Non-local bound states in the continuum for nanoscale alignment

In the semiconductor microelectronics industry, overcoming the limitations of the optical diffraction limit is crucial for multiple exposure alignment technology. Here we present a method that utilizes bound states in the continuum (BICs), a physical phenomenon in optics, to address this challenge. The transition from BIC to quasi-BIC caused by out-of-plane asymmetry (that is, displacements between different layers) is studied through simulations and experiments. Results illustrate the emergence of resonance and evolution in the quality factor with increasing asymmetry. Measured Q factors decrease from near-infinite to 66 as the displacement increases from 0 to 110 nm, providing a sensitive metric for nanoscale positional changes. This shows that quality factors of BIC resonances are valuable tools for precise chip patterning accuracy. This approach can be integrated with standard lithography marks and fabrication processes, offering a scalable solution compatible with complementary metal–oxide–semiconductor technology for high-precision nano-alignment in advanced semiconductor manufacturing. Researchers study the transition from bound states in the continuum (BICs) to quasi-BIC caused by out-of-plane asymmetry and illustrate how quality factors of BIC resonances are valuable tools for precise chip patterning accuracy.