How to control the temperature and humidity in the clean room?

Update:2021-06-07 9:12:40

Summary:The temperature and humidity of the clean space are mainly determined according to the process requirements, but the comfort of people should be taken into consideration when the process requirements are met. With the increase in air cleanliness requ......

The temperature and humidity of the clean space are mainly determined according to the process requirements, but the comfort of people should be taken into consideration when the process requirements are met. With the increase in air cleanliness requirements, there is a trend that the process has more and more stringent requirements on temperature and humidity.

The temperature requirements of the specific process will be listed later, but as a general principle, as the processing accuracy is getting more and more refined, the requirements for the temperature fluctuation range are getting smaller and smaller. For example, in the lithography exposure process of large-scale integrated circuit production, the difference between the thermal expansion coefficient of the glass and the silicon wafer as the mask material is required to be smaller and smaller. A silicon wafer with a diameter of 100 um will cause a linear expansion of 0.24 um when the temperature rises by 1 degree. Therefore, it must have a constant temperature of ±0.1 degrees. At the same time, the humidity value is generally required to be low, because after a person sweats, the product will be polluted, especially It is a semiconductor workshop that is afraid of sodium, this kind of workshop should not exceed 25 degrees.

Too high humidity causes more problems. When the relative humidity exceeds 55%, condensation will form on the wall of the cooling water pipe. If it occurs in precision devices or circuits, it will cause various accidents. It is easy to rust when the relative humidity is 50%. In addition, when the humidity is too high, the water molecules in the air will chemically adsorb the dust on the surface of the silicon wafer to the surface, which is difficult to remove. The higher the relative humidity, the adhesion is difficult to remove, but when the relative humidity is lower than 30%, the particles are also easily adsorbed on the surface due to the action of electrostatic force, and a large number of semiconductor devices are prone to breakdown. For silicon wafer production, the best temperature range is 35-45%.