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5 May 2005 Design rule considerations for 65-nm node contact using off axis illumination
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Perhaps the most critical lithographic challenge at teh 65 nm node can be found printing contact holes for random logic. Achieving all pitches from dense to isolated simultaneously in a single mask print requires high numerical aperture (NA) with novel low-k1 imaging techniques. As is typical in complex engineering problems, requirements compete against each other. The requirement to achieve the desired dense resolution suggests the use of off axis illumination (OAI) techniques such annular and Quasar. At the same time, the need to meet other figures of merit (FOM) such as depth of focus (DOF) and mask error enhancement factor (MEEF) for larger pitches are strong considerations for choosing the more conventional illumination conditions. Moreover, previously unconsidered FOMs such as contact asymmetry and displacement must now also be strongly considered. In particular, we discuss design limitations which may be incorporated to avoid fundamental patterning issues when using OAI and sub-resolution assist features (SRAF) for printing CT level at 65 nm node.
© (2005) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Scott Jessen, Mark Mason, Sean O'Brien, Mark Terry, Robert Soper, and Thomas Wolf "Design rule considerations for 65-nm node contact using off axis illumination", Proc. SPIE 5756, Design and Process Integration for Microelectronic Manufacturing III, (5 May 2005);

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