Sub- 50-nm track pitch mold using electron beam lithography for discrete track recording media

Using electron beam lithography and ZEP 520 resist, molds with a track pitch of 50 nm were fabricated on thermal silicon oxide for discrete track recording applications. In this article, the detailed process for patterning a mold with 50 nm track pitch and 10 nm feature size is described. Although bilayer polymethylmethacrylate of 120 nm thickness is able to pattern tracks of micrometer length and pitch down to 70 nm, patterned tracks with pitches below 70 nm exhibited waviness and edge roughness. In contrast, fine patterns with 50 nm pitch were achieved with a single 60 nm layer of ZEP 520 resist. Pattern transfer using ion milling followed by reactive ion etching produced 10 nm features. High resolution scanning electron microscopy was used to evaluate the size and uniformity of the tracks during each step of the process.