OPC and Modeling Solution towards 0.55NA EUV Stitching

Abstract

The new high numerical aperture (NA) Extreme Ultraviolet Lithography (EUVL) with a NA of 0.55 is being developed at ASML, which is using an anamorphic projection system with the demagnification of 4× in xdirection and 8× in y-direction. Compared to the traditional 0.33NA EUV scanner with full-field image size of 26 × 33mm2, 0.55NA EUVL reduces the exposure field size to half-field (26 × 16.5mm2), due to this 8× demagnification in y-direction and the reticle size remaining unchanged (six-inch square). Therefore, in-die stitching between two exposures is needed for the applications requiring larger than half-field size. To achieve in-die stitching in practical applications at advanced node, performing model based optical proximity correct (OPC) is an essential step. Therefore, a complete process modeling and OPC flow is required. To build an accurate OPC model, the interaction effects between two stitching fields require some special considerations, such as aerial image interaction, optical proximity effect among the stitching patterns, mask absorber reflection, black border proximity effect, as well as the stray light from the neighboring fields effect. All these effects must be captured by specific models. In this paper, we will investigate the in-die stitching effects and solutions through simulation and wafer data. Thus, to collect the wafer proof data, various stitching test patterns have been designed and placed on imec test masks, and the wafer data will be obtained on imec 0.33NA EUV scanner.