Aluminum Precursor Interactions with Alkali Compounds in Thermal Atomic Layer Etching and Deposition Processes

Area of Science:

• Materials Science
• Surface Chemistry
• Nanotechnology

Background:

• Atomic Layer Etching (ALE) of Al2O3 is typically achieved via surface fluorination and volatilization using hydrogen fluoride and trimethylaluminum (TMA).
• Previous work demonstrated enhanced TMA etching of Al2O3 in the presence of lithium fluoride (LiF) conditioning films.

Purpose of the Study:

• To investigate the extension of enhanced ALE of Al2O3 using other alkali halide compounds beyond LiF.
• To evaluate the impact of these compounds on Al2O3 etch rates, material-selective deposition, and processing temperatures.

Main Methods:

• Thermal Atomic Layer Etching (ALE) experiments using Al2O3.
• Utilized trimethylaluminum (TMA) as the etchant precursor.
• Investigated the effect of various alkali halide compounds (NaCl, KBr, CsI) as chamber-conditioning films.

Main Results:

• NaCl, KBr, and CsI demonstrated varying efficiencies in removing aluminum fluoride (AlF3), leading to increased Al2O3 etch rates.
• Effective compounds enabled continuous Al2O3 etching below 150 °C.
• Reduced processing temperatures facilitated material-selective thin-film deposition due to strong TMA-alkali halide interactions.

Conclusions:

• Alkali halides significantly enhance TMA-based ALE of Al2O3, allowing for lower temperature processing.
• This approach offers benefits for temperature-sensitive substrates and improved etch selectivity.
• The findings suggest potential for interface engineering in alkali-containing materials, such as lithium battery components.