Mechanism of Dry Etching of Silicon Dioxide: A Case of Direct Reactive Ion Etching

Reactive sputter etching of with plasmas has been investigated in a parallel‐plate reactor by combining etch‐rate measurements with concurrent determination of ion densities (using a Langmuir probe) and the composition of neutral plasma species (using a mass spectrometer), and by examining etched profiles in the SEM. The importance of geometrical variables, such as plate separation and plate area, and the electrical parameters appropriate for characterizing the discharge are discussed. Etch rates are found to follow the ion density and to be fairly independent of the plasma chemistry under most experimental conditions. Moreover, a comparison of reactive sputter etching and reactive ion beam etching of with and shows that etch yields per incoming ion are essentially independent of the flux of neutral radicals to the substrate. This strongly suggests as the dominant etch mechanism for direct reactive ion etching, where ions themselves are the main reactants in the etch reaction. Measured etch yields are consistent with this picture. However, the plasma chemistry has a decisive influence on the etch rate of Si, and thus on the etch selectivity of with respect to Si, and also on the exact shape of profiles etched into .