Split C-V measurements of low temperature MOSFET inversion layer mobility

Abstract

A combination of the high frequency split C-V method and numerical modelling was used to accurately measure the effective mobility of electrons in the inversion layer as a function of the inversion layer change, Q i, bulk charge, Q b, and temperature. These measurements clearly show that for a sufficiently large vertical field the effective mobility is a universal function of the linear combination of Q b and Q i, E eff = ( Q b + νQ i)/ ε si for different substrate biases. The weighting factor, ν, exhibits strong temperature dependence in the 60–300 K temperature range. The results of this work suggest that the ‘effective field’ concept commonly used to model the operation of MOSFETs at room temperature can be partially extended to describe the mobility variation with the vertical field at low temperatures; however, the range of fields where the back bias does not affect the μ( E eff) dependence narrows considerably as the temperature is reduced.