| 摘要 |
A method of determining the rate of change of optical thickness of a thin-film during deposition comprising the steps of illuminating the thin-film with electromagnetic radiation having a range of wavelengths, measuring the transmission spectrum of the thin-film at least twice during the deposition process to determine the wavelength lambda<SUB>t </SUB>or turning points in the transmission spectrum, and using the measurements to determine the rate to change of optical thickness of the thin-film as a function of time. The method further comprises the steps of predicting a time T in the growth process at which the wavelength lambda<SUB>t </SUB>of the turning point in the transmission spectrum of the thin-film will be substantially equal to the wavelength lambda<SUB>d </SUB>of the turning point in the transmission spectrum of thin-film at its optical design thickness, and interrupting the growth process such that growth ceases at time T.
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