JP2003112977A - Method for producing high purity silicon nitride powder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce high purity silicon nitride powder which is suitable for electronic parts such as an implement for a semiconductor, a circuit board by a direct nitriding method with excellent mass-productivity. SOLUTION: A metallic silicon powder raw material in which the total of the group 3B and 5B (exclusive of nitrogen) elements is <=100 μg/g, and the total of the group 7B elements is <=50 μg/g, and having a mean particle diameter of 10 to 20 μm is nitrided so that temperature is gradually raised in an atmosphere containing nitrogen or nitrogen and ammonia under the partial pressure of nitrogen of 30 KPa or more, and the mean reaction rate is controlled to <=2.0%/hr, and also, the cumulative reaction ratio until a temperature reaches 1,300 deg.C is controlled to >=85%, and the obtained silicon nitride ingot is pulverized to produce the silicon nitride powder.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing high-purity silicon nitride powder by direct nitriding of a raw material of metal silicon powder. [0002] Silicon nitride has excellent properties such as high strength and high creep properties and is used for applications such as cutting tools, automobile parts and industrial parts. In recent years, applications of electronic components such as jigs for semiconductors and circuit boards have been expanding, and accordingly, higher purity has been required. [0003] One of the methods for producing silicon nitride powder is a direct nitridation method in which a metal silicon powder raw material is nitrided with a nitriding gas such as nitrogen or ammonia to produce a silicon nitride ingot and pulverize it. This method is most widely used as a mass production process. A silicon nitride ingot is an aggregate of silicon nitride particles synthesized from a metal silicon powder raw material,
The characteristics, and thus the characteristics of the silicon nitride powder, largely depend on the characteristics of the metal silicon powder raw material and the nitriding conditions. Since the nitridation reaction of the metal silicon powder raw material is a large exothermic reaction, the ingot becomes a relatively strong agglomerate, and pulverization is required to obtain silicon nitride powder. As the grinding conditions become harsher, the chance of impurities being mixed in increases, and the quality of the grinding performance affects the properties of the silicon nitride powder. [0005] There are a wet method and a dry method for pulverizing a silicon nitride ingot. In the wet method, although fine pulverization is possible, contamination of impurities and an increase in the amount of oxygen occur due to wear of the pulverization media, and a purification treatment by acid cleaning or the like is required. On the other hand, in the dry method, there is no problem of the wet method, but the specific surface area does not increase so much, and the yield of the fine powder is lower than in the wet method. As described above, in the direct nitriding method silicon nitride, it is necessary to optimize the nitriding conditions of the metal silicon powder raw material to produce a silicon nitride ingot that can be easily pulverized.
It is important for purifying silicon nitride,
In addition, it is necessary to consider using a high-purity metal silicon powder material. [0007] As a technique for purifying silicon nitride by direct nitriding, Japanese Patent Application Laid-Open No. 2000-335907 discloses that the total content of metal impurities is 1.3% by weight or less and the Fe content is 0.3% by weight.
It is described that a metal silicon powder having a content of 3% by weight or less and an average particle size of 100 μm or less is used. In addition, Japanese Unexamined Patent Publication No.
Japanese Patent No. 32405 describes that high-purity metallic silicon powder having a purity of 99.999% by mass or more is nitrided. However, if such a high-purity metal silicon powder raw material is nitrided by conventional means, the reason is unknown, but probably, for example, the impurity components of the metal silicon powder raw material such as iron, aluminum, manganese, and titanium are reduced at a low temperature. Although it is a catalyst that promotes nitridation, it is thought to be due to its disappearance, but it becomes difficult for the reaction to proceed, and unreacted silicon tends to remain, so long-term nitridation is required to avoid it, A new problem was encountered in that the productivity of high-purity silicon nitride deteriorated. Further, if the silicon nitride powder contains a large amount of group 7B elements, it is difficult to apply it to electronic parts such as jigs for semiconductors and circuit boards. [0008] The present invention has been made in view of the above, and an object of the present invention is to provide a high-purity silicon nitride powder applicable to electronic parts such as jigs for semiconductors and circuit boards. It is to be manufactured by the direct nitriding method which is excellent in mass productivity. [0009] That is, the present invention provides a method of
B, 5B (not including nitrogen) group element is 100 μg /
g or less, a total of 7B group elements is 50 μg / g or less, and an average particle diameter is 10 to 20 μm.
Under an atmosphere of nitrogen or a partial pressure of nitrogen containing ammonia and nitrogen of 30 KPa or more, the temperature is gradually increased, and the average reaction rate is 2.0%.
A method for producing a silicon nitride powder, comprising nitriding at a rate of not more than / hr and a cumulative reaction rate of not less than 85% at a temperature of up to 1300 ° C., and pulverizing the obtained silicon nitride ingot. Hereinafter, the present invention will be described in more detail. [0011] The metal silicon powder raw material used in the present invention has a total of 100 µm of 3B, 5B (excluding nitrogen) group elements.
g / g or less, the total of group 7B elements must be 50 μg / g or less, and the average particle diameter must be 10 to 20 μm. Examples of such high-purity metallic silicon powder include pulverized single-crystal silicon or polycrystalline silicon for semiconductors. If the total of the 3B and 5B (excluding nitrogen) group elements of the metal silicon powder raw material is more than 100 μg / g or the total of the 7B group elements is more than 50 μg / g, they are contained in the silicon nitride powder. Most of these elements remain, making them unsuitable for use in electronic components. Furthermore, when the average particle size is less than 10 μm, the reaction rate sharply increases because the amount of fine powder is high and the reactivity is high, and the average reaction rate is 2.0% /
As a result of exceeding hr, the amount of dissolved / remaining silicon increases. On the other hand, if the average particle diameter is more than 20 μm, unreacted silicon remains even if the nitridation reaction conditions are highly controlled as described later. [0013] The metal silicon powder raw material may be subjected to nitriding as it is, but in order to reduce the heat of reaction, it may be mixed with a high-purity silicon nitride powder having the purity and particle diameter as produced in the present invention. preferable. The ratio is 50 parts or less of high-purity silicon nitride powder with respect to 100 parts (parts by mass, the same applies hereinafter) of the metal silicon powder raw material. Metal silicon powder raw material, or a mixed raw material of metal silicon powder raw material and high-purity silicon nitride powder (hereinafter, referred to as “metal silicon powder raw material”)
Both are simply referred to as “raw materials”. ) Is filled in a ceramic container such as alumina or silicon nitride, or molded by die molding, dry CIP molding or the like, and then subjected to nitriding. As the nitriding furnace, a reactor such as a box-type reactor, a rotary furnace, a pusher-type continuous furnace, and a fluidized-bed furnace is used. In the present invention, the raw material is nitrided while gradually increasing the temperature in an atmosphere of nitrogen or a partial pressure of nitrogen containing nitrogen and ammonia at a nitrogen partial pressure of 30 KPa or more. It is important to make the cumulative reaction rate at 1300 ° C. 85% or more for nitriding. If the nitrogen partial pressure of the nitriding atmosphere is less than 30 KPa, even if the reaction rate is controlled to 2.0% / hr or less,
The resulting silicon nitride has many fiber-like particle morphologies, and has a disadvantage such as an increase in bulk density and an increase in packing density during molding. Nitriding atmosphere is 100% nitrogen gas
By using a mixed atmosphere containing nitrogen and ammonia at a nitrogen partial pressure of 30 KPa or more, the nitrogen partial pressure can be changed quickly, and there is an advantage that the reaction rate can be finely controlled. If the average reaction rate exceeds 2.0% / hr, the heat of reaction becomes excessive, so that metallic silicon may be melted and deposited, resulting in incomplete nitriding. Furthermore, the temperature 1
If the cumulative nitridation rate up to 300 ° C. is less than 80%, the amount of silicon reacted at a high temperature increases, and the silicon is melted and precipitated by the heat generated during the reaction, leaving silicon in the generated silicon nitride powder. In the present invention, the average reaction rate and the temperature 1
Adjustment of the cumulative nitriding rate up to 300 ° C. is performed by controlling the partial pressure of nitrogen in a nitriding atmosphere and controlling the temperature rising rate up to 1300 ° C. The average reaction rate and the cumulative nitridation rate at a temperature of 1300 ° C. are determined by measuring the amounts of nitrogen and ammonia supplied to the nitriding furnace and the amounts of nitrogen and ammonia discharged from the nitriding furnace. Consumed in
That is, it is calculated assuming that silicon nitride has been generated. The obtained silicon nitride ingot is pulverized to a desired particle size by the above-mentioned wet method or dry method to obtain a high-purity silicon nitride powder. It is preferable that the inside of the crusher is lined with a lining material mainly composed of silicon nitride so as to minimize contamination of impurities from the crushing media. As the pulverizing media, those produced using high-purity silicon nitride powder equivalent to or more than that produced in the present invention are preferable. The average particle diameter of the high-purity silicon nitride powder produced in the present invention is preferably 3 μm or less, and preferably 3 μm or less.
If it exceeds m, the abundance ratio of the coarse particles becomes high, and the silicon nitride sintered body produced using the same becomes a fracture starting point, and the strength is reduced. Further, when the high-purity silicon nitride powder of the present invention is used as a release material, there is a possibility that the object to be released may be damaged. As for the impurities, the total of the 3B and 5B (not including nitrogen) group elements is 100 μg / g or less and 7
It is preferable that the total of the group B is 50 μg / g or less.
Total of 3B, 5B (without nitrogen) family is 100 μg / g
If the total of the super and 7B elements is more than 50 μg / g, it is not suitable for electronic parts. The present invention will be described more specifically below with reference to examples and comparative examples. Example 1 3 liters of 1 mm lower powder obtained by crushing a single crystal silicon lump with an alumina jaw crusher and 1.8 liters of silicon nitride balls were placed in a polyethylene pot, and the lid was closed. And crushed at 80 rpm for 10 hours. The amount of impurities and the average particle diameter of the obtained metal silicon powder raw material were measured. Table 1 shows the results. 5 kg of the above-mentioned metal silicon powder raw material is charged into a container made of silicon nitride, placed in a batch nitriding furnace, and purged while flowing nitrogen gas until the oxygen concentration in the furnace becomes 100 μg / g or less. 100 ° C under atmosphere
/ Hr. When the temperature reached 1000 ° C., a part of the nitriding atmosphere gas in the furnace was replaced with argon to adjust the partial pressure of nitrogen gas to 40 kPa, and the temperature was further increased to decrease the reaction rate by 0.5%.
/ Hr. Thereafter, the reaction rate was gradually increased to 1.5% / hr by controlling the flow rate of nitrogen and the rate of temperature rise, and nitriding was performed until the cumulative nitridation rate at 1300 ° C. reached 87% while maintaining this state. . Subsequently, the reaction rate was increased to 1.0% / h
The temperature was raised to 1450 ° C. and nitriding was performed. Even if the temperature is maintained at 1450 ° C. and the nitriding atmosphere in the furnace is entirely replaced with nitrogen, the reaction rate is 0.1% / hr.
This state was maintained until the following. Then, after the reaction rate became less than 0.1% / hr, cooling was started under a nitrogen atmosphere. After cooling to room temperature, the silicon nitride ingot was taken out, coarsely crushed by a jaw crusher provided with a silicon nitride lining, and finely ground by a vibration mill to produce a high-purity silicon nitride powder. The reaction rate and the cumulative reaction rate were calculated by measuring the amount of nitrogen supplied to the nitriding furnace and the amount of nitrogen discharged from the nitriding furnace, and assuming that the difference between the two was used in the reaction. The vibration mill pulverization was performed for 5 minutes in a silicon nitride container filled with silicon nitride balls. Comparative Examples 1 to 5 Metallic silicon powder raw materials having the amounts of impurities shown in Table 1 were used (Comparative Examples 1 and 2), and metallic silicon powder raw materials having an average particle diameter of 32 μm were used (Comparative Example 3). ), The average reaction rate was 2.8% / hr (Comparative Example 4), and the temperature was 1
A silicon nitride powder was produced in the same manner as in Example 1 except that the cumulative reaction rate at 300 ° C. was set to 80% (Comparative Example 5). Example 2 Example 2 was repeated except that a raw material consisting of a mixed powder of 100 parts of the metal silicon powder raw material prepared in Example 1 and 20 parts of the high-purity silicon nitride powder manufactured in Example 1 was used. In the same manner as in Example 1, a silicon nitride powder was produced. As a result, the reaction was promoted at a lower temperature than in Example 1, and finer particles were obtained. This silicon nitride powder had the advantage of increasing the strength of the sintered body. With respect to the silicon nitride powder obtained above,
The amount of impurities, the amount of oxygen, and the average particle size were measured. Further, a silicon nitride sintered body was manufactured, and the four-point bending strength and the volume resistivity were measured. Table 1 shows the results. (1) Impurity amount: 3 using chemiluminescence analysis
The total of B, 5B (excluding nitrogen) group elements was measured. Further, the total of the group 7B elements was measured by an ion chromatogram method. (2) Oxygen content: Measured using a tin capsule with an oxygen / nitrogen simultaneous analyzer manufactured by LECO. (3) Average particle diameter: Measured by a laser diffraction light scattering method using “Microtrack” (trade name, manufactured by Nikkiso Co., Ltd.). (4) Four-point flexural strength: measured at room temperature according to JIS R1601. (5) Volume resistivity: 92 g of silicon nitride powder, 4 g of aluminum oxide powder, and 4 g of yttrium oxide powder were mixed in a ball mill for 10 hours, molded into 80 × 80 × 3 mm, and then subjected to CIP molding at 200 MPa. This was held in a nitrogen atmosphere at 1900 ° C. for 5 hours to produce a silicon nitride sintered body, and both sides were polished and smoothed. Then, the volume resistivity was changed to “High Resistance Meter 4339A” manufactured by Hewlett-Packard Company. It measured using. [Table 1] From Table 1, it can be seen that the silicon nitride powder obtained in the examples has less silicon in the silicon nitride powder obtained as compared with the comparative example, and a silicon nitride sintered body excellent in strength can be obtained. According to the present invention, high-purity silicon nitride powder applicable to electronic parts such as jigs for semiconductors and circuit boards can be manufactured by a direct nitriding method which is excellent in mass productivity.

   ────────────────────────────────────────────────── ─── Continuation of front page    F term (reference) 4G001 BA62 BB32 BC01                 4G030 AA52 BA01 BA19 GA01

Claims (1)

Claims: 1. The total of group 3B, 5B (not including nitrogen) group elements is 100 μg / g or less, and the total of group 7B elements is 50 μg.
/ G or less, the temperature of the metal silicon powder raw material having an average particle diameter of 10 to 20 μm is gradually increased under an atmosphere of nitrogen or a partial pressure of nitrogen containing ammonia and a nitrogen partial pressure of 30 KPa or more, and the average reaction rate is 2.0% / hr or less. And at a temperature of 1300 ° C
A method of producing a silicon nitride powder, characterized in that the silicon nitride ingot is pulverized by nitriding with a cumulative reaction rate up to 85% or more and pulverizing the obtained silicon nitride ingot.