Stitching: High NA results

Abstract

High-NA EUV scanner has anamorphic optics with 8x demagnification in y direction and thus twice smaller exposure fields 26x16.5 mm2. In-die stitching may be required in order to create dies larger than High NA exposure field. In this work we introduce different stitching scenario’s including two reticles exposure (AB), a block and route option and feature stitching. We continue our study on at resolution stitching of lines and spaces exposed on High NA EUV system EXE:5000 in the joint ASML-imec High NA lab [1] and explore OPC approaches. In particular, we evaluate CD and LCDU impact between A and B exposures while keeping wafers in the controlled environment between exposures. For feature stitching we look at the stitch CD profile and its variability across wafer an as well as local CD uniformity for pitch 24 nm vertical and horizontal lines and spaces with metal oxide resists for tantalum-based reticle. We evaluate stitching with OPC and see whether it can improve stitching performance. We conclude on how ASML supports full field High NA imaging.