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

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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.