Operation of Bulk CMOS Devices at Very Low Temperatures

Operation of submicron MOS devices at very low temperatures opens the way to realization of superfast digital VLSI with a logic swing of several-tens of kT/q. Thus far, only operation of NMOS devices have been reported. 1),2),3) However, it has been found that the design of NMOS devices at such temperature is severely limited by the threshold voltage variation in depletion-load devices. Also, power consumption in NMOS devices usually increases at low temperature. This is a severe disadvantage for VLSI design. From these viewpoints, this paper reports on low-power, high-speed operation of bulk CMOS devices at liquid nitrogen (LN2) and liquid helium (LHe) temperatures.