Ultrapure Water (UPW)
Water is the hidden lifeblood of semiconductor manufacturing. Every wafer passes through hundreds of cleaning, rinsing, and chemical processes that require water purified to the strictest standards on Earth. This is called ultrapure water (UPW). Fabs consume millions of gallons per day, and without continuous supply, production halts immediately. Because water carries both operational and environmental impacts, it is central to the sustainability and resilience of semiconductor fabs.
Why UPW Is Essential
- Wafer Cleaning: Each wafer may undergo 300+ cleaning steps — all requiring particle-free UPW.
- Process Chemicals: Wet etching, CMP (planarization), and photoresist development rely on UPW rinses.
- Yield Protection: Even trace ions, particles, or organics can destroy features measured in nanometers.
- Continuous Availability: Water is used at nearly every step of wafer fabrication, making supply resilience critical.
Consumption Profile
| Parameter | Typical Requirement | Notes |
|---|---|---|
| Daily Use | 10–20 million gallons per day (MGD) | Advanced megafabs at the upper end of this range |
| Reuse Rate | 30–60% typical, 80%+ in best-in-class fabs | Recycling reduces both cost and environmental impact |
| Purity Standard | Resistivity ~18 MO·cm, virtually free of particles, ions, and organics | Stricter than drinking water by several orders of magnitude |
UPW Production Process
- Pre-Treatment: Municipal or industrial source water is screened, filtered, and softened.
- Reverse Osmosis (RO): Removes dissolved salts, bacteria, and particles.
- Deionization (DI): Ion exchange resins remove remaining charged particles.
- UV Oxidation: Breaks down trace organics that could interfere with lithography or etching.
- Final Filtration: Sub-micron filters ensure no particles larger than 0.05 µm remain.
Vendors & Integrators
- Evoqua Water Technologies: Global leader in UPW systems for fabs.
- Kurita Water: Japanese firm providing advanced water treatment solutions for semiconductor clients.
- Veolia Water Technologies: Supplier of UPW purification and recycling systems worldwide.
- Ovivo: Specializes in high-efficiency UPW systems and reclaim loops for water reuse.
Strategic Considerations
- Geographic Constraints: Arizona fabs face water scarcity, while Texas and New York have more abundant supply.
- Environmental Impact: Public concern about water withdrawals drives fabs to invest heavily in reuse systems.
- Cost & Complexity: Building a UPW plant often adds hundreds of millions to fab CAPEX.
- Resilience: Fabs maintain backup water reservoirs and redundant treatment systems to avoid downtime.
Case Examples
- Intel Oregon: Operates some of the most advanced water recycling facilities, achieving >80% reuse rates.
- TSMC Taiwan: Dependent on municipal reservoirs; droughts have forced emergency water trucking to fabs.
- Samsung Austin: Partners with local utilities to expand water infrastructure for fab operations.