U.S. patent application number 14/065323 was filed with the patent office on 2014-05-01 for coating for performance enhancement of semiconductor apparatus.
This patent application is currently assigned to Advanced Micro-Fabrication Equipment Inc, Shanghai. The applicant listed for this patent is Advanced Micro-Fabrication Equipment Inc, Shanghai. Invention is credited to Xingjian CHEN, Xiaoming HE, Tuqiang NI, Zhaoyang XU, Li ZHANG.
Application Number | 20140116338 14/065323 |
Document ID | / |
Family ID | 50545760 |
Filed Date | 2014-05-01 |
United States Patent
Application |
20140116338 |
Kind Code |
A1 |
HE; Xiaoming ; et
al. |
May 1, 2014 |
COATING FOR PERFORMANCE ENHANCEMENT OF SEMICONDUCTOR APPARATUS
Abstract
A plasma processing chamber having advanced coating for the
showerhead and for an extended bottom electrode. The extended
bottom electrode can be formed by one or more of the focus ring,
cover ring, and plasma confinement ring. The extended electrode can
be formed using a one-piece composite cover ring. The composite
cover ring may be made of Al.sub.2O.sub.3 and include a
Y.sub.2O.sub.3 plasma resistant coating. The plasma confinement
ring may include a flow equalization ion shield that may also be
provided with the plasma resistant coating. The plasma resistant
coating of the extended electrode may have elements matching that
of the showerhead.
Inventors: |
HE; Xiaoming; (Shanghai,
CN) ; ZHANG; Li; (Shanghai, CN) ; CHEN;
Xingjian; (Shanghai, CN) ; NI; Tuqiang;
(Shanghai, CN) ; XU; Zhaoyang; (Shanghai,
CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Advanced Micro-Fabrication Equipment Inc, Shanghai |
Shanghai |
|
CN |
|
|
Assignee: |
Advanced Micro-Fabrication
Equipment Inc, Shanghai
Shanghai
CN
|
Family ID: |
50545760 |
Appl. No.: |
14/065323 |
Filed: |
October 28, 2013 |
Current U.S.
Class: |
118/723E ;
118/723R; 29/460 |
Current CPC
Class: |
C23C 14/083 20130101;
C23C 14/028 20130101; Y10T 29/49888 20150115; C23C 14/0694
20130101; H01J 37/32559 20130101; H01J 37/32495 20130101; H01J
37/32623 20130101; H01J 37/32642 20130101; C23C 14/32 20130101;
C23C 14/5873 20130101; H01J 37/32477 20130101 |
Class at
Publication: |
118/723.E ;
118/723.R; 29/460 |
International
Class: |
C23C 16/44 20060101
C23C016/44 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 29, 2012 |
CN |
201210421964.4 |
Claims
1. A plasma processing chamber for processing substrate,
comprising: a showerhead assembly comprising a perforated gas plate
having a plurality of gas injection holes and a plasma-facing
surface, the plasma-facing surface having a plasma resistant
coating containing yttrium; a chuck for supporting the substrate; a
focus ring provided around the substrate; a cover ring provided
around the focus ring; and, a plasma confinement ring provided
around the chuck; and wherein plasma-facing surface of at least one
of the focus ring, cover ring, and plasma confinement ring is
coated with the plasma resistant coating.
2. The plasma processing chamber of claim 1, wherein the plasma
resistant coating on the plasma-facing surface of the perforate gas
plate and the plasma resistant coating on the plasma-facing surface
of the focus ring, cover ring and/or plasma confinement ring are of
the same material composition.
3. The plasma processing chamber of claim 1, wherein the perforated
plate further incorporates a grounding ring.
4. The plasma processing chamber of claim 3, wherein the perforated
plate comprises SiC.
5. The plasma processing chamber of claim 3, wherein the perforated
plate comprises Al alloy.
6. The plasma processing chamber of claim 1, wherein the focus ring
and the cover ring comprise a single-piece composite cover
ring.
7. The plasma processing chamber of claim 6, wherein the composite
cover ring comprises a yttrium-based coating.
8. The plasma processing chamber of claim 7, wherein the composite
cover ring comprises Al.sub.2O.sub.3 and the yttrium-based coating
comprises Y.sub.2O.sub.3.
9. The plasma processing chamber of claim 8, wherein the composite
cover ring is ungrounded to form an extended RF electrode.
10. The plasma processing chamber of claim 1, wherein the plasma
confinement ring comprises a flow equalization ion shield having
Y.sub.2O.sub.3 coating.
11. The plasma processing chamber of claim 1, wherein the focus
ring and the cover ring comprise a single composite ring made of
the solid material selected from Si, SIC, Y.sub.2O.sub.3, Quartz,
and Al.sub.2O.sub.3, and having plasma resistant coatings selected
from Y.sub.2O.sub.3, YF.sub.3, ErO.sub.2, SiC, Si.sub.3N.sub.4,
ZrO.sub.2, and Al.sub.2O.sub.3.
12. The plasma processing chamber of claim 1, wherein the plasma
resistant coating of the perforated plate comprises Y.sub.2O.sub.3
coating having a dense structure with random crystal orientation
and with a porosity less than 1% and a surface roughness above 1
um.
13. The plasma processing chamber of claim 12, wherein the
perforated plate further comprises an intermediate layer or coating
formed over the plasma-facing surface under the plasma resistant
coating, wherein the intermediate coating layer has a surface
roughness above 4 um.
14. The plasma processing chamber of claim 12, wherein the
plasma-facing surface of at least one of the focus ring, cover
ring, and plasma confinement ring is coated with the plasma
resistant coating that comprises Y.sub.2O.sub.3 coating having a
dense structure with random crystal orientation and with a porosity
less than 1%.
15. A method for fabricating a plasma processing chamber,
comprising: fabricating a showerhead assembly, the showerhead
assembly comprising a perforated plate; fabricating a focus ring, a
cover ring, and a plasma confinement ring; using a plasma enhanced
physical vapor deposition to apply a plasma resistant coating to
the perforated plate and to at least one of the focus ring, the
cover ring, and the plasma confinement ring.
16. The method of claim 15, wherein fabricating the showerhead
assembly comprises fabricating the perforated plate from SiC.
17. The method of claim 15, wherein fabricating the showerhead
assembly comprises fabricating the perforated plate from Al
alloy.
18. The method of claim 16, wherein fabricating the showerhead
assembly comprises fabricating an integrated perforated plate and
grounding ring.
19. The method of claim 15, wherein fabricating the focus ring and
the cover ring comprises fabricating a single-piece composite cover
ring.
20. The method of claim 19, wherein fabricating the composite cover
ring comprises fabricating the composite cover ring from
Al.sub.2O.sub.3 and applying a Y.sub.2O.sub.3 coating.
21. The method of claim 20, further comprising coupling the
composite cover ring to RF power supplier to form an extended
electrode.
22. The method of claim 15, wherein using a plasma enhanced
physical vapor deposition comprise using source material containing
Yttrium.
Description
[0001] This application claims the priority of Chinese Patent
Application No. 201210421964.4, entitled "COATING FOR PERFORMANCE
ENHANCEMENT OF SEMICONDUCTOR APPARATUS", filed with the Chinese
Patent Office on Oct. 29, 2012, which is incorporated by reference
in its entirety herein.
BACKGROUND
[0002] 1. Field
[0003] The subject invention relates to plasma processing chambers
and, in particular, to chamber arrangements using coating for
internal chamber parts, which enhance the performance of the plasma
chamber.
[0004] 2. Related Art
[0005] In plasma processing chambers, a showerhead is often used to
inject the process gas. In certain plasma chambers, such as
capacitively-coupled plasma chambers, the showerhead may also
function as an electrode, coupled to either ground or RF potential.
However, during processing the showerhead is exposed to the plasma
and is attacked by the active species within the plasma, such as
halogen plasma of CF.sub.4, Cl.sub.2, etc. This phenomenon is
especially troublesome for showerheads having a chemical vapor
deposited silicon carbide coating (CVD SiC).
[0006] Plasma chambers also utilize an electrostatic chuck,
attached to a pedestal, to hold the substrate during processing.
Generally, the diameter of the chuck and/or pedestal is larger than
that of the substrate. Therefore, various additional elements are
required to protect the chuck and/or pedestal from the active
species in the plasma, and also to control the RF power coupling so
as to sustain uniform plasma over the substrate. Such elements may
include a focus ring, a cover ring, flow equivalent ion shied, and
a plasma confinement ring, etc.
[0007] FIG. 1 is a schematic illustrating the general components of
a capacitively-coupled plasma chamber. The chamber includes a
chamber wall 100, ceiling 105, and floor 110, which together form a
vacuum enclosure. A showerhead assembly 120 may include a gas
distribution plate (GDP) 125, which can also function as an
electrode; and a cover plate 127. The GDP 125 is shown grounded,
and the cover ring 127 may also be conductive and grounded,
generally by being in physical contact with the GDP 125.
[0008] The substrate 130 is held in place by chuck 135, which is
attached to a pedestal 140. RF power is delivered to an electrode
that may be embedded in the chuck 135 or may be part of the
pedestal 140. A focus ring 140 is provided around the substrate and
helps to control plasma uniformity. A cover ring 145 is provided
around the focus ring and serves mainly for erosion protection from
active plasma species. A plasma confinement ring 150 prevents
plasma from igniting and/or sustaining below the plasma confinement
ring 150, such that the plasma is confined to the processing zone
of the vacuum enclosure.
[0009] As is known, during processing the plasma may be rather
corrosive to the various elements of the chamber, especially the
showerhead, since it forms a part of the capacitive RF power
circuit. Therefore, various coatings have been proposed and tested
in the prior art for protecting the showerhead from plasma erosion.
Yttria (Y.sub.2O.sub.3) coating is believed to be promising;
however, it has been very difficult to find a process that results
in good coating, especially one that does not crack or generate
particles. For example, there have been proposals to use plasma
spray (PS) to coat a showerhead made of metal, alloy or ceramic.
However, conventional PS Y.sub.2O.sub.3 coating is formed by the
sprayed Y.sub.2O.sub.3 particles, and generally results in a
coating having high surface roughness (Ra of 4 micron or more) and
relatively high porosity (volume fraction is above 3%). The high
surface roughness and porous structure makes the coating
susceptible to generation of particles, which may contaminate the
wafer being processed. In addition, the particle will come out from
the gas holes and dropped on the wafer when the as-coated shower
head is used in the plasma process, as the plasma sprayed coating
inside the gas hole is very rough and has poor adhesion to the
substrate.
[0010] Other proposals for forming Yttria coating involve using
chemical vapor deposition (CVD), physical vapor deposition (PVD),
ion assisted deposition (IAD), active reactive evaporation (ARE),
ionized metal plasma (IMP), sputtering deposition and plasma
immersion ion process (PIIP). However, all these deposition
processes have some technical limitations such that they have not
been actually used to scale up for the deposition of thick coating
on the chamber parts for the plasma attack protections. For
instance, CVD of Y.sub.2O.sub.3 can not be carried out on
substrates that cannot sustain temperatures above 600.degree. C.,
which excludes the deposition of plasma resistant coating on
chamber parts that are made of aluminum alloys. PVD process, such
as evaporation, can not deposit dense and thick ceramic coating
because of their poor adhesion to substrate. Other deposition
processes can not deposit thick coating either due to the high
stress and poor adhesion (such as sputtering deposition, ARE and
IAD) or the very low deposition rate (such as sputtering
deposition, IMP and PIIP). Therefore, so far no satisfactory
coating has been produced, that would have good erosion resistance,
while generating low or no particles and can be made thick without
cracking or delamination.
[0011] Moreover, when the showerhead assembly, e.g., showerhead and
ground ring, is coated or replaced by a one piece Y.sub.2O.sub.3
coated SiC showerhead, the RF coupling between the upper electrode
and the bottom electrode is maintained between Y.sub.2O.sub.3 and
silicon surfaces (i.e., wafer) or between Y.sub.2O.sub.3 showerhead
and silicon wafer and SiC focus ring surface. Consequently, the RF
induced plasma distribution on the wafer is quite different from
the plasma distribution on wafer when uncoated SiC showerhead is
used.
[0012] FIG. 2 is a plot of etch rate (ER) over the surface of
silicon wafer using SiC showerhead (diamonds plot) and using
Y.sub.2O.sub.3 coated showerhead (triangle plot). The plots of FIG.
2 clearly demonstrate that the use of Y.sub.2O.sub.3 showerhead
(SH) induces an ER distribution having a much higher etch rate than
the ER distribution that is created using an uncoated SiC
showerhead. However, the ER drops at the wafer edge area, which
induces an increased non-uniformity of the ER over the wafer
surface. As can be seen from FIG. 2, the ER uniformity variation
for Y.sub.2O.sub.3 coated showerhead is 10.74%. The increase of
non-uniformity limits the application of Y.sub.2O.sub.3 coated
showerhead (SH) to actual etching process. Similar thing happens in
the case where only a Y.sub.2O.sub.3 coated SiC showerhead (SH) is
used, which indicates the important and sensitive impact of the
electrode's surface or surface materials on the ER distributions
over the wafer in various plasma chemical etching processes.
[0013] In view of the above-described problems in the art, a
solution is needed for a showerhead coating that resists plasma
species attack and does not generate particle or cracks. The
coating should have acceptable roughness and porosity values, so
that it could provide long service life. Additionally, the solution
should maintain ER uniformity over the wafer. The process for
fabricating the coating should allow thick coating without being
susceptible to cracking or delamination.
SUMMARY
[0014] The following summary of the invention is included in order
to provide a basic understanding of some aspects and features of
the invention. This summary is not an extensive overview of the
invention and as such it is not intended to particularly identify
key or critical elements of the invention or to delineate the scope
of the invention. Its sole purpose is to present some concepts of
the invention in a simplified form as a prelude to the more
detailed description that is presented below.
[0015] According to an aspect of the invention, methods are
provided for the formation of advanced plasma resistant coatings on
showerheads. According to various embodiments, the process of the
coating the showerhead surface is provided so that the service
performance of the coated showerhead is improved. Other embodiments
involve the modification and installation of the coated showerhead
into the plasma chamber, so as to improve the plasma process
quality.
[0016] According to various embodiments, etch uniformity is
maintained, while the showerhead is protected by an effective
Y.sub.2O.sub.3 coating. In one example, a hardware configuration of
a capacitively coupled plasma (CCP) chamber is provided where at
least the perforated plate of the showerhead is coated with
Y.sub.2O.sub.3, while at least one opposing conductive surface of
the CCP is also coated with Y.sub.2O.sub.3. The opposing surface
may be any one or a combination of focus ring, cover ring, flow
equivalent ion shied, and/or plasma confinement ring. In one
embodiment, the perforated plate and ground ring are replaced by a
one-piece equivalent plate, which is made of conductive material,
e.g., SiC or Al alloy, and has a protective coating, e.g.,
Yttrium-based coating, such as Y.sub.2O.sub.3. To maintain good
plasma uniformity, the opposing surface is also coated. For
example, the focus ring and cover ring are coated using the same
coating as the showerhead. In some examples, the focus ring and
cover ring are combined into a single equivalent ring which is
coated. Also, if either is used, the plasma confinement ring or the
flow equivalent ion shield can be coated.
[0017] In an exemplary process, an advanced Yttria coating, e.g.,
Y.sub.2O.sub.3 or YF.sub.3 based coatings, with fine/compact grain
structure and random crystal orientation is created by a plasma
enhanced physical vapor deposition (PEPVD) process, in which (1)
the deposition is carried out in a low pressure or vacuum chamber
environment; (2) at least one deposition element or component is
evaporated or sputtered out off a material source and the
evaporated or sputtered material condenses on the substrate surface
(this part of the process is a physical process and is referred to
herein as the physical vapor deposition or PVD part); (3)
meanwhile, a plasma source (or sources) is (are) used to emit out
ions and to generate plasma that surrounds the showerhead surface
and at least one deposition element or component is ionized and
reacted with the evaporated or sputtered elements or components in
plasma or on the surface of the showerhead; and (4) the showerhead
is coupled to a negative voltage, such that it is bombarded by the
ionized atoms or ions during the deposition process. The actions
from (3) and (4) are referred to as the "plasma enhanced (PE)"
function of the PEPVD.
[0018] It should be mentioned that the plasma source(s) could be
used either (1) to ionize, decompose, and activate the reactive
gases so that the deposition process can be performed in a low
substrate temperature and with a high coating growth rate as more
ions and radicals are generated by plasma, or (2) to generate the
energetic ions aimed at the showerhead so that the ion impinges on
the surface of the shower head and helps to form the thick and
dense coatings thereon. More perfectly, the plasma sources will be
used as the alternative or the combinations of functions (1) and
(2), to lead the formation of the coating on the shower head. Such
a coating synthesized with the enough thickness and the dense
structure is generally referred to herein as "advanced coating"
(referred to A-coating herein), for instance, such as
A-Y.sub.2O.sub.3, A-YF.sub.3, or A-Al.sub.2O.sub.3 based
coatings.
[0019] In order to improve the coating formation, the deposition of
A-coating is performed on a roughened surface of the substrates or
showerhead, to improve the adhesion of the coating to substrate and
to increase the deposition thickness. This is because the increase
of surface roughness of the material increases the contact area in
the interfacial region between the coating and substrate surface,
and changes of the coating contact area from more 2-dimensional
fraction to more 3-dimensional fraction. The deposition on the
rough surface induces the formation of coating with random crystal
orientation and results in the release of the interfacial stress
between the A-coating and the substrates, which enhances the
coating adhesion to the substrate and promotes the formation of
thick and dense coating thereon. It has been expected that the
improved stability of A-coating on materials surface can be reached
if the coating is deposited on materials with the surface roughness
at least above 4 um.
[0020] In order to reduce the production cost, another embodiment
involves the formation of double layered coating combinations in
which the first layer or coating is formed on the showerhead base
as the anodization, the plasma spray Y.sub.2O.sub.3, or other
plasma resistant coatings, with a certain thickness designed to
maintain the required electrical properties of the formed
showerhead and the first layer has the surface roughness above 4
um. A second layer or coating is formed over the first layer that
is at least 4 um in roughness and the second layer or coating thus
has a top surface facing to plasma in the plasma processes. The
second coating can be formed as the A-coating (e.g.
A-Y.sub.2O.sub.3, A-YF.sub.3, etc.), and the formed coatings have
the specified roughness (surface roughness Ra.gtoreq.1.0 um) and
dense structure with random crystal orientation and with a porosity
less than 1% or without porous defects. Consequently, particle
contamination, which is usually induced by plasma spray coating due
to the rough surface and porous structure, can be reduced, while
A-coating is used as the showerhead exterior surface. In addition,
due to the dense crystal structure, the second coating has reduced
plasma erosion rate, which could further reduce metal contamination
in the plasma processes. The thicknesses of either the first
coating or the second coating can be adjusted according to the
performance requirement on the showerhead.
[0021] In another embodiment, the showerhead surface is coated by
double layered coating combinations, in which the first layer or
coating is formed on the showerhead base by anodization, by plasma
spray, or by other technologies, and with enough thickness to
provide the desired process functions of the showerhead in the
plasma processes (such as required electrical conductivity, thermal
conductivity or thermal barrier function, and other functions). The
second layer or coating is formed on the first layer or coating to
form a top surface facing the plasma in the plasma etch processes.
The first layer or coating could be either plasma resistant or
other function coatings with or without uniform distribution in
thickness and/or composition on the showerhead base surface. The
second coating is the A-coatings, such as A-Y.sub.2O.sub.3 coating.
Since the A-coating has the specified roughness (Ra.gtoreq.1.0 um)
and dense structure with random crystal orientation and with a
porosity less than 1% or without porous defects, the A-coating has
plasma erosion rate much lower than the first coating, which would
not create particles and should have reduced metal contamination in
the plasma processes. The thicknesses and the roughness of either
the first coating or the second coating can be adjusted according
to the performance requirement on the showerhead.
[0022] In another embodiment, the multi-layered coatings are
deposited on the showerhead, such that the coated showerhead has an
increased coating thickness, a stable surface facing the plasma
chemistry, and the desired functions to improve the process
performance of the plasma chamber. As different from the coating
that is deposited as a single layered structure, the same material
with the multilayered structure can be deposited to reach an
increased thickness with a reduced risk of crack formation, as the
increased interfacial areas due to the multi-layers can release the
coating stress that is usually increased with the increase of the
layer or coating thickness. The multilayered coating is composed by
either the multilayered A-coatings or the combination of the
multi-layered functions coating with the multi-layered A-coatings
whose top layer faces the plasma, for instance, when the coatings
are deposited on the showerhead. It has been confirmed that the
multi-layered A-coating with random crystal orientation can be
deposited on the showerhead to thicknesses above 50 um without
cracking and delamination if the showerhead has a surface roughness
above 4 um.
[0023] In another embodiment, in order further to improve the
performance of the coating packaged showerhead, surface processes
are applied on the as-coated showerhead, which includes, but not
limited to, surface smoothening or roughening to reduce the
particles, surface modification to enhance the surface density and
stability of the coatings, and surface chemical cleaning to remove
the particles and contamination that are formed on the coated
showerhead either due to the coating deposition process or due to
the plasma etching process.
[0024] According to one aspect, the surface roughness of the
A-coating is controlled, since if the surface is too smooth,
polymer deposition during etching will not adhere well to the
surface, and thus induce particles. On the other hand, too rough
surface will directly create particles due to the plasma etching.
The recommended surface roughness is at least 1 um or above for the
A-coatings, which can be reached by the adjustment of the substrate
roughness, by the deposition process, or by lapping, polishing and
other post surface treatment on the deposited coatings.
[0025] According to another aspect, the energetic ion bombardment
or plasma etching in the PEPVD is used to smooth/rough and densify
the surface of A-coating coated showerhead. The coated showerhead
surface can be cleaned by wet solution cleaning in which the
erosive solution or slurry or aerosol is used to blast away the
surface particles and to control the surface roughness of the
coating either on the flat plate or inside the gas holes. The dense
coating with the specified roughness could have the fine and
compact grain structure with reduced porous volume defects, and
thus reduce the plasma erosion rate and maintain clean environment
during the plasma etch processes.
[0026] To reach performance improved etch processes, the coated
showerhead can be formed with modification or combination of the
gas distribution plate, showerhead aluminum base and the upper
ground ring into one piece of coated showerhead, or the one piece
of showerhead with the build-in heater, so that the formation of
the new coated showerhead can reduce the production cost and the
coated showerhead is easy to be refurbished once it is used for a
certain service cycles. In essence, the various parts of the
showerhead can be coated so as to be "packaged" by or inside the
A-coating layer.
[0027] The base or intermediate coating could be of metals, alloys,
or ceramics (such as Y.sub.2O.sub.3, YF.sub.3, ErO.sub.2, SiC,
Si.sub.3N.sub.4, ZrO.sub.2, Al.sub.2O.sub.3 and their combinations
or combination of them with other elements). The second or the top
coating with the surface facing the plasma could be A-coating of
Y.sub.2O.sub.3, YF.sub.3, ErO.sub.2, SiC, Al.sub.2O.sub.3 and their
combinations or combination of them with other materials. As quite
different from the prior art, it is suggested that the A-coating is
deposited on the substrate materials that may have the element(s)
and/or component(s) which are also contained in the A-coating, such
as the deposition of A-Y.sub.2O.sub.3 on anodized surface,
Y.sub.2O.sub.3 surface, or Al.sub.2O.sub.3 surface. Since the same
elements or components occurred in both the coating and the
substrate will result in the formation of the atomic bondings from
the same elements or components in the interfacial region between
the A-coating and the substrates, which promotes the formation of
A-coating with the increased thickness and the improve adhesion to
the substrates or showerhead.
[0028] Various methods are disclosed for deposition of A-coating
with random crystal orientation and thickness of 50 microns or
more, without cracks or delamination. In one embodiment, the
surface of the part to be coated is roughened to Ra of 4 microns or
more prior to the coating. It was shown that the roughness of 4
micron is critical for reduction of cracks and delamination.
Additionally, rather than depositing a single-layer coating to the
desired thickness, a series of thinner coatings are deposited, that
add up to the desired thickness. For example, if a 50 micron
coating of A-Y.sub.2O.sub.3 is desired, rather than depositing a
single layer, several layers, e.g., five layers of ten microns each
are deposited sequentially. Normally, as the thickness of the
coating increases, the stress within the coating also increases.
However, depositing the coating as a multi-layer structure releases
the stress, thus reducing the risk of cracks and delamination.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] The accompanying drawings, which are incorporated in and
constitute a part of this specification, exemplify the embodiments
of the present invention and, together with the description, serve
to explain and illustrate principles of the invention. The drawings
are intended to illustrate major features of the exemplary
embodiments in a diagrammatic manner. The drawings are not intended
to depict every feature of actual embodiments nor relative
dimensions of the depicted elements, and are not drawn to
scale.
[0030] FIG. 1 is a schematic of a prior art capacitively coupled
plasma chamber;
[0031] FIG. 2 is a plot illustrating etch rate distribution for SiC
showerhead and coated showerhead;
[0032] FIG. 3 is a schematic illustrating capacitive coupling of RF
power between the showerhead assembly and the bottom electrode
assembly;
[0033] FIG. 4 illustrates a plasma chamber according to one
embodiment;
[0034] FIG. 5 is a plot demonstrating the effects of having
Y.sub.2O.sub.3 coated showerhead as upper electrode and
Y.sub.2O.sub.3 coated focus ring and cover ring as extended lower
electrode;
[0035] FIG. 6 illustrates the results obtained with the same
hardware set-up, but using Recipe 2 in Table 1;
[0036] FIG. 7 illustrates a plasma chamber according to another
embodiment;
[0037] FIG. 8 illustrates an apparatus for depositing advanced
coating in accordance with one embodiment of the invention;
[0038] FIG. 9A illustrates a conventional showerhead and electrode
assembly for a plasma chamber;
[0039] FIG. 9B illustrates a showerhead having generally the same
structure as that of FIG. 9A, except that it includes the advance
coating according to an embodiment of the invention;
[0040] FIG. 9C illustrates another embodiment, wherein the
showerhead assembly has one piece gas distribution plate that is
"packaged` in the A-coating;
[0041] FIG. 9D illustrates another embodiment, wherein the
perforated gas plate, conductive ring, and support ring are
fabricated as one piece perforated gas distribution plate (or
GDP);
[0042] FIG. 9E illustrates another embodiment, wherein the
showerhead assembly with one piece gas distribution plate is
"packaged" in the A-coating; and
[0043] FIG. 9F illustrates another embodiment, wherein the
showerhead assembly with one piece gas distribution plate is coated
with an intermediate coating and then with the A-coating.
DETAILED DESCRIPTION
[0044] Various embodiments will now be described, providing
improved coatings for showerheads, which improve erosion and
particle performance of the showerhead, together with coated
cathode assembly for enhancing etch rate and plasma uniformity.
FIG. 3 is a schematic illustrating the arrangement for a
capacitively coupled plasma chamber. In this embodiment, the top
electrode 322 is grounded and the RF power is applied to the bottom
electrode, which in this example is composed of electrode 362 and
extension 342. The top electrode 322 may be composed of the
perforated plate, or a combination of perforated plate and
grounding ring. The bottom electrode 362 may be embedded in the
chuck, or be part of the pedestal supporting the chuck. The
extension 342 may be composed of one or a combination of focus
ring, cover ring, flow equivalent ion shied, and/or plasma
confinement ring. By proper selection of the elements comprising
the upper and lower electrodes, and proper coating of these
elements, etch rate can be enhanced without deteriorating etch
uniformity. Moreover, coated parts are better protected from plasma
corrosion.
[0045] For example, in one embodiment the upper electrode is
fabricated as a combined showerhead and grounding ring, while the
bottom electrode is the combination of the chuck
electrode--coupling the power via the silicon wafer, plus an
extended electrode that is formed by the coated focus ring, the
coated cover ring, and the coated FEIS ring. In this embodiment,
the upper electrode is fabricated from SiC or Al alloy, and is
coated with Y.sub.2O.sub.3. The coating has fine/compact grain
structure and random crystal orientation, as will be described in
more details below. The extended electrode may be made of
conductive material and also has the Y.sub.2O.sub.3 coating.
[0046] FIG. 4 illustrates an embodiment where the upper electrode
is a combined showerhead and grounding ring, illustrated as
shower-plate 430. In this embodiment the shower-plate 430 is made
of either SiC or Al alloy, and has a protective coating 434. Also,
in this embodiment the coating is yttrium-based, such as, e.g.,
Y.sub.2O.sub.3, Y.sub.2F.sub.3, etc. For enhanced plasma-corrosion
resistance, it is best to coat the showerhead with the advanced
coating, as described more fully below.
[0047] Also shown in FIG. 4 are focus ring 440, cover ring 445, and
plasma confinement ring 450. The plasma confinement ring may
include flow equalization ion shied (FEIS) ring 447. The FEIS ring
447 functions to create equivalent flow to the vacuum pump and
block ions from flowing into the exhaust path to the vacuum pump.
In the embodiment of FIG. 4, at least one of the focus ring 440,
cover ring 445, plasma confinement ring 450 and/or flow equivalent
ion shied (FEIS) ring 447 is coated with the same coating as the
shower-plate 430.
[0048] FIG. 5 is a plot demonstrating the effects of having
Y.sub.2O.sub.3 coated showerhead as upper electrode and
Y.sub.2O.sub.3 coated focus ring and cover ring as extended lower
electrode. Notably, the etch rate is high as for the case where
only the showerhead was coated. However, uniformity has improved
dramatically to 2.66%. In fact, the uniformity is even better than
what it was prior to coating the showerhead. This result was
obtained by using the etch recipe indicated as Recipe 1 in Table 1.
FIG. 6, on the other hand, illustrates the results obtained with
the same hardware set-up, but using Recipe 2 in Table 1. As can be
seen by comparing the two plots of FIG. 5 and FIG. 6, the etch rate
remains the same, but the etch uniformity can be changed by
changing recipe parameters. Note that the uniformity for Recipe 2
is 2.88%, which is better than that uniformity achieved without the
coating.
TABLE-US-00001 TABLE 1 60 MHz 2 MHz Pressure Power Power CF.sub.4
C.sub.4F.sub.8 Ar N.sub.2 O.sub.2 Recipe mT W W sccm No 1 90-110
1300-1700 1600-2000 450-500 200-250 75-100 No 2 70-90 1300-1700
2300-2700 50-70 40-60 500-700 100-200 50-75
[0049] In the embodiment of FIG. 4, leading to the results plotted
in FIGS. 5 and 6, the focus ring was made of SiC or quartz and the
cover ring was made of quartz, both of which were coated with
Y.sub.2O.sub.3. However, according to another embodiment, the both
focus ring and cover ring are made using solid Y.sub.2O.sub.3.
According to this embodiment, the ER uniformity can be improved and
the service life of cover ring (CR) and focus ring (FR) can be
prolonged.
[0050] According to another embodiment, illustrated in FIG. 7, the
quartz cover ring (CR) and SiC focus ring (FR) are replaced by a
one piece composite cover ring 749, that is actually the
combination of the original quartz CR and SiC FR. The composite
cover ring (CCR) 749 can be made of solid Y.sub.2O.sub.3, or other
materials, such as but not limited to, Si, SiC, Quartz,
Al.sub.2O.sub.3 or other plasma resistant ceramics. On the other
hand, the one-piece composite cover ring 749 can be made of
materials, such as, but not limited to, Si, SiC, Y.sub.2O.sub.3,
Quartz, Al.sub.2O.sub.3 and other ceramics, and include a plasma
resistant coating. The plasma resistant coatings can be, such as,
but not limited to, Y.sub.2O.sub.3, YF.sub.3, ErO.sub.2, SiC,
Si.sub.3N.sub.4, ZrO.sub.2, Al.sub.2O.sub.3 and their combinations,
or a combination of them with other elements. The selection and
deposition of different coatings on the composite cover ring highly
depends on the combinations of the materials that are used to form
the upper electrode and the bottom electrode. The use of such
one-piece cover ring 749 reduces the production cost, but keeps the
benefits of etch rate and etch uniformity.
[0051] According to one specific another embodiment, the composite
cover ring 749 is made by the deposition of Y.sub.2O.sub.3 coatings
onto Al.sub.2O.sub.3 substrate. Comparing the properties of other
materials list in Table 2, Al.sub.2O.sub.3 has coefficient of
thermal expansion (CTE) that is almost the same as that of
Y.sub.2O.sub.3. This property ensures that thick Y.sub.2O.sub.3
coating can be synthesized on the Al.sub.2O.sub.3 surface, with a
stable structure and the good adhesion. The combination can also
withstand operating in high service temperatures. Additionally, the
Al.sub.2O.sub.3 based composite cover ring (CCR) will have enhanced
service function in various plasma environments, as Al.sub.2O.sub.3
substrate has good thermal conductivity, comparing to solid
Y.sub.2O.sub.3 CCR.
TABLE-US-00002 TABLE 2 Materials PS Y.sub.2O.sub.3 Si SiC
Al.sub.2O.sub.3 Al CTE, 10 - 6 K - 1 5.9 2.6-3.2 2.9-3.2 5.4 20
Thermal conductivity, 3.8 149 150 30 125 W m - 1 K - 1
[0052] As can be understood from the embodiments disclosed above,
when providing Y.sub.2O.sub.3 coated FR, Y.sub.2O.sub.3 coated CR,
and/or Y.sub.2O.sub.3 coated FEIS ring, which aren't grounded,
i.e., being floating or RF biased, they function as an extended
bottom electrode. When the plasma is ignited and maintained between
bottom electrode, i.e., the combined electrostatic chuck and wafer,
and upper electrode Y.sub.2O.sub.3 coated SH, the plasma is also
simultaneously ignited and maintained between the upper electrode
Y.sub.2O.sub.3 coated SH and the extended bottom electrode, i.e.,
the Y.sub.2O.sub.3 coated FR, the Y.sub.2O.sub.3 coated CR, and the
Y.sub.2O.sub.3 coated FEIS ring. Since the upper electrode and the
extended bottom electrode have the Y.sub.2O.sub.3 surfaces, it
helps to stable the RF coupling and maintain uniform plasma
distribution between the CCP electrodes and thus promote the
uniform plasma etch on the wafer's surface. It is noted that in the
embodiment of FIG. 3, the diameter of the extended bottom electrode
is larger than the diameter of the showerhead.
[0053] The description now turns to the apparatus and method for
forming the coating, which may be used to coat the showerhead and
the extended bottom electrode described above.
[0054] Unlike conventional plasma spray, in which the coating is
deposited in atmospheric environment, the advanced coating
disclosed herein is deposited in low pressure or vacuum
environment. Also, while in plasma spray the coating is deposited
using small powdery particles, the advanced coating is deposited by
the condensation of atoms, radicals, or molecules on the materials
surfaces. Consequently, the characteristics of the resulting
coating layer is different from the prior art coating, even when
the same material composition is used. For example, it was found
that a Y.sub.2O.sub.3 coating deposited according to embodiment of
the invention has practically no porosity, specified surface
roughness above 1 um, and has a much higher etch resistance than
the conventional PS Y.sub.2O.sub.3 coating.
[0055] The embodiments of the invention will now be described in
detail with reference to the Figures. First, the equipment and
method for depositing the advanced coating will be described. FIG.
8 illustrates an apparatus for depositing advanced coating in
accordance with one embodiment of the invention. This apparatus is
used for depositing the advanced coating using the process referred
to herein as PEPVD, where the PE and PVD components are highlighted
by the broken-line callouts in FIG. 8. Traditionally, chemical
vapor deposition (CVD) or plasma enhanced chemical vapor deposition
(PECVD) refer to a chemical process where a thin film is formed on
the substrate's surface by exposing the substrate to one or more
volatile precursors, which react and/or decompose on the substrate
surface to produce the desired deposited film. PVD, on the other
hand, refers to a coating method which involves purely physical
processes, where thin films are deposited on the surface of the
substrate by the condensation of a vaporized or sputtered form of
the desired film materials that can be usually the solid source
materials. Therefore, one may characterize PEPVD as somewhat of a
hybrid of these two processes. That is, the disclosed PEPVD
involves both physical process of atom, radicals, or molecular
condensation (the PVD part) and plasma induced chemical reaction in
the chamber and on the substrate's surface (the PE part).
[0056] In FIG. 8, chamber 800 is evacuated by vacuum pump 815. The
part 810 to be coated, in this example the showerhead, focus ring,
cover ring, confinement ring, etc., is attached to a holder 805.
Also, a negative bias is applied to the part 810, via holder
805.
[0057] A source material 820 containing species to be deposited is
provided, generally in a solid form. For example, if the film to be
deposited is Y.sub.2O.sub.3 or YF.sub.3 based, source material 820
would include yttrium (or fluorine)--possibly with other materials,
such as oxygen, fluorine (or yttrium) etc. To form the physical
deposition, the source material is evaporated or sputtered. In the
example of FIG. 8, the evaporation is achieved using electron gun
825, directing electron beam 830 onto the source material 820. As
the source material is evaporated, atoms and molecules drift
towards and condense on the part 810 to be coated, as illustrated
by the broken-line arrows.
[0058] The plasma enhanced part is composed of a gas injector 835,
which injects into chamber 800 reactive and non-reactive source
gases, such as argon, oxygen, fluorine containing gas, etc., as
illustrated by the dotted lines. Plasma 840 is sustained in front
of part 810, using plasma sources, e.g., RF, microwave, etc., one
of which in this example is shown by coil 845 coupled to RF source
850. Without being bound by theory, it is believed that several
processes take place in the PE part. First, non-reactive ionized
gas species, such as argon, impinging the part 810, so as to
condense the film as it is being "built up." The effects of ion
impinging may result from the negative bias on part 810 and part
holder 805, or from the ions emitted out from the plasma sources
and aimed at part 805. Second, reactive gas species or radicals,
such as oxygen or fluorine, react with the evaporated or sputtered
source material, either inside the chamber or on the surface of the
part 810. For example, the source Yttrium reacts with the oxygen
gas to result in Y containing coating, such as Y.sub.2O.sub.3 or
YF.sub.3. Thus, the resulting process has both a physical
(impingement and condensation) component and a chemical component
(e.g. oxidation and ionization).
[0059] FIG. 9A illustrates a conventional showerhead and electrode
assembly for a plasma chamber. Conductive plate 905, sometimes, can
be converted as the heater to control the temperature of the
showerhead, is sandwiched between back plate 910 and perforated gas
plate 915. Conductive ring 920 surrounds the perforated gas plate
915 and can work as the extended upper electrode or as a grounding
ring. Support ring 925 surrounds conductive plate 905 and is also
sandwiched between conductive ring 920 and back plate 910.
Perforated gas plate 915, actually working as a gas distribution
plate (or GDP), may be made of ceramic, quartz, etc., for example,
it may be made of silicon carbide, and may be assembled to the
lower surface of conductive plate 905. Conductive ring 920 may be
made of ceramic, quartz, etc., for example, it may be made of
silicon carbide, and may be assembled to the lower surface of
support ring 925. The support ring 925, the conductive plate 905
and the back plate 910 may be made of metal and alloy, e.g.,
aluminum, stainless steel, etc. The showerhead is affixed to the
ceiling of the plasma chamber, in a well-known manner.
[0060] FIG. 9B illustrates a showerhead having generally the same
structure as that of FIG. 9A, except that it includes the advance
coating according to an embodiment of the invention. In FIG. 9B the
advanced coating 935 (for example, A-Y.sub.2O.sub.3) is provided on
the bottom surface of the perforated gas plate 915, i.e., the
surface that faces the plasma during substrate processing. The
advanced coating 935 may be the single layer or the multilayered
coatings. In this embodiment, the perforated gas plate is
fabricated according to standard procedures, including formation of
gas injection holes/perforations. Then, the plate is inserted into
a PEPVD chamber and the bottom surface is coated with advanced
coating. Since the PEPVD coating uses atoms or molecules for
buildup of the coating, the interior of the gas injection holes is
also coated. However, unlike prior art coating, the advance coating
is formed by the condensation of atoms and molecules, and results
in a dense and uniform A-coating with the good adhesion to the
interior surface of the gas holes, thereby providing smooth gas
flow and avoiding any particle generation.
[0061] While according to above embodiment the surface of the
coated perforated gas plate is characterized with the specified
surface roughness (surface roughness is controlled equal to or
larger than Ra 1.0 um), according to one embodiment the surface is
roughened in order to promote polymer adhesion during plasma
processing. That is, according to one aspect, the surface roughness
of the A-coating is controlled, since if the surface is too smooth,
polymer deposition during etching will not adhere well to the
surface, and thus induce particles. On the other hand, too rough
surface will directly create particles due to the plasma etching.
Therefore, according to this embodiment the recommended surface
roughness Ra is equal to or above 1 um. Perfectly, the recommended
surface roughness Ra is above 1 um, but below 10 um (1
um<Ra<10 um). It has been found that in this range the
particle generation is minimized, while polymer adhesion is
controlled. That is, the noted range is critical because using
higher roughness leads to particle generation, while using smoother
coating diminishes adhesion of the polymers during plasma
processing. In all cases, the A-coating with either single or
multilayered structure has the dense structure with random crystal
orientation and porosity less than 1% and has no any crack or
delamination.
[0062] According to one embodiment this roughness is achieved by
the as-deposited coating, or by lapping, polishing or other post
PEPVD surface treatment on the as-deposited coatings. On the other
hand, according to one embodiment the surface of the perforated gas
plate is first roughened to the desired roughness (Ra>4 um), and
then the coating is deposited. Since the coating is done using
PEPVD, the resulting coating may have the same or different
roughness as the surface prior to the coating, according to the
thickness of the coating and the deposition process.
[0063] FIG. 9C illustrates another embodiment, where the showerhead
assembly is "packaged" in the A-coating. That is, as shown in FIG.
9C, the lower surface of the entire showerhead assembly is coated
with the A-coating 935 (for example A-Y.sub.2O.sub.3). In this
example, various parts forming the showerhead are first assembled,
and then are positioned inside the PEPVD chamber to form the
advanced coating over the lower surface of the entire assembly. In
this manner, the showerhead assembly is "packaged" by the advanced
coating and is fully protected from plasma erosion. As discussed
with reference to FIG. 9B, the surfaces may remain smooth, or may
be roughened so as to promote polymer adhesion. In all cases,
however, the coating thickness is above 50 um.
[0064] FIG. 9D illustrates another embodiment, where the perforated
gas plate 915, conductive ring 920 and support ring 925 in former
embodiments are united as one piece perforated gas plate (or GDP)
915 in this embodiment. As quite different from the prior art, the
one piece perforated gas plate 915 can be made of metals, for
instance, Al alloy, and the surface can be protected by the
deposition of A-coatings 935, such as A-Y.sub.2O.sub.3. As
comparing to the prior art, the formation of showerhead by
A-Y.sub.2O.sub.3 coating 935 over the perforated gas plate 915 can
reduce the product cost, simplifies the assembly and manufacture
procedure of shower head, and increase the work life time. Another
advantage is that it provides the possibility to refurbish the used
showerhead simply by the re-deposition of A-coating 935 over the
one piece perforate gas plate 915. In addition, it is more easy to
form the A-coating "packaged" showerhead, as again another
embodiment showing in FIG. 9E, since the deposition of A-coating is
carried out on the showerhead that formed only by the assembly of
the one piece perforated gas plate 915 to the conductive plate 905
and back plate 910.
[0065] FIG. 9F illustrates yet another embodiment of the invention.
FIG. 9F is drawn as a callout from FIG. 9E to indicate that it
depicts an enlarge section of a showerhead similar to that shown in
FIG. 9E, except that it has a different coating scheme. In the
embodiment of FIG. 9F, the perforated gas plate 915 has an
intermediate layer or coating 913. The intermediate layer is formed
on the roughened surface of the perforate gas plate 915, and the
surface of the intermediate layer where the A-coating is deposited
thereon also has a roughened surface. The intermediate layer may
be, for example, an anodized layer or a plasma sprayed
Y.sub.2O.sub.3 coating. Then an advanced coating 935, according to
any of the embodiments described herein, is deposited as a single
layer or multi-layered structure over the intermediate layer or
coating 913. Moreover, ach of the A-coating 935 and the
intermediate layer 913 can be formed as the multi-layered coatings,
so that the thickness of the coating can be increased and the
structure stability of the deposited coatings can be improved.
[0066] According to one example, the perforated gas plate is the
anodized plate where the surface and inside gas holes are all
protected by the anodization, such as the hard anodization. Then,
the deposition of A-coatings, such as A-Y.sub.2O.sub.3 is performed
either on the surfaces of perforate gas plate (expect the back side
surface contact to the conductive plate 905 and back plate 910) as
showing in FIG. 9D or on the surface of the assembled showerhead as
showing in FIG. 9E. Since the deposition of A-coating is directly
on the anodized surface, there is no interfacial issue between
A-coating and anodization, which usually exists between the PS
Y.sub.2O.sub.3 coating and the anodized surface as the PS
Y.sub.2O.sub.3 is normally deposited on the bare Al alloy, to reach
a good adhesion of PS Y.sub.2O.sub.3 coating to the chamber
parts.
[0067] According to various embodiments, the intermediate layer or
coating could be of metals, alloys, or ceramics (such as
Y.sub.2O.sub.3, YF.sub.3, ErO.sub.2, SiC, Si.sub.3N.sub.4,
ZrO.sub.2, Al.sub.2O.sub.3, AlN and their combinations or
combination of them with other elements). The second or the top
coating with the surface facing to plasma is the A-coating of
Y.sub.2O.sub.3, YF.sub.3, ErO.sub.2, SiC, Al.sub.2O.sub.3 and their
combinations or combination of them with other materials.
[0068] As quite different from the prior art, according to some
embodiments the A-coating is proposed to be deposited on the
substrate materials that could have at least one element or
component which is also contained in the A-coating, such as the
deposition of A-Y.sub.2O.sub.3 on anodized surface, Al.sub.2O.sub.3
or Y.sub.2O.sub.3 surface. Since the same elements or components
occurred in both the coating and the substrate will result in the
formation of the atomic bonding from the same elements or
components in the interfacial region between the A-coating and the
substrates, which promotes the formation of A-coating with the
increased thickness and the improve adhesion to the substrates or
showerhead.
[0069] It should be understood that processes and techniques
described herein are not inherently related to any particular
apparatus and may be implemented by any suitable combination of
components. Further, various types of general purpose devices may
be used in accordance with the teachings described herein. The
present invention has been described in relation to particular
examples, which are intended in all respects to be illustrative
rather than restrictive. Those skilled in the art will appreciate
that many different combinations will be suitable for practicing
the present invention.
[0070] Moreover, other implementations of the invention will be
apparent to those skilled in the art from consideration of the
specification and practice of the invention disclosed herein.
Various aspects and/or components of the described embodiments may
be used singly or in any combination. It is intended that the
specification and examples be considered as exemplary only, with a
true scope and spirit of the invention being indicated by the
following claims.
* * * * *