured radii are fit to a circle; and 4. The difference in
position between the known .theta. axis and the center of the
resultant fit circle is calculated and gives magnitude and angle of
wafer offset.
[0129] The centering routine measures and records .theta., T.sub.i,
(1 . . . n) and the laser micrometer 15 reading, L.sub.i, (1 . . .
n) which represents the edge position. Typically n=50 in this
application. The true radius of the wafer is assumed (100 mm or 150
mm). Theta is referenced using the wafer notch position. The
following values are computed for each data point:
X.sub.i=(R+L.sub.i)cos(T.sub.i) 1a Y.sub.i=(R+L.sub.i)sin(T.sub.i).
1b
[0130] The objective is to minimize the sum of squares of the
deviations given by
D.sub.i=(X.sub.i-X.sub.c).sup.2+(Y.sub.i-Y.sub.c).sup.2-R.sub.c-
.sup.2 2 where X.sub.c is the x-axis center point, Y.sub.c is the
y-axis center point and R.sub.c is the assumed radius. The
Gauss-Newton method is used to solve the set of non-linear
equations. An example of this method is given in "Least-Squares
Fitting of Circles and Ellipses" by Gander, et. al. published in
BIT, vol. 34, 1994, pp. 558-578.
[0131] As best in FIG. 11, the system 20 can include an optical
system 264 inspecting the wafer's edge. In this regard, the optical
system has at least one zoom lens 262 which is rotatably
positionable about the wafer's edge. The zoom lens is configured to
be able to take reflected light from the wafer's edge and collect
it into a CCD camera. It is envisioned that the zoom lens will have
a 2 .mu.m resolution and will be able to detect defects on the
wafer's edge as well as the effectiveness of the cleaning
process.
[0132] As shown in FIG. 12A, the system 20 described above remove
TA on the bottom level of the edge. Further, as shown in FIG. 12B,
the system is capable of removing polymer from the top of the
wafer, revealing a dielectric surface. Additionally, it is
envisioned the system can use thin film spectroscopic reflectivity.
Further, the optical system is disclosed in U.S. patent application
Ser. No. 11/417,297, filed on May 2, 2006 and titled "Substrate
Illumination and Inspection System," previously incorporated by
reference above.
[0133] As can be seen in FIGS. 13 through 16B, the wafer processing
system 20 includes the wafer movement system 27 having a spindle 60
configured to move the wafer in three or four axes of movement. In
this regard, the wafer movement system 27 is configured to move the
wafer within an isolated chamber 22 in xyz and .theta. directions
(motion occurs in r,z and theta directions). The isolated chamber
22 has a bottom wall 162 defining an aperture 164 and having a
first exterior bearing surface 166. The labyrinth seal 70 has a
sealing plate 168 having a second bearing surface 170 is slidably
positioned against the first bearing surface 166. The sealing plate
168 further defines a bore 172 which is annularly disposed about
the spindle 60. A first vacuum chamber 174 is defined between the
first and second bearing surfaces 160, 170. Additionally, a vacuum
source is coupled to the first vacuum chamber 174.
[0134] FIG. 13 represents and exploded view of a portion of the
wafer processing assembly 20. Shown is a portion of the chamber 22,
the labyrinth seal 70 and associated isolator assembly 25
components. As can be seen, the labyrinth assembly 70 is formed of
a sealing plate 168 and support plate 169. The support plate 169
defines a vacuum gallery 173 which is fluidly coupled to the vacuum
chamber 174 defined between the first and second bearing surfaces
160 and 170 of the chamber bottom wall 162 and sealing plate 168
bearing surface 170. Also shown is the relationship of the spindle
60 and the apertures 172 and 164 formed in the sealing plate 168
and the bottom wall 162. Also shown is the relationship of a
loading position 181 and the second processing position 186.
[0135] As best seen in FIGS. 14A-B and 15, either the first or
second bearing surfaces 166, 170 can define a groove 178. This
groove 178 forms a portion of the first vacuum chamber 174 defined
between the first and second bearing surfaces 166 and 170. This
chamber 174 is movable with respect to the bottom wall 162 upon
movement of the spindle 60 by the actuation mechanism.
[0136] Adjacent to the bore 172, the sealing plate 168 can define
second groove 180. A second vacuum chamber 182 can be defined
between the second groove 180 and the spindle 60. This second
vacuum chamber 182 can be independently coupled to the vacuum
source 176. As best seen in FIG. 15, the wafer movement system 27
comprises a wafer supporting chuck 28 that functions to fixably
hold the wafer 26 through the movement system 27. This wafer
movement system 27 is configured to move the wafer 26 from the
loading position 181 to a second processing position 186. In this
regard, the processing position can be an alignment position or can
be positioned adjacent to the nozzle assembly 84.
[0137] With reference to FIGS. 16A and 16B, the operation of the
wafer movement system 27 is disclosed. The spindle 60 is configured
to move the wafer 26 in a plurality of directions from the loading
position 181 to the processing location 186. The isolated chamber
22 is disposed about at least a portion of the wafer movement
system 27 in order to protect the mechanism of the wafer movement
system 27 from the reactive gases generated during the processing
of the wafers. The chamber 22 has bottom wall 162 defining an
elongated bore 164 which allows the movement of the spindle 60 with
respect to the chamber 22. The bottom wall 162 first bearing
surface 166 can either be located on an exterior or an interior
surface of the chamber 22.
[0138] FIGS. 17A-17B represent an exploded sectional view of
isolator 25. The isolator 25 has a nozzle plate 216 which provides
the mechanism to couple the nozzle assembly 84 and moat 51 gas
supply to the moat 51. The nozzle plate 216 defines a recess 218
which slidably accepts the nozzle of the nozzle assembly 84. The
recess 218 further defines a second recess aperture 220 which
accepts an optical interface for the heating element 122. The
nozzle plate 216 allows for the configurations of the nozzle
assembly 84 without the entire disassembly of the wafer processing
apparatus 20. As shown in FIGS. 17B and 17C, the nozzle plate 216
defines apertures and fixation pins which facilitate the alignment
of the various components to the isolator 25. In this regard, the
nozzle assembly 84, heater 122 and moat 51 gas supply lines are
precisely positioned.
[0139] FIGS. 18A and 18B show a plurality of nozzles 45,49 coupled
to a diffusion portion 221. The structure 221 forms a plenum when
installed against the nozzle plate 216. The support member 221 fits
within the recess 218 of the nozzle plate 216 to position the
nozzles 45 in their proper orientation.
[0140] As shown in FIGS. 19A and 19B, the nozzles are coupled to
the gas supply 55 through a plurality of welded stainless steel
tubes 222. To maintain flame stability, the gas supply 55 is
controlled by controller 52. As previously disclosed, the nozzles
have a stainless steel lead-in tube 224 having a very high aspect
ratio. For example, for H.sub.2 and O.sub.2 gas mixture, an aspect
ratio of greater than or equal to 10:1 is appropriate.
[0141] Disposed immediately before the lead-in portion 224 of the
nozzle 45 is a blowback flash suppressor device 226. This device
226 is a chamber 228 having a volume significantly larger than the
volume of the lead-in portion 224. Disposed within the volume is a
porous stainless steel member 228 which functions as an energy sink
to prevent the flame front from traveling up through the nozzle
45,49 and into the gas supply in the event of a system failure.
[0142] As shown in FIGS. 20A and 20B, the aspect ratio of the
nozzles 45 can vary depending on the fuel and oxidizer being used.
In this regard, in situations where a high percentage of NF.sub.3
is being used as an oxidizer, the nozzle 45,49 has a stainless
steel lead-in portion 224 having an aspect ratio of greater than
40:1, and preferably 80:1. As with the other nozzles, high purity
nozzle tips 230 of sapphire are preferred. The nozzle 45 has a
stainless steel body 225 with locator pin 227 which allows for the
coupling of the nozzle 45 with nozzle support member 221.
[0143] Disposed within the mass flow controller 52 is a normally
open valve (not shown) which functions to dump CDA into the fuel
supply source should the power be interrupted. Additionally, should
the system 20 desire to shut off the processing nozzles 45,49 the
normally opened valve is actuated and allows CDA at a pressure
higher than the pressure of the fuel source to flow into the
processing nozzles 45, effectively extinguishing the flames without
the risk of a system explosion.
[0144] FIGS. 21A and 21B represent an alternate method of coupling
nozzles to the isolator 25. Shown is an aperture 232 defined into
either the isolator 25 or the nozzle plate 216. Disposed within the
aperture 232 are a plurality of nozzle subplates 234 which have
individual nozzles 45. These nozzles subplates 234 are movable with
respect to each other in fore and aft directions to allow for
relative positioning of the subplates within the isolator 25. The
individual nozzle subplates 234 can be stacked immediately adjacent
to each other to form a nozzle assembly 84.
[0145] FIGS. 22A and 22B depict individual nozzle subplates 234.
Disposed on the inner face surfaces 236 of the nozzle subplates 234
are grooves 238 which function as fluid chambers 240. These fluid
chambers 240 are coupled to a vacuum or pressurized gas source (not
shown) and function to divert reaction gas products which might
leak from the processing chamber 22 during wafer processing. It is
envisioned that inert or oxygen containing gas can be supplied to
the nozzle plate, which will in turn flow into the isolator through
the aperture 232.
[0146] FIG. 22B depicts a cross-sectional view of the nozzle plate
234 shown in FIG. 22A. As can be seen, structures such as the high
aspect ratio lead-in tube 224 and blowback flash suppressor device
226 can be machined therein. These features significantly reduce
the cost of the assembly and increases the overall system
reliability.
[0147] In operation, fuel is provided to the nozzles 45, through
the flash suppressor device 226 from the mass flow controller 52.
The vacuum source draws a vacuum in the vacuum chamber 236
preventing corrosive reaction gases from leaking past the nozzle
assembly 84.
[0148] FIGS. 23A and 23B, represent an igniter assembly 78 which is
configured to cleanly ignite the nozzles 45 and 49 of the nozzle
assembly 84. The igniter assembly 78 has an optically clear or
sapphire hot body igniter 242 defining an interior cavity 244. The
hot body igniter 242 provides high chemical resistance, which is
non-particle forming. A heating element 246 is disposed within the
interior cavity 244. This heating element, which can be a Pt:Rh
element, functions to quickly bring the hot body igniter to a
predetermined temperature which will ignite a fuel oxidizer mixture
when the fuel touches the igniter hot body 242.
[0149] As seen in FIG. 23B, the ceramic hot body igniter 242 can be
physically and optically coupled to a laser diode 252. In this
configuration, the laser diode 252 is configured to produce photons
which past through the interior cavity 244. These photons strike
the heating element 246, thus producing a reliable ignition system.
Alternatively, the hot body 242 can be coated on an interior or
exterior surface with materials which increase photon absorbance at
wavelengths of interest.
[0150] Disposed at a distal end of the elongated cavity 244 is the
heating element 246. This heating element 246 can be electrically
coupled to a power source which functions to provide electric
current to heat the heating element. Alternatively, this element
can be inductively heated.
[0151] As shown in FIGS. 24 and 25B, operably disposed between an
igniter nozzle assembly 248 and the nozzle assembly 84 is an air
knife 250. The Air knife 250 is fluidly coupled to a source of CDA
or inert gas. The igniter nozzle assembly 248 is operably coupled
to a fuel source 52 and can have a sapphire nozzle tip 252 as
described above.
[0152] In operation, the system for initiating a clean flame,
needed in the processing of the wafer 26, includes disposing the
heating element 246 within an igniter assembly 78 and energizing
the heating element 246 so as to bring the assembly 78 to a
predetermined ignition temperature. Gas is then passed through an
ignition nozzle assembly 248 at a first gas rate pass the igniter
assembly 78 to ignite an initiation flame. The initiation flame is
then passed by a plurality of nozzles of a nozzle assembly 84 to
ignite a plurality of flames from the nozzles. After the plurality
of nozzles of the nozzle assembly 84 have been lit, an air dam is
passed in front of the initiation flame by actuating the air knife
250. A non-flammable gas is then passed through the initiator
nozzle 248 at a second predetermined rate. In this regard, a second
predetermined rate can be greater than the rate of fuel passing
through the nozzle. This prevents blow back into the ignition
system to the equipment. The use of the air knife 250 allows for
the extinguishment of the initiation flame without disruption of
the processing flames.
[0153] With reference to FIG. 26, shown is an alternate clean
ignition system. Similar to the system shown in FIGS. 23A and 23B,
the ignition system includes a nozzle 248 for injecting pressurized
fuel in proximity to the nozzle assembly 84. This nozzle 248
produces gas jet, which is temporally changed into a plasma and
ignited by a very high intensity laser 256. It is envisioned that
the ignition system can be disconnected by either shutting off the
source of the plasma gas, or disengaging the laser 256.
[0154] As shown in FIG. 27, optical analysis electronics (not
shown) are connected to a fiber optic coupler 210 disposed in the
upper section 38 of the isolator 25 in position to receive photon
emission from reactive processes. The optical analysis electronics
are used to observe and analyze reactive processes to determine
presence of reactive species and/or relative concentration of
reactive species. In another alternative mode of this feature,
optical emission spectroscopy can be used to infer etch end points
based on reactive species and/or etched products observed to be
present in the region where the chemical reaction in taking
place.
[0155] FIG. 27 represents a top view of a flame sense system for
use in the wafer processing system according to FIG. 1A. Shown is
the nozzle plate 216 which supports the nozzle assembly 84 having
processing nozzles 45 and 49. Directed to the nozzles 45 and 49 is
a CCD spectral analyzer 260. The spectrometer is configured to
receive emissions from the flames emitted from the nozzles 45 and
49.
[0156] FIG. 28 represents an intensity graph for a spectrum of
particular interest. In this regard, the graph depicts wavelength
between 200 and 400 nm. As can be seen, under the curve of
wavelength between 302 and 324 nm varies depending on the number of
flames initiated. It is envisioned that the system can determine
the quality and quantity of the number of flames being produced by
the system by analyzing the spectral output.
[0157] The spectral region of interest used for flame sensing with
H.sub.2 and O.sub.2 dominated gas mixtures is between about 300 and
325 nm. Emissions around 309 nm is from an intermediate O--H
species generated in the flame.
[0158] It is envisioned that the mass flow controller 52 of the
present system can be coupled to the spectral analyzer 260. In this
regard, it is envisioned that should the system determine that one
or more nozzles has not be properly emitted, the system will
signally fault and can shut the system down. As shown in FIG. 29,
varying the number of nozzles, varies the output of the system.
This can be detected to determine if the system is functioning
properly.
[0159] The foregoing discussion discloses and describes exemplary
embodiments of the present invention. One skilled in the art will
readily recognize from such a discussion, and from the accompanying
drawings and claims that various changes, modifications, and
variations can be made therein without departing from the spirit
and scope of the invention.
* * * * *