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

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 gm,max and measured subthreshold current Id(sub.), eliminating the effect of deviations of the mobility μ and effective channel length Leff that occurred in a previous method using μ. In addition, it eliminates the measurement error due to the drain induced barrier lowering (DIBL) effect in a previous method using Id(sub.). The tensile stress σt 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 σt for d > 0.2 μm. But, σt decreased when d decreased from 0.2 to 0.09 μm.