Etch, reticle, and track CD fingerprint corrections with local dose compensation

Meeting a specific CD uniformity roadmap becomes more and more difficult as different budget components affecting CD uniformity fail to meet their requirements. For example, reticle manufacturing is at the edge of its potential, and hotplates impact CD uniformity by design. Also, etch processes must be balanced between optimal settings for varying structures. While work continues to enhance the performance of individual budget components, applying local exposure dose compensation with a scanner can provide a near-term solution for improving CD uniformity. Within the wafer processing chain, only the scanner has the unique capability to influence the final quality across-field and field-to-field in a controlled manner, making it the most effective tool for compensation. This paper describes the subsystems required for dose compensation and presents a solution that allows full integration into an automated fabrication environment. Examples will show that both the reticle contribution as well as the process-induced across-wafer fingerprint, including etch, can be improved by up to 50 percent. This improvement is demonstrated both on test structures and on memory device layers.