Fabrication of three-dimensional silicon structure with smooth curved surfaces

Abstract

A blue-ray laser lithography along with a dry etching process was presented to fabricate a three-dimensional (3-D) silicon structure with smooth surface. Main findings include the reduction of corrugations on photo resist profiles by adjusting the focal depth of grayscale laser lithography, optimization of reactive ion etching process to decrease the surface roughness after dry etching as well as keeping a low etching selectivity, and the introduction of a procedure to design and fabricate arbitrary 3-D silicon structures. Silicon microstructures with a curved surface were fabricated successfully applying this approach and the root-mean-square surface roughness was down to 3.0 nm. This result reduces approximately one order of magnitude than the previously reported surface roughness of arbitrary 3-D silicon microstructures. This approach is promising for fabricating arbitrary shape components in MEMS, optics, and microfluidic applications.