Enhancing Grayscale E‐Beam Lithography: Thermal Treatment of Novolak‐Based Resist for 3D Nanostructures

Abstract Grayscale electron beam lithography enables the direct writing of 3D nanostructures, which are essential for advanced applications in photonics, biomimetics, and surface engineering, by spatially modulating exposure dose. However, realizing high‐resolution grayscale features remains challenging due to dose‐dependent variations in resist morphology and limited control over nanoscale surface roughness. Here, a systematic study of the thermally induced morphological and chemical evolution of a novolak‐based negative resist commonly used in electron beam lithography is presented. Using atomic force microscopy, scanning electron microscopy, and X‐ray photoelectron spectroscopy, the impact of post‐exposure thermal treatment on surface roughness, chemical bonding, and deformation behavior across a wide range of exposure doses are evaluated. These results offer new insights into how e‐beam dose and thermal treatment interact and highlight potential of thermally optimized novolak resists for high‐precision 3D nanofabrication and highlights the potential of thermally optimized novolak resists for high‐precision 3D nanofabrication.