B a c kg r o u n d
Software engineering
Clearing the critical software path For a highly complex machine like the Twinscan to be able to operate smoothly, its system control should run without any unnecessary interruptions. Within the Concerto project, ASML, ESI (TNO) and TUE have developed a model-based methodology to analyze the software execution and keep computational tasks out of the critical path as much as possible. The partners see great potential for the approach to be widely adopted in the high-tech industry. Nieke Roos
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n ASML’s lithographic systems, the Twinscan stage simultaneously moves two tables, each holding a silicon wafer. While one wafer is being exposed to – deep or extreme – ultraviolet light containing the chip pattern to be printed, the other is measured by the machine’s metrology sensors to optimize alignment. The tables are propelled electromagnetically, allowing frictionless acceleration as high as 7G. Every move the Twinscan stage makes has been precisely calculated by the sys-
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tem’s software. To ensure a smooth journey from A to B and prevent a wafer table from missing a turn, the computations need to be completed in time. “Imagine you’re on the highway, following the instructions of your navigation system,” ASML’s Jos Vaassen makes a comparison. “If the system takes too much time to calculate the route, you’re going to drive right past your exit. Likewise, we don’t want our scanners to miss a turn because our software is missing a deadline.”
Credit: ASML
As the chip patterns to be printed continue to shrink, however, the lithographic scanner grows ever more complex, requiring an increasing amount of computations to get the job done. This raises the likelihood of missing a turn and having to stop for some time to recalculate and get back on track. Such an interruption has widespread consequences. For example, it affects the focus of the lens system and the alignment of two subsequent chip layers. Ultimately, it will impact the machine’s performance. To prevent that from happening, the computations, realized in software, need to be continuously monitored. With that goal in mind, ASML and TNO’s high-tech joint innovation center ESI set up the Concerto project in 2016, together with Eindhoven University of Technology (TUE). In four years, they developed a model-based methodology to diagnose, predict and optimize system timing and throughput and to keep computational tasks out of the critical path as much as possible.
