A discovery of an ultra-pure water detection method based on water mark

The purity evaluation of deionized (DI) water is highly desirable for VLSI or ULSI industry, as the traditional "reverse osmosis filter" cannot always meet the requirement towards the DI water. The filtered DI water may still contain many contaminations which are not up to the standard for the wet cleaning of wafer surface. A novel method is presented by analyzing the residues of a water droplet after the low-temperature evaporation. The contamination contained in the water will remain during the gasification. By analyzing the residual contamination's morphology, the purity of the DI water can be estimated by employing merely a 3D laser microscope. Compared to the traditional fluorescence detecting system for water quality monitoring, it is simpler and has a lower cost. The paper describes an excellent water detection method which is meaningful for preparing ultra-pure water. Experimental results have shown that the deionized distilled (DID) water can repeatedly get a higher purity using this detection method. The DID water can be applied to the wet cleaning of wafer surface, preparation of chemical reagents and many other aspects.