Ablation and cutting of planar silicon devices using femtosecond laser pulses |
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Authors: | N Bärsch K Körber A Ostendorf KH Tönshoff |
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Institution: | (1) Laser Zentrum Hannover e.V., Hollerithallee 8, 30419 Hannover, Germany, DE |
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Abstract: | Although lasers are generally able to machine silicon, the major material in many microsystems applications, doing so without
influencing the physical properties of the bulk material remains an important challenge. Ultrafast lasers, in particular,
with their potential to precisely ablate all kinds of solid materials, are able to perform such processes with high efficiency
and accuracy. This article starts with an overview of the general interaction of ultrafast laser radiation with semiconductors,
explaining the absorption processes and different fluence regimes for the ablation of silicon. Major parameter influences,
especially for cutting processes in thin silicon, are described. By varying pulse energies, beam shaping methods, the beam
polarization, and temperatures, the cutting quality and speed can be significantly influenced. One important quality aspect,
besides kerf widths and surface roughness, is the amount of back-side chipping when cutting brittle materials. Achievements
in speed enhancement using linear focus shapes are presented, with cutting speeds up to five times higher than by conventional
spot-focusing. On the other hand, laser processes that cut with a spot focus offer the possibility of free-shape cutting,
which is explained using the example of wafers carrying silicon chips with highly increased package densities.
Received: 10 December 2002 / Accepted: 20 January 2003 / Published online: 28 May 2003
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ID="*"Corresponding author. Fax: +49-511/2788-100, E-mail: nb@lzh.de |
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Keywords: | PACS: 52 38 Mf 79 20 Ds 81 05 Cy |
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