J. Garofalo et al., MASK ASSISTED OFF-AXIS ILLUMINATION TECHNIQUE FOR RANDOM LOGIC, Journal of vacuum science & technology. B, Microelectronics and nanometer structures processing, measurement and phenomena, 11(6), 1993, pp. 2651-2656
While off-axis illumination has been demonstrated to improve contrast
and depth of focus for low k1, packed line-space (L/S) patterns [S. As
ai, 1. Hanyu, and K. Hikosaka, J. Vac. Sci. Technol. B 9, 2788 (1991);
K. Kamon et al., Jpn. Appl. Phys. 30, 3021 (1991); K. Tounai et al, P
roc. SPIE 1674, 75 3 ( 1992) 1, application of this approach to the mo
re discordant patternings associated with random logic levels is suspe
ct. We introduce a conventional mask ''assist'' feature technique that
extends the off-axis L/S enhancements to more isolated features (both
spaces and lines). It will be shown that the effective process window
is substantially improved and exhibited proximity effects are mitigat
ed for this technique. Also, a comparison to a phase-shifting mask sol
ution for the patterning mix expected in random logic layouts is perfo
rmed. Simulation results are verified on a 0.53 NA, DUV stepper.