Extensive Fault Isolation & Defect Localization of Subsurface Silicon Failures in TVS Devices
Extensive Fault Isolation & Defect Localization of Subsurface Silicon Failures in TVS Devices
Wednesday, October 7, 2026: 4:40 PM
Summary:
Elevated reverse leakage current in TVS devices can result from multiple failure mechanisms including package and mechanical issues, ionic contamination, charge trapping, EOS/ESD damage, and silicon defects. When the root cause is a crystallographic defect buried deep within the silicon active region, conventional top-down FA techniques such as chemical deprocessing, Wright etch staining, and SEM inspection may yield no visible anomalies, potentially leading to inconclusive analysis. This paper presents a comprehensive fault isolation approach applied to discrete TVS diodes in DFN packages exhibiting marginally elevated reverse leakage current. Backside PEM identified anomalous point emissions in the active diode area. Progressive deprocessing with electrical monitoring at each stage confirmed the defect persisted below the silicon surface. Cross-section PEM localized the emission beneath the depletion region of a single diode finger, while comparison to a known good finger showed typical junction emission. TEM analysis at the emission site revealed a silicon dislocation beneath the depletion region.
Elevated reverse leakage current in TVS devices can result from multiple failure mechanisms including package and mechanical issues, ionic contamination, charge trapping, EOS/ESD damage, and silicon defects. When the root cause is a crystallographic defect buried deep within the silicon active region, conventional top-down FA techniques such as chemical deprocessing, Wright etch staining, and SEM inspection may yield no visible anomalies, potentially leading to inconclusive analysis. This paper presents a comprehensive fault isolation approach applied to discrete TVS diodes in DFN packages exhibiting marginally elevated reverse leakage current. Backside PEM identified anomalous point emissions in the active diode area. Progressive deprocessing with electrical monitoring at each stage confirmed the defect persisted below the silicon surface. Cross-section PEM localized the emission beneath the depletion region of a single diode finger, while comparison to a known good finger showed typical junction emission. TEM analysis at the emission site revealed a silicon dislocation beneath the depletion region.