METHOD OF MANUFACTURING SILICON NITRIDE SUBSTRATE AND SILICON NITRIDE SUBSTRATE

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PROBLEM TO BE SOLVED : To provide a method of manufacturing a silicon nitride substrate capable of improving thermal conductivity and reducing cost by reducing a grain boundary phase as a result of obtaining a dense sintered body with reduced amount of a rare earth element, and a silicon nitride substrate having a high thermal conductivity in the thickness direction while maintaining excellent mechanical properties. SOLUTION : The method of manufacturing a silicon nitride substrate comprises a step of pulverizing a raw material powder containing silicon, an oxide of a rare earth element, and a magnesium compound to obtain a slurry, a step of molding the slurry into a sheet, and a step of sintering the molded body in a nitrogen atmosphere to obtain a silicon nitride sintered body. The raw material powder contains 0.5 mol% or more and less than 2 mol% of the oxide of a rare earth element and 8 mol% or more and less than 15 mol% of a magnesium compound (containing 87 mass% or more of MgSiN2), and a BET specific surface area (m2/g) and a median diameter D50(μm) of the silicon particles in the slurry satisfy 1.5≤BET≤4.5, 2.5≤D50≤6 and 13≤BET×D50≤18. SELECTED DRAWING : Figure 1 COPYRIGHT : (C)2019, JPO&INPIT