TI Switches Exhaust to Save Energy Costs
Texas Instruments Inc. is saving on the energy required to exhaust air from its dedicated implanter room. Working with an implanter vendor, TI reconfigured its implanter exhaust system to send air to general exhaust, producing significant annual energy savings at its 300 mm fab in Dallas, TI facilities engineer Steve Russo said at the recent ISMI Symposium.
David Lammers, News Editor -- Semiconductor International, 10/30/2009
Describing a "10 year journey" to reduce exhaust energy use, Steve Russo, a Texas Instruments Inc. (TI, Dallas) facilities engineering manager, said the company overcame a series of hurdles in its effort to change the way implanter gas exhaust is handled at TI's 300 mm fab.
Hoods are the largest consumer of exhaust gas in a fab, followed by implant tools, Russo said at the recent ISMI Symposium, held in Austin, Texas. "Hoods are hard to attack because of all the chemicals and vapors. With implanters, there is not a lot of gas usage," he said.
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TI saw an opportunity to reduce a major consumer of fab exhaust. |
TI determined that it could safely exhaust from its dedicated implant room to general exhaust, rather than to the more expensive gas exhaust. A decade ago, it set out to work with implant vendors to change the vendors' own exhaust and gas-delivery specifications. The facilities team urged the equipment engineering team to approach the two implant vendors it worked with, but failed to sway either vendor. At that time, energy consumption was less of an issue, and the vendor perception was that the proposed transition would only be an energy conservation effort, with no benefits for throughput or performance, he said.
In 2004-2005, TI began planning a dedicated implant room attached to the main cleanroom at its 300 mm fab in Dallas. The conventional design used at TI's 200 mm fabs had the implant gas box going out to gas exhaust. Working with the ESH engineers and gaining the approval of state government inspectors, TI determined that if it could only use gas exhaust during emergency gas release, the general exhaust system could be used during normal operations.
One implanter vendor agreed to work with TI to install subatmospheric safe delivery systems (SDS) on the gas supplies. A team of 10 TI facilities and ESH engineers developed an implanter outer shell exhaust system that routed back into the cleanroom.
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Exhaust is a major energy user as fresh air must be supplied to keep the clean room pressurized. |
Russo said the team's first step was to tackle shell-side exhaust requirements. "More than 99.9% of the time, this flow consisted entirely of heat and room air; the only way anything potentially toxic could enter the flow was if a system leak had occurred," he said. "With highly toxic gases stored in SDS Type 1 cylinders, multiple compounding failures would need to take place for any accidental discharge of these gases to occur."
To elevate on-site BF3 to a higher safety level, the team replaced the traditional pressurized cylinders with a VAC system, a Type 2 SAGS technology that stores gas at high pressure but extends the safety envelope by delivering it at subatmospheric pressure.
All non-inert gasses are in a subatmospheric bottle set up that he said "greatly reduces the risk of a leak." Since then, TI has experienced no leaks from the gas bottles, and the emergency damper system in the implant room has never been called upon for use.
By taking the gas box to general exhaust, TI saved $250,000 in capital costs, with an estimated annual operational savings of $75,000 per year, much of it from energy savings.
"It took five years to get these changes accomplished, which is kind of sad," Russo said. "Generally speaking, we are scared to make changes in this industry."
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