2. Water Purification for Electronics and Semiconductors: The Ultimate Pursuit of Ultrapure Water

The semiconductor manufacturing industry imposes the most stringent water quality requirements of any industrial sector. Ultrapure water comes into direct contact with wafers; therefore, even the slightest trace of impurities can cause short circuits, pattern defects, or yield loss. The production of advanced-node chips places extreme demands on ultrapure water quality. The water must meet the following specifications: resistivity reaching the theoretical limit of 18.2 MΩ·cm, total organic carbon below 0.5 µg/L, dissolved oxygen controlled to within 1 µg/L, and particle sizes smaller than one-tenth of the process node linewidth. To achieve this, the ultrapure water preparation system is constructed as an extremely rigorous, multi-stage purification process. In this process, raw water first undergoes multi-media filtration and activated carbon adsorption to remove suspended solids and residual chlorine, then passes through a softener or reverse osmosis for desalination, enters the core continuous electrodeionization unit for deep demineralization, and finally undergoes UV oxidation for TOC removal, membrane degassing for dissolved oxygen removal, and terminal ultrafiltration for particle retention. Every single treatment stage is indispensable, and together they form a complete water quality assurance chain.

Micro-contamination control is the core challenge of ultrapure water systems. Excessive TOC can cause a non-uniform native oxide layer to grow on the wafer surface, affecting etching precision; dissolved oxygen can re-oxidize cleaned silicon surfaces, leading to increased contact resistance; trace metal ions such as iron, copper, and sodium can migrate and contaminate the crystal lattice in high-temperature diffusion furnaces, ultimately causing device failure. The ultrapure water system uses 185 nm UV lamps to excite water molecules and generate hydroxyl radicals, which thoroughly mineralize organic matter; the resulting ionic residues are then adsorbed by a mixed bed or EDI unit. Boron removal is particularly challenging because it exists in water as weakly ionized boric acid, against which conventional RO and EDI have limited rejection rates, thus requiring specialized boron-selective resins. Furthermore, piping materials must be PVDF or high-purity polypropylene; plasticized plastics and standard stainless steel are strictly prohibited, as leachates from pipe walls can become a continuous source of secondary contamination.

Recycling and reclamation after the point of use represent a new challenge for semiconductor water purification. Wafer cleaning consumes enormous amounts of water—a single 12-inch fab can use tens of thousands of tons per day. The discharged cleaning wastewater is classified into several grades based on contamination levels. Lightly contaminated fluoride wastewater, ammonia wastewater, and general acidic wastewater must be collected separately and treated accordingly. Fluoride wastewater undergoes calcium salt precipitation to form calcium fluoride sludge; ammonia wastewater is treated by stripping or biological methods for ammonia nitrogen removal. After these treatments, the two streams are combined and treated by RO and CEDI. Once they meet the ultrapure water makeup standards, they are sent back for use in front-end grinding or rough cleaning processes. The difficulty of the entire reclamation system lies in the need for real-time online monitoring of dozens of parameters; the moment a specific ion breakthrough is detected, the system must instantaneously switch to drain mode to prevent contamination of the main ultrapure water loop. As chip manufacturing processes evolve beyond 3 nanometers, ultrapure water systems are advancing toward impurity control precision at the parts-per-trillion concentration level.

TJN's electronic semiconductor wastewater treatment system focuses on achieving zero liquid discharge and resource recovery for eight major categories of wastewater. Our independently developed system enables the high-quality recovery of electronic-grade chemicals and the extraction of precious metals as resources. The recovered products are of high purity and can be either reused internally by the enterprise or sold as raw materials, truly turning waste into treasure and driving the green circular development of the semiconductor industry.