Inside the cleanroom

Since they were invented, microchips have become ever more advanced. With transistors shrinking to just a few nanometers, the need for an ultra-clean environment has become critical. Any contamination, whether from dust, hair, or even skin cells, can cause defects in the chips. This leads to lower yields and higher production costs.

That’s why semiconductor chips are manufactured insides specialized cleanrooms. The primary purpose of a cleanroom is to protect semiconductor devices during the manufacturing process.

What is a semiconductor cleanroom?

A semiconductor cleanroom is a controlled space specifically designed to keep out contaminants like dust, airborne microbes, and chemical vapors. This ensures that the delicate manufacturing processes for microchips can proceed without interruption.

In a cleanroom, the air is continuously filtered through high-efficiency particulate air (HEPA) or ultra-low penetration air (ULPA) filters to remove particles. The air pressure is also kept higher inside the cleanroom than outside to prevent contaminated air from entering when doors are opened.

Temperature is kept stable, usually between 20°C and 22°C (68°F to 72°F). Humidity is carefully controlled to create the perfect conditions.

Because of these tightly regulated conditions, cleanrooms typically operate 24/7. Restarting from scratch every morning would be too costly.

Clean, cleaner, cleanest: different cleanroom classes

Semiconductor cleanrooms are classified based on the number and size of particles allowed per volume of air. These cleanroom classes range from ISO Class 1 (the cleanest) to ISO Class 9 (the least clean).

For example:

• An ISO Class 1 cleanroom allows no more than 10 particles of 0.1 micrometers per cubic meter.
• An ISO Class 5 cleanroom, commonly used in semiconductor manufacturing, allows up to 100,000 particles of 0.1 micrometers per cubic meter. That may still sound like a lot, but an ISO Class 5 cleanroom is 10,000 times cleaner than the air in a typical urban environment.

How is a cleanroom built?

Building a cleanroom requires meticulous planning and design. All surfaces, including walls and floors, are made from materials that don’t shed particles, such as stainless steel and special polymers. They’re designed to be smooth and easy to clean, minimizing the risk of contamination.

The airflow in a cleanroom is carefully controlled. Air is usually introduced at the ceiling and flows downward in a smooth, consistant manner, known as laminar flow. This steady, uniform airflow sweeps particles out of the cleanroom through vents in the floor. Since the air moves in only one direction, it prevents contaminants from settling on surfaces.

Because nanochip production operates on such a small scale, a cleanroom must not only be dust-free but also free of vibrations. This is why a cleanroom is anchored on pillars that are deeply embedded in the ground.

Working in a cleanroom

Scientists, engineers, technical operators, or cleaning staff—everyone who works in a cleanroom needs to strictly adhere to all procedures required to maintain the cleanliness of the environment.

Before entering, all workers go into controlled area to put on special clothes, including gowns, gloves, masks, or even full-body suits. These clothes are designed to minimize outside or human contaminations from entering the cleanroom environment. Makeup or jewelry are not allowed.

Once inside, workers must move slowly and deliberately to avoid stirring up particles. They must also follow strict rules for cleaning and handling materials to ensure that the cleanroom remains as uncontaminated as possible.

A peek inside one of the world’s most advanced cleanrooms

As technology continues to advance, the importance of cleanrooms in the semiconductor industry will only grow. You can find the most advanced semiconductor cleanroom for research purposes in Leuven, Belgium, at imec, a leading research institute in nanoelectronics.

This state-of-the-art cleanroom facility is designed for cutting-edge research and development in semiconductor technology. Featuring the latest in cleanroom technology and equipment, imec’s cleanroom supports the development of next-generation chips that will power future innovations in various fields, from artificial intelligence to healthcare.

Watch the movie of imec’s 300mm cleanroom to get a glimpse inside this cutting-edge facility.