Y-Function Analysis of the Low Temperature Behavior of Ultrathin Film FD SOI MOSFETs

Abstract

The respective transfer characteristics of the ultrathin body (UTB) and gate recessed channel (GRC) device, sharing sameW/Lratio but having a channel thickness of 46 nm, and 2.2 nm respectively, were measured at 300 K and at 77 K. By decreasing the temperature we found that the electrical behaviors of these devices were radically opposite: if for UTB device, the conductivity was increased, the opposite effect was observed for GRC. The low field electron mobility and series resistanceRSDvalues were extracted using a method based onY-function for both the temperatures. IfRSDlow values were found for UTB, very high values (>1 MΩ) were extracted for GRC. Surprisingly, for the last device, the effective field mobility is found very low (<1 cm2/Vs) and is decreasing by lowering the temperature. After having discussed the limits of this analysis.This case study illustrates the advantage of theY-analysis in discriminating a parameter of great relevance for nanoscale devices and gives a coherent interpretation of an anomalous electrical behavior.