Developments In In-Situ Ellipsometer Monitoring Of Thin Film Growth During Reactive Ion Plating Deposition

In situ ellipsometry is of interest for monitoring and control of growing films. Its extreme sensitivity to thin layers also allows the measurement of the interface film frequently formed between a growing film and the substrate. The installation and operation of an in situ system on two different vacuum coating machines is described. The system records Ψ and Δ measurements every 5 seconds during film growth. We present an algorithm for computing the thickness (d) and index (n-ik) of a growing and an interface film on a known substrate from five Ψ and Δ measurements at different times during film growth. Numerical solutions of the ellipsometer equations for d, n, and k performed using a 25 MHz 80386 microprocessor with an 80387 math co-processor require about 30 minutes. Additional solutions beyond the first five data sets require only two additional measurements. By taking data in repeated time intervals during the growth of a film, we obtain a depth profile of its optical properties