# Defect Characterization of the SiO2/Si Interface Investigated by Drift-Assisted Positron Annihilation Lifetime Spectroscopy

## TL;DR

Researchers used a new method to study defects at the SiO2/Si interface in a silicon device, finding different types of defects on each side of the interface.

## Contribution

The study introduces drift-assisted positron annihilation to characterize interface defects in MOS capacitors.

## Key findings

- The SiO2/Si interface has two distinct sides with void-like and vacancy-like defects.
- Positron trapping behavior is influenced by the charge state of Pb centers, which varies with MOS operation mode.

## Abstract

This study demonstrates drift-assisted positron annihilation lifetime spectroscopy on a p-type (100) silicon substrate in a MOS capacitor, using an applied electric field to control the spatial positron distribution prior to annihilation. The device was operated under accumulation, depletion, and inversion conditions, revealing that the internal electric field can drift-transport positrons either toward or away from the SiO2/Si interface, acting as a diffusion barrier or support, respectively. Key positron drift-transport parameters were derived from lifetime data, and the influence of the non-linear electric field on positron trapping was analyzed. The comparison of the presented results to our previous oxide-side drift experiment on the same metal-oxide–silicon capacitor indicates that the interface exhibits two distinct sides, with different types of defects: void-like and vacancy-like (Pb centers). The positron data also suggest that the charge state of the Pb centers likely varies with the operation mode of the MOS, which affects their positron trapping behavior.