Method and apparatus for controlling the growth of thin film during deposition process by measuring the rate of change of optical thickness of the thin-film

摘要

The method comprises illuminating the thin-film (5) with electromagnetic radiation (3) having a range of wavelengths, measuring the transmission spectrum (6) of the thin film (5) at least twice during the deposition process to determine the wavelength g SBt/SB of turning points in transmission spectrum, and using the measurements to determine the rate of change of optical thickness of the thin-film as a function of time. The method may include measuring cumulative charge supplied to the source at the same time. These measurement methods may be incorporated into a method of controlling the growth of a thin-film up to an optical design thickness. Such method may further comprise the steps of predicting a time T in the growth process at which the wavelength g SBt/SB of the turning point will be equal to the wavelength g SBd/SB of the turning point at its optical design thickness, and ceasing the growth process at time T. Alternatively, growth can be stopped when cumulative charge reaches a predicted value of C. The method may include measuring spectrum after interruption in grown thin-film and comparing g SBc/SB with g SBd/SB to determine error between them.