Low-Temperature Layer-by-Layer Epitaxy of Ferroelectric Al_0.63Sc_0.37N Thin Films for Back-End-of-Line Integration

Area of Science:

• Materials Science
• Solid State Physics
• Nanotechnology

Background:

• Scandium-doped aluminum nitride ((Al,Sc)N) exhibits promising ferroelectric properties for nonvolatile memory and MEMS.
• A high coercive field in (Al,Sc)N hinders its application, necessitating high scandium content films.
• Achieving high-Sc content epitaxial (Al,Sc)N thin films, especially at low temperatures for back-end-of-line (BEOL) integration, is challenging.

Purpose of the Study:

• To develop a method for low-temperature epitaxial growth of high-Sc content (Al,Sc)N thin films.
• To reduce the coercive field of (Al,Sc)N for improved ferroelectric device performance.
• To enable the integration of (Al,Sc)N into back-end-of-line processes for next-generation electronics.

Main Methods:

• Layer-by-layer epitaxial growth of Al_0.63Sc_0.37N thin films at 400 °C.
• Utilized a nitrogen-plasma-assisted pulsed laser deposition (N-PLD) technique.
• Employed X-ray photoelectron spectroscopy (XPS) for material analysis.

Main Results:

• Successfully grew epitaxial Al_0.63Sc_0.37N thin films with the highest reported Sc content.
• Demonstrated that an atomic nitrogen atmosphere is critical for suppressing nitrogen vacancies and stabilizing the wurtzite phase.
• Obtained high-quality films with remanent polarization >160 μC cm^-2 and a low coercive field of ∼2.9 MV cm^-1.

Conclusions:

• The N-PLD technique enables low-temperature epitaxial growth of high-Sc content (Al,Sc)N.
• The developed method overcomes previous limitations in achieving high-Sc content ferroelectric films.
• This research provides a pathway for integrating high-performance (Al,Sc)N into BEOL for advanced memory and MEMS applications.