• Abstract (English): Return Material Authorization (RMA) investigations are critical to semiconductor quality assurance, enabling latent functional failures to be traced back to their root causes. In this study, we examine an RMA case in which production devices exhibited degraded accuracy specifications within a precision measurement block after time in service. Automated Test Equipment (ATE) and bench characterization revealed clear channel-level divergence, with failing channels unable to maintain required accuracy limits while others remained within specification. To isolate and confirm the failure mechanism, targeted electrical stress testing was performed in conjunction with Early Life Failure Rate (ELFR) qualification experiments. These tests validated new ATE screening methods and were further corroborated by future RMAs, demonstrating their effectiveness in identifying latent device weaknesses. Localized electrical anomalies guided the subsequent failure analysis flow. Decapsulation followed by high-magnification optical inspection and Scanning Electron Microscopy (SEM) confirmed process-related defects in the affected circuitry, providing physical correlation to the observed electrical failures. This case study highlights the importance of defining precise test limits and augmenting ATE programs with stress-based qualification methods to improve detection of latent manufacturing defects. By combining dynamic specification boundaries with targeted ELFR-validated screens, test engineering teams can accelerate root-cause resolution and reduce RMA turnaround time. The integrated approach not only minimizes customer impact and associated costs but also enhances production screening effectiveness. We conclude with recommendations for optimizing test programs through adaptive limit setting, stress-based coverage, and close collaboration between product engineering and failure analysis teams to bolster long-term reliability in high-volume semiconductor manufacturing.
