The study of polycide gate formed by CVD tungsten silicide with amorphous/poly crystalline silicon

• Main Authors: Shiou-Hann Liaw, 廖修漢
• Other Authors: Tan-Fu Lei
• Format: Others
• Language: en_US
• Published: 1994
• Online Access: http://ndltd.ncl.edu.tw/handle/26302091662796393448

碩士 === 國立交通大學 === 電子研究所 === 82 === In this thesis,the polycide gate formed by a stacked amorphous- silicon(α-Si)/poly-silicon structure with CVD tungsten silicide have been studied. Fisrt,the N+ polycide gates ofα-Si/ poly-Si or poly-Si/poly-Si with POCl3 diffusion and CVD WSi were fabricated. For these structures after the annealing process at 900℃ for 30 minutes,we observed that the gate oxide ofα-Si/poly-Si/WSi structure contains less flourine atoms than poly-Si/poly-Si/WSix.As a result the effective gate oxide thickness ofα-Si/poly-Si/WSi is thinner than that of poly-Si/ poly-Si/WSi. Second, the P+ polycide gates ofα-Si/poly-Si/WSi with a cap of poly-Si on the WSi were studied.We obtained that the cap poly-Si layer above WSi pevented out-diffusion of boron to WSi surface, which will produce depletion gate. Moreover, the cap poly-Si could get the lower sheet resistance polycide. When we implant dopant to form shallow of the junction source and drain, the WSi was damaged.The cap poly-Si held on damage layer and resulted in tungsten/silicon ratio no change. Hence, for the electrical characteristics,the cap poly-Si process is an appropriate choice for the P+ polycide gate.