MIT researchers have developed a technique that combines laser pulses and ultrafast X-rays to measure heat moving through multilayered electronic materials at the nanoscale. The approach allows scientists to map thermal dissipation inside active devices where traditional tools fail to reach buried layers.
Existing measurement methods struggle with complex, modern chip architectures that stack five or more material layers. Optical techniques like time domain thermal reflectance capture only an average overall signal near the surface, while infrared cameras lack the spatial resolution and frame rate necessary to observe rapid changes at tiny scales.
X-ray mapping and laser pulses
To overcome those limits, the research team used laser pulses to heat a sample while applying bright ultrafast X-rays and laser-powered electron pulses to scan it. The electron pulses capture atomic-level changes in material strain, and the penetrating X-rays reveal how heat moves across internal interfaces through X-ray diffraction.
Researchers applied the method to a test device made of a gallium nitride thin film on top of silicon. Gallium nitride is widely studied for efficient heat conduction, but its thermal performance often degrades due to tiny defects introduced during processing.
Measuring defect impacts
The team discovered that a single micron-scale wrinkle defect caused a fourfold reduction in heat dissipation at that specific spot. The same defect caused a 25 percent drop in overall heat dissipation across materials and forced heat to spread unevenly, moving more easily in one direction than another.
Standard heat dissipation models assume perfect crystalline structures and omit large wrinkle defects common in two-dimensional materials. Mingda Li, associate professor of nuclear science and engineering at MIT and co-corresponding author, noted that a leading semiconductor industry consortium has already reached out to collaborate on applying the technique to various commercial chips.
The paper was published in Nature Communications by co-lead authors Thanh Nguyen and Chuliang Fu, co-corresponding authors Li and Jeehwan Kim, and collaborators from MIT, the University of Texas at Austin, and Argonne National Laboratory. Funding was provided by the U.S. Department of Energy, the U.S. National Science Foundation, and the MIT School of Engineering Distinguished Energy Efficiency Fellowship.
