Thermal Stability of the TiSi₂ Film Under the Dielectric Capping Layer

Abstract

The thermal stability of titanium disilicide (TiSi2) film under dielectric capping layers was studied. Dielectric capping layers prevent changes in sheet resistance and the film stress of the TiSi2 film during annealing at 900°C. The enhancement of thermal stability of the TiSi2 film was dependent on the nature of dielectric; thermal stability of the TiSi2 film was enhanced more effectively by the plasma-enhanced silicon nitride (PE-SiN) capping layer rather than the undoped silicate glass (USG; S1O2) capping layer. The dependence of thermal stability of the TiSi2 film with the nature of dielectrics was due to the difference in stress of dielectrics at anneal temperature. At 900°C, stress of the USG film was nearly twice of that of the PE-SiN film. Agglomeration of the TiSi2 film under the dielectric capping layer at high temperature annealing can be explained by a diffusional flow of atoms called Nabarro-Herring Microcreep. As the size of Ti-polycide lines becomes smaller, the nature of the dielectric film on the TiSi2 film will be more important for achieving thermal stability.