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

Abstract

Area-selective deposition (ASD) is a technique to deposit material only on a defined area of a prepatterned surface, while no deposition occurs on adjacent surface areas. It is the subject of intense investigations by the scientific and engineering communities as it offers the prospect to simplify and improve patterning processes for fabrication of nanoelectronic devices as well as to reduce the manufacturing costs. Numerous efforts have been dedicated to identify process conditions for highly selective ASD processes. Still, the search for optimal conditions is often an empirical process due to the limited understanding of the mechanisms that take place at the atomic scale. Understanding the links between precursor reactivity, surface treatments, and the reactor operating conditions could greatly contribute to the development of highly selective ASD processes. In this paper, we therefore combine first-principles calculations with statistical thermodynamics to understand the role of the precursors in area-selective TiO2 atomic layer deposition (ALD). First, we investigate the selectivity loss mechanisms for TiCl4/H2O ALD on SiO2 nongrowth surfaces with different surface terminations (e.g., OH groups and trimethylsilyl groups). We link the resulting thermodynamic driving forces to experimental reports. Subsequently, we extend the investigation to a total of 26 commercially available titanium precursors and to three different oxygen sources and rank their potential for TiO2 ASD for the SiO2 surfaces with different surface terminations (OH groups and trimethylsilyl groups). We find that the combination of TiCl4 with H2O offers the best performance in terms of selectivity. The theoretical approach proposed here is expected to greatly assist and accelerate the design of precursors for different ASD approaches.

Low-Temperature Dechlorosilylation Chemistry for Area-Selective Deposition of Ge2Sb2Te5 and Its Mechanism in Nanopatterns

“…The higher selectivity of GST ALD compared to those of other ALD processes may be related to the lower temperature of the deposition. Presumably, the much lower temperature of the GST ALD process prevents thermal degradation of the TMS-terminated SiO 2 surface. , Unfortunately, we cannot investigate the impact of the temperature on GST ALD due to the narrow temperature window of the process (70–80 °C). Another hypothesis is that the precursor chemistry itself with the lack of H 2 O as a co-reagent could be responsible for achieving high selectivity for GST, similar to that proposed previously for TiO 2 ALD .…”

Theoretical Design Strategies for Area-Selective Atomic Layer Deposition

“…Recent studies have aimed to enhance the adsorption selectivity of precursors in ASD processes through theoretical precursor screening using DFT. Activation ASD can be perceived as being similar to inherent ASD on the simulation scale, as it also induces reactivity differences in localized regions at the level of the activated molecule …”

Nucleation Delay in Selective Atomic Layer Deposition: Density Functional Insights Coupled Numerical Nucleation Model

“…plays an important role in the Au nucleation inhibition from the first-principles computations and in situ infrared spectroscopy. 19 The ALD reaction mechanisms of TiCl 4 , 20 (DFT) and thermodynamic calculations, and the surface termination plays an important role in the nucleation delay.…”

“…Many efforts have been devoted to study the mechanism of ALD nucleation delay by performing theoretical simulation methods assisted in situ charaterizations. − Hock et al resolve the nucleation delay and island growth of thermal ALD of gold on aluminum oxide by in situ quartz crystal microbalance, and it is found that surface chemistry (including the intermediates, volatile byproducts, etc.) plays an important role in the Au nucleation inhibition from the first-principles computations and in situ infrared spectroscopy .…”

“…plays an important role in the Au nucleation inhibition from the first-principles computations and in situ infrared spectroscopy . The ALD reaction mechanisms of TiCl 4 , CoCp 2 , and RuCp 2 on SiO 2 surfaces have been investigated by density functional theory (DFT) and thermodynamic calculations, and the surface termination plays an important role in the nucleation delay. The selective deposition is found to be highly dependent on the surface reactivity during the ALD reaction.…”