Effects of Al2O3 gate insulator on the instability of amorphous indium-gallium zinc oxide thin film transistors

Yu-Mi Kim,Ga-Won Lee

doi:10.1063/1.5043340

Abstract

This study analyzes bottom-gated amorphous indium-gallium zinc oxide (a-IGZO) thin film transistors (TFTs) with different gate insulators of Si3N4 and Si3N4/Al2O3. The aim is to investigate the effect of Al2O3 on the instability of IGZO TFTs with respect to native point defects. Although the DC properties of Si3N4/Al2O3 devices are inferior to those of Si3N4 devices, the bias stress-induced hump is not observed in Si3N4/Al2O3 devices. From calculations of the oxygen exchange kinetics between the insulator and IGZO, it appears that more oxygen atoms diffuse from Al2O3 to the IGZO than from the Si3N4. This oxygen diffusion is confirmed by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Auger electron spectroscopy depth-profiling analysis. In addition, more oxygen interstitials with fewer zinc interstitials are detected at the IGZO interface with Al2O3. From the results, it can be concluded that the distribution of native defects in Al2O3 devices reduces the instability of IGZO TFTs.

Highlights

Multi-component metal oxide thin film transistors (TFTs), such as amorphous indium-gallium zinc oxide (a-IGZO), are recognized as a very promising alternative to the conventional silicon-based TFTs, especially in active-matrix displays
That Al2O3 fabricated by conventional atomic layer deposition (ALD) at low temperatures contains some defects that result in mobility degradation.[19]
We investigated the effects of Al2O3 on the instability of bottom-gated a-IGZO TFTs by examining different gate insulators

Summary

INTRODUCTION

Multi-component metal oxide thin film transistors (TFTs), such as amorphous indium-gallium zinc oxide (a-IGZO), are recognized as a very promising alternative to the conventional silicon-based TFTs, especially in active-matrix displays. This is because of their excellent electrical properties, including a high field-effect mobility, optical clarity, and low processing temperature.[1,2,3] the instability of metal oxide TFTs remains an obstacle to practical applications. Spectroscopy (AES) depth-profiling used to analyze the native point defects based on the oxygen exchange kinetics

EXPERIMENTAL DETAILS

RESULTS AND DISCUSSION

CONCLUSION