EUV reaches angstrom resolution

Scientists at the University of Colorado (Boulder) recently had an astounding breakthrough with the invention of the EUV microscope.

The wavelength of visible light, 400nm to 700nm, makes it impossible with today's tools to take photographs of nanoscale objects with any sort of reasonable resolution. The answer has been to use scanning electron microscopy (SEM) and atomic force microscopy (ATM), which yield reasonable images. These tools, however, produce nothing close to the angstrom-level (tenth of a nanometre) resolution of a new type of microscope that uses femtosecond pulses of extreme ultraviolet light (EUV), the same wavelength light to be used for sub-10nm semiconductor lithography.

This image used false colours to bring out the details of a photo synthesised from the University of Colorado's EUV femtosecond laser pulses. (Source: University of Colorado)

The research grant was provided by Semiconductor Research Corp. (SRC).

"SRC is very happy with results of this experiment," said Kwok Ng, senior science director of Nanomanufacturing Materials and Processes at SRC. "In general when you go to less than 10nm features, it is a big problem to image them. The fact that the EUV microscope is a table-top device will be a big boon to the industry."

SEMs and ATMs are big, heavy, expensive devices that are built into their own dedicated table, but the EUV microscope can be set on a laboratory table-top and easily moved from location to location or even stored in a closet. Plus it allows measurements to be easily made from their ultra-high contrast images which rival those of the highest resolution visible wavelength camera, only with angstrom resolution.

The system works by boosting wavelength to ultra-high harmonics using an aperture reflection-mode microscope illuminated by a 30nm source. Full-field images of 40nm to 80nm lateral resolution result an axial resolution of just six angstroms (0.6nm) with an exposure time of about one minute. The team is also working toward making movies of functioning nano systems with a temporal resolution of 10fs.

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