A technology has been developed to precisely stack next-generation semiconductor materials at the atomic layer level. It is expected to be utilized in various electronic devices as it can be applied to nano-level 3D structures even at low temperatures.

A research team led by Professor Jun-Ki Seo of the Graduate School of Semiconductor Materials and Components and the Department of Materials Science and Engineering at UNIST (President Yong-Hoon Lee) announced on the 1st that, together with a research team led by Professor Bong-Keun Song of Hongik University and Professor Hoo-Young Jeong of UNIST, they have developed a thin film deposition process using atomic layer deposition (ALD) in which tellurium atoms are regularly arranged at a low temperature of 50 degrees.

Atomic layer deposition is a next-generation thin film processing method that enables thin, uniform film coating on the surface of a three-dimensional structure at low process temperatures and precise thickness control.

On the other hand, to apply it to next-generation semiconductors, such as atomic layer semiconductors, a process temperature of over 250 degrees and additional heat treatment work of over 450 degrees is generally required.

The research team applied atomic layer deposition to tellurium, a single-element atomic layer semiconductor being studied in various fields such as electronic devices and thermoelectric materials. They successfully fabricated high-quality thin films at a low temperature of 50 degrees without a heat treatment process. The manufactured thin film has atoms arranged regularly, allows for thickness control of nanometers (one billionth of a meter) or less, and is uniformly deposited on all surfaces.

The research team utilized two acid-basic precursors to enhance reactivity at low temperatures. They additionally utilized a co-reactant, a material for high surface reactivity and stability, and repeatedly injected the precursors in shorter intervals. This allowed them to successfully fabricate dense and high-density thin films compared to conventional methods that deposit low-density, discontinuous grains.

Using the developed manufacturing process, a tellurium thin film was applied across an entire 4-inch (100mm) wafer. The film enabled atomic-layer-level thickness control and uniform deposition. It was confirmed that deposition is possible even on vertical three-dimensional structures required for high device integration. This can be utilized in various electronic devices such as transistors, rectifiers, and selectors.

"This study overcame the limitations of existing thin film deposition methods and implemented a new deposition method for tellurium called atomic layer deposition," said researcher Chang-Hwan Kim, the first author. "Since tellurium thin films can be uniformly deposited even in complex three-dimensional device structures, they will be applicable to various electronic devices."

Professor Seo Jun-ki of the Graduate School of Semiconductor Materials and Components and the Department of Materials Science and Engineering stated, “This research was able to satisfy all the keywords required in semiconductor deposition processes, such as low temperature, large area, and high-quality synthesis.” He added, “The fact that we succeeded in realizing ‘unconventional’ two-dimensional novel materials and devices by adding new process elements to traditional deposition methods opens up possibilities for various application studies.”

This study was published online in the international nanoscience journal 'ACS Nano' on July 11 and was selected as a cover article in recognition of its outstanding results. The research was conducted with support from the Ministry of Science and ICT, the National Research Foundation of Korea (including the Excellent Young Researcher Program), the Korea Institute of Industrial Technology Evaluation and Management, and the Korea Semiconductor Industry Association.