Plasma enhanced atomic layer deposition of silicon nitride and silicon carbonitride using a single source precursor and different plasmas

Plasma enhanced atomic layer deposition of silicon nitride has found wide use for many semiconductor applications, but films with enhanced etch resistance and lower dielectric constant are needed. Incorporating carbon in silicon nitride to form silicon carbonitride offers a way to increase etch resistance and lower the dielectric constant, meeting property constraints that limit silicon nitride applications. However, increasing carbon concentrations increases leakage currents. Control of the carbon incorporation in terms of total concentration and the manner of constituent bonding is critical for this dielectric material to be useful. In this study, plasma enhanced atomic layer deposition was performed with bis(dimethylamino)dimethylsilane precursor thermal exposures as a single silicon, nitrogen, and carbon source in combination with different plasma exposures (N2/Ar plasma, NH3/Ar plasma, and H2/Ar plasma, and combinations of those). Changing the plasma condition had a large effect on carbon concentrations in deposited films, changing the C:Si ratio from 0 with an NH3/Ar plasma to 4.3 with a N2/Ar plasma. In addition to converting precursor-based adsorbates into a film, the choice of plasma changes the surface modalities (NHx, undercoordinated Si–N, or Si–H modes), thereby altering the precursor-surface interaction. This principle was exploited to tune film compositions to realize carbon concentrations ranging from C:Si ratios between 0.4 and 0.7 by using multiple plasma exposures to generate mixed modality surfaces for precursor adsorption.