Beneficial effect of hydrogen in aluminum oxide deposited through the atomic layer deposition method on the electrical properties of an indium-gallium-zinc oxide thin-film transistor

Abstract

Described herein is the role of hydrogen in aluminum oxide (Al2O3) gate dielectrics in amorphous indium-gallium-zinc oxide (a-InGaZnO or a-IGZO) thin-film transistors (TFTs). Compared to a-IGZO TFTs with a low-temperature (150 degrees C) Al2O3 gate dielectric, a-IGZO devices with a high-temperature (250-300 degrees C) Al2O3 gate dielectric exhibit poor transistor characteristics, such as low mobility, a high subthreshold slope, and huge hysteresis. Through DC and short-pulsed current-voltage (I-V) measurements, it was revealed that the degradation of the transistor performance stems from the charging and discharging phenomenon at the interface traps located in the interface between the a-IGZO semiconductor and the Al2O3 gate insulator. It was found that the low-temperature Al2O3 atomic layer deposition processed film contains a higher density of hydrogen atoms compared to high-deposition-temperature films. The study results show that a high concentration of hydrogen atoms can passivate the defect sites in the interface and bulk, which produces excellent transistor characteristics. This study demonstrated that hydrogen has a beneficial effect on the defect passivation for oxide TFTs.