Pyroelectric dependence of atomic layer-deposited Hf0.5Zr0.5O2 on film thickness and annealing temperature

Abstract

Ferroelectric Hf0.5Zr0.5O2 is a prime candidate material for integrated HfO2-based ferroelectric devices due to its simple composition, low crystallization temperature, and significant remanent polarization. It is particularly promising for integrated pyroelectric devices used in infrared sensing and energy harvesting, although the appearance of nonferroelectric tetragonal and monoclinic phases should be avoided to achieve high-performance pyroelectric sensors. Both nonferroelectric phases are strongly influenced by the Hf0.5Zr0.5O2 film thickness and annealing temperature. The sensitivity of the pyroelectric coefficient on film thickness is investigated with atomic layer-deposited Hf0.5Zr0.5O2 films within a 10–30 nm thickness range. The films are capped with TiN and undergo post-metallization anneals at 450 °C and 600 °C. An optimum pyroelectric coefficient of −56 μC K−1 m−2 is found in the 15 nm thick Hf0.5Zr0.5O2. The pyroelectric coefficient is found to be sensitive to thickness-dependent depolarization effects and monoclinic phase growth. Ferroelectric, dielectric, and pyroelectric properties are improved with a lower annealing temperature, demonstrating the back-end-of-line compatibility of Hf0.5Zr0.5O2 pyroelectric devices.

Direct Epitaxial Growth of Polar Hf0.5Zr0.5O2 Films on Corundum

“…The area is then 5.7 × 10 −6 cm 2 , from which a pyroelectric coefficient of 3.9 × 10 −5 µC·cm −2 ·K −1 is obtained. This figure is significantly lower than that recently reported for HZO polycrystalline films on Si-based substrates: 5.6 × 10 −3 µC·cm −2 ·K −1 for 15 nm thickness [ 34 ]. Note, however, that a spontaneous pyroelectric response is being measured in the current study, unlike in the case of [ 34 ], where the pyroelectric coefficient was measured after poling.…”

“…This figure is significantly lower than that recently reported for HZO polycrystalline films on Si-based substrates: 5.6 × 10 −3 µC·cm −2 ·K −1 for 15 nm thickness [ 34 ]. Note, however, that a spontaneous pyroelectric response is being measured in the current study, unlike in the case of [ 34 ], where the pyroelectric coefficient was measured after poling. This indicates film self-poling, which is not uncommon for films [ 35 ], and characteristic of epitaxial layers, for which strain gradients result in flexoelectric fields [ 36 ].…”

Relaxation Induced by Imprint Phenomena in Low-Temperature (400 °C) Processed Hf0.5Zr0.5O2-Based Metal-Ferroelectric-Metal Capacitors

“…The FE polarization extracted using a ±2.5 V WRITE and various READ voltage pulses (from −2.5 to +2.5 V only positive bias results shown in Figure a) decreases by increasing the measurement temperature. This decrease is a consequence of the pyroelectric effect and the material reaching close to its Curie temperature. , It can be seen from Figure b that even increasing the temperature up to 125 °C does not show drastic relaxation effects. In the case of pulse measurements, the V c was determined by calculating the voltage at which polarization is one-half of the saturation polarization.…”

High Quality Factors in Superlattice Ferroelectric Hf0.5Zr0.5O2 Nanoelectromechanical Resonators

“…10−12 In addition to the superior processing and integration benefits, the transforming advantage of hafnia-zirconia over conventional perovskite or emerging nitride ferroelectrics is its ability to sustain robust polarization when scaled to sub-10 nm thicknesses. 2,13,14 This unique dimensional scalability is not only pivotal for the realization of dense memory devices on advanced CMOS nodes but also highly favorable for the creation of high-performance nanoelectromechanical systems (NEMS). 11,12,15 Ultrascaled hafnia-zirconia piezoelectric transducers, with thicknesses of just a few nanometers, favor the creation of integrated NEMS sensors with enhanced detection limits.…”

“…Electrical measurements of pristine (uncycled) capacitors are depicted in FigureS1in the Supporting Information. Confirmation of film ferroelectricity within released, electrodeless, Hf 0.5 Zr 0.5 O 2 nanolaminates is achieved via grazing incident X-ray diffraction (GIXRD) analysis of ∼20 × 30 mm2…”