WO2023070748A1 - 一种基于HfO2/ZrO2或HfO2/Al 2O 3超晶格铁电忆阻器及其制备 - Google Patents

一种基于HfO2/ZrO2或HfO2/Al 2O 3超晶格铁电忆阻器及其制备 Download PDF

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WO2023070748A1
WO2023070748A1 PCT/CN2021/130012 CN2021130012W WO2023070748A1 WO 2023070748 A1 WO2023070748 A1 WO 2023070748A1 CN 2021130012 W CN2021130012 W CN 2021130012W WO 2023070748 A1 WO2023070748 A1 WO 2023070748A1
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superlattice
functional
functional layer
layer
ferroelectric
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孙华军
白娜
王文琳
缪向水
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华中科技大学
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    • H10N70/00—Solid-state devices having no potential barriers, and specially adapted for rectifying, amplifying, oscillating or switching
    • H10N70/801—Constructional details of multistable switching devices
    • H10N70/881—Switching materials
    • H10N70/883—Oxides or nitrides
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    • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
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    • C—CHEMISTRY; METALLURGY
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    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
    • C30B29/60—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape characterised by shape
    • C30B29/68—Crystals with laminate structure, e.g. "superlattices"
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N70/00—Solid-state devices having no potential barriers, and specially adapted for rectifying, amplifying, oscillating or switching
    • H10N70/011—Manufacture or treatment of multistable switching devices
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    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
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    • H10N70/00—Solid-state devices having no potential barriers, and specially adapted for rectifying, amplifying, oscillating or switching
    • H10N70/011—Manufacture or treatment of multistable switching devices
    • H10N70/021—Formation of switching materials, e.g. deposition of layers
    • H10N70/026—Formation of switching materials, e.g. deposition of layers by physical vapor deposition, e.g. sputtering
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N70/00—Solid-state devices having no potential barriers, and specially adapted for rectifying, amplifying, oscillating or switching
    • H10N70/801—Constructional details of multistable switching devices
    • H10N70/821—Device geometry
    • H10N70/826—Device geometry adapted for essentially vertical current flow, e.g. sandwich or pillar type devices
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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    • Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
    • Y02D10/00—Energy efficient computing, e.g. low power processors, power management or thermal management

Definitions

  • the invention belongs to the technical field of microelectronic devices, and more specifically relates to a superlattice ferroelectric memristor based on HfO 2 /ZrO 2 or HfO 2 /Al 2 O 3 and a preparation method thereof.
  • the superlattice thin film has high The advantages of dielectric constant, low interface trap charge and high thermal stability are beneficial to increase the ferroelectric phase content of the device film, promote the polarization reversal of the film and improve the ferroelectric performance of the device.
  • ferroelectric memory achieves the purpose of non-volatile storage by applying an external electric field to achieve device polarization reversal. Because of its advantages of high read/write speed, low power consumption and compatibility with traditional CMOS technology, it has wide application potential in the fields of storage, logic operation and neural network computing.
  • Traditional ferroelectric materials PbZrTiO 3 and BaTiO 3 have been implemented in silicon-based MOSFET devices, but there are problems such as compatibility with CMOS and degradation of ferroelectricity when the device size is reduced.
  • HfO 2 and ZrO 2 as a high-K material are considered to be ideal high dielectric materials compatible with CMOS.
  • HfO 2 exists in monoclinic, tetragonal, and cubic phases, respectively. Pure HfO 2 is a stable monoclinic phase, and its atomic center symmetry leads to no ferroelectric properties in the film. Through annealing, doping, etc., the transformation between different phases can be realized to form non-centrosymmetric tetragonal and cubic phases, and then the ferroelectric properties of the device can be realized.
  • Michael Hoffmann et al. M. Hoffmann, Nano Energy.18, (2015)
  • Stefan Mueller et al. (Mueller, S, Adv. Funct. Mater.
  • a superlattice material is a multilayer film in which two materials with a high degree of lattice matching are alternately grown in thin layers of a few nanometers to tens of nanometers and maintained in a strict periodic arrangement. Due to the unique quantum mechanical effect of superlattice, it can be used as a buffer layer to improve the performance of phase change memory, for example, by preparing Sb 2 Te 3 /Bi 2 Te 3 superlattice structure as a buffer layer for phase change memory (Chinese patent application " A Phase Change Memory Unit with a Superlattice Structure Buffer Layer and Its Preparation Method", CN112909162A).
  • the superlattice structure can effectively provide thin film grain boundaries and guide the formation path of conductive filaments to be applied to memristors to improve the consistency of devices (Chinese patent application "A Memristor with a Functional Layer of Superlattice Material Resistor and its preparation method", CN113078262A).
  • the object of the present invention is to provide a ferroelectric memristor based on HfO 2 /ZrO 2 or HfO 2 /Al 2 O 3 superlattice and its preparation, wherein by improving the device function Layer structure and composition are improved, different from traditional metal-doped HfO2- based ferroelectric memristors, the present invention uses stacked growth superlattice HfO2 layer and ZrO2 layer (or Al2O3 layer) as ferroelectric memristor
  • the device functional layer has good ferroelectric and memristive properties.
  • the functional layer is based on HfO 2 /ZrO 2 superlattice structure or HfO 2 /Al 2 O 3 superlattice structure, using HfO 2 and ZrO 2 (or Al 2 O 3 ) with equal atomic radii, similar crystal structure and lattice parameters , has a high degree of lattice matching, and the strong Hf-O bond and Zr-O bond (or Al-O bond) can well maintain the remnant polarization of the device and realize non-volatile storage; The stress between superlattice interfaces is more conducive to inducing the formation of ferroelectric phases.
  • the barriers between interfaces can effectively restrain the free diffusion of electrons and particles, effectively prevent polaron neutralization and phase separation, and improve the fatigue characteristics of ferroelectrics. At the same time, it provides an effective path for the migration of conductive filaments and stabilizes the memristive properties of the device.
  • the device Utilizing the electrical properties of the HfO 2 /ZrO 2 (or HfO 2 /Al 2 O 3 ) superlattice thin film, the device can stably cycle 30 cycles of memristive properties in the voltage range of -3V-3V.
  • the present invention can make the device exhibit ferroelectricity and memristive properties at the same time through simple annealing treatment, and provide important theoretical guidance and technical support for the preparation of high-performance ferroelectric memristors and memories.
  • a superlattice ferroelectric memristor which is characterized in that it includes a lower electrode layer, a functional layer and an upper electrode layer stacked sequentially from bottom to top, wherein,
  • the functional layer is a superlattice functional layer composed of at least one superlattice unit, each superlattice unit is formed by stacking the first functional material and the second functional material from bottom to top, and the functional layer
  • the thickness of any one of the sub-functional layers formed by the first functional material or the second functional material satisfies 0.6-5nm;
  • the superlattice ferroelectric memristor is specifically a superlattice ferroelectric memristor based on HfO 2 /ZrO 2 Resistors or superlattice ferroelectric memristors based on HfO 2 /Al 2 O 3 , the first functional material is tetragonal and/or cubic HfO 2 , and the second functional material is ZrO 2
  • the superlattice ferroelectric memristor has also undergone annealing treatment, the annealing temperature is 500°C-800°C; the annealing time is 20s-300s;
  • the annealing temperature is 650°C, and the annealing time is 30s.
  • the superlattice ferroelectric memristor can reverse the internal polarization direction of the superlattice functional layer or migrate internal oxygen vacancies through DC voltage regulation and limiting current regulation to realize the supercrystalline
  • the switching regulation of the high resistance value and the low resistance value of the ferroelectric memristor wherein, the DC voltage regulation is changed in the range of -5V to 5V, and the limit current regulation is changed in the range of 10uA to 10mA;
  • the adjustment range of the DC voltage is -3V to 3V, and the limiting current used is 10mA.
  • the superlattice ferroelectric memristor also adjusts the flipping direction of the ferroelectric domain inside the superlattice functional layer by pulse amplitude and frequency, so as to realize the superlattice ferroelectric memristor non-magnetic Volatile ferroelectric properties; among them, the pulse amplitude is controlled at 1V-4V, and the pulse frequency is controlled at 100Hz-5kHz;
  • the pulse signal applied by the pulse amplitude and frequency adjustment is a triangular pulse, the pulse amplitude is 4V, and the frequency is 1kHz.
  • the number of the superlattice units in the functional layer is 2n, and n is an integer greater than or equal to 1 and less than or equal to 5.
  • said n is equal to 3
  • said functional layer is composed of HfO 2 sub-functional layer, ZrO 2 sub-functional layer, HfO 2 sub-functional layer, ZrO 2 sub-functional layer, HfO 2 sub-functional layer and ZrO 2 Sub-functional layers These 6 sub-functional layers are stacked sequentially from bottom to top;
  • said functional layer is composed of HfO 2 sub-functional layer, Al 2 O 3 sub-functional layer, HfO 2 sub-functional layer, Al 2 O 3 sub-functional layer, HfO 2 sub-functional layer and Al 2
  • the 6 sub-functional layers of the O 3 sub-functional layer are stacked sequentially from bottom to top.
  • the functional layer is sequentially stacked on the lower electrode layer by means of atomic layer deposition (ALD), pulsed laser deposition (PLD), or molecular beam epitaxy (MBE).
  • ALD atomic layer deposition
  • PLD pulsed laser deposition
  • MBE molecular beam epitaxy
  • the thickness of each sub-functional layer in the functional layer is 2 nm; the total thickness of the functional layer is not more than 20 nm, more preferably 12 nm.
  • the electrode material used in the lower electrode layer is selected from Pt, Ti, ITO, Ag, Cu, TiN;
  • the electrode material used in the upper electrode layer is selected from TiN, Pt, TaN, TiW, Au , W;
  • the electrode material used for the lower electrode layer is Pt
  • the electrode material used for the upper electrode layer is TiN
  • the present invention provides a method for preparing the above-mentioned superlattice ferroelectric memristor, which is characterized in that the preparation method is to prepare the lower electrode layer on the substrate first, and then to prepare the lower electrode layer on the lower electrode layer Prepare the functional layer; followed by photolithography, and then deposit the upper electrode layer; finally, anneal in the annealing furnace;
  • the functional layer is deposited by atomic layer deposition (ALD) alternately depositing the first functional material and the second functional material; the temperature of the ALD reaction chamber is 260°C-330°C, more preferably 300°C.
  • ALD atomic layer deposition
  • the dielectric constant of the hafnium oxide film is reduced due to doping of the existing ferroelectric memristor film, and the doping of different concentrations, the lattice mismatch Lead to many key problems such as many internal defects in the film and large leakage current of the device.
  • the present invention adopts the ZrO2 material (or Al2O3 material) that is equal to the Hf atomic radius, similar to the lattice structure and lattice parameters, and low in lattice mismatch.
  • HfO 2 layer and ZrO 2 layer (or Al 2 O 3 layer) by stacking and growing HfO 2 layer and ZrO 2 layer (or Al 2 O 3 layer) by ALD to generate HfO 2 /ZrO 2 (or HfO 2 /Al 2 O 3 ) superlattice structure ferroelectric film, And further obtained based on the superlattice ferroelectric memristor, which can effectively use the characteristics of superlattice high dielectric constant, low interface trap charge density, high thermal stability and low leakage current to realize the optimization of device performance.
  • HfO 2 and ZrO 2 have the same atomic radius, similar crystal structure and lattice parameters, and have a high degree of lattice matching, and can be prepared by common deposition processes (ALD, PLD, and MBE) with high quality and low defect concentration.
  • Superlattice ferroelectric thin film; at the same time, strong Hf-O bond and Zr-O bond can well maintain the remnant polarization of the device and realize non-volatile storage.
  • the present invention utilizes the electrical characteristics of the HfO 2 /ZrO 2 (HfO 2 /Al 2 O 3 ) superlattice thin film, and the device can stably cycle for 30 cycles in the voltage range of -3V-3V.
  • the stress between superlattice interfaces is more conducive to inducing the formation of ferroelectric phase.
  • the barrier between interfaces can effectively restrain the free diffusion of electrons and particles, effectively prevent polaron neutralization and phase separation, and improve the fatigue characteristics of ferroelectricity. At the same time, it provides an effective formation path for the migration of conductive filaments and stabilizes the memristive properties of the device.
  • the invention utilizes the HfO 2 /ZrO 2 (HfO 2 /Al 2 O 3 ) superlattice film to optimize the ferroelectric performance of the device, and provides a new idea for the preparation and optimization of the ferroelectric memristor.
  • the superlattice ferroelectric memristor in the present invention exhibits excellent ferroelectric properties after annealing treatment, the annealing temperature is preferably 500°C-800°C, and the annealing time is preferably 20s-300s.
  • the annealing temperature is preferably 500°C-800°C
  • the annealing time is preferably 20s-300s.
  • ferroelectric phase and non-ferroelectric phase By characterizing the film, it is found that these phases are randomly distributed. Among them, the ferroelectric phase is tetragonal and/or cubic phase, and the non-ferroelectric phase is monoclinic. Mutually.
  • the device in the invention exhibits good ferroelectricity and memristive properties, and can especially optimize the performance of the ferroelectric device.
  • the ferroelectric properties are caused by the content of the ferroelectric phase inside the film and the degree of polarization reversal when the voltage is applied, which determines the ferroelectric performance of the device;
  • the memristive properties are caused by the presence of oxygen vacancies in the film, The migration of oxygen vacancies during the process leads to the formation of oxygen vacancy conductive filaments connecting the upper and lower electrodes inside the film.
  • the superlattice ferroelectric memristor in the present invention can adjust the migration of oxygen vacancies inside the superlattice film by using a suitable direct current voltage and limiting current, realize the control of high/low resistance of the device, and realize the electrical performance of the memristor.
  • the device of the present invention can realize a stable cycle of 30 cycles and can realize the self-limiting characteristic.
  • the superlattice ferroelectric memristor in the present invention can also use suitable pulse amplitude (such as 1V-4V) and frequency (such as 100Hz-5kHz) to adjust the direction of ferroelectric domain flipping inside the superlattice film to realize the device Non-volatile ferroelectric properties; use the characteristics of increased polarization charges at the superlattice interface to optimize and increase the polarization strength of the device, so as to realize the ferroelectric performance and optimization of the device.
  • the present invention preferably controls the thickness of the functional layer, the magnitude of the applied voltage, etc., and the following examples are taken as examples.
  • superlattice thin films with thicknesses of 12nm, 16nm and 20nm HfO 2 /ZrO 2 are respectively prepared.
  • HfO When the thickness of the 2 /ZrO 2 superlattice film is 12nm, the ferroelectric properties of the device are the best among the various embodiments, and the polarization intensity is 13.27uC/cm 2 .
  • the present invention can achieve the following beneficial effects compared with the prior art:
  • the present invention designs HfO 2 layers and ZrO 2 layer stacking growth to form a superlattice mode, and prepares ferroelectric devices with excellent ferroelectric properties, because the HfO 2 /ZrO 2 superlattice structure can have a better crystal lattice Therefore, the interface trap charge density is less, the leakage current of the device is reduced, and the stability of the ferroelectric performance of the device is increased. HfO 2 /ZrO 2 superlattice thin films can effectively improve the ferroelectric properties of ferroelectric memristive devices.
  • HfO 2 /ZrO 2 superlattice ferroelectric devices with different thicknesses were prepared, and the same triangular pulse was applied.
  • the experimental results show that the thickness of the HfO 2 /ZrO 2 superlattice has a significant effect on the ferroelectric properties of the device.
  • the polarization intensity of the device decreases gradually with the increase of thickness, and the polarization intensity decreases from 13.27uC/cm 2 to 6.54uC/cm 2 .
  • the preparation of HfO 2 /ZrO 2 superlattice ferroelectric thin film does not contain the toxic element lead and is environmentally friendly.
  • the superlattice structure has a higher degree of lattice matching, stronger Hf-O and Zr-O bonds, and high thermal stability, which can form a ferroelectric phase well and maintain Polarization strength of ferroelectric devices. It has great advantages for preparing high-performance ferroelectric devices.
  • HfO 2 /Al 2 O 3 superlattice ferroelectric thin film also has equivalent properties in the same way. Compared with ZrO 2 material, Al atomic radius in Al 2 O 3 material is smaller than Hf atomic radius, and it is similar to ZrO 2 material. Al 2 O 3 materials can also form dopant-oxygen bonds with O. Considering that dopant-oxygen bonds can promote the formation of ferroelectric phases in HfO 2 materials and improve the ferroelectric performance of devices, HfO 2 /Al 2 O 3 The superlattice ferroelectric thin film can also achieve technical effects equivalent to those of the HfO 2 /ZrO 2 superlattice ferroelectric thin film.
  • the present invention forms a superlattice structure ferroelectric thin film by constructing a HfO 2 /ZrO 2 superlattice structure or a HfO 2 /Al 2 O 3 superlattice structure, and further obtains a new type of high-performance HZO or HAO
  • the material system ferroelectric memristor is of great significance for the subsequent application of ferroelectric devices in computing and storage integrated chips.
  • Fig. 1 is the three-dimensional schematic diagram based on the HfO2 / ZrO2 superlattice structure ferroelectric memristor provided by the embodiment of the present invention 1 (there are 6 functional layers in the figure, 2nm thick HfO2 and 2nm thick ZrO2 and this overlap).
  • Fig. 2 is the DC IV characteristic of the ferroelectric memristor based on the HfO 2 /ZrO 2 superlattice structure provided by Embodiment 1 of the present invention. It can be seen from the figure that the ferroelectric memristor based on the HfO 2 /ZrO 2 superlattice structure can cycle stably for 30 times when the limited current is 10mA.
  • Fig. 3 is the voltage measured under the triangular pulse frequency of 1KHz and amplitudes of ⁇ 3, ⁇ 3.5 and ⁇ 4V for the ferroelectric memristor based on the HfO 2 /ZrO 2 superlattice structure provided by Example 1 of the present invention. Hysteresis test curve.
  • Fig. 4 is the structure diagram based on the HfO2 / ZrO2 superlattice structure ferroelectric memristor provided by the embodiment 2 of the present invention and the hysteresis loop test curve measured; wherein, (a) in Fig. 4 corresponds to Schematic diagram of the structure of the ferroelectric memristor based on the HfO2 / ZrO2 superlattice structure provided by Example 2 (the functional layer has 8 layers, and each layer is respectively 2nm-thick HfO2 and 2nm-thick ZrO2 stacked in sequence) , (b) in Fig. 4 corresponds to the hysteresis loop test curve (the remanent polarization intensity is 12.37uC/cm 2 ) measured at ⁇ 4V voltage after the device is annealed at a current frequency of 100Hz.
  • Fig. 5 is the structure schematic diagram of the ferroelectric memristor based on HfO 2 /ZrO 2 superlattice structure provided by the embodiment 3 of the present invention and the measured hysteresis loop test curve; wherein, (a) in Fig.
  • FIG. 5 corresponds to Schematic diagram of the structure of the ferroelectric memristor based on the HfO2 / ZrO2 superlattice structure provided by Example 3 (the functional layer has 10 layers, each layer is respectively 2nm thick HfO2 and 2nm thick ZrO2 overlapping)
  • (b) in Figure 5 corresponds to the 100 hysteresis loop test curves measured at a voltage of ⁇ 4V at a current frequency of 1KHz after the device is annealed.
  • Fig. 6 is a comparison curve of hysteresis loops measured at a voltage of ⁇ 4V at a current frequency of 1KHz after annealing of the three ferroelectric memristors provided by Examples 1, 2, and 3 of the present invention.
  • Fig. 7 is a schematic structural diagram of a ferroelectric memristor based on HfO 2 /Al 2 O 3 superlattice structure provided by Embodiment 4 of the present invention.
  • the superlattice structure in the device structure has a total of 6 sub-functional layers.
  • Fig. 8 is a schematic structural diagram of a ferroelectric memristor based on the HfO 2 /Al 2 O 3 superlattice structure provided by Embodiment 5 of the present invention.
  • the superlattice structure in the device structure has a total of 8 sub-functional layers.
  • FIG. 9 is a schematic structural diagram of a ferroelectric memristor based on HfO 2 /Al 2 O 3 superlattice structure provided by Embodiment 6 of the present invention.
  • the superlattice structure in the device structure has a total of 10 sub-functional layers.
  • the device of the present invention can be prepared by the ALD method.
  • the reaction chamber can be heated to a certain temperature (250°C-330°C, especially 300°C)
  • Hf[N(C 2 H 5 ) CH 3 ] 4 and Zr[N(C 2 H 5 )CH 3 ] 4 were used as precursors of Hf source and Zr source respectively
  • water was used as oxygen source
  • high-purity nitrogen (N 2 ) to clean the gas for the precursor carrier and the reaction chamber, and deposit the HfO 2 layer and the ZrO 2 layer in sequence (there will be a small amount of oxygen vacancies inside the film).
  • the total number of layers of HfO 2 layer and ZrO 2 layer can be 4, 6, 8, 10, 12, etc., for example.
  • Example 1 A preparation method of a superlattice ferroelectric memristor based on HfO 2 /ZrO 2
  • Embodiment 1 provides a superlattice ferroelectric memristor of HfO 2 /ZrO 2 , the device structure is TiN/ZrO 2 /HfO 2 /ZrO 2 /HfO 2 /ZrO 2 /HfO 2 / Pt, and its structure is shown in Figure 1 As shown, in this embodiment, 2nm-thick HfO 2 and 2nm-thick ZrO 2 are preferred, and there are 6 layers in total.
  • the lower electrode is made of Pt, and the upper electrode is made of TiN.
  • the Si substrate with SiO 2 was submerged in acetone and alcohol solution and ultrasonically cleaned for 10 min.
  • the samples were placed in plasma water and ultrasonically cleaned for 3 min.
  • a 100nm-thick Pt lower electrode was prepared on the substrate by magnetron sputtering.
  • the ALD method was used to prepare the functional layer on the Pt bottom electrode, and the specific process flow was as follows: 1 Firstly, the temperature of the reaction chamber was raised to 300 °C; 2 The reaction chamber was cleaned with N 2 ; 3 2nm of HfO 2 (precursor Hf[ N(C 2 H 5 )CH 3 ] 4 , the oxidant is H 2 O); 4 Deposit 2nm ZrO 2 (precursor Zr[N(C 2 H 5 )CH 3 ] 4 , the oxidant is H 2 O); 3 And 4 the process cycled 3 times to obtain the superlattice functional layer of HfO 2 /ZrO 2 .
  • defects may also exist in the superlattice thin film deposited by ALD.
  • the photolithography process for pattern transfer.
  • the upper electrode area is reserved by photolithography; the size of the upper electrode is a small square of 50 ⁇ m ⁇ 50 ⁇ m.
  • the photolithography process includes: uniform glue , Pre-baking, pre-exposure, post-baking, post-exposure, development and other steps.
  • a 100-nm-thick TiN top electrode was prepared using the magnetron sputtering method. Specific process parameters: the background vacuum of sputtering is 5 ⁇ 10 -5 Pa, and the sputtering pressure is 0.5 Pa. The power is 120W, and the sputtering time is 1200s.
  • the sample obtained in the upper electrode preparation step was immersed in an acetone solution and ultrasonically stripped and oscillated until the photoresist and the excess electrode material above it all fell off, then immersed in ethanol solution and deionized water for cleaning, and dried with a nitrogen gun.
  • An annealing furnace is used to anneal the device obtained in the sixth step, specifically: the background vacuum of the annealing is 4 ⁇ 10 ⁇ 2 Pa, the temperature is 650° C., and the time is 30 s.
  • the device after the seventh step of annealing was tested for memristive characteristics, and the DC response was tested for 30 cycles.
  • the voltage is -3V-3V, the device is stable for 30 cycles.
  • the device after the seventh step of annealing is subjected to a ferroelectric characteristic test.
  • the PE images of the ferroelectric properties of Example 1 under different pulse amplitudes it can be seen that the device has ferroelectricity at three voltages, and the remanent polarization values are 8.75uC/cm 2 and 9.85uC/cm 2 , respectively. cm 2 and 13.30 uC/cm 2 .
  • Example 2 is generally similar to Example 1, the main difference is that in the third step when the functional layer is plated by ALD, the processes 3 and 4 are cycled 4 times to obtain a superlattice functional layer of HfO 2 /ZrO 2 with a total thickness of 16 nm.
  • the PE curve of the ferroelectric characteristic of Example 2 is applied when the triangular pulse frequency is 100 Hz and the amplitude is ⁇ 4 V.
  • the thickness of the superlattice film increases, the remanent polarization of Example 2 is 12.37uC/cm 2 .
  • Example 3 is generally similar to Example 1, the main difference is that in the third step when the functional layer is plated by ALD, the processes 3 and 4 are repeated 5 times to obtain a superlattice functional layer of HfO 2 /ZrO 2 with a total thickness of 20 nm.
  • the cyclic ferroelectric characteristic PE curve of Example 3 is applied when the triangular pulse frequency is 100 Hz and the amplitude is ⁇ 4 V.
  • the remanent polarization of Example 3 is 6.58uC/cm 2 .
  • Examples 4, 5 and 6 A preparation method for a ferroelectric memristor based on HfO 2 /Al 2 O 3 superlattice structure
  • Embodiments 4, 5 and 6 provide ferroelectric memristors with HfO 2 /Al 2 O 3 superlattice structures.
  • the device structures are shown in FIGS. 7 , 8 and 9 , which are HfO 2 /Al 2 O 3 superlattice structures.
  • FIGS. 7 , 8 and 9 are HfO 2 /Al 2 O 3 superlattice structures.
  • 2nm thick HfO 2 and 2nm thick Al 2 O 3 are preferred, and the total number of layers of the HfO 2 /Al 2 O 3 structure is 2n, where n is 3, 4 and 5, respectively.
  • the lower electrode is made of Pt, and the upper electrode is made of TiN. Its device structure is shown in Figures 7, 8 and 9.
  • the ferroelectric properties of the device come from the amount of ferroelectric phase in the film.
  • the Al atomic radius in the Al 2 O 3 material is smaller than the Hf atomic radius, and similar to the ZrO 2 material, the Al 2 O 3 material can also form a dopant-oxygen bond with O, considering the doping
  • the substance-oxygen bond can promote the formation of ferroelectric phase of HfO2 material and improve the ferroelectric performance of the device. Therefore, embodiments 4, 5 and 6 will also be able to achieve technical effects equivalent to those of the above embodiments 1-3.

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Abstract

一种超晶格铁电忆阻器，属于微电子器件技术领域，包括自下而上依次堆叠的下电极层、功能层和上电极层，其中，功能层是由至少一个超晶格单元构成的超晶格功能层，每一个超晶格单元是由第一功能材料和第二功能材料自下而上依次堆叠形成；功能层中任意一个由第一功能材料或第二功能材料形成的子功能层的厚度均满足0.6-5nm；第一功能材料为HfO 2，第二功能材料为ZrO 2或Al 2O 3。通过对器件功能层结构及组成进行改进，区别于传统金属掺杂HfO 2基铁电忆阻器，采用堆叠生长超晶格HfO 2层和ZrO 2层(或Al 2O 3层)作为铁电忆阻器功能层，具有良好的铁电性和忆阻特性。

Description

一种基于HfO 2/ZrO 2或HfO 2/Al 2O 3超晶格铁电忆阻器及其制备 【技术领域】
本发明属于微电子器件技术领域，更具体地，涉及一种基于HfO 2/ZrO 2或HfO 2/Al 2O 3超晶格铁电忆阻器及其制备方法，该超晶格薄膜具有高介电常数、低界面陷阱电荷以及高热稳定性等优势，有利于增加器件薄膜铁电相含量，促进薄膜极化翻转并提高器件铁电性能。与此同时，HfO 2与ZrO 2(或Al 2O 3)子功能层间存在氧空位缺陷和势垒，促使器件同时兼具优异的忆阻特性。
【背景技术】
后摩尔时代的到来伴随着元件尺寸微缩逐渐趋于物理极限，导致器件成本、速度和功耗的提高。数据的存储单元数目远低于处理单元，再加上存储速度之间的频繁交换带来了延迟和功耗，导致冯·诺依曼瓶颈的存储墙和功耗墙问题。制备低功耗、性能稳定且适用于“存算一体化”的非易失性存储器件成为突破冯诺依曼瓶颈的最佳解决方案。
铁电存储器作为新兴存储技术，通过施加外加电场的方式实现器件电极化翻转进而达到器件非易失性存储的目的。因其高读写速度、低功耗与传统CMOS工艺兼容等优点在存储、逻辑运算和神经网络计算等领域有着广泛应用潜力。传统铁电材料PbZrTiO 3和BaTiO 3已经实现在硅基MOSFET器件中的应用，但是存在与CMOS兼容和器件尺寸减小铁电性退化等问题。HfO 2和ZrO 2作为一种高K材料被认为是与CMOS兼容的理想高介质材料。
HfO 2分别存在单斜相、四方相和立方相。纯HfO 2为稳定存在的单斜相，其原子中心对称导致薄膜没有铁电性能。通过退火、掺杂等方式可以实现不同相之间的转变，形成非中心对称的四方相和立方相，进而实现器件的铁电性能。Michael Hoffmann等人(M.Hoffmann,Nano Energy.18,(2015))通过Si 掺杂HfO 2的方式获得极化强度为10uC/cm 2的铁电器件。Stefan Mueller等人(Mueller,S，Adv.Funct.Mater.22:2412-2417，2012)则制备了Al掺杂HfO 2的方式获得极化强度为5uC/cm 2的铁电器件。但是由于Si、Al等元素介电常数较低导致氧化铪薄膜介电常数降低，不同浓度的掺杂因为晶格失配而导致薄膜内部缺陷较多，器件的漏电流增加，器件不能够形成稳定的四方相/立方相氧化铪且铁电性能较弱。因此，制备具有高介电常数，低漏电流且能形成稳定铁电性能的铁电器件具有重要的研究意义。
另一方面，超晶格材料是两种晶格匹配度较高的材料以几纳米到几十纳米的薄层交替生长并保持严格周期性排列的多层膜。由于超晶格独特的量子力学效应，可以作为缓冲层提高相变存储器性能，例如，通过制备Sb 2Te 3/Bi 2Te 3超晶格结构作为缓冲层应用于相变存储器(中国专利申请《一种具有超晶格结构缓冲层的相变存储单元及制备方法》，CN112909162A)。与此同时，超晶格结构可以有效提供薄膜晶界进而引导导电细丝的形成路径应用于忆阻器，提高器件的一致性(中国专利申请《一种具有类超晶格材料功能层的忆阻器及其制备方法》，CN113078262A)。
【发明内容】
针对现有技术的以上缺陷或改进需求，本发明的目的在于提供一种基于HfO 2/ZrO 2或HfO 2/Al 2O 3超晶格铁电忆阻器及其制备，其中通过对器件功能层结构及组成进行改进，区别于传统金属掺杂HfO 2基铁电忆阻器，本发明采用堆叠生长超晶格HfO 2层和ZrO 2层(或Al 2O 3层)作为铁电忆阻器功能层，具有良好的铁电性和忆阻特性。该功能层基于HfO 2/ZrO 2超晶格结构或HfO 2/Al 2O 3超晶格结构，利用HfO 2和ZrO 2(或Al 2O 3)原子半径相等，晶体结构、晶格参数相似，具有较高的晶格匹配度，并且，较强的Hf-O键和Zr-O键(或Al-O键)可以很好的保持器件的剩余极化强度，实现非易失性存储；而超晶格界面间的应力更有利于诱导铁电相形成，界面间势垒可以有效束缚 电子、粒子的自由扩散，有效防止极化子中和以及相分离，提高铁电的疲劳特性，与此同时又为导电细丝的迁移提供有效形成路径，稳定器件忆阻特性。利用HfO 2/ZrO 2(或HfO 2/Al 2O 3)超晶格薄膜电学特性，器件可以在-3V-3V的电压范围内稳定循环30圈忆阻特性。并且，本发明尤其可通过简单的退火处理，使器件可以同时展现出铁电性和忆阻特性，对高性能铁电忆阻器及存储器的制备提供重要的理论指导和技术支撑。
为实现上述目的，按照本发明的一个方面，提供了一种超晶格铁电忆阻器，其特征在于，包括自下而上依次堆叠的下电极层、功能层和上电极层，其中，所述功能层是由至少一个超晶格单元构成的超晶格功能层，每一个超晶格单元是由第一功能材料和第二功能材料自下而上依次堆叠形成，并且，该功能层中任意一个由第一功能材料或第二功能材料形成的子功能层的厚度均满足0.6-5nm；该超晶格铁电忆阻器具体为基于HfO 2/ZrO 2的超晶格铁电忆阻器或基于HfO 2/Al 2O 3的超晶格铁电忆阻器，所述第一功能材料为四方相和/或立方相的HfO 2，所述第二功能材料为ZrO 2或Al 2O 3。
作为本发明的进一步优选，所述超晶格铁电忆阻器还经过了退火处理，退火温度为500℃－800℃；退火时间为20s-300s；
优选的，所述退火温度为650℃，所述退火时间为30s。
作为本发明的进一步优选，所述超晶格铁电忆阻器能够通过直流电压调节和限制电流调节使所述超晶格功能层的内部极化方向翻转或内部氧空位迁移，实现该超晶格铁电忆阻器高阻值与低阻值的切换调控；其中，所述直流电压调节是在-5V～5V范围内变化，所述限制电流调节在10uA～10mA范围内变化；
优选的，所述直流电压调节范围为-3V～3V,所使用的限制电流为10mA。
作为本发明的进一步优选，所述超晶格铁电忆阻器还通过脉冲振幅和频率调节所述超晶格功能层内部铁电畴翻转方向，实现该超晶格铁电忆阻器的非易失性铁电特性；其中，脉冲振幅控制为1V-4V，脉冲频率控制为 100Hz-5kHz；
更优选的，所述脉冲振幅和频率调节所施加的脉冲信号为三角脉冲，脉冲振幅为4V，频率为1kHz。
作为本发明的进一步优选，所述功能层中所述超晶格单元的数量为2n个，n为大于等于1、且小于等于5的整数。
作为本发明的进一步优选，所述n等于3，所述功能层是由HfO 2子功能层、ZrO 2子功能层、HfO 2子功能层、ZrO 2子功能层、HfO 2子功能层及ZrO 2子功能层这6层子功能层自下而上依次堆叠形成的；
或者，所述n等于3，所述功能层是由HfO 2子功能层、Al 2O 3子功能层、HfO 2子功能层、Al 2O 3子功能层、HfO 2子功能层及Al 2O 3子功能层这6层子功能层自下而上依次堆叠形成的。
作为本发明的进一步优选，所述功能层是通过原子层沉积(ALD)、脉冲激光沉积(PLD)、或分子束外延(MBE)方式在所述下电极层上依次堆叠第一功能材料和第二功能材料制备得到的。
作为本发明的进一步优选，所述功能层中各子功能层的厚度均为2nm；所述功能层的总厚度不超过20nm，更优选为12nm。
作为本发明的进一步优选，所述下电极层采用的电极材料选自Pt、Ti、ITO、Ag、Cu、TiN；所述上电极层采用的电极材料选自TiN、Pt、TaN、TiW、Au、W；
优选的，所述下电极层采用的电极材料为Pt，所述上电极层采用的电极材料为TiN。
按照本发明的另一方面，本发明提供了上述超晶格铁电忆阻器的制备方法，其特征在于，该制备方法是先在基底上制备下电极层，然后在所述下电极层上制备功能层；接着光刻，然后沉积上电极层；最后，在退火炉中退火；
优选的，所述功能层的沉积是通过原子层沉积(ALD)交替沉积第一功能材料和第二功能材料进行的；原子层沉积反应腔温度为260℃-330℃，更 优选为300℃。
通过本发明所构思的以上技术方案，与现有技术相比，针对现有的铁电忆阻器薄膜由于掺杂导致氧化铪薄膜介电常数降低，以及不同浓度的掺杂，晶格失配导致薄膜内部缺陷多，器件的漏电流大等关键问题，本发明采用与Hf原子半径相等，晶格结构和晶格参数类似且晶格失配低的ZrO 2材料(或Al 2O 3材料)，可通过ALD等工艺堆叠生长HfO 2层和ZrO 2层(或Al 2O 3层)的方式，生成HfO 2/ZrO 2(或HfO 2/Al 2O 3)超晶格结构铁电薄膜，并进一步得到基于超晶格铁电忆阻器，可有效利用超晶格高介电常数，低界面陷阱电荷密度、高热稳定性和低漏电流等特点，实现对器件性能的优化。
HfO 2和ZrO 2原子半径相等，晶体结构、晶格参数相似，具有较高的晶格匹配度，且均可以通过常见的沉积工艺(ALD、PLD和MBE)制备高质量，缺陷浓度较少的超晶格铁电薄膜；与此同时，较强的Hf-O键和Zr-O键可以很好的保持器件的剩余极化强度，实现非易失性存储。其次，本发明利用HfO 2/ZrO 2(HfO 2/Al 2O 3)超晶格薄膜电学特性，器件可以在-3V-3V的电压范围内稳定循环30圈忆阻特性。超晶格界面间的应力更有利于诱导铁电相形成。界面间势垒可以有效束缚电子、粒子的自由扩散，有效防止极化子中和以及相分离，提高铁电的疲劳特性。与此同时又为导电细丝的迁移提供有效形成路径，稳定器件忆阻特性。本发明利用HfO 2/ZrO 2(HfO 2/Al 2O 3)超晶格薄膜，优化了器件铁电性能，为铁电忆阻器的制备及优化提供了一个新思路。
本发明中的超晶格铁电忆阻器经过退火处理后展现出优异的铁电性能，退火温度优选为500℃－800℃，退火时间优选为20s-300s。HfO 2退火后存在铁电相和非铁电相，通过对薄膜进行表征，发现这些相存在随机分布的特点，其中，铁电相为四方相和/或立方相，非铁电相为单斜相。
本发明中的器件表现出了良好的铁电性和忆阻特性，尤其能够优化铁电器件性能。铁电特性的成因是薄膜内部铁电相的含量多少，以及施加电压时，极化翻转的程度决定了器件铁电性能的好坏；忆阻特性的成因是薄膜内部存 在氧空位，施加电压的过程中氧空位迁移导致在薄膜内部形成连接上下电极的氧空位导电细丝。本发明中的超晶格铁电忆阻器，可以利用合适的直流电压和限制电流调节超晶格薄膜内部氧空位迁移，实现器件高/低阻值调控，实现忆阻电学性能。以后文中的实施例为例，本发明器件可以实现稳定循环30圈且能够实现自限流特性。本发明中的超晶格铁电忆阻器，还可以利用合适的脉冲振幅(如，1V-4V)和频率(如，100Hz-5kHz)调节超晶格薄膜内部铁电畴翻转方向，实现器件非易失性铁电特性；利用超晶格界面处极化电荷增加的特性，优化提高器件极化强度，从而实现器件铁电电学性能以及优化。本发明对功能层厚度、施加电压大小等进行优选控制，以后文中的实施例为例，实施例中分别制备厚度分别为12nm、16nm和20nm HfO 2/ZrO 2的超晶格结构薄膜，当HfO 2/ZrO 2的超晶格结构薄膜厚度为12nm时，器件铁电特性是各个实施例中最优的，极化强度为13.27uC/cm 2。
具体分析的话，以HfO 2/ZrO 2超晶格功能层构建的超晶格铁电忆阻器为例，本发明相较于现有技术，能够取得下列有益效果：
(1)本发明设计HfO 2层和ZrO 2层堆叠生长形成超晶格的方式，制备具有优异铁电性能的铁电器件，因HfO 2/ZrO 2超晶格结构可以具有较好的晶格匹配度，所以界面陷阱电荷密度较少，器件漏电流减小，器件的铁电性能稳定性增加。HfO 2/ZrO 2超晶格薄膜有效提高铁电忆阻器件铁电性能。
(2)HfO 2/ZrO 2超晶格界面处陷阱电荷密度较少，器件忆阻特性稳定。通过施加较大的电压可以实现内部氧空位迁移，当施加限制电流为10mA时，器件稳定循环30圈忆阻特性。
(3)通过控制HfO 2/ZrO 2超晶格厚度优化器件铁电性能。制备不同厚度的HfO 2/ZrO 2超晶格铁电器件，施加相同的三角脉冲。实验结果表明，器件HfO 2/ZrO 2超晶格厚度对器件铁电性能有较为明显的影响。器件极化强度随着厚度的增加逐渐减小，极化强度由13.27uC/cm 2减小到6.54uC/cm 2。
(4)此外，制备HfO 2/ZrO 2超晶格铁电薄膜相较于传统的钙钛矿和锆钛 酸铅铁电材料，不含有毒元素铅，对环境友好。相较于掺杂Si、Y等元素，超晶格结构具有较高的晶格匹配度、较强的Hf-O和Zr-O键以及高热稳定性，可以很好的形成铁电相且保持铁电器件极化强度。对制备高性能铁电器件有巨大的优势。
HfO 2/Al 2O 3超晶格铁电薄膜，同理也具有相当性质，相较于ZrO 2材料，Al 2O 3材料中的Al原子半径小于Hf原子半径，且与ZrO 2材料相似，Al 2O 3材料也可以与O形成掺杂物-氧键，考虑到掺杂物-氧键可以促进HfO 2材料形成铁电相、提高器件铁电性能，因此，HfO 2/Al 2O 3超晶格铁电薄膜也能够取得与HfO 2/ZrO 2超晶格铁电薄膜相当的技术效果。
综上，本发明通过构建HfO 2/ZrO 2超晶格结构或HfO 2/Al 2O 3超晶格结构，形成超晶格结构铁电薄膜，并进一步得到一种新型的高性能HZO或HAO材料体系铁电忆阻器，为铁电器件后续在计算存储一体化芯片中的应用有重要的意义。
【附图说明】
图1是本发明实施例1所提供的基于HfO 2/ZrO 2超晶格结构铁电忆阻器的立体示意图(图中功能层有6层，2nm厚的HfO 2和2nm厚的ZrO 2以此交叠)。
图2是本发明实施例1所提供的基于HfO 2/ZrO 2超晶格结构铁电忆阻器的直流I-V特性。由图可知，基于HfO 2/ZrO 2超晶格结构铁电忆阻器在限制电流为10mA时，器件稳定循环30次。
图3是本发明实施例1所提供的基于HfO 2/ZrO 2超晶格结构铁电忆阻器在三角脉冲频率为1KHz,振幅分别为±3、±3.5和±4V电压下测得的电滞回线测试曲线。
图4是本发明实施例2所提供的基于HfO 2/ZrO 2超晶格结构铁电忆阻器的结构示意图及测得的电滞回线测试曲线；其中，图4中的(a)对应实施例2所提供的基于HfO 2/ZrO 2超晶格结构铁电忆阻器的结构示意图(功能层有8层， 每一层分别为2nm厚的HfO 2和2nm的厚ZrO 2依次堆叠)，图4中的(b)对应该器件退火后在100Hz的电流频率，在±4V电压下测得的电滞回线测试曲线(剩余极化强度为12.37uC/cm 2)。
图5是本发明实施例3所提供的基于HfO 2/ZrO 2超晶格结构铁电忆阻器的结构示意图及测得的电滞回线测试曲线；其中，图5中的(a)对应实施例3所提供的基于HfO 2/ZrO 2超晶格结构铁电忆阻器的结构示意图(功能层有10层，每一层分别为2nm厚的HfO 2和2nm的厚ZrO 2交叠)，图5中的(b)对应该器件退火后在1KHz的电流频率，在±4V电压下测得的100次电滞回线测试曲线。
图6是本发明实施例1、2、3所提供的三种铁电忆阻器退火后在1KHz的电流频率，在±4V电压下测得的电滞回线对比曲线。
图7是本发明实施例4所提供的基于HfO 2/Al 2O 3超晶格结构铁电忆阻器的结构示意图。器件结构中的超晶格结构一共有6层子功能层。
图8是本发明实施例5所提供的基于HfO 2/Al 2O 3超晶格结构铁电忆阻器的结构示意图。器件结构中的超晶格结构一共有8层子功能层。
图9是本发明实施例6所提供的基于HfO 2/Al 2O 3超晶格结构铁电忆阻器的结构示意图。器件结构中的超晶格结构一共有10层子功能层。
【具体实施方式】
为了使本发明的目的、技术方案及优点更加清楚明白，以下结合附图及实施例，对本发明进行进一步详细说明。应当理解，此处所描述的具体实施例仅仅用以解释本发明，并不用于限定本发明。此外，下面所描述的本发明各个实施方式中所涉及到的技术特征只要彼此之间未构成冲突就可以相互组合。
以HfO 2/ZrO 2超晶格铁电器件为例，本发明器件的制备可以利用ALD方法制备，具体的，可以先将反应腔加热到一定温度(250℃-330℃，尤其是300℃)，Hf[N(C 2H 5)CH 3] 4和Zr[N(C 2H 5)CH 3] 4分别作为Hf源和Zr源的前驱 体，水作为氧源，高纯氮气(N 2)为前驱载体和反应室清理气体，依次沉积HfO 2层和ZrO 2层(薄膜内部会存在少量氧空位)。
HfO 2层和ZrO 2层的总层数例如可以是4、6、8、10、12等。
以下为具体实施例：
实施例1：一种基于HfO 2/ZrO 2的超晶格结构铁电忆阻器制备方法
实施例1提供HfO 2/ZrO 2的超晶格结构铁电忆阻器，器件结构为TiN/ZrO 2/HfO 2/ZrO 2/HfO 2/ZrO 2/HfO 2/Pt，其结构如图1所示，本实施例中优选2nm厚的HfO 2和2nm厚的ZrO 2，共有6层。下电极采用材料为Pt，上电极采用材料为TiN。
该HfO 2/ZrO 2的超晶格结构铁电忆阻器制备方法；具体步骤如下：
(1)第一步：衬底清洗：
将附有SiO 2的Si基片分别先后浸没在丙酮和酒精溶液中超声清洗10min。将样品放入等离子水中，超声清洗3min。
(2)第二步：下电极制备：
采用磁控溅射的方法在衬底上制备100nm厚的Pt下电极，具体工艺参数：溅射背景真空为5×10 -5Pa，溅射气压为0.5Pa，功率为35W，溅射时间为700s。
(3)第三步：功能层制备：
采用ALD方法在Pt底电极是上制备功能层，具体的工艺流程为：①先将反应腔体升温到300℃；②通入N 2清洗反应腔；③沉积2nm的HfO 2(前驱体Hf[N(C 2H 5)CH 3] 4，氧化剂为H 2O)；④沉积2nm的ZrO 2(前驱体Zr[N(C 2H 5)CH 3] 4，氧化剂为H 2O)；③和④过程循环3次得到HfO 2/ZrO 2的超晶格功能层。当然，受工艺条件制约，ALD沉积得到的超晶格薄膜中，也可能存在缺陷。
(4)第四步：图形转移：
使用光刻工艺进行图形转移，在第三步中得到的功能层上，通过光刻预留出上电极的区域；上电极的尺寸为50μm×50μm的小方块，光刻的工艺包括：匀胶，前烘，前曝，后烘，后曝，显影等步骤。
(5)第五步：上电极制备：
使用磁控溅射方法制备100nm厚的TiN上电极。具体工艺参数：溅射的背景真空为5×10 -5Pa，溅射气压为0.5Pa。功率为120W,溅射时间为1200s。
(6)第六步：剥离：
将上电极制备步骤中得到的样品浸入丙酮溶液中超声剥离振荡至光刻胶及其上方的多余电极材料全部脱落，依次将其浸入乙醇溶液和去离子水中清洗，并用氮气枪吹干。
(7)第七步：退火：
使用退火炉将第六步得到的器件进行退火，具体的：退火的背景真空为4×10 -2Pa，温度为650℃，时间为30s。
(8)第八步：对实施例1铁电忆阻器单元进行忆阻性能测试：
将第七步退火后的器件进行忆阻特性测试，测试了30个循环的直流响应，结果如图2所示，从图中可以看出，退火后的器件忆阻性能在限制电流为10mA，电压为-3V-3V时，器件稳定循环30圈。
(9)第九步：对实施例1铁电忆阻器单元进行铁电性能测试：
将第七步退火后的器件进行铁电特性测试。分别设置三角脉冲频率为1KHz，振幅为±3、±3.5和±4V。如图3所示为不同脉冲振幅下实施例1铁电性能P-E图像，从中可以看出器件在三个电压下都存在铁电性，剩余极化值分别为8.75uC/cm 2、9.85uC/cm 2和13.30uC/cm 2。
实施例2
实施例2与实施例1大体相似，主要的区别在于第三步在ALD镀功能层时，③和④过程循环4次得到总厚度为16nm的HfO 2/ZrO 2的超晶格功能层。如图4所示为实施例2在施加三角脉冲频率为100Hz，振幅为±4V时的铁电特性P-E曲线。当超晶格薄膜厚度增加时，实施例2的剩余极化为12.37uC/cm 2。
实施例3
实施例3与实施例1大体相似，主要的区别在于第三步在ALD镀功能层时，③和④过程循环5次得到总厚度为20nm的HfO 2/ZrO 2的超晶格功能层。如图5所示为实施例3在施加三角脉冲频率为100Hz，振幅为±4V时的循环铁电特性P-E曲线。当超晶格薄膜厚度增加时，实施例3的剩余极化为6.58uC/cm 2。
实施例4、5和6：一种基于HfO 2/Al 2O 3超晶格结构铁电忆阻器制备方法
实施例4、5和6提供HfO 2/Al 2O 3超晶格结构铁电忆阻器，器件结构如图7、8和9所示，为HfO 2/Al 2O 3超晶格结构。这些实施例中优选2nm厚的HfO 2和2nm厚的Al 2O 3，HfO 2/Al 2O 3结构的总层数2n,其中n分别为3、4和5。下电极采用材料为Pt，上电极采用材料为TiN。如图7、8和9所示为其器件结构。
器件铁电特性来源于薄膜铁电相含量多少。相较于ZrO 2材料，Al 2O 3材料中的Al原子半径小于Hf原子半径，且与ZrO 2材料相似，Al 2O 3材料也可以与O形成掺杂物-氧键，考虑到掺杂物-氧键可以促进HfO 2材料形成铁电相、提高器件铁电性能，因此，实施例4、5和6也将能够取得与上述实施例1－3相当的技术效果。
本领域的技术人员容易理解，以上所述仅为本发明的较佳实施例而已，并不用以限制本发明，凡在本发明的精神和原则之内所作的任何修改、等同替换和改进等，均应包含在本发明的保护范围之内。

Claims (10)

  1. 一种超晶格铁电忆阻器，其特征在于，包括自下而上依次堆叠的下电极层、功能层和上电极层，其中，所述功能层是由至少一个超晶格单元构成的超晶格功能层，每一个超晶格单元是由第一功能材料和第二功能材料自下而上依次堆叠形成，并且，该功能层中任意一个由第一功能材料或第二功能材料形成的子功能层的厚度均满足0.6-5nm；该超晶格铁电忆阻器具体为基于HfO 2/ZrO 2的超晶格铁电忆阻器或基于HfO 2/Al 2O 3的超晶格铁电忆阻器，所述第一功能材料为四方相和/或立方相的HfO 2，所述第二功能材料为ZrO 2或Al 2O 3。
  2. 如权利要求1所述超晶格铁电忆阻器，其特征在于，所述超晶格铁电忆阻器还经过了退火处理，退火温度为500℃－800℃；退火时间为20s-300s；
    优选的，所述退火温度为650℃，所述退火时间为30s。
  3. 如权利要求1所述超晶格铁电忆阻器，其特征在于，所述超晶格铁电忆阻器能够通过直流电压调节和限制电流调节使所述超晶格功能层的内部极化方向翻转或内部氧空位迁移，实现该超晶格铁电忆阻器高阻值与低阻值的切换调控；其中，所述直流电压调节是在-5V～5V范围内变化，所述限制电流调节在10uA～10mA范围内变化；
    优选的，所述直流电压调节范围为-3V～3V,所使用的限制电流为10mA。
  4. 如权利要求1所述超晶格铁电忆阻器，其特征在于，所述超晶格铁电忆阻器还通过脉冲振幅和频率调节所述超晶格功能层内部铁电畴翻转方向，实现该超晶格铁电忆阻器的非易失性铁电特性；其中，脉冲振幅控制为1V-4V，脉冲频率控制为100Hz-5kHz；
    更优选的，所述脉冲振幅和频率调节所施加的脉冲信号为三角脉冲，脉冲振幅为4V，频率为1kHz。
  5. 如权利要求1所述超晶格铁电忆阻器，其特征在于，所述功能层中所 述超晶格单元的数量为2n个，n为大于等于1、且小于等于5的整数。
  6. 如权利要求5所述超晶格铁电忆阻器，其特征在于，所述n等于3，所述功能层是由HfO 2子功能层、ZrO 2子功能层、HfO 2子功能层、ZrO 2子功能层、HfO 2子功能层及ZrO 2子功能层这6层子功能层自下而上依次堆叠形成的；
    或者，所述n等于3，所述功能层是由HfO 2子功能层、Al 2O 3子功能层、HfO 2子功能层、Al 2O 3子功能层、HfO 2子功能层及Al 2O 3子功能层这6层子功能层自下而上依次堆叠形成的。
  7. 如权利要求1所述超晶格铁电忆阻器，其特征在于，所述功能层是通过原子层沉积(ALD)、脉冲激光沉积(PLD)、或分子束外延(MBE)方式在所述下电极层上依次堆叠第一功能材料和第二功能材料制备得到的。
  8. 如权利要求1所述超晶格铁电忆阻器，其特征在于，所述功能层中各子功能层的厚度均为2nm；所述功能层的总厚度不超过20nm，更优选为12nm。
  9. 如权利要求1所述超晶格铁电忆阻器，其特征在于，所述下电极层采用的电极材料选自Pt、Ti、ITO、Ag、Cu、TiN；所述上电极层采用的电极材料选自TiN、Pt、TaN、TiW、Au、W；
    优选的，所述下电极层采用的电极材料为Pt，所述上电极层采用的电极材料为TiN。
  10. 如权利要求1－9任意一项所述超晶格铁电忆阻器的制备方法，其特征在于，该制备方法是先在基底上制备下电极层，然后在所述下电极层上制备功能层；接着光刻，然后沉积上电极层；最后，在退火炉中退火；
    优选的，所述功能层的沉积是通过原子层沉积(ALD)交替沉积第一功能材料和第二功能材料进行的；原子层沉积反应腔温度为260℃-330℃，更优选为300℃。
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CN104009156A (zh) * 2014-06-06 2014-08-27 湘潭大学 一种多晶铁电薄膜基铁电阻变存储器
CN113196490A (zh) * 2019-05-24 2021-07-30 桑迪士克科技有限责任公司 包含双终端选择器的三维nand存储器器件及其使用和制造方法
CN111009609A (zh) * 2019-12-24 2020-04-14 华中科技大学 一种超晶格忆阻器功能层材料、忆阻器单元及其制备方法
CN111223873A (zh) * 2020-01-16 2020-06-02 华中科技大学 非对称的铁电功能层阵列、铁电隧道结多值存储单元的制备方法
CN112701220A (zh) * 2020-10-23 2021-04-23 大连理工大学 一种带有金属Hf缓冲层的HfO2基忆阻器及其制作方法
CN113285020A (zh) * 2021-04-29 2021-08-20 华中科技大学 一种单通道忆阻器及其制备方法

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