Anisotropic oxygen reactive ion etching for removing residual layers from 45 nm-width imprint patterns

We designed and set up an apparatus of oxygen reactive ion etching (O₂ RIE) with parallel electrode configuration to remove a residual layer located on concave parts of ultraviolet nanoimprinted resist patterns and to maintain the pattern linewidth after dry etching. Imprint resist patterns with 45 nm line-and-space on a silicon wafer were fabricated with a bisphenol A-based UV-curable resin (NL-KK1) and a fluorinated replica mold under an easily condensable gas atmosphere. Cross-sectional field-emission scanning electron microscope observations revealed that the etching parameters of O₂ mass flow rate, O₂ pressure, and radio frequency (RF) bias power changed the resist pattern shapes. Steep resist patterns of the hardly changed linewidth could be left without the residual layer on the silicon substrates by tuning the parameters which caused anisotropic O₂ RIE. The imprint resist mask was applied for a subsequent dry etching of underneath silicon without any metal hard mask layers, and 45 nm line-and-space silicon pa tterns could be obtained.