Patent ID: 8543353
Filing Date: 2013-09-24
Classification: G01B

Abstract:
1. Apparatus for determining information relating to a surface characteristic of a sample in the form of a thin film structure comprising one or more thin film layers on a substrate, the apparatus comprising: a light source; a light director to direct light from the light source along a sample path towards a surface region of a said sample and along a reference path towards a reference surface such that light reflected by a sample surface region and light reflected by the reference surface interfere; a mover to effect relative movement along a measurement path between the sample and the reference surface; a sensing device operable to sense light representing the interference fringes produced by the sample surface region; a controller operable to carry out a measurement operation by causing the sensing device to sense light intensity at a number of locations along the measurement path to provide, for each location, a corresponding intensity value; and a data processor to receive first intensity data comprising a first series of the intensity values resulting from a measurement operation on a surface area of a substrate and second intensity data comprising at least a second series of the intensity values resulting from a measurement operation on a surface area of a thin film structure, the data processor comprising: a surface characteristic determiner to determine a substrate surface characteristic on the basis of the first intensity data, to determine an apparent thin film structure surface characteristic on the basis of the second intensity data, and to: