Deep plasma silicon etch for microfluidic applications

Abstract Various microfluidic devices like micro pumps, micro dispensers, micro pipettes, etc. are produced by the GeSiM mbH Groserkmannsdorf. Fabrication of such microsystems includes the realization of three-dimensional silicon substrates. Plasma-based silicon etch processes are key technologies for exact patterning the substrates from both surfaces. Typically, etch depths of 10 to 500 μm, aspect ratios >25 and the application of conventional mask systems are required. Etch rates between 2 and 6 μm/min, a uniformity (3σ) below 5%, an excellent anisotropy and a selectivity of >50:1 for photoresists and >150:1 for SiO2 can be realized using an etch system produced by Surface Technology Systems Limited (STS), UK and the ASE™ process based on fluorine etch chemistry. This technique overcomes the disadvantages of conventional wet silicon etch processes, like the influence of crystal orientation on etch rate. Our intention was to investigate the influence of gas flow rates, process gas pressure, supplied power and time sequence on etch rate and edge profile. The results should be used to vary process parameters according to the requirements of application.