Low-temperature mobility measurements on CMOS devices

Abstract

The surface channel mobility of carriers in n- and p-MOS transistors fabricated in a CMOS process was accurately determined at low temperatures down to 5 K. The mobility was obtained by an accurate measurement of the inversion charge density using a split C-V technique and the conductance at low drain voltages. The split C-V technique was validated at all temperatures using a one-dimensional Poisson solver (MOSCAP) which was modified for low-temperature application. The mobility dependence on the perpendicular electric field for different substrate bias values appeared to have different temperature dependences for n- and p-channel devices. The electron mobility increased with a decrease in temperature at all gate voltages. On the other hand, the hole mobility exhibited a different temperature behavior depending upon whether the gate voltage corresponded to strong inversion or was near threshold.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>