Chemically Stable Atomic-Layer-Deposited Al₂O₃ Films for Processability

Area of Science:

• Materials Science
• Nanotechnology
• Surface Chemistry

Background:

• Atomic-layer-deposited alumina (ALD Al2O3) is vital for electronics, but as-deposited amorphous films lack chemical stability.
• Crystalline ALD Al2O3 offers improved resistance, yet its behavior in manufacturing solutions requires detailed study.

Purpose of the Study:

• To investigate the chemical stability of crystalline ALD Al2O3 films after annealing at different temperatures.
• To elucidate the degradation mechanisms and microstructural factors influencing stability in aggressive chemical environments.

Main Methods:

• ALD Al2O3 deposition using four precursor combinations.
• Annealing treatments at 600, 800, and 1000 °C.
• Chemical stability testing in SC-1 and HF solutions.
• Characterization using ellipsometry, electron microscopy (TEM).

Main Results:

• Crystalline ALD Al2O3 achieved at 800 and 1000 °C.
• Films annealed at 800 °C showed degradation (nanocracks, reduced refractive index) in SC-1 and HF after 60 min.
• Films annealed at 1000 °C exhibited superior stability in SC-1 and minor reaction with HF.
• Degradation at 800 °C linked to amorphous regions and uneven interfaces; stability at 1000 °C linked to uniform Al-O-Si interfacial layer.

Conclusions:

• High-temperature annealing (1000 °C) is critical for achieving chemically stable crystalline ALD Al2O3 for electronics.
• Microstructure, particularly the interfacial layer uniformity, dictates the chemical resistance of ALD Al2O3 films.
• Understanding these factors is essential for reliable semiconductor processing and device fabrication.