Effects of β-Si3N4 Seeds on Microstructure and Performance of Si3N4 Ceramics in Semiconductor Package

Among the various ceramic substrate materials, Si3N4 ceramics have demonstrated high thermal conductivity, good thermal shock resistance, and excellent corrosion resistance. As a result, they are well-suited for semiconductor substrates in high-power and harsh conditions encountered in automobiles, high-speed rail, aerospace, and wind power. In this work, Si3N4 ceramics with various ratios of alpha-Si3N4 and beta-Si3N4 in raw powder form were prepared by spark plasma sintering (SPS) at 1650 degrees C for 30 min under 30 MPa. When the content of beta-Si3N4 was lower than 20%, with the increase in beta-Si3N4 content, the ceramic grain size changed gradually from 1.5 mu m to 1 mu m and finally resulted in 2 mu m mixed grains. However, As the content of beta-Si3N4 seed crystal increased from 20% to 50%, with the increase in fi-Si3N4 content, the ceramic grain size changed gradually from 1 mu m and 2 mu m to 1.5 mu m. Therefore, when the content of beta-Si3N4 in the raw powder is 20%, the sintered ceramics exhibited a double-peak structure distribution and the best overall performance with a density of 97.5%, fracture toughness of 12.1 MPa.m(1/2), and a Vickers hardness of 14.5 GPa. The results of this study are expected to provide a new way of studying the fracture toughness of silicon nitride ceramic substrates.