Signal analysis of the end point detection method based on motor current

Abstract

We first studied the factors affecting the motor current (MC) signal. It was found to be strongly affected by systematic hardware noise depending on the polishing recipe, such as pad conditioning and arm oscillation. We then studied the end point detection (EPD) for the chemical mechanical polishing (CMP) process of the shallow trench isolation (STI) structure with a reverse moat pattern. The MC signal showed a high amplitude peak in the fore part caused by the reverse moat pattern. We also found that the end point (EP) could not be detected properly and reproducibly due to the pad conditioning effect, especially when a conventional low selectivity slurry was used. Even when there was no pad conditioning effect, the EPD method could not be applied, since the measured end point was always the same due to the characteristics of the open nitride structure.