Onsite Water Reuse and Recovery Roundtable Insights

At the Ultrapure Micro 2022 roundtable session on Onsite Water Reuse and Recovery, facility owners from different world regions, as well as tool and technology vendors, discovered they were experiencing similar problems. A common thread of the discussion found that the primary barriers facing semiconductor facilities in improving their onsite water reuse rates were most often not related directly to the technical feasibility of achieving the necessary quality specification. According to the roundtable discussions at UPM 2022 on this topic, there are two primary human-driven factors inhibiting greater water reuse:

1. Financial constraints If a facility is designed with reuse in mind, it is likely that there will be cost savings overall. As such, greenfield sites have significant opportunities to improve water reuse. However, the challenges related to retrofitting water reuse technology or segregating streams at existing sites might mean that facilities face return-on-investment hurdles. Reusing water locally to the manufacturing tool also poses space constraints.

2. Fear Wafer yield is the industry’s most critical parameter, so fear about contaminants causing defects on the wafer is the primary inhibitor for returning reclaimed water back to the ultrapure water makeup phase. However, roundtable discussions also posed interesting questions about whether reclaimed water could actually be of a higher quality, or at least easier to control and measure, than a city water source, since the latter can be affected by seasonality (for example, pesticides spiking Total Organic Carbon concentrations). Overall, the industry would benefit from a change in philosophical focus, whereby facilities regard waste streams as valuable resource streams containing both water and chemicals which are reusable within the manufacturing process. Value streams Certain low hanging fruits exist for both water reuse and chemical reclaim. For example, cooling tower blowdown is a common target for water reuse, as the reclaimed water cannot affect the manufacturing process. Other non-process applications such as scrubbers provide good avenues for reuse. Even for facilities achieving a relatively high water reuse rate, there is the need to look more closely at the feasibility of recovering and recycling chemicals within that value stream. Applications which do not risk affecting wafer yield are common avenues for using reclaimed chemicals. For example, pH adjustment for neutralizing wastewater streams is an easy target for utilizing recycled chemicals. Acids and bases which are removed at the reverse osmosis (RO) stage – such as sodium hydroxide and sulfuric acid – can be recovered and reused in these neutralization steps. Other examples include using recovered acids or bases to rinse resin beds, as these chemicals do not need to be of ultrapure quality. Bipolar Membrane Electrodialysis is a beneficial technology which is useful in these processes to recover caustic and sulfuric from sodium sulphate salts in RO reject streams. The industry is also looking towards recycling other chemicals in the wastewater stream. For example, the industry has demonstrated the recycling of tetramethylammonium hydroxide (TMAH) which would normally be discharged into wastewater. Other examples of resource recovery exist within the lithium battery industry, where there is a drive to recover lithium. Emerging conversations A key emerging area of focus – both at semiconductor facilities and at the roundtable sessions at UPM 2022 – is the link between energy consumption and the reuse of water or chemicals. In many cases, facilities can actually save energy by reclaiming water and chemicals onsite, especially when using stream segregation techniques. However, there is an emerging conversation at facilities about which reuse technologies use the least energy, as well as ways to reclaim energy by methods such as heat recovery.

Comments and insights relayed by roundtable host Ryan Pavlick, Innovation Engineer - Wastewater at Intel