Hot Embossing of Thick Amorphous Fluoropolymer for Back End Processing of Infrared Arrays

A process is presented for patterning vias into thick amorphous fluoropolymer layers for a novel In bump fabrication process, achieved using a hot embossing technique. The technique uses a patterned Si stamp that employs a two-step etching process to obtain pillars with a controlled positive sidewall angle. After embossing with the Si stamp, vias are formed in amorphous fluoropolymer layers. A postembossing blanket reactive ion etch step is then used to remove excess fluoropolymer from the bottoms of the vias, exposing a Ni film. Successful electroplating of In bumps into vias initiated at the Ni layer is demonstrated, confirming complete removal of excess fluoropolymer.