Investigations of high-k oxide layers for a-InGaZnO Thin Film Transistors
Robert Mroczynski, Gwanghyeon Baek, and Jerzy Kanicki
Amorphous indium gallium zinc oxide thin-film transistors (a-IGZO TFTs) are forecasted to become the main switching and driving devices for the future generations of semiconductor-based flat-panel displays and photo-detectors. However, many important aspects have yet to be understood for a-IGZO TFTs technology and processing. Similarly to silicon technology, the quality and reliability of gate dielectric layer are very important issues to be addressed.
This work is devoted to the fabrication and characterization of high-k oxide layers which can be used as a gate dielectric and/or passivation layer in a-IGZO TFTs. As for now, aluminum trioxide (Al2O3) layers obtained by atomic layer deposition (ALD), as well as sputtering method were investigated. We have observed that a high temperature annealing (300°C in air) without aluminum on top results in better electro-physical properties of MOS structures, e.g. the higher permittivity value for 10 nm aluminum oxide (left-hand side picture). Similar behavior was obtained in the case of sputtered layer. However, in the case of insulating properties no significant difference was observed (right-hand side picture). Presented results proved that Al2O3 layer is a promising candidate for application in a-IGZO TFT structures.
