Carbon Nanotubes Used in Scanning Probe Microscopes

A new process that uses carbon nanotubes (CNTs) as surface sensors for scanning probe microscopes (SPMs) has been developed by researchers at Xidex Corp. and Sematech (both in Austin, Texas), enabling the measurement of devices as small as 1 nm. "Carbon nanotube tips will make AFMs much more effective as laboratory diagnostic tools, and also give them the capability needed for in-line metrology on the production floor," said Vladimir Mancevski, Xidex founder and CTO, who invented the company's patented CNT tip-manufacturing process. "The nanotube tip needs to have the right diameter and be oriented properly," he added. "Most importantly, it must be grown by design and not by chance, and the process must scale to allow batch production of many tips at the same time."

"This is the key to making well-defined ultrahigh-resolution SPM tips for critical dimension metrology applications," said Keith J. Stevenson, assistant professor and Jack S. Josey Fellow in Energy Studies in the Department of Chemistry and Biochemistry at the University of Texas. "Xidex's process allows for great control over the CNT tip structure such as diameter, length and orientation, which is crucial for the uses desired by Sematech's member companies. Since these CNT tips are electronically conductive and can also be chemically modified, it is also quite possible to manufacture specialized tips for advanced electrical and chemical testing."

Compared with conventional silicon tips, CNT tips can be made with much smaller end radii and very high aspect ratios, enabling them to reach into the difficult-to-access spaces between microscopic features, Xidex officials explained. CNT tips are also extremely wear-resistant, extending their useful life and enabling higher-precision measurements, they said.