Tapered walls via holes manufactured using DRIE variable isotropy process

This paper describes a method to manufacture through wafer via holes with tapered walls for RF applications. The main purpose was the need to obtain tapered walls for via holes that allow to deposit seed and barrier layers by Physical Vapor Deposition (PVD). Method consist in consecutively using of the two basic process types for DRIE technique: isotropic and anisotropic etchings. Thus via holes with 20μm and 100μm having tapered walls with angles between 14° and 18° were manufactured. Also, thin metal layers were deposited on the walls by e-beam technique.