3 April 2008 Production aspects of 45nm immersion lithography defect monitoring using laser DUV inspection methodology
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Abstract
Immersion lithography addresses the limits of optical lithography by providing higher NA's (NA > 1), which enable imaging of smaller features and hence it enables production of 45nm logic devices. One of the key challenges of this advanced technology, however, is controlling the defectivity level produced specifically by the Lithography immersion stepper and track systems. To control and monitor the immersion processes in production, consideration has been given to identifying an alternative to the traditional sensitivity approaches, using Darkfield (DF) and Brightfield (BF) wafer inspection methodologies. This unique method should provide for stable, reliable and sensitive inspection results which are capable of supporting a technology node introduction (product ramp) as well as monitoring the base line performance (in other words, capture excursions). The following study was done to explore laser DUV Brightfield inspection, utilizing the Applied Materials UVisionTM, which has the ability to detect defects as small as 20-40nm size. Additionally a joint project between AMD, ASML and AMAT developed an appropriate inspection strategy that combines, lithographic defect printing simulations and sensitive inspection routines to identify defect problems effectively, drive defect reduction efforts and result in stable production monitoring. We investigated the use of traditional Photo Test Monitor (PTM) as a valid technique to monitor the introduction of the immersion lithography at 45nm. In addition, we explored the correlation between these PTM wafers and the actual production wafers for new types of defects. It was found that the amount of small protrusion defects (~20-40nm size) increased on immersion PTM wafers compared to dry processed PTM wafers. Based on process experiments at AMD and immersion defect simulations provided by ASML we were able to isolate immersion specific defect problems from general lithography related defects also seen in Dry lithography. The results show that unique combination of high sensitivity defect inspection methods and simulation efforts can very effectively drive defect reduction efforts and accelerate yield on advanced technology like immersion lithography. Additionally, it is also possible to provide a production monitoring of 45nm immersion processes with such extreme sensitive inspection of PTM wafers of defects down to 20nm.
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Remo Kirsch, Remo Kirsch, Antje Martin, Antje Martin, Uzodinma Okoroanyanwu, Uzodinma Okoroanyanwu, Wolfram Grundke, Wolfram Grundke, Ute Vogler, Ute Vogler, Mirko Beyer, Mirko Beyer, Eran Valfer, Eran Valfer, Susan Weiher-Tellford, Susan Weiher-Tellford, Renana Perlovitch, Renana Perlovitch, Nurit Racah, Nurit Racah, Peter Vanoppen, Peter Vanoppen, Richard Moerman, Richard Moerman, } "Production aspects of 45nm immersion lithography defect monitoring using laser DUV inspection methodology", Proc. SPIE 6922, Metrology, Inspection, and Process Control for Microlithography XXII, 692204 (3 April 2008); doi: 10.1117/12.777371; https://doi.org/10.1117/12.777371
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