Higher humidity causes more problems. When relative humidity exceeds 55%, condensation will occur on the cooling pipe wall. If it occurs in precision devices or circuits, it will cause various accidents. When relative humidity is 50%, it is easy to rust. In addition, when the humidity is too high, the dust adhered to the silicon wafer surface will be chemically adsorbed on the surface by water molecules in the air, which is difficult to remove. The higher the relative humidity, the more difficult to remove the adhesion, but when the relative humidity is less than 30%, and because of the role of electrostatic force, particles are also easy to adsorb on the surface, at the same time, a large number of semiconductor devices are easy to breakdown. For silicon wafer production, the temperature range is 35 - 45%.

Specific process requirements for temperature will be listed later, but as a general principle, because the processing accuracy is becoming more and more sophisticated, so the temperature fluctuation range requirements are becoming smaller and smaller. For example, in the lithographic lithography process of LSI production, the difference between the thermal expansion coefficient of glass and silicon wafer as mask material is becoming smaller and smaller. A 100-um-diameter silicon wafer with a temperature rise of 1 degree will cause a linear expansion of 0.24 um, so it must have a constant temperature of (+0.1 degree) and require a low humidity value, because the operator will be contaminated after sweating, especially in the semiconductor workshop afraid of sodium, such a workshop should not exceed 25 degrees.