Method Images the Invisible

Just as x-ray technology, MRI and sonography transformed the practice of medicine, a newly created approach for seeing the invisible promises great potential for finding new ways to improve the health of human and microelectronic patients alike.

Semiconductor Research Corp. (SRC), a university-research consortium for semiconductors and related technologies, partnered with Northwestern University to successfully demonstrate a unique ultrasound holography approach that enables scientists to view the tiniest of buried structures.

New subsurface, embedded defect analysis will be more accurate than any other imaging process, spurring a spinoff company to commercialize the technology. (Image: Semiconductor Research Corp.)

The resulting three-dimensional information will provide benefits ranging from greater yields for semiconductor manufacturers to more effective treatments for medical patients.

Using a novel, nondestructive approach that combines, for the first time, scanning-probe microscopy (SPM) with ultrasound and holography, researchers at Northwestern have demonstrated the ability to view subsurface particles as small as 15 to 20 nm. Such capabilities have not previously been possible without slicing the sample, which changes both the composition and structure and sacrifices characteristics of the studied subject.

What makes the new approach revolutionary is the combined use of the SPM, ultrasound and holography. SPM offers nanoscale resolution. Ultrasound is nondestructive, transparent to all materials and sensitive to embedded structures, including nanosize defects.

Holography also can provide sophisticated 3-D representations of the buried information. Together, the three technologies offer unprecedented visibility to the increasingly important tiny parts of nature.

As there is neither a similar approach nor such a high class of result available anywhere, a high-tech startup company has been launched to further the commercial applications for these methods.

Named NanoSonix Inc., the spinoff will develop a nanoscale-imaging tool set capable of rapid evaluation of defects and flaws below the surfaces as well as valuable recognition of buried patterns and structures.

“Microelectronics, in particular, is a flaw-intolerant technology, where even nanoscale defects can compromise the performance and yield of the devices,” said Dan Herr, director of nanomanufacturing sciences for SRC-GRC, an entity of SRC. “The ability to see such defects is critical for yield enhancement as devices become smaller and such metrology techniques and tools become even more crucial. These results are very good news for multiple industries.”

Utilizing the new technology, the microelectronics and nanoelectromechanical systems industries can improve performance of their devices, time to yield and, ultimately, yield rates by deploying this technique in process development and as an in-line quality control tool. Thanks to the nondestructive imaging approach, the pharmaceutical industry should benefit from better understanding of how drugs distribute, accumulate and clear from various parts of the body.

“Biomedicine is moving toward use of nanobiostructures to interrogate cells and deliver therapeutic cargo. This requires a noninvasive view inside the cells to monitor what’s happening under physiologically viable conditions,” said Vinayak Dravid, professor of materials science and engineering and the director of the Nuance Center at Northwestern. “With the new imaging technology, it’s possible to sharply increase our understanding of the biodistribution of new drugs and the important interactions of nanoparticles and cells during intended or desirable therapeutic delivery or unintended environmental uptake.”

The next steps in development of the technology include system integration, material handling, faster scanning and high throughput of results. In-line tools and methods for addressing these needs will be created by NanoSonix; in the next 12 months, the spinoff will develop an add-on module for existing commercial SPM equipment to meet associated offline metrology requirements.

For more information, visit: www.src.org