We report on a combined experimental and theoretical study on pattern displacement by lens aberrations. The calculations and experiments were done using ArF lithography.
Theoretically, we have modeled pattern displacement using BIF lens aberration data and sensitivities for specific illumination conditions. We find a characteristic dependence of the pattern displacement on the illumination condition, feature type and orientation. Features with low and high sensitivities to lens aberrations are identified, together with a reference feature with low sensitivity for pattern placement error.
Experimentally, we have measured by CD-SEM the shift between patterns obtained with a multiple exposure and at different illumination conditions. The pattern shift observed through the scanner slit at the different illumination conditions shows the characteristic signature and amplitude from simulations based on the BIF lens aberration data. The effects of pattern pitch and orientation on pattern displacement, found experimentally, also matched the simulations. This demonstrates that BIF aberration data can be used to predict pattern placement errors.© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.