Abstract
Manufacturing processes are essential factors in determining structural reliability of many semiconductor devices. Fabrication of thin film typically results in residual stress in the film leading uncertain deformation, failure or damage. Thus, this study sets out to examine film thickness and temperature effect on residual stresses which could provide a guideline to improve reliability and performance of products. To analyze the influence of residual stresses, a physical model and experiments are needed in research. An energy-based modified Stoney’s model is proposed to improve the stress conversion by simultaneously considering the thermal effect and thickness effect. Here, residual stresses are categorized into thermal stresses, stresses induced from dislocation and stresses generated in film structure. Solutions obtained by this method were used to compare with experiment results which provided appropriate explanation to the stress variation in different thickness films. In addition, thermal cycling experiments were carried out to investigate thermal impact and mechanical properties of Al-Si-Cu and TiN films. The results show that residual stresses in thin films could be explained by using modified Stoney’s model and dislocation theory. Also, the observed mechanical properties difference between films with various thickness in this study is not significant. Finite element simulation is also included to analyze stress distribution in the film and stress conversion in thermal cycle processes. Simulation results indicate that the anisotropic substrate does not affect the stress distribution in the film and mechanical properties of thin films are only in good agreement with thicker films, while films of small thickness might underestimate the effect of intrinsic stress. Key words: Stoney’s formula, Residual stress, Intrinsic stress, Al-Si-Cu film, TiN film, Process modeling