We perform experimental and theoretical studies of image placement error induced by aberrations of the projection lens. The goal is to experimentally determine the magnitude of the image placement errors, to compare experiments and simulations, and to screen possible correction strategies. The calculations and experiments are done for ArF lithography. Theoretically, we simulate image placement error using the projection lens aberration data and simulators such as Prolith or Solid-C. Features with low and high sensitivities to lens aberrations are identified, together with a reference feature that has low sensitivity for image placement error. Dedicated reticles are fabricated to print various features at different illumination conditions on the same substrate. The resulting patterns could be analyzed using top-down scanning electron microscopy ͑SEM͒, but also optically with the standard optical overlay tool KLA5200. For both techniques, the experimentally found image placement errors are in excellent agreement with simulations. In simulations, we calculate the dependency of the image placement error on pattern density, pattern orientation, and illumination conditions. These tendencies are experimentally reproduced. We conclude with a case study that demonstrates a possible correction strategy for image placement error.

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.