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

A bubble-like, protrusion defect is found at the p⁺ and n⁺ 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