Semiconductor Ultra Pure Water Treatment
Introduction
Water for Semiconductor Industry – Semiconductor water treatment is Ultra-Pure Water treatment aiming to reduce in-organics, organics, particulates (inorganic, organic and biological) and gases in water to the ppb range.
The most widely used requirements for UPW quality are documented by ASTM D5127 “Standard Guide for Ultra-Pure Water Used in the Electronics and Semiconductor Industries”.
The technologies used are UF, RO, EDI, Mixed Bed Ion Exchange, Advanced Oxidation Processes (AOP’s), UV, Active Carbon Filtration, combustion/heat and sometimes Membrane Contactors for degasification. All piping used must be semiconductor grade to prevent particle and fibre shedding and leaching of any chemicals.
Chemicals Used
Chemicals used have to be semiconductor grade. Some semiconductor grade ion exchange resins are sometimes used. UPW tanks are usually blanketed with Nitrogen to prevent the dissolution of gases such as O2 and CO2.
Production and Assembly Facilities
Production facilities in the semiconductor industry are CleanRoom type with HEPA fitted HVAC systems that filter out dust from the air. There are several classes of clean rooms depending on the size and number of dust particles per m3 of air. Workers in a semiconductor fab are normally fitted with “bunny suits” to prevent particle, bacteria and hair shedding from the body.
Impurities in semiconductor processing water have a negative impact on production yields due to defects caused by impurities in the production and lithographic process. Pumps used in conveying ultra pure semiconductor grade water have to be of special design to minimise particle shedding.
Semiconductor Grade Water Treatment Process Schematic
Monitoring Semiconductor Water Quality
Monitoring the impurities in semicondcutor fab water requires specialised analytical instruments. From sampling and measuring to characterisation and more, Air Liquide’s world-class analytical services are key in helping electronics manufacturers control, monitor and improve their Fab throughput, and assure the quality of electronics devices.
TOC analysers, conductivity and particle counters are among the instruments used. I personally used to look at Silicon chips under the AFM microscope when I did my M.Sc research to identify contaminants.
Articles
Here is an interesting article from Wired Magazine about how “A Chip is Born“. I adapted this article to describe the semiconductor manufacturing process.
Here is an interesting article from Hager El Sasser on this subject.
Waste Water
Waste water from the rinsing operations are normally high in some heavy metals like Copper and could contain toxic ions such as Fluoride. Clarifiers/Precipitation are one technology used for purification of this waste water as well as selective Ion Exchange and RO membranes. It is possible to recycle this water internally as it is still quite clean water.
Here is an interesting article on waste water treatment for semiconductor industry.
Suppliers
Major suppliers of water treatment plants for the Semiconductor industry are:
GE Water aquired by SUEZ in 2017
Veolia
Siemens Water now Evoqua, acquired by Xylem
OVIVO
Bosch
DOW has Special Semiconductor Grade RO membranes.
Conclusion
Since I got my M.Sc. in Industrial Chemistry in 1998, I have been fascinated by semiconductors and ultra pure water treatment. I hope you have found this page useful.
Compiled by Rami E. Kremesti M.Sc. , CSci, CWEM, CEnv
Last updated October 2, 2017
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