Theory, Systems Design and Characterization of a Novel Full-Field Imaging Ellipsometer.

A novel approach for full-field high resolution ellipsometry called Dynamic Imaging Microellipsometry (DIM) is presented. DIM has been developed for in-situ studies of the localized breakdown processes in metallic passive films. The technique combines a modified approach to the conventional polarizer, specimen, compensator, and analyzer (PSCA) optical system with video and image processing. This approach has proven capable of rapidly capturing and analyzing surface maps of the ellipsometric parameters Delta and Psi termed ellipsograms. From the ellipsograms, instrument settings, and substrate refractive index, the thickness and index of refraction of the surface film may be determined. Test results from two DIM instruments are reported. The first, the proof of principle system demonstrated that the DIM radiometric approach was feasible and robust. Results from measurements in air of steel, copper, aluminum, and silicon are presented. The second, the prototype instrument was developed to more fully characterize the instrument's performance through measurements of random error, absolute accuracy and spatial resolution. Random errors below 0.08 degrees rms for delta and 0.025 degrees rms for psi with a spatial resolution better than 10 by 30 microns were demonstrated. Abnormal non-linearities in the electronics permitted only qualitative indications of absolute accuracy which were positive. Results from samples of tin, copper, niobium, and silicon dioxide on silicon measured in air are presented. A theoretical analysis of the DIM system is presented with two approaches shown for tuning the system to minimize random noise. A stochastic model of the random error is derived and verified using the experimental results. The absolute ellipsometric error is analyzed by defining the contributions of individual error sources using linear error coupling coefficients. Both the theoretical derivation and numerically derived maps of coupling coefficients over a range of delta and psi values are presented. These error models provide the necessary tools for tailoring DIM instrument design for specified measurement problems. Wide applications for the study and monitoring of the microstructure of thin films are anticipated.