BCB-Based Dry Film low k Permanent Polymer with sub 4-μm Vias for Advanced WLP and FO-WLP Applications

There is a strong demand to increase the routing density of the RDL to match the requirements for future microelectronic systems which are mainly miniaturization and performance. Photo-resists for structuring the metallization or acting as a mold for electroplating are common for very fine lines and spaces due to the developments in the front-end processing. For example chemical amplified Photo-resists are now moving in the back-end and wafer level packaging process. The results are mainly governed by the performance of the equipment i.e. the photo-tool. This is different for the permanent dielectric polymer material. The major difference in photo-resists and dielectric photo-polymer are the different functions of the material systems. Photo-resists are only temporary masks for subsequent process steps like etching and plating. This is different for the photo-polymers which are a permanent part of the future systems. In this paper a new technology is discussed which uses a laser scanning ablation process ...