Memory device

Abstract

To provide a storage device that includes a switching element having excellent characteristics. [Solution] The memory device according to the embodiment comprises a lower wiring 10, an upper wiring 20, and a memory cell 30 including a variable resistance memory element 40 and a switching element 50. The switching element includes a lower electrode 51, an upper electrode 52, and a switching material layer 53 provided between the lower electrode and the upper electrode, and the upper electrode includes a first layer portion 52a and a second layer portion 52b. The switching material layer is formed of a material containing Si, O and As, the first layer portion is formed of a conductive material containing C, and the second layer portion is formed of a conductive material containing at least one element selected from Ta, Ti, W, Ni, Mo, Cr, V, Zr, Al, Hf, In, Sn, Ru, Zn and Mg.

Description

Technical Field

[0001] Embodiments of the present invention relate to a memory device.

Background Art

[0002] A memory device in which a plurality of memory cells including variable resistance memory elements and selectors (switching elements) are integrated on a semiconductor substrate has been proposed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] To provide a memory device including a selector (switching element) having excellent characteristics.

Means for Solving the Problems

[0005] A memory device according to the embodiment comprises a lower wiring extending in a first direction, an upper wiring extending in a second direction intersecting the first direction, and a memory cell provided between the lower wiring and the upper wiring, which includes a variable resistance memory element and a switching element stacked in a third direction intersecting the first and second directions, wherein the switching element includes a structure in which a lower electrode, an upper electrode, and a switching material layer provided between the lower electrode and the upper electrode are stacked in the third direction, and the upper electrode includes a first layer portion and a second layer portion stacked in the third direction, and the switching material layer and the second layer portion The structure includes a first layer portion provided between the layers, wherein the switching material layer is formed of a material containing silicon (Si), oxygen (O), and arsenic (As), the first layer portion is formed of a conductive material containing carbon (C), and the second layer portion is formed of a conductive material containing at least one element selected from tantalum (Ta), titanium (Ti), tungsten (W), nickel (Ni), molybdenum (Mo), chromium (Cr), vanadium (V), zirconium (Zr), aluminum (Al), hafnium (Hf), indium (In), tin (Sn), ruthenium (Ru), zinc (Zn), and magnesium (Mg). [Brief explanation of the drawing]

[0006] [Figure 1] This is a schematic perspective view showing the configuration of the storage device according to the first embodiment. [Figure 2] This is a schematic cross-sectional view showing the configuration of a storage device according to the first embodiment. [Figure 3] This is a schematic cross-sectional view showing an example of the configuration of a magnetoresistive element in a storage device according to the first embodiment. [Figure 4] This is a schematic cross-sectional view showing another example of the configuration of a magnetoresistive element in a memory device according to the first embodiment. [Figure 5] This figure schematically shows the current-voltage characteristics of the selector in the storage device according to the first embodiment. [Figure 6]This is a schematic perspective view showing the configuration of a storage device according to the second embodiment. [Figure 7] This is a schematic cross-sectional view showing the configuration of a storage device according to the second embodiment. [Modes for carrying out the invention]

[0007] The embodiments will be described below with reference to the drawings.

[0008] (First embodiment) Figure 1 is a schematic perspective view showing the configuration of a storage device according to the first embodiment.

[0009] The memory device according to this embodiment is provided on a lower region (not shown) including a semiconductor substrate (not shown), and includes a plurality of lower wirings 10 each extending in the X direction, a plurality of upper wirings 20 each extending in the Y direction and located on the upper side of the plurality of lower wirings 10, and a plurality of memory cells 30 provided between the plurality of lower wirings 10 and the plurality of upper wirings 20.

[0010] One of the lower wiring 10 and the upper wiring 20 corresponds to a word line, and the other of the lower wiring 10 and the upper wiring 20 corresponds to a bit line.

[0011] Each memory cell 30 includes a magnetoresistive element 40, which is a variable resistance memory element, and a selector 50, which is a switching element. The magnetoresistive element 40 and the selector 50 are connected in series between the lower wiring 10 and the upper wiring 20 and stacked in the Z direction.

[0012] Note that the X, Y, and Z directions intersect each other. More specifically, the X, Y, and Z directions are orthogonal to each other.

[0013] Figure 2 is a schematic cross-sectional view showing the configuration of the storage device according to this embodiment.

[0014] As described above, the memory device according to the present embodiment includes a lower wiring 10, an upper wiring 20, and a memory cell 30 provided between the lower wiring 10 and the upper wiring 20.

[0015] In the present embodiment, the memory cell 30 includes a magnetoresistive element (also referred to as a magnetoresistive element body or a magnetoresistive element, and hereinafter, the description will be made using the term magnetoresistive element) 40, a selector 50, and an electrode 61 provided between the magnetoresistive element 40 and the upper wiring 20. Further, in the present embodiment, the selector 50 is provided on the lower layer side of the magnetoresistive element 40. Although not shown in the figure, sidewall insulating layers are provided on the side surfaces of the magnetoresistive element 40 and the selector 50, and an interlayer insulating layer is provided in the region between adjacent memory cells 30.

[0016] FIG. 3 is a cross-sectional view schematically showing an example of the configuration of the magnetoresistive element 40.

[0017] The magnetoresistive element 40 is a MTJ (magnetic tunnel junction) element, and includes a memory layer (first magnetic layer) 41, a reference layer (second magnetic layer) 42, a tunnel barrier layer (non-magnetic layer) 43, a shift canceling layer (third magnetic layer) 44, and an intermediate layer 45, and these layers 41 to 45 have a structure laminated in the Z direction.

[0018] The memory layer 41 is a ferromagnetic layer having a variable magnetization direction, and is formed of, for example, a CoFeB layer containing cobalt (Co), iron (Fe), and boron (B). The variable magnetization direction means that the magnetization direction changes with respect to a predetermined write current.

[0019] The reference layer 42 is a ferromagnetic layer having a fixed magnetization direction, and is formed of, for example, a CoFeB layer containing cobalt (Co), iron (Fe), and boron (B). The fixed magnetization direction means that the magnetization direction does not change with respect to a predetermined write current.

[0020] The tunnel barrier layer 43 is an insulating layer provided between the memory layer 41 and the reference layer 42, and is formed of, for example, a MgO layer containing magnesium (Mg) and oxygen (O).

[0021] The shift cancellation layer 44 is a ferromagnetic layer having a magnetization direction fixed antiparallel to the magnetization direction of the reference layer 42, and has a function of canceling the magnetic field applied from the reference layer 42 to the memory layer 41. The shift cancellation layer 44 is formed of, for example, a superlattice layer in which cobalt (Co) and platinum (Pt) are alternately laminated.

[0022] The intermediate layer 45 is provided between the reference layer 42 and the shift cancellation layer 44, and is formed of, for example, a ruthenium (Ru) layer.

[0023] When the magnetization direction of the memory layer 41 is parallel to the magnetization direction of the reference layer 42, the magnetoresistive effect element 40 is in a low-resistance state having a relatively low resistance, and when the magnetization direction of the memory layer 41 is antiparallel to the magnetization direction of the reference layer 42, the magnetoresistive effect element 40 is in a high-resistance state having a relatively high resistance. Therefore, the magnetoresistive effect element 40 can store binary data according to its resistance state.

[0024] FIG. 4 is a cross-sectional view schematically showing another example of the configuration of the magnetoresistive effect element 40.

[0025] The magnetoresistive effect element 40 shown in FIG. 3 is a bottom-free type magnetoresistive effect element in which the memory layer 41 is located on the lower layer side of the reference layer 42, while the magnetoresistive effect element 40 shown in FIG. 4 is a top-free type magnetoresistive effect element in which the memory layer 41 is located on the upper layer side of the reference layer 42. The magnetoresistive effect element 40 shown in FIG. 3 and the magnetoresistive effect element 40 shown in FIG. 4 have the lamination order of the layers 41 to 45 reversed.

[0026] Instead of the magnetoresistive effect element 40 as shown in FIG. 3, the magnetoresistive effect element 40 as shown in FIG. 4 may be used.

[0027] Returning to the explanation of Figure 2, the selector 50 includes a lower electrode 51, an upper electrode 52 provided on the upper side of the lower electrode 51, and a selector material layer (switching material layer) 53 provided between the lower electrode 51 and the upper electrode 52, and these layers 51 to 53 are stacked in the Z direction.

[0028] The lower electrode 51 is made of a conductive material and is provided between the selector material layer 53 and the lower wiring 10.

[0029] The upper electrode 52 is made of a conductive material and is provided between the selector material layer 53 and the magnetoresistive element 40. The upper electrode 52 functions as the upper electrode of the selector 50 and also as the lower electrode of the magnetoresistive element 40.

[0030] The upper electrode 52 includes a first layer portion 52a, a second layer portion 52b, and a third layer portion 52c, and has a structure in which these layers 52a, 52b, and 52c are stacked in the Z direction. Specifically, the first layer portion 52a and the second layer portion 52b are provided between the selector material layer 53 and the third layer portion 52c, the first layer portion 52a is provided between the selector material layer 53 and the second layer portion 52b, and the second layer portion 52b is provided between the first layer portion 52a and the third layer portion 52c.

[0031] The first layer portion 52a is formed of a conductive material containing carbon (C). Specifically, the first layer portion 52a is formed of a carbon (C) layer or a carbon nitride (CN) layer.

[0032] The second layer portion 52b is formed of a conductive material containing at least one element selected from tantalum (Ta), titanium (Ti), tungsten (W), nickel (Ni), molybdenum (Mo), chromium (Cr), vanadium (V), zirconium (Zr), aluminum (Al), hafnium (Hf), indium (In), tin (Sn), ruthenium (Ru), zinc (Zn), and magnesium (Mg).

[0033] The second layer portion 52b may be formed of a conductive material containing at least one of the above-mentioned elements and at least one element selected from nitrogen (N), silicon (Si), carbon (C), and oxygen (O). For example, the conductivity of the second layer portion 52b can be ensured by appropriately adjusting the proportions of these additive elements.

[0034] For example, the second layer portion 52b is formed from layers selected from Ta layer, TaN layer, Ti layer, TiN layer, TiC layer, W layer, WN layer, WSi layer, WSiN layer, Ni layer, Mo layer, Cr layer, V layer, CrN layer, ZrN layer, AlN layer, HfN layer, ITO (Indium Tin Oxide) layer, RuO layer, SnO layer, AlO layer, ZnO layer, and MgO layer.

[0035] The third layer portion 52c is not particularly limited, and can be made of a predetermined conductive material.

[0036] The selector material layer 53 is formed of a material containing silicon (Si), oxygen (O), and arsenic (As). Specifically, the selector material layer 53 is formed of silicon oxide containing arsenic (As). In addition to silicon (Si), oxygen (O), and arsenic (As), the selector material layer 53 may further contain at least one element selected from titanium (Ti), nitrogen (N), and carbon (C).

[0037] For example, the selector material layer 53 is formed from silicon oxide containing As, silicon oxide containing As and Ti, silicon oxide containing As and N, silicon oxide containing As and C, silicon oxide containing As, Ti and N, and silicon oxide containing As, Ti, N and C.

[0038] Figure 5 is a schematic diagram showing the current-voltage characteristics of the selector 50.

[0039] The selector 50 has the characteristic of transitioning from the off state to the on state when the voltage applied between the lower electrode 51 and the upper electrode 52 is equal to or greater than the threshold voltage Vth, and transitioning from the on state to the off state when the voltage applied between the lower electrode 51 and the upper electrode 52 is equal to or less than the hold voltage Vhold.

[0040] Therefore, when a voltage is applied between the lower wiring 10 and the upper wiring 20, and the voltage applied to the selector 50 becomes greater than or equal to the threshold voltage Vth, the selector 50 transitions from the off state to the on state, making it possible to write to or read from the magnetoresistive element 40 connected in series with the selector 50.

[0041] The electrode 61 is made of a conductive material and is provided between the magnetoresistive element 40 and the upper wiring 20, and functions as the upper electrode of the magnetoresistive element 40.

[0042] As described above, in this embodiment, the upper electrode 52 of the selector 50 includes a first layer portion 52a and a second layer portion 52b, with the first layer portion 52a provided between the selector material layer 53 and the second layer portion 52b. With this configuration, in this embodiment, it is possible to obtain a storage device including a selector 50 having excellent characteristics, as described below.

[0043] In this embodiment, the upper electrode 52 of the selector 50 includes a first layer portion 52a formed of a conductive material containing carbon (C). By providing the first layer portion 52a containing carbon adjacent to the selector material layer 53, it is possible to improve the characteristics of the selector 50.

[0044] Furthermore, by providing a second layer 52b on top of the first layer 52a, it is possible to prevent the diffusion of carbon contained in the first layer 52a to the upper layer. For example, the material used for the second layer 52b has properties such as a high melting point and excellent stability. Therefore, it is possible to effectively suppress the diffusion of carbon contained in the first layer 52a. In addition, the material used for the second layer 52b also has excellent thermal and electrical conductivity and is suitable as an electrode material.

[0045] Therefore, in this embodiment, by providing a first layer portion 52a on the selector material layer 53 and a second layer portion 52b on the first layer portion 52a, it is possible to obtain a selector 50 with excellent stability and characteristics.

[0046] In the embodiment described above, the upper electrode 52 of the selector 50 includes a third layer portion 52c in addition to the first layer portion 52a and the second layer portion 52b, but the third layer portion 52c does not need to be provided.

[0047] (Second embodiment) Next, a second embodiment will be described. The basic aspects are the same as in the first embodiment, and explanations of the matters described in the first embodiment will be omitted.

[0048] Figure 6 is a schematic perspective view showing the configuration of a storage device according to the second embodiment.

[0049] Similar to the first embodiment, this embodiment also provides a memory cell 30 including a magnetoresistive element 40 and a selector 50 between the lower wiring 10 and the upper wiring 20. However, in the first embodiment, the selector 50 was provided on the lower side of the magnetoresistive element 40, whereas in this embodiment, the selector 50 is provided on the upper side of the magnetoresistive element 40.

[0050] Figure 7 is a schematic cross-sectional view showing the configuration of the storage device according to this embodiment.

[0051] In this embodiment, the memory cell 30 includes a magnetoresistive element 40, a selector 50, and an electrode 62 provided between the magnetoresistive element 40 and the lower wiring 10.

[0052] The basic configuration of the magnetoresistive element 40 is the same as that of the magnetoresistive element 40 in the first embodiment, and it is possible to use a magnetoresistive element 40 as shown in Figure 3 or Figure 4.

[0053] The basic configuration of the selector 50 is the same as that of the selector 50 in the first embodiment. That is, the selector 50 includes a lower electrode 51, an upper electrode 52 provided on the upper side of the lower electrode 51, and a selector material layer 53 provided between the lower electrode 51 and the upper electrode 52, and these layers 51 to 53 are stacked in the Z direction.

[0054] The lower electrode 51 is made of a conductive material and is provided between the selector material layer 53 and the magnetoresistive element 40. The lower electrode 51 functions as both the lower electrode of the selector 50 and the upper electrode of the magnetoresistive element 40.

[0055] The lower electrode 51 includes a first layer portion 51a and a second layer portion 51b, and these layers 51a and 51b are stacked in the Z direction. Specifically, the first layer portion 51a is provided between the selector material layer 53 and the second layer portion 51b. For example, the first layer portion 51a can be made of the same conductive material as the first layer portion 52a of the upper electrode 52 in the first embodiment, and the second layer portion 51b can be made of the same conductive material as the second layer portion 52b of the upper electrode 52 in the first embodiment. However, in this embodiment, the materials of the first layer portion 51a and the second layer portion 51b of the lower electrode 51 are not particularly limited.

[0056] The upper electrode 52 is made of a conductive material and is provided between the selector material layer 53 and the upper wiring 20.

[0057] The upper electrode 52 includes a first layer portion 52a and a second layer portion 52b, and these layers 52a and 52b are stacked in the Z direction. Specifically, the first layer portion 52a is provided between the selector material layer 53 and the second layer portion 52b. The first layer portion 52a can be made of the same conductive material as the first layer portion 52a of the upper electrode 52 in the first embodiment, and the second layer portion 52b can be made of the same conductive material as the second layer portion 52b of the upper electrode 52 in the first embodiment.

[0058] The selector material layer 53 is provided between the lower electrode 51 and the upper electrode 52, and the same material as the selector material layer 53 in the first embodiment can be used for the selector material layer 53.

[0059] The electrode 62 is made of a conductive material and is provided between the magnetoresistive element 40 and the lower wiring 10, and functions as the lower electrode of the magnetoresistive element 40.

[0060] As described above, in this embodiment, as in the first embodiment, the upper electrode 52 of the selector 50 includes a first layer portion 52a and a second layer portion 52b formed of the same material as in the first embodiment, with the first layer portion 52a provided between the selector material layer 53 and the second layer portion 52b. Therefore, in this embodiment as well, as in the first embodiment, it is possible to prevent the diffusion of carbon contained in the first layer portion 52a to the upper layer, and it is possible to obtain a selector 50 with excellent stability and properties.

[0061] In the first and second embodiments described above, a magnetoresistive element was used as the variable resistance memory element, but other variable resistance memory elements may also be used.

[0062] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of symbols]

[0063] 10...Lower wiring 20...Upper wiring 30...Memory cell 40…Magnetoresistive element (variable resistance memory element) 41...Memory layer 42...Reference layer 43...Tunnel barrier layer 44... Shift-canceling layer 45... Intermediate layer 50... Selector (switching element) 51...Lower electrode 51a...First layer portion 51b...Second layer portion 52…Top electrode 52a...First layer 52b...Second layer 52c...Third layer 53…Selector material layer (switching material layer) 61, 62...electrode

Claims

1. Lower wiring extending in the first direction, An upper wiring extending in a second direction intersecting the first direction, A memory cell including variable resistance memory elements and switching elements is provided between the lower wiring and the upper wiring and stacked in a third direction intersecting the first direction and the second direction, A storage device comprising, The switching element includes a structure in which a lower electrode, an upper electrode, and a switching material layer provided between the lower electrode and the upper electrode are stacked in the third direction. The upper electrode includes a first layer portion and a second layer portion stacked in the third direction, and includes a structure in which the first layer portion is provided between the switching material layer and the second layer portion. The switching material layer is formed from a material containing silicon (Si), oxygen (O), and arsenic (As). The first layer portion is formed of a conductive material containing carbon (C), The second layer portion is formed of a conductive material containing at least one element selected from tantalum (Ta), titanium (Ti), tungsten (W), nickel (Ni), molybdenum (Mo), chromium (Cr), vanadium (V), zirconium (Zr), aluminum (Al), hafnium (Hf), indium (In), tin (Sn), ruthenium (Ru), zinc (Zn), and magnesium (Mg). A storage device characterized by the following features.

2. The switching element is provided on the lower side of the variable resistor memory element. The upper electrode is provided between the switching material layer and the variable resistance memory element. The storage device according to feature 1.

3. The switching element is provided on the upper side of the variable resistor memory element. The upper electrode is provided between the switching material layer and the upper wiring. The storage device according to feature 1.

4. The first layer portion is formed of a carbon (C) layer or a carbon nitride (CN) layer. The storage device according to feature 1.

5. The second layer portion further contains at least one element selected from nitrogen (N), silicon (Si), carbon (C), and oxygen (O). The storage device according to feature 1.

6. The second layer portion is formed of layers selected from Ta layer, TaN layer, Ti layer, TiN layer, TiC layer, W layer, WN layer, WSi layer, WSiN layer, Ni layer, Mo layer, Cr layer, V layer, CrN layer, ZrN layer, AlN layer, HfN layer, ITO (Indium Tin Oxide) layer, RuO layer, SnO layer, AlO layer, ZnO layer, and MgO layer. The storage device according to feature 1.

7. The switching material layer further contains at least one element selected from titanium (Ti), nitrogen (N), and carbon (C). The storage device according to feature 1.

8. The upper electrode further includes a third layer portion, The second layer portion is provided between the first layer portion and the third layer portion. The storage device according to feature 1.

9. The variable resistance memory element is a magnetoresistive element. The storage device according to feature 1.

10. The switching element has the characteristic of transitioning from an off state to an on state when the voltage applied between the lower electrode and the upper electrode exceeds a threshold voltage. The storage device according to feature 1.

11. When a voltage is applied between the lower and upper wiring, causing the switching element to turn on, it becomes possible to write to or read from the variable resistor memory element. The storage device according to claim 10.

Images