I did my postdoctoral research with Prof. Harold Craighead’s group at Cornell University to develop an innovative electron beam lithographic technology. The project was based on the micro-fabricated electron column technology from Dr. Philip Chen's group at IBM T. J. Watson Research Center, a joint venture between Prof. Craighead (then director of Cornell Nanofabrication Facility) and Dr. Chen, funded by the Advanced Research Projects Agency (ARPA).
My main focus was on wafer patterning using a very low energy electron beam (1-2kV), pattern transferring to semiconductor substrates, and Monte Carlo simulation to investigate how low energy electrons deposit energy into resists and substrates.
I pioneered an experimental method for the investigation of how very low energy electrons penetrate nano-meter scale metal films.
|
Nano fabrication and semiconductor processing. I pioneered an experimental method for the investigation of how very low energy electrons penetrate nano-meter scale metal films. This method employed PMMA resist and Atomic Force Microscopy (AFM). At the Cornell Nanofabrication Facility and its affiliated facilities, I conducted process development which included electron beam lithographic systems, resist development, plasma etcher (RIE), plasma enhanced chemical vapor deposition tool, physical deposition tool, ion sputter tool, magnetron reaction ion sputter tool, wet chemical processing, atomic force microscope, Rutherford back scattered spectroscopy, etc. Developed processing recipes for using 1kV electron beam patterning on resist, plasma etching into silicon substrates and surface coatings. Investigated how low energy (<2 kV) electrons deposit energy (elastic/inelastic scattering) into sub-micro films and silicon substrate. I then compared the simulation results based on several energy deposition models with the experimental results. Discovered the fundamental shortcomings of 1kV electron beam lithography when compared to an electron beam of 2kV or higher. |
Wrote a Monte Carlo simulation program (in C++ on Mac OS) consisting of graphic user interface, graphical display of electron trajectories and energy distribution; fundamental physics that simulate electron energy deposition due to elastic and inelastic scattering between electrons and atoms.
Learned C++ object oriented coding, the physics, and the Mac OS API and then demoed the simulation program to Prof. Craighead in less than 3 weeks. He was so impressed that he pressured the Cornell hiring agency to expedite my H-1 visa approval.
Publications D. M. Tanenbaum, C. W. Lo, M. Isaacson, H. G. Craighead, M. J. Rooks, k. Y. Lee, W. S. Huang, T. H. Chang, “High Resolution Electron Beam Lithography Using ZEP-520 and KRS Resists” at low voltages, J. Vac. Sci. Technol. B, 14, 3829(1996).
W. K. Lo, G. Parathasarathy, C. W. Lo, D. M. Tanunbaum, H. G. Craighead, and M. S. Isaacson, “Titanium Nitride Coated Tungsten Cold Field Emission Sources,” J. Vac. Sci. Technol. B, 14, 3787(1996).
C. W. Lo, W. K. Lo, M. J. Rooks, M. Isaacson, H. G. Craighead, and A. E. Novembre, “Monte Carlo and Experimental Studies of 1 and 2 kV Electron Beam Lithography using P(SI-CMS) and PMMA Resist”, J. Vac. Sci. Technol. B, 13, 2980(1995).
C. W. Lo, M. J. Rooks, W. K. Lo, M. Isaacson, and H. G. Craighead, “Resists and Processes for 1 kV Electron Beam Micro-column Lithography, “ J. Vac. Sci. Technol. B, 13, 812(1995).