A preliminary study on mist CVD-derived ferroelectric Hf_1−x Zr _x O₂ films featuring its possibility of suitable operation for non-volatile analog memory

Abstract

We have newly developed mist CVD-derived Hf1−xZrxO2 films and investigated their physical properties and basic electrical properties for application to ferroelectric analog memory device such as synaptic device for neuromorphic system. It is observed that the films consisted of microcrystal grain including ferroelectric orthorhombic phase by AFM and GIXRD measurements. Both HfO2 and ZrO2 film with 20 nm thickness showed good fatigue endurance against 109 counts of imposed pulse cycling, where some wakeup phenomena were observed. For a range of electric field (up to 1.5 MV cm−1) as memory-writing input with condition of minor ferroelectric hysteresis loop, a linear relationship between the input and resultant polarization at zero electric field, P(E = 0), was obtained. Finally, it is suggested that those films of HfO2, Hf0.55Zr0.45O2 and ZrO2 are basically applicable for the ferroelectric analog memory device. Further investigation is needed in view of degradation against the input electric field and imposed fatigue pulse.

Ferroelectric Hafnium Oxide Films for In‐Memory Computing Applications

“…Fujiwara et al deposited the Hf 1−x Zr x O 2 thin film by the CVD, and the devices display excellent ferroelectricity with the remanent polarization of about ≈12 µC cm −2 as well as good fatigue endurance against 109 counts of imposed pulse cycling. [60] The Hf 0.5 Zr 0.5 O 2 thin film prepared by the CVD was crystallized to the tetragonal phase (at 600 °C), which shows the saturated P-E hysteresis loop with a remanent polarization of 8 µC cm −2 . [61] As shown in Figure 7, The ALD mechanism is similar to CVD for film deposition.…”

Low‐Thermal‐Budget Fluorite‐Structure Ferroelectrics for Future Electronic Device Applications

“…Numerous studies conducted in several research groups in the last decade have demonstrated that fluorite‐structure ferroelectrics can be deposited using various deposition techniques such as ALD, sputtering, pulsed laser deposition (PLD), chemical vapor deposition (CVD), and chemical solution deposition (CSD). [ 1–19,22–54 ] Among these techniques, ALD was the most intensively studied deposition technique because it can form very thin conformal and uniform ferroelectric films based on a self‐limiting mechanism by chemical reactions between metal precursors, oxygen source, and the previously deposited film (or substrate). In this regard, the only controllable parameters during the ALD process are types of metal precursor/oxygen sources, [ 27–29 ] pulse/purge time, [ 30,31 ] and deposition temperature.…”