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12 May 2005 Full-chip single exposure vortex mask for contact/via
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Among many advanced contact-hole imaging methods, the vortex phase-shift mask had been shown to have excellent image quality by Marc Levenson et al. [1, 2]. Whereas, the double line-space phase shift mask [3] provides the ultimate resolution enhancement. However, both methods are restricted to uniform contact-hole arrays or contact holes on uniform grid requiring double exposures. In this paper, we show, step-by-step, how to convert a random contact-hole layout into a vortex PSM suitable for single exposure or double line-space PSM masks. We have developed a software program to automatically do the contact-hole pairing, phase-shifter creation, phase assignment and conflict resolution. Further, we present image quality evaluations of memory, uniform contact-hole array and basic vortex pairs. Our results indicate our method (general vortex phase-shift mask) enjoys a process window 2 times that of alternating phase-shift method for both memory and uniform contact-hole array. We further show how simple manual OPC can be added to correct image asymmetry issues associated with vortex mask. Finally, we will discuss the challenges remaining for OPC of single exposure vortex PSM for random logic layout.
© (2005) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Yong Liu, Dun Liu, and James Hu "Full-chip single exposure vortex mask for contact/via", Proc. SPIE 5754, Optical Microlithography XVIII, (12 May 2005);

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