Curvy Masks Ahead!
Learn how curvilinear mask shapes provide larger lithography entitlement than traditional rectilinear masks and became a viable option for IC manufacturing.
Why curvilinear masks?
IC Design and manufacturing has historically represented shapes as Manhattan. Rectilinear polygons are a very efficient way to use available space. Circles and curves waste space, but in the real world, corners are always rounded to some extent. Rectilinear designs exhibit rounded corners on wafer due mostly to the low-pass nature of projection optics. Rectilinear designs exhibit rounded corners on mask due to finite corner resolution by optical/e-beam writers.
Patterning requirements of next-generation lithographic processes have pushed lithographers to explore the advantages of curvilinear masks. The arrival of multi-beam mask writers (MBMW) addresses the mask write runtime penalty associated with high vertex counts and brings curvilinear (CL) masks closer to reality.
The industry is moving full speed ahead to enable CL mask tools, data handling, and flows.