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Study on the Near-field Thermal Radiation and Its Measurement Technology for Mciro-nano Device

Author: FengChong
Tutor: TangZuoAn; YuZuo
School: Dalian University of Technology
Course: Circuits and Systems
Keywords: Micro-hotplate Micro-nano devices Near-field thermal radiation CMOStechnology MEMS technology
CLC: TN432
Type: PhD thesis
Year: 2013
Downloads: 47
Quote: 0
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Abstract

The research on the near-field thermal radiation attracts many focuses recently. The study on the near-field thermal radiation in micro devices is important to improve the thermal insulated property of micro devices and develop new micro devices. Based on developing a novel device with self-aligned double suspended mciro-hotplates separated by a micro-nano gap (DMHP for short), the experimental measurement technology of the near-field thermal radiation in micro devices is studied in this thesis. By using DMHP, the near-field thermal radiation of silicon oxide was systematically investigated. The main contents of this thesis include the theoretical research of near-field thermal radiation, the design and fabrication of DMHP, the characteristic parameters measurement of DMHP and the experiment measurement of the near-field thermal radiation.Firstly, the micro mechanisms of thermal radiation were researched and a model was formed. The electromagnetic field of the thermal current was calculated by describing the spatial correlation function of the thermal current fluctuations based on the fluctuation-dissipation theorem and Maxwell’s equations solved by green’s function method. By taking an ensemble average on the Poynting vector, a calculation method of the near-field radia-tive heat transfer between two semi-infinite planes was given. Then, a model of near-field radiative heat transfer between two silicon oxide plates was formed. We obtained that the near-field thermal radiation is significantly enhanced while the distance between two silicon plates is less than1μm. So the near-field thermal radiation between two SiO2plates separated by the distances of550nm and1μm are chosen to study in this thesis. This work not only presents a theoretical basis for DMHP design, but provides reference data for related researchers.Secondly, the technologies of design and fabrication of DMHPs were investigated. Based on surface micromachining technology, the process flow of the two types of DMHP were designed. By using double sacrificial layers, the self-aligned double freestanding membranes of a DMHP were fabricated. By using CSMC0.5μm CMOS technology, a CMOS DMHP was developed, which the gap between the two freestanding membrane of the device is550nm; by using a customized MEMS (MicroElectroMechanical Systems) technology, a MEMS DMHP was developed, which the gap between the two freestanding membrane of the device is1μm. The appropriate manufacturing processed were designed, with many key technics were researched and solved, including window etching,sacrificial layer wet etching, the Auxiliary structure for judging the end of sacrificial layer etching and residual stress control of thin films. So, the output capacity was guaranteed.Thirdly, the performance testing system of DMHP were built up. First, we built the system above with a vacuum system and a computer. Then, under the conditions of the ambient temperature293K and vacuum (10-7mbar), the heating current limit of each micro-hotplate of DMHP, the thermal insulation performance of the two micro-hotplates and the thermal delay time of each micro-hotplate of DMHP were tested. The works above provide the necessary parameters for DMHP’s applications.Finally, experimental measurements of the near-field radiative heat transfer between two micro-hotplates was carried out. In these experiments, the bottom micro-hotplate was heated by constant currents and worked as a heat emitter, the top micro-hotplate worked as a heat absorber, the near-field thermal radiative heat transfer between the two micro-hotplate of DMHPs were evaluated by calibrating the relationship between the temperature rising and heating power of the absorber, and by detecting the heating power difference between heating the emitter to the same temperature before and after removing the absorber. For the cases that two SiO2plates separated by the distances of550nm or1μm, the measured values of thermal conductance of near-field thermal radiation are similar with others. The results above indicate the test technology brought forward in this thesis can be applied for investigating the near-field thermal radiation happened in micro-nano devices, and provide a new method for the measurement of the near-field thermal radiation.

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