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November 20, 2002


Dr. Steven Brueck
Center for High Technology Materials
University of New Mexico
"There are No Fundamental Limits to Optical Lithography" 

Abstract. Progress in optical lithography has paced the enormous progress in integrated circuit technology. The ultimate possible limits of optical lithography are explored. The spatial frequency transmission bandwidth of free-space is 2/A, leading to a dense (equal line/space) pattern at a critical dimension ofIJ4 (or 50 nm for a A of 200 nm) as is shown in Figure 1. Immersion provides another factor of ~ 1.5 down to a Y2 pitch of 33 nm at A ~ 200 nm Various strategies are being explored for extending this capability to arbitrary patterns rather than simple gratings and will be discussed.  Nonlinear processes, based on the chemistry of photoresist processing and pattern transfer, can further extend optics beyond the linear systems limits of single exposures. The conclusion is that there is no fundamental limit to the resolution of optical lithography; there are only process latitude and manufacturing (e.g. cost) issues.Nanotechnology is of great current interest. For many applications, large numbers of nanostructures with a well-defined long-range order are required. One such example is the use of nanostructuring for semiconductor materials development. Two examples will be discussed as time allows: nanoheteroepitaxy( NHE) for the growth of highly lattice mismatched systems( e.g . GaN on Si); and selective MBE growth of lnAs quantum dots on patterned GaAs substrates. An example of NHE for GaN on Si is shown in Figure 2.


Vanderbilt University