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How it works · Part 1

How EUV lithography prints a chip

Every advanced chip in the index above was patterned by a machine like this one. Follow the light through twelve steps, from a droplet of tin to a printed layer of silicon, or pick any step to pause and explore it.

Simplified and not to scale. EUV light is invisible; it's drawn here in blue. The animation runs about 35,000 times slower than a real machine.

Playing the tour

Step 1 of 12

Why chips needed a new kind of light

A chip is printed with light, through a stencil, one layer at a time. Light can't draw lines much finer than its own wavelength, and extreme ultraviolet light, at 13.5 nanometres, is about fourteen times shorter than the light it replaced.

Wavelength: 13.5 nm
Tin droplets: ~50,000 a second
Plasma: ~220,000 °C
Pattern shrink: 4×
Mirrors, plasma to wafer: about a dozen
Light that reaches the wafer: ~1%
Wafers an hour: ~220
Price of one machine: ~$200M

The words that come up

Twelve terms that make any article about chipmaking easier to read.

Nanometre (nm): A billionth of a metre. A human hair is about 70,000 nm across; a silicon atom about 0.2 nm.
Wavelength: The size of a light wave, which sets how fine a line it can draw. Deep-UV is 193 nm; EUV is 13.5 nm.
Numerical aperture (NA): How wide a cone of light the optics can gather. Higher NA resolves finer detail: 0.33 in today's EUV tools, 0.55 in High-NA.
Multilayer mirror: Around forty pairs of molybdenum and silicon layers that reflect EUV light by interference, since no single surface can.
Intermediate focus: The point where the light source's beam converges and hands over to the scanner. Source power is quoted here.
Reticle (mask): One layer's pattern, drawn four times larger, on a reflective glass plate. A chip needs a set of them, one per layer.
Pellicle: A membrane about 50 nm thick, stretched in front of the mask so that particles land out of focus instead of printing.
Photoresist: The light-sensitive film on the wafer. Exposed, then developed into a stencil that guides the etch or deposition step.
Overlay: How precisely each layer lands on the layers below: within a nanometre or two on a current machine.
Stochastics: Randomness in how few EUV photons land in a tiny feature, which can leave a line too fat or a hole unopened.
Multiple patterning: Splitting one layer across several masks when a single exposure can't resolve it. EUV mostly removes the need.
Throughput: Wafers exposed per hour: about 220 for the latest low-NA scanners, the number that sets a fab's output.

Figures from ASML, Zeiss, Trumpf and Intel's published materials and SPIE papers; prices and throughput as reported by the trade press. Simplified: a real scanner has more mirrors, sensors and stages than are shown here.

Next in the series: How a GPU works