Selective Anisotropic Dry Etching of Piezoelectric Silk Microstructures Using Oxygen Plasma Ashing

Micro patterning of FDA approved Silk fibroin polymer derived from Bombyx mori cocoons has wide range of applications in realizing Silk based MEMS and implantable biomedical micro devices. In the present study, a very simple and straightforward micro-pattering approach based on well known dry etching has been presented. The dry etching of silk microstructures was achieved using low pressure oxygen plasma ashing technique. Titanium based stencil mask patterned using photolithography, was used to transfer the desired microstructures onto the silk film. The optimum etching recipe was determined by optimizing the dry etching parameters like RF power delivered onto the carrier, duration of plasma and the oxygen flow rate. The etch rate and the etch uniformity were measured using standard metrological techniques. Selective complete removal of silk with an etch rate of 0.20 urn/min has been reported. Using the optimized dry etching recipe, a complex pattern with minimum feature size of 1.6 µm was achieved.