Proton micromachining: a new technique for the production of three-dimensional microstructures

A novel technique for the fabrication of high aspect ratio three-dimensional (3D) microstructures is presented. A suitable resist (e.g. PMMA or SU-8) is exposed using focused MeV (million electron volt) protons in a direct write process to produce 3D microstructures with sub-micrometer feature sizes, By adjusting the energy of the proton beam, the depth of the microstructures can be controlled very accurately (e.g. between 5 and 160 mu m). Single layer SU-8, a newly developed, chemically accelerated, negative tone, near UV, photo-resist, has been used in multiple exposures using different proton energies to produce intricate 3D microstructures. The combination of a well controlled exposure depth coupled with the ability to tilt the sample with respect to the beam increases the manufacturing capability, and allows the production of complex microstructures with well defined edges in single layers of resist.