Wuhan Eoptics Technology Co.

Wuhan, China

Wuhan Eoptics Technology Co.

Wuhan, China

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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.


Gu H.,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 3 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2016

The diagnosis and control of the polarization aberrations is one of the main concerns in a hyper numerical aperture (NA) lithography system. Waveplates are basic and indispensable optical components in the polarimetric diagnosis tools for the immersion lithography system. The retardance of a birefringent waveplate is highly sensitive to the incident angle of the light, which makes the conventional waveplate not suitable to be applied in the polarimetric diagnosis for the immersion lithography system with a hyper NA. In this paper, we propose a method for the optimal design of a wideview-angle waveplate by combining two positive waveplates made from magnesium fluoride (MgF2) and two negative waveplates made from sapphire using the simulated annealing algorithm. Theoretical derivations and numerical simulations are performed and the results demonstrate that the maximum variation in the retardance of the optimally designed wide-view-Angle waveplate is less than ± 0.35° for a wide-view-Angle range of ± 20°. © 2016 SPIE.


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).


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.


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.


Chen X.,Huazhong University of Science and Technology | Shi Y.,Huazhong University of Science and Technology | Jiang H.,Huazhong University of Science and Technology | Zhang C.,Huazhong University of Science and Technology | And 3 more authors.
Applied Surface Science | Year: 2016

Mueller matrix ellipsometry (MME) is applied to characterize lithographic patterns with natural line edge roughness (LER). A computationally efficient approach based on effective medium approximation is proposed to model the effects of LER in MME measurements. We present both the theoretical and experimental results on lithographic patterns with realistic LER which demonstrate that MME in combination with the proposed effective modeling method is capable of quantifying LER amplitudes. Quantitative comparisons between the MME and scanning electron microscopy measured results also reveal the strong potential of this technique for in-line nondestructive line roughness monitoring. © 2015 Elsevier B.V.


Zhu J.,Huazhong University of Science and Technology | Jiang H.,Huazhong University of Science and Technology | Shi Y.,Huazhong University of Science and Technology | Chen X.,Huazhong University of Science and Technology | And 4 more authors.
Journal of Optics (United Kingdom) | Year: 2015

Recently, we have indirectly demonstrated that nanostructure reconstruction accuracy is degraded by the outliers in optical scatterometry, and we have applied the robust estimation method to suppress these outliers. However, the existence of a possible heavy masking effect could result in the risk of low measurement accuracy, since the detection of outliers is simply based on the judgment of residual value. In this work, a novel method is introduced to directly detect outliers, which can provide the intuitional display of outliers in a two-dimensional coordinate system. Moreover, a robust correction step based on the principle of least trimmed squared estimator regression is proposed to replace the conventional Gauss-Newton iteration step, by which the more reliable and accurate nanostructure reconstruction is achieved. The improved reconstruction of a one-dimensional etched Si grating has demonstrated the feasibility of the proposed methods. © 2016 IOP Publishing Ltd.


Gu H.,Huazhong University of Science and Technology | Chen X.,Huazhong University of Science and Technology | Jiang H.,Huazhong University of Science and Technology | Zhang C.,Huazhong University of Science and Technology | And 3 more authors.
Journal of Optics (United Kingdom) | Year: 2016

Accurate measurement of the Mueller matrix over a broad band is highly desirable for the characterization of nanostructures and nanomaterials. In this paper, we propose a general composite waveplate (GCW) that consists of multiple waveplates with flexibly oriented axes as a polarization modulating component in the Mueller matrix ellipsometer (MME). Although it is a common practice to make achromatic retarders by combining multiple waveplates, the novelty of the GCW is that both the retardances and azimuths of fast axes of the single-waveplates in the GCW are flexible parameters to be optimized, which is different from the conventional design where single-waveplates are usually arranged in symmetrical layout or with their fast axes parallel or perpendicular to each other. Consequently, the GCW can provide many more flexibilities to adapt to the optimization of the MME over a broad band. A quartz triplate, as a concrete example of the GCW, is designed and used in a house-made MME. The experimental results on the air demonstrate that the house-made MME using the optimally designed quartz triplates has an accuracy better than 0.2% and a precision better than 0.1% in the Mueller matrix measurement over a broad spectral range of 200∼1000 nm. The house-made MME exhibits high measurement repeatability better than 0.004 nm in testing a series of standard SiO2/Si samples with nominal oxide layer thicknesses ranging from 2 nm to 1000 nm. © 2016 IOP Publishing Ltd.


Gu H.,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 4 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2015

Dual-rotating compensator Mueller matrix ellipsometer (DRC-MME) has been designed and applied as a powerful tool for the characterization of thin films and nanostructures. The compensators are indispensable optical components and their performances affect the precision and accuracy of DRC-MME significantly. Biplates made of birefringent crystals are commonly used compensators in the DRC-MME, and their optical axes invariably have tilt errors due to imperfect fabrication and improper installation in practice. The axis tilt error between the rotation axis and the light beam will lead to a continuous vibration in the retardance of the rotating biplate, which further results in significant measurement errors in the Mueller matrix. In this paper, we propose a simple but valid formula for the retardance calculation under arbitrary tilt angle and azimuth angle to analyze the axis tilt errors in biplates. We further study the relations between the measurement errors in the Mueller matrix and the biplate axis tilt through simulations and experiments. We find that the axis tilt errors mainly affect the cross-talk from linear polarization to circular polarization and vice versa. In addition, the measurement errors in Mueller matrix increase acceleratively with the axis tilt errors in biplates, and the optimal retardance for reducing these errors is about 80°. This work can be expected to provide some guidences for the selection, installation and commissioning of the biplate compensator in DRC-MME design. © 2015 Copyright SPIE.


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 4 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2015

Mueller matrix ellipsometry has been demonstrated as a powerful tool for nanostructure metrology in high-volume manufacturing. Many factors may induce depolarization effect in the Mueller matrix measurement, and consequently, may lead to accuracy loss in the nanostructure metrology. In this paper, we propose to apply a Mueller matrix decomposition method for the Mueller matrix measurement to separate the depolarization effect caused by the MME system. The method is based on the polar decomposition by decomposing the measured depolarizing Mueller matrix into a sequence of three matrices corresponding to a diattenuator followed by a retarder and a depolarizer. Since the depolarization effects will be only reflected in the depolarizer matrix, the other two matrices are used to extract the structure parameters of the measured sample. Experiments performed on a one-dimensional silicon grating structure with an in-house developed MME layout have demonstrated that the proposed method achieves a higher accuracy in the nanostructure metrology. © 2015 Copyright SPIE.

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