Three-Dimensional Micro/Nano Patterning of Phase Change Materials for Multi-Level Optical Elements

Owing to their exceptional tunability and reconfigurability, three-dimensional (3D) nanostructured functional devices based on phase change materials (PCMs) will become increasingly important in fields such as multilevel optical elements. The conventional fabrication method involves multiple alignment and overlay steps to etch the functional 3D structures layer by layer. However, with the increasing complexity of device structures and the demand for higher fabrication efficiency, there is an urgent need for a more precise, flexible, and simpler fabrication method. In this study, based on laser heat-mode lithography, a fabrication method for functional nanoscale structures based on the PCMs is proposed that does not require overlay or pattern transfer. Furthermore, an analytical process model was established to determine the relationship among the height of the fabricated 3D nanoscale structures, exposure dose, and development time. The fitted surface matches the experimental results. Exposure and development strategies are designed using this model. Subsequently, microstep-like structures featuring a maximum of 22 steps and a precision of 10 nm were successfully fabricated. The experimental results are in good agreement with the design. The fabrication accuracy was further optimized based on the preliminary results. We introduced an innovative multidimensional control strategy that employs the exposure dose for coarse regulation and exposure repetitions for fine regulation. This approach resulted in a reduction of 8.48 nm in the root-mean-square error (RMSE) and 30.54% in the coefficient of deviation (CVb), respectively. Finally, a series of potentially functional 3D nanostructures for multilevel optical elements based on PCMs was successfully fabricated. Furthermore, the application prospects of this fabrication method in data storage were discussed. The fabrication results demonstrate that this simple and efficient 3D structuring method exhibits significant application potential for high-end customized nanodevices in advanced fields such as dynamic imaging and data storage.