High-temperature stress measurement on chemical-vapor-deposited tungsten silicide and tungsten films

Stresses in chemical-vapor-deposited tungsten silicide and tungsten films at high temperatures were measured. Tungsten silicide films were formed from WF6 and SiH4 or Si2H6. Tungsten films were formed from WF6 and H2. The stress in tungsten silicide films is tensile and in the order of 109–1010 dynes/cm2. For a composition ratio of Si/W≤2.6, the stress of a film of more than 1000 Å has a maximum at about 500 °C. On the other hand, for a composition Si/W>2.9, the stress has no maximum. The maximum of the stress is caused by crystallization of the film. The stress has two components. One component is related to the difference of the thermal expansion coefficients between the film and the Si substrate. Another is related to the film crystallization. It was found that the stress concentrates in the portion of the film nearest the substrate. The stress in tungsten films also reaches a maximum at 550 °C, similar to the tungsten silicide films. However, the cause of this behavior is not clear.