Pattern density effect of trench isolation-induced mechanical stress on device reliability in sub-0.1μm technology

The effects of shallow trench isolation (STI)-induced mechanical stress on hot carrier-induced degradation of n-/p-MOSFETs with different source(S)/drain(D) areas and channel widths are studied. It is found that mechanical stress increase with S/D area reduction has no impact on the hot carrier degradation for n-/p-MOSFETs with large channel width. However, hot carrier lifetime can be improved when channel width is reduced. This hot carrier degradation phenomenon due to STI-induced mechanical stress cannot be explained by piezoresistance effect. Based on the simulation results of mechanical stress distributions at different channel regions and the finding of tensile pocket along STI edge, the mechanism of pattern density effect on hot carrier degradation is also provided.