Development of high aspect ratio via filling process for 3D packaging application

This paper presents our development work to achieve high aspect ratio void-free polymer via filling with various types of organic materials for potential application in 3D wafer level packaging. This study focuses on the development of via filling process using the conventional spin-coating and curing process. Thermoplastic polymers have been selected for this evaluation due to its ability to reflow and fill gaps easily. Test wafers with circular via patterns with diameters from 1-70 μm with aspect ratios from 1-10 have been evaluated. The various challenges to achieving void-free via filling have been presented and it has been demonstrated that a void-free filling is feasible for vias with aspect ratio of 1-8.