The effect of temperature on the ferroelectric properties of Hafnium Zirconium Oxide MFM thin-film varactors

In this work, the tuning properties of hafnium zirconium oxide (HZO) metal-ferroelectric-metal (MFM) thin film varactors are investigated. It is shown that varactors with 1:1 Hf:Zr stoichiometry and 10 nm thickness, crystallized with rapid thermal annealing (RTA) at 400°C for 60 s, show a maximum capacitance tunability of 32% at room temperature without electric field pre-cycling. The cycling and accompanying wake-up effect lead to a reduction of tunability. Furthermore, the influence of the temperature on the ferroelectric properties and tunability is explored. Upon increase of measurement temperature to 200°C, the maximum tunability decreases to 24%. An elevated temperature leads to an increase in aniferroelectric-like (AFE) behavior, which is consistent with recent studies of ferroelastic nature of AFE switching.