Metasurface array for single-shot spectroscopic ellipsometry

Wen et al. Light: Science & Applications (2024) 13:88 Official journal of the CIOMP 2047-7538 https://doi.org/10.1038/s41377-024-01396-3 www.nature.com/lsa A R T I C L E O p e n A c c e s s Metasurface array for single-shot spectroscopic ellipsometry Shun Wen1, Xinyuan Xue1, Shuai Wang 1, Yibo Ni1, Liqun Sun1 and Yuanmu Yang 1✉ Abstract Spectroscopic ellipsometry is a potent method that is widely adopted for the measurement of thin film thickness and refractive index. Most conventional ellipsometers utilize mechanically rotating polarizers and grating-based spectrometers for spectropolarimetric detection. Here, we demonstrated a compact metasurface array-based spectroscopic ellipsometry system that allows single-shot spectropolarimetric detection and accurate determination of thin film properties without any mechanical movement. The silicon-based metasurface array with a highly anisotropic and diverse spectral response is combined with iterative optimization to reconstruct the full Stokes polarization spectrum of the light reflected by the thin film with high fidelity. Subsequently, the film thickness and refractive index can be determined by fitting the measurement results to a proper material model with high accuracy. Our approach opens up a new pathway towards a compact and robust spectroscopic ellipsometry system for the high throughput measurement of thin film properties. Introduction For semiconductor processing, such as in the manu- facturing of integrated circuits and flat display panels, to ensure processing quality and efficiency, it is crucial to accurately measure the thickness and optical constant of nanometer-scale thin films in a high throughput1–4. Instruments such as white-light interferometers, scanning electron microscopes, and atomic force microscopes may allow the measurement of film thickness with high accuracy, yet they have a relatively slow measurement speed and high system complexity. The measurement may also require direct contact with the sample under test. Spectroscopic ellipsometry is an alternative method that enables highly accurate and non-destructive measure- ments of thin film thickness as well as its optical constant, which has been widely implemented in semiconductor metrology and process monitoring5–7. In a typical spectroscopic ellipsometry system, it first measures the change in the polarization state of light reflected from the thin film under test. The wavelength- dependent