A THICKNESS MODEL FOR THE TISI2 TIN STACK IN THE TITANIUM SALICIDE PROCESS MODULE/

A reliable TiSi2/TiN stack thickness model is an essential component f or modeling the titanium salicide process, and such a model is not wel l-developed in current process simulators and in the literature. To de termine this model, a design of experiments was set up to examine five process variables, namely, as-deposited Ti thickness, reaction temper ature, reaction time, As+ implanted dose, and the reaction ambient pre ssure. Weight and sheet resistance measurements were used to evaluate the thickness and efficiency of reaction (%Ti converted to silicide). A good first-order linear model was obtained, with a residual standard deviation (variation of model from data) of similar to 30 Angstrom. T he model establishes quantitatively, that the TiSi2 thickness is propo rtional to the as-deposited Ti thickness and reaction temperature, inv ersely proportional to the implanted As+ dose, and weakly proportional to the reaction time. Since TiN and TiSi2 are competing reactions, Ti N exhibits inverse functional relationships with the variables, as com pared with TiSi2. The efficiency of the reaction also has been quantif ied by the model. The ambient pressure has been found to have no impac t on either the TiSi2/TiN stack thickness, or the reaction efficiency. The model has been validated by cross-sectional transmission electron microscopy, which agrees with the model prediction within experimenta l error.