Multi-spectral snapshot diffraction-based overlay metrology

Diffraction-based overlay (DBO) metrology has been suc-cessfully introduced to deal with the tighter overlay control in modern semiconductor manufacturing. Moreover, DBO metrology typically needs to be performed at multiple wave-lengths to achieve accurate and robust measurement in the presence of overlay target deformations. In this Let-ter, we outline a proposal for multi-spectral DBO metrology based on the linear relation between the overlay errors and the combinations of off-diagonal-block Mueller matrix ele-ments increment M =Mij - ( - 1)jMji (i =1, 2; j = 3, 4) associated with the zeroth-order diffraction of overlay target gratings. We propose an approach that can realize snapshot and direct measurement of increment M over a broad spectral range without any rotating or active polarization component. The simu-lation results demonstrate the capability of the proposed method for multi-spectral overlay metrology in a single shot. & COPY; 2023 Optica Publishing Group