Neutral particle lithography: a simple solution to charge-related artefacts in ion beam proximity printing

Neutral particle lithography (NPL) is a high resolution, proximity exposure technique where a broad beam of energetic neutral atoms floods a stencil mask and transmitted beamlets transfer the mask pattern to resist on a substrate. It preserves the advantages of ion beam lithography, including extremely large depth-of-field, sub-5 nm resist scattering, and the near absence of diffraction, yet is intrinsically immune to charge-related artefacts including line-edge roughness and pattern placement errors due to charge accumulation on the mask and substrate. This paper reviews the principles of NPL, surveys recent advances in the field and discusses applications involving insulating substrates, large proximity gaps or ultra-small features where the approach has particular advantages.