Surface oxidation model in plasma enhanced atomic layer deposition for silicon oxide films including various aminosilane precursors

Abstract

In this study, a surface oxidation model for the plasma enhanced atomic layer deposition process for silicon oxide films formed by the combination of aminosilane with Ar/O2 plasma is proposed. After the discussion of the dominant oxidation pathways involving both reactive species generation and reaction energy barriers, the authors develop a surface oxidation model and compare it with experimental deposition results. From plasma simulation results, they confirmed two dominant species generated by Ar/O2 plasma; triplet oxygen atom (3O) and singlet oxygen molecule (1O2). The authors then compared the reaction energy barrier along the oxidation pathways for these oxidation species and the corresponding surface terminations by using density functional theory calculations. The calculated activation barriers were negligible in the oxidation paths with 3O, but not in the ones with 1O2. These results support that oxidation by 3O was dominant, especially at low substrate temperatures. The authors suggest a surface oxidation model having two kinds of surface terminations; hydrogen terminations (Si–H) and amino ligand terminations (Si–R). This model can explain the experimental saturation curve for surface oxidation against plasma irradiation time as a function of substrate temperature. The authors confirmed that saturation trends observed with various aminosilane precursors can successfully be explained by their differing ratios of Si–H and Si–R bonds present prior to oxidation.