The study of plasma resistance of the AR-N 7520 was carried out. The selectivity of the reactive ion etching (RIE) of silicon through the mask of negative electron resist AR-N 7520 also was investigated. The dependence for  selectivity was obtained at different fractions of SF6 in the feeding gas and at the different values of bias voltage. A high etching selectivity of 8.0 ± 1.8 was obtained for the etching process. The dependence of the resist line height  on the exposure dose is presented. The optimal value for the line exposure dose was found to be 8200 pC/cm.