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热膨胀系数是薄膜的重要热学性能参数,也是薄膜热应力和残余应力计算分析过程中的关键数据。文章基于热诱导弯曲原理,分别采用单基片法和双基片法对氮化钛(TiN)和铝(Al)薄膜的热膨胀系数进行测试,并着重对双基片法的测试误差和适用性进行了分析。研究结果表明,薄膜在不同材质基底上弹性模量的差异是影响双基片法薄膜热膨胀系数测试精度的重要因素。当不同材质基片上薄膜弹性模量差异较小时,双基片法测得的热膨胀系数与单基片法所获结果基本一致;而当不同材质基片上薄膜弹性模量相差较大时,双基片法将不再适用。此外,文章结合薄膜的形貌、结构和残余应力表征测试,对TiN和Al薄膜热膨胀系数与其块体材料的差异进行了分析,结果显示残余压应力会导致薄膜热膨胀系数增大,而残余拉应力则具有相反的效果。
Thermal expansion coefficient is an important thermal performance parameters of the film, but also the key data in the calculation and analysis of thermal stress and residual stress of the film. Based on the principle of thermal induced bending, the thermal expansion coefficients of titanium nitride (TiN) and aluminum (Al) films were tested by single substrate method and double substrate method, respectively. The test error and applicability Analyzed. The results show that the difference of the elastic modulus of the film on different substrates is an important factor that affects the test accuracy of the thermal expansion coefficient of the bimorph film. When the elastic modulus of thin films on different substrates is small, the thermal expansion coefficient measured by the two-substrate method is basically the same as that obtained by the single substrate method. When the elastic modulus of the thin films on different substrates is quite different, Film method will no longer apply. In addition, the paper analyzes the difference between the thermal expansion coefficients of TiN and Al thin films and their bulk materials based on the morphology, structure and residual stress characterization of the films. The results show that the compressive residual stress increases the thermal expansion coefficient of the films and the residual tensile stress It has the opposite effect.