U.S. patent application number 10/870044 was filed with the patent office on 2004-11-11 for low contamination plasma chamber components and methods for making the same.
This patent application is currently assigned to Lam Research Corporation. Invention is credited to Chang, Christopher C., Steger, Robert J..
Application Number | 20040224128 10/870044 |
Document ID | / |
Family ID | 25015751 |
Filed Date | 2004-11-11 |
United States Patent
Application |
20040224128 |
Kind Code |
A1 |
Chang, Christopher C. ; et
al. |
November 11, 2004 |
Low contamination plasma chamber components and methods for making
the same
Abstract
Components for use in plasma processing chambers having plasma
exposed surfaces with surface roughness characteristics that
promote polymer adhesion. The roughened surfaces are formed by
plasma spraying a coating material such as a ceramic or high
temperature polymer onto the surface of the component. The plasma
sprayed components of the present invention can be used for plasma
reactor components having surfaces exposed to the plasma during
processing. Suitable components include chamber walls, chamber
liners, baffle rings, gas distribution plates, plasma confinement
rings, and liner supports. By improving polymer adhesion, the
plasma sprayed component surfaces can reduce the levels of particle
contamination in the process chamber thereby improving yields and
reducing down-time required for cleaning and/or replacing chamber
components.
Inventors: |
Chang, Christopher C.;
(Sunnyvale, CA) ; Steger, Robert J.; (Los Altos,
CA) |
Correspondence
Address: |
BURNS DOANE SWECKER & MATHIS L L P
POST OFFICE BOX 1404
ALEXANDRIA
VA
22313-1404
US
|
Assignee: |
Lam Research Corporation
|
Family ID: |
25015751 |
Appl. No.: |
10/870044 |
Filed: |
June 18, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10870044 |
Jun 18, 2004 |
|
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09749917 |
Dec 29, 2000 |
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Current U.S.
Class: |
428/141 ;
428/332; 428/469; 428/698 |
Current CPC
Class: |
Y10T 428/263 20150115;
C23C 4/10 20130101; Y10T 428/26 20150115; Y10T 428/31681 20150401;
H01J 37/32477 20130101; Y10T 428/264 20150115; Y02T 50/60 20130101;
C23C 4/00 20130101; Y10T 428/31678 20150401; C23C 4/04 20130101;
Y10T 428/24355 20150115; Y10T 428/31721 20150401 |
Class at
Publication: |
428/141 ;
428/332; 428/469; 428/698 |
International
Class: |
B32B 019/00 |
Claims
1. A method of making a plasma reactor component having one or more
surfaces which are exposed to plasma during use, the method
comprising plasma spraying a coating material onto a plasma exposed
surface of the component to form a coating having surface roughness
characteristics that promote the adhesion of polymer deposits.
2. The method of claim 1, further comprising steps of; roughening
the plasma exposed surface of the component; and cleaning the
roughened surface prior to plasma spraying the coating
material.
3. The method of claim 1, further comprising cleaning exposed
surfaces of the plasma sprayed coating.
4. The method of claim 1, wherein the coating material is a ceramic
or a polymeric material.
5. The method of claim 1, wherein the component has openings
therethrough, the method further comprising plugging the openings
before plasma spraying the coating.
6. The method of claim 1, further comprising removing the component
from a plasma reaction chamber and cleaning the plasma exposed
surface thereof by removing any existing coating and/or adhered
polymer deposits therefrom prior to plasma spraying the coating
onto the cleaned surface.
7. The method of claim 4, wherein the plasma sprayed coating is a
ceramic material having a thickness of 2 to 5 mils.
8. The method of claim 4, wherein the component and the coating
material comprise the same ceramic material.
9. The method of claim 4, wherein the coating material is a
polyimide.
10. The method of claim 9, wherein the coating has a thickness of
10 to 30 mils.
11. The method of claim 1, wherein the component is selected from
the group consisting of a plasma confinement ring, a focus ring, a
pedestal, a chamber wall, a chamber liner and a gas distribution
plate.
12. The method of claim 2, wherein the roughening step comprises
bead blasting the surface of the component.
13. The method of claim 1, wherein the coating has an arithmetic
mean surface roughness value (Ra) of between 150 and 190
micro-inches.
14-31. (Canceled).
32. The method of claim 1, wherein the component comprises aluminum
having an anodized or non-anodized plasma exposed surface.
33. The method of claim 1, wherein the component is made from a
ceramic material selected from the group consisting of alumina,
yttria, zirconia, silicon carbide, silicon nitride, boron carbide
and boron nitride.
34. The method of claim 1, wherein the coating has an as-sprayed
surface roughness that promotes the adhesion of polymer
deposits.
35. The method of claim 1, wherein the component comprises a plasma
sprayed coating on a plasma exposed surface thereof, wherein the
coating has surface roughness characteristics that promote the
adhesion of polymer deposits.
36. The method of claim 1, wherein the coating is a ceramic or
polymeric material.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates generally to the fabrication
of semiconductor wafers, and, more particularly, to plasma etching
chambers having components that reduce particle contamination
during processing.
[0003] 2. Description of the Related Art
[0004] In the field of semiconductor processing, vacuum processing
chambers are generally used for etching and chemical vapor
depositing (CVD) of materials on substrates by supplying an etching
or deposition gas to the vacuum chamber and application of an RF
field to the gas to energize the gas into a plasma state. Examples
of parallel plate, transformer coupled plasma (TCP.TM.) which is
also called inductively coupled plasma (ICP), and
electron-cyclotron resonance (ECR) reactors and components thereof
are disclosed in commonly owned U.S. Pat. Nos. 4,340,462;
4,948,458; 5,200,232 and 5,820,723.
[0005] In semiconductor integrated circuit fabrication, devices
such as component transistors may be formed on a semiconductor
wafer or substrate, which is typically made of silicon. Metallic
interconnect lines, which are typically etched from a metallization
layer disposed above the wafer, may then be employed to couple the
devices together to form the desired circuit. The metallization
layers typically comprise copper, aluminum or one of the known
aluminum alloys such as Al--Cu, Al--Si or Al--Cu--Si. An
anti-reflective coating (ARC) layer and an overlying photoresist
(PR) layer, may be formed on top of the metallization layer. The
ARC layer typically comprises a titanium containing layer such as
TiN or TiW. To form the aforementioned metallic interconnect lines,
a portion of the layers of the layer stack, including the
metallization layer, can be etched using a suitable photoresist
technique. The areas of the metallization layer that are
unprotected by the mask may then be etched away using an
appropriate etching source gas, leaving behind metallization
interconnect lines or features.
[0006] To achieve greater circuit density, modern integrated
circuits are scaled with increasingly narrower design rules. As a
result, the feature sizes, i.e., the width of the interconnect
lines or the spacings (e.g., trenches) between adjacent
interconnect lines, have steadily decreased. To form the narrow
conductor lines of modern integrated circuits, highly anisotropic
etching is desired. Etch anisotropy refers to the rate of vertical
etching compared to the rate of lateral etching. In order to form
high aspect ratio features with vertical sidewalls, the rate of
vertical etching must be significantly greater than the rate of
lateral etching. In plasma etching, vertical profiles are often
achieved using sidewall passivation techniques. Such techniques
typically involve introducing a polymer forming species (usually
fluorocarbons such as CF.sub.4, CHF.sub.3, C.sub.4F.sub.8) into the
reaction chamber during etching. The polymer which forms during
etching is preferentially deposited on the sidewalls of the etched
features thereby reducing lateral etching of the substrate and
increasing etch anisotropy. During the etching process, however,
polymer deposits can also form on the interior surfaces of various
components of the etch chamber which are exposed to the plasma.
Over time, these polymer deposits can flake or peel off thus
becoming a source of particle contamination in the plasma
reactor.
[0007] The polymer deposits formed inside the plasma reactor
typically comprise chain molecules of carbon compounds. When the
polymer contacts and adheres to the substrate being processed, it
can contaminate that portion of the substrate and reduces the die
yield therefrom. Polymer deposits can accumulate on all chamber
surfaces, particularly on the surfaces of the chamber housing
adjacent the process gas inlet tubes, as well as the underside of
the chamber cover or gas distribution plate opposite the substrate
surface. The polymer deposited on the interior surfaces of the
chamber can migrate onto the substrate to create a substrate
defect. Polymer particulate contamination is exacerbated by the
thermal cycling of the reactor components during repeated plasma
processing cycles. The repeated heating and cooling of the plasma
exposed surfaces of reactor components can cause the adhered
polymer deposits to exfoliate or flake off due to CTE differentials
between the polymer deposits and the reactor surfaces. The polymer
deposits can also become dislodged by bombardment with reactant
species in the plasma.
[0008] As integrated circuit devices continue to shrink in both
their physical size and their operating voltages, their associated
manufacturing yields become more susceptible to particle
contamination. Consequently, fabricating integrated circuit devices
having smaller physical sizes requires that the level of
particulate contamination be less than previously considered to be
acceptable. Various methods have been employed to reduce particle
contamination in plasma reactors. See, for example, U.S. Pat. Nos.
5,366,585; 5,391,275; 5,401,319; 5,474,649; 5,851,343; 5,916,454;
5,993,594; 6,120,640; and 6,155,203.
[0009] In order to reduce particle contamination, plasma reactors
can be periodically cleaned to remove the polymer deposits. Plasma
cleaning processes are disclosed in U.S. Pat. Nos. 5,486,235;
5,676,759; and 5,685,916. Additionally, the plasma reactor parts
are typically replaced periodically with new reactor parts.
[0010] It would be desirable to provide plasma reactor components
that reduce the levels of particle contamination inside the reactor
chamber. The use of such parts would help to improve the yield
and/or increase the period of time between cleaning or replacement
of plasma reactor components.
SUMMARY OF THE INVENTION
[0011] The present inventors have discovered that particle
contamination in plasma reactors can be reduced by plasma spraying
a coating material such as a ceramic or high temperature polymer
onto plasma exposed surfaces of the reactor. The plasma sprayed
material forms a coating having desired surface roughness
characteristics to promote adhesion of polymer deposits. The
improved adhesion of the polymer deposits on chamber surfaces can
reduce the tendency of the deposits to flake or peel off of the
chamber surfaces thereby reducing the level of particulate
contamination in the reactor. By improving the adhesion of polymer
deposits on plasma reactor components, reactor components may need
to be cleaned or replaced less frequently thereby reducing the cost
of operating the plasma reactor.
[0012] According to one embodiment of the present invention, a
method of making a plasma reactor component is provided. The
reactor component has one or more surfaces which are exposed to
plasma during use. The method includes plasma spraying a coating
material onto a plasma exposed surface of the component to form a
coating having surface roughness characteristics that promote the
adhesion of polymer deposits.
[0013] According to another embodiment of the present invention, a
component of a plasma reactor having one or more surfaces exposed
to the plasma during processing is provided. The component includes
a plasma sprayed coating on a plasma exposed surface thereof. The
coating has surface roughness characteristics that promote the
adhesion of polymer deposits.
[0014] According to another embodiment of the present invention, a
plasma reactor including one or more components as set forth above
and a method of processing a substrate therein are also provided.
The method includes contacting an exposed surface of the substrate
with a plasma.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The invention will be described in greater detail with
reference to accompanying drawings in which like elements bear like
reference numerals, and wherein:
[0016] FIG. 1 illustrates a conventional plasma spray process;
[0017] FIG. 2 shows a metal etch chamber incorporating plasma
sprayed reactor components according to the present invention;
[0018] FIG. 3 shows a high density oxide etch chamber incorporating
plasma sprayed reactor components according to the present
invention; and
[0019] FIG. 4 is a top view of a gas distribution plate for the
etch chamber of FIG. 3 according to one embodiment of the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0020] The invention provides improvements in reducing particle
contamination of substrates such as semiconductor (e.g., silicon,
gallium arsenide, etc.) wafers, flat panel display substrates, and
the like. In particular, the present invention provides components
for use in plasma processing chambers having plasma exposed
surfaces with surface roughness characteristics that promote
polymer adhesion. The roughened surfaces are formed by plasma
spraying a coating material such as a ceramic or polymeric material
onto the surface. The plasma sprayed components of the present
invention can be used for any plasma reactor component that is
exposed to plasma during processing. Suitable components include,
for example, chamber liners, baffle rings, gas distribution plates,
focus rings, plasma confinement rings, pedestals, and liner
supports.
[0021] The reactor components of the present invention can be made
from metallic materials or ceramic materials. Suitable metallic
materials include aluminum. The aluminum surfaces to be plasma
spray coated can be bare (except for a native oxide layer) or
anodized. Alternatively, the reactor components can be made from
ceramic materials such as alumina, silica, quartz, titania,
zirconia, yttria, titanium carbide, zirconium carbide, silicon
carbide, boron carbide, aluminum nitride, titanium nitride, silicon
nitride, and/or boron nitride. The ceramic components can be made
by any conventional ceramic manufacturing technique such as hot
pressing and sintering ceramic powders into bulk parts.
[0022] In the present invention, any or all of the surfaces of the
reactor components which are exposed to the plasma during
processing can be coated with a plasma sprayed material such as a
ceramic or high temperature polymer. The plasma sprayed coating
according to the present invention provides interior surfaces of
the reactor with surface roughness characteristics that promote the
adhesion of polymer deposits formed in the plasma chamber during
etching. In the present invention, the inventive coatings
preferably have surface roughness values (Ra) suitable for
achieving improved adhesion of polymer byproducts produced during
processing of substrates in the plasma reactor. For example, the
arithmetic mean surface roughness (Ra) of the plasma sprayed
surfaces according to the present invention can range from 150 to
190 micro-inches. Surface roughness values in this range promote
the adhesion of polymer deposited on interior surfaces of the
reaction chamber during a plasma etch process such as a metal
etch.
[0023] The plasma spraying process typically involves spraying a
molten or heat softened material onto a surface. FIG. 1 illustrates
a typical plasma spraying process. The coating material, usually in
the form of a powder 112, is injected into a high temperature
plasma flame 114 where it is rapidly heated and accelerated to a
high velocity. The hot material impacts on the substrate surface
116 and rapidly cools to form a coating 118.
[0024] The plasma spray gun 120 typically comprises an anode 122
(usually made of copper) and a cathode 124 (usually made of
tungsten), both of which can be water cooled. Plasma gas 126 (e.g.,
argon, nitrogen, hydrogen, helium, etc.) flows around the cathode
in the direction generally indicated by arrow 128 and through the
anode 122 which is shaped as a constricting nozzle. The plasma is
initiated by a high voltage discharge which causes localized
ionization and a conductive path for a DC arc to form between the
cathode 124 and the anode 122. Resistance heating from the arc
causes the gas to reach extreme temperatures, dissociate and ionize
to form a plasma. The plasma exits the anode 122 as a free or
neutral plasma flame (plasma which does not carry electric
current). When the plasma is stabilized and ready for spraying, the
electric arc extends down the nozzle. Powder 112 is fed into the
plasma flame usually via an external powder port 132 mounted near
the anode nozzle exit 134. The powder 112 is rapidly heated and
accelerated such that the powder particles 112 in a molten or
heat-softened state are caused to impact on substrate 116.
[0025] Various bonding mechanisms may be present at the
coating/substrate interface and between the particles making up the
plasma sprayed coating. Generally, both mechanical interlocking and
diffusion bonding occur. Bonding mechanisms that may be present
include: mechanical keying or interlocking; diffusion bonding; and
other adhesive, chemical and physical bonding mechanisms (e.g., Van
der Waals forces). Factors effecting bonding and subsequent build
up of plasma sprayed coatings include: the cleanliness of the
substrate surface; the surface area available for bonding; the
surface topography or surface profile; the temperature (thermal
energy) of the particles and substrate; the time (e.g., reaction
rates and cooling rates etc.); the velocity (kinetic energy) of the
powder particles; the physical and chemical properties of the
substrate and the powder particles; and any physical and chemical
reactions that may occur during the process.
[0026] In the present invention, surface preparation techniques
such as cleaning and grit or bead blasting can be used to provide a
more chemically and physically active component surface for bonding
of the plasma sprayed coating. By grit or bead blasting, the
surface area available for bonding can be increased which can
result in increased coating bond strength. For alumina chamber
components, the surfaces to be coated are preferably grit blasted
with a contaminant free aluminum oxide media. The roughened surface
can then be cleaned to remove loose particles by any suitable
technique such as blasting the surface with air or CO.sub.2 and/or
washing the surface with an acid solution. The roughened surface
profile of the substrate resulting from this treatment can help
promote mechanical keying or interlocking of the coating with the
substrate.
[0027] Once the plasma sprayed coating has been applied, the
exposed surface of the coating can be cleaned using any suitable
technique. Suitable cleaning techniques include blasting the
surface with air or CO.sub.2 and/or ultra-sonic cleaning. These
cleaning steps can be repeated to achieve the desired level of
surface cleanliness or conditioning of the component surface prior
to using the component during plasma processing of substrates.
[0028] Plasma spraying has the advantage that it can spray very
high melting point materials such as refractory metals and
ceramics. Plasma sprayed coatings of ceramics, for example, have
been employed as protective coatings for various plasma reactor
components. See, for example, U.S. Pat. Nos. 5,560,780; 5,879,523;
5,993,594; and 6,120,640. Additionally, plasma spraying processes
have also been developed for high melting point thermoplastic and
thermosetting polymers such as polyimides.
[0029] In the present invention, the plasma sprayed coating can be
any material that is resistant to erosion by the plasma. For
example, any of the ceramic materials suitable for use as reactor
components may also be used as coatings as long as these materials
can be plasma sprayed. When the coating is a ceramic material, the
coating is preferably the same material as the underlying
component. By using the same material for the component and the
coating, differences in the coefficients of thermal expansion (CTE)
between the coating and component can be minimized or eliminated.
These differences in CTE values can result in exfoliation of the
coating material during thermal cycling of the reactor components
during use. When the coating is alumina, the coating is preferably
applied to the component at a thickness in the range of 2 to 5 mils
(0.002 to 0.005 inches).
[0030] The coating may also be a polymeric material. When the
coating is a polymer, the polymer should be capable of being plasma
sprayed to form a tightly adherent coating on the component. A
preferred high temperature polymer is a polyimide such as
VESPEL.RTM., which is a registered trademark of DuPont. Polyimide
coatings are preferably applied to the component at a thickness of
10 to 30 mils (0.010 to 0.030 inches).
[0031] In plasma etching of substrates, features are etched into
layers of various materials on substrates such as silicon wafers.
Materials that are typically etched include metals and dielectric
materials such as oxides (e.g., SiO.sub.2). In such etching
processes, a gas distribution plate can be used to control the
spatial distribution of gas flow in the volume of the reactor above
the plane of the substrate. Polymer build-up can be particularly
problematic in plasma reactors wherein an antenna coupled to a
radiofrequency (RF) source energizes gas into a plasma state within
a process chamber. Plasma reactor of this type are disclosed in
U.S. Pat. Nos. 4,948,458; 5,198,718; 5,241,245; 5,304,279;
5,401,350; 5,531,834; 5,464,476; 5,525,159; 5,529,657; and
5,580,385. In such systems, the antenna is separated from the
interior of the process chamber by a dielectric member such as a
dielectric window, gas distribution plate, encapsulating layer of
epoxy, or the like, and the RF energy is supplied into the chamber
through the dielectric member. Such processing systems can be used
for a variety of semiconductor processing applications such as
etching, deposition, resist stripping, etc.
[0032] During an oxide or metal etch of a semiconductor wafer in a
plasma reactor of the aforementioned type, polymer deposits can
build up on internal surfaces of the reactor including the exposed
surface of the dielectric member or gas distribution plate facing
the wafer. As the polymer build-up deepens, the polymer tends to
flake or peel off of the dielectric member. When the dielectric
member is located directly above the substrate and chuck, polymer
particles can fall directly onto the substrate or the chuck below.
These polymer particles can introduce defects into the substrate
thus decreasing yields. Alternatively, the particles can migrate to
the chuck surface causing chucking problems.
[0033] Typically, the etch process is stopped periodically and the
interior chamber surfaces cleaned (e.g., using a dry etch
treatment) to reduce the levels of particle contamination. Improper
or incomplete cleaning, however, can actually increase the particle
contaminant levels in the chamber. Further, the delay due to the
"down-time" required for cleaning also represents a substantial
loss in production yield. Therefore, control of the deposition of
polymer on the interior surfaces of the etch chamber is desirable
for achieving a high yield and maintaining through-put of the
substrates in the plasma reactor.
[0034] An exemplary metal etch reactor of the aforementioned type
is a transformer coupled plasma reactor known as the TCP.TM. 9600
plasma reactor, which is available from LAM Research Corporation of
Fremont, Calif. FIG. 2 illustrates a simplified schematic of the
TCP.TM. 9600 plasma reactor. In FIG. 2, a reactor 150 including a
plasma processing chamber 152 is shown. Above chamber 152, there is
disposed an antenna 156 to generate plasma, which is implemented by
a planar coil in the example of FIG. 2. The RF coil 156 is
typically energized by an RF generator 158 via a matching network
(not shown). Within chamber 152, there is provided a showerhead
154, which preferably includes a plurality of holes for releasing
gaseous source materials, e.g., the etchant source gases, into the
RF-induced plasma region between the showerhead and wafer 170.
[0035] The gaseous source materials may also be released from ports
built into the walls of chamber 152. Etchant source chemicals
include, for example, halogens such as Cl.sub.2 and BCl.sub.3 when
etching through aluminum or one of its alloys. Other etchant
chemicals (e.g., CH.sub.4, HBr, HCl, CHCl.sub.3) as well as polymer
forming species such as hydrocarbons, fluorocarbons, and
hydro-fluorocarbons for side-wall passivation may also be used.
These gases may be employed along with optional inert and/or
nonreactive gases.
[0036] In use, a wafer 170 is introduced into chamber 152 defined
by chamber walls 172 and disposed on a substrate support 162, which
acts as a lower or second electrode. The wafer is preferably biased
by a radio frequency generator 164 (also typically via a matching
network). The wafer can comprise a plurality of integrated circuits
(ICs) fabricated thereon. The ICs, for example, can include logic
devices such as PLAs, FPGAs and ASICs or memory devices such as
random access memories (RAMs), dynamic RAMs (DRAMs), synchronous
DRAMs (SDRAMs), or read only memories (ROMs). When the RF power is
applied, reactive species (formed from the etchant source gas) etch
exposed surfaces of the wafer 170. The by-products, which may be
volatile, are then exhausted through an exit port 166. After
processing is complete, the wafer can be diced to separate the ICs
into individual chips.
[0037] In the present invention, plasma exposed surfaces of a
plasma confinement ring (not shown), chamber wall 172, a chamber
liner (not shown) and/or showerhead 154 can be provided with a
plasma sprayed coating 160 with surface roughness characteristics
that promote polymer adhesion. In addition, plasma exposed surfaces
of the substrate support 168 can also be provided with a plasma
sprayed coating (not shown) according to the present invention. In
this manner, substantially all surfaces that confine the high
density plasma will have surface roughness characteristics that
promote polymer adhesion. In this manner, particulate contamination
inside the reactor can be substantially reduced.
[0038] The reactor components of the present invention can also be
used in a high-density oxide etch process. An exemplary oxide etch
reactor is the TCP 9100.TM. plasma etch reactor available from LAM
Research Corporation of Fremont, Calif. In the TCP 9100.TM.
reactor, the gas distribution plate is a circular plate situated
directly below the TCP.TM. window which is also the vacuum sealing
surface at the top of the reactor in a plane above and parallel to
a semiconductor wafer. The gas distribution ring feeds gas from a
source into the volume defined by the gas distribution plate. The
gas distribution plate contains an array of holes of a specified
diameter which extend through the plate. The spatial distribution
of the holes through the gas distribution plate can be varied to
optimize etch uniformity of the layers to be etched, e.g., a
photoresist layer, a silicon dioxide layer and an underlayer
material on the wafer. The cross-sectional shape of the gas
distribution plate can be varied to manipulate the distribution of
RF power into the plasma in the reactor. The gas distribution plate
material is made from a dielectric material to enable coupling of
this RF power through the gas distribution plate into the reactor.
Further, it is desirable for the material of the gas distribution
plate to be highly resistant to chemical sputter-etching in
environments such as oxygen or a hydro-fluorocarbon gas plasma in
order to avoid breakdown and the resultant particle generation
associated therewith.
[0039] A vacuum processing chamber for oxide etching according to
one embodiment of the present invention is illustrated in FIG. 3.
The vacuum processing chamber 10 includes a substrate holder 12 in
the form of a bottom electrode providing an electrostatic clamping
force to a substrate 13 as well as an RF bias to a substrate
supported thereon and a focus ring 14 for confining plasma in an
area above the substrate. The substrate may be back-cooled with a
heat transfer gas such as helium. A source of energy for
maintaining a high density (e.g. 10.sup.11-10.sup.12 ions/cm.sup.3)
plasma in the chamber such as an antenna 18 in the form of a flat
spiral coil powered by a suitable RF source and suitable RF
impedance matching circuitry inductively couples RF energy into the
chamber 10 so as to provide a high density plasma. The chamber
includes suitable vacuum pumping apparatus for maintaining the
interior of the chamber at a desired pressure (e.g. below 50 mTorr,
typically 1-20 mTorr). A substantially planar dielectric window 20
of uniform thickness is provided between the antenna 18 and the
interior of the processing chamber 10 and forms the vacuum wall at
the top of the processing chamber 10. A gas distribution plate,
commonly called a showerhead 22, is provided beneath the window 20
and includes a plurality of openings such as circular holes (not
shown) for delivering process gas supplied by the gas supply 23 to
the processing chamber 10. A conical liner 30 extends from the gas
distribution plate and surrounds the substrate holder 12. The
antenna 18 can be provided with a channel 24 through which a
temperature control fluid is passed via inlet and outlet conduits
25, 26. However, the antenna 18 and/or window 20 could be cooled by
other techniques such as by blowing air over the antenna and
window, passing a cooling medium through or in heat transfer
contact with the window and/or gas distribution plate, etc.
[0040] In operation, a wafer is positioned on the substrate holder
12 and is typically held in place by an electrostatic clamp, a
mechanical clamp, or other clamping mechanism. Process gas is then
supplied to the vacuum processing chamber 10 by passing the process
gas through a gap between the window 20 and the gas distribution
plate 22. Suitable gas distribution plate arrangements (i.e.,
showerhead) arrangements are disclosed in commonly owned U.S. Pat.
Nos. 5,824,605; 5,863,376; and 6,048,798.
[0041] The gas distribution plate can have various designs one
example of which is shown in FIG. 4. The gas distribution plate 40
shown in FIG. 4 includes eighty-nine holes 41 and four embossments
42 near the center thereof for providing a passage for supply of
process gas between the gas distribution plate and the dielectric
window.
[0042] As shown in FIG. 3, the plasma exposed surfaces of the gas
distribution plate 22, chamber liner 30, and/or focus ring 14 are
provided with plasma sprayed coatings 32 of ceramic or polymeric
materials having surface roughness characteristics that promote
polymer adhesion. In this manner, particulate contamination inside
the reactor can be substantially reduced.
[0043] After time in use, the interior surfaces of the reactor
components according to the present invention can become coated
with polymer deposits. According to another embodiment of the
present invention, the component can be removed from the reactor so
that the existing plasma sprayed coating and any accumulated
deposits can be physically removed from the component and a new
plasma sprayed coating applied. The old coating can be removed
using mechanical means such as grinding or grit blasting. In this
manner, the reactor components can be reused.
[0044] A tape test was performed to determine the adhesion
properties of the plasma sprayed coatings of the present invention.
An alumina gas distribution plate with a plasma sprayed coating of
alumina according to the present invention was installed and used
in a TCP 9600.TM. metal etch reactor. A standard hot-pressed and
sintered alumina gas distribution plate (without the plasma sprayed
coating) was used in the same type of reactor under similar
conditions. Substantial polymer deposits formed on the plasma
exposed surfaces of both gas distribution plates. In the tape test,
a piece of tape was adhered to the surface of each gas distribution
plate and peeled off. No polymer was visible on the piece of tape
removed from the plasma sprayed GDP. A visual inspection of the
tape removed from the standard (non-plasma sprayed) GDP, however,
revealed substantial polymer deposits thereon.
[0045] The foregoing has described the principles, preferred
embodiments and modes of operation of the present invention.
However, the invention should not be construed as being limited to
the particular embodiments discussed. Thus, the above-described
embodiments should be regarded as illustrative rather than
restrictive, and it should be appreciated that variations may be
made in those embodiments by workers skilled in the art without
departing from the scope of the present invention as defined by the
following claims.
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