Process Development and Material Characteristics of TSV-less Interconnection Technology for FOWLP

Abstract

Fan-out wafer-level-packaging (FO-WLP) technology is developed with the advantages of smaller package size, higher Input/Output (I/O) counts, lower cost, and better performance. In this study, the FO-WLP technology is applied to TSV-less inter-connection technology of 2.5D IC packaging and a novel RDL-first wafer level packaging is demonstrated. Firstly, a pre-coated laser release layer at the interface of RDL and carrier wafer is used for the separation of the reconfigured wafer and carrier wafer with laser de-bonding technology. Since release layer material is the key factor for de-bonding, these materials are evaluated to determine the quality. Test chips are flip-chip bonded onto a carrier wafer with 2 layers of RDL and passivation, following by wafer molding process. Wafers reveal a warp surface due to chemical material shrinkage and CTE mismatch during post mold curing. Warpage of molded wafer is needed to be optimized for equipment handling and the warpage characterization is collected to analyze by different processes. To examine the quality of the structure, electrical measurement is carried out and their respective results are presented.