Elimination of PolySilicon Residues Formation Induced by Watermark on Hydrophobic Surface

Defect density in wafer fabrication can be a significant source of yield loss and reliability risk especially as device feature size shrinks. Thus to identify the root cause of the defect and eliminate them effectively is very crucial. The mechanism of a defect density called polysilicon residues and the key processes that affect this defect are studied in the paper. This defect of interest was generated due to watermark formation on the hydrophobic polysilicon surface, the silicate precipitate from the watermark acts as an unwanted masking layer causing block etch to the subsequent polysilicon etch resulted in poly silicon residues. The watermark was found after the de-ionized water rinse step. Avoiding the wafer to be exposed to ambient air after the water rinse has been adopted as key solution to prevent the watermark formation and hence eliminating the polysilicon residues.