Thin film thickness monitor

Details Thin film thickness monitor Thin film thickness monitor

1992-03-04

1993-08-31

Rosenberger, Richard A.

Optics: measuring and testing

By configuration comparison

With photosensitive film or plate

356243, 356357, G01B 1106

Patent

active

052413667

ABSTRACT:
A thin film thickness monitor using successive reflection of a polychromatic light beam off of reference thin film of variable optical thickness and a sample thin film whose thickness is to be determined, in which a monochromatic light source is used beforehand to first determine the actual optical thickness of the reference thin film at each relative position of the beam and reference thin film. In one embodiment, the ratio S/R of detected light intensity S from the sample thin film and detected light intensity R from the reference thin film is found for each relative position and the position at which the ratio is a maximum is determined. In another embodiment, this ratio is corrected by a corresponding ratio S.sub.1 /R.sub.1 derived from a bare wafer substrate. The sample can then be located behind additional optical surfaces, such as a vacuum port without causing substantial errors. In yet a third embodiment, the detected light intensity R2 from two reflections off of the reference thin film is used in place of intensity R, allowing very thin films to be accurately measured.

REFERENCES:
patent: 4355903 (1982-10-01), Sandercock
patent: 4453828 (1984-06-01), Hershel et al.
patent: 4676647 (1987-06-01), Kikkawa et al.

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