Oxygen relocation during HfO₂ ALD on InAs

Area of Science:

• Materials Science
• Surface Chemistry
• Nanotechnology

Background:

• Atomic layer deposition (ALD) is crucial for electronic device fabrication, known for its atomic-scale accuracy and layer-by-layer growth.
• ALD typically exhibits a constant growth rate per cycle in its steady-state phase, independent of the substrate.
• The initial stage of ALD, however, deviates from steady-state kinetics and is heavily influenced by substrate surface composition.

Purpose of the Study:

• To investigate the initial growth phase of HfO2 ALD on InAs substrates.
• To understand the role of substrate surface composition and oxide layers in the early stages of ALD.
• To explore the implications of these findings for controlling ALD processes and self-cleaning effects in III-V semiconductors.

Main Methods:

• Atomic layer deposition (ALD) of HfO2 on InAs substrates with native or thermal oxide layers.
• Analysis of the initial ALD phase, focusing on growth kinetics, chemistry, and surface interactions.
• Investigation of oxygen relocation from the InAs substrate to the HfO2 overlayer.

Main Results:

• Evidence of oxygen relocation from InAs oxide (thermal or native) to the HfO2 overlayer during the initial ALD phase.
• Demonstrated control over the initial ALD layer thickness by manipulating pre-ALD substrate surface conditions.
• Complete removal of InAs native oxide (even >1 monolayer) within the first ALD half-cycle, with a self-limiting HfO2 layer thickness of approximately one monolayer.

Conclusions:

• The initial ALD phase is significantly influenced by substrate surface chemistry, challenging the universal applicability of the ligand exchange model.
• Oxygen relocation is a key phenomenon in the early stages of HfO2 ALD on InAs.
• Findings offer enhanced control over the self-cleaning effect in III-V semiconductors, vital for next-generation high-speed Metal-Oxide-Semiconductor (MOS) devices.