Generally, semiconductor clean rooms are divided into Class 1- Class 1000000 according to their levels. (Class 1: the number of particles below 0.1 microns cannot exceed 10 per cubic meter; and so on; the smaller the number, the higher the level.)
Why is it necessary to have a clean room in a semiconductor fab?
First, it must prevent wafer contamination. Generally speaking, the line width of products manufactured by semiconductor fabs is at the nm level, and cannot withstand any tiny dust, microorganisms or other pollutants. Therefore, a clean room is needed to further control pollutants in the environment and ensure the cleanliness of the running environment.
Second, control humidity and temperature. Clean rooms can control humidity and temperature, which is crucial for chemical reactions and physical processes in semiconductor manufacturing. Some processes are very sensitive to environmental conditions and require precise control.
Third, reduce static electricity. Static electricity can damage tiny circuits on semiconductor chips. Clean rooms reduce the generation of static electricity by controlling the environment and using antistatic materials.
Fourth, improve production efficiency. In a clean room, the production process can be more stable and predictable, reducing production interruptions and quality control problems caused by environmental factors, thereby improving production efficiency.
Fifth, protect staff. Clean rooms not only protect semiconductor products from contamination, but also protect staff from harmful chemicals and processes.
How does a clean room work?
Semiconductor clean workshops usually adopt a vertical unidirectional flow method, which discharges indoor polluted air to the outside through the push action, thereby achieving the purpose of purifying indoor air.
Clean room air purification is mainly divided into three stages:
First, use primary and secondary efficiency filters for pretreatment. The temperature and humidity are controlled by air conditioning, and the fresh air entering the room from the outside is pretreated through the filters carried in it to intercept the common large particles in the air. The equipment in this link is located outside the wall panel of the physical isolation layer of the clean room, and the pretreated air will enter the inside of the clean room wall panel.
Second, use a fan filter unit for deep filtration. The fan filter unit is located inside the clean room and is spread all over the top of the physical isolation layer of the clean room. It further processes other fine particles, gaseous molecular pollutants, and microorganisms that have not been processed in the first stage of pre-treatment in the air to meet the extremely high air purification level requirements of the semiconductor production workshop.
Third, the internal air is continuously circulated. The air inside the clean room is circulated and purified, and the return air is sent to the fan filter unit (including high-efficiency/ultra-high-efficiency filters, chemical filters, etc.) through the elevated floor and the return air channel, and then re-filtered and sent to the clean room for reuse.
