U.S. patent application number 09/179921 was filed with the patent office on 2001-11-01 for deposition reactor having vaporizing, mixing and cleaning capabilities.
Invention is credited to LIU, PATRICIA M., METZNER, CRAIG R., NARWANKAR, PRAVIN K., REDINBO, GREGORY F., SAHIN, TURGUT.
Application Number | 20010035127 09/179921 |
Document ID | / |
Family ID | 22658530 |
Filed Date | 2001-11-01 |
United States Patent
Application |
20010035127 |
Kind Code |
A1 |
METZNER, CRAIG R. ; et
al. |
November 1, 2001 |
DEPOSITION REACTOR HAVING VAPORIZING, MIXING AND CLEANING
CAPABILITIES
Abstract
An integrated deposition system is provided which is capable of
vaporizing low vapor pressure liquid precursors and delivering this
vapor into a processing region for use in the fabrication of
advanced integrated circuits. The integrated deposition system is
made up of a heated exhaust system, a remote plasma generator, a
processing chamber and a liquid delivery system which together
provide a commercially viable and production worthy system for
depositing high capacity dielectric materials from low vapor
pressure precursors, anneal those films while also providing
commercially viable in-situ cleaning capability.
Inventors: |
METZNER, CRAIG R.; (FREMONT,
CA) ; SAHIN, TURGUT; (CUPERTINO, CA) ;
REDINBO, GREGORY F.; (SAN JOSE, CA) ; NARWANKAR,
PRAVIN K.; (SUNNYVALE, CA) ; LIU, PATRICIA M.;
(SARATOGA, CA) |
Correspondence
Address: |
PATENT COUNSEL MS 2061
LEGAL AFFAIRS DEPT
APPLIED MATERIALS INC
3050 BOWERS AVENUE
SANTA CLARA
CA
95054
|
Family ID: |
22658530 |
Appl. No.: |
09/179921 |
Filed: |
October 27, 1998 |
Current U.S.
Class: |
118/715 ;
118/725 |
Current CPC
Class: |
C23C 16/4405 20130101;
C23C 16/4412 20130101; C23C 16/4411 20130101; C23C 16/44 20130101;
C23C 16/4557 20130101; C23C 16/452 20130101; C23C 16/4481 20130101;
C23C 16/54 20130101; C23C 16/45561 20130101; C23C 16/407 20130101;
C23C 16/448 20130101; C23C 16/45565 20130101 |
Class at
Publication: |
118/715 ;
118/725 |
International
Class: |
C23C 016/00 |
Claims
Thus, we claim,
1. An apparatus for dispersing gases within a processing chamber,
said apparatus comprising: (a) an upper surface having a circular
opening coupled to a cylindrically shaped first conduit; (b) a
lower surface having a circular opening coupled to a cylindrically
shaped second conduit; and (c) a conically shaped coupling conduit
in communication with said first and second conduits.
2. An apparatus according to claim 1 wherein said conically shaped
coupling region has diverging walls.
3. An apparatus according to claim 1 wherein said conically shaped
coupling region and said second cylindrically shaped conduit are
axially symmetric to a common centerline.
4. An apparatus for distributing gases within a processing chamber,
said apparatus comprising: (a) an inlet comprising a first
cylindrical region having a first diameter; (b) an outlet
comprising a second cylindrical region having a second diameter and
walls having a first length; and (c) a conical region in
communication with said first and second cylindrical regions said
conical region further comprising walls having a second length
wherein said walls form an angle.
5. An apparatus according to claim 4 wherein said second diameter
is greater than said first diameter.
6. An apparatus according to claim 4 wherein said angle formed
within said conical region is between about 20 degrees and 90
degrees.
7. An apparatus according to claim 4 wherein said first length is
greater than said second length.
8. A method for absorbing radiation within a gas distribution plate
said method comprising the steps of: (a) placing a substrate in a
processing apparatus having a gas distribution plate wherein said
gas distribution plate includes a plurality of gas inlets having a
first and second cylindrical region and a conical region; (b)
generating radiation from said substrate wherein said radiation is
incident to said gas distribution plate; and (c) absorbing a
portion of said incident radiation in said conical region.
9. A method according to claim 8 wherein a portion of said incident
radiation is reflected off said conical region and absorbed in said
first cylindrical region.
10. A method according to claim 8 wherein a portion of said
incident radiation is reflected off said conical region and
absorbed in said second cylindrical region.
11. A method of flowing gas through a gas distribution plate, said
method comprising the steps of: (a) flowing a gas through a first
cylindrical region having a first diameter; (b) flowing said gas
through a conical region; (c) flowing said gas through a second
cylindrical region having a second diameter;
12. The method according to claim 11 wherein said second diameter
is greater than said first diameter.
13. An apparatus for fabricating semiconductor devices said
apparatus defining an evacuable chamber comprising: (a) a substrate
support having a heated formed therein; (b) a lid having a heater
formed therein; (c) walls; and (d) a gas distribution plate coupled
to said lid.
14. An apparatus according to claim 13 wherein said heater formed
internal to said substrate support is a resistive heater.
15. An apparatus according to claim 13 wherein said heater formed
internal to said lid is a resistive heater.
16. An apparatus according to claim 13 wherein said gas
distribution plate coupled to said lid forms a gas box between said
lid and said gas distribution plate.
17. An apparatus according to claim 16 wherein said heater formed
internal to said lid heats that portion of said lid adjacent to
said gas box.
18. An apparatus for processing substrates, said apparatus
comprising: (a) a processing chamber said chamber having: (i) a
lid; (ii) walls; (iii) a heated substrate support; and (b) a
showerhead gas distribution plate, said showerhead gas distribution
plate having a surface wherein said surface of said showerhead gas
distribution plate faces said substrate support and wherein said
showerhead gas distribution plate is coupled to said lid and said
surface modified to increase the emissivity of the showerhead
surface.
19. An apparatus according to claim 18 wherein said showerhead
surface facing said substrate support is anodized.
20. An apparatus according to claim 18 wherein said showerhead
surface facing said substrate support is coated with a ceramic.
21. An apparatus according to claim 18 wherein said showerhead
surface facing said substrate support is coated with an oxide.
22. An apparatus according to claim 18 wherein said showerhead
surface facing said substrate support is bead blasted.
23. An apparatus according to claim 18 wherein said showerhead
surface facing said substrate has an emissivity between about 0.5
and 0.9.
24. An apparatus according to claim 18 wherein said gas
distribution plate includes a plurality of gas inlets having a
first cylindrical region forming an inlet, a second cylindrical
region forming an outlet and a conical region coupling said inlet
to said outlet.
25. An apparatus according to claim 24 wherein the diameter of an
outlet is large relative to the distance between adjacent outlets
thereby minimizing the reflective surface between adjacent
outlets.
26. An apparatus for vaporizing and delivering low vapor pressure
precursors to a processing chamber, said apparatus comprising: (a)
a vaporizer, (b) a first conduit, (c) a second conduit, (d) a third
conduit; and (e) a processing chamber, wherein said first conduit
is coupled to said vaporizer and said second conduit and said first
conduit further includes a first thermocouple, a first controller
and a first heater wherein said first thermocouple measures the
temperature of said first conduit which is provided to said first
controller which adjusts the output of said first heater to
maintain said first conduit at a set-point temperature, and wherein
said second conduit is coupled to said first conduit and said third
conduit and said second conduit further includes a second
thermocouple, a second controller and a second heater wherein said
second thermocouple measures the temperature of said second conduit
which is provided to said second controller which adjusts the
output of said second heater to maintain said second conduit at a
set-point temperature, and wherein said third conduit is coupled to
said second conduit and said processing chamber and said third
conduit further includes a third thermocouple, a third controller
and a third heater wherein said third thermocouple measures the
temperature of said third conduit which is provided to said third
controller which adjusts the output of said third heater to
maintain said third conduit at a set-point temperature.
27. An apparatus according to claim 26 wherein the diameter of said
first conduit is less than the diameter of said second conduit.
28. An apparatus according to claim 26 wherein the diameter of said
second conduit is less than the diameter of said third conduit.
29. An apparatus according to claim 26 wherein at least one conduit
and its associated heater and thermocouple are disposed internal to
the same structure.
30. An apparatus for controlling the temperature of a conduit which
delivers vaporized liquid to a processing chamber, said apparatus
comprising: (a) a conduit formed in a rigid thermally conductive
medium wherein said conduit is in communication with a vaporizing
means and a processing chamber; (b) a heater disposed internal to
said medium and thermally coupled to said conduit; (c) a
thermocouple disposed internal to said medium wherein said
thermocouple is thermally coupled to said conduit and produces an
output representing the temperature of said conduit; and (d) a
controller coupled to said thermocouple and said heater, wherein
said controller processes said thermocouple output and adjusts said
heater output to maintain said conduit at a set-point
temperature.
31. A method of delivering vaporized low vapor pressure precursors
to a processing chamber, said method comprising the steps of: (a)
forming a vaporized precursor gas stream by vaporizing a low vapor
pressure precursor; (b) providing said vaporized precursor gas
stream to a first conduit while independently controlling the
temperature of said first conduit; (c) providing said vaporized
precursor gas stream to a second conduit while independently
controlling the temperature of said second conduit; (d) providing
said vaporized precursor gas stream to a third conduit while
independently controlling the temperature of said third conduit;
and (e) providing said vaporized precursor gas stream to a
processing chamber.
32. The method according to claim 31 wherein the temperature of
said first conduit is lower than the temperature of said second
conduit and said third conduit.
33. The method according to claim 31 wherein the temperature of
said first and said second conduits is lower than the temperature
of said third conduit.
34. The method according to claim 31 wherein the cross-sectional
flow area of each successive conduit is greater than the
cross-sectional flow area of the immediately preceding conduit.
35. A method of delivering vaporized low vapor pressure precursors
to a processing chamber, said method comprising the steps of: (a)
forming a vaporized precursor gas stream by vaporizing a low vapor
pressure precursor; (b) providing said vaporized precursor gas
stream to a first conduit having a cross sectional flow area while
independently controlling the temperature of said first conduit;
(c) providing said vaporized precursor gas stream to a second
conduit having an increased cross sectional flow area while
independently controlling the temperature of said second conduit;
(d) providing said vaporized precursor gas stream to a third
conduit having an increased cross sectional flow area while
independently controlling the temperature of said third conduit;
and (e) providing said vaporized precursor gas stream to a
processing chamber.
36. A method of delivering vaporized precursor to a processing
chamber, said method comprising the steps of: (a) forming a
vaporized precursor gas stream by vaporizing a liquid precursor;
(b) maintaining said vaporized precursor gas stream at a first
temperature; (c) providing a process gas stream at a second
temperature; and (d) mixing said vaporized precursor gas stream and
said process gas stream while maintaining said second temperature
at least as high as said first temperature.
37. A method of incrementally heating a gas flow, said method
comprising the steps of: (a) flowing a gas in a first conduit while
maintaining said first conduit at a temperature; (b) flowing said
gas from said first conduit into a second conduit while maintaining
said second conduit at a temperature above said temperature of said
first conduit; (c) flowing said gas from said second conduit into a
third conduit while maintaining said third conduit at a temperature
above the temperature of said second conduit; and wherein, the
temperature of said first, second and third conduits is less than
the decomposition temperature of said gas.
38. A method according to claim 37 wherein the temperature of said
first, second and third conduits is above the condensation
temperature of said gas.
39. A method of delivering vaporized low vapor pressure precursors
to a processing chamber, said method comprising the steps of: (a)
forming a vaporized precursor gas stream by vaporizing a low vapor
pressure precursor; (b) providing said vaporized precursor gas
stream to a first conduit having a cross sectional flow area while
independently controlling the temperature of said first conduit;
(c) providing said vaporized precursor gas stream to a second
conduit having an cross sectional flow area greater than said cross
sectional flow area of said first conduit while independently
controlling the temperature of said second conduit; (d) providing a
process gas stream into said second conduit wherein said vaporized
precursor gas stream and said process gas stream merge forming a
mixed gas stream; (e) flowing said mixed gas stream for a distance
within said second conduit wherein said vaporized precursor gas
stream and said process gas stream are homogeneously mixed; and (f)
flowing said homogeneously mixed vaporized precursor gas stream and
process gas stream to a processing chamber.
40. An apparatus for processing semiconductor substrates, said
apparatus comprising: (a) a processing chamber comprising: (i) a
resistively heated substrate support disposed internal to said
chamber; (ii) a heated lid forming the top of said chamber; and
(iii) a showerhead gas distribution plate coupled to said lid of
said chamber wherein said gas distribution plate further comprises
a plurality of apertures; and (b) a fluid delivery system, said
system comprising: (i) a vaporizer; (ii) a first conduit having a
first diameter and maintained at a first temperature wherein said
first conduit is in communication with said vaporizer and said
second conduit; (iii) a second conduit having a second diameter and
maintained at a second temperature wherein said second conduit in
communication with said first conduit and said third conduit; and
(iv) a third conduit having a third diameter and maintained at a
third temperature wherein said third conduit in communication with
said second conduit and said processing chamber; and (c) an exhaust
system comprising: (i) a first conduit in communication with said
processing chamber wherein said first conduit is maintained at a
first temperature; (ii) a second conduit in communication with said
first conduit wherein said second conduit is maintained at a second
temperature; and (d) a remote plasma generator coupled to said
processing chamber.
41. An apparatus according to claim 40 wherein said fluid delivery
system third diameter is greater than each of said first and second
fluid delivery system diameters.
42. An apparatus according to claim 40 wherein fluid delivery
system second diameter is greater than said fluid delivery system
first diameter.
43. An apparatus according to claim 40 wherein said second conduit
temperature of said liquid delivery system is about the same or
greater than said first conduit temperature of said liquid delivery
system.
44. An apparatus according to claim 40 wherein said third conduit
temperature of said liquid delivery system is about the same or
greater than said first conduit temperature and said second conduit
temperature of said liquid delivery system.
45. An apparatus according to claim 40 wherein said gas
distribution plate apertures further comprise first and second
cylindrical regions and a conical region.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to an apparatus and process for the
vaporization of liquid precursors and the controlled delivery of
those precursors to form films on suitable substrates. More
particularly, this invention relates to an apparatus and a method
for the deposition of a high dielectric constant film, such as
Tantalum Oxide (Ta.sub.2O.sub.5), on a silicon wafer to make
integrated circuits useful in the manufacture of advanced dynamic
random access memory (DRAM) modules and other semiconductor
devices.
[0003] 2. Background of the Invention
[0004] The desire for greater capacity integrated circuits (ICs) on
smaller sized devices has increased interest in replacing today's
64 megabit DRAM with memory devices in the range of 256 megabit, 1
gigabit and higher. This need for increased capacity on the same or
smaller substrate footprint device makes it necessary to replace
conventional dielectric films previously used in stacked capacitor
formation, such as silicon dioxide (SiO.sub.2), with dielectric
films having higher dielectric constants. Capacitors containing
high-dielectric constant materials, such as Ta.sub.2O.sub.5,
usually have much larger capacitance densities than standard
SiO.sub.2--Si.sub.3N.sub.4--SiO.sub.2 stack capacitors making them
the materials of choice in IC fabrication. High dielectric constant
films are desirable because they provide higher capacitance which
enables closer spacing of devices without electrical interference
which can increase transistor density. One material of increasing
interest for stack capacitor fabrication is Tantalum Oxide which
has a relative dielectric constant more than six times that of
SiO.sub.2.
[0005] One common method of forming Tantalum oxide film is to
vaporize a liquid Tantalum precursor and then deliver the Tantalum
vapor to a deposition chamber. Such vapor delivery methods face
numerous challenges because of the low vapor pressure of typical
Tantalum precursors such as (Ta(OC2H.sub.5).sub.5) or TAETO and
Tantalum Tetraethoxide Dimethylaminoethoxide
(Ta(OEt).sub.4(OCH.sub.2CH.sub.2N(Me).sub.2) or TAT-DMAE, both of
which are liquid at room temperature and pressure. FIG. 1
graphically illustrates the large variation between the vapor
pressure of Tantalum precursors and other representative prior-art
precursors for other semiconductor related processes. For example,
at 100.degree. C. and 1 atm TAT-DMAE has about 0.3 Torr vapor
pressure while TAETO has about 0.03 Torr vapor pressure. The vapor
pressures for Tantalum precursors are remarkably lower than those
precursors typically used in prior art vapor delivery systems which
are intended to vaporize precursors having much higher vapor
pressures. Again referring to FIG. 1, at 100.degree. C. and 1 atm,
TEOS, (Tetra Ethyl OrthoSilicate) which is commonly used in
chemical vapor deposition processes to form SiO.sub.2 films and is
the subject of several prior art vapor delivery systems, has a
vapor pressure of almost 100 Torr. As a result of this vast
difference in vapor pressure, prior art vapor delivery systems did
not encounter nor provide solutions to many of the challenges
resulting from the use of very low vapor pressure precursors such
as TAETO and TAT-DMAE.
[0006] Prior art vapor delivery systems commonly involved the use
of an integrated liquid flow controller and vaporizer without a
positive liquid shut-off valve. Such a configuration, when used
with low vapor pressure Tantalum precursors, can lead to problems
stabilizing the Tantalum vapor output and difficulty achieving the
constant, repeatable Tantalum vapor output desirous in
semiconductor device fabrication. Previous delivery systems, based
upon experience with TEOS and other relatively high vapor pressure
materials, allow for the flow controller and vaporizer to be
separated by considerable distance or attach no significance to the
distance between vaporizer and liquid flow meter. Positioning the
vaporizer and flow meter according to prior art systems fail to
adequately control Tantalum precursor vapor. Previous delivery
systems are intended for use with higher vapor pressure precursors
whose residuals can be adequately removed by applying low pressure
or "pumping-down" the lines while flowing an inert gas like
nitrogen. Purging techniques such as these fail with Tantalum
systems because the low vapor pressure residual tantalum vapor
creates a need to introduce a solvent, such as isopropyl alcohol,
ethanol, hexane, or methanol into both the vaporization system and
supply lines to remove residual Tantalum precursor vapor.
[0007] Previous vapor delivery systems avoided precursor vapor
condensation by heating the delivery lines usually by resorting to
a flexible resistive heater which is wrapped around and held in
direct contact with the line, and then insulated. Since such
systems typically operated with precursor materials having a wide
temperature range within which the precursor remains vaporous, the
requirement to sample the temperature of any section of the heated
line was low and typically a single thermocouple would be used to
represent the temperature of piping sections as long as four to six
feet. Since the object of large scale temperature control systems,
such as wrapped lines and jacket-type heaters used in prior art
systems, is to heat and monitor an average temperature of a large
section of piping, such systems lack the ability to specifically
control a single, smaller section of the vapor piping and generally
have very low efficiency when higher line temperatures are desired.
Vaporized Tantalum delivery systems maintain the Tantalum vapor
above the vaporization temperature but below the decomposition
temperature for a given Tantalum precursor. Once formed, the
vaporous Tantalum must be maintained at elevated temperatures
between about 130.degree. C. and 190.degree. C. for TAT-DMAE and
between about 150.degree. C. and 220.degree. C. for TAETO. Because
of the relatively high temperatures needed and the narrow
temperature band available to low vapor pressure precursors such as
TAT-DMAE and TAETO, Tantalum and other low vapor pressure liquid
delivery systems would benefit from vapor delivery line temperature
controls and methods which can achieve and efficiently provide the
higher temperatures and greater temperature control needed for
Tantalum vapor delivery. Additionally, finer temperature controls
are desirous since the useable temperature range of vaporized low
pressure liquids is smaller than prior art liquids. Because higher
temperature vapor delivery is needed, Tantalum delivery systems
would benefit from designs which minimize the length of heated
vapor delivery lines. Minimizing the length of lines requiring
heating not only reduces the overall system complexity but also
decreases the footprint or overall size of the system.
[0008] Current methods of Tantalum Oxide deposition use reaction
rate limited chemical vapor deposition techniques. In reaction rate
limited deposition processes, the deposition rate achieved under
these conditions is largely influenced by the temperature of the
reaction environment. Existing chemical vapor deposition reactors
do not sufficiently address the thermal losses between the
substrate onto which the Tantalum film is to be formed and internal
chamber components such as the gas distribution showerhead. Such
thermal losses and the resultant non-uniform thickness of deposited
Tantalum illustrate the barriers to commercially viable Tantalum
oxide film formation techniques. However, with commercially viable
Tantalum deposition rates also comes the need for a viable, in-situ
cleaning process which can remove Tantalum deposition formed on
internal chamber components without harm to these components.
[0009] There is a need for a Tantalum deposition apparatus which
can deliver vaporized, measured Tantalum precursors which have been
adequately mixed with process gases to a reaction chamber which
provides a controlled deposition environment which overcomes the
shortcoming of the previous systems. Additionally, there is also a
need for a deposition apparatus capable of in-situ cleaning.
SUMMARY OF THE INVENTION
[0010] In one aspect of the present invention, a deposition
apparatus is provided for depositing tantalum oxides and other
materials especially those with low vapor pressure liquid
precursors which are provided as liquid to a vaporizer to be
converted into the vapor phase. The vapor is then transported from
the vaporizer into a substrate processing region via temperature
controlled conduits where the temperature within the conduits
allows neither condensation nor decomposition of the vaporized
precursor. Separate thermocouple, heater, controller units control
the temperature conduits so as to maintain a temperature within the
conduit above the condensation temperature but below the
decomposition temperature of a given precursor vapor or, more
particularly, between about 130.degree. C. and 190.degree. C. for a
Tantalum precursor such as TAT-DMAE or between about 150.degree. C.
and 220.degree. C. for a Tantalum precursor such as TAETO.
Additionally, the temperature controlled conduits could provide a
temperature gradient along the vapor flow path between the
vaporizer and the processing region. Other precursor source
materials and dopants, alone or in combination, are also
contemplated.
[0011] In another aspect of the present invention, a resistive
heater is embedded in the lid of the processing chamber which
provides for elevated temperatures within the gas box formed
between the lid and the showerhead gas distribution plate.
[0012] In another aspect of the showerhead gas distribution plate
of the present invention, the specific shape and spacing of the
apertures which allow gas to enter into the processing region of
the processing chamber present an angled lower surface towards a
substrate within the processing region. The spacing and specific
shape of the apertures allow more incident energy from the
substrate to be absorbed into instead of reflected off the
showerhead or where the emissivity of the showerhead is increased
by the angled lower surface. Another feature of the present
invention is modifying the surface of the showerhead lower surface
which faces a substrate in the processing region. The modification
results in a surface which has a high emissivity relative to the
emissivity changes which result from film accumulation on the
surface of the showerhead as well as other factors. Each of these
features alone or in combination helps minimize substrate heat
losses which contribute to temperature nonuniformities. The net
effect of the aperture hole shapes, spacing and high emissivity
modification or coating is that most of the radiation emitted from
the substrate surface is absorbed by the showerhead.
[0013] In another aspect of the present invention, a deposition
system is provided for depositing tantalum oxides and other
materials, especially those with low vapor pressures alone or in
combination with a variety of processing gases or dopants. The
deposition system is comprised of a heated exhaust system, a liquid
delivery system, a remote plasma generator, and a processing
chamber. In operation, the deposition system provides a method and
apparatus capable of the controlled delivery of a variety of
vaporized, low vapor pressure liquid precursors and activated
species into a substrate processing region for cleaning, deposition
or other operations.
BRIEF DESCRIPTION OF THE FIGURES
[0014] FIG. 1 is a graph of Vapor Pressure (Torr) vs. Temperature
(.degree. C.) of various compositions;
[0015] FIG. 2 is a perspective view of the processing system of the
present invention;
[0016] FIG. 3 is a perspective view of four representative
processing systems of the present invention mounted on a typical
central wafer handling system;
[0017] FIG. 4 is a cross sectional view of a processing chamber of
the present invention;
[0018] FIG. 5 is a top view of the lid of the present
invention;
[0019] FIG. 6 is a top view of a showerhead having apertures
249;
[0020] FIG. 7 is a sectional view of apertures 249;
[0021] FIG. 8 is a top view of a showerhead having apertures
238;
[0022] FIG. 9 is a sectional view of apertures 238;
[0023] FIG. 10 is a plan view of the spacing between aperture
outlets;
[0024] FIG. 11 is a table listing the representative distribution
of apertures 238;
[0025] FIG. 12 is a table listing the representative distribution
of apertures 249;
[0026] FIG. 13 is a sectional view of reflected and absorbed
radiation within apertures of the present invention;
[0027] FIG. 14 is a sectional view of gas delivery lines within a
heated gas feed through assembly of the present invention;
[0028] FIG. 15 is a perspective view of an embodiment of the
exhaust system and remote plasma generator of the present
invention;
[0029] FIG. 16 is a schematic view of a typical remote plasma
generator;
[0030] FIG. 17 is a perspective view of the vapor delivery system
of the present invention;
[0031] FIG. 18 is a schematic drawing of a representative liquid
mass flow controller of the present invention;
[0032] FIG. 19 is a schematic drawing of a representative liquid
delivery system having one vaporizer;
[0033] FIG. 20 is a schematic drawing of a representative liquid
delivery system having two vaporizers;
[0034] FIG. 21 is a table summarizing Liquid Alignment
Configurations of the vapor delivery system.
DETAILED DESCRIPTION OF THE INVENTION
[0035] The present invention is directed to a novel liquid delivery
system, chemical vapor deposition (CVD) chamber, exhaust system and
remote plasma generator which together comprise 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.
[0036] FIG. 2 is a perspective view of the processing system 100
showing the relative positions of the main components of the
present invention. System 100 contains a processing chamber 200, a
heated exhaust system 300, a remote plasma generator 400 and a
vapor delivery system 500. Also shown in FIG. 2 is a central
substrate transfer chamber 110 representative of a cluster tool
embodiment of the processing system of the present invention.
Processing chamber 200 is comprised of lid 205 and chamber body 210
and is attached to central transfer chamber 110. Gases supplied via
liquid delivery system 500 are provided into a processing region
202 (not shown) within chamber 200 via temperature controlled
conduits formed within inlet block 272, mixing block 266 and
central block 262. Cartridge style heaters 264 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. 2 but an aspect
of the present invention is embedded lid heater 235 located
integral to lid 205 beneath heater backing plate 234.
[0037] Chamber 200 processing by-products are exhausted via heated
exhaust system 300 which is coupled to chamber 200 via exhaust port
305. Also shown are isolation valve 310, throttle valve 315,
chamber by-pass 320, cold trap 325 and cold trap isolation valve
330. For clarity, specific embodiments of vacuum pump 335 and wafer
fabrication plant exhaust treatment systems 340 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 300, the jacket type heaters, thermocouples and
controllers used to maintain setpoint temperatures in exhaust port
305, isolation valve 310, throttle valve 315, chamber by-pass 320,
and by-pass line 322 have been omitted.
[0038] Activated species are generated by remote plasma generator
400 and provided to a processing region within chamber 200 via
conduits within activated species inlet block 420, activated
species block 270 and central block 262. Other components of remote
plasma generator 400 such as magnetron 402, auto tuner controller
410, and auto tuner 408 are visible in FIG. 2.
[0039] One of the main components of liquid delivery system 500 is
liquid flow meter 510 and vaporizer 520. Three-way inlet valve 588
allows either precursor 503 or solvent 591 into vapor delivery
system 500. Heat exchangers 530 and 582 preheat carrier gases and
process gases respectively. Heated carrier gases travel via a
carrier gas supply line 532 to vaporizer 520 in order to facilitate
more complete vaporization within vaporizer 520 as well as carry
vaporized liquids to chamber 200. After vaporization in vaporizer
520, chamber by-pass valve 545 allows vapor to be ported either to
processing region 202 in chamber 200 via outlet 582 or to exhaust
system 300 via outlet 555 which is coupled to heated by-pass line
322. A jacket style heater, thermocouple and controller which
maintain the temperature of chamber by-pass valve 545 and vaporized
precursor line 560 as well as the jacket style heater, thermocouple
and controller which maintain the temperature of by-pass line 322
have been omitted so as not to obscure the components of liquid
delivery system 500 and their relationship to chamber 200 and
heated exhaust system 300.
[0040] 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 performed. A preferred embodiment
of the invention will be described herein with reference to a
processing system 100 adapted to process a 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 200.
[0041] Turning now to FIG. 3, which is a perspective view of a
plurality of processing systems 100 arranged in a cluster tool
arrangement around central substrate transfer chamber 110 and
supported by common mainframe support structure 105. The
Centura.RTM. mainframe system, manufactured by Applied Materials,
Inc. of Santa Clara, Calif., is representative of one such cluster
tool arrangement. This arrangement allows multiple chambers, shown
here comprising four processing systems 100 of the present
invention, to share a common vacuum transfer 110. One advantage of
such an arrangement is that the central substrate transfer also has
attached to it a loadlock or loadlocks which hold a plurality of
substrates for processing in chambers attached to the central
substrate transfer 110. Although FIG. 3 illustrates four identical
processing systems 100, another advantage of the cluster tool
arrangement is the ability to place a variety of chamber types onto
a single central substrate transfer 110. In such an arrangement, a
substrate may move between chambers arranged around central
substrate transfer 110 without exposure to an air or oxygen
ambient. Not shown in FIG. 3, but a feature of the deposition
system 100 of the present invention, either one or a plurality of
deposition systems 100 may be arranged in communication with
central substrate transfer 110 with a variety of predetermined
chamber types such that a substrate could be loaded into the
loadlock attached a central substrate transfer 110, sequence
through the various chambers and as a result of the sequencing form
predetermined and desirous films on a substrate processed in this
manner. It is anticipated that deposition system 100, in
conjunction with other chamber types, would be capable of forming
complete portions of an IC. Specifically anticipated is the
selection of chamber types, sequencing and liquid delivery
configurations which would result in the formation of a
representative stack capacitor having polysilicon bottom and top
electrodes separated by silicon nitride and titanium nitride
barrier layers which are separated by a tantalum oxide dielectric
layer. Other layers and structures are also anticipated and are
intended to be included within the capabilities of the methods and
apparatus described herein. It is also specifically anticipated
that a single deposition system 100 would alone have the processing
capability of forming complete portions of an IC.
[0042] Chamber 200 is shown with protective cover 203 in place.
Cover 203 encloses heated chamber lid 205 and temperature
controlled conduit blocks 272, 266 and 262. Cover 203 is maintained
at a relatively safe temperature so as to prevent burn injuries
from contact with the heated components of lid 205.
[0043] Remote plasma generator 400 is also shown in an alternative
embodiment in which the generator is supported from the top of
mainframe 105 instead of from below as shown in FIG. 2. So as not
to obstruct the view of an alternative embodiment of remote plasma
generator 400, heated exhaust system 300 is not shown. Such a
support arrangement of remote plasma generator 400 provides easier
accessibility and maintenance of other components of deposition
system 100 as well as contributing to the reduction of the overall
footprint of deposition system 100. The embodiment of the plurality
of processing systems 100 of FIG. 3 further illustrate the compact
design features of system 100 of the present invention.
[0044] The Deposition Chamber
[0045] FIG. 4 is a cross sectional view of chamber assembly 200 of
processing system 100 of FIG. 2. Chamber body 210 and heated
chamber lid 205, which is hingedly connected to chamber body 210,
together with o-ring 245 form a temperature and pressure controlled
environment or processing region 202 which enables deposition
processes and other operations to be performed within processing
region 202. Chamber body 210 and lid 205 are preferably made of a
rigid material such as aluminum, various nickel alloys or other
materials having good thermal conductivity. O-ring 245 could be
formed from Chemraz, Kalrez, Viton or other suitable sealing
material.
[0046] When lid 205 is closed as shown in FIG. 4, an annular
processing region 202 is formed which is bounded by showerhead 240,
substrate support 250 and the walls of chamber body 210. Substrate
support 250 (shown in the raised position for processing) extends
through the bottom of chamber body 210. Imbedded within substrate
support 250 is a resistive heater which receives power via
resistive heating element electrical connector 257. A thermocouple
in thermal contact with substrate support 250 senses the
temperature of substrate support 250 and is part of a closed loop
control circuit which allows precise temperature control of heated
substrate support 250. Substrate support 250 and substrate 201 are
parallel to showerhead 240. Substrate 201 is supported by the upper
surface of support 250 and is heated by the resistive heaters
within substrate support 250 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.
[0047] Processing chamber 200 is coupled to central transfer
chamber 110 via opening 214. A slit valve 215 seals processing
region 202 from central transfer chamber 110. Substrate support 250
may also move vertically into alignment with opening 214 which,
when slit valve 215 is open, allows substrates to move between the
processing region 202 and central substrate transfer chamber 110.
Substrate 201 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.
[0048] Pumping passage 203 and outlet port 260 formed within
chamber body 210 for removing by products of processing operations
conducted within processing region 202. Outlet port 260 provides
fluid communication between components of heated exhaust system 300
and processing region 202.
[0049] Turning now to gas delivery features of chamber 200, both
process gas/precursor mixture from liquid delivery system 500, via
conduit 273, and activated species from remote plasma generator
system 400, via conduit 271, flow through central conduit 231 to
bore through 230 formed in lid 205. From there, gases and activated
species flow through blocker plate 237 and showerhead 240 into
processing region 202. A feature of showerhead 240 of the present
invention is the plurality of apertures 249, or alternative
aperture embodiment 238, which are not indicated in FIG. 4 so as
not to unnecessarily obscure understanding specific details and
features of chamber 200 and heated lid 205.
[0050] Process gas and vaporized precursors and mixtures thereof
are provided to central bore through 230 via temperature controlled
conduits formed integral to heated feed through assembly 220.
Heated feed through assembly 220 is comprised of central block 262,
mixed deposition gas feed through block 266 and inlet and mixing
block 272. Although the embodiment represented in chamber 200 of
FIG. 4 indicates a heated feed through assembly 220 comprising
three separate blocks 262, 266 and 272, one of ordinary skill will
appreciate that the blocks can be combined such as replacing inlet
and mixing block 272 and feed through block 266 with a single block
without departing from the spirit of the present invention.
Additionally, a plurality of cartridge heaters 264 are disposed
internal to each of the aforementioned blocks and proximate to the
conduits 231, 273, 278, 265, and 276 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.
[0051] Lid 205 is also provided with a cooling channel 244 which
circulates cooling water within that portion of lid 205 in
proximity to o-ring 245. Cooling channel 244 allows lid 205 to
maintain the temperatures preferred for advantageous heating of
showerhead 240 while protecting o-ring 245 from the high
temperatures which degrade the sealing qualities of o-ring 245
thereby making o-ring 245 more susceptible to attack by the
reactive species generated and supplied to processing region 202 by
remote plasma generator 400.
[0052] Another feature of processing chamber 200 of the present
invention also shown in FIG. 4 is embedded resistive heater 235
within lid 205. This feature of chamber assembly 200 provides
elevated temperatures in lid 205 in proximity to central bore
through 230 and the area between the lower surface of the lid 205
and showerhead upper surface 263. The region between lid 205 and
showerhead upper surface 263 is referred to as the "gas box".
Formed within the top surface of lid 205 is an annular groove
shaped according to the size and shape of imbedded heater 235 in
order to increase surface contact and heat transfer between
resistive heater 235 and lid 205. Without heater 235, cooling
channel 244 could continuously remove heat from lid 205. As a
result, cooling channel 244 also affects the temperature of
portions of lid 205 in contact with precursor vapor, such as the
area surrounding central bore through 230 and the gas box. While
cooler lid 205 temperatures improve conditions for o-ring 245,
cooler lid 205 temperatures could result in undesired condensation
of precursor vapor. Thus, it is to be appreciated that resistive
heater 235 is positioned to heat those portions of lid 205 in
contact with the vaporized precursor flow such as the gas box and
the area surrounding central bore through 230. As shown in FIG. 4,
for example, heater 235 is located between cooling channel 244 and
central bore through 230 while also positioned to provide heating
to the lid surface adjacent to blocker plate 237.
[0053] Referring now to FIG. 5 which is a top view of lid 205, the
relationship of embedded heater 235 to other components mounted on
lid 205 can be better appreciated. Embedded heater 235 is indicated
in phantom and is located beneath backing plate 234. Backing plate
234 and fasteners 243 help increase the surface area contact
between embedded heater 235 and lid 205 thereby improving the
efficiency of heat transfer between heater 235 and lid 205. Lid 205
also has an embedded thermocouple 204 for monitoring the
temperature within lid 205 in proximity to heater 235. Thermocouple
204 is part of a feedback control circuit which monitors and
controls the power supplied to heater 235 to obtain a set point
temperature within lid 205. Precise temperature control is desired
in lid 205, as in all components in contact with vaporized
precursor, in order to provide conditions which neither condense
nor decompose low vapor pressure precursors such as TAT-DMAE and
TAETO.
[0054] For a representative 200 mm embodiment of chamber 200 shown
in FIG. 4, heater 235 could have a 650 W output rating and is
commercially available from a variety of commercial sources such as
Watlow, Inc. of Richmond, Ill. Temperature set-points between about
80.degree. C. and 180.degree. C. are readily obtained in lid 205
utilizing a heater 235 rated at about 650 Watts. It will be
appreciate that various heater ratings, set-points and
configurations could be utilized to obtain a wide range of
temperature set-points depending upon the decomposition and
condensation temperatures and other characteristics of the
precursor material used. Although imbedded heater 235 is
represented by a single, continuous, circular element, one of
ordinary skill will appreciate that alternative embodiments wherein
a plurality of continuous or discontinuous embedded heaters 235 are
arranged within lid 205 to provide additional heat or greater
temperature control within lid 205 are within the scope of the
present invention.
[0055] Referring again to FIG. 4, heated lid 205 provides support
for showerhead 240 and blocker plate 237. As such, showerhead 240
is attached to lid 205 via a plurality of evenly spaced fasteners
242 and blocker plate 237 is attached to lid 205 by a plurality of
evenly spaced fasteners 217. Fasteners 217 and 242 are formed from
a rigid material such as aluminum, varieties of nickel alloys and
other materials having good thermal conductivity. Fasteners 242 and
217 provide clamping force which increases the contact area between
heated lid 205 and the and the gas distribution components 237 and
240. Fasteners 242 and 217 have been advantageously placed to
provide clamping force to increase contact between heated lid 205
and showerhead 240 in the case of fasteners 242 and heated lid 205
and blocker plate 237 in the case of fasteners 217. Increased
contact area produces greater heat transfer between heated lid 205
and blocker plate 237 and showerhead 240.
[0056] Turning now to FIGS. 6, 7, 8, 9 and 13, the reduced
reflection and increased absorption features of showerhead 240 of
processing chamber 200 the present invention can be better
appreciated. FIGS. 6 and 8 illustrate a plan views of showerhead
lower surface 284 as viewed from a substrate 201 positioned on
substrate support 250. Viewed from substrate 201 and looking
towards lid 205 as in FIGS. 6 and 8 evenly spaced fasteners 242 are
visible on the periphery of showerhead lower surface 284.
Showerhead 240 also comprises a plurality of apertures 249 (FIG. 6)
and 238 (FIG. 8) which allow gases and activated species to enter
processing region 202.
[0057] Referring now to FIG. 7 the specific details and unique
geometry of an aperture 249 can be better understood. FIG. 7 is a
sectional view of an embodiment of a plurality of representative
apertures 249 which is indicated as view L-L on FIG. 5. Aperture
249 includes an upper region 291, a conical region 290 and a lower
region 248. A plurality of apertures 249 are distributed across
showerhead 240 thereby allowing gases to flow from blocker plate
237 through aperture 249 to substrate 201. Gas from blocker plate
237 flows onto showerhead upper surface 263 and into inlets 291 of
apertures 249. Inlet 291 is axially symmetric to aperture
centerline 267 and could be cylindrically shaped with a diameter
247 of 0.028 inches. Inlet 291 is bounded by showerhead upper
surface 263 and inlet parallel walls 269. Gas flows out of inlet
291 and into lower conical region 290 which is defined by divergent
walls 255 which are axially symmetric to aperture centerline 267.
For example, lower conic region 290 has an upstream diameter 256
measured between walls 255 which is smaller than a downstream lower
conic region diameter 258. Extending divergent walls 255 to
intersect at vertex 259, as indicated by dashed lines 296, angle
.beta. is formed. Angle .beta. is axially symmetric to aperture
centerline 267 such that vertex 259 is on and bisected by aperture
centerline 267. Angle .beta. is measured between divergent walls
255 and vertex 259. Thus, the angled surfaces of divergent walls
255 are presented to substrate 201.
[0058] From lower conic region 290 gas flows into outlet 248 which
has parallel walls 281, a diameter 288 and is axially symmetric
about centerline 267. Parallel walls 281 have a length 283 measured
between the intersection of divergent walls 255 and parallel walls
281 and showerhead lower surface 284. Gas flowing out of outlet 248
flows towards substrate 201 within processing region 202.
[0059] The geometry and other specific aspects of aperture 249 are
more clearly understood by describing the ratios between various
aperture components. For example, inlet diameter 247 is less than
outlet diameter 288 or inlet diameter 247 could be about one-third
of outlet diameter 288 such as when a representative aperture 249
has an inlet diameter 247 of 0.028 inches and an outlet diameter
288 of 0.086 inches.
[0060] Another aspect of aperture 249 is the ratio between length
283 of outlet parallel walls 281 and outlet diameter 288 where
length 283 is greater than diameter 288 or where length 283 is
about 2.5 times outlet diameter 288. For example, a representative
aperture 249 could have an outlet diameter 288 of about 0.086
inches and a length 283 of about 0.221 inches. Another aspect of
aperture 249 is that length 283 of parallel walls 281 is greater
than the length of divergent walls 255 or where parallel walls 281
are about 5.5 times as long as divergent walls 255. For example,
the length 283 is about 0.221 inches and the length of divergent
walls 255 is about 0.041 inches which results in a ratio of the
length 283 of parallel walls 281 to the length of divergent walls
255 of about 5.39. Utilizing the ratios above, representative
dimensions for each of a plurality of apertures 249 in a
representative showerhead 240 fabricated from aluminum having a
thickness of about 0.5 inches are: an inlet diameter 247 of about
0.028 inches; with inlet parallel walls 269 of about 0.25 inches;
an outlet diameter 288 of about 0.086 inches with outlet parallel
walls length 283 of about 0.221 inches.
[0061] Referring now to FIG. 9 the specific details and unique
geometry of an alternative aperture embodiment, aperture 238, can
be better understood. FIG. 9 is a sectional view of an embodiment
of a single alternative aperture 238 indicated by view D-D on FIG.
8. A plurality of apertures 238, like aperture 249, are distributed
across showerhead 240 thereby allowing gases to flow from blocker
plate 237 through aperture 238 to substrate 201. Aperture 238
includes an upper region 291, an upper conical region 289, a
central region 246, a lower conical region 290 and a lower region
248. Gas from blocker plate 237 flows onto showerhead upper surface
263 and into inlet 291. Inlet 291 is axially symmetric to aperture
centerline 267 and could be cylindrically shaped with a diameter
247 of 0.110 inches. Inlet 291 is bounded by showerhead upper
surface 263 and inlet parallel walls 269. Gas flows through inlet
291 into upper conic region 289 which is bounded by converging
walls 251. Upper conic region 289 is axially symmetric to aperture
centerline 267 and has a decreasing downstream diameter such that
an upper conic region upstream diameter 252 is greater than an
upper conic region downstream diameter 253. Converging walls 251,
if extended to an intersection point as indicated by dashed lines
295, would intersect at vertex 254 forming an angle .alpha.. Angle
.alpha. is axially symmetric to aperture centerline 267 such that
vertex 254 is on aperture centerline 267 and angle .alpha. is
bisected by aperture centerline 267. Angle .alpha., measured
between convergent walls 251 and vertex 254, is between about
25.degree. and about 45.degree..
[0062] From upper conic region 289, gas flows into a central
conduit 246 which is axially symmetric to aperture centerline 267.
Central conduit 246 could be cylindrically shaped with a diameter
287 of about 0.028 inches. Central conduit 246 acts as a coupling
conduit joining the upper conic region 289 and the lower conic
region 290 thus allowing gas flow from inlet 291 to outlet 248. Gas
flows from central conduit 246 into lower conical region 290 which
is defined by divergent walls 255 and is axially symmetric to
aperture centerline 267. For example, lower conic region 290 has an
upstream diameter 256 between walls 255 which is smaller than a
downstream lower conic region diameter 258. Divergent walls 255, if
extended to an intersection point as indicated by dashed lines 296,
would intersect at vertex 259 forming an angle .beta.. Angle .beta.
is axially symmetric to aperture centerline 267 such that vertex
259 is on and bisected by aperture centerline 267. Angle .beta. is
measured between divergent walls 255 and vertex 259. The angled
surfaces within showerhead 240 formed by divergent walls 255 are
presented to substrate 201.
[0063] Gas flows from lower conic region 290 into outlet 248 which
is axially symmetric about centerline 267. Outlet 248 could be
cylindrically shaped having parallel walls 281 and a diameter 288.
Parallel walls 281 have a length 283 measured between the
intersection of divergent walls 255 and parallel walls 281 and
showerhead lower surface 284. Gas flowing out of outlet 248 flows
towards substrate 201 within processing region 202.
[0064] The geometry and other specific aspects of aperture 238 are
more clearly understood by describing the ratios between various
aperture components. One aspect of aperture 238 is that inlet
diameter 247 is less than outlet diameter 288 or inlet diameter 247
is about one-half of outlet diameter 288. A representative aperture
238 could have an inlet diameter 247 of 0.110 inches and an outlet
diameter 288 of 0.213 inches. Another aspect of aperture 238 is the
ratio between the inlet 247 and outlet 288 diameters and the
central region diameter 287 where central region diameter 287 is
less than both inlet diameter 247 and outlet diameter 288. Central
region diameter 287 is about 0.25 of inlet diameter 247 and about
0.13 of outlet diameter 288. For example, a representative aperture
238 could have an inlet diameter 247 of 0.110 inches, an outlet
diameter 288 of 0.213 inches and a central region diameter of about
0.028 inches.
[0065] Another aspect of aperture 238 is the ratio between length
283 of outlet parallel walls 281 and outlet diameter 288 where
length 283 is less than diameter 288. For example, length 283 is
about three quarters or about 0.7633 of diameter 288, as in an
outlet 248 having a length 283 of 0.1569 inches and a diameter 288
of 0.213 inches. Another aspect of aperture 238 is that the length
283 of parallel walls 281 is greater than the length of divergent
walls 255 or where parallel walls 281 are about 1.5 times as long
as divergent walls 255. For example, for the aperture 238
dimensions detailed above, the length 283 is about 0.1569 inches
and the length of divergent walls 255 is about 0.1021 inches which
results in a ratio of the length 283 of parallel walls 281 to the
length of divergent walls 255 of about 1.53. Given the above
ratios, dimensions for each of a plurality of representative
apertures 238 in an aluminum showerhead 240 having a thickness of
about 0.4 inches are: an inlet diameter 247 of about 0.110 inches;
a central cylindrical region diameter 287 of about 0.028 inches
with parallel walls 286 of about 0.080 inches; and an outlet
diameter 288 of about 0.213 inches with outlet parallel walls 281
length 283 of about 0.1569 inches and divergent walls 255 of about
0.1021 inches. Although described as circular, the general shape of
inlet 291, central conduit 246 and outlet 248 of an aperture 238 as
well as the inlet 291 and outlet 248 of an apparatus 249 may also
have various other shapes such as heptagonal, octagonal or other
higher order polygons without departing from the scope of the
present invention. It is to be appreciated that the above cited
specific details with respect to aperture 238 and 249 are only
representative embodiments of the unique aperture geometry of the
present invention.
[0066] As mentioned above, in reaction rate limited processes, such
as the deposition of tantalum pentaoxide or other transition metal
dielectrics, one key factor for controlling deposition rate is the
temperature of substrate 201. Thus, temperature variations which
influence substrate 201 should be minimized to assist in obtaining
more uniform deposition rates. One source of temperature variation
occurs when radiant energy from substrate 201 and heated substrate
support 250 reflects off showerhead 240 back to substrate 201. This
redirected reflected energy is uncontrolled and asymmetric
resulting in temperature variations within a single substrate 201
and in consecutively processed substrates 201. Showerhead lower
surface 284 and divergent walls 255 of apertures 249 and 238 are
reflected surfaces for radiant energy from substrate 201 and heated
substrate support 250. Advantageously selecting the aperture
geometry presented to substrate 201 is one method of increasing the
emissivity of showerhead 240.
[0067] Two features of apertures 238 and 249 of the present
invention which increase the emissivity of showerhead 240 are
spacing 261 between apertures and the advantageous geometry of
aperture outlets 248. The advantageous geometry of outlet 248 is
discussed in detail below with respect to FIG. 13. Turning now to
FIGS. 6 and 8 a plurality of apertures 249, shown in FIG. 6, and
apertures 238, shown in FIG. 8, are evenly distributed across
showerhead 240 resulting in a pattern of outlets 248 in showerhead
lower surface 284. FIG. 10, which is an enlarged view E indicated
on FIG. 8, represents the spatial relationship between adjacent
outlets 248 regardless of aperture type. Outlets 248 are spaced
across showerhead lower surface 284 such that the flat, reflective
space between adjacent outlets 248 is minimized. The spacing
between outlets 248, spacing 261, which represents the width of the
flat reflective space between outlets 248 should be as small as
possible. Another method of spacing outlets 248 across showerhead
240 lower surface 284 is to separate adjacent aperture centerlines
267 by some constant distance 285. Constant spacing distance 285 is
selected based on outlet diameter 248 and desired spacing 261. For
example, an aperture 238 having an outlet diameter 248 of 0.213
inches and a desired spacing 261 of 0.005 inches would have a
centerline spacing 285 of 0.218 inches. In another example, an
aperture 238 having an outlet diameter 248 of 0.086 inches and a
desired spacing 261 of 0.012 inches would have a centerline spacing
285 of 0.098 inches.
[0068] As the number of apertures increases, spacing 261 decreases
for a given size showerhead 240. This not only reduces the
reflective surface between outlets 248 but also increases the
amount of angled reflective surface created by divergent walls 255
of each aperture. In one respect, the distribution of apertures 249
and 238 can be viewed as replacing the flat, highly reflective
surface between outlets 248 of lower showerhead surface 284 with
divergent walls 255. Distributing apertures 249 and 238 by
minimizing outlet spacing 261 increases the number and density of
apertures 249 and 238 which correspondingly increases the number
and density of divergent walls 255 presented to substrate 201. As
the amount of divergent wall surface area increases, the
probability that incident radiation onto showerhead 240 will be
reflected and absorbed into showerhead 240 also increases.
[0069] Referring now to FIG. 11, a representative distribution of
apertures 238 for a showerhead 240 sized to process 200 mm
substrates can be better appreciated. FIG. 11 is a table listing
representative aperture 238 locations using a coordinate system
having X and Y axes similar to the system shown in FIG. 7 with an
origin in the center of showerhead 240. FIG. 11 indicates ordinate
and abscissa values for a first aperture 238 in a row of apertures
238 which form a representative distribution of apertures 238
having a minimized flat surface 261 between each aperture 238.
Using FIG. 11 as a guide for the placement of each aperture 238
results in the distribution of about 1574 apertures 238 across
showerhead 240. This distribution pattern is similar to the pattern
of outlets 248 illustrated in FIG. 8. Referring now to FIG. 12, a
distribution pattern for a plurality of apertures 249 can be better
appreciated. FIG. 12 is a table listing representative aperture 249
locations using a coordinate system having X and Y axes similar to
the system shown in FIG. 6 with an origin in the center of
showerhead 240 used for processing 200 mm diameter substrates 201.
FIG. 12 indicates ordinate and abscissa values for a first aperture
249 in a row of apertures 249 which form a representative
distribution of apertures 249 having a minimized flat surface 261
between each aperture 249. Using FIG. 12 as a guide for the
placement of each aperture 249 results in the distribution of about
6165 apertures 249 across showerhead 240. This distribution pattern
is similar to the pattern of outlets 248 illustrated in FIG. 6.
[0070] Turning now to FIG. 13, the novel reflective and absorptive
characteristics of apertures 238 and 249 of the present invention
can be better appreciated. Although FIG. 13 is a sectional view of
an aperture according to aperture 249, the aspects of the present
invention which follow also apply to aperture embodiment 238 as
well as to other specific aperture embodiments made according to
the present invention. In this aspect of the present invention, the
specific geometric arrangement between divergent walls 255, angle
.beta., parallel walls 281 and outlet diameter 288 is selected in
order to increase the emissivity of showerhead 240. More
specifically, by advantageously selecting an angle .beta., for
example, outlet diameter 288 and length of parallel walls 281 can
be selected such that radiation reflected off divergent walls 255
is absorbed into showerhead 240. The reflected radiation could
then, for example, be absorbed into showerhead 240 through single
reflections or multiple reflections with walls 281 or other
aperture surfaces within showerhead 240.
[0071] The minimized spacing between adjacent outlets feature
aspect of showerhead 240 of the present invention is also
illustrated in FIG. 13. Radiation 222 represents that radiation
normal to showerhead lower surface 284. When normal radiation 222
intersects the generally flat, highly reflective surface 284, the
result is normal reflected radiation 223. It will be appreciated
therefore, that as aperture spacing 261 decreases, more normal
radiation 222 will be incident onto divergent walls 255 and the
highly absorptive geometry of apertures 238 or apertures 249.
[0072] In another aspect of the present invention, the relationship
between divergent walls 255 and outlet walls 281 is utilized to
facilitate absorption of reflected radiation into showerhead 240.
Divergent walls 255 and the angle .beta. between them provide a
reflective surface to representative incident radiation 206 and
208. For example, incident radiation 208 intersects divergent wall
255. A portion of radiation 208 will be absorbed by wall 255 and a
portion will be reflected as radiation 209. Because of the angled
presentation of divergent wall 255, reflected radiation 209
intersects wall 269. A portion of radiation 209 is absorbed in the
first intersection and a portion is reflected. This process of
absorption and reflection continues as reflected radiation 209 is
reflected and absorbed by walls 269. In another example, incident
radiation 206 intersects divergent wall 255 and a portion of
radiation 206 is absorbed by wall 255. A portion of radiation 206
is reflected by wall 255 forming reflected radiation 207. As a
result of the selection of angle .beta., reflected radiation 207
crosses lower region 248 and intersects an adjacent divergent wall
255. In the second intersection, a portion of radiation 207 is
absorbed by wall 255 and a portion is reflected. FIG. 13
illustrates an aperture configuration where radiation 206--i.e.
radiation reflected into lower region 248--is absorbed into walls
281. It is to be appreciated that angle .beta., length 283 and
diameter 288 could be selected such that radiation reflected into
the lower region 248 would have multiple refection and absorption
reactions with walls 281 and 255. By advantageously selecting the
outlet diameter, angle .beta., and the length of walls 281,
apertures according to the present invention will first reflect
radiation using divergent walls 255 then absorb radiation via
parallel walls 281 thereby reducing reflective radiation produced
by showerhead 240. In order to absorb reflected radiant energy,
such as reflected energy 207, walls 281 are generally between about
1.5 and 5.5 times the length of divergent walls 255 for a given
angle .beta.. For a representative aperture 249 located within a
showerhead 240 having a thickness of about 0.5 inches and an angle
.beta. of about 90.degree., divergent walls 255 are about 0.041
inches while walls 281 are about 0.221 inches. In a representative
aperture 248 located within a showerhead 240 having a thickness of
about 0.4 inches and an angle .beta. of about 130.degree.,
divergent walls 255 are about 0.1021 inches while walls 281 are
about 0.1569 inches. One of ordinary skill in the art will
appreciate that numerous showerhead thicknesses, outlet diameters
288, lengths of walls 281 and angles .beta. may be combined to
provide a varieties of aperture geometry capable of absorbing
incident radiation according to the methods of the present
invention.
[0073] In another aspect of the present invention, the emissivity
(.di-elect cons.) of the surface of showerhead 240 is intended to
be as high as possible in order to approximate the emissivity of a
black body. An object of the present invention is to provide
showerhead 240 emissivity in the range of about 0.6 to about 0.9.
Those of ordinary skill in the art will appreciate that a variety
of surface finishing techniques, such as anodization, oxidation,
ceramic coating or bead blasting may be employed to obtain the
desired emissivity. Film accumulation on showerhead 240 occurs
during sequential deposition processes within processing region
240. A showerhead with film deposits absorbs more incident
radiation than a showerhead without those accumulations. The
resulting absorption variation and temperature difference film
accumulation causes is a source of thickness uniformity variation
between consecutively processed wafers. For purposes of
illustration, suppose the resulting accumulation of film causes an
average emissivity change (.di-elect cons..sub.ch) of 0.05 in
showerhead 240. For reaction rate limited processes--which rely on
temperature--such a seemingly minor variation in emissivity can
result in wafer-to-wafer temperature variations which can in turn
result in deposition rate and thickness non-uniformities between
wafers processed in the same chamber. For example, a showerhead
having a unpolished metal surface may have an emissivity (.di-elect
cons..sub.sum) of about 0.4. As a result of processing several
wafers, .di-elect cons..sub.um could have been increased by
.di-elect cons..sub.ch or 0.05 to 0.45 representing a 12.5% change
in emissivity. Even if oxidized metals with an emissivity
(.di-elect cons..sub.nm) of about 0.45 are used, the emissivity
change resulting from the same amount of film deposition--an 0.05
increase in emissivity--results in an emissivity change of 11.1%.
Not until highly oxidized metals (.di-elect cons..apprxeq.0.7) or
even anodized surfaces (.di-elect cons..apprxeq.0.9) are employed
does the impact of representative emissivity change .di-elect
cons..sub.ch produce emissivity variation below 10%. Utilizing a
showerhead 240 with a higher initial emissivity reduces the impact
of later emissivity varying events such as the accumulation of film
on showerhead 240. An object of the present invention is to
increase the absorptive characteristics or emissivity of showerhead
240 such that the emissivity variation induced by film accumulation
is reduced or, in other words, the emissivity of showerhead 240 is
sufficiently high that it could be said to be invariant. For
example, a showerhead 240 having an emissivity above about 0.6 or a
sufficiently high emissivity such as between 0.7 and 0.9 which
changes by less than 10% after repeated exposure to processing
environments like those found in processing region 202.
[0074] Another object of the present invention is to reduce the
temperature variations from one substrate 201 to another in a
continuously running reactor as in, for example, reactors utilized
in reaction rate limited processes such as the deposition of
tantalum pentaoxide. Either of the emissivity increasing methods
described above (i.e., modification of showerhead surface or
selecting highly absorptive aperture geometry) can be employed
alone or in combination to increase the emissivity of showerhead
240 and thereby reduce temperature variations. First, reflective
surfaces on lower showerhead surface 284 have been minimized by
adjusting the spacing 261 between outlets 248. Minimizing the
spacing 261 between outlets 248 effectively substitutes the
divergent walls 255 of apertures 238 and 249 in the place of flat,
highly reflective surfaces. Second, the divergent walls 255 and
shape of lower conic region 290 in conjunction with parallel walls
281 of each of the plurality of apertures 238, or alternatively
249, result in reflective radiation patterns which will likely be
absorbed by showerhead 240 instead of reflected back to substrate
201. Third, the emissivity of the material forming showerhead 240
has been modified resulting in a is sufficiently high emissivity
such that emissivity varying events, such as the accumulation of
deposits during substrate processing, result in an over all
emissivity change of less than 10%. The showerhead emissivity could
be said to be invariant since emissivity change as a result of
wafer processing operations within processing region 202 is slight
or less than 10% of total emissivity. As a result, sequentially
processed wafers are exposed to a more similar processing
environment since the emissivity of a showerhead of the present
invention is nearly constant or invariant between consecutive
wafers.
[0075] The elevated temperature of showerhead 240 which results
from increased absorption of radiation provides several advantages
to chamber 200. As mentioned above, the elevated temperature
achieved in showerhead 240 can reduce or completely prevent
undesirous vapor condensation which may likely occur or occur at a
greater rate at lower showerhead temperatures. Another advantage is
that as the temperature of showerhead 240 increases, the
temperature difference between showerhead 240 and substrate 201
decreases. As the temperature difference decreases, the rate of
heat transfer between the substrate and the showerhead also
decreases. Controlling or minimizing heat losses from substrate 201
is critically important in reaction rate limited processes, such as
the formation of Tantalum oxide which is an object of processing
system 100 of the present invention. The rate of heat loss from
substrate 201 impacts the deposition temperature which is one
influential factor for controlling deposition rate and thickness
uniformity of films formed on substrate 201. Therefore, decreasing
the rate of heat transfer from substrate 201 to showerhead 240
reduces a source of deposition rate and thickness variation.
[0076] Referring now to FIG. 14 which is a cross section of chamber
200 and schematic portions of vapor delivery system 500, specific
aspects of the temperature controlled conduits feature of chamber
200 of the present invention can more fully appreciated. Also shown
is one feature of the vapor delivery system of the present
invention illustrating the continuous, independent temperature
controlled conduits which couple the outlet of vaporizer 520 with
processing region 202. Given the low vapor pressure of the Tantalum
precursor, another feature of the vapor delivery system is the
shortened vapor flow path from vaporizer 520 to processing region
202. By shortening the precursor vapor flow path, pumping losses,
friction losses and other fluid dynamic inefficiencies associated
with the length of the pumping conduit as well as the inherent
difficulties of pumping low vapor pressure gases can be reduced.
The reduction of the above fluid losses is beneficial to the
effective vaporization and delivery of low vapor pressure
precursors according to the present invention. As a result of
minimizing the precursor flow path, the vapor delivery system of
the present invention is able to attain more stable and repeatable
vapor flow rates for low vapor pressure precursors.
[0077] Inlet and mixing block 272, mixed deposition gas feed
through block 266 and central mixing block 262, collectively
referred to as heated gas feed through 220, are formed from rigid
materials such as aluminum, varieties of nickel alloys or other
materials having good thermal conductivity. The various conduits
formed within heated gas feed through assembly 220 couple the
outlets of heated chamber feed through 225 and process gas feed
through 227 and lid bore throughs 226 and 228 to central chamber
bore through 230.
[0078] Inlet and mixing block 272 attaches to lid 205 forming a
sealed, continuous flow path between precursor lid bore-through 226
and precursor inlet conduit 265 and between process gas lid
bore-through 228 and process gas inlet conduit 276. Typically
o-rings formed of Chemraz.RTM. or Kalrez.RTM. are used at lid
bore-through outlets 226 and 228 to provide a seal at the mating
surfaces between lid 205 and inlet and mixing block 272. Mixing
manifold 278 merges the process gas and precursor vapor flows into
a single gas flow and begins the process of mixing precursor and
process gas or gases into a homogeneous mixture for delivery into
processing region 202. The length of conduit from the point within
mixing manifold 278 where the precursor vapor stream and the
process gas stream mix is sufficiently long such that the resulting
mixed gas stream is homogeneously mixed upon arrival in processing
region 202. Although specific lengths to achieve homogeneous mixing
will vary depending on a variety of factors such as the diameter of
the conduit and gas flow rates and temperatures, a representative
length from mixing manifold 278 to processing region 202 would be
about 12 inches for a 0.5 inch inner diameter mixed deposition gas
conduit 273, central conduit 231 and bore through 230 of FIG. 14.
In an alternative example, the length of conduit which could also
result in homogeneous mixing of precursor vapor and process gases
from mixing manifold 278 through mixed deposition gas conduit 273
and central conduit 231, both having inner diameters of 0.5 inches,
is about 10 inches.
[0079] Inlet and mixing block 272 attaches to mixed deposition gas
feed-through block 266 such that the outlet of mixing manifold 278
is coupled to mixed deposition gas conduit 273 formed within mixed
deposition feed-through block 266. Typically the mating surface
surrounding the conduit outlet of conduit 278 and the inlet of
mixed deposition gas conduit 273 is similarly sealed with an o-ring
formed of Kalrez.RTM. or Chemraz.RTM.. Mixed deposition gas
feed-through block 266 attaches to mixing block 262 and similarly
forms an o-ring sealed conduit between mixed deposition gas conduit
273 and central gas feed-through conduit 231. Mixing block 262 is
attached to heated lid 205 forming an o-ring sealed conduit between
central gas feed-through conduit 231 and central lid bore-through
230. In order to more clearly describe the unique temperature
controlled conduits feature of chamber 220 of the present
invention, inlet mixing block 272 and mixed deposition gas feed
through block 266 are described and discussed as separate pieces.
However, one of ordinary skill in the art will appreciate that a
single workpiece could be utilized having the described dimensions
and characteristics of both inlet mixing block 272 and mixed gas
feed through 266 without departing from the scope of the present
invention.
[0080] The temperature of each of the conduits formed internal to
heated manifold 220 (265, 276, 278, 273 and 231) are controlled by
a plurality of independent heaters 264, thermocouple 274 and
controller 277 units. One unit controls the temperature of conduits
265, 276 and 278 within inlet and mixing block 272; another
controls the temperature of conduit 273 within feed through block
266; and another controls the temperature of conduit 231 within
central block 262. In each block, a plurality of cartridge or
fire-rod type heaters 264 are advantageously arranged integral to
the given block in proximity to the conduit or conduits within a
given block. Multiple heaters provide the most efficient heating of
the particular conduit or conduits within a given block as the
heaters can be located based upon the size, shape, composition and
thermal conductivity of the particular block as well as the
particular geometry of the conduits. For the representative system
illustrated in FIG. 14, cartridge heaters 264 are about 0.25 inches
in diameter, cylindrical in shape, have various lengths, output
power capacities and are available commercially from Watlow Inc. of
Richmond, Ill. under the brand name "Firerod".
[0081] The set-point temperature is maintained within a given
conduit by inputting a desired temperature set-point into the
controller 277 for the particular conduit. Controller 277 could be
a PID type controller similar to Model 965 which is also
commercially available from Watlow, Inc. Thermocouples 274 are
embedded within gas feed through assembly 220 in proximity to each
conduit such that the temperature registered by each thermocouple
274 is approximately the same as the temperature within the gas
conduit by which the thermocouple is installed. The position of
thermocouple 274 relative to a given gas conduit varies depending
upon a number of factors such as the thermal conductivity of the
material used to fabricate the given block and the type of
thermocouple 274 used. The signal from thermocouple 274 is sent to
controller 277 which compares the temperature from thermocouple 274
to the input temperature set-point. Based on the result of
comparing the temperature from thermocouple 274 to the input
temperature setpoint, controller 277 will either increase, decrease
or maintain power supplied to cartridge heaters 264. One advantage
of utilizing a plurality of independent thermocouples 274 is that
the specific conditions of a given conduit block are taken into
account depending upon its location relative to other heat sources
such as heated lid 205, heat loses and geometry.
[0082] For example, inlet and mixing feed through block 272 is in
direct contact with heated lid 205 and, unless the temperatures
between them exactly match, will either gain energy from or lose
energy to lid 205. The effect of heat transfer between lid 205 and
mixing feed through block 272 on the temperature of conduits 265,
276 and 278 within block 272 will be reflected in the temperature
detected by a thermocouple 274 located within block 272. As a
result, the controller 277 associated with block 272 can increase
or decrease the power output of heaters 264 embedded within block
272 in proximity to conduits 265, 276 and 278 to compensate for
heat transfer between block 272 and lid 205. In much the same way,
energy transfer between mixing block 262 and lid 205 is compensated
for by the thermocouple, heater, controller unit associated with
block 262. Similarly, heat losses of mixed deposition gas feed
through block 266 which are different from heat transfer of blocks
272 and 262 since it has a higher potential for heat loss because
it is not in direct contact with heated lid 205 and has a larger
surface area exposed to the ambient conditions (about 70 degrees
Fahrenheit) within the wafer fabrication facility when protective
cover 203 is removed. However, when protective cover 203 is in
place as illustrated in FIG. 2, temperatures surrounding manifold
220 are increased to about 70 to 80 degrees Celsius. Thus, the
heater, thermocouple, controller unit dedicated to mixed deposition
gas feed-through block 266 is utilized to compensate for the
particular heat transfer characteristics of that block.
[0083] More generally, an aspect of the present invention is a
method to provide a predetermined temperature set-point within a
conduit by the selection, placement and use of a controller, heater
and thermocouple control unit which utilizes the method and
apparatus described above. Another feature of the multiple,
independent cartridge heater, thermocouple and controller units of
the present invention is that a uniform conduit temperature
throughout heated gas manifold 220 can be achieved. Because of
their independence, each controller is able to efficiently maintain
set points irrespective of conditions in surrounding blocks while
taking into account the specific heat losses and conditions
surrounding each block, the specific outer shapes of each block and
the geometry of the conduits formed within each block. In another
aspect of the present invention, the temperature set point of each
conduit could be set and maintained to induce a negative
temperature gradient where the temperature of block 262 is less
than block 266 which is less than the temperature of block 272.
Alternatively, a positive temperature gradient could be induced
where the temperature in block 272 is less than the temperature in
block 266 which is also less than the temperature of block 262.
[0084] In a specific embodiment of the apparatus of chamber 200 of
the present invention, mixed deposition and feed-through block 266
is an aluminum rectangle with the following dimensions: about 5
inches long, about 1.5 inches wide and about 0.75 inches high. For
the aluminum mixed deposition feed through block 266 described
above, a representative cartridge heater 264 could be cylindrically
shaped, 0.25 inches in diameter, 5.5 inches long with a power
output capacity of 500 Watts. In an embodiment of the method and
apparatus of the present invention, a single cartridge heater 264
or a plurality of heaters 264 of a selected power output capacity
of about 500 Watts could be employed within mixed deposition feed
through block 266 such that the temperature within mixed deposition
gas conduit 273 remains above the vaporization temperature and
below the decomposition temperature of the carrier gas/precursor
vapor/process gas mixture flowing within conduit 273. In a specific
embodiment where mixed deposition gas feed through block 266 is as
described above, a thermocouple 274 could be placed between about
0.125 inches to 0.5 inches away from mixed deposition gas conduit
273. In an embodiment of the present invention where the carrier
gas/precursor vapor/process gas mixture within conduit 273 is
comprised of a Tantalum precursor such as TAT-DMAE, a process gas
such as oxygen, and a carrier gas such as nitrogen, conduit 273
temperatures between about 130.degree. C. and 160.degree. C. would
prevent both condensation and decomposition of the
tantalum/oxygen/nitrogen mixture. Thus, using the TAT-DMAE example
above, a typical set-point temperature could be about 150.degree.
C. or between about 130.degree. C. and 160.degree. C.
Representative set-points for an embodiment of the present
invention employing TAETO could be about 170.degree. C. or between
about 150.degree. C. and 180.degree. C.
[0085] A further aspect of the temperature controlled conduits of
chamber 200 of the present invention provides temperature
controlled delivery of vaporized precursor from vaporizer 520 to
lid bore through 230. Vaporized precursor exits vaporizer 520 via
vaporizer outlet 540 and enters vaporizer outlet line 542 which is
coupled to precursor inlet 544 of chamber by-pass valve 545. When
three-way valve 545 is aligned to chamber, precursor vapor exits
three way valve 545 via chamber outlet 550 flowing then to
precursor chamber supply line 560 which is coupled to precursor
feed through 225. A jacket type temperature controlled conduit 292
is created between the outlet of vaporizer 520 and the inlet to
precursor feed through 225 and encompasses conduits 542 and 560 and
three way valve 545. A jacket type control unit comprises a jacket
or wrap style heater 275, a controller 277 and a thermocouple 274
is utilized to maintain a temperature set-point in the above
components 542, 560 and 545. From temperature controlled precursor
feed through 225, precursor vapor flows through lid bore through
226 into precursor inlet conduit 265 of inlet and mixing block 272.
From precursor inlet 265, the precursor vapor flows into mixing
manifold 278 where it mixes with process and ballast gases supplied
via process inlet conduit 276.
[0086] The temperature of precursor vapor within conduit 225 is
maintained by the temperature controlled chamber feed through 219
which includes a plurality of cartridge type heaters 264, a
thermocouple 274 and a controller 277. Another feature of
temperature controlled precursor feed through 219 is thermal choke
or air gap 212 which insulates thermal influences of chamber body
210 from the components of temperature controlled precursor feed
through 219. Thus, by utilizing the plurality of heater,
controllers and thermocouples described above and the features of
heated lid 205, chamber 200 and liquid delivery system 500 provide
a temperature controlled flow path for vaporized low vapor pressure
precursors from origin in vaporizer 520 to use in processing region
202.
[0087] Process gas heat exchanger 582 provides temperature control
to process gas and ballast gases for use in chamber 200. Process
gas heat exchanger 582 is located proximate to chamber body 210
and, more specifically, to process gas chamber feed through 227
such that the gas temperature exiting heat exchanger 582 is
approximately the same as the gas temperature entering feed through
227. From process gas feed through 227, temperature controlled
process and ballast gases pass through lid bore through 228 and
enter process gas inlet 276 of inlet and mixing block 272.
[0088] Another aspect of the present invention is the use of
process gas heat exchanger 582 to heat process and ballast gases
above the temperature of the vaporized precursor gas stream. As a
result, when the heated process gas stream and the vaporized
precursor gas stream intersect and mix within mixing conduit 278
the risk of condensation of the vaporized precursor is virtually
eliminated. For example, the temperature set-point of process gas
heat exchanger could be about 5-10.degree. C. above the temperature
set-point of vaporizer 520. In much the same way, the temperature
of process gas and ballast gas can be controlled to remain below a
set-point where, upon mixing with the precursor vapor stream,
decomposition of the precursor occurs. Alternatively, a set-point
could be utilized which results in process gas temperatures at
least as high as the merging precursor gas stream.
[0089] Utilizing the above described independent thermocouple,
controller, heater sets which are part of processing system 200 and
vapor delivery system 500, a series of temperature controlled
conduits is provided which can deliver vaporized low vapor pressure
precursors from the outlet of vaporizer 520 to processing region
202. Although temperature controlled conduits based on heater type
are described--cartridge heater temperature controlled conduits 293
and jacket or wrap style heater type temperature controlled
conduits 275--their description is not intended to be limiting as
one of ordinary skill in the art will appreciate that a variety of
heater types, thermocouples and controllers could be utilized
without departing from the scope of the present invention. The
independent temperature controlled conduits feature of the present
invention provides more precise means of temperature control than
previously available but also allows for vaporized liquid delivery
under a variety of thermal conditions which exist as a result of
the environment to which each conduit is exposed. For example, each
temperature controlled conduit could be set to maintain a set-point
2-3.degree. C. hotter than the previous conduit so that a slightly
positive thermal gradient is maintained between the vaporizer 520
and outlet of central conduit 231 into processing region 202 or,
more generally, an overall .DELTA.T could be maintained between the
vaporizer outlet temperature and the temperature in central conduit
231 or a .DELTA.T of about 20-25.degree. C.
[0090] Another aspect of the thermally controlled conduits of
processing chamber 200 and vapor delivery system 500 of the present
invention is that the conduits used downstream of vaporizer 520 in
the precursor flow path, as shown in FIG. 14 between vaporizer 520
and central lid bore through 205, have progressively larger
diameters which result in increasing cross-sectional flow areas
resulting in an expanded gas flow volume within these conduits. The
volume expansion and corresponding pressure drop within the
precursor delivery conduits further help maintain conduit
conditions which neither condense nor decompose the vaporized
precursor. Another aspect of the independent temperature controlled
conduits of chamber 200 is that temperature changes within a
specific conduit associated with the volume expansion can be
compensated for by the independent heater, controller and
thermocouple of that particular conduit. For example,
representative inner diameters for the chamber illustrated in FIG.
14, are a vaporizer outlet 542 with an inner diameter of 0.18
inches, a precursor supply line 560, chamber feed through 225 and
inlet 265 with inner diameters of 0.40 inches and a mixed
deposition gas conduit 278 and central conduit 231 with inner
diameters of about 0.5 inches. Another aspect of the present
invention is that the cross sectional area of downstream of the
intersection of the precursor gas flow and the process gas flow is
larger than the sum of the merging gas flows. This relationship
ensures that the downstream volume is larger thereby providing the
increasing flow volume/decreasing precursor pressure feature
discussed above. Additionally, the diameter of mixed deposition
precursor conduit 273 is also greater than either precursor inlet
265 or process gas inlet 276.
[0091] The increased volume and correspondingly decreased pressure
achieved by advantageously selecting the diameter of conduits
downstream of vaporizer 520 such as 542, 560, 225, 226, 265, 278,
273 and 231 in conjunction with the temperature control provided by
the thermocouple, heater and controller sets described above
provide a controlled temperature and pressure regime between
vaporizer 520 and processing region 202 such that very low vapor
pressure precursors, such as and including Tantalum precursors like
TAETO, TAT-DMAE or other similarly low vapor pressure precursors,
dopants or other processing materials may be delivered to
processing area 202 without undesired condensation or
decomposition.
[0092] The Remote Plasma Generator
[0093] Another aspect of the processing apparatus 100 of the
present invention is remote plasma apparatus 400 shown FIG. 15 in
relation to central substrate transfer chamber 110 and chamber 200
and components of heated exhaust system 300. Remote plasma
apparatus 400 creates a plasma outside of or remote to processing
region 202 for cleaning, deposition, annealing or other processes
within processing region 202. One advantage of a remote plasma
generator 400 is that the generated plasma or activated species
created by remote plasma generator 400 may be used for cleaning or
process applications within the processing region without
subjecting internal chamber components such as substrate support
250 or shower head 240 to plasma attack which usually results when
conventional RF energy is applied within process region 202 to
create a plasma. Several components of remote plasma apparatus 400
are visible in FIG. 15 such as magnetron 402, auto tuner controller
410, isolator 404, auto tuner 408, adapter tube 418 and adapter
tube heat insulation disc 424.
[0094] Turning now to FIG. 16 which is a schematic illustration of
Remote Plasma System 400, the components and operation of remote
plasma apparatus 400 can be better appreciated. Magnetron assembly
402 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 vane 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 402 to isolator 404 and wave
guide 406. Isolator 404 absorbs and dissipates reflected power to
prevent damage to magnetron 402. Wave guide 406 channels microwaves
from isolator 404 into auto tuner 408.
[0095] Auto tuner 408 matches the impedance of magnetron 402 and
microwave cavity 416 to achieve the maximum degree of reflected
power by adjusting the vertical position of three tuning stubs
located inside wave guide 406. Auto tuner 408 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 410 controls the position of the tuning stubs
within wave guide 406 to minimize reflected power. Auto tuner
controller 410 also displays the position of the stubs as well as
forward and reflected power readings.
[0096] Microwave applicator cavity 416 is where gas or gases
supplied via gas supply inlet 412 are ionized. Gas supplied via gas
supply inlet 412 enters a water cooled quartz or sapphire tube
within microwave applicator 416, is subjected to microwaves and
ionizes producing activated species which can then be used in
cleaning and processing operations within processing region 202.
One such cleaning gas is NF3 which can be used to supply activated
fluorine for cleaning processing region 202 when a substrate 201 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 201 positioned within processing
region 202. An optical plasma sensor 414 detects the existence of
plasma within cavity 416. Activated species generated within
microwave applicator cavity 416 are supplied to activated species
chamber feed through 229 via adapter tube 418. Adapter tube 418 is
insulated from the elevated temperature of chamber body 210 by
adapter tube isolation disc 424.
[0097] From activated species chamber feed through 229, the
activated species pass through lid bore-through 221 and enter
activated species inlet block 420 which, together with activated
species block 270, provide an o-ring sealed, air tight conduit
i.e., activated species conduit 271, between lid bore-through 221
and central gas feed-through 231 within central mixing block
262.
[0098] Heated Exhaust System
[0099] Referring again to FIG. 15, the components and features of
heated exhaust system 300 of processing system 100 can be better
appreciated. The components of heated exhaust system 300 are
collectively referred to as a foreline are in communication with a
vacuum pump 355 (not shown) and wafer fabrication facility exhaust
systems 340 (not shown) to provide for reduced pressure processing
operations within processing region 202. Exhaust from processing
and cleaning operations conducted within processing region 202 are
exhausted via chamber exhaust port 305. When closed, isolation
valve 310 shuts off chamber assembly 200 from down stream vacuum
pump systems. During normal operation, isolation valve 310 is open
and throttle valve 315 opens and closes to regulate pressure within
processing region 202. By-pass inlet 320 receives precursor
vapor/carrier gas mixture from chamber by-pass valve outlet 555
when chamber by-pass valve 545 is positioned to flow precursor
vapor/carrier gas mixture to temperature controlled by-pass line
322. Exhaust system components exhaust port 305, isolation valve
310, throttle valve 315 and by-pass 320 and by-pass line 322 are
temperature controlled to prevent unreacted precursor condensation.
Cold trap 325 and remaining downstream exhaust system components
are maintained at or below 75 degrees Fahrenheit. As a result, any
unreacted vapor remaining in the exhaust stream from processing
region 202 or vapor from chamber by-pass valve 545 will remain
gaseous in the temperature controlled or heated portion of exhaust
system 300 and then condense within cold trap 325 thus preventing
damage to the vacuum pumps or accumulation and resulting line
blockages within exhaust system piping. Additionally, collection of
unreacted vapor within cold trap 325 also minimizes the exposure of
maintenance personnel to potentially hazardous chemicals. Cold trap
325 is equipped with an isolation valve 330 for separating cold
trap 325 from vacuum pumping systems to allow for routine
maintenance or cleaning.
[0100] In order not to unnecessarily obstruct a clear illustration
of the relationships between the various components of exhaust
system 300 and the other components of processing system 100, the
independent thermocouple, controller, heater 275 utilized as part
of the temperature controlled feature of exhaust system 300 is not
shown in FIG. 15. Turning briefly to FIG. 18 which is a
representative schematic embodiment of processing system 100 of the
present invention, the temperature controlled conduits feature of
exhaust system 300 can be better appreciated. A jacket style
heater, thermocouple and controller 275 could be utilized to
measure and maintain a set point temperature in exhaust port 305,
isolation valve 310, throttle valve 315 and chamber bypass line 320
thereby creating a jacket heater controlled conduit 292 in the
exhaust components upstream of cold trap 325. A separate
thermocouple, controller and heater 275 operates on by-pass line
322 between chamber by-pass 545 and exhaust by-pass 320. As a
result, chamber by-pass line 322 becomes a jacket style heater
temperature controlled conduit 292 between chamber by-pass 545 and
exhaust by-pass 320.
[0101] Vapor Delivery System
[0102] Turning now to FIG. 17, the compact design feature of vapor
delivery system 500 of the present invention can be better
appreciated. Vapor delivery system 500 provides a method and an
apparatus for supplying controlled, repeatable, vaporization of low
vapor pressure precursors for film deposition on a substrate 201
located within processing region 202. 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 500 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 systems
or, specifically, precursors having vapor pressures below about 10
Torr at 1 atm and 100.degree. C. (FIG. 1).
[0103] The various components of vapor delivery system 500 are
placed in close proximity to chamber 200 in order to minimize the
length of temperature controlled vapor passageways between the
outlet of vaporizer 520 and processing region 202. 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 500 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
200 in close proximity to precursor and process gas chamber feed
throughs 225 and 227.
[0104] A low vapor pressure liquid precursor, such as TAT-DMAE or
TAETO, can be stored in bulk storage container 503 located remotely
or on mainframe support 105 in proximity to processing chamber 200.
Liquid precursor stored in tank 503 is maintained under pressure of
an inert gas such as Helium at about 15 to 60 psig. The gas
pressure within tank 503 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 503 is provided with
a shut-off valve 507 (not shown) to isolate bulk tank 503 for
maintenance or replenishment of the liquid precursor. As a result
of the pressure head on tank 503, liquid precursor from tank 503 is
provided to liquid supply line 508 and the precursor inlet 509 of
precursor/solvent inlet valve 588. When aligned for liquid
precursor, precursor/solvent valve 588 provides liquid precursor to
precursor/solvent outlet 594 and into precursor/solvent supply line
592 to liquid flow meter inlet 505. Liquid flow meter 510 measures
precursor flow rate and provides via liquid flow meter outlet 511
liquid precursor to vaporizer supply line 513 and then to vaporizer
inlet 515. Vaporizer 520 in conjunction with a heated carrier gas
(described below) converts the liquid precursor into precursor
vapor.
[0105] A carrier gas, such as nitrogen or helium, is supplied into
carrier gas heat exchanger inlet 525 at a pressure of about 15 psi.
Carrier gas heat exchanger 530 is a gas to resistive heater type
heat exchanger like Model HX-01 commercially available from Lintec.
Carrier gas heat exchanger 530 preheats the carrier gas to a
temperature such that the heated carrier gas stream entering
vaporizer 520 does not interfere with the efficient vaporization of
the precursor liquid undergoing vaporization within vaporizer 520.
Heated carrier gas is provided to vaporizer 520 via carrier gas
supply line 532 and carrier gas inlet to vaporizer 535. 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 520. Thus, carrier gas heat exchanger 530 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 520,
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 520 is at least as high if not higher than
the vaporization temperature of the precursor being vaporized in
vaporizer 520. Of particular concern is the prevention of precursor
vapor condensation within the small diameter conduits which exist
within vaporizer 520. As such, carrier gas temperatures below
vaporization conditions within vaporizer 520 could sufficiently
cool the vaporized precursor, result in condensation and should
therefore be avoided.
[0106] Referring now to FIG. 18, which schematically represents the
operation of liquid flow meter 510 in conjunction with vaporizer
520, which are referred to collectively as liquid mass flow
controller 528. Liquid precursor enters liquid flow meter 510 which
generates measured flow rate signal 512. A typical flow rate signal
is measured in milligrams per minute or mg/min. A representative
flow rate for a TAT-DMAE precursor is 35 mg/min. for a
representative Ta.sub.2O.sub.5 film produced utilizing the method
and apparatus of the present invention. The now measured precursor
flow exits liquid flow meter outlet 511 into vaporizer supply line
513 and then into vaporizer inlet 515. Vaporizer supply line 513 is
typically 0.125 inch outer diameter stainless steel piping. Another
aspect of liquid mass flow meter 528 is that the length of
vaporizer supply line 513 is minimized to attain controllable low
vapor pressure precursor output from vaporizer 520. Minimizing the
distance between liquid flow meter 510 and vaporizer 520 adds to
the number of vapor delivery system 500 components placed in
proximity to processing system 100 as well as increases the density
of equipment mounted on mainframe 105. However, vapor delivery
system 500, along with the remote plasma system 400 and heated
exhaust system 300 have been designed to minimize interference
between the subsystems of processing system 100 while achieving the
compact design desired in cluster tool wafer processing systems.
Although remote placement of liquid flow meter 510 further away
from vaporizer 520 would reduce the amount of vapor delivery
components in proximity to processing system 100, more effective
liquid metering and control is achieved by minimizing the distance
between the liquid flow meter outlet 511 and vaporizer inlet 515.
Vaporizer inlet 515 to liquid flow meter outlet 511 spacing of
about 6 inches or between about 4 inches and 15 inches leads to
more effective metering and controlled vaporization of low vapor
pressure precursors such as TAETO, TAT-DMAE or other liquid
precursors having a vapor pressure of below about 10 Torr at
100.degree. C. and 1 atm.
[0107] Another feature of a the liquid mass flow controller 528 of
the present invention is positive shut-off valve 522. Located
within vaporizer 520 between vaporizer inlet 515 and metering valve
524, positive shut-off valve 522 provides the capability to cut-off
liquid flow before the vaporization point within vaporizer 520.
Metering valve 524 can provide a shut-off capability when in a
`closed` or zero set-point condition. However, positive shut-off
valve 522 provides added assurance that no liquid will continue to
flow through vaporizer 520 when liquid mass flow controller 528 is
in a `closed` or zero set-point condition. The position of positive
shut-off valve 522 relative to metering valve 524 is such that
there is a minimal volume of liquid which could remain in the line
between shut-off valve 522 and metering valve 524. A representative
vaporizer 520 suitable for vaporization of low vapor pressure
liquids could position positive shut-off valve 522 about one inch
or less from metering valve 524. Thus, utilizing a 0.125 inch
diameter line between shut-off valve 522 and metering valve 524 a
minimal liquid volume of about 0.012 cubic inches of precursor is
created. By reducing the volume between these components the amount
of precursor which could vaporize after positive shut-off valve 522
is closed is minimized. Thus, positive shut-off valve 522 provides
redundancy to the shut-off capabilities of metering valve 524 as
well as provides a minimal volume of liquid which could still be
vaporized even if liquid mass flow controller 528 is in a open or
100% flow set-point condition and positive shut-off valve 522 is
closed.
[0108] Referring now to FIG. 17, vaporized precursor flows from
vaporizer outlet 540 into vaporizer outlet line 542 into vapor
inlet 544 of temperature controlled by-pass valve 545. When aligned
to "chamber" position, by-pass valve 545 supplies vapor to chamber
outlet 550 and then into temperature controlled vaporized precursor
supply line 560. A feature of the vapor delivery system 500, but
omitted for clarity, is the thermocouple, controller, jacket style
heater system 275 which maintains a temperature set-point within
vaporizer outlet line 542, chamber by-pass valve 545 and vaporized
precursor supply line 560. The internal piping of chamber by-pass
valve 545 allows vaporized precursor/heated carrier gas mixture to
be sent to processing region 202 via outlet to chamber 550.
Additionally or alternatively, while stabilizing vapor flow or
conducting cleaning operations within processing region 202,
chamber by-pass valve 545 could direct the vaporized
precursor/heated carrier gas mixture to heated by-pass line 320 of
heated exhaust system 300 (described above) via outlet to by-pass
555. One advantage of chamber by-pass valve 545 of the present
invention is that once liquid mass flow controller 528 attains a
desired set-point vapor flow rate the vaporized precursor/heated
carrier gas mixture can either be directed to the chamber for
deposition or to the foreline by-pass inlet 320 for disposal.
Independent of operations within processing region 202, liquid mass
flow controller 528 continues to produce a stable, consistent vapor
flow rate. Thus, chamber by-pass valve 545 used in conjunction with
liquid mass flow controller 528 provides the repeatable, stable
vapor flow rates to consecutive substrates 201 within processing
region 202. Such repeatable, stable vapor flow rates are necessary
for the deposition of transition metal dielectric materials such as
tantalum oxide for use in high capacity ICs such as stacked
capacitors.
[0109] Vaporizer outlet line 542 and precursor supply line 560 are
standard piping which could be made of stainless steel. Vaporized
precursor supply line 560 should be as short as possible to
minimize the length of travel of vaporized precursor within the
system or between about 4 to 6 inches. Precursor supply line 560 is
in communication with chamber outlet 550 and precursor chamber
heated feed-through 225. In order to prevent condensation of the
vaporized precursor within the vaporized precursor/heated carrier
gas mixture, heated precursor supply line 560 and vaporizer outlet
line 544, like all precursor supply conduits downstream of
vaporizer 520, have an inner diameter which is greater than the
inner diameter of the liquid supply line into vaporizer 520.
Typically, the vaporizer liquid supply line is made of stainless
steel with about a 0.125 inch inner diameter while the conduits
downstream of vaporizer 520 could have a larger diameter or an
outer diameter of about 0.5 inches or an inside diameter of about
0.4 inches. Larger diameter conduits downstream of vaporizer 520
exposes the vaporized precursor/heated carrier gas mixture to an
expansion volume and corresponding reduction in pressure which
helps maintain the vaporized low vapor pressure precursor within an
operational temperature region above the precursor condensation
temperature and below its decomposition temperature for the
conditions within the vapor supply conduits. Since vaporized
precursor supply line 560 and vaporizer outlet 542 are heated by a
thermocouple, controller, jacket style heater 275, temperatures
within vaporized precursor supply line 560 and vaporizer outlet 542
are maintained above the condensation temperature and below the
decomposition temperature of the vaporized precursor or between
about 100.degree. C. and 190.degree. C.
[0110] Vapor delivery system 500 also has a temperature controlled
process gas feature. Process gas heat exchanger 582 which is
similar to carrier gas heat exchanger 530 described above receives
process gas from process gas supply 580. Suitable process gases
depend on the desired film deposition. Typically, oxygen (O.sub.2)
and nitrous oxide (N.sub.2O) are suitable for oxidation processes
and ammonia (NH.sub.4) is suitable for nitride processes.
Additionally, nitrogen (N.sub.2) could be added to the process gas
flow as a ballast gas. The term process gas stream used below
refers to all gas flows out of heat exchanger 582 and is intended
to include process gas, ballast gases or other gases described
below. Process gases and ballast gases can be preheated by process
gas heat exchanger 582 so that the resulting process gas stream is
maintained above the temperature of the adjacent vaporized
precursor gas stream. Maintaining the process gas stream
temperature above about 10.degree.-15.degree. C. above the
temperature of the vaporized precursor gas stream assists in the
prevention of inadvertent condensation of the precursor vapor when
the gas streams intersect and begin to mix within mixing conduit
278. Similarly, heat exchanger 582 can also ensure process gas
stream temperatures are maintained below the decomposition
temperature of the precursor gas stream so that inadvertent
decomposition of the precursor vapor stream does not occur when the
gas streams mix within mixing conduit 278.
[0111] Thus, a temperature controlled gas stream exits process gas
heat exchanger 582 via outlet 584 and enters process gas supply
line 586. From process gas supply line 586 the process gas stream
flows through process gas chamber feed-through 227 which in turn
flows into heated process gas inlet conduit 276. Process gas inlet
conduit 276 flows into and mixes with vaporized precursor flow
stream in heated mixing manifold 278. Process gas heat exchanger
582 heats the process gas to a sufficient temperature such that
when the process gas mixes with the vaporized precursor in mixing
conduit 278 the precursor vapor neither decomposes nor
condenses.
[0112] Another feature of vapor delivery system 500 is the ability
to provide a solvent flush capability to those conduits which come
into contact with the vaporized low vapor pressure precursors. Such
solvent operations further the operability of the method and
apparatus of the present invention to vaporize low vapor pressure
liquids such as TAETO and TAT-DMAE. A solvent such as anhydrous
isopropyl alcohol, methanol, hexane, ethanol, or other suitable
solvent is supplied into precursor/solvent three-way valve 588 via
solvent inlet 590. From bulk solvent supply 591 solvent is
introduced into the vapor delivery system 500, via 3-way valve 588
and follows the same flow path as a vaporized precursor through the
various components of vapor delivery system 500 and, depending upon
chamber by-pass valve 545 alignment, to chamber 200 or exhaust
system 300 via by-pass line 322. As the solvent flows through the
various conduits which are exposed to liquid precursor such as the
conduits of and within liquid mass flow controller 528, the solvent
mixes with precursor liquid and purges the line of residual
precursor which then allows exposure of the components to air for
maintenance or component change. Without the solvent flush
capability and as a result of the low vapor pressure of typical
precursors vaporized using the methods and apparatus of the present
invention, residual precursor vapors within conduits exposed to the
low vapor pressure precursor would not be sufficiently evacuated
nor achieve reduced pressures in a timely--commercially
viable-manner simply utilizing only pumping systems 355 of exhaust
system 300. Additionally, the solvent flush feature can be utilized
to remove precursor vapor from process conduits and components to
prevent risk of exposure to potentially hazardous materials during
maintenance as well as prevent the undesired reaction of precursor
vapor with air, water vapor or other materials.
[0113] CVD Deposition System Operation
[0114] Referring now to FIGS. 19 and 20, an integrated method of
operating CVD deposition system 100 and the use and
interoperability of dopant, second dielectric or second precursor
materials within the various embodiments of the present invention
can be better understood. FIG. 19 schematically represents a system
configuration when a single vaporizer and process heat exchanger
are utilized to provide process gas/precursor vapor mixtures to
temperature controlled conduits 292 and 293 and processing region
202. FIG. 20 is similar to FIG. 19 with the addition of a second
vaporizer 520, bulk supply 504 and by-pass valve 570. Under the
representative configuration of FIG. 20, processing system 100 of
the present invention is further enabled to not only provide, mix,
and deposit films from a single precursor (FIG. 19) but also, by
modifying the liquid source contained in bulk supply 204, films
containing a second precursor, a dopant or a metal.
[0115] Deposition system 100 as embodied in FIG. 20 operates
similarly to previous descriptions of processing system 100 with
the addition of an additional bulk supply 504 which could be under
a pressure head as with bulk supply tank 503. Bulk supply 504 is
coupled to and supplies processing fluids to a second vaporizer 520
which operates similarly to the first vaporizer 520 as embodied in
FIG. 19 and described above. The vaporized precursor stream created
by the second vaporizer 520 is provided to a chamber by-pass valve
570 which can align--via outlet 571--the vaporized gas stream to
chamber 200 via process gas supply line 586. Alternatively, by-pass
valve 570 can align the vaporized precursor stream to exhaust
system 300 via outlet 572. In the embodiment of FIG. 20, bulk
supply 504 could contain a wide variety of fluid processing source
materials such as dopants, precursor materials, metals, or other
materials with a sufficiently high vapor pressure that vaporization
may occur without a carrier gas, heated carrier gas or will remain
vaporized without temperature controlled conduits described above
in relation to the low vapor pressure precursor utilized and
described above. Therefore, what is not shown, but an object of the
present invention is modification of the second vaporizer 520 and
other components of FIG. 20 to include a carrier gas or heated
carrier gas used in conjunction with second vaporizer 520 and the
use of the temperature control methods described above to provide
temperature controlled conduits from the outlet of the second
vaporizer 520 to three-way valve 570 and including process gas
supply line 586 in order that low vapor pressure precursors could
also be provided to and effectively utilized by second vaporizer
520 of FIG. 20.
[0116] Another object of the vapor delivery system 500 present
invention is the deposition of a variety of films on substrates 201
within process area 202 by advantageously selecting precursors bulk
supplies 504 and 503, process gases, process gases or ballast gases
for gas source 580 and by selective positioning of by-pass valves
570 and 545. One advantage of the 2 vaporizer--2 by-pass
configuration of FIG. 20 is that each vaporizer may be in operation
and producing stable, repeatable flow which, by aligning the
appropriate by-pass 570 or 545, could easily be ported to process
region 202 or exhaust system 300. Some of the possible combinations
mentioned above are detailed in FIG. 21.
[0117] Referring now to FIG. 21, several representative vapor
combinations utilizing the configuration of FIG. 20 can be
appreciated. FIG. 21 provides 10 liquid alignment configurations
which refer to the specific positions of chamber by-pass valves 545
and 570, the contents of bulk sources 503 and 504, process gas
source 580 and the resultant vapor mixture delivered to processing
area 202. The Liquid Alignment Configurations listed in FIG. 21 can
be categorized into three broad mixture groups: tantalum oxide
mixtures, dielectric mixtures and electrode mixtures.
[0118] Liquid Alignment Configurations 1-4 are directed towards
tantalum containing mixtures. Since only a single bulk source 503
and vaporizer 520 is utilized, configuration 1 could be embodied by
either FIG. 19 or on FIG. 20 where chamber by-pass valve 570 is
aligned to by-pass outlet 572. Whether FIG. 19 or 20 is used, bulk
source 503 contains a tantalum containing precursor such as
TAT-DMAE or TAETO which is vaporized and provided to chamber
by-pass 545. Chamber by-pass 545 is aligned to chamber or outlet
550 so the vaporized Tantalum flows through chamber by-pass outlet
550 through temperature controlled conduits 275, 219 and 293 into
mixing manifold 278. At the same time, process gas supply 580
provides an oxygen containing process gas to gas heat exchanger 582
which heats the gas to a setpoint and provides the gas to process
gas supply line 586. From process gas supply line 586, the process
gas flows through conduit 227 and temperature controlled conduit
276 into mixing manifold 278 where the process gas and tantalum
vapor flows converge, mix and form a homogenous mixture before
arriving in processing region 202. The vapor mixture described
above is suitable for deposition of tantalum oxides. In liquid
alignment configurations 2,3 and 4, the tantalum precursor is
vaporized and the oxygen containing process gas is heated as
described above. Additionally, bulk source 504 contains and is
utilized to provide material which is vaporized in second vaporizer
520. The vapor stream produced by second vaporizer 520 is provided
via chamber by-pass outlet to chamber 571 to process gas supply
line 586.
[0119] A heater, controller, thermocouple temperature control
system, similar to that utilized with the vaporized precursor
stream produced by the first vaporizer 520, could also be utilized
with the conduits which carry vaporized precursor stream provided
by second vaporizer 520 to process gas supply line 586 in order to
prevent inadvertent condensation or decomposition of the vaporized
precursor gas stream. FIG. 20 embodies a second bulk supply 504
with a material which can produce a stable output from second
vaporizer 520 without requiring a carrier gas, heated carrier gas
or temperature controlled conduit for the successful use of the
second vapor stream.
[0120] In liquid alignment configuration 2, bulk source 504
contains an aluminum precursor and chamber by-pass 570 is aligned
to outlet 571. One representative aluminum precursor is aluminum
nitrate dissolved in etoxide, ethynol, acilic acids or other
suitable solution. One of ordinary skill will appreciate that a
wide variety of liquid aluminum precursors could be utilized in the
aforementioned apparatus of the present invention. As a result of
this configuration, the vaporized aluminum precursor flow will
merge and mix with the oxygen containing process gas in process
supply line 586. The process gas/aluminum precursor mixture then
flows through conduit 227 into temperature controlled conduits 276
and then into mixing manifold 278 where the process gas/aluminum
vapor stream mixes with tantalum vapor gas stream. Homogenous
process gas/precursor mixtures can be obtained in processing area
202 by advantageously selecting the position of mixing manifold or
point 278 relative to processing region 202 so that sufficient
mixing occurs between mixing manifold 278 and a substrate 201
located within processing area 202. Similarly, a titanium
containing bulk supply 504 (Liquid Alignment Configuration 3) or a
dopant containing bulk supply 504 (Liquid Alignment Configuration
4) could be utilized resulting in vapor mixtures within process
region 202 which form titanium doped tantalum oxide or, more
generally, a doped tantalum oxide. One representative titanium
precursor is titanium tetratusisoprepoxide, referred to as TiPT.
Those of ordinary skill will appreciate that a wide variety of
titanium precursors may be efficiently utilized in processing
system 100 via the vapor delivery system 500 described above.
[0121] Liquid Alignment Configurations 5, 6 and 7 are directed
towards the use of the second bulk source to provide a dielectric
material into processing chamber 200. In these three
configurations, the first bulk delivery source 503 is not listed
since even if the first vaporizer 520 associated with bulk supply
503 were in operation the vapor stream produced by first vaporizer
520 is aligned via chamber by-pass outlet 555 to exhaust system
300. Liquid Alignment Configuration 5 utilizes a bulk supply 504
containing an aluminum liquid source which after vaporization is
provided to process gas supply line 586 via chamber by-pass outlet
571 is open. The vaporized aluminum precursor then mixes with an
oxygen containing process gas from supply 580 which has been
preheated by heat exchanger 582. The process gas and aluminum vapor
mix while flowing towards processing region 202 resulting in a
homogenous mixture suitable for aluminum oxides deposition on
substrates 201 located within processing region 202. Similarly, a
titanium containing source or, generally, a dielectric precursor
material may be placed in bulk source 504 (Liquid Alignment
Configurations 6 and 7) which would then result, respectfully, in
mixtures and deposition within processing region 202 of titanium
oxides or dielectric oxides.
[0122] Liquid Alignment Configurations 8, 9 and 10 provide
configurations which result in a variety of nitrides or electrode
materials in processing region 202. In Liquid Alignment
Configurations 8,9, and 10, the process gas source 580 contains
nitrogen, for example ammonia (NH.sub.3), and bulk source 504
contains aluminum, titanium or other electrode material precursor.
Utilizing the second vaporizer 520 associated with bulk supply 504,
deposition mixtures which result in aluminum based compounds
(configuration 8), titanium nitrides (configuration 9) and
generally nitrides suitable for forming electrodes (configuration
10) are provided to processing region 202.
[0123] As a result of the numerous liquid alignment configurations
enabled by the vapor delivery system embodied in FIG. 20, multiple
film layers can be deposited on a substrate within processing
region 202 by advantageously selecting precursor materials for bulk
supplies 503 and 504 and providing both oxygen and nitrogen
containing gases via process gas source 580. For example, a vapor
delivery system 500 having a bulk source 503 containing tantalum, a
bulk source 504 containing aluminum and a process gas source 580
containing both oxygen and nitrogen, with both the first and second
vaporizers 520 in operation can form films such as tantalum oxides
(Liquid Alignment Configuration 1) aluminum doped tantalum oxides
(Liquid Alignment Configuration 2), aluminum oxides (Liquid
Alignment Configuration 5) and aluminum nitrides (Liquid Alignment
Configuration 8) can be formed within processing region 202.
[0124] In another representative example, a vapor delivery system
500 which has a bulk source 503 containing tantalum, a bulk source
504 containing titanium and a process gas source 580 containing
both oxygen and nitrogen, with both the first and second vaporizers
520 in operation can form films such as tantalum oxides (Liquid
Alignment Configuration 1), titanium doped tantalum oxides (Liquid
Alignment Configuration 3), titanium oxides (Liquid Alignment
Configuration 6) and titanium nitrides (Liquid Alignment
Configuration 9) can be formed within processing region 202.
[0125] In another example, a vapor delivery system 500 could have a
bulk process gas supply 580 containing nitrogen, oxygen and other
processing gases and both chamber bypass 545 and 580 are aligned
such that outlets 555 and 572 are open and no vaporized precursor
reaches processing region 202. Such a configuration would allow
only process gases into processing region 202 or, if the flow of
all process gas were stopped, only activated species from remote
plasma system 400 would be provided to processing region 202.
Utilizing this configuration enables a variety of thermal and
activated processes to occur within processing region 202 such as
thermal or activated anneals, oxidation as well as utilizing
remotely activated species from remote plasma system 400 to clean
processing area 202.
[0126] While specific embodiments of the invention have been shown
and described, further modifications and improvements will occur to
those skilled in the art. It is desired that it be understood,
therefore, that the invention is not limited to the particular form
shown and it is intended in the appended claims which follow to
cover all modifications which do not depart from the spirit and
scope of the invention.
* * * * *