Method and apparatus for evaluating the thickness of thin films

Details Method and apparatus for evaluating the thickness of thin films Method and apparatus for evaluating the thickness of thin films

1991-12-23

1993-01-19

Evans, F. L.

Optics: measuring and testing

By configuration comparison

With photosensitive film or plate

356128, 356369, 356446, G01B 1106

Patent

active

051810808

ABSTRACT:
A method and apparatus is disclosed for measuring the thickness or other optical constants of a thin film on a sample. The apparatus includes a laser for generating a linearly polarized probe beam. The probe beam is tightly focused on the sample surface to create a spread of angles of incidence. The reflected probe beam is passed through a quarter-wave plate and linear polarizer before impinging on a quad cell photodetector. The output signals from the photodetector represent an integration of the intensity of individual rays having various angles of incidence. By taking the difference between the sums of the output signals of diametrically opposed quadrants, a value can be obtained which varies linearly with film thickness for very thin films. The subject device can be used in conjunction with other prior devices to enhance sensitivity for thicker films.

REFERENCES:
patent: 4999014 (1991-03-01), Gold et al.
patent: 5042951 (1991-08-01), Gold et al.

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