EUV - extreme ultraviolet lithography - is the technique used to print the smallest features on leading-edge chips, using 13.5-nanometer light produced by vaporizing tin droplets with a laser. ASML is the only company in the world that builds EUV scanners. That makes its annual report unusually important: it is the formal record of a genuine chokepoint.

The filing is ASML's Form 20-F filed February 15, 2023 (sec.gov; accession 0000937966-23-000014), the annual report covering the prior fiscal year. As a Dutch company listed in the US, ASML files the foreign-private-issuer 20-F rather than a domestic 10-K - the same lane as TSMC.

“We are the world’s only manufacturer of EUV equipment, the most advanced system with the capability of printing smaller features with higher density.”— SEC filing (20-F) source

Why study the chokepoint through its own filing? Because a single-supplier dependency concentrates risk and information in one place. Every leading-edge foundry's roadmap ultimately depends on ASML tool deliveries; the 20-F is where the company itself describes its business, its order position, and the risks around it for US investors.

The physics is what makes the monopoly durable. EUV requires a vacuum optical path, multilayer mirrors rather than lenses, and a plasma light source - an integration challenge no competitor has matched at production scale. The 20-F documents a business whose moat is decades of systems engineering, not a single patent.

For an explainer reader, the method is the message: to understand a chokepoint, go to the chokepoint's primary disclosure. The 20-F, filed as a foreign issuer, is where ASML's position is recorded on the public record - and knowing it is a 20-F is the first step to finding it.

The primary source is the sec.gov 20-F; it was located through SEC filings, an SEC-filing evidence index. The lithography bottleneck is best read where its owner discloses it - on Form 20-F.