CN117222306A - Ferroelectric cell, three-dimensional ferroelectric structure and ferroelectric memory - Google Patents
Ferroelectric cell, three-dimensional ferroelectric structure and ferroelectric memory Download PDFInfo
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- 230000015654 memory Effects 0.000 title claims abstract description 24
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 44
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 44
- 239000001301 oxygen Substances 0.000 claims abstract description 44
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 claims abstract description 14
- 229910052726 zirconium Inorganic materials 0.000 claims abstract description 14
- 229910052735 hafnium Inorganic materials 0.000 claims abstract description 13
- VBJZVLUMGGDVMO-UHFFFAOYSA-N hafnium atom Chemical compound [Hf] VBJZVLUMGGDVMO-UHFFFAOYSA-N 0.000 claims abstract description 13
- 239000000463 material Substances 0.000 claims description 62
- 229910052751 metal Inorganic materials 0.000 claims description 41
- 239000002184 metal Substances 0.000 claims description 41
- NRTOMJZYCJJWKI-UHFFFAOYSA-N Titanium nitride Chemical group [Ti]#N NRTOMJZYCJJWKI-UHFFFAOYSA-N 0.000 claims description 26
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 claims description 14
- 229910052721 tungsten Inorganic materials 0.000 claims description 14
- 239000010937 tungsten Substances 0.000 claims description 14
- KQHQLIAOAVMAOW-UHFFFAOYSA-N hafnium(4+) oxygen(2-) zirconium(4+) Chemical compound [O--].[O--].[O--].[O--].[Zr+4].[Hf+4] KQHQLIAOAVMAOW-UHFFFAOYSA-N 0.000 claims description 12
- 238000002161 passivation Methods 0.000 claims description 6
- 230000005684 electric field Effects 0.000 description 67
- 230000010287 polarization Effects 0.000 description 21
- 238000000151 deposition Methods 0.000 description 20
- 238000010586 diagram Methods 0.000 description 17
- 230000008021 deposition Effects 0.000 description 16
- 229910000449 hafnium oxide Inorganic materials 0.000 description 13
- 230000006870 function Effects 0.000 description 10
- 239000007769 metal material Substances 0.000 description 10
- 238000000034 method Methods 0.000 description 10
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 8
- 238000000231 atomic layer deposition Methods 0.000 description 7
- 238000004519 manufacturing process Methods 0.000 description 7
- 230000000739 chaotic effect Effects 0.000 description 5
- 238000009792 diffusion process Methods 0.000 description 5
- WIHZLLGSGQNAGK-UHFFFAOYSA-N hafnium(4+);oxygen(2-) Chemical compound [O-2].[O-2].[Hf+4] WIHZLLGSGQNAGK-UHFFFAOYSA-N 0.000 description 5
- 238000002360 preparation method Methods 0.000 description 5
- 230000008569 process Effects 0.000 description 5
- CIWBSHSKHKDKBQ-JLAZNSOCSA-N Ascorbic acid Chemical compound OC[C@H](O)[C@H]1OC(=O)C(O)=C1O CIWBSHSKHKDKBQ-JLAZNSOCSA-N 0.000 description 4
- 238000007254 oxidation reaction Methods 0.000 description 4
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 3
- 125000004429 atom Chemical group 0.000 description 3
- 238000002425 crystallisation Methods 0.000 description 3
- 230000008025 crystallization Effects 0.000 description 3
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 3
- 239000000243 solution Substances 0.000 description 3
- 239000000758 substrate Substances 0.000 description 3
- 238000000137 annealing Methods 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 239000010931 gold Substances 0.000 description 2
- CJNBYAVZURUTKZ-UHFFFAOYSA-N hafnium(IV) oxide Inorganic materials O=[Hf]=O CJNBYAVZURUTKZ-UHFFFAOYSA-N 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- 239000002243 precursor Substances 0.000 description 2
- 238000003860 storage Methods 0.000 description 2
- 230000003313 weakening effect Effects 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 125000004122 cyclic group Chemical group 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000011982 device technology Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 230000005621 ferroelectricity Effects 0.000 description 1
- -1 for example Substances 0.000 description 1
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 1
- 229910052737 gold Inorganic materials 0.000 description 1
- 230000010365 information processing Effects 0.000 description 1
- 230000010354 integration Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 125000004430 oxygen atom Chemical group O* 0.000 description 1
- RVTZCBVAJQQJTK-UHFFFAOYSA-N oxygen(2-);zirconium(4+) Chemical compound [O-2].[O-2].[Zr+4] RVTZCBVAJQQJTK-UHFFFAOYSA-N 0.000 description 1
- 229910052763 palladium Inorganic materials 0.000 description 1
- 238000000206 photolithography Methods 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 229910052715 tantalum Inorganic materials 0.000 description 1
- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 description 1
- 239000010409 thin film Substances 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
- 230000005641 tunneling Effects 0.000 description 1
- 229910001928 zirconium oxide Inorganic materials 0.000 description 1
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10B—ELECTRONIC MEMORY DEVICES
- H10B51/00—Ferroelectric RAM [FeRAM] devices comprising ferroelectric memory transistors
- H10B51/30—Ferroelectric RAM [FeRAM] devices comprising ferroelectric memory transistors characterised by the memory core region
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10B—ELECTRONIC MEMORY DEVICES
- H10B53/00—Ferroelectric RAM [FeRAM] devices comprising ferroelectric memory capacitors
- H10B53/20—Ferroelectric RAM [FeRAM] devices comprising ferroelectric memory capacitors characterised by the three-dimensional arrangements, e.g. with cells on different height levels
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10B—ELECTRONIC MEMORY DEVICES
- H10B53/00—Ferroelectric RAM [FeRAM] devices comprising ferroelectric memory capacitors
- H10B53/30—Ferroelectric RAM [FeRAM] devices comprising ferroelectric memory capacitors characterised by the memory core region
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N97/00—Electric solid-state thin-film or thick-film devices, not otherwise provided for
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Abstract
The embodiment of the application provides a ferroelectric unit, a three-dimensional ferroelectric structure and a ferroelectric memory, and the ferroelectric unit comprises: a first electrode; a first ferroelectric layer disposed on the surface of the first electrode; the second ferroelectric layer is arranged on the surface of the first ferroelectric layer and is far away from one side of the first electrode; the second electrode is arranged on the surface of the second ferroelectric layer and is far away from one side of the first ferroelectric layer; wherein the concentration of a first element in the first ferroelectric layer is higher than the concentration of the first element in the second ferroelectric layer, and the first element is one of hafnium element, zirconium element and oxygen element. The ferroelectric unit can flexibly adjust the electrical symmetry of the ferroelectric device, thereby improving the performance of the ferroelectric device.
Description
Technical Field
The embodiment of the application relates to the technical field of semiconductor devices, in particular to a ferroelectric unit, a three-dimensional ferroelectric structure and a ferroelectric memory.
Background
With the development of electronic technology, the demands for information processing capability and information storage capacity are also increasing. Ferroelectric materials are used for storage due to their inherent advantages of fast erasing speed, ultra low power consumption, multiple cycle times, non-volatile polarization stateIn the field, ferroelectric devices such as ferroelectric random access memories (FeRAM, ferroelectric random access memory) and ferroelectric tunnel junctions (FTJ, ferroelectric tunneling junction) based on ferroelectric materials have received a lot of attention. Wherein the ferroelectric hafnium oxide material, for example, solid solution HfO of hafnium oxide and zirconium oxide 2 :ZrO 2 The ferroelectric material is also called zirconium doped hafnium oxide (HfZrOx), and has the advantages of low crystallization temperature, high integration level, compatibility with CMOS technology and the like, so that the ferroelectric material is a research direction.
In the existing ferroelectric device technology based on ferroelectric hafnium oxide materials, the basic cell structures of FeRAM and FTJ are usually formed by disposing a ferroelectric thin film between two metal electrodes, that is, a sandwich structure of "metal-ferroelectric layer-metal". However, in this structure, since the metal electrodes on both sides of the ferroelectric layer are affected by various factors such as metal materials, deposition manner, element ratio, and crystallization degree, the work functions of the metal electrodes on both sides of the ferroelectric layer are generally different, which results in the ferroelectric device having electrical asymmetry mainly including: the polarization curve of the ferroelectric device shifts; under the applied electric fields with the same electric field strength and different polarities, the leakage current of the ferroelectric devices is different in size. In general, the magnitude of electrical asymmetry of a ferroelectric device is not controlled by the outside, and for some ferroelectric devices (such as FeRAM) requiring symmetry, the electrical asymmetry causes problems of asymmetry of positive and negative erasing of the ferroelectric device, incomplete inversion in a certain direction, asymmetry of anti-interference performance, and the like; in addition, for ferroelectric devices (e.g., FTJ) that require the device's switching ratio to be achieved with electrical asymmetry, ferroelectric devices of a target switching ratio are difficult to achieve due to uncontrolled electrical asymmetry of the ferroelectric device. Thus, how to effectively adjust the electrical asymmetry of the ferroelectric device to improve the performance of the ferroelectric device is a problem to be solved.
Disclosure of Invention
By adopting the ferroelectric unit, the three-dimensional ferroelectric structure and the ferroelectric memory which are shown in the embodiment of the application, the performance of the ferroelectric device can be improved.
In order to achieve the above purpose, the application adopts the following technical scheme:
in a first aspect, embodiments of the present application provide a ferroelectric cell comprising: a first electrode; a first ferroelectric layer disposed on the surface of the first electrode; the second ferroelectric layer is arranged on the surface of the first ferroelectric layer and is far away from one side of the first electrode; the second electrode is arranged on the surface of the second ferroelectric layer and is far away from one side of the first ferroelectric layer; wherein the concentration of a first element in the first ferroelectric layer is higher than the concentration of the first element in the second ferroelectric layer, and the first element is one of hafnium element, zirconium element and oxygen element.
According to the ferroelectric unit provided by the embodiment of the application, the concentration of the first element in the first ferroelectric layer is set to be higher than that in the second ferroelectric layer by arranging two ferroelectric layers between the two electrodes. Thus, by setting the first element concentration difference between the two ferroelectric layers, the concentration of oxygen vacancies between the first ferroelectric layer and the second ferroelectric layer can be made different, so that a first built-in electric field can be generated between the contact interfaces of the two ferroelectric layers; in addition, there is typically a second built-in electric field between the first electrode and the second electrode. In this way, by adjusting the positional relationship between the electrode and each ferroelectric layer, the first built-in electric field and the second built-in electric field can cancel or overlap each other, so as to improve the electrical symmetry of the ferroelectric device or reduce the electrical symmetry of the ferroelectric device, that is, flexibly adjust the electrical symmetry of the ferroelectric device, thereby improving the performance of the ferroelectric device.
In addition, the concentration of the first element in the two ferroelectric layers is changed to generate a built-in electric field between the contact interfaces of the two ferroelectric layers, so that the element is not required to be introduced between the ferroelectric layers and the electrodes to generate the built-in electric field at the contact interface between the ferroelectric layers and the electrodes, the contact interface between the electrodes and the ferroelectric layers is prevented from being in a chaotic state due to element diffusion, and the feasibility of practical production and use of the ferroelectric device is further improved.
The embodiments of the present application may achieve the above-described difference in oxygen vacancy concentration between the first ferroelectric layer and the second ferroelectric layer in various ways.
In a first possible implementation, the material of the first ferroelectric layer and the material of the second ferroelectric layer are both hafnium zirconium oxide; when the first element is hafnium, the concentration of the second element in the first ferroelectric layer is lower than that of the second element in the second ferroelectric layer, and the second element is zirconium.
In this implementation, when the first electrode is titanium nitride and the second electrode is tungsten, the built-in electric field of the ferroelectric cell is a superposition of the built-in electric field between the two electrodes and the built-in electric field between the two ferroelectric layers, because the concentration of oxygen vacancies in the first ferroelectric layer is lower than that of the second ferroelectric layer, in this implementation, the non-electrical symmetry of the ferroelectric cell can be improved to improve the performance of devices such as FTJ that implement the switching ratio.
In this implementation, when the first electrode is metallic tungsten and the second electrode is titanium nitride, the built-in electric field of the ferroelectric cell is the built-in electric field between the two electrodes minus the built-in electric field between the two ferroelectric layers, because the concentration of oxygen vacancies in the first ferroelectric layer is lower than that in the second ferroelectric layer, in this implementation, the electrical symmetry of the ferroelectric cell can be improved to improve the performance of ferroelectric devices such as FeROM.
In a second possible implementation manner, the material of the one ferroelectric layer and the material of the second ferroelectric layer are hafnium zirconium oxide; when the first element is zirconium, the concentration of the second element in the first ferroelectric layer is lower than that of the second element in the second ferroelectric layer, and the second element is hafnium.
In this possible implementation manner, the first electrode is titanium nitride, and the second electrode is tungsten metal; or the second electrode is titanium nitride, and the first electrode is tungsten metal.
In a third possible implementation manner, the material of the one ferroelectric layer and the material of the second ferroelectric layer are hafnium zirconium oxide; the concentration of oxygen element in the first ferroelectric layer is higher than the concentration of oxygen element in the second ferroelectric layer.
In this possible implementation manner, the first electrode is titanium nitride, and the second electrode is tungsten metal; or the second electrode is titanium nitride, and the first electrode is tungsten metal.
In a second aspect, embodiments of the present application provide a three-dimensional ferroelectric structure comprising: a first annular region formed by the plurality of passivation layers and the plurality of first electrode stacks; a first ferroelectric layer is arranged on the inner side of the first annular region, and the first ferroelectric layer is contacted with the passivation layers and the first electrodes; a second ferroelectric layer is arranged on one side of the first ferroelectric layer far away from the first annular region; a second electrode is arranged on one side of the second ferroelectric layer far away from the first ferroelectric layer; wherein the concentration of a first element in the first ferroelectric layer is higher than the concentration of the first element in the second ferroelectric layer, and the first element is one of hafnium element, zirconium element and oxygen element.
According to the embodiment of the application, the three-dimensional ferroelectric structure is arranged, so that a plurality of first electrodes can share the same ferroelectric layer, and a plurality of ferroelectric units are formed. For example, one ferroelectric cell is formed between one of the first electrode, the first ferroelectric layer, the second ferroelectric layer, and the second electrode.
In addition, in the ferroelectric unit provided by the embodiment of the application, the concentration of the first element in the first ferroelectric layer is set to be higher than that in the second ferroelectric layer by arranging two ferroelectric layers between the two electrodes. Thus, by setting the first element concentration difference between the two ferroelectric layers, the concentration of oxygen vacancies between the first ferroelectric layer and the second ferroelectric layer can be made different, so that a first built-in electric field can be generated between the contact interfaces of the two ferroelectric layers; in addition, there is typically a second built-in electric field between the first electrode and the second electrode. In this way, by adjusting the positional relationship between the electrode and each ferroelectric layer, the first built-in electric field and the second built-in electric field can cancel or overlap each other, so as to improve the electrical symmetry of the ferroelectric device or reduce the electrical symmetry of the ferroelectric device, that is, flexibly adjust the electrical symmetry of the ferroelectric device, thereby improving the performance of the ferroelectric device.
In addition, the concentration of the first element in the two ferroelectric layers is changed to generate a built-in electric field between the contact interfaces of the two ferroelectric layers, so that the element is not required to be introduced between the ferroelectric layers and the electrodes to generate the built-in electric field at the contact interface between the ferroelectric layers and the electrodes, the contact interface between the electrodes and the ferroelectric layers is prevented from being in a chaotic state due to element diffusion, and the feasibility of practical production and use of the ferroelectric device is further improved.
In one possible implementation, the material of the first ferroelectric layer and the material of the second ferroelectric layer are both hafnium zirconium oxide; when the first element is hafnium, the concentration of the second element in the first ferroelectric layer is lower than that of the second element in the second ferroelectric layer, and the second element is zirconium.
In one possible implementation, the material of the one ferroelectric layer and the material of the second ferroelectric layer are both hafnium zirconium oxide; when the first element is zirconium, the concentration of the second element in the first ferroelectric layer is lower than that of the second element in the second ferroelectric layer, and the second element is hafnium.
In one possible implementation, the material of the first electrode is tungsten; the second electrode is formed by two metal layers, the material in contact with the second ferroelectric layer in the two metal layers is titanium nitride, and the material in non-contact with the second ferroelectric layer in the two metal layers is tungsten.
In a third aspect, embodiments of the present application provide a ferroelectric memory including a plurality of memory cells arranged in an array; each memory cell of the plurality of memory cells comprises a transistor and a ferroelectric cell as described in the first aspect.
It should be understood that, the second aspect to the third aspect of the present application are consistent with the technical solutions of the first aspect of the present application, and the beneficial effects obtained by each aspect and the corresponding possible embodiments are similar, and are not repeated.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the description of the embodiments of the present application will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic diagram of a ferroelectric cell according to the prior art provided by the present application;
FIG. 2A is a schematic diagram showing a ferroelectric cell in which the polarization curve of the ferroelectric cell is not shifted according to the present application;
FIG. 2B is a schematic diagram showing the drift of the polarization curve of a ferroelectric cell according to the present application;
FIG. 2C is a schematic diagram showing the ferroelectric cell according to the present application without drift of leakage current;
FIG. 2D is a schematic diagram showing the drift of the leakage current of the ferroelectric cell according to the present application;
fig. 3 is a schematic diagram of another prior art ferroelectric cell according to the present application;
fig. 4A is a schematic structural diagram of a ferroelectric cell according to an embodiment of the present application;
FIG. 4B is a schematic diagram showing the built-in electric field weakening of the ferroelectric cell shown in FIG. 4A according to the embodiment of the present application;
FIG. 4C is a flow chart for preparing the ferroelectric cell shown in FIG. 4A provided by an embodiment of the present application;
fig. 5A is a schematic diagram of another structure of a ferroelectric cell according to an embodiment of the present application;
FIG. 5B is a schematic diagram of the built-in electric field enhancement of the ferroelectric cell shown in FIG. 5A according to an embodiment of the present application;
fig. 6 is a schematic diagram of still another structure of a ferroelectric cell according to an embodiment of the present application;
fig. 7 is a schematic view of still another structure of a ferroelectric cell according to an embodiment of the present application;
FIG. 8A is a schematic diagram of a three-dimensional ferroelectric structure provided by an embodiment of the present application;
FIG. 8B is a cross-sectional view of the three-dimensional ferroelectric structure shown in FIG. 8A along line AA';
fig. 9 is a schematic structural diagram of a ferroelectric memory according to an embodiment of the present application.
Detailed Description
The following description of the embodiments of the present application will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are some, but not all embodiments of the application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
The terms "first," "second," and the like, herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. Likewise, the terms "a" or "an" and the like do not denote a limitation of quantity, but rather denote the presence of at least one.
In embodiments of the application, words such as "exemplary" or "such as" are used to mean examples, illustrations, or descriptions. Any embodiment or design described herein as "exemplary" or "e.g." in an embodiment should not be taken as preferred or advantageous over other embodiments or designs. Rather, the use of words such as "exemplary" or "such as" is intended to present related concepts in a concrete fashion. In the description of the embodiments of the present application, unless otherwise indicated, the meaning of "a plurality" means two or more.
Referring to fig. 1, fig. 1 is a schematic structural diagram of a ferroelectric cell according to an embodiment of the present application. In fig. 1, a ferroelectric cell includes a top metal electrode, a bottom metal electrode, and a ferroelectric layer disposed between two metal electrodes formed over a substrate. Wherein the top metal electrode is a patterned metal layer formed by photolithography, the top electrode being formed of one or more metal materials including, for example, but not limited to, gold (Au), platinum (Pt), tantalum (Ta), titanium nitride (TiN), aluminum (Al), tungsten (W), or palladium (Pd), etc. The top electrode is schematically shown in fig. 1 as being formed of a W metal material. The bottom electrode is formed of a titanium nitride (TiN) material. The material of the ferroelectric layer is hafnium zirconium oxide (HaZrO, hafnium zirconium oxide). In the ferroelectric cell shown in fig. 1, the ferroelectric polarization of the ferroelectric cell is tuned by changing the material of the top electrode. When the top electrode is made of multiple metal materials and different metal materials are adopted between the top electrode and the bottom electrode, the polarization characteristic curves of the different metal materials are different, so that the polarization intensity of the ferroelectric unit is different due to the fact that the thermal expansion coefficients of the different metal materials are different, the coercive field of the ferroelectric unit is different due to the fact that the metal work functions of the different metal materials are different, the polarization curves of the ferroelectric device drift, and the leakage current of the ferroelectric device is different under the external electric fields with the same electric field intensity and different polarities. It should be noted that, when the top electrode and the bottom electrode of the ferroelectric cell shown in fig. 1 are made of the same metal material, the polarization curve and the leakage current of the ferroelectric device are also shifted due to different deposition modes, element ratios, crystallization degrees, thermal budget and other factors of the metal material. As shown in fig. 2A to 2D. Fig. 2A is a polarization curve of a ferroelectric cell, with an applied electric field on the abscissa and ferroelectric polarization intensity on the ordinate. In the situation shown in fig. 2A, the positive and negative polarization curves of the ferroelectric cell are symmetrical about the ordinate, i.e. in the case of opposite polarity and equal magnitude of the applied electric field, the positive and negative coercive fields are of the same magnitude and opposite polarity. Fig. 2B is a graph of polarization of a ferroelectric cell undergoing drift, wherein the solid line indicates that the polarization of the ferroelectric cell undergoes positive drift, and the dotted line indicates that the polarization of the ferroelectric cell undergoes negative drift. As can be seen from fig. 2B, after the polarization curve of the ferroelectric cell shifts, the positive and negative polarization curves are no longer symmetrical about the ordinate, i.e. the positive and negative coercive fields are of different magnitudes in the case of opposite polarities of the applied electric field. Fig. 2C is a graph of leakage current for a ferroelectric cell, with the applied electric field on the abscissa and leakage current on the ordinate. In the case shown in fig. 2C, the leakage current is the same in the applied electric fields of the same electric field strength and different polarities. Fig. 2D is a graph of leakage current of a ferroelectric cell with drift, wherein the solid line indicates positive drift of the leakage current of the ferroelectric cell, and the dotted line indicates negative drift of the leakage current of the ferroelectric cell. As can be seen from fig. 2D, after the leakage current curve of the ferroelectric cell shifts, the leakage currents under the applied electric fields with the same electric field strength and different polarities are different.
For most ferroelectric memories in which the polarization curve and the leakage current are expected not to drift, when the polarization curve and the leakage current curve of the ferroelectric cell are respectively as shown in fig. 2B and fig. 2D, the problems of asymmetry of the positive and negative erasing of the ferroelectric device, incomplete inversion in a certain direction, asymmetry of anti-interference performance, and the like are caused. However, for some ferroelectric devices, such as FTJ, it is desirable to utilize the drift of polarization curves and leakage currents to achieve the switching ratio of the device. In this case, it is necessary to adjust the polarization curve and the drift amount of the leakage current based on the magnitude of the switching ratio. In order to realize adjustment of the on-off ratio of FTJ and other devices, it is further proposed to adjust the symmetry of the ferroelectric cell by changing the atoms at the interface of the ferroelectric layer and the metal electrode, as shown in fig. 3. In fig. 3, the ferroelectric cell includes two TiN electrodes, and a ferroelectric layer disposed between the two TiN electrodes. In the ferroelectric cell shown in fig. 3, based on the material of the ferroelectric layer, different atoms are respectively introduced into the contact interface between each layer of TiN electrode and the ferroelectric layer to form a non-zero built-in electric field, so as to adjust the symmetry of the ferroelectric cell. For example, the ferroelectric layer material shown in fig. 3 is HfO 2 Hf atoms are introduced into the contact interface between the left TiN electrode and the ferroelectric layer, and O atoms are introduced into the contact interface between the right TiN electrode and the ferroelectric layer. Although the method of adjusting the symmetry of the ferroelectric cell shown in fig. 3 is theoretically possible, in actual production, high-temperature annealing is usually required to induce the ferroelectric cell to generate ferroelectricity. In the high-temperature annealing process, element diffusion occurs between the electrode layer and the ferroelectric layer, so that the contact interface between the electrode and the ferroelectric layer is in a relatively chaotic state, and the distribution of elements at the interface is difficult to accurately control.
As can be seen from the prior art shown in fig. 1 to 3, in the ferroelectric unit provided by the embodiment of the present application, by disposing two ferroelectric layers between two electrodes, the concentration of the first element contained in one ferroelectric layer is higher than that contained in the other ferroelectric layer. Thus, a first built-in electric field is generated between contact interfaces of the two ferroelectric layers due to the first element concentration difference between the two ferroelectric layers; in addition, due to the different materials of the two layers of electrodes, the work functions between the two layers of electrodes are different, namely a second built-in electric field is generated between the two layers of electrodes; by adjusting the position relation between the electrode and each ferroelectric layer, the first built-in electric field and the second built-in electric field can offset or overlap each other, so as to improve the electrical symmetry of the ferroelectric device or reduce the electrical symmetry of the ferroelectric device, and the electrical symmetry of the ferroelectric device can be flexibly adjusted, thereby improving the performance of the ferroelectric device. In addition, compared with the prior art shown in fig. 3, the embodiment of the application does not need to introduce elements between the ferroelectric layers and the electrodes to generate the built-in electric field at the contact interface between the ferroelectric layers and the electrodes by changing the concentration of the first element in the two ferroelectric layers so as to generate the built-in electric field between the contact interfaces of the two ferroelectric layers, thereby avoiding the contact interface between the electrodes and the ferroelectric layers from being in a relatively chaotic state due to element diffusion and further improving the feasibility of practical production and use of ferroelectric devices. The ferroelectric cells provided by embodiments of the present application are described in more detail below in connection with the embodiments shown in fig. 4A-8.
Referring to fig. 4A, fig. 4A is a schematic structural diagram of a ferroelectric cell 100 according to an embodiment of the present application. As shown in fig. 4A, the ferroelectric cell 100 includes an electrode M1, an electrode M2, a ferroelectric layer F1 and a ferroelectric layer F2 disposed between the electrode M1 and the electrode M2. The electrode M1 and the electrode M2 are metal electrodes, and the electrode M1 and the electrode M2 may be made of the same material or different materials. In one possible implementation, the material of electrode M1 may be tungsten (W) and the material of electrode M2 may be TaN. It should be noted that, in other possible implementations of the embodiment of the present application, the materials of the electrode M1 and the electrode M2 may be other materials, for example, the electrode M1 and the electrode M2 are both TaN, which is not limited in particular.The materials of the ferroelectric layer F1 and the ferroelectric layer F2 may be hafnium oxide (HfO) or hafnium zirconium oxide (HfZrO). In the embodiment of the application, the materials of the ferroelectric layer F1 and the ferroelectric layer F2 are HfZrO 2 Description is made for example. In the direction z shown in fig. 4A, the thickness of the ferroelectric layer F1 and the thickness of the ferroelectric layer F2 may be the same, for example, 5nm. In the embodiment of the application, the concentration of Zr element in the ferroelectric layer F1 is higher than that in the ferroelectric layer F2; the concentration of Hf element in the ferroelectric layer F2 is higher than that in the ferroelectric layer F2.
In the embodiment shown in FIG. 4A, since the materials of the electrode M1 and the electrode M2 shown in FIG. 4A are W and TaN, respectively, the electrode M1 and the electrode M2 have different work functions, and a built-in electric field is formed between the electrode M1 and the electrode M2Since the work function of TaN is about 5.27eV, the work function of W is about 4.55eV, and the work function of TaN is higher than that of W, the built-in electric field is +>From electrode M1 to electrode M2 (i.e. built-in electric field +.>From low work function electrode to high work function electrode) as shown in fig. 4B. When the ferroelectric cell is of the structure shown in fig. 1, the internal electric field of the ferroelectric cell is as shown in (1) of fig. 4B. When the ferroelectric cell is of the structure shown in FIG. 4A, since the concentration of Zr element in the ferroelectric layer F1 is higher than that in the ferroelectric layer F2, and the concentration of Hf element in the ferroelectric layer F2 is higher than that in the ferroelectric layer F2, i.e., zrO in the ferroelectric layer F1 2 Higher concentration of HfO in ferroelectric layer F2 2 Is higher. Due to ZrO 2 Is higher than HfO 2 The concentration of oxygen vacancies in the ferroelectric layer F1 is higher than the concentration of oxygen vacancies in the ferroelectric layer F1, i.e. there is an oxygen vacancy concentration difference between the ferroelectric layer F1 and the ferroelectric layer F2, so that a built-in electric field is formed between the ferroelectric layer F1 and the ferroelectric layer F2 based on the oxygen vacancy concentration difference>As shown in (2) in fig. 4B. The built-in electric field->From ferroelectric layer F1 to ferroelectric layer F2 (i.e.)>From a ferroelectric layer having a concentration of oxygen vacancies to a ferroelectric layer having a low concentration of oxygen vacancies). As can be seen from fig. 4B (2), a built-in electric field is formed between the two electrodesActing on the ferroelectric layer F1 and the ferroelectric layer F2, and forming a built-in electric field +.>Can inhibit built-in electric field +.>Thereby, the built-in electric field of ferroelectric cell 100 +.>Is a built-in electric field->And a built-in electric field->The difference, i.e. the built-in electric field +.>And a built-in electric field->And cancel each other. Thus, embodiments of the present application provide for the concentration of oxygen vacancies in ferroelectric layers F1 and F2 to be adjusted such thatThe total built-in electric field of ferroelectric cell 100>Weakening or cancellation may improve the electrical symmetry of the ferroelectric cell compared to the prior art shown in fig. 1 to improve performance such as FeRAM. In addition, compared with the prior art shown in fig. 3, elements are not required to be introduced between the ferroelectric layer and the electrode to generate a built-in electric field at the contact interface between the ferroelectric layer and the electrode, so that the contact interface between the electrode and the ferroelectric layer is prevented from being in a relatively chaotic state due to element diffusion, and the feasibility of actual production and use of the ferroelectric device is further improved.
Based on the principle that the ferroelectric cell 100 shown in fig. 4A and the ferroelectric cell 100 shown in fig. 4B improve the symmetry of the ferroelectric cell 100, the ferroelectric cell 100 shown in fig. 4 may be prepared based on an atomic layer deposition (Atomic Layer Deposition, ALD) process. With continued reference to fig. 4C, fig. 4C is a process step 200 for preparing the ferroelectric cell 100 as shown in fig. 4A, the process step 200 comprising:
in step 401, an electrode M1 is formed on a substrate. The material of the electrode M1 is W.
In step 402, a ferroelectric layer F1 is formed on the electrode M1. In this step, it is assumed that each ALD deposition cycle can deposit a 1A thickness, and HfO 2 With ZrO 2 When the deposition rate is the same every ALD deposition cycle, hfO2 of 3ALD deposition cycles and ZrO2 of 7ALD deposition cycles are alternately deposited on the electrode M1, so as to obtain a ferroelectric layer F1 of a predetermined thickness. The predetermined thickness is, for example, 5nm.
In step 403, a ferroelectric layer F2 is formed on the electrode M1. In this step, it is assumed that each ALD deposition cycle can deposit a 1A thickness, and HfO 2 With ZrO 2 When the deposition rate is the same every ALD deposition cycle, hfO2 of 7ALD deposition cycles and ZrO2 of 3ALD deposition cycles are alternately deposited on the ferroelectric layer F1, so that a ferroelectric layer F2 of a predetermined thickness can be obtained. The predetermined thickness is, for example, 5nm.
In step 404, a metal electrode M2 is formed over the ferroelectric layer F2. The material of the metal electrode M2 is TiN.
The application is thatIn an embodiment, tiCl based 4 With NH 3 The principle of reacting to form TiN is to prepare TiN. In a specific process, tiCl 4 As precursor of Ti ion, NH 3 TiCl is used as the precursor of N ion 4 With NH 3 Is a 1:1 cyclic ratio, and TiCl is deposited by atomic deposition technique 4 Materials and NH 3 A material. Deposited TiCl 4 Materials and NH 3 The materials react to form TiN. Stopping depositing TiCl after the thickness of the TiN material reaches the preset thickness (40 nm, for example) 4 Materials and NH 3 A material. Thus, a metal electrode M1 of TiN material was prepared.
The ferroelectric cell 100 shown in fig. 4A can be prepared through the above steps 401 to 404. Further, as can be seen from the above process step 200, the concentration of Zr element in the ferroelectric layer F1 is higher than the concentration of Zr element in the ferroelectric layer F2, and the concentration of Hf element in the ferroelectric layer F2 is higher than the concentration of Hf element in the ferroelectric layer.
The embodiments shown in fig. 4A-4C above describe the reduction of the total built-in electric field of ferroelectric cell 100 by setting the concentration of oxygen vacancies in ferroelectric layer F1 to be higher than the concentration of oxygen vacancies in ferroelectric layer F2Thereby improving the implementation of the electrical symmetry of the ferroelectric cell. In an embodiment of the present application, in order to make the ferroelectric cell 100 applicable to a device such as an FTJ that needs to achieve a switching ratio by improving the electrical asymmetry of the ferroelectric cell, in one possible implementation, the concentration of oxygen vacancies in the ferroelectric layer F1 may be set to be lower than the concentration of oxygen vacancies in the ferroelectric layer F2 to improve the total built-in electric field of the ferroelectric cell 100>Thereby improving the electrical asymmetry of the ferroelectric cell. Described in more detail below with the embodiment shown in fig. 5.
Referring to fig. 5A, fig. 5A is a schematic structural diagram of a ferroelectric cell 300 according to an embodiment of the present application. As with ferroelectric cell 100 shown in fig. 4A, ferroelectric cell 300 also includes electrode M1, electrode M2, ferroelectric layer F1, and ferroelectric layer F2. The material of the electrode M1 is W, and the material of the electrode M2 is TiN. Unlike the ferroelectric cell 100 shown in fig. 4A, in fig. 5A, the concentration of Hf element in the ferroelectric layer F1 is higher than that in the ferroelectric layer F2, and the concentration of Zr element in the ferroelectric layer F2 is higher than that in the ferroelectric layer.
In the embodiment shown in FIG. 5A, since the materials of electrode M1 and electrode M2 are W and TaN, respectively, there is a different work function between electrode M1 and electrode M2, thereby creating a built-in electric field in ferroelectric cell 300 directed from electrode M1 to electrode M2(for more details, refer to the associated description in FIG. 4B), as shown in FIG. 5B. When the ferroelectric cell is of the structure shown in fig. 1, the internal electric field of the ferroelectric cell is as shown in (1) of fig. 5B. In the ferroelectric cell 300 shown in FIG. 5A, the concentration of Hf element in the ferroelectric layer F1 is higher than that in the ferroelectric layer F2, and the concentration of Zr element in the ferroelectric layer F2 is higher than that in the ferroelectric layer F2, i.e., hfO in the ferroelectric layer F1 2 Higher concentration of ZrO in ferroelectric layer F2 2 Is higher. Due to ZrO 2 Is higher than HfO 2 The concentration of oxygen vacancies in the ferroelectric layer F2 is higher than the concentration of oxygen vacancies in the ferroelectric layer F1, i.e. there is an oxygen vacancy concentration difference between the ferroelectric layer F2 and the ferroelectric layer F1, so that a built-in electric field is formed between the ferroelectric layer F2 and the ferroelectric layer F1 based on the oxygen vacancy concentration difference>As shown in (2) in fig. 5B. The built-in electric field->From the ferroelectric layer F2 to the ferroelectric layer F1. As can be seen from (2) in FIG. 5B, a built-in electric field is formed between the two electrodes +.>Acting on ferroelectric materialsA layer F1 and a ferroelectric layer F2, and a built-in electric field is formed between the ferroelectric layer F1 and the ferroelectric layer F2>Can enhance the built-in electric field +.>Thereby, the built-in electric field of ferroelectric cell 100 +.>Is a built-in electric field->And a built-in electric field->The sum, i.e. the built-in electric field +.>And a built-in electric field->The superposition between them causes the built-in electric field of the ferroelectric cell 300 to be enhanced. Thus, the embodiment of the present application adjusts the concentration of oxygen vacancies in the ferroelectric layer F1 and F2 so that the total built-in electric field of the ferroelectric cell 100 +.>The enhancement can improve the non-electrical symmetry of the ferroelectric cell compared to the prior art shown in fig. 1 to improve the performance of devices such as FTJ that achieve a switching ratio.
The steps of the process preparation of ferroelectric cell 300 as shown in fig. 5A are similar to the steps of the process preparation of ferroelectric cell 100 as shown in fig. 4A, except that in preparing ferroelectric cell 300 as shown in fig. 5A, steps 402 and 403 as shown in fig. 4C are interchanged, i.e. electrode M1 is first formed on the substrate, unlike the process steps of preparing ferroelectric cell 100 as shown in fig. 4A; then, alternately depositing HfO2 with 7ALD deposition period and ZrO2 with 3ALD deposition period on the electrode M1 to obtain a ferroelectric layer F1 with preset thickness; secondly, alternately depositing HfO2 with 3ALD deposition period and ZrO2 with 7ALD deposition period on the ferroelectric layer F1 to obtain the ferroelectric layer F1 with preset thickness; finally, an electrode M2 is formed on the ferroelectric layer F1. The detailed steps refer to the preparation process shown in fig. 4C, and will not be described again.
In the ferroelectric cells shown in fig. 4A and 5A above, the concentration of oxygen vacancies in the ferroelectric layers F1 and F2 is adjusted by adjusting the ratio of Zr element and the ratio of Hf element between the ferroelectric layers F1 and F2 to adjust the electrical symmetry of the ferroelectric cells. In other possible implementations of the embodiments of the present application, the concentration of oxygen vacancies in each ferroelectric layer may also be adjusted by adjusting the concentration of the oxygen element that is introduced into each ferroelectric layer. Referring to fig. 6, fig. 6 is a schematic structural diagram of a ferroelectric cell 400 according to an embodiment of the present application. The ferroelectric cell 400 shown in fig. 6 has the same structure as that of the ferroelectric cell shown in the above embodiments, and includes an electrode M1, an electrode M2, a ferroelectric layer F1 and a ferroelectric layer F2 disposed between the two electrodes M1 and M2. The materials of the electrodes and the ferroelectric layers are the same as those of the electrodes and the ferroelectric layers in the above embodiments, and will not be described again. Unlike the above ferroelectric cells, in the ferroelectric cell 400 shown in fig. 6, the concentration of oxygen element introduced into the ferroelectric layer F1 during the preparation is lower than that of the ferroelectric layer F2 during the preparation. Thus, the concentration of the oxygen element in the ferroelectric layer F1 for participating in the oxidation reaction is lower than the concentration of the oxygen element in the ferroelectric layer F2 for participating in the oxidation reaction. Further, the concentration of oxygen vacancies in the ferroelectric layer F1 is higher than the concentration of oxygen vacancies in the ferroelectric layer F2. Thereby, a built-in electric field exists between the ferroelectric layer F1 and the ferroelectric layer F2The built-in electric field is directed from the ferroelectric layer F1 to the ferroelectric layer F2, thereby improving the electrical symmetry of the ferroelectric cell. The principle of the ferroelectric cell 400 shown in fig. 6 is the same as that of the ferroelectric cell 100 shown in fig. 4A, and the detailed description of the principle is described with reference to the principle shown in fig. 4B, and will not be repeated.
The ferroelectric cell 400 shown in fig. 6 is configured to improve the electrical symmetry of the ferroelectric cell by setting the concentration of oxygen element in the ferroelectric layer F1 to be lower than the concentration of oxygen element in the ferroelectric layer F2. In one possible implementation, the concentration of oxygen element introduced during the fabrication of ferroelectric layer F1 is higher than the concentration of oxygen element introduced during the fabrication of ferroelectric layer F2, as shown in ferroelectric cell 500 of fig. 7. Thus, the concentration of the oxygen element in the ferroelectric layer F1 for participating in the oxidation reaction is higher than the concentration of the oxygen element in the ferroelectric layer F2 for participating in the oxidation reaction. Further, the concentration of oxygen vacancies in the ferroelectric layer F1 is lower than the concentration of oxygen vacancies in the ferroelectric layer F2. Thereby, a built-in electric field exists between the ferroelectric layer F1 and the ferroelectric layer F2The built-in electric field is directed from the ferroelectric layer F2 to the ferroelectric layer F1, thereby improving the electrical asymmetry of the ferroelectric cell. The principle of the ferroelectric cell 500 shown in fig. 7 is the same as that of the ferroelectric cell 300 shown in fig. 5A, and the detailed description of the principle is described with reference to the principle shown in fig. 5B, and will not be repeated.
Ferroelectric cells of two-dimensional structure are described above with reference to fig. 4A-7. In one possible implementation, the ferroelectric cells may also be in a three-dimensional structure in which multiple electrodes share the same ferroelectric layer, thereby forming multiple ferroelectric cells. Referring to fig. 8A and 8B, fig. 8A is a top view of a three-dimensional ferroelectric structure 600, and fig. 8B is a cross-sectional view along AA' of the three-dimensional ferroelectric structure 600 shown in fig. 8A. As shown in fig. 8A and 8B, the top view of the three-dimensional ferroelectric structure 600 is circular. In the three-dimensional ferroelectric structure 600, the outermost layer is a stacked structure formed by stacking the passivation layer 82 and the metal layer 81, wherein the material of the metal layer M1 may be W. Inside the laminated structure formed of the passivation layer 82 and the metal layer 81 is a ferroelectric layer F1, inside the ferroelectric layer F1 is a ferroelectric layer F2, and inside the ferroelectric layer F2 is a metal layer 83. In the three-dimensional ferroelectric structure 600, one ferroelectric cell is formed among one metal layer, the ferroelectric layer F1, the ferroelectric layer F2, and the metal layer 83 of the multi-layer metal layer 81. Thus, the three-dimensional ferroelectric structure 600 includes a plurality of ferroelectric cells. The plurality of ferroelectric cells share the ferroelectric layer F1, the ferroelectric layer F2, and the metal layer 83. The metal layer 83 may be one or more layers, and when the metal layer 83 is one layer, the one metal layer may be TiN; when the metal layer 83 is two layers, the metal layer in contact with the ferroelectric layer F2 of the two metal layers is TiN, and the other layer is W. Preferably, the metal layer 83 comprises two metal layers. In the three-dimensional ferroelectric structure 600, when the electrical symmetry of the ferroelectric cell needs to be improved, the materials and the concentrations of the elements of the ferroelectric layers F1 and F2 are the same as those of the ferroelectric cell 100 shown in fig. 4A or the ferroelectric cell 400 shown in fig. 6, and detailed descriptions thereof are omitted. In the three-dimensional ferroelectric structure 600, when the non-electrical symmetry of the ferroelectric cell needs to be improved, the materials and the concentrations of the elements of the ferroelectric layers F1 and F2 are the same as those of the ferroelectric cell 300 shown in fig. 5A or the ferroelectric cell 500 shown in fig. 7, and detailed descriptions thereof are omitted.
Based on the ferroelectric cells described in the above embodiments, the embodiments of the present application also provide a ferroelectric memory 700 as shown in fig. 9. The ferroelectric memory 700 includes a plurality of memory cells 701, 702 … 70n arranged in an array. Each memory cell includes a transistor M and a ferroelectric cell C. The ferroelectric cell C may be the ferroelectric cell 100 shown in fig. 4A, the ferroelectric cell 300 shown in fig. 5A, the ferroelectric cell 400 shown in fig. 6, or the ferroelectric cell 500 shown in fig. 7. Further, the ferroelectric memory 700 further includes a plurality of word lines WL0, WL1 … WLm and a plurality of bit lines BL0, BL1 …, BLn, each of the plurality of memory cells being connected to one of the plurality of bit lines and one of the plurality of word lines, respectively. The connection relationship between each memory cell and the bit line and the word line are the same. Taking the memory cell 501 as an example, the gate of the transistor M is connected to the word line WL0, the source of the transistor M is connected to the bit line BL0, the drain of the transistor M is connected to one end of the ferroelectric cell C, and the other end of the ferroelectric cell C is connected to the plate line PL.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present application, and not for limiting the same; although the application has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the application.
Claims (10)
1. A ferroelectric cell, comprising:
a first electrode;
a first ferroelectric layer disposed on the surface of the first electrode;
the second ferroelectric layer is arranged on the surface of the first ferroelectric layer and is far away from one side of the first electrode;
the second electrode is arranged on the surface of the second ferroelectric layer and is far away from one side of the first ferroelectric layer;
wherein the concentration of a first element in the first ferroelectric layer is higher than the concentration of the first element in the second ferroelectric layer, and the first element is one of hafnium element, zirconium element and oxygen element.
2. The ferroelectric cell of claim 1, wherein the material of the first ferroelectric layer and the material of the second ferroelectric layer are both hafnium zirconium oxide;
when the first element is zirconium, the concentration of the second element in the first ferroelectric layer is lower than that of the second element in the second ferroelectric layer, and the second element is hafnium.
3. The ferroelectric cell of claim 1, wherein the material of said one ferroelectric layer and the material of said second ferroelectric layer are both hafnium zirconium oxide;
when the first element is hafnium, the concentration of the second element in the first ferroelectric layer is lower than that of the second element in the second ferroelectric layer, and the second element is zirconium.
4. A ferroelectric cell according to any one of claims 1 to 3, wherein said first electrode is titanium nitride and said second electrode is metallic tungsten.
5. A ferroelectric cell according to any one of claims 1 to 3, wherein said second electrode is titanium nitride and said first electrode is metallic tungsten.
6. A three-dimensional ferroelectric structure comprising:
a first annular region formed by the plurality of passivation layers and the plurality of first electrode stacks;
a first ferroelectric layer is arranged on the inner side of the first annular region, and the first ferroelectric layer is contacted with the passivation layers and the first electrodes;
a second ferroelectric layer is arranged on one side of the first ferroelectric layer far away from the first annular region;
a second electrode is arranged on one side of the second ferroelectric layer far away from the first ferroelectric layer;
wherein the concentration of a first element in the first ferroelectric layer is higher than the concentration of the first element in the second ferroelectric layer, and the first element is one of hafnium element, zirconium element and oxygen element.
7. The three-dimensional ferroelectric structure according to claim 6, wherein the material of the first ferroelectric layer and the material of the second ferroelectric layer are both hafnium zirconium oxide;
when the first element is hafnium, the concentration of the second element in the first ferroelectric layer is lower than that of the second element in the second ferroelectric layer, and the second element is zirconium.
8. The three-dimensional ferroelectric structure according to claim 6, wherein the material of said one ferroelectric layer and the material of said second ferroelectric layer are both hafnium zirconium oxide;
when the first element is zirconium, the concentration of the second element in the first ferroelectric layer is lower than that of the second element in the second ferroelectric layer, and the second element is hafnium.
9. The three-dimensional ferroelectric structure according to any one of claims 6 to 8, wherein the material of said first electrode is tungsten;
the second electrode is formed by two metal layers, the material in contact with the second ferroelectric layer in the two metal layers is titanium nitride, and the material in non-contact with the second ferroelectric layer in the two metal layers is tungsten.
10. A ferroelectric memory, characterized in that the ferroelectric memory comprises a plurality of memory cells arranged in an array; each of the plurality of memory cells comprising a transistor and a ferroelectric cell as claimed in any one of claims 1 to 5.
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