Jan. 25, 2007 -- One of the greatest obstacles for young scientists and engineers working to build nanoscale semiconductor devices is the lack of affordable fabrication equipment. They may have the enthusiasm, energy, and critical insight needed to produce the next breakthrough, but they simply can’t afford the apparatus required to produce a prototype quickly and find out if it works. “A basic electron beam lithography set-up can cost as much as $2 million,” notes Keith Williams, an assistant professor of physics. “That’s far from affordable for a junior faculty member.” As a result, potentially ground-breaking ideas languish.
With the help of a Fund for Excellence in Science and Technology (FEST) award from the University, Williams is on his way to producing a tabletop ultra-high resolution photolithography system for just $50,000. Williams has found that a deep ultraviolet light source, which he purchased with his FEST funding, can give him the resolution he seeks at a fortieth of the cost of an electron beam system. “This system can produce a resolution of 100 nanometers, which is more than adequate for over 90 percent of the research that people want to do,” he says.
Williams’ system has a number of additional advantages. It is a fraction of the size of a typical system, requires much less maintenance, and does not have to be shielded. Because it uses light, it can produce patterns on insulating as well as conductive materials.
To make affordable nanodevice fabrication a reality, Williams turned to near-field aperture techniques and a resist that is associated with conventional electron beam lithography. His research group is adapting near-field technology developed for visible light to the ultraviolet spectrum and is learning how to spin down the resist to a few tens of nanometers to take full advantage of the subwavelength resolution provided by the apertures.
The effort needed to overcome these particular challenges provided additional benefits. With a near-field aperture, Williams can write directly to the resist without a mask, simplifying the fundamental lithographic process. And the resist he has chosen does not leave a residue, which means it can be used in conjunction with biologically neutral surfaces for biomedical applications.
Reducing complexity is hard work, but Williams finds the results gratifying. Potentially, his near-field lithography system could be readily commercialized or easily replicated by other researchers, enabling them to follow up on their creative insights more quickly. Williams is also pleased to have involved an undergraduate student in the project. “I’ve been impressed that the undergraduates here are so bright and well-prepared,” he notes. “They’re capable of doing hands-on research and I’m happy to give them the opportunity. I know from my own experience that the time in the laboratory as a student can shape a career.”