Passivation of bottom-gate IGZO thin film transistors

Abstract

We have studied transparent bottom-gate TFTs (thin film transistors) using amorphous IGZO (In-Ga-Zn-O) as an active channel material. The TFT devices had inverse co-planar structures. Source/drain and gate electrodes were constituted by ITO sputtered with a DC-RF magnetron sputter system, and an alkaline-free glass was used as a substrate. The gate insulator was Al2O 3 formed by using an atomic layer deposition (ALD) method at 150 °C. An active layer was formed by off-axis RF magnetron sputtering and post-annealing was performed with a hot plate or a vacuum oven. The field effect mobilities and the sub-threshold swings of the IGZO TFTs were 12 ∼18 cm2/Vs and 0.2 ∼ 0.6 V/dec, respectively. However, the hysteresis on I-V characteristics was relatively large without passivation. Thus, we passivated the TFT devices with inorganic and organic materials. After the organic passivation and post-heat treatments, the hysteresis was remarkably reduced without deterioration of the electrical characteristics.