In making everything from digital cameras to central processing units and computer memory, the semiconductor manufacturing industry creates air-polluting nanoparticles that the industry today can’t totally trap.
Da-Ren Chen, Ph.D., assistant professor of mechanical engineering at Washington University in St. Louis, has designed a device to fit this need. Chen and visiting Washington University professor Chuen-Jinn Tsai have created a simple device called a coaxial cyclone that captures and removes particles in gas streams. The device, just 2″ by 3,” employs a guided vane that creates a swirling flow that nabs the particles and traps them. The device is designed to fit in the piping above a vacuum pump that provides the low-pressure environments needed for semiconductor manufacturing. The location of the device also protects the pump.
Currently the semiconductor manufacturing industry makes use of scrubbers to process the exhaust gases. Previous studies show that most of sub-micron-sized particles, including nanoparticles, elude scrubbers, which primarily are there to remove toxic gaseous species instead of capturing particles. The scrubbers do capture some particles, but mainly those in the micrometer-sized range, much larger than nanoparticles.
Making such a device available and affordable will be a boon to the semiconductor industry, which now is in compliance with E.P.A. pollution standards but is expected to exceed emissions standards soon because of improved manufacturing processing and higher volume production.
“The advantage of this device is that it can be built to fit in the current piping of existing semiconductor manufacturing systems, no modifications have to be made,” said Chen, a member of the Washington University Environmental Engineering Program. “It also is the only device designed to work in the low-pressure environment.’
The size of the device also is beneficial because the semiconductor industry places specialized equipment in rooms called clean rooms, where space is paramount.
“In a clean room of class 100, one square foot costs more than $300; the cost is even higher for the clean room of class 10 or 1, the current standard in the industry” Chen said. “In order to make a profit, the industry needs to squeeze as much equipment as they can in that space and they don’t have much space for a particle control device. So, placing it within existing equipment without occupying extra space is very efficient.”
A clean room 10 refers to one where ten particles greater than five microns are generated per cubic foot; clean room 100, 100 particles.
Chen and Tsai will describe his device at the Asian Aerosol Conference this July in Hong Kong.