【作者】 王志刚；

【导师】 黄正兴；

【作者基本信息】 大连理工大学 ， 电子科学与技术， 2017， 硕士

【摘要】 随着微电子器件的特征尺寸不断缩小以及性能的大幅提升,芯片内部短时间内集聚的大量热量会导致器件性能的下降甚至失效。因此,芯片的散热问题是制约微电子技术发展的最重要课题之一。传统的散热材料已经不能更好地解决芯片的散热问题,碳纳米管具有高热导率、耐高温以及柔性等优势,有望成为解决芯片散热问题的优良热管理材料。碳纳米管作为热界面材料会受到不同程度的压力作用,因此,研究碳纳米管在受压力作用下的热学特性具有重要意义。本文采用瞬态热反射法研究了垂直排列碳纳米管阵列的界面热特性。首先,组建了一套适用于测量碳纳米管薄膜热导率的瞬态热反射测试系统,介绍了系统的测试原理,分析了影响测试结果的因素以及给出了测试参数的选取。其次,使用此系统测试了去离子水的热导率,验证了双向热流瞬态热反射测试方法的可行性。接着采用了SiO2/CNT/Au三层结构模型,测试了厚度为860μm碳纳米管阵列与金薄膜之间的界面热阻。当在垂直方向上给碳纳米管阵列施加1.49MPa的压力时,金-碳纳米管阵列的界面热阻值约为1.90~3.26×10-6 m2·K/W,远小于小压力作用下的热阻值。这是因为在大的压力作用下碳纳米管阵列与金的接触面积增大,因此接触热阻减小。另外,由于金-玻璃之间没有过渡层,其界面热阻约为1.12×10-7 m2·K/W,相比理论的金属-介质层之间的接触热阻(10-8-10-7 m2·K/W)略大。在双向热流瞬态热反射测试过程中,发现界面热阻值越大,系统对待测样品的测试灵敏度越高。最后,基于SiO2/CNT/Au三层测试结构的实验结果,采用了可溶性衬底NaCl/Au/CNT双层结构,测试了不同长度的碳纳米管阵列与金之间的界面热阻。当在垂直方向给碳纳米管阵列施加2Mpa的压力时,厚度为230μm、860μm的碳纳米管阵列与金之间的界面热阻分别为4.63±1.02×10-6m2·K/W和2.04±0.37×10-6m2·K/W。结果表明:除了与金的接触面积的影响因素外,碳纳米管阵列与金的界面热阻还表现出与碳纳米管的长度有依赖关系,长度较长的碳纳米管与金之间的界面热阻值较小。总之,碳纳米管作为一种新型的热界面材料,具有无污染、耐高温等特点。在实际应用中,碳纳米管与金属界面的接触热阻较大依然是当前面临的重要问题之一。本文的研究工作对进一步减小碳纳米管与金属之间的界面热阻有着重要的参考价值。更多还原

【Abstract】 With the continuous shrinking of feature size and improvement of device performance in the microelectronics,the resulted large amount of heat gathered in a short time within the device will lead to the degradation or even failure of the device performance.Therefore,heat dissipation of the chip is one of the most significant issues which limiting the development of microelectronics technology.Since traditional thermal materials has failed to solve the problem of chip heat dissipation in a better way,carbon nanotubes(CNTs)with advantages of high thermal conductivity,thermal stability and flexibility,are expected to solve the problem of chip heat dissipation as excellent thermal management materials.In the applications of thermal interface materials,CNTs are subject to compressive stress in some degree,so it is of great significance to study the thermal properties of CNTs under compressive stress.In this paper,the thermal interface properties of vertically aligned CNT arrays are studied using a transient thermal reflection technique.Firstly,the experimental system of transient thermal reflection for measuring the thermal conductivity of CNT films is constructed and introduced.Factors which may have influence on the measured results are analyzed and the selection of parameters used in the experiments are given.Secondly,the thermal conductivity of deionized water is measured by the transient thermal reflection technique based on the bidirectional heat flow model,which verifies the feasibility of the experimental system.Then,the thermal interfacial resistance(TIR)between the 860μm CNT array and the gold(Au)thin film is measured by using a SiO2/CNT/Au three-layer sample.When the stress of 1.49 MPa is applied to the CNT array in the vertical direction,the TIR of the Au-CNT array is about 1.90~3.26×10-6m2·K/W,which is much smaller than the thermal resistance under small stress.This is because the contact area of the carbon nanotube array and the Au is increased as a consequence of the large stress applied,so that the contact thermal resistance is reduced.In addition,due to the absence of a transition layer between the Au and the glass,the TIR is about 1.12×10-7m2·K/W,which is slightly larger compared to the theoretical contact resistance(10-8-10-7m2·K/W)between metal and dielectric layer.It is found that higher sensitivity is achieved using the transient thermalreflection technique based on the bidirectional heat flow model when the TIR value of the sample is larger.Finally,according to the experimental results of the SiO2/CNT/Au three-layer sample,the NaCl /Au/ CNT double-layer structure with soluble substrate is used to measure the TIR between Au and CNT arrays with different heights.When 2Mpa stress is applied to the CNT arrays in the vertical direction,the TIR value is 4.63±1.02×10-6 m2·K/W and 2.04±0.37×10-6m2 · K/W for 230μm and 860μm CNT arrays,respectively.In addition to the influence of contact area on the TIR,the results show that the TIR also has a dependence on the length of the CNT arrays,and CNT arrays with a larger longitudinal length has a smaller TIR value.In short,as a novel and promising thermal interface materials,CNTs have advantages of no contamination and good thermal stability at high temperatures.However,the large contact thermal resistance at the CNTs/metal interface has been one of the important problems in the practical applications so far.Researches in this paper have valuable references for further reducing the TIR between CNTs and metals.更多还原