Multiexposure Grayscale Patterns with Low-Energy Electrons

High-energy electron beam exposure is generally recognized as the standard for achieving high-precision nanofabrication. Low-energy electron beam exposure techniques offer advantages in 3D manufacturing; however, they have received limited attention in traditional processes due to precision limitations and insufficient exposure, leading to an underestimation of their potential. In this article, we introduce a nanofabrication strategy using low-energy electrons in ice-assisted electron-beam lithography (iEBL) alleviating the compatibility issue between resolution and quasi-3D manufacturing. With in situ alignment and correction in the iEBL process, our optimized exposure strategy enables the creation of complex grayscale structures, demonstrated by 30-layer ladder formations with an average step height of 10 nm and width of 300 nm as well as line patterns with resolution below 30 nm. To further expand the utility of the low-energy exposure strategies, we demonstrate the transformation of grayscale ice sculptures into metal nanostructures, providing a pathway for the fabrication of contamination-free metal nanostructures. This work expands the potential of low-voltage techniques and enhances the manufacturing capabilities of iEBL, which is particularly significant for its applications in quasi-3D manufacturing.