Nanoscale Die-attach Technology for High-temperature Packaging of Power Devices
Studies on wide band gap semiconductor devices, such as SiC or GaN diodes and transistors, have shown great promise for revolutionizing the power electronics industry; their superior switching characteristics and ability to function at elevated temperatures of up to 350°C reduce heatsink and cooling equipment requirements. However, interconnecting and packaging these devices for high-temperature uses pose a significant challenge. The state-of-the-art technology for interconnecting power devices typically involves attaching one terminal of the semiconductor die to a heat-sinking substrate with a lead or lead-free solder alloy or with an electrically conductive epoxy, while its other terminal(s) are generally attached by wire-bonding fine aluminum wires. Such interconnections are not able to function at the high temperatures of the wide band gap devices because of the low melting temperatures of solder alloys and low decomposition temperatures of epoxies and the susceptibility of aluminum wire to electromigration-induced failure at elevated temperatures. Furthermore, the use of lead-containing solders raises a serious environmental and public health concern. We are developing an environmentally friendly die-attach technology that could allow wide band gap power semiconductor devices functioning at high temperatures. The technology is based on the synthesis and processing of nanoscale metal pastes that can be sintered at low temperatures to reliably join semiconductor devices with packaging materials. Successful development of this technology would remove a technology barrier for applications of wide band gap power semiconductor devices that hold great promise for improving the performance, reliability, and cost-effectiveness of power electronics systems, thus in turn significantly impact the future growth of the trillion-dollar electronics industry.