Patterning at the Nanoscale: From Silicon to DNA
23 10 2007Franco Cerrina
Electrical and Computer Engineering & Center for NanoTechnology
University of Wisconsin – Madison
Friday, October 26 at 11 a.m.
Sala Conferenze Edificio Ovest
FBK-irst
Abstract
In this talk I will present our research activity in the area of nanofabrication. I will review our work in the area of semiconductor lithography, showing the design and performance of our Extreme Ultraviolet Interference Lithography and Holography (EUV-IL and HL) setup operating at _ = 13.4 nm. This activity is geared to support the development of novel photoresist materials for the 50-10 nm domain lithography nodes of the ITRS. Many aspects of image formation involving EUV are still poorly understood, and in addition to the experimental work we have also developed an extensive set of simulation tools to model the image formation from aerial image to resist developed image. In particular, we include explicitly stochastic effects to model the Line Edge Roughness that affects severely the ability of current processes to pattern reliably below 50nm. Since EUV-IL generates patterns limited to periodic structures, we have also extended the application of holography to the EUV spectral range using Computer Generated Holograms (CGH) for arbitrary image synthesis; these holograms are particularly challenging to manufacture for use in the EUV because of the poor optical quality of the materials in that photon energy range. It is a truism to say that lithographic patterning is an essential part of any form of fabrication process involving semiconductor technology. Interestingly, in recent years lithography has been extended to biological problems. A classical example is the activity at Affymetrix, where DNA microarrays are synthesized using a combinatorial sequence of exposures to yield “chips” with hundreds of thousands of pixels, each one corresponding to a unique oligomer sequence. These “Gene chips” are widely used in genomic research. The process has been further extended by our introduction of the “Maskless Array Synthesizer”, or MAS, in 2000. The MAS is commercialized today by NimbleGen-Roche for the rapid turnaround production of custom sequences of high density chips. The application of lithographic techniques to biological problem does not stop with DNA microarrays. We are developing a “gene synthesis” process whereby the oligomers synthesized on-chip are harvested from the surface, amplified and stepwise assembled in longer constructs. These “synthetic genes” can be used to encode biological functions, or to enable the use of DNA as structural material. I firmly believe that the combination of high-resolution patterning (e.g., by E-beam lithography of functionalized surfaces) with on-demand synthesis of DNA (and other molecules) is paving the way to completely new applications. Thus, in summarizing my talk, I will put in context the merger of nanolithography (as a top-down technique) with DNA and other molecular synthesis (as a bottom up technique).
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