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Proceedings Paper

Raman studies of pulse repetition effect in laser processing of Si
Author(s): H. Qiu; Yongfeng Lu
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Paper Abstract

It is meaningful to avoid irreversible changes in laser processing of silicon wafer and find out the cause to which the laser induced damage threshold is decreased along with increasing frequency. We investigated the PRE in laser irradiation on c-Si wafer by Raman spectroscopy. Time- resolved Raman spectrometer was developed based on holographic notch filter, optical fiber and optical multichannel analyzer which was applied to detect transient structure changes and stress in silicon wafer under laser shock. The surface morphology was monitored by CCD through a microscope when pulses were on. We applied 1.06 micrometers Nd:YAG laser in our experiment to silicon wafer with and without silicon oxide top layer. Raman spectra was sampled in 100microsecond(s) after laser triggering. Our system could easily detect the surface absorption changes by comparing the intensity before and after laser shock while the surface was not damaged. A reversible weak peak emerged around 500cm-1 for c-Si with and without silicon oxide. It is attributed to grains under transient stress induced by laser which disappeared after seconds. No such peak is observed in sampling in 1ms after laser triggering. Such emergence of grain states may accelerate the damage process, which will contribute to PRE.

Paper Details

Date Published: 4 November 1999
PDF: 8 pages
Proc. SPIE 3898, Photonic Systems and Applications in Defense and Manufacturing, (4 November 1999); doi: 10.1117/12.368487
Show Author Affiliations
H. Qiu, National Univ. of Singapore (Singapore)
Yongfeng Lu, National Univ. of Singapore (United States)

Published in SPIE Proceedings Vol. 3898:
Photonic Systems and Applications in Defense and Manufacturing
Yee Loy Lam; Koji Ikuta; Metin S. Mangir, Editor(s)

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