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with a network of built-in sensors capable of in-situmonitoring.Temperature and pressure sensors have been integrated inorder to allow accurate measurements of the internal values.Initial simulation results obtained by FEA calculationsshowed that the use of an ultra-thin membrane of 1µm,micromachined in a SOI wafer, reveals a considerableincrease in the sensor response.A first prototype of the heat spreader with integratedtemperature and pressure microsensors has been realized andtested. A membrane thickness in the order of 1µm wasachieved using SOI substrates, providing good reproducibilityacross the wafer. The results show a good agreement of thetemperature sensors sensitivity (1.9mV/K for the diode basedtemperature sensors) and of the membrane stress distributionwith the simulation results. Experimental results give thetemperature distribution in a closed vapor chamber usingwater as cooling liquid. Direct longitudinal distribution oftemperature as well as local values are simultaneouslyobtained, the micro channel network design allowing pressuremeasurements both inside the vapor chamber (water vapor)and directly inside the partially water-filled channels.This original approach for a built-in heat spreader offers acombination of increased efficiency by the integration into thesubstrate of the device with the possibility of having in-situtemperature and pressure measurements inside the vaporchamber, providing an excellent tool for the characterizationand optimization of this type of cooling devices.24-26 September 2008, Rome, ItalySimulation and Experiments in Micro-Electronics and Micro-Systems,EuroSime 2006. 24-26 April 2006[10] A. Szmyrka-Grtebyk, L. Lipiriski, “Linear diode thermometer in the 4-300 K temperature range”, Cryogenics, Vol. 35, pp. 281-284 (1995)[11] B. Bercu, L. Montès, P. Morfouli, “Silicon chip Built-In Heat Spreader:Characterization And Optimization Using Integrated Sensors”, EuropeanAdvanced Technology Workshop on Micropackaging and ThermalManagement, 30th – 31st January, 2008, La Rochelle, FranceACKNOWLEDGEMENTSThe authors would like to thank to the Région Rhône-Alpes for the financial support, as well as to Ulf Södervallfrom MC2 Access program, Chalmers University,Gothenburg, Sweden.REFERENCES[1] I. Dolezel, P. Dvorak, K. Kalcik, V. Valouch, “Limit OperationRegimes of Selected Power Semiconductor Element”, 12thInternational Power Electronics & Motion Control Conference, pp. 50-53 (2006)[2] M. Le Berre, S. Launay, V. Sartre, M. Lallemand, “Fabrication andexperimental investigation of silicon micro heat pipes for coolingelectronics”, J. of Micromech. and Microeng., Vol. 13 (2003), pp. 436-441.[3] T. Q. Feng, J. L. Xu, “An analytical solution of thermal resistance ofcubic heat spreaders for electronic cooling”, Appl. Therm. Eng., Vol. 24(2004), pp. 323–337.[4] S. Tzanova, M. Ivanova, Y. Avenas, Ch. Schaeffer, “AnalyticalInvestigation of Flat Silicon Micro Heat Spreaders”, Proc. 2004 IEEEIndustry Applications Conf. - 39 th IAS Annual Meeting, October 2004,pp. 2296-2302 (Vol. 4)[5] R. Rulliere, F. Lefevre, M. Lallemand, “Modeling of a two phaseheatspreader”, 17th French Congress of Mechanics, 29 august - 2September 2005, Troyes, France[6] G. Blasquez, P. Pons, A. Eoukabache, “Capabilities and limits of siliconpressure sensors”, Sensor. Actuator. Phys., Vol. 17 (1989), pp. 387-404.[7] C. S. Smith, “Piezoresistance Effect in Germanium and Silicon”, Phys.Rev., Vol. 94, No. 1 (1954), pp. 42-49.[8] S. Renard, “Industrial MEMS on SOI”, J. Micromech. Microeng., Vol.10 (2000), pp. 245–249[9] B. Bercu, L. Montes, P. Morfouli, “FEA Calculations for Ultra ThinPiezoresistive Pressure Sensor on SOI for Heatspreader Integration”, 7thInternational Conference on Thermal, Mechanical and Multiphysics©EDA Publishing/THERMINIC 2008 176ISBN: 978-2-35500-008-9