Thermally Activated Defect Engineering for Highly Stable and Uniform ALD-Amorphous IGZO TFTs with High-Temperature Compatibility.

Highly stable IGZO thin-film transistors derived from atomic layer deposition are crucial for the semiconductor industry. However, unavoidable defect generation during high-temperature annealing results in abnormal positive bias temperature stress (PBTS). Herein, we propose a defect engineering method by controlling the gate insulator (GI) deposition temperature. Applying a GI deposition temperature of 400 °C to the In0.52Ga0.18Zn0.30O active layer effectively suppresses defects even after 600 °C annealing, preserving the amorphous phase of IGZO. The device exhibits a threshold voltage (VTH) of 0.05 V, a field-effect mobility of 27.6 cm2/Vs, a subthreshold swing of 61 mV/decade, and a hysteresis voltage of 0.01 V, demonstrating highly reliable PBTS and negative bias temperature stress. A power-law fit of the PBTS stability under 2 MV/cm of gate field stress and 120 °C of temperature stress predicts a VTH shift of -0.01 V after 10 years. Moreover, the proposed method ensures reliable uniformity over a large 4 in. area.

Selectively Nitrogen Doped ALD-IGZO TFTs with Extremely High Mobility and Reliability.

Achieving high mobility and reliability in atomic layer deposition (ALD)-based IGZO thin-film transistors (TFTs) with an amorphous phase is vital for practical applications in relevant fields. Here, we suggest a method to effectively increase stability while maintaining high mobility by employing the selective application of nitrous oxide plasma reactant during plasma-enhanced ALD (PEALD) at 200 °C process temperature. The nitrogen-doping mechanism is highly dependent on the intrinsic carbon impurities or nature of each cation, as demonstrated by a combination of theoretical and experimental research. The Ga2O3 subgap states are especially dependent on plasma reactants. Based on these insights, we can obtain high-performance indium-rich PEALD-IGZO TFTs (threshold voltage: -0.47 V; field-effect mobility: 106.5 cm2/(V s); subthreshold swing: 113.5 mV/decade; hysteresis: 0.05 V). In addition, the device shows minimal threshold voltage shifts of +0.45 and -0.10 V under harsh positive/negative bias temperature stress environments (field stress: ±2 MV/cm; temperature stress: 95 °C) after 10000 s.