In the Parsons Group we work to understand the underlying chemistry involved in individual ALD and MLD half-reactions. As technology becomes more complex and semiconductor device sizes decrease, it is increasingly important to understand the growth mechanisms to better control film quality and conformality. We use advanced techniques, such as in-situ tools, novel precursors, and analysis with collaborators, to observe changes in film growth at the nanoscale.
An example of a home-built ALD reactor incorporating in-situ ellipsometry measurements is shown on the left. Using this tool, we evaluate the growth differences of TiO2 on Si-OH and Si-H surfaces (right) for use in area-selective deposition (read more in our ASD section). By understanding when and how initial film nucleation occurs on each surface (e.g. via chemisorption, atom diffusion, particle aggregation), we can control these reaction parameters to further promote or inhibit growth for our desired application.
As another example, we evaluate the complex reactions possible during organic deposition (MLD), such as single or double chemisorption, physisorption, and monomer diffusion, shown on the left. We introduced a novel, highly flexible precursor that enabled us to identify thickness-dependence growth rates, which corresponded to a transition in film modulus (right) determined with picosecond acoustics measurements from our collaborators at UVA.
We utilize insight on fundamental reactions to better control the properties, growth rates, and quality of our films in microelectronic and energy storage applications. You can learn more in the following journal publications from our group:
- Saare, H.; Song, S. K.; Kim, J.-S.; Parsons, G. N. “Effect of Reactant Dosing on Selectivity during Area-Selective Deposition of TiO2 via Integrated Atomic Layer Deposition and Atomic Layer Etching.” Appl. Phys. 2020, 128 (10), 105302. DOI: 10.1063/5.0013552
- Nye, R. A.; Kelliher, A. P.; Gaskins, J. T.; Hopkins, P. E.; Parsons, G. N. Understanding Molecular Layer Deposition Growth Mechanisms in Polyurea via Picosecond Acoustics Analysis. Mater. 2020, 32 (4), 1553–1563. DOI: 10.1021/acs.chemmater.9b0472