Ferroelectric of HfO2 dielectric layer sputtered with TiN or ZrN for sandwich-like metal-insulator-metal capacitors

Abstract

In this study, metal-insulator-metal (MIM) capacitors, which use HfO2 as the intermediate insulating layer, and TiN or ZrN as the upper/lower capping layers were fabricated to form the sandwich-like structures, i.e. Al/TiN/HfO2/TiN/Mo/p-Si and Al/ZrN/HfO2/ZrN/Mo/p-Si. The crystallization of high-k HfO2 thin-film is induced by high power impulse magnetron sputtering (HIPIMS) during the deposition of TiN and/or ZrN capping layers. The ferroelectric performance became better in both two structures as the thickness of metal nitride layer decreased. As the rapid thermal annealing (RTA) temperature after TiN layer deposition increased, the ferroelectric performance of the structure with TiN layer became better. On the other hand, the structure with ZrN layer exhibited opposite trends. According to X-ray diffraction (XRD) measurement, both TiN and ZrN layers offered stress and produced orthorhombic phase on HfO2 layer. Both two layers at any thicknesses also protected Mo layer from the invasion of Hf atoms. The structure with TiN layer exhibited a higher remanent polarization (Pr) value as the roughness of TiN layer increased. However, the higher the roughness that the structure with ZrN layer had, the worse the ferroelectric performance obtained.