Film thickness control using spectral interferometry

The present invention relates to a technique for monitoring film thickness including a method of controlling etch and deposition processes. One specific embodiment of the present invention relates to a method of controlling and detecting the end point in a plasma etch process by using the plasma emission as a broadband light source and measuring the radiation reflected off the wafer being etched with a spectrometer. The present invention may be used to control a variety of plasma and non-plasma processes and is particularly useful in controlling plasma etch processes used in the manufacture of integrated circuits. A process for controlling a substrate processing operation such as a plasma etch operation. One embodiment of the method of the present invention forms a plasma within a substrate processing chamber to etch a wafer disposed within the chamber. The plasma emission is used by the process as a broadband light source. During the plasma etch process, a plurality of wavelengths of radiation reflected from the surface of the wafer being etched are measured with a spectrometer. These measurements are then compared using pattern recognition techniques to previous measurements taken during a previous plasma etch operation. Certain embodiments of the invention use principal component analysis (PCA) techniques to perform pattern recognition while other embodiment use programmed neural net pattern recognition techniques.