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2 May 2008 Characterizing the imaging performance of flash memory masks using AIMS
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Proceedings Volume 6792, 24th European Mask and Lithography Conference; 67920K (2008)
Event: 24th European Mask and Lithography Conference, 2008, Dresden, Germany
Flash memory has become one of the most important segments of the semiconductor industry in recent years. Flash memory is also an important driver of the lithography roadmap, with its dramatic acceleration in dimensional shrink, pushing for ever smaller feature sizes. The introduction of the XT:1700Fi and XT:1900Gi have brought the 45nm node and below within reach for memory makers. At these feature sizes mask topology and the material properties of the film stack on the mask play an important role on imaging performance. Furthermore, the break up of the array pitch regularity in the NAND-type flash memory cell by two thick wordlines and a central space, leads to feature-center placement (overlay) errors, that are inherent to the design. An integral optimization approach is needed to mitigate these effects and to control both the CD and placement errors tightly. In this paper we will present the results of aerial image measurements on mask level of a NAND-Flash Memory Gate layer using AIMSTM 45-193i. Various imaging relevant parameters, such as MEEF, EL, DoF and placement errors are measured for different mask absorber materials for features sizes ranging from 39nm half pitch to 41nm half pitch design rule on wafer level. The AIMSTM measurements are compared to experimental results obtained with a XT:1900Gi hyper-NA immersion system. Mask optimization strategies are sought to increase Depth of Focus and minimize feature-center placement errors.
© (2008) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Eelco van Setten, Onno Wismans, Kees Grim, Jo Finders, Mircea Dusa, Robert Birkner, Rigo Richter, and Thomas Scherübl "Characterizing the imaging performance of flash memory masks using AIMS", Proc. SPIE 6792, 24th European Mask and Lithography Conference, 67920K (2 May 2008);

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