Improvement of CoSi/sub 2/ stability on fine grain sized poly-Si using nitrogen implantation through Co monosilicide and its effect on 0.18 /spl mu/m dual gate CMOS

CoSi/sub 2/ has been studied for sub-quarter micron high speed CMOS logic devices, because of low sheet resistance on fine patterned poly-Si lines. For sub-quarter micron CMOS, dual gate is a key technology to realize high performance MOS devices. Recently, dual gate technology has been proposed using simultaneous gate and source/drain doping. In this case, small grain sized poly-Si is necessary to enhance diffusion and minimize gate depletion. However, the thermal stability of CoSi/sub 2/ on fine grain sized poly-Si has not been studied. Nitrogen implantation followed by Co deposition was investigated (Kuroi et al., 1993), but it was difficult to form CoSi/sub 2/ of low resistance, since cobalt to silicon reaction was greatly retarded by nitrogen atoms. In this paper, we found that nitrogen implantation through a Co monosilicide layer improved thermal stability up to 1000/spl deg/C for 30 s, without increase of sheet resistance in a small geometry. Furthermore, the implanted nitrogen also enhanced gate oxide reliability with high performance 0.18 /spl mu/m CMOS dual gate devices fabricated using simultaneous gate and source/drain doping.