Nitrogen plasma treatment of a TiO₂ layer for MIS ohmic contact on n-type Ge substrate

This work investigates the characteristics of ohmic contacts on an n-type Ge by combining TiO₂ with different metals. Metal-insulator-semiconductor (MIS) structures easily crystallize after post-metal annealing (PMA), with the subsequent characteristics dependent on the insulator thickness and process temperature. If 2 nm thick TiO₂ is doped with nitrogen, there is no obvious difference in the current-voltage characteristics before/after PMA. The transmission electron microscope (TEM) analysis also verified that a lightly nitrogen-doped process is useful in suppressing the crystalline transition. In this study, the tungsten (W) contact showed the best thermal stability. Therefore, this technique could be effective in suppressing TiO₂ crystallization with improved thermal stability.