Inverse Lithography Technology (ILT) is a promising resolution enhancement technology (RET) technique due to its superior ability to produce mask output that ensures enhanced process latitude and critical dimension (CD) control within fabrication facilities. With shrinking critical dimensions in IC manufacturing, the necessity for sub-resolution assist features (SRAF) becomes indispensable, particularly in deep ultraviolet (DUV) and extreme ultraviolet (EUV) lithography processes.
However, the synthesis of DUV and EUV SRAFs presents challenges, considering lithography-specific effects and critical metrics such as process variability (PV band), common depth-of-focus (cDOF), and image log-slope (ILS). While ILT SRAFs promise optimal lithography quality, their native application for full-chip IC manufacturing faces hurdles due to inherent inconsistencies and inadequate runtime.
To address these challenges, Calibre ILT-guided template-based SRAF synthesis offers lithography quality equivalent to ILT SRAFs in terms of PV band, cDOF, and ILS, while significantly improving runtime efficiency—approximately 50 times faster than native ILT SRAF synthesis. Moreover, the template-based approach ensures consistency in SRAF placement and compliance with multi-patterning rules (MRC).
The integration of ILT-guided SRAF synthesis combines the lithography-quality enablement of ILT with the rapid runtime and inherent consistency of template-based synthesis. This makes it a viable and efficient SRAF synthesis technology for full-chip IC manufacturing, addressing the stringent requirements of modern lithography processes and facilitating the production of advanced semiconductor devices.