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 via holes with tapered walls that allow depositing seed and barrier layers by Physical Vapor Deposition (PVD) to enable gold electroplating. Method consists in consecutively using of the two basic process types for DRIE technique: isotropic and anisotropic etchings. Thus via holes with 20μm and 100μm diameter having tapered walls with angles between 14° and 18° were manufactured. Thin metal layers were also deposited on the walls by e-beam technique