Mask Defect Auto Disposition based on Aerial Image in Mask Production

摘要

At the most advanced technology nodes, such as 45nm and below, aggressive OPC and Sub-Resolution Assist Features (SRAFs) are required. However, their use results in significantly increased mask complexity, making mask defect disposition more challenging than ever. In an attempt to mitigate such difficulties, new mask inspection technologies that rely on hardware emulation and software simulation to obtain aerial image at the wafer plane have been developed; however, automatic mask disposition based on aerial image is still problematic because aerial image does not give the final resist CD or contour, which are commonly used in lithography verification on post OPC masks. In this paper, an automated mask defect disposition system that remedies these shortcomings is described. The system, currently in use for mask production, works in both die-to-die and die-to-database modes, and can operate on aerial images from both AIMS? and aerial-image-based inline mask inspection tools. The disposition criteria are primarily based on wafer-plane CD variance. The system also connects to a post-OPC lithography verification tool that can provide gauges and CD specs, which are then used in the mask defect disposition.