Method for manufacturing silicon nitride substrate
The present invention relates to a method for manufacturing a silicon nitride substrate and, more specifically, comprises the steps of: forming a slurry by mixing silicon nitride powder, a ceramic additive, and a solvent; molding the slurry to form sheets; sandwiching at least one of the sheets between a lower plate and an upper plate to form a stacked structure; degreasing the stacked structure; and sintering the stacked structure. At least one of the lower plate and the upper plate comprises a plurality of protrusions provided on one surface thereof, and the protrusions extend in parallel to each other in one direction.
1 . A method for manufacturing a silicon nitride substrate, comprising: forming a slurry by mixing silicon nitride powder, a ceramic additive, and a solvent; molding the slurry to form sheets; forming a stacked structure by sandwiching at least one of the sheets between a lower plate and an upper plate; performing degreasing process on the stacked structure; and performing sintering process on the stacked structure, wherein: the lower plate comprises a plurality of first protrusions provided on an upper surface thereof, the upper plate comprises a plurality of second protrusions provided on a lower surface thereof, the first and second protrusions extend in parallel to each other in one direction, a first recess is defined between adjacent first protrusions, a second recess is defined between adjacent second protrusions, the stacked structure comprises a first gap defined by the adjacent first protrusions, the first recess, and a bottom surface of the sheet, and a second gap defined by the adjacent second protrusions, the second recess, and a top surface of the sheet, a heated gas is introduced which contacts the top surface and the bottom surface of the sheet through the first and second gap during the degreasing process, the sintering process comprises embedding the stacked structure, after the degreasing process, in bedding powder, the bedding powder comprises boron nitride powder and silicon nitride powder, and the bedding powder is in contact with the sheet through the first gap and the second gap.
2 . The method of claim 1 , wherein the ceramic additive comprises a yttrium oxide (Y 2 O 3 ), a magnesium oxide (MgO), and a zirconium oxide (ZrO 2 ),
a weight ratio of the yttrium oxide to the ceramic additive is 0.5 to 0.8,
a weight ratio of the magnesium oxide to the ceramic additive is 0.1 to 0.4, and
a weight ratio of the zirconium oxide to the ceramic additive is 0.1 to 0.3.
3 . The method of claim 1 , wherein the forming of the slurry comprises adding a binder and a plasticizer.
4 . The method of claim 1 , wherein the forming of the slurry comprises:
forming a first mixture by adding silicon nitride powder, the ceramic additive, and a dispersant to the solvent;
performing a first ball milling process on the first mixture;
forming a second mixture by adding a binder and a plasticizer to the first mixture on which the first ball milling process is completed; and
performing a second ball milling process on the second mixture.
5 . The method of claim 1 , wherein the molding of the slurry comprises a tape casting process.
6 . The method of claim 1 , further comprising forming a laminate sheet by stacking the sheets and performing a lamination process thereon, before the forming of the stacked structure.
7 . The method of claim 1 , wherein each of the lower plate and the upper plate has a density of 1.4 g/cm 3 to 1.7 g/cm 3 .
8 . The method of claim 1 , wherein each of the lower plate and the upper plate has an area of 1.00 times to 1.02 times of an area of the sheet.
9 . The method of claim 1 , wherein each of the first and second protrusions has a first width, each of the first and second recesses has a second width,
the first width is 4 mm to 15 mm, and
the second width is 4 mm to 15 mm.
10 . The method of claim 1 , wherein the first and second protrusions are arranged with a predetermined pitch.