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Proceedings Paper

Thermal mechanisms of subnanosecond ablation
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Paper Abstract

There is much interest in using subnanosecond pulsed lasers for micro-machining due to the ability of these lasers to machine very precise features. The micro-machining precision of these lasers is a result of the reduced thermal diffusion depth compared to that obtained using longer laser pulses. Experimental research in the literature shows evidence of thermal mechanisms, such as recast layers and thermal distributions of ejected particles, but claims that normal evaporation is responsible are not justified by kinetic calculations. This work critically reviews the experimental evidence from literature and the possible thermal mechanisms that may participate during subnanosecond laser ablation. Phase explosion (due to homogeneous vapor nucleation) is shown to be the most likely mechanism of mass removal; however, there are many questions regarding how phase explosion proceeds on a subnanosecond time scale. Theoretical estimates of the time lag required for reaching an equilibrium distribution of vapor nuclei have been associated with the time required for ablation to proceed. This time lag is on the order of one nanosecond or longer, raising many questions about the validity and applicability of this calculation. This work studies phase explosion and the associated time lag and discusses topics for future research.

Paper Details

Date Published: 29 June 2001
PDF: 8 pages
Proc. SPIE 4274, Laser Applications in Microelectronic and Optoelectronic Manufacturing VI, (29 June 2001); doi: 10.1117/12.432515
Show Author Affiliations
David A. Willis, Purdue Univ. (United States)
Xianfan Xu, Purdue Univ. (United States)

Published in SPIE Proceedings Vol. 4274:
Laser Applications in Microelectronic and Optoelectronic Manufacturing VI
Malcolm C. Gower; Henry Helvajian; Koji Sugioka; Jan J. Dubowski, Editor(s)

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