Carnegie Mellon's nano-facility a solid option for the fabless



PITTSBURGH, Pa.—Bridge Semiconductors is one of many tech start-ups that has chosen to go fabless, thanks to Carnegie Mellon University's Nanofabrication Facility.

The $10 million, 4,000-square-foot facility, includes 1,200 square feet of ISO Class 4 and 2,600 square feet of ISO Class 5 cleanroom space. The controlled environments are outfitted with tooling for developing the micro-electro mechanical systems (MEMS) made by Bridge, as well as chips that improve the sound in cell phones or gauge damage done to a disk drive when dropped by a user.

Controlled environments at Carnegie Mellon University are outfitted with tooling for developing MEMS.
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"Fundamentally, when you are spending venture money, it's costly money, so we did not want to invest in a lot of bricks and mortar. We put that money in research and development," says Charles Buenzli, Bridge's vice president and COO of Bridge Semiconductors, which uses wafers from Taiwan Semiconductor Manufacturing Corp. to build its MEMS-based integrated circuits.

Buenzli explains that going fabless by using Carnegie Mellon's facility provides convenient access to equipment and resources that would have cost the company more than $2 million if it chose to set up its own manufacturing facility.

"We can attribute the rapid progress in our device development to having access to the excellent resources at the facility," he says. "We have a nice, broad cross-section of processes available, from metal deposition to etchers; so, we didn't have to make a choice on day one. We can explore what gives us the best process. In an academic situation like that, you have a wider freedom to do things that may not be permitted in a traditional manufacturing environment."

Research projects at the Carnegie Mellon facility are "truly diverse," says Chris Bowman, director of the Nanofabrication Facility, adding that gone are the days of cleanrooms used exclusively for semiconductors.

"Semiconductor manufacturing—that's what drove cleanrooms in the beginning; but now, on a university campus, the cleanrooms have to accommodate so many more activities, from nanotechnology to MEMS," he says.

The devices differ vastly, Bowman says, but there is a lot of shared equipment and key tools for each area of research. Researchers, he says, not only share equipment, but ideas as well.

"A typical disk-drive researcher does not need a backside aligner, but the MEMS researcher does, and that sparks interdisciplinary research," Bowman says. "If you put these people together in the same lab, it sparks ideas and innovation."

So, how much does it cost to use Carnegie Mellon University's Nanofabrication Facility?

Each person entering cleanrooms is charged a $25 fee. Solvents, gloves, and wipes are stocked in the cleanroom for the users' convenience. The fee covers the maintenance cost of de-ionized water system, particle counters, airflow balancing equipment, as well as filters, ultraviolet lamps, cleanroom garment rental and cleaning, tacky mats, gloves, soaps, acids, solvents, first aid supplies, and numerous other cleanroom musts.

A fee is charged for using the majority of the equipment in the cleanroom, with the funds used to maintain the equipment's existing features and specifications. All upgrades and modifications are charged to individual or group research accounts. The fee is assessed by the run, hour, or day.

Use of sputtering, etch or evaporators costs $105 per run, while use of the wafer scrubber is $35 per run and the copper electroplating system is $85 per run. Fees for using other equipment are subject to hourly rates that range from $55 to $155. Use of a Micrion focused ion beam is $155 per hour, while use of a GCA stepper is $125 per hour. Using a Karl Suss mask aligner will cost $90 per hour while the Cobilt mask aligner is $55 per hour.

"Including myself, there are full-time staffers, including a process engineer and a technician," Bowman says. "The fees pay for staff salaries and equipment maintenance, upgrade and modification. Whatever money is left over is used to replenish capital equipment."

About 80 qualified end users use the facility, and typically, a dozen people are in the lab at any one time.

Along with Bridge Semiconductor, Akustica, IC Mechanics and several researchers from the University of Pittsburgh are also using the labs. Carnegie Mellon researchers also extensively use the laboratory, with most of the lab activity coming from the Electrical and Computer Engineering's Data Storage Systems Center and MEMS Laboratory.

Current lab projects include a 20-nm wide bolometer to be used for a more accurate measurement of the mass of the universe, hybrid magnetic and optical-storage devices to extend disc drives into the terabit per square inch realm, thin film batteries, an implantable wireless bone strain sensor, microfluidic valves and flow regulators for bio fluids, magnetic random access memory chips, artificial lung tissue research, micro fuel cells, inertial sensors and organic chemical sensors for health and safety.

During the past 20 years, the lab has acquired an impressive range of processing equipment, including 12 sputtering systems for depositing films of many different materials and alloys, a reactive ion etcher for deep silicon etching and a newly acquired backside wafer aligner—the workhorses of MEMS-related research.

The university's lab also sports a 5-nm focused ion beam etcher and a newly acquired 10-nm resolution electron beam lithography system extending the lab's capabilities into increased nanotechnology research. To minimize process variations, the lab's cleanroom environment is extremely stable year round, maintaining 68 degrees plus or minus one degree and 35 percent humidity plus or minus three percent.