No abstract

As reduction of k1 factor continues, it becomes more extensive to apply resolution enhancement techniques(RETs) such as phase shift mask(PSM), optical proximity correction(OPC) and off axis illumination(OAI). OPC has been playing a key role to control of pattern printing accuracy and maximize the overlapping process window especially for logic devices. However, RETs, including OPC, tend to increase the sensitivity of printed images to the projection lens aberrations. In order to improve the pattern uniformities and image qualities, lens aberration should be considered as one of the most important factor to OPC modeling.In this paper, we investigated the impact of lens aberration on data set for OPC model generation. The data of projection lens aberrations on exposure tools were extracted by LITEL In-situ Interferometer(ISI) and the sensitivity of CD variation with each lens aberration was simulated by SIGMA-C Solid-E Simulator. Among the lens aberrations, the significant error sources contributing to setting a limit to use one general OPC model with multiple exposure tools were analyzed. Also, the lens aberration specification to use one general OPC model was proposed. By considering the effect and specification of lens aberrations, further improvement of the OPC model accuracy and prevention of device yield loss originated from lens aberrations are expected.

We investigated the influence of lens aberration on the lithographic performance according to the phase error and topography effects of phase-shift mask (PSM). Twin-bar and isolated pattern showing high sensitivity to lens aberration were used for this study. The simulation of aberrated images was carried out using the Solid-CTM simulator. Specially, we quantified the relationship between patterning behaviors such as the isofocal tilt, the left-right (L-R) CD difference and the Z7 and Z9 individual Zernike coefficients. Isofocal tilt aberration sensitivity for Z9 was 0.4nm/nm, which resulted in 2nm CD variation using lens with 5nm Z9 value. When using the lens with 5nm Z7 value, the L-R CD difference and its sensitivity are 10nm and 2nm/nm, respectively. Finally, we evaluated the patterning performance by phase error effect, and determined the phase error criteria for PSM. The pattern placement error was increased by increasing phase error as well as Z7 value, while its slope to the defocus was similar regardless of lens aberration. However, it was found that the aberration sensitivity was not affected by phase error. The simulation predicted that the sensitivity of lens aberration could be increased due to mask topography effect. The nominal shift of phase edge attributed to mask topography was measured.