1 July 2002 Electron-beam lithography of isolated trenches with chemically amplified positive resist
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Electron beam lithography has been implemented with a commercially available DUV chemically amplified positive resist. Post exposure delay stability in vacuum was found to be non-critical. Post exposure delay after removal from vacuum in our clean room is a critical variable, with a change in critical dimension of approximately 0.6 nm per minute of PEB delay. This result was achieved without amine filtration. Wafers were transported in cassettes from the e- beam exposure tool to an FSI Polaris 2000 photocluster tool. The PEB delay effect on critical dimensions can be significantly reduced by using a water soluble protective top coat with a slight change in nominal does. E-beam lithography was performed with a Leica VB6 operating at 50eV, using a n 800 micrometers field, and a 12.5 nm minimum grid size. The original CAD had a negative bias added to compensate for any proximity effect, to take advantage of dose control to achieve targeted line width, and to optimize exposure latitude. Characterization with a dual beam FIB/SEM to obtain cross-sectional SEM images, typically demonstrate a foot on plated structures from the initial resist profile. A 30 percent decease in nominal dose was observed on device wafers compared to scout wafers. Device wafers have metal structures buried below the approximate 100 nm thick plating seed layer that also cause profile changes. This is presumably due to the back scattering of the electrons from the initial area of exposure. Plating rates in isolated trenches also show a strong dependence o n the critical dimension of the narrow resist trench. Plated structures with critical dimensions of 80 nm in 0.65 microns of resist were fabricated.
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Andrew R. Eckert, Andrew R. Eckert, Richard J. Bojko, Richard J. Bojko, Harold Gentile, Harold Gentile, Robert Harris, Robert Harris, Jay Jayashankar, Jay Jayashankar, Earl Johns, Earl Johns, Kevin Minor, Kevin Minor, Keith Mountfield, Keith Mountfield, Carl Seiler, Carl Seiler, XiaoMin Yang, XiaoMin Yang, } "Electron-beam lithography of isolated trenches with chemically amplified positive resist", Proc. SPIE 4688, Emerging Lithographic Technologies VI, (1 July 2002); doi: 10.1117/12.472361; https://doi.org/10.1117/12.472361

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