2光束レーザ干渉法による超精密段差膜厚測定

Abstract

Two new methods for thin film thickness measurement are described. The first method makes use of a polarization interferometer and the second method utilizes a double twin path interferometer. These methods are highly precise and can be used for research and development required for the evaluation of various lithographic processes. The polarization interferometer was found to possess excellent linearity and very high sensitivity 0.1nm. This was achieved by using a Rochon prism as a beam splitter-recombiner. Aluminium films with thickness ranging from 70nm to 300nm were measured under normal laboratory conditions, with a precision better than ±30nm. In the double twin path interferometer, a grating beam splitter-recombiner was used to maintain the reference surface level constant. Actual thickness measurements of aluminium films with thickness ranging from 70nm to 300nm shown a maximun error of about ±20nm. Remedies for an improvement of the precision are discussed.