NEXT GENERATION PURIFICATION METHOD FOR ACHIEVING LOW TRACE METALS IN ULTRA-HIGH PURITY CHEMICALS

摘要

The high purity requirements of materials used in semiconductor manufacturing are being pushed to unprecedented levels as demand for reliability in computer processors over increasingly longer lifetimes continues to rise. The production of these high purity chemicals requires new purification methods and technologies. One of the limiting factors in purification process is to bring the metal impurities into close contact with purifying surfaces. Current metal reduction techniques rely on ion exchange technology however, the pathways are large in comparison with the size of the unwanted metal species. A new approach is required to increase the probability of contact between the metal species with the exchange surface. In addition, fluid channels need to be mixed, rotated, and inverted in order to increase the probability of surface contact. The new approach discussed in this paper would present a method for dividing the fluid through micro-channels that form tortuous pathways. These micro-channels allow for further dividing and converging of the fluid thereby presenting the metal species to the purifying surfaces throughout the porous matrix. Several high purity chemicals such as PGMEA used in microelectronic industries were purified using the above approach. The metal concentrations of low parts per billion (ppb) were effectively reduced to low parts per trillion (ppt). The ion exchange capability was a function of the concentration and the presence of the species in the solution. Two ion exchange chemistries of strong acid and chelating were made into these structures and their purification performances were assessed and compared in terms of removal efficiencies. Furthermore, these two chemistries were evaluated in series to demonstrate the overall synergistic purification capabilities.