Title :
Impact of nitrogen (N2+) implantation into polysilicon gate on thermal stability of cobalt silicide formed on polysilicon gate
Author :
Sun, Wein-Town ; Liaw, Ming-Chi ; Hsieh, Kuang-Chien ; Hsu, Charles Ching-Hsiang
Author_Institution :
Dept. of Electr. Eng., Nat. Tsing Hua Univ., Hsinchu, Taiwan
fDate :
9/1/1998 12:00:00 AM
Abstract :
A novel process which uses N2+ implantation into polysilicon gates to suppress the agglomeration of CoSi2 in polycide gated MOS devices is presented. The thermal stability of CoSi2/polysilicon stacked layers can be dramatically improved by using N2+ implantation into polysilicon. The sheet resistance of the samples without N2+ implantation starts to increase after 875°C RTA for 30 s, while the sheet resistance of CoSi2 film is not increased at all after 950 and 1000°C RTA for 30 s if the dose of nitrogen is increased up to 2×1015 cm-2 and 6×1015 cm2, respectively, and TEM photographs show that the agglomeration of CoSi2 film is completely suppressed. It is found that the transformation to CoSi2 from CoSi is impeded by N2+ implantation such that the grain size of CoSi2 with N2+ implantation is much smaller than that without N2+ implantation. As a result, the thermal stability of CoSi2 is significantly improved by N2+ implantation into polysilicon
Keywords :
MOSFET; cobalt compounds; grain size; ion implantation; rapid thermal annealing; semiconductor device metallisation; thermal stability; transmission electron microscopy; 875 to 1000 C; CoSi2-Si:N; PMOSFET; RTA; TEM; agglomeration; cobalt silicide film; grain size; nitrogen implantation; polysilicon gate; sheet resistance; thermal stability; Boron; Cobalt; Grain size; MOSFET circuits; Nitrogen; Silicides; Sun; Thermal degradation; Thermal stability; Titanium;
Journal_Title :
Electron Devices, IEEE Transactions on
