Beam Pen Lithography (BPL)
Beam pen lithography (BPL) is a cantilever-free scanning probe lithography technique based on polymer pen lithography (PPL). In BPL, the transparent, two-dimensional elastomeric tip array employed in PPL is coated with a thin layer of metallic gold and then small apertures are physically or chemically generated at the apex of the tips. Light can then be passed through these holes to effect photochemistry (e.g., develop photoresist) and ultimately create nanoscale features with dimensions below the diffraction limit of the light source. When coupled to a digital micromirror device (DMD), each tip can be independently addressed, and arbitrary patterns can be generated. PPL, BPL, and related cantilever-free scanning probe lithography techniques have been commercialized by TERA-print, in the form of TERA-fab E and M series instruments. Mirkin co-founded TERA-print.
Left: Optical microscopy and scanning electron microscopy (SEM) (inset) images of ‘NU’ patterns comprised of 29 metal dots each (feature diameter ~430±80 nm) generated using BPL. Middle: SEM image with schematic (inset) showing how a mask can be utilized to address only selected tips to pattern only particular areas of a substrate using BPL. Left and Middle are taken from Nature Nanotechnol., 2010, 5, 637. Right: TERA-print’s TERA-Fab E series is the first commercial tool for performing BPL. Right is taken from: //www.tera-print.com/e-series.