U.S. patent application number 10/303374 was filed with the patent office on 2003-04-10 for method and apparatus for enhanced chamber cleaning.
Invention is credited to Harshbarger, William R., Law, Kam S., Shang, Quanyuan, Sun, Sheng, Yadav, Sanjay.
Application Number | 20030066541 10/303374 |
Document ID | / |
Family ID | 23256901 |
Filed Date | 2003-04-10 |
United States Patent
Application |
20030066541 |
Kind Code |
A1 |
Sun, Sheng ; et al. |
April 10, 2003 |
Method and apparatus for enhanced chamber cleaning
Abstract
A system for processing substrates within a chamber and for
cleaning accumulated material from chamber components is provided.
The system includes a reactive species generator adapted to
generate a reactive gas species for chemically etching accumulated
material from chamber components, and a processing chamber having
at least one fluoropolymer coated component which is exposed to the
reactive species. Preferably to have the greatest impact on chamber
cleaning efficiency, the fluoropolymer coated component(s) are
large components such as a gas distribution plate or a backing
plate, and/or a plurality of smaller components (e.g., a shadow
frame, chamber wall liners, a susceptor, a gas conductance line) so
as to constitute a large percentage of the surface area exposed to
the reactive species. Most preferably all surfaces which the
reactive species contacts are coated with fluoropolymer.
Inventors: |
Sun, Sheng; (Fremont,
CA) ; Shang, Quanyuan; (Saratoga, CA) ; Yadav,
Sanjay; (Redwood City, CA) ; Harshbarger, William
R.; (San Jose, CA) ; Law, Kam S.; (Union City,
CA) |
Correspondence
Address: |
PATENT COUNSEL
APPLIED MATERIALS, INC.
Legal Affairs Department
P.O. BOX 450A
Santa Clara
CA
95052
US
|
Family ID: |
23256901 |
Appl. No.: |
10/303374 |
Filed: |
November 25, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10303374 |
Nov 25, 2002 |
|
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09322893 |
May 29, 1999 |
|
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Current U.S.
Class: |
134/1.1 ; 134/19;
134/22.1; 134/5 |
Current CPC
Class: |
C23C 16/4404 20130101;
B08B 17/06 20130101; B08B 7/0035 20130101; H01L 21/67017 20130101;
H01L 21/67028 20130101; C23C 16/4405 20130101 |
Class at
Publication: |
134/1.1 ; 134/5;
134/19; 134/22.1 |
International
Class: |
C25F 001/00 |
Claims
The invention claimed is:
1. A method of cleaning a processing chamber using a reactive
species, the method comprising: flowing an amount of fluoropolymer
precursor gas into the processing chamber; generating a plasma
within the processing chamber so as to form fluoropolymer on
chamber components; heating the processing chamber so as to melt
the fluoropolymer and form a fluoropolymer coating on the chamber
components, wherein the amount of fluoropolymer precursor gas is
controlled so as to form a uniform fluoropolymer coating of
approximately 0.5-10 .mu.m on the chamber components; thereafter
processing one or more substrates within the processing chamber;
and thereafter flowing reactive species into the processing chamber
and thereby cleaning accumulated material from the chamber
components.
2. The method of claim 1 wherein the fluoropolymer coating is
continuously formed.
3. The method of claim 1 wherein the fluoropolymer precursor gas is
CHF.sub.3.
4. The method of claim 1 wherein the fluoropolymer coating
comprises PTFE.
5. The method of claim 1 wherein the fluoropolymer coating
comprises FEP.
6. The method of claim 1 wherein the fluoropolymer coating
comprises PFA.
7. A method of comprising: flowing an amount of fluoropolymer
precursor gas into the processing chamber; generating a plasma
within the processing chamber so as to form fluoropolymer on
chamber components; and heating the processing chamber so as to
melt the fluoropolymer and form a fluoropolymer coating on the
chamber components, wherein the amount of fluoropolymer precursor
gas is controlled so as to form a uniform fluoropolymer coating of
approximately 0.5-10 .mu.m on the chamber components.
8. The method of claim 7 wherein the fluoropolymer coating is
continuously formed.
9. The method of claim 7 wherein the fluoropolymer precursor gas is
CHF.sub.3.
10. The method of claim 7 wherein the fluoropolymer coating
comprises PTFE.
11. The method of claim 7 wherein the fluoropolymer coating
comprises FEP.
12. The method of claim 7 wherein the fluoropolymer coating
comprises PFA.
Description
[0001] This application is a division of U.S. patent application
Ser. No. 09/322,893, filed May 29, 1999, which is hereby
incorporated by reference herein in its entirety.
FIELD OF THE INVENTION
[0002] The present invention relates to an improved method and
apparatus for enhancing chamber cleaning rates. More specifically,
the present invention relates to a method and apparatus for
enhancing the effective etch rate of a reactive chemical species
which etches accumulated materials from process chamber
components.
BACKGROUND OF THE INVENTION
[0003] The manufacture of liquid crystal displays, flat panel
displays, thin film transistors and other semiconductor devices
occurs within a plurality of chambers, each of which is designed to
perform a specific process on the substrate. Many of these
processes can result in an accumulation of material (e.g., material
deposited on the substrate in layers, such as by chemical vapor
deposition, physical vapor deposition, thermal evaporation,
material etched from substrate surfaces, and the like) on chamber
surfaces. Such accumulated material can crumble from the chamber
surfaces and contaminate the sensitive devices being processed
therein. Accordingly, process chambers must be cleaned of
accumulated materials frequently (e.g., every 1-6 substrates).
[0004] To clean chamber surfaces, an in-situ dry cleaning process
is preferred. In an in-situ dry cleaning process one or more gases
are dissociated to form one or more reactive gas species (e.g.,
fluorine ions, radicals). The reactive species clean chamber
surfaces by forming volatile compounds with the material
accumulated on those surfaces. Unfortunately, as described further
below, such chamber cleaning processes conventionally require
considerable time and consume considerable amounts of cleaning
gases, and thus undesirably increase the cost per substrate
processed within a processing chamber. Further, large cleaning rate
variations often are observed between processing chambers cleaned
by identical cleaning processes. Accordingly, there is a need for
an improved method and apparatus for etching accumulated material
from chamber surfaces.
SUMMARY OF THE INVENTION
[0005] The present inventors have discovered that chamber cleaning
rates may be increased by as much as 20-100% when chamber surfaces
exposed to reactive cleaning gas species are coated with a
fluoropolymer (e.g., polytetrafluoroethylene (PTFE), a
tetrafluoroethylene and hexafluoropropylene copolymer (FEP), a
copolymer of tetrafluoroethylene and perfluoropropylvinyl ether
(PFA)). The present invention therefore comprises a system for
processing substrates within a chamber and for cleaning accumulated
material from chamber components. The system includes a reactive
species generator adapted to generate a reactive gas species for
chemically etching accumulated material from chamber components,
and a processing chamber having at least one flouropolymer coated
component which is exposed to the reactive species. Preferably to
have the greatest impact on chamber cleaning efficiency, the
fluoropolymer coated component(s) include large components such as
a gas distribution plate or a backing plate, and/or a plurality of
smaller components (e.g., the chamber's shadow frame, wall liners,
susceptor, gas conductance line, etc.) so as to constitute a large
percentage of the surface area exposed to the reactive species.
Most preferably all surfaces which the reactive species contacts
are coated with a fluoropolymer.
[0006] By coating exposed chamber components with PTFE, FEP or PFA,
not only have cleaning rate enhancements been observed, cleaning
rate variations between processing chambers can be virtually
eliminated, process chamber throughput increased significantly and
the amount of precursor gas required for cleaning reduced. Because
of the high costs associated with precursor gases such as NF.sub.3,
both monetarily and environmentally (e.g., global warming), any
reduction in precursor gas consumption is beneficial.
[0007] Other objects, features and advantages of the present
invention will become more fully apparent from the following
detailed description of the preferred embodiments, the appended
claims and the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a side elevational view of a processing system
configured in accordance with the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0009] FIG. 1 is a side elevational view of a processing system 10
configured in accordance with the present invention. Any suitable
processing system may be modified as described herein such as a
model AKT-1600 PECVD System manufactured by Applied Kamatsu
Technology and described in U.S. Pat. No. 5,788,778, which is
hereby incorporated by reference herein in its entirety, the
GIGAFILL.TM. processing system manufactured by Applied Materials,
Inc. and described in U.S. Pat. No. 5,812,403, which is hereby
incorporated by reference herein in its entirety, thermal
deposition chambers and the like. For convenience an AKT-1600 PECVD
System configured in accordance with the present invention is shown
in FIG. 1. The AKT-1600 PECVD System is designed for fabricating
active-matrix liquid crystal displays and may be used to deposit
amorphous silicon, silicon dioxide, silicon oxynitrides and silicon
nitride as is known in the art.
[0010] With reference to FIG. 1, the processing system 10 comprises
a deposition chamber 11 having a gas distribution plate 12 having
apertures 12a-u and a backing plate 13 adapted to deliver process
gases and cleaning gases into the deposition chamber 11, and a
susceptor 14 for supporting a substrate 16 to be processed within
the deposition chamber 11. The susceptor 14 includes a heater
element 18 (e.g., a resistive heater) coupled to a heater control
20 for elevating the temperature of the substrate 16 to a
processing temperature and for maintaining the substrate 16 at the
processing temperature during processing. A lift mechanism 22 is
coupled to the susceptor 14 via a lift member 24 to allow the
substrate 16 to be lifted from the susceptor 14. Specifically, a
plurality of lift pins 26 (fixedly held by a lift pin holder 28)
penetrate the susceptor 14 (via a plurality of lift pin apertures
30) so as to contact and lift the substrate 16 from the susceptor
14 when the susceptor 14 is lowered by the lift mechanism 22. The
deposition chamber 11 further comprises a chamber wall liner 29
which blocks material from accumulating on the chamber wall and
which can be removed and cleaned, and a shadow frame 31 which
overhangs the substrate's edge and thereby prevents material from
depositing or accumulating on the wafer's edge.
[0011] In addition to their above described functions, the gas
distribution plate 12 and the susceptor 14 also serve as parallel
plate upper and lower electrodes, respectively, for generating a
plasma within the deposition chamber 11. For example, the susceptor
14 may be grounded and the gas distribution plate 12 coupled to an
RF generator 32 via a matching network 34. An RF plasma thereby may
be generated between the gas distribution plate 12 and the
susceptor 14 through application of RF power supplied thereto by
the RF generator 32 via the matching network 34. A vacuum pump 36
is coupled to the deposition chamber 11 for evacuating/pumping the
same before, during or after processing as required.
[0012] The processing system 10 further comprises a first gas
supply system 38 coupled to an inlet 40 of the deposition chamber
11 for supplying process gases thereto through the backing plate 13
and the gas distribution plate 12. The first gas supply system 38
comprises a valve controller system 42 (e.g., computer controlled
mass flow controllers, flow meters, etc.) coupled to the inlet 40
of the deposition chamber 11, and a plurality of process gas
sources 44a, 44b coupled to the valve controller system 42. The
valve controller system 42 regulates the flow of process gases to
the deposition chamber 11. The specific process gases employed
depend on the materials being deposited within the deposition
chamber 11.
[0013] In addition to the first gas supply system 38, the
processing system 10 comprises a second gas supply system 46
coupled to the inlet 40 of the deposition chamber 11 (via a gas
conductance line 48) for supplying cleaning gases thereto during
cleaning of the deposition chamber 11 (e.g., to remove accumulated
material from the various interior surfaces of the chamber 11). The
second gas supply system 46 comprises a remote plasma chamber 50
coupled to the gas conductance line 48 and a precursor gas source
52 and a minor carrier gas source 54 coupled to the remote plasma
chamber 50 via a valve controller system 56 and a valve controller
system 58, respectively. Typical precursor cleaning gases include
NF.sub.3, CF.sub.4, SF.sub.6, C.sub.2F.sub.6, CCl.sub.4,
C.sub.2Cl.sub.6, etc., as are well known in the art. The minor
carrier gas, if employed, may comprise any non-reactive gas
compatible with the cleaning process being employed (e.g., argon,
helium, hydrogen, nitrogen, oxygen, etc.). The precursor and minor
carrier gas sources 52, 54 may comprise a single gas source if
desired.
[0014] A high power microwave generator 60 supplies microwave power
to the remote plasma chamber 50 to activate the precursor gas
within the remote activation chamber (as described below). A flow
restrictor 62 preferably is placed along the gas conductance line
48 to allow a pressure differential to be maintained between the
remote plasma chamber 50 and the deposition chamber 11.
[0015] During cleaning of the deposition chamber 11, a precursor
gas is delivered to the remote plasma chamber 50 from the precursor
gas source 52. The flow rate of the precursor gas is set by the
valve controller system 56. The high power microwave generator 60
delivers microwave power to the remote plasma chamber 50 and
activates the precursor gas to form one or more reactive species
(e.g., fluorine radicals) which travel to the deposition chamber 11
through the gas conductance line 48. The one or more reactive
species then travel through the inlet 40, through the backing plate
13, through the gas distribution plate 12 and into the deposition
chamber 11. A minor carrier gas may be supplied to the remote
plasma chamber 50 from the minor carrier gas source 54 to aid in
transport of the one or more reactive species to the chamber 11
and/or to assist in chamber cleaning or plasma
initiation/stabilization within the deposition chamber 11 if an RF
plasma is employed during chamber cleaning.
[0016] Exemplary cleaning process parameters for the deposition
chamber 11 when an NF.sub.3 precursor cleaning gas is employed
include a precursor gas flow rate of about 2 liters per minute and
a deposition chamber pressure of about 0.5 Torr. A microwave power
of 3-12 kW, preferably 5 kW, is supplied to the remote plasma
chamber 50 by the high power microwave generator 60 to activate the
NF.sub.3 precursor gas. Preferably the remote plasma chamber 50 is
held at a pressure of at least 4.5 Torr and preferably about 6
Torr. Other cleaning process parameter ranges/chemistries are
described in previously incorporated U.S. Pat. No. 5,788,778.
[0017] As previously described, common problems with conventional
cleaning processes include low cleaning rates and large variations
in cleaning rates between process chambers. The present inventors
have discovered that cleaning rates and cleaning rate variations
between chambers are dependent on the internal chamber surface
condition, and that all internal surfaces between a remote plasma
source (e.g., remote plasma chamber 50) and a chamber (e.g.,
deposition chamber 11) ("downstream surfaces") affect cleaning
rates. Specifically, a surface controlled deactivation process is
believed to cause reactive species employed during cleaning (e.g.,
active etchant species such as F radicals) to combine to form
non-reactive species (e.g., F.sub.2 in the case of F radicals)
which do not assist in chamber cleaning. This surface controlled
deactivation process appears to occur at many material surfaces
including both bare and anodized aluminum surfaces.
[0018] The present inventors have found that by coating one or more
downstream components with PTFE, FEP or PFA, known generally as
fluoropolymers, significantly higher cleaning rates are achieved
and cleaning rate variations between chambers are virtually
eliminated. Components found to have the most significant affect on
cleaning performance include a chamber's gas distribution plate and
backing plate. Components found to have a slight affect on cleaning
performance include a chamber's shadow frame, wall liners,
susceptor and gas conductance line. Components found to have little
effect on cleaning performance include a chamber's microwave power
supply, magnetron and microwave applicator. In order to affect an
improvement in chamber cleaning rates, a certain percentage of the
chamber components should be coated with a fluoropolymer. Although
this percentage may vary, higher percentages are preferred to
achieve faster cleaning rates, with 100% coating of exposed
surfaces being most preferred. Note that an increase in cleaning
rate (e.g., up to 15%) also can be achieved by using an RF plasma
within a processing chamber in conjunction with a remote plasma
source, i.e., by powering electrode 12 to form the radicalized
gases entering from the remote plasma source, or secondarily
introducing cleaning gases into a plasma. However, applied RF power
should be limited to avoid damage to processing chamber components
due to ion bombardment.
[0019] With reference to the processing system 11 of FIG. 1, to
affect increased cleaning rate and reduced cleaning rate variations
between the deposition chamber 11 and other deposition chambers
(not shown), one or more downstream components of the processing
system 11 are coated with a polytetrafluoroethylene (PTFE), a
tetrafluoroethylene and hexafluoropropylene copolymer (FEP), or a
copolymer of tetrafluoroethylene and perfluoropropylvinyl ether
coating ("fluoropolymer coating 64"). As shown in FIG. 1, the
interior surfaces of the deposition chamber 11, the gas
distribution plate 12 the backing plate 13, the susceptor 14, the
inlet 40, the gas conductance line 48, the chamber wall liner 29
and the shadow frame 31 are coated with the protective coating 64.
Fewer components may be coated with the fluoropolymer coating 64 if
desired.
[0020] With respect to the PECVD deposition chamber 11 of FIG. 1,
the fluoropolymer coating 64 significantly increases the cleaning
rate and significantly reduces chamber-to-chamber cleaning rate
variations while neither producing process drift nor changes in the
properties of PECVD films deposited within the deposition chamber
11. The fluoropolymer coating 64 is believed to cover surface
adsorption sites at which the surface controlled deactivation
process is believed to occur (e.g., maintaining a high and a
uniform F radical concentration) and is also believed to reduce the
amount of material deposited on component surfaces of the
deposition chamber 11 during processing therein (e.g., reducing the
amount of material that must be cleaned from component surfaces and
the time required for material removal during cleaning).
[0021] The inventive fluoropolymer coating may be applied either
in-situ or ex-situ. For in-situ application of PTFE coatings, a
precursor gas such as CHF.sub.3 may be employed to coat process
chamber components using either a microwave or RF plasma. For
example, within the processing system 10, a CHF.sub.3 precursor gas
source 52 may feed CHF.sub.3 to the remote plasma chamber 50
wherein microwave power applied via the high power microwave
generator 60 dissociates the CHF.sub.3 into CF.sub.2 and HF. The
CF.sub.2 and HF travel to the deposition chamber 11, and, en route,
the CF.sub.2 forms a fluoropolymer coating on the gas conductance
line 48, the flow restrictor 59, the inlet 40, the backing plate
13, the gas distribution plate 12, the susceptor 14 and the
interior surfaces of the deposition chamber 11. Alternatively,
CHF.sub.3 (and, if desired, CF.sub.2 from the remote plasma chamber
50) may be flowed into the deposition chamber 11 while an RF plasma
is generated within the deposition chamber 11 via the RF generator
32. As with the microwave plasma of the remote plasma chamber 50,
the RF plasma within the deposition chamber 11 will dissociate
CHF.sub.3 into CF.sub.2 which in turn will coat chamber components
with a fluoropolymer coating. Thereafter, the chamber 11 may be
heated (e.g., via the heater control 20 and the resistive heating
element 18 or via any conventional heating mechanism capable of
heating the entire chamber to the desired temperature) so as to
melt/reflow the fluoropolymer coating. Preferably a heater
temperature of about 500-800.degree. F. is employed. In this
manner, a uniform fluoropolymer coating, preferably about 0.5-10
.mu.m in thickness, is formed on the chamber components.
[0022] For ex-situ application of protective coatings, chamber
components such as the gas distribution plate 12 and the backing
plate 13 preferably are uniformly coated with a thin layer (e.g.,
about 0.5 to 10 microns) of a PTFE, a FEP- or a PFA-contained in a
solution or suspension fluid such as water, isopropyl alcohol, etc.
After a few minutes of air drying or after an oven bake at
500-800.degree. F. heater temperature, the chamber components may
be reinstalled within the processing chamber. Care should be taken
to prevent clogging of the small gas injection holes of the gas
distribution plate due to capillary effect.
[0023] It should be noted that the inventive protective coating
described herein differs from flouropolymers which undesirably
accumulate over time on chamber surfaces as a result of
flouropolymer deposition on a underlying substrate, or which are
formed as a byproduct of certain CVD processes (i.e., are not
continuously formed), in that such undesirably accumulated material
is characteristically non-uniform, often exhibiting both areas of
thick accumulation which can crumble from chamber surfaces, and
areas where no material accumulates. Accordingly, such undesirable
byproduct and deposited material accumulation must be cleaned from
chamber surfaces. However, these undesirable fluoropolymer
accumulations do not react with reactive fluorine gas species and
therefore must be cleaned by other, less efficient means.
[0024] By coating downstream chamber components with PTFE, FEP or
PFA, cleaning rate enhancements of as much as 100% have been
observed, and cleaning rate variations between processing chambers
have been virtually eliminated. Accordingly, process chamber
throughput increases significantly with use of the present
invention, and the amount of precursor gas required for cleaning is
reduced. Because of the high costs associated with precursor gases
such as NF.sub.3, both monetarily (e.g. NF.sub.3 presently costs
$100/lb) and environmentally (e.g., NF.sub.3 is a "global warming"
gas,) reduction in precursor gas consumption is extremely
beneficial. Moreover, flouropolymers are non-brittle, inexpensive
and easy to apply, unlike coatings (e.g., AlF.sub.3) which
conventionally have been applied to prevent corrosion of chamber
surfaces or to prevent accumulated material from crumbling
therefrom.
[0025] The foregoing description discloses only the preferred
embodiments of the invention, modifications of the above disclosed
apparatus and method which fall within the scope of the invention
will be readily apparent to those of ordinary skill in the art. For
instance, while the present invention has been described with
reference to a PECVD chamber, it will be understood that the
invention has applicability to a wide variety of process chambers
including thermal deposition chambers. Additionally, cleaning
processes employing reactive species (e.g., reactive species
generated by an RF plasma within a process chamber, or remote
plasma source generated reactive species etc.) may be improved by
employing the fluoropolymer coatings described herein. Finally,
although any fluoropolymer is believed to enhance cleaning when
applied as described herein, the fluoropolymers PTFE, FEP and PFA
have been found to significantly enhance cleaning and are
preferred.
[0026] Accordingly, while the present invention has been disclosed
in connection with the preferred embodiments thereof, it should be
understood that other embodiments may fall within the spirit and
scope of the invention, as defined by the following claims.
* * * * *