Selector device and semiconductor memory device

Abstract

Embodiments of the present application provide a selector device capable of improving the heat confinement effect of a selector layer to improve characteristics. A selector device (1) of an embodiment includes a first electrode (2), a second electrode (3), and a selector layer (4) disposed between the first electrode (2) and the second electrode (2). At least one of the first electrode (2) and the second electrode (3) includes a laminated film (11) having a first layer (9) including a first material having a first Debye temperature (T1) and a second layer (10) disposed in contact with the first layer (9) and including a second material having a second Debye temperature (T2) lower than the first Debye temperature (T1). The ratio (T1 / T2) of the first Debye temperature (T1) to the second Debye temperature (T2) is 5 or more.

Description

[0001] Related applications

[0002] This application enjoys priority to Japanese Patent Application No. 2021-046830 (filed on March 22, 2021). This application incorporates the entire contents of the basic application by reference to that basic application. Technical Field

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

[0004] For switching current to / from variable resistive memory devices such as Resistive Random Access Memory (ReRAM), Phase Change Memory (PCM), and Magnetoresistive Random Access Memory (MRAM), a selector device with a selector layer that undergoes a phase change between an insulator and a conductor due to the applied voltage is used. In such a selector device, it is necessary to improve the thermal confinement effect of the selector layer to enhance its characteristics. Summary of the Invention

[0005] The problem to be solved by the present invention is to provide a selector device and a semiconductor memory device that can improve the characteristics by enhancing the thermal confinement effect of the selector layer.

[0006] The selector device of one embodiment includes a first electrode, a second electrode, and a selector layer disposed between the first electrode and the second electrode. At least one of the first electrode and the second electrode has a laminated film. The laminated film has a first layer and a second layer. The first layer contains a first material having a first Debye temperature (T1), and the second layer is disposed in contact with the first layer and contains a second material having a second Debye temperature (T2) lower than the first Debye temperature. In a first embodiment of the selector device, the ratio of the first Debye temperature (T1) to the second Debye temperature (T2) (T1 / T2) is 5 or more. In a second embodiment of the selector device, the first layer and the second layer of the laminated film are stacked 4 times or more. Attached Figure Description

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

[0008] Figure 2 This is a cross-sectional view showing the configuration of a variable resistive semiconductor memory device using a selector device according to an embodiment.

[0009] Figure 3 It means Figure 1 A cross-sectional view of the configuration of a first example of the electrodes used in the selector device shown.

[0010] Figure 4 It means Figure 1 A cross-sectional view of the configuration of a second example of electrodes used in the selector device shown.

[0011] Figure 5 It is a table representing the Debye temperature of various materials.

[0012] Figure 6 This is a table representing the Debye temperature ratio (T1 / T2) between the first material and the second material.

[0013] Figure 7 This is a graph showing the relationship between the Debye temperature ratio and the total thermal resistance in a laminated film of material 1 and material 2.

[0014] Figure 8 This is a graph showing the relationship between the Debye temperature ratio and the total thermal resistance in a laminated film of material 1 and material 2.

[0015] Figure 9 This is a graph showing the relationship between the Debye temperature ratio and the total thermal resistance in a laminated film of material 1 and material 2.

[0016] Figure 10 This is a table representing the Debye temperature ratio (T1 / T2) between the first material and the second material.

[0017] Figure 11 This is a graph showing the relationship between the number of repeated layers in a laminated film of material 1 and material 2 and the total thermal resistance.

[0018] Figure 12 This is a graph showing the relationship between the number of repeated layers in a laminated film of material 1 and material 2 and the total thermal resistance.

[0019] Figure 13 This is a graph showing the relationship between the number of repeated layers in a laminated film of material 1 and material 2 and the total thermal resistance.

[0020] Explanation of symbols

[0021] 1…selector device, 2…first electrode, 3…second electrode, 4…selector layer, 5…third electrode, 6…resistivity variation layer, 7…fourth electrode, 8…variable resistivity semiconductor memory device, 9…first layer, 10…second layer, 11…layer film. Detailed Implementation

[0022] Hereinafter, the selector device and semiconductor memory device of the embodiments will be described with reference to the accompanying drawings. In each embodiment, substantially the same component is labeled with the same symbol, and sometimes part of the description is omitted. The accompanying drawings are schematic diagrams, and the relationship between thickness and planar dimensions, the thickness ratio of each part, etc., may sometimes differ from reality.

[0023] Figure 1 This is a cross-sectional view showing the configuration of the selector device 1 in the implementation method. Figure 1 The selector device 1 shown includes a first electrode 2, a second electrode 3, and a selector layer 4 disposed between the first electrode 2 and the second electrode 3. The selector layer 4 has the function 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 below a threshold voltage (Vth) is applied, it becomes an off state with high resistance; when a voltage above the threshold voltage (Vth) is applied from this state, it abruptly changes from the off state with high resistance to an on state with low resistance.

[0024] When the voltage applied to the selector layer 4 is less than the threshold value (Vth), the selector layer 4 functions as an insulator, blocking the current flowing in the functional layer, such as the resistance variation layer attached to the selector layer 4, thus setting the functional layer to an off state. If the voltage applied to the selector layer 4 is greater than or equal to the threshold value (Vth), the resistance value of the selector layer 4 decreases sharply, and it functions as a conductor, allowing current to flow through the functional layer. The selector device 1 with the selector layer 4 is used, for example, in various electronic devices to control the on / off state of the current to the functional layer.

[0025] Figure 1 The selector device 1 shown is applied, for example, to a device such as... Figure 2 The variable resistive semiconductor memory device 8 shown includes a first electrode 2, a second electrode 3, a selector layer 4, a third electrode 5, a resistance-changing layer 6 functioning as a non-volatile memory layer, and a fourth electrode 7. The third electrode 5 and the fourth electrode 7 may also be omitted. In this case, a laminated film of the selector layer 4 and the resistance-changing layer 6 is used, and the first electrode 2 and the second electrode 3 function as a pair of electrodes relative to the laminated film of the selector layer 4 and the resistance-changing layer 6. In the above-described laminated film, the selector layer 4 and the resistance-changing layer 6 can be a directly laminated structure, or a structure with other layers such as intermediate layers or additional layers sandwiched between them. The resistance-changing layer 6 only needs to be directly or indirectly laminated with the selector layer 4 and electrically connected to the selector layer 4.

[0026] like Figure 2As shown, the first electrode 2 of the variable resistive semiconductor memory device 8 is electrically connected to the word line WL, and the fourth electrode 7 is electrically connected to the bit line BL. The variable resistive semiconductor memory device 8 is positioned at the intersection of the word line WL and the bit line BL, which are arranged in an alternating manner, and functions as a memory cell of the semiconductor memory device. Figure 3 The figure only shows one variable resistive memory device 8, but in reality, variable resistive semiconductor memory devices 8 are arranged as memory cells at the intersections of most bit lines BL and word lines W to form a cross-point type semiconductor memory device.

[0027] The selector layer 4 of the selector device 1 uses a material (selector material) having the following electrical characteristics: it is in an off state with high resistance when the applied voltage is below a threshold voltage (Vth) as described above, and it rapidly changes from an off state with high resistance to an on state with low resistance when the voltage is above the threshold voltage (Vth). There are no particular limitations on the specific selector material. Examples of selector materials include materials containing at least one chalcogenide selected from the group consisting of tellurium (Te), selenium (Se), and sulfur (S). Such selector materials may also contain compounds containing chalcogenides, i.e., chalcogenides.

[0028] The aforementioned materials containing chalcogenides may also contain at least one element selected from the group consisting of aluminum (Al), gallium (Ga), indium (In), silicon (Si), germanium (Ge), tin (Sn), arsenic (As), phosphorus (P), antimony (Sb), and bismuth (Bi). Furthermore, materials containing chalcogenides may also contain at least one element selected from the group consisting of nitrogen (N), oxygen (O), carbon (C), and boron (B). Examples of such selector materials include GeSbTe, GeTe, SbTe, SiTe, AlTeN, and GeAsSe. However, the selector material is not limited to materials containing chalcogenides and may also be materials that do not contain chalcogenides. Selector layer 4 may also have an amorphous structure.

[0029] For the resistance-changing layer 6, a memory layer from a variable-resistivity memory is used. Known variable-resistivity memories include Resistive Random Access Memory (ReRAM), Phase Change Memory (PCM), and Magnetoresistive Random Access Memory (MRAM). The memory layers of these various variable-resistivity memories are used as the resistance-changing layer 6. The resistance-changing layer 6 is not limited to a single-layer structure; it can also be a multi-layer film necessary to function each memory. The selector device 1 is not limited to the variable-resistivity semiconductor memory device 8 and can be used as a selector in various electronic devices.

[0030] exist Figure 2 In the variable resistive memory device 8 shown, the selector layer (switch layer) 4 is electrically connected to the resistance changing layer 6 and has the function of switching the current to and from the resistance changing layer 6. When the voltage applied to the selector layer 4 is lower than a threshold (Vth), the selector layer 4 functions as an insulator, blocking the current flowing in the resistance changing layer 6 and setting the resistance changing layer 6 to an off state. If 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, allowing current to flow through the resistance changing layer 6, thus enabling write or read operations on the resistance changing layer 6. The selector device 1 in the variable resistive memory device 8 has the function of switching the resistance changing layer 6, which serves as the memory layer, on and off.

[0031] In the selector device 1 described above, the first electrode 2 and the second electrode 3 are as follows: Figure 3 As shown, a laminated film 11 is formed by stacking a first layer 9 containing a first material and a second layer 10 containing a second material in contact. The first material contained in the first layer 9 has a first Debye temperature (T1). The second material contained in the second layer 10 has a second Debye temperature (T2) that is lower than the first Debye temperature (T1). The laminated film 11 is not limited to... Figure 3 As shown, the structure of layer 1 (9) and layer 2 (10) each stacked one layer can also be, for example, as shown in the diagram. Figure 4 As shown, it has a structure formed by repeatedly stacking a laminated film 11 having a first layer 9 and a second layer 10. Figure 4 This indicates a state in which a second laminated film 11-2 having a first laminated film 11-1 having a first laminated film 9 and a second laminated film 10 is laminated on top of the first laminated film 11-1 having a first laminated film 9 and a second laminated film 10, and such a laminated film 11 is laminated n times (the state from the first laminated film 11-1 to the nth laminated film 11-n). Figure 4The number of laminations in the laminated film 11 shown is the number of repetitions n of the first layer 9 and the second layer 10.

[0032] The laminated film 11 is not limited to the laminated structure in which the second layer 10 is disposed on the first layer 9 as shown in Figure 3 . Figure 1 It represents a structure in which the first layer 9, the second layer 10, the first layer 9, the second layer 10, the selector layer 4, the first layer 9, the second layer 10, the first layer 9, and the second layer 10 are laminated in sequence. However, it is not limited to this, and it may also be a structure in which the first layer 9, the second layer 10, the first layer 9, the second layer 10, the selector layer 4, the second layer 10, the first layer 9, the second layer 10, and the first layer 9 are laminated in sequence, a structure in which the second layer 10, the first layer 9, the second layer 10, the first layer 9, the selector layer 4, the first layer 9, the second layer 10, the first layer 9, and the second layer 10 are laminated in sequence, or a structure in which the second layer 10, the first layer 9, the second layer 10, the first layer 9, the selector layer 4, the second layer 10, the first layer 9, the second layer 10, and the first layer 9 are laminated in sequence. The layer in contact with the selector layer 4 can be either the first layer 9 or the second layer 10. The same applies to the case where the number of laminations of the laminated film 11 shown in Figure 4 is set to n.

[0033] The laminated film 11 having the first layer 9 and the second layer 10 is applied to at least one of the first electrode 2 and the second electrode 3. For example, an electrode layer having the laminated film 11 may be applied to the first electrode 2, and an electrode layer having a single-layer structure may be applied to the second electrode 3. Alternatively, the opposite structure may also be applied. As the electrode layer having a single-layer structure, a carbon layer such as a diamond-like carbon layer, a graphene layer, a carbon nanotube layer, or a fullerene layer, a metal layer such as a tungsten (W) layer, a copper (Cu) layer, an aluminum layer (Al), or an alloy layer containing at least one of these elements, or a compound layer such as a titanium nitride (TiN) layer or a titanium boride (TiB) layer is applied. However, since the electrode layer having the laminated film 11 has excellent thermal confinement effects as described below, it is preferably applied to both the first electrode 2 and the second electrode 3.

[0034] In the case where the laminated film 11 having the first layer 9 containing the first material having the first Debye temperature (T1) and the second layer 10 containing the second material having the second Debye temperature (T2: T2 < T1) lower than the first Debye temperature (T1) is applied to the first electrode 2 and the second electrode 3, an interfacial thermal resistance Rinterface is generated at the interface (contact surface) between the first layer 9 and the second layer 10 having different Debye temperatures, and thus a greater thermal resistance can be expected.

[0035] When the thermal resistance of the first layer 9 is set to R1, the thermal resistance of the second layer 10 is set to R2, and the thermal resistance at the interface between the first layer 9 and the second layer 10 is set to Rinterface, the total thermal resistance (Rtotal) of the laminated film 11 formed by stacking one layer of the first layer 9 and one layer of the second layer 10 is expressed by the following formula (1).

[0036] Rtotal=R1+R2+Rinterface (1)

[0037] In addition, the total thermal resistance Rtotal of the laminated film 11 formed by repeatedly stacking the first layer 9 and the second layer 10 n times is expressed by the following formula (2).

[0038] Rtotal=R1×n+R2×n+Rinterface×(2n-1) (2)

[0039] As shown in equation (1) or (2) above, the magnitude and number of interface thermal resistances (Rinterface) of the total thermal resistance (Rtotal) of the laminated film 11 are greatly helpful. The magnitude of the interface thermal resistance (Rinterface) is considered to be derived from the ratio (T1 / T2) of the first Debye temperature (T1) to the second Debye temperature (T2). The larger the Debye temperature ratio (T1 / T2), the larger the interface thermal resistance (Rinterface). Here, the larger the total thermal resistance (Rtotal) of the laminated film 11, the more the thermal confinement effect of the selector layer 4 can be enhanced. Moreover, by enhancing the thermal confinement effect of the selector layer 4, the threshold voltage (Vth), threshold current (Ith), and voltage (Vhold) when in the ON state of the selector device 1 can be reduced, thereby increasing the current ratio. In terms of obtaining the thermal confinement effect of the selector layer 4, it is important to increase the total thermal resistance (Rtotal) of the first electrode 2 and the second electrode 3 present around the selector layer 4.

[0040] Regarding the Debye temperature ratio between the first layer 9 and the second layer 10 of the laminated film 11, setting the ratio (T1 / T2 ratio) of the first Debye temperature (T1) of the first layer 9 to the second Debye temperature (T2) of the second layer 10 to 5 or more is effective. By setting the Debye temperature ratio (T1 / T2 ratio) to 5 or more, the total thermal resistance (Rtotal) of the laminated film 11 can be sufficiently improved. Regarding the number of times n of re-lamination of the first layer 9 and the second layer 10 in the laminated film 11, setting the number of re-laminations n to 4 or more is effective. By setting the number of times n of re-lamination of the first layer 9 and the second layer 10 to 4 or more, the total thermal resistance (Rtotal) of the laminated film 11 can be sufficiently improved.

[0041] The aforementioned Debye temperature ratio (T1 / T2 ratio) and the number of repetitions n can be satisfied independently, or both can be satisfied. That is, even if the number of repetitions n for the first layer 9 and the second layer 10 is less than 4 (e.g., n = 1), as long as the Debye temperature ratio (T1 / T2 ratio) is 5 or more, the total thermal resistance (Rtotal) of the laminated film 11 can be sufficiently increased. Furthermore, conversely, even if the Debye temperature ratio (T1 / T2 ratio) is less than 5, by setting the number of repetitions n for the first layer 9 and the second layer 10 to 4 or more, the total thermal resistance (Rtotal) of the laminated film 11 can be sufficiently increased. More preferably, the Debye temperature ratio (T1 / T2 ratio) and the number of repetitions n are satisfied simultaneously.

[0042] Next, the Debye temperature ratio (T1 / T2 ratio) of the first layer 9 and the second layer 10 of the laminated film 11 was determined with reference to... Figures 5-9 To narrate. Figure 5 The Debye temperatures of representative materials are shown in the figure. For example... Figure 5 As shown, the Debye temperature is a value determined by the material. Figure 6 The diagram shows a combination of a first material (material 1) having a first Debye temperature (T1) and a second material (material 2) having a second Debye temperature (T2), and the Debye temperature ratio (T1 / T2 ratio) in each combination. Figure 6 The diagram also shows the bulk materials used in the electrodes as reference materials, namely carbon bulk, TiN bulk, W bulk, and diamond-like carbon (DLC) bulk. Since these bulk materials are monolithic materials, their Debye temperature ratio (T1 / T2 ratio) is 1.

[0043] Figure 7 , Figure 8 and Figure 9 shown in the Figure 6 The relationship between the Debye temperature ratio (T1 / T2 ratio) and the total thermal resistance (Rtotal) of the laminated film formed by the first material (material 1) layer and the second material (material 2) layer is shown. Figure 7 The value of the total thermal resistance (Rtotal) is shown when the total film thickness of the laminated film is set to 10 nm. Figure 8 The value of the total thermal resistance (Rtotal) is shown when the total film thickness of the laminated film is set to 20 nm. Figure 9 This shows the total thermal resistance (Rtotal) when the total film thickness of the laminated films is set to 30 nm. For example... Figure 7 , Figure 8 and Figure 9 As shown, the greater the Debye temperature ratio (T1 / T2 ratio) between layer 1 (9) and layer 2 (10), the greater the increase in the value of the total thermal resistance (Rtotal). Figure 7 , Figure 8 and Figure 9The total thermal resistance (Rtotal) of the carbon block layer with a total film thickness of 30 nm is shown by the dashed line. The 30 nm thick carbon block layer has the highest total thermal resistance (Rtotal) among bulk materials, at 2 × 10⁻⁶. -8 km 2 / W.

[0044] like Figure 7 As shown, based on a stacked film of the first and second materials with a Debye temperature ratio (T1 / T2 ratio) of 5 or higher (total film thickness: 10 nm), a total thermal resistance (Rtotal) of 2 × 10⁻⁶ can be obtained compared to a carbon block layer with a film thickness of 30 nm. - 8 km 2 The higher the total thermal resistance (Rtotal) of the laminated film 11, the greater the Debye temperature ratio (T1 / T2 ratio) between the first and second materials becomes. This enhances the thermal confinement effect of the selector layer 4 provided by the first electrode 2 and the second electrode 3 using the laminated film 11. Therefore, by using electrodes 2 and 3, the characteristics of the selector device 1 can be improved.

[0045] The improvement in the total thermal resistance (Rtotal) of the laminated film 11 of the first and second materials due to such a Debye temperature ratio (T1 / T2 ratio) is as follows: Figure 8 and Figure 9 As shown, the same effect can be achieved when the total thickness of the laminated film 11 is 20 nm or 30 nm. Regarding achieving this improvement in total thermal resistance (Rtotal), the total thickness of the laminated film 11 consisting of the first layer 9 and the second layer 10 is preferably 10 nm to 30 nm. If the total thickness of the laminated film 11 is less than 10 nm, sufficient total thermal resistance (Rtotal) cannot be obtained. If the total thickness of the laminated film 11 exceeds 30 nm, the electrodes 2 and 3 of the selector device 1 become too thick, failing to meet the required characteristics of the selector device 1. Furthermore, the thickness of each of the first layer 9 and the second layer 10 constituting the laminated film 11 is preferably 0.5 nm or more. If the thickness of the first layer 9 or the second layer 10 is less than 0.5 nm, the functions of each layer 9 and 10, and the functions at their interfaces, may not be sufficiently obtained.

[0046] For the first material, at least one nitride selected from the group consisting of boron (B), titanium (Ti), zirconium (Zr), hafnium (Hf), aluminum (Al) and vanadium (V) may be used; at least one carbide selected from the group consisting of silicon (Si), tungsten (W), titanium (Ti), zirconium (Zr), aluminum (Al), tantalum (Ta), tungsten (W) and calcium (Ca) may be used; at least one boride selected from the group consisting of titanium (Ti) and lanthanum (La) may be used; at least one fluoride selected from the group consisting of magnesium (Mg), lithium (Li) and calcium (Ca) may be used; and at least one oxide selected from the group consisting of aluminum (Al), beryllium (Be), magnesium (Mg), titanium (Ti), rhenium (Re), calcium (Ca), iron (Fe), silicon (Si), zinc (Zn), nickel (Ni) and ruthenium (Ru) may be used. The first material may also include at least one selected from the group consisting of beryllium (Be), silicon (Si), rhodium (Rh), scandium (Sc), chromium (Cr), sulfur (S), germanium (Ge), aluminum (Al), vanadium (V), cobalt (Co), titanium (Ti), nickel (Ni), magnesium (Mg), copper (Cu), tungsten (W), tin (Sn), zirconium (Zr), gallium (Ga), zinc (Zn), platinum (Pt), calcium (Ca), cadmium (Cd), and silver (Ag), for example, using such a metallic material. The second material may also include at least one material selected from the group consisting of cobalt (Co), platinum (Pt), magnesium (Mg), copper (Cu), tungsten (W), indium (In), antimony (Sb), niobium (Nb), tin (Sn), strontium (Sr), gallium (Ga), arsenic (As), zirconium (Zr), zinc (Zn), calcium (Ca), silver (Ag), yttrium (Y), cerium (Ce), sulfur (S), antimony (Sb), tellurium (Te), gold (Au), thulium (Tm), samarium (Sm), terbium (Tb), bromine (Br), cerium (Ce), indium (In), manganese (Mn), bismuth (Bi), lutetium (Lu), mercury (Hg), thorium (Th), potassium (K), thallium (Tl), lead (Pb), rubidium (Rb), and cesium (Cs), for example, using such metallic or compound materials. The combination of the first and second materials is selected based on the Debye temperature of each material in a manner that satisfies the above conditions.

[0047] Next, for the number of times n of repeated stacking of the first layer 9 and the second layer 10 in the laminated film 11, refer to Figures 10-13 To narrate. Figure 10 The diagram shows a combination of a first material (material 1) having a first Debye temperature (T1) and a second material (material 2) having a second Debye temperature (T2), and the Debye temperature ratio (T1 / T2 ratio) in each combination. Figure 6 The image shows a carbon block with a Debye temperature ratio (T1 / T2 ratio) of 1, which is used as a reference material.

[0048] Figure 11 , Figure 12 and Figure 13 The middle shows Figure 10 The relationship between the number of times n of the first material (material 1) layer and the second material (material 2) layer are stacked and the total thermal resistance (Rtotal) shown. Figure 11 This represents the total thermal resistance (Rtotal) when the total film thickness of the laminated film is set to 10 nm. Figure 12 This represents the total thermal resistance (Rtotal) when the total thickness of the laminated films is set to 20 nm. Figure 13 This represents the total thermal resistance (Rtotal) when the total film thickness of the laminated films is set to 30 nm. For example... Figure 11 , Figure 12 and Figure 13 As shown, the greater the number of times layer 1 (9) and layer 2 (10) are stacked (n), the greater the increase in the total thermal resistance (Rtotal). Figure 11 , Figure 12 and Figure 13 In the figure, the total thermal resistance (Rtotal) of a 30nm thick carbon block layer is shown as 2×10⁻⁶, indicated by a dashed line. -8 km 2 / W.

[0049] like Figure 11 As shown, based on the stacked film of the first material and the second material (total film thickness: 10 nm) 11, where the number of repetitions n of the first layer 9 and the second layer 10 is 4 or more, it is possible to obtain a total thermal resistance (Rtotal) of 2 × 10⁻⁶ compared to a carbon block layer with a film thickness of 30 nm. -8 km 2 The higher the total thermal resistance (Rtotal), the greater the number of repetitions (n) of the first layer 9 and the second layer 10, the higher the total thermal resistance (Rtotal) of the laminated film 11. This increase in total thermal resistance (Rtotal) based on the number of repetitions (n) can be achieved even when the Debye temperature ratio (T1 / T2 ratio) is below 5, by setting the number of repetitions (n) to 4 or higher. Furthermore, by using the laminated film 11, which has increased total thermal resistance (Rtotal) based on the number of repetitions (n), for the first electrode 2 and the second electrode 3, the thermal confinement effect of the selector layer 4 can be enhanced, thereby improving the characteristics of the selector device 1.

[0050] The improvement in the total thermal resistance (Rtotal) of the laminated film 11 based on the number of repetitions n of layer 1 (9) and layer 2 (10) is as follows: Figure 12 and Figure 13As shown, the same effect can be achieved when the total film thickness of the laminated film 11 is 20 nm or 30 nm. When the total film thickness is 20 nm or 30 nm, even if the Debye temperature ratio (T1 / T2 ratio) is less than 5, an improvement in the total thermal resistance (Rtotal) of the laminated film 11 can be obtained as long as the number of re-laminations n is 4 or more. Regarding the improvement in total thermal resistance (Rtotal), the total film thickness of the laminated film 11 consisting of the first layer 9 and the second layer 10 is preferably 10 nm to 30 nm. If the total film thickness of the laminated film 11 is less than 10 nm, sufficient total thermal resistance (Rtotal) cannot be obtained. If the total film thickness of the laminated film 11 exceeds 30 nm, the electrodes 2 and 3 of the selector device 1 become too thick, failing to meet the required characteristics of the selector device 1. Furthermore, the film thickness of each of the first layer 9 and the second layer 10 constituting the laminated film 11 is preferably 0.5 nm or more. If the thickness of the first layer 9 or the second layer 10 is less than 0.5 nm, it may be impossible to fully obtain the functions of each layer 9, 10 or the functions at their interfaces.

[0051] As described above, by applying a laminated film 11 that satisfies at least one of the following conditions—a Debye temperature ratio (T1 / T2 ratio) of the first layer 9 and the second layer 10 being 5 or more (first condition) and a number of repetitions n of the first layer 9 and the second layer 10 being 4 or more (second condition)—to at least one of the first electrode 2 and the second electrode 3, the total thermal resistance (Rtotal) of the first electrode 2 and the second electrode 3 can be increased. Furthermore, by enhancing the thermal confinement effect of the selector layer 4 based on the total thermal resistance (Rtotal) of the first electrode 2 and the second electrode 3, it becomes possible to improve characteristics of the selector device 1 such as the threshold voltage (Vth), threshold current (Ith), and voltage (Vhold) when in the ON state. Regarding improving the thermal confinement effect of the selector layer 4, it is preferable to simultaneously satisfy both the first condition and the second condition of the laminated film 11. A laminated film 11 that satisfies at least one of the first and second conditions, and further satisfies both the first and second conditions, is preferably applied to both the first electrode 2 and the second electrode 3.

[0052] For the first material applied to the first layer 9 of the laminated film 11 and the second material applied to the second layer 10, provided that the Debye temperature ratio (T1 / T2 ratio) of the first layer 9 and the second layer 10 is 5 or higher, the first condition is met. There are no particular limitations provided that the second condition is met. For the first and second materials, the following can be applied... Figure 5 The table Figure 6 The table Figure 10The materials and combinations thereof are as shown in the table. Furthermore, considering the required properties for the electrodes, the first material preferably includes at least one selected from the group consisting of carbon (C), titanium nitride (TiN), and titanium boride (TiB). The second material preferably includes at least one selected from the group consisting of tellurium (Te), gold (Au), silver (Ag), lead (Pb), bismuth (Bi), indium (In), tungsten (W), and manganese (Mn). Examples of carbon used in the first material include diamond-like carbon, graphene, graphite, carbon nanotubes, fullerenes, and amorphous carbon, without particular limitation. The second material is not limited to materials containing the above elements as monomers, but may also include compounds or alloys containing at least one of the above elements, such as tellurides like MnTe or SnTe, or selenides like ZrSe.

[0053] The selector device 1 of the embodiment includes a first electrode 2 and / or a second electrode 3 that applies an electrode layer of a laminated film 11 that satisfies at least one of the following conditions: a Debye temperature ratio (T1 / T2 ratio) of the first layer 9 and the second layer 10 is 5 or more (first condition); and the number of repetitions n of the first layer 9 and the second layer 10 is 4 or more (second condition). Based on the total thermal resistance (Rtotal) of the laminated film 11 applied to at least one of the first electrode 2 and the second electrode 3, it becomes possible to provide a selector device 1 that enhances the thermal confinement effect of the selector layer 4. Therefore, the characteristics of the selector device 1 can be improved, and consequently, the characteristics and reliability of the variable resistive semiconductor memory device 8 using such a selector device 1 can be improved.

[0054] It should be noted that several embodiments of the present invention have been described, but these embodiments are provided as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other ways, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments or their variations are included in the scope and spirit of the invention, and are also included in the invention described in the claims and its equivalents.

Claims

1. A selector device comprising a first electrode, a second electrode, and a selector layer disposed between the first electrode and the second electrode, wherein, At least one of the first electrode and the second electrode comprises a laminated film having a first layer and a second layer, the first layer comprising a first material having a first Debye temperature (T1), and the second layer being disposed in contact with the first layer, comprising a second material having a second Debye temperature (T2) lower than the first Debye temperature. The ratio (T1 / T2) of the first Debye temperature (T1) to the second Debye temperature (T2) is 5 or more. The first and second layers of the laminated film are repeated four times or more.

2. The selector device according to claim 1, wherein, The total thickness of the laminated film is 10 nm to 30 nm.

3. The selector device according to claim 2, wherein, The thickness of the first layer and the second layer is 0.5 nm or more.

4. The selector device according to any one of claims 1 to 3, wherein, The first material comprises at least one selected from the group consisting of carbon, titanium nitride, and titanium boride, and the second material comprises at least one selected from the group consisting of tellurium, gold, silver, lead, bismuth, indium, tungsten, and manganese.

5. The selector device according to any one of claims 1 to 3, wherein, The first material is a nitride comprising at least one selected from the group consisting of boron, titanium, zirconium, hafnium, aluminum and vanadium.

6. The selector device according to any one of claims 1 to 3, wherein, The first material is a carbide comprising at least one selected from the group consisting of silicon, tungsten, titanium, zirconium, aluminum, tantalum, and calcium.

7. The selector device according to any one of claims 1 to 3, wherein, The first material is a boride comprising at least one of the groups selected from titanium and lanthanum.

8. The selector device according to any one of claims 1 to 3, wherein, The first material is a fluoride comprising at least one of the groups selected from magnesium, lithium and calcium.

9. The selector device according to any one of claims 1 to 3, wherein, The first material is an oxide comprising at least one of the following: aluminum, beryllium, magnesium, titanium, rhenium, calcium, iron, silicon, zinc, nickel, and ruthenium.

10. The selector device according to any one of claims 1 to 3, wherein, The first material comprises at least one selected from the group consisting of beryllium, silicon, rhodium, scandium, chromium, sulfur, germanium, aluminum, vanadium, cobalt, titanium, nickel, magnesium, copper, tungsten, tin, zirconium, gallium, zinc, platinum, calcium, cadmium and silver.

11. The selector device according to any one of claims 1 to 3, wherein, The second material comprises at least one selected from the group consisting of cobalt, platinum, magnesium, copper, tungsten, indium, antimony, niobium, tin, strontium, gallium, arsenic, zirconium, zinc, calcium, cadmium, silver, yttrium, cerium, sulfur, antimony, tellurium, gold, thulium, samarium, terbium, bromine, cerium, indium, manganese, bismuth, lutetium, mercury, thorium, potassium, thallium, lead, rubidium, and cesium.

12. The selector device according to any one of claims 1 to 3, wherein, The first electrode and the second electrode each have the laminated film.

13. A selector device comprising a first electrode, a second electrode, and a selector layer disposed between the first electrode and the second electrode, wherein, At least one of the first electrode and the second electrode comprises a laminated film having a first layer and a second layer, the first layer comprising a first material having a first Debye temperature (T1), and the second layer being disposed in contact with the first layer, comprising a second material having a second Debye temperature (T2) lower than the first Debye temperature. The first and second layers of the laminated film are repeated four times or more.

14. The selector device according to claim 13, wherein, The total thickness of the laminated film is 10 nm to 30 nm.

15. The selector device according to claim 14, wherein, The thickness of the first layer and the second layer is 0.5 nm or more.

16. The selector device according to any one of claims 13 to 15, wherein, The first material comprises at least one selected from the group consisting of carbon, titanium nitride, and titanium boride, and the second material comprises at least one selected from the group consisting of tellurium, gold, silver, lead, bismuth, indium, tungsten, and manganese.

17. The selector device according to any one of claims 13 to 15, wherein, The first electrode and the second electrode each have the laminated film.

18. A semiconductor memory device comprising: The selector device according to any one of claims 1 to 3 or any one of claims 13 to 15; and A resistance variation layer is electrically connected to the selector layer of the selector device and is stacked with the selector layer.

Images