Impact of STI on Statistical Variability and Reliability of Decananometer MOSFETs

The impact of shallow trench isolation (STI) on the statistical variability introduced by random discrete dopants and trapped interface charge is clarified for the first time using 3-D statistical numerical simulations. The possible influence of the STI on the p-n junction shape is also taken into account. The simulated test bed devices are contemporary 35-nm gate-length high-performance nMOSFETs typical for the 45-nm technology generation. In transistors with straight junction edges, the STI-related fringing effects increase the equivalent channel width, reducing the statistical variability. Changes in the junction shape in the STI vicinity can further reduce or increase the variability.