Uncovering the True Root Cause: Fabrication Defects Behind EOS-like Failures in GaAs MIM Capacitor Structures
Uncovering the True Root Cause: Fabrication Defects Behind EOS-like Failures in GaAs MIM Capacitor Structures
Tuesday, November 18, 2025: 10:50 AM
2 (Pasadena Convention Center)
Summary:
This paper presents the failure analysis of multiple customer returns from a GaAs-based product exhibiting damage localized on a Metal-Insulator-Metal (MIM) capacitor-resistor network connected in parallel with an on-chip ESD protection structure. Initial electrical signatures pointed to Electrical Overstress (EOS); however, extensive Transmission Line Pulse (TLP) testing across a range of conditions failed to replicate the observed damage. This outcome redirected the investigation toward potential manufacturing-induced defects or structural design vulnerabilities. Detailed optical inspection revealed additional damage along the edges within the MIM structure, beyond the initially suspected dielectric breakdown. Process reviews confirmed the possibility of random defectivity within the MIM dielectric, accelerating Time Dependent Dielectric Breakdown (TDDB) and leading to Early Life Failures (ELF). The failure mechanism was subsequently reclassified from EOS to a fabrication-induced reliability concern. Process improvements were implemented, including an enhanced optical inspection at the foundry. This case highlights the critical role of thorough root cause analysis and cross-functional collaboration in uncovering hidden reliability risks and implementing effective corrective actions throughout the design and fabrication process.
This paper presents the failure analysis of multiple customer returns from a GaAs-based product exhibiting damage localized on a Metal-Insulator-Metal (MIM) capacitor-resistor network connected in parallel with an on-chip ESD protection structure. Initial electrical signatures pointed to Electrical Overstress (EOS); however, extensive Transmission Line Pulse (TLP) testing across a range of conditions failed to replicate the observed damage. This outcome redirected the investigation toward potential manufacturing-induced defects or structural design vulnerabilities. Detailed optical inspection revealed additional damage along the edges within the MIM structure, beyond the initially suspected dielectric breakdown. Process reviews confirmed the possibility of random defectivity within the MIM dielectric, accelerating Time Dependent Dielectric Breakdown (TDDB) and leading to Early Life Failures (ELF). The failure mechanism was subsequently reclassified from EOS to a fabrication-induced reliability concern. Process improvements were implemented, including an enhanced optical inspection at the foundry. This case highlights the critical role of thorough root cause analysis and cross-functional collaboration in uncovering hidden reliability risks and implementing effective corrective actions throughout the design and fabrication process.