N2/O2 Plasma-Tuned Hydrogen-Bonding Configurations for Suppressed Charge Trapping in PEALD SiON Films

Abstract

Hydrogen incorporation in silicon oxynitride (SiON) dielectric films plays a dual role by passivating electrically active defects while simultaneously acting as a potential source of charge trapping, depending on the chemical-bonding configuration. In this study, plasma-enhanced atomic layer-deposited (PEALD) SiON thin films were fabricated using diisopropylaminosilane and a mixed N2/O2 plasma, and the hydrogen-bonding states were systematically engineered by controlling the N2:O2 plasma flow ratio. Increasing the N2:O2 ratio progressively transformed the SiON network from oxide-rich to nitrogen-rich, resulting in an increased dielectric constant from 4.95 to 6.67 while decreasing the induced trap density from 6.15 × 1011 to 1.84 × 1011 cm–2. An optimized N2:O2 ratio of 250:1 yielded the lowest capacitance–voltage hysteresis (0.10 V), whereas the N2-only plasma process caused a substantial increase in hysteresis (1.85 V) despite its highest hydrogen concentration. Time-of-flight secondary ion mass spectrometry analyses revealed that hydrogen incorporation shifted from O–H-dominated to Si–H/N–H-dominated bonding environments as the nitrogen content increased. Density functional theory calculations further demonstrated that Si–H and Si–N bonds have lower bond dissociation energies than O–H and Si–O bonds, thereby explaining the instability of oxygen-deficient SiNx-like networks under electrical stress. These results demonstrate that the charge-trapping behavior of PEALD SiON films is governed not by the total hydrogen concentration but by the hydrogen-bonding configuration and the structural stability of the Si–O–N network, thereby providing an effective strategy for defect passivation and suppressed charge trapping in dielectric films for advanced semiconductor devices.