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This sampling tool can use different inputs (production, tools, APC…) in a dynamic way. This means that the system is dynamic for both process and metrology aspects, and can be adapted to integrate different variables and external events. A real time communication flow was created between APC and sampling tool. Even if the measurement skip decision is taken by the sampling tool, the APC feedback is systematically requested when run to run is involved, like for all lithography process steps. The strength is to deal with high products / mix complexity and react in real time to new product introduction, process deviation, atypical lots including R&D projects and sudden change of the products mix. Both tools are so linked that the sampler remains invisible. Process engineers continue to manage and control lithography process through APC tool mainly. In parallel, different alarms and triggers have been implemented, including a specific “crisis” mode to quickly respond to the metrology equipment loading or availability variability. The sampler introduction allowed an optimization of the metrology toolset costs and lot cycle time improvement. Also as a consequence, a more efficient metrology control plan, with an optimized balance between process criticality and metrology requirements. Future opportunities are related to more dynamic behaviors, as a dynamic sampling rate adapted to metrology capacity, function of the real time metrology capacity or sampling decision dynamically based on process variability components. |
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