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29 June 1998 Impact of coma on CD control for multiphase PSM designs
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Alternating PSM applied selectively to transistor regions on the poly gate mask is one way to achieve smaller gate CDs and tighter CD control. When using multiphase PSMs we have observed, experimentally, a difference between the CDs of isolated lines when the phase shifter is on the right side compared to the left side (we have called this effect the PSM right-left effect). The effect is shown to correlate with lens coma and the magnitude of the effect is also a strong function of defocus. In this paper we present experimental data showing the magnitude of the effect and how it can be minimized by choosing optimum values of numerical aperture (NA) and partial coherence ((sigma) ). The magnitude of the effect within the stepper field is shown to correlate with measured coma values. The sensitivity of the effect to defocus was calculated. Aerial Image simulation was performed and found to predict the experimental behavior to within a factor of two. Variations in PSM design were explored using simulation. In general, the effect is reduced if the PSM layout is symmetrical. By comparing the sensitivity to coma of various PSM designs with the sensitivity of line pair structures on binary masks we were able to determine which designs had acceptable coma sensitivity.
© (1998) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Regina T. Schmidt, Chris A. Spence, Luigi Capodieci, Zoran Krivokapic, Bernd Geh, and Donis G. Flagello "Impact of coma on CD control for multiphase PSM designs", Proc. SPIE 3334, Optical Microlithography XI, (29 June 1998);

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