Electron Beam Lithography for Fabrication of Nano Phase-change Memory

In this work, we report two methods to fabricate the nano phase-change memory: (1) electron beam lithography (EBL) using the positive resist ZEP-520A followed by phase-change material deposition and lift-off processes, (2) EBL using the negative resist hydrogen silsesquioxane (HSQ) followed by reactive ion etching (RIB) after phase-change material deposition. For the former method, the optimized exposure dosage is around 40 mu C/cm(2) and the finest nanowire is about 80 nm in width. On the other hand, the latter method shows that the finest nanowire can be as small as about 15 nm in width after RIB process and the optimized exposure dosage is around 2.0 mC/cm(2). In this case, collapse-preventing pattern becomes necessary for fabrication of such a fine nanowire.