Bong+Jae+Lee
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Researchers finds a way to reduce the overheating of semiconductor devices
The demand to shrink the size of semiconductors coupled with the problem of the heat generated at the hot spots of the devices not being effectively dispersed has negatively affected the reliability and durability of modern devices. Existing thermal management technologies have not been up to the task. Thus, the discovery of a new way of dispersing heat by using surface waves generated on the thin metal films over the substrate is an important breakthrough.
KAIST (President Kwang Hyung Lee) announced that Professor Bong Jae Lee's research team in the Department of Mechanical Engineering succeeded in measuring a newly observed transference of heat induced by 'surface plasmon polariton' (SPP) in a thin metal film deposited on a substrate for the first time in the world.
☞ Surface plasmon polariton (SPP) refers to a surface wave formed on the surface of a metal as a result of strong interaction between the electromagnetic field at the interface between the dielectric and the metal and the free electrons on the metal surface and similar collectively vibrating particles.
The research team utilized surface plasmon polaritons (SPP), which are surface waves generated at the metal-dielectric interface, to improve thermal diffusion in nanoscale thin metal films. Since this new heat transfer mode occurs when a thin film of metal is deposited on a substrate, it is highly usable in the device manufacturing process and has the advantage of being able to be manufactured over a large area. The research team showed that the thermal conductivity increased by about 25% due to surface waves generated over a 100-nm-thick titanium (Ti) film with a radius of about 3 cm.
KAIST Professor Bong Jae Lee, who led the research, said, "The significance of this research is that a new heat transfer mode using surface waves over a thin metal film deposited on a substrate with low processing difficulty was identified for the first time in the world. It can be applied as a nanoscale heat spreader to efficiently dissipate heat near the hot spots for easily overheatable semiconductor devices.”
The result has great implications for the development of high-performance semiconductor devices in the future in that it can be applied to rapidly dissipate heat on a nanoscale thin film. In particular, this new heat transfer mode identified by the research team is expected to solve the fundamental problem of thermal management in semiconductor devices as it enables even more effective heat transfer at nanoscale thickness while the thermal conductivity of the thin film usually decreases due to the boundary scattering effect.
This study was published online on April 26 in 'Physical Review Letters' and was selected as an Editors' Suggestion. The research was carried out with support from the Basic Research Laboratory Support Program of the National Research Foundation of Korea.
< Figure. Schematic diagram of the principle of measuring the thermal conductivity of thin Titanium (TI) films and the thermal conductivity of surface plasmon polariton measured on the Ti film >
2023.06.01 View 4625 -
Technology to Control Near-Field Thermal Radiation
(from left clockwise: Professor Seung Seob Lee, Professor Bong Jae Lee, PhD Mikyung Lim and PhD candidate Jaeman Song)
A KAIST research team succeeded in measuring and controlling the near-field thermal radiation between metallo-dielectric (MD) multilayer structures.
Their thermal radiation control technology can be applied to next-generation semiconductor packaging, thermophotovoltaic cells and thermal management systems. It also has the potential to be applied to a sustainable energy source for IoT sensors.
In the nanoscale gaps, thermal radiation between objects increases greatly with closer distances. The amount of heat transfer in this scale was found to be from 1,000 to 10,000 times greater than the blackbody radiation heat transfer, which was once considered the theoretical maximum for the rate of thermal radiation. This phenomenon is called near-field thermal radiation. With recent developments in nanotechnology, research into near-field thermal radiation between various materials has been actively carried out.
Surface polariton coupling generated from nanostructures has been of particular interest because it enhances the amount of near-field thermal radiation between two objects, and allows the spectral control of near-field thermal radiation. This advantage has motivated much of the recent theoretical research on the application of near-field thermal radiation using nanostructures, such as thin films, multilayer nanostructures, and nanowires. Nevertheless, thus far, most of the studies have focused on measuring near-field thermal radiation between isotropic materials.
A joint team led by Professor Bong Jae Lee and Professor Seung Seob Lee from the Department of Mechanical Engineering succeeded in measuring near-field thermal radiation according to the vacuum distance between MD multilayer nanostructures by using a custom MEMS (Micro-Electro-Mechanical Systems)-device-integrated platform with three-axis nanopositioner.
MD multilayer nanostructures refer to structures in which metal and dielectric layers with regular thickness alternate. The MD single-layer pair is referred to as a unit cell, and the ratio of the thickness occupied by the metal layer in the unit cell is called the fill factor.
By measuring the near-field thermal radiation with a varying number of unit cells and the fill factor of the multilayer nanostructures, the team demonstrated that the surface plasmon polariton coupling enhances near-field thermal radiation greatly, and allows spectral control over the heat transfer.
Professor B. J. Lee said, “The isotropic materials that have so far been studied experimentally had limited spectral control over the near-field thermal radiation. Our near-field thermal radiation control technology using multilayer nanostructures is expected to become the first step toward developing various near-field thermal radiation applications.”
This research, led by PhD Mikyung Lim and PhD candidate Jaeman Song, was published in Nature Communications on October 16.
Figure 1. Experimental setup for measuring near-field thermal radiation between MD multilayers
Figure 2. Investigation of manipulated near-field heat flux by modifying the surface conditions with MD multilayers
2019.01.04 View 5446