JPH05208867A - Highly corrosive glassy carbon material - Google Patents

Abstract

PURPOSE:To provide a highly corrosive glassy carbon material capable of being stably used for a long period under severe conditions such as an oxidative condition in the atmosphere or a plasma spattering condition. CONSTITUTION:The objective highly anticorrosive glassy carbon material is characterized by material properties consisting of a specific gravity of >=1.50, a total ash content of <=700ppm, a total sulfur content of <=500ppm, a crystal surface distance of <=0.375nm and a crystal size of >=1.3nm. This glassy carbon material has preferably pores having sizes of <20mum in the tissue of the material and a pore content of <=1% in addition to the above-mentioned properties.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a highly corrosion resistant glassy carbon material having excellent durability against corrosion such as oxidation.

[0002]

2. Description of the Related Art A glassy carbon material is a heterogeneous carbon material having a vitreous structure obtained by firing and carbonizing a carbonizing thermosetting resin in a non-oxidizing atmosphere. As it has an extremely dense homogeneous structure and excellent mechanical strength, gas impermeability and corrosion resistance,
For example, it is widely used as various members in various fields such as battery electrodes, electrolysis electrodes, and semiconductor manufacturing crucibles. In particular, recently, it has been clarified that the homogeneous and non-polluting material structure is suitable as an electrode for plasma etching of a silicon wafer or a member for an ion implantation apparatus, and it has already entered a practical stage.

When the glassy carbon material is immersed in a mixed acid consisting of concentrated sulfuric acid and concentrated nitric acid, there is almost no change in appearance and weight over a period of 150 days or more. This is compared to normal graphite materials that completely disintegrate within 2 days in mixed acid,
This shows that the corrosion resistance is remarkably high. Also,
The oxidation resistance in dry air is also superior to that of pyrolytic graphite having high crystallinity.

However, in the field of semiconductors and the like mentioned above, durability against oxidization under severe conditions, sputtering by plasma / ion beam, chemical or electrochemical corrosion, etc. is strongly demanded more than ever. ing. To meet this requirement, it is known that a high-purity glassy carbon material obtained by molding a cyclic-refined cyclic melt polymer of phenol / formaldehyde, firing it, and treating it at a high temperature of 2000 ° C exhibits high corrosion resistance. [Fluorocarbon, “Production Engineering” Vol.
48, No. 7 (1977)].

[0005]

However, although the above-mentioned high-purity glassy carbon material has good resistance to chemical corrosion, it is not suitable for oxidation or plasma sputtering in a high oxygen concentration atmosphere (atmosphere). However, it does not show sufficient durability.

In view of such circumstances, the present inventors have made various studies on the correlation between the material properties of the glassy carbon material and the corrosion resistance, especially the durability against oxidation and plasma sputtering. It was found that the density, purity, impurity components, crystal structure, etc. of the glassy carbon material are entangled with each other, and each characteristic element is adjusted to a specific range. Clarified the fact that it exerts its power.

The present invention was developed based on the above findings, and its purpose is a highly corrosion-resistant glassy carbon material which can be stably used for a long period of time even under severe conditions such as oxidation in the air or plasma sputtering. To provide.

[0008]

The highly corrosive glassy carbon material according to the present invention for achieving the above object has a specific gravity of
The structural feature is that the material property is 1.50 or more, total ash content is 700 ppm or less, total sulfur content is 50 ppm or less, crystal face spacing is 0.375 nm or less, and crystallite size is 1.3 nm or more. In addition to this, it is more preferable that the size of the contained pores is less than 20 μm and the content of the pores is 1% or less.

The values of the properties of each material in the above constitution are JIS R7222-1979 "Physical test method of high purity graphite material" for specific gravity and total ash content, and JIS M8813 for total sulfur content.
−1988 Measured values by “method of elemental analysis of coals and cokes”, crystal face spacing and crystallite size are “Measurement of lattice constant and crystallite size of artificial graphite” prepared by the 117th Committee of the Japan Society for the Promotion of Science. Method, and the measured value of the (002) plane.
Further, the pore diameter is the maximum pore diameter measured by observation with an optical microscope or a scanning electron microscope, and the pore content rate (porosity) is a value calculated from true specific gravity and specific gravity.

The glassy carbonaceous material having the material property specified in the present invention can be obtained by appropriately adjusting the conditions of each step in the manufacturing technique by the conventional process. First, in order to increase the density of the material, a phenol-based, furan-based, or polyimide-based resin having a residual carbon rate of at least 40% is selectively used as a thermosetting resin as a raw material. Usually, the form of the raw material resin is powdery or liquid, but depending on the form, the most suitable molding means is selected from mold forming, injection molding, cast molding, multiple molding, etc., for example, plate form, pipe form, Molded into desired shape such as crucible shape, 1
Curing treatment is performed in the temperature range of 00 to 180 ° C. At this time, the target specific gravity, pore diameter, and pore content rate are secured by controlling the conditions of selection of raw material resin, molding and curing.

The firing and carbonization treatment is carried out by filling the cured resin molded body in a graphite crucible or sandwiching it between graphite plates with nitrogen,
It is carried out by heating in an electric furnace replaced with an inert gas such as argon, or by encapsulating with a carbonaceous packing in a combustion gas heating type lead hammer furnace and heating. The treatment temperature is usually about 800 to 1500 ° C, but if necessary, graphitization treatment is performed at a high temperature of 2000 ° C or higher. At this time, the crystal plane spacing and the crystallite size of the glassy carbon material obtained by controlling the treatment temperature are adjusted to the target ranges.

In order to secure the target purity properties, a method of curing and firing a specially manufactured high-purity raw material resin containing no components other than organic substances in an environment free from external contamination by impurities is usually used. A method of subjecting the glassy carbon material produced according to the method to a secondary purification treatment of heating in a halogen-based gas atmosphere, or a method of combining both of them is used. The high-purity raw material resin is preliminarily subjected to adsorption separation, high-purity distillation, chromatography or the like to remove impurities, and then synthesized in a clean room or an environment equivalent thereto in order to prevent environmental pollution from the outside.
In order to prevent impurity contamination during curing and firing, the processing environment is shut off from the outside and replaced with an inert gas such as ultra-high-purity argon or nitrogen gas used in semiconductor manufacturing.

[0013]

[Function] According to the highly corrosion-resistant glassy carbon material of the present invention, the dense structure having a specific gravity of 1.5 or more prevents gas diffusion into the material, and the high purity of total ash content of 700 ppm or less and total sulfur content of 50 ppm or less is oxidized. It functions to reduce the catalytic action of iron, vanadium, calcium, sulfur, etc., which promotes corrosion reactions such as. The characteristic that the crystal plane spacing is 0.375 nm and the crystallite size is 1.3 nm or more is a property in which graphitization is relatively developed, and it has the function of increasing the resistance to oxidation and the like.

The functions due to such specific material properties act synergistically and the chemical stability is greatly improved. Particularly, the erosion phenomenon based on severe oxidizing conditions such as high temperature atmosphere or plasma sputtering is effective. To be prevented.
This effect of improving the corrosion resistance is further promoted when the size of the pores contained in the glassy carbon structure is less than 20 μm and the pore content is 1% or less, and higher corrosion resistance is imparted.

[0015]

EXAMPLES Examples of the present invention will be described below in comparison with comparative examples.

Examples 1 to 3 and Comparative Examples 1 to 3 Using phenol and formalin purified by vacuum distillation as raw materials, an addition condensation reaction was carried out by a conventional method to prepare a phenol resin initial condensate (liquid resin). The phenol resin initial condensate is poured into a polyethylene vat, put in a vacuum desiccator, degassed at a reduced pressure of 10 torr or less, then transferred to an electric oven and cured at a temperature of 180 ° C. to a length of 100 mm, a thickness of 100 mm. A 4 mm plate was molded. At this time, the specific gravity and the pore state were adjusted by controlling the degree of pressure reduction and the deaeration time.

Then, the molded plate-like body is treated with impurities of 5 ppm.
Less than high purity graphite plate [Tokai Carbon Co., Ltd., G347SS]
Packed in an electric furnace in a state of being sandwiched between, and the surrounding ash content is 10 ppm
After encapsulating with the following high-purity graphite powder, the temperature was raised to 1000 ° C. and calcined and carbonized. Subsequently, heat treatment was performed in a temperature range of 2000 ° C. or higher while introducing chlorine gas into the furnace. In this step, the purity characteristics and the degree of graphitization were adjusted by controlling the heat treatment temperature and the treatment time.

Each of the six types of glassy carbon materials having different specific gravities, total ash content, total sulfur content, crystal face spacing, crystallite size, contained pore size, and pore content ratio produced by the above-mentioned process were used. A corrosion resistance test was conducted by an evaluation method in which the sample was placed in an electric furnace maintained at a temperature of 800 ° C in the atmosphere and the time until the weight was reduced by 10% was measured. The evaluation results of corrosion resistance (oxidation time) thus obtained are shown in Table 1 in comparison with the material properties of each glassy carbon material.

[0019]

[Table 1]

Comparative Example 1 has a specific gravity of less than 1.5, Comparative Example 2 has a total sulfur content of more than 50 ppm, and Comparative Example 3 has a crystal plane spacing of more than 0.375 nm, both of which satisfy the material property requirements specified in the present invention. It is a glassy carbon material that comes off. From the results in Table 1, it is recognized that the glassy carbon materials of Examples satisfying the requirements of the present invention have significantly improved corrosion resistance as compared with the Comparative Examples. In particular, in Example 3 in which the pore size was less than 20 μm and the pore content was 1% or less, the corrosion resistance improving effect was remarkable. In this example, the corrosion resistance was evaluated by the degree of oxidation resistance, but similar results were obtained in the evaluation of corrosion resistance such as plasma sputtering and electrolytic oxidation.

[0021]

INDUSTRIAL APPLICABILITY As described above, the glassy carbon material provided by the present invention exhibits extremely excellent corrosion resistance performance based on the specified material properties. Therefore, there is an effect that it can be stably used for a long period of time as a member used under severe environmental conditions, especially as a member for the semiconductor field.

Claims (2)

[Claims] 1. A corrosion-resistant glassy carbon material characterized by having a specific gravity of 1.50 or more, a total ash content of 700 ppm or less, a total sulfur content of 50 ppm or less, a crystal face spacing of 0.375 nm or less, and a crystallite size of 1.3 nm or more. .. 2. The corrosion-resistant glassy carbon material according to claim 1, wherein the size of the contained pores is less than 20 μm and the pore content is 1% or less.