Selector device and semiconductor memory device

Abstract

The present application relates to a selector device and a semiconductor storage device. An embodiment provides a selector device with improved cycle characteristics. The selector device (1) of the embodiment is provided with: a first electrode (2); a second electrode (2); a selector layer (4) disposed between the first electrode (2) and the second electrode (3); and a laminated film (5) disposed between at least one of the first electrode (2) and the selector layer (4) and the second electrode (3) and the selector layer (4), the laminated film (5) having a first layer (6) containing at least one first element selected from the group consisting of carbon and metal and not containing nitrogen and a second layer (7) containing a nitride of the first element. The first layer (6) is disposed in contact with the selector layer (4).

Description

[0001] [Related Applications]

[0002] This application claims priority to Japanese Patent Application No. 2021-044885 (filed on March 18, 2021). This application incorporates the entire contents of that basic application by reference. Technical Field

[0003] Embodiments of the present invention relate to a selector device and a semiconductor memory device. Background Technology

[0004] When switching the current to / from resistive random access memory (ReRAM), phase change memory (PCM), and magnetoresistive random access memory (MRAM) on / off, a selector device is used. This selector device has a selector layer that generates a phase change between an insulator and a conductor based on the applied voltage. For this type of selector device, the industry is seeking to improve the cycling characteristics of its selector layer. Summary of the Invention

[0005] The problem to be solved by the present invention is to provide a selector device that can improve the cycle characteristics and a resistive switching memory device using the selector device.

[0006] The selector device of the embodiment includes: a first electrode; a second electrode; a selector layer disposed between the first electrode and the second electrode; and a laminated film disposed between at least one of the first electrode and the selector layer and between the second electrode and the selector layer, having a first layer containing at least one first element selected from the group consisting of carbon and metals and free of nitrogen, and a second layer containing a nitride of the first element; and the first layer is disposed in contact with the selector layer. Attached Figure Description

[0007] Figure 1 This is a cross-sectional view showing the configuration of the first example of the selector device in the implementation method.

[0008] Figure 2 This is a cross-sectional view showing the configuration of the second example of the selector device in the implementation method.

[0009] Figure 3 This is a cross-sectional view showing the configuration of the third example of the selector device in the implementation method.

[0010] Figure 4This is a cross-sectional view showing the configuration of a semiconductor memory device using a selector device in an embodiment.

[0011] Figure 5 It means Figure 4 A perspective view of the semiconductor memory device shown.

[0012] Figure 6 (a)~(c) represent the energy changes (E) when the constituent atoms of the selector layer exist as isolated atoms and when the constituent atoms of the selector layer exist in the carbon layer and the carbon nitride layer. int (The image is shown.)

[0013] Figure 7 It is a graph showing the trend of potential energy at the interface between the carbon layer and the selector layer as temperature and time change.

[0014] Figure 8 This is a graph showing the trend of potential energy change at the interface between the carbon nitride layer and the selector layer as temperature and time change. Detailed Implementation

[0015] Hereinafter, the selector device and semiconductor memory device according to embodiments will be described with reference to the accompanying drawings. In each embodiment, substantially identical components are labeled with the same symbols, and sometimes descriptions of these components are omitted. The accompanying drawings are schematic diagrams, and the relationship between thickness and planar dimensions, the thickness ratios of various parts, etc., may sometimes differ from the actual object.

[0016] Figure 1 This is a cross-sectional view showing the configuration of the selector device 1 in the embodiment. Figure 1 The selector device 1 shown includes a first electrode 2, a second electrode 3, a selector layer 4 disposed between the first electrode 2 and the second electrode 3, and a laminated film 5. The selector layer 4 has a switching function, capable of switching the current flowing between the first electrode 2 and the second electrode 3 on / off. The selector layer 4 has the following electrical characteristics: when a voltage less than a threshold voltage (Vth) is applied, it is in an off state with high resistance; and if a voltage greater than the threshold voltage (Vth) is applied from this state, it will abruptly switch from the off state with high resistance to the on state with low resistance.

[0017] When the voltage applied to the selector layer 4 is less than the threshold voltage (Vth), the selector layer 4 functions as an insulator, blocking the current flowing to the functional layers such as the resistive switching layer in the selector device 1, thus turning the functional layers off. When the voltage applied to the selector layer 4 is above the threshold voltage (Vth), the resistance of the selector layer 4 decreases sharply, and it functions as a conductor, allowing current to flow through the selector layer 4 to the functional layers. The selector device 1 with the selector layer 4 is suitable for controlling the on / off state of the current flowing to the functional layers in, for example, various electronic devices.

[0018] exist Figure 1 In the selector device 1 shown, the laminated film 5 has a first layer 6 and a second layer 7. The first layer 6 is arranged in connection with the selector layer 4. Figure 1 In this configuration, the second layer 7 is arranged in connection with the first electrode 2. For example... Figure 2 As shown, the laminated film 5 may also have a third layer 8. Figure 2 In this configuration, the third layer 8 is disposed in connection with the first electrode 2, and the second layer 7 is disposed between the first layer 6 and the third layer 8. The first layer 6 and the third layer 8 contain at least one first element selected from the group consisting of carbon and metals, and do not contain nitrogen. The second layer 7 contains a nitride of at least one first element selected from the group consisting of carbon and metals. Their composition will be described below.

[0019] Figure 1 and Figure 2 The diagram shows a configuration where the laminated film 5 is disposed between the first electrode 2 and the selector layer 4, but the laminated film 5 can also be disposed between the second electrode 3 and the selector layer 4. The laminated film 5 only needs to be disposed between at least one of the first electrode 2 and the selector layer 4 and the second electrode 3 and the selector layer 4. Furthermore, when the laminated film 5 is disposed only between the first electrode 2 and the selector layer 4, as shown... Figure 3 As shown, a fourth layer 9, containing at least one first element selected from the group consisting of carbon and metals and free of nitrogen, can be disposed between the second electrode 3 and the selector layer 4. The specific structure and function of the first layer 6, the second layer 7, the third layer 8, and the fourth layer 9 will be described in detail below.

[0020] For example, such as Figure 4 and Figure 5 As shown, Figures 1 to 3 The selector device 1 shown is combined with the resistive switching device 10 and applied to the resistive switching semiconductor memory device 11. Figure 4 and Figure 5 The resistive switching semiconductor memory device 11 shown includes a selector device 1 and a resistive switching device 10 disposed on the selector device 1. The resistive switching device 10 includes a third electrode 12, a resistive switching layer 13 that functions as a non-volatile memory layer, and a fourth electrode 14. That is, the resistive switching semiconductor memory device 11 includes a first electrode 2, a laminated film 5, a selector layer 4, a second electrode 3, a third electrode 12, a resistive switching layer 13, and a fourth electrode 14. Although Figure 4 The illustration is omitted, but a fourth layer 9 can also be configured between the selector layer 4 and the second electrode 3.

[0021] The second electrode 3 and the third electrode 12 can also be omitted. In this case, the laminated film 5, the selector layer 4, and the resistive switching layer 13 are arranged in a laminated state between the first electrode 2 and the fourth electrode 14. Alternatively, the laminated film 5, the selector layer 4, the fourth layer 9, and the resistive switching layer 13 can be arranged in a laminated state between the first electrode 2 and the fourth electrode 14. In this case, the selector layer 4 and the resistive switching layer 13 can be directly laminated, or other layers such as intermediate layers or additional layers can be interposed between them. The selector layer 4 and the resistive switching layer 13 can also be laminated with the fourth layer 9 in between. The resistive switching layer 13 only needs to be directly laminated with the selector layer 4 or laminated with other layers in between, and be electrically connected to the selector layer 4. Furthermore, one of the second electrode 3 and the third electrode 12 can be omitted.

[0022] The materials used to construct the first electrode 2, which is connected to the selector layer 4, and the second electrode 3, which is directly or indirectly connected to the selector layer 4, are not particularly limited. For example, W film, TiN film, W / TiN laminate, TiN / Ti laminate, C / TiN / Ti laminate, and C / W / TiN laminate can be used for the first and second electrodes 2 and 3. Alternatively, metal electrodes used as electrodes in various semiconductor devices, including W alloys, Cu, Cu alloys, Al, and Al alloys, can be applied to the first and second electrodes 2 and 3.

[0023] The resistive switching layer 13 uses the memory layer in a resistive random access memory (RRAM). Resistive random access memory (ReRAM), phase change memory (PCM), and magnetoresistive random access memory (MRAM) are known examples of RRAM. The memory layer of these various RRAMs is used as the resistive switching layer 5. The resistive switching layer 5 is not limited to a single-layer structure and can be a multilayer film necessary for the function of each memory. For example, in a phase change memory, the phase change material used as the resistive switching layer includes at least one element selected from the group consisting of germanium (Ge), tin (Sn), lead (Pb), silicon (Si), and carbon (C), and at least one element selected from the group consisting of antimony (Sb), bismuth (Bi), and arsenic (As), and also includes at least one element selected from the group consisting of tellurium (Te), selenium (Se), and sulfur (S). Specific examples of such phase change materials include GeSbTe, GeTe, CrGeTe, CuGeTe, SbTe, ScSbTe, AgInSbTe, etc.

[0024] The materials used to construct the third and fourth electrodes 12 and 14, which are directly or indirectly connected to the resistive switching layer 13, are not particularly limited. They can be made of materials such as W film, TiN film, W / TiN laminated film, TiN / Ti laminated film, C / TiN / Ti laminated film, C / W / TiN laminated film, W alloy film, Cu film, Cu alloy film, Al film, Al alloy film, etc., just like the first and second electrodes 2 and 3.

[0025] like Figure 4 and Figure 5 As shown, the first electrode 2 of the resistive switching semiconductor memory device 11 is electrically connected to the word line WL, and the fourth electrode 14 is electrically connected to the bit line BL. The resistive switching semiconductor memory device 11 is disposed at the intersection of the word line WL and the bit line BL, which are arranged in an interleaved manner, and functions as a memory cell. Figure 4 and Figure 5 The figure only shows one resistive switching semiconductor memory device 11, but in reality, resistive switching semiconductor memory devices 11 as memory cells are arranged at each intersection of multiple word lines W and bit lines BL, thus forming a cross-point semiconductor memory device.

[0026] The selector layer 4 of the selector device 1 uses a material (selector material) having the electrical characteristics described above. Specifically, it is in an off state with high resistance when the applied voltage is less than a threshold voltage (Vth), and it rapidly transitions from an off state with high resistance to an on state with low resistance when the voltage is above the threshold voltage (Vth). The specific selector material is not particularly limited; for example, a material containing at least one chalcogenide element (the third element) selected from the group consisting of tellurium (Te), selenium (Se), and sulfur (S) can be used. This selector material may contain compounds containing chalcogenides, i.e., sulfides.

[0027] Materials containing chalcogenides may include materials containing at least one second element selected from the group consisting of germanium (Ge), gallium (Ga), tin (Sn), silicon (Si), indium (In), aluminum (Al), carbon (C), boron (B), antimony (Sb), arsenic (Ab), and phosphorus (P), and materials containing at least one third element selected from the group consisting of tellurium (Te), selenium (Se), and sulfur (S). Materials containing chalcogenides may also include at least one fourth element selected from the group consisting of silver (Ag), bismuth (Bi), scandium (Sc), copper (Cu), chromium (Cr), titanium (Ti), zirconium (Zr), and hafnium (Hf), or at least one fifth element selected from the group consisting of oxygen (O) and nitrogen (N). Specific examples of such selector materials include GeAsSe, GeAsSeSi, GeAsSeSiIn, GeSbTe, GeTe, SbTe, SiTe, and AlTeN.

[0028] exist Figure 4In the resistive switching semiconductor memory device 11 shown, the selector layer (switch layer) 4 is electrically connected to the resistive switching layer 13 and has the function of switching the current flowing to the resistive switching layer 13 on / off. When the voltage applied to the selector layer 4 is lower than the threshold (Vth), the selector layer 4 functions as an insulator, blocking the current flowing to the resistive switching layer 6, making the resistive switching layer 6 in an off state. When the voltage applied to the selector layer 4 exceeds the threshold (Vth), the resistance value of the selector layer 4 decreases sharply and it functions as a conductor, and the current flows through the selector layer 4 to the resistive switching layer 6, thereby enabling the write or read operation of the resistive switching layer 6. The selector device 1 has the function of switching the resistive switching layer 13, which serves as the memory layer, on / off in the resistive switching semiconductor memory device (resistive switching memory) 11.

[0029] As described above, the selector device 1 of the embodiment includes a selector layer 4 and a laminated film 5. The laminated film 5 has a first layer 6 disposed in contact with the selector layer 4, a second layer 7 disposed in contact with the first layer 6, and a third layer 8 disposed in contact with the second layer 7. Here, it has a configuration in which a selector layer containing Ge, As, Se, Si, In, etc., is sandwiched between a carbon layer (C layer) and a carbon nitride layer (CN layer). In this case, the C layer is disposed on the side where the resistive switching layer is located to improve the thermal conductivity between it and the resistive switching layer. On the other hand, the CN layer with low thermal conductivity is disposed on the opposite side of the resistive switching layer (the side of the first electrode 2) to thermally seal the selector layer 4. When this C / GeAsSeSiIn / CN laminated structure is applied, it is known that during use, the applied heat will cause atoms such as Ge, As, and Se in the selector material to migrate into the CN layer. When the atoms constituting this selector material migrate and diffuse, the cycling characteristics of the selector device 1 will deteriorate. Furthermore, no migration of Ge, As, Se atoms was observed between the C layer and the GeAsSeSiIn layer.

[0030] The difference between the C layer and the CN layer is considered to be based on their difference in cohesive energy. Cohesive energy, as referred to here, is the energy required for, for example, layered atoms to disperse. For instance, the cohesive energy of an amorphous C layer is 6.76 eV / atom, while that of an amorphous CN layer is 6.19 eV / atom. Lower cohesive energy means easier decomposition. That is, the CN layer, with its lower cohesive energy and easier decomposition, is more prone to incorporation of impurity elements. On the other hand, the C layer, with its higher cohesive energy and less decomposition, is less prone to incorporation of impurity elements. Therefore, atoms such as Ge, As, and Se easily migrate to the CN layer, and these atoms tend to exist stably within it.

[0031] Further investigation was conducted on the stability of Ge, As, and Se atoms in the C and CN layers. The stability of Ge, As, and Se atoms as isolated atoms was compared with that of Ge, As, and Se atoms in the C and CN layers. 73 N 27 Energy changes (E) in the layer int ) shown in Figure 6 . Figure 6 The energy changes of Ge (Figure (a)), As (Figure (b)), and Se (Figure (c)) are shown. Figure 6 In the diagram, the arrows represent the average energy changes of each atom in the C and CN layers. For example... Figure 6 As shown in (a), Ge is stable at ~0.6 eV in the CN layer. Figure 6 As shown in (b), As is stable at ~0.2 eV in the CN layer. Figure 6 As shown in (c), Se is stable at ~0.1 eV in the CN layer. Thus, Ge, As, and Se atoms are more stable in the CN layer than in the C layer. This also indicates that Ge, As, and Se atoms easily migrate to the CN layer and remain stable there.

[0032] and then, Figure 7 This indicates the trend of potential energy change at the interface between the C layer and the GeAsSeSiIn layer as temperature and time change. Figure 8 CN(C) represents 80 N 20 The trend of potential energy change at the interface between the GeAsSeSiIn layer and the GeAsSeSiIn layer under varying temperatures and times. Figure 7 and Figure 8 The comparison shows that the potential energy change at the interface with the CN layer is larger, making mixing (reaction) more likely. Furthermore, it can be seen that at the interface with the CN layer, a potential energy change occurs above 3000 K, while at the interface with the C layer, a potential energy change occurs above 4000 K. Therefore, it is known that mixing (reaction) easily occurs in the CN layer at lower temperatures. For example, when a reset current flows through the resistive switching layer 13 containing the phase change material, the temperature of the selector layer 4 reaches approximately 3400 K. Therefore, at the GeAsSeSiIn / CN interface, when a reset current flows through the resistive switching layer 13, Ge, As, and Se atoms easily migrate into the CN layer.

[0033] The relationship between the carbon (C) layer and the carbon nitride (CN) layer is not unique to carbon; even metals such as tungsten (W), titanium (Ti), molybdenum (Mo), and tantalum (Ta) exhibit the same tendency. That is, in single-component carbon or metal layers, the constituent elements of selector layer 4 (Ge, As, Se, etc.) are less likely to migrate through the interfaces of these single-component layers. In contrast, in carbon or metal nitride layers, the constituent elements of selector layer 4 easily migrate through the interfaces of these nitride layers, and the constituent elements of selector layer 4 tend to be stably present within the nitride layer. Therefore, when the nitride layer is configured to be directly connected to selector layer 4, the cycling performance is easily degraded due to the migration of the constituent elements of selector layer 4. The constituent elements of selector layer 4 are not limited to Ge, As, and Se; the constituent elements of other selector materials also exhibit the same tendency.

[0034] Therefore, in the laminated film 5 of the selector device 1 in this embodiment, the first layer 6, which is disposed in contact with the selector layer 4, is a layer containing at least one first element selected from the group consisting of carbon and metals and is free of nitrogen. Examples of suitable first elements for the first layer 6 include at least one selected from the group consisting of carbon (C), tungsten (W), titanium (Ti), molybdenum (Mo), and tantalum (Ta). As described above, the first layer 6, containing these elements and free of nitrogen (N), makes it difficult for the constituent elements of the selector layer 4 to migrate, thus suppressing the degradation of cycling characteristics caused by the migration of the constituent elements of the selector layer 4. Furthermore, the first layer 6 also exhibits an effect of suppressing drift.

[0035] The laminated film 5 of the selector device 1 has a second layer 7 containing a nitride of the first element. Although the first layer 6 can suppress the migration of constituent elements of the selector layer 4, the thermal conductivity of carbon or the metal alone is greater than that of the nitride, so the effect of heat containment in the selector layer 4 cannot be achieved by the carbon layer or the metal layer alone. For example, the thermal conductivity of carbon is 1.30 W / m·K, while that of carbon nitride is 1.08 W / m·K. Therefore, by arranging the second layer 7 containing a nitride of the first element on the side of the first layer 6 opposite to the side in contact with the selector layer 4, the migration of constituent elements of the selector layer 4 can be suppressed, and the effect of heat containment in the selector layer 4 can also be achieved. The nitride contained in the second layer 7 is not limited to CN; the same effect can be achieved by using WN, TiN, MoN, TaN, etc.

[0036] The laminated film 5 of the selector device 1 preferably further comprises a third layer 8, which is disposed on the side opposite to the surface of the second layer 7 that is in contact with the first layer 6. Like the first layer 6, the third layer 8 contains the first element but is nitrogen-free. By applying such a third layer 8, the migration of constituent elements (e.g., W or Ti) of the first electrode 2 can be suppressed, as well as drift. Here, "nitrogen-free" in the first layer 6 or the third layer 8 means that it does not contain nitrogen to the extent that it functions as a nitride, but allows for the inclusion of nitrogen to the extent that it is an impurity.

[0037] In the selector device 1 of the embodiment, the laminated film 5 can be disposed between the selector layer 4 and the second electrode 3, similar to how it is disposed between the first electrode 2 and the selector layer 4, but preferably as described above. Figure 3 As shown, a fourth layer 9 containing the first element and without nitrogen is configured. The thermal conductivity of the fourth layer 9 containing the first element and without nitrogen is greater than that of nitrides. By configuring such a fourth layer 9 on the resistive switching layer 13 side of the selector layer 4, the thermal conductivity between the selector layer 4 and the resistive switching layer 13 can be improved, and drift can be further suppressed.

[0038] In the selector device 1 of the embodiment, the overall thickness of the laminated film 5 is preferably 10 nm or more and 11 nm or less. The film thicknesses of the first layer 6 and the third layer 8 are preferably more than 0 nm and less than 1 nm. The film thickness of the second layer 7 is preferably 8 nm or more and 10 nm or less. Furthermore, when the fourth layer 9 is applied, its film thickness is preferably 15 nm or more and 16 nm or less. The film thickness of the selector layer 4 can be adjusted appropriately.

[0039] In the selector device 1 of this embodiment, a selector layer 4 and a laminated film 5 having a first layer 6 and a second layer 7 are disposed between the first electrode 2 and the second electrode 3. The first layer 6 is a layer containing at least one first element selected from the group consisting of carbon and metals and free of nitrogen, and the second layer 7 is a layer containing a nitride of the first element. Furthermore, the first layer 6 of the laminated film 5 is disposed in contact with the selector layer 4. According to this selector device 1, the migration of elements constituting the selector layer 4 can be suppressed by the first layer 6, while the thermal sealing effect of the selector layer 4 can be improved by the second layer 6. Therefore, the characteristics of the selector device 1, and even the characteristics and reliability of the semiconductor memory device 11 using the selector device 1, can be improved.

[0040] Furthermore, although several embodiments of the present invention have been described, these embodiments are provided as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in many other forms and can be omitted, substituted, or modified in various ways 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 scope of the invention as described in the claims and its equivalents.

[0041] [Symbol Explanation]

[0042] 1: Selector device

[0043] 2: Electrode 1

[0044] 3: Second electrode

[0045] 4: Selector layer

[0046] 5: Laminated film

[0047] 6: Level 1

[0048] 7: Level 2

[0049] 8: Level 3

[0050] 9: 4th floor

[0051] 10: Resistance converter

[0052] 11: Semiconductor memory devices

[0053] 13: Resistance switching layer.

Claims

1. A selector device comprising: Electrode 1; Second electrode; A selector layer is disposed between the first electrode and the second electrode; and A laminated film, disposed between the first electrode and the selector layer and between the second electrode and the selector layer, having at least one of the following: a first layer containing at least one first element selected from the group consisting of carbon and metals and containing no nitrogen, and a second layer containing a nitride of the first element; The first layer is configured to be connected to the selector layer; and The first layer contains carbon without nitrides, and the second layer contains carbon nitrides.

2. The selector device according to claim 1, wherein The laminated membrane has a third layer containing the first element but free of nitrogen. The third layer is configured to be connected to at least one of the first electrode and the second electrode, and the second layer is disposed between the first layer and the third layer.

3. The selector device according to claim 2, wherein The laminated film is disposed only between the first electrode and the selector layer, and between the second electrode and the selector layer. Furthermore, in the other of the two electrodes, which are not configured with the stacked film, a fourth layer containing the first element and not containing nitrogen is provided.

4. The selector device according to claim 3, wherein The third layer contains carbon without nitrogen oxides.

5. The selector device according to claim 1 or 2, wherein The selector layer comprises at least one second element selected from the group consisting of germanium, gallium, tin, silicon, indium, aluminum, carbon, boron, antimony, arsenic and phosphorus, and at least one third element selected from the group consisting of tellurium, selenium and sulfur.

6. The selector device according to claim 4, wherein The selector layer also includes at least one fourth element selected from the group consisting of silver, bismuth, scandium, copper, chromium, titanium, zirconium, and hafnium.

7. The selector device according to claim 4, wherein The selector layer also includes at least one fifth element selected from the group consisting of oxygen and nitrogen.

8. The selector device according to claim 5, wherein The selector layer contains germanium, silicon, indium, arsenic, and selenium.

9. A semiconductor memory device comprising: The selector device according to any one of claims 1 to 7; and A resistive switching layer is electrically connected to the selector layer of the selector device and is stacked with the selector layer.

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