Reactive Ion Etching of 6H‐SiC in SF 6 / O 2 and CF 4 / O 2 with N 2 Additive for Device Fabrication

Abstract

Reactive ion etching (RIE) of 6H‐SiC in fluorinated plasmas, such as and with oxygen and nitrogen addition, has been investigated. Extreme anisotropic mesa structures necessary for p‐n diodes were fabricated. The influence of oxygen and nitrogen gas flow on etching rates and selectivity to Si was examined. For the pure system etching rates were very small, whereas in pure the results were relatively high (probably due to the higher reactivity of S). As expected the etching rates increase drastically in with the addition of ; in the behavior is more complicated. The addition of to plasmas largely enhances the etching rate, whereas in the etching rates decrease with addition due to formation of complex molecules under F participation. A selectivity higher than unity for the SiC:Si system was observed for oxygen flows higher than 25 sccm and 60 sccm . The etching rate of SiC depends linearly on applied RF power in ; nitrogen addition enhances etching by a factor of approximately 1.4. In nitrogen has only minor effects on etching rates but for applied RF powers higher than 200 W the etching rates increase strongly, indicating a change in plasma chemistry more suitable for SiC etching. Atomic force microscopy proved the usefulness of RIE for surface preparation, like polishing damage removal and smoothing for oxidation or epitaxy. Anisotropic etching behavior of the C‐ and Si‐face of SiC samples under certain plasma conditions give way to the formulation of a new three‐step etching model for RIE of SiC.