Using N2+ Implantation into Poly-Si/a-Si Films to Improve the Thermal Stability of Cobalt Silicide

• Main Authors: Yi-Chieh Huang, 黃奕介
• Other Authors: Kow-Ming Chang
• Format: Others
• Language: en_US
• Published: 1999
• Online Access: http://ndltd.ncl.edu.tw/handle/04536741022007457422

碩士 === 國立交通大學 === 電子物理系 === 87 === Due to its low resistivity and better chemical stability, CoSi2 is more anticipated to be the silicide material of deep sub-micrometer dimension CMOS devices. However, CoSi2 films on polysilicon would be decomposed and agglomerated during post-formation annealing at high temperature. In this thesis, we present two kinds of silicidation processes to improve the thermal stability of CoSi2 films as follows: (1) using N2+ implantation into poly-Si films (CoSi2/Poly-Si with N2+ I/I), (2) using amorphous Si instead of poly-Si films (CoSi2/α-Si). In the CoSi2/Poly-Si with N2+ I/I case, the nucleation of CoSi2 transformation from CoSi is impeded by N2+ I/I. Since the nucleation temperature is increased, CoSi2 films are formed incompletely at the as-formed state so that the grain size of CoSi2 is small which improves the thermal stability. In the CoSi2/α-Si case, the better thermal stability is due to the amorphous-Si film results in less grain boundary density and fewer diffusion pipelines than the columnar polysilicon film. Moreover, we used these new silicidation process in polyside gated MOS capacitors. They all showed better electrical characteristics. This indicates that these new structures not only suppress the agglomeration of CoSi2, but also have more superior gate oxide integrity.