Decoupling Moisture and Hydrogen Barrier Properties in Silicon Nitride Films Deposited by Plasma-Enhanced Atomic Layer Deposition at 100 °C via Precursor-Defined Bonding Networks

초록

Thin-film encapsulation for next-generation organic light-emitting diode displays faces a coupled barrier challenge, where moisture ingress and hydrogen transport must be suppressed simultaneously. This study shows that these metrics can be decoupled in low-temperature (100 °C) plasma-enhanced atomic layer deposition (PEALD) of SiNx, and the relationship between this behavior and the precursor-defined film chemistry is investigated. SiNx films deposited using two aminosilanes with contrasting ligand structures, trisilylamine (TSA, carbon-free) and bis(tert-butylamino)silane (BTBAS, bulky tert-butyl groups), are compared. First-principles density functional theory calculations indicate that BTBAS has a higher ligand-exchange barrier (86.4 vs 26.2 kcal/mol), which is consistent with the fact that its growth per cycle (0.45 Å) is lower than that of TSA (0.93 Å). Barrier testing reveals an unusual trade-off where the denser TSA film (2.94 g/cm3) exhibits superior moisture blocking (water vapor transmission rate: 1.94 × 10–4 g/m2·day), and the lower-density BTBAS film (2.15 g/cm3) exhibits lower hydrogen permeability (1.50 × 10–4 vs 6.04 × 10–4 Barrer for TSA). Auger electron spectroscopy, X-ray photoelectron spectroscopy, and Fourier-transform infrared spectroscopy show higher rates of carbon and oxygen incorporation and oxygen-influenced bonding in the BTBAS films. Hydrogen pressurization followed by dynamic secondary ion mass spectrometry and thermal desorption spectrometry indicates precursor-dependent differences in hydrogen uptake, retention, and thermally activated release, which may be associated with impurity-influenced hydrogen-responsive local environments. These results provide a process–chemistry–property guideline for decoupling moisture and hydrogen barrier performance in low-temperature PEALD SiNx, offering insights for the design of reliable, flexible, and hydrogen-sensitive electronics.

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