Integrated ODP Metrology Matching To Reference Metrology For Lithography Process Control

Advanced DRAM manufacturing demands rigorous and tight process control using high measurement precision, accurate, traceable and high throughput metrology solutions. Scatterometry is one of the advanced metrology techniques which satisfies all of these requirements. Scatterometry has been implemented in semiconductor manufacturing for monitoring and controlling critical dimensions and other important structural parameters. One of the major contributing factors to the acceptance and implementation of scatterometry systems is the ability to match to reference metrology. Failure to understand the optimum matching conditions, can lead to wrong conclusions with respect to hardware stability and/or incorrect analysis of production data. This paper shows the use of the integrated scatterometry system to control the lithography processes in a real production environment. In the control system, the scatterometry Optical Digital Profilometry (ODP(trademark sign)) data is referenced to sampled CD-SEM data. A significant improvement in matching between the two metrology systems was achieved following the implementation of a new ODP-function. The results also reveal a clearer roadmap for the implementation of an integrated scatterometry based control loop system. The results also pointed to how to achieve a reduced setup time as well as a deeper understanding of the relationship between test data and production data. It has been clearly shown that to achieve the desired sub-nanometer matching in scatterometry measurements for advanced process control, we need to pay scrupulous attention to matching data not only from test wafers but from production data in order to derive functions that will produce the optimum matching conditions.