Rethinking mask strategies for high vertical resolution grayscale lithography

Grayscale PhotoLithography (GPL) enables the patterning of various 3D microstructures in a single lithography step with high throughput. For various 3D optical filtering devices to be functional, high vertical resolution and accuracy are key factors. This precision can, in part, be improved by an adapted mask design construction when using GPL as the 3D patterning method. Here we study different mask design approaches to achieve high resolution staircase like structures patterning using GPL. We found that by using different design flavors, we enlarge the range of available densities for grayscale applications. A relevant design choice also allows us to increase the theoretical vertical resolution enough so that the remaining limitations come not from the mask itself but from the process. The Mask Error Enhancement Factor (MEEF) is also shown to be improvable by tuning the dose sensibility of the design.