Four key sustainability themes: UPM Community Event recap

The following key themes have been distilled from roundtable conversations led by our hosts: Paul Kerr at Intel, Chuck Dale at SUEZ WTS, Gerd Heser at Pall, Brad Herbert at Corbin Consulting Engineers, Joerg Winter and Nadine Siebdrath at DAS Environmental Expert, Jim De Boer at SCREEN SPE, Bonnie Marion at FTD Solutions, Brian Jenkins at Nalco (Ecolab) and Hiep Le at Gradiant. Access some of the roundtable slides here & access the roundtable topic list here.

1. Costs remain a key determinant for environmental sustainability Water reuse projects tend to attract much less investment than those targeting optimized wafer yields, as the industry views water mainly as a cost which must be reduced. Environmental sustainability efforts vary geographically according to local water and energy costs. Reclamation is more economically viable in water-stressed areas – such as Austin, Dallas, and Phoenix in the US, as well as Singapore and Taiwan – where city water costs may be similar or higher than advanced treatment costs. In locations where water is cheap and abundant, and/or energy costs are higher –such as the northeastern US – expensive and energy-intensive water reclamation is less common.

On the other hand, the construction boom is changing the conversation. New fabs do not face the same space constraints and retrofitting difficulties that legacy facilities do and are therefore more likely to be planned with sustainability in mind. Also expected to contribute to spending on water reuse is the fact that some new fabs are even being built in anticipation of stricter regulatory requirements.

2. Monitoring is critical to water reuse in fabs, but a huge challenge. Instrumentation and system monitoring are important for site water modeling since water flow rates and water balance assessments will determine which processes or site areas offer the best potential return-on-investment in implementing water reclaim and recovery methods.

Decision-making driven by quality data is paramount, but semiconductor facilities have complex interconnected water systems, making data analytics a huge challenge. To identify reuse strategies, it is necessary to map all fab water systems, including those for incoming water, ultrapure (UPW) water, fabrication tools, waste and cooling towers. Mapping changes in water flows, chemistries, equipment operations and tools is critical, as waste streams with different characteristics can be generated by such adjustments, which are not always communicated by fab engineers to facility engineers.

3. Bacteria-controlling rinses are a significant area for improving water reduction and reuse Slow leak purges and idle flow rinses are used to prevent bacteria accumulation on tools. There is significant opportunity to reduce rinse water usage through process optimization. In addition, rinse water is relatively contaminant-free, so can be easily recycled back into UPW systems, or recovered through segregated streams for non-process uses, such as scrubbers and cooling towers. 

Jim De Boer, Senior Product Engineer at SCREEN SPE, described how the company tackles overuse of deionized (DI) water in tools while maintaining control over problematic bacteria. Instead of running slow leak purges which go down the drain, SCREEN found that stopping the water flow and allowing DI water to lie stagnant will prevent bacteria growth for up to 24 hours. In such a way, it is possible to save thousands of liters of water per day and enable reclaim back to the DI water system.

4. Small adjustments to water management decisions can go a long way towards improving sustainability Facilities may benefit from revisiting options for recovery from reverse osmosis (RO) systems. RO recovery rates are typically around 70-80%, but it is possible to increase this by a small but meaningful percentage. Frequent cleaning of RO membranes, including regular adjustment to maintenance processes as water sources change seasonally, will increase RO recovery. Although higher RO recovery leads to greater energy usage and more scaling, slight adjustments will impact operations and costs minimally.