Formation and characterization of Ti–Si–N–O barrier films

Ti–Si–N–O barrier films are successfully formed by RF reactive magnetron sputtering of Ti target with different SiH4 gas flow rate. Si/Ti ratio in the formed film is found to increase with increasing SiH4 gas flow rate. The film resistivity ranges from 3.63 × 103 μΩ cm to 6.45 × 106 μΩ cm due to microstructure variation. X-ray diffraction (XRD) of these films reveals the formation of crystalline titanium nitrides, silicon nitrides and titanium silicide compounds. XPS further unveils that titanium oxide, silicon oxide, and silicon oxynitride compounds are present; however, these non-crystalline compounds are not detectable by XRD. High-resolution transmission electron microscopy (HRTEM) confirms that the film consists of Ti–N, Si–N, and Ti–Si nanocrystals embedded in amorphous matrix. This type of microstructure gives rise to very high stability against copper diffusion under bias temperature stressing (BTS) at 200 °C and 0.5 MV/cm. Furthermore, this process delivers a very smooth film with surface roughness (RMS) between 2.2 and 3.3 nm. Field emission secondary electron microscopy (FESEM) shows a surface morphology of Ti–Si–N–O films with particles size less than 100 nm. By controlling the process parameters, we are able to control the properties of Ti–Si–N–O films as the diffusion property is behaved differently.