Can Advanced Oxidation Technology Help Control TOC In Semiconductor Water?
By Glen Sundstrom, Bruce Coulter, Chris Hall & Alan Knapp
This article will discuss typical organic removal methods commonly applied in a semiconductor ultrapure water (UPW*) system and new methods for improving the removal of organic contaminants from the critical process water. An equipment manufacturer has developed an advanced oxidation processes that specifically addresses total organic carbon (TOC) levels, to reduce them to sub-part-per-billion (ppb) levels. This has been shown to have significant benefits in the integrated chip (IC) manufacturing process.
By using advanced oxidation in addition to other TOC-removal technologies with accurate performance measurement and predictive control algorithms, sub-ppb levels of TOC can be consistently achieved to improve quality and yield in the integrated chip manufacturing process. The International Technology Roadmap for Semiconductors (ITRS) (now known as International Roadmap for Devices and Semiconductors), SEMI, and the American Society for Testing and Materials International (ASTM) have all stated their respective water quality guidelines have been developed to ensure semiconductor manufacturing quality and improve yield from the water perspective. This article will examine the use of advanced oxidation for TOC control.
Typical TOC Species and their Sources
TOC in water systems comes from a variety of sources and is generally classified as naturally occurring organic matter (NOM) or synthetic organic matter (SOM).
NOM consists of typical humic substances and their decomposition products (resulting from vegetation decay), biopolymers (proteins, extracellular polymeric substances), trihalomethanes (THM) and haloacetic acids (HAA), both of which are disinfection byproducts that could also be considered SOM).
SOM consists of chemical contaminants that originate from a variety of sources such as agricultural runoff, spills, and leaks. They typically include pesticides, herbicides and fertilizers (especially urea), and trace hydrocarbons. More common in the semiconductor industry are solvents from manufacturing such as isopropyl alcohol (IPA), residual chemicals from the assembly of the UPW system, and the system components themselves (piping, fittings, valves, reverse osmosis (RO) and ultrafiltration (UF) membranes, and ion exchange (IX) resins, oxidation byproducts of ultraviolet light (UV) treatment, and trace chemicals introduced by reclaiming and recycling rinse waters.
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