EUV Systems

EUV Scanner Architecture

ASML's EUV scanners are the most complex and expensive machines in the world. The product line evolves rapidly:

• Source: A 25 kW CO₂ laser fires 50,000 pulses/second at 30 µm tin droplets traveling at 70 m/s. Each droplet is hit twice — a pre-pulse flattens it, then the main pulse creates a 13.5 nm-emitting plasma. Source power: 250–500W.
• Collector mirror: A huge ellipsoidal mirror with Mo/Si multilayer coating captures roughly 5 sr of solid angle (~40% of the 4π emission) and focuses it to the intermediate focus.
• Illuminator & projection optics: ~10 mirrors total (4 illuminator + 6 projection), each with ~65–70% reflectivity. Combined optical efficiency is ~2%, so the 250 W source delivers only ~5 W at the wafer.
• Vacuum system: The entire optical path is in ultra-high vacuum. Hydrogen gas flows over mirrors to remove tin debris.
• Reticle handling: EUV masks are reflective and must be stored and transported in special protective pods (no pellicle was available initially).

An EUV scanner contains 100,000+ parts, weighs 180 tons, requires 3 cargo planes to ship, and costs $350+ million.

Living with an EUV Source: LPP, Debris, and Uptime

The hardest engineering problem in EUV is keeping the source running. The laser-produced plasma (LPP) module fires 50,000 times per second, every second, for months:

• Droplet generator: 30 µm Sn droplets at ~50 kHz; alignment to the laser focus is closed-loop within microns
• Pre-pulse + main pulse: A short pre-pulse from a Nd:YAG laser flattens the droplet into a pancake; a 25 kW CO₂ main pulse vaporises it into a 200,000 K plasma that radiates at 13.5 nm
• Collector mirror: A ~700 mm ellipsoidal Mo/Si mirror sits in line-of-sight to the plasma — it accumulates tin debris and must be cleaned or swapped every ~1–3 months
• H₂ flow: Hydrogen gas (1–10 Pa partial pressure) sweeps tin debris away from the mirrors and re-volatilises deposited Sn as SnH₄

Reliability and uptime