Data feed-forward for improved optical CD and film metrology

Advanced integrated circuit (IC) manufacturing requires high quality metrology for process disposition and control in order to achieve high yields. As the industry advances in high volume manufacturing of 3x and 2x nm nodes with the associated advanced materials and complex structures, understanding and reducing film and critical dimension (CD) measurement uncertainty is more critical than ever. Optical film metrology is used for measurement of critical film parameters such as n & k, thickness and composition, while optical CD metrology is used for measurement of CD, sidewall angle (SWA), height, and other structure-related parameters. Both optical film and CD metrologies utilize advanced structure modeling that includes fitting parameters of the device stack for multiple layers simultaneously. These methods have been proven and established in both R&D and high volume manufacturing scenarios. As film stacks and structures become more complex and design tolerances shrink, however, additional parameters need to be included in the modeling, in some cases leading to reduced parameter precision and unwanted parameter correlation. In this paper we discuss a new methodology, Data Feed Forward, that utilizes multiple metrology steps, and the feed forward of the derived parameters to next metrology steps, for improved measurement sensitivity and quality. In addition, we discuss Data Feed Forward requirements for fab-wide implementation.