Multilayer thin film cooling devices (non-reviewed)

Abstract

Solid state thermoelectric cooling devices have been of current interest for hot-spot thermal management. Cooling hot-spots with high heat flux is becoming one of the most important technical challenges facing today's IC industry. The rising temperature limits device minimization and decreases its lifetime. The thermoelectric effect is the appearance of an electric field along a temperature gradient established in a material. The inverse effect, called the Peltier effect, can be used for refrigeration, which uses electricity to pump heat from the cold end to the hot end. In this paper, we report to fabricate an in-plan solid-state thermoelectric cooling device using multilayered Bi₂Te₃/Sb₂Te₃ and Bi₂Te₃/Bi₂Te_3-xSe_x thin films. A solid-state in-plan thin film cooling device has been fabricated using multilayered thermoelectric thin films. Bi₂Te₃/Sb₂Te₃ and Bi₂Te₃/Bi₂Te_3-xSe_x multilayer thin films were deposited using e-beam evaporation. Solid antimony (III) telluride and bismuth (III) telluride were evaporated to grow the Bi₂Te₃ and Sb₂Te₃ layers for the Bi₂Te₃/Sb₂Te₃ multilayer films. Bi, Te, and Se powders were mixed with the ratio of 2:2.7:0.3 and were heated at 700degC under nitrogen and melted into solid Bi₂Te_3-xSe_x. The thermally-grown solid Bi₂Te_3-xSe_x was then evaporated to grow the Bi₂Te_3-xSe_x layer for the Bi₂Te₃/Bi₂Te_3-xSe_x multilayer thin film together with the Bi₂Te₃ layer using e-beam evaporation. The Bi₂Te₃/Sb₂Te₃ and Bi₂Te₃/Bi₂Te_3-xSe_x multilayer thin films have a periodic structure consisting of alternating Bi₂Te₃ and Sb₂Te₃ layers or Bi₂Te₃ and Bi₂Te_3-xSe_x layers, where each layer is about 10 nm thick. The films were analyzed by XRD, SEM, and AFM. The e-beam-grown Bi₂Te₃/Sb₂Te₃ multilayered thin film has a resistivity of 7.1times10^-4 Omegaldrcm and an in-plan Seebeck coefficient of 110 muV/K, and the e-beam-grown Bi₂Te₃/Bi₂Te_3-xSe_x multilayered thin film has a resistivity of 1.6times10^-4 Omegaldrcm and an in-plan Seebeck coefficient of -95 muV/K. An in-plan cooling device was fabricated with the Bi₂Te₃/Sb₂Te₃ and Bi₂Te₃/Bi₂Te_3-xSe_x films using the standard integrated circuit (IC) fabrication process; the cooling device is consisted of 2080 pairs of p-type and n-type elements, where each element is 200 mum long and 50 mum wide; pn junction diodes were fabricated as thermometers for the measurement of temperature difference between the two ends of device. Temperature difference was achieved between the hot and cold ends under an applied DC current. The developed in-plan cooling device can be a good candidate for the application of highly-efficient micro- cooling.