Polarized holographic lithography system for high-uniformity microscale patterning with periodic tunability

Periodic microscale array structures play an important role in diverse applications involving photonic crystals and diffraction gratings. A polarized holographic lithography system is proposed for patterning high-uniformity microscale two-dimensional crossed-grating structures with periodic tunability. Orthogonal two-axis Lloyd’s mirror interference and polarization modulation produce three sub-beams, enabling the formation of two-dimensional crossed-grating patterns with wavelength-comparable periods by a single exposure. The two-dimensional-pattern period can also be flexibly tuned by adjusting the interferometer spatial positioning. Polarization states of three sub-beams, defining the uniformity of the interference fringes, are modulated at their initial-polarization states based on a strict full polarization tracing model in a three-dimensional space. A polarization modulation model is established considering two conditions of eliminating the unexpected interference and providing the desired identical interference intensities. The proposed system is a promising approach for fabricating high-uniformity two-dimensional crossed gratings with a relatively large grating period range of 500–1500 nm. Moreover, our rapid and stable approach for patterning period-tunable two-dimensional-array microstructures with high uniformity could be applicable to other multibeam interference lithography techniques.

Fabrication of a Two-Dimensional Diffraction Grating with Isolated Photoresist Pattern Structures

This paper presents a fabrication method of a two-dimensional (2D) diffraction grating with isolated photoresist pattern structures in order to reduce fluctuation in the grating pitch due to the thermal expansion. At first, theoretical calculations for the fabrication of a 2D diffraction grating with isolated photoresist pattern structures are carried out to estimate the influences of exposure and development time on the pattern structures to be fabricated through the pattern exposure and development process. A diode laser-based compact non-orthogonal two-axis Lloyd’s mirror interferometer system designed in a size of 500 mm × 840 mm is then built on a breadboard for stable mask-less interference lithography. Basic performances of the newly developed compact interferometer system are evaluated through the fabrication of 2D diffraction gratings to demonstrate the feasibility of the theoretical calculations and the developed lithography system.