High Frequency Guided Wave Defect Imaging In Monocrystalline Silicon Wafers

Micro-cracks can be induced in thin monocrystalline silicon wafers during the manufacture of solar panels. High frequency guided waves allow for the monitoring of wafers and characterization of defects. Selective excitation of the first anti-symmetric A(0) guided wave mode was achieved experimentally using a custom-made wedge transducer. The Lamb wave scattered field in the vicinity of artificial defects was measured using a noncontact laser interferometer. The surface extent of the shallow defects varying in size from 30 mu m to 100 mu m was characterized using an optical microscope. The characteristics of the scattered wave field were correlated to the defect size and the detection sensitivity was discussed.