Thermal and thermomechanical studyof micro-refrigerators on a chip based on semiconductor heterostructures


S. Dilhaire1, S. Grauby1, L-DPatiño Lopez1, Y. Ezzhari1, I. Abbadi1,W. Claeys1,

J.Christofferson2, Y. Zhang2, A. Shakouri2


1CPMOH – University of Bordeaux, 351cours de la Libération, 33 405 TALENCE

2Baskin School of Engineering, University ofCalifornia, 1156 High St, Santa Cruz, CA 95064


We present resultsfrom optical characterization of active solid-state thermoelectric/ thermionicmicro coolers with sizes ranging from 10x10 up to 150x150 micron square. Thinfilm micro refrigerators are fabricated from a variety of semiconductormaterials such as SiGe, SiGeC, GaAs and InP and they are manufactured usingstandard IC fabrication technology. These devices have achieved 7K cooling at100C ambient temperature. Theoretical calculations show that up to 20K coolingis possible. These micro refrigerators can be used to remove hot spots in ICchips and achieve localized temperature control. Transient thermoreflectancemeasurements have shown that the cooling speed of these thin film coolers is onthe order of 20-30 microseconds, 104 times faster than thecommercial BiTe thermoelectric coolers.

We characterizedseveral micro-refrigerators devices by various optical non-contact methods suchas interferometry or thermoreflectance to measure temperature and strain fieldswith sub micron spatial resolution.

The thermoreflectancetechnique exploits the change in the reflection coefficient of material withtemperature. Using visible wavelength one can achieve submicron spatialresolution.

Interferometry allowsimaging the normal surface displacement with nanometric resolution and recordthe single point normal displacement with a resolution better than afemtometer.

We present in thiscontribution some comparative results obtained by reflectometry andinterferometry for the micro refrigerator devices and discuss key parametersaffecting their overall performance.