Self-heating effects in SOI MOSFET´s operated at low temperature

In this work, self-heating effects are studied as a function of temperature. The electrical properties of fully depleted thin Si film N- and P-channel SIMOX MOSFETs are investigated between room and liquid helium temperatures. The P-and N-channel devices used in this study have been fabricated at LETI (Grenoble) with a conventionally-doped and a degenerately-doped LDD structures, respectively. The devices have an 11.5 nm gate oxide and a 380 nm buried oxide thicknesses. The article shows the drain current-drain voltage characteristics at 300 K for an N-channel SIMOX MOSFET fabricated with a degenerately doped LDD structure. The characteristics present a low negative differential resistance phenomenon for gate voltage up to 5 V. However, at 77 K, a strong negative differential resistance is observed for high gate voltages. The self heating effects are therefore significantly increased by reducing the temperature. This dependence is supposed to be due to the mobility variations and, also, the change with temperature of the threshold voltage