Sub-10-nm Electron-Beam Lithography

High-resolution electron-beam lithography has many applications in nanoelectronics, nanophotonics, and nanoelectromechanical systems. As ultra-large-scale integration circuits is approaching to 22 nm technology node and beyond, electron-beam lithography plays a more and more important role in semiconductor manufacturing. Approaching higher resolution is the critical issue for electron-beam lithography.In this dissertation, we measured point-spread function experimentally and did Monte-Carlo simulation for different-voltage exposures, which can be used to study the resolution limits and correct the proximity effect of electron-beam lithography. We analyzed the trade-off between resolution, efficiency, and structure uniformity. Furthermore, we discussed the difficulties of ultra-high-resolution electron-beam lithography for applications and proposed possible ways to solve them.With optimized exposure and development processes,9-nm-pitch hydrogen silsesquioxane (HSQ) nanostructures were fabricated. By using high-resolution transmission electron microscopy and atomic force microscopy, we found that 4 nm structures could be readily fabricated in sparse patterns but 16-nm-pitch structures was difficult to yield in dense structures. By analyzing the spread function and development contrast curve, we hypothesized that the resolution limit of electron-beam lithography is primarily limited by developer-diffusion.One of difficulties of high-resolution electron-beam lithography is pattern transferability. We proposed to fabricate functional nanostructures directly by electron-beam lithography and irradiation. By using ultrathin electrospun PMMA nanofibers as the precursor, we studied the decomposition, carbonization, and graphitization processes of a polymer by in situ high-resolution transmission electron microscopy and fabricated graphene nanoribbons, fullerene-like nanostructures, and graphitic nanotips. By using this method, patterned graphitic nanostructures were fabricated by electron-beam lithography combined with thermal treatment.To overcome low efficiency, proximity effect, and irradiation damage of electron-beam lithography, we developed a new self-assembly method based on capillary-force-induced cohesion and collapse. With this method, sparse high-aspect-ratio nanostructures were self-assembled into complex networks or three-dimensional structures to improve the efficiency, decrease the proximity effect, and avoid irradiation damage of electron-beam lithography.The research in this dissertation solved several critical issues for high-resolution electron-beam lithography, which will have many applications in developing nanodevices.