U.S. patent application number 15/220652 was filed with the patent office on 2017-02-02 for yttrium-base sprayed coating and making method.
This patent application is currently assigned to Shin-Etsu Chemical Co., Ltd.. The applicant listed for this patent is Shin-Etsu Chemical Co., Ltd.. Invention is credited to Noriaki Hamaya, Yasushi Takai.
Application Number | 20170029628 15/220652 |
Document ID | / |
Family ID | 57886442 |
Filed Date | 2017-02-02 |
United States Patent
Application |
20170029628 |
Kind Code |
A1 |
Takai; Yasushi ; et
al. |
February 2, 2017 |
YTTRIUM-BASE SPRAYED COATING AND MAKING METHOD
Abstract
An yttrium-base sprayed coating is obtained by thermally
spraying yttrium oxide, yttrium fluoride or yttrium oxyfluoride
onto a substrate to form a coating of 10-500 .mu.m thick, and
chemically cleaning the coating with a cleaning liquid of organic
acid, inorganic acid or a mixture thereof until the population of
particles with a size of up to 300 nm becomes no more than 5
particles/mm.sup.2 of the coating surface. The yttrium-base sprayed
coating exhibits high corrosion resistance even in a halogen gas
plasma atmosphere and prevents yttrium-base particles from spalling
off during etching treatment.
Inventors: |
Takai; Yasushi;
(Echizen-shi, JP) ; Hamaya; Noriaki; (Echizen-shi,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Shin-Etsu Chemical Co., Ltd. |
Tokyo |
|
JP |
|
|
Assignee: |
Shin-Etsu Chemical Co.,
Ltd.
Tokyo
JP
|
Family ID: |
57886442 |
Appl. No.: |
15/220652 |
Filed: |
July 27, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C23C 4/185 20130101;
C23C 4/06 20130101; C23C 4/11 20160101; C23C 4/18 20130101; C23C
4/04 20130101; C09D 1/00 20130101 |
International
Class: |
C09D 5/08 20060101
C09D005/08; C23C 4/04 20060101 C23C004/04; C23C 4/11 20060101
C23C004/11; C23C 4/18 20060101 C23C004/18; C09D 1/00 20060101
C09D001/00; H01L 21/67 20060101 H01L021/67 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 31, 2015 |
JP |
2015-151568 |
Claims
1. An yttrium-base sprayed coating comprising at least one compound
selected from the group consisting of yttrium oxide, yttrium
fluoride, and yttrium oxyfluoride and having a thickness of 10 to
500 .mu.m, wherein particles with a size of up to 300 nm are
present on a coating surface in a population of no more than 5
particles per square millimeters.
2. The yttrium-base sprayed coating of claim 1 having a thickness
of 80 to 400 .mu.m.
3. The yttrium-base sprayed coating of claim 1 which is sprayed
onto a surface of a substrate of metallic aluminum, aluminum oxide
or metallic silicon.
4. A method for preparing a yttrium-base sprayed coating,
comprising the steps of: thermally spraying a particulate spray
material comprising at least one compound selected from the group
consisting of yttrium oxide, yttrium fluoride, and yttrium
oxyfluoride to form a yttrium-base sprayed coating having a
thickness of 10 to 500 .mu.m and chemically cleaning a surface of
the coating with a cleaning liquid which is an organic acid aqueous
solution, inorganic acid aqueous solution or organic acid/inorganic
acid aqueous solution until a population of particles with a size
of up to 300 nm is no more than 5 particles per square millimeters
of the coating surface.
5. The method of claim 4 wherein the cleaning liquid is an aqueous
solution of an acid selected from the group consisting of a
monofunctional carboxylic acid, difunctional carboxylic acid,
trifunctional carboxylic acid, hydroxy acid, sulfonic acid, nitric
acid, sulfuric acid, carbonic acid, hydrofluoric acid, and acidic
ammonium fluoride or a mixture thereof.
6. The method of claim 5 wherein in the cleaning liquid, the
monofunctional carboxylic acid is formic acid or acetic acid, the
difunctional carboxylic acid is maleic acid, tartaric acid or
phthalic acid, the trifunctional carboxylic acid is citric acid,
the hydroxy acid is lactic acid, and the sulfonic acid is
methanesulfonic acid.
7. The method of claim 4 wherein the chemical, cleaning step
includes immersing the yttrium-base sprayed coating in the cleaning
liquid to dissolve the coating to a depth of at least 0.01 .mu.m
from its surface for thereby removing particles with a size of up
to 300 nm on the coating surface.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This non-provisional application claims priority under 35
U.S.C. .sctn.119 (a) on Patent Application No. 2015-151568 filed in
Japan on Jul. 31, 2015, the entire contents of which are hereby
incorporated by reference.
TECHNICAL FIELD
[0002] This invention relates to an yttrium-base sprayed coating
formed by thermally spraying yttrium oxide, yttrium fluoride and/or
yttrium oxyfluoride, which is suited as a low dusting coating on
parts and articles used in a corrosive plasma atmosphere as
encountered in a semiconductor device fabrication process.
BACKGROUND ART
[0003] In the prior art process for manufacturing semiconductor
devices, treatment is often carried out in a corrosive halogen-base
gas plasma atmosphere. Typical corrosive halogen-base gases are
fluorine-base gases such as SF.sub.6, CF.sub.4, CHF.sub.3,
ClF.sub.3 and HF and chlorine-base gases such as Cl.sub.2,
BCl.sub.3 and HCl. The equipment used for such treatment typically
includes parts or components having corrosion resistant coatings on
their surface. For example, parts or components having coatings
formed by spraying yttrium oxide (Patent Document 1) and yttrium
fluoride (Patent Documents 2 and 3) to the surface of metallic
aluminum and aluminum oxide ceramic substrates are known to be
fully corrosion resistant and used in practice.
[0004] As the current semiconductor technology aims at higher
integration, the size of interconnections is approaching to 20 nm
or less. In the device fabrication process, yttrium-base particles
may spall off the surface of yttrium-base coatings on the parts
during etching treatment and fall onto silicon wafers to interfere
with the etching treatment. This causes to reduce the manufacture
yield of semiconductor devices. There is a tendency that the number
of yttrium-base particles spalling off the yttrium-base coating
surface is high at the early stage of etching treatment and
decreases with the lapse of etching time. Patent Documents 4 and 5
relating to the spraying technology are also incorporated herein by
reference.
CITATION LIST
[0005] Patent Document 1: JP 4006596 (U.S. Pat. No. 6,852,433)
[0006] Patent Document 2: JP 3523222 (U.S. Pat. No. 6,685,991)
[0007] Patent Document 3: JP-A 2011-514933 (US 20090214825)
[0008] Patent Document 4: JP-A 2008-133528 (U.S. Pat. No.
8,349,450)
[0009] Patent Document 5: JP 4591722 (US 20130122218)
DISCLOSURE OF INVENTION
[0010] An object of the invention is to provide an yttrium-base
sprayed coating which is formed by thermally spraying one or more
compounds selected from among yttrium oxide, yttrium fluoride, and
yttrium oxyfluoride, capable of substantially preventing
yttrium-base particles from spalling off the coating surface during
etching or similar treatment, and thus suited for use as a low
dusting coating on parts or articles used in a corrosive plasma
atmosphere during the semiconductor device fabrication process.
[0011] When a coating of yttrium oxide, yttrium fluoride or yttrium
oxyfluoride is formed by plasma spraying, a particulate material is
melted in a plasma flame into droplets, after which droplets
deposit and solidify on a substrate to form a coating. If the size
of material particles is too small,, some particles may not enter
the flame, but deposit on the coating in the unmelted state. Also,
once particles are melted, sometimes droplets may burst on the
coating into finer droplets, which will deposit on the coating as
finer particles. Such fine (unmelted or burst)
[0012] particles which deposit on the coating surface in the course
of spraying are covered with the following droplets and thus
integrated into a dense coating, whereas foreign particles which
deposit on the coating surface near the end of spraying remain
bonded as such. It is difficult to remove the bonded particles by
ultrapure water cleaning, ultrasonic cleaning or the like. If fine
particles spall off during etching treatment, they become a source
of dusting. Patent Document 5 proposes physical removal of sticky
particles (i.e., particles which are not removable by ultrapure
water cleaning or ultrasonic cleaning) by polishing or blasting.
However, physical removal such as polishing is not so effective
because the treatment itself generates fine particles.
[0013] The inventors have found that an improved yttrium-base
sprayed coating is obtained by thermally spraying one or more
compounds selected from among yttrium oxide, yttrium fluoride, and
yttrium oxyfluoride to form a coating of 10 to 500 .mu.m thick, and
chemically cleaning the coating with a cleaning liquid in the form
of an aqueous solution of organic acid or inorganic acid or a
mixture thereof for effectively removing yttrium-base particles
anchored to the coating surface until the population of particles
having a size of up to 300 nm becomes no more than 5
particles/mm.sup.2 of the coating surface. Since the resulting
yttrium-base sprayed coating prevents yttrium-base particles from
spalling off to cause a failure during subsequent etching
treatment, it is suitable for use as a low dusting coating on parts
and articles used in a corrosive plasma atmosphere in the
semiconductor device fabrication process.
[0014] In one aspect, the invention provides an yttrium-base
sprayed coating comprising one or more compounds selected from the
group consisting of yttrium oxide, yttrium fluoride, and yttrium
oxyfluoride and having a thickness of 10 to 500 .mu.m, wherein
particles with a size of up to 300 nm are present on a coating
surface in a population of no more than 5 particles per square
millimeters.
[0015] Preferably the yttrium-base sprayed coating has a thickness
of 80 to 400 .mu.m.
[0016] Typically the yttrium-base sprayed coating is sprayed onto a
surface of a substrate of metallic aluminum, aluminum oxide or
metallic silicon.
[0017] In another aspect, the invention provides a method for
preparing a yttrium-base sprayed coating, comprising the steps of
thermally spraying a particulate spray material comprising at least
one compound selected from the group consisting of yttrium oxide,
yttrium fluoride, and yttrium oxyfluoride to form a yttrium-base
sprayed coating having a thickness of 10 to 500 .mu.m and
chemically cleaning a surface of the coating with a cleaning liquid
which is an organic acid aqueous solution, inorganic acid aqueous
solution or organic acid/inorganic acid aqueous solution until a
population of particles with a size of up to 300 nm is no more than
5 particles per square millimeters of the coating surface.
[0018] The cleaning liquid is preferably an aqueous solution of an
acid selected from the group consisting of a monofunctional
carboxylic acid, difunctional carboxylic acid, trifunctional
carboxylic acid, hydroxy acid, sulfonic acid, nitric acid, sulfuric
acid, carbonic acid, hydrofluoric acid, and acidic ammonium
fluoride or a mixture thereof. Typically, the monofunctional
carboxylic acid is formic acid or acetic acid, the difunctional
carboxylic acid is maleic: acid, tartaric acid or phthalic acid,
the trifunctional carboxylic acid is citric acid, the hydroxy acid
is lactic acid, and the sulfonic acid is methanesulfonic acid.
[0019] In a preferred embodiment, the chemical cleaning step
includes immersing the yttrium-base sprayed coating in the cleaning
liquid to dissolve the coating to a depth of at least. 0.01 .mu.m
from its surface for thereby removing particles with a size of up
to 300 nm on the coating surface.
ADVANTAGEOUS EFFECTS OF INVENTION
[0020] The yttrium-base sprayed coating of the invention exhibits
high corrosion resistance during treatment in a corrosive
halogen-base gas plasma atmosphere, and prevents dusting as a
result of yttrium-base particles spalling off during etching or
similar treatment in the semiconductor device fabrication process,
which is effective for improving the fabrication yield of
semiconductor devices. The yttrium-base sprayed coating is thus
suitable for use as a low dusting coating on parts and articles
which are exposed to a corrosive plasma atmosphere.
BRIEF DESCRIPTION OF DRAWINGS
[0021] FIGS. 1, 2, 3 and 4 are SEM images of the surface of
yttrium-base sprayed coatings in Examples 1, 2, 3 and 4,
respectively.
[0022] FIGS. 5 and 6 are SEM images of the surface of yttrium-base
sprayed coatings in Comparative Examples 1 and 2, respectively.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0023] The yttrium-base sprayed coating of the invention is formed
by thermally spraying one or more compounds selected from among
yttrium oxide, yttrium fluoride, and yttrium oxyfluoride.
[0024] Thermal spraying to a substrate is desirably atmospheric
plasma spraying or vacuum plasma spraying. The plasma gas used
herein may be nitrogen/hydrogen, argon/hydrogen, argon/helium,
argon/nitrogen, argon alone, or nitrogen gas alone, but not limited
thereto. Examples of the substrate subject to thermal spraying
include, but are not limited to, substrates of stainless steel,
aluminum, nickel, chromium, zinc, and alloys thereof, metal
silicon, aluminum oxide, aluminum nitride, silicon nitride, silicon
carbide, and quartz, glass when parts or components of the
semiconductor fabrication equipment are contemplated. The
conditions under which yttrium oxide, yttrium fluoride or yttrium
oxyfluoride is thermally sprayed are not particularly limited. The
thermal spraying conditions may be determined as appropriate
depending on the identity of substrate, the particle size and
composition of spray material, and a particular application of the
resulting sprayed component.
[0025] For example, when an yttrium oxide coating is formed on a
metal aluminum substrate, it may be deposited by argon/hydrogen
atmospheric plasma spraying using yttrium oxide powder having an
average particle size D50 of about 20 .mu.m and a gas mixture of 40
L/min of argon and 5 L/min of hydrogen. The thermal spraying
conditions including a spray distance, current value and voltage
value may be determined as appropriate depending on a particular
application of the sprayed component. Likewise, the feed rates of
argon and hydrogen gases may be suitably adjusted.
[0026] The sprayed coating, i.e., yttrium-base sprayed coating
should have a thickness of 10 to 500 .mu.m. A coating of less than
10 .mu.m thick may be less corrosion resistant or allow the
substrate surface to be partly exposed in the cleaning step to be
described below. A coating of more than 500 .mu.m thick may simply
add to the cost because no further improvement in corrosion
resistance is expectable. The thickness of the coating is
preferably 80 to 400 .mu.m, more preferably 100 to 400 .mu.m, and
even more preferably 100 to 300 .mu.m.
[0027] According to the invention, the surface of the yttrium-base
sprayed coating is then cleaned with a preselected cleaning liquid
to remove yttrium-base particles anchored thereto until the
population (or number) of yttrium-base particles with a size of up
to 300 nm becomes no more than 5 particles/square millimeters
(mm.sup.2) of the coating surface. It is, of course, most preferred
that the population of yttrium-base particles with a size of up to
300 nm on the coating surface be 0. As long as the population is no
more than 5 particles/mm.sup.2, dusting to such an extent as to
invite a substantial loss of production yield does not occur during
etching treatment in the semiconductor device fabrication process.
As used herein, the "size" of yttrium-base particles refers to the
maximum diameter of individual particles measured by microscopy
under a scanning electron microscope (SEM) or the like. As seen
from the images of FIGS. 5 and 6, no or only a few particles with a
size in excess of 300 nm are present on the sprayed coating
surface. Removal of particles with a size of up to 300 nm means
removal of substantially all inhibitory particles.
[0028] The cleaning liquid is an aqueous solution of organic acid,
aqueous solution of inorganic acid or aqueous solution of mixed
organic: and inorganic acids. The organic acid is not particularly
limited as long as it is water-soluble. Suitable organic acids
include, but are not limited to, monofunctional carboxylic acids
such as formic acid and acetic acid, difunctional carboxylic acids
such as maleic acid, tartaric acid and phthalic acid, trifunctional
carboxylic acids such as citric acid, hydroxy acids such as lactic
acid, and sulfonic acids such as methanesulfonic acid. Inter alia,
tartaric acid and citric acid are preferred because they are
edible, nontoxic and easy to handle. The inorganic acid is not
particularly limited as long as it is water-soluble. Suitable
inorganic acids include nitric acid, sulfuric acid, carbonic acid,
hydrofluoric acid, and acidic ammonium fluoride.
[0029] The cleaning technique is not particularly limited.
Preferably, a part or component in the form of a substrate having
the yttrium-base sprayed coating formed on its surface is wholly
immersed in the cleaning liquid because this technique is effective
and efficient. For those substrates of metallic aluminum and
silicon which are readily dissolved in acid, the area of the
substrate that should avoid corrosion with acid is desirably masked
with resin tape or sheet when a strong acid is used for cleaning.
Cleaning without masking is possible when a weak organic acid is
used for cleaning, for example, a carboxylic acid or hydroxy acid
such as phthalic acid, tartaric acid or citric acid. For those
substrates of quart glass or Al.sub.2O.sub.3 ceramics which are
acid resistant, cleaning without masking is possible even with a
strong acid solution such as nitric acid. In some cases, a buffer
solution based on a combination of acid and salt may be used as the
cleaning liquid.
[0030] The yttrium-base sprayed coating is chemically cleaned with
the cleaning liquid to dissolve a thin layer from the coating
surface for removing particles with a size of up to 300 nm which
become a source of dusting. The dissolution depth is preferably at
least 0.01 .mu.m from the original coating surface. Although the
upper limit of dissolution depth is not critical, the dissolution
depth is preferably up to 20 .mu.m. More preferably the dissolution
depth is 1 to 20 .mu.m from the coating surface. A dissolution
depth of less than 0.01 .mu.m may be insufficient to remove
particles with a size of up to 300 nm and fail to reach a
population of no more than 5 particles/mm.sup.2. A dissolution
depth in excess of 20 .mu.m may simply make the coating thinner
without further improvements in particle removal.
[0031] After cleaning, the coating is rinsed with ultrapure water
to thoroughly remove the acid and dried in vacuum or under
atmospheric pressure.
[0032] When a secondary electron image (magnification .times.10,000
or more) of the dry coating surface is observed under SEM,
yttrium-base particles having a size of up to 300 nm on the coating
surface are detectable. According to the invention, yttrium-base
particles are removed from the coating surface by the cleaning step
until the population of particles reaches no more than 5
particles/mm.sup.2 of the surface.
EXAMPLE
[0033] Examples are given below by way of illustration and not by
way of limitation.
Examples 1 to 4 and Comparative Examples 1 and 2
Preparation of Sprayed Coating
[0034] An yttrium-base sprayed coating was obtained by thermally
spraying the coating material shown in Table 1 onto a surface of a
substrate of the material shown in Table 1, immersing the coated
substrate in a cleaning liquid, which was an aqueous solution of
the cleaning agent shown in Table 1, to clean the coating surface,
thoroughly rinsing with ultrapure water, and vacuum drying. The
surface of the yttrium-base coating thus obtained was observed
under SEM, and yttrium-base particles having a size of up to 300 nm
on the surface were inspected and counted. The results are shown in
Table 1 and SEM images are shown in FIGS. 1 to 6. Notably, the
yttrium-base sprayed coating was formed by atmospheric plasma
spraying using a gas mixture of 40 L/min of argon and 8 L/min of
hydrogen.
TABLE-US-00001 TABLE 1 Example Comparative Example 1 2 3 4 1 2
Spray material Y.sub.2O.sub.3 Y.sub.2O.sub.3 + YF.sub.3 YF.sub.3
YOF Y.sub.2O.sub.3 YF.sub.3 Coating thickness, 200 300 100 200 200
200 .mu.m Substrate material Al Al.sub.2O.sub.3 Si Al Al Al
Cleaning Cleaning agent tartaric citric hydrofluoric lactic no no
conditions acid acid acid + acid cleaning cleaning acidic ammonium
fluoride Concentration, 2 1 0.05 + 0.1 2 -- -- mol/L Temperature,
.degree. C. 30 50 30 50 -- -- Time, hr 4 12 0.5 12 -- --
Dissolution 2 20 2 10 -- -- depth, .mu.m Particle population 0 0 0
0 numerous numerous on surface (particles/mm.sup.2) SEM image FIG.
1 FIG. 2 FIG. 3 FIG. 4 FIG. 5 FIG. 6
[0035] As is evident from Table 1 and FIGS. 1 to 6, the
yttrium-base sprayed coatings in Examples 1 to 4 bear no particles
on their surface whereas numerous particles are on the yttrium-base
sprayed coatings in Comparative Examples 1 and 2 which omit
cleaning with an aqueous solution of acid or cleaning agent. It is
readily presumed that these particles cause dust generation during
etching treatment. When parts or components having yttrium-base
sprayed coatings of Examples 1 to 4 deposited thereon are used,
dusting as a result of yttrium-base particles spalling off during
etching treatment in a semiconductor device fabrication process is
substantially prevented. This will eventually improve the
fabrication yield of semiconductor devices.
[0036] Japanese Patent Application No. 2015-151568 is incorporated
herein by reference.
[0037] Although some preferred embodiments have been described,
many modifications and variations may be made thereto in light of
the above teachings. It is therefore to be understood that the
invention may be practiced otherwise than as specifically described
without departing from the scope of the appended claims.
* * * * *