WO2013111548A1 - 不揮発性記憶素子及びその製造方法 - Google Patents
不揮発性記憶素子及びその製造方法 Download PDFInfo
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- WO2013111548A1 WO2013111548A1 PCT/JP2013/000225 JP2013000225W WO2013111548A1 WO 2013111548 A1 WO2013111548 A1 WO 2013111548A1 JP 2013000225 W JP2013000225 W JP 2013000225W WO 2013111548 A1 WO2013111548 A1 WO 2013111548A1
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- metal oxide
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Images
Classifications
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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
- H10N70/00—Solid-state devices having no potential barriers, and specially adapted for rectifying, amplifying, oscillating or switching
- H10N70/20—Multistable switching devices, e.g. memristors
- H10N70/24—Multistable switching devices, e.g. memristors based on migration or redistribution of ionic species, e.g. anions, vacancies
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C13/00—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00
- G11C13/0002—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00 using resistive RAM [RRAM] elements
- G11C13/0007—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00 using resistive RAM [RRAM] elements comprising metal oxide memory material, e.g. perovskites
-
- 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
- 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
- H10N70/011—Manufacture or treatment of multistable switching devices
- H10N70/041—Modification of switching materials after formation, e.g. doping
-
- 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
-
- 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
- H10N70/881—Switching materials
- H10N70/883—Oxides or nitrides
-
- 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
- H10N70/881—Switching materials
- H10N70/883—Oxides or nitrides
- H10N70/8833—Binary metal oxides, e.g. TaOx
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C2213/00—Indexing scheme relating to G11C13/00 for features not covered by this group
- G11C2213/30—Resistive cell, memory material aspects
- G11C2213/32—Material having simple binary metal oxide structure
Definitions
- the present invention relates to a variable resistance nonvolatile memory element in which a resistance state is changed by application of a voltage pulse, and a manufacturing method thereof.
- the resistance variable element has a property that the resistance state reversibly changes by application of a voltage pulse, and information can be stored in a nonvolatile manner by associating information with each resistance state. This means a simple element.
- variable resistance element has a simple configuration including a variable resistance layer formed using a variable resistance material between the first electrode layer and the second electrode layer.
- a resistance change phenomenon appears in the resistance change layer. That is, for example, when a negative voltage pulse is applied between the electrodes, the resistance change layer is in a low resistance state. Conversely, when a positive voltage pulse is applied between the electrodes, the resistance change layer is in a high resistance state.
- Such a resistance variable element can store two values by assigning “0” to one of the low resistance state and the high resistance state and “1” to the other, for example.
- a nonvolatile memory device using a resistance variable element is in a resistance state with respect to each of the resistance variable elements by utilizing the fact that the resistance variable layer changes to at least two states, a high resistance state and a low resistance state. It is a storage device that writes and reads information accordingly.
- a resistance change element in which two tantalum oxide layers having different oxygen contents are stacked and used for the resistance change layer is disclosed (for example, see Patent Document 1).
- a break voltage is applied once in the initial stage after manufacturing in order to cause a layer formed by stacking two tantalum oxide layers having different oxygen contents to function as a resistance change layer.
- the voltage value of the break voltage is generally larger than the voltage value of the voltage pulse applied to change the resistance state of the resistance change layer during the normal operation of the nonvolatile memory device.
- an object of the present invention is to reduce the break voltage applied to the nonvolatile memory element used for the resistance change layer by laminating metal oxide layers having different degrees of oxygen deficiency.
- a nonvolatile memory element is interposed between a first electrode, a second electrode, the first electrode, and the second electrode, and A resistance change layer whose resistance state changes reversibly based on an electrical signal applied between one electrode and the second electrode, and the resistance change layer is made of a first metal oxide.
- a second resistance change layer including a first resistance change layer and a second resistance change layer made of a second metal oxide having a smaller oxygen deficiency and a higher resistance value than the first metal oxide.
- a metal-metal bond region having a metal bond between metal atoms constituting the second metal oxide is provided.
- the method for manufacturing a nonvolatile memory element includes a step of forming a first electrode layer, and a first resistance change composed of a first metal oxide on the first electrode layer. Forming a layer, and forming a second variable resistance layer composed of a second metal oxide having a lower oxygen deficiency and a higher resistance value than the first metal oxide on the first variable resistance layer. Forming a metal-metal bond region having a metal bond between metal atoms constituting the second metal oxide in the second resistance change layer, and on the second resistance change layer. Forming a second electrode layer.
- the non-volatile memory element is a non-volatile memory element in which metal oxide layers having different degrees of oxygen deficiency are stacked and used as a resistance change layer, and the break voltage can be reduced as compared with the conventional one.
- FIG. 1 is a cross-sectional view schematically illustrating a configuration example of a nonvolatile memory device including the nonvolatile memory element according to the first embodiment.
- FIG. 2A is a process cross-sectional view illustrating a process of forming a first wiring on a substrate.
- FIG. 2B is a process cross-sectional view illustrating a process of forming a first interlayer insulating layer on the substrate so as to cover the first wiring.
- FIG. 2C is a process cross-sectional view illustrating a process of forming a first contact hole so as to expose the first wiring through the first interlayer insulating layer.
- FIG. 2D is a process cross-sectional view illustrating a process of filling the first contact hole with a conductive material.
- FIG. 2E is a process cross-sectional view illustrating a process of forming the first contact plug by removing the conductive material above the upper end surface of the first interlayer insulating layer.
- FIG. 2F is a cross-sectional view showing a process of forming a first electrode material layer constituting the first electrode layer and a first metal oxide layer constituting the first resistance change layer so as to cover the first contact plug. It is.
- FIG. 2G is a cross-sectional view showing a step of forming a second metal oxide layer constituting the second resistance change layer on the upper surface of the first metal oxide layer in the first embodiment.
- FIG. 2H is a cross-sectional view showing a step of forming a metal-metal bond region in part of the second metal oxide layer in the first embodiment.
- FIG. 2I is a cross-sectional view showing a step of forming a second electrode material layer constituting the second electrode layer on the first metal oxide layer in the first embodiment.
- FIG. 2J shows the first electrode material layer, the first metal oxide layer, the second metal oxide layer, and the second electrode material layer patterned in the first embodiment, It is sectional drawing which shows the process of forming a 1st resistance change layer, a 2nd resistance change layer, and a 2nd electrode layer.
- FIG. 2K is a cross-sectional view illustrating a step of forming a second interlayer insulating layer that covers the nonvolatile memory element.
- FIG. 2L is a cross-sectional view illustrating a process of filling the second contact hole formed in the second interlayer insulating layer with the second contact plug and forming the second wiring on the second contact plug.
- FIG. 3 is a graph showing differences in oxygen profiles in the Ir, Ta 2 O 5 layer, and TaO x layer, which are upper electrodes, in the conventional nonvolatile memory element and the nonvolatile memory element of the first embodiment.
- FIG. 4 is an enlarged view of the difference in oxygen profile in the vicinity of the Ir and Ta 2 O 5 layers, which are upper electrodes, in the conventional nonvolatile memory element and the nonvolatile memory element of the first embodiment. It is an enlarged view.
- FIG. 3 is a graph showing differences in oxygen profiles in the Ir, Ta 2 O 5 layer, and TaO x layer, which are upper electrodes, in the conventional nonvolatile memory element and the nonvolatile memory element of the first embodiment.
- FIG. 4 is an enlarged view of the difference in oxygen profile in the
- FIG. 5 is a graph showing the binding energy distribution on the surface of the Ta 2 O 5 layer in the nonvolatile memory element of the first embodiment.
- FIG. 6 is a graph showing resistance change characteristics of the nonvolatile memory element according to the first embodiment.
- FIG. 7 is a graph comparing the break voltage in the conventional nonvolatile semiconductor memory element with the break voltage in the nonvolatile memory element of the first embodiment.
- FIG. 8 is a cross-sectional view schematically illustrating a configuration example of a nonvolatile memory device including the nonvolatile memory element according to the second embodiment.
- FIG. 9A is a process cross-section illustrating a process of forming a second metal oxide layer constituting the second resistance change layer on the upper surface of the first metal oxide layer in the method for manufacturing a nonvolatile memory element according to the second embodiment.
- FIG. 9B is a process sectional view showing a process of forming a metal-metal bond region in the second embodiment.
- FIG. 9C shows that in the second embodiment, a second metal oxide layer constituting the second resistance change layer and a second electrode material layer constituting the second electrode layer are formed on the metal-metal bond region. It is process sectional drawing which shows a process.
- FIG. 9A is a process cross-section illustrating a process of forming a second metal oxide layer constituting the second resistance change layer on the upper surface of the first metal oxide layer in the method for manufacturing a nonvolatile memory element according to the second embodiment.
- FIG. 9B is a process sectional view showing a process of forming a metal-metal bond region in the second embodiment.
- FIG. 10 is a cross-sectional view showing an example of a schematic configuration of the nonvolatile memory device disclosed in Patent Document 1. In FIG.
- the “oxygen content” is indicated by the ratio of the number of oxygen atoms contained to the total number of atoms constituting the metal oxide.
- the “oxygen deficiency” refers to the ratio of oxygen deficiency to the amount of oxygen constituting the oxide having the stoichiometric composition in each metal oxide.
- Oxygen-deficient metal oxide is a metal with a low oxygen content (atomic ratio: the ratio of the number of oxygen atoms to the total number of atoms) compared to a metal oxide having a stoichiometric composition. Refers to oxide.
- the stoichiometric oxide composition of the metal oxide is Ta 2 O 5 , and thus can be expressed as TaO 2.5 .
- the degree of oxygen deficiency of TaO 2.5 is 0%.
- the oxygen-deficient metal oxide has a negative oxygen deficiency.
- the oxygen deficiency is described as including a positive value, 0, and a negative value.
- the metal which comprises a 2nd metal oxide can take several stoichiometric composition as an oxide, it is good also considering the composition of a metal oxide with the highest resistance value among them as a reference
- the metal which comprises a 1st metal oxide can take a some stoichiometric composition as an oxide, oxygen whose resistivity is lower than the metal oxide which comprises a 2nd metal oxide among them. A deficient metal oxide may be used.
- the oxygen content is a ratio of the number of oxygen atoms contained to the total number of atoms constituting the metal oxide as described above.
- the oxygen content of Ta 2 O 5 is the ratio of the number of oxygen atoms to the total number of atoms (O / (Ta + O)), which is 71.4 [atm%]. Therefore, the oxygen-deficient tantalum oxide has an oxygen content larger than 0 and smaller than 71.4 [atm%].
- the oxygen content has a corresponding relationship with the degree of oxygen deficiency. That is, when the oxygen content of the second metal oxide is larger than the oxygen content of the first metal oxide, the oxygen deficiency of the second metal oxide is smaller than the oxygen deficiency of the first metal oxide.
- FIG. 10 is a cross-sectional view showing an example of a schematic configuration of a conventional nonvolatile memory device disclosed in Patent Document 1.
- FIG. 10 is a cross-sectional view showing an example of a schematic configuration of a conventional nonvolatile memory device disclosed in Patent Document 1.
- the nonvolatile memory device 20 includes a substrate 200 on which the first wiring 201 is formed, a first interlayer insulating film 202 formed so as to cover the substrate 200 and the first wiring 201, and a first And a first contact plug 204 embedded in the first contact hole 203 that reaches the first wiring 201 through the interlayer insulating film 202.
- the nonvolatile memory device 20 further includes a first electrode layer 205, a resistance change layer 206, and a second electrode layer formed on the first interlayer insulating film 202 so as to cover the exposed surface of the first contact plug 204. 207 and the resistance variable element 212 configured by stacking in this order.
- the first wiring 201 and the first electrode layer 205 are electrically connected through the first contact plug 204.
- the nonvolatile memory device 20 further includes a second interlayer insulating layer 208 covering the resistance variable element 212 and a second electrode layer 207 penetrating the second interlayer insulating layer 208 and reaching the second electrode layer 207 of the resistance variable element 212.
- a second contact plug 210 embedded in the contact hole 209 and a second wiring 211 formed so as to cover the upper surface of the second contact plug 210 are provided.
- the second electrode layer 207 and the second wiring 211 are electrically connected through the second contact plug 210.
- the resistance change layer 206 has a stacked structure of a first tantalum oxide layer 206a and a second tantalum oxide layer 206b.
- the oxygen content of the second tantalum oxide layer 206b is higher than that of the first tantalum oxide layer 206a.
- the material constituting the second tantalum oxide layer 206b has a composition represented by TaO y that satisfies 2.1 ⁇ y ⁇ 2.5, for example.
- the material constituting the first tantalum oxide layer 206a has a composition represented by TaO x satisfying example 0.8 ⁇ x ⁇ 1.9.
- the resistivity of the second tantalum oxide layer 206b is the resistivity of the first tantalum oxide layer 206a. Higher than.
- a nonvolatile memory element is interposed between a first electrode, a second electrode, the first electrode, and the second electrode, and includes the first electrode and the second electrode.
- a resistance change layer whose resistance state reversibly changes based on an electrical signal applied therebetween, wherein the resistance change layer includes a first resistance change layer made of a first metal oxide,
- a second resistance change layer composed of a second metal oxide having a smaller oxygen deficiency and a higher resistance value than that of the first metal oxide, and the second resistance change layer includes the second resistance change layer.
- a metal-metal bond region having a metal bond between metal atoms constituting the metal.
- the break voltage is reduced by including a metal-metal bond region including a metal bond in part of the second metal oxide layer. More specifically, in the nonvolatile memory element according to the present invention, when a certain level of voltage (break voltage) is applied to the resistance change element, the metal bond serves as a base point, and oxygen is contained in the second resistance change layer. Defects are induced, and a conductive path showing metallic conduction due to the oxygen vacancies is formed in the resistance change layer.
- the metal-metal bond region may exist at an interface between the second electrode and the second resistance change layer.
- the region in which the resistance state in the second resistance change layer changes can be changed between the second electrode and the second electrode. Can be fixed in the vicinity of the interface. Thereby, the resistance change operation of the nonvolatile memory element can be further stabilized.
- the metal-metal bond region may exist inside the second variable resistance layer except for the surface thereof.
- the metal-metal bond region inside the second variable resistance layer except for the surface, the conductive path from the second electrode to the second variable resistance layer does not increase, and the resistance in the second variable resistance layer is increased. It is possible to suppress the leakage current outside the region where the state changes.
- the first metal oxide, the second metal oxide, and the metal-metal bond region may each be composed of a transition metal oxide or an aluminum oxide.
- the first metal oxide, the second metal oxide, and the metal-metal bond region are made of a material containing tantalum, hafnium, or zirconium.
- the second variable resistance layer may be made of an insulator.
- the metal-metal bond region is present in the vicinity of the interface between the second resistance change layer and the second electrode in the second resistance change layer, and the second resistance change layer includes the second resistance change layer.
- the degree of oxygen deficiency may gradually increase from the two-resistance change layer toward the second electrode.
- the method for manufacturing a nonvolatile memory element according to the present invention includes a step of forming a first electrode layer, and a step of forming a first resistance change layer made of a first metal oxide on the first electrode layer. And forming a second resistance change layer composed of a second metal oxide having a lower oxygen deficiency and a higher resistance value than the first metal oxide on the first resistance change layer; Forming a metal-metal bond region having metal bonds between metal atoms constituting the second metal oxide in the second variable resistance layer; and a second electrode layer on the second variable resistance layer. Forming a step.
- the metal-metal bond region may be formed by desorbing oxygen from the second resistance change layer.
- the second electrode layer is formed by sputtering, and in the step of forming the metal-metal bond region, the second electrode constituting the second electrode layer is formed.
- the sputtering method may be executed on the condition that the material is a target and the film forming pressure is lower than the film forming pressure when forming the second electrode layer.
- the first stacking step of stacking the second metal oxide after the step of forming the first resistance change layer, and the metal-metal bond You may perform the 2nd lamination process which laminates
- FIG. 1 is a cross-sectional view showing a configuration example of the nonvolatile memory device 10 including the nonvolatile memory element (resistance change element 113) according to the present embodiment.
- the nonvolatile memory device 10 includes a substrate 100, a first wiring 101, a first interlayer insulating layer 102, and a first contact hole 103 formed in the first interlayer insulating layer 102. And a first contact plug 104 embedded in the first contact plug 104.
- the nonvolatile memory device 10 further includes a first electrode layer 105, a resistance change layer 106 in which a first resistance change layer 106a and a second resistance change layer 106b are stacked on the first interlayer insulating layer 102, and a second electrode.
- the variable resistance element 113 (corresponding to the nonvolatile memory element according to the present invention) configured by stacking the layers 108 in this order is provided.
- the nonvolatile memory device 10 further includes a second interlayer insulating layer 109 covering the resistance change element 113 and a second contact embedded in the second contact hole 110 formed in the second interlayer insulating layer 109.
- a plug 111 and a second wiring 112 formed so as to cover the upper surface of the second contact plug 111 are formed.
- the nonvolatile memory element of the present embodiment includes the resistance variable element 113. That is, the substrate 100, the first wiring 101, the first interlayer insulating layer 102, the first contact hole 103, the first contact plug 104, the second interlayer insulating layer 109, the second contact hole 110, The two-contact plug 111 and the second wiring 112 will be described as arbitrary configurations.
- the substrate 100 is a silicon substrate in the present embodiment.
- a transistor and the like are formed on the substrate 100.
- the first wiring 101 is formed on the substrate 100 using, for example, copper or aluminum.
- the first interlayer insulating layer 102 is configured to cover the substrate 100 and the first wiring 101, and in this embodiment, is configured of a silicon oxide film having a thickness of 300 to 500 [nm].
- the first contact hole 103 is formed so as to penetrate the first interlayer insulating layer 102 and expose the surface of the first wiring 101.
- the first contact hole 103 is formed in a cylindrical shape having a diameter of 50 to 300 [nm]. Has been.
- the first contact plug 104 is made of a material mainly composed of tungsten.
- the first contact plug 104 is electrically connected to the first wiring 101 and the first electrode layer 105.
- the first electrode layer 105 constituting the resistance variable element 113 is made of a first electrode material having a standard electrode potential lower than that of a second electrode material constituting a second electrode layer 108 described later.
- the film thickness is 5 to 100 [nm].
- the standard electrode potential represents a characteristic that the higher the value, the more difficult it is to oxidize.
- the first electrode material for example, when tantalum oxide is used as the material of the first resistance change layer 106a and the second resistance change layer 106b described later, for example, tantalum nitride (TaN), tungsten (W), nickel (Ni), Tantalum (Ta), Titanium (Ti), Aluminum (Al), Tantalum Nitride (TaN), Titanium Nitride (TiN), etc. You may comprise with a lower material.
- variable resistance layer 106 constituting the variable resistance element 113 exists in the first variable resistance layer 106a, the second variable resistance layer 106b, and the second variable resistance layer 106b formed on the first electrode layer 105. And a metal-metal bonding region 107 to be configured.
- the first resistance change layer 106a is composed of an oxygen-deficient first metal oxide.
- the first resistance change layer 106a has a thickness of 5 to 100 [nm].
- the first metal oxide may be a transition metal oxide or an aluminum oxide. More specifically, the first metal oxide may be composed of at least one metal oxide selected from the group consisting of transition metal oxides such as tantalum oxide, hafnium oxide, zirconium oxide, and aluminum oxide. Good.
- transition metal oxides such as tantalum oxide, hafnium oxide, zirconium oxide, and aluminum oxide. Good.
- TaO x tantalum oxide, x is the number of oxygen (O) atoms when the number of tantalum (Ta) atoms is 1) is used as the first metal oxide.
- x may satisfy 0.8 ⁇ x ⁇ 1.9.
- the film thickness of the first resistance change layer 106a is appropriately set according to the manufacturing process, the film thickness and shape of other layers, and the like.
- the second resistance change layer 106b is made of a second metal oxide having a lower oxygen deficiency and a higher resistance value than the first metal oxide constituting the first resistance change layer 106a.
- the second resistance change layer 106b has a thickness of 2 to 10 [nm].
- the second metal oxide may be composed of a transition metal oxide or an aluminum oxide. More specifically, the second metal oxide may be composed of at least one metal oxide selected from the group consisting of tantalum oxide, hafnium oxide, zirconium oxide, aluminum oxide, and the like.
- the second metal oxide may be composed of an oxide of the same metal as the first metal oxide, or may be composed of an oxide of a metal different from the first metal oxide.
- the second metal oxide when the second metal oxide is composed of the same metal oxide as the first metal oxide, the second metal oxide has a higher oxygen content than the first metal oxide.
- the oxygen content rate in this case is not specifically limited.
- the oxygen deficiency of the second metal oxide may be a value smaller than the oxygen deficiency of the first metal oxide, and may be an oxygen deficiency serving as an insulator. That is, the second resistance change layer 106b may be made of an insulator.
- the second metal oxide is TaO y (tantalum oxide, y is the number of O atoms when the number of Ta atoms is 1).
- TaO x x: the number of O atoms when the number of Ta atoms is 1
- y may satisfy 2.1 ⁇ y ⁇ 2.5.
- the film thickness of the second resistance change layer 106b is appropriately set according to the manufacturing process, the film thickness and shape of other layers, and the like.
- the metal-metal bond region 107 is a region having a metal-metal bond (that is, metal bond) in which the metals constituting the second metal oxide are bonded to each other, and the second electrode layer 108 in the second resistance change layer 106b. Formed at the interface.
- the metal-metal bond region 107 may be formed in a layer shape having the same surface area as the second resistance change layer 106b, or may exist in a part of the surface of the second resistance change layer 106b. Moreover, when it exists in a part of surface of the 2nd resistance change layer 106b, you may be comprised by the some discontinuous area
- the metal-metal bond region 107 has an Ta-Ta bond (an example of a metal-metal bond, in other words, an example of a metal bond).
- the metal-metal bond is formed in the second resistance change layer 106b. This means that the degree of oxygen deficiency of the second resistance change layer 106b gradually increases toward the second electrode.
- the second electrode layer 108 constituting the resistance variable element 113 is composed of a metal constituting the second metal oxide and a second electrode material having a higher standard electrode potential than the first electrode material constituting the first electrode layer 105.
- a metal constituting the second metal oxide and a second electrode material having a higher standard electrode potential than the first electrode material constituting the first electrode layer 105 has been.
- the tantalum oxide is used as the first metal oxide and the second metal oxide as the second electrode material
- iridium (Ir), platinum (Pt), palladium (Pd), gold (Au), copper (Cu), silver (Ag), or the like can be used. That is, when tantalum oxide is used as the first metal oxide and the second metal oxide, the standard electrode potential of the first electrode layer 105 is V 1 , the standard electrode potential of tantalum is V Ta , and the standard of the second electrode layer 108 is used.
- V Ta ⁇ V 2 and V 1 ⁇ may be satisfied V 2 becomes relevant.
- a redox reaction occurs selectively in the second resistance change layer 106b near the interface between the second electrode layer 108 and the second resistance change layer 106b, and a stable resistance change phenomenon occurs. can get.
- V 1 may be ⁇ V Ta.
- the standard electrode potential of the metal may be used in place of the above VTa .
- the second electrode layer 108 has a thickness of 5 to 100 [nm] in this embodiment.
- the second interlayer insulating layer 109 is configured to cover the resistance variable element 113, and in this embodiment, is configured of a silicon oxide film having a thickness of 300 to 500 [nm].
- the second contact hole 110 is formed so as to penetrate the second interlayer insulating layer 109 and expose the surface of the second electrode layer 108 constituting the resistance variable element 113.
- the second contact hole 110 has a diameter of 50 to It is formed in a cylindrical shape of 300 [nm].
- the second contact plug 111 is made of a material mainly composed of tungsten.
- the second contact plug 111 is electrically connected to the second wiring 112 and the second electrode layer 108.
- the second wiring 112 is formed on the second interlayer insulating layer 109 so as to cover the second contact plug 111 using, for example, copper or aluminum.
- the step of forming the first electrode layer 105 and the formation of the first variable resistance layer 106 a made of the first metal oxide on the first electrode layer 105 a step of forming a second resistance change layer 106b made of a second metal oxide having a lower oxygen deficiency and a higher resistance value than the first metal oxide on the first resistance change layer 106a.
- the metal-metal bond region 107 is formed by desorbing oxygen from the second resistance change layer 106b formed in the step of forming the second resistance change layer 106b.
- a metal bonding region 107 is formed.
- FIGS. 2A to 2L are schematic process sectional views showing a method of manufacturing the nonvolatile memory device 10 shown in FIG.
- the first wiring 101 is formed on the substrate 100. More specifically, the first wiring 101 is formed by depositing aluminum as an example of the first wiring material layer on the silicon substrate 100 to a thickness of 400 to 600 [nm] on the silicon substrate 100 by sputtering. By patterning using etching, a desired shape is formed. More specifically, for example, the first wiring 101 may have a width of 0.25 [ ⁇ m] and a thickness of 450 [nm].
- a first interlayer insulating layer 102 is formed on the substrate 100 so as to cover the first wiring 101. More specifically, here, the first interlayer insulating layer 102 is formed by depositing a silicon oxide film using TEOS (tetraethyl orthosilicate) as a raw material by CVD and planarizing it by CMP.
- TEOS tetraethyl orthosilicate
- the thickness of the first interlayer insulating layer 102 is 500 to 1000 [nm].
- TEOS tetraethyl orthosilicate
- a low-k material such as fluorine-containing oxide (eg, FSG: Fluorinated Silicate Glass) is also used in the sense of reducing parasitic capacitance between wirings. ) May be used.
- fluorine-containing oxide eg, FSG: Fluorinated Silicate Glass
- a first contact hole 103 is formed in the first interlayer insulating layer 102. More specifically, the first contact hole 103 is formed by patterning the first interlayer insulating layer 102 using, for example, a desired mask and dry etching.
- the diameter of the first contact hole 103 may be smaller than the width of the first wiring 101. Therefore, in the present embodiment, it is assumed that the diameter of the first contact hole 103 is 50 to 300 [nm].
- a conductive material layer 104M is deposited so as to fill the first contact hole 103.
- the first contact plug 104 is formed by removing the conductive material layer 104M above the upper end surface of the first interlayer insulating layer 102.
- the conductive material layer 104M has a three-layer structure of W / Ti / TiN. Specifically, first, a material containing titanium oxide is deposited to a thickness of 5 to 30 [nm] by sputtering to form a titanium nitride layer (TiN layer) that functions as a diffusion barrier. To do.
- a material containing titanium is deposited so as to have a thickness of 5 to 30 [nm] by CVD, thereby forming a titanium layer (Ti layer) functioning as an adhesion layer.
- tungsten which is a main component of the contact plug, is deposited by CVD to have a thickness of 200 to 400 nm.
- the first contact hole 103 is filled with the conductive material layer 104M having a laminated structure. Further, for example, the conductive material layer 104M above the upper end surface of the first interlayer insulating layer 102 is removed by CMP to form the first contact plug 104.
- the resistance variable element 113 is formed on the first interlayer insulating layer 102 so as to cover the first contact plug 104.
- the resistance variable element 113 is formed by stacking a first electrode layer 105, a resistance variable layer 106, and a second electrode layer 108.
- the first electrode material layer 105M constituting the first electrode layer 105 and the first metal oxide constituting the first resistance change layer 106a are formed so as to cover the first contact plug 104.
- the first metal oxide layer 106aF is formed (corresponding to the step of forming the first electrode layer and the step of forming the first variable resistance layer in combination with the patterning step shown in FIG. 2J).
- first, for example, tantalum nitride (TaN) is deposited as a first electrode material layer 105M to a thickness of 20 to 50 [nm] by sputtering.
- the first electrode material layer 105M is deposited using the sputtering method, but a CVD method (Chemical Vapor Deposition) or an ALD method (Atomic Layer Deposition) may be used.
- the first metal oxide layer 106aF is formed by reactive sputtering using tantalum as a target and sputtering in an atmosphere containing oxygen.
- the first metal oxide layer 106aF is made of, for example, TaO x (0.8 ⁇ x ⁇ 1.9). More specifically, the conditions of the reactive sputtering method are, for example, a power output of 1000 [W], a film forming pressure of 0.05 [Pa], an argon flow rate of 20 [sccm], and an oxygen gas flow rate of 21 [sccm].
- the composition of the TaO x layer created under the same conditions is expressed as TaO 1.22 .
- the resistivity of the first metal oxide layer 106aF was 3 [m ⁇ cm].
- the thickness of the first metal oxide layer 106aF can be set to, for example, 20 to 50 [nm] as a measurement value using a spectroscopic ellipsometry method.
- the first metal oxide layer 106aF is formed by reactive sputtering, but CVD, ALD, or the like may be used.
- a second metal oxide layer 106bF made of the second metal oxide is deposited on the first metal oxide layer 106aF (a second process is performed in combination with the patterning step shown in FIG. 2J). Equivalent to the step of forming the resistance change layer).
- the second metal oxide layer 106bF is formed, for example, by subjecting a part of the surface of the first metal oxide layer 106aF to plasma oxidation treatment with oxygen plasma.
- the thickness of the second metal oxide layer 106bF may be 4 to 7 [nm], for example.
- the conditions for the plasma oxidation treatment are, for example, an RF power output 50 [W], a substrate temperature 270 [° C.], and an O 2 flow rate 0.3 [SLM].
- the resistivity of the second metal oxide layer 106bF obtained by the plasma oxidation treatment under the above conditions was measured by a four-terminal measurement method, but exceeded the measurable upper limit (10 8 [ ⁇ / sq.]). It was. Therefore, the resistivity is considered to be at least 5 ⁇ 10 5 [m ⁇ ⁇ cm] or more.
- the surface of the first metal oxide layer 106aF is subjected to plasma oxidation treatment to form the second metal oxide layer 106bF.
- thermal oxidation treatment may be used, sputtering, CVD,
- the second metal oxide layer 106bF may be deposited by the ALD method.
- a metal-metal bond region 107 is formed on the surface of the second metal oxide layer 106bF (corresponding to a step of forming a metal-metal bond region).
- a second electrode material constituting the second electrode layer 108 for example, iridium, is implanted onto the surface of the second metal oxide layer 106bF by a sputtering method. With this configuration, oxygen on the surface of the second metal oxide layer 106bF is released, and a metal-metal bond region 107 is formed on a part of the surface of the second metal oxide layer 106bF.
- the processing conditions are, for example, an RF power output of 1000 [W] and a film forming pressure of 0.05 [Pa].
- the metal-metal bond region 107 is formed by releasing oxygen on the surface of the second metal oxide layer 106bF.
- the degree of oxygen deficiency increases as the metal-metal bond region 107 approaches the surface. Therefore, in this embodiment, it can be said that the degree of oxygen deficiency of the second resistance change layer 106b gradually increases toward the second electrode.
- a second electrode material layer 108M constituting the second electrode layer 108 is deposited on the second metal oxide layer 106bF (the second electrode in combination with the patterning step shown in FIG. 2J). Equivalent to the step of forming a layer).
- the second electrode material layer 108M is formed by depositing iridium (Ir) to a thickness of 80 [nm] by sputtering.
- the processing condition is, for example, a film forming pressure of 0.2 [Pa].
- the step of forming the metal-metal bond region 107 and the step of depositing the second electrode material layer 108M are performed by sputtering using iridium (Ir) as a target by changing the pressure. .
- the step of forming the metal-metal bond region 107 and the step of depositing the second electrode material layer 108M can be executed as the same step by substantially controlling the pressure condition. For this reason, compared with the case where the new process from which a method differs is added, the increase in a man-hour can be suppressed substantially.
- the sputtering method is used, but a CVD method or an ALD method may be used.
- the first electrode material layer 105M, the first metal oxide layer 106aF, the second metal oxide layer 106bF, and the second electrode material layer 108M are patterned to form the first electrode.
- the layer 105, the first resistance change layer 106a, the second resistance change layer 106b, and the second electrode layer 108 are formed.
- the patterning is performed using, for example, a desired mask and dry etching. Thereby, the resistance variable element 113 is formed.
- 2K is a diagram illustrating a process of forming the second interlayer insulating layer 109 so as to cover the first interlayer insulating layer 102 and the resistance variable element 113 as shown in FIG. 2K.
- the second interlayer insulating layer 109 is formed using the same material and the same method as the first interlayer insulating layer 102.
- the second interlayer insulating layer 109 is heat-treated for 10 minutes in a heating furnace heated to 400 degrees Celsius.
- a second contact hole 110 is formed so as to penetrate the second interlayer insulating layer 109 so that the surface of the second electrode layer 108 of the resistance variable element 113 is exposed.
- the second contact plug 111 is formed by filling the material constituting the second contact plug 111 in the 110, and the second wiring 112 is formed on the second contact plug 111.
- the second contact hole 110 is formed by the same method as the first contact hole 103.
- the second contact plug 111 is formed using the same material and the same method as the first contact plug 104.
- the second wiring 112 is formed using the same material and the same method as the first wiring 101.
- the element is placed in a heating furnace heated to 400 degrees Celsius, for example, for the purpose of suppressing corrosion of aluminum constituting the second wiring. Heat treatment for 10 minutes.
- each layer may be sequentially formed inside a through hole formed in an interlayer insulating layer. Further, a part of the plurality of layers may be formed outside the through hole, and the other part may be formed inside the through hole.
- the first resistance change layer 106a is a single layer.
- the first resistance change layer 106a has a laminated structure including a plurality of layers made of a plurality of metal oxides having different degrees of oxygen deficiency. Also good.
- a fourth resistance change layer formed of a metal oxide having a different oxygen content from the metal oxide constituting the first resistance change layer 106a between the first electrode layer 105 and the first resistance change layer 106a. May be formed.
- a layer may be formed.
- the resistance variable element 113 of the present embodiment may be used as a nonvolatile memory element such as ReRAM.
- the experimental apparatus first, 50 [nm] of TaO x corresponding to the first resistance change layer 106a was deposited on the silicon nitride film.
- the reaction conditions were a power output of 1000 [W], a film forming pressure of 0.05 [Pa], an argon flow rate of 20 [sccm], and an oxygen gas flow rate of 21 [sccm].
- the film thickness of the first resistance change layer was 50 [nm].
- the first resistance change layer 106a was treated with oxygen plasma from the intermediate oxide layer side.
- the processing conditions were RF power output 50 [W], wafer temperature 270 [° C.], O 2 flow rate 0.3 [SLM], 57 seconds.
- the film thickness of the Ta 2 O 5 layer corresponding to the second resistance change layer 106b thus obtained was measured by spectroscopic ellipsometry, the film thickness of the sample Ta 2 O 5 layer was 5.1 [nm]. there were.
- iridium as the second electrode material was deposited by sputtering.
- the horizontal axis indicates the sputtering time of the AES analysis method, and corresponds to the distance corresponding to the depth direction of the resistance element.
- the binding state of each element was analyzed by the XPS method (X-ray Photoelectron Spectroscopy, Quantum 2000 manufactured by ULVAC-PHI). The result is shown in FIG.
- the horizontal axis represents the photoelectron binding energy [eV] with the irradiated X-ray as a reference, and the vertical axis represents the observed number of detected photoelectrons (photoelectron signal intensity) [arbitrary unit].
- the two left peaks near 26.7 eV and near 28.4 eV
- the peaks indicate that photoelectrons are detected with the binding energy of Ta—Ta bond.
- Ta 2 O 5 the bonding state of each element of the second resistance change layer (Ta 2 O 5 ) and the first resistance change layer (TaO x ) is analyzed by the same XPS method without performing Ir deposition
- Ta—Ta bonds are detected in addition to Ta—O bonds.
- the Ir pressure is reduced to 0.05 [Pa]
- the mean free path of Ir ions becomes longer, and the energy when reaching Ta 2 O 5 increases, so that oxygen desorption from Ta 2 O 5 occurs. It became clear that this occurred.
- the apparatus to be tested first deposits aluminum on a silicon substrate by sputtering, processes it into a desired shape by patterning using a mask and dry etching, and forms a first wiring (thickness 400 to 600 [thickness]). nm]).
- the width of the first wiring is 0.25 [ ⁇ m].
- a first interlayer insulating layer (thickness 500 to 1000 [nm]) is formed by CVD using TEOS so as to cover the first wiring formed on the substrate.
- the upper end surface was flattened by CMP.
- a first contact hole (diameter 260 [nm]) was formed in the first interlayer insulating layer so that the upper surface of the first wiring was opened. Further, the first contact hole was filled with a conductive material layer having a laminated structure of W / Ti / TiN to form a first contact plug.
- the Ti layer was formed to a thickness of 5 to 30 [nm] by sputtering.
- the TiN layer was formed to a thickness of 5 to 30 [nm] by the CVD method.
- the W layer was formed by a CVD method.
- a first electrode layer (thickness 400 to 600 [nm]) was formed so as to cover the first contact plug.
- a first variable resistance layer composed of tantalum oxide was formed on the first electrode layer by using a target composed of tantalum and performing reactive sputtering in an atmosphere containing oxygen.
- the reaction conditions were a power output of 1000 [W], a film forming pressure of 0.05 [Pa], an argon flow rate of 20 [sccm], and an oxygen gas flow rate of 21 [sccm].
- the oxygen content of the tantalum oxide constituting the first variable resistance layer is about 55% from the result of the first experimental example.
- the first resistance change layer was treated with oxygen plasma to form a second resistance change layer.
- the processing conditions were RF power output 50 [W], wafer temperature 270 [° C.], O 2 flow rate 0.3 [SLM], 57 seconds. From the result of the first experimental example, the film thickness of the second variable resistance layer is about 5.1 [nm].
- a second electrode (thickness: about 80 [nm]) made of iridium was formed on the second variable resistance layer by sputtering.
- the sputtering pressure of iridium was set to 0.2 [Pa] and 0.05 [Pa] for each wafer.
- each element was separated by a mask and dry etching.
- the size of each element is a substantially square of 0.38 [ ⁇ m] ⁇ 0.38 [ ⁇ m], and 1000 pieces were prepared.
- a second interlayer insulating layer (thickness 500 to 1000 [nm]) was formed by CVD using TEOS so as to cover all the elements.
- the upper end surface was flattened by CMP.
- FIG. 6 is a diagram showing resistance change characteristics of a resistance variable element formed with the Ir sputtering pressure set to 0.05 [Pa].
- the experiment was performed by alternately applying two kinds of voltage pulses having a pulse width of 100 [ns] and different polarities between the electrodes of the first electrode layer and the second electrode layer, and measuring the resistance value after the application. It was. By alternately applying two kinds of voltage pulses between the electrodes, the resistance value of the resistance change layer changed reversibly.
- a load resistance of 5 [k ⁇ ] is connected in series to the resistance variable element immediately after manufacture.
- a threshold voltage at which a part of the second resistance change layer 106b is locally short-circuited and a resistance change is started is measured as a break voltage.
- the break voltage can be reduced by setting the sputtering pressure during Ir deposition to 0.05 [Pa] and forming Ta—Ta bonds on Ta 2 O 5 .
- the variable resistance element 113 of the nonvolatile memory device 30 of the second embodiment is different from the variable resistance element 113 of the nonvolatile memory device 10 of the first embodiment in that the metal-metal bonding region 107 has a second resistance. It is a point formed inside the change layers 106b and 106c. That is, in the first embodiment, the metal-metal bonding region 107 exists at the interface between the second resistance change layer 106b and the second electrode layer 108, whereas in the second embodiment, the second resistance change.
- the layer has a two-layer structure of a layer 106b and a layer 106c, and the metal-metal bond region 107 exists between the second resistance change layers 106b and 106c.
- FIG. 8 is a cross-sectional view showing a configuration example of the nonvolatile memory device 30 including the nonvolatile memory element (resistance change element 113) according to the present embodiment.
- the nonvolatile memory device 30 includes a substrate 100, a first wiring 101, a first interlayer insulating layer 102, and a first contact hole 103 formed in the first interlayer insulating layer 102.
- a second contact plug 111 embedded inside, and a second wiring 112 formed so as to cover the upper surface of the second contact plug 111 are formed.
- the nonvolatile memory element according to the present invention includes a resistance variable element 113, and includes a substrate 100, a first wiring 101, a first interlayer insulating layer 102, and a first contact.
- the hole 103, the first contact plug 104, the second interlayer insulating layer 109, the second contact hole 110, the second contact plug 111, and the second wiring 112 are not essential components of the present invention.
- the structure of the substrate 100, the first wiring 101, the first interlayer insulating layer 102, the first contact plug 104, the second interlayer insulating layer 109, the second contact plug 111, and the second wiring 112 is as described above. The same as in the first embodiment.
- the resistance change element 113 of this embodiment includes a first electrode layer 105, a first resistance change layer 106a, second resistance change layers 106b and 106c having a two-layer structure, and a second electrode layer 108 in this order.
- a metal-metal bond region 107 is interposed between the second resistance change layers 106b and 106c. Note that the materials, shapes, and the like of the first electrode layer 105 and the second electrode layer 108 are the same as those in the first embodiment.
- the first resistance change layer 106a is made of an oxygen-deficient first metal oxide and has a thickness of 5 to 100 [nm].
- the first metal oxide may be composed of a transition metal oxide or an aluminum oxide, as in the first embodiment. More specifically, the first metal oxide may be composed of at least one metal oxide selected from the group consisting of tantalum oxide, hafnium oxide, zirconium oxide, aluminum oxide, and the like.
- x may satisfy 0.8 ⁇ x ⁇ 1.9.
- the film thickness of the first resistance change layer 106a is appropriately set according to the manufacturing process, the film thickness and shape of other layers, and the like.
- the second resistance change layers 106b and 106c have a two-layer structure. Similar to the second metal oxide of the first embodiment, the second metal oxide constituting the second resistance change layers 106b and 106c is deficient in oxygen than the first metal oxide constituting the first resistance change layer 106a. It is composed of a metal oxide having a low degree of resistance and a large resistance value.
- the second metal oxide may be composed of a transition metal oxide or an aluminum oxide, as in the first embodiment. More specifically, the second metal oxide is composed of at least one metal oxide selected from the group consisting of tantalum oxide, hafnium oxide, zirconium oxide, aluminum oxide and the like, as in the first embodiment. May be.
- the second metal oxide may be composed of the same metal oxide as the first metal oxide, or may be composed of an oxide of a metal different from the first metal oxide.
- the second metal oxide constituting the second resistance change layer 106b is TaO y1
- the second metal oxide constituting the second resistance change layer 106c is TaO y2.
- TaO x is assumed as the metal oxide constituting the first resistance change layer 106a, and therefore x ⁇ y1 and y2 may be satisfied.
- y1 and y2 may satisfy 2.1 ⁇ y1 and y2 ⁇ 2.5.
- the second resistance change layers 106b and 106c may be made of an insulator.
- the second resistance change layers 106b and 106c have a thickness of 2 to 10 [nm] in this embodiment.
- the film thicknesses of the second resistance change layers 106b and 106c are appropriately set according to the manufacturing process, the film thickness and shape of other layers, and the like.
- the metal-metal bond region 107 is a region having a metal-metal bond in which the metals constituting the second metal oxide are bonded to each other, as in the first embodiment.
- the metal-metal bond region 107 of this embodiment is formed between the second resistance change layers 106b and 106c.
- the metal-metal bonding region 107 may be formed in a layer shape having the same surface area as that of the second resistance change layers 106b and 106c, or may exist in a part.
- the step of forming the first electrode layer 105 and the formation of the first variable resistance layer 106 a made of the first metal oxide on the first electrode layer 105 a step of forming a second resistance change layer 106b composed of a second metal oxide having a smaller oxygen deficiency and a higher resistance value than the first metal oxide on the first resistance change layer 106a.
- the first stacking step of stacking the second metal oxide after the step of forming the first resistance change layer 106a, and the metal-metal In the step of forming the metal-metal bond region 107, the second stacking step of stacking the second metal oxide is performed after the step of forming the bonding region 107, and the step of forming the metal-metal bond region 107 is performed after the first stacking step.
- a metal-metal bond region is formed by laminating a third metal oxide having a greater degree of oxygen deficiency than the two metal oxides.
- FIGS. 9A to 9D show a part of the manufacturing method of the nonvolatile memory device 30 shown in FIG. 8 (particularly, the step of forming the second resistance change layer 106b to the step of forming the second electrode layer 108). It is a typical process sectional view showing this process.
- the second metal oxide layer 106bF made of the second metal oxide is formed on the first metal oxide layer 106aF.
- the second metal oxide layer 106bF is formed, for example, by plasma oxidation in which a part of the first metal oxide layer 106aF is processed with oxygen plasma to treat the substrate surface, similarly to the second metal oxide layer 106bF of the first embodiment. To do.
- the thickness of the second metal oxide layer 106bF may be 3 to 4 nm, for example.
- the conditions for the plasma oxidation treatment are, for example, an RF power output 50 [W], a substrate temperature 270 [° C.], and an O 2 flow rate 0.3 [SLM].
- a measurable upper limit (10 8 [ ⁇ / sq.]).
- the resistivity is considered to be at least 5 ⁇ 10 5 [m ⁇ ⁇ cm] or more.
- a metal-metal bond region 107 is formed on the second metal oxide layer 106bF (corresponding to a step of forming a metal-metal bond region). Specifically, for example, it is formed by sputtering using tantalum as a target. The thickness of the metal-metal bonding region 107 can be 0.3 nm.
- the processing conditions of the reactive sputtering method are, for example, a power output of 1000 [W], a film forming pressure of 0.05 [Pa], and an argon flow rate of 20 [sccm].
- the composition of the TaO z layer created under the same conditions is expressed as TaO 1.78 .
- the resistivity was 15 [m ⁇ cm].
- a layer 106cF made of the second metal oxide is laminated on the second metal oxide layer 106bF and the metal-metal bond region 107 (step of forming a second resistance change layer).
- the second electrode material layer 108M constituting the second electrode layer is deposited on the layer 106cF (corresponding to the step of forming the second electrode layer together with the patterning step shown in FIG. 9D). ).
- the second metal oxide layer 106cF is formed, for example, by reactive sputtering using tantalum as a target and sputtering in an atmosphere containing oxygen, as with the first metal oxide layer 106aF.
- the conditions of the reactive sputtering method are, for example, a power output of 1000 [W], a film forming pressure of 0.05 [Pa], an argon flow rate of 20 [sccm], and an oxygen gas flow rate of 21 [sccm].
- the layer 106cF has a resistivity of 10 7 [m ⁇ cm] or more and a film thickness of 2 nm.
- the second electrode material layer 108M is formed by depositing iridium (Ir) to a thickness of 80 [nm] by sputtering as in the first embodiment.
- the processing condition of the sputtering method is, for example, a film forming pressure of 0.2 [Pa].
- the first electrode material layer 105M, the first metal oxide layer 106aF, the second metal oxide layer 106bF, the second metal oxide cF, and the second electrode material layer 108M are formed.
- the patterning is performed using, for example, a desired mask and dry etching. Thereby, the resistance variable element 113 is formed.
- the step of forming the second interlayer insulating layer 109 shown in FIG. 2K and the step of forming the second contact hole 110, the second contact plug 111, and the second wiring 112 shown in FIG. 2L are executed.
- the nonvolatile memory device 30 shown in FIG. Note that the process of forming the second interlayer insulating layer 109 shown in FIG. 2K and the process of forming the second contact hole 110, the second contact plug 111, and the second wiring 112 shown in FIG. This is the same as the embodiment, and the description is omitted.
- Ta—Ta bonds can be formed inside Ta 2 O 5 constituting the second resistance change layer, and the break voltage can be reduced.
- tantalum, hafnium, zirconium, or aluminum is used as the material constituting the first metal oxide, the second metal oxide, and the metal-metal bond region.
- the description has been made on the assumption that the metal oxide material is included.
- the present invention is not limited to this.
- a material containing titanium may be used.
- the first metal oxide layer 106aF (first hafnium oxide layer) using hafnium oxide can be generated by, for example, reactive sputtering using an Hf target and sputtering in argon gas and oxygen gas. .
- the second metal oxide layer 106bF (second hafnium oxide layer) using hafnium oxide can be formed, for example, by exposing the surface of the first hafnium oxide layer 106aF to plasma of argon gas and oxygen gas. .
- the oxygen content of the first hafnium oxide layer 106aF can be easily adjusted by changing the flow ratio of oxygen gas to argon gas during reactive sputtering, as in the case of the tantalum oxide described above.
- the substrate temperature can be set to room temperature without any particular heating.
- the thickness of the second hafnium oxide layer 106bF can be easily adjusted by the exposure time of the argon gas and the oxygen gas to the plasma.
- the film thickness of the second hafnium oxide layer 106bF may be 3 nm or more and 4 nm or less.
- the metal-metal bond region 107 is a region having an Hf-Hf bond.
- the first metal oxide layer 106a (first zirconium oxide layer) using zirconium oxide can be generated by, for example, a reactive sputtering method using a Zr target and sputtering in argon gas and oxygen gas. .
- the second metal oxide layer 106bF (second zirconium oxide layer) using zirconium oxide can be formed, for example, by exposing the surface of the first zirconium oxide layer 106aF to argon gas and oxygen gas plasma.
- the oxygen content of the first zirconium oxide layer 106aF can be easily adjusted by changing the flow ratio of oxygen gas to argon gas during reactive sputtering, as in the case of the tantalum oxide described above.
- the substrate temperature can be set to room temperature without any particular heating.
- the thickness of the second zirconium oxide layer 106bF can be easily adjusted by the exposure time of the argon gas and oxygen gas to the plasma.
- the film thickness of the second zirconium oxide layer 106bF may be 1 nm or more and 5 nm or less.
- the metal-metal bond region 107 is a region having a Zr—Zr bond.
- hafnium oxide layer and zirconium oxide layer can also be formed by using a CVD method or an ALD (Atomic Layer Deposition) method instead of sputtering.
- the first metal constituting the first metal oxide and the second metal constituting the second metal oxide may be different metals.
- the second resistance change layer 106b made of the second metal oxide is less oxygen deficient than the first resistance change layer 106a made of the first metal oxide, that is, even if the resistance is increased. Good.
- the voltage applied between the first electrode layer 105 and the second electrode layer 108 at the time of resistance change is distributed more to the second resistance change layer 106b, and the second resistance is changed.
- the oxidation-reduction reaction generated in the change layer 106b can be more easily caused.
- the standard electrode potential of the second metal may be lower than the standard electrode potential of the first metal. This is because the resistance change phenomenon is considered to occur due to an oxidation-reduction reaction occurring in a minute filament (conductive path) formed in the second resistance change layer 106b having a high resistance, and its resistance value changes.
- the standard electrode potential represents a characteristic that the higher the value is, the more difficult it is to oxidize.
- a metal oxide having a lower standard electrode potential than the first resistance change layer 106a in the second resistance change layer 106b By disposing a metal oxide having a lower standard electrode potential than the first resistance change layer 106a in the second resistance change layer 106b, a redox reaction is more likely to occur in the second resistance change layer 106b.
- oxygen-deficient tantalum oxide (TaO x ) may be used for the first resistance change layer 106 a and aluminum oxide (Al 2 O 3 ) may be used for the second resistance change layer 106 b. .
- the resistance change phenomenon in the resistance change layer including the oxygen-deficient metal oxide is expressed by the movement of oxygen, at least the movement of oxygen is possible even if the type of the base metal is different. That's fine. Therefore, the same metal is used for the first metal constituting the first resistance change layer 106a and the second metal constituting the second resistance change layer 106b even when different metals are used. It is thought that there is an effect similar to the case.
- the first resistance change layer 106a and the second resistance change layer 106b only need to include an oxide layer such as tantalum, hafnium, and zirconium as a main resistance change layer that exhibits resistance change.
- an oxide layer such as tantalum, hafnium, and zirconium
- a trace amount of other elements may be contained. It is also possible to intentionally include a small amount of other elements by fine adjustment of the resistance value, and such a case is also included in the scope of the present invention. For example, if nitrogen is added to the resistance change layer, the resistance value of the resistance change layer increases and the reactivity of resistance change can be improved.
- the resistance change layer is formed of an oxygen-deficient type having a composition represented by MO x (where 0 ⁇ x ⁇ 2.5). And a second resistance change including an oxygen-deficient second metal oxide having a composition represented by MO y (where x ⁇ y ⁇ 2.5).
- the first variable resistance layer and the second variable resistance layer include a predetermined impurity (for example, an additive for adjusting the resistance value). Does not prevent inclusion).
- an unintended trace element may be mixed into the resistive film due to residual gas or outgassing from the vacuum vessel wall. Naturally, it is also included in the scope of the present invention when mixed into the film.
- variable resistance nonvolatile element realized by making various modifications conceived by those skilled in the art without departing from the gist of the present invention or by arbitrarily combining the constituent elements in the embodiment and a method for manufacturing the variable resistance nonvolatile element are also included in the present invention. included.
- the nonvolatile memory element of the present invention is useful as a nonvolatile memory element in which metal oxide layers having different degrees of oxygen deficiency are stacked and used as a resistance change layer, particularly as a nonvolatile memory element that can reduce the break voltage.
- storage device 20 Nonvolatile memory
- storage device 30 Nonvolatile memory
- substrate 101 1st wiring 102 1st interlayer insulation layer 103 1st contact hole 104 1st contact plug 104M Conductive material layer 105 1st electrode layer 105M 1st Electrode material layer 106 variable resistance layer 106a first variable resistance layer 106aF first metal oxide layer 106b second variable resistance layer 106bF second metal oxide layer 106c second variable resistance layer 106cF second metal oxide layer 107 metal-metal Coupling region 108 Second electrode layer 108M Second electrode material layer 109 Second interlayer insulating layer 110 Second contact hole 111 Second contact plug 112 Second wiring 113 Resistance variable element 200 Substrate 201 First wiring 202 First interlayer insulating film 203 1 contact hole 204 1st contact plug 205 1st electrode layer 206 resistance change layer 206a 1st tantalum oxide layer 206b 2nd tantalum oxide layer
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Abstract
Description
本発明の一形態に係る不揮発性記憶素子は、第1電極と、第2電極と、前記第1電極と前記第2電極との間に介在し、前記第1電極と前記第2電極との間に与えられる電気的信号に基づいて可逆的に抵抗状態が変化する抵抗変化層と、を備え、前記抵抗変化層は、第1金属酸化物で構成される第1抵抗変化層と、前記第1金属酸化物より酸素不足度が小さく、抵抗値が大きい第2金属酸化物で構成される第2抵抗変化層と、を有し、前記第2抵抗変化層中に、前記第2金属酸化物を構成する金属原子同士の金属結合を有する金属-金属結合領域を備える。
第1実施形態の不揮発性記憶素子、及び、第1実施形態の不揮発性記憶素子の製造方法について、図2~図7を基に説明する。
先ず、本実施形態の不揮発性記憶素子の構成について説明する。ここで、図1は、本実施形態に係る不揮発性記憶素子(抵抗変化型素子113)を備える不揮発性記憶装置10の一構成例を示す断面図である。
次に、本実施形態の不揮発性記憶素子の製造方法について説明する。
第1実験例では、抵抗変化層であるTaOxとTa2O5における酸素プロファイル、及び、Ta、Oの化学結合状態が第2電極であるイリジウムの成膜条件でどのように変化するかを調査した。
2つのサンプルIrスパッタ圧力=0.2[Pa]と、サンプルIrスパッタ圧力=0.05[Pa]の夫々について、タンタル、酸素、イリジウムの深さ方向のプロファイルをAES(Auger Electron Spectroscopy、アルバック-ファイ社製 PHI700)で分析した。
第2実験例では、Irスパッタ圧力を0.2[Pa]と0.05[Pa]に設定して、夫々実際に不揮発性記憶装置(実験対象装置)を製造し、抵抗変化動作の確認とブレイク電圧の比較を行った。
図6は、Irスパッタ圧力を0.05[Pa]に設定して形成された抵抗変化型素子の抵抗変化特性を示す図である。実験は、第1電極層と第2電極層との電極間に、パルス幅が100[ns]で極性が異なる2種類の電圧パルスを交互に印加し、印加後に抵抗値を測定することにより行った。電極間に2種類の電圧パルスを交互に印加することにより、抵抗変化層の抵抗値は可逆的に変化した。具体的には、抵抗変化層が高抵抗状態の抵抗変化型素子に対し、負電圧パルス(電圧-1.5[V]、パルス幅100[ns])を電極間に印加した場合、抵抗変化層の抵抗値が減少して約10000[Ω](104[Ω]、低抵抗状態)となった。低抵抗状態となった後、正電圧パルス(電圧+2.4[V]、パルス幅100[ns])を電極間に印加した場合、抵抗変化層の抵抗値が増加して100000[Ω](105[Ω]、高抵抗状態)となった。なお、電圧は、第1電極層を基準として第2電極層の電位が高い場合を正電圧と表記している。
本発明に係る不揮発性記憶素子、及び、本発明に係る不揮発性記憶素子の製造方法の第2実施形態について、図8及び図9を基に説明する。
先ず、本実施形態の不揮発性記憶素子の構成について説明する。ここで、図8は、本実施形態に係る不揮発性記憶素子(抵抗変化型素子113)を備える不揮発性記憶装置30の構成例を示す断面図である。
次に、本実施形態の不揮発性記憶素子の製造方法について説明する。
(1)上記第1実施形態及び第2実施形態において、第1金属酸化物、第2金属酸化物、及び、金属-金属結合領域を構成する材料として、タンタル、ハフニウム、ジルコニウム、または、アルミニウムを含む金属酸化物材料を想定して説明したが、これに限るものではなく、例えば、チタンを含む材料であっても良い。
20 不揮発性記憶装置
30 不揮発性記憶装置
100 基板
101 第1配線
102 第1層間絶縁層
103 第1コンタクトホール
104 第1コンタクトプラグ
104M 導電性材料層
105 第1電極層
105M 第1電極材料層
106 抵抗変化層
106a 第1抵抗変化層
106aF 第1金属酸化物層
106b 第2抵抗変化層
106bF 第2金属酸化物層
106c 第2抵抗変化層
106cF 第2金属酸化物層
107 金属-金属結合領域
108 第2電極層
108M 第2電極材料層
109 第2層間絶縁層
110 第2コンタクトホール
111 第2コンタクトプラグ
112 第2配線
113 抵抗変化型素子
200 基板
201 第1配線
202 第1層間絶縁膜
203 第1コンタクトホール
204 第1コンタクトプラグ
205 第1電極層
206 抵抗変化層
206a 第1タンタル酸化物層
206b 第2タンタル酸化物層
207 第2電極層
208 第2層間絶縁層
209 第2コンタクトホール
210 第2コンタクトプラグ
211 第2配線
212 抵抗変化型素子
Claims (11)
- 第1電極と、
第2電極と、
前記第1電極と前記第2電極との間に介在し、前記第1電極と前記第2電極との間に与えられる電気的信号に基づいて可逆的に抵抗状態が変化する抵抗変化層と、を備え、
前記抵抗変化層は、第1金属酸化物で構成される第1抵抗変化層と、前記第1金属酸化物より酸素不足度が小さく、抵抗値が大きい第2金属酸化物で構成される第2抵抗変化層と、を有し、前記第2抵抗変化層中に、前記第2金属酸化物を構成する金属原子同士の金属結合を有する金属-金属結合領域を備える
不揮発性記憶素子。 - 前記抵抗変化層において、前記金属-金属結合領域は、前記第2電極と前記第2抵抗変化層の界面に存在する
請求項1に記載の不揮発性記憶素子。 - 前記抵抗変化層において、前記金属-金属結合領域は、前記第2抵抗変化層の表面を除く内部に存在する
請求項1に記載の不揮発性記憶素子。 - 前記金属-金属結合領域は、前記第2抵抗変化層中のうち前記第2抵抗変化層と前記第2電極との界面近傍に存在し、
前記第2抵抗変化層は、前記第2抵抗変化層から第2電極に向かって酸素不足度が段階的に大きくなっている
請求項1に記載の不揮発性記憶素子。 - 前記第1金属酸化物、前記第2金属酸化物、及び前記金属-金属結合領域は、それぞれ、遷移金属酸化物またはアルミニウム酸化物から構成される
請求項1~4の何れか一項に記載の不揮発性記憶素子。 - 前記第1金属酸化物と、前記第2金属酸化物と、前記金属-金属結合領域とは、タンタル、ハフニウム、または、ジルコニウムを含む材料で構成される
請求項1~5の何れか一項に記載の不揮発性記憶素子。 - 前記第2抵抗変化層は絶縁物から構成される
請求項1~6の何れか一項に記載の不揮発性記憶素子。 - 第1電極層を形成する工程と、
前記第1電極層の上に、第1金属酸化物で構成される第1抵抗変化層を形成する工程と、
前記第1抵抗変化層の上に、前記第1金属酸化物より酸素不足度が小さく、抵抗値が大きい第2金属酸化物で構成される第2抵抗変化層を形成する工程と、
前記第2抵抗変化層中に、前記第2金属酸化物を構成する金属原子同士の金属結合を備える金属-金属結合領域を形成する工程と、
前記第2抵抗変化層の上に、第2電極層を形成する工程と、を備える
不揮発性記憶素子の製造方法。 - 前記金属-金属結合領域を形成する工程では、前記第2抵抗変化層から酸素を脱離させることにより、前記金属-金属結合領域を形成する
請求項8に記載の不揮発性記憶素子の製造方法。 - 前記第2電極層を形成する工程では、スパッタ法により前記第2電極層を形成し、
前記金属-金属結合領域を形成する工程では、前記第2電極層を構成する第2電極材料をターゲットとし、前記第2電極層を形成するときの成膜圧力よりも低い成膜圧力を条件として、スパッタ法を実行する
請求項9に記載の不揮発性記憶素子の製造方法。 - 前記第2抵抗変化層を形成する工程では、前記第1抵抗変化層を形成する工程の実行後に、前記第2金属酸化物を積層する第1積層工程と、前記金属-金属結合領域を形成する工程の実行後に、前記第2金属酸化物を積層する第2積層工程とを実行する
請求項8に記載の不揮発性記憶素子の製造方法。
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WO2015125449A1 (ja) * | 2014-02-24 | 2015-08-27 | 株式会社アルバック | 抵抗変化素子及びその製造方法 |
CN106030800A (zh) * | 2014-02-24 | 2016-10-12 | 株式会社爱发科 | 电阻可变元件及其制造方法 |
JPWO2015125449A1 (ja) * | 2014-02-24 | 2017-03-30 | 株式会社アルバック | 抵抗変化素子及びその製造方法 |
KR101815799B1 (ko) * | 2014-02-24 | 2018-01-05 | 가부시키가이샤 아루박 | 저항 변화 소자 및 그 제조 방법 |
TWI637485B (zh) * | 2014-02-24 | 2018-10-01 | 日商愛發科股份有限公司 | 電阻變化元件及其製造方法 |
US10103328B2 (en) | 2016-03-18 | 2018-10-16 | Toshiba Memory Corporation | Nonvolatile memory device |
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