Manufacturing // Radiation Damage Bigger Problem in Microelectronics © Based on Material by Vanderbilt University / Journal of Applied Physics

The amount of damage that radiation causes in electronic materials may be at least 10 times greater than previously thought. That is the surprising result of a new characterization method that uses a combination of lasers and acoustic waves to provide scientists with a capability tantamount to X-ray vision: It allows them to peer through solid materials to pinpoint the size and location of defects buried deep inside with unprecedented precision.

"The ability to accurately measure the defects in electronic materials becomes increasingly important as the size of microelectronic devices continues to shrink," researcher N. Tolk explained. "When an individual transistor contains millions of atoms, it can absorb quite a bit of damage before it fails. But when a transistor contains a few thousand atoms, a single defect can cause it to stop working."

Previous methods used to study damage in electronic materials have been limited to looking at defects and deformations in the atomic lattice. The new method is the first that is capable of detecting disruption in the positions of the electrons that are attached to the atoms. This is particularly important because it is the behavior of the electrons that determine a material’s electrical and optical properties.

Image: Silicon wafer with radiation damage. © Meroli Stefano / CERN

"An analogy is a thousand people floating in a swimming pool. The people represent the atoms and the water represents the electrons," said researcher A. Steigerwald. "If another person – representing an energetic particle – jumps into the pool, the people in his vicinity change their positions slightly to make room for him. However, these shifts can be fairly subtle and difficult to measure. But the jumper will also cause quite a splash and cause the level of the water in the pool to rise. Much like the water in the pool, the electrons in a material are more sensitive to defects than the atoms."