JP2009035452A - Porous article and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a porous article which is reduced in the formation of particles and suitable for a semiconductor manufacturing apparatus or a flat panel display manufacturing apparatus. <P>SOLUTION: The porous article is characterized by comprising 100 mass% of SiC powder, 5 mass% or less of carbon and 20 mass% or more of metal silicon, and has a structure in which particles of the metal silicon are mutually necked. The manufacturing method for the porous article comprises a process of press-molding a mixed powder formed by mixing 100 mass% of a SiC powder, an organic binder containing 5 mass% or less of carbon powder or 5 mass% or less of carbon, and 20 mass% or more of metal silicon to form a molded article, and a process of heat-treating the compact at a temperature of 1,200-1,350°C in a nonoxidative atmosphere, to thereby mutually neck the metal silicon particles. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to various industrial fields that require a process in which generation of particles becomes a problem, such as an exposure apparatus used in a flat panel display manufacturing apparatus such as a semiconductor manufacturing apparatus and a liquid crystal panel.

The ceramic porous body is excellent in heat resistance and corrosion resistance, so air supply members and liquid supply members for supplying filters, atmospheric gases, cleaning liquids, etc. in semiconductor manufacturing equipment and liquid crystal manufacturing equipment to wafers, glass substrates, etc. And a suction plate of a suction device for a wafer or a glass substrate. There are many suction devices that make grooves or holes in a metal material such as aluminum or stainless steel, and suck from the holes. However, in recent years, when wafers and substrate glass are becoming larger and thinner, when sucked from specific parts such as grooves and holes, the wafer or substrate glass that is the object to be adsorbed is deformed and high-precision suction cannot be performed. In addition, problems such as insufficient suction force occur. Therefore, many porous bodies that can be adsorbed on the entire surface are used as adsorption devices. Especially, since SiC has a small difference in thermal expansion coefficient from the Si wafer, it is widely used in Si wafer transfer devices and the like, and the use of porous materials using SiC other than the adsorption device is also spreading.

Various techniques relating to such a porous body have been proposed. For example, there are those that add metallic silicon powder and an organic substance such as phenol to SiC powder, react them to form SiC, and join SiC particles, and those that contain a foaming agent. The strength of the porous body is lower than that of a normal dense body, and therefore, the particles are easily shed. In addition, there is a problem that many particles are generated due to remaining carbon or the like.

Patent Document 1 discloses a porous body containing refractory particles and metal silicon as aggregates. This porous body is formed into a refractory particle raw material by adding metal silicon and an organic binder, mixing and kneading, and molding the kneaded material, and calcining the obtained molded body to form an organic binder in the molded body. After removal, it is obtained by a production method in which the main firing is performed. According to this method, since the binder is removed, it is expected that generation of particles due to residual carbon can be suppressed.
JP 2002-201082 A

However, according to the study by the present inventor, even if the binder is removed, the generation of particles cannot be sufficiently suppressed. Therefore, when such a porous body is used as a member of a semiconductor manufacturing apparatus or the like, particles adhere to the wafer or glass substrate, resulting in a decrease in processing accuracy. Specifically, in the air supply member or the liquid supply member, particles may be mixed into the supplied gas or liquid, and in some cases, the particles may be transferred to the wafer or the glass substrate because they are in direct contact with the adsorption device. In particular, in recent years, in the field of semiconductor manufacturing apparatuses and flat panel display manufacturing apparatuses, the processing accuracy has been remarkably advanced, and a porous body having a lower particle property has been desired.

The present invention solves such problems and provides a porous body in which the generation of particles is suppressed.

In order to solve these problems, the present inventor has found that a porous body with a small amount of generated particles can be obtained by lowering the heat treatment temperature, and has led to the present invention.

That is, the present invention provides a porous body comprising 100% by mass of SiC powder, 5% by mass or less of carbon, and 20% by mass or more of metallic silicon.

Particle generation sources include residual carbon degranulation and SiC degranulation. It is considered that the residual carbon is caused by an organic substance such as phenol used as a bonding material for the SiC porous body. As described above, when producing a SiC porous body, usually, a carbon source and metal silicon are added, and these are reacted to form SiC, thereby joining SiC particles together. At this time, all of the carbon is not converted to SiC, and a part of the carbon remains as fine residual carbon, which becomes particles. The residual carbon can be removed to some extent by washing with an organic solvent after the main firing. However, since it is difficult to remove completely, it is preferable to reduce as much as possible.

Therefore, according to the invention described in Patent Document 1, it is expected that particles can be reduced because carbon is removed, but it cannot be sufficiently reduced. Thus, when the particle component was examined, it was found that although the carbon content was reduced, SiC was degranulated.

Here, normally, free carbon is contained in SiC, and free carbon cannot be removed at a binder removal temperature of 150 ° C. to 700 ° C. Therefore, when the metal silicon is softened and bonded by heating to 1400 ° C. or more as in the invention described in Patent Document 1, the reactivity with carbon increases, so it reacts with free carbon contained in SiC. Fine SiC is generated. This is considered to be the particle source.

In the present invention, since heat treatment is performed at a temperature of 1200 ° C. to 1350 ° C. without softening the metal silicon, fine SiC is not generated by reacting with free carbon. Therefore, the generation of particles can be significantly reduced.

As for carbon of a porous body, 5 mass% or less is desirable with respect to 100 mass% of SiC powder contained in a porous body. This is because if the amount of carbon is large, the carbon itself tends to be a particle source, and the necking of metal silicon may be hindered. Further, the carbon content is desirably 1% by mass or more. If the addition amount is less than that, it is difficult to produce a molded body before the main firing. Further, the molded body cannot be held until necking with metallic silicon occurs.

The porous metallic silicon is preferably 20% by mass or more with respect to 100% by mass of the SiC powder contained in the porous body. If the metallic silicon is less than 20% by mass, the strength of the entire porous body is lowered, which is not preferable. Further, the upper limit of the amount of metal silicon added is desirably 60% by mass or less. If it is added in an amount of more than 60% by mass, it becomes difficult to control the porosity due to the necking of the metal silicon.

The porous body of the present invention has a structure in which the metal silicon particles are necked together. As described above, the heat treatment is performed at 1200 to 1350 ° C., so that the metal silicon particles are necked to each other and are firmly bonded. Here, in the present invention, since heating is performed in a non-oxidizing atmosphere, an oxide film that inhibits necking does not occur on the surface of the metal silicon. Accordingly, necking of metal silicon particles proceeds even at a low temperature, and a strongly bonded porous body is obtained. By adding a sufficient amount of metal silicon and proceeding the necking of the metal silicon, the distance between the metal silicon particles is reduced, and the SiC powder is also firmly clamped, so that the degranulation can be prevented.

As described above, since the porous body of the present invention has a low particle property, it can be suitably used for a semiconductor manufacturing apparatus or a flat panel display manufacturing apparatus.

The porous body of the present invention is a mixed powder of 100% by mass of SiC powder, 5% by mass or less of carbon powder or 5% by mass or less of carbon-based organic binder, and 20% by mass or more of metal silicon powder. And a step of necking metal silicon particles by heat-treating the molded body at 1200 to 1350 ° C. in a non-oxidizing atmosphere. be able to.

The reason why the temperature range is set is to prevent the metallic silicon from reacting with the carbon to form SiC by lowering the heat treatment temperature. When SiC is generated, the portion becomes brittle and easily falls off the metal silicon. Further, the generated SiC is fine and cannot be easily removed by cleaning or the like. Moreover, if it is the said temperature range, necking of metal silicon will advance and bond strength can be raised. Since it is considered that the metal silicon and the SiC powder do not react with each other, the fixing of the SiC powder becomes a problem. However, since the SiC powder is firmly tightened by the necking of the metal silicon, it is possible to prevent the degranulation. Here, the amount of carbon contained in the organic binder is the amount of residual carbon (Conradson method; JISK2270).

As described above, by using a structure in which metal silicon is necked, generation of particles can be suppressed, and a porous body suitable for a semiconductor manufacturing apparatus or a flat panel display manufacturing apparatus can be provided.

A SiC powder having an average particle size (D50) of 20 to 200 μm and a purity of 99% or more is used. When the average particle size is smaller than 20 μm, a sufficient pore size as a porous body cannot be secured. Moreover, since the surface area of particle | grains is large when an average particle diameter is larger than 200 micrometers, sufficient intensity | strength as a porous body cannot be ensured. Further, it is sufficient that the purity is 98% or more, and a purity of about a commercially available abrasive is sufficient. In addition, the average particle diameter (D50) said here is a measured value using the laser diffraction / scattering type | formula particle size distribution measuring apparatus (LA-920, Horiba, Ltd. (trademark) make).

Metallic silicon having an average particle diameter (D50) of 10 to 50 μm and a purity of 99.9% or more is used. When metal silicon with an average particle size of less than 10 μm is used, there is a high possibility that a large amount of oxide film is formed on the surface, and necking necessary to express the strength of the porous material occurs due to the influence of the oxide film at the stage of heat treatment do not do. On the other hand, when the average particle size is larger than 50 μm, the dispersion of the metal silicon is biased and the strength of the porous body is lowered. As for the purity, when metal silicon having a low purity is used, the melting point is lowered. Therefore, the metal silicon may melt at a temperature of about 1200 to 1350 ° C. and react with carbon.

Carbon may be liquid or powder as long as it is an organic binder. However, considering the strength at high temperature, a phenolic binder is desirable. As the residual carbon ratio (carbon amount) of the binder, 40 to 60% by mass is suitable for forming the mixed powder.

A known method can be adopted as a method for forming the mixed powder. For example, CIP, press molding, extrusion molding, etc. can be applied. Depending on the binder to be added, heat may be applied to increase the strength of the molded body.

The atmosphere of the heat treatment for necking the metal silicon is preferably a non-oxidizing atmosphere. Specifically, heat treatment can be performed in a vacuum or an inert gas such as Ar.

The porous body of the present invention preferably has a pore diameter of 10 μm or more. If it is less than 10 μm, the ventilation resistance is large, which is not preferable when used as a filter. Moreover, although there is no provision | regulation on use about an upper limit, the average pore diameter of 100 micrometers or more is difficult to produce on the intensity | strength of a porous body from the particle size of the SiC powder to be used.

The porosity is preferably 30 to 60%. If the porosity is within this range, the ventilation resistance when used as a filter or the like is optimal. If the porosity is larger than 60%, there arises a problem that the strength of the porous body is lowered.

EXAMPLES Hereinafter, the Example of this invention is specifically given with a comparative example, and this invention is demonstrated in detail.
[Examples 1-8, Comparative Examples 1-3]
Table 1 shows commercially available SiC powder (particle size (D50) 135 μm, purity 99%), Si powder (particle size (D50) 45 μm, purity 99.9%) and phenol powder (novolak type, residual carbon ratio 50 mass%). And in a dry manner for 1 hour. Thereafter, hot pressing was performed at 150 ° C. for 1 hour while applying a pressure of 20 kg / cm ² . After hot pressing, a curing treatment was performed at −150 ° C. for 12 hours, and then a heat treatment (Ar atmosphere) was performed at the temperature shown in Table 1. The porous body thus obtained was processed into a □ 30 mm × t3 mm shape in order to measure particles. After the processing, ultrasonic cleaning with methanol (40 kHz) is performed for 15 minutes, followed by immersion in a hydrocarbon-based detergent for 30 minutes, immersion in ultra pure water for 10 minutes, and ultrasonic cleaning with ultra pure water (40 kHz) for 10 minutes. For a minute, and finally showered with ultrapure water. Then, after drying, measurement was performed.

For the measurement of particles, KC-24 manufactured by Rion (registered trademark) was used. Nitrogen gas was sucked through the porous body, and particles contained in the sucked gas were measured. The measurement gas uses nitrogen extracted from liquid nitrogen, and a porous body is attached to the outlet of the container filled with nitrogen, and this porous body is connected to a φ10 mm suction part extending from the measuring instrument. Connected to the measurement part. The suction flow rate of the particle measuring device was 28 l / min. The measured particle diameter was 0.5 μm or more, measured for 10 minutes, and the amount of particles was counted. The number of blank particles was 10 or less on average. Table 1 shows the particle measurement results. The porosity was measured by the Archimedes method.

[Comparative Example 4]
What was molded in the same manner as in the above example was heated in the air up to 700 ° C. in the heat treatment to remove carbon derived from the binder, and then heated in an Ar atmosphere. Other steps were performed in the same manner as in the above example.

In all the examples, the number of particles was 50 or less. In Comparative Examples 1 to 3, the number of particles was remarkably increased compared to the Examples. In Comparative Example 4 where the binder was removed, the number of particles was large. Therefore, particles can be reduced by the porous body obtained by heat treatment at a low temperature of 1200 to 1350 ° C. consisting of 5% by mass of carbon and 20% by mass or more of metal silicon with respect to 100% by mass of SiC powder. I understood. When the porous body of the present invention (Examples 1 to 8) was observed with an optical microscope, the metal silicon particles were not melted but were adjacent to the adjacent particles, and wetting with the SiC powder particles was not observed.

From the above, it has been shown that the porous body of the present invention has a metal silicon necking structure, generates less particles, and can be suitably used for a semiconductor manufacturing apparatus or a flat panel display manufacturing apparatus.

Claims (4)

A porous body comprising 100% by mass of SiC powder, 5% by mass or less of carbon, and 20% by mass or more of metallic silicon. The porous body according to claim 1, wherein the metal silicon particles have a structure of necking. The porous body according to claim 1, which is used in a semiconductor manufacturing apparatus or a flat panel display manufacturing apparatus. A mixed powder of 100% by mass of SiC powder, 5% by mass or less of carbon powder or 5% by mass or less of carbon-based organic binder, and 20% by mass or more of metal silicon powder is press-molded to form a molded body. Process,
A method for producing a porous body comprising a step of necking metal silicon particles by heat-treating the molded body at 1200 to 1350 ° C. in a non-oxidizing atmosphere