Patent ID: 6411389
Filing Date: 2002-06-25
Classification: G01B

Abstract:
A method for monitoring etch depth and etch rate, comprising:providing a common path monolithic interferometer that uses a single shearing interferometer for measurement of phase of a reference image and a signal image; providing an optic having a surface to be etched; directing light along an optical path through said common path monolithic interferometer to produce said reference image and said signal image; measuring the phase of said reference image and said signal image by translating said shearing interferometer in a lateral direction with respect to the optical path so as to phase-shift the light; measuring a phase difference between said reference image and said signal image to obtain a starting phase value; contacting said surface to be etched with an etchant; measuring the phase of said signal image as said optic is being etched by translating said shearing interferometer in a lateral direction with respect to the optical path so as to phase-shift the light and obtain a current phase value of said signal image; and measuring a phase difference between said starting phase value and said current phase value to obtain a difference phase value.