YORKTOWN HEIGHTS, N.Y., August 14 -- IBM and Nion Co. researchers have developed technology that extends the capabilities of the electron microscope to look at small, atomic-scale details in materials -- such as those used in manufacturing semiconductors -- at a resolution never
As reported in the August 8 issue of Nature, for the past 50 years electron optics engineers have sought to improve the precision of electron microscopes by counteracting the image-blurring effects of lens imperfections, or "aberrations." The largest imperfection, "spherical aberration," cannot be fixed in a single lens. To fix the problem, the IBM and Nion scientists combined seven new sets of magnetic lenses with modern computers to actively correct the aberration in real-time. After this correction, the microscope can make an electron beam that is only 75 thousandths of a nanometer (3 billionths of an inch), which is smaller than a single hydrogen atom. This is the smallest electron beam produced in an electron microscope to date.
"We can't fix what we can't see," said Philip Batson, the lead scientist on the project at IBM Research. "As the dimensions of computer chips shrink, scientists need new tools to explore the structures and properties of materials used in these chips. This breakthrough improves our ability to see and thoroughly explore properties of electronic materials."
Before the correction, the electron microscope yielded tantalizing but incomplete information about the atomic structure of important defects -- atomic level mistakes such as missing or extra atoms -- in semiconductor materials. Using this correction technique, scientists now can see those defects, and if necessary, find ways to fix them, the researchers said.
Spying on Silicon
Before the correction, the electron microscope yielded tantalizing but incomplete information about the atomic structure of important defects, the companies said. Atomic level mistakes such as missing or extra atoms -- in semiconductor materials. Using this correction technique, scientists now can see those defects, and if necessary, find ways to fix them.
For example, by examining the interaction of silicon (a semiconductor) with silicon oxide (an insulator), scientists can look at how the silicon and oxygen atoms bond to each other and determine the quality of the insulator. If the insulator has any defects, scientists can suggest ways to fix them, such as setting the right conditions to optimize the growth of silicon and silicon oxide materials.
The breakthrough could also help scientists improve the properties of silicon through a better understanding of how the atoms inside of materials interact in certain environmental conditions. Watching how atoms assemble, move around and interact with other atoms is fundamental to understanding the properties of materials and may lead to a better understanding of how to control environmental conditions so components of future computer chips could self-assemble.
The authors of the Nature report, "Sub-angstrom Resolution Using Aberration Corrected Electron Optics," are Philip E. Batson of IBM's T.J. Watson Research Laboratory in Yorktown Heights, N.Y., and Niklas Dellby and Ondrej L. Krivanek of Nion Co. in Kirkland, Wash.