Publication Date
8-1-2025
Date of Final Oral Examination (Defense)
7-17-2025
Type of Culminating Activity
Thesis
Degree Title
Master of Science in Materials Science and Engineering
Department
Materials Science and Engineering
Supervisory Committee Chair
Elton Graugnard, Ph.D.
Supervisory Committee Member
David Estrada, Ph.D.
Supervisory Committee Member
Jeffrey W. Elam, Ph.D.
Abstract
Atomic layer etching (ALE) has emerged as a pivotal technique in the precise fabrication of two-dimensional (2D) materials, particularly molybdenum disulfide (MoS2), which holds promise for energy-efficient semiconductor devices due to its large band gap and high mobility in monolayer form. The ability to precisely etch amorphous and crystalline MoS2 films provides a pathway for controlling thickness, which is critical to achieving desired electrical and optical properties. Previous studies used MoF6 and H2O in thermal ALE of MoS2. Here, we report studies of alternate fluorination and oxygenation sources and evaluate their impact on thermal ALE of amorphous MoS2 films. Oxygen sources included water, oxygen, and ozone, while fluorine sources included HF/pyridine and MoF6. Etch per cycle (EPC), morphology, and surface chemistry post ALE were characterized using spectroscopic ellipsometry, atomic force microscopy, and X-ray photoelectron spectroscopy. Results indicate HF with the combination of H2O showed no signs of etching at temperatures between 200 to 300 °C, while HF and O3 showed an EPC of 0.037 ± 0.002 nm and an average mass loss per cycle of 25 ± 13 ng/cm^2 at 200 °C. Further, MoF6 and O3 at 200 °C exhibited a substantially higher EPC of 0.9 ± 0.1 nm and an average mass loss of 126 ± 70 ng/cm2 per ALE cycle. The results indicate a strong influence by the fluorine and oxygen sources on the etch behavior for MoS2. The high EPC for MoF6 and O3 at 200 °C appears to be continuous etching rather than ALE, which involves self-limiting chemistry. Etching with MoF6 and O3 at 150 °C exhibited traits of self-limiting surface chemistry, consistent with an ALE process. These results provide insights into precursor options for tailoring the etching processes needed to integrate MoS2 into high volume semiconductor manufacturing.
DOI
https://doi.org/10.18122/td.2433.boisestate
Recommended Citation
Tenorio, Jacob Anthony, "Influence of Fluorination and Oxygenation Sources on the Thermal Atomic Layer Etching of Amorphous MoS2" (2025). Boise State University Theses and Dissertations. 2433.
https://doi.org/10.18122/td.2433.boisestate