Removing dissolved oxygen from ultrapure water

The ultrapure water (UPW) used to rinse wafers must contain very low levels of dissolved gases such as oxygen, nitrogen and carbon dioxide. The Lucent Technologies fab outside of Madrid, Spain, used a two-phase upgrade project to remove dissolved oxygen from the UPW loop. After introducing a nitrogen sparging system to the loop, a membrane contactor degassing system was installed within the two-pass Reverse Osmosis system. It uses vacuum with a nitrogen sweep gas to reduce the dissolved oxygen level below 10 ppb from a 56 m3/h UPW loop. It has run continuously, except for scheduled year-end downtime, since May 1995.