Hafnium-based ferroelectric thin film with multifunctional interface layer, preparation and capacitor

Abstract

The application belongs to the field of ferroelectric memory devices, and relates to a hafnium-based ferroelectric film with a multifunctional interface layer, preparation and a capacitor. The hafnium-based ferroelectric film comprises a hafnium-based ferroelectric layer, and a multifunctional interface layer arranged in the hafnium-based ferroelectric layer and directly contacting the hafnium-based ferroelectric layer; the multifunctional interface layer is a ZrO2-based material stabilized by at least one oxide of Y, Sc, Ca, Ce and Mg. The multifunctional interface layer is arranged in the hafnium-based ferroelectric layer, the multifunctional interface layer is used for the synergistic regulation of local strain, oxygen defect state and interface charge, the multifunctional interface layer guides the multiphase evolution in the film, thereby the nucleation barrier of ferroelectric orthorhombic phase is significantly reduced and the formation of non-ferroelectric monoclinic phase is effectively inhibited. The corresponding ferroelectric capacitor improves the structural defects of the polycrystalline and multiphase hafnium-based film, improves the content and crystallization quality of the ferroelectric phase, improves the residual polarization intensity and storage window of the device, and further improves the long-term reliability of the memory.

Description

Technical Field

[0001] This invention belongs to the fields of ferroelectric thin films, semiconductor devices and non-volatile memory technology, and more specifically, relates to a hafnium-based ferroelectric thin film with a multifunctional interface layer, its preparation and capacitor. Background Technology

[0002] Hafnium-based ferroelectric thin films possess high dielectric constants, wide band gaps, and compatibility with existing CMOS processes. They can maintain reversible polarization at the nanoscale, making them important candidate materials for non-volatile devices such as ferroelectric random access memory, ferroelectric field-effect transistors, and ferroelectric tunnel junctions. HfO2 typically exists as a non-ferroelectric monoclinic phase in bulk conditions, while the ferroelectric non-centrosymmetric polar phase is metastable. Its formation and stability are influenced by factors such as composition, film thickness, stress state, oxygen vacancies, grain size, electrode clamping, and interfacial chemical state.

[0003] In the HfO2-ZrO2 system (HZO), a relatively significant ferroelectric response can be obtained when the ratio of Hf to Zr is close to 1:1. However, conventional HZO thin films may still contain monoclinic, tetragonal, and polar phases simultaneously, and suffer from problems such as inconsistent grain orientation, uneven distribution of local defects, and excessive leakage current. These problems can cause fluctuations in remanent polarization, coercive voltage, and device reliability, limiting its application in high-density memory devices.

[0004] Existing technologies typically promote ferroelectric phase formation through elemental doping, altering electrode materials, adjusting annealing conditions, or controlling film thickness. For example, in elemental doping, the introduction of Y into the HfO2 or HZO lattice can alter lattice distortion and oxygen defect states due to differences in valence state and ionic radius; at appropriate concentrations, this can help suppress non-ferroelectric monoclinic phases and stabilize highly symmetric or polar phases. However, homogeneous bulk doping simultaneously alters the composition and defect level of the entire ferroelectric layer, making it difficult to independently control local interfacial stress, oxygen vacancy distribution, and barrier characteristics.

[0005] Interface engineering can modulate the electrode / ferroelectric layer interface or local regions within the ferroelectric layer without completely altering its bulk composition. By creating a transition layer between HZO and the electrode, or by constructing a heterostructure within HZO, interfacial reactions, element diffusion, lattice strain, oxygen vacancy migration, and the nucleation environment can be modified. However, the actual effect of the interface layer depends on the local lattice, defect chemistry, and nucleation environment it forms with the HZO bulk. If a clearly defined and continuous heterostructure cannot be formed within HZO, it remains difficult to simultaneously achieve polar phase stability, enhanced polarization, and leakage current suppression.

[0006] Therefore, how to alleviate the polycrystalline and multiphase problem of HZO thin films, improve the polarity-related preferred orientation, further increase the remnant polarization while reducing the leakage current and improving the surface morphology, is still a technical problem to be solved in the art. Contents of the Invention

[0007] In view of the above defects or improvement demands of the prior art, the present invention provides a hafnium-based ferroelectric thin film with a multifunctional interface layer, preparation method and capacitor, aiming to alleviate the polycrystalline and multiphase problem of HZO thin films, improve the polarity-related preferred orientation and remnant polarization while reducing the leakage current.

[0008] To achieve the above objective, in a first aspect of the present invention, a hafnium-based ferroelectric thin film with a multifunctional interface layer is provided, comprising a hafnium-based ferroelectric layer and a multifunctional interface layer sandwiched inside the hafnium-based ferroelectric layer and in direct contact with the hafnium-based ferroelectric layer; the multifunctional interface layer is a ZrO2-based material stabilized by at least one oxide among the corresponding oxides of Y, Sc, Ca, Ce, and Mg.

[0009] Preferably, the number of the multifunctional interface layers is 1 to 3;; When there are at least 2 multifunctional interface layers, the types of material components in the at least 2 multifunctional interface layers, and the molar content of at least one oxide among the corresponding oxides of Y, Sc, Ca, Ce, and Mg are consistent; Alternatively, when there are at least 2 multifunctional interface layers, the types of material components in the at least 2 multifunctional interface layers, and the molar content of at least one oxide among the corresponding oxides of Y, Sc, Ca, Ce, and Mg in the at least 2 multifunctional interface layers along the thickness direction changes in a gradient manner.

[0010] Preferably, the thickness of each layer of the multifunctional interface layer is 0.3 nm -10 nm.

[0011] Preferably, the hafnium-based ferroelectric layer is Hf k Zr 1-k O2, where 0<k<1; or, the hafnium-based ferroelectric layer is HfO2 doped with at least one of Si, Al, Y, La, Gd, Sr, Sc, Ca and Mg; The total thickness of the hafnium-based ferroelectric layer is 2 nm -50 nm.

[0012] Preferably, the multifunctional interface layer is a Y2O3-stabilized ZrO2-based material, and the content of Y2O3 in the Y2O3-stabilized ZrO2-based material is 2-12 mol%.

[0013] Preferably, the multifunctional interface layer is a Y2O3-stabilized ZrO2-based material with a thickness of 1 nm -3 nm, and the hafnium-based ferroelectric layer is Hf with a total thickness of 3 nm-10 nm0.5 Zr 0.5 O2, the multifunctional interface layer is disposed in the middle of the hafnium-based ferroelectric layer; wherein the Y2O3 content in the Y2O3-stabilized ZrO2-based solid solution is 6-10 mol.

[0014] In a second aspect of the present invention, a method for preparing a hafnium-based ferroelectric thin film having a multifunctional interface layer as described in any one of the first aspects is provided, comprising: preparing a multifunctional interface layer during the preparation of a portion of the hafnium-based ferroelectric layer; wherein the multifunctional interface layer and the hafnium-based ferroelectric layer are prepared by pulsed laser deposition, atomic layer deposition, magnetron sputtering, chemical vapor deposition or molecular beam epitaxy, respectively.

[0015] Preferably, the multifunctional interface layer and the hafnium-based ferroelectric layer are prepared by pulsed laser deposition, specifically including: maintaining the temperature in the pulsed laser deposition system at 600℃-800℃, the cavity atmosphere being pure oxygen, adjusting the gas pressure in the cavity to 5 Pa-30 Pa, and rotating the sample stage at a speed of 2 r / min-30 r / min, and sequentially depositing the first hafnium-based ferroelectronic layer, the multifunctional interface layer, and the second hafnium-based ferroelectronic layer under the conditions of laser single pulse energy of 100 mJ-500 mJ and pulse frequency of 1 Hz-20 Hz.

[0016] In a third aspect of the invention, a ferroelectric capacitor is provided, comprising, from bottom to top, a substrate, a bottom electrode, a hafnium-based ferroelectric thin film of a multifunctional interface layer as described in any of the first aspects, and a top electrode.

[0017] Preferably, the bottom electrode and the top electrode each include La 1-x Sr x At least one of MnO3, SrRuO3, LaNiO3, TiN, TaN, W, Ru, Pt, Ir and Au, where x is 0.2 to 0.5.

[0018] In summary, compared with the prior art, the above-described technical solutions conceived by this invention mainly possess the following technical advantages: 1. This invention provides a hafnium-based ferroelectric thin film with a multifunctional interface layer. The multifunctional interface layer is formed within the hafnium-based ferroelectric layer by a ZrO2-based material composed of at least one stable oxide containing Y, Sc, Ca, Ce, or Mg. Local lattice strain is transferred to adjacent hafnium-based ferroelectric layers through the ion size and oxide lattice structure of the aforementioned elements. Simultaneously, the local lattice distortion caused by the substitution of these elements in the ZrO2 lattice, and the charge compensation effect generated by the anisovalent substitution, are utilized to adjust the oxygen vacancy concentration, interface charge, and elemental distribution near the interface. This synergistically regulates at least two of the following: lattice strain, oxygen vacancy, interface charge, elemental distribution, and ferroelectric phase formation. On the one hand, this overcomes the control effect of relying solely on doping, single electrode clamping, or a single buffer layer; on the other hand, it allows the strain, defect, and charge control effects to be simultaneously transferred from the internal interface to the hafnium-based ferroelectric layers on both sides, forming a locally tunable ferroelectric phase nucleation and growth environment without altering the overall composition of the hafnium-based ferroelectric layer. Therefore, by forming a multifunctional interface layer inside the hafnium-based ferroelectric layer and adjusting its material and interface state, a local structure and defect chemical environment conducive to the nucleation and stability of the ferroelectric phase can be formed, reducing the tendency of non-ferroelectric monoclinic phase formation and local enrichment of oxygen vacancies. This helps to alleviate the problem of polycrystalline multiphase HZO thin films, improve polarity-related preferred orientation and residual polarization, and reduce leakage current.

[0019] 2. The present invention preferably achieves this by setting 1 The three-layer multifunctional interface layer further enhances the flexibility and structural adaptability of interface control. When multiple interface layers are set with consistent material composition and content in each layer, multiple equivalent internal heterogeneous interfaces can be formed within the hafnium-based ferroelectric layer, enhancing the cumulative control effect on local strain, oxygen defect distribution, and nucleation environment. Simultaneously, the structure is uniform, the fabrication process has good repeatability, and this is beneficial for stable mass production. When multiple interface layers are set with a gradient of the total molar content of the corresponding oxides of Y, Sc, Ca, Ce, and Mg along the thickness direction, the lattice parameters, oxidation potential, and dielectric properties can smoothly transition between the interface layer and the adjacent hafnium-based ferroelectric layer. This effectively reduces stress concentration and space charge accumulation caused by abrupt changes in interface properties. Furthermore, different sublayers can focus on strain transfer, oxygen defect regulation, or barrier control respectively, improving the synergistic effect between multiple control functions, thereby further optimizing the polarization intensity, leakage characteristics, and device reliability of the ferroelectric thin film.

[0020] 3. Preferably, the multifunctional interface layer of this invention is a Y2O3-stabilized ZrO2-based (YSZ) material, wherein the Y2O3 content is 2%. 12 mol%. This content range is beneficial for adjusting the lattice parameters and oxygen vacancy concentration of YSZ to a suitable range, so as to form a lattice mismatch and oxidation potential difference between it and the hafnium-based ferroelectric layer that are conducive to the nucleation of ferroelectric orthorhombic phases. Based on this, it is preferable to set a 1 nm thick YSZ layer on a 3 nm thick Hf layer. 0.5 Zr 0.5 The central position of the O2 ferroelectric layer (with a Y2O3 content of 10 mol%) maximizes the bifacial interface modulation effect of YSZ, ensuring symmetrical strain transfer and oxygen defect regulation while avoiding series dielectric effects caused by excessive interface layer thickness. Examples show that, with this preferred scheme, the remanent polarization intensity increased from approximately 31 μC / cm² to approximately 39 μC / cm², the surface roughness decreased from approximately 0.209 nm to approximately 0.128 nm, and the leakage current was significantly reduced, achieving a synergistic effect of polar phase enhancement, morphology improvement, and leakage current suppression.

[0021] 4. The improved ferroelectric properties and interface state of the hafnium-based ferroelectric thin film with a multifunctional interface layer in this invention further facilitate the expansion of the storage window of memory devices built based on this capacitor, reduce the possibility of misjudgments caused by signal fluctuations during device read / write operations, and improve the operational stability and reliability of the device. Therefore, this invention provides a controllable and promising technical approach for fabricating non-volatile ferroelectric memory devices with high performance and reliability. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the layered structure of the ferroelectric capacitor in Embodiment 1 of the present invention.

[0023] Figure 2 The images are XRD patterns of Example 1 and Comparative Example 1 of the present invention.

[0024] Figure 3 These are the polarization curves of Embodiment 1 and Comparative Example 1 of the present invention.

[0025] Figure 4 These are the leakage current curves of Embodiment 1 and Comparative Example 1 of the present invention.

[0026] Figure 5 The surface roughness maps are those of Example 1 and Comparative Example 1 of the present invention.

[0027] Figure 6 These are the XPS spectra of Embodiment 1 and Comparative Example 1 of the present invention; wherein Figure 6 a) is a comparison of the fine XPS spectrum of Hf 4f, b) is a comparison of the fine XPS spectrum of Zr 3d, c) is a comparison of the fine XPS spectrum of O 1s, and d) is a fine XPS spectrum of Y 3d.

[0028] Figure 7 The HADDF spectrum and EDS elemental distribution spectrum are from Embodiment 1 of the present invention. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0030] To achieve the above objectives, the following solutions are provided: In a first aspect of the present invention, a hafnium-based ferroelectric thin film having a multifunctional interface layer is provided, comprising a hafnium-based ferroelectric layer and a multifunctional interface layer sandwiched inside the hafnium-based ferroelectric layer and in direct contact with the hafnium-based ferroelectric layer; the multifunctional interface layer is at least one stable ZrO2-based material selected from the oxides of Y, Sc, Ca, Ce, and Mg.

[0031] In this invention, the multifunctional interface layer is at least one stable ZrO2-based material selected from the oxides of Y, Sc, Ca, Ce, and Mg. The stabilization refers to the introduction of the oxides of Y, Sc, Ca, Ce, and Mg, which enhances the stability or retention capacity of the tetragonal, cubic, and / or associated high-symmetry structures of ZrO2 relative to ZrO2, and suppresses or reduces its tendency to transform into a monoclinic phase. The stabilization can be partial, tetragonal, or complete, and does not require the stabilized ZrO2-based material to be a single cubic phase at room temperature. The aforementioned oxides of Y, Sc, Ca, Ce, and Mg can be introduced during thin film deposition, target preparation, precursor mixing, co-deposition, alternating deposition, and heat treatment, and at least partially participate in stabilizing the lattice or crystal phase of the ZrO2-based material through solid solution, diffusion, or phase formation processes. Therefore, the stable ZrO2-based material of this invention includes, but is not limited to, preparation methods using doping.

[0032] Y, Sc, Ca, Ce, and Mg correspond to oxide-stabilized ZrO2-based materials. A specific example of a multifunctional interface layer is (Y2O3). a (ZrO2) 1-a a is taken as 0.02-0.12; (Sc2O3) b (ZrO2) 1-b b is taken as 0.04-0.12; (CaO) c (ZrO2) 1-c c is taken as 0.04-0.16; (CeO2) d (ZrO2) 1-dd is taken as 0.07-0.16; (MgO) e (ZrO2) 1-e e is taken as 0.08-0.16; (Y2O3) f (Sc2O3) g (ZrO2) 1-f-g f takes a value of 0.005-0.006, g takes a value of 0.07-0.08, and specifically, it can be (Y2O3). 0.05 (Sc2O3) 0.07 (ZrO2) 0.88 (Sc2O3) h (CeO2) i (ZrO2) 1-h-i h takes values ​​of 0.08-0.1, and i takes values ​​of 0.01-0.02. Specifically, it can be (Sc2O3). 0.1 (CeO2) 0.01 (ZrO2) 0.89 (Y2O3) j (CeO2) k (ZrO2) 1-j-k j takes values ​​of 0.01-0.03, k takes values ​​of 0.06-0.07, and specifically, it can be (Y2O3). 0.03 (CeO2) 0.07 (ZrO2) 0.9 (CaO) l (Y2O3) m (ZrO2) 1-l-m l is taken as 0.02-0.03, m is taken as 0.005-0.02, specifically, it can be (CaO). 0.03 (Y2O3) 0.02 (ZrO2) 0.95 (CeO2) n (CaO) p (ZrO2) 1-n-p n takes values ​​of 0.1-0.12, p takes values ​​of 0.002-0.010, and specifically, it can be (CeO2). 0.1 (CaO) 0.01 (ZrO2) 0.89 .

[0033] This internal layer can form at least two directly contacting internal heterostructures in the hafnium-based ferroelectric layer, allowing the local lattice confinement, oxidation potential change, and defect chemical regulation effects generated by the multifunctional interface layer to be transmitted to the hafnium-based ferroelectric layers on both sides. This enables local regulation of the ferroelectric phase-related nucleation and orientation environment inside the thin film without changing the overall composition of the hafnium-based ferroelectric layer.

[0034] Both the interface layer and the ferroelectric layer of ZrO2-based materials possess oxide lattices based on metal-oxygen coordination structures. Direct contact between them facilitates the formation of internal interface regions with continuously changing structures and chemical states, and transmits local strain. The differences in ionic size and / or valence state between elements such as Y, Sc, Ca, Ce, and Mg and Hf can cause local lattice distortion in the ferroelectric thin film. Among these, elements with different valences, such as Y, Sc, Ca, or Mg, can also regulate the oxygen defect state and local charge distribution near the interface through charge compensation, while the effect of Ce is related to its valence state and deposition oxidation conditions. Therefore, the dual-interface effect generated by the internal interface layer, combined with the lattice and defect chemistry effects stabilizing the ZrO2-based material, is beneficial for regulating local strain, oxygen defect-related chemical states, and ferroelectric phase-related nucleation and orientation environments, thereby enhancing polarity-related preferred orientation, improving remanent polarization, and suppressing leakage current.

[0035] In some implementations, the multi-functional interface layer has 1 to 3 layers.

[0036] When two or more multifunctional interface layers are set, a hafnium-based ferroelectric layer is set between adjacent multifunctional interface layers to ensure that each multifunctional interface layer is located inside the hafnium-based ferroelectric layer. Limiting the number of layers to 1-3 layers increases the internal control interface while avoiding excessive segmentation of the hafnium-based ferroelectric layer due to an excessive number of interface layers, which could reduce the effective volume fraction of the ferroelectric material or produce obvious series dielectric effects.

[0037] When there are at least two multifunctional interface layers, the material composition of the at least two multifunctional interface layers, the molar content of at least one oxide among the corresponding oxides of Y, Sc, Ca, Ce, and Mg is consistent, and each multifunctional interface layer can be independently a uniform composition layer. A uniform composition layer is beneficial for forming an internal interface with stable composition and easy to prepare repeatedly.

[0038] Alternatively, when there are at least two multifunctional interface layers, the material composition of the at least two multifunctional interface layers is consistent, and the total molar content of at least one oxide of Y, Sc, Ca, Ce, and Mg corresponding oxides varies in a gradient along the thickness direction. Specifically, a gradient layer in which the content of Y, Sc, Ca, Ce, and Mg corresponding oxides varies continuously or segmentally along the thickness direction, and the total molar content of Sc, Ca, Ce, and Mg corresponding oxides varies in a gradient, can mitigate the abrupt changes in lattice parameters, oxidation potential, and dielectric properties between the ZrO2-based material and the hafnium-based ferroelectronic layer, allowing for a smooth transition of strain, defect states, and local charges along the thickness direction. The composite interface layer can allow sublayers with different contents of Y, Sc, Ca, Ce, and Mg corresponding oxides to focus on strain transfer, oxygen defect regulation, or barrier regulation, respectively, thereby improving the coordination between different regulatory functions.

[0039] In some embodiments, the single layer thickness of the multifunctional interface layer is 0.3 nm - 10 nm, and the total thickness thereof is less than the total thickness of the hafnium-based ferroelectric layer. When the multifunctional interface layer is too thin, its coverage degree and regulation effect may be insufficient; when the multifunctional interface layer is too thick, strain relaxation may occur, and the proportion of non-ferroelectric materials in the functional stack will be too high, resulting in a series dielectric effect or additional voltage drop, which weakens the effective polarization contribution of the hafnium-based ferroelectric layer. Therefore, limiting the total nominal thickness of the multifunctional interface layer to 0.3-10 nm and making it less than the total thickness of the hafnium-based ferroelectric layer is beneficial to balancing the internal interface regulation effect and the effective polarization of the hafnium-based ferroelectric layer.

[0040] In some embodiments, the hafnium-based ferroelectric layer is Hf k Zr 1-k O2, where 0<k<1; alternatively, the hafnium-based ferroelectric layer is HZ doped with at least one of Si, Al, Y, La, Gd, Sr, Sc, Ca and Mg O ; the total thickness of the hafnium-based ferroelectric layer is 2 nm - 50 nm. Two or more doping elements may be used in combination, and the type, relative proportion and total doping amount thereof shall be selected according to the composition, film thickness and heat treatment conditions of the hafnium-based material, so that the obtained hafnium-based ferroelectric layer maintains the main structure of the hafnium-based oxide and has switchable polarization.

[0041] In some embodiments, the multifunctional interface layer is a Y2O3-stabilized ZrO2-based material, that is, YSZ. Based on the total molar amount of Y2O3 and ZrO2, the content of Y2O3 is 2-12 mol%, and the content of YSZ is adjusted by the metering method of the target material or precursor. For example, the multifunctional interface layer is a Y2O3-stabilized ZrO2-based material with a thickness of 1 nm, the hafnium-based ferroelectric layer is HZO with a total thickness of 3 nm, and the multifunctional interface layer is arranged at the middle position of the hafnium-based ferroelectric layer; wherein the Y2O3 content in the Y2O3-stabilized ZrO2-based solid solution is 10 mol%. The above content range can adjust the phase stability, local lattice distortion and defect compensation degree of the ZrO2-based material; when the Y2O3 content is too low, the regulation of the structure and defect state of the ZrO2-based material may be insufficient, and when the content is too high, the lattice parameters and oxygen defect state of the interface layer may be excessively changed, which deteriorates the positive effect of stabilizing the ferroelectric polarization phase of HZO.

[0042] The YSZ layer and the HZO ferroelectric layers on either side form two internal oxide heterojunction interfaces. The Zr-O coordination environment in the YSZ exhibits good structural and chemical compatibility with HZO, which is beneficial for transferring local strain and altering the ferroelectric nucleation environment. The lattice distortion and charge compensation effects induced by the Y element can modulate the oxygen defect-related chemical state near the interface. These effects collectively alter the local structure, defect state, and grain growth process of the HZO layer, thereby enhancing polarity-related preferred orientation, increasing polarization intensity, reducing leakage current, and improving surface morphology.

[0043] Examples show that, with a total ferroelectric layer thickness of approximately 3 nm, the addition of an internal YSZ layer of approximately 1 nm enhances the diffraction peak related to ferroelectric polarity at approximately 2θ 30°; the remanent polarization intensity increases from approximately 31 μC / cm² in the control device without YSZ to approximately 39 μC / cm², a relative increase of approximately 25.8%; the root mean square roughness of the film surface decreases from approximately 0.209 nm to approximately 0.128 nm, a decrease of approximately 38.8%, and the leakage current is lower than that of the control device under the same test conditions.

[0044] In a second aspect of the present invention, a method for preparing a hafnium-based ferroelectric thin film having a multifunctional interface layer is provided, comprising: preparing a hafnium-based ferroelectric layer, preparing a multifunctional interface layer on the hafnium-based ferroelectric layer, and then further preparing a hafnium-based ferroelectric layer on the multifunctional interface layer; wherein the multifunctional interface layer and the hafnium-based ferroelectric layer are prepared by at least one of pulsed laser deposition, atomic layer deposition, magnetron sputtering, chemical vapor deposition or molecular beam epitaxy.

[0045] In some embodiments, to reduce interface contamination and unintended oxidation, the multifunctional interface layer and the adjacent hafnium-based ferroelectric layer are preferably deposited continuously in the same vacuum system to form a multifunctional interface layer sandwiched inside the hafnium-based ferroelectric layer and in direct contact with the hafnium-based ferroelectric layer.

[0046] The multifunctional interface layer is prepared under a controlled atmosphere, which refers to a deposition environment in which at least one of the following is regulated: atmosphere composition, oxygen partial pressure, total pressure, and / or gas flow rate. The controlled atmosphere is selected based on the deposition method of the multifunctional interface layer and the target material or precursor system used. For pulsed laser deposition, an O2 atmosphere or a mixed atmosphere containing O2 can be used, and the deposition environment of the thin film can be controlled by adjusting the oxygen partial pressure and total pressure. For magnetron sputtering, an Ar, O2, or Ar / O2 mixed atmosphere can be used depending on the target type, and the sputtering process and thin film deposition environment can be controlled by adjusting the working gas pressure, Ar / O2 flow rate, or their ratio. For molecular beam epitaxy, oxygen-containing sources such as molecular oxygen, ozone, active oxygen, or oxygen plasma can be used, and the deposition environment during the growth process can be controlled by adjusting the oxygen source supply conditions. For atomic layer deposition, at least one of O2, O3, H2O, or oxygen plasma can be used as an oxygen-containing reactant, and the deposition environment can be controlled by adjusting the supply amount of precursor and oxygen-containing reactant, exposure time, and purging conditions. For chemical vapor deposition, O2, O3, H2O, or other suitable oxygen-containing reactants can be selected according to the precursor system used, and the deposition environment of the thin film can be controlled by adjusting the reactant partial pressure, flow rate, supply ratio, and reaction pressure. The atmosphere composition and process parameters used in different deposition methods should be matched with the corresponding deposition mechanism, target material or precursor system. It is not advisable to apply the same atmosphere conditions indiscriminately to all deposition methods.

[0047] When preparing a multifunctional interface layer using at least one of pulsed laser deposition, atomic layer deposition, magnetron sputtering, chemical vapor deposition, or molecular beam epitaxy, the heat treatment temperature and time should be further determined based on the deposition method, film thickness, electrode heat resistance, and target phase structure. Controlling the heat treatment temperature and time within the aforementioned ranges is beneficial for promoting the formation of hafnium-based ferroelectric phase-related structures and stabilizing the internal interface state. If the temperature is too low or the time is too short, the film may not crystallize sufficiently; if the temperature is too high or the time is too long, it may lead to excessive interdiffusion between the interface layer and the hafnium-based ferroelectron layer, uncontrolled oxygen vacancy states, or unexpected reactions between the electrode and the film.

[0048] In a third aspect of the invention, a ferroelectric capacitor is provided, comprising, from bottom to top, a substrate, a bottom electrode, a hafnium-based ferroelectric thin film of a multifunctional interface layer as described in any of the first aspects, and a top electrode.

[0049] The following example illustrates a ferroelectric capacitor in which a multifunctional interface layer is disposed within a hafnium-based ferroelectric layer. Preferably, the structure is formed from top to bottom as follows: a top electrode, a second hafnium-based ferroelectric layer with a thickness of T2, a multifunctional interface layer, a first hafnium-based ferroelectric layer with a thickness of T1, and a bottom electrode. The first and second hafnium-based ferroelectric layers have the same composition and satisfy T1 + T2 = T, where T is the total thickness of HZO in the hafnium-based ferroelectric layer.

[0050] Among them, a multifunctional interface layer refers to a material layer whose material, crystal structure, thickness, and layer position are configured to simultaneously achieve at least two of the following functions: lattice matching, strain transfer, or stress clamping; regulation of oxidation potential, oxygen ion migration, or oxygen vacancy distribution; regulation of interface charge, shielding capability, or barrier; and ferroelectric phase nucleation or orientation growth template.

[0051] In some embodiments, the bottom electrode and the top electrode each include La 1-x Sr x At least one of MnO3, SrRuO3, LaNiO3, TiN, TaN, W, Ru, Pt, Ir, and Au, with x ranging from 0.2 to 0.5. The bottom and top electrodes can have the same or different compositions. Oxide electrodes are suitable for the orientation growth and oxygen exchange regulation of oxide thin films; metal nitride or metal electrodes can be selected based on work function, conductivity, thermal budget, and semiconductor process compatibility. Since the multifunctional interface layer is located inside the hafnium-based ferroelectric layer, its main regulatory function is not contingent on a specific electrode material, thus it can be used in combination with various electrode systems to improve the adaptability of ferroelectric capacitors to different device structures and integration processes.

[0052] The following example illustrates a method for preparing a hafnium-based ferroelectric capacitor, comprising the following steps: (1) Fabricate the bottom electrode on the substrate; (2) A first hafnium-based ferroelectronic layer, a multifunctional interface layer, and a second hafnium-based ferroelectronic layer are sequentially fabricated on the bottom electrode. The multifunctional interface layer is located inside the hafnium-based ferroelectric layer and is in direct contact with the first and second hafnium-based ferroelectronic layers, respectively. By controlling the material composition, thickness, deposition atmosphere, and heat treatment process of the multifunctional interface layer, the multifunctional interface layer is made to simultaneously perform at least two of the following functions: lattice or strain regulation, oxidation potential or oxygen vacancy regulation, charge or barrier regulation, diffusion blocking, and ferroelectric phase nucleation template function. For example, the multifunctional interface layer and the hafnium-based ferroelectric layer are prepared by pulsed laser deposition, specifically including: keeping the sample in the pulsed laser deposition system, adjusting the substrate temperature to 600℃-800℃, introducing high-purity oxygen into the deposition system chamber, simultaneously evacuating the vacuum to regulate the dynamic oxygen partial pressure in the chamber to 5 Pa-30 Pa, and rotating the sample stage at a speed of about 2 r / min-30 r / min. Under the conditions of laser single pulse energy of 100 mJ-500 mJ and pulse frequency of 1 Hz-20 Hz, the first hafnium-based ferroelectronic layer, the multifunctional interface layer, and the second hafnium-based ferroelectronic layer are deposited sequentially.

[0053] (3) Prepare a top electrode on the side of the hafnium-based ferroelectric layer away from the bottom electrode; (4) The stack of bottom electrode, multifunctional interface layer, hafnium-based ferroelectric layer and top electrode obtained in step (3) is heat-treated to promote the formation of hafnium-based ferroelectric phase and stabilize the interface state.

[0054] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings.

[0055] Example 1: This embodiment uses a ferroelectric capacitor with a metal-ferroelectric-metal structure, such as... Figure 1 As shown, from bottom to top, the structure includes a substrate, a bottom electrode, a hafnium-based ferroelectric thin film, and a top electrode. The hafnium-based ferroelectric thin film includes a hafnium-based ferroelectric layer and a multifunctional interface layer disposed therein. The substrate is a 1cm × 1cm SrTiO3 single crystal substrate with a thickness of 500 μm, and the bottom electrode is a 40nm thick La... 0.7 Sr 0.3 The MnO3 thin film and the hafnium-based ferroelectric layer are made of Hf with a total thickness of 3 nm (including the first and second HZO sublayers with the same composition and deposition conditions). 0.5 Zr 0.5 The top electrode is an O2 thin film with a thickness of 100 nm using Au, and the multifunctional interface layer is a YSZ thin film with a thickness of 1 nm. The YSZ thin film is a Y2O3-stabilized ZrO2-based material, and the Y2O3 content in the YSZ is 10 mol%.

[0056] The preparation process includes the following steps: (1) The SrTiO3 substrate is ultrasonically cleaned in acetone, ethanol and isopropanol in sequence, and then dried. Subsequently, the SrTiO3 substrate is placed into a pulsed laser deposition cavity, the substrate temperature is raised to 700℃, and under the conditions of dynamic oxygen partial pressure of 15 Pa, laser single pulse energy of 250 mJ and pulse frequency of 5 Hz, a La layer with a thickness of about 40 nm is deposited on the SrTiO3 substrate. 0.7 Sr 0.3 MnO3 thin film, used as bottom electrode.

[0057] (2) Complete La 0.7 Sr 0.3 After the MnO3 bottom electrode was deposited, the sample was kept in the pulsed laser deposition system. High-purity oxygen was introduced into the deposition system chamber, the substrate temperature was adjusted to 800℃, the dynamic oxygen partial pressure in the chamber was adjusted to 10 Pa, and the sample stage was rotated at a speed of about 5 r / min. Under the conditions of laser single pulse energy of 300 mJ and pulse frequency of 2 Hz, the first HZO sublayer, the YSZ internal interface layer, and the second HZO sublayer were deposited sequentially.

[0058] Specifically, first switch to Hf 0.5 Zr 0.5O2 target material, under conditions of 800℃, dynamic oxygen partial pressure of 10 Pa, laser single pulse energy of 300 mJ, and pulse frequency of 2 Hz, in La 0.7 Sr 0.3 A first HZO sublayer was deposited on the MnO3 bottom electrode. Then, without disrupting the cavity vacuum and exposing the first HZO sublayer to ambient air, the target was switched to a YSZ target, and using the same substrate temperature, dynamic oxygen partial pressure, laser single-pulse energy, and pulse frequency as the first HZO sublayer, a YSZ internal interface layer with a nominal thickness of approximately 1 nm was deposited on the first HZO sublayer. Afterwards, the target was switched back to an Hf target. 0.5 Zr 0.5 Using an O2 target, and under the same deposition conditions, a second HZO sublayer was deposited on the internal interface layer of YSZ.

[0059] The first and second HZO sublayers have the same composition and deposition conditions, and their combined thickness is approximately 3 nm. Preferably, the first and second HZO sublayers have the same or substantially the same thickness, i.e., their nominal thicknesses are each approximately 1 nm, so that the YSZ internal interface layer is located in the middle of the HZO thickness direction. The thickness of each layer is controlled by controlling the number of laser pulses or according to a pre-calibrated deposition rate, thereby obtaining a ferroelectric stack consisting of the first HZO sublayer / YSZ internal interface layer / second HZO sublayer, the total thickness of which is approximately 4 nm.

[0060] The first HZO sublayer, the YSZ internal interface layer, and the second HZO sublayer are continuously formed in the same vacuum system, which can reduce the adsorption of water vapor and carbonaceous pollutants on the surface of adjacent layers, reduce the formation of unintended oxidation or intermediate contamination layers, maintain the interface state of continuous and direct contact between the YSZ internal interface layer and the HZO sublayers on both sides, and improve the repeatability of the interface layer thickness and layer position.

[0061] After the deposition of the ferroelectric stack is completed, the oxygen partial pressure in the cavity is increased to 20 Pa and heat-treated for 10 min. Then, the sample is cooled to room temperature in the oxygen environment at a cooling rate of about 10 °C / min to stabilize the oxidation state and internal interface state of the ferroelectric stack.

[0062] (3) After the sample is cooled to room temperature, it is removed and Au top electrode is deposited on the surface of the second HZO sublayer using a small ion sputtering device through a patterned metal mask with a diameter of about 100 μm. This results in a substrate consisting of SrTiO3 and La. 0.7 Sr 0.3 A ferroelectric capacitor consisting of a MnO3 bottom electrode, a first HZO sublayer, a YSZ internal interface layer, a second HZO sublayer, and an Au top electrode is denoted as a Mid-YSZ device.

[0063] Comparative Example 1: Its structure is basically the same as that of Example 1, except that it does not have a YSZ layer.

[0064] During fabrication, a 4 nm thick HZO layer is directly fabricated on the same bottom electrode, followed by the direct fabrication of an Au top electrode, resulting in a top electrode / HZO layer / bottom electrode structure, denoted as a Control device.

[0065] Characterization and testing: To avoid interference from the Au top electrode on the thin film structure and surface testing, XRD, AFM, and XPS tests were performed on the functional oxide stacks before the formation of the Au top electrode in Example 1 and Comparative Example 1. In Example 1, the test object was a functional oxide stack consisting of a first HZO sublayer / YSZ internal interface layer / second HZO sublayer, while in Comparative Example 1, the test object was an HZO thin film without a YSZ internal interface layer. These tests reflect the overall structure, surface morphology, and chemical state of the functional oxide stack. Cross-sectional HAADF-STEM and EDS analyses were performed on the sample from Example 1 to observe the layered structure and elemental distribution of the HZO / YSZ / HZO stack. The electrical performance of the complete ferroelectric capacitor after the formation of the Au top electrode was tested.

[0066] Figure 2 In the XRD tests shown, both the Mid-YSZ and Control samples exhibited diffraction peaks at approximately 30° 2θ, while no obvious monoclinic phase characteristic peaks were detected at approximately 28.3° 2θ, indicating that the introduction of the internal YSZ layer interface did not induce a detectable non-ferroelectric monoclinic phase. Compared to the Control sample, the Mid-YSZ sample showed enhanced diffraction peak intensity at approximately 30° 2θ, indicating enhanced preferred orientation corresponding to ferroelectric polarization. Simultaneously, the increased full width at half maximum (FWHM) of this diffraction peak may be attributed to changes in local strain state and reduced grain size, which to some extent contributes to the stability of the ferroelectric polarized phase.

[0067] Characterization of the surface morphology, chemical state, and microstructure of the examples and comparative samples.

[0068] Figure 5 The AFM test results show that the root mean square roughness of the Control film is about 0.209 nm, which decreases to about 0.128 nm after the introduction of a 1 nm YSZ intermediate interface layer. This indicates that the intermediate YSZ layer is beneficial to forming a smoother film surface, which in turn helps to improve subsequent electrode contact and reduce local electric field concentration.

[0069] Figure 6XPS measurements detected Y 3d signals in the Mid-YSZ sample, with a semi-quantitative Y content of approximately 1.2%. Compared to the Control sample, the binding energies of Hf 4f and Zr 3d both shifted towards higher binding energies by approximately 0.3 eV; the O 1s peak fractionation results showed an increase in the peak area associated with oxygen vacancies. These results indicate that the intermediate YSZ layer alters the local chemical environment and oxygen vacancies state of the HZO stack.

[0070] Figure 7 As shown, cross-sectional HAADF-STEM and EDS analyses of the Mid-YSZ sample revealed a dark contrast layer of YSZ in the middle of the HZO stack. The Hf signal was significantly reduced and the Zr signal was slightly enriched in this region, confirming the formation of the YSZ intermediate interface layer. The overall thickness of the HZO stack was approximately 3 nm, and the interface between the bottom electrode and the ferroelectric stack was clear. The measured local interplanar spacing was approximately 0.29 nm, consistent with polarity-dependent interplanar spacing.

[0071] Electrical performance tests were performed on the Mid-YSZ device and Control device after forming the Au top electrode. During testing, La... 0.7 Sr 0.3 A MnO3 bottom electrode and an Au top electrode with a diameter of approximately 100 μm were used as the two test terminals, and both devices were subjected to the same test temperature, voltage waveform, test frequency, pulse width, and electrode area. Polarization-voltage testing was performed using the Remanent Hysteresis mode of a ferroelectric tester to reduce the influence of non-flipping charge, linear dielectric response, and leakage current on the residual polarization test results. [The text then abruptly shifts to a seemingly unrelated topic:] ...at the Au top electrode and La... 0.7 Sr 0.3 A bipolar test voltage is applied between the MnO3 bottom electrodes, with a maximum test voltage of approximately 11 V.

[0072] Figure 3 The electrical tests shown indicate that the remanent polarization intensity P of the Mid-YSZ device r The polarization reversal voltage of the Mid-YSZ device is approximately 39 μC / cm², which is better than the approximately 31 μC / cm² of the control device without the YSZ interface layer. The polarization reversal voltage of the Mid-YSZ device is approximately 8.9 V, while that of the control device is approximately 7.8 V.

[0073] At Au top electrode and La 0.7 Sr 0.3 Applying MnO3 bottom electrode A scanning voltage of 8-8 V is used, and the measured current is converted into current density based on the effective area of ​​the Au top electrode. The Mid-YSZ device and the Control device use the same voltage scanning direction, voltage step size, dwell time, current limiting conditions, and electrode area to ensure the comparability of test results.

[0074] Figure 4 The JV test results show that, under the same test conditions, the leakage current of the Mid-YSZ device is lower than that of the control device. This result indicates that the YSZ layer disposed inside HZO can enhance the polar phase-correlated diffraction response and improve remanent polarization, while also reducing the leakage current of the ferroelectric capacitor. This is related to the regulatory effect of the internal YSZ interface on the local barrier, oxygen defect-related state, defect migration path, and grain growth state.

[0075] In summary, based on XRD, electrical, AFM, XPS, and cross-sectional structure characterization, the introduction of the YSZ intermediate interface layer forms a local heterogeneous interface within HZO, altering the stress and nucleation environment of the thin film; the Y element and related defect chemistry change the distribution of oxygen defects near the interface; the intermediate layer regulates grain growth and surface morphology; all of these effects collectively promote the orientation of the phase with favorable polarity, enhance polarization, and reduce leakage current.

[0076] The above embodiments demonstrate that the differences in the technical effects of the multifunctional interface layer depend on the material and the interface state formed between it and the hafnium-based ferroelectric layer. In the YSZ / HZO system of Example 1, it is preferable to place approximately 1 nm of YSZ inside the HZO layer. For other material systems, while maintaining comparable composition, deposition conditions, and electrode structure of the hafnium-based ferroelectric layer, forming a multifunctional interface layer located inside the hafnium-based ferroelectric layer and ensuring the formation of a corresponding multifunctional interface layer with the hafnium-based ferroelectric layer can guarantee the achievement of the corresponding optimized effect.

[0077] For ZrO2-based materials containing at least one stabilizing element from Y, Sc, Ca, Ce, or Mg, as long as they can form the aforementioned double-sided direct contact, continuous or substantially continuous, and thickness-controlled internal heterogeneous interface within the hafnium-based ferroelectric layer, and enable this interface to regulate at least two of the following: local strain, oxygen defect-related chemical state, and ferroelectric phase-related nucleation environment, they can be used as the multifunctional interface layer of this invention, without requiring them to have the exact same specific composition as YSZ in Example 1. The multifunctional interface layer can be a homogeneous layer, a gradient layer, or a composite interface layer. Regardless of the hierarchical configuration, as long as it is located within the hafnium-based ferroelectric layer, forms a double-sided direct contact internal heterogeneous interface with the adjacent hafnium-based ferroelectronic layer, and possesses the aforementioned at least two interface regulation functions, the corresponding modification effect can be obtained. The degree of modification obtained by different material compositions, interface layer thicknesses, and hierarchical configurations can vary, and it is not required that all achieve the same quantitative results as the approximately 1 nm YSZ internal interface layer in Example 1.

[0078] In the YSZ / HZO system of Example 1, placing a YSZ layer with a nominal thickness of approximately 1 nm inside the HZO is a preferred solution that satisfies the above-mentioned structural characteristics. This example is used to demonstrate that the above-mentioned internal multifunctional interface structure can produce corresponding interface modification effects, but it does not constitute the sole limitation on the specific materials, composition, and hierarchical configuration of the multifunctional interface layer.

[0079] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A hafnium-based ferroelectric thin film with a multifunctional interface layer, characterized in that, It includes a hafnium-based ferroelectric layer and a multifunctional interface layer sandwiched inside the hafnium-based ferroelectric layer and in direct contact with the hafnium-based ferroelectric layer; the multifunctional interface layer is a ZrO2-based material stabilized by at least one oxide of the corresponding oxides of Y, Sc, Ca, Ce, and Mg.

2. The hafnium-based ferroelectric thin film with a multifunctional interface layer according to claim 1, characterized in that, The multi-functional interface layer has 1-3 layers; When the multifunctional interface layer has at least two layers, the material composition of the at least two multifunctional interface layers is consistent, with the molar content of at least one oxide among the oxides of Y, Sc, Ca, Ce, and Mg being the same. Alternatively, when the multifunctional interface layer consists of at least two layers, the types of material composition in the at least two multifunctional interface layers vary in a gradient along the thickness direction, with the molar content of at least one oxide among the corresponding oxides of Y, Sc, Ca, Ce, and Mg varying.

3. The hafnium-based ferroelectric thin film with a multifunctional interface layer according to any one of claims 1-2, characterized in that, The thickness of each of the multifunctional interface layers is 0.3 nm - 10 nm.

4. The hafnium-based ferroelectric thin film with a multifunctional interface layer according to claim 1, characterized in that, The hafnium-based ferroelectric layer is Hf k Zr 1-k O2, where 0<k<1; or, the hafnium-based ferroelectric layer is HfO2 doped with at least one of Si, Al, Y, La, Gd, Sr, Sc, Ca and Mg; The total thickness of the hafnium-based ferroelectric layer is 2 nm - 50 nm.

5. The hafnium-based ferroelectric thin film with a multifunctional interface layer according to claim 1, characterized in that, The multifunctional interface layer is a Y2O3-stabilized ZrO2-based material, and the Y2O3 content in the Y2O3-stabilized ZrO2-based material is 2-12 mol.

6. The hafnium-based ferroelectric thin film with a multifunctional interface layer according to claim 5, characterized in that, The multifunctional interface layer is a Y₂O₃-stabilized ZrO₂-based material with a thickness of 1-3 nm, and the hafnium-based ferroelectric layer is an Hf₂O₃ material with a total thickness of 3 nm-10 nm. 0.5 Zr 0.5 O2, the multifunctional interface layer is disposed in the middle of the hafnium-based ferroelectric layer; wherein the Y2O3 content in the Y2O3-stabilized ZrO2-based material is 6-10 mol.

7. A method for preparing a hafnium-based ferroelectric thin film with a multifunctional interface layer according to any one of claims 1-6, characterized in that, include: A multifunctional interface layer is prepared during the preparation of a partial hafnium-based ferroelectric layer; wherein the multifunctional interface layer and the hafnium-based ferroelectric layer are prepared by pulsed laser deposition, atomic layer deposition, magnetron sputtering, chemical vapor deposition or molecular beam epitaxy, respectively.

8. The method for preparing a hafnium-based ferroelectric thin film with a multifunctional interface layer according to claim 7, characterized in that, The multifunctional interface layer and the hafnium-based ferroelectric layer are prepared by pulsed laser deposition, specifically including: maintaining the temperature in the pulsed laser deposition system at 600℃-800℃, the cavity atmosphere being pure oxygen, adjusting the gas pressure in the cavity to 5 Pa-30 Pa, and rotating the sample stage at a speed of 2 r / min-30 r / min. Under the conditions of laser single pulse energy of 100 mJ-500 mJ and pulse frequency of 1 Hz-20 Hz, the first hafnium-based ferroelectronic layer, the multifunctional interface layer, and the second hafnium-based ferroelectronic layer are deposited sequentially.

9. A ferroelectric capacitor, characterized in that, From bottom to top, it includes a substrate, a bottom electrode, a hafnium-based ferroelectric thin film of the multifunctional interface layer as described in any one of claims 1-6, and a top electrode.

10. The ferroelectric capacitor according to claim 9, characterized in that, The bottom electrode and the top electrode each include La. 1-x Sr x At least one of MnO3, SrRuO3, LaNiO3, TiN, TaN, W, Ru, Pt, Ir and Au, where x is 0.2 to 0.5.

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