Double patterning (double exposure and double etch) is definitely a viable solution for overcoming the physical resolution limit of k1=0.25 of imaging systems. This article presents the overlay budget for a double patterning technique using a 45nm technology node flash memory device with k1∼0.20 and 193nm dry lithography. Adopting double exposure, the final pattern is composed of two lithography patterns within the resolution capability of the exposure tool and then combined with the double etching processes. The photoetch photoetch approach creates the overlay between the two exposures which is the most critical issue to be addressed. This article presents the adopted scanner setup, mask requirements, and efficient overlay metrology setup in order to achieve the overlay roadmap of 6nm for the 45nm technology node.

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