JP2008239414A - Ceramic member and corrosion-resistant member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ceramic member having high density, a small particle diameter and excellent plasma resistance. <P>SOLUTION: A ceramic member consisting essentially of a rare earth oxide is composed of a fine structure comprising fine particles. By constituting the ceramic member to have an average particle diameter of less than 3 μm, an open porosity of less than 0.3% measured by an Archimedes method and the maximum particle diameter of less than 5 μm so as to decrease open pores, portions as start points of plasma corrosion can be decreased, and thereby, the obtained ceramic member is excellent in plasma resistance. By constituting the member of small particles while suppressing abnormal particle growth, particle contamination due to production of dust can be decreased. <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 has a high plasma property during etching, and dust due to erosion of the member is generated, and it is said that there is a problem that particle contamination is caused by adhering to the processing substrate, so proposal of a member made of fine particles 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.

Patent Document 2 discloses that a member having high plasma resistance can be obtained by forming a thin film or a single crystal of a compound such as an oxide, nitride, carbide or fluoride of a group 3a element, and Sc2O3 and Yb2O3. , Eu2O3, Dy2O3 PVD films.
JP 2006-21990 A Japanese Patent Laid-Open No. 10-4083

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 made of rare earth oxide as a main component and obtained by firing, the average particle diameter of particles constituting the ceramic member is less than 3 μm, and obtained by measurement by the Archimedes method. A ceramic member having an open porosity of less than 0.3% was obtained.

In another embodiment of the present invention, in a ceramic member obtained by firing with a rare earth oxide as a main component, the maximum particle size of particles constituting the ceramic member is less than 5 μm, and obtained by measurement by the Archimedes method. A ceramic member having an open porosity of less than 0.3% was obtained.

In a preferred embodiment of the present invention, the rare earth oxide is a ceramic member composed of an oxide of Ho element or Er element.

In a preferred embodiment of the present invention, a ceramic member containing a rare earth oxide as a main component and a ceramic member obtained by firing is a ceramic member containing a compound of a rare earth element and boron in the ceramic member.

In a preferred embodiment of the present invention, the ceramic member includes the rare earth element and boron compound containing at least one of LnBO ₃ and Ln ₃ BO ₆ (Ln: Ho, Er).

In a preferred embodiment of the present invention, a ceramic member mainly composed of a rare earth oxide and obtained by firing is a ceramic member having a thickness of 0.3 mm or more.

In a preferred embodiment of the present invention, the ceramic member is a corrosion-resistant member formed by disposing the ceramic member in a portion requiring 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 rare earth oxide powder, and the surface of the ceramic member may be a burned surface, a polished / ground surface, or the like. The phrase “having a rare earth oxide as a main component” means that a metal element constituting a ceramic member occupies a main part is a rare earth 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)) 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 500 ° 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.

(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 1 to 3 μm and the maximum particle size is less than 5 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 a ceramic member mainly composed of a rare earth oxide and obtained by firing, the average particle size of particles constituting the ceramic member is less than 3 μm, more preferably less than 2.5 μm, and the measurement by Archimedes method is used. By obtaining a ceramic member composed of fine particles having fine pores with small pores when the obtained open porosity is less than 0.3%, more preferably less than 0.2%, the plasma resistance and particle resistance characteristics are improved. It can be improved.

In a preferred embodiment of the present invention, in a ceramic member obtained by firing with a rare earth oxide as a main component, the maximum particle size of the particles constituting the ceramic member is less than 5 μm, and an opening obtained by measurement by the Archimedes method is used. By having a porosity of less than 0.3%, more preferably less than 0.2%, it is possible to obtain a ceramic member composed of fine particles with dense and few pores. The characteristics can be improved.

The rare earth oxide is composed of an oxide of at least one element of La, Nd, Sm, Eu, Dy, Ho, Er, Tm, Yb, Lu, or Sc, more preferably an oxide of Ho element or Er element. By using a ceramic member, plasma resistance and particle resistance can be improved.

A ceramic member mainly composed of a rare earth oxide and obtained by firing is a ceramic member including a compound of a rare earth element and boron in the ceramic member, thereby obtaining a ceramic member composed of fine particles having fine pores and few pores. As a result, plasma resistance and particle resistance can be improved.

The compound of the rare earth element and boron is LnBO ₃ , Ln ₃ BO ₆ (Ln: La, Nd, Sm, Eu, Dy, Ho, Er, Tm, Yb, Lu or Sc, more preferably Ho, Er). By using a ceramic member containing at least one of the above, a ceramic member composed of fine particles with fine pores and few pores can be obtained, whereby plasma resistance and particle resistance characteristics can be improved.

Furthermore, in the ceramic member obtained by firing with a rare earth oxide as a main component, the thickness of the ceramic member is preferably 0.3 mm or more, more preferably 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 form of the present invention, the rare earth oxide powder is molded and fired at 1200 to 1600 ° C., preferably 1300 to 1550 ° C., and ground and polished as necessary. By firing at this temperature, a ceramic member composed 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 the rare earth oxide. By adding a sintering aid, the sinterability can be enhanced, and firing at the above temperature becomes easy.

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. The particle diameter of the rare earth oxide raw material powder is not limited, but is preferably 10 μm or less on average, more preferably 2 μm or less. 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, the baking can be performed at a temperature lower than 1700 ° C. in an air atmosphere, 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, and preferably firing at 1300 to 1550 ° C. By firing at this temperature, a ceramic member composed of fine particles can be obtained while suppressing grain growth.

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 a rare earth and boron compound during the firing process, and forms a liquid phase at a temperature of 1100 to 1600 ° C. to promote sintering. The generation of the rare earth-boron compound liquid phase suppresses the particle growth of the ceramic particles by firing at a low temperature, and a ceramic member composed of fine particles can be obtained.

The obtained sintered body can be subjected to HIP treatment in a temperature range below the firing temperature. Thereby, a dense sintered body having a theoretical density can be obtained.

The boron compound that forms the rare earth-boron compound crystal phase is not limited to boron oxide, and boron compounds such as boric acid, boron nitride, boron carbide, LnBO ₃ , and Ln ₃ BO ₆ can be used. Among them, boron oxide, boric acid, and LnBO ₃ can be preferably used. Ln is Ho or Er.

The obtained ceramic member was mirror-polished, heated to a temperature lower by 300 to 500 ° 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, the ceramic member of the present invention can be used in 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 holmium oxide powder (particle size: 0.41 μm), erbium oxide powder (particle size: 1.31 μm), gadolinium oxide powder (particle size: 0.41 μm) and boron oxide (reagent grade) as raw materials. The amount of boron added was 4.5 and 9 mol%, a dispersant, a binder, and a release agent were added, and the mixture was pulverized, stirred and mixed by a ball mill, and granulated. The obtained granulated powder was press-molded and then CIP-molded. Granulation may be performed by a spray dryer. The obtained molded body was degreased and then fired at 1400 ° C. to 1500 ° C. in an air atmosphere. Table 1 shows the relationship between the obtained sintered body, the average particle size, the maximum particle size, and the open porosity.

Examples 1 to 3 are results of performing a firing test of Er ₂ O ₃ and Ho ₂ O ₃ . The average particle diameter of the sintered body is in the range of 1 to 3 μm and is composed of fine particles. Furthermore, the maximum particle size is 5 μm or less, and the sintered body has a narrow particle size distribution. As a result, the open porosity showed a low value of 1.15% or less.

(Comparative example)
Comparative Example 1 and Comparative Example 2 are the results of firing a sample obtained by adding boron to Gd ₂ O ₃ at 1400 ° C. It has an open porosity of 1.67 to 1.85% and many pores. In Comparative Example 1 and Comparative Example 2, although they were relatively dense sintered bodies, there were many fine cracks and the open porosity was high.

The evaluation method of plasma resistance is as follows.
As the evaluation sample, one that was polished so that the surface roughness (Ra) of each fired body was 0.1 μm or less was used. After masking half of the surface of this sample, a parallel plate type RIE apparatus (DEA506 / ANEVA) is used, and the etching gas is CF ₄ (40 sccm) + O ₂ (10 sccm), 1000 W, 13.56 MHz, plasma for 30 hours. Was irradiated. After irradiation, the masking was removed, the level difference between the masked part and the unmasked part was measured, and the erosion depth was measured. It can be seen from the erosion depth that the sample with a high porosity is easily eroded.

From the above results, it is composed of fine particles having an average particle diameter of less than 3 μm, and that the abnormally grown particles present in the sintered body are less than 5 μm at the same time can be the starting point of plasma erosion. Is effective for plasma resistance, and is effective for resistance to particles because it is composed of fine particles.

Claims (7)

In a ceramic member mainly composed of a rare earth oxide and obtained by firing, the average particle diameter 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 0.3% A ceramic member characterized by the above. In a ceramic member mainly composed of a rare earth oxide and obtained by firing, the maximum particle size of particles constituting the ceramic member is less than 5 μm, and the open porosity obtained by measurement by the Archimedes method is less than 0.3% A ceramic member characterized by the above. The ceramic member according to claim 1 or 2, wherein the rare earth oxide is composed of an oxide of Ho element or Er element. 4. A ceramic member comprising a rare earth oxide as a main component and obtained by firing, wherein the ceramic member contains a compound of a rare earth element and boron. Element. 5. The ceramic according to claim 1, wherein the rare earth element and boron compound includes at least one of LnBO ₃ and Ln ₃ BO ₆ (Ln: Ho, Er). Element. The ceramic member according to any one of claims 1 to 5, wherein a ceramic member comprising a rare earth oxide as a main component and obtained by firing has a thickness of 0.3 mm or more. The ceramic member according to any one of claims 1 to 6, wherein the corrosion-resistant member is disposed at a site requiring corrosion resistance.