In a paper published last week in the journal Nature Communications, researchers from the Department of Physics and the Department of Electronics Engineering at the UAB, and from the Birck Nanotechnology Center at Purdue University (USA), studied the heating of small current lines placed on top of a silicon substrate, simulating the behaviour of current transistors.
This work shows how these metal lines heat up in a way that cannot be explained with the laws ruling heat behaviour in our everyday experience. A theoretical model developed by students Pol Torres and Àlvar Torelló, under the supervision of UAB professors Francesc Xavier Àlvarez and Xavier Cartoixà, has allowed explaining the experimental observations, showing that heat flow finds it difficult to make a sharp turn when going from metal to the substrate, similar to what would happen in a viscous fluid exiting a tube. This phenomenon makes it more difficult for the metal line to cool, and therefore its temperature rises to values which cannot be explained with present day models.
During operation, the most active parts of an electronic device may accumulate high amounts of thermal energy in very localized zones, called Hot Spots. This energy accumulation can be very detrimental to the correct functioning of the device, and represents a bottleneck limiting the performance of current processors.
This discovery paves the way to a better thermal management in electronic devices, since the proposed description represents a significant improvement over the models with which device engineers currently work, based on Fourier's law. These results represent a new positive test of the theory of Extended Thermodynamics, developed in the 1990s by UAB professors David Jou and José Casas.
Amirkoushyar Ziabari, Pol Torres, Bjorn Vermeersch, Yi Xuan, Xavier Cartoixà, Àlvar Torelló, Je-Hyeong Bahk, Yee Rui Koh, Maryam Parsa, Peide D. Ye, F. Xavier Àlvarez & Ali Shakouri, Full-field thermal imaging of quasiballistic crosstalk reduction in nanoscale devices. Nature Communications 9, Article number: 255 (2018)