AC and DC bias effect on capacitance–voltage nonlinearities in Au/HfO₂/M (M = Pt, TiN, W, and AlCu) MIM capacitors: effect of the bottom electrode material

Metal–Insulator–Metal (MIM) capacitors based on high-k oxides require stability with the applied electric field. However, experiment reveals a nonlinear behavior of capacitance with ac or dc bias. In this work, we measure capacitance–voltage nonlinearities for Au/10-nm HfO₂/M (where M = TiN, Pt, W, and AlCu alloys). It is observed that ac capacitance is strongly dependent on the bottom electrode material. This dependency is discussed through the correlated barrier hopping (CBH) model. Accordingly, the ac nonlinearity is ascribed to the polarization of isolated defect pairs, which in turn increase as the maximum barrier height decreases. This induces higher nonlinearity as compared to the dc one. For the dc bias, oxygen affinity of active metal electrode may describe the origin of dc nonlinearities.