In the relentless pursuit of miniaturization, the field of nanofabrication has witnessed significant advancements, driven by the demand for higher component density and performance in chip manufacturing, nanophotonics, and quantum devices. A recent article published in Engineering, titled “Advancing Manufacturing Limits: Ultrafast Laser Nanofabrication Techniques,” provides an in-depth overview of the latest developments in ultrafast laser nanofabrication, highlighting both near-field and far-field laser techniques and addressing the challenges that lie ahead.

The article, authored by Zhenyuan Lin, Lingfei Ji, and Minghui Hong, notes that traditional nanofabrication techniques such as electron beam lithography and nanoimprint lithography have achieved manufacturing resolutions at the tens-of-nanometers scale. However, the semiconductor industry's push for even smaller feature sizes, exemplified by the current 3 nm process technology and the future 2 nm process, necessitates further innovation in material processing techniques. Lasers, introduced in 1960, have long been considered a viable technology for maskless nanolithography and direct 3D writing. Yet, nanopatterning beyond the optical diffraction limit remains a significant challenge in far-field and atmospheric environments.

The authors delve into the mechanisms and applications of optical near-field laser nanomanufacturing, which manipulates the optical field via discontinuous interfaces with nanoscale dimensions. This technique, which relies on evanescent waves, has demonstrated the ability to create nanostructures with feature sizes as small as 11 nm. However, the short working distance and sensitivity to surface disturbances limit its practicality for large-scale applications. To overcome these limitations, various precision controls, such as optical tweezers and atomic force microscopy, have been employed to enhance the resolution and working distance of near-field laser processing.

In contrast, optical far-field laser nanomanufacturing offers simpler optical setups and broader material applicability, making it more suitable for industrial-scale production. Despite being constrained by the diffraction limit, recent advancements in far-field laser techniques, such as stimulated emission depletion (STED), multiphoton absorption, and optical far-field-induced near-field enhancement (O-FIB), have enabled feature sizes as small as tens of nanometers. For instance, STED has been used to create 3D nanoengravings with a minimum size of approximately 55 nm, while multiphoton absorption with a femtosecond laser has achieved a feature size of 26 nm.

The article also highlights several innovative strategies that have further pushed the boundaries of far-field laser nanofabrication. These include the use of dual-beam overlapping and backscattering interference crawling, which have demonstrated the potential to achieve sub-10 nm feature sizes. For example, dual 405 nm nanosecond laser overlapping has produced a minimum linewidth of 5 nm, while dual orthogonal polarization overlapping of an 800 nm femtosecond laser has enabled the fabrication of 12 nm nanostructures on silicon surfaces.

Despite these advancements, the authors identify several challenges that remain unresolved. Achieving nanometric high-aspect-ratio processing is one such challenge, as the diffraction-limited propagation of light conflicts with the need for uniform axial and subwavelength lateral energy deposition. Additionally, the instability of the nonlinear threshold phenomenon limits the processing size to approximately 10 nm. To address these issues, researchers are exploring solutions such as axially stretched or multifocus beam irradiation and dicing technologies based on Bessel–Gaussian beams.

The article underscores the significant progress made in ultrafast laser nanofabrication while emphasizing the need for further research to overcome existing limitations. The development of new laser sources, pulse-shaping technologies, and parallel laser beam manufacturing techniques holds promise for achieving high-resolution, high-efficiency, and large-scale nanofabrication. As the semiconductor industry continues to push for smaller and more complex devices, the advancements in ultrafast laser nanofabrication will undoubtedly play a crucial role in shaping the future of nanotechnology.

The paper “Advancing Manufacturing Limits: Ultrafast Laser Nanofabrication Techniques,” is authored by Zhenyuan Lin, Lingfei Ji, Minghui Hong. Full text of the open access paper: https://doi.org/10.1016/j.eng.2025.03.017. For more information about Engineering, visit the website at https://www.sciencedirect.com/journal/engineering.