Researchers from Tsinghua-Berkeley Shenzhen Institute (TBSI) have revealed a new holographic lithography method for processing large-area nanostructured arrays. These arrays play an important role in areas such as light-field control, molecular screening and assembly, and material deposition. However, conventional technologies are unable to simultaneously achieve high throughput, structural consistency and feature-size adjustability.
In a recent article published in the Nature journal Microsystems & Nanoengineering, Assistant Prof. Xinghui Li’s research group proposed a polarized holographic lithography system for patterning high-uniformity microscale two-dimensional (2D) crossed-grating structures with periodic tunability, and experimentally investigated the feasibility of using an orthogonal two-axis Lloyd’s-mirror interferometer. The paper was titled “Polarized holographic lithography system for high-uniformity microscale patterning with periodic tunability.”
The interferometer unit, consisting of a grating holder and two mirrors with a corner-cube-like configuration, is capable of dividing a single beam into three sub-beams as per the wavefront-division scheme to realize 2D crossed interference fringes. The group analyzed the non-orthogonality of the polarization vectors to determine precisely the interference level between any two sub-beams. A polarization-modulation model was established considering two conditions: (a) eliminating unexpected interference between the two reflected sub-beams, and (b) providing identical interference intensities between the incident sub-beam and the two reflected sub-beams. For different initial-polarization-state combinations of sub-beams 1–3, 2D crossed gratings with different grating periods of 500, 750, 1000, 1250, and 1500 nm were obtained. Importantly, the experimental results closely match the simulated interference fringes. Results showed that the systematic polarization-manipulation method as applied to the two-axis Lloyd’s-mirror interference system is a promising approach to fabricating high-uniformity 2D crossed gratings with a relatively large grating-period range of 500 to >1500 nm.
The study systematically revealed the holographic lithography mechanism based on two-axis Lloyd’s-mirror interferometer, and realized a new method for rapidly and stably processing large-area high-uniformity nanostructured arrays, which have diverse application potentials involving photonic crystals, light-field control, optical encoding, and more. In addition, this polarized holographic lithography method is expected to be applicable to other multi-beam interference-lithography techniques.
For this study, Assistant Prof. Xinghui Li is the corresponding author, while post-doctor Dr. Gaopeng Xue and TBSI master’s student Qihang Zhai are the co-first authors. Other contributors include Tsinghua SIGS Prof. Xiaohao Wang, Associate Prof. Kai Ni, Associate Prof. Qian Zhou, doctoral student Haiou Lu and master’s student Liyu Lin. This project was supported by the National Natural Science Foundation of China.
Link to full article: https://www.nature.com/articles/s41378-021-00256-z
Writer: Gaopeng Xue
Editor: Karen Lee, Manyuan Li