Patent ID: 7570366
Filing Date: 2009-08-04
Classification: G01B

Abstract:
1. A method of characterizing a topography of a substrate comprising; providing a radiation beam comprising a coherence length less than about 300 μm; splitting the radiation beam into a probe beam and a reference beam; intercepting the probe beam with a first reflective element; steering the probe beam with the first reflective element to perpendicularly irradiate a specular local surface of a non-flat substrate, and wherein the probe beam is reflected from the local surface; intercepting and reflecting with the first reflector the probe beam reflected from the local surface; intercepting and reflecting the reference beam with a second reflective element such that optical path lengths of the probe beam and the reference beam are substantially equal; collecting the probe beam reflected from the first reflective element and the reference beam reflected from the second reflective element; combining the reflected reference beam and the probe beam reflected from the first reflective element to produce an interference pattern; detecting the interference pattern across a two-dimensional array of pixels; and using a phase shifting interferometer to determine a topography of the local surface.