Stabilizing the ferroelectric phase in HfO₂-based films sputtered from ceramic targets under ambient oxygen

Area of Science:

• Materials Science
• Solid State Physics
• Nanotechnology

Background:

• Ferroelectric materials are crucial for advanced electronic devices.
• Hafnium oxide (HfO2) and its alloys are promising candidates for next-generation ferroelectric thin films.
• Controlling the phase and properties of these oxides is essential for device optimization.

Purpose of the Study:

• To investigate the ferroelectric properties of undoped hafnium oxide and hafnium-zirconium oxide thin films.
• To understand the influence of sputtering oxygen concentration and zirconium doping on film characteristics.
• To correlate structural phases with observed ferroelectric behavior.

Main Methods:

• Preparation of metal-insulator-metal capacitors using sputtering techniques.
• Electrical characterization to assess ferroelectric properties.
• Structural analysis to determine film phases and crystallite characteristics.

Main Results:

• Undoped hafnium oxide films display distinct ferroelectric properties dependent on oxygen concentration.
• Incorporation of zirconia and controlled oxygen levels enhance ferroelectric performance.
• Phase stabilization (tetragonal, orthorhombic, monoclinic) is achievable by tuning oxygen and zirconia content.
• Film stress, influenced by oxygen vacancies and interstitials, correlates with phase and ferroelectricity.

Conclusions:

• Ferroelectric properties of HfO2-based films can be tailored through careful control of sputtering conditions and composition.
• The interplay between oxygen, zirconia, and film stress is critical for achieving desired ferroelectric phases and performance.
• These findings offer pathways for designing optimized ferroelectric thin films for capacitor applications.