A comparative study of fin-last and fin-first SOI FinFETs

Two FinFET fabrication processes are compared with simulation: the conventional fin-first process and the novel fin-last process. With the fin-last process, more longitudinal strain can be incorporated into the channel from source and drain SiGe stressor than fin-first. pFET mobility advantage is 15% at fully-strained condition and with silicon recess. Maintaining vertical junction uniformity is the main challenge for fin-last. However, its impact on parasitic resistance and capacitances are small. Vertical junction non-uniformity is improved with source and drain recess and doping optimization.