The Xzero-system reaches higher purity by reducing the number of process steps, there are fewer sources of error than in today’s cutting-edge technology. Fewer steps mean fewer complications and higher reliability, which, is considered important in the industry.
To ensure that the outcome is absolutely pure, several auxiliary aspects are included. Nitrogen blanketing and vacuum ensures that the water is not recontaminated by volatiles. And, careful design and selection of inert materials ensures that the process equipment itself does not contaminate water.
There are three applications for which Xzero’s systems are built for: Production of UPW, recovering of water after use and cleaning of IPA.
High-purity water, by itself or as solvent to other chemicals, is used to remove chemicals and reaction products. The size of potential contaminants to be eliminated reduces as chips get more compact.
There are differences in pattern of use with all producers having a central plant where make up water is prepared. The average is 1.5 million liters (400,000 US gallons) but an increasing number of plants being set up are many times that size. Water is pumped from the central plant to fabs or clean rooms and the average plant may have two to five such points.
Actual consumption of UPW varies from plant to plant and over time with emphasis changing between processes and tools. Despite awareness that water consumption must be minimized, the industry is increasing water use, simply because more advanced chips need more rinsing.
UPW is a valuable material to be used in an optimal way and simply dumping contaminated water is fast becoming unacceptable. In the US, utilities and regional authorities have made water use and dumping central to relations with the industry and the EPA is keeping a close watch on the situation.
Early attempts at reusing water took advantage of the fact that some of the water could be recovered to water lawns or in cooling towers and scrubbers. Achieving the first 40% reduction in water consumption is therefore far easier than reaching 70% and above. Of greatest interest is the possibility of re-using water for rinsing of chips. Most new plants take some initiative to lower water consumption at an additional capital investment. The Xzero system allows close to 100% recovery with little additional cost.