直流法测试薄膜热导的数值模拟研究

薄膜的热导率是薄膜热学性能的最重要参数之一, 相对于多数文献的二维或三维测试结构, 本文采用一维双端支撑悬臂梁结构研究了薄膜热导率的测试方法. 悬臂梁包含上层的兼做加热电阻及测温电阻的金属条和下层的待测试薄膜. 利用一维热传导方程推导并获得了在直流电流加热条件下, 悬臂梁的温升分布(Δ T)及加热电阻两端电压增量(Δ U) 表达式与薄膜热导率之间的关系. 采用ANSYS有限元软件仿真了不同仿真参数时的Δ T及Δ U, 仿真结果与温升表达式计算结果符合得很好. 与常用的3倍频率法(3ω) 薄膜热学性能测试方法相比, 一维悬臂梁直流法测试结构及手段较为简单且可以获得更为精确的结果.

Numerical simulation of direct current method of measuring thermal conductivities of thin films

Thermal conductivity is one of the most important physical properties of thin films.Different from two-or three-dimensional measurement structures in most reports,in this work,one-dimensional(1D) two-end supported cantilever beam is provided.The structure of cantilever includes a metal heater(which also serves as a thermometer) and thin film(s) underneath for measurement. 1D heat flow equation is employed to obtain the expression of temperature rise distribution(△T(x) along the cantilever beam and voltage drop changes along the heater(△U) when a direct current(DC) follows in the heater.To confirm the correctness of theoretical deduction,ANSYS finite element software is employed to simulate△T(x) and△U.Results demonstrate that the simulations are in good agreement with the theoretic calculations obtained from expressions of△T(x) and△U.Compared with conventional 3-times frequency(3ω) method,the DC method with 1D cantilever beam is relatively simple and accurate.