Hafnium oxide-based ferroelectric thin film structure based on van der Waals force and preparation method thereof

Abstract

The present invention discloses a hafnium oxide-based ferroelectric thin film structure and preparation method based on van der Waals forces. The preparation method comprises: providing a buffer layer; forming a hafnium oxide-based ferroelectric thin film on the surface of the buffer layer to obtain a stable hafnium oxide-based ferroelectric thin film structure; wherein the buffer layer is made of a two-dimensional material, and the buffer layer and the hafnium oxide-based ferroelectric thin film are connected by van der Waals forces. The preparation method of the hafnium oxide-based ferroelectric thin film structure of the present invention uses an ultra-thin two-dimensional material as the buffer layer. Compared with the traditional chemical bonding between a silicon substrate and a ferroelectric thin film, the present invention uses van der Waals forces to connect the two-dimensional buffer layer and the hafnium oxide-based ferroelectric thin film to form a van der Waals heterogeneous interface, thereby exposing the hafnium oxide-based ferroelectric thin film and the two-dimensional material buffer layer, thereby increasing the surface energy of the film, promoting the transition to the ferroelectric phase, and ensuring the free growth and crystallization of the hafnium oxide-based ferroelectric thin film in a stress-free state.

Description

Technical Field

[0001] The present invention belongs to the technical field of ferroelectric thin films, and in particular relates to a hafnium oxide-based ferroelectric thin film structure based on van der Waals force and a preparation method thereof. Background Art

[0002] Hafnium oxide-based ferroelectric memory is considered one of the most promising next-generation new memory devices due to its radiation resistance, high-speed read / write speed, low power consumption, and high retention. For hafnium oxide-based ferroelectric memory, the stable ferroelectric phase and controllable domain flipping in the hafnium oxide-based ferroelectric film are directly related to the storage capacity of high-performance, high-density ferroelectric memory. Existing hafnium oxide-based ferroelectric film structures directly form the hafnium oxide-based ferroelectric film on a silicon substrate. However, the hafnium oxide-based ferroelectric film is chemically bonded to the traditional silicon substrate, resulting in a low surface energy of the ferroelectric phase, which is not conducive to the transformation of the metastable ferroelectric phase into a non-ferroelectric phase. Furthermore, lattice mismatch generates severe dislocations and numerous defects, which affect the ferroelectric performance and durability of the hafnium oxide-based film. Summary of the Invention

[0003] (1) Purpose of the invention

[0004] The purpose of the present invention is to provide a hafnium oxide-based ferroelectric thin film structure based on van der Waals force and a preparation method thereof to solve the technical problems in the prior art of defects in the interface between the substrate and the ferroelectric thin film of the hafnium oxide-based ferroelectric thin film structure and low ferroelectric phase content in the hafnium oxide-based ferroelectric thin film.

[0005] (2) Technical solution

[0006] To solve the above problems, the first aspect of the present invention provides a method for preparing a hafnium oxide-based ferroelectric thin film structure based on van der Waals force, comprising: providing a buffer layer; forming a hafnium oxide-based ferroelectric thin film on the surface of the buffer layer to obtain a stable hafnium oxide-based ferroelectric thin film structure; wherein the buffer layer is made of a two-dimensional material, and the buffer layer and the hafnium oxide-based ferroelectric thin film are connected by van der Waals force to form a van der Waals heterointerface, thereby increasing the surface energy of the hafnium oxide-based ferroelectric thin film.

[0007] Furthermore, the buffer layer is a nanoscale multilayer structure.

[0008] Furthermore, the method further includes: providing a substrate; and forming the buffer layer on the surface of the substrate.

[0009] Furthermore, the buffer layer is an ultra-thin single crystal mica layer or an ultra-thin molybdenum disulfide layer.

[0010] Furthermore, providing the buffer layer includes: obtaining an ultra-thin molybdenum disulfide layer by chemical vapor deposition, and the thickness of the ultra-thin molybdenum disulfide layer is 1-100 nm.

[0011] Furthermore, providing the buffer layer also includes: using a dual-temperature zone tubular furnace to perform chemical vapor deposition to obtain an ultra-thin molybdenum disulfide layer; the low-temperature zone of the dual-temperature zone tubular furnace is sulfur powder, and the high-temperature zone of the dual-temperature zone tubular furnace is molybdenum trioxide, and a mixed gas of hydrogen and argon is used for preparation in the dual-temperature zone tubular furnace.

[0012] Furthermore, the providing of the buffer layer includes: mechanically peeling off the single crystal mica sheet to obtain the ultra-thin single crystal mica layer; the thickness of the ultra-thin single crystal mica layer is 1-100 nm.

[0013] Furthermore, the hafnium oxide-based ferroelectric film is a zirconium-doped hafnium oxide-based ferroelectric film, and the molar ratio of hafnium to zirconium is 1:1; the zirconium-doped hafnium oxide-based ferroelectric film is prepared by atomic layer deposition technology and has a thickness of 5-15 nm.

[0014] Furthermore, the hafnium oxide-based ferroelectric thin film is a cerium-doped hafnium oxide-based ferroelectric thin film, and the molar ratio of hafnium to cerium is 1:0.15; the cerium-doped hafnium oxide-based ferroelectric thin film is prepared by a sol-gel method and has a thickness of 60-120 nm.

[0015] Furthermore, the hafnium oxide-based ferroelectric film is a yttrium-doped hafnium oxide-based ferroelectric film, and the molar ratio of hafnium to yttrium is 1:0.05; the yttrium-doped hafnium oxide-based ferroelectric film is prepared by a sol-gel method and has a thickness of 15-30 nm.

[0016] According to another aspect of the present invention, a hafnium oxide-based ferroelectric thin film structure is provided, which is prepared by adopting the preparation method described in any one of the above technical solutions.

[0017] Furthermore, the hafnium oxide-based ferroelectric thin film structure includes: a buffer layer of two-dimensional material; a hafnium oxide-based ferroelectric thin film, wherein the hafnium oxide-based ferroelectric thin film is covered on the buffer layer, and the buffer layer and the hafnium oxide-based ferroelectric thin film are connected by van der Waals force to form a van der Waals heterointerface, thereby increasing the surface energy of the hafnium oxide-based ferroelectric thin film and promoting the transition to the ferroelectric phase.

[0018] According to another aspect of the present invention, a capacitor structure is provided, comprising the hafnium oxide-based ferroelectric thin film structure according to any one of the above technical solutions.

[0019] According to another aspect of the present invention, an electronic device is provided, comprising the hafnium oxide-based ferroelectric thin film structure described in any one of the above technical solutions or the capacitor structure described in any one of the above technical solutions.

[0020] (3) Beneficial effects

[0021] The above technical solution of the present invention has the following beneficial technical effects:

[0022] The present invention discloses a method for preparing a hafnium oxide-based ferroelectric thin film structure using an ultrathin two-dimensional material as the buffer layer. Compared to conventional chemical bonding on a silicon substrate, this method eliminates the mismatch between chemical bonds. The present invention utilizes van der Waals forces for bonding, rather than conventional chemical bonds. Because the materials above and below the interface are different, conventional chemical bonds would not fully match and thus produce defects. The buffer layer is connected to the hafnium oxide-based ferroelectric thin film via van der Waals forces to form a van der Waals heterointerface, maintaining the free growth and crystallization of the film. Furthermore, the formation of the van der Waals heterointerface increases the surface energy of the hafnium oxide-based ferroelectric thin film, promoting the internal transformation of the hafnium oxide-based ferroelectric thin film into a ferroelectric phase.

[0023] The buffer layer of the hafnium oxide-based ferroelectric thin film structure of the present invention is connected to the hafnium oxide-based ferroelectric thin film via a weak interface van der Waals bond, thereby achieving direct regulation of the thin film properties by the weak interface van der Waals bond; and solving the problem of interface defects between the hafnium oxide-based ferroelectric thin film and the silicon substrate hindering ferroelectric phase transition and ferroelectric domain reversal.

[0024] The present invention reduces the negative effects of stress, charged impurities and oxygen vacancies between the hafnium oxide-based ferroelectric film and the traditional silicon substrate by adding a buffer layer between the hafnium oxide-based ferroelectric film and the silicon substrate, reduces the leakage current density and enhances the fatigue resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 4 is a flow chart of a method for preparing a hafnium oxide-based ferroelectric thin film structure according to one embodiment of the present invention.

[0026] Figure 2 FIG. 4 is a flow chart of a method for preparing a hafnium oxide-based ferroelectric thin film structure according to another embodiment of the present invention.

[0027] Figure 3 FIG. 4 is a schematic diagram of a hafnium oxide-based ferroelectric thin film structure according to another embodiment of the present invention.

[0028] Figure 4 3 is a performance comparison diagram of a hafnium oxide-based ferroelectric thin film structure according to an embodiment of the present invention and a hafnium oxide-based ferroelectric thin film structure in the prior art.

[0029] Figure 5 FIG. 4 is a polarization distribution diagram of a hafnium oxide-based ferroelectric thin film structure according to an embodiment of the present invention.

[0030] Figure 6 FIG. 4 is a polarization simulation diagram of a hafnium oxide-based ferroelectric thin film structure according to one embodiment of the present invention.

[0031] Reference numerals:

[0032] 100: buffer layer; 200: hafnium oxide-based ferroelectric thin film; 400: point electrode; 500: substrate.

[0033] Figure 4 middle:

[0034] Electric field (MV / cm) is the electric field strength, and its unit is MV / cm (megavolts per centimeter).

[0035] Polarization (μC / cm 2 ) is the polarization intensity value, the unit is μC / cm 2 (10 -6 coulombs per square centimeter).

[0036] mica is a performance curve of a hafnium oxide-based ferroelectric thin film structure prepared by the invented method for preparing a hafnium oxide-based ferroelectric thin film structure (using an ultra-thin single crystal mica layer as the buffer layer 100).

[0037] Si is the structural performance curve of hafnium oxide-based ferroelectric thin films in the prior art DETAILED DESCRIPTION

[0038] To make the objectives, technical solutions, and advantages of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings. It should be understood that these descriptions are merely exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present invention.

[0039] The accompanying drawings illustrate schematic diagrams of layer structures according to embodiments of the present invention. These figures are not drawn to scale; for clarity, some details are exaggerated and some details may be omitted. The shapes, relative sizes, and positional relationships of the various regions and layers shown in the figures are merely exemplary and may deviate in practice due to manufacturing tolerances or technical limitations. Those skilled in the art may design regions / layers with different shapes, sizes, and relative positions based on actual needs.

[0040] Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0041] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0042] The present invention will be described in more detail below with reference to the accompanying drawings. In each of the accompanying drawings, identical elements are represented by similar reference numerals. For the sake of clarity, the various parts in the accompanying drawings are not drawn to scale.

[0043] In one embodiment of the invention, a method for preparing a hafnium oxide-based ferroelectric thin film structure based on van der Waals force is provided, which may include: providing a buffer layer 100; forming a hafnium oxide-based ferroelectric thin film 200 on the surface of the buffer layer 100 to obtain a stable hafnium oxide-based ferroelectric thin film structure; wherein the buffer layer 100 is made of a two-dimensional material, and the buffer layer 100 and the hafnium oxide-based ferroelectric thin film (200) are connected by van der Waals force to form a van der Waals heterogeneous interface, thereby increasing the surface energy of the hafnium oxide-based ferroelectric thin film.

[0044] The present invention's method for fabricating a hafnium oxide-based ferroelectric thin film structure utilizes an ultrathin two-dimensional material as the buffer layer 100. Compared to conventional chemical bonding with silicon substrates, this method eliminates chemical bond mismatches. Instead of conventional chemical bonds, the present invention utilizes van der Waals forces to connect the layers. Because the materials above and below the interface are different, conventional chemical bonds would not fully match and thus produce defects. Instead, the buffer layer 100 and the hafnium oxide-based ferroelectric thin film 200 are connected by van der Waals forces to form a van der Waals heterointerface, maintaining the film's free growth and crystallization.

[0045] The buffer layer 100 of the hafnium oxide-based ferroelectric thin film structure of the present invention is connected to the hafnium oxide-based ferroelectric thin film 200 via weak interfacial van der Waals bonds, thereby achieving direct regulation of the film properties by the weak interfacial van der Waals bonds; and solving the problem of interface defects between the hafnium oxide-based ferroelectric thin film 200 and the traditional silicon substrate hindering ferroelectric phase transition and ferroelectric domain reversal.

[0046] The present invention reduces the negative effects of stress, charged impurities, and oxygen vacancies between the hafnium oxide-based ferroelectric film 200 and the traditional silicon substrate by adding a buffer layer 100 between the hafnium oxide-based ferroelectric film 200 and the substrate, lowers the leakage current density, and enhances the fatigue resistance.

[0047] The generation of the van der Waals heterojunction increases the surface energy of the hafnium oxide-based ferroelectric thin film 200 and promotes the transformation of the ferroelectric phase inside the hafnium oxide-based ferroelectric thin film 200 .

[0048] Furthermore, the establishment of the van der Waals heterointerface makes the hafnium oxide-based ferroelectric film 200 and the buffer layer 100 more exposed. The increased surface energy can promote the ferroelectric metastable phase-stable phase transition, achieve controllable ferroelectric domain flipping, and thus obtain better ferroelectric performance.

[0049] In an optional embodiment, the method for preparing the hafnium oxide-based ferroelectric thin film structure based on van der Waals force may further include: providing a substrate 500 ; and forming the buffer layer 100 on the surface of the substrate 500 .

[0050] In an optional embodiment, the substrate 500 is made of a conductive material.

[0051] In a preferred embodiment, P-type silicon is used as the substrate 500 .

[0052] Figure 1 4 is a flow chart of a method for preparing a hafnium oxide-based ferroelectric thin film structure according to one embodiment of the present invention.

[0053] like Figure 1 As shown, in one embodiment of the invention, a method for preparing a hafnium oxide-based ferroelectric thin film structure based on van der Waals force is provided, which comprises at least the following steps:

[0054] S100 , providing a buffer layer 100 .

[0055] S200 , forming a hafnium oxide-based ferroelectric thin film 200 on the surface of the buffer layer 100 to obtain a stable hafnium oxide-based ferroelectric thin film structure.

[0056] The present invention uses a two-dimensional buffer layer 100 to grow the hafnium oxide-based ferroelectric film 200. A van der Waals heterointerface characterized by no stress and no mismatch is formed between the buffer layer 100 and the hafnium oxide-based ferroelectric film 200. By utilizing the van der Waals heterointerface between them, the performance of the hafnium oxide-based ferroelectric film 200 is significantly enhanced.

[0057] The present invention adopts the two-dimensional buffer layer 100 to grow the hafnium oxide-based ferroelectric film 200, and uses the van der Waals force between the interfaces to regulate the ferroelectric properties of the film, thereby achieving few defects or even no defects in a lattice-matching-free manner, and increasing the surface energy of the ferroelectric film to stabilize the hafnium oxide ferroelectric metastable phase, promote ferroelectric domain reversal, and optimize the performance of the hafnium oxide-based ferroelectric film.

[0058] In an optional embodiment, the method for preparing the hafnium oxide-based ferroelectric thin film structure based on van der Waals force may further include the following steps:

[0059] S10 , providing a substrate 500 .

[0060] In an optional embodiment, the step S100 of providing the buffer layer 100 may include the following steps:

[0061] S110 , forming the buffer layer 100 on the surface of the substrate 500 .

[0062] In an optional embodiment, the method for preparing the hafnium oxide-based ferroelectric thin film structure based on van der Waals force may further include the following steps:

[0063] S300 , forming a point electrode 400 on the surface of the hafnium oxide-based ferroelectric thin film 200 .

[0064] Figure 2 FIG. 4 is a flow chart of a method for preparing a hafnium oxide-based ferroelectric thin film structure according to another embodiment of the present invention.

[0065] like Figure 2 As shown, in an optional embodiment, the method for preparing the hafnium oxide-based ferroelectric thin film structure based on van der Waals force may include the following steps:

[0066] S10 ′, providing a P-type silicon substrate 500 .

[0067] S110 ′, forming the buffer layer 100 on the surface of the P-type silicon substrate 500 .

[0068] S200 , forming a hafnium oxide-based ferroelectric thin film 200 on the surface of the buffer layer 100 to obtain a stable hafnium oxide-based ferroelectric thin film structure.

[0069] S300 , forming a point electrode 400 on the surface of the hafnium oxide-based ferroelectric thin film 200 .

[0070] In an optional embodiment, the buffer layer 100 is an ultra-thin single crystal mica film layer or an ultra-thin molybdenum disulfide layer.

[0071] In an optional embodiment, the hafnium oxide-based ferroelectric thin film 200 may be formed on the buffer layer 100 first, and then the buffer layer 100 with the hafnium oxide-based ferroelectric thin film 200 may be fixed on the surface of the substrate 500. The buffer layer 100 is located between the substrate 500 and the hafnium oxide-based ferroelectric thin film 200.

[0072] In an optional embodiment, the molybdenum disulfide may be directly deposited on the surface of the substrate 500 to form the ultra-thin molybdenum disulfide layer (ie, the buffer layer 100 ).

[0073] In an optional embodiment, a single crystal mica sheet may be first fixed on the surface of the substrate 500 , and then the single crystal mica sheet may be mechanically peeled off to obtain the ultra-thin single crystal mica layer (ie, the buffer layer 100 ).

[0074] In an optional embodiment, the hafnium oxide-based ferroelectric thin film 200 can be formed on the surface of a single-crystalline mica sheet, and then the single-crystalline mica sheet is mechanically peeled off to obtain the ultra-thin single-crystalline mica layer (i.e., the buffer layer 100). The buffer layer 100 with the hafnium oxide-based ferroelectric thin film 200 is then fixed on the surface of the substrate 500. The buffer layer 100 is located between the substrate 500 and the hafnium oxide-based ferroelectric thin film 200.

[0075] In an optional embodiment, the method for preparing the hafnium oxide-based ferroelectric thin film structure based on van der Waals force may further include: forming a point electrode 400 on a surface of the hafnium oxide-based ferroelectric thin film 200 away from the buffer layer 100 .

[0076] By directly growing the hafnium oxide-based ferroelectric thin film 200 on the buffer layer 100 and using the P-type silicon substrate and the point electrode 400, the hafnium oxide-based ferroelectric thin film 200 can be intrinsically grown without affecting the performance of the hafnium oxide-based ferroelectric thin film 200. The structure can also be used to detect the performance of the hafnium oxide-based ferroelectric thin film.

[0077] In an optional embodiment, the method for preparing the hafnium oxide-based ferroelectric thin film structure based on van der Waals force may further include: performing gold spraying on the substrate 500 having the hafnium oxide-based ferroelectric thin film 200 to form the bottom electrode 400 .

[0078] In an optional embodiment, a small magnetron sputtering device may be used to perform gold spraying on the surface of the hafnium oxide-based ferroelectric thin film 200 having the buffer layer 100 to form the point electrode 400 .

[0079] In an optional embodiment, the buffer layer 100 may be a nanoscale multi-layer structure.

[0080] In an optional embodiment, the buffer layer 100 is made of a two-dimensional material and has a thickness of 1-100 nm.

[0081] In an optional embodiment, the buffer layer 100 may be made of an ultrathin single-crystal mica sheet or an ultrathin molybdenum disulfide sheet. The material of the buffer layer 100 is not limited to an ultrathin single-crystal mica layer or an ultrathin molybdenum disulfide layer. The material of the buffer layer 100 includes any material that can generate van der Waals force to connect with the hafnium oxide-based ferroelectric thin film 200, preferably a two-dimensional material.

[0082] In an optional embodiment, providing the buffer layer 100 may include: obtaining a sheet-like ultra-thin single-crystal mica layer by mechanical peeling.

[0083] In an optional embodiment, providing the buffer layer 100 may include: selecting a smooth, crack-free ultra-thin two-dimensional material sheet, then sticking it on an operating table with double-sided tape, and tearing it off layer by layer with a syringe needle and pointed tweezers, taking care not to scratch the surface. Mechanical peeling can be performed under a high-power microscope.

[0084] In an optional embodiment, providing the buffer layer 100 may include: selecting a blue film tape specifically for two-dimensional materials, peeling off an ultra-thin two-dimensional material layer, and then transferring the layer to the substrate using a PDMS film material (abbreviation of Polydimethylsiloxane).

[0085] In an optional embodiment, providing the buffer layer 100 may include: obtaining a sheet-shaped ultra-thin molybdenum disulfide layer by chemical vapor deposition.

[0086] In an optional embodiment, the thickness of the ultra-thin molybdenum disulfide sheet is 1-100 nm.

[0087] In an optional embodiment, providing the buffer layer 100 may further include: performing chemical vapor deposition using a dual-temperature zone tube furnace to obtain an ultra-thin molybdenum disulfide layer.

[0088] In an optional embodiment, the low temperature zone of the dual-temperature zone tubular furnace may be filled with sulfur powder.

[0089] In an optional embodiment, the high temperature zone of the dual-temperature zone tubular furnace may be molybdenum trioxide.

[0090] In an optional embodiment, a mixed gas of hydrogen and argon may be used for preparation in a dual-temperature zone tube furnace.

[0091] In an optional embodiment, the atmosphere in the dual-temperature zone tubular furnace is 5% hydrogen and 95% argon.

[0092] The atmosphere gas is blown from the low temperature zone of the dual-temperature zone tubular furnace to the high temperature zone of the dual-temperature zone tubular furnace. The molybdenum trioxide is converted into molybdenum dioxide through high temperature in the high temperature zone. The atmosphere gas drives the steam formed by the sulfur powder to react with the molybdenum dioxide to generate molybdenum disulfide.

[0093] In an optional embodiment, providing the buffer layer 100 may include: mechanically peeling a single crystal mica sheet to obtain the ultra-thin single crystal mica layer.

[0094] In an optional embodiment, the thickness of the ultra-thin single crystal mica sheet may be 1-100 nm.

[0095] In an optional embodiment, the hafnium oxide-based ferroelectric film 200 may be a zirconium-doped hafnium oxide-based ferroelectric film 200, wherein the molar ratio of hafnium to zirconium is 1:1; the zirconium-doped hafnium oxide-based ferroelectric film 200 is prepared by atomic layer deposition technology and has a thickness of 5-15 nm.

[0096] In an optional embodiment, the hafnium oxide-based ferroelectric film 200 may be a cerium-doped hafnium oxide-based ferroelectric film 200, with a molar ratio of hafnium to cerium of 1:0.15; the cerium-doped hafnium oxide-based ferroelectric film 200 is prepared by a sol-gel method and has a thickness of 60-120 nm.

[0097] In an optional embodiment, the hafnium oxide-based ferroelectric film 200 may be a yttrium-doped hafnium oxide-based ferroelectric film 200, with a molar ratio of hafnium to yttrium of 1:0.05; the yttrium-doped hafnium oxide-based ferroelectric film 200 is prepared by a sol-gel method and has a thickness of 15-30 nm.

[0098] In an optional embodiment, the thickness of the point electrode 400 of the hafnium oxide-based ferroelectric thin film structure is 10-15 nm.

[0099] In an optional embodiment, the method for preparing the hafnium oxide-based ferroelectric thin film structure may further include: performing an electrical performance test on the hafnium oxide-based ferroelectric thin film structure.

[0100] In an optional embodiment, the performing electrical performance test on the hafnium oxide-based ferroelectric thin film structure may include: placing the hafnium oxide-based ferroelectric thin film structure on a conductive silver paste board to perform the electrical performance test.

[0101] When conducting an electrical performance test, the hafnium oxide-based ferroelectric thin film structure is flattened and placed on a conductive silver paste board, and the silver paste board and the top electrode on the film surface are connected to the negative and positive electrodes respectively for testing.

[0102] Example 1

[0103] Example 1 of the present invention uses an ultra-thin single-crystal mica sheet as a buffer layer 100. The buffer layer 100 is arranged on the surface of a P-type silicon substrate 500. A hafnium oxide-based ferroelectric film 200 is directly grown by a sol-gel method, and then a top electrode (point electrode 400) is formed on the hafnium oxide-based ferroelectric film 200 to form a capacitor structure, which is then tested.

[0104] 1.1 Preparation of a ferroelectric film precursor solution of a cerium-doped hafnium oxide-based ferroelectric film 200 by a sol-gel method: (1) Calculate the amount of hafnium acetylacetonate and cerium nitrate required for the cerium-doped hafnium oxide ferroelectric film. The cerium doping amount is 15% and the concentration is 0.1 mol / L. (2) Dissolve hafnium acetylacetonate in an acetic acid solution and stir on a magnetic stirrer until completely dissolved to obtain solution A. (3) Dissolve cerium nitrate and acetylacetone completely in the above solution A to obtain solution B, and stir on the magnetic stirrer for 20 minutes until completely dissolved. (4) Heat the solution B in a water bath for 40 minutes, and then stir on a magnetic stirrer for 6 hours to obtain a film precursor solution C. (5) Filter the above solution C to obtain a ferroelectric film precursor solution.

[0105] 1.2 Preparation of hafnium oxide-based ferroelectric thin film 200 based on van der Waals growth

[0106] 1.2.1 Use a dropper to draw the ferroelectric thin film precursor solution and drop it onto the single crystal mica sheet;

[0107] 1.2.2 Spin-coat the ferroelectric thin film precursor solution onto the single crystal mica sheet to form a uniform wet film. Spin-coat the buffer layer 100 to form a uniform, smooth wet film. The spin-coating speeds are: low speed 500 r / min for 15 seconds, high speed 3000 r / min for 30 seconds.

[0108] 1.2.3 Drying and pyrolysis of the uniform wet film of hafnium oxide doped with cerium prepared above; the drying temperature is 180°C for 200 seconds; the pyrolysis temperature is 350°C for 180 seconds;

[0109] 1.2.4 Repeat step 1.2.3 six times; then perform annealing to obtain the target van der Waals-grown hafnium oxide-based ferroelectric thin film 200. The annealing temperature is 800° C., and the annealing time is 400 seconds. The thickness of the ferroelectric thin film is 90 nm.

[0110] 1.3 The hafnium oxide-based ferroelectric thin film grown based on van der Waals forces obtained above is placed on an operating table, and thinned layer by layer using a syringe needle and pointed tweezers, until it is peeled off to a specified thickness, and then transferred to a P-type silicon substrate 500 using a PDMS thin film material.

[0111] 1.4 The upper surface of the hafnium oxide-based film is treated with gold using a small magnetron sputtering device to form a stable hafnium oxide-based ferroelectric film structure for testing. The top electrode (point electrode 400) grown on the surface of the obtained film includes: Step 1, using a circular hole mask with a diameter of 60-110um to cover the film surface; Step 2, presetting the temperature in the ion sputtering system chamber to room temperature 25℃ and the vacuum degree to 10 -1 -6 -1mbar / pa, and a current of 10-30 mA for 1-3 minutes to obtain a top electrode (point electrode 400).

[0112] 1.5 Testing was performed using a conductive silver paste board to conduct P-type silicon (serving as the bottom electrode and substrate 500). The hafnium oxide-based ferroelectric thin film structure 200 was placed on a conductive silver paste board. The silver paste board and the top electrode (point electrode 400) on the film surface were connected to the negative and positive electrodes, respectively, for testing.

[0113] Example 2

[0114] The second embodiment of the present invention uses a sheet-like ultra-thin molybdenum disulfide nanolayer (ultra-thin molybdenum disulfide sheet) deposited by chemical vapor deposition as a buffer layer 100. The buffer layer 100 is deposited on the surface of P-type Si, which can serve as both a bottom electrode and a substrate 500. The hafnium oxide-based ferroelectric film 200 is directly grown by a sol-gel method, and then a top electrode (point electrode 400) is formed on the hafnium oxide-based ferroelectric film 200 to form a capacitor structure, which is then tested.

[0115] 2.1 Preparation of Ultrathin Flake MoS2 Nanolayers. Using molybdenum trioxide and sulfur powder as raw materials, a highly crystallized, uniformly thick, ultrathin flake MoS2 nanolayer was prepared in a dual-zone tubular furnace. The sulfur powder was placed in the low-temperature zone, while the MoT was placed in the high-temperature zone. A hydrogen-argon mixture was used for the preparation. The resulting MoS2 was deposited onto a P-type Si substrate 500 in the high-temperature zone, resulting in an ultrathin MoS2 layer with a thickness of 100 nm.

[0116] 2.2 Preparation of cerium-doped hafnium oxide-based ferroelectric thin film by sol-gel method 200 ferroelectric thin film precursor solution: (1) By calculating the amount of hafnium acetylacetonate and cerium nitrate required for the cerium-doped hafnium oxide ferroelectric thin film, the cerium doping amount is 15% and the concentration is 0.1 mol / L. (2) Dissolve hafnium acetylacetonate in acetic acid solution and stir on a magnetic stirrer until completely dissolved to obtain solution A. (3) Dissolve cerium nitrate and acetylacetone completely in the above solution A to obtain solution B, and stir on the magnetic stirrer for 20 minutes until completely dissolved. (4) Heat the solution B in a water bath for 40 minutes, and then stir on a magnetic stirrer for 6 hours to obtain a thin film precursor solution C. (5) Filter the above solution C to obtain a ferroelectric thin film precursor solution.

[0117] 2.3 Preparation of Hafnium Oxide-Based Ferroelectric Thin Film 200 Based on Van der Waals Force Growth

[0118] 2.3.1 Use a dropper to draw the ferroelectric thin film precursor solution and drop it onto the buffer layer 100 of the ultra-thin MoS2 nanosheet;

[0119] 2.3.2 Spin-coat the ferroelectric thin film precursor solution onto the ultra-thin MoS2 nanosheet to form a uniform wet film. Spin-coat the buffer layer 100 to form a uniform, smooth wet film. The spin-coating speeds are: low speed 500 r / min for 15 seconds, high speed 3000 r / min for 30 seconds.

[0120] 2.3.3 Drying and pyrolysis of the uniform wet film of hafnium oxide doped with cerium prepared above; the drying temperature is 180°C for 200 seconds; the pyrolysis temperature is 350°C for 180 seconds;

[0121] 2.3.4 Repeat step 2.3.3 six times; then perform annealing to obtain the target van der Waals-grown hafnium oxide-based ferroelectric thin film 200. The annealing temperature is 800° C. and the time is 400 seconds. The thickness of the hafnium oxide-based ferroelectric thin film 200 is 90 nm.

[0122] 2.4 The upper surface of the hafnium oxide-based ferroelectric film 200 is subjected to gold sputtering treatment using a small magnetron sputtering device to form a stable hafnium oxide-based ferroelectric film structure for testing. The top electrode (point electrode 400) is grown on the surface of the obtained hafnium oxide-based ferroelectric film 200, including the following steps: Step 1: Cover the film surface with a circular hole mask with a diameter of 60-110 μm; Step 2: Preset the temperature in the ion sputtering system chamber to room temperature (25°C) and the vacuum degree to 10 -1 -6 -1 mbar / pa, and a current of 10-30 mA for 1-3 minutes to obtain a top electrode (point electrode 400).

[0123] 2.5 Testing was performed using a conductive silver paste board to connect the P-type silicon (serving as the bottom electrode and substrate 500). The hafnium oxide-based ferroelectric thin film structure 200 was flattened and placed on a conductive silver paste board. The silver paste board and the top electrode (point electrode 400) on the film surface were connected to the negative and positive electrodes, respectively, for testing.

[0124] Figure 3 FIG. 1 is a schematic diagram of a hafnium oxide-based ferroelectric thin film structure according to one embodiment of the present invention.

[0125] like Figure 3 As shown, in another embodiment of the invention, a hafnium oxide-based ferroelectric thin film structure is provided, which can be prepared by adopting the preparation method described in any one of the above technical solutions.

[0126] In an optional embodiment, the hafnium oxide-based ferroelectric thin film structure may include: a buffer layer 100; a hafnium oxide-based ferroelectric thin film 200, wherein the hafnium oxide-based ferroelectric thin film 200 is covered on the buffer layer 100, and the buffer layer 100 and the hafnium oxide-based ferroelectric thin film 200 are connected by van der Waals force to form a van der Waals heterointerface, thereby increasing the surface energy of the hafnium oxide-based ferroelectric thin film and promoting the transition to the ferroelectric phase.

[0127] The hafnium oxide-based ferroelectric thin film structure of the present invention uses an ultra-thin two-dimensional material as the buffer layer 100, directly grows the hafnium oxide-based ferroelectric thin film 200, and forms a van der Waals heterogeneous interface due to the absence of dangling bonds on the surface of the buffer layer 100, thereby reducing the negative effects of stress, interface defects, impurities and oxygen vacancies on the film, thereby optimizing the performance of the ferroelectric thin film.

[0128] The hafnium oxide-based ferroelectric thin film structure of the present invention breaks through the surface interface effect between the hafnium oxide-based ferroelectric thin film 200 and the traditional substrate by establishing a van der Waals heterogeneous interface. Through its unique bonding structure, controllable matching, smooth interface, flexibility and other advantages, the hafnium oxide-based ferroelectric thin film 200 with no lattice mismatch on the surface, thermal adaptability and atomic flatness is formed. While reducing the formation of a dead layer on the interface, it increases the surface energy, promotes the transition to the ferroelectric phase, and significantly enhances the ferroelectric performance.

[0129] In an optional embodiment, the hafnium oxide-based ferroelectric thin film structure may include: a substrate 500 , wherein the substrate 500 is disposed on a side of the buffer layer 100 away from the hafnium oxide-based ferroelectric thin film 200 .

[0130] In an optional embodiment, the hafnium oxide-based ferroelectric thin film structure may include: a point electrode 400 , and the point electrode 400 is located on a side of the hafnium oxide-based ferroelectric thin film 200 away from the buffer layer 100 .

[0131] In an optional embodiment, the point electrodes 400 may be evenly distributed on the hafnium oxide-based ferroelectric thin film 200 .

[0132] In an optional embodiment, P-type silicon is used as the substrate 500. The P-type silicon can be used as both the substrate 500 and the electrode. When the P-type silicon substrate 500 is used, the bottom electrode can be omitted.

[0133] In an optional embodiment, the thickness of the point electrode 400 of the hafnium oxide-based ferroelectric thin film structure is 10-15 nm.

[0134] Figure 4 3 is a performance comparison diagram of a hafnium oxide-based ferroelectric thin film structure according to an embodiment of the present invention and a hafnium oxide-based ferroelectric thin film structure in the prior art.

[0135] like Figure 4 As shown, Figure 4 The solid line in the middle is the performance curve of the hafnium oxide-based ferroelectric thin film structure prepared by the invented method for preparing the hafnium oxide-based ferroelectric thin film structure (with P-type silicon as the substrate and an ultra-thin single-crystal mica sheet as the buffer layer 100), and the dotted line is the performance curve of the hafnium oxide-based ferroelectric thin film structure in the prior art (with only P-type silicon as the substrate and no buffer layer).

[0136] The hafnium oxide-based ferroelectric thin film 200, grown via van der Waals forces on a buffer layer 100 and prepared via a sol-gel method, exhibits excellent ferroelectric properties, with a highly rectangular PV curve. The remanent polarization of the hafnium oxide-based ferroelectric thin film on a silicon substrate is only 15 μC / cm². However, when an ultrathin single-crystal mica sheet is used as the buffer layer 100, the remanent polarization reaches 23 μC / cm², significantly enhancing the film's performance. Its coercive voltage is also significantly reduced. This demonstrates that the creation of a van der Waals heterointerface significantly enhances the ferroelectric performance of the hafnium oxide-based ferroelectric thin film.

[0137] Figure 5 The COMSOL software was used to simulate the polarization distribution of surface energy variables in hafnium oxide-based ferroelectric thin films. Following the martensitic phase transition theory, a non-ferroelectric phase field method was employed to construct a ferroelectric-non-ferroelectric coexistence model for HfO2-based ferroelectric films by introducing a non-ferroelectric phase into the ferroelectric film.

[0138] like Figure 5 As shown, Figure 5 This is a polarization distribution diagram of surface energy variables obtained through simulation of a hafnium oxide-based ferroelectric thin film structure. τ is the coefficient that correlates surface energy in density functional theory and phase field theory. When τ increases, the proportion of surface energy in the total energy increases, indicating a more pronounced surface effect. P2 represents the polarization in the out-of-plane direction of the film, and P1 represents the polarization in the in-plane direction of the film. As the proportion of surface energy in the total energy increases, the out-of-plane and in-plane polarization regions within the HfO2 grains increase.

[0139] Figure 6 This is a polarization simulation diagram of hafnium oxide-based ferroelectric thin film structures with different surface energy coefficients.

[0140] like Figure 6 As shown, Figure 6 The polarization simulation diagram of grains with different surface energy coefficients after applying AC electric field. τ is 0.1, 0.11, 0.13 and 0.14 respectively. The hysteresis loop of each grain is as follows Figure 6 As shown. The larger the surface energy coefficient, the greater the polarization value of the grain under the electric field. From the perspective of computational simulation, Figure 4 The experimental results are more consistent with that in which a van der Waals heterointerface is formed by a two-dimensional material buffer layer to increase the surface energy and promote the ferroelectric phase transition.

[0141] In yet another embodiment of the invention, a capacitor structure is provided, which may include the hafnium oxide-based ferroelectric thin film structure described in any one of the above technical solutions.

[0142] In another embodiment of the invention, an electronic device is provided, which may include the hafnium oxide-based ferroelectric thin film structure described in any one of the above technical solutions or the capacitor structure described in any one of the above technical solutions.

[0143] The present invention is intended to protect a hafnium oxide-based ferroelectric thin film structure based on van der Waals forces, a preparation method thereof, a capacitor structure, and an electronic device. The preparation method may include: providing a buffer layer 100; forming a hafnium oxide-based ferroelectric thin film 200 on the surface of the buffer layer 100 to obtain a stable hafnium oxide-based ferroelectric thin film structure. The preparation method of the hafnium oxide-based ferroelectric thin film structure of the present invention uses an ultra-thin two-dimensional material as the buffer layer. Compared with traditional silicon substrate chemical bonding, the present invention uses van der Waals forces to form a van der Waals heterointerface, rather than ordinary chemical bonds. Because the materials above and below the interface are different, ordinary chemical bonds will not be completely matched and will produce defects. The two-dimensional material (i.e., the buffer layer 100) is connected to the hafnium oxide-based ferroelectric thin film through van der Waals forces to form a van der Waals heterointerface, which maintains the free growth and crystallization of the film, while increasing the surface energy of the hafnium oxide-based ferroelectric film, promoting its transformation to the ferroelectric phase, and effectively enhancing the ferroelectric performance.

[0144] It should be understood that the above-described specific embodiments of the present invention are merely illustrative or illustrative of the principles of the present invention and do not constitute limitations of the present invention. Therefore, any modifications, equivalent substitutions, improvements, etc. made without departing from the spirit and scope of the present invention should be included within the scope of protection of the present invention. In addition, the appended claims are intended to cover all variations and modifications that fall within the scope and metes and bounds of the appended claims, or equivalents thereof.

Claims

1. A method for preparing a hafnium oxide-based ferroelectric thin film structure based on van der Waals force, characterized in that: include: providing a buffer layer (100); forming a hafnium oxide-based ferroelectric thin film (200) on the surface of the buffer layer (100) to obtain a stable hafnium oxide-based ferroelectric thin film structure; The buffer layer (100) is made of a two-dimensional material, and the buffer layer (100) is connected to the hafnium oxide-based ferroelectric film (200) through van der Waals forces to form a van der Waals heterogeneous interface, thereby increasing the surface energy of the hafnium oxide-based ferroelectric film and promoting the transformation of the internal ferroelectric phase.

2. The method for preparing a hafnium oxide-based ferroelectric thin film structure according to claim 1, wherein: Also includes: providing a substrate (500); forming the buffer layer (100) on the surface of the substrate (500); Wherein, the substrate (500) is made of a conductive material.

3. The method for preparing a hafnium oxide-based ferroelectric thin film structure according to claim 1 or 2, wherein: Providing a buffer layer (100) includes: An ultra-thin molybdenum disulfide layer is obtained by chemical vapor deposition, and the thickness of the ultra-thin molybdenum disulfide layer is 1-100 nm.

4. The method for preparing a hafnium oxide-based ferroelectric thin film structure according to claim 1 or 2, wherein: Providing a buffer layer (100) includes: Mechanically exfoliate the single crystal mica sheet to obtain an ultra-thin single crystal mica layer; The thickness of the ultra-thin single crystal mica layer is 1-100 nm.

5. The method for preparing a hafnium oxide-based ferroelectric thin film structure according to claim 1, wherein: The hafnium oxide-based ferroelectric film (200) is a zirconium-doped hafnium oxide-based ferroelectric film (200), and the molar ratio of hafnium to zirconium is 1:1; the zirconium-doped hafnium oxide-based ferroelectric film (200) is prepared by atomic layer deposition technology and has a thickness of 5-15 nm; or The hafnium oxide-based ferroelectric thin film (200) is a cerium-doped hafnium oxide-based ferroelectric thin film (200), and the molar ratio of hafnium to cerium is 1:0.15; the cerium-doped hafnium oxide-based ferroelectric thin film (200) is prepared by a sol-gel method, and has a thickness of 60-120 nm; or The hafnium oxide-based ferroelectric film (200) is an yttrium-doped hafnium oxide-based ferroelectric film (200), wherein the molar ratio of hafnium to yttrium is 1:0.05; the yttrium-doped hafnium oxide-based ferroelectric film (200) is prepared by a sol-gel method and has a thickness of 15-30 nm.

6. A hafnium oxide-based ferroelectric thin film structure, characterized in that: It is prepared by the preparation method according to any one of claims 1 to 5.

7. The hafnium oxide-based ferroelectric thin film structure according to claim 6, wherein: include: A buffer layer (100) of a two-dimensional material; A hafnium oxide-based ferroelectric film (200) is provided, wherein the hafnium oxide-based ferroelectric film (200) is covered on the buffer layer (100), and the buffer layer (100) and the hafnium oxide-based ferroelectric film (200) are connected via van der Waals forces to form a van der Waals heterogeneous interface, thereby increasing the surface energy of the hafnium oxide-based ferroelectric film and promoting the transition to a ferroelectric phase.

8. A capacitor structure, characterized in that: The invention comprises the hafnium oxide-based ferroelectric thin film structure as claimed in claim 6 or 7.

9. An electronic device, characterized in that: The invention comprises the hafnium oxide-based ferroelectric thin film structure according to any one of claims 6 to 7 or the capacitor structure according to claim 8.

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