Selective Epoxy Mold Compound Slurry for Advanced Packaging Technology

Traditionally, chemical mechanical polishing (CMP) process have been heavily utilized in the front-end, mid-section, back-end, or far back-end of the semiconductor manufacturing for decades. However, CMP process did not get implemented in semiconductor packaging until in the latter part of the heterogeneous advanced packaging adaptation. Early version of the heterogeneous packaging utilized heavily on the mechanical grind and/or surface planer (single point diamond planarization). Today, even though CMP process is still in its infancy for advanced packaging, it is becoming an integral part of the 2D advanced packaging and beyond in order to achieve smaller pitch and improve re-distribution layer (RDL) process. Although there are many advantages with implementation of CMP process from topography improvement and Cu protrusion/dishing reduction to Cu smearing post grind improvement. There are several issues observed with implementation of CMP process such as: low removal rate, poor selectivity, and elevated surface roughness and defects on the organic polymer film.In this paper, we focus on highly tunable removal rate and selectivity, and low defectivity performance slurry for epoxy mold compound (EMC) with silica filler and Cu pads. Conventionally, Ceria has been one of the abrasive choices to achieve high removal rate on dielectric materials, and various chemical species and complex formulation are typically required to achieve high Cu removal rate. This conventional approach not only makes handling more difficult, but it also reduces slurry stability. Therefore, a different path was chosen to develop slurry with tunable EMC to Cu selectivity and low silica filler drop and scratches, while maintaining high EMC removal rate. This CMP scheme for removing epoxy resin film containing silica filler was possible through combination of wettability control, chemical reaction between Ceria and EMC, and pad effect in the presence of abrasive through mechanical polishing.