Design of implantable microprobe for silicon wet bulk micromachining

The paper presents the design features of silicon microprobe with a cross-sectional size less than 100 μm, taking into account the number of electrodes, as well as the conditions of anisotropic wet etching. Analytical calculations were carried out for the probe structure, represented by n-regions of various widths, carrying up to 2n-1 electrodes. The dependences of bottom width of the trapezoidal section of the probe and width of related mask on the thickness and top width of the probe are obtained. The permissible dimension ranges for several cases of one- to four-level microprobes have been established. The correction value of the mask size was estimated, reflecting the effect of etching conditions on the geometry of the probe. Modeling was carried out in an anisotropic wet etching simulator taking into account the conditions of KOH etching (in 20-40% solution at 60-80°C). It allowed to refine the results of the analytical calculations, refine dimensions of the silicon microprobe structure, the geometry of related masks, as well as the extent undercutting effect. The obtained results could be used in development of silicon microprobes formed by anisotropic wet etching.