On-Chip Thermoelectric Hotspot Cooling
On-Chip Thermoelectric Hotspot Cooling
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Date
2015
Authors
Manno, Michael Vincent
Advisor
Bar-Cohen, Avram
Citation
DRUM DOI
Abstract
Increased power density and non-uniform heat dissipation present a thermal
management challenge in modern electronic devices. The non-homogeneous heating
in chips results in areas of elevated temperature, which even if small and localized,
limit overall device performance and reliability. In power electronics, hotspot heat
fluxes can be in excess of 1kW/cm2. Although novel package-level and chip-level
cooling systems capable of removing the large amounts of dissipated heat are under
development, such “global” cooling systems typically reduce the chip temperature
uniformly, leaving the temperature non-uniformity unaddressed. Thus, advanced
hotspot cooling techniques, which provide localized cooling to areas of elevated heat
flux, are required to supplement the new “global” cooling systems and unlock the full
potential of cutting-edge power devices. Thermoelectric coolers have previously been
demonstrated as an effective method of producing on-demand, localized cooling for
semiconductor photonic and logic devices. The growing need for the removal of
localized hotspots has turned renewed attention to on-chip thermoelectric cooling,
seeking to raise the maximum allowable heat flux of thermoelectrically-cooled
semiconductor device hotspots.
This dissertation focused on the numerical and empirical determination of the
operational characteristics and performance limits of two specific thermoelectric
methods for high heat flux hotspot cooling: monolithic thermoelectric hotspot cooling
and micro-contact enhanced thermoelectric hotspot cooling. The monolithic cooling
configuration uses the underlying electronic substrate as the thermoelectric material,
eliminating the need for a discrete cooler and its associated thermal interface resistance.
Micro-contact enhanced cooling uses a contact structure to concentrate the cooling
produced by the thermoelectric module, enabling the direct removal of kW/cm2 level
heat fluxes from on-chip hotspots. To facilitate empirical validation of on-chip
thermoelectric coolers and characterization of advanced thin film thermoelectric
coolers, it was found necessary to develop a novel laser heating system, using a high power laser and short-focal length optics. The design and use of this illumination
system, capable of creating kW/cm2-level, mm-sized hotspots, will also be described.