Characterization of a novel photoresist redistribution material for advanced packaging applications

Abstract

The widespread adoption of advanced packaging techniques is primarily driven by electrical device performance and chip form factor considerations. Flip chip packaging is currently growing at a 27% compound annual rate and it is expected that by 2005 over 60% of all 300 mm wafers will be bumped. To ensure optimal productivity and cost of ownership it is imperative to provide lithographic materials that are optimized for these applications. Flip chip packaging frequently uses one or more redistribution levels to increase the number of pads that can be bumped in the minimum form factor. The redistribution level requires a photosensitive dielectric material to be used as a permanent insulating layer. The mechanical, electrical and lithographic properties of the material for this level are all important. This study will characterize a novel photosensitive siloxane material (Shin-Etsu SINRT Photoresist) for the use in the redistribution layer. Siloxanes are a good choice for redistribution because of their excellent physical properties, ease of processing and relatively low curing temperatures. The lithographic performance of SINR photoresist has been optimized using a broad band 1X stepper to control critical dimensions (CD). This study evaluates process capability at multiple exposure wavelengths and post exposure bake (PEB) conditions. Cross sectional SEM analysis, process linearity, Bossung plots and process windows are used to establish the lithographic capabilities. Material modifications also were investigated to control the photoresist sidewall angles.