27 March 2018 Silicon wafer defect detection using high frequency guided waves
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In the photovoltaic industry monocrystalline silicon wafers are employed for the manufacture of solar panels with high conversion efficiency. The cutting process induces micro-cracks on the thin wafer surface. High frequency guided ultrasonic waves are considered for the structural monitoring of the wafers and the nondestructive characterization of the micro-cracks. The material anisotropy of the monocrystalline silicon leads to variations of the wave characteristics depending on the propagation direction relative to the crystal orientation. In non-principal directions of the crystal, wave beam skewing occurs. Selective excitation of the fundamental Lamb wave modes was achieved using a custom-made angle beam transducer and holder to achieve a controlled contact pressure. The out-of-plane component of the guided wave propagation was measured using a noncontact laser interferometer. Artificial defects were introduced in the wafers using a micro indenter with varying loads. The defects were characterized from microscopy images to measure the indent size and combined crack length. The scattering of the A0 Lamb wave mode was measured experimentally and the characteristics of the scattered wave field were correlated to the defect size. The detection sensitivity is discussed.
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Michael Lauper, Michael Lauper, Paul Fromme, Paul Fromme, Jean-Luc Robyr, Jean-Luc Robyr, Bernard Masserey, Bernard Masserey, } "Silicon wafer defect detection using high frequency guided waves", Proc. SPIE 10600, Health Monitoring of Structural and Biological Systems XII, 106000G (27 March 2018); doi: 10.1117/12.2294523; https://doi.org/10.1117/12.2294523

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