Modulation of the Growth Per Cycle in Atomic Layer Deposition Using Reversible Surface Functionalization

A methodology to modulate precursor-surface reactivity and tailor the growth per cycle in Atomic Layer Deposition (ALD) is described. Our approach relies on in situ surface functionalization to control the density of reactive sites on the growing surface using the sequential dosing of a surface inhibitor, the ALD precursor, and the coreactant. Here we apply this methodology to ALD processes based on alkyl, cyclopentadienyl, halide, alkylamido, alkoxide, and beta-diketonate precursors, and a wide-range of inhibitors, including alkyl alcohols, ketones, carboxylic acids, and beta-diketones, in all cases resulting in a modulation of the growth per cycle because of the presence of functional groups on the surface. Mechanistic studies carried out using in situ quartz crystal microbalance and in situ surface- and gas phase-infrared absorption spectroscopy show that the underlying mechanism can be more complex than the surface site-blocking previously invoked to explain growth inhibition during chemical vapor deposition. For trimethylaluminum, our results are consistent with the presence of self-limited ligand-exchange between the precursor and adsorbed alkoxy moieties, leading to the formation of volatile alkyl alkoxy aluminum compounds as reaction byproducts, all while maintaining the self-limiting nature of the inhibition process.