How to improve ultrapure water system in integrated circuit factory?

It is well known that impurities in ultrapure water can cause a series of adverse effects on devices! Therefore, how to determine the process of water purification to ensure quality of water that is feed to the production equipment become the primary problem to be solved in making ultrapure water system.

The ultrapure water system should be determined by the quality of raw water and the requirement of water quality by the integrated circuit production equipment. The ultrapure water system generally consists of the following four parts: pretreatment system, primary pure water system, ultra-pure water system, and water recovery system.

The purpose of pretreatment is to remove suspended matter, colloid, polymer organic matter and other impurities contained in raw water. It should be noted that activated carbon is very effective in removing TOC, but it also tends to be a breeding ground for microorganisms. Therefore, when the activated carbon treatment unit is used in the pretreatment system, the water intake of the activated carbon treatment unit should be adjusted to acidity to prevent the breeding of microorganisms.
　

In the primary pure water system, often to use reverse osmosis (RO) membrane. The shortage of this membrane is: oxidation resistance is poor, oxidizing substances can lead to membrane polymer decomposition. While activated carbon has good effect in removing residual chlorine in water and oxidizing substances such as water peroxide. Therefore, it is necessary to adopt activated carbon treatment unit in the pretreatment system of ultrapure water system for integrated circuit factory. The purpose of the primary pure water treatment system is to further treat the effluent of the pretreatment system. The representative devices of primary pure water system are reverse osmosis, mixed ion exchange, primary membrane degassing, EDI(electrical regeneration and desalination), UV(ultraviolet), and primary polishing. Among them, reverse osmosis and UV further remove the TOC from the pure water treatment system. Mixed ion exchange can remove both TOC and SiO2 from the pure water treatment system. Membrane degassing was used to treat the dissolved oxygen in the pretreatment water. A high purity resin is used to process metal ions.

The ultrapure water system is set up to remove the trace impurities remaining in the primary pure water system. It is worth noting that while the ultrapure water system removes all kinds of impurities in the water, how to ensure the removal of pollution caused by the equipment due to its own material. That is to say, a complete ultrapure water system, not only must have a reasonable water production process, but also must research for the problem of micro dissolution by each treatment part. In addition, ultrapure water transport method, material selection of piping and valve should also cause people's attention.

The very large scaled cleaning equipment for integrated circuit requires ultrapure water. Drainage from all use points of the cleaning equipment can be recycled. After recovery treatment, part of water can be feed to cooling tower and exhaust column, and another part water can flow into the pretreatment water pool as water supplement preparation. Currently, the water recovery rate can reach 70% in practical projects. In order to achieve a good effect of the recycled water system, in addition to determine a reasonable treatment process, classification collection of drainage by the production equipment is also very important, so as to prevent high concentration of TOC and other impure substances into the recycled water system.