Polysilicon CMP

Depending on its crystalline structure, silicon can exist in single-crystalline, polycrystalline, or amorphous form. Polysilicon (p-Si) is short for polycrystalline silicon, which is a form of silicon composed of many crystals, as opposed to amorphous silicon (a-Si), which is an unordered form with a random internal structure. The polysilicon CMP process can be used for several applications such as... 

Most poly-Si CMP processes involve patterned oxide filled with polysilicon. The generation mechanism and physical appearance of the scratches for polysilicon CMP are the same as in the oxide CMP described earlier. Most Polysilicon CMP processes are rather selective toward silicon oxide. More specifically, the polysilicon removal rate is usually much higher than that for oxide. Such slurries usually contain low concentration of abrasive, which usually translates to low defect density. At low magnification, scratches on the poly-Si film after CMP usually look like a continuous line rather than chatter marks. At higher magnification, the scratch usually looks like irregular trench with multifaceted walls. 

Defects Existing Before and Revealed After Polysilicon CMP... 

The types of defects existing before polysilicon CMP are similar to the types of defects that can be observed before oxide CMP. The main difference is that the poly-Si film is not as transparent as an oxide film. The thicker the poly silicon film, the less transparent it is. 

Removal Rate WIWNU and Defect in a Polysilicon CMP Extended Run... 

Raymond Jin, Shijian Li, Simon Fang, Fritz Redeker, Proven practice and future application of polysilicon CMP in IC fabrication , proceedings of 1998 SEMICON Taiwan, pp. 263-274. 

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