Impact of nitrogen (N-14) implantation into polysilicon gate on high-performance dual-gate CMOS transistors

The effect of nitrogen (N-14) implant into dual-doped polysilicon gates was investigated, The electrical characteristics of sub-0.25-mu m dual-gate transistors (both p- and n-channel), MOS capacitor quasi-static C-V curve, SIMS profile, poly-Si gate R-s, and oxide Q(bd) were compared at different nitrogen dose levels, A nitrogen dose of 5 x 10(15) cm(-2) is the optimum choice at an implant energy of 40 KeV in terms of the overall performance of both p- and n-MOSFET's and the oxide Q(bd). The suppression of boron penetration is confirmed by the SIMS profiles to be attributed to the retardation effect in bulk polysilicon with the presence of nitrogen, High nitrogen dose (1 x 10(16) cm(-2)) results in poly depletion and increase of sheet resistance in both unsilicided and silicided p(+) poly, degrading the transistor performance, Under optimum design, nitrogen implantation into poly-Si gate is effective in suppressing boron penetration without degrading performance of either p- or n-channel transistors.