25 August 1999 Electron-beam lithography simulation for maskmaking: IV. Effect of resist contrast on isofocal dose
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Proceedings Volume 3748, Photomask and X-Ray Mask Technology VI; (1999) https://doi.org/10.1117/12.360220
Event: Photomask and X-Ray Mask Technology VI, 1999, Yokohama, Japan
Abstract
There is a certain exposure dose at which variations in electron-beam (e-beam) spot size have virtually no impact on the resulting feature width. In optical lithography, this phenomenon is well characterized and is called the isofocal point. The exposure that produces a flat response of linewidth versus spot size is called the isofocal dose, and the resulting feature width is called the isofocal critical dimension (CD). It is intuitive that operating in the flat portion of the curve will have advantages from a process latitude perspective. Also, it is significant to note that the isofocal CD occurs at widths that are overexposed with respect to the target spacewidth. Typically, this difference is resolved by sizing data so that the dose to size approaches the amount needed to reach the isofocal point. As linewidths continue to shrink, sizing will become a point of contention, because resolution can be limited by the magnitude of data bias. In this paper, we examine the effect of resist contrast on the difference between dose to size and dose to isofocal. ZEP 7000, a resist from Nippon Zeon, is examined and compared to resists with other different dissolution rates. Included in the resist selection is a high gamma resist that is modeled on chemically amplified resists (CARs).
© (1999) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Charles A. Sauer, Chris A. Mack, "Electron-beam lithography simulation for maskmaking: IV. Effect of resist contrast on isofocal dose", Proc. SPIE 3748, Photomask and X-Ray Mask Technology VI, (25 August 1999); doi: 10.1117/12.360220; https://doi.org/10.1117/12.360220
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