61.
The effect of a thin RuO
x layer formed on the Ru/TiN/doped poly-Si/Si stack structure was compared with that on the RuO
x/TiN/doped poly-Si/Si stack structure over the post-deposition annealing temperature ranges of 450–600°C. The Ru/TiN/poly-Si/Si
contact system exhibited linear behavior at forward bias with a small increase in the total resistance up to 600°C. The RuO
x/TiN/poly-Si/Si contact system exhibited nonlinear characteristics under forward bias at 450°C, which is attributed to no
formation of a thin RuO
x layer at the RuO
x surface and porous-amorphous microstructure. In the former case, the addition of oxygen at the surface layer of the Ru film
by pre-annealing leads to the formation of a thin RuO
x layer and chemically strong Ru-O bonds. This results from the retardation of oxygen diffusion caused by the discontinuity
of diffusion paths. In particular, the RuO
x layer in a nonstoichiometric state is changed to the RuO
2-crystalline phase in a stoichiometric state after post-deposition annealing; this phase can act as an oxygen-capture layer.
Therefore, it appears that the electrical properties of the Ru/TiN/poly-Si/Si contact system are better than those of the
RuO
x/TiN/poly-Si/Si contact system.
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