JP5132034B2 - High resistivity silicon carbide sintered body - Google Patents

Description

  The present invention is a high resistivity silicon carbide sintered body suitable for ceramic members used in steppers, chamber parts, static electricity removal terminals, etc. in semiconductor manufacturing apparatuses, liquid crystal device manufacturing apparatuses, etc., and sliding parts such as mechanical seals and bearings. About.

Among semiconductor and liquid crystal device manufacturing apparatuses, for example, aluminum is conventionally used as a material that is lightweight and difficult to discharge on a stage that is a stepper member.
In this case, the surface of the aluminum material is subjected to black alumite treatment in order to suppress the reflection of short wavelength light such as ultraviolet rays and perform exposure with high accuracy.

In recent years, with the increase in size of liquid crystal substrates, the size of liquid crystal stages has increased. As a material to replace aluminum, ceramics (sintered bodies) such as alumina, mullite, silicon carbide, and silicon nitride, which are lightweight and highly rigid, are used. Use is under consideration.
Among these, the silicon carbide sintered body is black to black brown and has an ultraviolet reflectance of less than 3%, which is advantageous compared to other ceramics that must be subjected to blackening treatment.

However, ceramics such as alumina, mullite, and silicon nitride are insulating materials, whereas silicon carbide sintered bodies exhibit a specific resistance over a wide range of 10 ³ to 10 ⁶ Ω · cm.
Moreover, when the silicon carbide sintered body is used for a stepper member as described above, it must be neutralized for each process, and in particular, in the case of a large-sized member, the time required for the neutralization treatment becomes long. also had to be prevented adhesion of dust or adsorption.

  Therefore, a lightweight, high-rigidity, low-reflectance silicon carbide sintered body can be suitably used for a large-size liquid crystal stepper member, in addition to these excellent characteristics, as long as the resistance can be increased. It becomes a material that can be made.

By the way, conventionally, in the manufacture of a silicon carbide sintered body, boron carbide has been added as a sintering aid to the silicon carbide raw material in order to make the sintered body dense.
However, the silicon carbide sintered body obtained in this way has high rigidity and strength and can cope with an increase in size, but the specific resistance is at most on the order of 10 ⁶ Ω · cm. It could not be said that the specific resistance was sufficient to be applied to the member or the like that requires insulation in the apparatus.

  On the other hand, as a method of obtaining a silicon carbide sintered body having a high specific resistance, for example, in Patent Document 1, beryllium or a beryllium compound is added to a silicon carbide powder raw material and hot press sintering is performed. It is disclosed that a silicon carbide sintered body having a specific resistance of 1 GΩ · cm can be obtained.

Patent Document 2 discloses that high resistivity silicon carbide sintered by hot press sintering using boron nitride 1-20 mass% and carbon or / and boron carbide as a sintering aid. the body obtained is disclosed.
JP-A-57-156373 JP JP 2003-277152 JP (paragraph 0013, etc.)

  However, although the silicon carbide sintered body described in Patent Document 1 has a very high specific resistance, the added beryllium or beryllium compound has a problem of toxicity, and in hot press sintering, It has been difficult to obtain a silicon carbide sintered body corresponding to the increase in size, accuracy, and complexity of manufacturing apparatus members accompanying the increase in the size of liquid crystals in recent years.

  The silicon carbide sintered body described in Patent Document 2 is also densified by hot press sintering, and a high specific resistance is obtained. This is also the same as the silicon carbide sintered body described in Patent Document 1. In addition, it has been difficult to obtain a sintered body having a large and complicated shape.

  The present invention has been made in order to solve the above technical problem, and can be suitably used as an insulating member for a semiconductor manufacturing apparatus, a liquid crystal device manufacturing apparatus, etc. An object of the present invention is to provide a high resistivity silicon carbide sintered body that can cope with complications.

The high resistivity silicon carbide sintered body according to the present invention is obtained by atmospheric pressure sintering by adding a binder having an amount of carbon content of 0.5 wt% or more and 4 wt% or less to silicon carbide raw material powder. The silicon carbide sintered body has a nitrogen content of 0.4 wt% or more and 0.5 wt% or less, a part of the nitrogen is dissolved in the silicon carbide crystal, and the remainder is the silicon carbide crystal grain boundary And a specific resistance of 0.1 GΩ · cm or more.
Since the silicon carbide sintered body having a high specific resistance as described above has low ultraviolet reflectance, is light and highly rigid, it is suitably used as a large-sized insulating ceramic material in semiconductor manufacturing equipment, liquid crystal device manufacturing equipment, and the like. be able to.

As described above, the high resistivity silicon carbide sintered body according to the present invention has low reflectance of short wavelength light, is lightweight and highly rigid, has a high specific resistance of 0.1 GΩ · cm or more, and generates static electricity. Even if static electricity is generated, it can be easily removed.
Therefore, the high resistivity silicon carbide sintered body according to the present invention is used as a ceramic member used for a large stage or chamber part, a static electricity removal terminal, etc. exceeding 1 m in a semiconductor manufacturing apparatus and a liquid crystal device manufacturing apparatus, and as a mechanical seal. , it can be suitably used for the sliding parts of the bearing and the like.

Hereinafter, the present invention will be described in more detail.
The high resistivity silicon carbide sintered body according to the present invention is a silicon carbide sintered body obtained by a normal pressure sintering method, includes boron nitride particles, and has a nitrogen content of 0.4 wt% or more and 0.5 wt%. The specific resistance is 0.1 GΩ · cm or more.
As described above, the silicon carbide sintered body according to the present invention has high specific resistance in addition to the general characteristics of ceramics that are lightweight and highly rigid, and has little reflection of short wavelength light such as ultraviolet rays.

The high resistivity silicon carbide sintered body according to the present invention as described above is prepared, for example, by mixing a slurry using boron nitride, carbon black and an organic binder as a sintering aid to a silicon carbide powder raw material. It is easy to manufacture by granulating the slurry, followed by a step of forming the slurry by pressure molding, and a step of sintering the molded body at 2100 to 2300 ° C. under normal pressure. Can do.
According to such a manufacturing method, since it is not necessary to perform sintering by hot pressing as in the prior art, even a member having a complicated shape such as a chamber part in a semiconductor manufacturing apparatus or a liquid crystal device manufacturing apparatus is relatively It can be easily manufactured, and it is possible to cope with an increase in size and accuracy of the member.

As the silicon carbide powder raw material, commercially available silicon carbide powder made of α-SiC having a purity of about 98% can be used.
The silicon carbide powder may contain 100 to 300 ppm of Al. Since this Al is a p-type forming element, the electric resistance is lowered to the semiconductor level. In the present invention, when such silicon carbide powder is used, the n-type is used to maintain a high resistance. which is a forming element N by adding a powder containing more than 300ppm be used.
Further, the particle diameter of the silicon carbide powder raw material is preferably an average particle diameter of 1.0 μm or less from the viewpoint of dispersibility during slurry preparation.

The boron nitride added to the silicon carbide powder raw material is preferably in the range of 0.7 wt% to 1 wt%.
When the added amount of boron nitride is less than 0.7 wt%, as described later, N is not sufficiently introduced into the obtained silicon carbide sintered body, and the resistivity cannot be improved. On the other hand, when the addition amount of boron nitride exceeds 1 wt%, the moldability is remarkably lowered in the molding step, and molding becomes difficult.
As the boron nitride, a powder having an average particle size of about 5 μm or less is preferable because of excellent dispersibility during slurry preparation.

The content of B in the obtained silicon carbide sintered body is substantially equal to the content of B in the added boron nitride.
On the other hand, the content of N in the silicon carbide sintered body is less than the content of N in the boron nitride added when a part of N is volatilized.
Therefore, the amount of boron nitride added must be such that N can remain in the silicon carbide sintered body in the form of boron nitride crystals. it is possible to achieve high resistance.
In addition, it can be confirmed by electron energy loss spectroscopy (EELS: Electron Energy-Loss Spectroscopy) that the boron nitride crystal remains in the grain boundary of the silicon carbide sintered body according to the present invention.

As described above, the silicon carbide sintered body according to the present invention requires the presence of boron nitride crystals. The aggregated phase of the boron nitride crystals is formed almost at the triple point of the silicon carbide crystal grain boundary. Is done. When the size of the boron nitride crystal is too large or too large, the density of the silicon carbide sintered body is lowered and the strength is lowered.
For this reason, it is preferable that there are few boron nitride crystals present in the silicon carbide sintered body according to the present invention, that is, the diameter is 4 μm or less, and the number density is preferably 120 pieces / mm ² or less, more preferably 100 or / mm ² or less.

In the slurry preparation step, auxiliary agents such as a dispersant and a binder may be added as appropriate for the purpose of improving dispersibility and homogenizing and densifying the sintered body.
As the binder, a phenolic resin is preferably used because of its high carbonization rate.
It is preferable that the binder is added in an amount such that the C content is 0.5 to 4 wt% with respect to the silicon carbide raw material powder.
If the C content is less than 0.5 wt%, the moldability is inferior. On the other hand, when it exceeds 4 wt%, the amount of C remaining in the obtained silicon carbide sintered body increases, leading to a decrease in specific resistance.
Moreover, it is preferable that the dispersion medium used at the time of slurry preparation is a volatile liquid, for example, it is preferable to use water, alcohol, etc.

The granulation method from the slurry is not particularly limited, but is usually performed by spray drying.
In the molding step, it is preferable to perform pressure molding in order to increase the density of the sintered body. For example, uniaxial press molding, CIP, or the like can be used.

The silicon carbide sintered body according to the present invention is obtained by firing the molded body obtained by pressure-molding the granulated powder as described above at 2100 to 2300 ° C.
When the firing temperature is less than 2100 ° C., the sintering does not proceed sufficiently, and the density and resistance decrease. On the other hand, when the firing temperature exceeds 2300 ° C., voids are generated due to evaporation of boron nitride added in the sintered body, leading to a decrease in density and a decrease in resistance.
In order to obtain a sintered body having a high specific resistance, it is preferable to sinter in an inert gas atmosphere from the viewpoint of preventing impurities from being mixed.
The sintering time and other sintering conditions are appropriately adjusted depending on the shape, size, application, etc. of the silicon carbide sintered body to be produced.

Since the silicon carbide sintered body according to the present invention obtained as described above has a high specific resistance, it can be suitably used as an insulating ceramic material in a semiconductor manufacturing apparatus, a liquid crystal device manufacturing apparatus or the like.
Note that a high specific resistance is disadvantageous from the standpoint of static elimination, but is difficult to generate a dielectric. For example, in a stepper, it prevents discharge during exposure work and prevents pattern destruction due to discharge with the substrate. And can be suitably used for sliding parts such as large stages and chamber parts exceeding 1 m, static electricity removal terminals, etc., mechanical seals, bearings, and the like.

EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example, this invention is not restrict | limited by the following Example.
[Example 1]
For silicon carbide powder raw material (α-SiC, purity 98%) with an average particle size of 0.7μm, boron nitride 0.8wt% as a sintering aid and phenol resin binder 2wt% in terms of C Alcohol as a medium was mixed with a resin ball mill to prepare a slurry.
After the slurry was granulated by spray drying, a molded body of 80 mm × 13 mm × 10 mm was formed.
The formed body was uniaxial press-molded at a pressure of 1200 kg / cm ² and fired at 2100 ° C. for 1 hour to produce a silicon carbide sintered body.

The obtained silicon carbide sintered body has a density of 3.15 ± 0.03 g / cm ³ , a dynamic elastic modulus of about 400 GPa, and a density and strength comparable to those of a normal silicon carbide sintered body having no high specific resistance. it has been found to have.
It was 0.42 wt% when the nitrogen content in this silicon carbide sintered body was measured.
Further, TEM observation confirmed that boron nitride particles were present at the silicon carbide grain boundaries.

Furthermore, the silicon carbide sintered body was processed into a 3 mm × 4 mm × 40 mm test piece, and the specific resistance was measured by the four-terminal method (JIS R1637 and JIS K7194). As a result, the specific resistance at room temperature exceeded 1 GΩ · cm. Was recognized.
In addition, the relative dielectric constant according to the Cole-Cole plot is 220 ± 20, and the dielectric loss is 0.8 or less, compared with the case where a normal silicon carbide sintered body has a relative dielectric constant of 300 and a dielectric loss of 1.4. both low, it was recognized in which hardly dielectric.

[Example 2]
A silicon carbide sintered body was produced in the same manner as in Example 1 except that the amount of boron nitride added was 0.95 wt%, and the nitrogen content and specific resistance were measured.
The measurement results are shown in Table 1.

[Comparative Examples 1 and 2]
As shown in Comparative Examples 1 and 2 in Table 1, a silicon carbide sintered body was produced in the same manner as in Example 1 except that the addition amount of boron nitride was changed, and the nitrogen content and ratio were Resistance was measured.
These measurement results are shown in Table 1.

[Comparative Example 3]
Instead of boron nitride, 0.15% by weight of boron carbide was added. Otherwise, a silicon carbide sintered body was produced in the same manner as in Example 1, and the nitrogen content and specific resistance were measured.
The measurement results are shown in Table 1.
In Comparative Example 3, the nitrogen content in the sintered body is derived from impurities contained in the silicon carbide raw material.

Claims (1)

A silicon carbide sintered body obtained by atmospheric pressure sintering by adding a binder having an amount of carbon content of 0.5 wt% or more and 4 wt% or less to a silicon carbide raw material powder , wherein the nitrogen content is 0.4 wt% or more and 0.5 wt% or less, a part of the nitrogen is dissolved in the silicon carbide crystal, the remaining is present as a boron nitride crystal in the silicon carbide crystal grain boundary, and the specific resistance is 0 A high specific resistance silicon carbide sintered body characterized by being 1 GΩ · cm or more.