Region-Selective Oxygen Vacancy Engineering for Ferroelectric Hf_0.5Zr_0.5O₂ Thin Films Processed at 300 °C.

Area of Science:

• Materials Science
• Solid State Physics
• Nanotechnology

Background:

• Ferroelectricity in hafnium oxide (HfO2) thin films is crucial for next-generation nonvolatile memory.
• Integrating HfO2-based ferroelectric films into back-end-of-line (BEOL) processes is hindered by the high temperatures needed for the orthorhombic (O) phase.

Purpose of the Study:

• To develop a low-thermal-budget method for stabilizing the ferroelectric O-phase in HfO2-based thin films.
• To enable the integration of ferroelectric HfO2 into advanced semiconductor manufacturing processes.

Main Methods:

• Region-selective oxygen vacancy engineering during atomic layer deposition (ALD) to create oxygen vacancy engineering layers (Vo-ELs) in Hf0.5Zr0.5O2 (HZO) films.
• Modifying the ALD process by delaying oxygen precursor introduction to create a vertical oxygen vacancy concentration gradient.
• Utilizing electron energy loss spectroscopy (EELS) and first-principles calculations to analyze oxygen vacancy distribution and phase transition energetics.

Main Results:

• Achieved robust stabilization of the ferroelectric O-phase at a significantly reduced annealing temperature of 300 °C.
• Demonstrated that oxygen vacancies lower the phase transition energy barrier and enhance O-phase stability.
• Fabricated HZO ferroelectric capacitors with high remanent polarization (36.4 μC/cm2) and excellent endurance (>10^9 cycles) using the low-temperature process.

Conclusions:

• Oxygen vacancy engineering via Vo-ELs effectively stabilizes the ferroelectric O-phase at low temperatures.
• This technique facilitates the fabrication of high-performance ferroelectric devices compatible with BEOL integration.
• The developed method offers a pathway for advanced, low-power memory technologies.