16 March 2009 High-order distortion effects induced by extreme off-axis illuminations at hyper NA lithography
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Aggressive pitch requirements for line/space pattern devices require the usage of extreme off-axis illumination schemes to enhance the resolution of the exposure tools. These illumination schemes stress the quality of the optics because of the anisotropy of the optical paths through the lens. Moreover, the marginalities on the patterning are dramatically enhanced if two or more illumination modes are requested in the lithography process. The effects on overlay between double exposure layers exposed with different illumination settings, with one being an extreme illumination setting, will be discussed and two approaches will be addressed to compensate the resulting overlay fingerprint. The first approach optimizes the lens setup by means of a dedicated scanner option to minimize the lens effects on overlay and reduce the distortion for each layer: in this case the simulation time and the impact on other imaging parameters will be carefully evaluated. The second methodology corrects the induced misalignment by a high order modelling compensation. This approach requests the insertion of a suitable set of overlay measurement targets into the product frame to appropriately fit the distortion matching of the two layers.
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Pierluigi Rigolli, Pierluigi Rigolli, Gianfranco Capetti, Gianfranco Capetti, Elio De Chiara, Elio De Chiara, Leonardo Amato, Leonardo Amato, Umberto Iessi, Umberto Iessi, Paolo Canestrari, Paolo Canestrari, Christine Llorens, Christine Llorens, Sanne Smit, Sanne Smit, Lionel Brige, Lionel Brige, Johannes Plauth, Johannes Plauth, } "High-order distortion effects induced by extreme off-axis illuminations at hyper NA lithography", Proc. SPIE 7274, Optical Microlithography XXII, 72742T (16 March 2009); doi: 10.1117/12.814148; https://doi.org/10.1117/12.814148

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