Remarkable Suppression of Local Stress in 3D IC by Manganese Nitride-Based Filler with Large Negative CTE

A local bending stress is induced by coefficient of thermal expansion (CTE) mismatch between underfill material and metal microbumps in three-dimensional IC (3D IC). A high concentration of filler in underfill is effective to suppress the local bending stress. However, it is difficult to apply high concentration of filler due to fine pitch microbumps. On the other hand, manganese nitride-based compound has large negative CTE compared with conventional negative-CTE materials. In this study, we have investigated the effect of manganese nitride-based filler on local bending stress induced by CTE mismatch between underfill and metal microbumps in 3D IC. We observed that manganese nitride-based filler can decrease CTE of underfill compared with conventional silica-based filler. This result indicated that manganese nitride-based filler can reduce keep-out-zone (KOZ) in 3D IC by local bending stress suppression.