Extreme Service Packaging for Silicon Carbide Electronic Devices
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Extreme Service Packaging for Silicon Carbide Electronic Devices Maxime J. F. Guinel1, Diego Rodriguez-Marek1, M. Grant Norton1, Robert B. Davis2 and David F. Bahr1 1 School of MME, Washington State University, Pullman WA 99164 2 Caldus Semiconductor, Inc. 350 Hills Street, Richland, WA 99352 ABSTRACT Electronic devices based on single crystal SiC represent a good choice for a variety of new high temperature, high power electronics applications. The challenge is to develop a package that is resistant to thermal degradation in harsh environments. Conditions are extreme and this all but rules out only a handful of materials and materials systems. Polycrystalline SiC is the material that we have chosen to study as a suitable package and materials suitability/compatibility has been considered on several levels. INTRODUCTION The introduction of accurate, reliable and low cost solid-state electronics that function at elevated temperatures and in harsh environments will be followed by breakthroughs in many sectors. The market for harsh environment sensors is predicted to reach almost $3 billion by 2010 [1] with fuel cell applications accounting for 10% of this market. A limitation to fuel cell technology and the use of hydrogen fuels is the lack of electronic sensors and devices that function in these harsh conditions. The recent move of fuel cells into the mainstream of energy generation provides a huge need for robust sensor technology. Electronic devices based on single crystal SiC will be the building blocks of such sensors. An associated challenge is to develop a package that is resistant to thermal degradation in aggressive and harsh environments. In addition to maintaining electronic functionality, the package must remain hermetic, erosion and corrosion resistant for durations of at least 10,000 hours. Elevated temperatures place severe loads on the electronic components and package. A critical concern for the package is high temperature mechanical compatibility and the continuity of the electrical interconnects. The thermal cycle is often extreme and this all but rules out a handful of materials and materials systems. SiC is the material that we have chosen to investigate as a package material for high temperature, harsh environment conditions. Materials selection and design must be optimized to compensate for high cyclic strain. Materials suitability/compatibility needs to be considered on several levels: package body, package sealing, and package electrical interconnects and contacts. PACKAGE BODY The first issue that was investigated was the reliability of the package base material when exposed to high temperatures and thermal cycling. The SiC substrates used in this study were high purity slip cast SiC. The samples were cut into coupons, polished,
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and oxidized in air at temperatures between 1270 and 2050 K. Upon completion of each cycle, the sample surface was examined using a SEM. Silica scales were observed to form at all temperatures. Above 1773 K there was evidence of a reaction at the SiC
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