High molecular weight polystyrene as very sensitive electron beam resist

0167-9317/$ see front matter 2012 Elsevier B.V. A http://dx.doi.org/10.1016/j.mee.2012.07.005 ⇑ Corresponding author. Tel.: +1 519 729 3582. E-mail addresses: [email protected], j24 (J. Zhang). Previously we demonstrated ultra-dense patterning using 2 kg/mol polystyrene negative electron beam resist that has low sensitivity [16]. To drastically improve its sensitivity, here we studied the exposure behavior of polystyrene with molecular weight of 90 and 900 kg/mol. Very high sensitivity of 1 lC/cm was obtained for 900 kg/mol when exposed at 2 keV. The sensitivity for 90 kg/mol polystyrene is about one order lower. The resist has a contrast around 1.5 that is nearly independent of molecular weight for the current range of molecular weight. It can achieve fairly well-defined patterns of 150–200 nm period line arrays. Polystyrene is a simple and low-cost resist with easy process control and practically unlimited shelf life. It is also considerably more resistant to drying etching than PMMA. Therefore, the current high molecular weight polystyrene could be employed for applications that need moderate resolution but high sensitivity for a reasonable exposure time. 2012 Elsevier B.V. All rights reserved.