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

Abstract

Plasma-enhanced atomic layer deposition (PE-ALD) has been applied to prepare high-quality ultrathin films for microelectronics, catalysis, and energy applications. The possible pathways for SiO2 PE-ALD using aminosilanes and O2 plasma have been investigated by density functional theory calculations. The silane half-reaction between SiH4 and surface -OH is very difficult and requires a high activation free energy of 57.8 kcal mol(-1). The introduction of an aminosilane, such as BDMAS, can reduce the activation free energy to 11.0 kcal mol(-1) and the aminosilane plays the role of a self-catalyst in Si-O formation through the relevant half-reaction. Among the various species generated in O2 plasma, (3)O2 is inactive towards surface silane groups, similar to ordinary oxygen gas. The other three species, (1)O2, (1)O, and (3)O, can strongly oxidize surface silane groups through one-step or stepwise pathways. In the (3)O pathway, the triplet must be converted into the singlet and follow the (1)O pathway. Meanwhile, both (1)O and (3)O can decay to (1)O2 and enter into the relevant oxidation pathway. The concept of self-catalysis of aminosilanes may be invoked to design and prepare more effective Si precursors for SiO2 ALD. At the same time, the mechanism of strong surface oxidation by O2 plasma may be exploited in the PE-ALD preparation of other oxides, such as Al2O3, HfO2, ZrO2, and TiO2.

Surface chemistry of copper metal and copper oxide atomic layer deposition from copper(ii) acetylacetonate: a combined first-principles and reactive molecular dynamics study

“…Recently, quantum chemistry (QC), in particular density functional theory (DFT) calculations, has become a powerful tool to explicit the ALD chemistry at an atomic scale. [30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49] Dey et al 31 investigated the transmetalation reactions in Cu ALD using diethylzinc as the reducing agent, following experiments by Lee et al 8 Lin et al 32 have investigated the competition between ligand-exchange reactions and surface decomposition of Cu(acac) 2 on a Si(100)-2 Â 1 surface. More recently, we have studied the surface reactions of ( n Bu 3 P) 2 Cu(acac) and Cu(acac) 2 precursors on a Ta(110) surface.…”

Stepwise mechanism and H2O-assisted hydrolysis in atomic layer deposition of SiO2 without a catalyst

“…The reason for this is mainly that H 2 O can form hydrogen bonding interactions through H 2 O…H 2 O bonds and lower the activation energy of Si-O bond formation and Cl elimination via a six-member ring (6MR) transition state, H 2 O-assisted-TS1 B1 , shown in Figure 4 . The accelerated half-reaction via the hydrogen bonding interaction of H 2 O…H 2 O may be termed as H 2 O-assisted hydrolysis, which is similar to Lewis-base catalysis in SiO 2 ALD through the OH…N hydrogen bond [ 14 , 23 , 24 ]. As a matter of fact, there are H 2 O-assisted reactions in nature, such as hydrolysis or solvolysis [ 25 - 28 ], tautomerization or proton transfer [ 29 - 34 ], decomposition [ 35 - 37 ], and catalysis [ 38 , 39 ].…”

Recent progress on non-thermal plasma technology for high barrier layer fabrication

“…With the high energy species, the PEALD, which can enhance the reactivity at low temperatures, is suitable for the temperaturesensitive deposition process. Now PEALD has been applied to prepare high-quality ultrathin films for microelectronics, catalysis, and new energy applications [217,218]. Lee et al [219] reported a low frequency plasma assisted ALD technique to deposit Al x O y layer on polyethylene naphthalate substrates as barrier layer.…”