Ultrapure Water

Ovivo’s technologies remove impurities from water at the limits of their detection with an ultimate reliability. Ovivo provides complete Ultrapure Water Treatments systems including: 

• Ultrapure Water Treatment Plant
• Pre-treatment section
• Make-up section
• Polishing  section
• Distribution loops

The ultrapure water needed for semiconductor manufacture is the purest water feasible. It is produced by combining conventional, membrane, ion exchange, thermal and oxidising treatment processes. Ovivo designs and builds ultrapure water treatment plants that meet the following criteria:

• Ultrapure water (UPW) according to the latest ITRS road map specifications with total organic content (TOC) of <0.5 ppb and Boron < 20 ppt.
• Lowest cost of ownership
• A robust system for removal of the most difficult organics in raw water (urea)

The pre-treatment section of an ultrapure water plant uses filtration, ion exchange and membrane processes to produce permeate of lowest TOC and salt content. Ovivo’s experience shows that multimedia filtration with micro-flocculation followed by an activated carbon filter unit is one of the most effective pre-treatment combinations to remove traces of suspended matter and produces the optimum feed water for reverse osmosis. Ion exchange further removes salt and reduces fouling in the reverse osmosis units to the lowest possible levels. Raw water ultra-filtration is an alternative with even better outlet qualities. To a certain extent, activated carbon filters reduce TOC levels of reclaimed last rinses, too.

• Ovivo’s unique RO design for improved permeate quality

In the following make-up section, the main focus is on gas removal such as oxygen and CO2 as well as some volatile organics, which are subsequently removed in degasifying units (e.g. a vacuum degasifier or membrane degasifier). The permeate is then purified to almost the highest theoretical resistivity level by mixed-bed ion exchangers in a merry-go-round arrangement with external regeneration (MOVEX). Alternatively, the demand for chemical-free treatment may require the application of electro-deionization (EDI) systems.

• External mixed bed regeneration to avoid traces of contaminants in the ultrapure water system
• Modular membrane degasification systems
• State-of-the-art organic removal

The polishing section provides for the final adjustment of the quality parameters, as well as for the temperature and pressure control in the distribution loop. Any remaining TOC is destroyed by LUMOSTIL™ UV units and, to achieve low oxygen levels, an additional degasification system can be employed. All remaining ionic impurities are removed by polishing mixed-bed ion exchangers. Finally, the last remaining particles are removed by ULTRASTIL™ ultra-filtration systems before the ultrapure water is distributed to the cold or hot consumers. 

• Qualified polishing mixed bed ion exchange resins producing ultrapure water with the lowest Boron and Silica concentrations
• Polishing membrane degasification system for Oxygen removal and Nitrogen adjustment
• Online monitoring for all critical parameters such as TOC, particles, Silica, Boron, Oxygen, NVR, Ions
• Highest quality ultra-filtration membranes

The ultrapure water is typically distributed to the process equipment on the fab floor through a looped piping system designed for a continuous flow to avoid bacteria growth. Unconsumed ultrapure water is continuously recirculated to the UPW tank for repurification in the polishing plant. Ovivo provides design, installation, supervision and certification of PVDF and/ or PP distribution systems, including hook-up installations to the process tools.

• Dead lag free design
• Pressure drop optimisation
• Distribution system mass balance
• Qualification/certification