A process technology has been developed that can uniformly and stably deposit a film of atomic layer thickness at low temperatures.

UNIST (President Yong-Hoon Lee) Graduate School of Semiconductor Materials and Components and the Department of New Materials Engineering, Professor Jun-Ki Seo’s research team, together with Professor Ding Feng from the Shenzhen Advanced Institute of Science and Technology, Chinese Academy of Sciences, Professor Seong-Kyu Kim from Sejong University, and Professor Chang-Wook Jeong from UNIST, announced on the 2nd that they have developed a thin-film deposition process that can deposit thin films on large areas such as wafers at a low temperature of 200 degrees using metal-organic chemical vapor deposition (MOCVD) using a customized process for each tin-cellaide material.

The organic metal chemical vapor deposition method is a next-generation process with excellent precision that utilizes gaseous precursors that participate in chemical reactions. It can deposit thin films on large areas, such as wafers that are semiconductor materials. However, in order to synthesize the reactants, the ligands had to be decomposed at high temperatures of over 650 degrees.

The research team applied the organic metal chemical vapor deposition method to two types of tin selenide materials (SnSe2, SnSe) that are being studied in various fields such as electronic devices, optical devices, and thermoelectric devices. Both types of tin-selenide thin films were uniformly deposited at a thickness of several nanometers on a wafer scale.

The research team physically separated the temperature range where the ligand decomposes and the temperature range where the thin film is deposited in order to perform deposition at a low temperature. They adjusted the ratio of tin and selenium precursors used in the deposition method and also precisely controlled the flow rate of argon gas that carries the precursor.

The thin film manufactured in this way has high crystallinity. It is arranged in a regular manner. The phase and thickness of the material can also be controlled during the deposition process. Even though the organic metal chemical vapor deposition method was used, it was uniformly deposited regardless of the substrate type at a low temperature of about 200 degrees.

The research team applied the developed process to the entire wafer. Both types of thin films were chemically unchanged and had high crystallinity. Atomic layer-level thickness control and uniform deposition were also possible. This shows that the developed process can be applied to a wide range of electronic devices.

First author and researcher Kim Seong-yeon said, “This study overcame the limitations of existing organic metal chemical vapor deposition methods and was able to deposit multiphase materials over a large area without changing their chemical compositions.” He added, “It will likely be applicable not only to future research on tin-selenide thin films but also to various electronic devices.”
Professor Seo Jun-ki said, “This study is a case that presents a process strategy based on unique thermodynamic and dynamic behavior according to the phase of semiconductor thin film materials,” and added, “It will accelerate research on electronic device applications as it succeeded in developing a customized process for next-generation semiconductor materials.”

This study was published online on April 10 in the international academic journal in the field of nanoscience, 'Advanced Materials.' The research was conducted with the support of the Ministry of Science and ICT, the National Research Foundation of Korea’s Excellent New Researcher Project, the Next-Generation Intelligent Semiconductor Technology Development (Device) Project, and Ulsan National Institute of Science and Technology.