Rapid atomic layer deposition of silica nanolaminates: synergistic catalysis of Lewis/Brønsted acid sites and interfacial interactions

Abstract

Rapid atomic layer deposition (RALD) has been applied to prepare various nanolaminates with repeated multilayer structures. The possible reaction pathways for RALD of the Al2O3/SiO2 nanolaminate using trimethylaluminum (TMA) and tris(tert-butoxy)silanol (TBS) are investigated by using density functional theory (DFT) calculations. The introduction of a Lewis-acid catalyst, TMA, can result in the formation of the catalytic site, which accelerates the propagation of the siloxane polymer. The rate-determining step of whole RALD is the elimination of isobutene of the tert-butoxy groups. The Brønsted acid site of [AlO4] can catalyze the elimination of isobutene. At the same time, the interfacial interactions, such as hydrogen bonding interactions between tert-butoxy groups and the surface, further catalyze the elimination of isobutene and accelerate SiO2 RALD reactions. The synergistic catalysis of Lewis/Brønsted acid sites and interfacial interactions may be applied in the RALD fabrication of other silica nanolaminates, such as HfO2/SiO2, ZrO2/SiO2, and TiO2/SiO2, in microelectronics, catalysis, energy storage, and conversion.

Design of efficient mono-aminosilane precursors for atomic layer deposition of SiO2 thin films

“…Previously, ALD growth of high-quality SiO 2 lms required high temperature (>600 C) and large uxes because there were no suitable effective Si precursors. Later, this problem was solved by using Lewis base catalyst, such as ammonia (NH 3 ) or pyridine (NC 5 H 5 ), 21,22 or Lewis acid catalyst 23,24 to lower the energy barrier of an ALD reaction. Similarly, through the introduction of an amino group, aminosilane precursors play an important role of self-catalysing in Si-O formation of SiO 2 ALD.…”

Self-catalysis by aminosilanes and strong surface oxidation by O2 plasma in plasma-enhanced atomic layer deposition of high-quality SiO2

“…[10][11][12][13][14][15][16][17][18] Another mechanism of rapid atomic layer deposition (RALD) of SiO 2 employing a Lewis-acid catalyst, such as Al(CH 3 ) 3 , has also been reported. [19][20][21] Recently, as an energy-enhanced ALD technique, plasmaenhanced atomic layer deposition (PE-ALD) has been developed to prepare high-quality SiO 2 thin films at low temperatures. 22 SiO 2 PE-ALD usually employs a Si precursor bearing an amino ligand and O 2 plasma as the oxidant.…”

Theoretical Understanding of the Reaction Mechanism of SiO2 Atomic Layer Deposition

“…30 The overall RALD reaction of the Al 2 O 3 /SiO 2 nanolaminate is complex and may include four steps: (A) TMA reaction, (B) silanol reaction, (C) propagation reaction, and (D) cross-linking reaction. 30,63 The introduction of a Lewis acid catalyst, TMA, can lead to the formation of a Lewis acid catalytic site [AlO 3 ], which further results in insertions of a large number of silanol molecules and accelerates the propagation of the siloxane polymer chain. Meanwhile, as the rate-determining step of the overall RALD, the elimination of isobutene from the tert-butoxy group of TBS can be catalyzed by the Brønsted acid site of [AlO 4 ] and interfacial interactions, such as hydrogen-bonding interactions between tert-butoxy groups and the surface.…”