AFM study on the surface morphologies of TiN films prepared by magnetron sputtering and Al₂O₃ films prepared by atomic layer deposition

This paper reports the results of a comprehensive study conducted on the effect of surface morphology of titanium nitride (TiN) electrodes deposited by magnetron sputtering and the possibility of improving metal/insulator/metal (MIM) capacitor characteristics with Al₂O₃ dielectric obtained by atomic layer deposition (ALD). From the atomic force microscopy (AFM) study, we found that the bottom TiN layer is rougher for thicker films. Post metallization annealing can slightly reduce the roughness. In the case of the Al₂O₃ dielectric layer deposition, low-temperature ALD is preferred in order to obtain smaller surface roughness. Deposition of a dielectric layer at higher temperatures results in rougher surface because of poor chemisorption of precursors on the rough surface and the forming of crystalline phases. Electrical measurements show that the barrier at the top electrode is much larger than that at the bottom electrode due to the smaller roughness of the Al₂O₃ surface. Trade-off is required for depositions of both the bottom electrode and the dielectric layer.