PFOS Setbacks Taught Important EHS Lessons


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PFOS Setbacks Taught Important EHS Lessons

Through a decade-long struggle to find suitable alternatives to perfluorooctanyl sulfonate (PFOS), the semiconductor industry has learned how to better understand the materials supply chain, and how to bridge the gap from environmentally hazardous but critical materials.

By Aaron Hand

May 27, 2010 – As scaling continues along Moore’s Law, the semiconductor materials supply chain faces increasing demands. As an alternative to physical scaling, functional scaling takes advantage of new materials that can make semiconductors behave as if they have been scaled physically. “That’s where we get really, really concerned about critical materials,” says Jim Jewett, principal engineer and manager of Global Fab Materials’ EHS group at Intel Corp.

At the same time, the list of materials available that can get these critical jobs done is getting shorter, especially as the industry learns more about how potential materials could threaten environment, health and safety (EHS) welfare. EHS policy is driven not only by government regulations and legislative mandates, but also by customer requirements and public expectations. Policy drivers are just as critical to the industry as technology drivers, “but they’re not in our control,” Jewett says. “The trend for all of this is it’s becoming very precautionary. You stop something in its track until you figure out if it’s good or bad.”

Jewett spoke at this year’s SEMI Strategic Materials Conference about the lessons the semiconductor industry learned as it struggled over the past decade to deal with new legislative and voluntary restrictions on perfluorooctanyl sulfonate (PFOS), which is highly persistent in the environment, and has a strong tendency to bioaccumulate. PFOS was a critical substance in coating uniformity for resist films, top antireflective coatings (TARCs) and photoacid generators (PAGs), although its use has since dropped significantly.

Among the lessons learned from PFOS was the need to better understand the full supply chain, and how to bridge the gap for highly critical materials that pose environmental hazards. “About 10% of the materials we look at in each generation are critical,” Jewett says. “There’s probably only one thing we can find that works. And if it works, we hope it’s successful. Many times, if you can just find something that fulfills a need from a materials standpoint, you land on it, and you go try to develop it.”

For PFOS, however, that began to unravel in mid-2000, when 3M announced, in conjunction with the U.S. Environmental Protection Agency (EPA), that it would voluntarily phase out the production of PFOS-based products. 3M was the only U.S.-based supplier of PFOS precursors and a major supplier worldwide. “We all went into a panic,” Jewett says. “We didn’t even know this was happening.”

Later in 2000, the EPA released a significant new use rule (SNUR) for PFOS, proposing severe limitations for the use of 90 PFOS chemicals and derivatives. The semiconductor industry had to jump to action. Together, SEMI and the Semiconductor Industry Association (SIA) formed the PFOS Working Group, a coalition of semiconductor and resist manufacturers, and successfully persuaded the EPA to exempt the semiconductor industry’s use of PFOS. “We did have problems, but we also had intent,” Jewett says.

But of course it didn’t end there. “We had to do the whole thing over again in Europe,” Jewett notes. Following the EPA’s lead, the UK’s Department for Environment, Food and Rural Affairs (DEFRA) put a risk reduction strategy into place for PFOS, and in 2008 the European Union introduced new restrictions as well.

In 2009, a U.N.-sponsored treaty to combat highly dangerous chemicals was expanded to include nine more toxic substances, including PFOS. “All the member countries had their own enabling legislation, and they all worked differently,” Jewett says. “In Japan, it was illegal to manufacture with PFOS right away because of the treaty. We had to work to get an exemption in Japan so the semiconductor industry could keep manufacturing.”

The domino effect was a critical component to understand, Jewett says. “It’s a never-ending story, and it changes as we go.” Cascading was also an issue, with related materials presenting problems as well. “It just became an exacerbating problem as we went through this.”

Today, almost all non-critical uses of PFOS have been eliminated, according to Jewett. Although the use of PFOS has dropped significantly in PAGs and other critical applications, it still has exemption status in almost all cases in photolithography. “So we do have the ability to continue to use PFOS where we really critically need it,” he says.

The industry has only recently found a suitable replacement for PFOS, according to Jewett, “after about 10 years of looking.” The industry was very happy early on when it found alternatives that would work, but those alternatives already don’t work anymore, he says, so the alternatives in place now are still being scrutinized.

Perhaps the most important lesson learned through the PFOS ordeal has been understanding what are the most critical materials now and in the future, and understanding each and every player in the supply chain, which for PFOS had 10 or 11 links, Jewett says. “That was a big surprise for us.”

Major challenges in finding material alternatives, Jewett says, are IP, time and affordability. However, he is careful to differentiate affordability from cost. “We’re not saying we’d rather trash the environment than spend money,” he explained. “But what comes out may not be a marketable product.”

Many of the lessons learned from PFOS can be applied across the materials supply chain. The 2010 SEMICON West and Intersolar North America agendas will feature a variety of EHS programs (see table), including a government environmental briefing.

Environment, Health and Safety (EHS) sessions at SEMICON West/Intersolar North America

Monday, July 12

8:00am–5:00pm

Global Care Sustainability Practitioners Workshop

S.F. Marriott Marquis

Tuesday, July 13

2:00pm–6:00pm

Government Environmental Briefing for High Tech Manufacturing

S.F. Marriott Marquis

Wednesday, July 14

1:00pm–6:00pm

Energy Conservation Workshop

S.F. Marriott Marquis

Thursday, July 15

9:00am–1:00pm

Delivering on the Promise of Sustainable PV Manufacturing

San Francisco InterContinental Hotel