REFRACTIVE-INDEX MEASUREMENT OF SILICON THIN-FILMS USING SLAB OPTICALWAVE-GUIDES

Measurement of the real part of the refractive index (n(f)') of silico n thin films using a slab optical waveguide (SOW) is discussed. Upon d eposition of thin films on a SOW, the transmittance decreases with per iodic oscillation owing to the multiple reflection. It is clarified fr om a simulation of a four-layer SOW that the period of oscillation is reduced when n(f)' increases. In this paper, we discuss a method of de termining the n(f)' from correspondence of the minimum film thickness (d(0)) in which the oscillation valley appears as a calculation result of transmittance for the TE(0) mode to d(0) in an experiment in which the refractive index and sizes of SOW are known without considering h igher modes or the TM mode. Good agreement is observed in comparison o f the result of the measurement with that of the ellipsometer at a wav elength of 632.8 nm. Therefore, it can be shown that the distributions of n(f)' of a-Si:H and SiN thin films at wavelengths from 400 to 800 nm are obtained in the same manner. In order to achieve higher accurac y of the measurement, a SOW with a larger refractive index is used.