Patent ID: 7480598
Filing Date: 2009-01-20
Classification: G01R,H01L

Abstract:
1. A characteristic evaluation method for insulated gate type transistors, comprising: a) forming at least two insulated gate type transistors including first and second insulated gate type transistors that differ from each other only in mask channel width; b) extracting a threshold voltage of said first transistor that has a mask channel width larger than that of said second transistor, estimating a threshold voltage of said second transistor, and employing a value of the estimated threshold voltage as a first estimated value; c) when a difference between a gate voltage of said first transistor and said extracted threshold voltage of said first transistor is defined as a first gate overdrive, a difference between a gate voltage of said second transistor and said first estimated value is defined as a second gate overdrive, and an X-Y plane is assumed whose X-axis is said mask channel width and whose Y-axis is source-drain conductance, (i) extracting a virtual point at which a change in Y coordinate value is estimated to be approximately zero when said first and second gate overdrives are changed, from a first characteristic curve exhibiting a relationship between said mask channel widths of said first and second transistors and said source-drain conductance, and employing a value of an X-coordinate at said virtual point as a second estimated value or (ii) employing a value of an X intercept of said first characteristic curve as said second estimated value; d) repeating said step c) while varying said first estimated value; after said steps c) and d), (e) finding, based on said first and second estimated values, an optimum first estimated value with which a second characteristic curve exhibiting a relationship between said second gate overdrive and said second estimated value in an X-Y plane whose X-axis is said second gate overdrive and whose Y-axis is a value related to said second estimated value having a predetermined shape within a predetermined range of said second gate overdrive, and determining a true threshold voltage of said second transistor based on said optimum first estimated value; and f) determining a difference between said mask channel width and an effective channel width based on said true threshold voltage.