Power Device Packaging Technologies for Extreme Environments

Silicon carbide is a wide bandgap semiconductor capable of operation at temperatures in excess of 600degC. However, high temperature contacts and packaging to interface with the other elements of the electrical system are required. Contact pad stacks, die attach, wire bonding and passivation materials and techniques have been demonstrated for use at temperatures from 300-350degC. The contacts stacks use amorphous TaSi₂:N₂ as a diffusion barrier to prevent oxidation of the Ni or Al:Ti based contacts. Liquid transient phase bonding has been developed with Au-Sn:Au, yielding high die shear strength after 2000 hours at 350degC. The die attach system has also shown no degradation after 500 hours at 400degC. Large diameter gold wire bonding was used for top side electrical contact. Polyimide has been demonstrated for use as a passivation layer at 300degC. Alternate passivation materials must still be developed for higher temperature, higher voltage applications