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 gate s was investigated, The electrical characteristics of sub-0.25-mu m du al-gate transistors (both p- and n-channel), MOS capacitor quasi-stati c C-V curve, SIMS profile, poly-Si gate R-s, and oxide Q(bd) were comp ared 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 o f 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 profi les to be attributed to the retardation effect in bulk polysilicon wit h the presence of nitrogen, High nitrogen dose (1 x 10(16) cm(-2)) res ults in poly depletion and increase of sheet resistance in both unsili cided and silicided p(+) poly, degrading the transistor performance, U nder optimum design, nitrogen implantation into poly-Si gate is effect ive in suppressing boron penetration without degrading performance of either p- or n-channel transistors.