Patent ID: 7808652
Filing Date: 2010-10-05
Classification: G01B

Abstract:
1. An interferometric method for profiling a sample surface covered with a coating layer, the method comprising the following steps: measuring a sample modulation produced by the sample surface using an interferometer operating with a predetermined illumination intensity; measuring a reference modulation produced by a reference surface using said interferometer and illumination intensity; calculating a thickness of said coating layer from said sample and reference modulations; and correcting a height calculated from said sample modulation by accounting for said thickness of the coating layer at each of a plurality of pixels of the sample surface; wherein said calculating step is carried out assuming a predetermined relationship between an average modulation and reflectivity, thereby producing a sample-modulation equation based on said predetermined relationship between an average of the sample modulation and a value of sample reflectivity, said sample reflectivity being expressed in terms of the thickness of the coating layer and of known optical parameters for the sample surface; and further producing a reference-modulation equation also based on said predetermined relationship between an average reference modulation and a value of reference reflectivity, said reference reflectivity being expressed in terms of known optical parameters for the reference surface.