Patent ID: 8994918
Filing Date: 2015-03-31
Classification: G01M,G03F

Abstract:
1. An apparatus for in situ measurement of reticle distortion, comprising: a reticle stage that retains and moves a reticle; at least one optical source that provides an optical beam that is directed to a pattern of the reticle; at least one detector situated so as to receive at least a portion of the optical beam from the pattern of the reticle within a movement of the reticle relative to the optical beam, and to produce a corresponding signal; and a signal processing system coupled to the at least one detector so as to receive the signal, and provide an indication of a reticle deformation by using at least two signals that are produced by the at least one detector, wherein one of the at least two signals is produced from a first movement of the reticle relative to the optical beam and another of the signals is produced from a second movement of the reticle relative to the optical beam, wherein the second movement is performed at a time different than a time at which the first movement is performed.