Analysis of threshold voltage variation in fin field effect transistors: separation of short channel effects

Abstract

The variation in the threshold voltage caused by fluctuations in a device parameter is given by the product of a sensitivity coefficient and the fluctuation amount. In this paper, the sensitivity coefficient for each device parameter was separated into two factors: one due to an intrinsic mechanism [one-dimensional (1D) factor] and another due to short-channel effects [two-dimensional (2D) factor]. Using this concept, the variations in the threshold voltage and the sensitivity coefficients in doped fin field effect transistors (FinFETs), undoped FinFETs and planar metal-oxide-semiconductor FETs (MOSFETs), whose structures are based on the ITRS, were evaluated for the fluctuations in the principal device parameters. It was found that the 2D factor rather than the 1D factor dominated the sensitivity coefficients, although the degree of domination varies between the fluctuating parameters. The 1D and 2D factors were found to cancel each other out, thereby reducing the sensitivity coefficient. Based on these results, FinFETs with various structures were examined and controlling short-channel effects was demonstrated to be an effective way to reduce the variation in the threshold voltage.