THREE-DIMENSIONAL MICROSTRUCTURES IN SILICON VIA THE COMBINATION OF LIGHT-ION BEAM WRITING AND ELECTROCHEMICAL ETCHING

摘要

Many state-of-the-art technologies, such as micro-ano-electromechanical systems, optoelectronics and photonics, require the fabrication of precise three-dimensional structures in semiconductor materials. A major limitation of conventional lithography and silicon etching technologies is that multiple processing steps are required to fabricate free-standing multilevel structures. However, it is known that the mechanism by which a silicon wafer can be electrochemically etched in solutions of hydrofluoric acid depends on its conductivity. This has enabled the development of an alternative mask-less patterning process that combines proton irradiation with electrochemical etching. A high-energy beam of light-ions focused to a small spot by a nuclear microprobe, selectively damages the semiconductor lattice in the irradiated regions. This damage acts as an electrical barrier during subsequent electrochemical etching, so the un-irradiated regions are preferentially removed, leaving a copy of the patterned microstructure. Furthermore the ability to control the depth of damage/implantation introduces the possibility of producing three-dimensional structures.