The temperature and humidity of clean space are mainly determined by process requirements, but the comfort degree should be taken into account in meeting the technological requirements. With the improvement of air cleanliness requirement, the requirement of temperature and humidity is more and more strict. The specific process of temperature requirements will be listed later, but as a general principle, as the processing precision is becoming more sophisticated, so the temperature fluctuation range of requirements is getting smaller and smaller. For example, in the lithography exposure process where large scale integrated circuits are produced, the difference between thermal expansion coefficients of glass and silicon wafers used as mask material is getting smaller and smaller. The wafer diameter is 100 um, the temperature rise of 1 degrees by 0.24um linear expansion, so there must be a constant plus or minus 0.1 degrees, and the humidity value is generally low, because people sweating later, there will be pollution on the products, especially if semiconductor plant sodium, the workshop temperature should not exceed 25 degrees, more moisture the problem of high. When the relative humidity is above 55%, the cooling water pipe wall will dew. If it occurs in the precision device or circuit, it will cause all kinds of accidents. When relative humidity is 50%, it is easy to rust. In addition, humidity is too high, will be through the water molecules in the air, the surface of the silicon chip adhesion of dust on the surface of the chemical, difficult to remove. The higher the relative humidity, the more difficult to remove the adhesive, but when the relative humidity is less than 30%, but also due to the role of electrostatic force, the particles are also easy to adsorb on the surface, while a large number of semiconductor devices prone to breakdown. For wafer production, the optimum humidity range is 35 - 45%.