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14 March 2006 Full-field exposure control implications of the mask error function
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This report considers a detailed method of rapid and accurate experimental calculation of the Mask Error Enhancement Function (MEF or MEEF) using localized CD variation across the exposure field. MEEF is defined as the non-constant bias of wafer-image replication to small changes in the reticle image. The extraction method of the MEEF response of a reticle to it's process environment is shown to contain a method of measuring the robustness of the OPC design structures on the reticle and their ability to compensate wafer-image replication across the scope of production-process perturbations. This study demonstrates that a MEEF response can be characterized by a regressive comparison of reticle and wafer image sizes for any reticle OPC structure. Expanding the analysis to a focus-dose matrix that approximates normal production variations allows the MEEF response sensitivities to be deconvolved into their component contributions to critical feature variation across the wafer. IntraField dependencies such as sensitivity to the direction of the scan, and thus reticle-stage drive loading are investigated and their contributions are presented at the end of the report. Process induced perturbations such as focus and dose can also change the MEEF and their response is characterized and shown to be a significant contributing factor. An algorithm is then used to extract the full-wafer systematic sensitivity of MEEF to slowly changing perturbations such as film thickness changes in the Anti-Reflective Coating (ARC) and Photoresist thickness. Correlation of the MEEF response to film thickness is discussed and shown to be significant for some films. A budget summary of the systematic perturbation inherent in these MEEF factors is compared against the needs of sub-90 nm nodes with considerations toward the necessity of process-specific OPC design for critical layers.
© (2006) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Terrence E. Zavecz "Full-field exposure control implications of the mask error function", Proc. SPIE 6155, Data Analysis and Modeling for Process Control III, 61550E (14 March 2006);


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