Patent ID: 7511293

Claim:
A scatterometer for evaluating a microstructure on a workpiece, comprising: an irradiation system configured to produce a first beam of radiation having a first wavelength and a second beam of radiation having a second wavelength; an optical system having a first optics assembly configured to condition the first and second beams, and an object lens assembly configured to (a) individually focus the first and second beams to an area at an object focal plane through at least a 150Â° range of altitude angles and at least a 900Â° range of azimuth angles simultaneously, and (b) present return radiation scattered from a microstructure in a radiation distribution at a second focal plane; a detector having a two-dimensional sensor array positioned to receive the radiation distribution and configured to produce a representation of the radiation distribution on the two-dimensional sensor array; and a computer system operatively coupled to the detector and including a computer operable medium, wherein the computer operable medium includes instructions that cause the computer system to acquire a measured selected radiation distribution by reading data from selected pixels of the two-dimensional sensor array, the selected pixels being less than the total number of illuminated pixels in the two-dimensional sensor array.