Amorphous boron nitride shows excellent insulating properties for the next generation of electronics

Graphene Flagship researchers at ICN2, Spain, and the University of Cambridge, UK, collaborated with  the Ulsan National Institute of Science and Technology (UNIST) and the Samsung Advanced Institute of Technology, Korea, to prepare and study ultrathin films of amorphous boron nitride (a-BN) with extremely low dielectric characteristics, high breakdown voltage and superior metal barrier properties. This newly fabricated material has great potential as interconnect insulator in the next generation of electronic circuits. The results of this study have just been published in Nature and represent a significant achievement for future electronics.

In the ongoing process of miniaturization of logic and memory devices in electronic circuits, reducing the dimensions of interconnects – metal wires that link different components on a chip – is crucial to guarantee fast response of the device and improve its performance.  Research efforts have been focused on developing materials with excellent insulating properties to separate the interconnects from each other.  Suitable materials should serve as a diffusion barrier against migration of metals into semiconductors and be thermally, chemically, and mechanically stable.

The quest for such a heavily insulating material has driven the semiconductor industry for at least the past 20 years. Whenever materials with the desirable characteristics were reported, they systematically failed to be successfully integrated in interconnects due to poor mechanical properties or insufficient chemical stability upon integration, causing reliability failures. 

Ultrathin amorphous boron nitride film could speed up the miniaturisation of electronics.

In a paper published today in Nature, Graphene Flagship researchers, in collaboration with the Samsung and UNIST teams in Korea, reported the large-scale synthesis of thin film of amorphous boron nitride, a material that shows record low dielectric characteristics. This suggests that a-BN is an excellent candidate for application in high-performance electronics. Researchers synthesised a-BN layers as thin as 3nm using a silicon substrate and inductively coupled plasma-chemical vapor deposition. The resulting material showed an exceptionally low dielectric constant, very close to 1. Moreover, diffusion barrier tests for this new material, conducted in very harsh conditions, also demonstrated that it can prevent metal atom migration from the interconnects into the insulator. Together with a high breakdown voltage, these characteristics make a-BN very attractive for practical electronic applications.

"Amorphous forms of layered materials such as h-BN are an emerging field of research. This discovery shows how collaborations across multiple institutions from around the world can lead to groundbreaking research with significant technological implications," says Manish Chhowalla, based at Graphene Flagship partner University of Cambridge, UK. Chhowalla, who was visiting professor of UNIST, helped to supervise the project and worked closely with the teams at UNIST and Samsung to design experiment and, interpret the results.

The group of Stephan Roche, based at Graphene Flagship partner ICN2, Spain, performed theoretical and computational calculations that allowed to explain the structural and morphological properties and the dielectric response of the a-BN film. "Our calculations helped identifying the key factors for the excellent performances of a-BN: the nonpolar character of the BN bonds and the lack of order preventing dipoles alignment. The results of this simulation have contributed to understanding the structural morphology of this amorphous material as well as to explaining its superior dielectric performances," explains Roche.

Mar García-Hernández, Graphene Flagship 'Enabling Materials' Leader, says: "This outstanding work reveals the path to follow. There is no dilemma between current technologies in foundries or new coming ones based on layered materials, the line to follow is the integration of both. A-BN can provide a solution for a long-standing problem of interconnects in CMOS integrated circuits fabrication, enabling further miniaturisation of electronic devices as it combines all the requirements sought for an ultra-low k dielectrics, with great mechanical properties, high density and chemical and thermal stability. This result encourages the search for new amorphous layered materials capable of providing new solutions for challenging problems."

Korean researchers at Samsung and UNIST led collaboration with Graphene Flagship to develop ultrathin boron nitride films with great potential for next generation electronics.

Andrea C. Ferrari, Science and Technology Officer of the Graphene Flagship and Chair of its Management Panel, adds: "Crystalline h-BN plays a key role in layered materials photonics and optoelectronics. A-BN has been investigated for many years, and this paper shows promising electronic properties when its thickness approaches that of exfoliated layered materials. The advantage is that large area deposition is much easier to achieve than for the crystalline counterpart. Amorphous ultrathin films join the family of layered and two-dimensional materials, and this paper will be the first of many to explore this new promising area of science and technology."  

Reference

"Ultra-low dielectric constant amorphous boron nitride." S. Hong, C.-S. Lee, M.-H. Lee, Y. Lee, K. Y. Ma, G. Kim, S. I. Yoon, K. Ihm, K-J. Kim, T. J. Shin, S. W. Kim, E.-C- Jeon,  H- Jeon, J.-Y. Kim, H.-I. Lee, Z. Lee, A. Antidormi, S. Roche, M. Chhowalla, H.-J. Shin, H. S. Shin. Nature, 2020, DOI: 10.1038/s41586-020-2375-9.