Mechanisms of suboxide growth and etching in atomic layer deposition of tantalum oxide from TaCl5 and H2O

In the present study, the possible surface processes during the atomic layer deposition (atomic layer epitaxy) of tantalum oxide thin films from TaCl5 and H2O were studied. Surface mass exchange was detected by means of quartz crystalline mass sensor (QCM) during the growth process. Using the results of QCM measurements and those of electron-probe composition analysis, ClTa and OTa atomic ratios as well as stable surface concentration of Ta and Cl atoms in the intermediate surface layer were calculated versus growth temperature. The mechanisms of suboxide growth and etching in the continuous precursor flow was evaluated on the basis of the measurement results and thermodynamical probability for different reactions.