Engineering new technology at the molecular level

In the new Pritzker Nanofabrication Facility at the University of Chicago an ISO Class 5 cleanroom has been kitted out and is being used for research into the advanced lithographic processing of hard and soft materials

A researcher working in the Pritzker Nanofabrication Facility prepares to create a pattern on a silicon wafer. Using lithography, a process similar to photography, the researchers will expose this pattern onto a photosensitive film on the silicon wafer using ultraviolet light

Academic and industrial researchers have begun working side-by-side at the University of Chicago’s Pritzker Nanofabrication Facility, using some of the world’s most advanced tools to exploit the atomic and molecular properties of matter for emerging applications in science and technology.

‘You can’t really do engineering systems from the molecular level up like we’re aiming to do without something like the Pritzker Nanofabrication Facility,’ says Matthew Tirrell, Dean and Pritzker Director of the Institute for Molecular Engineering.

It is located in located in the new Eckhardt Research Center and since the facility opened in February, its biggest users have been University of Chicago students in molecular engineering, physics, and chemistry working on their own projects and in collaboration with faculty members. There are also users from other university campuses as well as industry.

‘We have students working on a variety of different projects, including making devices for applications in quantum information, working on devices that use microfluidic technology, and developing detectors for astrophysical applications,’ says Andrew Cleland, the John A. McClean Sr. Professor of Molecular Engineering Innovation and Enterprise and Faculty Director of the Pritzker facility.

Microfluidic devices can be used to detect and measure the properties of single cells, viruses, or other biological components. In the astrophysical realm, researchers fabricate sensors for the South Pole Telescope to detect the cosmic microwave background radiation, the afterglow of the Big Bang.

The facility’s tools offer the capability of manufacturing devices ranging in size from a few inches down to the minuscule 10 nanometres (nm). ‘Being able to craft objects on the nanometre scale with state-of-the-art equipment is going to enable extraordinary experiments on the campus,’ says David Awschalom, the Liew Family Professor in Molecular Engineering and IME’s Deputy Director for space, infrastructure, and facilities.

Large nanofacility

Support for the 10,000ft2 (929m2) facility in the William Eckhardt Research Centre came partly from a US$15 million gift from the Pritzker Foundation.

The National Science Foundation provided an additional $5m to establish the Soft and Hybrid Nanotechnology Experimental Resource, a partnership between the University of Chicago and Northwestern University. The NSF grant provides funding for support staff and training for external industrial and academic users who seek to develop nanostructure fabrication capabilities at the Pritzker facility and at Northwestern.

‘Today’s cleanroom is the machine shop of our time,’ says Awschalom. ‘A generation ago it was all about state-of-the-art mills, lathes, making very tiny structures with wire-cutting tools. Today it’s the nanofabrication facility and advanced etching techniques.’

But launching new technological products requires the involvement of industry, he notes. ‘Universities are fantastic at generating creative concepts and ideas and developing proof-of-concept prototypes.

To transition these ideas into society, it will be vital to engage the expertise of start up companies and industry.’

Facility users will complete training before using the cleanroom. They will pay an hourly fee for access, and may pay additional fees for the use of specific tools and equipment. The proceeds will go to support the facility’s operations.

‘Our plans are that this facility will eventually be open 24/7, meaning that it will have access for graduate students as well as external users any time of the day or night,’ Cleland says. ‘Industrial users will be an important part of our user base, and they will also tie in our graduate students to the industrial efforts that are related to their research.’

An unusual feature of the Pritzker Facility is its corridor-facing glass walls. Visitors can watch scientists and engineers conduct their work.

Ultra-clean bays

As an ISO Class 5 cleanroom, the Pritzker Facility contains air with 100 or fewer particles measuring five microns (one tenth of the width of a human hair) or larger per cubic foot. Outside air typically contains more than a million dust particles of this size per cubic foot. The facility sports a bay-and-chase design, with six bays (ultra-clean work spaces) alternating with chases (return-air spaces).

‘One positive impact of our gift from the Pritzker Foundation was our ability to purchase new equipment for the facility,’ says Sally Wolcott, the facility’s Business Manager. ‘This allowed the Pritzker Nanofabrication Facility to design and plan tool purchases such that bay one is completely empty, giving us room for expansion. We have money already earmarked, and we will continue to acquire tools based on need.’

The chases serve as giant vacuum cleaners, recirculating the air through nearly 1,000 filters to keep the facility clean. People working in the facility also must wear a special coverall, a hairnet, gloves, and covers for mouth and shoes.

‘In its simplest terms, the Pritzker Facility is used for three primary activities,’ said Technical Director Peter Duda. ‘We add materials, we remove materials, and we use different techniques to create patterns in those materials. By layering all of those patterned materials that you’ve added and subtracted, you can create devices.’

Peter Duda, Technical Director of the University of Chicago’s Pritzker Nanofabrication Facility, holds a pure, four-inch silicon wafer

The work is extremely precise. With the facility’s atomic-layer deposition tools, researchers can deposit a film one atomic layer at a time. One such material that can be grown this way is aluminium oxide, ‘a ceramic very similar to what your coffee cup is made of,’ Duda says.

But as an electrical insulator it is used in integrated circuits and in superconducting devices. Superconducting devices are among the interests of David Schuster, Assistant Professor in physics and an IME fellow. Schuster plans to install his multi-angle electron-beam evaporation system in the Pritzker Facility.

‘It supports the evaporation of superconducting metals, such as aluminium, niobium and tantalum on wafers up to four inches in diameter,’ Schuster says. The system can create high-quality superconducting Josephson junctions, which are a key element in superconducting circuits.

Schuster’s collaboration with Awschalom and Cleland signals more synergy to come between IME and other departments.

‘Working with the Awschalom and Cleland groups has been wonderful, making the University Chicago one of the premier destinations in the world for quantum physics,’ Schuster says.

This article was reprinted with permission from Newswise.