One of the important characteristics of the gas laser is that the working material of the laser is a mixture or a single pure gas. Therefore, there are special requirements for the purity of the components of the laser mixture. The steel cylinder packaging the mixture must also be dried before filling to prevent contamination of the mixture. If helium (He) neon (Ne) laser is used as the first generation of gas laser, and carbon dioxide laser is the second generation of gas laser, the krypton fluoride (KrF) laser that will be widely used in the semiconductor manufacturing field can be called the third generation laser.