Performance of Digital Integrated Circuit Technologies at Very High Temperatures

Results of detailed investigations of the performance and reliability of digital bipolar and complementary metal-oxide-semiconductor (CMOS) integrated circuits over the 25-340°C range are reported. Included in these results are both parametric variation information and analysis of the functional failure mechanisms. Although most of the work was done using commercially available circuits (TTL and CMOS) and test chips from commercially compatible processes, some results from experimental simulations of dielectrically isolated CMOS are also discussed. In general, it was found that commercial Schottky-clamped transistor-transistor logic (TTL) and dielectrically isolated, low power Schottky-clamped TTL functioned to junction temperatures in excess of 325°C. Standard gold-doped TTL functioned only to 250°C, while commercial isolated integrated injection logic (l²L) functioned to the range of 250-275°C. Commercial junction-isolated CMOS, buffered and unbuffered, functioned to the range of 280-310+°C, depending on the manufacturer. Experimental simulations of simple dielectrically isolated CMOS integrated circuits, fabricated with heavier doping levels than normal, functioned to temperatures in excess of 340°C. High temperature life testing of experimental, silicone-encapsulated simple TTL and CMOS integrated circuits have shown no obvious lifelimiting problems to date. No barrier to reliable functionality of TTL bipolar or CMOS integrated circuits at temperatures in excess of 300°C has been found.