Electric Field-aided Selective Activation for Indium-Gallium-Zinc-Oxide Thin Film Transistors.

Heesoo Lee,Won-Gi Kim,Chan Bae Jeong,Young Jun Tak,Jusung Chung,Jeong Woo Park,Ki Soo Chang,Tae Soo Jung,Hyun Jae Kim

doi:10.1038/srep35044

Abstract

A new technique is proposed for the activation of low temperature amorphous InGaZnO thin film transistor (a-IGZO TFT) backplanes through application of a bias voltage and annealing at 130 °C simultaneously. In this ‘electrical activation’, the effects of annealing under bias are selectively focused in the channel region. Therefore, electrical activation can be an effective method for lower backplane processing temperatures from 280 °C to 130 °C. Devices fabricated with this method exhibit equivalent electrical properties to those of conventionally-fabricated samples. These results are analyzed electrically and thermodynamically using infrared microthermography. Various bias voltages are applied to the gate, source, and drain electrodes while samples are annealed at 130 °C for 1 hour. Without conventional high temperature annealing or electrical activation, current-voltage curves do not show transfer characteristics. However, electrically activated a-IGZO TFTs show superior electrical characteristics, comparable to the reference TFTs annealed at 280 °C for 1 hour. This effect is a result of the lower activation energy, and efficient transfer of electrical and thermal energy to a-IGZO TFTs. With this approach, superior low-temperature a-IGZO TFTs are fabricated successfully.

Highlights

The a-IGZO TFTs annealed at 280 °C (TATs, sample number 1) exhibited sufficient transfer characteristics, such as field-effect mobility; it is known that annealing at temperatures around 300 °C is required to control the properties of AOS films and TFTs12
A non-activated TFT (NAT) that was annealed at 130 °C for 1 hour without an applied bias in Fig. 2d and the EATs were annealed at the same temperature, but only the EATs demonstrated activated transfer characteristics
The results indicate that the electrical characteristics of a-IGZO films vary with the carrier concentration

Summary

Introduction

A non-activated (thermal) TFT (NAT) that was annealed at 130 °C for 1 hour without an applied bias in Fig. 2d and the EATs were annealed at the same temperature, but only the EATs demonstrated activated transfer characteristics. Self-heating occurs during the electrical activation process due to the high drain current, increasing the temperature of the channel region[15,16,17].

Results

Conclusion