Ferroelectric Characterization in Ultrathin Hf0.5Zr0.5O2 MFIS Capacitors by Piezoresponse Force Microscopy (PFM) in Vacuum

Abstract

Ferroelectric HfO2-doped compounds, which are well-known CMOS compatible dielectric materials, have the promising applications in memory, logic and neuromorphic devices [1]. Based on typical metal ferroelectric insulator semiconductor (MFIS) capacitor structure with the sub-5nm ferroelectric layer, the ferroelectric characterization becomes the challenge since the presence of tunneling leakage or screening effects from surface charge traps dramatically reduce the signal to noise ratio. Since the devices obtain a weak signal from polarization (P) itself, this leads to the complicated evaluation of ferroelectric properties of such ultrathin layers [2]–[3]. In this study, we fabricated 5 nm and 2 nm Hf0.5Zr0.5O2 (HZO) MFIS capacitors and demonstrate alternative vacuum-based piezoresponse force microscopy (PFM) characterization, which is still enables to see P-response in ultrathin films due to increased quality factor of the tip-surface resonance. Electrical measurements such as polarization-voltage (P-V) and capacitance-voltage (C-V) characterristics gives additional information about remnant and saturated polarizations: Pr and Ps, respectively.