Mr. David R. Cho Profile

David R. Cho

Senior Director Operations Central Team

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Publications (5)

Proceedings Article | 20 March 2015 Paper

Process variation challenges and resolution in the negative-tone develop double patterning for 20nm and below technology node

Sohan Mehta, Lakshmi Ganta, Vikrant Chauhan, Yixu Wu, Sunil Singh, Chia Ann, Lokesh Subramany, Craig Higgins, Burcin Erenturk, Ravi Srivastava, Paramjit Singh, Hui Peng Koh, David Cho

Proceedings Volume 9425, 94250B (2015) https://doi.org/10.1117/12.2087546

KEYWORDS: Critical dimension metrology, Binary data, Double patterning technology, Etching, Photomasks, Photoresist processing, Nanoimprint lithography, Image processing, Optical lithography, Neodymium

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Immersion based 20nm technology node and below becoming very challenging to chip designers, process and integration due to multiple patterning to integrate one design layer . Negative tone development (NTD) processes have been well accepted by industry experts for enabling technologies 20 nm and below. 193i double patterning is the technology solution for pitch down to 80 nm. This imposes tight control in critical dimension(CD) variation in double patterning where design patterns are decomposed in two different masks such as in litho-etch-litho etch (LELE). CD bimodality has been widely studied in LELE double patterning. A portion of CD tolerance budget is significantly consumed by variations in CD in double patterning.

The objective of this work is to study the process variation challenges and resolution in the Negative Tone Develop Process for 20 nm and Below Technology Node. This paper describes the effect of dose slope on CD variation in negative tone develop LELE process. This effect becomes even more challenging with standalone NTD developer process due to q-time driven CD variation. We studied impact of different stacks with combination of binary and attenuated phase shift mask and estimated dose slope contribution individually from stack and mask type. Mask 3D simulation was carried out to understand theoretical aspect. In order to meet the minimum insulator requirement for the worst case on wafer the overlay and critical dimension uniformity (CDU) budget margins have slimmed. Besides the litho process and tool control using enhanced metrology feedback, the variation control has other dependencies too. Color balancing between the two masks in LELE is helpful in countering effects such as iso-dense bias, and pattern shifting. Dummy insertion and the improved decomposition techniques [2] using multiple lower priority constraints can help to a great extent. Innovative color aware routing techniques [3] can also help with achieving more uniform density and color balanced layouts.

Proceedings Article | 8 October 2014 Paper

Best-practice evaluation-methods for wafer-fab photomask-requalification inspection tools

Chan Seob Cho, Ashish Mungmode, Ron Taylor, David Cho, Hui Peng Koh

Proceedings Volume 9235, 92351I (2014) https://doi.org/10.1117/12.2068466

KEYWORDS: Inspection, Defect detection, Photomasks, Reticles, Particles, Air contamination, Optical proximity correction, Contamination, SRAF, Image analysis

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Proceedings Article | 2 April 2014 Paper

Evaluation of lens heating effect in high transmission NTD processes at the 20nm technology node

Bumhwan Jeon, Sam Lee, Lokesh Subramany, Chen Li, Shyam Pal, Sheldon Meyers, Sohan Mehta, Yayi Wei, David Cho

Proceedings Volume 9050, 90501U (2014) https://doi.org/10.1117/12.2034206

KEYWORDS: Semiconducting wafers, Reticles, Calibration, Photomasks, Critical dimension metrology, Source mask optimization, Computational modeling, Optical lithography, Wavefronts, Overlay metrology

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Proceedings Article | 2 April 2014 Paper

20nm MOL overlay case study

Lokesh Subramany, Michael Hsieh, Chen Li, Hui Peng Koh, David Cho, Anna Golotsvan, Vidya Ramanathan, Ramkumar Karur Shanmugam, Lipkong Yap

Proceedings Volume 9050, 90502Q (2014) https://doi.org/10.1117/12.2046598

KEYWORDS: Overlay metrology, Semiconducting wafers, Chemical mechanical planarization, Optical alignment, Metrology, Image quality, Optical filters, Image processing, Reticles, Scanners

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Proceedings Article | 29 March 2013 Paper

Investigation of trench and contact hole shrink mechanism in the negative tone develop process

Sohan Singh Mehta, Craig Higgins, Vikrant Chauhan, Shyam Pal, Hui Peng Koh, Jean Raymond Fakhoury, Shaowen Gao, Lokesh Subramany, Salman Iqbal, Bumhwan Jeon, Pedro Morrison, Chris Karanikas, Yayi Wei, David Cho

Proceedings Volume 8682, 86820O (2013) https://doi.org/10.1117/12.2012331

KEYWORDS: Diffusion, Critical dimension metrology, Polymers, Photoresist processing, Image processing, Manufacturing, Lithography, Optical lithography, Data modeling, Modulation

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