Atomic Layer Deposition of WO₃-Doped In₂O₃ for Reliable and Scalable BEOL-Compatible Transistors

Area of Science:

• Materials Science
• Semiconductor Device Physics
• Nanotechnology

Background:

• Indium oxide (In2O3) based field-effect transistors (FETs) are crucial for advanced electronics.
• Achieving stable device operation and compatibility with 3D integration remains a challenge.
• Tungsten oxide (WO3) doping is explored to enhance In2O3 properties.

Purpose of the Study:

• To demonstrate tungsten oxide (WO3) doped indium oxide (IWO) FETs synthesized by atomic layer deposition (ALD).
• To investigate the effect of WO3 doping concentration on the electrical properties and stability of IWO FETs.
• To assess the suitability of ALD IWO FETs for 3D integration and back-end-of-line (BEOL) compatibility.

Main Methods:

• Synthesis of IWO films using atomic layer deposition (ALD) by adjusting precursor cycle ratios.
• Fabrication of IWO field-effect transistors (FETs).
• Characterization of electrical properties including subthreshold slope, hysteresis, threshold voltage, and stability under bias stress.

Main Results:

• Low-concentration WO3 doping (1-4 atom %) in In2O3 films was achieved via ALD.
• Doping suppressed oxygen deficiency, enabling stable device turn-off and enhancing threshold voltage stability.
• ALD IWO FETs exhibited a low subthreshold slope (67 mV/decade), negligible hysteresis, and tunable threshold voltage.
• Devices showed remarkable stability under bias stress and maintained performance at sub-100 nm channel lengths.

Conclusions:

• ALD-synthesized IWO FETs offer a promising pathway for stable, high-performance electronic devices.
• The tunable threshold voltage and excellent stability make IWO FETs suitable for monolithic 3D integrated circuits.
• WO3 doping effectively addresses oxygen deficiency issues in In2O3, enhancing device reliability.