Spacer-defined double patterning for 20nm and beyond logic BEOL technology

Spacer-defined double patterning was investigated as a patterning option for 20/14-nm logic technology's back-end-of-line (BEOL), and compared with the double patterning options of front-end-of-line (FEOL). Negative spacer-defined double patterning was used to provide less overlay impact and variable CD control on the metal lines compared with other double patterning techniques. Block lithography as a 2nd exposure was able to maintain better tip-to-tip and tip-to-line fidelity by forming lines that behave as a additive etch block. SiO2 spacer was directly deposited on resist core-mandrel via a low-temperature deposition process. Resist integrity was optimized through aerial image and mask optimization as well as resist selection processes. Design decomposition of the BEOL layout was identified as a major challenge in enabling the spacer-defined double patterning. Finally, successful integration of the patterning into the BEOL device was demonstrated.