Single Shot Line Profile Measurement of Multi-layered Film Thicknesses
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International Journal of Precision Engineering and Manufacturing https://doi.org/10.1007/s12541-020-00410-z
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Single Shot Line Profile Measurement of Multi‑layered Film Thicknesses Jin Sub Kim1 · Hyo Mi Park1 · Ki‑Nam Joo1 Received: 1 April 2020 / Revised: 9 July 2020 / Accepted: 24 August 2020 © Korean Society for Precision Engineering 2020
Abstract We propose a novel spectroscopic ellipsometry capable of measuring line profile of the film thicknesses with a single image at once. By adopting a polarization-pixelated CMOS camera and an imaging spectrometer, spatial, spectral and polarization information of the film structure can be acquired at the frame rate of the camera without any mechanical or electrical adjustments of polarizing optical components. The proposed system is beneficial not only to provide film thickness of the specimen with a single image acquisition, but also to analyze the spatial features of the film layers. Keywords Single shot measurement · Spectroscopic imaging ellipsometry · Line profile of multi-layered film thickness measurement · Polarization-pixelated camera
1 Introduction Ellipsometry has been very important for the characterization of thin film structures as a non-destructive metrological tool [1, 2]. Comparing the measured quantities such as ellipsometric angles of 𝛹 and Δ with their counterparts of theoretical model, ellipsometry can determine the thin film thicknesses with high sensitivity, and even a spectroscopic ellipsometry (SE) provides the reliability and robustness of the measurement results with sufficient spectral data of 𝛹 (𝜆) and Δ(𝜆) [3, 4]. However, most of SE only measure film thicknesses at a single point of the interest and adopt polarization adjustment of the light by using rotation of polarizing optic elements [5, 6] or electrical phase modulation [7, 8], which leads to time consumption. Imaging ellipsometry has capability of obtaining 3D or line profile of film thicknesses, but it still needs rotating mechanism for the polarization changes [9]. Even though several types of real time SE was proposed with multi-channel techniques [10, 11] and spatial
Jin Sub Kim and Hyo Mi Park these authors equally contributed this work. * Ki‑Nam Joo [email protected] 1
Department of Photonic Engineering, Chosun University, 309, Pilmun‑daero, Dong‑gu, Gwangju 61452, South Korea
phase retardation [12] recently, their measuring capabilities are limited into the specific point measurement. In this investigation, we propose a novel type of spectroscopic ellipsometry capable of measuring line profile of the film thicknesses at once. By adopting a polarizationpixelated CMOS camera and an imaging spectrometer, the ellipsometric parameters can be acquired without any mechanical or electrical moving parts, and their spectral and spatial profile are obtained with a single image.
2 Principle Figure 1 shows the optical configuration of the proposed system. As a light source, a spatially coherent broadband light is used and the beam size of the light is enlarged by a
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