AVS 51st International Symposium
    Materials Solutions for Cooling Technology Topical Conference Monday Sessions
       Session CT+TF-MoM

Invited Paper CT+TF-MoM6
Thin Film Micro Refrigerators for on Chip Thermal Management

Monday, November 15, 2004, 10:00 am, Room 303B

Session: Thermal Transport in Thin Films and Nanostructured Materials
Presenter: A. Shakouri, University of California at Santa Cruz
Correspondent: Click to Email
In this talk, we review design considerations for high cooling power density thermoelectric/thermionic coolers. Conventional bismuth telluride-based thermoelectric modules have a maximum cooling of about 70° C, however the cooling power density is low, on the order of 1-10 W/cm2. The micro and nanoscale electronic devices can generate thousands of watts per centimeter square heating, which is far beyond the capability of current TE modules. The maximum cooling power density of a TE module is inversely proportional to the length of its elements (distance between hot and cold junctions). Thus it is possible to increase the cooling power density with the use of thin film material. 100 micron thick Peltier modules with cooling power density exceeding 100W/cm2 have been demonstrated. Further increase requires significant improvement in metal-semiconductor contact resistance and in heat sink thermal resistance. An alternative solution is to use the thermoelectric properties of silicon or III-V substrate material. Heat and current spreading in 3D electrode configuration, allow removal of hot spots in IC chips. Furthermore, addition of a 1-5 micron thick superlattice can improve the cooling performance by increasing the selection between hot and cold carrier transport via thermionic emission and by reducing thermal resistance between hot and cold junctions. Several III-V and silicon heterostructure integrated thermionic (HIT) microcoolers have been fabricated and characterized. They have achieved cooling, on the order of 4.5° C at room temperature and 12° C at 200° C ambient temperature. Cooling power density was also characterized and values ranging from 100-680W/cm2 were measured. Finally, an optical technique based on thermoreflectance imaging was used to obtain temperature distributions on top of devices with sub micron spatial resolution and <0.1° C temperature resolution.@footnote 1@ @Footnotetext@ @footnote 1@ Work supported by DARPA and ONR MURI.