Session: 11-07-01 Measurements of Thermophysical Properties

Paper Number: 73000

Start Time: Tuesday, 03:40 PM

73000 - Direct Measurement of Thermal Boundary Resistance Reduction Due to Electron Carriers by Photothermal Radiometery 

A thermal boundary resistance occurs between any two surfaces that are not in perfect contact with each other. It is well predicted that this thermal resistance decreases as heat carriers cross the contact surface. These carries are typically either phonons or electrons. While phonon transport and electron transport is well documented in a number of conditions, direct measurement of the electron contribution to thermal boundary resistance across micro layers has not been shown. Understanding the effect of electrons on the heat transfer of thin layer is very important in understanding the thermal behavior of micro-electronics, which has impact on both life and reliability of electronics. This will also provide the foundation of thermal predictions in nano-electronics, where this work ultimately aims to lead in future studies. This paper presents an experimental test on the heat transfer as electrons cross the boundary of a closed, n-doped Schottky Diode. This diode was fabricated by depositing 50 µm of titanium onto an n-doped silicon substrate. Photothermal Radiometry (PTR) measurements were then taken in order to determine the thermal boundary resistance. PTR operates by irradiating a sample surface with a modulated heat source, typically a laser beam, to periodically heat the sample. The infrared response, which is also then periodic, is collected in a detector. The response of the detector is then passed into a lock-in amplifier which has a reference signal identical to the signal from the modulator. This allows the amplitude and phase of the IR response to be recorded at any measured frequency. This response, in terms of amplitude and phase, then defines the complex temperature response and can be used to determine various parameters of interest; in this case, this means the thermal boundary resistance. Measurements were made on the same diode in both the open and closed state. The results are normalized against a known sample in order to account for the various artefacts of the optics, detector, and the lock-in amplifier. This provides data that has been shown to accurately match the physical properties to the theoretical fit parameters. The obtained open and closed fit parameters were then compared with each other to determine the reduction in thermal boundary resistance. It was found that the thermal boundary resistance of the diode in its closed state was 8.4 K m /Gw; while the thermal boundary resistance was 6.4 K m /GW when the Schottky diode was opened with current of 100 mA. This represents a reduction in the thermal boundary resistance of approximately 24% for the case where the electrons were crossing the boundary. This result confirms experimentally that the electron heat transport effectively reduces the thermal resistance across boundaries.

Presenting Author: Ezekiel Villarreal University of Pittsburgh

Authors:

Ezekiel Villarreal University of Pittsburgh
Nicolas Horny Université de Reims Champagne-Ardenne
Heng Ban University of Pittsburgh,