Identification and removal of defects on silicon wafer processed with a rinse with/without megasonics in DI water

Watermark generation during wafer cleaning, which is the most repeated step in IC manufacturing, was investigated. Watermark formed during the HF last cleaning was monitored by KLA and SEM. It was found that megasonics at the final rinse (F/R) stage was the source of the defects. Megasonics in F/R step can generate a damage on the hydrophobic wafer surface. This damage may be a cause of watermark. Under the same rinse condition, which generate watermark on bare wafer, watermark density of patterned wafer is much less than that of bare wafer. A geometrical combination of hydrophilic and hydrophobic wafer surface can prevent the watermark on a part of the hydrophobic wafer surface. It was confirmed that micro watermark did not affect the quality of gate oxide of 58 Å thickness