Low-temperature characterization of CMOS devices

The low-temperature characterization of the field-dependent mobility, the transient response and the flicker noise in NMOS (n-channel metal-oxide-semiconductor) and PMOS (p-channel MOS) devices fabricated in a CMOS (complementary MOS) process are described. It is found that NMOS and PMOS devices exhibit different perpendicular field dependence. Whereas the electron mobility improves with a reduction in temperature all the way down to 5 K, the total mobility increases initially with a decrease in temperature and reaches a peak around 70 K. The transient response in drain current due to the slow formation of the depletion region when the gate voltage is switched into inversion at cryogenic temperatures has been measured experimentally and also simulated using a one-dimensional Poisson solver. The results of low-frequency noise measurements at low temperatures are also reported