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Wednesday, July 24, 2024

Want to Win a Chip War? You’re Gonna Need a Lot of Water

Building a semiconductor factory requires enormous quantities of land and energy, then some of the most precise machinery on Earth to operate. The complexity of chip fabs, as they are called, is one reason why the US Congress last year committed more than $50 billion to boost US chip production in a bid to make the country more technologically independent.But as the US seeks to boot up more fabs, it also needs to source more of a less obvious resource: water. Take Intel’s ambitious plan to build a $20 billion mega-site outside Columbus, Ohio. The area already has three water plants that together provide 145 million gallons of drinking water each day, but officials are planning to spend heavily on a fourth to, at least in part, accommodate Intel.

Water might not sound like a conventional ingredient of electronics manufacturing, but it plays an essential role in cleaning the sheets, or wafers, of silicon that are sliced and processed into computer chips. A single fab might use millions of gallons in a single day, according to the Georgetown Center for Security and Emerging Technology (CSET)—about the same amount of water as a small city in a year.

Chip companies hoping to take advantage of the CHIPS and Science Act, last year’s federal spending package aiming to boost US chip manufacturing, are now constructing new water processing facilities alongside their fabs. And cities trying to attract new factories funded by the legislation are studying the potential impact on their water supplies. In some places it may be necessary to secure the water supply; in others, new infrastructure must be installed to recycle water used by fabs.

“Local leaders need to engage in candid conversations with their city’s water resources staff and economic development staff to ensure that any new high-volume user is a good fit with the community,” says Sarah Porter, director of the Kyl Center for Water Policy at Arizona State University.

In some places, fab-prompted upgrades to water infrastructure are already in the works. Columbus plans to open its fourth water plant sometime in 2028, just a few years after the Intel site is scheduled to start producing its first chips. The city says a new water facility, which will collect water from the nearby Scioto River, is needed to support the area’s growing population—including Intel, which is set to become the area’s largest consumer of water.

Several states away in dry Arizona, the world’s largest contract chip manufacturer, Taiwan Semiconductor Manufacturing Company (TSMC), plans to build a new water recycling facility to support its new fabs under construction in Phoenix—while also, it appears, sourcing some water from nearby rivers and water infrastructure. To prepare for a $100 million fab built by memory chip maker Micron in upstate New York, there are already massive water storage tanks, which can each hold about 15 million gallons.

Great Gulpers

The chip industry’s thirst for water springs from the need to keep silicon wafers free from even the tiniest specks of dust or debris to prevent contamination of their microscopic components.

To give chips their quintessential circuits, fabs use incredibly powerful lithography tools, which etch intricate patterns into silicon sheets called wafers. Eventually, these large discs of processed silicon need to be sliced into individual computer chips small enough to be packaged into our phones and computers. Throughout these processes, the chips accumulate residue that needs to be removed by washing it away with water.

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The volume required can be huge. In the US, chip fabs use far less water than the agriculture and power generation industries, and semiconductors haven’t spurred political tensions over water resources at national scale, says Chris Miller, a history professor at Tufts University in Massachusetts and author of the recent book Chip War. Still, squeezes have been a concern in TSMC’s home of Taiwan, where droughts have pitted local farmers, who saw their irrigation systems shut off, against the chip maker.

Not just any water will do. Just as the air inside a chip fab must be so free from dust that people must wear all-enveloping coveralls, the semiconductor industry uses a special category of “ultrapure” water to clean silicon wafers throughout the manufacturing process. While standard drinking water might have a purity of 100 to 800 microsiemens per centimeter—a measure of electrical conductivity used as one indicator of contamination—ultrapure water has less than .055 microsiemens per centimeter, according to Gradiant, a water recycling startup based in Boston that works with chip makers. Ultrapure water needs to have an extremely low conductivity, which correlates to only a small number of troublesome ions, or charged atoms.

"If you want to have the highest possible performance of the material, very often you have to go to extreme purity," says Cornell electrical and computer engineering professor Grace Xing, who also directs a new cross-university semiconductor research center called SUPREME. "That's one of the reasons the semiconductor industry requires a lot of water.”

Producing ultrapure water is a multistep process that removes a variety of contaminants, including microbes and other microscopic creatures that you might find in oceans and lakes, as well as smaller particles, including even salt ions. One technique used is reverse osmosis, also used in desalination plants, which involves pushing water through a membrane with pores small enough to filter out salts. (Chip fabs also use less-pure water, similar to that which flows from household faucets, for cooling manufacturing equipment.)Given water’s crucial role in chip manufacturing, recovering and reusing wastewater has become a priority for the industry. The more that can be reused within a fab, the less its need to tap the local water supply. Right now, the proportion of waste water that can be recycled varies between companies and fabs, depending on the manufacturing processes in use and the investment in water treatment. Still, they’re all confronting the same basic problem: As wafers are cleaned, ultrapure water becomes contaminated and requires thorough cleaning before it can be reused by a fab or discharged into a public wastewater treatment system.

Cleaning up the soiled water is a complicated process because myriad contaminants can be found in fab wastewater. Lithography and etching can produce acidic wastewater, and can even contaminate it with powerful hydrofluoric acid. Suspended silicon particles can show up when wafers are thinned down, while the use of solvents including isopropyl alcohol can leave organic carbon residues.

The industry has developed ways to separate out different components of that wastewater, similar to how the general population sort recycling, says Prakash Govindan, cofounder and COO of Gradiant. “The semiconductor industry is actually very advanced when it comes to dealing with wastewater,” he says. “The advanced companies, the American multinationals we work with—but also the Korean and Taiwanese companies we work with—all of them segregate their wastewater into more than 10 kinds, minimum, and some of them into 15 or 16.”

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From there, that wastewater might, for example, be treated for reuse, rerouted to a sewer, or cleaned and redirected to cooling towers.

Chipmakers are investing in improving the filtration and cleaning process to make more water reusable. Intel, for instance, is targeting net positive water use globally by 2030, in part based on plans to desalinate and treat seawater and rainwater. Micron, meanwhile, aims to conserve 75 percent through “reuse, recycling, and restoration” by the end of the decade. Gradiant says that by tinkering with the reverse osmosis process and using an improved, proprietary membrane, it’s even been able to achieve a 98 percent water recovery rate.

In the meantime, at a time of industry expansion, cities and regions need to prepare for what the arrival of a chip factory might mean for their water systems and communities. The stakes are high. About 85 percent of the water funneled to a chip fab will eventually leave the facility, explains Porter, the water policy expert from Arizona State. For example, while the arrival of chip plants hasn’t impacted the availability of water in the state, the city of Phoenix has a plan to up-cycle wastewater into drinking water.

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