CD uniformity improvement by active scanner corrections

Abstract

As resolution shrinks, also the demands for litho CD Uniformity are becoming tighter. In replicating the mask pattern into photoresist, a sequence of modules within the patterning cluster (coat, expose, develop, etch) is responsible for CD non-uniformity. So far, the strategy has been to make the contribution of each of these modules as small as possible. The CD Uniformity can be improved in a more efficient way by compensating the various error sources with adapted dose profiles on the scanner. An inventory is made of the requirements for this compensation mechanism. In more detail a description is given how the scanner can apply these dose corrections. With experiments, the feasibility of the concept is proven. Improvements in CD Uniformity over 5nm are demonstrated, both on test structures as well as on real device layers.