Chemistry of inorganic compounds – Silicon or compound thereof – Binary compound
Reexamination Certificate
2000-05-23
2003-09-30
Hendrickson, Stuart L. (Department: 1754)
Chemistry of inorganic compounds
Silicon or compound thereof
Binary compound
C501S088000
Reexamination Certificate
active
06627169
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to silicon carbide powder and a production method thereof, and specifically to silicon carbide powder which can provide a high purity, high density silicon carbide sintered body, and a production method thereof.
2. Description of the Related Art
Conventionally, holding jigs of semiconductor-related components such as wafers and the like have been made of quartz material. However, because wafer processing temperatures have increased and processing times have shortened, there have been problems with the quartz material being thermally deformed and being deteriorated by cleaning with chemicals such as hydrofluoric acid and the like. As a means for solving these problems, a silicon carbide sintered body whose strength at high temperature, heat resistance, wear resistance, chemical resistance and the like are excellent has been desired for use as a replacement material.
In order to use a silicon carbide sintered body for semiconductor-related components, purification is necessary. Silicon carbide sintered bodies have conventionally been produced by burning silicon carbide powder having impurities in amounts of at most 0.1 ppm. However, in the future, higher purification will of necessity be required. Thus, development of higher purity silicon carbide powder is required.
SUMMARY OF THE INVENTION
Accordingly, the present invention was achieved in view of the conventional problems above. An object of the present invention is to provide a high purity silicon carbide powder which is useful as a raw material for a high purity silicon carbide sintered body, a production method thereof, and the high purity silicon carbide sintered body.
A first aspect of the present invention is a silicon carbide powder, which contains impurity elements, each of the impurity elements being contained in an amount of not more than 0.01 ppm.
A second aspect of the present invention is a production method of a silicon carbide powder, the method comprising the steps of: burning a silicon-containing compound and a carbon-containing compound in an inert atmosphere; and heat-treating, in a vacuum atmosphere, a silicon carbide powder which is obtained from the burning step.
A third aspect of the present invention is a silicon carbide powder produced by a method comprising the steps of: burning a silicon-containing compound and a carbon-containing compound in an inert atmosphere; and heat-treating, in a vacuum atmosphere, a silicon carbide powder which is obtained from the burning step.
A fourth aspect of the present invention is a silicon carbide sintered body which is formed by sintering a silicon carbide powder which contains impurity elements, each of the impurity elements being contained in an amount of not more than 0.01 ppm, wherein the silicon carbide powder has an average particle diameter (D
50
) of 1 &mgr;m-50 &mgr;m, and a value calculated from particle size distribution of a ratio (D
90
/D
10
) of a 90% cumulative diameter (D
90
) to a 10% cumulative diameter (D
10
) is not more than 5.0.
The silicon carbide powder of the present invention is useful as a raw material for the silicon carbide sintered body. In particular, the silicon carbide sintered body obtained from the silicon carbide powder of the present invention can be highly purified, and is suitable for use for semiconductor-related components.
In the production method of the silicon carbide sintered body of the present invention, because the silicon carbide powder obtained in the burning is heat-treated, impurities adhered at a surface of the powder and at a vicinity of the surface can be removed. As a result, high purity silicon carbide powder can be obtained.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention is described more specifically below.
A silicon carbide powder of the present invention contains impurity elements, each of the impurity elements being contained in an amount of at most 0.01 ppm. Thus, a high purity silicon carbide sintered body can be obtained by using this silicon carbide powder.
The amount of each impurity element can be measured using an ICP-mass spectrometer or a flameless atomic absorption spectrometer.
The term “impurity element” means an element which belongs to one of groups
1
to
16
of the periodic table of the 1989 revised version of IUPAC inorganic chemistry nomenclature and which has an atomic number of at least 3, excepting atomic numbers
6
to
8
and
14
.
Preferably, the silicon carbide powder of the present invention has an average particle diameter (D
50
) of 1 &mgr;m-50 &mgr;m and a value of a ratio (D
90
/D
10
) of a 90% cumulative diameter (D
90
) to a 10% cumulative diameter (D
10
), which are calculated from particle size distribution, is at most 5.0.
The average particle diameter (D
50
) is preferably 1 &mgr;m-50 &mgr;m, and more preferably 1 &mgr;m-40 &mgr;m. If the average particle diameter (D
50
) is less than 1 &mgr;m, handling in processes of measuring, mixing and the like may become difficult. If the average particle diameter (D
50
) exceeds 50 &mgr;m, specific surface area of the powder becomes small; i.e., contact surface areas between particles become small and densification of the silicon carbide sintered body may become difficult.
The value of the ratio (D
90
/D
10
) of the 90% cumulative diameter (D
90
) to the 10% cumulative diameter (D
10
), calculated from the particle size distribution, is preferably at most 5.0. If the value of (D
90
/D
10
) exceeds 5.0, the particle size distribution will be wide. Thus, many particles which are larger or smaller than a suitable average particle diameter will be mixed in and, however particle diameters are biased, particle diameters may be irregular.
The silicon carbide powder of the present invention can be preferably obtained by the following production method of silicon carbide powder of the present invention.
The production method of the silicon carbide powder of the present invention is described in detail herebelow.
The production method of the silicon carbide powder of the present invention includes a burning step in which a silicon-containing compound and a carbon-containing compound are burned in an inert atmosphere, and a heat treatment step in which the silicon carbide powder obtained in the burning is heat-treated in a vacuum atmosphere. By means of the production method of silicon carbide powder of the present invention, a high purity silicon carbide powder, such as the silicon carbide powder of the present invention, can be obtained.
The burning step is described in detail herebelow.
In the burning step, with regard to obtaining silicon carbide powder having uniform particle diameters, detecting amounts of carbon monoxide generated in the burning and controlling adjustment of burning temperature in accordance with the detected amounts is preferable.
In the burning step, generally, when at least two compounds which react while generating gas when heated (shown as compound AB (solid) and compound CD (solid) below) are heated, a reaction as shown in the reaction formula model below is caused. As a result, a specified substance, particulate compound AC, is obtained and, depending on the reaction, gas compound BD is produced as a by-product.
(Reaction formula model)
AB (solid)+CD (solid)→AC (solid)+BD (gas)
In investigations by the inventors of the present invention, it was found that, if raw material compounds AB and CD are burned and reacted in an inert atmosphere and amounts of gas generated in burning are detected, there is a correlation between an amount of gas generated and a state of progress of the reaction.
In other words, the amount of gas generated varies depending upon progress of the reaction. In an initial stage of the reaction, a medium amount of gas is generated; in a middle stage of the reaction, a large amount of gas is generated; and in a final stage of the reaction, a medium amount of gas is generated. Further, in a particle diameter growth stage of a target compound AC, a small amount of gas is generate
Endo Shigeki
Itoh Michio
Bridgestone Corporation
Hendrickson Stuart L.
Oliff & Berridg,e PLC
LandOfFree
Silicon carbide powder and production method thereof does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Silicon carbide powder and production method thereof, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Silicon carbide powder and production method thereof will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3091722