Fault detector for small circuits

Scientists at Brown University have created a magnetic-sensing microscope that allows them to watch electricity flow through the tiniest components. They are using the device to find defects in integrated circuits and micro-machinery.

The scanning microscope can uncover defects in the smallest and most complex integrated circuits at a resolution 1000 times greater than current technology. The scanner removes a barrier to further shrinking of integrated circuits: As circuits get smaller, non-visual defects become harder to find.

Although magnetic sensing is used extensively, it is not applied widely for imaging electrical current flow, said Ben Schrag who co-developed the instrument with Professor Gang Xiao. The only method that uses magnetic imaging to see current flow is restricted to extremely low temperatures, employing cryogenic aids such as liquid nitrogen. However, the Brown device works at room temperature, opening the way to greater use of this technology.

Xiao and Schrag are using the technology to pinpoint how electrical current can form pinholes in state-of -the-art devices called magnetic tunnel junctions. These tiny sandwiches of ferromagnetic layers and insulating material are candidate memory storage cells to replace standard cells used in computer memory chips.

The researchers have 'imaged' current flow in electrical components as small as 50 nanometers, the smallest commercially available components, half the size of conventional chips.