A review of recent MOSFET threshold voltage extraction methods

The threshold voltage value, which is the most important electrical parameter in modeling MOSFETs, can be extracted from either measured drain current or capacitance characteristics, using a single or more transistors. Practical circuits based on some of the most common methods are available to automatically and quickly measure the threshold voltage. This article reviews and assesses several of the extraction methods currently used to determine the value of threshold voltage from the measured drain current versus gate voltage transfer characteristics. The assessment focuses specially on single-crystal bulk MOSFETs. It includes 11 different methods that use the transfer characteristics measured under linear regime operation conditions. Additionally two methods for threshold voltage extraction under saturation conditions and one specifically suitable for non-crystalline thin film MOSFETs are also included. Practical implementation of the several methods presented is illustrated and their performances are compared under the same challenging conditions: the measured characteristics of an enhancement-mode n-channel single-crystal silicon bulk MOSFET with state-of-the-art short-channel length, and an experimental n-channel a-Si:H thin film MOSFET. 2002 Elsevier Science Ltd. All rights reserved.