U.S. patent application number 14/273426 was filed with the patent office on 2014-08-28 for coating of shield surfaces in deposition systems.
This patent application is currently assigned to SEMATECH, INC.. The applicant listed for this patent is ASAHI GLASS CO., LTD., SEMATECH, INC.. Invention is credited to Vibhu Jindal, Junichi Kageyama.
Application Number | 20140242501 14/273426 |
Document ID | / |
Family ID | 48903187 |
Filed Date | 2014-08-28 |
United States Patent
Application |
20140242501 |
Kind Code |
A1 |
Jindal; Vibhu ; et
al. |
August 28, 2014 |
Coating Of Shield Surfaces In Deposition Systems
Abstract
A deposition chamber shield having a stainless steel coating of
from about 100 microns to about 250 microns thick wherein the
coated shield has a surface roughness of between about 300
microinches and about 800 microinches and a surface particle
density of less than about 0.1 particles/mm.sup.2 of particles
between about 1 micron and about 5 microns in size and no particles
below about 1 micron in size, and process for production thereof is
disclosed.
Inventors: |
Jindal; Vibhu; (Albany,
NY) ; Kageyama; Junichi; (Yokohama, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SEMATECH, INC.
ASAHI GLASS CO., LTD. |
Albany
Tokyo |
NY |
US
JP |
|
|
Assignee: |
SEMATECH, INC.
Albany
NY
ASAHI GLASS CO., LTD.
Tokyo
|
Family ID: |
48903187 |
Appl. No.: |
14/273426 |
Filed: |
May 8, 2014 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
13365070 |
Feb 2, 2012 |
8734907 |
|
|
14273426 |
|
|
|
|
Current U.S.
Class: |
430/5 ;
204/298.11; 204/298.16 |
Current CPC
Class: |
C23C 14/564 20130101;
B82Y 40/00 20130101; C23C 14/35 20130101; B82Y 10/00 20130101; G03F
1/22 20130101; C23C 14/34 20130101; G03F 1/60 20130101 |
Class at
Publication: |
430/5 ;
204/298.11; 204/298.16 |
International
Class: |
C23C 14/56 20060101
C23C014/56; G03F 1/22 20060101 G03F001/22; C23C 14/35 20060101
C23C014/35 |
Claims
1. A coated deposition chamber shield, comprising: a shield having
a stainless steel coating wherein the coated shield has a surface
roughness of between about 300 microinches and about 800
microinches and a surface particle density of less than about 0.1
particles/mm.sup.2 of particles between about 1 micron and about 5
microns in size and no particles below about 1 micron in size.
2. The coated deposition chamber shield of claim 1, wherein the
coated shield comprises a stainless steel shield.
3. A deposition method for the production of EUVL mask blank,
comprising providing in a deposition chamber the coated shield of
claim 1 and depositing a layer on the blank.
4. An EUVL mask blank comprising the layer deposited by the method
of claim 3.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. patent application
Ser. No. 13/365,070, titled "Coating Of Shield Surfaces In
Deposition Systems," filed Feb. 2, 2012, which is hereby
incorporated by reference in its entirety.
FIELD
[0002] The present disclosure relates to stainless steel coated
deposition system shields, and in particular, deposition system
shields coated with stainless steel having a high surface roughness
and low particle residue, and methods for the production and use
thereof.
BACKGROUND
[0003] A substrate deposition system may be used to process a
substrate with an energized gas, such as plasma. Typically, the
system includes a deposition chamber which encloses a process zone
into which a gas is introduced, a gas energizer to energize the
gas, a target which provides a source of material and an exhaust to
remove the energized gas. The deposition chamber may, for example,
be used to deposit material on the substrate.
[0004] The chamber components exposed to the energized gas and
sputtered material are often covered with removable shields which
protect the surface of the chamber components from the sputtered
residues used to deposit material on the substrate. The sputtered
material coats the shields during use and unless the shields are
removed and replaced, the layer can reach a thickness such that
particles begin to flake off and contaminate the process chamber.
In subsequent processing cycles, the deposited process residues can
flake off of the shield surfaces and fall upon and contaminate the
substrate. Therefore, the shields must be frequently and
periodically removed and cleaned of surface residue. Manufacturers
often use sandblasting to roughen the shield, which allows them to
run the sputtering chamber for longer periods of time without a
shield change, reducing the down time of process equipment.
However, sandblasting leaves particle residue on the surface of the
shields which can increase the chances of contamination of the
substrate.
[0005] U.S. Patent Application Publication No. 2002/0090464 to
Jiang et al. relates to a method for preparing a shield for use in
physical vapor deposition systems. Initially, a base plate material
is shaped to fit inside the physical vapor deposition chamber. The
surface of the shield is then degreased with moderate acid etch to
prepare for roughening by sand or grit blasting. The grit blasting
typically provides an initial surface texture with a roughness
value (R.sub.a) up to 250 microinches. The shield is then cleaned
and a coating layer between about 0.005 inch to 0.002 inch in
thickness is applied by a thermal spraying process, such as thermal
arc spraying to produce a surface roughness (R.sub.a) typically in
the range of 400 microinches to 1200 microinches. After deposition,
the shield is cleaned in an ultrasonic bath and blasted with
pressurized air and then baked.
[0006] Thus, it is desirable to provide a coated shield which
minimizes the amount of flake off of process residue. It is further
desirable to provide a coated shield having a high surface
roughness and low particle residue to deposit low defect films on
substrates and process a larger number of substrates in the chamber
while reducing the frequency of chamber downtime for cleaning and
replacing of shields.
SUMMARY
[0007] One aspect of the present invention provides a method for
coating a deposition chamber shield, including: a) providing a
deposition shield having a primed surface, b) coating the primed
shield surface with a stainless steel coating having a thickness of
from about 100 microns to about 250 microns, and c) cleaning the
coated surface to remove loose particles to provide a stainless
steel coated shield having a surface roughness of between about 300
microinches and about 800 microinches and a surface particle
density of less than about 0.1 particles/mm.sup.2 of particles
between about 1 micron and about 5 microns in size and no particles
below about 1 micron in size.
[0008] Another aspect of the present invention provides a coated
deposition chamber shield, including: a shield having a stainless
steel coating wherein the coated shield has a surface roughness of
between about 300 microinches and about 800 microinches and a
surface particle density of less than about 0.1 particles/mm.sup.2
of particles between about 1 micron and about 5 microns in size and
no particles below about 1 micron in size.
[0009] Another aspect of the present invention provides a EUVL mask
blank and a deposition method including providing in a deposition
chamber the coated shield and depositing a layer on the EUVL mask
blank.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] These and other aspects of the present invention will become
apparent upon a review of the following detailed description,
accompanying claims, and appended drawings, which illustrate
examples of the invention, where:
[0011] FIG. 1 is a schematic side view of an embodiment of a used
shield in accordance with the present invention;
[0012] FIG. 2 is a schematic side view of the shield of FIG. 1
following grit blasting to roughen the surface to between 100 and
200 microinches and showing embedded grit particles after a
conventional cleaning process;
[0013] FIG. 3 is a schematic side view of the primed shield of FIG.
2 undergoing stainless steel coating to cover the embedded grit
particles;
[0014] FIG. 4 is a schematic side view of the shield of FIG. 3
undergoing a post coating cleaning process to remove surface
particles showing a roughened and cleaned shield surface;
[0015] FIG. 5 is pair of SEM images of a shield surface cleaned
with a conventional cleaning process according to Comparative
Example A;
[0016] FIG. 6 is an SEM image of a shield surface stainless steel
("SS") coated according to Example 1 of the present invention;
[0017] FIG. 7 is an SEM image of a shield surface SS coated
according to Example 1 of the present invention; and
[0018] FIG. 8 is an SEM image of a shield surface cleaned with
conventional cleaning process according to Comparative Example
A.
DETAILED DESCRIPTION
[0019] During the sputtering process, such as manufacturing for
mask blank for extreme ultraviolet lithography ("EUVL"), material
is deposited on the substrate as well as the shields used to
protect the deposition chamber surfaces. Materials adhere to the
shield surfaces and over time tend to flake off the shields onto
the substrates and contaminate the substrates. To minimize
contamination from the shields, the shields are periodically
removed and cleaned.
[0020] The present invention relates to a process for coating
pre-cleaned shield surfaces with stainless steel. Preferably, the
shields are made of stainless steel. The stainless steel coated
shield has a surface roughness of between about 300 microinches and
about 800 microinches and a surface particle density of less than
about 0.1 particles/mm.sup.2 of particles between about 1 micron
and about 5 microns in size. Preferably, the surface roughness is
between about 400 microinches and about 600 microinches, more
preferably between about 450 microinches and about 550 microinches,
particularly preferably between about 480 microinches and about 520
microinches, and more particularly preferably about 500
microinches. Preferably the surface has no particle residue below
about 1 micron in size. The stainless steel coating can be applied
by techniques known in the art such as by thin wire arc spray
process, plasma spray and thermal spray process.
[0021] When the surface roughness of shields that have been
previously cleaned and coated with a layer of material is less than
about 300 microinches, the defects coming from the shields and
deposition on the shields are increased. The deposition film growth
of deposited material on shields will cause stress buildup with
time. The stress is relieved by cracking of the thin film
deposition which causes particle generation. The roughness of the
surface area can be increased to avoid film cracking The high
surface roughness of the shield surface does not let stress build
up as the deposited thin film is discontinuous. However, when the
surface roughness of the shields is increased to more than about
800 microinches, the defects coming from the shields and depositing
on the substrate are increased due to particles, such as
Al.sub.2O.sub.3, that reside on the shields as a result of the grit
blasting process to generate such a high surface roughness shield
surface. Coating a layer of material on the surface is not
sufficient to prevent these large particles from dislodging.
[0022] Surface roughness is defined as R.sub.a which is the
arithmetic average of the absolute values of the collected
roughness data points. These values characterize the surface based
on the vertical deviations of the roughness profile from the mean
line. The average roughness, R.sub.a, is expressed in units of
height, which is typically expressed in "millionths" of an inch and
is also referred to as "microinches". The surface roughness for
such high roughness can be determined by electronic gauges, e.g.,
Mitutoyo Surftest SJ-201, where a stylus records the vertical
movement along the surface measuring the displacement. The vertical
displacement of the stylus is further amplified, recorded and
processed to calculate the roughness value.
[0023] The pre-cleaning of the shields prior to the coating process
can be achieved by processes known in the art. The pre-cleaning
process provides a shield surface suitable for coating with
stainless steel. A shield having a surface suitable for accepting a
stainless steel coating is referred to herein as a primed shield. A
primed shield has a surface that has been sufficiently cleaned to
remove residue that would inhibit adherence of coating material.
The residues removed include deposition from previous processes,
oil, grease, contaminants due to handling, shipping, etc. A primed
shield preferably has a surface roughness of between about 100
microinches and about 200 microinches, preferably at least about
150 microinches, and has little particle residue left on the
surface after various etching and cleaning techniques. A suitable
method for cleaning a shield to provide a primed shield is
disclosed in U.S. patent application entitled "Process for Cleaning
Shield Surfaces in Deposition Systems" by Jindal et al., filed
concurrently herewith, which is hereby incorporated by reference in
its entirety.
[0024] Initially, as shown in FIG. 1, there is provided a used
shield in need of restoration. FIG. 2 is a schematic side view of
the used shield of FIG. 1 showing embedded grit particles following
grit blasting to remove deposition residue and roughen the surface
to between about 100 microinches and about 200 microinches and
after a conventional cleaning process. Thus, the primed shield of
FIG. 2 has a surface in which the deposition residue has been
removed and the surface is suitable to accept a coating.
Optionally, the surface of the primed shield may be treated with
adhesion promoters to facilitate adhesion of the coating. Masking
can be applied to the shield portions that are not desired to be
coated.
[0025] FIG. 3 is a schematic side view of the primed shield of FIG.
2 undergoing stainless steel coating to cover the embedded grit
particles. The stainless steel coating is applied to the unmasked
portions by conventional processes, such as thin wire arc spray or
plasma spray. The coating is applied to provide a thickness of from
about 100 microns to about 250 microns, preferably from about 110
microns to about 150 microns, more preferably from about 115
microns to about 135 microns. Coatings having a thickness of less
than about 100 microns are too thin and tend to crack during
subsequent use of the shields. The cracking of films can cause
particle generation which is not desired as they become deposited
on the target as surface defects. Coatings having a thickness of
from about 100 microns to about 250 microns have a thickness
sufficient to cover all surface particles. Coatings having a
thickness of greater than about 250 microns exhibit flaking which
can cause particle generation. During application of the stainless
steel coating, the surface roughness is adjusted to between about
300 microinches and about 800 microinches, preferably between about
400 microinches and about 600 microinches, more preferably between
about 450 microinches and about 550 microinches, and particularly
preferably about 500 microinches.
[0026] FIG. 4 is a schematic side view of the shield of FIG. 3
undergoing a post coating cleaning process, which includes at least
one of a chemical cleaning, wash, and ultrasonication, to remove
surface particles showing a roughened and cleaned coated shield
surface. In accordance with one embodiment, the mask coating is
removed and the coated shield parts are exposed to a high pressure
water rinse, preferably at a temperature of between about
50.degree. C. and about 80.degree. C., a pressure of from about 1
kPa to about 5 kPa, and for a time of from about 10 minutes to
about 50 minutes, more preferably at a pressure of about 2 kPa for
a rinse time of about 30 minutes at a temperature of about
50.degree. C. The coated shield parts can then be exposed to a
chemical clean. Suitable chemical clean solutions include an acid
clean, a basic clean, and combinations thereof. Suitable acidic
clean solutions include aqueous solutions of HNO.sub.3+HF,
preferably an approximately 0.5% HNO.sub.3+0.5% HF+H.sub.2O
solution. Suitable basic clean solutions include aqueous solutions
of KOH+KMnO.sub.4 solution, preferably an approximately 15 to 25%
KOH+20 to 35% KMnaO.sub.4+H.sub.2O solution. Preferably, the
shields are exposed to the chemical clean solutions for a dip time
of between about 30 seconds and about 30 minutes. The dip time can
extend beyond 30 minutes so long as the coating is not excessively
etched. The chemically cleaned shield parts are then exposed to a
high pressure water rinse under the conditions noted above. The
shield parts can then be ultrasonicated, preferably for a suitable
time at a setting of from about 1 kHz to about 1 GHz, more
preferably for about 5 minutes at about 5 kHz and for about 5
minutes at about 20 kHz. The different cleaning methods, are used
alone or combined to preferably ensure that no particle residue is
left on top of the coating surface as a result of coating process
or handling. The process provides stainless steel coated shields
having a surface roughness of between about 300 microinches and
about 800 microinches and a surface particle density of less than
about 0.1 particles/mm.sup.2 of particles between about 1 micron
and about 5 microns in size with no particle residue below about 1
micron on the surface. The coated shield parts are optionally
vacuum baked and can be packed for storage or shipping.
[0027] The SS coated shields of the present invention are useful in
applications where low particle residue is important, e.g., mask
blank manufacturing for EUVL. The present invention provides SS
coated shields having the following qualities: (a) 300 micoinches
or higher roughness, (b) little or no particle residue, (c) a
strongly adhered stainless steel shield surface, (d) does not
generate particles under ion beam deposition, and (e) can be
cleaned by simple processes that restore surfaces to their original
condition. In contrast, different coating materials on shield
surfaces were investigated, including arc-sprayed Al,
Al.sub.2O.sub.3 and Y.sub.2O.sub.3. Although the conventional
arc-sprayed Al coating on shield surfaces achieved very high
roughness, effectively reducing Si-related defects, particles
generated by the Al coatings during deposition were problematic and
offset any overall improvement in total defect counts.
[0028] A mask blank is a laminate before patterning, to be used for
the production of a photomask. An EUV mask blank has a structure
wherein a reflective layer to reflect EUV light and an absorber
layer to absorb EUV light are formed in this order on a substrate
made of, e.g., glass. As the reflective layer, a Mo/Si multilayer
reflective film is usually employed wherein a molybdenum (Mo) film
as a low refractive index layer and a silicon (Si) film as a high
refractive index layer are alternately laminated to increase the
light reflectance when the layer surface is irradiated with EUV
light.
[0029] For the absorber layer, a material having a high EUV light
absorption coefficient, specifically a material containing chromium
(Cr) or tantalum (Ta) as the main component, is employed.
[0030] A protective layer is usually formed between the reflective
layer and the absorber layer. Such a protective layer is provided
for the purpose of protecting the reflective layer so that the
reflective layer will not be damaged by the etching process carried
out for the purpose of forming a pattern in the absorber layer.
Accordingly, for the protective layer, it is preferred to employ a
material not susceptible to influence by the etching process.
Further, the protective layer is required not to lower the
reflectance of EUV ray, since the reflective layer of the mask
blank is irradiated with EUV light in a state where the protective
layer is formed. For these reasons, as the constituting material
for the protective layer, Ru or a Ru compound (such as RuB, RuNb or
RuZr) is preferred.
[0031] In the production of an EUV mask blank, a sputtering method
is preferably employed for the formation of the Mo/Si multilayer
reflective film, the protective layer and the absorber layer in
order that a uniform film thickness can easily be obtained, the
takt time is short, the film thickness can easily be controlled,
etc. For the formation of the Mo film and the Si film constituting
the Mo/Si multilayer reflective film, and the protective layer, an
ion beam sputtering method is preferably used, and for the
formation of the absorber layer, a magnetron sputtering method is
preferably employed.
[0032] The sputtering method is a film-forming method wherein a
sputtering target surface is bombarded by charged particles to beat
out sputtered particles from the target so that the sputtered
particles are deposited on a substrate disposed to face the target
thereby to form a thin film. For a sputtering target to be used for
such a film forming method, it is common to apply a structure
wherein a target main body made of a film-forming material is held
by a substrate so-called a backing plate.
EXAMPLES
[0033] The invention will be further illustrated with reference to
the following specific examples. It is understood that these
examples are given by way of illustration and is not meant to limit
the disclosure or the claims to follow.
Comparative Example A
[0034] Used stainless steel shield parts were cleaned by the
following conventional chemical cleaning treatment process. The
shield parts were grit blasted with 80 grit size under a pressure
of 30 psi. The grit surface residue was then blown off with dry
air. The shield parts were then immersed in HCl (20%) for 5
minutes. After spray rinse with de-ionized water, the parts were
blown dry with dry air. The cleaned shields had a surface roughness
of from 125 to 150 microinches with a surface particle density of
100 particles/mm.sup.2. FIG. 5 shows a pair of SEM images and FIG.
8 shows an SEM image of shield surfaces cleaned with a conventional
cleaning process according to Comparative Example A.
Comparative Example B
[0035] Used stainless steel shield parts were cleaned to provide a
primed surface after which they were coated with Aluminum (Al) by
an arc-spray process. The shield parts that had been used in a
deposition process before were removed and pre-cleaned by a grit
blast process with 80 grit size followed by chemical etching of the
surface to remove loose particles. The surface roughness of the
primed shields was found to be 150 microinches. The shields were
then masked to provide the Al coating. An arc spray process was
used to put an Al coating of 100 microns having a surface roughness
of more than about 650 microinches. The mask coating was then
removed. The shield surface with coating was then cleaned with a
high pressure water rinse at 2 kPa for 30 minutes. The shield parts
were then dipped in a 0.5% HNO.sub.3+0.5% HF+H.sub.2O solution for
15 minutes. The shield parts were then again exposed to a high
pressure water rinse as that noted above. The shield parts were
ultrasonicated for 5 minutes at 5 kHz and then for 5 minutes at 20
kHz. This process provided shields having a surface roughness of
about 550 microinches and a surface particle density of 100
particles/mm.sup.2. The shield parts were then vacuum baked and
packed.
Example 1
[0036] Coating of primed shields with stainless steel--Stainless
steel shields that had been used in a deposition process were
removed from the deposition chamber and pre-cleaned to provide
primed shields. Masking was applied to the primed shields in
preparation for the stainless steel coating. The coating was
applied by a thin wire arc spray process to provide a stainless
steel coating having a thickness of 100 microns and a surface
roughness of from 450 to 550 microinches. The coating process
leaves particle residue on top of the surface, thus the post
cleaning of the coating is desired to remove the loose particles
sitting on top of the coated surface. The mask coating was removed
and shield parts were then exposed to a high pressure water rinse
at a pressure of 2 kPa for a rinse time of 30 minutes. The shield
parts were then dipped in a 0.5% HNO.sub.3+0.5% HF+H.sub.2O
solution for 15 minutes. The shield parts were then again exposed
to a high pressure water rinse as that noted above. The shield
parts were ultrasonicated for 5 minutes at 5 kHz and then for 5
minutes at 20 kHz. This process provided shields having a surface
roughness of about 500 microinches and a surface particle density
of less than about 0.1 particles/mm.sup.2 of particles between
about 1 micron and about 5 microns in size and no particles below
about 1 micron in size. The shield parts were then vacuum baked and
packed. FIG. 6 shows a pair of SEM images and FIG. 7 shows an SEM
image of stainless steel coated shield surfaces according to
Example 1.
Example 2
[0037] The restored shields of Comparative Example A and Example 1
were each placed in separate deposition chambers. 150 EUVL mask
blanks were produced in each chamber. These blanks for each chamber
were examined for defects and the ratio of the average defect count
per target for shields prepared in Comparative Example A compared
to those coated in Example 1 was determined to be a ratio of about
6.4 to 1.
Example 3
[0038] The restored shields of Comparative Example B and Example 1
were each placed in separate deposition chambers. 150 EUVL mask
blanks were produced in each chamber. These blanks for each chamber
were examined for defects and the ratio of the average defect count
per target for shields coated in Comparative Example B compared to
those coated in Example 1 was determined to be a ratio of about 4.6
to 1. The coated shields of Example B generated more particles than
those of Example 1 as the aluminum coating was easier to sputter as
compared to stainless steel, thus generating more particles during
the deposition process. Additionally the deposition material
provided better adherence to the stainless coatings as compared to
the aluminum coatings generating less particle defects.
[0039] Developing stainless steel arc-sprayed coatings on a
stainless steel shield surface proved the best solution to maintain
the surface roughness of the shields as compared to coating the
shields with Al coatings, which produced particle defects from the
use of Al coated shields in deposition systems. The arc-spray
deposited stainless steel coatings provided very high roughness
(higher than 500 microinches) as shown in FIG. 3. The adherence of
the coating with the shield surface was found to be excellent.
Since the coating material was hard, aggressive post-cleaning
processes were implemented, leaving little particle residue on the
coating surface, as shown in FIG. 4. Additionally, during use of
the shields of the present invention, the Mo and Si deposition also
adhered well to the stainless steel coatings, which reduced flaking
and particle generation.
[0040] While the invention has been described with preferred
embodiments, it is to be understood that variations and
modifications are to be considered within the purview and the scope
of the claims appended hereto.
* * * * *