Multi-foci division of nonlinear energy absorption on ultrashort pulse laser singulation of sapphire wafers

The multi-foci division of through thickness nonlinear pulse energy absorption on ultrashort pulse laser singulation of single side polished sapphire wafers has been investigated. Firstly, it disclosed the enhancement of energy absorption by the total internal reflection of the laser beam exiting fr...

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Main Authors: Lye, Celescia Siew Mun, Wang, Zhongke, Lam, Yee Cheong
Other Authors: School of Mechanical and Aerospace Engineering
Format: Article
Language:English
Published: 2022
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Online Access:https://hdl.handle.net/10356/159401
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Institution: Nanyang Technological University
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spelling sg-ntu-dr.10356-1594012022-06-18T20:11:36Z Multi-foci division of nonlinear energy absorption on ultrashort pulse laser singulation of sapphire wafers Lye, Celescia Siew Mun Wang, Zhongke Lam, Yee Cheong School of Mechanical and Aerospace Engineering SIMTech-NTU Joint Laboratory Singapore Institute of Manufacturing Technology Engineering::Mechanical engineering Pulse Energy Division Spatial Proximity of Foci The multi-foci division of through thickness nonlinear pulse energy absorption on ultrashort pulse laser singulation of single side polished sapphire wafers has been investigated. Firstly, it disclosed the enhancement of energy absorption by the total internal reflection of the laser beam exiting from an unpolished rough surface. Secondly, by optimizing energy distribution between foci and their proximity, favorable multi-foci energy absorption was induced. Lastly, for effective nonlinear energy absorption for wafer separation, it highlighted the importance of high laser pulse energy fluence at low pulse repetition rates with optimized energy distribution, and the inadequacy of increasing energy deposition through reducing scanning speed alone. This study concluded that for effective wafer separation, despite the lower pulse energy per focus, energy should be divided over more foci with closer spatial proximity. Once the power density per pulse per focus reached a threshold in the order of 1012 W/cm2, with approximately 15 μm between two adjacent foci, wafer could be separated with foci evenly distributed over the entire wafer thickness. When the foci spacing reduced to 5 μm, wafer separation could be achieved with pulse energy concentrated only at foci distributed over only the upper or middle one-third wafer thickness. Agency for Science, Technology and Research (A*STAR) Published version The research work was supported by A*STAR Research Agency, Singapore Institute of Manufacturing Technology (SIMTech) under SIMTech-NTU Joint Laboratory with project No. U12-M-007JL. 2022-06-16T01:20:01Z 2022-06-16T01:20:01Z 2021 Journal Article Lye, C. S. M., Wang, Z. & Lam, Y. C. (2021). Multi-foci division of nonlinear energy absorption on ultrashort pulse laser singulation of sapphire wafers. Micromachines, 12(11), 1328-. https://dx.doi.org/10.3390/mi12111328 2072-666X https://hdl.handle.net/10356/159401 10.3390/mi12111328 34832740 2-s2.0-85118499459 11 12 1328 en U12-M-007JL Micromachines © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). application/pdf
institution Nanyang Technological University
building NTU Library
continent Asia
country Singapore
Singapore
content_provider NTU Library
collection DR-NTU
language English
topic Engineering::Mechanical engineering
Pulse Energy Division
Spatial Proximity of Foci
spellingShingle Engineering::Mechanical engineering
Pulse Energy Division
Spatial Proximity of Foci
Lye, Celescia Siew Mun
Wang, Zhongke
Lam, Yee Cheong
Multi-foci division of nonlinear energy absorption on ultrashort pulse laser singulation of sapphire wafers
description The multi-foci division of through thickness nonlinear pulse energy absorption on ultrashort pulse laser singulation of single side polished sapphire wafers has been investigated. Firstly, it disclosed the enhancement of energy absorption by the total internal reflection of the laser beam exiting from an unpolished rough surface. Secondly, by optimizing energy distribution between foci and their proximity, favorable multi-foci energy absorption was induced. Lastly, for effective nonlinear energy absorption for wafer separation, it highlighted the importance of high laser pulse energy fluence at low pulse repetition rates with optimized energy distribution, and the inadequacy of increasing energy deposition through reducing scanning speed alone. This study concluded that for effective wafer separation, despite the lower pulse energy per focus, energy should be divided over more foci with closer spatial proximity. Once the power density per pulse per focus reached a threshold in the order of 1012 W/cm2, with approximately 15 μm between two adjacent foci, wafer could be separated with foci evenly distributed over the entire wafer thickness. When the foci spacing reduced to 5 μm, wafer separation could be achieved with pulse energy concentrated only at foci distributed over only the upper or middle one-third wafer thickness.
author2 School of Mechanical and Aerospace Engineering
author_facet School of Mechanical and Aerospace Engineering
Lye, Celescia Siew Mun
Wang, Zhongke
Lam, Yee Cheong
format Article
author Lye, Celescia Siew Mun
Wang, Zhongke
Lam, Yee Cheong
author_sort Lye, Celescia Siew Mun
title Multi-foci division of nonlinear energy absorption on ultrashort pulse laser singulation of sapphire wafers
title_short Multi-foci division of nonlinear energy absorption on ultrashort pulse laser singulation of sapphire wafers
title_full Multi-foci division of nonlinear energy absorption on ultrashort pulse laser singulation of sapphire wafers
title_fullStr Multi-foci division of nonlinear energy absorption on ultrashort pulse laser singulation of sapphire wafers
title_full_unstemmed Multi-foci division of nonlinear energy absorption on ultrashort pulse laser singulation of sapphire wafers
title_sort multi-foci division of nonlinear energy absorption on ultrashort pulse laser singulation of sapphire wafers
publishDate 2022
url https://hdl.handle.net/10356/159401
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