The Northwestern University has developed beam pen lithography technology which offers a means to rapidly and inexpensively make and prototype circuits, optoelectronics and medical diagnostics and promises many other applications in the electronics, photonics and life sciences industries.
Using beam-pen lithography, the researchers patterned 15,000 replicas of the Chicago skyline (featuring the Willis Tower and the John Hancock Center) simultaneously in about half an hour. Each skyline pattern is made up of 182 dots, with each dot approximately 500 nanometers in diameter, like each pen tip. The time of light exposure for each dot was 20 seconds. The current method allows researchers to make structures as small as 150 nanometers, but refinements of the pen architecture likely will increase resolution to below 100 nanometers. (Although not reported in the paper, the researchers have created an array of 11 million pens in an area only a few centimeters square.)
Beam-pen lithography is the third type of “pen” in Mirkin’s nanofabrication arsenal. He developed polymer-pen lithography (PPL) in 2008 and Dip-Pen Nanolithography (DPN) in 1999, both of which deliver chemical materials to a surface and have since been commercialized into research-grade nanofabrication tools that are now used in 23 countries around the world.
Like PPL, beam-pen lithography uses an array of tiny pens made of a polymer to print patterns over large areas with nanoscopic through macroscopic resolution. But instead of using an “ink” of molecules, BPL draws patterns using light on a light-sensitive material.
Lithography techniques are currently being developed to fabricate nanoscale components for integrated circuits, medical diagnostics and optoelectronics. In conventional far-field optical lithography, lateral feature resolution is diffraction-limited. Approaches that overcome the diffraction limit have been developed but these are difficult to implement or they preclude arbitrary pattern formation. Techniques based on near-field scanning optical microscopy can overcome the diffraction limit, but they suffer from inherently low throughput and restricted scan areas. Highly parallel two-dimensional, silicon-based, near-field scanning optical microscopy aperture arrays have been fabricated, but aligning a non-deformable aperture array to a large-area substrate with near-field proximity remains challenging. However, recent advances in lithographies based on scanning probe microscopy have made use of transparent two-dimensional arrays of pyramid-shaped elastomeric tips (or ‘pens’) for large-area, high-throughput patterning of ink molecules. Here, we report a massively parallel scanning probe microscopy-based approach that can generate arbitrary patterns by passing 400-nm light through nanoscopic apertures at each tip in the array. The technique, termed beam pen lithography, can toggle between near- and far-field distances, allowing both sub-diffraction limit (100 nm) and larger features to be generated.
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