Patent ID: 8818754
Filing Date: 2014-08-26
Classification: G01B,H01L

Abstract:
1. A method of determining properties of a surface of an object, the method comprising: illuminating the surface of the object with an illumination source; detecting light reflected from the surface to produce a measurement signal; processing the measurement signal to remove a height contribution from the measurement signal leaving a film contribution in the measurement signal to produce a film measurement signal; comparing the film measurement signal to a plurality of film signals in a library to determine film parameters of the surface of the object, the library comprising the plurality of film signals and a plurality of full signals, wherein the plurality of film signals are associated with the plurality of full signals and the plurality of film signals are produced by removing height contributions from the plurality of full signals; generating a reduced set of full signals using the film parameters of the surface, the reduced set of full signals having fewer signals than the plurality of film signals; comparing the measurement signal to the reduced set of full signals to determine a height parameter of the surface of the object; and storing the height parameter and the film parameters.