The Cryogenic Temperature Behavior of Bipolar, MOS, and DTMOS Transistors in Standard CMOS

Abstract

Both CMOS bandgap voltage references and temperature sensors rely on the temperature behavior of either CMOS substrate BJTs or MOS transistors in weak inversion. Bipolar transistors are generally preferred over MOS transistors because of their lower spread. However, at deep-cryogenic temperatures, the performance of BJTs deteriorates due to a significant reduction in current gain and a substantial increase in the base resistance. On the contrary, MOS devices show more stable performance even down to 4 K, but accurate device characterization for the design of such a circuit is currently missing. We present the characterization and analysis over the temperature range from 4 K to 300 K of both substrate bipolar PNP transistors and MOS transistors in standard and dynamic threshold MOS (DTMOS) configurations implemented in a standard 0.16- \mu \text{m} CMOS technology. These results demonstrate that employing MOS or DTMOS enables the operation of bandgap references and temperature sensors in standard CMOS technologies even at deep-cryogenic temperatures.