Real time thickness measurement of thin film for end-point detector (EPD) of 12-inch spin etcher using the white light interferometry

Abstract

A real time thickness measurement method based on the wide band white light interferometry for spin etcher is presented for the silicon-oxide and poly-silicon film deposited on 12-inch silicon wafer subject to a rotational vibration and chemical flow. Mathematical model for the vibration and chemical flow is described using a statistical method and analyzed to investigate their effects on the interference of reflected lights from the thin films. A white light interferometry system for the real time thickness measurement of thin films have been also developed to evaluate the performance of the method in experiment and determine the thickness of the films using signal processing techniques including curve-fitting and adaptive filtering. Experiments conducted for thin films ranging form 100 nm to 600 nm in thickness show that the method proposed in the paper is proved to be effective with a good accuracy of maximum 1.8% error.