Patent ID: 7663752
Filing Date: 2010-02-16
Classification: G01N

Abstract:
1. A polarization modulation imaging ellipsometer comprising: a light source unit that emits light whose amplitude periodically changes at a predetermined frequency; a sample holder on which a sample is placed; an incident-light optical unit having a collimator, a polarizer, and a photoelastic phase modulator which modulates light emitted from the light source unit to sinusoidally vary a phase difference between a p polarized light and an s polarized light of the light and applies the light to a measurement plane of the sample placed on the sample holder; an emitted-light optical unit having an analyzer which analyzes a polarization state of light that has been reflected from or transmitted through the sample and a two-dimensional detector which converts light received from the analyzer to an electrical signal and outputs the electrical signal; a control/analysis unit which operates the light source unit and the photoelastic phase modulator at the same frequency in a range of several tens of kHz to several hundreds of kHz, and to which an output signal emitted from the two-dimensional detector is input; wherein the polarizer, the photoelastic phase modulator, the sample, and the analyzer are arranged in this order on a light path, resulting in a PMSA type (polarizer-modulator-sample-analyzer) arrangement; the light source unit sequentially produces a measuring beam having a predetermined time lag relative to an operation clock of the photoelastic phase modulator; and the control/analysis unit calculates ellipsometric parameters Ψ and Δ for each pixel of a two-dimensional image of a surface of the sample to be observed with the two-dimensional detector using an output signal of the two-dimensional detector under conditions (1) to (3): (1) amplitude intensity of light that has passed through the photoelastic phase modulator being expressed as “α”, an mth order Bessel function of the first kind being expressed as J (2) a direct-current component of light intensity detected by the detector being expressed as I I (3) a sine wave component of the output signal of the two-dimensional detector being expressed as S when the photoelastic phase modulator is ideal, the ellipsometric parameters Ψ and Δ are calculated based on equation 1: and when the photoelastic phase modulator has static phase difference δ