Boron Nitride Capacitors for Advanced Power Electronic Devices

Silicon carbide (SiC) and gallium nitride (GaN) are being used to break barriers with respect to the design and fabrication of high-temperature high-power transistors, but capacitors remain the weak link in achieving higher temperature electronics. In particular, the use of SiC should allow future power devices to operate safely at temperatures up to 400°C, but at these temperatures, the capacitors have been shown to severely degrade. Therefore, high-temperature-capable capacitors will be needed for SiC power components such as device gate drive circuits and RF power transistors. This project will fabricate long-life boron nitride (BN) capacitors for advanced SiC power electronics, using a physical vapor deposition (PVD) process. The BN capacitor will match the silicon carbide device operating at temperatures above 300°C. In Phase I, layers for the BN capacitors were first grown on a silicon substrate using an ion-source-assisted PVD technique. The use of vapor deposition provided for precise control and quality material formation. The capacitors were subjected to electrical and thermal characterization. The BN material exhibited high thermal stability, high thermal conductivity, and high breakdown voltage, and met the SiC power requirements. Phase II will further develop the advanced BN capacitors by fabricating and testing different capacitor structures, and by fabricating pre-commercial capacitor prototypes. Commercial Applications and other Benefits as described by the awardee: High-energy density capacitors that can operate at hige temperatures should find use in ballistic missiles, electric guns, and high power microwave sources; microwave systems for communications such as cellular telephony and data transmission; satellite communications systems; high power pulsed amplifiers for ground, airborne and space-based radar; and high frequency switching power supplies.