Large-scale (4-inch) plasma etching technology for the next generation of two-dimensional semiconductor mass production

(Nanowerk News) Breakthrough plasma etching technology has been developed that holds promise for forming bedrock for the industrial production of molybdenum disulfide (MoS2), the next generation of two-dimensional (2D) semiconductors. This large-scale (4-inch), highly uniform, and defect-free technology stands as a very important advance.

The joint research team led by Hyeong-U Kim, Senior Researcher of the Department of Plasma Engineering at the Korea Institute of Machinery and Materials (KIMM) and Professor Taesung Kim of Sungkyunkwan University, announced that the team has successfully developed a large-scale. scale (4-inch) atomic layer etching technology for MoS2a next-generation semiconductor, using plasma-based reactive ion etching (RIE) equipment.

This study, in which Senior Researcher Muyoung Kim and Postdoctoral Researcher Changmin Kim of KIMM participated as first co-authors, has been published as the cover article for the February 2023 issue of Material Chemistry (“First Principle Calculations of Guided High Purity Coating Control 4 in. MoS2 by Plasma RIE”).

As the line width of conventional silicon-based semiconductors decreases gradually, it becomes necessary to control the manufacturing process at the atomic level. However, it is difficult to process single atomic layers of silicon-based semiconductors complexly due to the tunneling effect* that occurs during the accumulation of atomic layers. Therefore, it becomes necessary to develop new materials for the advancement of the next generation of semiconductors.

Meanwhile, with MoS2, it is possible to stably control the movement of electrons without tunneling effects, even in structures that are 1 nanometer (nm) thick. Therefore, MoS2 has received attention as a promising new material capable of overcoming the limitations of silicon-based semiconductors.

However, even though MoS2 has better electrical and physical properties compared to silicon even in terms of atomic layer thickness, the development of MoS2based semiconductors remain at the basic research stage in the laboratory because of the difficulty of forming MoS2 uniform on a large scale for mass manufacture.

In particular, although it is required to form layers that are one atom thick to achieve semiconductor precision, the commercialization of MoS is likely2 not proven due to lack of technology to precisely etch MoS2 into atomic layers.

In this study, a process that allows large-scale (4-inch) etching of MoS.2 with the desired atomic layer thickness using two plasma-enhanced chemical vapor deposition (PECVD) and RIE plasma processes have been developed for the first time in the world. As a result, research has opened up new horizons for the industrial utilization of MoS2semiconductor based.

The plasma etching process has received great attention as the most likely technology that can break through the limits of conventional etching processes. However, one of the main drawbacks of plasma etching is that impurities (fluorine, “F”) remain on the surface of the semiconductor after the process, and therefore, additional steps are required to remove these residues. For this reason, the design of highly sophisticated plasma processes is a longstanding desire to fulfill atomic level precision and very high purity in MoS2 layer.

In the latest study, the research team solved the problem by adopting a computational filtering system based on density functional theory (DFT). Muyoung Kim, Ph.D., one of the first co-authors, proposed a state-of-the-art computational screening system that simulates surface reactions of candidate gases and combines the best gas mixtures for ultrafine process qualities. One important advance of this approach is that screening systems greatly reduce the development time and cost of the plasma process, compared to conventional experiment-based manufacturing. Specifically, he investigated the atomistic mechanisms of surface reactions and identified the role of process gases on MoS2 substrate, which rationalizes the gas mixture recipe (Ar + O2 + CF4).*

Senior Researcher Hyeong-U Kim from KIMM who led the research said, “In recent days, future industries such as AI, GPT, IoT, self-driving, and cloud, etc. All of them fall into the category of non-memory sectors. Therefore, even Samsung Electronics, the memory market leader, is also focusing its investment on the foundry sector. The semiconductor memory manufacturing process focuses on the mass production of limited items, whereas the casting process seeks limited production of a wide variety of items. Therefore, processes that are able to control fine line widths are becoming increasingly important, especially in casting processes.”

Kim added, “To overcome integration limitations, it is important to develop processes where even single atomic layers can be controlled, as demonstrated in our recent research. Therefore, a lot of research has been done since about a decade ago. However, prior to our latest study, no researcher had been able to demonstrate the possibility of uniformly and reproducibly etching atomic layers on a large scale.”