A study of implant damage induced thin oxide film expansion during photoresist dry etching

A bubble-like, protrusion defect is found at the p/sup +/ and n/sup +/ source/drain areas after the photoresist stripping process of source/drain implant mask. We can find it easily at active areas of wafer's flat or round site. Only one wafer suffered this issue each lot. This defect size range from 0.2 to 8 microns. The root cause is the expansion (by gas outlet) of a thin oxide film on the silicon surface. In deep submicron process, it will cause a severe reliability failure issue because of stress voiding caused by the formation of a vacancy beside metal interconnections. This study focuses on the root cause and the protrusion's formation mechanism. Various methods used to prevent and eliminate this problem are discussed.