7 July 1997 Detecting lithography's variations: new types of defects for automatic inspection machines
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Photolithography for silicon semiconductor device manufacturing is a crucial technology in the race to denser and more highly integrated circuits. To achieve an acceptable wafer throughput, most steppers use a combination of global and site-to-site alignment. Focus and exposure are controlled based on a limited number of fields. Post develop evaluation of the pattern quality is typically limited to a few fields on a few wafers. Focus and exposure shifts cause small variations in CDs that rapidly become critical yield limiters. Trends toward larger stepper fields and wafers render very small variations in magnification, distortion, rotation and translation of the patten. Rapid closed loop feedback of a photolithography problem prior to etch is critical for measuring and controlling stepper performance, reducing wafer scrap and yield loss. In this article we will demonstrate how sub-micron variations can be quickly detected with laser scanning tool, combined with pixel-to- pixel image processing. The WF-720 automatic defect inspection tool, utilizing a unique PDI configuration, enables detection of minor changes in pattern shapes based on the global pixel population behavior of the distorted patterns on the wafer.
© (1997) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Paul Gudeczauskas, Erez Ravid, "Detecting lithography's variations: new types of defects for automatic inspection machines", Proc. SPIE 3050, Metrology, Inspection, and Process Control for Microlithography XI, (7 July 1997); doi: 10.1117/12.275939; https://doi.org/10.1117/12.275939


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