Computational ASCAL verification with inline ASCAL in high volume manufacturing fab for ArF XT:1460K with LOCO-B

In DRAM process development history, lens heating is always a huge problem that affects overlay and focus control, especially when using high dose and special DOEs like dipole and quasar. Computational ASCAL (cASCAL) is the offline simulation method to create Lens Heating Feed Forward (LHFF) models with input of reticle layout and illumination without system output loss. cASCAL is able to support ArF XT:1460K tools since 2019. It is proven that on-product overlay results are comparable between cASCAL and inline-ASCAL for ArF XT:1460K tool under LOCO-B with LSC (Lens Specific Calibration) enabled.