Method of measuring a thickness of a multilayered sample using u

Details Method of measuring a thickness of a multilayered sample using u Method of measuring a thickness of a multilayered sample using u

1994-08-11

1995-08-08

Nelms, David C.

Radiant energy

Photocells; circuits and apparatus

With circuit for evaluating a web, strand, strip, or sheet

356357, 250226, G01N 2186, G01V 904

Patent

active

054401410

ABSTRACT:
Spectral reflection ratios with respect to a second wavelength range are obtained and Fourier transformed to derive frequency converted spectrum. A power spectrum is obtained from the frequency converted spectrum to identify a peak which expresses interference caused by a silicon film. An approximate value d2' of the film thickness of the silicon film is calculated based on the peak position. After filtered by low-pass filtering, the frequency converted spectrum is reverse Fourier transformed to obtain spectral reflectance. From the spectral reflectance, theoretical spectral reflection ratios which are theoretically derived on only one transparent film of the thickness d3 which is formed on a silicon layer are subtracted. An approximate value d1' of the thickness of a silicon oxide film is then calculated from the spectral reflectance which are obtained by subtraction.

REFERENCES:
patent: 4645349 (1987-02-01), Tabata
patent: 4984894 (1991-01-01), Kondo
patent: 4988198 (1991-01-01), Kondo
patent: 4999509 (1991-03-01), Wada et al.
patent: 5120966 (1992-06-01), Kondo
patent: 5358333 (1994-10-01), Schmidt et al.

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