Ferroelectricity Improvement in Ultra-Thin Hf0.5Zr0.5O2 Capacitors by the Insertion of a Ti Interfacial Layer

The effect at the nanoscale of a Ti interfacial layer on the performances of TiN/HfZrO2/TiN capacitors is reported. Ferroelectric hafnium zirconium oxide (HZO) is synthesized by magnetron sputtering of a Hf0.5Zr0.5O2ceramic target. Titanium nitride top and bottom electrodes are grown by reactive magnetron sputtering. The insertion of an ultra-thin Ti layer at the top electrode/HZO interface impacts the crystalline phase and the electrical properties of the ferroelectric HZO. Following post-deposition annealing, the Ti layer is oxidized and becomes titanium oxide. Compositional and structural characterization is performed using glancing incidence X-Ray diffraction and electron energy-loss spectroscopy. The TiOz layer is clearly distinguishable at the top electrode/HZO interface. Electrical characterization is conducted by positive-up-negative-down (PUND) technique. The remnant polarization reaches a maximum value of 25 mu C cm-2 for 6 nm thick HZO. The results are discussed in the framework of structural, compositional, and physical properties of the electrode/HZO interfaces and their effect on the electrical performances of thin HZO-based junctions, which could subsequently be considered for the demonstration of synaptic learning mechanisms for neuromorphic applications.