A silicon-on-insulator circuit for high-temperature, high-voltage applications

The authors previously proposed the concept of a composite high-voltage device using series-connected low-voltage SOI (silicon-on-insulator) MOSFETs. In the present work, they demonstrate how the composite device can circumvent the fundamental materials limitations of bulk devices for high-voltage, high-temperature applications. Experimental circuits were fabricated on SIMOX (separation by implanted oxygen) substrates using an SOI NMOS process. For the purpose of demonstrations, external resistors were used as the bias elements. Individual transistor breakdown voltages were about 6-7 V, and did not vary significantly from 24°C to 400°C. The composite device characteristics closely resemble those of the individual MOSFETs. In particular, the breakdown voltage (typically 26-30 V) is nearly constant over the temperature range studied. Drain characteristics of a typical five-transistor composite device are shown for several stage temperatures