Abstract
Sequential compensatory strategies are developed for the overflow tank wafer rinsing process, which can result in a substantial reduction in ultra-pure water usage. The basic idea is to sequentially change the direction or relative flow rate of the two incoming rinsing water streams so that the flow field induced dead zone, formed during the first rinsing period, can be most effectively rinsed. Both slot and nozzle rinsings are investigated. For the slot rinsing, a maximum reduction of 46% in rinsing time can be achieved by rotating the wafer (equivalent to rotation of the two head-on incoming rinsing water streams) by 45° after a suitably set first rinsing period has elapsed. The nozzle rinsing, under the same rinsing flow rate, is found to be much more effective than the slot rinsing. A six-fold reduction in rinsing time can be achieved. The efficiency of nozzle rinsing can be improved as much as 19% by switching the unequal flow rate of the two head-on rinsing streams after a suitably set first rinsing period has elapsed.