Impact of top electrode on electrical stress reliability of metal-insulator-metal capacitor with amorphous ZrTiO_4 film

摘要

For metal-insulator-metal (MIM) capacitors with an amorphous ZrTiO_4 film as the dielectric, the impact of top electrode including Ni and Al on electrical stress reliability was studied and the mechanisms to explain the electrode-dependent reliability were also proposed in this work. It has been found that the Ni-electrode MIM capacitors reveal good reliability in terms of 0.91% capacitance change after ten-year operation under -2 V constant voltage stress while that for those with Al electrode degrades to 1.92%. This undesirable higher capacitance change can be mainly ascribed to a larger permittivity modulation in the dielectric that is due to higher leakage current and consequently more trapped charges and dipoles caused by a lower electrode work function. In addition, a parasitic Al_2O_3 film in the Al-electrode MIM capacitors also worsens the integrity of the dielectric because of the existence of additional traps.