What sets a High-NA EUV lithography patent apart at the claim level, and how is it classified? High-numerical-aperture extreme-ultraviolet (EUV) scanners raise the numerical aperture of the projection optics to print smaller features, but doing so at the reflective EUV mask creates a problem: a higher angle of incidence on the mask degrades imaging unless the system demagnifies more steeply. The solution adopted in High-NA systems is anamorphic optics — the projection optics demagnify the mask pattern by a larger factor in one direction than the other (in the deployed systems, 4x in one axis and 8x in the perpendicular axis). That unequal, two-direction demagnification is the optical signature of High-NA EUV, and it propagates into how masks and patterns must be designed. The patents that address it recite modelling that anamorphic behavior. In the Cooperative Patent Classification (CPC) scheme, that modelling-and-patterning work is classified at G03F 7/705, which the USPTO titles "Modelling or simulating from physical phenomena up to complete wafer processes or whole workflow in wafer productions." The class sits under G03F 7/70, "Microphotolithographic exposure; Apparatus therefor."

A granted ASML patent shows how the anamorphic limitation enters the claims. ASML Netherlands B.V. holds US Patent 11,886,124 (issued January 30, 2024), titled "Flows of optimization for patterning processes." Its independent claim 1 recites:

...obtaining a simulation model that models projection of radiation by the projection optics toward the substrate, wherein the simulation model models an effect of an obscuration in the projection optics and/or models anamorphic demagnification imparted to radiation by the projection optics; evaluating a patterning device manufacture rule, based on data regarding a simulated pattern at the substrate produced by the model, to identify one or more locations at the substrate of violation of the patterning device manufacturing rule...— US 11,886,124 B2, claim 1, source

The operative limitations are about the model, not the hardware. First, the model "models projection of radiation by the projection optics toward the substrate." Second, that model "models anamorphic demagnification imparted to radiation by the projection optics" — the explicit anamorphic limitation. Third, the model is used to evaluate a "patterning device manufacture rule" and find where the simulated pattern violates it, then to reconfigure the mask pattern accordingly. The claim is a computational-lithography claim: it protects the method of accounting for the anamorphic optics when designing the mask, because in an anamorphic system a mask feature does not scale to the wafer by a single factor. Dependent claim 3 isolates the point — "the model models anamorphic demagnification imparted to radiation by the projection optics" — and claim 14 adds taking "into account an anamorphic manufacturing rule or anamorphic manufacturing rule ratio." Claim 9 ties the optics to EUV specifically: "the model models reflective projection optics designed to project extreme ultraviolet radiation."

Why the anamorphic limitation matters to the landscape

For a portfolio map of High-NA EUV, the anamorphic-demagnification limitation is the discriminator that separates High-NA-relevant claims from general EUV computational-lithography claims. In a conventional isomorphic 4x system, a single demagnification factor governs the mask-to-wafer mapping, and a manufacturing rule applies uniformly. In an anamorphic system, the two axes scale differently, so a mask feature's allowed size and spacing depend on direction — hence the "anamorphic manufacturing rule ratio" the dependents recite. A patent that recites modelling anamorphic demagnification is, by that limitation, addressing the High-NA regime. A searcher building a thicket map therefore reads claims for the anamorphic language directly, rather than relying on titles, because many of these patents are titled generically ("Flows of optimization for patterning processes") and reveal the High-NA relevance only in the claim limitations.

The obscuration and co-optimization limitations

Claim 1 recites the anamorphic limitation in the alternative with another High-NA-specific effect: the model "models an effect of an obscuration in the projection optics and/or models anamorphic demagnification." Obscuration refers to a central blockage in the pupil of certain High-NA EUV optical designs, where part of the imaging light is occluded; modelling it is, like the anamorphic factor, a High-NA-regime concern. Claim 2 adds that the simulation "accounts for variation of the obscuration across an exposure window," recognizing that the effect is not uniform across the printed field. The patent's other independent claims describe how the model is used in the optimization flow: claim 11 recites performing "an illumination and patterning device pattern co-optimization" based on the model, then a "patterning device pattern only optimization," and claim 16 makes the anamorphic-aware co-optimization its own independent path, requiring the configuration to take "into account an anamorphic manufacturing rule or anamorphic manufacturing rule ratio." The presence of three independent claims — one keyed to obscuration-or-anamorphic modelling, one to the staged co-optimization, and one specifically to anamorphic-rule-aware optimization — shows the patentee claiming the High-NA computational flow from several directions, which is what a thicket map of this area has to account for.

How the CPC class frames it

G03F 7/705 is the right field for these claims because it captures "Modelling or simulating from physical phenomena up to complete wafer processes" — computational lithography that simulates the optics to drive mask and process decisions, which is exactly what an anamorphic-aware optimization does. The class note records that G03F 7/705 has been impacted by reclassification into more specific G03F 7/706xx subgroups, so a thorough search reads both the parent and the newer children. The parent G03F 7/70, "Microphotolithographic exposure; Apparatus therefor," anchors the broader lithography apparatus field. Reading the classification alongside the claims confirms the division of labor: the optics hardware is described elsewhere in G03F 7/70, while the computational method that compensates for the anamorphic optics sits in the simulation subgroup G03F 7/705.

What the record shows is that, in the patent literature, High-NA EUV is identified by anamorphic demagnification at the claim level. US 11,886,124 claim 1 recites a simulation model that models the anamorphic demagnification of the projection optics and uses it to find and fix mask-rule violations, with dependents adding the "anamorphic manufacturing rule ratio" and tying the optics to reflective EUV projection. CPC G03F 7/705 classifies that modelling-and-simulation work. The general idea of EUV computational lithography is not what the anamorphic limitation protects; accounting for the two-direction, unequal demagnification of High-NA optics is. How far any such claim reaches against a specific computational-lithography flow depends on that claim's own limitations and prosecution history.