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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Autores principales:	Celescia Siew Mun Lye, Zhongke Wang, Yee Cheong Lam
Formato:	article
Lenguaje:	EN
Publicado:	MDPI AG 2021
Materias:	pulse energy division spatial proximity of foci sapphire wafer singulation surface morphology multi-foci laser micro processing Mechanical engineering and machinery TJ1-1570
Acceso en línea:	https://doaj.org/article/f2b91d5bb57d4b8989b379d0ab137222
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id	oai:doaj.org-article:f2b91d5bb57d4b8989b379d0ab137222
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spelling	oai:doaj.org-article:f2b91d5bb57d4b8989b379d0ab1372222021-11-25T18:23:09ZMulti-Foci Division of Nonlinear Energy Absorption on Ultrashort Pulse Laser Singulation of Sapphire Wafers10.3390/mi121113282072-666Xhttps://doaj.org/article/f2b91d5bb57d4b8989b379d0ab1372222021-10-01T00:00:00Zhttps://www.mdpi.com/2072-666X/12/11/1328https://doaj.org/toc/2072-666XThe 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/cm<sup>2</sup>, with approximately 15 <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi mathvariant="sans-serif">μ</mi></semantics></math></inline-formula>m between two adjacent foci, wafer could be separated with foci evenly distributed over the entire wafer thickness. When the foci spacing reduced to 5 <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi mathvariant="sans-serif">μ</mi></semantics></math></inline-formula>m, wafer separation could be achieved with pulse energy concentrated only at foci distributed over only the upper or middle one-third wafer thickness.Celescia Siew Mun LyeZhongke WangYee Cheong LamMDPI AGarticlepulse energy divisionspatial proximity of focisapphire wafer singulationsurface morphologymulti-foci laser micro processingMechanical engineering and machineryTJ1-1570ENMicromachines, Vol 12, Iss 1328, p 1328 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	pulse energy division spatial proximity of foci sapphire wafer singulation surface morphology multi-foci laser micro processing Mechanical engineering and machinery TJ1-1570
spellingShingle	pulse energy division spatial proximity of foci sapphire wafer singulation surface morphology multi-foci laser micro processing Mechanical engineering and machinery TJ1-1570 Celescia Siew Mun Lye Zhongke Wang Yee Cheong Lam 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/cm<sup>2</sup>, with approximately 15 <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi mathvariant="sans-serif">μ</mi></semantics></math></inline-formula>m between two adjacent foci, wafer could be separated with foci evenly distributed over the entire wafer thickness. When the foci spacing reduced to 5 <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi mathvariant="sans-serif">μ</mi></semantics></math></inline-formula>m, wafer separation could be achieved with pulse energy concentrated only at foci distributed over only the upper or middle one-third wafer thickness.
format	article
author	Celescia Siew Mun Lye Zhongke Wang Yee Cheong Lam
author_facet	Celescia Siew Mun Lye Zhongke Wang Yee Cheong Lam
author_sort	Celescia Siew Mun Lye
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
publisher	MDPI AG
publishDate	2021
url	https://doaj.org/article/f2b91d5bb57d4b8989b379d0ab137222
work_keys_str_mv	AT celesciasiewmunlye multifocidivisionofnonlinearenergyabsorptiononultrashortpulselasersingulationofsapphirewafers AT zhongkewang multifocidivisionofnonlinearenergyabsorptiononultrashortpulselasersingulationofsapphirewafers AT yeecheonglam multifocidivisionofnonlinearenergyabsorptiononultrashortpulselasersingulationofsapphirewafers
_version_	1718411294753685504

Multi-Foci Division of Nonlinear Energy Absorption on Ultrashort Pulse Laser Singulation of Sapphire Wafers

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