Mechanism of Improving Etching Selectivity for E-Beam Resist AR-N 7520 in the Formation of Photonic Silicon Structures

The selectivity of the reactive ion etching of silicon using a negative electron resist AR-N 7520 mask was investigated. The selectivity dependencies on the fraction of SF6 in the feeding gas and bias voltage were obtained. To understand the kinetics of passivation film formation and etching, the type and concentration of neutral particles were evaluated and identified using plasma optical emission spectroscopy. Electron temperature and electron density were measured by the Langmuir probe method to interpret the optical emission spectroscopy data. A high etching selectivity of 8.0 ± 1.8 was obtained for the etching process. The optimum electron beam exposure dose for defining the mask was 8200 pC/m at 30 keV.