A study of photoresist residue defect induced by substrate surface condition

In order to improve the semiconductor device performance, a special lithography process with high mask transmission rate is needed. But we recently found a kind of serious photoresist residue defect on substrate surface. This defect was like a circular-pattern about one hundred micron in diameter with thin photoresist residue, and some massive photoresist residue was also observed at the interface between Active Area (AA) and Shallow Trench Isolation area (STI). After performing some experiments by improving lithography recipe parameters, such photoresist residue defect count will be decreased but cannot be totally removed. So this residue defect generation mechanism was analyzed and the substrate surface condition was found contribute to the residue defect. Therefore, different surface treatment methods were tried, and finally an optimized process was applied to remove the photoresist residue defect totally.