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Proceedings Paper

Utilizing the transparency of semiconductors via "backside" machining with a nanosecond 2 um Tm:fiber laser
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Paper Abstract

Semiconductors such as Si and GaAs are transparent to infrared laser radiation with wavelengths >1.2 μm. Focusing laser light at the back surface of a semiconductor wafer enables a novel processing regime that utilizes this transparency. However, in previous experiments with ultrashort laser pulses we have found that nonlinear absorption makes it impossible to achieve sufficient optical intensity to induce material modification far below the front surface. Using a recently developed Tm:fiber laser system producing pulses as short as 7 ns with peak powers exceeding 100 kW, we have demonstrated it is possible to ablate the “backside” surface of 500-600 μm thick Si and GaAs wafers. We studied laser-induced morphology changes at front and back surfaces of wafers and obtained modification thresholds for multipulse irradiation and surface processing in trenches. A significantly higher back surface modification threshold in Si compared to front surface is possibly attributed to nonlinear absorption and light propagation effects. This unique processing regime has the potential to enable novel applications such as semiconductor welding for microelectronics, photovoltaic, and consumer electronics.

Paper Details

Date Published: 6 March 2014
PDF: 7 pages
Proc. SPIE 8968, Laser-based Micro- and Nanoprocessing VIII, 89680W (6 March 2014); doi: 10.1117/12.2040306
Show Author Affiliations
Nils Gehlich, CREOL, The College of Optics and Photonics, Univ. of Central Florida (United States)
Fraunhofer-Institut für Lasertechnik (Germany)
Tobias Bonhoff, CREOL, The College of Optics and Photonics, Univ. of Central Florida (United States)
Fraunhofer-Institut für Lasertechnik (Germany)
Laura Sisken, CREOL, The College of Optics and Photonics, Univ. of Central Florida (United States)
Mark Ramme, CREOL, The College of Optics and Photonics, Univ. of Central Florida (United States)
TRUMPF North America (United States)
Christian Gaida, Friedrich-Schiller-Univ. Jena (Germany)
Martin Gebhardt, Friedrich-Schiller-Univ. Jena (Germany)
Ilya Mingareev, CREOL, The College of Optics and Photonics, Univ. of Central Florida (United States)
Fraunhofer-Institut für Lasertechnik (Germany)
Lawrence Shah, CREOL, The College of Optics and Photonics, Univ. of Central Florida (United States)
Martin C. Richardson, CREOL, The College of Optics and Photonics, Univ. of Central Florida (United States)


Published in SPIE Proceedings Vol. 8968:
Laser-based Micro- and Nanoprocessing VIII
Udo Klotzbach; Kunihiko Washio; Craig B. Arnold, Editor(s)

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