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Trial Implementation of Operando PL Spectrum Mapping Using a Mini-Spectrometer in EVC Screening of 4H-SiC Wafers
Abstract:
We have been developing the expansion–visualization–contraction (EVC) method as an inspection technique for 4H-SiC wafers, in which Shockley-type stacking faults (SSFs) are intentionally expanded by UV irradiation and subsequently visualized to identify converted dislocations that are not directly detectable by conventional PL inspection. In this study, we demonstrate a low-cost “operando” PL spectrum mapping approach for the EVC tool by using the 355-nm expansion laser as the PL excitation source and adding only a miniature spectrometer via an optical fiber, avoiding the need for an expensive hyperspectral camera.Two experiments were performed. In Experiment 1, proton-implanted and non-implanted regions on n-type 4H-SiC epilayers were compared using EVC screening and PL imaging. The proton-implanted regions exhibited narrower SSF widths, and a two-sample t-test yielded extremely small p-values, indicating a statistically significant suppression effect that remained after activation annealing. In Experiment 2, a thick epilayer wafer containing polytype inclusions was screened. PL spectrum mapping identified not only 1SSF-related emission (~420 nm) but also Frank-type components (~488 nm) and polytype-inclusion-related emission (~540 nm), revealing composite stacking faults expanded from inclusions. The results suggest that operando PL spectrum mapping can help distinguish stacking-fault types during EVC screening and potentially prevent unnecessary expansion of thermally uncontractable faults, thereby reducing yield loss.
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27-35
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May 2026
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