Origin of Indium Diffusion in High-k Oxide HfO2

Area of Science:

• Materials Science
• Semiconductor Physics
• Surface Science

Background:

• Indium (In) out-diffusion through high-k oxides compromises thermal reliability in III-V/high-k metal oxide semiconductor (MOS) devices.
• The precise microscopic mechanism of Indium diffusion in these structures remains incompletely understood.

Purpose of the Study:

• To investigate the mechanism of Indium diffusion in high-k hafnium dioxide (HfO2) using experimental and theoretical approaches.
• To determine the impact of oxygen vacancies on Indium diffusion barriers.

Main Methods:

• Angle-resolved X-ray photoelectron spectroscopy (ARXPS) was employed to detect Indium diffusion.
• Density functional theory (DFT) calculations were performed to model diffusion pathways and energy barriers.

Main Results:

• ARXPS confirmed Indium diffusion through both as-prepared and annealed HfO2 layers on an Indium Phosphide (InP) substrate.
• DFT calculations revealed a significantly reduced Indium diffusion barrier (∼0.88 eV) in the presence of oxygen vacancies, compared to pristine HfO2 (∼4.78 eV).
• Indium's weak nonbonding interactions with neighboring atoms were identified as a key factor for its high diffusion feasibility.

Conclusions:

• Oxygen vacancies critically facilitate Indium diffusion in HfO2 by lowering the energy barrier.
• The findings provide fundamental insights into Indium diffusion mechanisms, applicable beyond HfO2 to other material systems.