JP2008230901A - Ceramic member and corrosion resistant member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ceramic member having high density, small particle diameter and excellent plasma resistance. <P>SOLUTION: The ceramic member is constituted of a fine structure comprising fine particles. The ceramic member having excellent plasma resistance is structured to have <1.5 μm average particle diameter, <0.1% open porosity measured by an Archimedes method and <3 μm maximum particle diameter, thereby reducing places becoming start points of erosion. Abnormal growth of the particles is suppressed and the ceramic member is constituted of small particles to reduce particle contamination due to dusting. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a corrosion-resistant member used in a processing apparatus for processing a substrate to be processed, and is an invention related to a ceramic member having excellent plasma resistance and particle resistance.

A member inside a chamber for a semiconductor or liquid crystal manufacturing apparatus is in a plasma processing apparatus into which fluorine-based or chlorine-based gas is introduced, and a material having high plasma resistance is required. Many proposals of high-purity ceramic materials such as high-purity aluminum oxide have been made as materials having excellent plasma resistance. In recent years, it has been noted that yttria is excellent in plasma resistance. In addition, it is considered that there is a problem that the etching has a high plasma property, and dust accompanying the erosion of the member is generated and adheres to the processing substrate to cause particle contamination. Therefore, a member made of fine particles is proposed. In addition, a material with a small amount of impurities with little grain boundary erosion has been proposed.

It is known that ceramics generally require a high temperature during the firing process, and are therefore sintered with particle growth, and thus become larger than the particle diameter of the starting material. It is known that ceramics composed of large particles are likely to fall off.

Further, it is known that if there are pores in a portion exposed to plasma, plasma erosion becomes a starting point and plasma resistance deteriorates.

In the conventional technology as a plasma member, a method is adopted in which the particle size is reduced to make it difficult to degranulate and the porosity contained in the sintered body is reduced. Since yttria is a difficult-to-sinter material, firing at a high temperature is necessary to obtain a dense sintered body, particle growth proceeds, and a sintered body having a small particle diameter cannot be obtained. For example, Patent Document 1 discloses a yttria sintered body having an average particle diameter of 4 μm and a bulk density of 4.90 g / cm ³ when fired at 1700 ° C. using a raw material powder having an average particle diameter of 0.7 μm. ing.

Further, Patent Document 2 provides a yttria sintered body having an average particle diameter of 2 μm and a bulk density of 4.64 g / cm ³ when fired at 1650 ° C. using a raw material powder having an average particle diameter of 1.2 μm. It is disclosed that an yttria sintered body having an average particle diameter of 12 μm and a bulk density of 4.90 g / cm ³ can be obtained when fired at a temperature of 0 ° C. From this, it can be seen that when a dense yttria sintered body is produced by a normal firing method, it is necessary to perform firing at a temperature of 1700 ° C. or higher.
JP 2006-21990 A JP 2005-8482 A

The present invention has been made in order to solve the above-mentioned problems. The problem of the present invention is to suppress abnormal grain growth in the ceramic member, to reduce the generation of pores, and to generate degranulation by constituting from small particles. It is to provide a ceramic member that is difficult to plasma and excellent in plasma resistance.

In order to achieve the above object, in the present invention, in a ceramic member having yttria as a main component and obtained by firing, the average particle diameter of particles constituting the ceramic member is less than 1.5 μm, and the measurement by Archimedes method By using a ceramic member having an open porosity of less than 0.1%, plasma resistance and particle resistance can be improved.

In a preferred embodiment of the present invention, in a ceramic member mainly composed of yttria and obtained by firing, the maximum particle size of particles constituting the ceramic member is less than 3 μm, and the open porosity obtained by measurement by the Archimedes method When the ceramic member is characterized by being less than 0.1%, plasma resistance and particle resistance can be improved.

In a more preferred embodiment, the ceramic member according to claim 1 or 2, characterized in that yttria is a main component and the ceramic member obtained by firing contains Y ₃ BO ₆ in the ceramic member. As a result, plasma resistance and particle resistance can be improved.

In a more preferred embodiment, the ceramic member according to any one of claims 1 to 3, wherein yttria is a main component, and the ceramic member obtained by firing is further heat-treated in a pressurized atmosphere. By doing so, plasma resistance and particle resistance can be improved.

In the present invention, yttria is the main component, and in a ceramic member obtained by firing, the thickness of the ceramic member is 0.3 mm or more. It is a ceramic member.

A corrosion-resistant member according to the present invention is a ceramic member according to any one of claims 1 to 5, and is a corrosion-resistant member that is disposed at a site that requires corrosion resistance.

According to the present invention, by reducing the number of open pores, it is possible to provide a ceramic member excellent in plasma resistance because the number of starting points of plasma erosion can be reduced, and to suppress abnormal particle growth and to configure with small particles. This makes it possible to reduce particle contamination due to dust generation.

The words used in this case are explained below.

(Ceramic material)
The ceramic member in the present invention is a ceramic member obtained by firing yttria powder, and the surface of the ceramic member may be a burned surface, a polished / ground surface, or the like. The expression “yttria as a main component” means that the element occupying the main portion of the metal elements constituting the ceramic member is the yttrium element.

(Particle size)
The particle diameter in the present invention is the size of each solid crystal particle constituting the ceramic member, and in the ceramic member is the size of individual particles separated from each other at the particle interface.

(Average particle size)
The average particle diameter in the present invention refers to a value calculated by a planimetric method. The average particle size was measured by mirror-polishing the sample, performing thermal etching in the air atmosphere, and calculating the average particle size by a planimetric method using an image observed by SEM.

(Planimetric method)
The average particle size in the present invention was measured using Jeffries' planimetric method. (Reference: Z. Feffries, Chem. Met. Engrs., 16,503-504 (1917); ibid., 18, 185 (1918).) SEM images of any two to three locations of the thermally etched sample at a magnification of 10,000. It was carried out, draw a known circular area (a) on the photograph to determine the number of particles n _C per unit area from suffering particle number n _i the number of particles n _C and the circumference of the circle by the following equation.
N _G = (n _C + 1 / 2n _i ) / (A / 10000 ² )
1 / _NG is the area occupied by one particle. From this, the equivalent circle diameter (D) was calculated using the following formula, and the average particle diameter was determined.
D = 2 / (πN _G ) ^1/2

(Thermal etching)
In the thermal etching in the present invention, the sample is mirror-polished, then heated to a temperature lower by 300 to 400 ° C. than the firing temperature at a heating rate of 300 ° C./h, held for 10 to 30 minutes, and then allowed to cool in the furnace. It is a process to be performed. By this heat treatment, each particle is thermally expanded, and a dent is formed at the particle interface when shrinking due to cooling. Thereby, the size of the particles can be observed.

(Maximum particle size)
The maximum particle diameter in the present invention is a size obtained by taking a sample subjected to thermal etching by SEM observation at a magnification of 10,000 times and obtaining the maximum diameter (Krumbein diameter) of the maximum particle observed.

(Archimedes method)
The Archimedes method in the present invention is a density measuring method shown in the JIS standard (JIS R 1634). The water saturation method was measured using a vacuum method, and the medium was measured using distilled water.
The calculation method of open porosity was also performed according to JIS R1634. Since numerical values are difficult to compare when rounded to the first decimal place, in this experimental example, up to two digits were displayed for comparison.

(Specific surface area)
The specific surface area used for the description of the raw material powder particle diameter in the present invention is based on the BET method shown in the JIS standard (JIS R 1626).

It is well known that it is necessary to reduce the presence of pores in order to improve plasma resistance. In general, a process of reducing pores by HIP processing is known, but coarse pores of several μm or more existing in a sintered body that has been densified are difficult to remove. Therefore, it is necessary to reduce pores during sintering.
In general, the pore size is said to be about 1/10 of the particle size of the sintered body constituting the pores. Further, it is known that the following relational expressions hold for the limit particle diameter, the average pore diameter, and the pore volume constituting the sintered body.
D = d / f
D: Limit particle diameter of constituent particles d: Average diameter of pores f: Volume of pores In order to reduce the volume of pores, it is necessary to reduce the size of the pores. For that purpose, it is necessary to make the sintered compact particles smaller and to suppress abnormal particle growth and to make the particles from homogeneous particles. However, grain growth is indispensable in the sintering process in order to promote densification and remove pores, and a certain degree of grain growth is necessary.
In the present invention, it has been found that when the average particle size is about 0.2 to 1 μm and the maximum particle size is less than 3 μm, the pores in the sintered body are effectively suppressed.
From the viewpoint of particle resistance, it is desirable to further reduce the average particle size and the maximum particle size, but a dense ceramic member cannot be obtained. The movement of the particles constituting the ceramic member depends on the temperature and also on the temperature at which sintering is promoted. In the present invention, a limit value that can be determined as a constituent particle size region in which a fine structure can be achieved simultaneously with sufficient sintering has been found.

In the present invention, in the ceramic member obtained mainly by yttria and obtained by firing, the average particle diameter of the particles constituting the ceramic member is less than 1.5 μm, preferably 1.0 μm or less, more preferably 0.6 μm or less. In addition, the open porosity obtained by measurement by the Archimedes method is less than 0.1%, and preferably 0.05% or less, so that a ceramic member composed of fine particles with fine pores can be obtained. .

In a preferred embodiment of the present invention, in a ceramic member mainly composed of yttria and obtained by firing, the maximum particle size of the particles constituting the ceramic member is less than 3 μm, preferably 2.0 μm or less, and by the Archimedes method. The open porosity obtained by the measurement is less than 0.1%, preferably 0.05% or less, so that a ceramic member composed of fine particles having fine pores and few pores can be obtained.

In a more preferable form, yttria is the main component, and the ceramic member obtained by firing is further heat-treated at a temperature lower than that of temporary firing in an inert atmosphere such as argon or a pressurized atmosphere using oxygen, whereby Plasma properties and particle resistance can be improved.

Furthermore, in the ceramic member obtained mainly by yttria and obtained by firing, the thickness of the ceramic member is preferably 0.3 mm or more. More preferably, it is 1 mm or more. By making the ceramic member thick, it can be used for a long time in a corrosive environment.

In a preferred embodiment of the present invention, yttria powder is molded, fired at 1200 to 1600 ° C., and subjected to HIP treatment at 1200 to 1550 ° C. in a pressurized atmosphere using an inert atmosphere gas such as argon or oxygen. , Grind and polish as necessary. By firing at this temperature, a ceramic member made of fine particles can be obtained while suppressing grain growth.

More preferably, an auxiliary agent that generates a liquid phase at the above temperature is added to yttria. By adding a sintering aid, the sinterability can be enhanced and firing at the above temperature is facilitated.

As the auxiliary, for example, boron compounds such as boron oxide and boric acid, lithium compounds such as lithium fluoride, potassium compounds such as potassium fluoride, and the like can be suitably used. Most preferably, a boron compound is added.

(Mixed and raw powder)
As a raw material mixing method, a general method used in a ceramic manufacturing process such as a ball mill can be used. Although there is no restriction | limiting in the particle diameter of a yttria raw material powder, 10 micrometers or less are preferable on average, More preferably, 2 micrometers or less are preferable. Although there is no restriction | limiting of a lower limit, since there exists a fall of a moldability, about submicron is preferable. A mixing method involving a pulverizing step such as a ball mill has an effect of not only reducing the particle diameter but also pulverizing coarse particles, and is preferable for obtaining a ceramic member composed of uniform and fine particles.

(Molding)
In the molding method according to the embodiment of the present invention, a granulated powder can be obtained by a dry molding method such as press molding or CIP. The molding is not limited to dry molding, and a molded body can be obtained using a molding method such as extrusion molding, injection molding, sheet molding, cast molding, gel cast molding, and the like. In the case of dry molding, it can be used as a granule by adding a binder and using a spray dryer.

(Baking)
In the embodiment of the present invention, firing can be performed at an air atmosphere of less than 1600 ° C., and can be performed in an electric furnace having a SiC heating element or a Kanthal heating element. Firing is not limited to the air atmosphere, but can be performed in an inert atmosphere such as nitrogen or argon or in a vacuum. The firing time can be selected between 0.5 and 8 hours. The firing temperature can be selected in the range of 1200 to 1600 ° C. By firing at this temperature, a ceramic member composed of fine particles can be obtained while suppressing grain growth.
The HIP treatment is preferably a treatment at a temperature equal to or lower than the primary firing temperature for the purpose of suppressing grain growth of the primarily fired ceramic member. The treatment temperature can be selected in the range of 1200 to 1550 ° C.

In order to enhance the sinterability, when a boron compound is put in the ceramic member, the boron compound is likely to evaporate during firing. The boron compound forms Y ₃ BO ₆ during the firing process, forms a liquid phase at a temperature of 1100 to 1600 ° C., and promotes sintering. The production of the liquid phase of Y ₃ BO ₆ is performed at a low temperature to suppress the growth of ceramic particles, and a ceramic member composed of fine particles can be obtained.

The boron compound that forms the Y ₃ BO ₆ crystal is not limited to boron oxide, and boron compounds such as boric acid, boron nitride, boron carbide, YBO ₃ , and Y ₃ BO ₆ can be used. Of these, boron oxide, boric acid, and YBO ₃ can be suitably used.

The obtained ceramic member was mirror-polished, heated to a temperature lower by 300 to 400 ° C. than the firing temperature at a heating rate of 300 ° C./h, held for 10 to 30 minutes, and subjected to thermal etching. The obtained sample can be observed for particle shape using SEM.

The ceramic member obtained by the present invention includes a chamber, a bell jar, a susceptor, a clamp ring, a focus ring, a capture ring, a shadow ring, an insulating ring, a liner, a dummy wafer, a tube for generating high-frequency plasma, and a high-frequency plasma. Semiconductors exposed to plasma atmosphere such as dome, lift pins to support semiconductor wafer, shower plate, baffle plate, bellows cover, upper electrode, lower electrode, screws for fixing members inside chamber, screw cap, robot arm, etc. Or it can utilize for the member for liquid crystal manufacturing apparatuses.

Furthermore, since the ceramic member of the present invention has a volume resistance of 10 ¹⁴ Ω · cm or more, it can be used for an electrostatic chuck such as an etching apparatus that performs fine processing on a semiconductor wafer or a quartz wafer.

In addition, the ceramic member of the present invention includes a corrosion prevention member such as a transport pipe for transporting a corrosive solution or corrosive gas such as hydrogen fluoride, or a crucible used when performing a chemical treatment for a corrosive solution. Etc. can be used.

(Example)
Prepare yttria powder (specific surface area 11-15 g / cm ³ ) and boron oxide (reagent grade) as raw materials, add boron oxide to 0-8 wt%, add dispersant, binder, mold release agent and ball mill The mixture was pulverized and stirred. After mixing, granulation was performed with a spray dryer. The obtained granulated powder was press-molded and then CIP-molded. When the density of the molded body is improved by granulation with a spray dryer and CIP treatment, a fired body can be obtained stably. The obtained molded body was degreased and then fired at 1300 ° C. to 1550 ° C. in an air atmosphere. The fired sample was subjected to HIP treatment in a temperature range of 1200 to 1500 ° C. in an argon atmosphere of 20 to 200 MPa. Table 1 shows the relationship between the obtained sintered body, the average particle size, the maximum particle size, and the open porosity.

In Examples 1-5, it is the result of having tested by changing boron addition amount and baking conditions. The average particle diameter of the sintered body is in the range of 0.2 to 1.5 μm, and is composed of very fine particles. Furthermore, the maximum particle size is 3 μm or less, and the sintered body has a fine and narrow particle size distribution. Accordingly, the open porosity showed a low value of 0.05% or less.

(Comparative example)
Comparative Example 1 is the result of firing a boron-free sample at 1600 ° C. The average particle size is 0.35 μm and the maximum particle size is 0.8 μm, which is very small. However, it has many pores with an open porosity of 0.76%.

Comparative Example 2 is a system to which 8 wt% of boron is added. In Comparative Example 2, abnormally grown particles were confirmed, and consisted of large particles exceeding 3 μm. Although it was confirmed in the above examples that a certain degree of particle growth is necessary for sintering, it was confirmed that excessive particle growth tends to inhibit sintering. Therefore, there were many pores and the open porosity showed a high value of 24%.

The comparative example 3 showed the case where the raw material powder with a specific surface area of 35-45 m <2> / g was used. Although the sintered body obtained by firing at 1400 ° C. in the air atmosphere has not been fully densified to a bulk density of 3.87 g / cm ³ , the average particle diameter of the constituent particles is 0.26 μm, and it seems that the grains are growing. confirmed. However, it is not a dense body with an open porosity of 20%.

From the above results, it is composed of fine particles having an average particle size of 0.2 to 1.5 μm, and abnormally grown particles existing in the sintered body are observed to be less than 3 μm at the same time. It has the effect of suppressing the presence of open pores that can be the starting point, is effective in plasma resistance, and is effective in resistance to particles because it is composed of fine particles.

In order to evaluate the plasma resistance of the ceramic member of the present invention, Example 4 and Comparative Example 1 were exposed to a plasma atmosphere using an RIE type etcher, CF4 + O2 as a corrosive gas, microwave output 1 kW, and irradiation time 30 hours. did. The results are shown in FIGS. Compared with the comparative example, the implemented product was confirmed to have a very good surface shape even after plasma irradiation.

It is an electron micrograph showing the surface state before plasma irradiation of the ceramic member of the present invention shown in Example 3. It is an electron micrograph showing the surface state after plasma irradiation of the ceramic member of the present invention shown in Example 3. 4 is an electron micrograph showing the surface state of the ceramic member shown in Comparative Example 1 before plasma irradiation. 4 is an electron micrograph showing the surface state of the ceramic member shown in Comparative Example 1 after plasma irradiation.

Claims (6)

In a ceramic member mainly composed of yttria and obtained by firing, the average particle diameter of particles constituting the ceramic member is less than 1.5 μm, and the open porosity obtained by measurement by Archimedes method is less than 0.1% A ceramic member characterized by the above. In a ceramic member mainly composed of yttria and obtained by firing, the maximum particle size of particles constituting the ceramic member is less than 3 μm, and the open porosity obtained by measurement by the Archimedes method is less than 0.1%. A ceramic member characterized by the above. The ceramic member according to claim 1 or 2, characterized in that, in the ceramic member obtained mainly by yttria and obtained by firing, Y ₃ BO ₆ is contained in the ceramic member. The ceramic member according to any one of claims 1 to 3, wherein yttria is a main component, and the ceramic member obtained by firing is further heat-treated in a pressurized atmosphere. The ceramic member according to any one of claims 1 to 4, wherein the ceramic member is made of yttria as a main component and obtained by firing, and the thickness of the ceramic member is 0.3 mm or more. The ceramic member according to any one of claims 1 to 5, wherein the corrosion-resistant member is disposed at a site requiring corrosion resistance.

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