Numerical Analysis of Oxygen-Related Defects in Amorphous In-W-O Nanosheet Thin-Film Transistor

Area of Science:

• Materials Science
• Semiconductor Physics
• Device Engineering

Background:

• Amorphous indium tungsten oxide (a-IWO) with hafnium oxide (HfO2) high-κ gate dielectrics are promising for amorphous oxide semiconductor (AOS) thin-film transistors (TFTs).
• Understanding defect behavior is crucial for optimizing TFT performance.

Purpose of the Study:

• To investigate the impact of oxygen ratio during a-IWO deposition on TFT characteristics.
• To correlate chemical species with bulk and interface density of states (DOS).
• To develop a numerical methodology for monitoring oxygen interstitial (Oi) defects.

Main Methods:

• Material measurements and Technology Computer Aided Design (TCAD) analysis.
• Quantum modeling of a-IWO nanosheet TFTs.
• Density Functional Theory (DFT) calculations.

Main Results:

• Increased oxygen ratio led to a more positive threshold voltage shift (ΔVTH) and reduced ON-current (ION).
• Oxygen interstitial (Oi) defects were identified as key modulators of bulk dopant concentration (Nd) and interface Gaussian acceptor trap density (NGA).
• A correlation between Oi defect formation energy and Fermi level position was established.

Conclusions:

• Oxygen content significantly impacts a-IWO TFT transfer characteristics by altering bulk and interface defect states.
• The study provides a validated physical model and a numerical approach for defect monitoring in AOS TFTs.
• This work offers insights for precise control over a-IWO TFT performance through defect engineering.