Mr. David Xu Profile

David Xu

at ASML

SPIE Involvement:

Author

Publications (3)

Proceedings Article | 26 May 2022 Presentation + Paper

A novel solution on KrF pixel layer with thick photo resist (PR) by single exposure multi-focal imaging (SE MFI) technique

Zhenhai Yao, Lequn Jin, Yuhua Li, Maoqun Jiang, Fabin Huang, Min Fang, Xichen Sheng, Rongkuo Zhao, Michael Crouse, Chris Kaplan, Dongqing Zhang, Dongxiang Shi, Zhonghua Xu, Chaoqun Guo, Pieter Scheijgrond, Xiaoyang Jason Li, Stephen Hsu, Will Conley, Zhen Tang

Proceedings Volume 12051, 1205109 (2022) https://doi.org/10.1117/12.2616830

KEYWORDS: Semiconducting wafers, Chromatic aberrations, Data modeling, Calibration, Source mask optimization, Photomasks, SRAF, Copper indium disulfide, Optical lithography, Image processing

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Advancing technology nodes in CMOS Image Sensors (CIS) continues to drive a shrinking process to acquire higher resolution and low power consumption as well as more cost-effective production. With the sensor pixel size scaling down, a thicker photoresist (with aspect ratios greater than 10:1) is introduced to block high-energy implants with extremely localized implant profiles. Then double exposures/double focus (DE/DF) is applied to make sure the resist profile and process window is comparable or better. However, this process is a big challenge at high volume manufacturing (HVM) phase because of throughput loss. To recover it due to DE/DF, we invented SE MFI which uses two wavelengths (“colors”) generated by the KrF excimer laser to solve the problem. Due to the chromatic aberrations in the lens, the focal plane shift of different wavelength produces nearly the same result as DE/DF. However, the use of two-wavelengths brings some challenges. The first is the loss of image contrast and the second is the impact of chromatic aberrations across the slit which results in image shift and image asymmetry. In this work, we demonstrated that the use of ASML’s Tachyon KrF MFI source mask optimization (SMO) that can match the MFI SE process to DE/DF process of record (POR). We first used Tachyon Focus-Exposure Modeling plus (FEM+) to calibrate a DE resist model by using DE POR wafer data. Then we converted the DE model to a SE MFI model. At the end, we use the Tachyon MFI-SMO to optimize the SE MFI to match the DE/DF and MFI sidewall profiles through process window conditions at the center slit. We achieved making the MFI and DE/DF sidewall difference significantly smaller than other noises which can be measured on wafer at the center slit. We evaluated the chromatic aberration impact on through slit sidewall profiles also meet the specification. The through slit matching between MFI and DE/DF was further improved by through-slit mask optimization. This is done by inserting asymmetry sub resolution assist features (SRAFs). Tachyon Optical Proximity Correction plus (OPC+) can support full chip mask corrections for full-chip HVM. The above MFI technology including Tachyon optimization capability will be verified by wafer exposure via comparison between MFI and DE wafer results.

Proceedings Article | 22 February 2021 Poster + Presentation + Paper

Accuracy aware pixel selection in multi-wavelength uDBO metrology enables higher robustness and accuracy for DRAM

Chia Hung Chen, Sheng-Tsung Tsao, Jie Du, Wenkang Song, Hongwei Zhu, Ji-Ling Hou, Longfei Shen, Sunny Xia, Simon Mathijssen, Marc Noot, Farzad Farhadzadeh, Kimi Yang, Xing Ma, Zhi-Qiang Tang, Jing Wang, Yu Liu, David Xu, Herman Heijmerikx, Eason Su, Elliott Mc Namara, Kaustuve Bhattacharyya

Proceedings Volume 11611, 116112Z (2021) https://doi.org/10.1117/12.2583818

KEYWORDS: Metrology, Overlay metrology, High volume manufacturing, Front end of line, Detection and tracking algorithms

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Proceedings Article | 20 March 2019 Paper

Robust alignment mark design for DRAM using a holistic computational approach

Danying Li, Stella Zhang, Chia-Huang Chen, Youping Zhang, Alex Huang, David Xu, Yufeng Wang, Zhen Shi, Shi-lu Wang, Sheng-Tsung Tsao, Angmar Li, Andy Yang, Junwei Lu

Proceedings Volume 10961, 109610Z (2019) https://doi.org/10.1117/12.2532841

KEYWORDS: Optical proximity correction, Optical alignment, Semiconducting wafers, Optical lithography, Signal processing, Printing, Metrology, Overlay metrology

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