Influence of dummy active patterns on mechanical stress induced by spin-on-glass-filled shallow trench isolation in n-MOSFETs

Abstract

This paper proposes an electrical method of extracting mechanical stress in n-MOSFETs and analyzes the influence of dummy active patterns on mechanical stress induced by spin-on-glass-filled shallow trench isolation (SOG-filled STI). The proposed method requires only the maximum transconductance g(m.max) and measured subthreshold current I-d(sub.), eliminating the effect of deviations of the mobility mu and effective channel length L-eff that occurred in a previous method using mu. In addition, it eliminates the measurement error due to the drain induced barrier lowering (DIBL) effect in a previous method using I-d(sub.). The tensile stress sigma(t) in the experimental n-MOSFETs was measured as several hundred mega Pascals. An increase of separation distance d between dummy active regions and the Si active region resulted in a decrease of sigma(t) for d > 0.2 mu m. But, sigma(t) decreased when d decreased from 0.2 to 0.09 mu m. (c) 2010 Elsevier B.V. All rights reserved.