Sintered reaction-bonded silicon nitride ceramics for power-device substrates-review-

This review addressed the recent progress of sintered reaction-bonded Si3N4 (SRBSN) ceramics which are expected to be used as ceramic substrates of the next-generation power devices. Following an overview of thermal conductivities of Si3N4 ceramics and their improvement strategies, we described the advantages of the SRBSN routes. Because of the low content of lattice oxygen, the SRBSN ceramics possess significantly high thermal conductivities, compared to Si3N4 ceramics prepared by conventional methods. This material also showed exceptionally high fracture toughness and the strong rising R-curve behavior. The properties of the SRBSN ceramics are largely affected by the nitridation conditions, including the temperature, pressure and heating rate, and the sintering additive ratios. The thermal fatigue tests revealed the excellent thermal fatigue resistance of the SRBSN substrates, compared with those of other ceramic substrates. The strength retention ratio after thermal fatigue was clearly proportional to the fracture toughness. The dielectric breakdown strength (DBS) of the SRBSN ceramics with large fibrous grains showed a thickness dependency reverse to the normal (lower DBS in thinner substrates).