Avoiding at-resolution stitching for logic and DRAM applications in high-NA EUV lithography

Abstract

We present innovative design strategies to eliminate the need for at-resolution field stitching in high-numerical aperture extreme ultraviolet lithography. For logic applications, two complementary approaches at the inter- and intra-cell levels are proposed. These include the insertion of dummy filler cells or relaxed-pitch cells, combined with metal routing blockages, which can be seamlessly implemented within a modified place-and-route flow, thereby simplifying process complexities associated with at-resolution stitching. For dynamic random access memory applications, a die aspect ratio optimization methodology is introduced to maximize mask area utilization and improve manufacturing throughput. Depending on the die arrangement in the full imaging field, two stitching scenarios are identified: an even number of dies in the Y-direction, enabling pitch-tolerant field stitching along the scribe lane, and an odd number of dies, which eliminates the need for critical-dimension-critical stitching at the stitching boundary.