5 April 2012 Overlay control methodology comparison: field-by-field and high-order methods
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Overlay control in advanced integrated circuit (IC) manufacturing is becoming one of the leading lithographic challenges in the 3x and 2x nm process nodes. Production overlay control can no longer meet the stringent emerging requirements based on linear composite wafer and field models with sampling of 10 to 20 fields and 4 to 5 sites per field, which was the industry standard for many years. Methods that have emerged include overlay metrology in many or all fields, including the high order field model method called high order control (HOC), and field by field control (FxFc) methods also called correction per exposure. The HOC and FxFc methods were initially introduced as relatively infrequent scanner qualification activities meant to supplement linear production schemes. More recently, however, it is clear that production control is also requiring intense sampling, similar high order and FxFc methods. The added control benefits of high order and FxFc overlay methods need to be balanced with the increased metrology requirements, however, without putting material at risk. Of critical importance is the proper control of edge fields, which requires intensive sampling in order to minimize signatures. In this study we compare various methods of overlay control including the performance levels that can be achieved.
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Chun-Yen Huang, Chui-Fu Chiu, Wen-Bin Wu, Chiang-Lin Shih, Chin-Chou Kevin Huang, Healthy Huang, DongSub Choi, Bill Pierson, John C. Robinson, "Overlay control methodology comparison: field-by-field and high-order methods", Proc. SPIE 8324, Metrology, Inspection, and Process Control for Microlithography XXVI, 832427 (5 April 2012); doi: 10.1117/12.916427; https://doi.org/10.1117/12.916427


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