Process characterisation of DuPont MXA140 dry film for high resolution microbump application

The dry film has shown improved thickness uniformity and cost competitiveness versus liquid photoresists. However, traditional dry film photoresists for high pillar bump plating show limited resolution capabilities. DuPont has developed the MXAdvance100 series dry film photoresist for high resolution applications for high density wafer level packages. It offers unique characteristics like the smooth side wall, high aspect ratio and high resolution. It is an ideal photoresist material for sharply defined metal plating on wafer. The paper describes how to achieve the high resolution and how process conditions impact on the resolution and material performance including the micro pillar plating. The detailed process evaluation includes the entire lithographic process including the remove process. Cross section SEM analysis, process window and process linearity were studied for copper micro pillar fabrication. The key factors were identified for achieving a good high density micro pillar structure.