Strategies for Managing Charge in Electron-Beam Lithography on Glass

Optical metasurfaces fabricated via electron beam lithography (EBL) are increasingly pivotal for biosensing and bioimaging applications. However, charge accumulation on insulating glass substrates persists as a critical barrier, causing distortion of the incident electron beam and degradation of patterning fidelity manifested as pattern deflection, increased line-edge roughness (LER), and overlay inaccuracy. Here, we evaluate three charge-mitigation strategies: optimization of electron-beam resist (EBR) thickness, spin-coated conductive polymer layers, and thin metal capping layers. A reduction in EBR thickness from 800 nm to 150 nm led to a significant improvement in LER attributed to a shortened charge dissipation path. The introduction of a conductive polymer further enhanced pattern integrity, whereas the most substantial improvement was attained by depositing a 20 nm Au layer, which offers a highly conductive pathway for rapid charge dissipation and resulted in the lowest LER of 0.24. Our comparison establishes a clear hierarchy of effectiveness and identifies metal capping as the most reliable approach for high-fidelity nanofabrication on insulating substrates, thereby offering practical solutions for advancing glass-based photonic and meta-optical devices.