A First-Principles Investigation of the Driving Forces Defining the Selectivity of TiO₂ Atomic Layer Deposition

Area-selective deposition (ASD) is a technique to depositmaterialonly on a defined area of a prepatterned surface, while no depositionoccurs on adjacent surface areas. It is the subject of intense investigationsby the scientific and engineering communities as it offers the prospectto simplify and improve patterning processes for fabrication of nanoelectronicdevices as well as to reduce the manufacturing costs. Numerous effortshave been dedicated to identify process conditions for highly selectiveASD processes. Still, the search for optimal conditions is often anempirical process due to the limited understanding of the mechanismsthat take place at the atomic scale. Understanding the links betweenprecursor reactivity, surface treatments, and the reactor operatingconditions could greatly contribute to the development of highly selectiveASD processes. In this paper, we therefore combine first-principlescalculations with statistical thermodynamics to understand the roleof the precursors in area-selective TiO2 atomic layer deposition(ALD). First, we investigate the selectivity loss mechanisms for TiCl4/H2O ALD on SiO2 nongrowth surfaceswith different surface terminations (e.g., OH groups and trimethylsilylgroups). We link the resulting thermodynamic driving forces to experimentalreports. Subsequently, we extend the investigation to a total of 26commercially available titanium precursors and to three differentoxygen sources and rank their potential for TiO2 ASD forthe SiO2 surfaces with different surface terminations (OHgroups and trimethylsilyl groups). We find that the combination ofTiCl(4) with H2O offers the best performance interms of selectivity. The theoretical approach proposed here is expectedto greatly assist and accelerate the design of precursors for differentASD approaches.