In recent years, the ceramic substrates that have been mass-produced and widely used are mainly: Al2O3, BeO, SiC, Si3N4, AlN and so on.
Properties of different kinds of ceramic substrates (Source: Liao Shengjun. Preparation and Properties of Silicon nitride ceramic Materials for substrate
Al2O3 because of its simple preparation process, good insulation, and high temperature resistance, currently occupies an important position in the heat dissipation substrate industry. However, the low thermal conductivity of Al2O3 cannot meet the development requirements of high-power and high-voltage devices, and is only suitable for working environments with low heat dissipation requirements, and due to the low bending strength, the application range of Al2O3 ceramics as a heat dissipation substrate is also limited.
Although BeO ceramic substrate has high thermal conductivity and low dielectric constant to meet the requirements of efficient heat dissipation, but because of its toxicity, it has an impact on the health of workers and is not conducive to large-scale application.
AlN ceramics have high thermal conductivity and are considered as candidate materials for heat dissipation substrates. However, AlN ceramics have poor thermal shock resistance, easy deliquescent, low strength and toughness, which is not conducive to working in complex environment and difficult to ensure the reliability of its application.
SiC ceramics have high thermal conductivity, but because of their high dielectric loss and low breakdown voltage, it is not conducive to the application of high frequency and high voltage working environment.
Silicon nitride is recognized as the best ceramic substrate material with high thermal conductivity and high reliability at home and abroad. Although the thermal conductivity of Si3N4 ceramic substrate is slightly lower than that of AlN, its bending strength and fracture toughness can reach more than twice that of AlN. At the same time, the thermal conductivity of Si3N4 ceramics is much higher than that of Al2O3 ceramics. In addition, the thermal expansion coefficient of the Si3N4 ceramic substrate is close to that of the third-generation semiconductor substrate SiC crystal, making it more stable to match the SiC crystal material. This makes Si3N4 the preferred material for high thermal conductivity substrates for 3rd generation SiC semiconductor power devices.