High-pressure Point-of-Use Purification of Corosive Gases: Effect on Gas Distribution Components

Source gas and point-of-use (POU) purification of process gases is necessary to meet the stringent demands of the semiconductor industry. Gas purity levels are tested in the cylinder at the production site and sometimes at the fab prior to connecting the cylinder to the gas distribution system. However, this only ensures that the gas coming out of the cylinder meets the designated purity specifications of the cylinder. Unfortunately, many contaminants can be added to the process gas prior to it reaching the tool or point of use. It has been reported that the gas distribution system is responsible for 68% of contamination in a CMOS process [ 1] .Impurity molecules can be introduced into the gas distribution system during cylinder changing, inadequate purge procedures, or exposure to contaminated equipment. It should be noted that although the gas from the cylinder is changed and analysed frequently, the gas distribution components are continuously exposed to the process gas and gradually become contamination sources for the wafer tool. This effect is enhanced when using corrosive process gases.