Fabrication of metallic microstructures by electroplating using deep-etched silicon molds

A new technology is presented here to fabricate three-dimensional micromachined metal structures. The microstructures are manufactured by electroplating in deep-etched silicon structures followed by a separation from their mold. Up to 140-μm-deep silicon structures with vertical sidewalls are realized by an anisotropic plasma etching process producing the mold for electroplating. An etching gas mixture of SF_6s and CBrF₃ is used to achieve both an anisotropic etching behavior by protective film formation of CF₂ -radicals and high etching rates. The anisotropy is due to photoresist masking, which enhances the polymer formation. The vertical trenches are electroplated from the trench base filling the structures uniformly to the substrate surface. By avoiding overplating across the whole substrate the resulting structures are suitable for micromechanical devices. If needed, released microstructures from the silicon mold can be obtained by direct lift-off