Thermal Atomic Layer Deposition of Gold: Mechanistic Insights, Nucleation, and Epitaxy

Abstract

An in situ microbalance and infrared spectroscopic study of alternating exposures to Me2Au­(S2CNEt2) and ozone illuminates the organometallic chemistry that allows for the thermal atomic layer deposition (ALD) of gold. In situ quartz crystal microbalance (QCM) studies resolve the nucleation delay and island growth of Au on a freshly prepared aluminum oxide surface with single cycle resolution, revealing inhibition for 40 cycles prior to slow nucleation and film coalescence that extends over 300 cycles. In situ infrared spectroscopy informed by first-principles computation provides insight into the surface chemistry of the self-limiting half-reactions, which are consistent with an oxidized Au surface mechanism. X-ray diffraction of ALD-grown gold on silicon, silica, sapphire, and mica reveals consistent out-of-plane oriented crystalline film growth as well as epitaxially directed in-plane orientation on closely lattice-matched mica at a relatively low growth temperature of 180 °C. A more complete understanding of ALD gold nucleation, surface chemistry, and epitaxy will inform the next generation of low-temperature, nanoscale, textured depositions that are applicable to high surface area supports.

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 . 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.…”