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Chen X.,Huazhong University of Science and Technology | Jiang H.,Huazhong University of Science and Technology | Zhang C.,Huazhong University of Science and Technology | Zhang C.,Wuhan Eoptics Technology Co. | And 2 more authors.
Journal of Applied Physics | Year: 2015

The Mueller matrix differential decomposition is applied to interpret Mueller matrices of asymmetric gratings and to understand the use of Mueller matrix ellipsometry (MME) in distinguishing the direction of profile asymmetry, as reported in our recent work [Chen et al., J. Appl. Phys. 116, 194305 (2014)]. We show that both linear and circular birefringence-dichroism pairs can be extracted from the collected Mueller matrices, which provide a complete description of the sample polarization properties. We present both theoretical and experimental results, which demonstrate that the linear birefringence and dichroism, LB′ and LD′, along the ±45° axes are the origin of the MME in distinguishing the direction of profile asymmetry. We also demonstrate that equal magnitude of profile asymmetry in opposite directions always yields LB′ and LD′ of the same absolute deviation from zero and of opposite sign, when the plane of incidence is no longer perpendicular to grating lines. The sensitivity of LB′ and LD′ to both the magnitude and direction of profile asymmetry is useful in monitoring processes in which symmetric structures are desired. © 2015 AIP Publishing LLC. Source


Li W.,Huazhong University of Science and Technology | Jiang H.,Huazhong University of Science and Technology | Zhang C.,Huazhong University of Science and Technology | Zhang C.,Wuhan Eoptics Technology Co. | And 4 more authors.
Journal of Vacuum Science and Technology B: Nanotechnology and Microelectronics | Year: 2016

The authors apply Mueller matrix ellipsometry to characterize the curved surface layers, by utilizing the noticeable anisotropy observed from the measured data. The authors demonstrate that this anisotropy is introduced by the curved surface shape as well as the misalignment between the illumination spot and the surface vertex. An optical model is proposed to expound the anisotropy, and is applied to evaluate the curved thin thermal oxide layer on a silicon sphere crown. After incorporating the proposed optical model in the parameter extraction, the experimental results show that not only will the accuracy of the oxide layer thickness measurement at an arbitrary location on the surface be improved, the curvature radius as well as the position of detection can also be determined directly. © 2016 American Vacuum Society. Source


Honggang G.U.,Huazhong University of Science and Technology | Chen X.,Huazhong University of Science and Technology | Jiang H.A.O.,Huazhong University of Science and Technology | Zhang C.,Huazhong University of Science and Technology | And 4 more authors.
Applied Optics | Year: 2016

The biplate that consists of two single wave plates made from birefringent materials with their fast axes oriented perpendicular to each other is one of the most commonly used retarders in many optical systems. The internal alignment of the optical axes of the two single wave plates is a key procedure in the fabrication and application of a biplate to reduce the spurious artifacts of oscillations in polarization properties due to the misalignment error and to improve the accuracy and precision of the systems using such biplates. In this paper, we propose a method to accurately align the axes of an arbitrary biplate by minimizing the oscillations in the characteristic parameter spectra of the biplate detected by a spectroscopic Mueller matrix ellipsometer (MME). We derived analytical relations between the characteristic parameters and the misalignment error in the biplate, which helps us to analyze the sensitivity of the characteristic parameters to the misalignment error and to evaluate the alignment accuracy quantitatively. Experimental results performed on a house-developed MME demonstrate that the alignment accuracy of the proposed method is better than 0.01° in aligning the optical axes of a quartz biplate. © 2016 Optical Society of America. Source


Chen X.,Huazhong University of Science and Technology | Du W.,Huazhong University of Science and Technology | Yuan K.,Huazhong University of Science and Technology | Chen J.,Huazhong University of Science and Technology | And 5 more authors.
Review of Scientific Instruments | Year: 2016

In this paper, we describe the development of a spectroscopic Mueller matrix imaging ellipsometer (MMIE), which combines the great power of Mueller matrix ellipsometry with the high spatial resolution of optical microscopy. A dual rotating-compensator configuration is adopted to collect the full 4 × 4 imaging Mueller matrix in a single measurement. The light wavelengths are scanned in the range of 400-700 nm by a monochromator. The instrument has measurement accuracy and precision better than 0.01 for all the Mueller matrix elements in both the whole image and the whole spectral range. The instrument was then applied for the measurement of nanostructures combined with an inverse diffraction problem solving technique. The experiment performed on a photoresist grating sample has demonstrated the great potential of MMIE for accurate grating reconstruction from spectral data collected by a single pixel of the camera and for efficient quantification of geometrical profile of the grating structure over a large area with pixel resolution. It is expected that MMIE will be a powerful tool for nanostructure metrology in future high-volume nanomanufacturing. © 2016 Author(s). Source


Li W.,Huazhong University of Science and Technology | Zhang C.,Huazhong University of Science and Technology | Zhang C.,Wuhan Eoptics Technology Co. | Jiang H.,Huazhong University of Science and Technology | And 3 more authors.
Journal of Optics (United Kingdom) | Year: 2016

Noticeable depolarization effects are observed in the measurement of the air using an in-house developed dual rotating-compensator Mueller matrix ellipsometer. We demonstrate that these depolarization effects are essentially artifacts and mainly induced when the compensator with wavelength-dependent optical properties is integrated with the finite bandwidth detector. We define a general formula to represent the actual Mueller matrix of the compensator by taking into account the depolarization artifacts. After incorporating this formula into the system model, a correction method is further proposed, and consequently, improved accuracy can be achieved in the Mueller matrix measurement. © 2016 IOP Publishing Ltd. Source

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