A BASELINE STUDY ON THE PERFORMANCE OF STENCIL AND SCREEN PRINT PROCESSES FOR WAFER BACKSIDE COATING

摘要

The application of adhesive materials on the non-active side of silicon wafers can serve as B-staged die attach or provide a protective laser-markable cover layer that safeguards it from damage in dicing. Traditional solder paste stencil printing equipment is a manufacturing system type that can be used to deposit such adhesive coatings on wafers. This paper will report results of dedicated screen and stencil print baseline testing for the wafer backside coating process. Two commercially standard, nonconductive epoxy based materials of quite contrasting rheologies are compared in trials consuming 48 200mm diameter wafers. Deposit thickness planarity across the wafers is a key metric used to evaluate the performance of the coating process. Results of controlled experiments are showing thickness control capability and surface roughness trends achieved by the printing process are presented. This study demonstrates coating coplanarity success accomplishing ±12.5μm @ 6 sigma control down to 30μm cured thickness.