Patent ID: 7221459
Filing Date: 2007-05-22
Classification: G01B

Abstract:
1. An interferometric method for measuring, said method comprising: generating a first coherent light beam and a second coherent light beam; reflecting at least said first coherent light beam from a first region into a first return beam and reflecting said second coherent light beam from a second region into a second return beam; measuring at least a first reflectivity of said first region; detennining a topography-dependent phase shift of said first return beam and said second return beam based on said first reflectivity; measuring a height based on said topography-dependent phase shift; comparing said first reflectivity and a second reflectivity of said second region; using a total phase shift of said first return beam and said second return beam for said height measurement, if said first reflectivity and said second reflectivity are equal; and outpuffing said height measurement.