A flexible multi-valued hafnium oxide-based ferroelectric capacitor and a preparation method and application thereof

Abstract

This invention discloses a flexible multi-value hafnium oxide-based ferroelectric capacitor and its preparation method. It still has stable ferroelectricity under bending deformation and can realize 32 storage states. It not only meets the multi-value storage requirements of storage pool computing, but also effectively solves the problem that ferroelectric materials are difficult to maintain stability under strain in the wearable field.

Description

Technical Field

[0001] This invention belongs to the field of micro-nano electronic device technology, specifically relating to a flexible multi-value hafnium oxide-based ferroelectric capacitor, its preparation method, and its application, which can be used for multi-value analog memory cell calculations. Background Technology

[0002] The unique physical form and function of flexible electronic devices have shown great potential in fields such as flexible health monitoring devices, wearable medical devices, and biomimetic robots. Memory pool computing is an emerging computing architecture that integrates storage and computing functions, breaking down the separation of storage and processing in traditional computer architectures. Its core lies in using storage elements to directly process data, reducing data transfer between the processor and memory, thereby significantly reducing power consumption and improving computing efficiency. Therefore, memory pool computing can provide efficient computing support for flexible electronic applications.

[0003] Currently, most memory cells used in memory pool networks are based on simplified device structure models, which typically ignore complex nonlinear dynamic behaviors and their impact on information processing. In memory pool computing, ferroelectric memories can be used as computing units, performing logical operations and efficient data processing through their different polarization states. The ferroelectric size effect and environmental issues of traditional perovskite and other ferroelectric materials have become key bottlenecks restricting their widespread application and the development of semiconductor device integration. In contrast, hafnium oxide-based ferroelectric materials offer advantages such as complete CMOS compatibility, miniaturization, high speed, and low power consumption. However, it is difficult to balance ferroelectricity and stability when using hafnium oxide-based ferroelectric materials in flexible memories.

[0004] Based on the above problems, it is crucial to develop a flexible hafnium oxide-based ferroelectric memory with multi-value storage capabilities. Summary of the Invention

[0005] To address the problem of balancing ferroelectricity and stability when using hafnium oxide-based ferroelectric materials in flexible memory, this invention provides a flexible multi-valued hafnium oxide-based ferroelectric capacitor, its preparation method, and its application. It maintains stable ferroelectricity even under bending deformation and can achieve 32 storage states. This not only meets the multi-value storage requirements of memory cell computing but also effectively solves the problem of maintaining stability of ferroelectric materials under strain in wearable applications.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A flexible multi-value hafnium oxide-based ferroelectric capacitor includes: a flexible substrate, a buffer layer, a lower electrode layer, a dielectric layer, and an upper electrode layer;

[0008] The buffer layer is located on the flexible substrate;

[0009] The lower electrode layer is located above the buffer layer;

[0010] The dielectric layer is located above the lower electrode layer;

[0011] The upper electrode layer is located above the dielectric layer;

[0012] The flexible substrate is made of one of polyurethane (PU), thermoplastic polyurethane rubber (TPU), polydimethylsiloxane (PDMS), polyethylene terephthalate (PET), and polyimide (PI), and has a thickness of 50μm-100μm.

[0013] The material of the buffer layer is selected from one of silicon oxide (SiO2), aluminum oxide (Al2O3), silicon nitride (Si3N4), and boron nitride (BN), and the thickness is 100nm-150nm;

[0014] The materials of the lower electrode layer and the upper electrode layer are selected from at least one of titanium nitride (TiN), tantalum nitride (TaN), platinum (Pt), gold (Au), iridium (Ir), tungsten (W), nickel (Ni), ruthenium (Ru), and palladium (Pd), and the thickness is 30nm-50nm;

[0015] The dielectric layer is doped hafnium oxide, and the doping element is selected from one of silicon (Si), aluminum (Al), zirconium (Zr), yttrium (Y), strontium (Sr), lanthanum (La), and gadolinium (Gd); the ratio of hafnium to doping element is 0.4 to 0.8, and the thickness is 9 nm to 11 nm.

[0016] The flexible multi-value hafnium oxide-based ferroelectric capacitor described above has the following performance indicators:

[0017] The thickness of the HfZrO dielectric layer in the hafnium oxide-based ferroelectric capacitor is 10 nm, and the remanent polarization intensity (2P) is... r >55μC / cm 2 Durability exceeds 10 10 Once, the retention time exceeds 10 6 s; It has the same performance at bending radii of 0mm, 2mm, 4mm, 6mm, and 8mm, and at the limiting bending radius of 2mm, 10 5 It maintains stable performance after several bending and stretching cycles.

[0018] Furthermore, the flexible substrate is selected from PI substrates and has a thickness of 50 μm.

[0019] Furthermore, the material of the buffer layer is selected from Al2O3 thin film with a thickness of 140nm.

[0020] Furthermore, both the lower and upper electrode layers are W thin films with a thickness of 40 nm.

[0021] Furthermore, the dielectric layer is an HfZrO thin film with a hafnium element to dopant ratio of 0.5 and a thickness of 10 nm.

[0022] This invention also relates to a method for preparing a flexible multi-valued hafnium oxide-based ferroelectric capacitor, comprising the following steps:

[0023] (1) Clean the flexible substrate by ultrasonic cleaning with acetone, anhydrous ethanol and deionized water in sequence and then blow-drying it to remove impurities and oxides from the substrate.

[0024] (2) A buffer layer was deposited on a flexible substrate by magnetron sputtering with a power of 100W-140W and an argon flow rate of 12sccm-20sccm during the growth process.

[0025] (3) Using magnetron sputtering, radio frequency sputtering process is adopted, the power during the growth process is 100W-140W, the argon flow rate is 12sccm-20sccm, and the lower electrode layer is grown on the basis of the structure in step (2).

[0026] (4) Atomic layer deposition is used for cyclic processing using the following process: tetra(methylethylamino)hafnium is heated to 70℃-80℃, pulsed for 300ms, purged with nitrogen for 4s, pulsed with deionized water for 150ms, purged with nitrogen for 4s, and tetra(methylethylamino)zirconium is heated to 70℃-80℃, pulsed for 300ms, purged with nitrogen for 4s, pulsed with deionized water for 150ms, and purged with nitrogen for 4s. The processing temperature of the atomic layer deposition is 260℃-280℃.

[0027] A ferroelectric dielectric layer is grown on the basis of the structure in step (3), and oxide films are deposited in a cycle until the dielectric layer thickness reaches the preset thickness.

[0028] (5) Based on the structure of (4) above, perform homogenization, photolithography, development and patterning to form the pattern of the upper electrode: coat the dielectric layer with negative adhesive, bake at 95°C and expose, bake at 110°C after exposure, expose and soak in developer for 60s, rinse with deionized water and blow dry.

[0029] (6) Using magnetron sputtering, radio frequency sputtering process is adopted, the power during the growth process is 100W-140W, the argon flow rate is 12sccm-20sccm, and the upper electrode layer is grown on the basis of the structure in step (5).

[0030] (7) Rapid thermal annealing under nitrogen protection yields a flexible multi-value hafnium oxide-based ferroelectric capacitor, which has the following performance indicators:

[0031] The thickness of the HfZrO dielectric layer in the hafnium oxide-based ferroelectric capacitor is 10 nm, and the remanent polarization intensity (2P) is... r >55μC / cm 2 Durability exceeds 10 10 Once, the retention time exceeds 10 6 s; It has the same performance at bending radii of 0mm, 2mm, 4mm, 6mm, and 8mm, and at the limiting bending radius of 2mm, 10 5 It maintains stable performance after several bending and stretching cycles.

[0032] Furthermore, the photoresist mentioned in step (5) can also be positive photoresist, but the corresponding process parameters need to be adjusted.

[0033] Furthermore, the annealing temperature in step (7) is 400℃-450℃, and the annealing time is 30s.

[0034] This invention also relates to the application of the aforementioned flexible multi-valued hafnium oxide-based ferroelectric capacitor. The flexible multi-valued hafnium oxide-based ferroelectric capacitor serves as a storage unit, and a storage pool computing implementation scheme is designed. This scheme primarily involves inputting five different pulse sequences, which are processed by the flexible multi-valued hafnium oxide-based ferroelectric capacitor into corresponding current output signals. Utilizing the dynamic characteristics of the multi-valued capacitor, multi-state storage and parallel computing functions are achieved, effectively realizing the hidden layer of a traditional recurrent neural network. This provides a hardware solution for constructing a storage pool computing system capable of real-time processing of complex time-series tasks.

[0035] Compared with the prior art, the present invention has the following advantages:

[0036] 1. The flexible multi-valued hafnium oxide-based ferroelectric capacitor of the present invention exhibits a large remanent polarization value (2Pr>55μC / cm) at a relatively low voltage. 2 It exhibits consistent ferroelectricity in a flat state and under different bending radii.

[0037] 2. The flexible multi-valued hafnium oxide-based ferroelectric capacitor of this invention generates multiple ferroelectric domain intermediate states by controlling the amplitude of an applied pulse. A 5-bit binary pulse sequence testing scheme is used, and each state produces a different current output. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the basic structure of the flexible multi-valued hafnium oxide-based ferroelectric capacitor described in Embodiment 1 of the present invention;

[0039] Figure 2 This is a schematic diagram of the preparation method of the flexible multi-valued hafnium oxide-based ferroelectric capacitor according to Embodiment 2 of the present invention;

[0040] Figure 3This is a schematic diagram of the polarization hysteresis curves of the flexible multi-value hafnium oxide-based ferroelectric capacitor described in this invention under flat and bent states.

[0041] Figure 4 This is a schematic diagram of the storage cell characteristic test results of the flexible multi-value hafnium oxide-based ferroelectric capacitor described in this invention. Detailed Implementation

[0042] The present invention will be further described in detail below through embodiments, but these embodiments should not be considered as limiting the present invention.

[0043] Example 1:

[0044] A flexible multi-valued hafnium oxide-based ferroelectric capacitor, such as Figure 1 As shown, it includes:

[0045] Flexible substrate 1;

[0046] Buffer layer 2 is located above the flexible substrate;

[0047] Lower electrode layer 3 is located above the buffer layer;

[0048] Dielectric layer 4 is located above the lower electrode layer;

[0049] Upper electrode layer 5 is located above the dielectric layer;

[0050] The flexible substrate is made of one of the following materials: PU, TPU, PDMS, PET, and PI.

[0051] To further optimize the above technical solution, the flexible substrate 1 is a PI substrate with a thickness of 50 μm;

[0052] The material of the buffer layer is selected from one of SiO2, Al2O3, Si3N4, and BN;

[0053] Buffer layer 2 is an Al2O3 thin film with a thickness of 140 nm;

[0054] The electrode layer material is at least one of TiN, TaN, Pt, Au, Ir, W, Ni, Ru, and Pd;

[0055] Both the lower electrode layer 3 and the upper electrode layer 5 are W thin films with a thickness of 40 nm;

[0056] The ferroelectric dielectric layer is doped hafnium oxide, and the doping element is one of Si, Al, Zr, Y, Sr, La, and Gd;

[0057] The dielectric layer 4 is an HfZrO thin film with a hafnium element to dopant ratio of 0.5 and a thickness of 10 nm.

[0058] Example 2:

[0059] A method for preparing a flexible multi-valued hafnium oxide-based ferroelectric capacitor includes the following steps:

[0060] The fabrication process of the flexible multi-valued hafnium oxide-based ferroelectric capacitor in this embodiment will be described in detail below, such as... Figure 2 The above includes:

[0061] Step (1) Clean the PI flexible substrate 1 by ultrasonic cleaning with acetone, anhydrous ethanol and deionized water in sequence and then blowing it dry to remove impurities and oxides on the substrate.

[0062] Step (2) Using magnetron sputtering, Al2O3 is deposited on a flexible substrate as a buffer layer. The radio frequency sputtering process is used, with a power of 100W-140W and an argon flow rate of 12sccm-20sccm during the growth process.

[0063] Step (3) Using magnetron sputtering, the W electrode layer is grown on the basis of the structure in step (2). The radio frequency sputtering process is used, and the power during the growth process is 100W-140W and the argon flow rate is 12sccm-20sccm.

[0064] Step (4) uses atomic layer deposition (ALD) technology to grow an HfZrO dielectric layer on the structure of step (3). The ALD process is carried out in a cycle as follows: tetra(methylethylamino)hafnium is heated to 70℃-80℃, pulsed for 300ms, purged with nitrogen for 4s, pulsed with deionized water for 150ms, and purged with nitrogen for 4s; tetra(methylethylamino)zirconium is heated to 70℃-80℃, pulsed for 300ms, purged with nitrogen for 4s, pulsed with deionized water for 150ms, and purged with nitrogen for 4s. The ALD process temperature is 260℃-280℃. One layer of HfO2 is deposited in sequence, followed by one layer of ZrO2, and the deposition is repeated until the last ZrO2 layer is capped. The molar ratio of Hf to Zr is close to 1:1, which can achieve the maximum residual polarization intensity.

[0065] Step (5) Based on the structure of (4) above, perform homogenization, photolithography, development and patterning to form the pattern of the upper electrode. Specifically, the negative photoresist is coated on the dielectric layer, pre-baked at 95°C and then exposed, and then post-baked at 110°C. After general exposure, it is soaked in the developer for 60 seconds, rinsed with deionized water and dried. Alternatively, the photoresist can also be positive photoresist, but the corresponding process parameters need to be adjusted.

[0066] Step (6) uses magnetron sputtering to grow an electrode layer on the structure of step (5). The radio frequency sputtering process is used, with a power of 100W-140W and an argon flow rate of 12sccm-20sccm.

[0067] Step (7) Perform rapid thermal annealing under nitrogen protection at a temperature of 400℃-450℃ for 30s to obtain the capacitor.

[0068] In this example, the stress effect of the electrode is generally considered to be one of the necessary conditions for inducing the ferroelectric orthorhombic phase. Choosing an electrode material with a low coefficient of thermal expansion, and generating strong tensile stress during annealing, is beneficial for the formation of the ferroelectric phase. Compared to TiN, the most commonly used electrode material for hafnium-based ferroelectric thin films (with a coefficient of thermal expansion of approximately 9.4 × 10⁻⁶), this material offers advantages. -6 W has a smaller coefficient of thermal expansion (approximately 4.5 × 10⁻⁶ °C). -6 The increased tensile stress (°C) helps induce the formation of ferroelectric orthorhombic phases in the HfZrO thin film, thereby improving the ferroelectricity of the capacitor. Secondly, the increased tensile stress lowers the required annealing temperature, thus reducing the likelihood of cracking due to thermal effects on the flexible substrate. Furthermore, the thermal budget constraints of CMOS back-end processes are typically around 400°C, lower than the optimal annealing temperature for existing hafnium oxide-based ferroelectric capacitors. Therefore, the ferroelectric capacitor of this invention maintains good ferroelectricity even at 400°C, effectively improving the process compatibility of hafnium oxide-based ferroelectric capacitors during large-scale integration.

[0069] Example 3:

[0070] The electrical performance of the flexible multi-valued hafnium oxide-based ferroelectric capacitor of Example 2 is verified below.

[0071] A voltage excitation was applied to a flexible multi-value hafnium oxide-based ferroelectric capacitor in a flat state, and the polarization hysteresis curve was measured. Then, the capacitor was placed on a mold with different bending radii, and a voltage excitation was applied to the flexible multi-value hafnium oxide-based ferroelectric capacitor in a bent state, and the polarization hysteresis curve was measured.

[0072] like Figure 3 The figure shows the polarization hysteresis curves of the ferroelectric material tested under different curvatures, reflecting the relationship between polarization intensity and electric field strength. This demonstrates that the flexible multi-valued hafnium oxide-based ferroelectric capacitor of Example 2 exhibits a large remanent polarization value (2Pr > 55 μC / cm) at lower voltages. 2 On the other hand, it shows that the ferroelectricity of the flexible multi-valued hafnium oxide-based ferroelectric capacitor in Example 2 is basically the same in the flat state and the bending state under different bending radii, that is, the flexible multi-valued hafnium oxide-based ferroelectric capacitor can remain stable after bending.

[0073] Example 4:

[0074] The following verifies the multi-value storage characteristics of the flexible multi-value hafnium oxide-based ferroelectric capacitor of Example 2.

[0075] The memory pool in a neural network has the ability to remember and transform time-series data, a characteristic that enables it to effectively capture and process dynamically changing information. Current research on implementing memory pool networks using devices is mostly based on simplified structural models. These models typically ignore complex nonlinear dynamic behaviors and their impact on information processing. Therefore, applying multi-state memory cells to multi-valued analog memory pool computing systems can achieve flexible and efficient processing of complex time-series information.

[0076] The multi-value storage characteristics of the flexible multi-value hafnium oxide-based ferroelectric capacitor in this embodiment are tested using a 5-bit binary pulse sequence test scheme, represented by "00000" to "11111". "0" represents no pulse at that bit; "1" represents a pulse applied to that bit. There are 32 possible variations in the 5-bit sequence, and the pulse uses a triangular wave with a voltage of -1.05V and a width of 10μs.

[0077] Figure 4 The output current of the flexible multi-valued hafnium oxide-based ferroelectric capacitor is clearly shown to change with the pulse sequence. The 32 states are distributed differently in the output current range of 130μA-1030μA, indicating that the flexible multi-valued hafnium oxide-based ferroelectric capacitor of this embodiment has successfully realized the function of the memory cell unit, has the ability to process 5-bit pulse sequences, and has great potential for application in multi-valued analog memory cell calculation.

[0078] Example 5:

[0079] The following describes the implementation scheme of memory pool computing using the flexible multi-valued hafnium oxide-based ferroelectric capacitor from Example 2 as a storage unit. It mainly involves inputting 5 different pulse sequences, which are processed by the flexible multi-valued hafnium oxide-based ferroelectric capacitor into corresponding current output signals. The dynamic characteristics of the multi-valued capacitor are used to realize multi-state storage and parallel computing functions, which is equivalent to realizing the hidden layer of a traditional recurrent neural network. This provides a hardware solution for building a memory pool computing system that can process complex time-series tasks in real time.

[0080] Comparative Example 1:

[0081] Both Comparative Example 1 and Example 1 use HfZrO as the ferroelectric layer. The difference is that the substrate of Comparative Example 1 is a silicon wafer; the electrode material is TiN; the Al2O3 thin film layer is located between the ferroelectric layer and the top electrode layer; and the annealing temperature is 650°C.

[0082] A hafnium oxide-based ferroelectric capacitor and its preparation method are described below:

[0083] Step (1) Clean the silicon wafer substrate to remove impurities and oxide layers from the substrate;

[0084] Step (2) The cleaned silicon wafer substrate is subjected to surface magnetron sputtering to deposit a TiN bottom electrode layer with a thickness of 30nm; the magnetron sputtering power is 250W, and the magnetron sputtering process uses argon and nitrogen gas with a reaction atmosphere of 50sccm:4sccm.

[0085] Step (3) Ozone treatment is performed on the surface of the TiN bottom electrode layer to oxidize the shallow surface part of the metal TiN electrode layer to form a TiON layer; the ozone treatment time is 30s to 60s, the ozone treatment temperature is 250℃, the ozone is turned off after the reaction is completed, and the surface of the silicon wafer substrate is purged with N2 for 50s.

[0086] Step (4): Atomic layer deposition is performed on the surface of the TiON layer to grow a HfZrO layer with a thickness of 15 nm; wherein the atomic layer deposition process is performed in a cycle using the following process: tetratetra(methylethylamino)hafnium pulse treatment for 1.5 s, N2 purging for 3 s, ozone pulse for 2 s, N2 purging for 2 s, tetratetra(methylethylamino)zirconium pulse treatment for 1.5 s, N2 purging for 3 s, ozone pulse for 2 s, N2 purging for 2 s; the temperature of the atomic layer deposition process is 250 °C.

[0087] Step (5): Atomic layer deposition is performed on the surface of the HfZrO layer to deposit an Al2O3 thin film layer with a thickness of 1 nm; wherein the atomic layer deposition process is performed by the following cycle process: trimethylaluminum pulse treatment for 0.4 s, N2 purging for 3 s, H2O pulse treatment for 0.3 s, N2 purging for 2 s; the temperature of the atomic layer deposition process is 250 °C.

[0088] Step (6) involves homogenizing the Al2O3 thin film surface, performing photolithography and development to form a photoresist pattern for the top electrode array;

[0089] Step (7) Then, magnetron sputtering is performed to deposit TiN with a thickness of 30 nm, and then a stripping process is performed to obtain a TiN top electrode layer with an array pattern.

[0090] Step (8) Annealing is performed under nitrogen protection to obtain the capacitor; wherein the annealing temperature is 650℃ and the annealing time is 30s;

[0091] Step (9) Apply an electric field between the upper and lower electrodes of the capacitor for 10 cycles. 7 This yielded a high-performance hafnium oxide-based ferroelectric capacitor.

[0092] The remanent polarization intensity (2P) of the hafnium oxide-based ferroelectric capacitor obtained in Comparative Example 1 was measured. r ) is 30μC / cm 2 -40μC / cm 2Durability is 10 8 Next -10 10 Second-rate.

[0093] Comparative Example 2:

[0094] Both Comparative Example 2 and Example 1 used HfZrO as the ferroelectric layer. The difference was that Comparative Example 2 used a silicon wafer as the substrate; a thin ZrO2 seed layer was grown before the ferroelectric layer was deposited; the Al2O3 thin film layer was located between the ferroelectric layer and the top electrode layer; and the annealing step was performed before the top electrode was deposited.

[0095] A hafnium oxide-based ferroelectric capacitor and its preparation method are described below:

[0096] Step (1) Use magnetron sputtering technology to grow a 30nm-50nm metal W as the bottom electrode on a Si / SiO2 substrate. During the growth process, the Ar gas flow rate is 50sccm and the sputtering power is 150W.

[0097] Step (2): A 1nm-2nm ZrO2 seed layer is grown using atomic layer deposition at a growth temperature of 250℃-280℃. Each cycle of the atomic layer deposition process includes a 0.2s tetrakis(dimethylaminozirconium)TDMAZr pulse, a 2s N2 purge, a 0.2s oxygen plasma pulse, and a 2s N2 purge.

[0098] Step (3) Use atomic layer deposition to grow 10nm-20nm hafnium oxide ferroelectric thin films. The growth process temperature is 250℃-280℃. Each cycle of the atomic layer deposition process includes a 0.2s tetradimethylaminozirconium or tetradimethylaminohafnium TDMAZr / TDMAHf pulse, a 2s N2 purge, a 0.2s oxygen plasma pulse, and a 2s N2 purge.

[0099] Step (4) Use atomic layer deposition to grow 1nm-2nm Al2O3 thin film. The growth process temperature is 250℃-300℃. Each cycle of the atomic layer deposition process includes a 0.2s trimethylaluminum TMA pulse, a 2s N2 purge, a 0.2s deionized water pulse, and a 2s N2 purge.

[0100] Step (5) The wafer is subjected to rapid thermal annealing in a nitrogen atmosphere. The heating rate is 15℃ / s-20℃ / s, the annealing temperature is 330℃-450℃, and the annealing time is 60s-300s.

[0101] In step (6), the device electrode region is defined by ultraviolet lithography; the top electrode is grown with 10nm-15nm Ti / 40nm-50nm Au by electron beam evaporation technology, wherein the deposition rate of Ti is 0.16nm / s and the deposition rate of Au is 0.2nm / s; the wafer in step (6) is stripped by a stripping process: first, the wafer is immersed in acetone and left to stand until the top electrode structure is clear, then isopropanol is used to remove the residual acetone and other organic matter on the wafer surface, and finally deionized water is used to clean and nitrogen is used to dry.

[0102] The remanent polarization (Pr) of the hafnium oxide-based ferroelectric capacitor obtained in Comparative Example 2 was measured to be 20 μC / cm. 2 -25μC / cm 2 Durability is 10 8 Next -10 9 Second-rate.

[0103] Comparative Example 3:

[0104] Both Comparative Example 3 and Example 1 use PI as a flexible substrate and HfZrO as a ferroelectric layer. The difference is that the bottom electrode and top electrode of Comparative Example 3 are sputtered with TiN using ion beam sputtering.

[0105] A flexible ferroelectric capacitor and its manufacturing method are described below:

[0106] Step (1): Clean the polyimide (PI) substrate. The substrate is sequentially immersed in acetone and anhydrous ethanol for cleaning, then dried, and then rinsed with deionized water, followed by drying. For example, a substrate with a thickness of 500 μm is cleaned using this method.

[0107] Step (2) On the substrate, an Al2O3 functional layer was prepared using the ALD process. The Al precursor and deionized water were maintained at room temperature (20°C), with N2 as the carrier gas at a flow rate of 100 sccm. The functional layer was prepared on the substrate using trimethylaluminum (TMA) as the Al precursor, deionized water as the oxygen source, a reaction chamber pressure of less than 2 mbar, and a deposition temperature of 200°C. The functional layer 102 was prepared on the substrate with a thickness of 100 nm.

[0108] Step (3) The TiN lower electrode layer was prepared by sputtering using ion beam sputtering. A TiN target was used, the beam voltage was 800V, the beam current was 46mA, the accelerating voltage was 160V, the gas was an Ar / N2 mixed gas, and the flow rates were 8sccm / 5sccm. The thickness of the prepared TiN lower electrode layer was 40nm.

[0109] Step (4) Deposit a dielectric layer on the lower electrode layer using the ALD process. Specifically, first select a hafnium (Hf) precursor, a zirconium (Zr) precursor, and an oxygen source. Then heat the Hf and Zr precursors to 100℃-140℃, keep the deionized water (as the oxygen source) at room temperature of 20℃, select N2 as the carrier gas with a flow rate of 40 sccm-80 sccm, and set the deposition temperature to 280℃-300℃ to deposit a zirconium-doped hafnium oxide (HfZrO) dielectric layer on the lower electrode layer. During the deposition process, sequentially deposit one ZrO2 film, then one HfO2 film, until the last layer is deposited. The last layer is capped with a ZrO2 film to form the dielectric layer.

[0110] Step (5) Coat the photoresist onto the dielectric layer and expose and develop it. Specifically, coat the negative photoresist onto the dielectric layer, preheat it to 150°C for 3 minutes; after exposure, preheat it to 120°C for 3 minutes, immerse it in the developer for 45 seconds, and then rinse it with deionized water and dry the dielectric layer.

[0111] Step (6) A TiN top electrode layer is prepared by sputtering on the dielectric layer using an ion beam sputtering process. A TiN target is used, the beam voltage is 800V, the beam current is 46mA, the accelerating voltage is 160V, the gas is an Ar / N2 mixed gas, and the flow rates are 8sccm / 5sccm respectively. The thickness of the prepared TiN top electrode layer is 40nm.

[0112] Step (7) involves removing photoresist and excess metal from the prepared flexible ferroelectric capacitor. The device is immersed in acetone solution until the photoresist and excess metal detach. Next, the device is immersed in anhydrous ethanol to remove the acetone. Then, it is rinsed with deionized water and dried. Finally, the rinsed and dried device is annealed for 60 seconds under a N2 atmosphere at 430°C to obtain the flexible ferroelectric capacitor.

[0113] The remanent polarization intensity (P) of the flexible ferroelectric capacitor obtained in Comparative Example 3 was tested. r ) is 20μC / cm 2 -25μC / cm 2 .

[0114] Results and Discussion:

[0115] 1. By comparing Comparative Example 1 with Example 1, it is shown that the flexible multi-value hafnium oxide-based ferroelectric capacitor of the present invention has a lower annealing temperature, which can effectively improve the process compatibility of hafnium oxide-based ferroelectric capacitors in large-scale integration.

[0116] 2. By comparing Comparative Example 2 with Example 1, it is shown that the preparation method of the flexible multi-valued hafnium oxide-based ferroelectric capacitor of the present invention is simpler and has better ferroelectric properties (2P). r >55μC / cm2 ), with stronger tolerance (>10) 10 Second-rate).

[0117] 3. By comparing Comparative Example 3 with Example 1, it is shown that the present invention uses electrode metal W with smaller thermal expansion, which helps to induce the generation of ferroelectric orthorhombic phase in ferroelectric thin film, thereby improving the ferroelectricity of capacitor.

[0118] The above comparative examples do not cover the multi-value storage capability and applications of capacitors. This demonstrates that the flexible multi-value hafnium oxide-based ferroelectric capacitor of the present invention has broad application prospects in wearable devices and neural network computing.

[0119] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. Various process solutions that are not substantially different from the concept of the present invention are all within the scope of protection of the present invention.

Claims

1. A flexible multi-valued hafnium oxide-based ferroelectric capacitor, characterized in that: include: Flexible substrate, buffer layer, lower electrode layer, dielectric layer and upper electrode layer; The buffer layer is located on the flexible substrate; The lower electrode layer is located above the buffer layer; The dielectric layer is located above the lower electrode layer; The upper electrode layer is located above the dielectric layer; The flexible substrate is made of one of polyurethane, thermoplastic polyurethane rubber, polydimethylsiloxane, polyethylene terephthalate, and polyimide, and has a thickness of 50μm-100μm. The material of the buffer layer is selected from one of silicon oxide, aluminum oxide, silicon nitride, and boron nitride, and the thickness is 100nm-150nm; The materials of the lower electrode layer and the upper electrode layer are selected from at least one of titanium nitride, tantalum nitride, platinum, gold, iridium, tungsten, nickel, ruthenium, and palladium, and the thickness is 30nm-50nm; The dielectric layer is doped hafnium oxide, and the doping element is selected from one of silicon, aluminum, zirconium, yttrium, strontium, lanthanum, and gadolinium; the ratio of hafnium to the doping element is 0.4 to 0.8, and the thickness is 9nm-11nm. The flexible multi-value hafnium oxide-based ferroelectric capacitor described above has the following performance indicators: The thickness of the HfZrO dielectric layer in the hafnium oxide-based ferroelectric capacitor is 10 nm, and the remanent polarization intensity (2P) is... r >55μC / cm 2 Durability exceeds 10 10 Once, the retention time exceeds 10 6 s; It has the same performance at bending radii of 0mm, 2mm, 4mm, 6mm, and 8mm, and at the limiting bending radius of 2mm, 10 5 It maintains stable performance after several bending and stretching cycles.

2. The flexible multi-valued hafnium oxide-based ferroelectric capacitor according to claim 1, characterized in that: The flexible substrate is selected from PI substrates and has a thickness of 50 μm.

3. The flexible multi-valued hafnium oxide-based ferroelectric capacitor according to claim 1, characterized in that: The material of the buffer layer is selected from Al2O3 thin film with a thickness of 140nm.

4. A flexible multi-valued hafnium oxide-based ferroelectric capacitor according to claim 1, characterized in that: Both the lower electrode layer and the upper electrode layer are W thin films with a thickness of 40 nm.

5. A flexible multi-valued hafnium oxide-based ferroelectric capacitor according to claim 1, characterized in that: The dielectric layer is an HfZrO thin film with a hafnium-to-doped element ratio of 0.5 and a thickness of 10 nm.

6. The method for preparing a flexible multi-valued hafnium oxide-based ferroelectric capacitor according to claim 1, characterized in that: Includes the following steps: (1) Clean the flexible substrate by ultrasonic cleaning with acetone, anhydrous ethanol and deionized water in sequence and then blow-drying it to remove impurities and oxides from the substrate. (2) A buffer layer was deposited on a flexible substrate by magnetron sputtering with a power of 100W-140W and an argon flow rate of 12sccm-20sccm during the growth process. (3) Using magnetron sputtering, radio frequency sputtering process is adopted. The power during the growth process is 100W-140W and the argon flow rate is 12sccm-20sccm. The lower electrode layer is grown on the basis of the structure in step (2). (4) Atomic layer deposition is used for cyclic processing using the following process: tetra(methylethylamino)hafnium is heated to 70℃-80℃, pulsed for 300ms, purged with nitrogen for 4s, pulsed with deionized water for 150ms, purged with nitrogen for 4s, and tetra(methylethylamino)zirconium is heated to 70℃-80℃, pulsed for 300ms, purged with nitrogen for 4s, pulsed with deionized water for 150ms, and purged with nitrogen for 4s. The processing temperature of the atomic layer deposition is 260℃-280℃. A ferroelectric dielectric layer is grown on the basis of the structure in step (3), and oxide films are deposited in a cycle until the dielectric layer thickness reaches the preset thickness. (5) Based on the structure of (4) above, perform homogenization, photolithography, development and patterning to form the pattern of the upper electrode: coat the dielectric layer with negative adhesive, bake at 95°C and expose, bake at 110°C after exposure, expose and soak in developer for 60s, rinse with deionized water and blow dry. (6) Using magnetron sputtering, radio frequency sputtering process is adopted, the power during the growth process is 100W-140W, the argon flow rate is 12sccm-20sccm, and the upper electrode layer is grown on the basis of the structure in step (5). (7) Rapid thermal annealing under nitrogen protection yields a flexible multi-value hafnium oxide-based ferroelectric capacitor; the flexible multi-value hafnium oxide-based ferroelectric capacitor has the following performance indicators: The thickness of the HfZrO dielectric layer in the hafnium oxide-based ferroelectric capacitor is 10 nm, and the remanent polarization intensity (2P) is... r >55μC / cm 2 Durability exceeds 10 10 Once, the retention time exceeds 10 6 s; It has the same performance at bending radii of 0mm, 2mm, 4mm, 6mm, and 8mm, and at the limiting bending radius of 2mm, 10 5 It maintains stable performance after several bending and stretching cycles.

7. The method for preparing a flexible multi-valued hafnium oxide-based ferroelectric capacitor according to claim 6, characterized in that: The annealing temperature in step (7) is 400℃-450℃, and the annealing time is 30s.

8. The application of a flexible multi-valued hafnium oxide-based ferroelectric capacitor according to claim 1, characterized in that: The flexible multi-valued hafnium oxide-based ferroelectric capacitor is used as a storage unit to design a storage pool computing implementation scheme. By inputting 5 different pulse sequences, the flexible multi-valued hafnium oxide-based ferroelectric capacitor processes them into corresponding current output signals. The dynamic characteristics of the multi-valued capacitor are used to realize multi-state storage and parallel computing functions, which is equivalent to realizing the hidden layer of a traditional recurrent neural network. This serves as a hardware scheme for building a storage pool computing system that can process complex time-series tasks in real time.

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