Accurate Surface-to-Bulk Feature Alignment and Feature Size Preservation During Double-Sided Wafer Processing Using $\hbox {C}_{4}\hbox {F}_{8}$ Plasma Polymer for the Fabri

An accurate alignment of surface-to-bulk features (within ±2 μm) during a double-sided silicon wafer processing can be extremely difficult. This is due to a combination of mask misalignment errors and unreliability of bulk etching techniques in translating the bulk feature shapes down to the surface side. In this paper, we present a fabrication process for an electrostatically actuated cantilever device where an accurate surface-to-bulk feature alignment is imperative to the operation of the device. The fabrication process compensates for the bulk etch-induced feature size variation and mask misalignment errors using a combination of self-aligning features and C₄F₈ plasma polymer passivation.