Optics: measuring and testing – By dispersed light spectroscopy – Utilizing a spectrometer
Patent
1992-05-05
1994-08-09
Turner, Samuel A.
Optics: measuring and testing
By dispersed light spectroscopy
Utilizing a spectrometer
356355, G01B 902
Patent
active
053371445
ABSTRACT:
An etch rate monitor for use with semiconductor wafer etching processes includes a source of light of normal incidence to the wafer surface through a window in the etching chamber. In a first embodiment, a Fresnel or positive lens is used to collect some of the diffraction orders caused by the repetitive patterns on the wafer surface which merge from the window. In alternate embodiments, a concave spherical mirror and/or a photodetector system are used to collect the diffraction orders. A collimating lens applies these diffraction orders of normal incidence to interference filters which reject plasma and ambient light and pass the diffraction orders to a photodetector to monitor etch rate as a function of the cycle period between interference minima or maxima caused by the difference in path length between the etched and not etched surfaces of the wafer.
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patent: 4131365 (1978-12-01), Pryor
patent: 4615620 (1986-10-01), Noguchi et al.
patent: 4704033 (1987-11-01), Fay et al.
patent: 4873430 (1989-10-01), Juliana et al.
patent: 4927485 (1990-05-01), Cheng et al.
de Geus Richard
Ebbing Peter
Strul Bruno
Applied Materials Inc.
Morris Birgit E.
Turner Samuel A.
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