AVS 50th International Symposium
    QSA-10 Topical Conference Tuesday Sessions
       Session QS-TuP

Paper QS-TuP6
An Analysis of Rotating-Compensator Ellipsometers for Metrology

Tuesday, November 4, 2003, 5:30 pm, Room Hall A-C

Session: Aspects of Quantitative Surface Analysis
Presenter: D.E. Aspnes, North Carolina State University
Authors: D.E. Aspnes, North Carolina State University
M. Asar, North Carolina State University
T. Mori, Tohoku University, Japan
K.A. Ebert, Thermawave, Inc.
Correspondent: Click to Email
Increasing demands on accuracy are moving spectroscopic-ellipsometry technology from rotating-analyzer and -polarizer (RAE, RPE) configurations to rotating-compensator (RCE) designs. The additional 4@omega@t component generated in the transmitted intensity by an RCE makes it intrinsically more powerful for analysis, yet questions concerning relative performance, optimum configurations, and optimal component settings remain. Here, we discuss aspects relevant for achieving maximum accuracy for nm-scale thin-film metrology. First, calculations show that precisions on sample parameters obtained by an RCE are often better than those attainable with an RAE or RPE even for compensator retardations near 180 degrees, thereby resolving the optimum-sensitivity issue. Second, a comparison of RAE and RCE data obtained on a bench system that was operated as an RAE for over 25 years revealed a previously unsuspected polarizer-leakage artifact that affected the RAE data to about 1%, highlighting the more powerful diagnostic capabilities of an RCE. Third, we treat depolarization artifacts in general, using a system-transfer-matrix approach that also allows sample parameters to be extracted from RCE data without having to Fourier analyze the transmitted intensity. Finally, we analyze monoplate and biplate compensators, in particular discussing the multiple-internal-reflection artifacts that lead to the appearance of interference oscillations in spectra obtained with systems using biplate compensators. The optimum ellipsometer configuration is an RCE operating with a monoplate compensator.