Accurate dry etching technique for germanium waveguide by using CHF₃ based inductively coupled plasma

A CHF₃ inductively coupled plasma (ICP) based dry etching method is proposed for accurate etching of Ge waveguides. CHF₃ ICP based dry etching produces excellent anisotropy along with good selectivity with regards to regular polymeric photoresist, which leads to the elimination of under-cut. As a result, an almost vertical sidewall angle of 85° with an etching rate of 190 nm/min was realised with a relatively high selectivity ratio of 5:1 against regular photoresist.