  The most direct definition of a patterning process' resolution is the
smallest half-pitch feature it is capable of transferring onto the substrate.
Here we demonstrate that thermal Scanning Probe Lithography (t-SPL) is capable
of fabricating dense line patterns in silicon and metal lift-off features at
sub 20 nm feature size. The dense silicon lines were written at a half pitch of
18.3 nm to a depth of 5 nm into a 9 nm polyphthalaldehyde thermal imaging layer
by t-SPL. For processing we used a three-layer stack comprising an evaporated
SiO2 hardmask which is just 2-3 nm thick. The hardmask is used to amplify the
pattern into a 50 nm thick polymeric transfer layer. The transfer layer
subsequently serves as an etch mask for transfer into silicon to a nominal
depth of 60 nm. The line edge roughness (3 sigma) was evaluated to be less than
3 nm both in the transfer layer and in silicon. We also demonstrate that a
similar three-layer stack can be used for metal lift-off of high resolution
patterns. A device application is demonstrated by fabricating 50 nm half pitch
dense nickel contacts to an InAs nanowire.
