Preparation of stopping masks for the P-LIGA technique with focused ion beams

Abstract

Planoconcave structures with depths of 4–16 μm were sputtered into silicon foils with a thickness of ≈80 μ m in order to use them as masks for MeV-H +-implantations within the P-LIGA technique. The irradiations were performed with a Ga +-beam focused to a diameter of ≈1 μ m at a current of 20 nA in the target. Before doing that, for dose-depth calibration and optimization of the sputter energy, test squares were irradiated to ion fluences between 3×10 14 and 1×10 18 Ga + cm −2 using ion energies ranging from 10 to 45 keV. The structure depth and the rms-roughness were measured by means of atomic force microscopy. The energy dependence of the sputter yield could be fitted in good agreement to the experimental data with the program code TRIM 87 using a surface binding energy of 2.1 eV as an input parameter.