Dr. Wenhua Zhu Profile

Dr. Wenhua Zhu

Research Scientist at KLA Corporation

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Publications (13)

Proceedings Article | 16 October 2020 Presentation + Paper

Quadriwave lateral shearing phase imaging of EUV masks

Wenhua Zhu, Ryan Miyakawa, Patrick Naulleau

Proceedings Volume 11517, 115170X (2020) https://doi.org/10.1117/12.2574605

KEYWORDS: Photomasks, Extreme ultraviolet, Phase shifts, Phase shift keying, Phase imaging, Lens design, Charge-coupled devices, Phase measurement, 3D modeling, Logic

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Proceedings Article | 20 April 2020 Presentation + Paper

Quantitative phase imaging of EUV masks

Ryan Miyakawa, Stuart Shwerwin, Wenhua Zhu, Markus Benk, Patrick Naulleau

Proceedings Volume 11323, 113231H (2020) https://doi.org/10.1117/12.2553133

KEYWORDS: Phase shifts, Zone plates, Photomasks, Extreme ultraviolet, Microscopes, Near field optics, Objectives, Phase measurement, Phase imaging, Phase contrast

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Proceedings Article | 23 March 2020 Presentation + Paper

How we are making the 0.5-NA Berkeley mirco-field exposure tool stable and productive

Chris Anderson, Arnaud Allezy, Weilun Chao, Lucas Conley, Carl Cork, Will Cork, Rene Delano, Jason DePonte, Michael Dickinson, Geoff Gaines, Jeff Gamsby, Eric Gullikson, Gideon Jones, Lauren McQuade, Ryan Miyakawa, Patrick Naulleau, Seno Rekawa, Farhad Salmassi, Brandon Vollmer, Daniel Zehm, Wenhua Zhu

Proceedings Volume 11323, 113230B (2020) https://doi.org/10.1117/12.2552125

KEYWORDS: Mirrors, Scanners, Semiconducting wafers, Scanning electron microscopy, Camera shutters, Image processing, Vibration isolation, Projection systems

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Proceedings Article | 4 June 2019 Paper

Interferometric measurement of phase in EUV masks

Wenhua Zhu, Ryan Miyakawa, Lei Chen, Patrick Naulleau

Proceedings Volume 10957, 109571W (2019) https://doi.org/10.1117/12.2518057

KEYWORDS: Phase shifts, Photomasks, Extreme ultraviolet, Phase measurement, Interferometry, Phase shifting, Phase interferometry, Diffraction gratings, Reconstruction algorithms, Optical design

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Proceedings Article | 26 March 2019 Presentation + Paper

Overview and status of the 0.5NA EUV microfield exposure tool at Berkeley Lab

Christopher Anderson, Arnaud Allezy, Weilun Chao, Carl Cork, Will Cork, Rene Delano, Jason DePonte, Michael Dickinson, Geoff Gaines, Jeff Gamsby, Eric Gullikson, Gideon Jones, Stephen Meyers, Ryan Miyakawa, Patrick Naulleau, Senajith Rekawa, Farhad Salmassi, Brandon Vollmer, Daniel Zehm, Wenhua Zhu

Proceedings Volume 10957, 1095708 (2019) https://doi.org/10.1117/12.2516339

KEYWORDS: Scanning electron microscopy, Critical dimension metrology, Semiconducting wafers, Extreme ultraviolet lithography, Optical lithography, Monochromatic aberrations, Line width roughness, Photoresist materials, Image processing, Projection systems

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Proceedings Article | 26 March 2019 Paper

Achieving diffraction-limited performance on the Berkeley MET5

Ryan Miyakawa, Chris Anderson, Wenhua Zhu, Geoff Gaines, Jeff Gamsby, Carl Cork, Gideon Jones, Michael Dickenson, Seno Rekawa, Weilun Chao, Sharon Oh, Patrick Naulleau

Proceedings Volume 10957, 109571X (2019) https://doi.org/10.1117/12.2516384

KEYWORDS: Wavefronts, Diffraction gratings, Interferometry, Shearing interferometers, Optical alignment, Diffraction, Optical design, Sensors, Multiplexing, Monochromatic aberrations

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Proceedings Article | 12 October 2018 Presentation

Berkeley MET5 update: commissioning, interferometry, and first prints (Conference Presentation)

Ryan Miyakawa, Wenhua Zhu, Geoff Gaines, Chris Anderson, Patrick Naulleau

Proceedings Volume 10809, 1080911 (2018) https://doi.org/10.1117/12.2501953

KEYWORDS: Wavefronts, Error analysis, Interferometry, Data modeling, Extreme ultraviolet, Shearing interferometers, Monochromatic aberrations, Projection lithography, Objectives, Optical resolution

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The Berkeley MET5, funded by EUREKA, is the world’s highest-resolution EUV projection lithography tool. With a 0.5-numerical aperture (NA) Schwartzchild objective, the Berkeley MET5 is capable of delivering 8-nm resolution for dense line/space patterns. In order to achieve this resolution, optical aberrations must be accurately characterized and compensated, a task that is complicated by the difficulty in finding a bright, high quality reference wave, and nonlinear effects associated with high incident angles on interferometry targets. The Berkeley MET5 was designed with an in-situ lateral shearing interferometer (LSI) to provide real-time wavefront diagnostics alongside its imaging capabilities. The geometry of the MET5 makes it a particularly difficult optical system to measure interferometrically. Unlike EUV production tools, the 2-bounce Schwartzchild design is non-telecentric at the image, with an image plane whose normal vector is tilted 1.12 degrees with respect to the optical axis. Shearing interferometers have shown good results measuring EUV wavefronts at low to medium NAs (0.1 - 0.33) with telecentric geometry. However, to accommodate the MET5 geometry, a generalized model of LSI was developed to inform the design and build of a lateral shearing interferometer capable of operating at high-NA and with a tilted image plane. This model predicts non-negligible systematic errors that must be compensated in the analysis. Specialized pinhole arrays were patterned onto the mask to fill the pupil with spatially filtered light that is incoherently multiplexed from multiple apertures. Due to the relatively large amount of DC flare compared with the signal in the interferograms, illumination profiles were chosen to match the NA of the obscuration so that zero-order light coming through the mask absorber is blocked in the pupil, which results in a finite coherence function width. Because of this, the design of the arrays required balancing the efficiency of the pattern while maintaining enough separation between apertures to accommodate the coherence function width. Analysis of the interferometric data shows a total RMS wavefront error of 0.6 nm after removal of systematic errors predicted by the LSI model. The bulk of this error lies in astigmatism and coma terms which can be corrected by field position and small adjustments to the alignment of the Schwartzchild optic respectively. The aberration signature of this wavefront is in good agreement with preliminary print data of aberration targets according to aerial image modeling of these features. The interferometric capability of the Berkeley MET5 is an indispensable part of commissioning the tool, and will allow for the diagnosing and monitoring of tool performance as it begins user operations in the coming months.

Proceedings Article | 9 October 2018 Presentation + Paper

Lateral shearing interferometry for high-NA EUV wavefront metrology

Wenhua Zhu, Ryan Miyakawa, Lei Chen, Patrick Naulleau

Proceedings Volume 10809, 108091S (2018) https://doi.org/10.1117/12.2501989

KEYWORDS: Wavefronts, Extreme ultraviolet, Sensors, Interferometry, Wavefront metrology, Mathematical modeling, Interferometers, Geometrical optics, Diffraction, Shearing interferometers

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SPIE Journal Paper | 14 November 2017

Simultaneous phase-shifting Twyman interferometer with a point source array

Donghui Zheng, Lei Chen, Yu Ding, Qinyuan Sun, Wenhua Zhu, Jinpeng Li

OE, Vol. 56, Issue 11, 115103, (November 2017) https://doi.org/10.1117/12.10.1117/1.OE.56.11.115103

KEYWORDS: Phase shifts, Interferometers, Diffraction, Diffraction gratings, Imaging systems, Charge-coupled devices, Optical engineering, Phase measurement, Picosecond phenomena, Polarization

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Proceedings Article | 26 June 2017 Paper

Spatial-temporal phase shifting interferometry: suppressing phase errors in dynamic Fizeau interferometer

Wenhua Zhu, Lei Chen, Rihong Zhu, Rui Zhang, Donghui Zheng

Proceedings Volume 10329, 1032909 (2017) https://doi.org/10.1117/12.2271189

KEYWORDS: Error analysis, Mirrors, Phase interferometry, Fizeau interferometers, Interferometers, Interferometry, Phase shifting, Phase shift keying, Modulation, Phase shifts, Phase measurement

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SPIE Journal Paper | 16 December 2016

Absolute measurement for optical inhomogeneity of parallel plate using phase-shifting interferometry

Donghui Zheng, Lei Chen, Qinyuan Sun, Wenhua Zhu, Jinpeng Li, Jianxin Li

OE, Vol. 55, Issue 12, 124103, (December 2016) https://doi.org/10.1117/12.10.1117/1.OE.55.12.124103

KEYWORDS: Optical testing, Reflectivity, Phase interferometry, Wavefronts, Interferometers, Refractive index, Photovoltaics, Lithium, Optical engineering, Error analysis

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Proceedings Article | 27 September 2016 Paper

Near infrared reflective shearing point diffraction interferometer for dynamic wavefront measurement

Wenhua Zhu, Lei Chen, Donghui Zheng

Proceedings Volume 9684, 968405 (2016) https://doi.org/10.1117/12.2240632

KEYWORDS: Wavefronts, Near infrared, Reflectivity, Point diffraction interferometers, Diffraction, Interferometry, Phase measurement, Charge-coupled devices, Calibration, Spherical lenses, Beam splitters, Monochromatic aberrations, Fourier transforms

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Proceedings Article | 27 September 2016 Paper

Research on adjusting and testing of off-axis paraboloid mirror with large aperture

Donghui Zheng, Lei Chen, Wenhua Zhu

Proceedings Volume 9684, 968406 (2016) https://doi.org/10.1117/12.2240476

KEYWORDS: Off axis mirrors, Mirrors, Optical testing, Monochromatic aberrations, Wavefront aberrations, Interferometers, Imaging systems, Zoom lenses, Optical coherence tomography, Zemax

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Showing 5 of 13 publications

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