Purdue uses nanotechnology cleanroom to expand undergrad class, expose students to high-end research

September 14, 2015  


Siddarth Sridharan, left, a teaching assistant for ECE 557, helps undergraduate student Michael Barrow use the optical microscope to take images of samples fabricated inside the cleanroom in the Scifres Nanofabrication Laboratory at Purdue's Birck Nanotechnology Center. The microscope has several objective lenses for capturing images at different resolutions. (Purdue University photo/Charles Jischke)
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WEST LAFAYETTE, Ind. - The Purdue College of Engineering is using the university's advanced cleanroom at Birck Nanotechnology Center (BNC) for the laboratory to expand an electrical and computer engineering class that exposes undergraduate students to high-end research.

What's more, the use of the cleanroom in the Scifres Nanofabrication Laboratory at BNC for the Principles of Microfabrication class (ECE 557) is giving Purdue engineers a significant competitive advantage for graduate school or if they pursue a career in industry.

Birck's role as a key component for Purdue Moves and its focus on undergraduate research, transformative education and commercialization also comes as the Discovery Park center this fall marks the 10th anniversary of its opening.

"To be successful in industry or if they plan to continue their studies and research, our students in all areas of engineering, the sciences and technology understand the value of learning by using the most advanced facilities possible," said electrical and computer engineering professor David Janes.

"Birck's 25,000-square-foot cleanroom allows students from the many disciplines at Purdue to experience firsthand a micro- and nanofabrication process," he said. "It also exposes them to the relevant gowning, safety and operational protocols, educating our students about the critical role cleanrooms play in manufacturing for designing and producing integrated circuits, memory devices, biomedical test structures and other applications."

The only undergraduate class in the nation that uses this level of cleanroom as a laboratory, Purdue's ECE 557 requires a minimum weekly time commitment of six hours for the lecture and lab component. Joining ECE in supporting the class is the Purdue School of Mechanical Engineering. Through ECE 557, Purdue students leave with an ability to demonstrate:

* A basic understanding of silicon electronic device and MEMS (micro-electromechanical systems) device fabrication processes.

* Hands-on experience and working knowledge of microelectronics or MEMS processing steps and process modules as well as device testing and characterization methods.

* Proper lab procedures and lab-notebook maintenance.

"These undergraduate students are learning the principles behind the processing and characterization of integrated circuits as well as micro-machined components such as pressure sensors, accelerometers and 'lab on a chip' components used for biological and medical testing," Janes said.

Elizabeth Grubbs of Wilmington, Delaware, a spring 2015 electrical and computer engineering graduate, used ECE 557 and the access to the BNC cleanroom for gaining expertise in her study of integrated nanophotonic circuits and plasmonic metamaterials.

Grubbs, who is pursuing her doctoral degree, is now the teaching assistant for ECE 311 and has been working with her research group on multi-probe characterization and photo-luminescent excitation of thin-film photovoltaic materials. The research group, led by ECE professor Peter Bermel, also is researching high-performance and multi-junction cells in tandem with the Bay Area Photovoltaic Consortium at Stanford University.  

"My favorite part of ECE 557 and working in the cleanroom is that I got to fabricate the devices that I have been studying my entire undergraduate education," Grubbs said. "Anyone can purchase individual discrete transistors and passive electronic components and then breadboard their circuit design. Being able to design a custom integrated circuit and then fabricate it on one single chip yourself is almost unimaginable."

Although dust particles are microscopic, they're actually larger than many of the features in devices built through nanotechnology, making cleanrooms critical to any research at this tiny scale. Nano is a prefix meaning one-billionth. A nanometer is one-billionth of a meter, or only about 10 atoms wide. You could put 60,000 nanometer-wide lines across the diameter of a human hair.

The Birck cleanroom provides the particle-free environment needed for fabricating microscale and nanoscale devices, as well as the biological-pharmaceutical-grade environment needed for work with pathogen-detecting biochips and other biological nanotechnology. To maintain the high level of cleanliness, researchers must wear specialized jumpsuits, hoods, face-veils, gloves, and shoe coverings, and pass through air showers before entering.

The BNC cleanroom contains multiple clean zones that are defined by the number of 500 nanometer particles per cubic foot of air. The least-clean portion of the cleanroom, which is about 15 percent of the total area, is about 500 times cleaner than the average office, containing less than 1,000 particles per cubic foot. The cleanest portion of the cleanroom, about 45 percent of the area, allows less than one particle per cubic foot of air. No university cleanroom in the country is cleaner and only one other meets this standard.

"Humans are major particle generators, and as research advances the lack of vibrations and particles becomes that much more important," said BNC engineering manager Ron Reger. "The ultimate goal is try to mitigate that."

Undergraduates involved in BNC are primarily through ECE 557 and the Summer Undergraduate Research Fellowships (SURF) program.

For ECE 557, Purdue students coming from the engineering disciplines as well as physics and chemistry have access to a specific section of the cleanroom, referred to as the Teaching Bay. Here they learn to operate high-powered microscopes, mask aligners, acid hoods and solvent hoods. ­This training is directly relevant for careers in research and development or production in a number of high-tech fields.

"The cleanroom is compa­rable to a full industrial-style cleanroom," said BNC strategic facilities officer John Weaver, who spent over 40 years working with cleanrooms at RCA, Hughes Aircraft Co. and Delphi Electronics and Safety before coming to Purdue a decade ago to help design, build and launch BNC. "Experiencing work in the cleanroom prepares students for both a job in industry or for graduate school."

The types of fabrication processes used in this cleanroom research include:

* Patterning - Creating nanoscale patterns on wafers with an electron beam.

* Maskmaking - Creating photo masks, which act like photographic negatives in patterning silicon wafers.

* Etching - The transfer of patterns generated with the lithography process into three-dimensional structures.

* Deposition - Depositing films of various materials on surfaces to use in the creation of structures.

* Diffusion - Using temperatures of up to 1,200 degrees Celsius to alter the electrical characteristics in specific areas of the silicon wafer.

"We continue to update our equipment in order to keep our research moving forward," Reger said. "We are constantly advancing to the point that unless we stay on the cutting edge of technology we risk becoming stalled."


In the cleanroom at the Birck Nanotechnology Center, Purdue student Jiawei Zhou uses a photoresist spinner - a programmable machine that spins a single wafer at a high speed for manual photoresist coating - to perform optical lithography. (Purdue University photo/Charles Jischke) 
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Grubbs worked on a few theoretical designs with new applications, as well as waveguide characterization, neither of which would have been possible without her experiences in ECE 557. She sees BNC not only as a remarkable facility but as a place where creative minds merge with outstanding technologies.

"Birck is a place where I can learn and explore all of my ideas with a group of people containing not only intellect but also unparalleled insight that inspires me on a daily basis," she said.

The Scifres Nanofabrication Laboratory is named for Purdue alumni Donald and Carol Scifres, who donated $10 million to the construction of BNC. The 187,000-square-foot BNC, which opened to researchers in October 2005, involves Purdue faculty, staff, post-docs, and students - graduate and undergraduate - from 27 schools and departments.

The BNC is named for the late Michael and Katherine (Kay) Birck, of Hinsdale, Ill. The Bircks contributed $30 million for the building. A Purdue alumnus, Michael Birck was a member of the Purdue board of trustees and co-founder and chairman of Naperville, Illinois-based Tellabs Inc. He died on July 6 after a three-year battle with an uncommon form of bone marrow cancer.

Writers: Emily Sigg, 765-494-4719, esigg@purdue.edu

Phillip Fiorini, Purdue University, 765-496-3133, pfiorini@purdue.edu

Sources: David Janes, 765-494-9263, janes@purdue.edu 

John Weaver, 765-494-5494, jrweaver@purdue.edu 

Ron Reger, 765-494-6667, rreger@purdue.edu 

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