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

Area of Science:

• Materials Science
• Semiconductor Physics
• Thin-Film Electronics

Background:

• Amorphous Indium Gallium Zinc Oxide (IGZO) thin-film transistors (TFTs) are crucial for display technologies.
• Achieving high mobility and operational stability in amorphous IGZO TFTs remains a significant challenge.
• Existing methods often involve trade-offs between transistor performance and reliability.

Purpose of the Study:

• To develop a method for enhancing the stability of amorphous IGZO TFTs while maintaining high field-effect mobility.
• To investigate the role of nitrogen doping via nitrous oxide plasma in improving TFT performance.
• To optimize the plasma-enhanced atomic layer deposition (PEALD) process for high-performance IGZO TFTs.

Main Methods:

• Utilized plasma-enhanced atomic layer deposition (PEALD) at 200 °C.
• Employed selective application of nitrous oxide plasma as a reactant.
• Combined theoretical calculations and experimental research to understand nitrogen doping mechanisms.
• Fabricated indium-rich PEALD-IGZO TFTs.

Main Results:

• Achieved high-performance IGZO TFTs with a threshold voltage of -0.47 V and field-effect mobility of 106.5 cm²/ (V s).
• Demonstrated excellent device stability with minimal hysteresis (0.05 V).
• Observed minimal threshold voltage shifts (+0.45 V and -0.10 V) under harsh bias-temperature stress conditions (±2 MV/cm, 95 °C for 10000 s).

Conclusions:

• Selective nitrous oxide plasma application in PEALD effectively enhances the stability of amorphous IGZO TFTs.
• Nitrogen doping mechanism is influenced by intrinsic carbon impurities and cation properties, particularly in Ga2O3 subgap states.
• The developed PEALD process yields high-performance and reliable IGZO TFTs suitable for practical applications.