Defect Studies in Thin-Film SiO of a Metal-Oxide-Silicon Capacitor Using Drift-Assisted Positron Annihilation Lifetime Spectroscopy.

This work investigates the impact of an internal electric field on the annihilation characteristics of positrons implanted in a 180(10)nm SiO layer of a Metal-Oxide-Silicon (MOS) capacitor, using Positron Annihilation Lifetime Spectroscopy (PALS). By varying the gate voltage, electric fields up to 1.72MV/cm were applied. The measurements reveal a field-dependent suppression of positronium (Ps) formation by up to 64%, leading to an enhancement of free positron annihilation. The increase in free positrons suggests that vacancy clusters are the dominant defect type in the oxide layer. Additionally, drift towards the SiO/Si interface reveals not only larger void-like defects but also a distinct population of smaller traps that are less prominent when drifting to the Al/SiO interface. In total, by combining positron drift with PALS, more detailed insights into the nature and spatial distribution of defects within the SiO network and in particular near the SiO/Si interface are obtained.