An analysis of wet anisotropic etching based bulk micromachining for the fabrication of Si tips

Silicon tip fabrication by wet anisotropic etching using Potassium Hydroxide (KOH) and Tetra Methyl Ammonium Hydroxide (TMAH) was studied under varying process conditions using thermal oxide as a mask. The fabrication was carried out using only wet etching with a single layer of optical lithography. The mask structures used for the formation of tips were circles of different dimeter ranging from 30 μm to 120 μm to fabricate the tips with diameter from 40nm to 400nm, without post oxidation sharpening method. Experiments were carried out under two different conditions: a) Beaker containing small volume with constant stirring and b) Bulk volume MEMS bath with and without recirculation and filtration. The results were analyzed to understand the nature of alkali solution and the effect of temperature and method of recirculation/filtration on the dimensions and nature of the tips formed, along with the behavior of the oxide mask in the two different solutions.