Oxygen tracer diffusion in amorphous hafnia films for resistive memory

Area of Science:

• Materials Science
• Solid-State Physics
• Nanotechnology

Background:

• Oxygen diffusion in hafnia (HfO2) is critical for nonvolatile data retention in resistive memory devices.
• A significant discrepancy exists between expected retention times based on oxygen diffusion and experimentally observed values in HfO2 devices.

Purpose of the Study:

• To investigate and resolve the discrepancy between oxygen diffusion rates and retention times in HfO2-based resistive memory.
• To accurately measure oxygen diffusion in amorphous hafnia (a-HfO2) thin films using isotope tracer techniques.

Main Methods:

• Oxygen isotope tracer diffusion measurements were performed on amorphous hafnia (a-HfO2) thin films.
• Comparison of diffusion rates in a-HfO2 films deposited by atomic layer deposition (ALD) versus sputtering.
• Analysis of the correlation between oxygen diffusion times and device retention times.

Main Results:

• Oxygen tracer diffusion in a-HfO2 films is orders of magnitude lower than in monoclinic hafnia (m-HfO2) pellets.
• Denser a-HfO2 films produced by ALD exhibit significantly lower oxygen diffusion rates compared to less dense films from sputtering.
• Oxygen diffusion times in ALD-deposited films align with experimentally measured device retention times.

Conclusions:

• Processing conditions, particularly atomic layer deposition, can precisely control oxygen transport in amorphous hafnia.
• The study reconciles the long-standing discrepancy between oxygen diffusion measurements and device retention times in HfO2 resistive memory.
• This work provides a pathway for optimizing amorphous materials for enhanced data retention in electronic devices.