by Mark A. DeSorbo
Facility cultivates newly developed high-temperature superconductivity and semiconductor devices
Renovating an older facility to accommodate controlled environments can present a plethora of challenges, and DuPont (Wilmington, DE) tackled several when it set out to develop an advanced superconductivity technology that will not only meet the needs of the U.S Department of Defense, but will have broad commercial applications as well.
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According to DuPont, the $1.2-million facility will be home to new microwave and communications products that use high-temperature superconductivity and semiconductor devices, forming a new area of technology called cryoelectronics, says Daniel B. Laubacher, DuPont's product development manager.
With this type of technology, ISO Class 6 (Class 1,000) cleanrooms were a must, for operations conducted within include epitaxial thin-film deposition; photolithographic patterning of microwave structures; and electrostatic discharge-free packaging of communications products.
“This is a major investment by the company in a new and developing technology with an exciting set of potential products that will enhance wireless communications over the next few years,” Laubacher says. “This facility will be our major R&D and product development facility.”
Planning began in June 1998, while the approval to break ground came in January 1999. The cleanrooms portion of the project sparked bids from three vendors. Servicor Inc. (San Carlos, CA), a manufacturer of modular cleanrooms for the medical device, biotechnology and microelectronics industries, was awarded the contract and finished the job in mid-October 2000.
Cleanroom construction was within a 30-year-old building, which has been rented to the U.S. Army for about 10 years. The building needed total refurbishing, including a new structural concrete flooring, roof, electrical substation and HVAC.
“There were walls that were six-feet deep. The facility was a nightmare. The army retrofitted the building several times over, and DuPont had to come in and gut it,” says Will Stambaugh, Servicor's regional sales manager.
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Asbestos and lead removal as well as poor-quality concrete flooring presented challenges. But perhaps the most intriguing problem was the lack of subcontractor availability due to the booming economy, according to Laubacher. “Also, since the construction was phased over two years, there was difficulty in maintaining continuity between subcontractors and crafts,” he says. “Long lead items, like electropolished piping for process gasses, were difficult to obtain and did impact the completion schedule.”
The controlled environment comprises 14 Class 6 cleanrooms, totaling just over 12,600 square feet.
“It's not a boutique, it's a strip mall of cleanrooms,” Stambaugh says.
Seven of the 14 areas are soft-wall cleanrooms making up 2,600 square feet of the clean space. They are constructed with 2-inch by 2-inch powder-coated steel tube framing, with sheets of PVC film stretched over the structure. These areas are used for product inspection and final testing.
The other seven cleanrooms are constructed with hard-walls made of quarter-inch clear acrylic. “In our design, the quarter-inch paneling isn't the support, it is the structure. Therefore, the walls do not have to be two to three inches thick. The frame supports the weight,” says Reza Kazemi, director of sales and marketing for Servicor, adding that the cleanrooms are also seismically rated.
The project also included a ceiling grid that features custom process piping access panels and yellow lighting. Stambaugh adds that Servicor's “Ultra” envelope system supports DuPont's bulkhead-mounted process equipment and built-in Servicor stainless steel laminar airflow benches. A thallium room was also designed to have low wall exhaust HEPA filtration in the event that an unexpected excursion would have to be contained.
A special part of the new facility is the thallium-containing superconductor PVD development area. Beyond the engineering controls in place for handling thallium materials, this area has both incoming and special outgoing reverse flow HEPA filtering. This isolation facility is kept at negative pressure, while the rest of the facilities utilize air supplied by separate ductwork from the main facility HVAC unit.
The majority of the facilities are used for non-hazardous PVD operations, component assembly and necessary non-cleanroom equipment service chases. The amount of once-through conditioned air is dramatically reduced. The main HVAC system was fabricated by Buffalo Forge and provides 50,000-cubic-feet-per-minute (CFM) capacity. Seven Liebert air conditioning units supplied to the cleanrooms provide localized cooling.
Although Servicor and DuPont did not want to speculate, a facility to meet the commercial market is also planned. “We have already begun talking about the commercial facility, and those discussions will continue once this facility is up and running to full capacity,” Stambaugh says.