Failure Analysis of Latent Defects in Flip Chip Controllers Under Bias-HAST: Insights from Assembly and Test Processes

Flip chip controller plays a critical role in 3D NAND technology, enabling high-speed data transfer and efficient power management in advanced semiconductor devices. However, latent defects in flip chip controller, particularly under accelerated stress conditions such as Bias-Highly Accelerated Stress Test (Bias-HAST), pose significant challenges to reliability. This study investigates failure mechanism observed in affected units, where electrical overstress (EOS) and die chipping were identified. However, no conclusive correlation was established between the two failure modes in the affected units. A Design of Experiments (DOE) was planned to simulate the failure mode, based on the hypothesis that the reliability stress test might exacerbate the chipped die condition. It was found that as the unit underwent further stress, the power pin could induce localized metal melting, leading to a short circuit and subsequent EOS. The findings provide actionable strategies to optimize process parameters, enhance defect detection, and improve the overall reliability of flip chip controllers. This research bridges gaps in understanding failure modes under Bias-HAST, offering valuable guidance for manufacturing and quality assurance in advanced semiconductor packaging.