Ultrapure water semiconductor industry

The present ED industry has experienced a steady growth rate of about 15% since 15 years (Srikanth, 2004). The most important industrial ED application is still the production of potable water from brackish water. However, other applications either in the semiconductor industry for the production of ultrapure, that is, completely deionized water without the chemical regenerations of IERs or in the food industry (i.e., whey demineralization, tartaric stabilization of wine, fruit juice deacidification, and molasses desalting) are gaining increasing importance with large-scale industrial installations. 

Separation of isopropanol (IPA) and water by pervaporation has also reached production scale. Much of the current capacity is devoted to azeotrope breaking and dehydration during IPA synthesis. Recently, anhydrous isopropanol has become a preferred drying solvent in the semiconductor industry, where chip wafers are first washed with ultrapure water, then rinsed with the alcohol to promote uniform drying. The water-laden isopropanol generated can be conveniently reused after dehydration by pervaporation. Unlike with pressure-driven membrane processes such as RO or UF, particulates and nonvolatile substances such as salts are not carried over during pervaporation. This helps maintain the effectiveness of contamination control. 

The pharmaceutical industry lead the way in adoption of CEDI for the production of ultrapure water. Since the early 1990 s, the power industry has been employing CEDI as a polisher for RO effluent for steam generation. Other industries currently using CEDI include general industry for boiler make-up or high-purity process applications, including semiconductor manufacture. Commercially-available industrial CEDI modules range in size from less than 1 gpm to 80 gpm. 

Field-amplified or electrokinetic injection stacking can provide impressive LODs, so long as injections are made from solutions with very low conductivity [50], For small anions and cations, LODs easily reach the low-ppb range when the sample is ultrapure water. This technique is commonly employed to monitor water quality in the semiconductor industry. 

This technology clearly has potential for use in organophilic solute recovery or removal from chemical process streams and industrial or municipal wastewaters. Another important field of application ofBOHLM is the production of ultrapure water for semiconductor manufacturing [91, 92]. 

Ion chromatography is frequently used to determine anions and cations at very low concentration levels, often in the low xg/L (ppb) range. In the electric power industry the water used in steam generators must be almost free of Na", Cl" and other ions to avoid stress corrosion cracking. The ionic content of ultrapure water used in the electronics industry must be kept to extremely low levels. Semiconductor chip manufacturers require clean-rooms with utility impurities of no more than 1 ppb for 0.35 pm devices [1]. 

B. Vishwanath, K. Kekre, G.H. Tao, Reclaimed water an alternate source for high-purity water production in the semiconductor industry, Ultrapure Water 20 (5) (2003) 41—46. 

Most of applications arc in the purification of water, mainly the desalination of brackish and especially seawater to produce potable water (10-13). The amount of salt present in brackish water is between 1000-5000 ppm, whereas in seawater the salt concentration is about 35,000 ppm. Another important application is in the production of ultrapure water for the semiconductor industry. 

Water, semiconductor grade (cleaning) Water that is pure enough to meet the requirements of the semiconductor processing industry. See also Water, ultrapure. 

Membrane-based technologies have become the industry standard for the ultrapure water systems in the semiconductor, pharmaceutical, and power industries. The seminal discovery that changed membrane separation from a laboratory to an industrial process was the development, in the early 1960s, of the Loeb-Sourtrajan process for making defect-free, high-flux, anisotropic reverse osmosis membranes (Loeb and Sourirajan, 1963). The most important development in the 1980s was the innovation of industrial membrane gas separation process. 

A typical ultrapure water system for the semiconductor industry is illustrated in Eigure 13.1. The reverse osmosis (RO)/electrodeionization (EDI) system is gaining more and more in importance in a typical UPW system due to its contamination-free design. 

Figure 13.1 Typical ultrapure water system in the semiconductor industry.

Nagel, R., and WiU, T. (1999). Membrane processes for water treatment in the semiconductor industry. Ultrapure Water, Oct., pp. 35-39. 

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