Thermal Atomic Layer Etching of MoS2 Using MoF6 and H2O.
Jake Soares1, Anil U Mane2, Devika Choudhury2
1Micron School of Material Science and Engineering, Boise State University, 1910 University Dr., Boise, Idaho83725, United States.
Chemistry of Materials : a Publication of the American Chemical Society
|February 23, 2023
Summary
A new thermal atomic layer etching (ALE) process precisely removes molybdenum disulfide (MoS2) films using MoF6 and H2O. This scalable method enables low-temperature integration of 2D MoS2 for advanced electronic devices.
Area of Science:
- Materials Science
- Nanotechnology
- Chemical Engineering
Background:
- Two-dimensional (2D) layered materials like molybdenum disulfide (MoS2) are crucial for next-generation electronics and optoelectronics.
- Scalable and precise fabrication processes, including etching, are essential for integrating 2D materials into semiconductor manufacturing.
- Existing removal processes for 2D materials are less developed compared to deposition techniques.
Purpose of the Study:
- To develop and characterize a thermal atomic layer etching (ALE) process for molybdenum disulfide (MoS2) films.
- To investigate the etching mechanism and reaction kinetics of MoS2 using MoF6 and H2O.
- To demonstrate the potential of this ALE process for fabricating crystalline, few-layer MoS2 films for device applications.
Main Methods:
- Development of a thermal ALE process utilizing alternating exposures of molybdenum hexafluoride (MoF6) and water (H2O).
- In situ characterization using quartz crystal microbalance (QCM), Fourier transform infrared (FTIR) spectroscopy, and quadrupole mass spectrometry (QMS).
- Ex situ analysis including ellipsometry, X-ray reflectivity, and transmission electron microscopy (TEM) to determine etch rates and film properties.
Main Results:
- The thermal ALE process effectively etches both amorphous and crystalline MoS2 films.
- Etch rates of 0.5 Å/cycle for amorphous and 0.2 Å/cycle for annealed films were achieved.
- In situ studies elucidated the reaction mechanism involving fluorination and oxidation, leading to volatile byproducts like MoF2O2 and H2S.
Conclusions:
- A novel fluorination-based thermal ALE process for MoS2 has been successfully demonstrated.
- This low-temperature process offers precise control over material removal, enabling the fabrication of high-quality MoS2 films.
- The developed ALE technique is suitable for high-volume manufacturing of 2D MoS2-based electronic and optoelectronic devices with tight thermal budgets.
