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Polarization and interface reflection effects are examined for technology issues in mask making of chrome edge shape, overcoating, double phase-shifting removal of defects, and reflective masks. This study is based on the massively parallel rigorous electromagnetic simulator TEMPEST1, with extensions to include the TM polarization and boundary conditions for outgoing waves in optical materials. The analysis was carried out on a CM-2 connection machine with remote electronic access. A local workstation was used to write and preview the geometry as well as process images from files of diffraction efficiencies downloaded to the workstation from the network. Through this remote analysis procedure, the four proto-typical mask case studies described by Doi et al.2 were examined for polarization and boundary condition effects.
For chrome masks of one wavelength wide opening in a IX system at 0.248 |im, moderate differences between the TE and the TM polarizations were observed in the peak intensities (10%). The TM polarization in general showed higher transmission and lower sidelobes. The two polarizations showed a similar increase in linewidth and peak intensity with decreasing chrome edge slope. The difference was not as pronounced for a 5X system at 0.365 |Lim. Overcoating chrome masks with anti-reflection layers improved resolution for both polarizations. For 5X chromeless phase-shifting masks at 0.365 pm, neither polarization effect nor phase-shifter edge slope was important. The peak intensity at the phase-shifting section changed by only 1% and the linewidth varied by less than 2% when the phase-shifter edge slope changed from 90° to 45°, keeping the mid-points of the phase-shifter edge fixed. To remove defects on such masks by double phase-shifting may drop the intensity level to 70% of the clear field value for a 0.1 X/NA sized defect. For IX reflective masks at one wavelength, both polarizations displayed similar behaviors. These reflective masks with built-in material-based phase-shifting improved the image slope, and the TM polarization was found to have slightly less ringing than the TE polarization.
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