Aberration correction for improving performance of DMHL system

摘要

Dynamic maskless holographic lithography (DMHL) is a new micro-manufacturing technique that has no moving parts. The laser light used for patterning is directed in all three dimensions with a hologram displayed on a liquid-crystal spatial light modulator (SLM). Optical aberrations, like spherical aberration due to refractive index mismatch between the photoresist and the immersion oil of the high-NA objective or astigmatism due to the deformations in the surface of the SLM, can degrade the performance of the system. Degraded performance includes a decrease in potential patterning volume and pattern fidelity and an increase in patterning time. This paper presents a way to correct for these aberrations using Zernike polynomials. The optimal Zernike coefficients are found by maximizing a sharpness metric. The effect of aberration correction on the DMHL process is quantified by measuring the patterning volume. DMHL manufactured features made with this aberration correction method show a marked improvement over features made without correction. It is even possible to correct for misaligned optics with this method.