Fabrication of Sub-micro Silicon Waveguide with Vertical Sidewall and Reduced Roughness for Low Loss Applications

Abstract

Abstract This paper reports onpost-lithography fabrication techniques for sub-micron wide silicon waveguides with vertical and smooth sidewalls. Silicon waveguides of 500 nm wide and 220 nm thick with smooth vertical sidewalls have been fabricated by optimizing the ICP reactive ion etching recipe based on SF6/C4F8 chemistry and employing dry thermal oxidation/HF etch and low-concentration TMAH etch with relatively high Triton x-100 surfactant concentration. The results show that significant reduction in roughness well in sub-nm can be achieved without compromising the verticality of the sidewalls. The rms roughnesses of 0.65 nm and 0.84 nm have been achieved through dry thermal oxidation and TMAH with Triton approaches, respectively.