JPS6355182A - Glassy carbon coated body - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a glassy carbon coating used as a constituent material of semiconductor processing jigs such as susceptors and graphite heaters used in the semiconductor manufacturing process A. .

[Conventional technology]

Susceptors, graphite heaters, and the like are indispensable components when manufacturing semiconductors such as silicon. For example, since the susceptor comes into contact with a product such as a high-purity silicon substrate, it is required to have the property of not contaminating the product. It is also required to have etching properties in a hydrogen chloride atmosphere at high temperatures and heat impact resistance that can be used repeatedly up to 1200°C.

Furthermore, since the graphite heater used in the Czochralski method has a heating temperature of 1000°C, impurities such as metals contained in the graphite easily volatilize, which has the disadvantage of contaminating semiconductor products such as silicon. was there.

To compensate for this drawback, chemical vapor deposition (CVD) has traditionally been applied to carbon molded products, or even ceramic molded products.
A coated body coated with silicon carbide by a method is used (see Japanese Patent Application Laid-open No. 10921/1983).

However, silicon carbide coatings have different thermal expansion coefficients between the silicon carbide skin and carbon or ceramics.
Cracks occur in the coating due to thermal cycles caused by repeated use, and impurities seep out from the carbon or cage ceramic molded product through the cracks, contaminating the product.

As a means to overcome these drawbacks, there is a proposal to coat carbon or ceramic molded products with glassy carbon (Japanese Patent Publication No. 39684/1984).

The positive carbon coating obtained by this method has superior coating uniformity compared to the silicon carbide coating described above, and the coating has a thickness of 10 μm, which is thinner than the approximately 100 μm of the silicon carbide coating. It has a number of advantages, such as cracking and peeling caused by thermal cycling.

However, because the above-mentioned glassy carbon coating is thin, it is easily affected by the underlying graphite base material, and due to variations in the physical properties of the graphite base material, the coating is not performed adequately.
There was a drawback that pinholes were likely to occur.

[Problem that the invention seeks to solve]

The object of the present invention is to eliminate the above-mentioned drawbacks and provide a glassy carbon coating with extremely few pinholes.

[Means for solving problems]

As a result of repeated research, the present inventors have found that there is a clear correlation between the presence or absence of pinholes and the graphite base material. It turns out that you just have to be selective.

That is, the present invention provides a glassy carbon coated body in which a graphite base material is coated with carbon laths, the graphite base material comprising:
The bulk density is 1.6597 cm3 or more, the graphite particle size is 100 μmlJ or less, and the ratio of open porosity to total porosity is 0.1 or more and 0.8 or less. The glassy carbon coating of the present invention is a glassy carbon coating made by dissolving an incomplete thermal decomposition product of an organic polymer (hereinafter referred to as PC substance) in a solvent and adding an inorganic powder to the solution if necessary. It is obtained by applying the slurry to the surface of a graphite base material and firing it.

The present invention will be explained in detail below.

The organic polymer used in this invention is preferably vinyl chloride resin, polyvinyl alcohol, oil-soluble phenol resin, alkylphenol resin, chlorinated/marafine, chlorinated polypropylene, vinyl acetate resin or polycargonate resin.

In particular, when the article coated with impermeable carbon is used as a susceptor for semiconductor manufacturing, vinyl chloride resin is particularly preferred from the viewpoint of impurities. Regardless of the type, thermal decomposition of these organic polymers results in granular product or powder in an inert atmosphere, e.g. argon gas, for 200 min.
This is done by heating at ~500"C for 30 minutes or more. However, it is preferable not to completely carbonize. The desired temperature and time for this heating vary depending on the heating device and the type of organic polymer, but the carbon atoms of the decomposition products and The weight ratio of hydrogen atoms (C/H ratio) may be determined by experiment to fall within the range of 10 to 25:1. Add the agent and stir to a concentration of 200 to 500.
ji/l m liquid? make. The solvent is preferably an aliphatic chlorine solvent from the viewpoint of solubility. If any undissolved matter remains, filter it to remove it. Heat-resistant inorganic powder (
(also referred to as aggregate) is a substance such as graphite, silicon carbide, or alumina, and its form may be spherical or irregular with a diameter of 50 μm or less, and rod-shaped with a major diameter of 500 μm or less is fiber. It may be in the form of It is particularly preferable to use carbonized organic polymers as the aggregate, since the final coating layer will be substantially homogeneous and will not penetrate back into the coating layer. From the viewpoint of the surface condition of the coating layer, it is preferable to grind the particles as finely as possible so that the average particle size is less than 20 μm per gram. The solution thus obtained is applied to a graphite substrate.

At this time, particular attention should be paid to the selection of the graphite base material.

That is, if the bulk density of the base material is less than 1,659/cr113, the overall porosity will be too large, and the coating will not be uniform, making pinholes likely to occur.

Furthermore, when the particle size of graphite exceeds 100 μm, even if the graphite density is 1.6597 cm3 or more, there is a high probability that open pores with a very large diameter will exist, which also prevents uniform coating. This will cause it not to be carried out.

In addition, even if it has the above two characteristics, if the ratio of open porosity to total porosity is smaller than 0.1, the anchoring effect of the graphite base material will appear when the PC material is applied and fired. Unfortunately, the glassy carbon skin 1@ peels off, which is undesirable. If the ratio exceeds 0.8, it will still be difficult to apply the PC material, which will also cause pinholes.

[Implementation row]

Hereinafter, the present invention will be specifically explained with reference to Examples and Comparative Examples.

Examples 1 to 7 As shown in the table, the bulk density is 1.65 g/cm3 or more, the graphite particle size is 100 μm or less, and the ratio of open porosity to total porosity is 0.1 or more. A graphite base material having a diameter of 0.8 or less was prepared and processed into a plate shape of 10 holes x 50 cm x 1 cIn. Next, vinyl chloride resin (5S-110 manufactured by Keikagaku Kogyo Co., Ltd.) was heated at 380° C. under an Aldef atmosphere.
Incomplete pyrolysis was carried out for 40 minutes at a temperature of .degree.

The obtained nine PC substances were dissolved in Trikunun at a ratio of 200 g/l to prepare a solution. By immersing the graphite base material in this liquid, a coating film of the PC material is provided on the graphite base.

This was fired in a vacuum at 1200°C for 45 minutes to obtain a test piece of a glassy carbon coated body.

The thickness of each glassy carbon layer in each of these test pieces was 5
Atsuno in μm.

The number of pinholes can be calculated by observing the front and back sides of the obtained test piece using a 100x optical microscope. the result,
As shown in the table, there were no large holes.

Comparison columns 1-7 As shown in the table, the ratio f! In Examples 1 and 6, a graphite base material having a bulk density of less than 1.65.97 cm3 was used.

Comparative Examples 2.6 and 7 have a particle size of 100 μm in the graphite base material.
A material containing large graphite particles exceeding .

In Comparative Example 6, the ratio of open porosity to total porosity of the graphite base material was 0.1.
I used one without a beak. Comparative Examples 4 and 5 used Black 8 base materials in which the ratio of open porosity to total porosity exceeded 0.8.

Except for the above, there was no difference from the actual series, and the experiments were carried out in accordance with Examples 1 to 7. As a result, as shown in the table, 9
1 to 20 pinholes were observed.

In addition, the bulk density, maximum particle diameter, and ratio of open porosity to total porosity in the above-mentioned actual series and comparative examples were measured by the following method.
After being incubated in an air bath at ±5° C. for about 2 hours and cooled to room temperature in a desiccator, the weight was immediately measured. Next, the dimensions of the graphite base material are measured, and the volume V (cI
n3) was calculated. Next, the bulk density was calculated from the formula: bulk density=w7v.

How to measure the maximum particle size: First, the surface of the graphite base material is buffed and polished. The surface was observed under a polarized light microscope at a magnification of 100 times, and the diameter of each grain was determined by dividing the sum of the long and short axes of 20 randomly selected crystal grains by 2. Among these, the one with the largest diameter was defined as the maximum particle size.

How to measure the ratio of open porosity to total porosity...First, assume that the true specific gravity of graphite is 2.26. Next, the bulk concavity of the graphite material was determined by the above method, and after fc, it was kept in water at 20 ± 5°C for 5 hours or more, and the weight was determined while it was suspended in water with a wire of 1 mx or less in diameter. The weight in saturated water (w2.9) was calculated by subtracting the weight of the sample.

At step A, the graphite substrate was taken out of the water, and the surface was quickly wiped with a compress to remove water droplets. After t, the saturated type t (W3, ri) was determined. Let the dry weight of the graphite substrate be Wl (g). The underwater apparent ratio ji dW is dw = W1/ (W3- W2
).

Next, the open porosity is (dw-d
)/aw x 100 (%).

Also, since the total porosity is given by d/2.26×100 (%), the ratio of the open porosity to the total porosity is as follows.

〔Effect of the invention〕

Since the glassy carbon coating of the present invention has no pinholes,
There is no risk of impurities seeping out from the black M1 base material,
It is particularly suitable as a constituent material for semiconductor processing jigs.

Claims (1)

[Claims] In the glassy carbon coated body formed by coating glassy carbon on a graphite base material, the graphite base material has a bulk density of 1.65.
g/cm^3 or more, the graphite particle size is 100 μm or less, and the ratio of open porosity to total porosity is 0.1 or more and 0.8 or less. Covering body.