Sub-nanometer misalignment sensing for lithography with structured illumination

Lithography for the next generation of integrated-circuit manufacturing at the 3 nm node requires sub-1-nm misalignment measurement accuracy, which is almost impossible for existing systems due to the optical diffraction limit. Herein, we propose a misalignment sensing strategy based on structured illumination. By virtue of the distinctive modulation effect of a Talbot diffractive illuminated field on moiré fringes, the measurement signals can pass unhindered through the optical system and be used for sensing. Experiments are used to demonstrate that the proposed method can implement real-time-lapse (100 Hz) misalignment sensing with an accuracy of sub-1-nm (0.31 nm @ 3σ), making it suitable for various lithography techniques (e.g., proximity, x ray, projective, and nanoimprint lithography) and fields requiring advanced precision measurement (e.g., quantum measurement, gravitational wave detection, and molecular biology).