Effect of Cross-linker on Photosensitive Polyimide to Achieve Full Imidization and Lower Stress for Good Reliability

Abstract

Advanced packaging technology requires low temp. curable and low residual stress material as dielectric layer. Because wafer warpage will be increased with increasing the number of redistribution layers (RDLs) and higher residual stress could induce reliability failure due to cracking and delamination. One method to make residual stress lower is to decrease curing temperature. However, lower warpage by decreasing cure temp. is in a trade-off relation with lower reliability performance due to insufficient imidization ratio of polyimide dielectric layer. To overcome the trade-off relationship, we investigated the effects of number of functional groups and backbone in cross-linker agent. High imidization and low residual stress by curing at 160deg.C have been demonstrated by applying bi-functional cross-linking agent.