Oxygen plasma reactive ion etching of tetrahedral amorphous carbon

The reactive ion etching (RIE) of tetrahedral amorphous carbon (ta-C) has been studied using an O-2 rf plasma. The ta-C films were deposited using a filtered cathodic vacuum are (FCVA) system. A series of films was deposited by varying the substrate bias and hence the energy of the depositing carbon ions. The dependence of etch rate on ri power, oxygen flow rate and reactor pressure has been investigated. Under the same etching conditions lower etch rates were observed for films deposited at higher negative substrate bias. This can be explained from the fact that the diamond-like nature of such films increases with increasing ion energy up to a maximum around 120 eV. The addition of hydrogen to the growing film was found to cause a decrease in the sp(3) bond fraction of the film and hence led to an increase in the etch rate.