High dynamic wavefront stability control for high-uniformity periodic microstructure fabrication

Abstract

Periodic microstructures are widely used in optical communication, sensing, and imaging systems for their superior performance in optical modulation. Among their fabrication methods, interference lithography stands out for its high precision and uniformity, making it applicable for the fabrication of large-area periodic microstructures. However, the exposure wavefront is subject to the environmental perturbations, and the resulted drifts compromise the quality of produced photoresist mask. To address this problem, a method for exposure wavefront control aimed at high-uniformity periodic microstructures fabricating is proposed. Embedded in a dual-beam interference lithography system, the method monitors the drifts based on high-speed CCD image acquisition of the Moiré pattern generated by a reference grating, computes the magnitude of drifts based on a line-sampling cross-correlation algorithm and compensates for the drifts based on mirrors driven by piezoelectric actuators. The proposed method achieves simultaneous monitoring and controlling of phase and period drifts at a bandwidth of over 250 Hz. Experiments demonstrate that this system can effectively suppress low-frequency disturbances-induced drifts and reduce the root mean square (RMS) value of phase drifts to $9\times 10^{-3}$ grating periods and period drifts to $2.27\times 10^{-5}$ grating periods during exposure, providing a solid foundation for fabricating high-uniformity periodic microstructures.