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

The scanner removes a barrier to further shrinking of integrated circuits: as circuits get smaller, non-visual defects become harder to find.

They 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.

The microscope is described in a paper in the May 12, 2003, issue of Applied Physics Letters. It features some of the same magnetic-scanning technology found in computer hard drives. A scanner does not touch what it reads. Instead, a magnetic sensor the size of a small pea moves quickly back and forth over a circuit through which current flows. The sensor collects information, which is then converted by algorithms into a color picture of electron flow.