This chapter provides an overview of advanced dielectric materials developed by HD MicroSystems (HDM) that are based on polyimide (PI) and polybenzoxazole (PBO) technologies and that are targeted for use as redistribution layers (RDL) in fan‐out wafer‐level package (FO‐WLP) applications where lithographic and reliability performances are important requirements. The PI/PBO dielectric materials are supplied in liquid form and, as such, are typically applied onto reconstituted wafers using standard spin‐coating processes that include spin coating, soft baking, exposure, development, and final cure.
14.2 Brief History of PI/PBO‐Based Materials in Semiconductor Applications
The first PI products for semiconductor applications were introduced in the early 1970s for use as stress buffers or passivation layers on integrated circuits as well as interlayer dielectrics in high density interconnects on multi‐chip modules. These products, later termed non‐photo‐definable PI (non‐PDPI), were based on polyamic acids (PI precursors) synthesized by reacting dianhydrides with diamines dissolved in a suitable solvent such as N‐methyl pyrrolidone (NMP) and where the dianhydride and diamine were chosen for end‐use performance . These materials were typically processed on a silicon wafer by spin coating, soft ...