Influence of the amorphous/crystalline phase of Zr1-xAlxO2 high-k layers on the capacitance performance of metal insulator metal stacks

The capacitance behavior of metal insulator metal (MIM) structures with Zr1-xAlxO2 dielectrics and TiN metal electrodes is analyzed. The capacitance nonlinearity, the dielectric relaxation, and the loss phenomena are found to depend strongly on the Al content, the dielectric thickness, and the amorphous/crystalline phase of the dielectric layer. Two different kinds of phenomena-crystallization-related and interface-related, are considered to explain the observed results, especially the polarity asymmetry in the dielectric behavior. It is found that crystallization of the films enhances the effects of dielectric relaxation and loss, most likely due to charge trapping at grain boundaries. Further on, reactions between the oxidizing ambient (ozone) and the bottom electrode during high-k deposition result in structural changes (formation of TiOx interfacial layer) and thus in generation of defects which cause a different electrical behavior of the two TiN/Zr1-xAlxO2 interfaces at the top and the bottom electrode and a polarity asymmetry of the capacitance performance.