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By Michael Gostein, John Byrnes, Alex Mazurenko & Tony Bonanno, Advanced Metrology Systems; Peter Weidner & Alexander Kasic, Qimonda Dresden, Germany;
Philip Abromitis, Qimonda Richmond, USA

ABSTRACT
An important metrology challenge in the high-volume manufacturing of deep trench DRAM devices is the measurement of recess structures, formed in the poly fill near the top of the deep trench. These recesses are used to form final elements of the DRAM capacitor structure. For the shallow poly recess 2 and recess 3 structures, which are less than 300nm deep, AFM has until recently been the primary metrology method. However, infrared optical metrology is an increasingly attractive alternative because it provides higher throughput and better scalability to smaller critical dimensions. In this article we address the application of infrared metrology to these shallow recess structures for 90nm and 75nm trench DRAM, and discuss the potential benefits for future technology nodes.