Flexible multi-valued hafnium oxide-based ferroelectric capacitor and preparation method and application thereof

Abstract

The invention discloses a flexible multi-valued hafnium oxide-based ferroelectric capacitor and a preparation method thereof, the flexible multi-valued hafnium oxide-based ferroelectric capacitor still has stable ferroelectricity in a bending deformation state, can realize 32 storage states, not only meets the requirement of storage pool calculation for multi-valued storage, but also effectively solves the problem that a ferroelectric material is difficult to maintain stability under strain in the wearable field.

Description

Technical Field

[0001] The present invention belongs to the technical field of micro-nano electronic devices, and in particular relates to a flexible multi-value hafnium oxide-based ferroelectric capacitor and a preparation method and application thereof, which can be used for multi-value analog storage pool calculation. Background Art

[0002] The unique physical form and functions of flexible electronic devices have shown great potential in the fields of flexible health monitoring devices, wearable medical devices and bionic robots. Memory pool computing is an emerging computing architecture that breaks the separation of storage and processing in traditional computer architecture by integrating storage and computing functions. Its core is to use storage elements to directly process data, reduce data transmission between processors and memories, thereby greatly reducing power consumption and improving computing efficiency. Therefore, memory pool computing can provide efficient computing support for flexible electronic applications.

[0003] Currently, most storage units used to implement storage pool networks are based on simplified device structure models, which usually ignore complex nonlinear dynamic behaviors and their impact on information processing. In storage pool computing, ferroelectric memory can be used as a computing unit, and logical operations and efficient data processing can be performed through its different polarization states. The ferroelectric size effect and environmental issues of traditional ferroelectric materials such as perovskites have become key bottlenecks restricting their widespread application and the development of semiconductor device integration. In contrast, hafnium oxide-based ferroelectric materials have the advantages of full CMOS compatibility, miniaturization, high speed and low power consumption. However, it is difficult to take into account both ferroelectricity and stability when using hafnium oxide-based ferroelectric materials for flexible memory.

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

[0005] In view of the problem in the prior art that it is difficult to take into account both ferroelectricity and stability when using hafnium oxide-based ferroelectric materials for flexible memory, the present invention provides a flexible multi-value hafnium oxide-based ferroelectric capacitor and a preparation method and application thereof. The capacitor still has stable ferroelectricity under a bent deformation state and can achieve 32 storage states, which not only meets the needs of storage pool calculations for multi-value storage, but also effectively solves the problem that ferroelectric materials are difficult to maintain stability under strain in the wearable field.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] A flexible multi-value hafnium oxide-based ferroelectric capacitor, comprising: 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 on the buffer layer;

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

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

[0012] The material of the flexible substrate is selected from one of polyurethane (PU), thermoplastic polyurethane rubber (TPU), polydimethylsiloxane (PDMS), polyethylene terephthalate (PET), and polyimide (PI), and the thickness is 50 μm-100 μm;

[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 material of the lower electrode layer and the upper electrode layer is 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, 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 element to doping element is 0.4 to 0.8, and the thickness is 9nm-11nm;

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

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

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

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

[0020] Furthermore, both the lower electrode layer and the upper electrode layer are W thin films, and the thickness is 40 nm.

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

[0022] The present invention also relates to a method for preparing the above-mentioned flexible multi-value hafnium oxide-based ferroelectric capacitor, comprising the following steps:

[0023] (1) cleaning the flexible substrate by ultrasonic cleaning with acetone, anhydrous ethanol, and deionized water in sequence and drying the substrate to remove impurities and oxides on the substrate;

[0024] (2) depositing a buffer layer on a flexible substrate by magnetron sputtering using a radio frequency sputtering process with a power of 100 W to 140 W and an argon gas flow rate of 12 sccm to 20 sccm during the growth process;

[0025] (3) using magnetron sputtering treatment, adopting radio frequency sputtering process, the power during the growth process is 100W-140W, the argon gas flow rate is 12sccm-20sccm, and growing the lower electrode layer on the basis of the structure in step (2);

[0026] (4) using atomic layer deposition, the following process is used for cyclic treatment: tetrakis(ethylamino)hafnium is heated to 70°C-80°C, pulsed for 300ms, nitrogen purged for 4s, deionized water pulsed for 150ms, nitrogen purged for 4s, tetrakis(ethylamino)zirconium is heated to 70°C-80°C, pulsed for 300ms, nitrogen purged for 4s, deionized water pulsed for 150ms, nitrogen purged for 4s, and the atomic layer deposition treatment temperature is 260°C-280°C;

[0027] Growing a ferroelectric dielectric layer on the basis of the structure in step (3), and cyclically depositing an oxide film in sequence until the dielectric layer reaches a preset thickness;

[0028] (5) Based on the structure of (4), a coating, photolithography, and development patterning are performed to form a pattern of the upper electrode: a negative resist is coated on the dielectric layer, pre-baked at 95° C. and then exposed, and then post-baked at 110° C. After flooding, the layer is immersed in a developer for 60 seconds, and then rinsed with deionized water and blown dry;

[0029] (6) using magnetron sputtering treatment, adopting radio frequency sputtering process, the power during the growth process is 100W-140W, the argon gas flow rate is 12sccm-20sccm, and growing the upper electrode layer on the basis of the structure in step (5);

[0030] (7) Rapid thermal annealing treatment is performed under nitrogen protection to obtain a flexible multi-value hafnium oxide-based ferroelectric capacitor, wherein the flexible multi-value hafnium oxide-based ferroelectric capacitor has the following performance indicators:

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

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

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

[0034] The present invention also relates to the application of the above-mentioned flexible multi-valued hafnium oxide-based ferroelectric capacitor. The flexible multi-valued hafnium oxide-based ferroelectric capacitor is used as a storage unit. An implementation scheme for storage pool calculation is designed, which mainly inputs 5 different pulse sequences, which are processed into corresponding current output signals through the flexible multi-valued hafnium oxide-based ferroelectric capacitor. 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 recursive neural network, and provides a hardware solution for building a storage pool computing system that can process complex timing tasks in real time.

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

[0036] 1. The flexible multi-value hafnium oxide-based ferroelectric capacitor of the present invention has a large residual polarization value (2Pr>55μC / cm 2 ), with consistent ferroelectricity in the flat state and at different bending radii.

[0037] 2. The flexible multi-value hafnium oxide-based ferroelectric capacitor of the present invention generates multiple ferroelectric domain intermediate states by controlling the amplitude of the applied pulse. Using a 5-bit binary pulse sequence test scheme, each state generates a different current output. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a schematic diagram of the basic structure of the flexible multi-value hafnium oxide-based ferroelectric capacitor according to Example 1 of the present invention;

[0039] Figure 2 This is a schematic flow chart of a method for preparing a flexible multi-value hafnium oxide-based ferroelectric capacitor according to Example 2 of the present invention;

[0040] Figure 3It is a schematic diagram of polarization hysteresis curves of the flexible multi-value hafnium oxide-based ferroelectric capacitor described in the present invention in a flat state and a bent state;

[0041] Figure 4 It is a schematic diagram of the test results of the storage pool characteristics of the flexible multi-value hafnium oxide-based ferroelectric capacitor described in the present invention. DETAILED DESCRIPTION

[0042] The present invention is further described in detail below by way of examples, but these examples should not be considered as limiting the present invention.

[0043] Embodiment 1:

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

[0045] Flexible substrate 1;

[0046] A buffer layer 2, located above the flexible substrate;

[0047] A lower electrode layer 3, located above the buffer layer;

[0048] A dielectric layer 4, located above the lower electrode layer;

[0049] An upper electrode layer 5, located above the dielectric layer;

[0050] The material of the flexible substrate is selected from one of PU, TPU, PDMS, PET, and PI;

[0051] In order 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] The buffer layer 2 is an Al2O3 film with a thickness of 140 nm;

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

[0055] The lower electrode layer 3 and the upper electrode layer 5 are both W 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 a HfZrO thin film, the ratio of hafnium element to doping element is 0.5, and the thickness is 10 nm.

[0058] Embodiment 2:

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

[0060] The following is a detailed description of the manufacturing process of the flexible multi-value hafnium oxide-based ferroelectric capacitor of this embodiment. Figure 2 Said, including:

[0061] Step (1) cleaning the PI flexible substrate 1 by ultrasonic cleaning with acetone, anhydrous ethanol, and deionized water in sequence and drying the substrate to remove impurities and oxides on the substrate;

[0062] Step (2) depositing Al2O3 as a buffer layer on the flexible substrate by magnetron sputtering, using a radio frequency sputtering process, with a power of 100W-140W and an argon gas flow rate of 12sccm-20sccm during the growth process;

[0063] Step (3) using magnetron sputtering to grow a W lower electrode layer on the basis of the structure in step (2), using a radio frequency sputtering process, with a power of 100W-140W and an argon gas flow rate of 12sccm-20sccm during the growth process;

[0064] Step (4) using atomic layer deposition technology to grow a HfZrO dielectric layer on the basis of the structure of step (3), wherein the atomic layer deposition is cyclically treated by the following process: tetra(methylethylamino)hafnium is heated to 70°C-80°C, pulsed for 300ms, nitrogen purged for 4s, deionized water pulsed for 150ms, nitrogen purged for 4s, tetra(methylethylamino)zirconium is heated to 70°C-80°C, pulsed for 300ms, nitrogen purged for 4s, deionized water pulsed for 150ms, nitrogen purged for 4s, and the treatment temperature of the atomic layer deposition is 260°C-280°C; a layer of HfO2 is deposited in sequence, and then a layer of ZrO2 is deposited, and the deposition is cyclically carried out until the last layer of ZrO2 is capped; the molar component ratio of Hf and Zr is close to 1:1, which can achieve the maximum residual polarization intensity;

[0065] Step (5) is to perform photoresist, photolithography, and development and patterning on the basis of the structure of (4) above to form a pattern of the upper electrode, specifically: coating a negative resist on the dielectric layer, pre-baking at 95°C and then exposing, post-baking at 110°C after exposure, soaking in a developer for 60s after flooding, rinsing with deionized water and drying; in addition, a positive resist may also be selected for the photoresist, but the corresponding process parameters need to be adjusted;

[0066] Step (6) using magnetron sputtering to grow an electrode layer on the basis of the structure in step (5), using a radio frequency sputtering process, with a power of 100 W to 140 W and an argon gas flow rate of 12 sccm to 20 sccm during the growth process;

[0067] Step (7) performs rapid thermal annealing under nitrogen protection, with the annealing temperature being 400° C.-450° C. and the annealing time being 30 seconds to obtain a capacitor.

[0068] In this example, it is generally believed that the stress effect of the electrode is one of the necessary conditions for inducing the ferroelectric orthorhombic phase. Selecting an electrode material with a smaller thermal expansion coefficient will produce a stronger tensile stress during annealing, which is conducive to the formation of the ferroelectric phase. Compared with TiN, the most commonly used electrode material for hafnium-based ferroelectric films (the thermal expansion coefficient is about 9.4×10 -6 / ℃), W has a smaller thermal expansion coefficient (about 4.5×10 -6 / ℃), which helps to induce the generation of ferroelectric orthorhombic phase in HfZrO film, thereby improving the ferroelectricity of the capacitor. Secondly, due to the increase of tensile stress, the required annealing temperature can be reduced, thereby reducing the phenomenon of cracks in the flexible substrate due to thermal effects. In addition, the thermal budget limit of CMOS back-end process is usually around 400℃, which is lower than the optimal annealing temperature of existing hafnium oxide-based ferroelectric capacitors. Therefore, the ferroelectric capacitor of the present invention can still have good ferroelectricity at the annealing temperature of 400℃, which can effectively improve the process compatibility of hafnium oxide-based ferroelectric capacitors during large-scale integration.

[0069] Embodiment 3:

[0070] The electrical properties of the flexible multi-value hafnium oxide-based ferroelectric capacitor of Example 2 are verified below.

[0071] Voltage excitation is applied to the flexible multi-valued hafnium oxide-based ferroelectric capacitor in a flat state, and the polarization hysteresis curve is measured; then, the capacitor is placed on a mold with different bending radii, and voltage excitation is applied to the flexible multi-valued hafnium oxide-based ferroelectric capacitor in a bent state, and the polarization hysteresis curve is measured.

[0072] like Figure 3 , which shows the polarization hysteresis curves of ferroelectric materials tested at different bending degrees, reflecting the relationship between polarization intensity and electric field intensity. On the one hand, it shows that the flexible multi-value hafnium oxide-based ferroelectric capacitor of Example 2 has a larger residual polarization value (2Pr>55μC / cm 2 ); on the other hand, it illustrates that the ferroelectric properties of the flexible multi-valued hafnium oxide-based ferroelectric capacitor of Example 2 are basically the same in a flat state and in a bent state at different bending radii, that is, the flexible multi-valued hafnium oxide-based ferroelectric capacitor can remain stable after bending.

[0073] Embodiment 4:

[0074] Next, the multi-value storage characteristics of the flexible multi-value hafnium oxide-based ferroelectric capacitor of Example 2 are verified.

[0075] The memory pool in the neural network has the function of memorizing and converting time series data, which enables it to effectively capture and process dynamically changing information. At present, the research on using devices to implement memory pool networks is mostly based on simplified structural models. These models usually ignore complex nonlinear dynamic behaviors and their impact on information processing. Therefore, applying multi-state memory units to multi-value 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 of this embodiment adopts a 5-bit binary pulse sequence test scheme, which is represented by "00000" to "11111". "0" represents that there is no pulse at this bit; "1" represents that a pulse is applied at this bit. There are 32 variations in the 5-bit sequence, and the pulse adopts a triangular wave with a voltage of -1.05V and a width of 10μs.

[0077] Figure 4 The data clearly demonstrates how the output current of the flexible multi-valued hafnium oxide-based ferroelectric capacitor changes with the pulse sequence, with 32 states differently distributed in the output current range of 130μA-1030μA, indicating that the flexible multi-valued hafnium oxide-based ferroelectric capacitor of this embodiment successfully realizes the storage pool unit function, has the ability to process 5-bit pulse sequences, and has great potential for application in multi-valued analog storage pool calculations.

[0078] Embodiment 5:

[0079] The following uses the flexible multi-value hafnium oxide-based ferroelectric capacitor of Example 2 as a storage unit to design an implementation scheme for storage pool calculation. It mainly inputs 5 different pulse sequences, which are processed into corresponding current output signals by the flexible multi-value hafnium oxide-based ferroelectric capacitor. The dynamic characteristics of the multi-value capacitor are used to realize multi-state storage and parallel computing functions, which is equivalent to the hidden layer of the traditional recursive neural network. It provides a hardware solution for building a storage pool computing system that can process complex timing tasks in real time.

[0080] Comparative Example 1:

[0081] Comparative Example 1 and Example 1 both use HfZrO as the ferroelectric layer, the difference is that the substrate of Comparative Example 1 uses a silicon wafer; the electrode material uses 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 a preparation method thereof, the steps are as follows:

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

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

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

[0086] Step (4), performing atomic layer deposition on the surface of the TiON layer to grow a HfZrO layer with a thickness of 15 nm; wherein the atomic layer deposition treatment is performed by cyclic treatment using the following process: tetrakis(ethylmethylamino)hafnium pulse treatment for 1.5 s, N2 purge for 3 s, ozone pulse for 2 s, N2 purge for 2 s, tetrakis(ethylmethylamino)zirconium pulse treatment for 1.5 s, N2 purge for 3 s, ozone pulse for 2 s, N2 purge for 2 s; the temperature of the atomic layer deposition treatment is 250°C;

[0087] Step (5), performing atomic layer deposition 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 treatment is cyclically treated by the following process: trimethylaluminum pulse treatment for 0.4 s, N2 purge for 3 s, H2O pulse treatment for 0.3 s, and N2 purge for 2 s; the temperature of the atomic layer deposition treatment is 250°C;

[0088] Step (6) coating the surface of the Al2O3 thin film layer, performing photolithography, and developing and patterning to form a photoresist pattern of a 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) performing annealing treatment under nitrogen protection to obtain a capacitor; wherein the annealing temperature is 650° C. and the annealing time is 30 s;

[0091] Step (9) applying an electric field cycle 10 between the upper and lower electrodes of the capacitor 7 times, a high-performance hafnium oxide-based ferroelectric capacitor was obtained.

[0092] After testing, the residual polarization intensity (2P r ) is 30μC / cm 2 -40μC / cm 2, durability is 10 8 Times - 10 10 Second-rate.

[0093] Comparative Example 2:

[0094] Comparative Example 2 and Example 1 both use HfZrO as the ferroelectric layer, the difference is that the substrate of Comparative Example 2 uses a silicon wafer; a thin ZrO2 seed layer is grown before depositing the ferroelectric layer; the Al2O3 thin film layer is located between the ferroelectric layer and the top electrode layer; and the annealing step is before depositing the top electrode.

[0095] A hafnium oxide-based ferroelectric capacitor and a preparation method thereof, the steps are as follows:

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

[0097] Step (2), growing a 1nm-2nm ZrO2 seed layer by atomic layer deposition, the growth process temperature is 250°C-280°C, each cycle growth process of the atomic layer deposition process includes a 0.2s tetrakis(dimethylamino)zirconium (TDMAZr) pulse, a 2s N2 purge, a 0.2s oxygen plasma pulse, and a 2s N2 purge;

[0098] Step (3) growing a 10nm-20nm hafnium oxide-based ferroelectric thin film by atomic layer deposition, the growth process temperature is 250°C-280°C, and each cycle growth process of the atomic layer deposition process includes a 0.2s tetrakis(dimethylamino)zirconium or tetrakis(dimethylamino)hafnium TDMAZr / TDMAHf pulse, a 2s N2 purge, a 0.2s oxygen plasma pulse, and a 2s N2 purge;

[0099] Step (4) growing a 1 nm to 2 nm Al2O3 film by atomic layer deposition, the growth process temperature being 250° C. to 300° C., and each cycle growth process of the atomic layer deposition process comprising a 0.2 s trimethylaluminum TMA pulse, a 2 s N2 purge, a 0.2 s deionized water pulse, and a 2 s N2 purge;

[0100] Step (5) performing rapid thermal annealing on the wafer in a nitrogen atmosphere, with a heating rate of 15°C / s-20°C / s, an annealing temperature of 330°C-450°C, and an annealing time of 60s-300s;

[0101] Step (6), using ultraviolet lithography to define the device electrode area; using electron beam evaporation technology to grow 10nm-15nmTi / 40nm-50nmAu on the top electrode, wherein the deposition rate of Ti is 0.16nm / s, and the deposition rate of Au is 0.2nm / s; using a stripping process to strip the wafer in step (6): first, soak the wafer in acetone and let it stand until the top electrode structure is clear, then soak it in isopropanol to remove the acetone and other organic matter remaining on the surface of the wafer, and finally rinse it with deionized water and blow it dry with nitrogen.

[0102] After testing, the residual polarization intensity (Pr) of the hafnium oxide-based ferroelectric capacitor obtained in Comparative Example 2 is 20 μC / cm 2 -25μC / cm 2 , durability is 10 8 Times - 10 9 Second-rate.

[0103] Comparative Example 3:

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

[0105] A flexible ferroelectric capacitor and a method for making the same, the steps are as follows:

[0106] Step (1), cleaning the polyimide PI substrate. The substrate is sequentially soaked and cleaned with acetone and anhydrous ethanol, then blow-dried, then soaked and rinsed with deionized water, and then blow-dried. Exemplarily, the substrate with a thickness of 500 um is cleaned by the method of cleaning the substrate;

[0107] Step (2) Prepare an Al2O3 functional layer on the substrate using an ALD process. The Al precursor and deionized water are kept at room temperature of 20°C, N2 is selected as the carrier gas, and the gas flow rate is 100 sccm to prepare the functional layer on the substrate. The Al precursor is trimethylaluminum TMA, deionized water is used as the oxygen source, the reaction chamber pressure is less than 2 mbar, the deposition temperature is 200°C, and the functional layer 102 is prepared on the substrate. The thickness of the functional layer is 100 nm;

[0108] Step (3) sputtering a TiN lower electrode layer using an ion beam sputtering process, using a TiN target, a beam voltage of 800 V, a beam current of 46 mA, an acceleration voltage of 160 V, an Ar / N2 mixed gas, and a flow rate of 8 sccm / 5 sccm, respectively, to prepare a TiN lower electrode layer with a thickness of 40 nm;

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

[0110] Step (5) coating the dielectric layer with photoresist, and exposing and developing. Specifically, coating the dielectric layer with negative resist, controlling the temperature to be 150°C for pre-baking for 3 minutes; after exposure, controlling the temperature to be 120°C for post-baking for 3 minutes, soaking in developer for 45 seconds for development, and then rinsing with deionized water, and drying the dielectric layer;

[0111] Step (6) sputtering a TiN top electrode layer on the dielectric layer using an ion beam sputtering process, using a TiN target, a beam voltage of 800 V, a beam current of 46 mA, an acceleration voltage of 160 V, an Ar / N2 mixed gas, and a flow rate of 8 sccm / 5 sccm, respectively, and the thickness of the prepared TiN top electrode layer is 40 nm;

[0112] Step (7) removes the photoresist and excess metal from the prepared flexible ferroelectric capacitor. Soak the device in an acetone solution until the photoresist and excess metal fall off. Next, soak the device in anhydrous ethanol to remove the acetone. Then, rinse with deionized water and blow dry the device. Finally, anneal the rinsed and dried device in a N2 atmosphere at a temperature of 430°C for 60s to obtain a flexible ferroelectric capacitor.

[0113] After testing, the residual polarization intensity (P 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 low annealing temperature, which can effectively improve the process compatibility of the hafnium oxide-based ferroelectric capacitor during large-scale integration.

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

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

[0118] The above comparative examples do not involve the multi-value storage capacity and application of capacitors, which indicates that the flexible multi-value hafnium oxide-based ferroelectric capacitor of the present invention has broad application prospects in the fields of wearable devices and neural network computing.

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

Claims

1. A flexible multi-value 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 on the buffer layer; The dielectric layer is located on the lower electrode layer; The upper electrode layer is located on the dielectric layer; The material of the flexible substrate is selected from one of polyurethane, thermoplastic polyurethane rubber, polydimethylsiloxane, polyethylene terephthalate, and polyimide, and has a thickness of 50 μm-100 μm; 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 material of the lower electrode layer and the upper electrode layer is 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, the doping element is selected from one of silicon, aluminum, zirconium, yttrium, strontium, lanthanum, and gadolinium; the ratio of hafnium element to doping element is 0.4 to 0.8, and the thickness is 9nm-11nm; The flexible multi-value hafnium oxide-based ferroelectric capacitor has the following performance indicators: The thickness of the HfZrO dielectric layer of the hafnium oxide-based ferroelectric capacitor is 10nm, and the residual polarization intensity (2P r )>55μC / cm 2 , durability exceeds 10 10 times, retention time exceeds 10 6 s; It has the same performance at the bending radius of 0mm, 2mm, 4mm, 6mm, and 8mm, and at the extreme bending radius of 2mm, 10 5 Maintains stable performance after bending and stretching cycles.

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

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

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

5. The flexible multi-value hafnium oxide-based ferroelectric capacitor according to claim 1, characterized in that: The dielectric layer is a HfZrO film, the ratio of hafnium element to doping element is 0.5, and the thickness is 10nm.

6. The method for preparing a flexible multi-value hafnium oxide-based ferroelectric capacitor according to claim 1, characterized in that: The following steps are involved: (1) cleaning the flexible substrate by ultrasonic cleaning with acetone, anhydrous ethanol, and deionized water in sequence and drying the substrate to remove impurities and oxides on the substrate; (2) depositing a buffer layer on a flexible substrate by magnetron sputtering using a radio frequency sputtering process with a power of 100 W to 140 W and an argon gas flow rate of 12 sccm to 20 sccm during the growth process; (3) using magnetron sputtering treatment, adopting radio frequency sputtering process, the power during the growth process is 100W-140W, the argon gas flow rate is 12sccm-20sccm, and growing the lower electrode layer on the basis of the structure in step (2); (4) using atomic layer deposition, the following process is used for cyclic treatment: tetrakis(ethylamino)hafnium is heated to 70°C-80°C, pulsed for 300ms, nitrogen purged for 4s, deionized water pulsed for 150ms, nitrogen purged for 4s, tetrakis(ethylamino)zirconium is heated to 70°C-80°C, pulsed for 300ms, nitrogen purged for 4s, deionized water pulsed for 150ms, nitrogen purged for 4s, and the atomic layer deposition treatment temperature is 260°C-280°C; Growing a ferroelectric dielectric layer on the basis of the structure in step (3), and cyclically depositing an oxide film in sequence until the dielectric layer reaches a preset thickness; (5) Based on the structure of (4), a coating, photolithography, and development patterning are performed to form a pattern of the upper electrode: a negative resist is coated on the dielectric layer, pre-baked at 95° C. and then exposed, and then post-baked at 110° C. After flooding, the layer is immersed in a developer for 60 seconds, and then rinsed with deionized water and blown dry; (6) using magnetron sputtering treatment, adopting radio frequency sputtering process, the power during the growth process is 100W-140W, the argon gas flow rate is 12sccm-20sccm, and growing the upper electrode layer on the basis of the structure in step (5); (7) Performing rapid thermal annealing under nitrogen protection to obtain 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 of the hafnium oxide-based ferroelectric capacitor is 10nm, and the residual polarization intensity (2P r )>55μC / cm 2 , durability exceeds 10 10 times, retention time exceeds 10 6 s; It has the same performance at the bending radius of 0mm, 2mm, 4mm, 6mm, and 8mm, and at the extreme bending radius of 2mm, 10 5 Maintains stable performance after bending and stretching cycles.

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

8. The use of a flexible multi-value hafnium oxide-based ferroelectric capacitor according to claim 1, characterized in that: The flexible multi-value hafnium oxide-based ferroelectric capacitor is used as a storage unit, and an implementation scheme for storage pool calculation is designed. By inputting 5 different pulse sequences, the flexible multi-value hafnium oxide-based ferroelectric capacitor is processed into a corresponding current output signal, and the dynamic characteristics of the multi-value capacitor are used to realize multi-state storage and parallel computing functions, which is equivalent to realizing the hidden layer of a traditional recursive neural network, as a hardware solution for building a storage pool computing system that can process complex timing tasks in real time.

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