A Three-Step Atomic Layer Deposition Process for SiN _x Using Si₂Cl₆, CH₃NH₂, and N₂ Plasma.

Area of Science:

• Materials Science
• Nanotechnology
• Chemical Engineering

Background:

• Traditional two-step SiNx ALD using Si2Cl6 and N2 plasma yields poor film quality with rapid oxidation.
• Nonhydrogenated chlorosilanes often result in SiNx films with undesirable properties.

Purpose of the Study:

• To develop an improved SiNx atomic layer deposition (ALD) process.
• To enhance film conformality and reduce hydrogen content in SiNx films.
• To investigate the reaction mechanisms during SiNx ALD using in situ surface infrared spectroscopy.

Main Methods:

• A novel three-step SiNx ALD process was developed using Si2Cl6, CH3NH2, and N2 plasma.
• In situ surface infrared spectroscopy was employed to monitor surface reactions.
• The process was optimized at 400 °C.

Main Results:

• The three-step ALD process significantly improved SiNx film quality and conformality on high-aspect-ratio nanostructures (approx. 90%).
• Atomic hydrogen content in the SiNx films was reduced to approximately 12%.
• A growth per cycle of approximately 0.9 Å was achieved at 400 °C.

Conclusions:

• The intermediate CH3NH2 step is crucial for forming Si-N-Si bonds and improving film properties.
• The developed ALD process offers a pathway to high-quality SiNx films for advanced applications.
• Understanding surface reactions is key to optimizing ALD processes.