- A HSQ/PMMA bilayer negative tone lift-off process has recently been used for the fabrication of nano-structures on metallic and semi-conducting substrates with high precision and high aspect ratios. In this study, the HSQ/PMMA bilayer process was further extended to the fabrication of nano-structures on insulating substrates through introducing an additional conducting polymer layer to eliminate resist/substrate charging and proximity effects during e-beam lithography. With this new approach, nano-structures with high aspect ratios and high spatial resolutions can be fabricated on a wide range of substrates. High numerical aperture micro zone plates (MZPs) and phase micro zone plates (PMZPs) with focus distances 3 m have been demonstrated with this new approach on fused silica substrates. The focusing characteristics of resulting MZPs and PMZPs showed good consistency with the design values of the specified working wavelength (409 nm). 2011 IOP Publishing Ltd.