<title>New method for end-point detection in reactive ion etching of polysilicon</title>

Abstract

Reactive ion etching (RIE) is commonly used, as a process tool, for the etching of polysilicon, silicon dioxide, silicon nitride and other thin film deposits. One of the key requirements of the etching process is the accurate end-point detection of the process. There exist a number of process monitoring techniques for end-point detection, these however are costly to install and maintain. In response to this requirement, a new method for end-point detection of polysilicon topography etching in single wafer plasma reactive ion etcher is presented here, which incurs no added costs. The method is based upon experimental results correlating polysilicon etching end-point with the increase in the cathodic self-bias voltage developed across the substrate. It is shown that the end-point of polysilicon topography etching can be found by monitoring the first derivative of the self- bias voltage with time. Using this method it has been demonstrated that accurate end-point detection of polysilicon etching can be obtained with a residue free field, near- vertical polysilicon profile and critical dimension loss of less than 0.05 micrometer.