March 17, 2020
Under long-term support from the “Taiwan Consortium of Emergent Crystalline Materials” (TCECM) program of the Ministry of Science and Technology (MOST), Taiwan, a research team at National Chiao Tung University (NCTU) collaborated with Taiwan Semiconductor Manufacturing Company (TSMC) to form an industry-university joint research team, reporting a breakthrough in the synthesis of one-atom-thick boron nitride (BN). The joint research team successfully developed a method to synthesize wafer-scale and single-crystal BN, which may be applied toward the fabrication of advanced logic integrated circuits. This outstanding fundamental research result was published in the top journal ⟪Nature⟫ in March 2020.
The semiconductor industry continues to push forward in scaling down the size of transistors to boost the efficiency of IC chips. However, silicon transistors are reaching their physical limits as it becomes difficult for electrons to travel through channels only a few nanometers thick. That is why scientists around the globe are trying to find new materials to continue transistor scaling. Two-dimensional (2D) materials, which are crystalline sheets of atoms (only approximately 0.7 nm thick) with flat surfaces free from defects, can enable electrons to flow freely through atomically thin channels. Therefore, 2D semiconductors (such as molybdenum disulfide, MoS2) are considered promising candidates to overcome this bottleneck to transistor shrinking. While electrons can flow well in 2D semiconductors, they still need 2D insulators to prevent disturbances from adjacent materials. One atomic layer thick boron nitrides (BN), the thinnest insulator in nature, has been found to be an ideal material to block such disturbances. However, previous approaches found it hard to synthesize high-quality, single-crystal and wafer-scale BN for practical applications. Under a joint research project led by Dr. Lain-Jong Li at TSMC and Prof. Wen-Hao Chang at NCTU, the paper lead author Dr. Tse-An Chen (TSMC) successfully identified a way to synthesize BN one atomic layer thick on a 2 inches wafer and demonstrated its usefulness in improving the performance of transistors made of 2D semiconductors. This success goes beyond technology development to explore fundamental research, finding the underlying physics of BN molecules on a copper surface, and eventually achieving the technology to form single-crystal BN on a full wafer.
Establishing a solid base of fundamental research is crucial for the future advance of the high-tech industry in Taiwan. The success of this joint research project also represents a milestone for industry-university collaboration in the research of fundamental science in Taiwan and meets the objectives of the TCECM program.
Professor Wen-Hao Chang
Department of Electrophysics, National Chiao-Tung University
Dr. Ting-Yang Kuo
Department of Natural Sciences and Sustainable Development,
Ministry of Science and Technology