Single-instrument morphology: Single-element polarizer (SEP) ellipsometers, reflecsometers, elliptometers, and reflectometers

摘要

We present a collective, integrative view and a comprehensive, detailed analysis of the single-element polarizer (SEP) instrument, where it is composed of only a polarizer in the incident beam. A light detector receives the reflected beam from the sample, which is a film-substrate system in general. Seven modes of operation of this instrument are discussed; seven techniques of ellipsometry, reflecsometry (defined as ellipsometry-based reflectometry), elliptometry (defined as reflectometry-based ellipsometry), and reflectometry. First: one ellipsometer is where the polarizer is rotated and the angle of incidence is scanned for a specific condition of the detector signal. That way, specific corresponding points in the ρ-plane of the film-substrate sample are detected. Second: another ellipsometer is where the polarizer is rotated and the angle of incidence is kept un-changed, and the ac/dc signal ratio is detected, yielding the ellipsometric angle ψ of the sample. Third: one reflecsometer is where the angle of incidence is scanned, while the polarizer is stationary, and a specific condition of the detector signal is detected, indicating a corresponding specific condition of the sample performance. Four more techniques of ellipsometry, reflecsometry, elliptometry, or reflectometry are also presented. For all modes of operation, heuristic and/or mathematical inversion methods exist to fully characterize the film-substrate system: determine the substrate optical constant and that of the film, in addition to the film thickness, or a subset thereof. We briefly present some of the available inversion methods with reference to the SiO2-Si film-substrate system in some cases.