U.S. patent application number 13/971889 was filed with the patent office on 2014-02-27 for rare earth element oxyflouride powder spray material and sprayed article.
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 | 20140057078 13/971889 |
Document ID | / |
Family ID | 50148226 |
Filed Date | 2014-02-27 |
United States Patent
Application |
20140057078 |
Kind Code |
A1 |
Hamaya; Noriaki ; et
al. |
February 27, 2014 |
RARE EARTH ELEMENT OXYFLOURIDE POWDER SPRAY MATERIAL AND SPRAYED
ARTICLE
Abstract
A spray material comprising rare earth element oxyfluoride
particles having an aspect ratio of up to 2, an average particle
size of 10-100 .mu.m, and a bulk density of 0.8-2 g/cm.sup.3, and
containing not more than 0.5 wt % of carbon and 3-15 wt % of oxygen
is suitable for air plasma spraying. An article having a sprayed
coating of rare earth element oxyfluoride has high resistance
against plasma etching and a long lifetime.
Inventors: |
Hamaya; Noriaki;
(Echizen-shi, JP) ; Takai; Yasushi; (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: |
50148226 |
Appl. No.: |
13/971889 |
Filed: |
August 21, 2013 |
Current U.S.
Class: |
428/148 ;
428/402 |
Current CPC
Class: |
C09D 5/18 20130101; Y10T
428/24413 20150115; C23C 4/134 20160101; C23C 4/11 20160101; Y10T
428/2982 20150115 |
Class at
Publication: |
428/148 ;
428/402 |
International
Class: |
C09D 5/18 20060101
C09D005/18 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 22, 2012 |
JP |
2012-183302 |
Claims
1. A spray material comprising rare earth element oxyfluoride
particles having an aspect ratio of up to 2, an average particle
size of 10 to 100 .mu.m, and a bulk density of 0.8 to 2 g/cm.sup.3,
and containing not more than 0.5% by weight of carbon and 3 to 15%
by weight of oxygen.
2. The spray material of claim 1 wherein the rare earth element is
one or more elements selected from the group consisting of Y and
Group 3A elements from La to Lu.
3. The spray material of claim 2 wherein the rare earth element is
selected from the group consisting of Y, Gd and Er.
4. The spray material of claim 1 which is obtained by mixing 10 to
70% by weight of rare earth element oxide having an average
particle size of 0.01 to 5 .mu.m and the balance of rare earth
element fluoride having an average particle size of 0.1 to 5 .mu.m,
agglomerating, and firing.
5. A rare earth element oxyfluoride-sprayed article comprising a
substrate and a sprayed coating which is deposited on the substrate
by plasma spraying the spray material of any one of claims 1 to 4,
the sprayed coating having a carbon content of not more than 0.1%
by weight and an oxygen content of 3 to 15% by weight.
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. 2012-183302 filed in
Japan on Aug. 22, 2012, the entire contents of which are hereby
incorporated by reference.
TECHNICAL FIELD
[0002] This invention relates to a thermal spraying material in the
form of rare earth element oxyfluoride powder, especially suited
for use to form a sprayed coating having high corrosion resistance
in a corrosive plasma atmosphere as encountered in the
semiconductor device fabrication process, and an article having a
sprayed coating of the thermal spraying material.
BACKGROUND ART
[0003] In the prior art, sprayed coatings having high corrosion
resistance are used for protecting substrates in a variety of
service environments. While aluminum, chromium and similar metal
oxides are often used as the thermal spray material, the sprayed
coatings of these oxide materials are susceptible to corrosion upon
exposure to hot plasma. These materials are thus inadequate for use
in the semiconductor manufacturing process which may typically
involve treatment in a halogen-based corrosive gas plasma
atmosphere.
[0004] The halogen-based corrosive gas plasma atmosphere used in
the fabrication of semiconductor devices contains fluorine-based
gases such as SF.sub.6, CF.sub.4, CHF.sub.3, ClF.sub.3 and HF or
chlorine-based gases such as Cl.sub.2, BCl.sub.3 and HCl.
[0005] Known articles which can be used in such extremely corrosive
atmospheres include, for example, articles having corrosion
resistant coatings formed thereon by spraying yttrium oxide (Patent
Document 1) and yttrium fluoride (Patent Documents 2 and 3) to
their surface. While rare earth element oxide sprayed articles are
generally prepared by plasma spraying rare earth element oxide,
they are long used as the sprayed articles in the industrial
semiconductor fabrication process because of least technical
problems. On the other hand, the rare earth element fluoride
sprayed coatings suffer from a technical problem despite good
corrosion resistance. The plasma spraying of rare earth element
fluoride has the problem that when the rare earth element fluoride
is passed through a flame at 3,000.degree. C. or higher for
melting, the fluoride can be decomposed so that the material
partially converts to a mixture of rare earth element fluoride and
rare earth element oxide. For this reason, practical utilization of
rare earth element fluoride sprayed articles is delayed as compared
with the rare earth element oxide sprayed articles.
CITATION LIST
[0006] Patent Document 1: JP 4006596 (US 6852433) [0007] Patent
Document 2: JP 3523222 (US 20020015853) [0008] Patent Document 3:
JP-A 2011-514933 (US 20090214825)
DISCLOSURE OF INVENTION
[0009] An object of the invention is to provide a thermal spray
material in the form of rare earth element oxyfluoride powder which
is used to form sprayed coatings having higher corrosion resistance
than conventional sprayed coatings of rare earth element oxide or
fluoride, and a sprayed article having a sprayed coating of rare
earth element oxyfluoride.
[0010] The inventors have found that a spray material comprising
rare earth element oxyfluoride particles having an aspect ratio of
up to 2 as shape index, an average particle size of 10 to 100
.mu.m, and a bulk density of 0.8 to 2 g/cm.sup.3, and containing
not more than 0.5% by weight of carbon and 3 to 15% by weight of
oxygen is effective for plasma spraying, and that better results
are obtained by plasma spraying the rare earth element oxyfluoride
spray material onto a substrate such that the sprayed coating may
have a carbon content of up to 0.1% by weight and an oxygen content
of 3 to 15% by weight.
[0011] In one aspect, the invention provides a spray material
comprising rare earth element oxyfluoride particles having an
aspect ratio of up to 2, an average particle size of 10 to 100
.mu.m, and a bulk density of 0.8 to 2 g/cm.sup.3, and containing
not more than 0.5% by weight of carbon and 3 to 15% by weight of
oxygen.
[0012] Preferably, the rare earth element is one or more elements
selected from the group consisting of Y and Group 3A elements from
La to Lu. Typically, the rare earth element is Y, Gd or Er.
[0013] The spray material is preferably obtained by mixing 10 to
70% by weight of rare earth element oxide particles having an
average particle size of 0.01 to 5 .mu.m and the balance of rare
earth element fluoride particles having an average particle size of
0.1 to 5 .mu.m, agglomerating, and firing.
[0014] In another aspect, the invention provides a rare earth
element oxyfluoride-sprayed article comprising a substrate and a
sprayed coating which is deposited on the substrate by plasma
spraying the spray material defined herein, the sprayed coating
having a carbon content of not more than 0.1% by weight and an
oxygen content of 3 to 15% by weight.
ADVANTAGEOUS EFFECTS OF INVENTION
[0015] The spray material in the form of rare earth element
oxyfluoride powder is amenable to atmospheric plasma spraying. An
article having a sprayed coating of the rare earth element
oxyfluoride has higher resistance against plasma etching than those
articles having sprayed coatings of rare earth element oxide and
fluoride when used in a halogen gas plasma. High corrosion
resistance ensures a long lifetime.
DESCRIPTION OF EMBODIMENTS
[0016] One embodiment of the invention is a thermal spray material
comprising rare earth element oxyfluoride particles having an
aspect ratio of up to 2 as shape index, an average particle size of
10 .mu.m to 100 .mu.m, and a bulk density of 0.8 g/cm.sup.3 to 2
g/cm.sup.3, and containing not more than 0.5% by weight of carbon
and 3% to 15% by weight of oxygen. This thermal spray material is
effective for plasma spraying a rare earth element oxyfluoride in
air. In general, the thermal spray powder should desirably meet the
requirements including (1) smooth flow and (2) that the material is
not decomposed into oxides by plasma spraying. The spray material
defined herein has these advantages.
[0017] The thermal spray material should preferably comprise
particles of spherical shape. When a spray material is fed into a
flame for thermal spraying, a poor fluidity may make the material
inconvenient to feed such as by clogging a feed tube. To ensure
smooth flow, the spray material should preferably consist of
spherical particles. The particles have an aspect ratio of up to 2,
preferably up to 1.5. The "aspect ratio" is used herein as one
shape index of the three dimensions and refers to a ratio of length
to breadth of a particle.
[0018] The rare earth element used in the rare earth element
oxyfluoride spray material may be selected from among yttrium (Y)
and Group 3A elements inclusive of lanthanum (La) to lutetium (Lu).
Of these, yttrium (Y), gadolinium (Gd) and erbium (Er) are
preferred. A mixture of two or more rare earth elements is also
acceptable. When such a mixture is used, the spray material may be
obtained by agglomerating a mixture of raw materials, or by forming
particles of a single element and mixing such particles of
different elements prior to use.
[0019] The spray material has an average particle size of 10 .mu.m
to 100 .mu.m, preferably 15 .mu.m to 60 .mu.m. As used herein, the
average particle size is determined as a weight average value
D.sub.50 (i.e., a particle diameter or median diameter when the
cumulative weight reaches 50%) by a particle size distribution
measurement unit based on the laser light diffractometry. If the
particle size of spray material is too small, such particles may
evaporate in the flame, resulting in a lower yield of spraying. If
the size of spray material is too large, such particles may not be
completely melted in the flame, resulting in a sprayed coating of
deteriorated quality.
[0020] Particles as agglomerated to constitute the spray material
should be solid, i.e., filled to the interior (or free of voids),
because solid particles are stable (or do not chip or collapse)
during handling, and because the problem arising from voids in
particles that undesirable gas component can be trapped in voids is
avoidable. In this respect, the spray material should have a bulk
density of 0.8 g/cm.sup.3 to 2 g/cm.sup.3, preferably 1.2
g/cm.sup.3 to 1.8 g/cm.sup.3.
[0021] The atmospheric plasma spraying of rare earth element
oxyfluoride has a possibility that the oxyfluoride is decomposed
into oxide. Particularly when the spray material (or powder)
contains a noticeable amount of water or hydroxyl, it facilitates
decomposition of the oxyfluoride into a rare earth element oxide
and the liberated fluorine forms a gas such as hydrogen fluoride.
The resulting sprayed coating becomes a mixture of rare earth
element oxide and rare earth element fluoride. In this regard, the
raw material to be agglomerated into the spray powder should
preferably have a water or hydroxyl content of up to 10,000 ppm,
more preferably up to 5,000 ppm, and even more preferably up to
1,000 ppm.
[0022] The spray material (or powder) contains carbon in a
concentration of not more than 0.5% by weight, preferably not more
than 0.3% by weight, and more preferably not more than 0.1% by
weight. If the carbon content is too high, such carbon can react
with oxygen of the rare earth element oxyfluoride to form carbon
dioxide, causing decomposition of the rare earth element
oxyfluoride. As long as the carbon content is limited low,
decomposition of the rare earth element oxyfluoride during thermal
spraying is inhibited and a satisfactory coating of rare earth
element oxyfluoride is deposited.
[0023] The rare earth element oxyfluoride spray material defined
above can be prepared by agglomerating (or granulating) rare earth
element oxyfluoride or by mixing rare earth element oxide and rare
earth element fluoride and agglomerating the mixture. For example,
the spray material is prepared by dispersing a starting powder in a
solvent such as water or an alcohol of 1 to 4 carbon atoms to form
a slurry having a concentration of 10 to 40% by weight and
agglomerating the slurry by spray drying or analogous technique.
When rare earth element oxide and rare earth element fluoride are
mixed, the mixture may consist of 10 to 70% by weight of rare earth
element oxide and the balance of rare earth element fluoride.
[0024] Alternatively, the spray material may be prepared by mixing
a rare earth element oxyfluoride with an organic polymer serving as
a binder such as carboxymethyl cellulose and deionized water to
form a slurry and agglomerating by spray drying or analogous
technique. Examples of the binder used herein include polyvinyl
alcohol and polyvinyl pyrrolidone as well as carboxymethyl
cellulose. The binder is typically added in an amount of 0.05 to
10% by weight based on the weight of the rare earth element
oxyfluoride to form a slurry.
[0025] The particles as agglomerated are fired at a temperature of
600.degree. C. to 1600.degree. C. in air, vacuum or an inert gas
atmosphere for the purpose of removing the binder and water. Firing
in an oxygen-containing atmosphere is preferred for carbon
removal.
[0026] By plasma spraying the resulting spray material to a
substrate, a rare earth element oxyfluoride-sprayed article is
obtainable. The sprayed coating on the substrate should have a
carbon content of not more than 0.1% by weight, preferably 0.01 to
0.03% by weight and an oxygen content of 3 to 15% by weight,
preferably 5 to 13% by weight.
[0027] Thermal spraying to a component of the semiconductor
fabrication equipment 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 aluminum, nickel, chromium, zinc,
and alloys thereof, alumina, aluminum nitride, silicon nitride,
silicon carbide, and quartz glass which constitute components of
the semiconductor equipment. The sprayed coating typically has a
thickness of 50 to 500 .mu.m. The conditions under which the rare
earth element oxyfluoride powder is thermally sprayed are not
particularly limited. The thermal spraying conditions may be
determined as appropriate depending on the identity of substrate, a
particular composition of the rare earth element oxyfluoride spray
material, and a particular application of the resulting sprayed
article.
[0028] The resulting sprayed article has higher resistance against
plasma etching (i.e., corrosion resistance) than sprayed coatings
of rare earth element oxide and fluoride. Thus a long lifetime is
available.
EXAMPLE
[0029] 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 Spray Powder
[0030] A spray powder material was obtained by providing a starting
powder or mixing ingredients in a predetermined ratio to form a
starting powder as shown in Table 1, dispersing the starting powder
in a binder (Table 1) to form a slurry, agglomerating in a spray
dryer, and firing under selected conditions (Table 1). The
resulting spray powder was measured for particle aspect ratio,
particle size distribution, bulk density, and oxygen, fluorine and
carbon concentrations. The results are shown in Table 1. Notably,
the particle size distribution was measured by the laser
diffraction method, the fluorine concentration analyzed by
dissolution ion chromatography, and the carbon and oxygen
concentrations analyzed by the combustion and infrared (IR)
spectroscopy method. The aspect ratio of particles was determined
by taking a scanning electron microscope (SEM) photo, measuring the
length and breadth of 180 particles in the photo, and
averaging.
Preparation of Sprayed Article
[0031] The spray powder materials in Examples 1 to 4 and
Comparative Examples 1 and 2 were air plasma sprayed to aluminum
substrates using a gas mixture of 40 L/min of argon and 5 L/min of
hydrogen. The resulting articles had a sprayed coating of about 200
.mu.m thick. The sprayed coatings of powder materials in Examples 1
to 4 looked black, whereas the sprayed coatings of powder materials
in Comparative Examples 1 and 2 were white. The carbon and oxygen
concentrations of each sprayed coating were measured by the
combustion and IR method. The results are shown in Table 1.
Corrosion Resistance Test
[0032] Each article was masked with masking tape to define a masked
and exposed section before it was mounted on a reactive ion plasma
tester. A plasma corrosion test was performed under conditions:
frequency 13.56 MHz, plasma power 1,000 watts, gas mixture
CF.sub.4+O.sub.2 (20 vol %), flow rate 50 sccm, gas pressure 50
mTorr, and time 12 hours. At the end of the test, a step formed
between the exposed and masked sections due to corrosion. The
height of the step was measured at 4 points by a laser microscope
and averaged as an index for corrosion resistance. The results are
shown in Table 1.
TABLE-US-00001 TABLE 1 Example Comparative Example 1 2 3 4 1 2
Start powder, particle size Y.sub.2O.sub.3 15 YOF 100
Gd.sub.2O.sub.3 30 Er.sub.2O.sub.3 40 Y.sub.2O.sub.3 YF.sub.3 100
D.sub.50 0.3 .mu.m wt % 2.0 wt % 1.1 .mu.m wt % 0.3 .mu.m wt % 1.0
100 2.0 wt % YF.sub.3 85 .mu.m GdF.sub.3 70 ErF.sub.3 60 .mu.m wt %
.mu.m 1.8 .mu.m wt % 1.5 .mu.m wt % 2.5 .mu.m wt % Agglomeration
Start 30 wt % 20 wt % 25 wt % 35 wt % 35 wt % 25 wt % powder
Binder* CMC 12 CMC 8 PVP 8 PVP 5 CMC 10 CMC 5 wt % wt % wt % wt %
wt % wt % Firing Atmosphere Air N.sub.2 Air Vacuum Air Air
Temperature 800.degree. C. 900.degree. C. 900.degree. C.
900.degree. C. 1500.degree. C. 800.degree. C. Time 4 h 3 h 3 h 6 h
15 h 20 h Analysis of Aspect ratio 1.2 1.5 1.3 1.3 1.5 1.5 spray
powder D.sub.10 26 .mu.m 18 .mu.m 25 .mu.m 30 .mu.m 17 .mu.m 35
.mu.m D.sub.50 46 .mu.m 28 .mu.m 48 .mu.m 50 .mu.m 30 .mu.m 57
.mu.m D.sub.90 68 .mu.m 48 .mu.m 75 .mu.m 80 .mu.m 46 .mu.m 80
.mu.m Bulk density 1.4 g/cm.sup.3 1.3 g/cm.sup.3 1.6 g/cm.sup.3 1.8
g/cm.sup.3 1.6 g/cm.sup.3 1.5 g/cm.sup.3 Oxygen 4 wt % 13 wt % 4 wt
% 5 wt % 21.3 wt % 0.5 wt % Fluorine 31 wt % 16 wt % 2.3 wt % 20 wt
% 0 wt % 38 wt % Carbon 0.01 wt % 0.01 wt % 0.01 wt % 0.01 wt %
0.01 wt % 0.01 wt % Analysis of Oxygen 6 wt % 13 wt % 6 wt % 8 wt %
21 wt % 2 wt % sprayed coating Carbon 0.02 wt % 0.01 wt % 0.02 wt %
0.02 wt % 0.05 wt % 0.11 wt % Corrosion resistance, step 3.6 .mu.m
3.7 .mu.m 3.8 .mu.m 4.2 .mu.m 4.7 .mu.m 5.1 .mu.m *Carboxymethyl
cellulose, polyvinyl alcohol, and polyvinyl pyrrolidone are
abbreviated as CMC, PVA, and PVP, respectively.
[0033] As is evident from Table 1, the sprayed coatings obtained
from the rare earth element oxyfluoride powder materials in
Examples 1 to 4 have higher resistance against plasma etching
(corrosion resistance) than the sprayed coatings from the rare
earth element oxide and fluoride in Comparative Examples 1 and
2.
[0034] Japanese Patent Application No. 2012-183302 is incorporated
herein by reference.
[0035] 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.
* * * * *