Dr. Aymen Mili Profile

Dr. Aymen Mili

at STMicroelectronics SA

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Publications (1)

Proceedings Article | 26 March 2019 Presentation + Paper

New approach for APC and measurement sampler interaction in a complex process mix logic fab

L. Lecarpentier, A. Mili, J. Decaunes, B. Le Gratiet

Proceedings Volume 10959, 109591Q (2019) https://doi.org/10.1117/12.2514943

KEYWORDS: Metrology, Overlay metrology, Semiconducting wafers, Process control, Reticles, Lithography, Logic, Photomasks, Process engineering, Scanners

Read Abstract +

Since the beginning of the Crolles 300mm fab, more and more complex logic technologies, down to 28nm node, have been developed. At the same time, the products mix increased at a very high level : Specifically for the lithography area, this complexity leads to an intricate management of thousands of masks, hundreds of track process recipes, used on various lithography clusters types (193nm including immersion, 248nm and 365nm). In order to apply the best process parameters, APC software is used since many years, and was continuously improved. It now takes into account multi-variate parameters coming from various process contexts. A new sampling tool was developed to adjust the measurements control plan. All kind of in-line measures are addressed (thickness, critical dimensions, overlay…). Since the beginning of this software development, the approach was to keep in mind the APC model. The objective was to use the APC data’s (alarms and warnings) to secure the sampling decisions without compromising the regulation loops stability.

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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