| AVS 66th International Symposium & Exhibition | |
| Thin Films Division | Monday Sessions |
| Session TF+2D+AP+EL+SS-MoA |
| Session: | ALD and CVD: Nucleation, Surface Reactions, Mechanisms, and Kinetics |
| Presenter: | Brent Sperling, National Institute of Standards and Technology (NIST) |
| Authors: | B.A. Sperling, National Institute of Standards and Technology (NIST) B. Kalanyan, National Institute of Standards and Technology (NIST) J.E. Maslar, National Institute of Standards and Technology (NIST) |
| Correspondent: | Click to Email |
Until recently, the CH3 groups produced by surface reactions of trimethylaluminum (TMA) during atomic layer deposition were widely believed to always be highly reactive toward H2O, but in situ measurements have shown this is not the case below about 200 °C.[1] At these temperatures, some CH3 groups react slowly, and a significant amount persists from cycle to cycle under typical growth conditions. Interestingly, these persistent CH3 groups are not incorporated as carbon impurities. We have observed these CH3 groups using in situ reflection infrared spectroscopy and have confirmed low carbon concentrations in our films using ex situ XPS. Furthermore, we have measured the kinetics of the reaction with H2O and have found them to be well-described by a double-exponential decay function. A simple Monte Carlo simulation that incorporates cooperative effects by clustered surface reactants (as suggested by DFT calculations[2]) reveals that a double-exponential decay of coverage can result even when only one species of reactant is present. Furthermore, the short-range distributions of coverage that result in the simulation differ from purely random ones. This difference implies that measurements sensitive to dipole-dipole interactions when combined with an independent measurement of surface coverage could be used to confirm or disprove the cooperative reaction model.
[1] V. Vandalon and W. M. M. Kessels, J. Vac. Sci. Techol. A35 (2017) 05C313
[2] M. Shirazi and S. D. Elliott, Nanoscale7 (2015) 6311.