Semiconductor industries have grown exponentially according to Moore’s law over the past half-century, which has led human society into theera of information and communicationswith revolutionary economic and social impact. In recent years, however,Moore’s law has gradually come to an enddue to ever-increasing production costs, technology barriers, and fundamental physics limits. Most current semiconductor manufacturing processes encounter challenges to meet the future demands of ever-growing transistor performance and integration density, which lead to the crisis for the future development of emerging technologies, such as artificial intelligence (AI), 5G/6G, internet of things (IoT).To date,two critical development trends are gradually emerging and recognized to have the potential to address the above challenges. First, traditional 2D planar semiconductor devices and manufacturing processes are gradually evolving towards 3D semiconductor integrated devices and manufacturing processes. Second, single silicon-based semiconductor devices and integrated manufacturing processes are gradually evolving towards the integrated assembly of more functional semiconductor materials and high-density integrated manufacturing, which is expected to expand the integrated circuits into multi-functional integrated systems, such as optoelectronic chips, intelligent integrated systems that integrate sensing, computing, self-actuating modules, etc. Hence the research on how to achive the fabrication of high-precision heterogeneous 3D semiconductor micro-nano structures and functional devices is of great significance for the future development of 3D integrated systems with higher functionality and integration density. Among the numerous technologies for 3D manufacturing,femtosecond laser-induced 3D printing based on two-photon polymerization(TPP) has evolved as a prospective manufacturing technique due to its combination of real 3D fabrication capability and sub-micron spatial resolution. The development of functional photoresins has always been a key aspect in supporting TPP technology toward application. However, the conventional approach to achieve functional photoresins is to dope functional nanomaterials into organic resins to achieve 3D micro-nano structures with different functional properties. Such methods require a photoresin containing highly loaded nanoparticle dopants which can cause severe light absorption and/or scattering effects during TPP processing, resulting in unavoidable particle agglomeration, micro-explosion, and relatively low spatial resolution. Therefore, the development of a high-performance photoresin for 3D semiconductor nanofabrication remains a great challenge.
To address this challenge, Prof. Wei Xiong’s group at Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology has developed a class of versatile and customizable metal-bound composite photoresins using metal-organic framework (MOF) precursors. Through TPP femtosecond laser 3D printing and subsequent pyrolysis process, the additive manufacturing of 3D nano-architected ZnO and Co3O4semiconductors was achieved. In addition, the 2D and 3D micro-UV detectors based on ZnO were produced to demonstrate the possibility of realizing 3D semiconductor devices by this method.
The versatile and customizable metal-bound composite photoresin proposed by Prof. Xiong’s research team can be prepared from a variety of MOF precursors and resin monomers (such as acrylates, epoxy resins, and water-soluble monomers), in which the metal ions are bonded with the acrylic groups through coordination bonds to form the metal acrylate. The metal acrylate can act as a monomer to achieve polymerization in the TPP processing due to its unsaturated vinyl group. Therefore, the metal ions in the prepared polymer are covered or attached to the long organic chains through ionic/coordination bonds to eliminate the loss of metal ions during the development process, ensuring the shape fidelity of subsequent pyrolysis structure. Based on this principle, Prof. Xiong’s team explored two MOF precursors (ZIF-8 and ZIF-67) to prepare metal-bound composite photoresins containing zinc and cobalt, respectively. Complex 3D microstructures of ZnO and Co3O4with high spatial resolution (170 nm), high shape fidelity, and high surface quality were produced by TPP femtosecond laser 3D printing and pyrolysis process. Meanwhile, the potential of this method for 2D and 3D device fabrication was also demonstrated, and 2D and 3D micro-UV detectors based on ZnO were produced. This research opens a way for the fabrication of a variety of functional materials such as composite metal oxides and even metal micro-nano structures, which is expected to promote the development of 3D integrated functional devices in the fields of micro-nano photonics, electronics, MEMS, and energy storage.
The related work was published in Advanced Materials Technologies (DOI: 10.1002/admt.202101230) with the title “3D Printing Nano-Architected Semiconductors Based on Versatile and Customizable Metal-Bound Composite Photoresins”. Dr. Jingwei Liu of Huazhong University of Science and Technology is the first author of this paper, and Prof. Wei Xiong of Huazhong University of Science and Technology is the corresponding author of this paper. The research was supported by the National Key R&D Program of China (2018YFB1105400) and the National Natural Science Foundation of China (61774067 and 61805094).
