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Laser lithography system could speed 3D nanofabrication

Researchers have developed a parallel peripheral-photoinhibition lithography (P3L) system capable of high-efficiency nanoscale fabrication.

Peripheral photoinhibition direct laser writing (DLW) is a lithography technique used to fabricate intricate 3D nanostructures widely employed in photonics and electronics. 

The technique typically uses two beams, one to excite a substrate and cause polymerization, and the other to inhibit and quench the excitation at the edges.

However, the throughput of such systems is often limited, and while this has been addressed in part through the use of multifocal arrays, computing the beams can be both time- and memory-intensive.

In Advanced Photonics the scientists, from Zhejiang University, have described their own take on a P3L system that enables the printing of complex 3D nanostructures at high scanning speeds.

Their system consists of a physical arrangement of eight modules. It begins with two printing channels, consisting of an excitation solid spot and a doughnut-shaped inhibition beam. The two beams are first stabilised and are then split into two sub-beams using a polarisation filter. This allows the individual on–off control of each sub-beam through an acoustic-optical modulator. Next, the two sub-beams are recombined to reform the excitation and inhibition beams. The beams are then modulated using spatial light modulators. Finally, the two beams are combined and passed through a microscope, after which they focus on the substrate as two spots. Adjusting the position and separation of the two spots can be done simply, according to the researchers. 

The individual control of each focussed sub-beam enables the printing of nonperiodic and complex patterns simultaneously, without compromising on scanning speed. The parallel scanning feature of the system also reduces the time and cost required to fabricate large-scale, complex structures and patterns. Overall, according to the researchers, their new P3L system achieves a lithography efficiency twice that of conventional systems, regardless of whether the structure is uniform or complex. 

The researchers confirmed the feasibility and potential of their system by fabricating a variety of nanostructures, including a 2D sub-40nm nanowire and a sub-20nm-thick suspended nanowire. After that, the researchers created two rows of alphabet patterns by printing dots – each 200nm apart. Finally, they fabricated 3D structures, including nonperiodic cubic frames, hexagonal grids, wire structures, and spherical architectures, all demonstrating exceptional resolution.

Discussing the future potential of the published work, senior author Xu Liu said: “Multifocus parallel scanning and peripheral photoinhibition have the ability to overcome the current challenges in DLW optical fabrication and enhance the fabrication of blazed gratings, microlens arrays, microfluidic structures, and metasurfaces. The proposed system could, furthermore, facilitate the realisation of portable, high-resolution, high-throughput DLW. Based on these results, it is clear that the proposed P3L system will serve as a useful tool for the development of a wide range of fields that use nanotechnology.”

The Advanced Photonics article can be read here.


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