San Diego, California

The team at ASML San Diego designs, develops and qualifies the EUV (extreme ultraviolet) laser-produced plasma light source, and manufactures a critical system component called the droplet generator. The droplet generator is the heartbeat of the light source, delivering a steady stream of 50,000 liquid tin droplets per second, which fly at more than 241 km per hour in a vacuum vessel. The size, spacing and frequency of the droplets all impact the amount of EUV light produced.

Each droplet – whose size is a fraction of the thickness of a human hair – is individually imaged and targeted by two high-powered CO2 laser pulses, generating a plasma that emits EUV light. A highly polished, multilayered mirror collects and reflects the 13.5-nanometer EUV light to a precise exit point of the vessel directed at the scanner.

This requires a veritable orchestra of lasers, cameras and other sensors (collectively called ‘vessel metrology’) to ensure the creation, optimization and regulation of stable plasma for EUV light generation. ASML engineers in San Diego must determine the optimal points in space and time for the laser to target droplets to generate the plasma, requiring extreme precision and synchronization. The resulting EUV light output must meet precise energy profile requirements for the scanner so that the surface of the wafer is evenly exposed with EUV light.

Tin management is also a unique and challenging problem within the EUV source, since the material is both necessary and problematic: it is required to create the light source, but it can contaminate the optics. ASML San Diego focuses on researching and developing effective mechanisms to capture and remove tin from the vessel, as well as transport the tin out of the system.