Preparation method of samarium-doped hafnium dioxide ferroelectric thin film with high remanent polarization value

Abstract

The application belongs to the field of ferroelectric material preparation, and specifically provides a preparation method of a samarium-doped hafnium dioxide ferroelectric film with high residual polarization value. First, hafnium salt and samarium salt are used as raw materials to prepare a clear light yellow samarium-doped hafnium dioxide precursor solution, then the precursor is coated on a treated platinum substrate according to experimental requirements, and finally, the Sm-HfO2 ferroelectric film with high residual polarization value is obtained through drying, preheating and annealing treatment. The hafnium oxide-based ferroelectric film prepared by the chemical solution method can realize accurate control of the film thickness, has good film uniformity, is simple to operate, has flexible and controllable doping element content, has simple equipment requirements, is low in cost, is repeatable in process, and is easy to realize industrialized production.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of ferroelectric material preparation, and particularly relates to a preparation method of a samarium-doped hafnium dioxide ferroelectric film with a high residual polarization value. BACKGROUND

[0002] In recent years, with the rapid development of the microelectronic industry, electronic equipment has become an indispensable part of people's daily life. As a carrier of data, memory devices need to process a large amount of data in a short time, so it is urgent to manufacture a new device with smaller size, faster read-write speed and low power consumption.

[0003] As a new type of non-volatile storage device, ferroelectric memory has attracted widespread attention in the microelectronic field due to its low power consumption, fast response, repeatable read-write and high stable storage. Compared with traditional ferroelectric materials, HfO2 ferroelectric film material is highly compatible with complementary metal-oxide-semiconductor (CMOS) technology, so research and improvement of its ferroelectric properties can help promote the further development of ferroelectric memory.

[0004] Through existing research, it is shown that HfO2 mainly exists in the following three crystal phases under standard pressure: 1) at room temperature, the crystal exists in a low-temperature monoclinic phase (m phase, space group: P21 / c); 2) above 2050 K, the crystal exists in a medium-temperature tetragonal phase (t phase, space group: P42 / nmc); and 3) above 2803 K, the crystal exists in a high-temperature cubic phase (c phase, space group: ) exists.

[0005] The non-centrosymmetric orthorhombic phase (o phase) is considered to be the source of the ferroelectricity of hafnium oxide-based films, but this crystal phase is not stable at room temperature. At present, the ways to maintain the stability of the o phase mainly include doping, mechanical strain engineering, surface / interface / grain boundary energy effect and oxygen vacancy regulation. Among them, doping can induce phase transition and regulate oxygen vacancy concentration to improve the ferroelectric properties of hafnium oxide-based films.

[0006] In the prior art, there are documents on the ferroelectricity of hafnium oxide films doped with different elements. The results show that trivalent cation dopants are more conducive to the ferroelectricity of hafnium-based films than divalent cation dopants, and dopants with larger ionic radius are more conducive to the formation of orthorhombic phase of hafnium-based films than dopants with smaller ionic radius. Therefore, the doping elements in hafnium-based films with excellent ferroelectric properties are mostly lanthanide elements and large ionic radius metal elements.

[0007] Currently, there are many methods for preparing HfO2-based thin films, which can be roughly divided into atomic layer deposition (ALD), physical vapor deposition (PVD), chemical vapor deposition (CVD), chemical solution deposition (CSD), etc. The traditional sol-gel method for preparing HfO2 thin film has the disadvantages of large sol particle size, slow deposition speed, easy formation of holes and cracks during heating, poor process repeatability, low residual polarization value, etc. Chemical solution deposition (CSD) is a technology for depositing materials in a precursor solution on the surface of a substrate through a chemical reaction to form a thin film. Chemical solution deposition has the advantages of simple and easy process, strong controllability, environmental friendliness and sustainability, good thin film quality and uniformity, etc. Therefore, it is of great significance to provide a preparation method of hafnium oxide ferroelectric thin film using chemical solution deposition and its application. SUMMARY

[0008] In order to solve the above technical problems, the present application provides a preparation method of samarium-doped hafnium oxide ferroelectric thin film with high residual polarization value.

[0009] The technical scheme of the present application is as follows: a preparation method of samarium-doped hafnium oxide ferroelectric thin film with high residual polarization value, comprising the following steps:

[0010] S1: preparing a precursor solution, specifically comprising the following sub-steps:

[0011] S11: adding hafnium salt into a solvent and stirring until completely dissolved;

[0012] S12: adding samarium salt and stirring until a clear solution is obtained;

[0013] S13: avoiding light and aging to obtain a clear light yellow samarium-doped hafnium oxide precursor solution;

[0014] S2: cleaning the substrate;

[0015] S3: coating and drying treatment; specifically, the precursor solution obtained in S1 is coated on the cleaned substrate in S2, and the surface impurities are removed before coating; after each coating layer, the substrate is dried on a rubber coating machine, then the heated and dried substrate is transferred to a heating table for pyrolysis, and then the dried and pyrolyzed thin film is cooled for the next coating layer; the above steps are repeated until the desired thickness of the thin film is prepared;

[0016] S4: thin film preheating treatment: the thin film obtained in S3 is placed in an annealing furnace filled with protective gas for pre-annealing treatment, then annealing is performed, and the furnace is cooled to room temperature to prepare a samarium-doped hafnium oxide ferroelectric thin film;

[0017] S5: Electrode is plated on the samarium-doped hafnium dioxide ferroelectric thin film prepared in S4.

[0018] Further, the hafnium salt added in S11 is C 20 H 28 HfO8; the samarium salt added in S12 is Sm(NO3)3·6H2O; the molar percentage of samarium ranges from 1 to 15 mol%.

[0019] Further, the concentration of the samarium-doped hafnium dioxide precursor solution in S13 ranges from 0.1 to 0.2 mol / L, preferably from 0.1 to 0.15 mol / L.

[0020] Further, the molar percentage of samarium ranges from 1 to 5 mol%, preferably from 1.25 to 3.75 mol%, and in the precursor solution, the molar percentage is calculated based on the sum of the molar percentage of samarium and the molar percentage of hafnium being 100 mol%.

[0021] Further, the solvent in S11 is a mixed solution of acetic acid solution and acetylacetone solution, wherein the volume ratio of the acetic acid solution to the acetylacetone solution ranges from 1 to 2, and the acetylacetone solution is adjusted to a pH of 3 to 5; when the solvent is added, the acetic acid solution should be added first, and after stirring, it is observed whether the solute is dissolved in the solvent, and then the acetylacetone solution is added as a stabilizer.

[0022] Further, the substrate in S2 is a Pt(111) / TiN / SiO2 / Si(100) substrate; the surface pretreatment method of the dried substrate is ultraviolet ozone cleaning machine treatment.

[0023] Further, the substrate in S2 is cleaned by ultrasonic cleaning method, and after each ultrasonic cleaning, water is used to rinse to remove impurities and dirt on the surface of the substrate, anhydrous ethanol is used for soaking, and the substrate is dried before use; the dried substrate is then subjected to surface pretreatment; when ultrasonic cleaning is performed, water is used for ultrasonic cleaning for 4 to 6 minutes, anhydrous ethanol is used for ultrasonic cleaning for 5 to 15 minutes, water is used for ultrasonic cleaning for 4 to 6 minutes, acetone is used for ultrasonic cleaning for 5 to 15 minutes, and water is used for ultrasonic cleaning for 4 to 6 minutes.

[0024] Further, in S3, after each coating, the substrate needs to be placed on a rubber drying machine at 150 to 180 °C for 3 to 5 minutes, then the heated and dried substrate is transferred to a heating table at 300 to 400 °C for pyrolysis for 5 to 10 minutes, then the dried and pyrolyzed thin film is cooled for 3 to 5 minutes, and then the next layer of coating is performed.

[0025] Further, the coating mode in S3 is spin coating, specifically, sequentially performing low-speed spin coating and high-speed spin coating; the speed of the low-speed spin coating is 300-600 r / min, the time of the low-speed spin coating is 10-20 s; the speed of the high-speed spin coating is 3000-5000 r / min, the time of the high-speed spin coating is 25-45 s; the coating and drying treatment steps in S3 can be repeated multiple times according to the film thickness requirement, and the thickness of the single-layer samarium-doped hafnium dioxide film is controlled to be 10-20 nm.

[0026] Further, the process parameters of the annealing in S4 are as follows: heating from room temperature to 180-300 DEG C at a heating rate of 3-10 DEG C / s, then heating to 400-950 DEG C at a heating rate of 10-40 DEG C / s, keeping the temperature for 100-600 s, and then cooling to room temperature in the furnace; the gas in the furnace is one or more of oxygen, nitrogen, argon or air.

[0027] Compared with the prior art, the present application has the following advantages:

[0028] 1. The samarium-doped hafnium dioxide precursor solution is prepared by the chemical solution method, and by controlling the film thickness, the content of the doping element and the annealing process, a stable monoclinal phase, cubic phase or mixed phase samarium-doped hafnium dioxide ferroelectric film can be obtained at room temperature, and the initial intrinsic and low ferroelectric performance induced by the external electric field of the film is improved.

[0029] 2. The film thickness prepared by the method is accurately controllable, the film forming uniformity is good, the operation is simple, the content of the doping element is flexibly controllable, the concentration of the doping element can be accurately controlled, the composition of the film does not need to be quantitatively analyzed after deposition, the equipment requirement is simple, energy saving and environmental protection, the cost is low, the efficiency is high, the process repeatability is high, and the industrialized production is easy to realize.

[0030] 3. By controlling the amount of each source and the pH of the precursor solution, the coating times and the annealing process, the prepared film has a large remanent polarization value and a low coercive field.

[0031] 4. The samarium-doped hafnium dioxide film prepared by the present application is dense and uniform, and has a small leakage current.

[0032] 5. The film thickness can be controlled by adjusting the amount of solvent added in the colloid, the number of film deposition layers and the spin coating process parameters, and the operation is simple and controllable.

[0033] 6. The present application does not need advanced and expensive film coating equipment, nor does it need harsh operating environment, and the experimental operation can be completed at room temperature, the equipment and environmental requirements are simple, and the cost of the batch production equipment is low.

[0034] 7. Compared with the traditional sol-gel method for preparing HfO2 thin films, this invention can avoid the disadvantages of large sol particles, slow deposition rate, easy formation of pores and cracks when heated, and poor process repeatability. Attached Figure Description

[0035] Figure 1 The image shows the GIXRD pattern of the sample with a samarium doping concentration of 2.5 mol% in Example 1.

[0036] Figure 2 The image shows the hysteresis loop and transient current-electric field curves of the sample with a samarium doping concentration of 2.5 mol% in Example 1.

[0037] Figure 3 The image shows the leakage current of the sample with a samarium doping concentration of 2.5 mol% in Example 1.

[0038] Figure 4 The image shows the hysteresis loop and transient current-electric field curves of the sample with a samarium doping concentration of 1.25 mol% in Example 2.

[0039] Figure 5 The hysteresis loop and transient current-electric field curves of the sample with a samarium doping concentration of 3.75 mol% in Example 3 are shown. Detailed Implementation

[0040] To make the process and purpose of this invention clearer, the following description is provided in conjunction with the appendix. Figures 1-5 The present invention will be further described in more detail below with reference to specific embodiments. Example 1

[0041] A method for preparing a samarium-doped hafnium dioxide ferroelectric thin film with high remanent polarization includes the following steps: preparing a samarium-doped hafnium dioxide precursor solution with a samarium doping molar percentage of 2.5 mol%.

[0042] S1: Preparation of the precursor solution; specifically including the following sub-steps: S11: Adding hafnium salt to the solvent and stirring until completely dissolved; the added hafnium salt is C 20 H 28 HfO8; S12: Add samarium salt and stir for more than 2 hours until a clear solution is obtained; the samarium salt added is Sm(NO3)3•6H2O.

[0043] Specifically, S11 and S21 involve weighing appropriate amounts of hafnium acetylacetonate and samarium nitrate hexahydrate and dissolving them in 3 ml of acetic acid to prepare a samarium-doped hafnium dioxide precursor solution. The concentration of the hafnium dioxide precursor solution is 0.1 mol / L, in which the molar percentage of samarium doping is 2.5 mol%, i.e., the molar concentration of samarium is 0.0025 mol / L. After all the solutes have dissolved, an appropriate amount of acetylacetonate solution is added, with a volume ratio of acetic acid solution to acetylacetonate solution of 1.5. The pH value is adjusted to 4 to ensure stable solution chemistry. After obtaining a pale yellow clear solution, the solution is transferred to a magnetic stirrer at 25 °C and stirred for 2 hours until a clear solution is obtained.

[0044] S13: After obtaining a clear solution, age it in the dark for more than 72 hours to obtain a clear, light yellow samarium-doped hafnium dioxide precursor solution.

[0045] S2: Perform substrate cleaning. During the preparation process, a Pt(111) / TiN / SiO2 / Si(100) substrate is used. The surface pretreatment of the dried substrate is treated with an ultraviolet ozone cleaner for 3 minutes.

[0046] When cleaning the substrate, first use deionized water for ultrasonic cleaning for 5 minutes, then use anhydrous ethanol for ultrasonic cleaning for 10 minutes, continue to use deionized water for ultrasonic cleaning for 5 minutes, then use acetone for ultrasonic cleaning for 10 minutes, and finally use deionized water for ultrasonic cleaning for 5 minutes.

[0047] After each ultrasonic cleaning step, rinse with plenty of deionized water to remove impurities and dirt from the substrate surface to prevent stains from adhering to the substrate surface. Soak in anhydrous ethanol, dry the substrate before use, and then perform surface pretreatment on the dried substrate to increase the adsorption of the substrate surface with the precursor solution.

[0048] S3: Perform coating and drying treatment; specifically, coat the precursor solution obtained in S1 onto the substrate cleaned in S2. Before coating, use a blower to gently blow away surface impurities. After each coating layer, place the substrate on a 165°C baking machine to dry for 4 minutes, then transfer the heated and dried substrate to a 350°C heating stage for pyrolysis for 8 minutes, then cool the dried and pyrolyzed film for 4 minutes before coating the next layer; repeat the above steps until the required film thickness is obtained.

[0049] The coating process employs spin coating, sequentially performing low-speed spin coating and high-speed spin coating: [The text abruptly shifts to a different topic] ...the size is... The Pt(111) / TiN / SiO2 / Si(100) substrate was placed on a spin coater, and a precursor solution was dropped onto the substrate surface until it was fully covered. Then, it was first spin-coated at a low speed of 500 r / min for 15 s, and then at a high speed of 4000 r / min for 40 s. After that, it was placed in a baking machine and heated at 165 ℃ for 4 min and 350 ℃ for 8 min. The coating and drying steps can be repeated multiple times according to the film thickness requirements. The thickness of the single-layer samarium-doped hafnium dioxide film needs to be controlled to be 10~20 nm. In this embodiment, the above operation was repeated, and 4 layers were spin-coated to obtain a samarium-doped hafnium dioxide film with a thickness of 66 nm.

[0050] S4: Thin film preheating treatment: The thin film obtained in S3 is placed in an annealing furnace filled with protective gas for preheating treatment, followed by annealing. It is then cooled to room temperature in the furnace to prepare a samarium-doped hafnium dioxide ferroelectric thin film. The specific annealing method is as follows: The substrate with the film deposited in S3 is placed in an annealing furnace for annealing. Annealing includes a preheating process and a formal annealing process. The protective atmosphere is oxygen. The annealing process parameters are set as follows: During preheating, the temperature is first slowly heated from room temperature to 200 ℃ at a heating rate of 5 ℃ / s, held for 3 min, and then heated to 300 ℃ at a heating rate of 10 ℃ / s, held for 3 min. The process begins with formal annealing. During formal annealing, the temperature is increased to 500°C at a rate of 20°C / s and held for 5 minutes. Finally, the temperature is increased to 800°C at a rate of 40°C / s and held for 180 seconds. The furnace is then cooled to room temperature before removal. The gas inside the furnace is one or more of oxygen, nitrogen, argon, or air. In this embodiment, the gas inside the furnace is oxygen.

[0051] S5: The samarium-doped hafnium dioxide ferroelectric thin film prepared in S4 is plated with an electrode, which is an Au electrode.

[0052] The prepared samarium-doped hafnium dioxide ferroelectric thin film was integrated into a capacitor structure, and its electrical performance was tested using a ferroelectric analyzer and a semiconductor measuring instrument. The capacitor structure was a metal-Sm-HfO2 ferroelectric thin film-metal (MIM) structure. Finally, the ferroelectric performance was tested.

[0053] The sample was found to be predominantly orthorhombic, with residual polarization values ​​ranging from 12.59 to 16.26 μC / cm. 2 The coercive field ranges from 0.9 to 1.2 MV / cm. The GIXRD patterns, hysteresis loops, transient current-electric field curves, and leakage currents of the samples are shown below. Figure 1 , Figure 2 and Figure 3 As shown. Example 2

[0054] A method for preparing a samarium-doped hafnium dioxide ferroelectric thin film with high remanent polarization includes the following steps: preparing a samarium-doped hafnium dioxide precursor solution with a samarium doping molar percentage of 1.25 mol%.

[0055] S1: Preparation of the precursor solution; specifically including the following sub-steps: S11: Adding hafnium salt to the solvent and stirring until completely dissolved; the added hafnium salt is C 20 H 28 HfO8; S12: Add samarium salt and stir for more than 2 hours until a clear solution is obtained; the samarium salt added is Sm(NO3)3•6H2O.

[0056] Specifically, S11 and S21 involve weighing appropriate amounts of hafnium acetylacetonate and samarium nitrate hexahydrate and dissolving them in 3 ml of acetic acid to prepare a samarium-doped hafnium dioxide precursor solution. The concentration range of the precursor solution is 0.15 mol / L, in which the molar percentage of samarium doping is 1.25 mol%. After all the solutes have dissolved, an appropriate amount of acetylacetonate solution is added, with a volume ratio of acetic acid solution to acetylacetonate solution of 1. The pH value is adjusted to 3 to ensure stable solution chemical properties. After obtaining a pale yellow clear solution, the solution is transferred to a magnetic stirrer at 25 °C and stirred for 2 hours until a clear solution is obtained.

[0057] S13: After obtaining a clear solution, age it in the dark for more than 72 hours to obtain a clear, light yellow samarium-doped hafnium dioxide precursor solution.

[0058] S2: Perform substrate cleaning. During the preparation process, a Pt(111) / TiN / SiO2 / Si(100) substrate is used. The surface pretreatment of the dried substrate is treated with an ultraviolet ozone cleaner for 1 min.

[0059] When cleaning the substrate, first use deionized water for ultrasonic cleaning for 4 minutes, then use anhydrous ethanol for ultrasonic cleaning for 5 minutes, continue to use deionized water for ultrasonic cleaning for 4 minutes, then use acetone for ultrasonic cleaning for 5 minutes, and finally use deionized water for ultrasonic cleaning for 4 minutes.

[0060] After each ultrasonic cleaning step, rinse with plenty of deionized water to remove impurities and dirt from the substrate surface to prevent stains from adhering to the substrate surface. Soak in anhydrous ethanol, dry the substrate before use, and then perform surface pretreatment on the dried substrate to increase the adsorption of the substrate surface with the precursor solution.

[0061] S3: Perform coating and drying treatment; specifically, coat the precursor solution obtained in S1 onto the substrate cleaned in S2. Before coating, use a blower to gently blow away surface impurities. After each coating layer, place the substrate on a 150°C baking machine to dry for 3 minutes, then transfer the heated and dried substrate to a 300°C heating stage for pyrolysis for 5 minutes, then cool the dried and pyrolyzed film for 3 minutes before coating the next layer; repeat the above steps until the required film thickness is obtained.

[0062] The coating process employs spin coating, sequentially performing low-speed spin coating and high-speed spin coating: [The text abruptly shifts to a different topic] ...the size is... The Pt(111) / TiN / SiO2 / Si(100) substrate was placed on a spin coater, and a precursor solution was dropped onto the substrate surface until it was fully covered. Then, it was first spin-coated at a low speed of 300 r / min for 10 s, and then at a high speed of 3000 r / min for 25 s. After that, it was placed in a baking machine and heated at 150 ℃ for 3 min and then at 300 ℃ for 5 min. The coating and drying steps can be repeated multiple times according to the film thickness requirements. The thickness of the single-layer samarium-doped hafnium dioxide film needs to be controlled to be 10~20 nm. In this embodiment, the above operation was repeated, and 4 layers were spin-coated to obtain a samarium-doped hafnium dioxide film with a thickness of 40 nm.

[0063] S4: Thin film preheating treatment: The thin film obtained in S3 is placed in an annealing furnace filled with protective gas for preheating treatment, followed by annealing. It is then cooled to room temperature in the furnace to prepare a samarium-doped hafnium dioxide ferroelectric thin film. The specific annealing method is as follows: The substrate with the film deposited in S3 is placed in an annealing furnace for annealing. Annealing includes a preheating process and a formal annealing process. The protective atmosphere is oxygen. The annealing process parameters are set as follows: During preheating, the temperature is first slowly heated from room temperature to 180 ℃ at a heating rate of 3 ℃ / s, held for 3 min, and then heated to 300 ℃ at a heating rate of 10 ℃ / s, held for 3 min. The process begins with formal annealing. During formal annealing, the temperature is increased to 400°C at a rate of 10°C / s and held for 100s. Finally, the temperature is increased to 700°C at a rate of 30°C / s and held for 200s. The furnace is then cooled to room temperature before being removed. The gas inside the furnace is one or more of oxygen, nitrogen, argon, or air. In this embodiment, the gas inside the furnace is argon.

[0064] S5: The samarium-doped hafnium dioxide ferroelectric thin film prepared in S4 is plated with an electrode, which is an Au electrode.

[0065] A samarium-doped hafnium dioxide precursor solution with a samarium doping molar percentage of 1.25 mol% was prepared to obtain a metal-Sm:HfO2 thin film-metal (MIM) capacitor. The ferroelectric properties of the capacitor were tested using a ferroelectric analyzer and a semiconductor tester.

[0066] The sample was determined to be a mixed phase of monoclinic and orthorhombic phases, with a residual polarization range of 8.47–12.74 μC / cm. 2 The coercive field ranges from 1.0 to 1.5 MV / cm. The sample hysteresis loop and transient current-electric field curves are shown below. Figure 4 As shown. Example 3

[0067] A method for preparing a samarium-doped hafnium dioxide ferroelectric thin film with high remanent polarization includes the following steps: preparing a samarium-doped hafnium dioxide precursor solution with a samarium doping molar percentage of 3.75 mol%.

[0068] S1: Preparation of the precursor solution; specifically including the following sub-steps: S11: Adding hafnium salt to the solvent and stirring until completely dissolved; the added hafnium salt is C 20 H 28 HfO8; S12: Add samarium salt and stir for more than 2 hours until a clear solution is obtained; the samarium salt added is Sm(NO3)3•6H2O.

[0069] Specifically, S11 and S21 involve weighing appropriate amounts of hafnium acetylacetonate and samarium nitrate hexahydrate and dissolving them in 3 ml of acetic acid to prepare a samarium-doped hafnium dioxide precursor solution. The concentration range of the precursor solution is 0.2 mol / L, in which the molar percentage of samarium doping is 3.75 mol%. After all the solutes have dissolved, an appropriate amount of acetylacetonate solution is added, with a volume ratio of acetic acid solution to acetylacetonate solution of 2. The pH value is adjusted to 5 to ensure stable solution chemical properties. After obtaining a pale yellow clear solution, the solution is transferred to a magnetic stirrer at 25 °C and stirred for 2 hours until a clear solution is obtained.

[0070] S13: After obtaining a clear solution, age it in the dark for more than 72 hours to obtain a clear, light yellow samarium-doped hafnium dioxide precursor solution.

[0071] S2: Perform substrate cleaning. During the preparation process, a Pt(111) / TiN / SiO2 / Si(100) substrate is used. The surface pretreatment of the dried substrate is treated with an ultraviolet ozone cleaner for 5 minutes.

[0072] When cleaning the substrate, first use deionized water for ultrasonic cleaning for 6 minutes, then use anhydrous ethanol for ultrasonic cleaning for 15 minutes, continue to use deionized water for ultrasonic cleaning for 6 minutes, then use acetone for ultrasonic cleaning for 15 minutes, and finally use deionized water for ultrasonic cleaning for 6 minutes.

[0073] After each ultrasonic cleaning step, rinse with plenty of deionized water to remove impurities and dirt from the substrate surface to prevent stains from adhering to the substrate surface. Soak in anhydrous ethanol, dry the substrate before use, and then perform surface pretreatment on the dried substrate to increase the adsorption of the substrate surface with the precursor solution.

[0074] S3: Perform coating and drying treatment; specifically, coat the precursor solution obtained in S1 onto the substrate cleaned in S2. Before coating, use a blower to gently blow away surface impurities. After each coating layer, place the substrate on a 180°C baking machine to dry for 5 minutes, then transfer the heated and dried substrate to a 400°C heating stage for pyrolysis for 10 minutes, then cool the dried and pyrolyzed film for 5 minutes before coating the next layer. Repeat the above steps until the required film thickness is obtained.

[0075] The coating process employs spin coating, sequentially performing low-speed spin coating and high-speed spin coating: [The text abruptly shifts to a different topic] ...the size is... The Pt(111) / TiN / SiO2 / Si(100) substrate was placed on a spin coater, and a precursor solution was dropped onto the substrate surface until it was fully covered. Then, it was first spin-coated at a low speed of 600 r / min for 20 s, and then at a high speed of 5000 r / min for 45 s. After that, it was placed in a baking machine and heated at 180 ℃ for 5 min and 400 ℃ for 10 min. The coating and drying steps can be repeated multiple times according to the film thickness requirements. The thickness of the single-layer samarium-doped hafnium dioxide film needs to be controlled to be 10~20 nm. In this embodiment, the above operation was repeated, and 4 layers were spin-coated to obtain a samarium-doped hafnium dioxide film with a thickness of 80 nm.

[0076] S4: Thin film preheating treatment: The thin film obtained in S3 is placed in an annealing furnace filled with protective gas for preheating treatment, followed by annealing. It is then cooled to room temperature in the furnace to prepare a samarium-doped hafnium dioxide ferroelectric thin film. The specific annealing method is as follows: The substrate with the film deposited in S3 is placed in an annealing furnace for annealing. Annealing includes a preheating process and a formal annealing process. The protective atmosphere is oxygen. The annealing process parameters are set as follows: first, the temperature is slowly heated from room temperature to 180 ℃ at a heating rate of 4 ℃ / s, held for 3 min, and then heated to 300 ℃ at a heating rate of 15 ℃ / s, held for 3 min. The process begins with formal annealing. During formal annealing, the temperature is increased to 350°C at a rate of 15°C / s and held for 100s. Finally, the temperature is increased to 950°C at a rate of 40°C / s and held for 600s. The furnace is then cooled to room temperature before being removed. The gas inside the furnace is one or more of oxygen, nitrogen, argon, or air. In this embodiment, the gas inside the furnace is nitrogen.

[0077] S5: The samarium-doped hafnium dioxide ferroelectric thin film prepared in S4 is plated with an electrode, which is an Au electrode.

[0078] A samarium-doped hafnium dioxide precursor solution with a samarium doping molar percentage of 3.75 mol% was prepared to obtain a metal-Sm:HfO2 thin film-metal (MIM) capacitor. The ferroelectric properties of the capacitor were tested using a ferroelectric analyzer and a semiconductor tester.

[0079] The sample was determined to be a mixed phase of monoclinic and orthorhombic phases, with a residual polarization range of 9.24–13.46 μC / cm. 2 The coercive field ranges from 1.0 to 1.5 MV / cm. The sample hysteresis loop and transient current-electric field curves are shown below. Figure 5 As shown.

[0080] In the above embodiments, hafnium dioxide films with different samarium doping concentrations all exhibited ferroelectricity, with the largest and most optimal hysteresis loop window observed when the molar percentage of samarium doping was 2.5 mol%.

[0081] Although embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for preparing a samarium-doped hafnium dioxide ferroelectric thin film with high remanent polarization, characterized in that, Includes the following steps: S1: Preparation of the precursor solution; specifically including the following sub-steps: S11: Add hafnium salt to the solvent and stir until completely dissolved; The hafnium salt added in S11 is C. 20 H 28 The samarium salt added to HfO8;S12 is Sm(NO3)3•6H2O; the molar percentage of samarium ranges from 1 to 15 mol%. S12: Add samarium salt and stir until a clear solution is obtained; S13: Aging in the dark to obtain a clear, pale yellow samarium-doped hafnium dioxide precursor solution; S2: Perform substrate cleaning; S3: Perform coating and drying treatment; specifically, coat the precursor solution obtained in S1 onto the substrate cleaned in S2, removing surface impurities before coating; after each coating layer, place the substrate on a baking sheet to dry, then transfer the heated and dried substrate to a heating stage for pyrolysis, then cool the dried and pyrolyzed film before coating the next layer; repeat the above steps until the required film thickness is obtained; S4: Perform thin film preheating treatment: Place the thin film obtained in S3 in an annealing furnace filled with protective gas for preheating treatment, then perform annealing, and cool to room temperature with the furnace to prepare samarium-doped hafnium dioxide ferroelectric thin film. S5: Deposit the samarium-doped hafnium dioxide ferroelectric thin film prepared in S4 onto the electrode.

2. The method for preparing a samarium-doped hafnium dioxide ferroelectric thin film with high remanent polarization according to claim 1, characterized in that, The molar percentage of samarium ranges from 1 to 5 mol%, preferably from 1.25 to 3.75 mol%.

3. The method for preparing a samarium-doped hafnium dioxide ferroelectric thin film with high remanent polarization according to claim 1, characterized in that, The concentration range of the samarium-doped hafnium dioxide precursor solution in S13 is 0.1~0.2 mol / L, preferably 0.1~0.15 mol / L.

4. The method for preparing a samarium-doped hafnium dioxide ferroelectric thin film with high remanent polarization according to claim 1, characterized in that, The solvent in S11 is a mixture of acetic acid solution and acetylacetone solution, wherein the volume ratio of acetic acid solution to acetylacetone solution is in the range of 1~2, and the pH of acetylacetone solution is adjusted to 3~5. When adding the solvent, acetic acid solution should be added first, and after stirring, it should be observed whether the solute is dissolved in the solvent, and then acetylacetone solution should be added as a stabilizer.

5. The method for preparing a samarium-doped hafnium dioxide ferroelectric thin film with high remanent polarization according to claim 1, characterized in that, The substrate in S2 is a Pt(111) / TiN / SiO2 / Si(100) substrate; the surface pretreatment of the dried substrate is treated with an ultraviolet ozone cleaner.

6. The method for preparing a samarium-doped hafnium dioxide ferroelectric thin film with high remanent polarization according to claim 1, characterized in that, In S2, ultrasonic cleaning is used to clean the substrate. After each ultrasonic cleaning, water is used to rinse and remove impurities and dirt from the substrate surface. The substrate is then soaked in anhydrous ethanol and dried before use. The dried substrate is then subjected to surface pretreatment. During ultrasonic cleaning, the following methods are used: ultrasonic cleaning with water for 4-6 minutes, ultrasonic cleaning with anhydrous ethanol for 5-15 minutes, ultrasonic cleaning with water for 4-6 minutes, ultrasonic cleaning with acetone for 5-15 minutes, and ultrasonic cleaning with water for 4-6 minutes.

7. The method for preparing a samarium-doped hafnium dioxide ferroelectric thin film with high remanent polarization according to claim 1, characterized in that, After each layer of coating in S3, the substrate needs to be dried on a baking machine at 150~180℃ for 3~5 minutes. Then, the heated and dried substrate is transferred to a heating platform at 300℃~400℃ for pyrolysis for 5~10 minutes. After drying and pyrolysis, the film is cooled for 3~5 minutes before the next layer is coated.

8. The method for preparing a samarium-doped hafnium dioxide ferroelectric thin film with high remanent polarization according to claim 1, characterized in that, The coating method in S3 is spin coating, specifically low-speed spin coating and high-speed spin coating are performed sequentially; the low-speed spin coating speed is 300~600 r / min and the low-speed spin coating time is 10~20 s; the high-speed spin coating speed is 3000~5000 r / min and the high-speed spin coating time is 25~45 s; the coating and drying steps in S3 can be repeated multiple times according to the film thickness requirements to control the thickness of the single-layer samarium-doped hafnium dioxide film to be 10~20 nm.

9. The method for preparing a samarium-doped hafnium dioxide ferroelectric thin film with high remanent polarization according to claim 1, characterized in that, The annealing process parameters in S4 are as follows: heating from room temperature to 180-300℃ at a heating rate of 3-10℃ / s, then heating to 400-950℃ at a heating rate of 10-40℃ / s, holding at that temperature for 100-600 s, and then cooling to room temperature with the furnace; the gas inside the furnace is one or more of oxygen, nitrogen, argon, or air.

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