The discovery of ferroelectricity in thin doped hafnium oxide films revived the interest in ferroelectric (FE) memory concepts. Zirconium‐doped hafnium oxide (HZO) crystallizes at low temperatures (e.g., 400 °C), which makes this material interesting for the implementation of FE functionalities into the back end of line (BEoL). So far, the FE phase of prior amorphous HZO films is achieved by using a dedicated rapit thermal annealing (RTA) treatment. However, herein, it is shown that this dedicated anneal is not needed. A sole furnace treatment given by the thermal budget present during the interconnect formation is sufficient to functionalize even ultrathin 5 nm HZO films. This result helps to optimize the integration sequence of HZO films (e.g., involving a minimum number of BEoL process steps), which saves process time and fabrication costs. Herein, metal–FE–metal capacitors with Hf0.5Zr0.5O2 films of different thicknesses (5–20 nm) are fabricated annealed at 400 °C for various durations within different types of ovens (RTA and furnace). Structural and electrical characterization confirms that all furnace‐annealed samples have similar X‐ray diffraction patterns, remanent polarization, endurances, and thickness dependencies as RTA‐annealed ones. With respect to remanent polarization, leakage current, and endurance, the HZO film of 10 nm thickness shows the most promising results for the integration into the BEoL.

Research data are not shared.

The local crystal phase and orientation of ferroelectric grains inside TiN/Hf0.5Zr0.5O2/TiN have been studied by the analysis of the local electron beam scattering Kikuchi patterns, recorded in transmission. Evidence was found that the ferroelectric phase of the layers is derived from an orthorhombic phase, most likely of space group Pca21. The orientation analysis reveals a strong out-of-plane texture of the polycrystalline film which is in accordance with a high remanent polarization Pr observed for P-V measurements. The results of this analysis help us to further optimize the ratio of ferroelectric grains and their orientation for many applications, e.g., in the field of emerging memory or infrared sensors.

The pyroelectric response of polycrystalline, Si-doped HfO2 layers in a thickness range of 10 nm to 50 nm is investigated employing the temperature oscillation method. The largest value of the pyroelectric coefficient is obtained for the 20 nm layer with p = 84 μC m−2 K−1, which is similar to that of lithium niobate. Furthermore, the pyroelectric coefficient is analyzed with respect to field cycling and is found to increase proportionally with the remanent polarization during wake-up, providing further evidence that the hysteresis of the material is truly ferroelectric. However, for different material thicknesses, the switchable polarization and pyroelectric coefficient are not proportional, indicating that only part of the domains is pyroelectrically active, which suggests potential for further improvement of the pyroelectric response. Due to its CMOS compatibility and conformal deposition using atomic layer deposition (ALD), Si-doped HfO2 is a promising candidate for future energy harvesting and sensor applications.

Piezoelectric thin films are of current interest in science and industry for highly integrated nano-electro-mechanical-systems and sensor devices. In this study, the dependence of the piezoelectric properties on the doping concentration in Si:HfO2 thin films and their crystallographic origin are investigated. The Si:HfO2 films with a thickness of 20 nm and various Si doping concentrations in the range of 2.7–5.6 cat.% were examined. The relationship between the piezoelectric displacement and remanent polarization is studied during wake-up from the antiferroelectric-like pristine state until the cycled ferroelectric state, which reveals an application-dependent optimal doping concentration. Furthermore, the piezoelectric and ferroelectric properties, as well as the relative permittivity, were measured over wake-up, thus giving a glimpse at the underlying mechanism of the transition from a pristine antiferroelectric-like behavior to a ferroelectric/piezoelectric one, revealing a pre-existing polar phase that is reorienting during wake-up. The studied samples show a strong displacement and polarization dependence on the doping concentration. Hence, the stoichiometry is an excellent parameter for the application-specific adjustment of complementary metal–oxide–semiconductor compatible piezoelectric thin films.