Requirements and Limitations for Nanoscale Electron-Beam Patterning
Argonne National Laboratory
Electron beam lithography still represents the most effective way to pattern materials at the nanoscale. The success of this technology relies on the ability of electron optics to be able to focus electrons to nanometer scale spot sizes and to be able to steer and direct the spot with equal control. The resolution achievable with focused electrons depends also on the interaction of these electrons with the patterning material, typically a polymer based resist. Therefore, the success of e-beam lithography depends on the availability of suitable resists. There is a substantial variety of resist materials, from PMMA to calixarenes, to choose from to achieve high resolution in electron-beam lithography. However, these materials suffer from the limitation of poor sensitivity and contrast. In order to make the most efficient use of the available current, the resist must be as sensitive as possible. This leads to the use of chemically amplified (CA) systems. Unfortunately, in the quest for smaller feature size and higher sensitivity, even chemically amplified materials are limited: sensitivity and resolution are not independent. In this situation detailed models are the only way to understand material performance and limitations. Detailed models that describe this performance and alternative methods of nanopatterning will be discussed
Leonidas E. Ocola recieved his B.Sc., Lic., M.Sc., and Ph.D. degrees in physics in 1988, 1988, 1991 and 1996 respectively. He is presently with the Center for Nanoscale Materials at Argonne National Laboratory. Prior to this he held industry positions at Bell Laboratories, first with Lucent Technologies and then with Agere Systems, a later spinoff, working in the areas of projection electron beam lithography (SCALPEL) and then in high resolution electron beam nanolithography. His research interests include electron beam lithography and high-energy electron beam interactions with polymer materials, scanning probe characterization techniques, FTIR micro-spectroscopy and single molecule spectroscopy. He is a member of the technical advisory board responsible for lithography facilities planning for the Center for Nanoscale Materials at Argonne, and has close to 40 refereed publications in lithography, resist modeling, and processing.