Lithography System

Computer chips consist of billions of tiny switches sitting in ultra-thin layers on a round silicon disc. This disc is called a wafer and is the raw material from which individual chips are later cut. A lithography system is the machine that transfers the pattern of this circuit onto the wafer using light. The principle resembles a slide projector that casts an image onto a screen. Only here the image is not enlarged but greatly shrunk and projected onto a light-sensitive layer. These machines are as large as a minibus and cost between 50 and over 350 million euros apiece.

The bottleneck of the chip industry

How powerful a chip is depends above all on how small its structures are. Smaller switches mean more computing power in the same area and lower power consumption. How small it can get is ultimately determined by the lithography system. No development department, however good, can build structures that its machines cannot image.

The most advanced of these machines work with extreme ultraviolet light, EUV for short. Worldwide they are built by only a single company, the Dutch corporation ASML. There is no second supplier and no short-term alternative. This means the entire production of modern processors hangs on a single supply chain.

That is exactly why lithography systems regularly appear in political news. The Netherlands and the USA have restricted the export of the most advanced models to China. Whoever does not get these machines simply cannot manufacture the latest AI chips. A machine thus becomes a lever in trade policy.

From flash of light to circuit diagram on the wafer

First, the wafer is coated with a light-sensitive lacquer, the so-called photoresist. It then moves into the machine. There, a mask is ready: a kind of stencil carrying the desired circuit pattern. Light falls through or onto this mask and is cast onto the wafer, greatly reduced in size by a lens or mirror system. Wherever light hits, the resist changes chemically and can later be washed away.

The wafer is not exposed all at once but field by field. Mask and wafer move synchronously beneath the light beam, which is why the machines are also called scanners. This movement must be accurate to within a few nanometers, that is, millionths of a millimeter. A modern chip is created from 80 to 100 such exposure steps layered on top of one another, each for a different layer.

With EUV machines it becomes especially elaborate. The light with a wavelength of 13.5 nanometers is generated by hitting tiny tin droplets with a powerful laser, up to 50,000 times per second. This light is absorbed by air and glass. That is why the entire process takes place in a vacuum, and instead of lenses, extremely precisely ground mirrors are used. Older DUV machines use longer-wavelength light, are cheaper, and continue to be used for less demanding chips.

Why the topic ends up in business news

You practically never see a lithography system directly, it stands in a handful of ultra-clean factory halls worldwide. Indirectly, its output is found in every smartphone, every game console, and every graphics processor on which AI models compute. When a manufacturer announces a new chip in a more modern manufacturing generation, this is almost always due to a new or improved lithography technique.

In stock market news, the name ASML above all comes up. The number of machines delivered per quarter is considered a leading indicator for the entire semiconductor industry. Reports about factories run by TSMC, Intel, or Samsung also often revolve around the question of when which machine will be delivered. Incidentally, a common misconception is that a lithography system already produces chips. It only handles one of many steps. Etching, coating, and inspection are carried out by other machines in the same factory.