Evalution of bulk titanium DRIE Using SU-8 as soft mask

This paper reports the characterization of bulk titanium deep etching using inductively coupled chlorine plasma using SU-8 as softmask. SU-8 has many advantages over the traditional employed hardmask, such as selective stripping, cost efficiency and the ability to accommodate ultra deep etching. The effects of process parameters (ICP source power, platen power and Cl₂ flow rate) on etch rate, selectivity and the etch profile were investigated. With the optimized process parameters (400 W ICP source power, 100 W platen power, 60 sccm Cl₂ flow rate, 3 mT chamber pressure), an etch rate of 1.06 mum/min has been achieved with an aspect ratio of 5:1 and smooth surface. Ultra-deep titanium etching up to 200 mum has been realized with SU-8 softmask, which is among the best of the present reports.