| 摘要 |
This invention relates to a method for forming a buffer layer, more particularly, to the method for forming a mixed layer which comprises silicon oxynitride and silicon dioxide to be a buffer layer over a polysilicon gate by using a nitrogen ions implantation and a thermal oxidation. The present invention uses the ions implantation to implant nitrogen ions to the surface of the polysilicon gate at first. After passing through a thermal oxide process, the hard mixed layer, which comprises silicon oxynitride and silicon dioxide, is formed over the surface of the polysilicon gate. The mixed layer, which comprises silicon oxynitride and silicon dioxide, formed over the polysilicon gate can prevent another ions entering to the polysilicon gate to affect the critical dimention of the polysilicon gate.
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