Development of reliability evaluation with ultrasonic and residual stress analyses on fabricating multilayered structure ultra LSIs

多层结构的超大规模集成电路有望成为制造超高集成电路的器件。残余应力是制造过程中产生的残余应力，而残余应力的存在也给超细硅片带来了一定的困扰。因此，残余应力对于评价超细钢板的可靠性具有重要意义。在本研究中，首先用扫描声学显微镜对衬底上薄膜的弹性模量进行了评估，然后用x射线法对衬底上的残余应力进行了测量。第三，用有限元法分析了铝引线的残余应力，最后用扫描声显微镜分析了铝引线的塑性变形等内部缺陷。所得结果如下：(1)在分析超声波传播过程的基础上，利用扫描声显微镜可以计算基底上薄膜的弹性模量。(2)基材上铝的弹性模量比本体数据低10%。(3) x射线法观察界面附近残余应力存在应力奇异性。(4) x射线法测得的残余应力具有较大的散射带，但平均值变化不大。(5)二维有限元模型计算的残余应力近似较差，但将基于平面应力模型和基于平面应变模型的计算结果叠加，可以得到较好的残余应力近似。(6)用扫描声显微镜可以观察到塑性变形等内部缺陷。

Multilayered structure ultra LSI is hoped as a device with which ultra high integrated circuit can be made. In this ULSI, residual stresses yield at fabrication and this residual stresses bring the ULSI some troubles. Therefore, the residual stresses are important for evaluating the reliability of the ULSI. In this study, elastic moduluses of thin films on the substrate were evaluated with a scanning acoustic microscope on the first, and the residual stresses were measured with a X-ray method on the second. On the third, the residual stresses were analyzed with a finite element method and the internal defect like plastic deformation of the aluminium lead line was evaluated with a scanning acoustic microscope on the last. The results obtained are as follow. (1) The elastic modulus of a thin film on a substrate can be evaluated with a scanning acoustic microscope based on the analyze of ultra sonic wave propagation. (2) The elastic modulus of the aluminum on the substrate is 10% lower than the bulk data. (3) The residual stresses near the interface have stress singularity with a X-ray method. (4) The residual stresses measured with a X-ray method have large scatter band but the mean value does not change largely. (5) The residual stresses calculated with the 2-dimensional FEM model gives bad approximation but good one will be obtained if the result based on the plain stress model and on the plain strain model are superimposed. (6) The internal defect like th plastic deformation can be observed with a scanning acoustic microscope.