Title: Modified-layer formation mechanism into silicon with permeable nanosecond laser

Authors: E. Ohmura, Fumitsugu Fukuyo, Kenshi Fukumitsu, Hideki Morita

Addresses: Division of Materials and Manufacturing Science, Osaka University, 2-1, Yamada-Oka, Sita, Osaka, Japan. ' Hamamatsu Photonics K.K., 314-5, Shimo-Kanzo, Iwata, Shizuoka, Japan. ' Hamamatsu Photonics K.K., 314-5, Shimo-Kanzo, Iwata, Shizuoka, Japan. ' Hamamatsu Photonics K.K., 314-5, Shimo-Kanzo, Iwata, Shizuoka, Japan

Abstract: The purpose of this study is to clarify the formation mechanism of modified layer. A coupling problem composed of focused laser propagation in a silicon single crystal is examined, considering laser absorption, temperature rise and heat conduction, with particular attention to an experimental result that the absorption coefficient varies with temperature. Simple thermal stress analysis was also conducted based on those results. As a result, the formation mechanism of the modified layer could be explained clearly. It was seen that the temperature dependence of absorption coefficient is the most important factor of the modified layer formation. This present analysis can be applied to find the optimum laser irradiation condition for Stealth Dicing (SD) method, and it is a future subject to confirm it experimentally. It was supported by this present analysis that the problem of thermal effect on the device region can be solved by the SD method. [Received 7 May 2006; Accepted 2 February 2007]

Keywords: machining; laser dicing; silicon; internal modification; layer formation; permeable nanosecond lasers; modified layers; laser absorption; temperature rise; heat conduction; thermal stress analysis; stealth dicing.

DOI: 10.1504/IJCMSSE.2007.017923

International Journal of Computational Materials Science and Surface Engineering, 2007 Vol.1 No.6, pp.677 - 691

Published online: 23 Apr 2008 *

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