The use of optical metrology techniques in process control for microelectronic manufacturing has become widespread. These techniques are fast and non-destructive, allowing a higher sampling rate than non-optical methods like scanning electron or atomic force microscopy. One drawback of most optical metrology tools is the requirement that special measurement structures be fabricated in the scribe line between chips. This poses significant limitations regarding the characterization of lithography processes that may be overcome via in-chip measurements. In this paper we present experimental results for an in-chip optical metrology technique that allows direct measurement of both critical dimensions and overlay displacement errors in the DRAM manufacturing process. This technique does not require special target structures and is performed on the actual semiconductor devices.
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