Method for preparing hafnium-zirconium-oxide ferroelectric thin films based on decoupled oxidation and annealing processes

Abstract

The application discloses a preparation method of hafnium-zirconium-oxygen ferroelectric thin film based on decoupling oxidation and annealing process and relates to the technical field of wafers. The method comprises the following steps: S1, depositing a hafnium-zirconium metal laminated thin film on the surface of a substrate; S2, performing oxidation treatment on the hafnium-zirconium metal laminated thin film obtained in the step S1 to obtain an amorphous hafnium-zirconium oxide thin film; and S3, performing recrystallization treatment on the amorphous hafnium-zirconium oxide thin film to obtain a crystalline hafnium-zirconium-oxygen ferroelectric thin film. The application proposes a growth strategy with high process compatibility and wafer-level uniform growth and interface protection, and effectively regulates the valence evolution and spatial distribution of elements at the thin film and interface by decoupling the highly coupled high-concentration oxidation process and high-temperature crystallization process in the traditional process.

Description

Technical Field

[0001] This invention relates to the field of wafer technology, and in particular to a method for preparing hafnium zirconium ferroelectric thin films based on decoupled oxidation and annealing processes. Background Technology

[0002] Against the backdrop of research aimed at exceeding Moore's Law and developing ultra-high-density information storage and novel energy devices, the deep integration of ferroelectric materials with three-dimensional device architectures faces two fundamental challenges. First, as material thickness or device feature size shrinks below the critical scale, the stability of ferroelectric domains decreases significantly, spontaneous polarization intensity decays accordingly, and ferroelectricity may even disappear completely. Second, existing thin-film deposition processes still face significant limitations in achieving large-area fabrication, controllable interface quality, and compatibility with downstream integrated circuit processes.

[0003] Among numerous ferroelectric material systems, hafnium oxide-based ferroelectric materials are widely considered ideal candidates for realizing ferroelectric functions in advanced integrated circuits due to their combination of high spontaneous polarization intensity and excellent silicon process compatibility. These materials not only maintain stable ferroelectric properties at nanoscale thicknesses but can also be grown controllably using mature semiconductor processes such as atomic layer deposition and physical vapor deposition. Furthermore, the various novel deposition techniques developed in recent years at the laboratory scale have further enriched the selection of their film formation pathways.

[0004] However, despite the significant application potential of hafnium oxide-based ferroelectric materials, their mainstream preparation methods still have considerable limitations. For example, pulsed laser deposition typically relies on high substrate temperatures and oxygen partial pressures, making it difficult to meet the thermal budget and process compatibility requirements of silicon-based integrated circuits. Furthermore, the spatial distribution of sputtering plumes hinders the achievement of uniform thickness and composition in large-area films. While atomic layer deposition offers excellent coverage and thickness control, insufficient dangling bonds or chemically active sites on the substrate surface reduce the chemisorption efficiency of the precursor, easily leading to uneven initial nucleation, rough interfaces, and the accumulation of film defects. In contrast, the continuous bombardment of the substrate by high-energy particles in magnetron sputtering can induce lattice damage and interface defects, thereby degrading ferroelectric properties. Summary of the Invention

[0005] To address the key issues mentioned above, such as insufficient process compatibility, difficulty in large-area uniform growth, and frequent interface defects, this invention provides a method for preparing hafnium-zirconium ferroelectric thin films based on decoupled oxidation and annealing processes. This method decouples the highly coupled high-temperature, high-oxygen partial pressure annealing steps in the traditional hafnium-zirconium ferroelectric thin film preparation process, effectively controlling the phase evolution path of the film and reducing the probability of interface reactions and defect formation.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for preparing hafnium zirconium ferroelectric thin films based on decoupled oxidation and annealing processes includes the following steps:

[0008] S1: Deposit a hafnium-zirconium metal stacked thin film on the surface of the substrate;

[0009] S2: The hafnium-zirconium metal laminate film obtained in step S1 is subjected to oxidation treatment to obtain an amorphous hafnium-zirconium oxide film;

[0010] S3: Recrystallize the amorphous hafnium zirconium oxide film to obtain a crystalline hafnium zirconium ferroelectric film.

[0011] In step S1, the hafnium-zirconium metal stacked thin film is amorphous, and the hafnium-zirconium ferroelectric thin film obtained in step S3 is a ferroelectric orthorhombic crystal structure.

[0012] The oxidation treatment in step S2 is carried out at a low temperature of 100-200°C for 1-3 hours.

[0013] The oxidation treatment in step S2 is achieved through ultraviolet ozone oxidation.

[0014] The recrystallization process in step S3 is achieved under vacuum conditions through a high-temperature annealing process.

[0015] The high-temperature annealing process is carried out at a temperature of 350-750℃ and a holding time of 2 hours; the cooling rate of the high-temperature annealing process is not less than 5℃ / min.

[0016] In step S1, a hafnium-zirconium metal stack film is deposited on the substrate by electron beam evaporation without introducing oxygen.

[0017] In step S1, the number of zirconium metal layers and the number of hafnium metal layers in the hafnium-zirconium metal laminate film are equal; the number of zirconium metal layers is 1 to 4.

[0018] The zirconium metal layer and the hafnium metal layer each have three layers.

[0019] The substrate is any one of the following: a Nb-doped strontium titanate single crystal substrate, a P-type doped silicon substrate, an Au metal substrate, and a substrate supporting two-dimensional materials.

[0020] The beneficial effects of this invention are as follows:

[0021] (1) This invention proposes an interface-protected growth strategy, which has the characteristics of high process compatibility and wafer-level uniform growth. By decoupling the highly coupled high-concentration oxidation process and high-temperature crystallization process in the traditional process, the valence state evolution and spatial distribution of elements at the thin film and interface are effectively controlled at different process stages.

[0022] (2) The preparation strategy proposed in this invention has good versatility and scalability. It has been successfully applied to a variety of different types of substrate systems, including silicon substrates, strontium titanate single crystal substrates, metal electrode substrates and layered two-dimensional material substrates. It can achieve the growth of high-quality hafnium zirconium ferroelectric thin films with uniform composition and thickness at the wafer scale, meeting the requirements of consistency and repeatability for integrated manufacturing.

[0023] (3) Because the present invention employs metal stacking deposition and low-temperature oxidation processes, the material as a whole remains in an amorphous state in the early stages of film formation. Monoclinic phase grains and their grain boundaries, which are easily stable at room temperature in traditional processes, are effectively avoided in this preparation path, thereby reducing the free energy barrier that needs to be overcome during the formation of the ferroelectric phase. This characteristic is beneficial to the stable acquisition of the ferroelectric phase and provides a material and process basis for realizing low-power, high-reliability ferroelectric devices. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the process flow of an embodiment of the method for preparing hafnium zirconium ferroelectric thin films based on decoupled oxidation and annealing processes according to the present invention.

[0025] Figure 2 The XRD patterns of the thin film during the preparation process of Example 1 are shown in the three stages of metal stacking, low-temperature oxidation, and high-temperature vacuum post-annealing.

[0026] Figure 3 The image shows the XPS analysis results of the hafnium-zirconium metal laminate thin film obtained in Example 1.

[0027] Figure 4 The image shows the XPS analysis results of the amorphous hafnium zirconium oxide thin film obtained in Example 1.

[0028] Figure 5 The image shows the XPS analysis results of the hafnium zirconium ferroelectric thin film obtained in Example 1.

[0029] Figure 6 The image shows a STEM-HAADF (scanning transmission electron microscopy-high angle annular dark field imaging) image of the hafnium zirconium ferroelectric thin film prepared in Example 1.

[0030] Figure 7 STEM-HAADF image of the thin film prepared for comparison.

[0031] Figure 8 The image shows the STEM-HAADF image of the sample obtained after the thin film went through three stages in the preparation process of Example 1: metal stacking, low-temperature oxidation, and high-temperature vacuum annealing.

[0032] Figure 9 The images show the ferroelectric domains and SSPFM (Scanning Kelvin Probe Force Microscopy) test results of the hafnium zirconium ferroelectric thin film prepared in Example 1. The left image shows the ferroelectric domain test results, and the right image shows the SSPFM test results.

[0033] Figure 10 The images show the ferroelectric domains and SSPFM test results of the hafnium zirconium ferroelectric thin film prepared in Example 2, with the left image showing the ferroelectric domain test results and the right image showing the SSPFM test results.

[0034] Figure 11 The images show the ferroelectric domains and SSPFM test results of the hafnium zirconium ferroelectric thin film prepared in Example 3, with the left image showing the ferroelectric domain test results and the right image showing the SSPFM test results.

[0035] Figure 12 The images show the ferroelectric domains and SSPFM test results of the hafnium zirconium ferroelectric thin film prepared in Example 4, with the left image showing the ferroelectric domain test results and the right image showing the SSPFM test results.

[0036] Figure 13 The results of ferroelectric performance testing and analysis of the hafnium zirconium ferroelectric thin films prepared in Examples 1, 5 to 7 are presented.

[0037] Figure 14 Photographs and two-dimensional distribution maps of the uniformity of remanent polarization of the wafer-level hafnium zirconium ferroelectric thin film prepared in Example 8 are shown. The left image is a photograph of the wafer-level hafnium zirconium ferroelectric thin film, and the right image is a map of the remanent polarization. Detailed Implementation

[0038] 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.

[0039] High-temperature annealing of functional oxide crystal materials typically requires an oxygen-containing atmosphere. This strong oxidizing environment easily induces undesirable oxidation reactions in the substrate or electrode materials, leading to interface coarsening, chemical composition imbalance, and increased defect density. This type of interface degradation not only directly restricts the improvement of the crystal quality and electrical performance of epitaxial oxide films but also adversely affects the long-term stability and reliability of devices, becoming one of the key bottlenecks limiting the integrated application of high-performance oxide films. To address these issues, this invention proposes a method for preparing hafnium zirconium ferroelectric thin films based on decoupled oxidation and annealing processes. The preparation method of this invention employs an interface-protected growth strategy. This strategy decouples the highly coupled oxidation step from the high-temperature crystallization step in traditional processes, avoiding direct exposure of the substrate and electrode interfaces to a high-temperature, strong oxidizing environment during the critical stage of film formation, effectively mitigating the inherent risk of interface degradation from the process path.

[0040] Specifically, this invention breaks down the traditional high-temperature recrystallization annealing step in the preparation of hafnium-based ferroelectric thin films, which relies on an oxygen-containing atmosphere, into two independent processes: low-temperature oxidation and high-temperature vacuum annealing followed by recrystallization. First, a hafnium-zirconium metal stack is deposited on the substrate surface under high vacuum conditions using electron beam evaporation. This metal stack initially forms a stable and dense interfacial contact with the substrate. Subsequently, a low-temperature oxidation process fully oxidizes the metal stack. The final high-temperature recrystallization stage is performed in a vacuum environment, thus achieving in-situ protection of the substrate and electrode interface throughout the high-temperature treatment process. Through this process design, the deposited hafnium-zirconium metal stack not only serves as a precursor structure for the hafnium-zirconium-based ferroelectric thin film but also acts as an interface buffer and protector during oxidation and high-temperature annealing, effectively reducing the probability of undesirable interface oxidation reactions and providing a reliable process guarantee for obtaining high-quality, interface-stable hafnium-zirconium ferroelectric thin films.

[0041] See Figure 1 The method for preparing hafnium zirconium ferroelectric thin films based on decoupled oxidation and annealing processes of the present invention specifically includes the following steps:

[0042] 1) Prepare the target substrate for hafnium zirconium ferroelectric thin film deposition.

[0043] The hafnium zirconium oxy ferroelectric thin film prepared by this invention does not have strict limitations on the substrate type, and different types of substrates can be selected according to the device application requirements. The substrate can be selected from, but is not limited to, the following types: Nb-doped strontium titanate single crystal substrate, P-type doped silicon substrate, Au metal substrate, and substrate supporting two-dimensional materials. When an Au substrate is selected, a silicon wafer with an approximately 285 nm thick silicon dioxide layer can be placed in a thermal evaporation or electron beam evaporation device to deposit an approximately 30 nm thick gold film on the silicon dioxide surface to form the target substrate for hafnium zirconium oxy ferroelectric thin film deposition. When a two-dimensional material substrate is selected, the target number of two-dimensional layers can be obtained from a bulk crystal by mechanical exfoliation and transferred to the surface of a silicon substrate or metal substrate as the deposition substrate for the hafnium zirconium oxy ferroelectric thin film.

[0044] 2) Metal stack growth: Hafnium-zirconium metal stacks were prepared using zirconium and hafnium metal evaporation sources.

[0045] The prepared substrate was placed in an electron beam evaporation chamber, with zirconium and hafnium metal evaporation sources positioned at two separate evaporation source locations. The chamber was then evacuated to a substrate vacuum level not exceeding 5 × 10⁻⁶. -7 mbar. Under conditions where no oxygen is introduced, a 1 nm thick zirconium metal layer is first deposited, followed by a 1 nm thick hafnium metal layer deposited at the same evaporation rate. This process constitutes one deposition cycle. The deposition cycle is repeated multiple times to form a hafnium-zirconium metal stack film on the substrate surface.

[0046] 3) Low-temperature oxidation - ultraviolet ozone oxidation:

[0047] The obtained hafnium-zirconium metal laminate film was placed in an ultraviolet ozone oxidation device for oxidation treatment, so that the hafnium-zirconium metal laminate was fully oxidized to form a uniform amorphous hafnium-zirconium oxide film.

[0048] 4) Recrystallization treatment - vacuum post-annealing recrystallization:

[0049] The amorphous hafnium zirconium oxide film was placed in a vacuum annealing furnace, and the furnace chamber was evacuated to a substrate vacuum level not exceeding 5 × 10⁻⁶. -7 The film was then subjected to a vacuum annealing process, which caused recrystallization and the formation of a high-temperature tetragonal phase structure. After high-temperature annealing, the sample was rapidly cooled to suppress the formation of non-ferroelectric phases, ultimately yielding a hafnium zirconium ferroelectric thin film with ferroelectric properties.

[0050] Example 1

[0051] This embodiment uses a pure silicon substrate.

[0052] A method for preparing hafnium zirconium ferroelectric thin films based on decoupled oxidation and annealing processes includes the following steps:

[0053] S1: Preparation of hafnium-zirconium metal stacks using zirconium and hafnium metal evaporation sources:

[0054] The pure silicon substrate was placed in an electron beam evaporation chamber, with zirconium and hafnium metal evaporation sources positioned at two separate evaporation source locations. The chamber was then evacuated to a substrate vacuum level not exceeding 5 × 10⁻⁶. -7 mbar. Under conditions without the introduction of oxygen, a 1 nm thick zirconium metal layer is first deposited at an evaporation rate of 0.1 Å / s, followed by a 1 nm thick hafnium metal layer at the same evaporation rate. This process constitutes one deposition cycle. The deposition cycle is repeated three times (i.e., 3 cycles) to form a hafnium-zirconium metal stack film on the substrate surface.

[0055] S2: Low-temperature oxidation - ultraviolet ozone oxidation:

[0056] The obtained hafnium-zirconium metal laminate film was placed in an ultraviolet ozone oxidation device and treated at the device operating temperature of 200°C for 2 hours to allow the hafnium-zirconium metal laminate to undergo sufficient oxidation, forming a uniform amorphous hafnium-zirconium oxide film.

[0057] S3: Recrystallization treatment - High-temperature vacuum annealing:

[0058] The amorphous hafnium zirconium oxide film after oxidation treatment was placed in a vacuum annealing furnace, and the furnace chamber was evacuated to a substrate vacuum level not exceeding 5 × 10⁻⁶. -7 The film was then subjected to vacuum post-annealing at 750 °C to induce recrystallization and form a high-temperature tetragonal phase structure. After high-temperature annealing, the sample was subjected to rapid cooling (cooling rate of 8 °C / min) to suppress the formation of non-ferroelectric phases, ultimately obtaining a hafnium zirconium ferroelectric thin film with ferroelectric properties.

[0059] Comparative Example

[0060] This comparative example also uses a pure silicon substrate, on which a hafnium zirconium ferroelectric thin film is prepared using a conventional pulsed laser deposition process. The conventional pulsed laser deposition process uses a 248 nm KrF laser at a frequency of 1-5 Hz and a pressure of 1-2 J / cm². 2 The hafnium zirconium oxide target was bombarded with a single laser beam for 10-30 mins to sputter plasma plumes onto the target substrate. The temperature of the sample stage inside the cavity was 700-900 ℃ and the oxygen pressure inside the cavity was 10-30 Pa.

[0061] To systematically evaluate the structural evolution and crystallinity quality of the prepared hafnium zirconium ferroelectric thin films at each process stage, X-ray diffraction was used to characterize samples from different preparation stages to analyze their crystalline phase composition. The results are as follows: Figure 2 As shown. Figure 2The results show that during the hafnium-zirconium metal stack deposition stage and the subsequent ultraviolet ozone oxidation stage, only (002) and (004) diffraction peaks from the silicon substrate were observed in the corresponding XRD patterns. No crystal phase characteristic peaks related to the hafnium-zirconium oxide thin film were detected, indicating that the film remained amorphous in the above two stages and had not yet crystallized. After completing the vacuum high-temperature annealing and recrystallization treatment, obvious (111) oriented hafnium-zirconium oxide ferroelectric orthorhombic phase diffraction peaks appeared in the XRD patterns, indicating that the formation of the hafnium-zirconium oxide ferroelectric phase was successfully induced by the high-temperature vacuum recrystallization annealing process, which verifies the effectiveness of this decoupled process path in achieving stable crystallization of the ferroelectric phase.

[0062] To reveal the chemical state evolution of materials at different process stages, X-ray photoelectron spectroscopy was used to analyze the binding energy shifts of elements in samples from different preparation stages, thereby identifying their chemical states and bonding environments, clarifying the changes in chemical composition and electronic structure of the thin film surface, and the results are as follows: Figures 3 to 5 As shown. Among them. Figure 3 This is an XPS analysis result of the hafnium-zirconium metal laminate thin film obtained in Example 1. Figure 4 This is an XPS analysis result of the amorphous hafnium zirconium oxide thin film obtained in Example 1. Figure 5 The image shows the XPS analysis results of the hafnium-zirconium ferroelectric thin film obtained in Example 1. Comparing the O 1s XPS spectra of the three stages reveals that: in the electron beam evaporation metal stack stage (i.e., the hafnium-zirconium metal stack film), a secondary peak related to free oxygen vacancies exists at 532.7 eV; however, after UV ozone oxidation treatment, this secondary peak disappears significantly, while the intensity of the main peak at 531.1 eV is significantly enhanced, indicating that the hafnium-zirconium metal stack has been fully oxidized. Furthermore, the characteristic peak appearing at 528.6 eV can be attributed to the oxygen-rich chemical environment formed by oxygen and surface hafnium, further demonstrating the sufficiency and uniformity of the oxidation process. After vacuum annealing and recrystallization, the O 1s spectrum further evolves. Compared with the sample after UV ozone oxidation, the intensity of the lattice oxygen main peak at 531.1 eV is further enhanced, while the relative intensity of the surface hafnium-containing oxygen-rich layer-related peak at 528.5 eV is also increased. This change indicates that the chemical environment of oxygen is further stabilized during high-temperature annealing, and the presence of oxygen-rich structures on the surface is maintained.

[0063] To evaluate the interfacial structure characteristics of the hafnium-zirconium ferroelectric thin film prepared in Example 1, scanning transmission electron microscopy with high-angle annular dark-field imaging was performed on the prepared hafnium-zirconium ferroelectric thin film in this example. The results are as follows: Figure 6 As shown in the figure. Simultaneously, scanning transmission electron microscopy was also performed on the comparative thin film (i.e., the thin film prepared using the conventional pulsed laser deposition process), and the results are shown in the figure. Figure 7 As shown. Figure 6 and Figure 7The comparative results show that in the traditional pulsed laser deposition process, due to the use of high temperature and high oxygen partial pressure conditions for post-annealing and recrystallization, a significant oxidation reaction occurs at the interface between the silicon substrate and the hafnium zirconium oxide film, and the thickness of the interface oxide layer can reach about 5 nm. In contrast, in the sample prepared by the decoupled oxidation and high temperature annealing process of this invention, the thickness of the oxide layer at the interface between the silicon and hafnium zirconium oxide film material is only about 1.3 nm, which is comparable to the thickness of the natural oxide layer formed on a pure silicon substrate in air.

[0064] Further scanning transmission electron microscopy-high-angle annular dark-field imaging tests were performed on the samples prepared according to the present invention. The results are shown in […]. Figure 8 .from Figure 8 It can be seen that ultra-large single-crystal layer structures with lateral dimensions exceeding 230 nm can be obtained during recrystallization.

[0065] The above results demonstrate that the decoupled oxidation and high-temperature annealing process employed in this invention effectively prevents the substrate interface from being exposed to a high-temperature, strong oxidizing environment throughout the entire preparation process, thereby significantly suppressing the occurrence of interfacial oxidation reactions and achieving effective protection of the substrate interface. This verifies the feasibility and effectiveness of the interface-protected growth strategy. Furthermore, the material obtained during the metal stacking deposition and low-temperature oxidation stages in this invention remains generally amorphous. Monoclinic phase grains and their grain boundary structures, which are easily stable at room temperature in the traditional hafnium-zirconium oxide system, do not form in this growth path, thus reducing the free energy barrier required to overcome for the ferroelectric phase transformation. Therefore, during the subsequent vacuum post-annealing recrystallization process, the grains can grow sufficiently.

[0066] Example 2

[0067] This embodiment uses an Nb-doped strontium titanate single crystal substrate. Other preparation processes are the same as in Embodiment 1, except that the oxidation treatment in step S2 is performed at a low temperature of 100°C for 3 hours; the high-temperature annealing process in step S3 is performed at 350°C for 2 hours; and the cooling rate of the high-temperature annealing process is 10°C / min.

[0068] Example 3

[0069] This embodiment uses an Au metal substrate. Other preparation processes are the same as in Example 1.

[0070] Example 4

[0071] This embodiment uses a two-dimensional material substrate. Other preparation processes are the same as in Embodiment 1.

[0072] The ferroelectric domains and SSPFM test results of the hafnium zirconium ferroelectric thin films obtained in Examples 1 to 4 are as follows: Figures 9 to 12 As shown. Figures 9 to 12Experimental results show that the preparation method of the present invention can obtain stable and reversible ferroelectric domain reversal behavior on the above four types of substrates. SSPFM test results show that the ferroelectric domains of all substrate samples flipped by 180° phase angle, indicating that the growth scheme proposed in this invention can effectively induce and maintain ferroelectric polarization reversal under different substrate conditions, and has good substrate versatility.

[0073] Example 5

[0074] The preparation process in this embodiment is basically the same as that in Example 1, except that the number of cycles in S1 when preparing the hafnium-zirconium metal stack using a zirconium and hafnium metal evaporation source is 1 cycle.

[0075] Example 6

[0076] The preparation process in this embodiment is basically the same as that in Example 1, except that the number of cycles in S1 when preparing the hafnium-zirconium metal stack using a zirconium and hafnium metal evaporation source is 2.

[0077] Example 7

[0078] The preparation process in this embodiment is basically the same as that in Example 1, except that the number of cycles in S1 when preparing the hafnium-zirconium metal stack using a zirconium and hafnium metal evaporation source is 4.

[0079] To systematically evaluate the macroscopic ferroelectric properties of the hafnium-zirconium ferroelectric thin film prepared in this invention, a chromium / gold electrode is fabricated on the film surface as the top electrode of a capacitor testing device, and a pure silicon substrate is used as the bottom electrode to construct a capacitor device with a metal-ferroelectric-metal structure. Specifically, a metal top electrode is formed on the surface of the hafnium-zirconium ferroelectric thin film using micro-nano fabrication technology, combined with ultraviolet lithography and thermal evaporation and lift-off processes, to construct a ferroelectric capacitor structure for ferroelectric testing.

[0080] The ferroelectric performance test and analysis results of the hafnium zirconium ferroelectric thin films prepared in Examples 1, 5 to 7 are shown in the figure. Figure 13 . Figure 13 The test results show that the number of metal stack deposition cycles has a significant impact on the ferroelectric performance of the device. When the number of metal stack deposition cycles is three, the device exhibits the best ferroelectric performance, with a residual polarization intensity of approximately 14 μC / cm after deducting the influence of leakage current. 2 The above results demonstrate that by controlling the number of metal stack deposition cycles, the thickness of hafnium zirconium ferroelectric thin films and their macroscopic ferroelectric performance parameters can be effectively adjusted, providing a process control method for device performance optimization.

[0081] Example 8

[0082] To evaluate the uniformity and process stability of the hafnium zirconium ferroelectric thin film prepared under large-area preparation conditions, this embodiment uses a 6-inch wafer-level pure silicon substrate and employs the decoupled oxidation and annealing process of this invention to prepare the wafer-level hafnium zirconium ferroelectric thin film.

[0083] Eighty-one capacitor test devices were uniformly arranged on the entire test wafer, and their ferroelectric properties were systematically measured. Based on the experimental data of the above 81 test devices, the remanent polarization intensity map within the wafer scale was obtained by interpolation reconstruction. The results are shown in […]. Figure 14 . Figure 14 The images shown are photographs of the wafer-level hafnium zirconium ferroelectric thin film prepared in Example 8 and a two-dimensional distribution map of the remanent polarization intensity uniformity; the left image is a photograph of the wafer-level hafnium zirconium ferroelectric thin film, and the right image is a map of the remanent polarization intensity. It should be noted that the above wafer-level mapping results are all reconstructed based on all 81 actual measurement points. No original data was discarded during the interpolation process; the interpolation was only used to enhance the intuitive visualization of the spatial distribution.

[0084] Figure 14 The test results show that the hafnium zirconium ferroelectric thin film prepared by the decoupled oxidation and annealing process of this invention exhibits good remanent polarization and coercive field uniformity on a wafer scale. These results further verify that the fabrication process possesses good consistency and process stability under wafer-level fabrication conditions, making it suitable for large-area integrated manufacturing.

[0085] Based on the above results, the preparation method of hafnium zirconium ferroelectric thin film based on decoupled oxidation and annealing processes of the present invention has the following advantages:

[0086] (1) Hafnium-zirconium metal stack material is used as a substrate interface protection layer to achieve interface protection growth.

[0087] This invention fundamentally alters the evolution path of the film-substrate interface by decoupling the high-temperature recrystallization annealing step, which relies on an oxygen-containing atmosphere, in the traditional hafnium-based ferroelectric thin film preparation process into two independent processes: low-temperature oxidation and high-temperature vacuum annealing followed by recrystallization. Under high vacuum conditions, hafnium-zirconium metal stacks are deposited on the substrate surface using electron beam evaporation. Compared to thermal evaporation and ion beam sputtering, electron beam evaporation offers advantages such as lower particle energy and less incident damage, which helps reduce the introduction of defects in the initial growth stage of the thin film. In this process, the hafnium-zirconium metal stack initially deposited on the substrate surface not only serves as a precursor structure for the subsequent hafnium-zirconium ferroelectric thin film but also acts as an interface protective layer, providing in-situ shielding and buffering for the substrate interface during the subsequent low-temperature oxidation and high-temperature vacuum annealing processes. Cross-sectional scanning transmission electron microscopy characterization results show that the thickness of the substrate interface oxide layer prepared by the method of the present invention is only about 1.3 nm, which is close to the thickness of the natural oxide layer and significantly smaller than the thickness of the interface reaction layer of about 5 nm in the traditional pulsed laser deposition process. This fully demonstrates the effectiveness of the interface protection growth strategy in suppressing interface oxidation and degradation.

[0088] (2) Hafnium-zirconium metal stacks can be directly deposited on a variety of substrates, achieving excellent substrate compatibility.

[0089] This invention proposes a novel hafnium-zirconium ferroelectric thin film preparation method based on metal stack deposition—oxidation—vacuum annealing and recrystallization. Under stable evaporation conditions, hafnium-zirconium metal stacks can be directly deposited in metallic form on the surface of various types of substrates without imposing stringent requirements on the chemical activity or crystal structure of the substrate. In the subsequent low-temperature oxidation and high-temperature vacuum annealing and recrystallization processes, the hafnium-zirconium metal stacks can be transformed into hafnium-zirconium ferroelectric thin film layers under in-situ conditions, achieving a controllable transformation from a metal precursor to a functional oxide thin film. This process route avoids the strong dependence on substrate interface conditions in the traditional direct deposition of oxide thin films, thereby significantly improving the substrate adaptability and versatility of the thin film growth process.

[0090] (3) Preparation of wafer-level hafnium zirconium ferroelectric thin films.

[0091] The key equipment used in this invention, such as electron beam evaporation, ultraviolet ozone oxidation, and vacuum annealing furnaces, is not limited by substrate size and has the technological basis for scaling up to the wafer scale. Based on the above preparation scheme, this invention successfully achieved uniform growth of 6-inch wafer-level hafnium zirconium ferroelectric thin films. Systematic ferroelectric performance tests on different regions of the wafer show that the prepared ferroelectric thin film exhibits good uniformity across the wafer scale, with a remanent polarization intensity reaching approximately 16 μC / cm. 2 This verifies that the process can maintain stable ferroelectric properties even under large-area fabrication conditions, providing reliable process feasibility for subsequent integrated applications.

[0092] (4) Amorphous growth path to construct ultra-large single crystal layer.

[0093] In this invention, the material obtained during the hafnium-zirconium metal stack deposition and low-temperature oxidation stages remains in an amorphous state. Because this process avoids the formation of stable monoclinic grains and their grain boundaries at room temperature or medium-low temperatures, the polycrystalline grain boundaries commonly found in traditional hafnium-zirconium-oxygen systems do not form during the early stages of film growth. This characteristic significantly reduces the free energy barrier that needs to be overcome during ferroelectric phase formation, allowing for sufficient grain growth during subsequent high-temperature vacuum annealing and recrystallization. Experimental results show that the method of this invention can obtain ultra-large single-crystal layer structures with lateral dimensions exceeding 230 nm, providing an important structural basis for achieving high-performance, low-defect-density hafnium-zirconium-oxygen ferroelectric thin films.

[0094] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention. The above embodiments are provided only for the purpose of describing the present invention and are not intended to limit the present invention. Parts not described in detail in this specification are well-known in the art and are not intended to limit the scope of the present invention. The scope of the present invention is defined by the appended claims. All equivalent substitutions and modifications made without departing from the spirit and principle of the present invention should be covered within the scope of the present invention.

Claims

1. A method for preparing hafnium zirconium ferroelectric thin films based on decoupled oxidation and annealing processes, characterized in that, Includes the following steps: S1: Not higher than 5×10 -7 Hafnium-zirconium metal multilayer thin films are deposited on the surface of a substrate by electron beam evaporation under a high vacuum of mbar; the number of zirconium metal layers and hafnium metal layers in the hafnium-zirconium metal multilayer thin film deposited in step S1 is equal; the number of zirconium metal layers is 1 to 4. S2: The hafnium-zirconium metal laminate film obtained in step S1 is oxidized to obtain an amorphous hafnium-zirconium oxide film; the oxidation treatment is carried out at a low temperature of 100-200℃ for 1-3 hours. S3: Amorphous hafnium zirconium oxide thin films are recrystallized to obtain crystalline hafnium zirconium ferroelectric thin films; the recrystallization process is carried out under vacuum conditions by high-temperature annealing, with a vacuum degree not exceeding 5 × 10⁻⁶. -7 mbar, the temperature of the high-temperature annealing process is 350-750℃, and the holding time is 2 hours; The hafnium zirconium ferroelectric thin film has a transverse grain size exceeding 230 nm.

2. The method for preparing hafnium zirconium ferroelectric thin films based on decoupled oxidation and annealing processes according to claim 1, characterized in that, The hafnium-zirconium metal laminated film in step S1 is amorphous, while the hafnium-zirconium ferroelectric film obtained in step S3 is a ferroelectric orthorhombic crystal structure.

3. The method for preparing hafnium zirconium ferroelectric thin films based on decoupled oxidation and annealing processes according to claim 1, characterized in that, The oxidation treatment in step S2 is achieved by ultraviolet ozone oxidation.

4. The method for preparing hafnium zirconium ferroelectric thin films based on decoupled oxidation and annealing processes according to claim 1, characterized in that, The cooling rate of the high-temperature annealing process is not less than 5℃ / min.

5. The method for preparing hafnium zirconium ferroelectric thin films based on decoupled oxidation and annealing processes according to claim 1, characterized in that, Both the zirconium metal layer and the hafnium metal layer have three layers.

6. The method for preparing hafnium zirconium ferroelectric thin films based on decoupled oxidation and annealing processes according to any one of claims 1 to 5, characterized in that, The substrate is any one of the following: a Nb-doped strontium titanate single crystal substrate, a P-type doped silicon substrate, an Au metal substrate, and a layered two-dimensional material substrate.

Images