The YieldStar by ASML - software to squeeze more wafers per day

YieldStar by ASML is one of those tools you only notice when it’s missing: a slim measurement system sitting quietly next to the lithography scanners, its doors humming softly as wafers slide in and out under cold white cleanroom light. Operators in full bunny suits watch dashboards, not lenses. For them, YieldStar is less a box of optics and more a stream of numbers that tells them whether their fab will hit its output target tonight.

ASML’s metrology software backbone

ASML built YieldStar as an integrated optical metrology platform to measure critical parameters like overlay, focus and CD (critical dimension) on wafers, tightly linked with its lithography scanners and computational lithography software. ASML describes YieldStar as its optical metrology family. The system does not print patterns itself; instead it reads them and feeds process data back into ASML’s control software including its Litho InSight platform. ASML groups YieldStar tightly with its software solutions portfolio.

The software side is crucial. ASML’s CTO, Martin van den Brink, has repeatedly stressed that metrology and software now represent a growing share of customer value compared with pure scanner hardware, as fabs chase ever finer patterning at nodes like 3 nm and below. YieldStar’s analysis tools help fabs adjust exposure settings on the fly, tune focus and correct for drift, which in turn lets them run more wafers through the same scanners per day without losing yield. Reuters reports strong demand for ASML’s metrology and software.

What YieldStar actually measures

Walk up to a YieldStar tool in a high-volume fab and you see a compact cabinet with a small front loading interface, not the towering mass of an EUV scanner. Inside, though, the optics are tuned to read tiny test structures on the wafer with high speed and precision. ASML explains that YieldStar uses diffraction-based optical metrology to measure overlay, focus, and CD on dedicated targets as well as some product structures. The YieldStar overview details its diffraction-based approach.

Overlay is the key metric that tells the fab how accurately one patterned layer sits on top of the previous one. At 5 nm or 3 nm nodes, overlay budgets are on the order of single-digit nanometers. YieldStar samples wafers from the line, measures overlay on targets and passes that information straight into ASML’s scanner control software, which can adjust alignment and dose recipes. That feedback loop runs almost continuously in modern fabs, according to process engineers.

Software: from data to action

YieldStar’s hardware only matters because of its software. The metrology system connects to ASML’s Litho InSight analytics platform, which aggregates data across many scanners and metrology tools in a fab. Litho InSight then applies models and algorithms to recommend recipe changes or send corrections automatically to scanners. ASML positions this as part of its holistic lithography control stack, where predictive, model-based control replaces manual tweaking. The Litho InSight product page shows how metrology data feeds optimization.

In practice, that means fewer excursions. A process engineer at a leading foundry might pull up a heatmap of overlay by scanner, by lot, by time of day, all driven by YieldStar measurements. Instead of chasing each outlier, they can set guardrails and let the system nudge scanner and track settings back into the sweet spot. Peter Wennink, ASML’s CEO, regularly points out that this type of software-driven productivity is one reason customers keep ordering more service and software content alongside new scanners.

Why fabs pay for metrology capacity

Metrology tools like YieldStar do not directly print more chips, so it’s fair to ask why fabs invest heavily in them. The answer, according to ASML and several fab operators, is that they preserve yield as patterning grows more fragile. Each percentage point of yield gains on an advanced logic node translates into millions of dollars per year for a large fab. YieldStar’s ability to catch drift early and tighten process windows helps avoid scrapping lots or running long process investigations.

For example, if focus drifts on a scanner, the first sign might be subtle changes in CD on line-space structures. YieldStar picks up those changes across its measurement patterns and flags them in Litho InSight dashboards. Engineers can then adjust focus signatures or schedule maintenance before the drift turns into a yield loss event. That scenario is attractive enough that leading foundries and memory manufacturers have expanded their metrology fleets as they add EUV capacity.

Product variants and integration

ASML offers several YieldStar configurations tuned for different fab needs, including versions optimized for immersion lithography and for EUV lines. The company highlights variants with higher throughput and improved accuracy, designed to sit in-line with scanners and to share wafer handling where possible. ASML’s technical information page breaks down YieldStar system options.

In some fabs, YieldStar tools are located in clusters so they can sample from multiple lithography cells. Automation systems route carriers to metrology and back to production tools with minimal human intervention. Metrology engineers talk about “keeping the metrology loop tight” – which essentially means having enough YieldStar capacity to measure critical lots quickly, so process corrections apply before the next batches run.

Competitive landscape and customers

ASML is not alone in optical metrology, but YieldStar enjoys a particular advantage as the in-house partner to ASML’s scanners. Other players such as KLA focus on broader inspection and metrology portfolios, but ASML can bundle YieldStar with scanner and software packages, ensuring tight integration and calibration. Analysts at major brokerages have noted that this ecosystem approach strengthens ASML’s lock-in for advanced nodes, especially at leading logic foundries and memory makers. Bloomberg has highlighted ASML’s ecosystem strategy.

On the customer side, ASML does not usually name specific YieldStar orders, but it lists metrology as a key part of its installed base and service revenue. Major foundries and integrated device manufacturers in Asia, the United States and Europe use YieldStar tools alongside ASML’s scanners. The adoption tends to track scanner installs: when a fab ramps a new EUV line, additional optical metrology capacity often follows.

Financial relevance and stock angle

From a revenue standpoint, YieldStar sits in ASML’s metrology and inspection category, which alongside software and services contributes meaningfully to recurring sales. That recurring element matters for investors because it smooths the otherwise cyclical pattern of scanner orders. When chipmakers tighten capital spending, they still fund the metrology and software they need to run existing tools efficiently. ASML stresses this in its investor presentations as a way to underline the durability of its business model. ASML’s investor materials break out metrology and software contributions.

The ASML Holding N.V. share is listed in Amsterdam and reflects expectations not only for scanner volumes but also for the attach rate and utilization of metrology platforms like YieldStar. For holders of ASML stock, understanding how YieldStar and related software help fabs eke out more wafers and better yield provides context for why metrology demand often remains resilient when broader chip cycles wobble.