Personnel in the Cleanroom

Semiconductor manufacturing places exceptionally high demands on environmental cleanliness. One of the most important sources of contamination in a cleanroom is the human body itself. Skin flakes, hair, fibers from clothing and tiny particles from shoes are released into the environment with every movement. Skin oils, perspiration, cosmetics and other organic substances add further sources of contamination. For the structures of modern semiconductor devices, particles and residues that are completely invisible to the naked eye can already be problematic.

The primary purpose of a cleanroom suit is therefore to protect the product from the person. It forms a barrier between the body and the cleanroom and retains a large fraction of the particles generated by personnel. A cleanroom suit, however, is not automatically personal protective equipment against process chemicals. When working with acids, bases, solvents or other hazardous substances, additional safety goggles, face protection, chemical-resistant gloves or protective aprons may be required.

The number of people in the cleanroom is also kept as low as practical. Every additional person increases the particle load and adds heat that must be removed by the air-conditioning system. Access is therefore normally restricted to trained personnel who are authorized for the respective area.

Access to the cleanroom is not made directly from an ordinary corridor. Personnel enter through a personnel airlock with a gowning area, which forms the transition between the normal environment and the controlled cleanroom zone.

The exact gowning procedure differs from one fab to another. The basic principle is always the same: with every step toward the cleanroom, the environment becomes cleaner, and clothing or footwear that has already reached the clean side must not come into contact with the less clean side again.

Requirements may already apply to normal clothing before cleanroom garments are put on. Shoes may have to be fully enclosed, legs covered, and strongly linting garments avoided. Hair is completely contained under a hair cover; personnel with facial hair may also need a beard cover. Cosmetics may be restricted or prohibited because powders, make-up and other products can release additional particles or organic substances.

Before entering the cleaner part of the gowning area, shoes may for example be passed over a tacky mat and covered with shoe covers. Depending on the gowning concept, a bench or another physical boundary separates the less clean side from the clean side. When crossing this boundary, only the already protected foot is placed on the clean side.

Tools, measuring instruments, samples and other objects must likewise not be brought into the cleanroom unchecked. Their surfaces are cleaned or wiped with suitable cleanroom wipes when necessary. Ordinary cardboard, wood and many types of paper are unsuitable because they can release fibers and particles. Special cleanroom paper can therefore be used for documentation.