EUV secondary electron blur at the 22nm half pitch node

Abstract

In this paper the Arrhenius behavior of blur upon EUV exposure is investigated through variation of the PEB temperature. In this way, thermally activated parameters that contribute to blur (such as acid/base diffusion) can be separated from non-thermally activated parameters (such as secondary electron blur). The experimental results are analyzed in detail using multi-wavelength resist modeling based on the continuum approach and through fitting of the EUV data using stochastic resist models. The extracted blur kinetics display perfectly linear Arrhenius behavior, indicating that there is no sign for secondary electron blur at 22nm half pitch. At the lowest PEB setting the total blur length is ~4nm, indicating that secondary electron blur should be well below that. The stochastic resist model gives a best fit to the current data set with parameters that result in a maximum probability of acid generation at 2.4nm from the photon absorption site. Extrapolation of the model predicts that towards the 16nm half pitch the impact on sizing dose is minimal and an acceptable exposure latitude is achievable. In order to limit the impact on line width roughness at these dimensions it will be required to control acid diffusion to ~5nm.

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