High-Temperature Ferroelectric Behavior of Al_0.7Sc_0.3N

Area of Science:

• Materials Science
• Electrical Engineering
• Solid-State Physics

Background:

• Existing nonvolatile memory (NVM) technologies face limitations operating above 200 °C.
• Conventional perovskite ferroelectrics exhibit performance degradation at elevated temperatures.
• There is a critical need for NVM solutions capable of continuous high-temperature operation.

Purpose of the Study:

• To investigate Aluminum Scandium Nitride (AlScN) as a potential material for high-temperature NVM.
• To evaluate the performance and stability of AlScN-based capacitors at temperatures exceeding 200 °C.
• To demonstrate the feasibility of AlScN for NVM applications in extreme thermal environments.

Main Methods:

• Fabrication of c-axis textured AlScN thin films via reactive radiofrequency magnetron sputtering on Pt (111) substrates.
• Construction of capacitor stacks with photolithographically defined Pt top electrodes.
• Electrical characterization, including polarization-electric field hysteresis loops and retention measurements, up to 400 °C in a high-temperature vacuum probe station.

Main Results:

• AlScN capacitors exhibited stable remanent polarization values across the tested temperature range (23 °C to 400 °C).
• The coercive field decreased from 4.3 MV/cm at room temperature to 2.6 MV/cm at 400 °C.
• Negligible polarization loss was observed up to 1000 s even at 400 °C, indicating excellent retention.
• Fatigue behavior showed moderate temperature dependence, warranting further investigation into degradation mechanisms.

Conclusions:

• AlScN is a promising material for developing nonvolatile memory (NVM) devices capable of operating continuously above 200 °C.
• The stable ferroelectric properties of AlScN at high temperatures address a key limitation in current NVM technology.
• Further research into fatigue mechanisms is necessary to fully optimize AlScN for demanding high-temperature NVM applications.