Abstract

A new method of monitoring layer thickness during thin film deposition is presented. A beam of linearly polarized light of fixed azimuth strikes the film at oblique incidence. The reflected light is intercepted by a fixed arrangement of two partially specularly reflecting photodetectors with nonparallel surfaces. As the layer is deposited, the ratio of the detector currents varies as a periodic, linear sawtooth function of film thickness. Precalibration of the two-detector arrangement provides a plot of the expected path of the ratio. The thickness of the growing film is monitored continuously by comparing the measured ratio to its predetermined value. An example of the application of the CRUST-M is given for the deposition of common dielectric films on Si. The resolution is ~1 Å for monitoring the oxidation of Si.

© 1989 Optical Society of America