RF-Characterization of HZO Thin Film Varactors

Abstract

A microwave characterization at UHF band of a ferroelectric hafnium zirconium oxide metal-ferroelectric-metal (MFM) capacitors for varactor applications has been performed. By using an impedance reflectivity method, a complex dielectric permittivity was obtained at frequencies up to 500 MHz. Ferroelectric Hf0.5Zr0.5O2 of 10 nm thickness has demonstrated a stable permittivity switching in the whole frequency range. A constant increase of the calculated dielectric loss is observed, which is shown to be an effect of electric field distribution on highly resistive titanium nitride (TiN) thin film electrodes. The C-V characteristics of a “butterfly” shape was also extracted, where the varactors exhibited a reduction of capacitance tunability from 18.6% at 10 MHz to 15.4% at 500 MHz.

THz Thin Film Varactor Based on Integrated Ferroelectric HfZrO2

“…For example, in a previous study we applied the annular ring method, with which we were able to extract the capacitance–voltage ( C – V ) characteristics up to 0.5 GHz. 8 But due to the imperfectness of the extraction and due to the inhomogeneous distribution of electric fields on bottom thin film TiN electrodes at high frequencies, which is similar to the well-known skin effect, both the permittivity and tunability appear to be decreasing at frequencies higher than 0.5 GHz. So far, the highest frequency up to which the dielectric HfO 2 was characterized with proper high-frequency fixture by using a coplanar waveguide (CPW) transmission line was 20 GHz.…”

“…The high-frequency characterization of ferroelectric hafnium oxide thin films was a topic of different research groups up to microwave frequencies. − The possible use for varactor implementations up to millimeter wave frequencies was predicted from simulation. , Previously, the wide-band characterization of dielectric HfO 2 thin films has been intensively investigated. However, not a clear consensus could be drawn for millimeter wave frequencies.…”

“…Our simulations predict inaccuracies in the device fixture for this uncertainty. For example, in a previous study we applied the annular ring method, with which we were able to extract the capacitance–voltage ( C – V ) characteristics up to 0.5 GHz . But due to the imperfectness of the extraction and due to the inhomogeneous distribution of electric fields on bottom thin film TiN electrodes at high frequencies, which is similar to the well-known skin effect, both the permittivity and tunability appear to be decreasing at frequencies higher than 0.5 GHz.…”