Nanopattern transfer from high-density self-assembled nanosphere arrays on prepatterned substrates

We have fabricated nanoimprint moulds with high-density well-defined nanopatterns by pattern transfer from self-assembled nanosphere arrays on prepatterned substrates. Silica nanospheres of 100 and 25?nm diameter were regularly arranged over large areas in a self-assembling manner by capillary force via a dip-coating technique on topographically patterned substrates having 220?nm pitch line/space patterns. The nanosphere arrays were used as etching masks, and nanodot arrays with the same arrangements were created on the silica substrate surfaces by reactive ion etching (RIE). By developing a combined pattern transfer process using Ru and SiOx mask layers and CF4 and O2 RIE, the aspect ratio between the height and diameter of the nanodots made from the 25?nm nanospheres is improved to about two. It is demonstrated that the nanopatterns of the moulds can be inversely transferred into polymer surfaces reproducibly by UV nanoimprint process.