Reactive ion etching of silica in a hollow cathode reactor using a CHF3/Ar gas mixture has been studied as a function of masking material, rf power, sample temperature, and O-2 and CF4 additions. Etch rates in excess of 0.5 mu m/min are typically obtained with a selectivity over amorphous silicon and photoresist of more than 10. The sidewall roughness for etching with an amorphous silicon mask is of the order of 0.05 mu m, whereas for a photoresist mask, under similar etching conditions, the sidewall roughness is up to 0.1 mu m. For the a-Si mask a further improvement in the sidewall roughness down to 0.02 mu m can be obtained by adding O-2 to the discharge or elevating the sample temperature, however both parameters cause lateral etching of the a-Si mask and therefore linewidth loss. Nonetheless, when using sample temperature as a control parameter, a process window was found which allows smooth sidewalls to be obtained without dimension loss. In the case of O-2 additions such a process window was not found. Possible mechanisms accounting for this difference are discussed. Etching in a CHF3/Ar discharge occurs in competition with simultaneous polymer deposition. The polymer deposition rate was measured in areas shielded from ion bombardment. A phenomenological model describing the effects of polymer deposition on etch rates, sidewall slope, and roughness is proposed. This model assumes that a polymer film with different steady-state thickness can form on different etched structure surfaces, as a result of a balance between polymer etching and deposition. The model is used to explain the tendencies in etch rates, profile slope, and sidewall roughness obtained in this study.