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30 October 2007 Exploring the sources of MEEF in contact SRAMs
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Optical Proximity Correction (OPC) relies on predictive modeling to achieve consistent wafer results. To that end, understanding all sources of variation is essential to the successful implementation of OPC. This paper focuses on challenging SRAM layouts of contacts to study the sources of wafer variation. A range of shape geometries and contact configurations are studied. Contact shapes are no longer restricted to simple rectangles on the mask, some more complex OPC outputs may include shapes like H's or T's or even more fragmented figures. The result is a large group of parameters that can be measured at both mask and wafer level. The dependence of mask variation on geometry is studied through the statistical distributions of parameter variations. The mask metrology output is expanded from traditional linear dimensional measurements to include area, line edge roughness, corner rounding, and shape-to-shape metrics. Wafer mask error enhancement factor (MEEF) is then calculated for the various contact geometries. This collection of data makes it possible to study variation on many levels and determine the underlying source of wafer variations so that, ultimately, they can be minimized.
© (2007) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Emily Gallagher, Ian Stobert, Masaru Higuchi, and Donald Samuels "Exploring the sources of MEEF in contact SRAMs", Proc. SPIE 6730, Photomask Technology 2007, 67302I (30 October 2007);

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