Cleanroom

A cleanroom is a workspace kept particularly clean. Inside it, the air is constantly filtered so that as few dust particles as possible float within it. In normal room air, millions of such particles float per cubic meter, whereas in a very strict cleanroom there are only a few hundred left. The people inside wear protective suits, hoods, masks, and gloves. The reason is not protection from danger, but the opposite: humans are the greatest source of contamination. A single hair or a flake of skin can render unusable a product that took months to work on.

Why a speck of dust destroys a chip

Computer chips consist of circuit traces that are thinner than any speck of dust. In modern chips, the smallest structures measure just a few nanometers. A nanometer is a millionth of a millimeter. A typical dust particle, by contrast, is a thousand times larger. If it lands on the surface, it interrupts circuit traces or causes a short circuit.

The economic damage is considerable. A silicon wafer, from which hundreds of chips will later be cut, goes through several hundred processing steps over the course of weeks. If it fails at the end, all that work is lost. Experts speak of yield: the proportion of chips that actually function. Even a few percentage points less yield can determine whether an entire factory makes a profit or a loss.

That is why the cleanroom is not a side issue, but the most expensive part of the facility. A modern chip factory costs tens of billions of dollars. A large share of that is invested not in the machines themselves, but in the building, the ventilation, and the vibration damping of the floor.

Filtered air, positive pressure, and airlocks

The basic principle is simple: the air is pushed from the ceiling downward through the room and continuously filtered along the way. This is called laminar flow, meaning an even flow without turbulence. Particles are thus carried downward and extracted rather than swirling around in the air. The entire room air is exchanged several hundred times per hour in the process.

The room also has slight positive pressure. If someone opens a door, air flows outward rather than inward. Dirt from outside is thus actively pushed away. The area can only be entered through airlocks, where employees change their clothing. Putting on the protective clothing follows a fixed sequence and often takes several minutes.

How clean a room is is specified in cleanroom classes. These are defined in the ISO 14644 standard. A lower number means greater cleanliness: ISO 1 is the strictest level, while ISO 9 corresponds roughly to ordinary room air. A common misconception is that a cleanroom is germ-free. Sterility is a separate requirement and is additionally demanded primarily in medicine.

Chip factories, vaccines, and headlines

The best-known cleanrooms come from the semiconductor industry. When news reports discuss new factories in Taiwan, the USA, or Magdeburg, they are essentially talking about such rooms. The images from these plants are also familiar: people in white full-body suits, often under yellowish light that protects sensitive coatings.

However, cleanrooms are used far beyond this. Vaccines and infusion solutions are bottled in them, and pacemakers and artificial joints are assembled there. Displays, camera lenses, and satellite components are also produced under such conditions. NASA’s Mars rovers were built in cleanrooms so that no terrestrial microbes would travel along.

For the AI industry, the connection is indirect but crucial. The graphics processors on which AI models are trained are manufactured exclusively in such facilities. When chips become scarce, it is rarely due to the design. It is because there are only a few cleanrooms worldwide that are even capable of this kind of manufacturing.