Save costs by conserving energy in the sub-fab

By Pete Singer, Editor-in-Chief

Opportunities for cost savings abound in the “sub-fab” of semiconductor operations where the vacuum pumps and gas abatement systems

Dr. Michael Czerniak, Environmental Solutions Business Development Manager, at Edwards Ltd.

Dr. Michael Czerniak, Environmental Solutions Business Development Manager, at Edwards Ltd.

reside. Typically, these systems are running full tilt, no matter what’s going on in the process tool.

In a case where the cobbler’s children may finally be getting new shoes, work is underway to improve the communication between sub-fab equipment and process tools so that fuel in gas abatements systems can be turned off if there’s nothing to abate, and vacuum pumps can be throttled back or slowed if there’s nothing to pump.

“If you have equipment that is enabled with this capability, you can access these savings by essentially turning down the power or the fuel gas consumption when they’re not actually required for chip processing, said Dr. Michael Czerniak, Environmental Solutions Business Development Manager, at Edwards Ltd.

Czerniak gave a talk at 2:00pm on Tuesday at SEMICON West as part of the Sustainable Manufacturing Forum. The forum, held on Tuesday in Moscone North, Hall E, Room 132 from 10:00am to 5:00pm, allows experts to share the latest information on the environmental and social impacts of advanced technologies that are likely to be introduced into semiconductor manufacturing in the near future.

At SEMICON West in 2014, Czerniak was honored with SEMI’s Merit Award, along with Daniel Chlus (IBM) and Lance Rist (RistTex). The trio, were part of the Energy Saving Equipment Communication Task Force responsible for developing new standards designed to help reduce energy consumption in production equipment, specifically the SEMI E167 standard.

While production equipment and support equipment are all capable of reduced utility consumption, implementation has been slow due to lack of a standard.

SEMI’s E167 solved one piece of the puzzle – enabling the factory host to tell the process too that there are no wafers coming, for example – another standard is needed for the tool to communicate with sub-fab equipment that it, too, can power down. That is where a new standard, SEMI S23 comes in. “Once the tool has decided it doesn’t need pumps and abatement for the next 45 minutes or so — whatever it decides — it can then cascade that message down to the subfab where the energy savings will actually take place,” Czerniak explained.

At SEMICON West, a working group of the SEMI S23 task force is preparing additions to the Related Information section of SEMI S23 to provide for suggested utility-consumption test conditions and report formats for some components and peripheral equipment commonly used in semiconductor manufacturing equipment systems.

The components initially considered are dry vacuum pumps, refrigerated chillers and heat exchangers, although other components such as process power equipment may be considered soon. Also under discussion is the inclusion of Related Information for the application of efficiency rating systems for components and peripheral equipment. The goal of the working group is to produce suggested new Related Information in SEMI S23 for consideration on a future SEMI Standards Ballot.

“We’re working pretty hard as part of a SEMI standards committee – to get standardized signaling for that sort of information – so that all pump and abatement suppliers can get access to signals that allow them to do these energy savings,” Czerniak said.

Czerniak said this will work best in a new facility, once the tools have the ability to communicate directly with the pumps and abatement systems. In a retrofit scenario, it can be a challenge to get those signals. “We’re talking about getting signals derived from loadlock pumps,” he said.

In practice, it may be impossible to actually turn off vacuum pumps completely, particularly those that are pumping byproducts that tend to condense inside the pump. “You generally don’t want to switch them off due to the risk of not being able to restart them. In those cases, what you do is typically reduce the frequency at which you spin them and save maybe 10-15% of the running power. To get them back to full speed and full operating temperature isn’t such a long period of time,” Czerniak said.

On the other hand, with gas abatement systems, particularly those that burn fuel (i.e., natural gas) to destroy the byproducts, it’s possible to shut them to near zero. “In our case, we usually just leave them running on a pilot flame. They come back on line in tens of seconds, and you save about 90% of your fuel gas. There are very significant savings,” Czerniak said. “At the same time, you also save on your CO2 footprint. It gets to be quite an important factor when people do CO2 audits of their manufacturing process so they can put green stickers on their end products.”

This has been the focus of one of the working groups in the European EEM450PR project, which is focused on 450mm tool developed (similar work is underway at the G450C Consortium in Albany).

In his talk on Tuesday, Czerniak described those models that were constructed as part of the EEM450PR project to simulate the impact of green modes, at various levels of wafer inactivity, initially for 300mm, and then extended for a hypothetical 450mm fab. It was also noted that additional savings would be possible in the facility, e.g. reduced process cooling water when the pump and abatement thermal load is reduced. The model was then validated by looking at data from a HVM 300mm fab, simulating the effect of green modes (without actually implementing them), and also live green mode implementation on pumps and abatement at imec’s R&D lab in Europe.

A live demonstration was also conducted in the G450C Albany fab on some installed 450mm toolsets, as part of the complementary and collaborative engagement between the regions on the 450mm topic, in order to validate the assumptions for future 450mm fabs.

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