Fabrication of cantilever arrays with nano-aperture hollow tips for parallel microplasma etching

For the application of parallel microplasma etching, cantilever arrays with nano-aperture hollow pyramid tips have been successfully fabricated. The SiO₂ cantilever arrays and hollow tips are formed by thermal oxidation on a Si (1 0 0) wafer with pyramid cavities. Due to the stress-dependent nonuniform oxidation, the oxide thickness is about 400 nm at the tip apexes which is much thinner than the 1.2 μm thick sidewalls. Based on these nonuniform oxide hollow tips, nano-apertures of 50-200 nm in diameter are obtained at the apexes after the following 1:10 water-diluted HF isotropic etching. The base widths of the hollow tips are designed to be 50 and 100 μm with the final sidewall thickness of only 600 nm. Consequently, the width-thickness ratio (hollow pyramid tip base width/sidewall thickness) is up to 150:1. Some improvements are made in the fabrication process and these fragile tips are obtained with a product yield of more than 90%. Then, cantilever arrays with hollow tips are released consistently and the bending behavior is discussed. In addition, preliminary experiments and simulations of microplasma generation and extraction confirm the application feasibility of this structure in parallel microplasma etching.