Impact of TiN post-treatment on metal insulator metal capacitor performances

When deposited by chemical vapor deposition (CVD), TiN layers must be post-treated with N2/H2 plasma. Metal-insulator-metal (MIM) capacitors using CVD–TiN as electrodes and Al2O3 as insulator are studied from both electrical and physico-chemical points of view. We verify that N2/H2 plasma is efficient concerning the TiN layers, while ensuring a low and uniform resistivity. However, the MIM capacitor figures of merit are impacted by the N2/H2 plasma, especially by the top electrode post-treatment. In particular, capacitance at 0 V has been found to increase with TiN post-treatment, as well as the quadratic linearity coefficient. As for leakage currents, the top electrode densification induces non-standard mechanism and trapping phenomenon. Finally, the dielectric relaxation is also degraded when top electrode is post-treated. Electron energy loss spectroscopy (EELS) shows that the top electrode post-treatment is associated to Nitrogen diffusion, from the TiN top electrode into the alumina. Thus, chemical interactions between top electrode and alumina layer, induced by the top electrode post-treatment, may be at the origin of such behaviours.