Catalyzed Atomic Layer Deposition of Silicon Oxide at Ultralow Temperature Using Alkylamine.

We report the catalyzed atomic layer deposition (ALD) of silicon oxide using Si2Cl6, H2O, and various alkylamines. The density functional theory (DFT) calculations using the periodic slab model of the SiO2 surface were performed for the selection of alternative Lewis base catalysts with high catalytic activities. During the first half-reaction, the catalysts with less steric hindrance such as pyridine would be more effective than bulky alkylamines despite lower nucleophilicity. On the other hand, during the second half-reaction, the catalysts with a high nucleophilicity such as triethylamine (Et3N) would be more efficient because the steric hindrance is less critical. The in situ process monitoring shows that the calculated atomic charge is a good indicator for expecting the catalyst activity in the ALD reaction. The use of Et3N in the second half-reaction was essential to improving the growth rate as well as the step coverage of the film because the Et3N-catalyzed process deposited a SiO2 film with a step coverage of 98% that is better than 93% of the pyridine-catalyzed process. The adsorption of pyridine, ammonia (NH3), or trimethylamine (Me3N) salts was more favorable than that of Et3N, n-Pr3N, or iPr3N salts. Therefore, Et3N was expected to incorporate less amine salts in the film as compared to pyridine, and the compositional analyses confirmed that the concentrations of Cl and N by the Et3N-catalyzed process were significantly lower than those by the pyridine-catalyzed process.

Reaction Mechanism Underlying Atomic Layer Deposition of Antimony Telluride Thin Films.

The mechanism underlying the deposition of SbTe films by alternating exposures to Sb(NMe2)3 and Te(GeMe3)2 was investigated. Sb(NMe2)3 and Te(GeMe3)2 were selected because they have very high vapor pressure and are free of Si, Cl, and O atoms in the molecules. The mechanism of deposition was proposed by density functional theory (DFT) calculation and was verified by in-situ quartz crystal microbalance (QCM) analysis. DFT calculation expected the ligand-exchange reactions between the Sb and Te precursors to form Me2NGeMe3 as the byproduct. QCM analysis indicated that a single -NMe2 group in Sb(NMe2)3 reacts with -TeGeMe3 on the surface to form an Sb2Te3 film, and that a small fraction of Sb is incorporated into the film by the thermal decomposition of Sb(NMe2)3. The Te(GeMe3)2 molecules were thermally stable up to 120 degrees C, while the Sb(NMe2)3 molecules decomposed at temperatures of 60 degrees C and higher. Sb-rich SbTe films with different Sb contents were prepared by controlling the partial decomposition of Sb(NMe2)3 molecules, which was enhanced by increasing the pulse time of the precursor.

Plasma-Enhanced Atomic Layer Deposition of Silicon Nitride Using a Novel Silylamine Precursor.

We report the plasma-enhanced atomic layer deposition (PEALD) of silicon nitride thin film using a silylamine compound as the silicon precursor. A series of silylamine compounds were designed by replacing SiH3 groups in trisilylamine by dimethylaminomethylsilyl or trimethylsilyl groups to obtain sufficient thermal stability. The silylamine compounds were synthesized through redistribution, amino-substitution, lithiation, and silylation reactions. Among them, bis(dimethylaminomethylsilyl)trimethylsilyl amine (C9H29N3Si3, DTDN2-H2) was selected as the silicon precursor because of the lowest bond dissociation energy and sufficient vapor pressures. The energies for adsorption and reaction of DTDN2-H2 with the silicon nitride surface were also calculated by density functional theory. PEALD silicon nitride thin films were prepared using DTDN2-H2 and N2 plasma. The PEALD process window was between 250 and 400 °C with a growth rate of 0.36 Å/cycle. The best film quality was obtained at 400 °C with a RF power of 100 W. The PEALD film prepared showed good bottom and sidewall coverages of ∼80% and ∼73%, respectively, on a trench-patterned wafer with an aspect ratio of 5.5.