Active devices for high temperature microcircuitry. [Silicon and gallium arsenide devices]

As part of a program to develop high temperature electronics for geothermal well instrumentation, a number of solid state diode and transistor types were characterized from room temperature to 300/sup 0/C. The temperature dependence and aging stability of transport and leakage properties were measured. Included in the study were silicon diodes, bipolar transistors, JFETs, MOSFETs, and GaAs MESFETs and JFETs. In summary the results are: diodes and bipolar transistors became extremely leaky at high temperature and are therefore of limited use; silicon MOSFETs and GaAs devices showed unacceptable aging instabilities at high temperatures; silicon JFETs from certain manufacturers were sufficiently stable and had suitable temperature dependent characteristics so that operational circuits could be made. Comparisons were made of experimental device characteristics and those predicted by theory. The theoretical calculations were done using standard equations revised to include appropriate temperature dependent parameters. Close agreement between theory and experiment was found, indicating that unexpected high temperature effects were insignificant. In order to facilitate the use of devices in high temperature hybrids, it was necessary to develop bonding and prescreening techniques. A large variance of JFET 300/sup 0/C operating parameters was found even within a single production lot. Consequently, high temperature prescreening allowed each circuit to be specifically ''pretuned.'' Standard solder, epoxy, and chip and wire attachment technologies were not functional at 300/sup 0/C. Gold-germanium solder, aluminum wire to DuPont 9910 gold film, and diffusion barrier pads were developed to allow high temperature attachment