Polarized-light scatterometer for measuring the thickness of a film

Abstract

A polarized-light scatterometer for measuring the thickness of a film coated on the partial of a substrate, the film having a straight line edge on the surface of the substrate coated with the film. The polarized-light scatterometer is composed of means for generating an incident beam (a fixed polarization state input beam) striking the straight line edge of the film; means for detecting the intensity of a scattered beam which is scattered by the incident beam within a predetermined angular range; means for rotating the detecting means about the Z-axis within the predetermined angular range; means for adjusting the intensity of the scattered beam; means for obtaining the Mueller matrix by using the Bickel-Bailey method; means for normalizing all the elements of the Mueller matrix; means for recording the corresponding scattered angle of the scattered beam having maximum intensity variation; means for obtaining the relation diagrams between the normalized elements and the thickness of the film respectively, and all the relation diagrams are obtained under the scattered angle having maximum intensity variation; means for choosing the relation diagrams that the normalized elements have greater sensitivity to the thickness of the film; means for obtaining the values of normalized elements of an unknown thickness of the same film; means for obtaining the thicknesses of the film of unknown thickness corresponding to the relation diagrams by using the values of the normalized elements; and means for determining the thickness of the unknown thickness film by choosing common thickness among the relation diagrams.