Thermal Conductivity and Interface Thermal Conductance in Films of Tungsten–Tungsten Silicide on Si

Samples of tungsten film deposited on Si substrate at room temperature by magnetron sputtering were annealed at different temperatures up to 900 °C in argon atmosphere. X-ray diffraction and scanning electron microscopy were used to follow the changes in the film and determine the formation of WSi₂ phase along the interface. The formation of WSi₂ phase has been detected in the sample annealed at 675 °C and above. Polycrystalline WSi₂ was found to form upon annealing at 900 °C. Thermal conductivity and interface thermal conductance of the film in the as deposited and annealed condition was studied by transient thermoreflectance from the tungsten film. The variation of thermoreflectance signal with time was modeled using 1-D thermal diffusion equation. The results showed that the thermal conductivity of the film is improved but the interface thermal conductance is reduced upon annealing at higher temperature. Voids generated by the formation of WSi₂ along the interface and incomplete thermal contact between the different regions in the film and the Si substrate are shown to be responsible for the lower interface thermal conductance. It is concluded that growth of epitaxial silicide on Si with good thermal contact will help reduce the thermal resistance in the devices.