19 March 2015 Improvement of process control using wafer geometry for enhanced manufacturability of advanced semiconductor devices
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Aggressive advancements in semiconductor technology have resulted in integrated chip (IC) manufacturing capability at sub-20nm half-pitch nodes. With this, lithography overlay error budgets are becoming increasingly stringent. The delay in EUV lithography readiness for high volume manufacturing (HVM) and the need for multiple-patterning lithography with 193i technology has further amplified the overlay issue. Thus there exists a need for technologies that can improve overlay errors in HVM. The traditional method for reducing overlay errors predominantly focused on improving lithography scanner printability performance. However, processes outside of the lithography sector known as processinduced overlay errors can contribute significantly to the total overlay at the current requirements. Monitoring and characterizing process-induced overlay has become critical for advanced node patterning. Recently a relatively new technique for overlay control that uses high-resolution wafer geometry measurements has gained significance. In this work we present the implementation of this technique in an IC fabrication environment to monitor wafer geometry changes induced across several points in the process flow, of multiple product layers with critical overlay performance requirement. Several production wafer lots were measured and analyzed on a patterned wafer geometry tool. Changes induced in wafer geometry as a result of wafer processing were related to down-stream overlay error contribution using the analytical in-plane distortion (IPD) calculation model. Through this segmentation, process steps that are major contributors to down-stream overlay were identified. Subsequent process optimization was then isolated to those process steps where maximum benefit might be realized. Root-cause for the within-wafer, wafer-to-wafer, tool-to-tool, and station-to-station variations observed were further investigated using local shape curvature changes – which is directly related to stresses induced by wafer processing. In multiple instances it was possible to adjust process parameters such as gas flow rate, machine power, etc., and reduce non-uniform stresses in the wafer. Estimates of process-induced overlay errors were also used to perform feedforward overlay corrections for 3D-NAND production wafers. Results from the studies performed in an advanced semiconductor fabrication line are reported in this paper.
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Honggoo Lee, Honggoo Lee, Jongsu Lee, Jongsu Lee, Sang Min Kim, Sang Min Kim, Changhwan Lee, Changhwan Lee, Sangjun Han, Sangjun Han, Myoungsoo Kim, Myoungsoo Kim, Wontaik Kwon, Wontaik Kwon, Sung-Ki Park, Sung-Ki Park, Pradeep Vukkadala, Pradeep Vukkadala, Amartya Awasthi, Amartya Awasthi, J. H. Kim, J. H. Kim, Sathish Veeraraghavan, Sathish Veeraraghavan, DongSub Choi, DongSub Choi, Kevin Huang, Kevin Huang, Prasanna Dighe, Prasanna Dighe, Cheouljung Lee, Cheouljung Lee, Jungho Byeon, Jungho Byeon, Soham Dey, Soham Dey, Jaydeep Sinha, Jaydeep Sinha, "Improvement of process control using wafer geometry for enhanced manufacturability of advanced semiconductor devices", Proc. SPIE 9424, Metrology, Inspection, and Process Control for Microlithography XXIX, 94240M (19 March 2015); doi: 10.1117/12.2085862; https://doi.org/10.1117/12.2085862

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