Patent ID: 7348192

Claim:
A method for monitoring a thickness of an uppermost film deposited on an underlying multi-layer structure, the underlying multi-layer structure comprising a plurality of thin films formed on a substrate, the method comprising: determining thickness data of each of the thin films of the underlying multi-layer structure before the uppermost film is formed on the underlying multi-layer structure, and storing the thickness data of the thin films of the underlying multi-layer structure in a thickness memory; measuring an optical spectrum profile of the uppermost film after the uppermost film is formed on the underlying multi-layer structure; reading the thickness data of each of the thin films of the underlying multi-layer structure from the thickness memory; calculating a plurality of theoretical optical spectrum profiles of the uppermost film based upon corresponding candidate film thicknesses of the uppermost film, using a measurement recipe for the uppermost film and the thickness data of each of the thin films of the underlying multi-layer structure; and searching one of the theoretical profiles of the optical spectrum of the uppermost film, which is closest to the measured optical spectrum profile of the uppermost film so as to determine a thickness of the uppermost film by the closest theoretical profile.