Characterization of ion tracks in PMMA for single ion lithography

Abstract

The ultimate resolution in ion beam lithography (IBL) can be achieved by etching tracks modified by the passage of a single ion impact which has a diameter in the order of 10 nm. For precise counting of single ions, a Si photodiode is used as a substrate onto which a PMMA film is spun. We have macroscopically investigated the sensitivity of PMMA using 3 MeV H and found that a deposited energy density of greater than 1 eV/nm3 is required to remove the PMMA film for 60 s developing in a water:IPA 1:4 solution. From this sensitivity measurement we have determined that 8 MeV F, 71 MeV Cu and 88 MeV I ions should produce enough damage in a single ion strike to create a hole etched along the laten..