Lithographic technology has progressed through a number of "waves," beginning with contact printing and progressing to today's DUV step-and-scan exposure methods. Measurement capabilities have also evolved commensurate with changes in the exposure technology and feature sizes. The greatest measurement challenges today are related to gate CD control requirements, as these have been greatly accelerated during the past 10 years. Scatterometry represents a new method that may help to address this need, but something else is likely required for measurement of line-edge roughness (LER). More direct measurements of parameters such as lens aberrations, are also required. Overlay measurement will also be challenged to meet the needs of future lithographic technologies, and solutions must address the interplay between lens aberrations and overlay errors. Next-generation lithographic technologies will require a host of new metrology capabilities, and the late availability of the means for measurement could delay the introduction of the new technologies.
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