Silicidation Reaction and Stress in Ti/Si

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Abstract
In situ stress measurement in titanium silicide (TiSi2) during silicidation is performed at temperatures ranging from 30 to 900°C. In a 900 Å-thick Ti layer, the stress changes from tensile to compressive at 500°C and reaches a maximum of 6.8×108 Pa at 650°C. The stress decreases abruptly at 700°C. This clearly indicates that the silicidation reaction has been accomplished under higher stress conditions in the conventional silicidation process. The abrupt stress change appearing at 600∼650°C is due to the diffusion of Si from the Si substrate into the Ti layer in the silicidation reaction. This stress, however, decreases rapidly with grain growth of C54 TiSi2. However, lower stress with weak temperature dependence is obtained in the silicidation of a thin Ti layer. Lower-stress silicidation can be achieved when a thin Ti layer is silicided at higher temperatures, above 650∼700°C, or a thick (900 Å thick) layer at 700°C.