Nick Kepler

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

The effect of nitrogen (N/sub 14/)implant into dual-doped polysilicon gates was investigated. The electrical characteristics of sub-0.25-/spl mu/m dual-gate transistors (both p- and n-channel), MOS capacitor quasi-static C-V curve, SIMS profile, poly-Si gate R/sub s/, and oxide Q/sub bd/ were compared at different nitrogen dose levels. A nitrogen dose of 5/spl times/10/sup 15/ cm/sup -2/ is the optimum choice at an implant energy of 40 KeV in terms of the overall performance of both p- and n-MOSFETs and the oxide Q/sub 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/spl times/10/sup 16/ cm/sup -2/) results in poly depletion and increase of sheet resistance in both unsilicided and silicided p/sup +/ 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.

CMOS transistor reliability and performance impacted by gate microstructure

This paper investigate the impact of CMOS (complementary metal-oxide-semiconductor) gate microstructure on the reliability and performance of deep-submicrometer CMOS transistors. The amorphous silicon (/spl alpha/-Si) gate provides better capability for suppression of boron penetration in p/sup +/ doped gate p-channel MOSFETs, but gate depletion in the /spl alpha/-Si gate is slightly more severe than that of the poly-Si gate. The gate-length-dependent gate-depletion effect, in which the difference in linear g/sub m/ between MOSFETs with two different gate microstructures shows a strong L/sub g/-dependence, is reported and interpreted by impurity diffusion along the grain boundary. A gate nitrogen implant as an effective method for suppression of the boron diffusion is also discussed with emphasis on the impact on both device reliability and performance.

Impact of Gate Microstructure on Complementary Metal-Oxide-Semiconductor Transistor Performance

This letter reports on the impact of gate microstructure on deep-submicron complementary metal-oxide-semiconductor (CMOS) device performance. Transistors with different gate microstructures (α-Si gate vs poly-Si gate) were fabricated using a 2.5 V sub-0.25 µ m CMOS process and their performances were compared. The α-Si gate provides better capability for suppressing boron penetration in p-channel metal-oxide-semiconductor field-effect transistors (MOSFETs), but the depletion effect is more severe than that of the poly-Si gate. A modified gate doping (MGD) effect, in which the difference of linear transconductance (g m) between transistors with two different gate microstructures shows a strong gate-length dependence, is reported for the first time and evaluated by the impact of grain boundary segregation on the electrically activated gate impurity density. The MGD effect makes the poly-Si gate more advantageous in the design of high-performance CMOS transistors with gate critical lengths shorter than 0.25 µ m.