JPH0224794B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for manufacturing a glassy carbon coating used as a constituent material of semiconductor processing jigs such as susceptors and graphite heaters used in semiconductor manufacturing processes. [Prior Art] Susceptors, graphite heaters, and the like are indispensable 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 resistance in a hydrogen chloride atmosphere at high temperatures and thermal shock resistance that can withstand repeated use up to approximately 1200°C. Furthermore, since the graphite heater used in the Czyochralski method has a heating temperature of over 1,600°C, impurities such as metals contained in the graphite easily volatilize, which has the disadvantage of contaminating semiconductor products such as silicon. Ta. To compensate for this drawback, a coating in which silicon carbide is coated on a carbon molded product or a ceramic molded product using a chemical vapor deposition (CVD) method has been used.
Publication No. 10921). However, since the silicon carbide coating and the carbon or ceramics in the silicon carbide coating have different coefficients of thermal expansion, cracks occur in the coating due to thermal cycles caused by repeated use, and impurities from the carbon or ceramic molded product seep through the cracks. This has the disadvantage that it oozes out and contaminates the product. As a means to overcome these drawbacks, a solution prepared by dissolving the incomplete thermal decomposition product of an organic polymer in a solvent is applied to a carbon or ceramic molded product, dried, and then fired in an inert environment. There is a proposal to coat glassy carbon by
Publication No. 39684). The glassy carbon coated body obtained by this method has superior film uniformity compared to the silicon carbide coated body described above, and the film thickness is 10 μm, which is thinner than the silicon carbide film, which is about 100 μm. It has many advantages in that it is resistant to cracking and peeling due to thermal cycles. 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 may not be sufficient and pinholes may occur. There was a simple flaw. [Problems to be Solved by the Invention] An object of the present invention is to eliminate the above-mentioned drawbacks and provide a method for producing a glassy carbon coating with extremely few pinholes. [Means for Solving the Problems] As a result of extensive 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 has been found that in order to suppress the occurrence, it is necessary to carefully select the graphite base material. That is, in the present invention, a solution obtained by dissolving an incomplete thermal decomposition product of an organic polymer (hereinafter referred to as PC substance) in a solvent is applied to the surface of a graphite base material, dried, and then placed in an inert environment. When coating the surface of ^the graphite base material with glassy carbon by firing with This is a method for producing a glassy carbon coated body, characterized in that a glassy carbon coated body having a ratio to porosity of 0.1 or more and 0.8 or less is used. The present invention will be explained in more detail below. The present invention provides a solution in which a PC substance is dissolved in a solvent.
If necessary, a heat-resistant inorganic powder is mixed to form a slurry, which is applied to the surface of a specific graphite base material, dried, and then fired. The organic polymer used in the present invention is preferably vinyl chloride resin, polyvinyl alcohol, oil-soluble phenol resin, alkylphenol resin, chlorinated paraffin, chlorinated polypropylene, vinyl acetate resin, or polycarbonate 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. Thermal decomposition of these organic polymers is carried out by heating granular products or powders of any type at 200 to 500° C. for 30 minutes or more in an inert atmosphere, such as argon gas. 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 weight ratio of carbon atoms to hydrogen atoms (C/H ratio) of the decomposition product
may be determined by experiment so that the ratio falls within the range of 10 to 25:1. A solvent is added to the PC substance obtained in this way and dissolved to form a solution with a concentration of 200 to 500 g/g. 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 (hereinafter referred to as
Aggregate) is a substance such as graphite, silicon carbide, alumina, etc., and its form may be spherical or irregular with a diameter of 50 μm or less, or rod-like or fibrous with a diameter of 500 μm or less. It is particularly preferable to use a carbonized organic polymer as the aggregate, since the interior of the coating layer will ultimately be substantially homogeneous, resulting in impermeability. 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 20 μm or less. 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 1.65 g/cm ³ , the overall porosity becomes too large, and the coating is not uniformly applied, making pinholes more likely to occur. Furthermore, if the particle size of graphite exceeds 100 μm, even if the bulk density is 1.65 g/cm ³ or more,
The probability of the presence of open pores of very large diameter increases, which also causes uneven coating. In addition, even if it has the above two characteristics, if the ratio of open porosity to total porosity is less than 0.1, the anchoring effect of the graphite base material will be difficult to express when the PC material is applied and fired. This is not preferable because the glassy carbon film peels off. If the ratio exceeds 0.8, it becomes difficult to apply the PC material, which also causes pinholes. Methods for applying the solution include ultrasonic impregnation, brushing, spraying, and dipping.
It is desirable to dry at a relatively low temperature of about 50 to 100°C. After coating, the temperature should be 800°C or more in an inert environment such as nitrogen or argon, or a reduced pressure atmosphere.
PC material can be vitrified by firing at around 1300℃ for 30 minutes or more. [Example] 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/cm ³ or more, the graphite particle size is 100 μm or less, and
A graphite base material having a ratio of open porosity to total porosity of 0.1 or more and 0.8 or less was prepared and processed into a plate shape of 10 cm x 50 x 1 cm. Next, vinyl chloride resin (SS-110 manufactured by Denki Kagaku Kogyo Co., Ltd.) was heated at 380° C. under an argon atmosphere.
Incomplete pyrolysis was carried out for 40 minutes at a temperature of °C. The obtained PC substance was dissolved in trichlene at a rate of 200 g/ml to form a solution. A coating film of the PC material was provided on the graphite substrate by immersing the graphite substrate in this solution. This was baked in a vacuum at a temperature of 1200°C for 45 minutes to obtain a test piece of a glassy carbon coated body. The thickness of the glassy carbon coating on these specimens is
It was 5 μm. The number of pinholes was calculated by observing the entire front and back surfaces of the obtained test piece using a 100x optical microscope. As a result, as shown in the table, there were no pinholes. Comparative Examples 1 to 7 As shown in the table, in Comparative Examples 1 and 6, graphite base materials having a bulk density of less than 1.65 g/cm ³ were used. Comparative Examples 2, 6 and 7 have a particle size of 100μ in the graphite base material.
A material containing large graphite particles exceeding m was used.
Comparative Example 3 has a ratio of open porosity to total porosity of the graphite base material.
A value less than 0.1 was used. Comparative Examples 4 and 5 used graphite base materials in which the ratio of open porosity to total porosity exceeded 0.8. Other than the above, there is no difference from Examples 1 to 7.
This was done in accordance with the. As a result, as shown in the table, 1 to 20 pinholes were observed per test piece. In addition, the bulk density, maximum particle diameter, and ratio of open porosity to total porosity in the above Examples and Comparative Examples were measured by the following methods. Measuring method of bulk density...First, the graphite base material is heated to
It was kept in an air bath at 110±5° C. for about 2 hours, cooled to room temperature in a desiccator, and immediately weighed W (g). Next, the dimensions of the graphite base material were measured, and the volume V (cm ³ ) was calculated. Next, the bulk density was calculated from the formula: bulk density=W/V. Method for measuring maximum particle size: First, the surface of the graphite base material was buffed to a mirror finish. Next, using a 100x polarized light microscope,
The surface was observed and the sum of the long and short axes of 20 randomly selected crystal grains divided by 2 was determined as the grain size of each grain. Among these, the one with the largest value 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, after determining the bulk density of the graphite material using the above method, it was kept in water at 20±5°C for more than 3 hours, and its weight was determined while it was suspended in water using a wire with a diameter of 1 mm or less. The weight in saturated water (W ₂ , g) was determined by subtracting the weight. Next, the graphite substrate was taken out of the water, the surface was quickly wiped with a compress to remove water droplets, and the saturated weight (W ₃ ,
g) was determined. If the dry weight of the graphite base material is W ₁ (g), the apparent specific gravity in water dW is dW = W ₁ / (W ₃ − W ₂ )
becomes. Next, the open porosity is given by the bulk specific gravity as d.
It is given by (dW - d)/dW x 100 (%). Also, since the total porosity is given by d/2.26×100 (%), the ratio of open porosity to total porosity is dW−d/dW×100×2.26/d×100=(dW−d)× 2.26／
It becomes dW×d.

【table】

〔Effect of the invention〕

Since the manufacturing method of the glassy carbon coating of the present invention has no pinholes, there is no fear that impurities will seep out from the graphite base material, and it is particularly suitable as a constituent material for semiconductor processing tools.

Claims (1)

[Claims] 1 A solution prepared by dissolving an incomplete thermal decomposition product of an organic polymer in a solvent is applied to the surface of a graphite substrate and dried, and then baked in an inert environment to make the surface of the graphite substrate glassy. When coating with carbon, the graphite base material has a bulk density of 1.65/cm ³ or more, a graphite particle size of 100 μm or less, and a ratio of open porosity to total porosity of 0.1 to 0.8. A method for producing a glassy carbon coated body, characterized by using peach.