EUV Light Source: How ASML Makes 13.5nm Light from Tin Plasma
ASML's EUV lithography machines generate 13.5-nanometer extreme ultraviolet light by vaporizing molten tin droplets with a 20,000-watt CO2 laser, producing plasma at roughly 220,000 Kelvin — about 40 times hotter than the surface of the Sun. The system hits 50,000 droplets per second with three laser pulses each, never missing.
To extend Moore's Law past the 193nm deep-UV wall reached in the late 2000s, chip manufacturers needed a much shorter wavelength of light. ASML's extreme ultraviolet lithography machines use light at 13.5 nanometers, and the only scalable way to produce it at sufficient power is laser-produced plasma from tin droplets. The process works in three precisely timed steps. Molten tin is pushed through a vibrating microscopic nozzle that generates 50,000 droplets per second, each roughly the size of a white blood cell, traveling at about 250 km/h. As each droplet flies through the vacuum chamber, it is struck by a pre-pulse that flattens it into a pancake shape, a second pre-pulse that rarifies the pancake into a low-density gas cloud, and finally a main pulse from a 20,000-watt CO2 laser that vaporizes the cloud into plasma. The resulting tin plasma reaches roughly 220,000 Kelvin — about 40 times hotter than the surface of the Sun. The shockwave physics governing this expansion are described by the Taylor-von Neumann-Sedov solution, the same mathematics normally applied to nuclear blast modeling and supernova simulation. ASML engineers describe the machine as 'making tiny type-Ia supernovas 50,000 times per second.' Current production machines run 500-watt sources at 60,000 droplets per second, with a laboratory roadmap to 100,000 droplets per second already demonstrated. Each laser shot must hit a target the size of a single cell, traveling at highway speed, three times within 20 microseconds, and miss none of the 50,000 per second — a precision regime with no other industrial analogue.