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A model explaining gate-charging damage in MOSFETs observed during inter-layer-dielectric (ILD)-related plasma processes is reported. It indicates that the charging damage associated with the ILD plasma process can be related to the effect of photoconduction and/or capacitive impedance coupling of plasma potential through the multiple ILD layers. The model leads to a conclusion that by placing a larger-area lower-layer metal (such as Metal-1) plate or polysilicon plate at the gate terminal of MOSFETs, this ILD process-related charging damage can be eliminated or significantly reduced due to a substantial reduction in the gate-to-substrate impedance of the transistors.
Date of Publication: Jan. 2003