Stress Analysis of Transistor Structures Considering Internal Stress of Thin Films

Stress analysis of transistor structures is performed considering internal stress of thin fims. Internal stress of newly employed films such as amorphous-silicon and tungsten-silicide films are measured by detecting surface curvature change of the film-covered substrates, as a function of temperature. Internal stress of both films changes upon annealing due to phase transition, and reaches about 1 000 MPa. The predicted stress of transistor structures without considering the internal stress of the films differs markedly from the measured result obtained using microscopic Raman spectroscopy. On the other hand, the predicted stress considering the internal stress of the films agrees very well with the measured data. Stress design is performed on the actual transistor structure considering annealing temperature dependence on internal stress of the amorphous-silicon thin film to eliminate dislocation generation. It is confirmed that stress design is effective in improving device reliability.