Importance of source and drain extension design in cryogenic MOSFET operation: causes of unexpected threshold voltage increases

Abstract

Increased threshold voltages have been observed during linear-mode operation of short-channel bulk metal-oxide-semiconductor field-effect transistors (MOSFETs) employing shallow source and drain extension technology at cryogenic temperatures. These increases were suppressed during saturation-mode operation, which resulted in the increase of a threshold voltage mismatch between linear- and saturation-modes as if drain-induced barrier lowering occurred. Numerical simulations revealed that these increases originate from enhanced depletion in the extension region and subsequent increases in channel resistance at cryogenic temperatures. These data suggest that shallow extensions should be designed more carefully in the case of MOSFETs intended for cryogenic operation.

Temperature Dependent Variations of Low-Frequency Noise Sources in Cryogenic Short-Channel Bulk MOSFETs

“…These data indicate increases in the threshold voltage with decreasing temperature, attributed to increases in the bulk Fermi potential at lower temperatures [17,18]. The distortion of the Id-Vg plot obtained from the p-type MOSFET at 3 K is ascribed to depletion at the source and drain extension edges, as observed in our previous study [19].…”

MOSFET series resistance extraction at cryogenic temperatures

“…Recently, a similar mechanism was suggested to explain the apparent increase of drain-induced barrier lowering (DIBL) for pchannel FETs at low temperatures. 30) SC1023-3 © 2023 The Japan Society of Applied Physics results for the p-channel devices (enclosed by dotted lines) are included here, since reasonable values were extracted using high drain bias data (V D = 125 ∼ 200 mV). It should be noted that these data points are less reliable.…”

22FDX Cryogenic Modeling

“…• Electron Mobility [2] • Phonon scattering, coulomb scattering [3] • Capacitance effects [4] • Resistance due to self-heating [5] • Source drain extension resistance [6] • Velocity saturation [7][8]…”