Maskless lithography is an increasingly popular method of micro-patterning in research settings. This technical note presents methods for controlling the feature size and sidewall profile of thick-resist features, when exposed using maskless direct imaging systems. Maskless lithographic systems use focussed, uncollimated light, and therefore do not naturally produce the vertical sidewalls that may be required for soft lithography and other secondary processes. We explore exposure dose energy, placement of the focal plane, and the use of multiple focal planes to optimize features in thick (∼800 μm) SU-8 resist. We find that placing the image plane at the mid-height of the resist film produces structures with a good compromise of sidewall angle and feature sharpness. We also find that using multiple exposures at multiple heights can produce sidewall angles that are stable over a range of dose energies.

无掩模光刻是研究环境中越来越流行的微图案化方法。本技术说明介绍了在使用无掩模直接成像系统曝光时控制厚抗蚀剂特征的特征尺寸和侧壁轮廓的方法。无掩模光刻系统使用聚焦的非准直光，因此不会自然地产生软光刻和其他二次工艺可能需要的垂直侧壁。我们探索了曝光剂量能量、焦平面的放置以及使用多个焦平面来优化厚（~800 μm) SU-8 抵抗。我们发现将图像平面放置在抗蚀剂膜的中间高度会产生侧壁角度和特征清晰度的良好折衷的结构。我们还发现在多个高度使用多次曝光可以产生在一定剂量能量范围内稳定的侧壁角度。