TOC Setting a New Benchmark for Ultrapure Water TOC Reduction with Nuvonic TOCLine™ 

Total Organic Carbon (TOC) is a measure of organic contaminants present in water. In ultrapure water (UPW) systems used by semiconductor, electronics and advanced materials manufacturers, controlling TOC is critical because even trace levels of organic contamination can affect process consistency, product quality and manufacturing yield.

Reducing Total Organic Carbon (TOC) below 0.1 ppb requires UV oxidation using low wavelength lamps to break down residual organic molecules that conventional filtration cannot remove.

Standard purification methods (RO membranes, ion exchange resins, mixed bed polishing) remove particulates, ions, and larger organic compounds, but they leave low molecular weight organics behind. These residual organics are what keep TOC readings stuck in the single or double digit ppb range. UV closes that gap by generating hydroxyl radicals that oxidize the remaining organic bonds, converting them into ionizable byproducts that downstream polishing resins can capture.

The most effective systems also address TOC at multiple points in the treatment train. In this case study, Nuvonic implemented a two-stage approach that brought TOC down to 0.03 ppb, surpassing the sub-ppb threshold required for advanced semiconductor manufacturing.

UV oxidation improves ultrapure water quality by transforming complex organic compounds into carbon dioxide (CO₂), water, and ionized byproducts that are easily removed downstream via deionization and vacuum degasification. Unlike filtration or ion exchange, UV changes the chemistry of organic molecules rather than simply separating them from water.

This occurs through two principal mechanisms:

Direct Photolysis

UV photons break chemical bonds within organic molecules, reducing them into smaller compounds.

Indirect Photolysis

Short-wavelength UV generates highly reactive hydroxyl radicals that non-selectively oxidise organic contaminants, converting them into carbon dioxide, water, and ionic species.

For semiconductor manufacturing, this helps reduce contamination risk, protect wafer yield, maintain process consistency, and support increasingly stringent UPW specifications.

Typical semiconductor ultrapure water specifications require TOC levels below 1 ppb, consistent with SEMI F63 industry guidance. However, in leading edge fabs even sub-ppb organic contamination can affect wafer cleaning, photolithography, and critical process steps. As nodes move towards 3 nm and below, production yield is becoming dependant on achieving TOC levels below 0.5 – 0.1 ppb.

TOC fluctuations typically result from variations in both water quality and system operation. Common causes include:

• Seasonal changes in source water quality.
• Variability in upstream treatment performance.
• Changes in process demand and flow rates.
• Altered recirculation patterns within polishing loops.
• Water reuse and reclaim systems introducing different organic compounds.
• Resin ageing and changes in polishing efficiency.
• Variations in dissolved organic species entering the system.

These challenges become more significant when operating at sub-ppb levels because very small changes in contaminant loading can have a measurable impact on final water quality. This is why semiconductor facilities increasingly favour treatment strategies designed to provide stable performance across changing operating conditions.

A well-designed TOC reduction system can lower maintenance costs by reducing equipment complexity, minimising service interventions, and helping downstream polishing equipment operate more efficiently. In this case study, the customer replaced an existing competitor UV oxidation system with a solution that used fewer lamps while delivering better TOC reduction performance. The result was reduced maintenance requirements alongside improved water quality.

Using fewer lamps can reduce:

• Spare-parts inventory requirements.
• Routine maintenance activities.
• Time spent servicing UV equipment.
• Operational disruption associated with maintenance interventions.

In high-purity manufacturing environments, reducing maintenance activities can also help minimise operational risk and improve overall system availability.

Minimising operational risk in an ultrapure water (UPW) system requires more than achieving low TOC levels. Semiconductor and advanced manufacturing facilities depend on continuous water quality, so many operators incorporate redundancy into their TOC reduction strategy. By installing parallel UV TOC reduction units or designing spare treatment capacity into the system, water treatment can continue while one unit is offline for lamp replacement, routine servicing, or planned maintenance. This approach helps maintain stable TOC performance, reduces the risk of process interruptions, and supports consistent production uptime.

The most effective redundancy strategy depends on factors such as flow rate, treatment train design, water quality targets, available footprint, and operational requirements. Nuvonic works with customers to evaluate make-up loops, polishing loops, measurement points, and maintenance practices to help identify the most appropriate level of resilience for their application. Ask our engineers about redundancy options for your UPW system to support long-term operational reliability.