Advances in CD-AFM Scan Algorithm Technology Enable Improved CD Metrology

摘要

Improving device performance and yield is one of the primary goals of microelectronic research and development. In order to attain this goal, process engineers are focusing on the integration of new materials and the development of new device architectures. For production process control, the two main techniques to monitor device dimensions are CD-SEM and Scatterometry. Despite the excellent repeatability of these techniques, SEM and Scatterometry often suffer from unacceptably large measurement uncertainty, particularly when applied to newly developed device technologies. A consequence of these metrology limitations is a delay in the transition of new process technologies into production. Furthermore, these techniques have not been proven to be effective in measuring 3-dimensional characteristics such as Line Edge Roughness and Line Width Roughness in the Bottom-CD region. A potential alternative to SEM and Scatterometry in many applications is CD-AFM, a highly versatile metrology technique, which is capable of providing consistent, precise 3-dimensional measurements for a wide range of sample types and geometries. In this paper we present a recent CD-AFM scan algorithm enhancement that significantly improves Bottom-CD measurement bias and precision. In addition, we present a separate but complementary enhancement in the CD-AFM scan algorithm, which we have demonstrated to improve overall CD measurement resolution and precision, while increasing scan speed when using advanced CD-AFM Tips. Our results show that the use of these two techniques enhances Line-Edge Roughness and Line-Width Roughness resolution, precision and accuracy.