U.S. patent application number 12/868899 was filed with the patent office on 2011-05-19 for method of decontamination of process chamber after in-situ chamber clean.
This patent application is currently assigned to APPLIED MATERIALS, INC.. Invention is credited to Hua Chung, Jacob Grayson, Sang Won Kang, Olga Kryliouk, Dong Hyung Lee, Sandeep Nijhawan, Jie Su, Lori D. Washington.
Application Number | 20110117728 12/868899 |
Document ID | / |
Family ID | 43625330 |
Filed Date | 2011-05-19 |
United States Patent
Application |
20110117728 |
Kind Code |
A1 |
Su; Jie ; et al. |
May 19, 2011 |
METHOD OF DECONTAMINATION OF PROCESS CHAMBER AFTER IN-SITU CHAMBER
CLEAN
Abstract
A method and apparatus for removing deposition products from
internal surfaces of a processing chamber, and for preventing or
slowing growth of such deposition products. A halogen containing
gas is provided to the chamber to etch away deposition products. A
halogen scavenging gas is provided to the chamber to remove any
residual halogen. The halogen scavenging gas is generally activated
by exposure to electromagnetic energy, either inside the processing
chamber by thermal energy, or in a remote chamber by electric
field, UV, or microwave. A deposition precursor may be added to the
halogen scavenging gas to form a deposition resistant film on the
internal surfaces of the chamber. Additionally, or alternately, a
deposition resistant film may be formed by sputtering a deposition
resistant metal onto internal components of the processing chamber
in a PVD process.
Inventors: |
Su; Jie; (Santa Clara,
CA) ; Washington; Lori D.; (Union City, CA) ;
Nijhawan; Sandeep; (Los Altos, CA) ; Kryliouk;
Olga; (Sunnyvale, CA) ; Grayson; Jacob;
(Midland, MI) ; Kang; Sang Won; (San Jose, CA)
; Lee; Dong Hyung; (Yongin-si, KR) ; Chung;
Hua; (San Jose, CA) |
Assignee: |
APPLIED MATERIALS, INC.
Santa Clara
CA
|
Family ID: |
43625330 |
Appl. No.: |
12/868899 |
Filed: |
August 26, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61237505 |
Aug 27, 2009 |
|
|
|
Current U.S.
Class: |
438/478 ;
134/1.1; 134/22.1; 134/4; 257/E21.09 |
Current CPC
Class: |
C23C 16/4404 20130101;
H01L 21/67115 20130101; C23C 16/45574 20130101; C23C 16/4405
20130101 |
Class at
Publication: |
438/478 ;
134/22.1; 134/4; 134/1.1; 257/E21.09 |
International
Class: |
H01L 21/20 20060101
H01L021/20; B08B 9/00 20060101 B08B009/00 |
Claims
1. A method of cleaning group III nitride deposits formed on a gas
distributor during a processing run in a deposition chamber, the
method comprising: forming a sacrificial coating on the gas
distributor prior to the processing run; after the processing run,
exposing the group III nitride deposits and the sacrificial coating
to an activated halogen containing gas; and etching the sacrificial
coating and the group III nitride deposits, wherein the sacrificial
coating is etched faster than the group III nitride deposits.
2. The method of claim 1, wherein the sacrificial coating comprises
aluminum, silicon, or both.
3. The method of claim 1, wherein etching the group III nitride
deposits comprises converting the group III nitride deposits to
group III halide solids and removing the group III halide
solids.
4. The method of claim 1, wherein the halogen gas is activated by
heating to a temperature above 600.degree. C.
5. The method of claim 1, wherein the sacrificial coating comprises
nitrogen and at least one of silicon and aluminum.
6. The method of claim 1, wherein providing a sacrificial coating
on the gas distributor comprises reacting an organoaluminum
compound, an organosilicon compound, or a mixture thereof with a
nitrogen containing compound to deposit a layer comprising nitrogen
and at least one of silicon and aluminum on the gas
distributor.
7. The method of claim 6, wherein the organoaluminum and
organosilicon compounds are provided to the deposition chamber
through a first pathway and the nitrogen containing compound is
provided to the deposition chamber through a second pathway.
8. The method of claim 7, wherein one of the first pathway and the
second pathway bypasses the gas distributor.
9. The method of claim 6, wherein the gas distributor comprises a
first gas pathway and a second gas pathway, the organosilicon or
organoaluminum compounds are flowed through the first gas pathway
at a first volumetric flow rate, an inert gas is flowed through the
second gas pathway at a second volumetric flow rate, and the first
and second volumetric flow rates are substantially equal.
10. The method of claim 9, wherein the nitrogen containing compound
is flowed through a third gas pathway that bypasses the gas
distributor.
11. The method of claim 3, wherein converting the group III nitride
deposits to group III halide solids comprises reacting the
activated halogen containing gas with the group III nitride
deposits and the sacrificial coating at a temperature above about
600.degree. C.
12. The method of claim 3, wherein removing the group III halide
solids comprises heating the group III halide solids to a
temperature above about 1,000.degree. C. at a pressure below about
50 Torr.
13. The method of claim 3, wherein the converting and removing are
repeated.
14. A method of removing group III nitride deposits from a gas
distributor in a process chamber, comprising: exposing the gas
distributor to a halogen containing gas; reacting the halogen
containing gas with the group III nitride deposits to form volatile
species; and exposing the gas distributor to an active nitrogen
containing gas.
15. The method of claim 14, wherein the halogen containing gas is a
mixture of chlorine gas and a carrier gas.
16. The method of claim 14, wherein the active nitrogen containing
gas comprises ammonia, hydrazine, nitrogen gas, or any mixture
thereof heated to at least about 500.degree. C.
17. The method of claim 16, wherein the active nitrogen containing
gas comprises ammonia heated to at least about 1,000.degree. C.
18. The method of claim 14, further comprising exposing the gas
distributor to a plasma formed from an inert gas and exposing the
gas distributor to an activated scavenging gas.
19. A method of operating a deposition chamber having a gas
distributor with a surface exposed to the processing environment,
the method comprising: forming a sacrificial coating on the surface
of the gas distributor; depositing a group III nitride material on
a substrate in the deposition chamber and on the coated surface of
the gas distributor by providing a group III metal precursor and a
nitrogen containing precursor to the deposition chamber; purging
the group III metal precursor from the deposition chamber using the
nitrogen containing precursor; providing a halogen containing gas
to the deposition chamber; activating the halogen containing gas by
heating the halogen containing gas to a temperature above about
600.degree. C.; reacting the active halogen containing gas with the
sacrificial layer and with the group III nitride deposits on the
sacrificial coating at a pressure between about 100 Torr and about
200 Torr to remove the sacrificial coating and convert the group
III nitride deposits to group III halide deposits; removing the
group III halide deposits by increasing the temperature to at least
about 1,000.degree. C. and reducing the pressure to less than about
50 Torr; and heat-soaking the gas distributor at a temperature
above about 1,000.degree. C. under an inert atmosphere.
20. The method of claim 19, wherein reacting the active halogen
containing gas with the sacrificial layer and with the group III
nitride deposits and removing the group III halide deposits are
repeated.
21. The method of claim 20, wherein depositing a group III nitride
material on a substrate is repeated.
22. The method of claim 21, wherein purging the group III metal
precursor from the deposition chamber comprises cycling the chamber
pressure.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims benefit of U.S. Provisional Patent
Application 61/237,505, filed Aug. 27, 2009, which is incorporated
by reference herein.
FIELD
[0002] Embodiments described herein generally relate to manufacture
of devices such as light emitting diodes, and to processes for
forming group IIIN materials for such devices. More specifically,
embodiments described herein relate to methods and apparatus for
preventing contamination from particles or chemical residue
dislodged from internal surfaces of a deposition chamber.
BACKGROUND
[0003] Group III-V films are finding greater importance in the
development and fabrication of a variety of semiconductor devices,
such as short wavelength light emitting diodes (LEDs), laser diodes
(LDs), and electronic devices including high power, high frequency,
high temperature transistors and integrated circuits. For example,
short wavelength (e.g., blue/green to ultraviolet) LEDs are
fabricated using the Group III-nitride semiconducting material
gallium nitride (GaN). It has been observed that short wavelength
LEDs fabricated using GaN can provide significantly greater
efficiencies and longer operating lifetimes than short wavelength
LEDs fabricated using non-nitride semiconducting materials, such as
Group II-VI materials.
[0004] One method that has been used for depositing Group
III-nitrides, such as GaN, is metal organic chemical vapor
deposition (MOCVD). This chemical vapor deposition method is
generally performed in a reactor having a temperature controlled
environment to assure the stability of a first precursor gas which
contains at least one element from Group III, such as gallium (Ga).
A second precursor gas, such as ammonia (NH.sub.3), provides the
nitrogen needed to form a Group III-nitride. The two precursor
gases are injected into a processing zone within the reactor where
they mix and move towards a heated substrate in the processing
zone. A carrier gas may be used to assist in the transport of the
precursor gases towards the substrate. The precursors react at the
surface of the heated substrate to form a Group III-nitride layer,
such as GaN, on the substrate surface. The quality of the film
depends in part upon deposition uniformity which, in turn, depends
upon uniform mixing of the precursors across the substrate.
[0005] To accomplish deposition of the layer on substrates,
multiple substrates may be arranged on a substrate carrier and each
substrate may have a diameter ranging from 50 mm to 100 mm or
larger. The uniform mixing of precursors over larger substrates
and/or more substrates and larger deposition areas is desirable in
order to increase yield and throughput. These factors are important
since they directly affect the cost to produce an electronic device
and, thus, a device manufacturer's competitiveness in the market
place.
[0006] The different gases, which when combined react to form the
deposition layer, are generally provided through different pathways
in a gas distributor to the reaction chamber. As the gases exit the
gas distributor, they mix and begin reacting. Generally, the gas
distributor is kept at a temperature well below the substrate
temperature to avoid decomposition of gases in the precursor
pathways before the precursor gases reach the substrate. Although
most reaction products are formed near the heated substrate, some
begin forming as the precursors mix near the exit of the gas
distributor, and condense and deposit on the gas distributor. The
deposits build up over many deposition cycles, until there is an
unacceptable risk that particles formed from this unwanted
deposition will dislodge during deposition and contaminate
substrates being processed in the chamber. Thus, there is a need
for methods and apparatus to prevent or retard buildup of such
deposits.
SUMMARY
[0007] Embodiments disclosed herein provide a method of cleaning
group III nitride deposits formed on a gas distributor during a
processing run in a deposition chamber, the method comprising
forming a sacrificial coating on the gas distributor prior to the
processing run, after the processing run, exposing the group III
nitride deposits and the sacrificial coating to an activated
halogen containing gas, and etching the sacrificial coating and the
group III nitride deposits, wherein the sacrificial coating is
etched faster than the group III nitride deposits.
[0008] Other embodiments provide a method of removing group III
nitride deposits from a gas distributor in a process chamber,
comprising exposing the gas distributor to a halogen containing
gas, reacting the halogen containing gas with the group III nitride
deposits to form volatile species, and exposing the gas distributor
to an active nitrogen containing gas.
[0009] Other embodiments provide a method of operating a deposition
chamber having a gas distributor with a surface exposed to the
processing environment, the method comprising forming a sacrificial
coating on the surface of the gas distributor, depositing a group
III nitride material on a substrate in the deposition chamber and
on the coated surface of the gas distributor by providing a group
III metal precursor and a nitrogen containing precursor to the
deposition chamber, purging the group III metal precursor from the
deposition chamber using the nitrogen containing precursor,
providing a halogen containing gas to the deposition chamber,
activating the halogen containing gas by heating the halogen
containing gas to a temperature above about 600.degree. C.,
reacting the active halogen containing gas with the sacrificial
layer and with the group III nitride deposits on the sacrificial
coating at a pressure between about 100 Torr and about 200 Torr to
remove the sacrificial coating and convert the group III nitride
deposits to group III halide deposits, removing the group III
halide deposits by increasing the temperature to at least about
1,000.degree. C. and reducing the pressure to less than about 50
Torr, and heat-soaking the gas distributor at a temperature above
about 1,000.degree. C. under an inert atmosphere.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] So that the manner in which the above-recited features of
the present invention can be understood in detail, a more
particular description of the invention, briefly summarized above,
may be had by reference to embodiments, some of which are
illustrated in the appended drawings. It is to be noted, however,
that the appended drawings illustrate only typical embodiments of
this invention and are therefore not to be considered limiting of
its scope, for the invention may admit to other equally effective
embodiments.
[0011] FIG. 1 is a flow diagram summarizing a method for cleaning a
chamber according to one embodiment.
[0012] FIG. 2 is a flow diagram summarizing a method for forming a
deposition resistant layer on internal surfaces of a chamber
according to another embodiment.
[0013] FIG. 3 is a flow diagram summarizing a method for removing
unwanted deposits from, and providing a deposition resistant layer
for, internal surfaces of a chamber according to another
method.
[0014] FIG. 4 is a schematic cross-sectional view of a gas
distributor useful for practicing embodiments of the invention.
[0015] FIG. 5A is a cross-sectional view of a gas distributor
according to one embodiment.
[0016] FIGS. 5B and 5C are close-up views of portions of the gas
distributor of FIG. 5A.
[0017] To facilitate understanding, identical reference numerals
have been used, where possible, to designate identical elements
that are common to the figures. It is contemplated that elements
disclosed in one embodiment may be beneficially utilized on other
embodiments without specific recitation.
DETAILED DESCRIPTION
[0018] Embodiments disclosed herein generally provide methods and
apparatus for preventing buildup of deposits on components of a
deposition chamber. Some embodiments provide methods for cleaning
the chamber components periodically, and other embodiments provide
methods for reducing or preventing deposits. In some embodiments, a
coating is applied in situ to a gas distributor to reduce formation
of deposits on the gas distributor around gas flow portals. In
other embodiments, the gas distributor is cleaned using active
reagents, such as radicals. Such cleaning processes may follow a
halogen cleaning process, and may precede a coating process.
[0019] During an MOCVD or HVPE deposition process, for example,
group III materials may deposit on the gas distributor due to low
vapor pressure of the reaction products produced in the chamber.
This buildup of deposition products on the gas distributor and/or
other chamber components, such as the chamber walls, may result in
unwanted particles flaking therefrom and depositing on a substrate
disposed in the chamber. Some embodiments described below provide
an apparatus for forming a metal nitride layer on a substrate,
comprising a chamber enclosing a substrate support and, facing the
substrate support, a gas distributor having a deposition resistant
coating. The deposition resistant coating will generally reduce
deposition on the gas distributor, reducing the frequency of
cleaning needed. The coating may be a gallium deposition-resistant
coating, such as tungsten, chromium, molybdenum, or another coating
resistant to deposition thereon, such as silicon carbide, silicon
nitride, gallium nitride, or aluminum nitride. In some embodiment,
it is also useful to use a deposition resistant coating in
combination with one or more chamber component cooling devices to
further inhibit the deposition of the group III materials on the
exposed surfaces. In one example, the one or more chamber component
cooling devices include the thermal control channel 422 and heat
exchanging system 424 used to control the temperature of the gas
distributor 400, which are further described below.
[0020] In one embodiment, a gas distributor resistant to deposition
in a process chamber may be formed by depositing a metal coating,
such as tungsten, chromium, or molybdenum on an outer surface of a
gas distributor using a physical vapor deposition process, or by
depositing a metal or ceramic coating, such as tungsten, chromium,
molybdenum, silicon carbide, silicon nitride, gallium nitride, or
aluminum nitride on the outer surface of the gas distributor using
a chemical vapor deposition process. In some embodiments, a coating
may be formed in-situ by providing CVD precursors such as TMG, TMA,
silane, TMS, ammonia, and/or methane to a chamber having a gas
distributor to be coated. In some embodiments, the coating forms a
seasoning layer on the gas distributor. Exemplary CVD coatings
formed from such precursors include gallium nitride, aluminum
nitride, silicon nitride, and silicon carbide.
[0021] Deposits that build up during deposition may be removed by
one or more cleaning processes. In one embodiment, a halogen
containing gas is provided to the chamber through the gas
distributor having deposits to be removed. The halogen gas reacts
with the deposits, which generally contain metal-rich group III/V
deposition products such as gallium (Ga), indium (In), aluminum
(Al), gallium nitride (GaN), indium nitride (InN), aluminum nitride
(AlN), and combinations thereof, producing halid solids and
nitrogen containing gases which are removed from the chamber, the
halide solids being removed from the chamber by volatilizing at
high temperature. In another embodiment, halide residues that may
be left by a halogen cleaning process are removed by providing
active species to the chamber. In some cases the active species are
formed by applying electrical energy (e.g., generating RF plasma),
optical energy, or thermal energy to the gas or vapor species. The
active species scavenge any remaining deposits, including halide
residues. In some embodiments, the two cleaning processes are
combined in a two-stage cleaning process, while in others the two
cleaning steps may be performed at different times. Additionally,
cleaning processes may be combined with coating processes in some
embodiments.
[0022] Cleaning Methods
[0023] FIG. 1 is a flow diagram summarizing a cleaning method 100
according to one embodiment. At 102, a cleaning gas, such as a
halogen containing gas, is provided to a chamber having a coating
of deposition products, such as metal-rich group III nitrides or
other group III/V reaction products, such as group III metals, on
internal components thereof, such as on the gas distributor. Some
exemplary group III deposition products that may be removed by the
cleaning method 100 include Ga, In, Al, GaN, InN, AlN, aluminum
gallium nitride (AlGaN), indium gallium nitride (InGaN) and the
like. The coating may be continuous or discontinuous, and may be
merely deposits from the deposition process formed on gas flow
portals of a gas distributor. The halogen containing gas may be an
elemental halogen gas, such as chlorine, fluorine, bromine, or
iodine gas, or a hydrogen halide gas, or any mixture thereof. In
some examples, the cleaning gas comprises a chlorine (Cl.sub.2)
gas, a fluorine (F.sub.2) gas, a hydrogen iodide (HI) gas, an
iodine chloride (ICl) gas, an HCl gas, an HBr gas, a HF gas, a
BCl.sub.3 gas, a CH.sub.3Cl gas, a CCl.sub.4 gas and/or an NF.sub.3
gas.
[0024] In one embodiment, to clean a gas distributor having
deposits thereon as described above, chlorine gas (Cl.sub.2) is
provided to a chamber containing the gas distributor, optionally
with a non-reactive carrier gas, such as argon, helium, or nitrogen
gas. The chlorine gas is heated to a temperature of at least about
600.degree. C., such as between about 650.degree. C. and about
750.degree. C., by heating an internal surface of the chamber, such
as a substrate support disposed in the chamber facing the gas
distributor. The resulting gas mixture may be about 5-100% chlorine
gas in carrier gas, by total gas volume, such as between about 50%
and about 80% chlorine gas in carrier gas. The chamber pressure is
maintained between about 100 Torr and about 200 Torr during
exposure of the gas distributor surfaces to the chlorine gas. The
chlorine gas converts the group III nitrides on the gas distributor
surfaces to group III halide solids.
[0025] At 104, the coating of deposition products is etched away
from the interior of the chamber. The halogen containing gas reacts
with the deposits to form volatile metal halides, which are removed
from the chamber. In embodiments featuring chlorine gas, the
chlorine reacts with the metal-rich deposits to form gallium
chloride (GaCl.sub.3), indium chloride (InCl.sub.3), and aluminum
chloride (AlCl.sub.3), which are volatile at low pressures. In the
embodiment featuring chlorine gas as the reactant, the chlorine gas
may be provided at a flow rate between about 1 slm and about 20
slm, with carrier gas flow rate between about 0 slm and about 20
slm, at pressures between about 0.01 Torr and 1,000 Torr, such as
between about 100 Torr and about 200 Torr, and temperatures between
about 20.degree. C. and about 1,200.degree. C., such as above
600.degree. C., for example between about 650.degree. C. and about
750.degree. C.
[0026] The halogen gas converts the group III nitride deposits to
group III halide solids. Following conversion of the group III
nitrides to group III halide solids, the group III halide solids
are removed by vaporization or sublimation. The chamber temperature
is increased to at least about 1,000.degree. C., such as between
about 1,050.degree. C. and about 1,200.degree. C., for example
about 1,100.degree. C. The chamber pressure is lowered to about 50
Torr or below. The halogen gas flow may be maintained during a
first phase of the removal operation, and then the halogen gas flow
may be discontinued and the carrier gas flow continued during a
second phase of the removal operation. During such a second phase,
the chamber temperature may be further increased to at least about
1,100.degree. C. In the embodiment described above, conversion of
the group III nitride deposits to group III halide salts takes
about 5-60 minutes, depending on the thickness of the coating, and
removal of the group III halide solids takes at least about 10
minutes, such as between about 10 minutes and about 20 minutes, to
complete.
[0027] In some embodiments, the conversion and removal may be
accomplished in cycles. In one embodiment, conversion may proceed
for about 1 minute and removal for between about 10 seconds and
about 20 seconds in one cycle. The cycle is then repeated until the
group III nitride deposits are removed, which may take between 50
and 100 cycles. In another embodiment, conversion may proceed for
about 5 minutes and removal for about 1 minute, the cycle being
repeated about 10 times. In each cycle, the temperature and
pressure of the chamber are moved between the conversion and
removal conditions described above. Cycle repetitions and
conversion and removal times per cycle depend on the thickness of
the group III nitride deposits on the chamber surfaces. Thicker
deposits take more time and repetitions to remove.
[0028] The halogen treatment may leave halogen containing residues
on chamber surfaces, so a second optional cleaning process may be
performed at 106 and 108. At 106, a nitrogen containing gas is
provided to the chamber, and at 107 the nitrogen containing gas is
activated. At 108, the active nitrogen containing gas is allowed to
react with residual halogen species in the chamber to purge the
halogen species from the chamber. In some embodiments, the nitrogen
containing gas, which may be ammonia (NH.sub.3), nitrogen gas
(N.sub.2), hydrazine (H.sub.2N.sub.2) or other simple nitrogen
containing compound, may be activated into ions or radicals. In one
embodiment, ammonia is heated to a temperature of at least about
500.degree. C. by heating the substrate support. The heating
activates the nitrogen containing gas, causing compounds in the gas
to dissociate, pyrolyze, ionize, or form radicals. In other
embodiments, the nitrogen containing gas may be heated remotely and
provided to the gas distributor as a hot gas. The gas distributor
is generally cooled during deposition processes to avoid unwanted
reactions inside and near the distributor. During some cleaning
processes, cooling of the gas distributor may be discontinued to
facilitate thermal activation of cleaning compounds. Heating of the
substrate support may be accomplished by any convenient means, such
as by disposing heat lamps proximate the substrate support. In one
embodiment, heat lamps are arrayed below the substrate support.
Other embodiments may feature a substrate support heated by
internal means, such as resistive or hot fluid heating.
[0029] The nitrogen containing gas may be provided with a carrier
gas. In one example ammonia is provided along with nitrogen gas as
a carrier. The gas mixture may be between about 10% ammonia and
about 80% ammonia by volume in nitrogen gas.
[0030] The activation of operation 107 may proceed by different
methods. In one embodiment, the gas distributor is exposed to hot
ammonia gas, heated to at least about 1,000.degree. C., to form
highly reactive radical species that scavenge the remaining halogen
from the chamber. The heating may be accomplished by heating the
substrate support or the gas distributor, or by heating the ammonia
remotely and providing the heated gas to the chamber. In another
embodiment, a nitrogen containing gas is activated in a remote
chamber by applying electromagnetic energy, such as electric fields
or thermal, UV, or microwave radiation. The activated nitrogen gas,
containing radical species, is then provided to the chamber to
remove halogen residues. The activated nitrogen species convert the
remaining halogen residues back to metal nitride to prevent halogen
species from being incorporated into devices subsequently formed in
the chamber. The risk that the nitrides will contaminate such
devices is reduced because most of the nitride deposits are
removed, leaving at most a very thin coating or residue that is
very unlikely to separate from the gas distributor or other chamber
component. In other embodiments, the gas may be exposed to electric
fields, thermal, UV, or microwave radiation in situ.
[0031] A nitrogen containing gas may be provided at a flow rate
between about 1 slm and about 50 slm, at chamber pressure of
between about 0.01 Torr and about 1,000 Torr. The nitrogen
containing gas may be activated by heating to a temperature between
about 500.degree. C. and about 1,200.degree. C., such as between
about 900.degree. C. and about 1,100.degree. C., by contacting the
gas with a heated substrate support spaced apart from the gas
distributor, or by heating outside the chamber. At such
temperatures, the thermal energy activates the nitrogen containing
gas. If UV, microwave, or electrical energy is used to activate the
nitrogen containing gas, the chamber temperature may be between
about 20.degree. C. and about 600.degree. C., such as between about
100.degree. C. and about 300.degree. C.
[0032] Prior to the halogen gas exposure of FIG. 1, the chamber may
be purged to remove gases or substances that may be incompatible
with the halogen gas. Metal precursor species such as TMG, TMA, and
TMI, in particular, are removed prior to feeding halogen gas to
avoid unwanted reactions that may consume the halogen gas and
generate further deposits. The chamber may be purged using an inert
gas such as nitrogen gas or argon, or the chamber may be purged
using a non-metal reagent such as ammonia. In a deposition process
wherein a metal nitride is formed from a metal precursor and
ammonia, flow of the metal precursor may be discontinued and the
chamber purged using the ammonia gas. Alternately, the ammonia gas
may be replaced with an inert gas such as nitrogen, argon, or
hydrogen to purge the chamber. During the chamber purge, the
chamber pressure may be cycled to enhance removal of fugitive
species adhering the chamber surfaces. A throttle valve between the
chamber and the vacuum pump may be opened and closed repeatedly to
cycle the chamber pressure up and down a desired number of times,
for example 3-5 times.
[0033] Prior to the halogen gas exposure of FIG. 1, the chamber may
be subjected to a baking operation to remove metal nitride deposits
from chamber surfaces such as the substrate support and chamber
liner, if any. Chamber temperature is increased to at least about
1,050.degree. C. for a duration of 5-10 minutes or more. Hydrogen
gas may be provided to enhance removal of deposits. The baking
operation also enhances removal of deposits from the gas
distributor.
[0034] Following the halogen gas clean and residual halogen removal
operations of FIG. 1, the chamber may be subjected to a baking
operation to enhance removal of halogen species from chamber
surfaces. Chamber temperature is set to at least about
1,050.degree. C. If a mixture of ammonia and nitrogen gas is used
for residual halogen removal, the flow of ammonia may be
discontinued, and the flow of nitrogen maintained during the
post-clean baking operation. To aid removal of fugitive halogen
species, the chamber pressure may be cycled between about 200 Torr
and about 1 Torr by opening and closing the vacuum throttle valve.
The post-clean baking operation may proceed for a duration of about
5-10 minutes or more. In one embodiment, flow of nitrogen gas may
be replaced during the baking operation by a flow of hydrogen gas
to help scavenge residual halogen species.
[0035] Coating Methods
[0036] FIG. 2 is a flow diagram summarizing a method 200, according
to another embodiment, for forming a layer resistant to deposition
of gallium or gallium compounds on internal surfaces of a chamber.
A method such as the method 200 is useful for treating chamber
components to prevent or slow deposition of gallium-rich compounds
on the components of a processing chamber. In this method, one or
more precursor gases are provided to a processing chamber at 202.
The gases are generally selected to facilitate deposition of a
layer on the internal components of the chamber. The gases may be
provided through different pathways, if desired, to prevent
reaction before the gases arrive in the chamber. For example, if
two gases are used, a first gas may be provided to the chamber
through a first pathway, and a second gas through a second pathway.
A gas distributor having multiple pathways is further described in
connection with FIGS. 5A and 5B.
[0037] It should be noted that the method 200 may be performed in
the chamber having the internal surfaces to be coated, or
components of the chamber may be placed in another processing
chamber to be coated. For example, if a PVD process is performed,
the chamber components may be disposed in a PVD chamber, and the
process gas provided to the chamber may be a PVD process gas, such
as argon or helium.
[0038] At 204, a layer is deposited on internal surfaces of the
chamber. In one embodiment, two or more gases react to deposit a
layer by a CVD process, which may be performed in the chamber
having the internal surfaces to be coated, or in a separate chamber
having components to be coated disposed therein. In one embodiment,
the layer is deposited by a PVD process in which a material
resistant to gallium or gallium compounds, or other group III
compounds, is sputtered onto chamber components. In another
embodiment, a layer is deposited by providing activated species to
the chamber having the surfaces to be coated, and reacting the
activated species to form the layer.
[0039] The layer may have a thickness between about 10 .ANG., about
two unit cell dimensions of a crystal lattice, and about 1 mm. A
layer or coating having a thickness of at least about two unit cell
layers, such as about 10 .ANG., will retard growth of deposits on a
gas distributor in most cases. The coating may be any thickness up
to about 1 mm, but will generally be applied in a way to avoid
occluding openings in the gas distributor for dispensing process
gases. In one embodiment, a metal, such as tungsten, chromium,
molybdenum, or a combination or alloy thereof, or another
refractory metal, is sputtered onto a gas distributor to a
thickness of between about 10 .ANG. and about 1 mm, such as between
about 10 .ANG. and about 10 .mu.m, for example between about 10
.ANG. and about 1,000 nm. In another embodiment, TMG and ammonia
are provided to a chamber containing the gas distributor to be
coated thereby, depositing gallium nitride on the gas distributor.
In another embodiment, TMA and ammonia are provided to the chamber
to deposit aluminum nitride on the gas distributor. In another
embodiment, silane and methane are provided to the chamber to
deposit silicon carbide on the gas distributor. In another
embodiment, silane and/or TMS and ammonia are provided to deposit
silicon nitride on the gas distributor. Coatings formed by CVD
processes may have thickness between about 100 nm and about 200 nm
because gas flowing through the openings in the gas distributor
reduces film formation in and around the openings.
[0040] In other embodiments, a refractory metal such as tungsten,
chromium, molybdenum, titanium, zirconium, hafnium, vanadium,
niobium, tantalum, ruthenium, osmium, rhodium, yttrium, and
iridium, or ceramics (oxides) thereof, other derivatives thereof,
combinations thereof, or alloys thereof, may be sputter coated or
plated onto a stainless steel gas distributor according to
processes such as CVD, PVD, plasma spraying, electroplating, and/or
electroless plating that are known in the art. Various aluminum
containing materials may also be applied by CVD or PVD, including
aluminum itself, alumina, aluminum nitride, and alloys of aluminum
with other metals listed above, silicon, or carbon. Other
dielectric materials that may be used for coatings include boron
nitride and silicon carbide. Any material that forms a tight
metallurgical bond with stainless steel, such as aluminized steel,
is suitable for coating a stainless steel gas distributor of an
MOCVD chamber to retard or prevent buildup of deposition
products.
[0041] Formation of the coating may be aided by activation of one
or more chemical precursors. A precursor is generally activated by
electromagnetic means, such as by exposure to an electric field,
for example an RF field, to ionize a portion of the precursor, by
exposure to thermal energy to dissociate, crack, or ionize the
precursor, or by exposure to radiation, such as UV or microwave
radiation. In some embodiments, one or more precursors may be
irradiated by UV or microwave radiation, or exposed to an RF field,
in an activation chamber, and the active precursors provided to the
chamber containing the gas distributor to be coated. In one
embodiment, the substrate support is heated to a temperature of
about 600.degree. C. to about 1,000.degree. C. to activate one or
more precursors and cause a reaction to deposit a coating on the
gas distributor. In one embodiment, a first precursor is provided
to the chamber at a flowrate between about 10 sccm and about 1,000
sccm, such as about 50 sccm, and a second precursor is provided at
a flowrate between about 10 slm and about 300 slm, such as about 50
slm. A carrier gas, such as nitrogen gas, argon, or helium, may be
provided with either the first or second precursors. As described
above, the first precursor may be silane, TMS, TMG, or TMA, or
another electrophillic metal or metalloid compound, or a mixture
thereof. The second precursor is generally ammonia or methane, or
another nucleophile.
[0042] In one embodiment, a deposition precursor and a radical
precursor are provided to a processing chamber to deposit a coating
on a gas distributor for an MOCVD or HVPE reactor. The deposition
precursor may contain a group 13 transition metal or a metalloid,
and the radical precursor may contain radicals comprising nitrogen,
hydrogen, carbon, or any mixture thereof. The radicals may be
generated in the processing chamber by exposing the radical
precursor to electromagnetic energy such as an electric field, for
example a capacitive RF field, a magnetic field, for example an
inductive RF field, or electromagnetic radiation. The
electromagnetic radiation may be thermal, which may be delivered by
heating the gas distributor, or UV or microwave delivered by an
emitter. In other embodiments, exposure to the electromagnetic
energy may be performed in a separate activation chamber, and the
radical precursor containing radicals may then be provided to the
processing chamber containing the gas distributor to be coated. In
embodiments wherein the radical precursor is activated in a
separate processing chamber, deposition of a coating on the gas
distributor is performed at temperatures of at least about
200.degree. C.
[0043] The deposited layer may optionally be heat treated at 206.
During the heat treatment, flow of reactive gases is generally
discontinued, and components having the newly deposited layer are
heated to a temperature of at least about 500.degree. C. to cure or
harden the deposited layer. Heating to high temperatures may also
result in smoothing of some deposited layers, such as metals. High
temperature treatment may also aid in driving away fugitive
reactive species that may remain in the deposited layer.
[0044] Precursor gases may be purged from the chamber at 208 to
prepare for subsequent processing. In an embodiment wherein a
deposition resistant layer is deposited in situ, the precursor
gases are purged from the chamber to draw fugitive reactive species
out of the deposited layer, and to purge any reactive species
adsorbed onto any surface of the chamber interior.
[0045] Cleaning and Seasoning
[0046] FIG. 3 is a flow diagram illustrating a method 300 according
to another embodiment. At 302, a cleaning gas, such as a halogen
gas is provided to the chamber to etch away surface contaminants.
The contaminants are generally the undesirable deposition products
described earlier. In one example, the halogen gas may be an
elemental halogen, such as chlorine gas (Cl.sub.2) or fluorine gas
(F.sub.2), or a hydrogen halide gas, such as HCl or HF. The halogen
species react with the surface contaminants, which are generally
metal or metal nitride, to produce volatile metal halides. The
chamber is maintained under vacuum to minimize halogen residues on
chamber surfaces. Because some metal halides decompose at
relatively low temperatures, chamber temperature may be maintained
below about 200.degree. C., such as between about 20.degree. C. and
about 200.degree. C., for example about 100.degree. C. Exposure to
the halide species continues for between about 5 min and about 10
min.
[0047] At 304, the halogen gas is purged from the chamber using an
inert gas such as argon (Ar), helium (He), or nitrogen (N.sub.2). A
plasma is formed from the inert gas at 306. The inert gas is
provided to a plasma chamber and energized using any appropriate
form of electromagnetic energy, such as electric fields (DC or RF)
or electromagnetic radiation such as thermal, UV, or microwave
radiation.
[0048] The inert gas plasma is provided to the process chamber at
308. The process chamber may have residual halogen species from the
halogen cleaning stage 302. The inert gas plasma comprises reactive
species, such as ions and radicals, that react with, soften, and
etch away the contaminants. In some embodiments, a plasma
pre-treatment may increase the effectiveness of a subsequent
seasoning process. In one embodiment, argon, helium, or nitrogen,
or any combination thereof, is activated in a plasma chamber by
flowing a gas mixture comprising one or more of those components at
a flow rate of about 1 slm to about 40 slm through the plasma
chamber and applying electromagnetic energy to the gas in the
chamber. The electromagnetic energy may take the form of an RF or
DC electric field applying between about 200 Watts and about 5,000
Watts of power to the gas, or it may take the form of thermal, UV,
or microwave energy at similar power levels.
[0049] At 310, the inert gas plasma is purged from the chamber
using a gas that scavenges any residual halogen from chamber
surfaces. Residual halogen is purged from the chamber and scavenged
from chamber surfaces to avoid incorporation of halogen species in
subsequent deposition processes. Examples of gases that may
scavenge residual halogen from chamber surfaces are nitrogen
containing gases, such as ammonia (NH.sub.3), nitrogen gas
(N.sub.2), or hydrazine (H.sub.2N.sub.2), and hydrogen containing
gases, such as simple hydrocarbons methane (CH.sub.4), ethane
(C.sub.2H.sub.6), ethylene (C.sub.2H.sub.4), and acetylene
(C.sub.2H.sub.2), or other hydrides, such as silane (SiH.sub.4) or
germane (GeH.sub.4).
[0050] The scavenging gas may be activated to increase reactivity.
Radicals of nitrogen or hydrogen may be formed from compounds such
as these by activating them using electromagnetic energy such as
electric fields, for example an RF field, or electromagnetic
radiation, such as thermal, UV, or microwave radiation. Thermal
energy may be provided by maintaining the chamber at a temperature
of about 600.degree. C. or higher, such as between about
900.degree. C. and about 1,100.degree. C., for example about
1,000.degree. C. UV or microwave radiation may be coupled into the
gas in an activation chamber remote from the chamber being cleaned.
Purging with the scavenging gas is generally maintained for between
about 5 min and about 10 min. Prior to introducing the scavenging
gas, plasma generation using the inert gas may be discontinued, and
flow of the inert gas continued for a duration of between about 10
seconds and about 30 seconds to purge most of the active species
and cleaning byproducts from the chamber.
[0051] A deposition resistant film may be applied to chamber
components at 312 or 314. At 312, a metal or silicon containing gas
such as TMG, TMA, TMI, or TMS may be added to the scavenging gas
from 310 to deposit a film on internal surfaces of the chamber. A
film such as silicon carbide (SiC), silicon nitride (SiN), gallium
nitride (GaN), aluminum nitride (AlN), which may be p-doped or
n-doped by including dopants such as boron, derived from borane or
diborane, or phosphorus, derived from phosphine, or films composed
of more than one such component, may be more resistant to
deposition in an MOCVD or HVPE process than the clean chamber
surfaces themselves. Formation of the deposition resistant film may
be enhanced by maintaining activation of the scavenging gas, so
that radical species from the activated scavenging gas react with
the metal or silicon containing gas. Maintaining the chamber
temperature high enough to activate the scavenging gas, but low
enough to encourage deposition of the reaction products on the
chamber surfaces, such as between about 600.degree. C. and about
800.degree. C., also enhances formation of the deposition resistant
film. Chamber temperature may be maintained by heating the
substrate support, in some embodiments.
[0052] Alternately, at 314, a deposition resistant film may be
deposited using a PVD process. Chamber components to be coated with
the resistant film are disposed in a PVD chamber, and a coating is
sputtered onto the components. Materials such as those described
above may be sputter coated onto the chamber components.
Alternately, resistant metals, such as tungsten, chromium,
molybdenum, or combinations or alloys thereof, may be sputter
coated.
[0053] A heat treatment operation may be advantageously performed
at any stage of the processes of FIGS. 2 and 3. A heat treatment
process may comprise setting an internal temperature of the chamber
between about 800.degree. C. and about 1,200.degree. C. at a
pressure between about 5 Torr and about 300 Torr for a duration of
about 30 seconds to 10 minutes, such as a duration of about 60
seconds to 5 minutes. The heat treatment may have different effects
when performed at different stages, but is generally used to
densify and/or harden coatings and seasoning layers and to
volatilize surface-adhered species.
[0054] In some embodiments, prior to performing a deposition
process, it may be beneficial to pre-coat chamber internal
surfaces, including the gas distributor, with a stabilizing layer
without performing a cleaning operation. Coating with a stabilizing
layer may be faster than a full cleaning operation, and may allow
processing to continue without performing the entire cleaning
operation. A stabilizing layer may have similar composition to
layers that may be deposited on a substrate in the chamber to
minimize the possibility of contaminating such substrates with
foreign material. A stabilizing layer may be formed by flowing a
metal organic precursor such as TMS, TMA, TMG, and/or TMI and a
reducing reagent, such as NH.sub.3 and/or H.sub.2 into the chamber
and activating the gas mixture, according to process conditions
described above. A silicon carbide stabilizing layer may also be
formed from a mixture of silane and methane. A stabilizing layer
having a thickness between about 0.2 .mu.m and about 2.0 .mu.m will
stabilize any deposits that may remain on chamber surfaces from
prior processes.
[0055] The processes of cleaning, coating, seasoning, baking, and
stabilizing may be performed in any advantageous combination with
respect to deposition processes. In one embodiment, after each
deposition process, cleaning, coating, seasoning, and stabilizing
are performed prior to the next deposition process. In another
embodiment, baking and stabilizing, or just stabilizing, are
performed after each deposition process, while cleaning, coating,
and seasoning are performed after a plurality of deposition
processes. In another embodiment, N deposition processes are
performed between stabilizing operations, and M stabilizing cycles
are performed between cleaning and seasoning operations, with N
being 1-20 deposition processes, and M being 0-5 stabilization
cycles. Thickness of the stabilization layer may be adjusted based
on number of deposition cycles between stabilization operations.
For example, a thicker stabilization layer may be formed after a
high number of sequential deposition processes.
[0056] Stabilizing may be accomplished in some embodiments by
soaking the chamber in an atmosphere comprising the metal organic
compound to be used in a subsequent deposition process. For
example, before depositing a gallium containing layer, a gas
comprising TMG, optionally with an inert carrier gas such as
nitrogen or hydrogen, may be provided to the chamber for a soak
period of about 30 seconds to about 30 minutes, for example about
10 minutes. Soaking is generally performed at a chamber pressure
between about 10 Torr and about 300 Torr at temperatures ranging
from about 20.degree. C. to about 1,000.degree. C. Deposition may
then begin by adding a deposition precursor such as ammonia to the
gas mixture in the chamber. Similar stabilizing may be performed
prior to deposition of aluminum, silicon, and indium layers by
soaking in TMA, TMS, and TMI, respectively. Prior to deposition
cycles in which dicyclopentadienyl magnesium (Cp.sub.2Mg) is used
as a p-type dopant for a multi-quantum well layer, the chamber may
be advantageously soaked in Cp.sub.2Mg to accomplish stabilization.
Stabilizing with a soak process may be performed in addition to, or
instead of, forming a stabilization layer.
[0057] In some embodiments, more than one film may be applied to
chamber components to retard formation of deposits on chamber
internal surfaces during a deposition process. For example, chamber
components may be sputter coated with a resistant metal such as
those described above in a PVD chamber, and then CVD coated with
silicon or metal compounds. Deposits formed on such films may be
stripped using processes described elsewhere herein, leaving the
metal film, and perhaps portions of the CVD film, and the CVD film
may be replaced following the stripping process, as described
above. In other embodiments, a homogeneous film comprising two or
more resistant materials, for example gallium nitride, silicon
nitride, silicon carbide, or aluminum nitride doped with tungsten,
chromium, molybdenum, or any combination thereof, may also be
formed by adding one or more precursors comprising any of those
metals to a CVD film formation process.
[0058] Apparatus
[0059] FIG. 4 is a schematic cross-sectional view of a gas
distributor 400 that may be used in a MOCVD or HVPE deposition
chamber, and may be useful for practicing embodiments described
herein. The gas distributor 400 is shown in proximity to a chamber
wall 402 and a substrate support 404. In operation, a substrate is
generally disposed on the substrate support 404, and gases are
provided to a processing region 406 defined by the substrate
support 404, the chamber wall 402, and the gas distributor 400.
[0060] The gases are provided through the gas distributor 400 by a
chemical delivery module 408 via a plurality of pathways. A first
pathway 410 and a second pathway 412 are in communication with the
chemical delivery module 408. The first pathway 410 delivers a
first precursor or gas mixture to the processing region 406 via a
first conduit 414 and a first plurality of outlets 416. The second
pathway 412 delivers a second precursor or gas mixture to the
processing region 406 via a second conduit 418 and a second
plurality of outlets 420. A thermal control channel 422 is coupled
to a heat exchanging system 424 via a thermal control pathway 426.
A thermal control fluid flows from the heat exchanging system 424
through the thermal control pathway 426, through the thermal
control channel 422, and exits through an exit portal 428, from
which the thermal control fluid may be returned to the heat
exchanging system 424, if desired. Process gases generally exit the
chamber through an exhaust channel 436 that communicates with one
or more exhaust ports 438, which communicate with a vacuum system
(not shown).
[0061] In some embodiments, a central pathway 432 is provided
through the gas distributor 400 for use with a remote plasma source
430. The remote plasma source 430 receives precursors from the
chemical delivery module 408, activates them by forming a plasma in
the remote plasma source 430, and provides the activated species to
the processing region 406 via the central pathway 432. The central
pathway 432 may also be used, in some embodiments, to provide gases
that have not been activated to the processing region 406. In some
embodiments, a cleaning gas or precursor may be provided directly
to the processing region 406 via, for example, the central pathway
432.
[0062] The gas distributor 400 of FIG. 4 has a bypass pathway 434
disposed through a peripheral region of the gas distributor 400 for
supplying process gases to the processing region 406 without using
the precursor pathways 414 and 418. Such bypass pathways may be
useful for cleaning, seasoning, conditioning or other
processes.
[0063] FIG. 5A is a cross-sectional view of a gas distributor 500
for a deposition chamber that may benefit from one or more
processes described herein. The gas distributor 500 comprises a
first plurality of openings 502 and a second plurality of openings
504, each of which surrounds one of the first plurality of openings
502, such that each opening 502 is concentrically aligned with an
opening 504. The first plurality of openings 502 is in
communication with a first gas pathway 506 and a first gas inlet
508, the first gas pathway comprising a plenum 518 and a blocker
plate 520 having a plurality of portals 522 formed therethrough.
The second plurality of openings 504 is in communication with a
second gas pathway 510 and a second gas inlet 512. The first and
second pluralities of openings 502 and 504 are formed in a surface
514 of the gas distributor 500 that faces a processing volume 516
adjacent to the surface 514. The first and second gas pathways 506
and 510 facilitate providing process gases to the processing volume
516 without prior mixing.
[0064] A central opening 524 in the surface 514 is in communication
with a third pathway 526 and a third gas inlet 528. The third
pathway 526 provides a means to flow process gases into a central
portion of the processing volume 516 while bypassing the first and
second plurality of openings 502 and 504, if desired. A side wall
530 and lid portion 534 of the gas distributor 500 may have one or
more openings 532 formed therethrough and in communication with a
fourth gas inlet 536, or a plurality thereof, for flowing process
gases into the processing volume 516 while bypassing the gas
distributor altogether.
[0065] FIG. 5B is a close-up view of a portion of the gas
distributor 500 of FIG. 5A. A coating 538 is provided over the
surface 514 of the gas distributor 500. The coating 538 of FIG. 5A
is a CVD coating, as described elsewhere herein. The coating 538
covers portions of the surface 514 facing the processing volume
516, but does not penetrate the openings 502, 504, and 524.
[0066] FIG. 5C is a detail view of the region around an opening 504
of the gas distributor 500. The opening 504 has a dimension "d",
defined by the distance between opposite walls of the opening 504.
The coating has a thickness "t", which is generally between about
100 nm and about 200 nm. An exclusion zone "e" surrounding the
opening 504 is not coated due to flow and mixing of gases exiting
opening 504 during deposition. By forming the coating using gas
flow rates substantially similar to those used when depositing a
layer on a substrate, the coated area of the gas distributor
substantially matches the area that receives deposits when
processing a substrate, so the exclusion zone "e" is sized such
that metal nitride deposits do not form in the exclusion zone "e".
In one embodiment, the exclusion zone "e" has a dimension that is
less than about 50% of the opening dimension "d". The coating 538
tapers in thickness approaching the exclusion zone "e". The
distance over which the coating 538 tapers is typically between
about 10% and about 20% of the dimension "d" of the opening 504,
such that the average taper angle .alpha. is between about
0.degree. and about 5.degree., depending on the thickness "t".
[0067] In one embodiment, the coating may comprise more than one
deposited layer. For example, a tungsten film may be deposited
first on the gas distributor 500, followed by a CVD film of the
kind described above (i.e., silicon nitride, silicon carbide,
gallium nitride, aluminum nitride). In another embodiment, a
tungsten-doped CVD film may be formed on the gas distributor 500 to
improve the resistance of the film to deposition products. In a CVD
process to form a film of one of the compounds listed above, a
tungsten precursor may be provided to the chamber with the other
precursors to add tungsten to the deposited film. In another
embodiment, a tungsten-doped CVD film may be formed over a tungsten
film deposited by PVD or CVD processes known in the art. In each of
these embodiments, chromium or molybdenum may be used in place of,
or in addition to, tungsten.
[0068] The coating 538 may be heat treated to improve its hardness,
smoothness, or inertness to deposition. Additionally, a bilayer or
multilayer film may be heat treated to improve adhesion of the
various layers together. A heat treatment such as that described
above will generally suffice to harden the film to process
conditions.
[0069] In operation, a first precursor is provided to the
processing volume 516 through the first gas pathway 506, and a
second precursor is provided to the processing volume 516 through
the second gas pathway 510. The first precursor may comprise a
group III material such as gallium, aluminum, or indium. The group
III material may be a metal organic precursor such as trimethyl
gallium (TMG), trimethyl aluminum (TMA), or trimethyl indium (TMI),
or other metal organic compound. The second precursor is typically
a nitrogen containing precursor, such as ammonia. The first and
second precursors mix upon exiting the gas distributor, and react
to form a group III nitride layer on the substrate, which is
generally disposed on a substrate support arranged facing the gas
distributor, as in the substrate support 404 of FIG. 4. A carrier
gas such as nitrogen, hydrogen, argon, or helium, may be provided
with the first or second precursors, and the first and second
precursors may be blends of multiple components. For example, the
first precursor may be a mixture of TMG, TMA, and/or TMI, and the
second precursor may be a mixture of ammonia and other nitrogen
compounds, such as hydrazine or a lower amine.
[0070] Sacrificial Coating
[0071] In one embodiment, the coating applied to the gas
distributors of FIGS. 5A-5B may be a sacrificial layer comprising
silicon, aluminum, or both. A layer comprising nitrides of silicon
and/or aluminum may be formed on a surface of the gas distributor
facing the processing environment. During the cleaning operations
described above to remove metal nitride deposits formed on the
sacrificial layer, the active halogen gas etches the sacrificial
layer faster than the deposits are converted or removed, removing
the sacrificial layer behind the deposit layer, and exposing more
surface area of the deposit layer to the halogen gas, increasing
the rate of reaction with the halogen gas. The sacrificial layer
may be an aluminum nitride layer, a silicon nitride layer, or a
mixture thereof. In some embodiments, the sacrificial layer may be
a bilayer of, for example, silicon and silicon nitride or aluminum
and aluminum nitride. In some embodiment, after performing a
cleaning process (e.g., FIG. 3, at 302), which removes the prior
deposited sacrificial layer and other chamber deposits, a new
sacrificial layer is deposited on the surface of the chamber
components before a device formation layer (e.g., one or more group
III layers) is deposited on one or more substrates in the
processing chamber.
[0072] The sacrificial layer may be formed in a CVD process by
providing a silicon or aluminum precursor, or both, such as TMS,
silane or TMA, to the chamber to form the sacrificial layer on the
chamber components. In one embodiment, a silicon or aluminum
precursor and a nitrogen containing gas, such as any of those
described above, are provided to the processing region of the
processing chamber. In one embodiment, ammonia is used as the
nitrogen containing gas. A carrier gas such as hydrogen or argon
may be provided with both the precursor gas mixture and the
nitrogen containing gas. Chamber temperature is generally
maintained above 1,000.degree. C., for example between about
1,100.degree. C. and about 1,200.degree. C., during formation of
the sacrificial layer, and chamber pressure is maintained between
about 100 Torr and about 200 Torr.
[0073] In one embodiment, a mixture of ammonia and hydrogen is
flowed into the chamber at about 60 sLm. The ammonia flow rate may
be between about 5 sLm and about 30 sLm, for example about 25 sLm.
The flow of the ammonia/hydrogen mixture may be established by
starting flow of the hydrogen gas and then flowing the ammonia gas
into the hydrogen carrier gas. Chamber temperature and pressure are
established as described above, and flow of a precursor mixture
comprising TMA and hydrogen is started. Flow rate of the precursor
mixture is generally close to the flow rate of the ammonia/hydrogen
mixture, about 60 sLm, with TMA flow between about 0 sLm and about
20 sLm, for example about 15 sLm. The streams mix and react,
depositing a layer of aluminum nitride on the gas distributor.
Maintaining the reaction for a duration of between about 10 minutes
and about 30 minutes will deposit a layer having a thickness
between about 100 nm and about 200 nm on the gas distributor.
[0074] In another embodiment, the sacrificial layer may include a
layer of metal nitride, for example gallium nitride. The flow of
the silicon or aluminum precursor is generally replaced with a
metal precursor as the reaction continues, and deposition of
silicon or aluminum transitions to deposition of metal. In one
embodiment, flow of TMA is replaced with flow of TMG at the same
flow rate to deposit a thin layer of gallium nitride over a layer
of aluminum nitride. In another embodiment, the sacrificial layer
may comprise three layers, for example a layer of aluminum, a layer
of aluminum nitride, and a layer of gallium nitride.
[0075] At the conditions described above, the coating of gallium
nitride, or other metal nitride (indium, etc.), doped or undoped,
is a low quality layer, rich in metal and having a morphology that
comprises a metal matrix with metal nitride domains. The metal
nitride domains will also typically have nitrogen vacancies. The
structure of the layer reduces affinity for deposition of metal
nitrides on the layer.
[0076] In all the embodiments of deposition and cleaning described
above, it should be noted that operations depending on interaction
of process gases with the gas distributor may be enhanced by
flowing one or more process gases through a gas inlet that bypasses
the gas distributor. For example, in the embodiment of FIG. 5A, the
opening 532 formed through the sidewall 530 of the gas distributor
500 may be beneficially used to route a halogen gas for a cleaning
operation, a purge gas for a purge operation, or a nitrogen
containing gas for a scavenging or deposition operation. Flowing
one or more gases through a bypass pathway directs the process
gases into more intimate contact with the surface of the gas
distributor.
[0077] The foregoing description describes embodiments wherein
internal surfaces of a chamber are cleaned, and one or more films
are optionally deposited on internal surfaces of a processing
chamber by feeding CVD precursors through the gas distribution
assembly of the chamber. It should be noted that alternate
embodiments may feed precursors through one or more portals in
sidewalls of the chamber, or through one or more portals in the
bottom of the chamber, or any combination of feed through the gas
distributor, sidewalls, and bottom of the chamber. Feeding
precursor and/or cleaning gases through the sidewalls and bottom of
the chamber may enhance exposure of chamber internal surfaces to
the reactive components of the precursors by altering gas flow
patterns through the chamber.
[0078] While the foregoing is directed to embodiments of the
invention, other and further embodiments of the invention may be
devised without departing from the basic scope thereof.
* * * * *