Application of TOC in Ultra Pure Water in Semiconductor Industry

author: Otis

2022-11-24

Background information
Ultrasure water is the most effective and powerful solvent used by the semiconductor industry in cleaning and producing wafers. The number of circuits that the electronics industry has etched onto silicon chips has grown exponentially over the past few decades. The increase in the number of circuits greatly reduces the line width, thus requiring more accurate and continuous measurement of ultrapure water systems. Semiconductor manufacturing processes have nearly stringent regulations on ion and organic matter pollution control specifications in pure water and ultra-pure water systems. Monitoring these pollutants in ultra-pure water systems can help semiconductor manufacturers improve product quality and maximize production. Improvproved water purification technologies and innovations in pollutant monitoring instruments have played a great role in improving and measuring ultrapure water quality. In turn, these developments have prompted the industry to set lower standard values for pollutant content in ultra-pure water systems.
Total organic carbon (TOC) analysis has a strong technical capability both for monitoring organic pollutants in ultrapure water and for monitoring the "healthy" levels of ultrapure water systems. Over the past few decades, TOC specification has fallen by several orders of magnitude, with TOC monitoring concentrations evolving from PPb (one billion) to lower PPT (one trillion). With the future generation of chip technology expected to reach a narrower linewidth, semiconductor manufacturers are constantly requiring their ultra-pure water to have very low levels of organic and ionic pollutants, but the instruments must also be able to detect and respond accurately and more quickly.

Source of organic matter within the water system
The main source of organic matter is supply water, the content of organic matter in surface water is higher than groundwater. But in many areas, groundwater resources are drying up. As a result, people rely more on surface water, reclaimed water and even municipal waste water as raw water, but the problem is that the content and type of organic matter in surface water sources usually change significantly with the season. Treatment systems that produce low-organic water in one season can face serious problems in another season.
If you need to use high organic surface waters in wet season and switch to mineral high groundwater in dry season,
Then the huge changes in the water source composition may have an impact on the treatment system. There are many unit operations that reduce organic matter in the recharge water, including improved flocculation, membrane processes, and final oxidation. Treatment must be tailored to the specific water composition and site conditions.
Another important source of organic matter is the ion exchange resin in the treatment system, that is, the exchange resin made of organic polymers, if not removed by suitable size filtration, then the fine resin particles produced after physical decomposition may enter the process. The chemical decomposition of the resin produces trace pollutants: sulfonic acids produced by cationic resin and amines produced by anionic resin. In addition, it is possible to discharge microtreatment reagents, which may include inorganic components, such as chlorides and sulfuric acid
Other sources of organic pollutants are directly present in the process and distribution systems, such as: pump lubricant, pump seals, polishing resin, and system dead corners.

Pollutant detection
Conductivity is a common and economical measure of ionic contaminants (usually minerals and ionic salts). Although the conductivity can detect organic acids and bases, it is not sensitive to most organic pollutants. Therefore, the TOC analyzer oxidizes organic matter to fully oxidized ionic forms for detection by electrical conductivity. The conductivity increments before and after oxidation can measure the difference in the conductivity readings, and perform TOC measurements. We Optosky developed the online TOC analyzer TOC-1700.

1. spiral quartz glass tube; 2. UV lamp; 3. conductivity sensor; 4. delay coil; 5. peristaltic pump

After the deionization phase, monitoring the TOC in an ultrapure water system is an important checkpoint for organic matter, preventing it from entering the polishing and distribution loop. Other measurements, both upstream and downstream, can help diagnose the locations where the organic matter breaks through, such as: reverse osmosis (RO) membrane failure, ion exchange resin deterioration, or pump failure. Further measurements in the distribution loop can reduce the risk of organic contamination during production. Ultraplure water is usually produced by the multi-stage treatment of the drinking water sources, and the organic compounds in the feed water are both natural and synthetic.
The former is mainly a complex mixture of humic acid, humic acid, and tannins (from leaf and grass decomposition or peat or swamp land). In addition, there are bacteria, other living organisms, and their byproducts. The sources of synthetic compounds include industrial waste and household waste (e. g., cleaners, solvents, and oils), and agricultural chemicals (e. g., chemical fertilizers, herbicides, and pesticides). Because it is suitable for domestic or industrial use through water treatment, many impurities are removed, but other impurities are introduced, such as plasticizer introduced from plastic tubes and tanks, and other compounds are produced by reaction with treatment chemicals such as chlorine and ozone.
In the treatment of feed water to produce ultrapure water, organic compounds are removed by a combination of some or all of the following methods: reverse osmosis, microfiltration, ion exchange, adsorption, and UV oxidation. These methods remove the vast majority of contaminants, and only a small number of multiple impurities remain.

Measure the TOC in an ultrapure water system
Microbial contamination can cause defective wafers and chips, causing millions of dollars in damage. Although it is difficult to directly correlate the organic matter in the water system with the microbial pollution, the organic matter content is an important indicator of the "health" status of the water system. Organics will provide a food source for any bacteria that may be present in the distribution system, storage tanks, and process technology or treatment modules. Accurate, fast and easy measurement of organic content in ultrapure water systems can prevent product loss and save millions of dollars. The TOC-1700 low maintenance volume of continuous online measurement, the approved multi-parameter measurement of the industrial package, equipped with a conductivity detector to quantify the TOC concentration, the TOC-1700 can work in online mode for real-time monitoring.It is to measure and monitor microelectronics water, purification water, injection water, etc.

TOC-1700 Features:
● Automatic sample sample, one-key setting, no sample pollution, no harm to the operators and the environment.
● UV oxidation, without the addition of acid, gas or catalysis, greatly reduces experimental and maintenance costs.
● 7-inch touch screen, with smart user interface, easy to operate and read test data.
● The meets the requirements of the FDA-21 CFR Part 11 and that of the USP, EP, JP, and ChP.
● The autosampler is optionally available according to different experimental requirements.
● The online and offline modes can be easily switched.(TOC-1700)
● 8GB with large storage capacity, no data and time limits.
● Rapid test, taking less than 3 minutes per analysis.
● All histories can be tracked by searching for test dates.
● The data can be directly retrieved and saved to the USB.
● The comes with a Bluetooth printer for fast and convenient data printing.
● Modular design for quick installation and easy maintenance.