Enhancing InGaZnO transistor current through high-κ dielectrics and interface trap extraction using single-pulse...

Area of Science:

• Materials Science
• Semiconductor Physics
• Device Engineering

Background:

• Enhancing drive current in oxide semiconductor transistors is critical for advanced electronics like high-resolution displays and faster memory.
• High-mobility materials improve current but pose manufacturing challenges; thus, improving current without changing channel material is desirable.
• High-κ gate dielectrics offer a route to boost gate capacitance and transistor performance.

Purpose of the Study:

• To systematically investigate the effect of different high-κ gate dielectrics on Indium Gallium Zinc Oxide (InGaZnO) transistor performance.
• To identify the factors limiting drive current enhancement when using high-κ dielectrics.
• To quantify the role of interface traps and propose methods for their reduction.

Main Methods:

• Fabrication and electrical characterization of InGaZnO transistors with SiO₂, HfO₂, and ZrO₂ gate insulators.
• Analysis of drive current enhancement relative to the dielectric constant (κ) of the gate insulators.
• Device simulations to understand the interplay of contact resistance, channel capacitance, and interface trap density.
• Quantification of interface trap densities using the single-pulse charge pumping method.

Main Results:

• Drive current increased with higher dielectric constants, but less than theoretically predicted based on κ alone.
• HfO₂ (κ=17) and ZrO₂ (κ=30) showed drive current enhancements of 2.8x and 7x, respectively, compared to SiO₂ (κ=3.9).
• Device simulations and experiments identified interface trap density as a primary limiting factor, especially for HfO₂.
• Single-pulse charge pumping confirmed high interface trap densities in HfO₂, correlating with reduced transconductance.

Conclusions:

• While high-κ dielectrics effectively increase gate capacitance, their full potential for enhancing InGaZnO transistor drive current is significantly limited by interface trap density.
• Reducing interface traps is crucial for maximizing the benefits of high-κ dielectrics and achieving substantial drive current improvements.
• This research provides a pathway for optimizing oxide semiconductor transistors by focusing on interface engineering alongside dielectric selection.