硅晶体薄膜热传导性质的计算机模拟

发布时间：2018-03-07 10:09

本文选题：微机电系统　切入点：硅晶体薄膜　出处：《湖南师范大学》2016年硕士论文　论文类型：学位论文

【摘要】：随着微机电系统(MEMS)与半导体技术的发展,人们对于其构件热传导性质的研究越来越多。硅晶体薄膜是MEMS构件与半导体中应用最为广泛的一种材料。它的热传导性质是一种能决定材料散热能力的性质,也是保证MEMS器件在一定的温度下保持正常工作的决定性因素。本文运用晶格动力学以及计算机模拟的方法计算了硅晶体薄膜的热导率,并分析了其与自身厚度之间的关系。现有的常用方法是分子动力学模拟,该方法从分子与原子层面出发讨论了材料的热传导性质。但分子动力学模拟有较大的局限性,因此本文考虑采用晶格动力学。本文首先从大块晶体出发,运用晶格动力学方法得到其晶格动力学矩阵、三次非和谐势能,并利用声子Green函数得到声子寿命与声子谱线宽度的表达式,再推广到晶体薄膜上,从而得到晶体薄膜的晶格动力学矩阵、三次非和谐势能以及声子Green 函数的表达式,并对硅晶体薄膜的声子谱,晶格振动波形以及声子谱线宽度进行了计算机模拟。在前面晶体薄膜的晶格动力学基础上,利用Hardy能量通量公式以及Green-Kubo公式,得到晶体薄膜的热传导系数公式。该公式表明硅晶体薄膜热传导系数主要与声子谱线宽度和声子谱相关,声子谱线宽度和声子谱均与晶体薄膜的厚度相关,因此硅晶体薄膜的热传导系数与其厚度有关。硅晶体薄膜的热传导计算结果表明,硅晶体薄膜的热传导系数随着晶体薄膜厚度的减小而减小。这一结果对于人们在对硅晶体薄膜构件的正确设计制造和使用具有很大的指导作用。根据这个结果,人们应该在设计微电子器件和MEMS时考虑晶体薄膜厚度对热传导的影响,防止因晶体薄膜散热问题而导致器件失效。
[Abstract]:With the development of MEMS and semiconductor technology, More and more researches have been done on the heat conduction properties of its components. Silicon crystal thin film is the most widely used material in MEMS components and semiconductors. Its heat conduction property is a kind of property that can determine the heat dissipation ability of materials. It is also a decisive factor to ensure that MEMS devices work normally at a certain temperature. In this paper, the thermal conductivity of silicon crystal thin films is calculated by lattice dynamics and computer simulation. The existing methods are molecular dynamics simulation, which discusses the heat conduction properties of materials from the molecular and atomic levels. However, molecular dynamics simulation has some limitations. Therefore, the lattice dynamics is considered in this paper. Firstly, the lattice dynamics matrix is obtained by using the method of lattice dynamics from bulk crystals, and the cubic nonharmonious potential energy is obtained. The expressions of phonon lifetime and phonon spectral line width are obtained by using the phonon Green function, and then extended to the crystal thin film. The lattice dynamics matrix, the cubic nonharmonious potential energy and the expression of the phonon Green function of the crystal thin film are obtained. The phonon spectrum, lattice vibration waveform and the width of phonon spectrum of silicon crystal thin film are simulated by computer. On the basis of lattice dynamics of the previous crystal thin film, the formula of Hardy energy flux and Green-Kubo formula are used. The formula shows that the thermal conductivity of silicon crystal film is mainly related to the width of phonon line and phonon spectrum, and the width of phonon line and phonon spectrum are related to the thickness of crystal film. Therefore, the heat conduction coefficient of silicon crystal film is related to its thickness. The heat conduction coefficient of silicon crystal thin film decreases with the decrease of the thickness of crystal film. This result has a great instructive effect on the correct design, manufacture and use of silicon crystal thin film components. In the design of microelectronic devices and MEMS, the effect of thickness of crystal film on heat conduction should be taken into account to prevent the device from failure due to the heat dissipation of crystal films.
【学位授予单位】：湖南师范大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TN304.12

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