Electrodeless constrained annealing hafnium oxide-based ferroelectric thin film, preparation method and application thereof

Abstract

This invention discloses an electrode-free constrained annealed hafnium oxide-based ferroelectric thin film, its preparation method, and its application. The method employs ALD technology to alternately deposit a predetermined number of hafnium oxide layers on a substrate. 0.5 Zr 0.5 O2 thin film and a layer of Al2O3 thin film were used to obtain Al with different doping concentrations. x -(Hf) 0.5 Zr 0.5 O2) y Ferroelectric thin films, where x represents the number of Al2O3 layers deposited using ALD, and y represents the number of Hf layers deposited using ALD. 0.5 Zr 0.5 The number of O2 layers; for the obtained Al x -(Hf) 0.5 Zr 0.5 O2) y Ferroelectric thin films are subjected to high-temperature annealing to obtain Al. x -(Hf) 0.5 Zr 0.5 O2) y Ferroelectric thin film samples; for the obtained Al x -(Hf) 0.5 Zr 0.5 O2) y A hafnium oxide-based ferroelectric thin film was obtained by depositing a top electrode and a bottom electrode onto a ferroelectric thin film sample. This invention improves the performance of annealed ferroelectric thin films without electrode constraint, deepens the understanding of the ferroelectric principle of HfO2 thin films, and promotes the development of the field of novel practical ferroelectric thin films.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field, and particularly relates to a hafnium oxide-based ferroelectric thin film subjected to electrode-free constraint annealing and a preparation method and application thereof. BACKGROUND

[0002] In this data-driven era, data storage has always been a hot topic of concern. In many high-tech fields such as high-performance computing, artificial intelligence and big data analysis, the progress of storage technology is relied on to improve system efficiency. Moreover, as the core link of information processing and preservation, the performance of the memory directly affects the efficiency of the entire system. However, the currently widely used memory has various shortcomings, such as SRAM, which is high-speed but has high power consumption / high cost, DRAM, which has large storage capacity but needs constant electrical refresh to ensure data security, and Flash, which has large storage capacity and non-volatility but has slow write speed. In the face of such a background, developing more efficient storage technology has become an important task of the scientific and technological community.

[0003] Ferroelectric memory is expected to be the key to solving this problem. Ferroelectric memory represents different storage states according to the different resistance values of the device caused by the different polarization states of the ferroelectric layer. Compared with traditional memory, ferroelectric memory has a series of advantages. First, it has non-volatility, and the retention time of its polarization state can be up to 10 5 min at room temperature. It also has very high read / write speed, and some devices can achieve a switching speed of 0.5 ns under a 5v voltage. It has low power consumption, and the current density can be reduced to 10 -6 A / cm 2 when reading data. It also has a longer write lifespan, and the optimized switching times can reach 10 11 times.

[0004] The most widely used ferroelectric material at present is the perovskite-based material, such as lead zirconate titanate, barium titanate, strontium bismuth tantalate, etc. Although they have the advantage of large remanent polarization, they also have disadvantages. For example, they have large leakage current, have larger power consumption, have large frequency band offset, have smaller bandwidth, are not compatible with CMOS process and need additional production line, have large thickness and are not conducive to integrated design. In contrast, HfO2-based ferroelectric materials have smaller leakage current, smaller frequency band offset, smaller thickness and are compatible with CMOS preparation process, and the HZO thin film doped with Zr also has higher remanent polarization and higher durability, and is expected to become the best choice for the next generation of memory materials.

[0005] However, the currently published HZO thin films all need to be annealed at a certain temperature under the condition of being plated with specific electrodes (such as TiN, W, Au, etc.) and then clamped by the electrodes to achieve a high residual polarization strength. The strong demand for specific electrodes limits the structure of the HZO thin film, such as an additional interface layer in the ferroelectric gate used to adjust the performance of two-dimensional CMOS devices, which seriously affects the performance of the device. In addition, the noble metal electrode means higher cost and additional process flow, which seriously affects the application of the HZO thin film. SUMMARY

[0006] The technical problem to be solved by the present application is to provide a hafnium oxide-based ferroelectric thin film without electrode constraint annealing and a preparation method and application thereof, to solve the technical problem that the HZO ferroelectric thin film needs to be annealed after being plated with specific electrodes.

[0007] The present application adopts the following technical solutions:

[0008] A hafnium oxide-based ferroelectric thin film without electrode constraint annealing and a preparation method thereof, comprising the following steps:

[0009] ALD technology is used to alternately deposit a set number of layers of Hf 0.5 Zr 0.5 O2 thin film and an Al2O3 thin film on a substrate to obtain Al x -(Hf 0.5 Zr 0.5 O2) y ferroelectric thin film, x represents the number of layers of Al2O3 deposited by ALD, and y represents the number of layers of Hf 0.5 Zr 0.5 O2 deposited by ALD;

[0010] The obtained Al x -(Hf 0.5 Zr 0.5 O2) y ferroelectric thin film is annealed at a high temperature to obtain an Al x -(Hf 0.5 Zr 0.5 O2) y ferroelectric thin film sample;

[0011] The obtained Al x -(Hf 0.5 Zr 0.5 O2) y ferroelectric thin film sample is plated with a top electrode and a bottom electrode to obtain a hafnium oxide-based ferroelectric thin film.

[0012] Preferably, ALD technology is used to alternately deposit a set number of layers of Hf 0.5Zr 0.5 The O2 film and one layer of Al2O3 film are specifically as follows:

[0013] Using the plasma enhanced atomic layer deposition technology, Hf 0.5 Zr 0.5 O2 films are alternately deposited on the p-type Si substrate;

[0014] Using the plasma enhanced atomic layer deposition technology, one layer of Al2O3 film is deposited on the HZO film;

[0015] The process is repeated until an Al x -(Hf 0.5 Zr 0.5 O2) y ferroelectric film is obtained.

[0016] Preferably, [(CH3)2N]4Hf (TDMAH) is used as the Hf source, [(CH3)2N]4Zr (TDMAZ) is used as the Zr source, oxygen plasma is used as the oxygen source, the growth temperature is 220-300°C, one cycle of ZrO2 and one cycle of HfO2 are alternately grown on the substrate, and the process is repeated y / 2 times to obtain a Hf 0.5 Zr 0.5 O2 film.

[0017] Preferably, (CH3)3Al (TMA) is used as the Al source, oxygen plasma is used as the oxygen source, the growth temperature is 220-300°C, one layer of Al2O3 film is grown on the Hf 0.5 Zr 0.5 O2 film, and the Al doping of the Hf 0.5 Zr 0.5 O2 film is completed.

[0018] Preferably, the concentration of the Al doping is 2.04%-5.88%.

[0019] Preferably, the high-temperature annealing conditions are specifically as follows:

[0020] In an oxygen atmosphere, the Al x -(Hf 0.5 Zr 0.5 O2) y ferroelectric film is subjected to high-temperature annealing treatment at 500-700°C for 20-40s under standard atmospheric pressure at a temperature rising rate of 40-60K / s.

[0021] Preferably, the obtained Al x -(Hf 0.5 Zr 0.5 O2) y ferroelectric film sample is plated with a top electrode and a bottom electrode, and the top electrode and the bottom electrode are specifically as follows:

[0022] Using the electrode material as the target, a bottom electrode and a dotted top electrode with a diameter of 500~700μm were grown by magnetron sputtering deposition at a temperature of 0~300℃ and an argon partial pressure of 1.0~5.0×10⁻⁶. -1 Pa, substrate rotation speed of 2~10 rpm, sputtering power of 20~50 W, sputtering time of 2~4 min.

[0023] Preferably, the thickness of the top electrode and the bottom electrode is 80–120 nm.

[0024] Another technical solution of the present invention is a hafnium oxide-based ferroelectric thin film annealed without electrode constraint.

[0025] Another technical solution of the present invention is the application of hafnium oxide-based ferroelectric thin films with electrode-free constrained annealing in resistive random access memory and ferroelectric field-effect transistors.

[0026] Compared with the prior art, the present invention has at least the following beneficial effects:

[0027] A method for preparing hafnium oxide-based ferroelectric thin films via electrode-free constrained annealing yields Al-doped HZO thin films exhibiting ferroelectric properties. Compared to existing technologies, this method employs plasma-enhanced atomic layer deposition (PEALD) to grow HZO ferroelectric and Al-doped films of varying thicknesses and numbers on a substrate. The process is simple and controllable. On one hand, the uniform Al-doped layer creates a clamping effect similar to that of electrodes, promoting the formation of the ferroelectric orthorhombic phase in the HZO ferroelectric thin film during rapid annealing. On the other hand, the relatively small Al... 3+ Replacement for Hf 4+ The Al doping caused lattice distortion in the HfO2 unit cell and promoted the formation of the ferroelectric orthorhombic phase. Under the influence of these two Al doping methods, the ferroelectricity of the HZO film was not only improved, but the coercive field was also significantly reduced, which improved the durability of the HZO ferroelectric film. This allowed the HZO film to achieve a high remanent polarization intensity without electrode constraint during annealing.

[0028] Furthermore, by employing ALD technology to alternately deposit a set number of Hf layers on the substrate 0.5 Zr 0.5 An O2 thin film and an Al2O3 thin film were used to achieve the addition of Al elements in Hf 0.5 Zr 0.5 Effective doping of O2 thin films is achieved, thereby enabling the doping process to proceed.

[0029] Furthermore, the concentration of Al doping greatly affects Al... x -(Hf 0.5 Zr 0.5 O2) y The ferroelectric properties of thin films, at low doping concentrations, Alx -(Hf 0.5 Zr 0.5 O2) y Thin films cannot achieve good ferroelectricity without electrode constraint; at high doping concentrations, Al... x -(Hf 0.5 Zr 0.5 O2) y Thin films readily exhibit antiferroelectric or paraelectric properties, thus requiring adjustment of the Al doping concentration. When the Al doping concentration is between 2.04% and 5.88%, Al... x -(Hf 0.5 Zr 0.5 O2) y Thin films readily exhibit good ferroelectric properties.

[0030] Furthermore, the annealing process of the sample was completed under electrode-free conditions, which helps to prevent the obstruction effect of electrodes during annealing. The use of an oxygen atmosphere reduces the concentration of oxygen vacancies in the sample, thereby reducing crystal defects. This prevents the built-in electric field caused by crystal defects from hindering the polarization state transition of ferroelectric domains in the ferroelectric thin film, suppressing the wake-up effect of the ferroelectric thin film. It also reduces the change in the residual polarization intensity of the ferroelectric thin film with increasing cycle number after an initial certain number of electrical cycles, which helps to increase the effective switching count of the ferroelectric thin film and improve its stability. Simultaneously, fewer defects improve the durability and lifespan of the ferroelectric thin film.

[0031] In summary, this invention utilizes Hf 0.5 Zr 0.5 By introducing a certain concentration of Al element doping into O2 thin films, Al films with excellent ferroelectric properties were prepared under electrode-free conditions. x -(Hf 0.5 Zr 0.5 O2) y This invention significantly improves the cycling characteristics of hafnium oxide-based ferroelectric thin films and reduces their dependence on specific electrode materials, thereby simplifying the fabrication process. Furthermore, it reduces the fabrication steps required for integrating hafnium oxide-based ferroelectric thin films into other devices (such as optoelectronic devices and sensors), broadening the application scope of hafnium oxide thin films. This doping strategy optimizes the ferroelectric properties of the film, which is of great significance for developing high-performance non-volatile memories and other electronic devices.

[0032] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the following description of the relative embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This is a flowchart illustrating the preparation of hafnium oxide-based ferroelectric thin films without electrode constraint annealing according to the present invention.

[0035] Figure 2 Hysteresis loop diagrams of hafnium oxide-based ferroelectric thin films provided in Examples 1 to 4 of this invention;

[0036] Figure 3 Hysteresis loop diagrams of hafnium oxide-based ferroelectric thin films provided in Examples 5 to 8 of this invention;

[0037] Figure 4 Hysteresis loop diagrams of hafnium oxide-based ferroelectric thin films provided in Examples 9 to 12 of this invention;

[0038] Figure 5 The hysteresis loop and current-voltage curve of the hafnium oxide-based ferroelectric thin film of Example 6 provided by the present invention;

[0039] Figure 6 Cyclic characteristic curves of hafnium oxide-based ferroelectric thin films provided in Example 6 of the present invention. Detailed Implementation

[0040] The technical solution of the present invention will be clearly and completely described below. 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 those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] Unless otherwise specified, all embodiments and preferred embodiments mentioned herein can be combined to form new technical solutions.

[0042] Unless otherwise specified, all the technical features and preferred features mentioned herein can be combined to form new technical solutions.

[0043] In this invention, unless otherwise specified, percentage (%) or parts refer to weight percentage or parts relative to the composition.

[0044] Unless otherwise specified, the components or preferred components involved in this invention can be combined with each other to form new technical solutions.

[0045] In this invention, unless otherwise specified, the numerical range "a~b" represents an abbreviation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "6~22" means that all real numbers between "6~22" have been listed in this document, and "6~22" is simply an abbreviation of these numerical combinations.

[0046] The "scope" disclosed in this invention can be in the form of a lower limit and an upper limit, and can be one or more lower limits and one or more upper limits, respectively.

[0047] In this invention, the term "and / or" as used herein refers to any combination of one or more of the associated listed items, as well as all possible combinations, and includes such combinations.

[0048] In this invention, unless otherwise stated, the various reactions or operation steps may be performed sequentially or in a particular order. Preferably, the reaction methods described herein are performed sequentially.

[0049] Unless otherwise stated, the technical and scientific terms used herein have the same meanings as those familiar to those skilled in the art. Furthermore, any methods or materials similar to or equivalent to those described herein may also be used in this invention.

[0050] This invention provides an electrode-free annealed hafnium oxide-based ferroelectric thin film, its preparation method, and its applications. It places no special requirements on the electrode material. Compared to other hafnium oxide-based ferroelectric thin films that require annealing with noble metal electrodes to achieve good performance, this application achieves the same result with electrode-free annealing. The lack of special electrode requirements saves on electrode material costs and electrode plating process costs. Furthermore, the electrode-free ferroelectric thin film means fewer interface effects in some applications (such as 2D CMOS). In applications, the sample proposed in this application can maintain higher performance while keeping power consumption lower, thereby saving costs.

[0051] The integration of HfO2-based ferroelectric gates not only effectively modulates the electro-, optical, and mechanical properties of two-dimensional materials but also facilitates the miniaturization of modern CMOS technology, significantly increasing transistor density. This advancement paves the way for the development of nanoelectronics. However, existing HfO2 material preparation techniques all require annealing under electrode coverage, relying on the clamping effect of the electrodes to promote the growth of the ferroelectric phase. This results in additional interface effects in the devices produced during application due to the electrode layer, affecting device performance. Furthermore, the electrodes required by existing HfO2 material preparation techniques are mostly noble metal electrodes, which also increases the material cost of the devices.

[0052] Please see Figure 1 The present invention discloses a method for preparing hafnium oxide-based ferroelectric thin films by electrode-constrained annealing, comprising the following steps:

[0053] S1, Substrate pretreatment;

[0054] S101. Clean the heavily doped p-type Si substrate with alcohol and high-purity water respectively.

[0055] The substrate is any one of silicon dioxide / silicon, silicon, germanium, sapphire, mica or gold foil.

[0056] S102. Perform ultrasonic cleaning on the pre-cleaned p-type Si substrate, use HF solution to etch the Si substrate to remove the SiO2 oxide layer on the surface of the silicon wafer, and set the cleaning time to 30s.

[0057] S103. Clean the Si substrate again with alcohol and high-purity water respectively.

[0058] S2. Using ALD technology, a certain number of Hf layers are alternately deposited on the p-type Si substrate obtained in step S1. 0.5 Zr 0.5 O2 thin film and one layer of Al2O3 thin film were used to obtain Al with different doping concentrations. x -(Hf 0.5 Zr 0.5 O2) y Ferroelectric thin films, where x represents the number of Al2O3 layers deposited using ALD, and y represents the number of Hf layers deposited using ALD. 0.5 Zr 0.5 The number of O2 layers;

[0059] S201. Using plasma-enhanced atomic layer deposition (PEALD) technology, a certain number of Hf layers are alternately deposited on a p-type Si substrate. 0.5 Zr 0.5 O2 thin film;

[0060] Using [(CH3)2N]4Hf(TDMAH) as the Hf source, [(CH3)2N]4Zr(TDMAZ) as the Zr source, and oxygen plasma as the oxygen source, the growth temperature was 220~300℃. One cycle of ZrO2 and one cycle of HfO2 were alternately grown on a p-type Si substrate. This alternating deposition was repeated y / 2 times (uniform doping) to obtain HfO2 of a predetermined thickness. 0.5 Zr 0.5 O2 thin film;

[0061] S202. A layer of Al2O3 film is deposited on the HZO film using plasma-enhanced atomic layer deposition technology.

[0062] Using (CH3)3Al(TMA) as the Al source and oxygen plasma as the oxygen source, the growth temperature was 220~300℃, in Hf 0.5 Zr 0.5A layer of Al2O3 film is grown on the O2 film to complete the Hf... 0.5 Zr 0.5 Al doping of O2 thin films.

[0063] Preferably, the concentration of Al doping is 2.04% to 5.88%.

[0064] S203. Repeat steps S201 and S202 until Al with a certain cycle ratio is generated. x -(Hf 0.5 Zr 0.5 O2) y Ferroelectric thin films.

[0065] S3. Perform high-temperature annealing on the sample obtained in step S2;

[0066] Under an oxygen atmosphere, the sample obtained from S2 was subjected to high-temperature annealing at 500-700℃ for 20-40 seconds at a heating rate of 40-60K / s under standard atmospheric pressure.

[0067] S4. The top and bottom electrodes of the sample obtained in step S3 are deposited to obtain a hafnium oxide-based ferroelectric thin film.

[0068] Using the electrode material as the target, a bottom electrode and a dotted top electrode with a diameter of 500~700μm were grown by magnetron sputtering deposition at a temperature of 0~300℃ and an argon partial pressure of 1.0~5.0×10⁻⁶. -1 Pa, substrate rotation speed of 2~10 rpm, sputtering power of 20~50 W, sputtering time of 2~4 min, and top and bottom electrode thickness of 80~120 nm.

[0069] The electrode material can be any one of the following: common metallic materials (such as Cu, Au), carbon-based materials (such as graphite, carbon nanotubes, etc.), alloy materials (such as Ni-Cr alloy, titanium alloy, etc.), or coating materials (such as platinum plating, ITO).

[0070] A hafnium oxide-based ferroelectric thin film with electrode-free constrained annealing, its preparation method, and its application are disclosed. The film is prepared by the above method and has high residual polarization intensity, no obvious wake-up effect, and high durability. At the same time, it has no special requirements for electrode materials and can be used to fabricate resistive random access memory, ferroelectric field-effect transistors, and other devices.

[0071] The present invention discloses a hafnium oxide-based ferroelectric thin film with electrode-free confinement annealing, which can be applied in resistive random access memory and ferroelectric field-effect transistor.

[0072] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0073] All examples are hafnium oxide-based ferroelectric thin films prepared by the above steps without electrode constraint annealing. The differences between the different examples are the differences in Al doping concentration and the differences in the annealing temperature of the samples in an oxygen atmosphere at a certain doping concentration.

[0074] Example 1: Al x -(Hf 0.5 Zr 0.5 O2) y The ferroelectric thin film had an Al doping concentration of 2.04%, and the sample was annealed at 400℃ in an oxygen atmosphere.

[0075] Example 2: Al x -(Hf 0.5 Zr 0.5 O2) y The ferroelectric thin film had an Al doping concentration of 2.04%, and the sample was annealed at 500℃ in an oxygen atmosphere.

[0076] Example 3: Al x -(Hf 0.5 Zr 0.5 O2) y The ferroelectric thin film had an Al doping concentration of 2.04%, and the sample was annealed at 600℃ in an oxygen atmosphere.

[0077] Example 4: Al x -(Hf 0.5 Zr 0.5 O2) y The ferroelectric thin film had an Al doping concentration of 2.04%, and the sample was annealed at 700℃ in an oxygen atmosphere.

[0078] Example 5: Al x -(Hf 0.5 Zr 0.5 O2) y The ferroelectric thin film had an Al doping concentration of 4%, and the sample was annealed at 400℃ in an oxygen atmosphere.

[0079] Example 6: Al x -(Hf 0.5 Zr 0.5 O2) y The ferroelectric thin film had an Al doping concentration of 4%, and the sample was annealed at 500℃ in an oxygen atmosphere.

[0080] Example 7: Al x -(Hf 0.5 Zr 0.5 O2) y The ferroelectric thin film had an Al doping concentration of 4%, and the sample was annealed at 600℃ in an oxygen atmosphere.

[0081] Example 8: Al x -(Hf 0.5 Zr 0.5 O2) y The ferroelectric thin film had an Al doping concentration of 4%, and the sample was annealed at 700℃ in an oxygen atmosphere.

[0082] Example 9: Al x -(Hf 0.5 Zr 0.5 O2) y The ferroelectric thin film had an Al doping concentration of 4%, and the sample was annealed at 400℃ in an oxygen atmosphere.

[0083] Example 10: Al x -(Hf 0.5 Zr 0.5 O2) y The ferroelectric thin film had an Al doping concentration of 5.88%, and the sample was annealed at 500℃ in an oxygen atmosphere.

[0084] Example 11: Al x -(Hf 0.5 Zr 0.5 O2) y The ferroelectric thin film had an Al doping concentration of 5.88%, and the sample was annealed at 600℃ in an oxygen atmosphere.

[0085] Example 12: Al x -(Hf 0.5 Zr 0.5 O2) y The ferroelectric thin film had an Al doping concentration of 5.88%, and the sample was annealed at 700℃ in an oxygen atmosphere.

[0086] Please see Figure 2 , Figure 3 and Figure 4As can be seen from the hysteresis loop diagram of the hafnium oxide-based ferroelectric thin film, the hafnium oxide-based ferroelectric thin film without electrode constraint annealing proposed in this application exhibits certain ferroelectricity within the preferred doping concentration range.

[0087] from Figure 2 It can be seen that the Al-doped HZO film with a doping concentration of 2.04% exhibits the highest remanent polarization intensity at an annealing temperature of 500℃~600℃, with its 2Pr reaching 21.4 μC / cm. 2 ;

[0088] from Figure 3 It can be seen that the Al-doped HZO film with a doping concentration of 4% exhibits the highest remanent polarization intensity at an annealing temperature of 500℃~600℃, with its 2Pr reaching 48.1 μC / cm. 2 ;

[0089] from Figure 4 It can be seen that the Al-doped HZO film with a doping concentration of 5.88% exhibits the highest remanent polarization intensity at an annealing temperature of 500℃~600℃, with its 2Pr reaching 24.5 μC / cm. 2 .

[0090] In summary, the sample with an Al doping concentration of 4% and an annealing temperature of 500℃~600℃ exhibited the highest residual polarization intensity, and its polarization intensity was not weaker than that of the sample annealed under electrode coverage conditions.

[0091] Please see Figure 5 As can be seen from the current-voltage curve of the hafnium oxide-based ferroelectric thin film, the hafnium oxide-based ferroelectric thin film of Example 6, which was annealed without electrode constraint, exhibited obvious ferroelectric characteristic peaks under the conditions of Al doping concentration of 4% and annealing at 500℃.

[0092] Please see Figure 6 As can be seen from the cyclic characteristic curve of Example 6, Example 6 does not have a significant wake-up effect at 10 8 After one cycle, the film still exhibits a temperature of 35.6 μC / cm. 2 The residual polarization intensity indicates that the hafnium oxide-based ferroelectric thin film with electrode-free confinement annealing proposed in this application has good cycling characteristics.

[0093] In summary, this invention provides an electrode-free constrained annealing method for hafnium oxide-based ferroelectric thin films, along with its preparation and applications. This method enables the uniform Al-doped layer of the sample to exhibit a clamping effect similar to that of an electrode, promoting the formation of ferroelectric orthorhombic phases in the HZO ferroelectric thin film during rapid annealing. Furthermore, the relatively small Al... 3+ Replacement for Hf 4+The Al doping process caused lattice distortion in the HfO2 unit cell and promoted the formation of the ferroelectric orthorhombic phase in the sample. Under the influence of these two Al doping methods, the ferroelectricity of the HZO film was not only enhanced, but the coercive field was also significantly reduced, improving the durability of the HZO ferroelectric film. This allowed the HZO film to achieve high remanent polarization intensity even after annealing without electrode constraint. The technology provided in this application improves the performance of ferroelectric films annealed without electrode constraint, deepens the understanding of the ferroelectric principle of HfO2 films, and promotes the development of the field of novel practical ferroelectric films.

[0094] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing hafnium oxide-based ferroelectric thin films by electrode-free constrained annealing, characterized in that, Includes the following steps: A set number of Hf layers were alternately deposited on the substrate using ALD technology. 0.5 Zr 0.5 O2 thin film and a layer of Al2O3 thin film were used to obtain Al with different doping concentrations. x -(Hf 0.5 Zr 0.5 O2) y Ferroelectric thin films with Al doping concentrations ranging from 2.04% to 5.88%, where x represents the number of Al₂O₃ layers deposited using ALD, and y represents the number of Hf layers deposited using ALD. 0.5 Zr 0.5 The number of O2 layers; Under an oxygen atmosphere and at standard atmospheric pressure, the obtained Al was heated at a rate of 40–60 K / s. x -(Hf 0.5 Zr 0.5 O2) y Ferroelectric thin films are subjected to high-temperature annealing at 500~700℃ for 20~40s to obtain Al. x -(Hf 0.5 Zr 0.5 O2) y Ferroelectric thin film samples; For the obtained Al x -(Hf 0.5 Zr 0.5 O2) y A top electrode and a bottom electrode were deposited on the ferroelectric thin film sample to obtain a hafnium oxide-based ferroelectric thin film.

2. The method for preparing hafnium oxide-based ferroelectric thin films by electrode-free constrained annealing according to claim 1, characterized in that, A set number of Hf layers were alternately deposited on the substrate using ALD technology. 0.5 Zr 0.5 The O2 thin film and the Al2O3 thin film are specifically as follows: Plasma-enhanced atomic layer deposition (PEALD) was used to alternately deposit a certain number of Hf layers on a p-type Si substrate. 0.5 Zr 0.5 O2 thin film; A single Al2O3 film was deposited on an HZO film using plasma-enhanced atomic layer deposition (PEALD). Repeat until Al with a certain cycle ratio is generated. x -(Hf 0.5 Zr 0.5 O2) y Ferroelectric thin films can be used in resistive random access memory and ferroelectric field-effect transistors.

3. The method for preparing hafnium oxide-based ferroelectric thin films by electrode-free annealing according to claim 2, characterized in that, Using [(CH3)2N]4Hf(TDMAH) as the Hf source, [(CH3)2N]4Zr(TDMAZ) as the Zr source, and oxygen plasma as the oxygen source, the growth temperature was 220~300℃. One cycle of ZrO2 and one cycle of HfO2 were alternately grown on the substrate, and this alternating deposition was repeated y / 2 times to obtain Hf of a predetermined thickness. 0.5 Zr 0.5 O2 thin film.

4. The method for preparing hafnium oxide-based ferroelectric thin films by electrode-free annealing according to claim 2, characterized in that, Using (CH3)3Al(TMA) as the Al source and oxygen plasma as the oxygen source, the growth temperature was 220~300℃, in Hf 0.5 Zr 0.5 A layer of Al2O3 film is grown on the O2 film to complete the Hf... 0.5 Zr 0.5 Al doping of O2 thin films.

5. The method for preparing hafnium oxide-based ferroelectric thin films by electrode-free confinement annealing according to claim 1, characterized in that, For the obtained Al x -(Hf 0.5 Zr 0.5 O2) y The top and bottom electrodes of the ferroelectric thin film sample are specifically as follows: Using the electrode material as the target, a bottom electrode and a dotted top electrode with a diameter of 500~700μm were grown by magnetron sputtering at a temperature of 0~300℃ and an argon partial pressure of 1.0~5.0×10⁻⁶. -1 Pa, substrate rotation speed of 2~10 rpm, sputtering power of 20~50 W, sputtering time of 2~4 min.

6. The method for preparing hafnium oxide-based ferroelectric thin films by electrode-free confinement annealing according to claim 5, characterized in that, The thickness of the top and bottom electrodes is 80–120 nm.

7. Hafnium oxide-based ferroelectric thin films prepared by the method according to any one of claims 1 to 6 without electrode constraint annealing.

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