Introduction
TSMC are at the forefront of semiconductor technology, constantly pushing the boundaries of innovation to meet the evolving demands of the industry, example being the upcoming IEDM using MoS2 material, a 2D material known for powerful properties. A particularly exciting development within this field involves the utilization of ultra-thin transition metal dichalcogenides (TMDs), specifically MoS₂, as the channel material in NMOS nanosheets. Led by a collaborative research team from TSMC, National Yang Ming Chiao Tung University, and National Applied Research Laboratories, their groundbreaking study titled “Monolayer-MoS₂ Stacked Nanosheet Channel with C-type Metal Contact” by Y-Y Chung et al. represents a significant leap forward in nanosheet scaling using TMDs.
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ALD Deposition for MoS₂ Synthesis by TSMC at IEDM
Atomic Layer Deposition (ALD) has emerged as a precise and uniform synthesis technique for MoS₂, particularly for semiconductor applications on large-scale wafers. The choice of precursors is of paramount importance in achieving optimal deposition characteristics.
In this context, Mo (CO)₆ and H₂S have been identified as primary precursors for molybdenum and sulfur components. These precursors exhibit self-limiting growth behavior within a specific temperature range, leading to uniform MoS₂ layers.
One notable accomplishment is the successful upscaling of ALD for 300 mm SiO₂/Si wafers, demonstrating its potential for industrial-level manufacturing. Maintaining uniformity and thickness control on such wafers highlights the importance of selecting the right precursors for optimal deposition results.
Researchers have explored different molybdenum sources, like MoCl₅ and MoF₆, and various sulfur precursors, such as (CH₃)₂S. These choices directly affect the properties of the resulting MoS₂ film in the ALD process.
These ALD advancements have the potential to integrate MoS₂ into next-generation electronic devices, contributing to the ongoing evolution of semiconductor technology.
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Thermal Atomic Layer Etching (ALE) for MoS₂ by TSMC at IEDM
While deposition methods for MoS₂ are abundant, etching processes have been comparatively scarce. However, recent research by Elton Graugnard and his team introduces a thermal Atomic Layer Etching (ALE) technique for MoS₂.
This innovative approach leverages MoF₆ for fluorination, alternated with H₂O exposures, to etch both crystalline and amorphous MoS₂ films.
The etching process is temperature-dependent, with a significant increase in mass change per cycle as the temperature rises. The mechanism involves a two-stage oxidation of Mo, producing volatile byproducts.
The resultant etch rates have been established for different films, and post-etch annealing has been shown to render crystalline MoS₂ films.
The thermal MoS₂ ALE offers a promising low-temperature method for embedding MoS₂ films in large-scale device manufacturing.
TSMC will display this breakthrough at IEDM, opening up new possibilities for etching processes and the development of MoS₂-based electronic devices.
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Conclusion
Significant advancements are occurring in MoS₂ semiconductor technology, including precise synthesis through ALD and the Atomic Layer Etching.
These innovations have the potential to revolutionize the semiconductor industry by integrating MoS₂ into next-generation electronic devices.
Careful precursor selection and etching method development play a crucial role in achieving optimal results. As technology evolves, MoS₂’s applications in semiconductors are poised to grow, ushering in a new era of electronic devices with improved performance and efficiency.
[1] https://www.ieee-iedm.org/press-kit
