Study on Si integrated circuits operating up to 462°C

In order to develop a silicon IC operating up to and above 450°C, integrated injection logic (IIL) was chosen for its peculiar characteristics to high temperature operation. New structures for the IIL were designed through the experimental and theoretical studies of p-n junctions, transistors, and IILs at high temperature. We made Si ICs consisting of nine-stage ILL ring-oscillators by fabrication processes developed by Toyota, where the low temperature epitaxial growth and ion implantation processes were alternately repeated. The first generation IC oscillator made by a 10 μm design rule operated from room temperature up to 370°C in 1990, the second made by a self-aligned technology increased the maximum operating temperature to 415°C in 1991, and the third made by a 5 μm design rule increased this temperature to 454°C in 1992. New ideas were introduced to the IIL design concept, and the IC fabrication processes were redesigned. In 1994, we succeeded in creating a new IIL structure by this fabrication process, with steps reduced from 52 to 39. The newly developed IC oscillator operated up to a temperature of 462°C. Two-bit microcomputers were designed and fabricated using 852 IILs and operated at temperatures from 24 to 265°C with a clock frequency of 100 kHz. No failure occurred in more than 1000 hours of operation at a temperature of 250°C