Analysis of abnormal Pch Vt distribution in wafer caused by implanter

In this paper, we report an analysis in which the abnormal p-channel threshold voltage (Pch Vt) distribution in a wafer was found to be due to the malfunction of an implanter at the Pch Vt adjustment step. The analysis was performed using a pulse C-V method and experiments with production wafers. As the conventional thermal wave and Rs measurements were not sensitive enough for this problem, the methodology of the monitoring method is discussed through our experiences.