8 June 1998 Implementation of a closed-loop CD and overlay controller for sub-0.25-μm patterning
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Abstract
The traditional approach for CD and overlay control in lithography has been based upon statistical control of the critical inputs to the lithographic process. This SPC approach has the disadvantage that the process equipment must be taken out of manufacturing whenever a parameter goes out of control, so that the root cause may be diagnosed and addressed. In the case of leading-edge lithography, it is often not trivial to determine the cause of such disturbances, and productivity can be greatly increased if output data is used to dynamically tune the system inputs. We have successfully implemented a fully automated, closed-loop CD and overlay control system in manufacturing for both I-line and DUV lithography. This system features automatic metrology data upload, host control of stepper/track clusters, and utilizes tool-based lot data for manipulation of future lot inputs. CD control to within 1 nm of target and less than 20 nm 3(sigma) lot to lot variability has been demonstrated. Mean overlay errors of less than 50 nm have been realized as well. Process Cpk values were improved in some cases by more than 50% with implementation of the controller.
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John L. Sturtevant, John L. Sturtevant, Michele R. Weilemann, Michele R. Weilemann, Kent G. Green, Kent G. Green, John Dwyer, John Dwyer, Eric Robertson, Eric Robertson, Robert R. Hershey, Robert R. Hershey, } "Implementation of a closed-loop CD and overlay controller for sub-0.25-μm patterning", Proc. SPIE 3332, Metrology, Inspection, and Process Control for Microlithography XII, (8 June 1998); doi: 10.1117/12.308788; https://doi.org/10.1117/12.308788
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