Fixed-polarizer ellipsometry: a simple technique to measure the thickness of very thin films

The fixed-polarizer ellipsometer measures thickness of thin films. It is si mple, inexpensive, and provides a linear response over a range of 800 Angst rom. We develop a matrix formulation to describe the optical characteristic s of the instrument and apply it to the case of a single thin film on a sub strate. Excellent agreement is found between experimental and simulated res ults. Applying the instrument to optical immunoassay, we show that its sens itivity can extend to 4 pg/ml, depending upon the analyte. This compares fa vorably with commercially available manual and automated immunoassay system s. The fixed-polarizer ellipsometer appears to be well-suited for use in la boratory and production environments. (C) 1999 Society of Photo-Optical Ins trumentation Engineers. [S0091-3286(99)02205-9].