Towards the Atomic Limit in Nanoscale Manufacturing

Dr. Haozhe ‘Harry’ Wang

KNI Prize Postdoctoral Fellow at California Institute of Technology, USA

The figures of merit of advanced devices based on semiconductors and quantum materials are increasingly limited by imperfections introduced in nanoscale manufacturing. Further technological advances demand both additive and subtractive manufacturing methods with vastly improved precision compared to typical approaches.

In this seminar, I will first describe our development of Angstrom-precise additive manufacturing for 2D materials leveraging chemical vapor deposition and ‘smart’ processes. While the number of exciting physical phenomena observed in bilayer graphene increases, a significant gap persists in transforming these discoveries into practical applications, owing to the small-scale superlattices obtained via top-down approaches. We realized layer-by-layer (that is, Frank-van der Merwe) manufacturing in large-scale bilayer graphene, with no island impurities, which is unprecedented in any van der Waals-stacked semiconductors. After growth, we utilized the Marangoni effect, also known as the ‘tears of wine’, to enable ‘autonomous’ transfer by building a surface tension gradient in transfer liquids. Furthermore, machine learning is adopted to assist spectroscopy, enabling the ‘smart’ characterization following Angstrom-precise manufacturing.

In addition, I will showcase an application of single-layer graphene to address one of the key challenges in integrated circuit packaging – the reliability of bonding (welding) technology. Specifically, the bonding temperature is lowered by introducing nano-cone features to increase local stress. A one-atomic-thick graphene interlayer on the Cu was introduced to prevent the diffusion to form the intermetallic compounds that are harmful to the reliability of the bonding. The proposed scheme inherently solves both high bonding temperature and interfacial diffusion issues. Interestingly, the insertion of Angstrom-scale graphene on the Cu nanostructures allows us to observe a macro-scale phenomenon where reliable bonding joints are manufactured at a bonding temperature as low as 150 ºC, which is also the lowest reported value to date for Cu bonding technology.

 At last, I will discuss our recent progress in the subtractive manufacturing of nanomaterials in monolayer precision for quantum applications. Our development of atomic layer etching, a reversal process of conventional atomic layer deposition, enables layer-by-layer engineering of the surfaces of nanomaterials to remedy Angstrom-scale imperfections in photonic and electronic quantum devices.

Haozhe ‘Harry’ Wang is currently KNI Prize Postdoctoral Fellow at the California Institute of Technology (Caltech). His research focuses on atomic layer etching (ALE) technology to engineer surface imperfections with Angstrom precision. Haozhe ‘Harry’ Wang received his BSc and MSc at Shanghai Jiao Tong University. Prior to joining Caltech, he obtained his Ph.D. at Massachusetts Institute of Technology (MIT), working on the scalable synthesis and application of 2D materials.

https://columbiauniversity.zoom.us/j/99613802394?pwd=MmY3dHhpL01UZ2IvTUxMTWtUQXhRUT09