Two-level electrochemical micromachining of titanium for device fabrication

The electrochemical micromachining of titanium structures relevant for biom edical applications was studied using a sulfuric acid methanol electropolis hing electrolyte. Single-step etching of large sized cavities was performed and the effect on the dissolution depth of the presence of features of dif ferent sizes was evaluated. The fabrication of two-level structures by a tw o-step process was studied using consecutive dissolution steps through patt erned photoresist masks. Two different strategies were compared for produci ng a model geometry consisting of a 10 mm diameter, 10 Am deep, flat-bottom ed cavity containing a grid of 30 mum grooves. Results show that it is poss ible to fabricate the two-level model geometry by either first etching the cavity or the grooves. For the latter approach a numerical simulation of th e shape evolution of the grooves during cavity etching permitted us to iden tify the most useful process window.