Resistance change material, material for switching element, switching layer, switching element, and memory device

Abstract

The invention provides a resistance change material, a material for a switching element, a switching layer, a switching element, and a memory device capable of obtaining excellent OTS characteristics. The resistance change material is a resistance change material containing Te, and the OFF current density is 3.1 * 102 A / cm2 or less when the current density when a voltage equal to 1 / 2 of the threshold voltage is applied is defined as the OFF current density.

Description

Technical Field

[0001] The present invention relates to a resistance variable material, a material for a switching element, a switching layer, a switching element, and a storage device. Background Art

[0002] Next-generation nonvolatile memory devices are attracting attention as a replacement for NAND flash memory. For example, resistance-variable and phase-change memory devices have been proposed as next-generation nonvolatile memory devices, and are being developed with the goal of increasing capacity and speed.

[0003] In addition, as a next-generation non-volatile memory device structure, cross-point memory devices are attracting attention (Patent Documents 1 and 2). A cross-point memory device includes word lines, bit lines that are orthogonal to the word lines when viewed from above, and memory elements and switching elements arranged at the intersection of the two when viewed from above. In the prior art, triodes (transistors) and diodes are used as switching elements, but with the miniaturization, high capacity, and high integration of memory devices, the use of bidirectional switching elements (Ovonic Threshold Switches: OTS elements) whose resistance changes according to the applied voltage has attracted attention.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2006-086526

[0007] Patent Document 2: Japanese Patent Application Publication No. 2018-164085

[0008] Non-patent literature

[0009] Non-patent document 1: Lencer, D. et al., “A map for phase-change materials”, Nat. Mater. 7, 972-977 (2008) Summary of the Invention

[0010] Technical problem to be solved by the invention

[0011] In order to obtain a stable switching action in an OTS element, it is required to exhibit a stable resistance change with respect to an applied voltage (that is, to have excellent OTS characteristics).

[0012] In view of the above circumstances, an object of the present invention is to provide a variable resistance material, a switching element material, a switching layer, a switching element, and a memory device having excellent OTS characteristics.

[0013] Technical means for solving technical problems

[0014] Each aspect of a variable resistance material, a switching element material, a switching layer, a switching element, and a memory device that solves the above-mentioned technical problems will be described.

[0015] The resistance variable material of embodiment 1 is a resistance variable material containing Te, and is characterized in that when the current density when a voltage of 1 / 2 of the threshold voltage is applied is defined as the OFF current density, the OFF current density is 3.1×10 2 A / cm 2 Here, the threshold voltage refers to the voltage at which the resistance changes abruptly from a high resistance state to a low resistance state. The OFF current density is the value obtained by dividing the current value (OFF current value) flowing when a voltage of 1 / 2 the threshold voltage is applied by the contact area with the electrode.

[0016] The resistance variable material of embodiment 2 is preferably such that, in embodiment 1, the ON current density is 1×10 6 A / cm 2 Here, the ON current density refers to a value obtained by dividing the current value (ON current value) flowing when a voltage equal to or higher than the threshold voltage is applied by the contact area with the electrode.

[0017] The variable resistance material of embodiment 3 preferably has a carrier mobility of 5×10 -3 cm / Vs or less.

[0018] The resistance variable material of embodiment 4, in any of embodiments 1 to 3, preferably has an ON / OFF current ratio obtained by dividing the ON current density by the OFF current density, where the current density when a voltage equal to or higher than the threshold voltage is applied is defined as the ON current density. 4 above.

[0019] In the variable resistance material of aspect 5 in any of aspects 1 to 4, it is preferable that the threshold voltage is within a range of 0.5V to 10V.

[0020] The resistance variable material of aspect 6 in any one of aspects 1 to 5 preferably contains, in atomic %, 0.1% to 50% of Ge and 40% to 90% of Te.

[0021] In any one of aspects 1 to 6, the resistance variable material of aspect 7 preferably contains 1% to 59% by atomic % of Si+Al+Ga+Sn+Bi+Cu+Ag+Zn+Y+In+Ca+Mg.

[0022] The resistance variable material of aspect 8, in any one of aspects 1 to 7, preferably contains Sb in an atomic % content of 0% or more and less than 5%.

[0023] In any one of the aspects 1 to 7, the resistance variable material of aspect 9 preferably contains substantially no Sb, Se, or As.

[0024] In the resistance variable material of aspect 10 in any one of aspects 1 to 9, it is preferable that the oxygen content is less than 1 atomic %.

[0025] The resistance variable material of aspect 11 in any of aspects 1 to 10 is preferably a thin film.

[0026] The switching element material according to aspect 12 is characterized by being composed of the resistance variable material according to any one of aspects 1 to 11.

[0027] The switching layer of aspect 13 is characterized in that it is composed of the resistance variable material described in any one of aspects 1 to 11.

[0028] The switching element of aspect 14 is characterized by including the switching layer of aspect 13 and a first electrode arranged on the switching layer.

[0029] The switching element of embodiment 15 is characterized by comprising: a switching layer; a first electrode disposed on the switching layer; and a second electrode disposed at a position opposing the first electrode across the switching layer, wherein the switching layer is composed of a variable resistance material containing Te, and wherein the OFF current density is 3.1×10 2 A / cm 2 the following.

[0030] In the switching element of aspect 16 according to aspect 15, it is preferable that the first electrode is arranged on an outer peripheral surface of the switching layer, and the second electrode is arranged on an inner peripheral surface of the switching layer.

[0031] In the switching element of aspect 17 in aspect 15 or 16, it is preferable that the first electrode and the second electrode are at least one selected from tungsten, titanium, copper, platinum, tungsten nitride, and titanium nitride.

[0032] The switching element of embodiment 18 is preferably such that, in any one of embodiments 15 to 17, the ionicity of the switching layer is σ ′ and hybridization π -1 Satisfy the following values,

[0033] r σ ′≥0.05,

[0034] r π -1 ≤2.0.

[0035] In the switching element of mode 19, in any of modes 15 to 18, when the carrier activation energy when an applied voltage of 0.15 V is applied to the switching layer is set to a, and the carrier activation energy when an applied voltage of 0.30 V is applied to the switching layer is set to b, it is preferred that a / b<1 is satisfied.

[0036] The storage device of aspect 20 preferably includes the switching element of any one of aspects 15 to 19.

[0037] The memory device of aspect 21 preferably includes the switching element of any one of aspects 15 to 19 and a memory element.

[0038] The memory device of embodiment 22 is characterized by comprising a stacked body in which a switching element and a memory element are stacked, wherein the switching element comprises a switching layer and a first electrode arranged on the switching layer, and the switching layer comprises a first electrode arranged on the switching layer, wherein the first electrode has an OFF current density of 3.1×10 2 A / cm 2 The following resistance variable material composition is used, and the memory element is composed of any one of a resistance variable memory element, a magnetoresistive memory element, a phase change memory element, and a ferroelectric memory element.

[0039] Effects of the Invention

[0040] According to the present invention, a variable resistance material, a switching element material, a switching layer, a switching element, and a memory device having excellent OTS characteristics can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is a schematic cross-sectional view of a switching element according to one embodiment of the present invention.

[0042] Figure 2 is a schematic cross-sectional view of a memory element according to one embodiment of the present invention.

[0043] Figure 3 This is a schematic perspective view of a storage device according to the first embodiment of the present invention.

[0044] Figure 4 This is a schematic enlarged perspective view of the storage device according to the first embodiment of the present invention.

[0045] Figure 5 It is a schematic perspective view of a modified example of the storage device according to the first embodiment of the present invention.

[0046] Figure 6 It is a schematic perspective view of a storage device according to a second embodiment of the present invention.

[0047] Figure 7It is a schematic perspective view of a modified example of the storage device according to the second embodiment of the present invention.

[0048] Figure 8 The ionicity of the switching layer is plotted. σ ′ and hybrid r π -1 Picture. DETAILED DESCRIPTION

[0049] Hereinafter, preferred embodiments will be described. However, the following embodiments are merely examples, and the present invention is not limited to the following embodiments. In the following description, "%" refers to "atomic %" unless otherwise specified. In addition, in the present invention, "x+y+z+······" refers to the sum of the contents of each component. Here, each component may not necessarily be contained as an essential component, and there may also be a component that is not contained (content 0%). In addition, "A% to B% of x+y+z+······" includes, for example, "x=0%, A% to B% of y+z+······", "x=0%, y=0%, A% to B% of z+······".

[0050] <Resistance Variable Materials>

[0051] The resistance variable material of the present invention is a resistance variable material containing Te, characterized in that when the current density when a voltage of 1 / 2 of the threshold voltage is applied is defined as the OFF current density, the OFF current density is 3.1×10 2 A / cm 2 the following.

[0052] The present inventors have found that a resistance-changing material whose OFF current density satisfies a specified value can obtain excellent OTS characteristics. The OTS characteristic refers to the characteristic that the resistance value of a chalcogenide-based thin film changes due to the application of voltage. In detail, it is described as follows. The resistance-changing material exhibits high resistance in the initial state (OFF state). When a voltage is applied in this state, the high resistance state is maintained before exceeding the threshold voltage, and when the threshold voltage is exceeded, it is rapidly switched (switched) to a low resistance state (ON state). When the applied voltage is reduced from the ON state, it returns to the OFF state again. The resistance difference between the high resistance state and the low resistance state of the resistance-changing material with excellent OTS characteristics is large. In other words, the difference between the current density in the low resistance state and the current density in the high resistance state (ON / OFF current ratio) is large. Therefore, it can be stably used as a switching layer and a switching element. Here, the ON / OFF current ratio (i.e., the on / off current ratio) refers to the value obtained by dividing the ON current density by the OFF current density.

[0053] The resistance variable material of the present invention has an upper limit of 3.1×10 2 A / cm 2 Below, preferably 3×10 2 A / cm 2 Below, 2.8×10 2 A / cm 2 Below, particularly preferably 2.6×10 2 A / cm 2 By making the OFF current density satisfy the above value, it is easy to increase the ON / OFF current ratio. Therefore, a stable OTS characteristic can be obtained. The lower limit of the OFF current density is not particularly limited and can be 5×10 - 3 A / cm 2 Above, 6×10 -3 A / cm 2 Above, 1×10 -2 A / cm 2 above.

[0054] In the variable resistance material of the present invention, when the current density when a voltage equal to or higher than the threshold voltage is applied is defined as the ON current density, the lower limit of the ON current density is preferably 1×10 6 A / cm 2 Above, 2×10 6 A / cm 2 Above, 3.1×10 6 A / cm 2 Above, 3.2×10 6 A / cm 2 Above, 3.5×10 6 A / cm 2 Above, 4.1×10 6 A / cm 2 Above, 4.2×10 6 A / cm 2 Above, 4.3×10 6 A / cm 2 Above, 4.4×10 6 A / cm 2 Above, particularly preferably 4.5×10 6 A / cm 2 By making the ON current density satisfy the above value, the ON / OFF current ratio can be further increased. The upper limit of the ON current density is not particularly limited, for example, it can be 1×10 9 A / cm 2 Below, 1×10 8 A / cm 2Below, 1×10 7 A / cm 2 the following.

[0055] The lower limit of the ON / OFF current ratio of the resistance variable material of the present invention is preferably 1×10 4 Above, 1.2×10 4 Above, 1.5×10 4 Above, 1.8×10 4 Above, 5×10 4 Above, 1×10 5 Above, 1.5×10 5 Above, 3.1×10 5 Above, 3.9×10 5 Above, 5×10 5 Above, 6.3×10 5 More than 1×10 6 Or, when the ON / OFF current ratio is set to x, log 10 The lower limit of x is preferably 4 or more, 4.1 or more, 4.2 or more, 4.3 or more, 4.7 or more, 5 or more, 5.2 or more, 5.5 or more, 5.6 or more, 5.7 or more, or 5.8 or more, and particularly preferably 6 or more. In this way, since the ON / OFF current ratio is large, the difference between the current density in the low resistance state and the current density in the high resistance state (ON / OFF current ratio) becomes large. That is, an excellent OTS effect can be obtained. The upper limit of the ON / OFF current ratio is not particularly limited, and can be, for example, 2×10 10 Below, 1×10 9 Below, 1×10 8 Below, especially 1×10 7 In addition, log 10 The upper limit of the value of x is preferably 10.3 or less, 9 or less, or 8 or less, and particularly preferably 7 or less.

[0056] The variable resistance material of the present invention preferably has a threshold voltage within the range of 0.5V to 10V. More specifically, the upper limit of the threshold voltage is preferably 10V or less, 8V or less, or 6V or less, and particularly preferably 5V or less. By keeping the threshold voltage within this range, switching elements, etc., can be driven with less energy. The lower limit of the threshold voltage is not particularly limited and can be 0.5V or more, 0.8V or more, 1V or more, or 1.2V or more, and particularly preferably 1.5V or more.

[0057] The OFF current density, ON current density, ON / OFF current ratio and threshold voltage can be obtained as follows. First, a voltage of 0V to 10V is applied to the switching element, and the current value flowing through the switching element and the threshold voltage are measured. The voltage applied at this time is not limited to DC voltage, AC voltage, pulse voltage, etc., but from the viewpoint of preventing heat accumulation in the switching element, it is preferably measured with a pulse voltage. The threshold voltage can be a voltage value when the resistance value changes sharply from a high resistance state to a low resistance state. The OFF current density can be a value obtained by dividing the current value (OFF current value) flowing when a voltage of 1 / 2 of the threshold voltage is applied by the contact area with the first electrode or the second electrode. The ON current density can be a value obtained by dividing the current value (ON current value) flowing when a voltage greater than the threshold voltage is applied by the contact area with the first electrode or the second electrode. Next, the ON / OFF current ratio can be obtained by dividing the ON current value by the OFF current value. Furthermore, when the contact area between the switching element and the first electrode and the contact area between the switching element and the second electrode are the same, the current density can be calculated using the contact area of ​​the first electrode or the second electrode, as described above. Furthermore, when the contact area between the switching element and the first electrode and the contact area between the switching element and the second electrode are different, the current density can be calculated using the smaller contact area.

[0058] The upper limit of the carrier mobility of the resistance variable material of the present invention is preferably 5×10 -3 cm 2 / Vs or less, 4.5×10 -3 cm 2 / Vs or less, 4×10 -3 cm 2 / Vs or less, 3.5×10 -3 cm 2 / Vs or less, particularly preferably 3×10 -3 cm 2 / Vs or less. By making the carrier mobility satisfy the above value, the OFF current density is easily reduced. Therefore, it is easy to increase the ON / OFF current ratio. The lower limit of the carrier mobility is not particularly limited, for example, it can be 1×10 -8 cm 2 / Vs or above, 1×10 -7 cm 2 / Vs or above, 1×10 -6 cm 2 The carrier mobility can be measured using a resistivity-Hall measurement system.

[0059] The resistance variable material of the present invention contains Te. Te constitutes the resistance variable material and is an essential component for obtaining the OTS characteristic. The Te content is preferably 40% to 90%. More specifically, the lower limit of the Te content is preferably 40% or more, 42% or more, 47% or more, 50% or more, more than 50%, 51% or more, 53% or more, 55% or more, 60% or more, 61% or more, 65% or more, 67% or more, 70% or more, and particularly preferably 71% or more. The upper limit of the Te content is preferably 90% or less, 89% or less, 85% or less, 82.5% or less, 80% or less, 75% or less, and particularly preferably 72.5% or less. When the Te content is too low, the amorphous state tends to become unstable. In addition, it is difficult to obtain the OTS characteristic. When the Te content is too high, the amorphous state tends to become unstable. In addition, the carrier mobility becomes too large, and the OFF current density tends to become large.

[0060] The resistance variable material of the present invention may contain components other than Te. For example, it preferably contains 0.1% to 50% Ge and 40% to 90% Te in atomic %. Furthermore, it may contain components other than Ge and Te.

[0061] Ge is a component that stabilizes the amorphous state of the resistance variable material. The Ge content is preferably 0.1% to 50%. More specifically, the lower limit of the Ge content is preferably 0.1% or more, 1% or more, 3% or more, 5% or more, 7% or more, 10% or more, 11% or more, and particularly preferably 13% or more. The upper limit of the Ge content is preferably 50% or less, 40% or less, 30% or less, and particularly preferably 20% or less. When the Ge content is too low, the amorphous state tends to become unstable. When the Ge content is too high, it is difficult to obtain OTS characteristics. In addition, the manufacturing cost tends to increase.

[0062] The lower limit of the Ge+Te content (the total amount of Ge and Te) is preferably 41% or more, 45% or more, 50% or more, 60% or more, 65% or more, 70% or more, 75% or more, and particularly preferably 80% or more. The upper limit of the Ge+Te content is preferably 99% or less, 98% or less, 97% or less, and particularly preferably 95% or less. When the Ge+Te content is too low, the amorphous state tends to become unstable. In addition, it is difficult to obtain OTS characteristics. When the Ge+Te content is too high, it is difficult to obtain OTS characteristics.

[0063] Si, Al, Ga, Sn, Bi, Cu, Ag, Zn, Y, In, Ca, and Mg are components that stabilize the amorphous state of the variable resistance material. Furthermore, these components facilitate increasing the ON / OFF current ratio by reducing the OFF current density. Therefore, the variable resistance material of the present invention preferably has a Si+Al+Ga+Sn+Bi+Cu+Ag+Zn+Y+In+Ca+Mg content (the total amount of Si, Al, Ga, Sn, Bi, Cu, Ag, Zn, Y, In, Ca, and Mg) of 1% to 59%. More specifically, the lower limit of the Si+Al+Ga+Sn+Bi+Cu+Ag+Zn+Y+In+Ca+Mg content is preferably 1% or more, and particularly preferably 2% or more. The upper limit of the content of Si+Al+Ga+Sn+Bi+Cu+Ag+Zn+Y+In+Ca+Mg is preferably 59% or less, 58% or less, 55% or less, 50% or less, 45% or less, 40% or less, 35% or less, 30% or less, 25% or less, 20% or less, 15% or less, 14% or less, 13% or less, or 10% or less, and particularly preferably 9% or less. In other words, the above content can also be said to contain one or more components selected from Si, Al, Ga, Sn, Bi, Cu, Ag, Zn, Y, In, Ca, and Mg. If the content of these components is too low, it is difficult to obtain the above effects. When the content of these components is too high, the amorphous state easily becomes unstable. In addition, it is difficult to obtain OTS characteristics. The lower limit of the content of each of Si, Al, Ga, Sn, Bi, Cu, Ag, Zn, Y, In, Ca, and Mg is preferably 0% or more, more than 0%, 0.1% or more, 0.5% or more, or 1% or more, and particularly preferably 2% or more. The upper limit of the content of each of Si, Al, Ga, Sn, Bi, Cu, Ag, Zn, Y, In, Ca, and Mg is preferably 59% or less, 58% or less, 55% or less, 50% or less, 45% or less, 40% or less, 35% or less, 30% or less, 25% or less, 20% or less, 15% or less, 14% or less, 13% or less, or 10% or less, and particularly preferably 9% or less.

[0064] Among the above components, Ga and Ag are components that tend to reduce carrier mobility and lower the OFF current density, and therefore are particularly helpful in improving the ON / OFF current ratio. Furthermore, they are also components that tend to stabilize the amorphous state. The lower limit of the Ga+Ag content (the total amount of Ga and Ag) is preferably 0% or more, more than 0%, 0.1% or more, 0.5% or more, 1% or more, 2% or more, 3% or more, and particularly preferably 5% or more. The upper limit of the Ga+Ag content is preferably 59% or less, 58% or less, 55% or less, 50% or less, 45% or less, 40% or less, 35% or less, 30% or less, 25% or less, 20% or less, 15% or less, 14% or less, 13% or less, 10% or less, and particularly preferably 9% or less. Excessive Ga+Ag content can easily destabilize the amorphous state.

[0065] In particular, from the perspective of reducing the OFF current density, the lower limit of Ga / (Ga+Ag) is preferably 0.1 or greater, particularly preferably 0.2 or greater, and the upper limit of Ga / (Ga+Ag) is preferably 1.2 or less, less than 1.2, particularly preferably 1.1 or less. Here, Ga / (Ga+Ag) refers to the value obtained by dividing the Ga content by the total amount of Ga and Ag.

[0066] In particular, from the perspective of increasing the number of cycles described later, the lower limit of Ag / (Ga+Ag) is preferably 0.1 or more, particularly preferably 0.2 or more, and the upper limit of Ag / (Ga+Ag) is preferably 1.2 or less, less than 1.2, particularly preferably 1.1 or less. Here, Ag / (Ga+Ag) refers to the value obtained by dividing the Ag content by the total amount of Ga and Ag.

[0067] Sb is a component that easily destabilizes the amorphous state at high temperatures. Therefore, the Sb content is preferably 0% to less than 5%. More specifically, the upper limit of the Sb content is preferably less than 5%, less than 4%, less than 3%, less than 2%, and particularly preferably substantially free of Sb. In this specification, "substantially free of" means that the raw material intentionally does not contain Sb, and does not exclude the inclusion of impurities. Objectively, it means that the content of each component is less than 0.1%.

[0068] Se is a component that easily stabilizes the amorphous state of the resistance variable material. The upper limit of the Se content is preferably 58% or less, 55% or less, and particularly preferably 50% or less. The lower limit of the Se content is preferably 0% or more, 1% or more, 5% or more, or 10% or more, and particularly preferably 20% or more. If the Se content is too high, the amorphous state tends to become unstable. In addition, Se is a toxic component. Therefore, from the perspective of reducing the load on the environment, the upper limit of the Se content is preferably 40% or less, 30% or less, 20% or less, or 10% or less, and particularly preferably substantially no Se is contained.

[0069] As is a component that tends to stabilize the amorphous state of the variable resistance material. However, since As is toxic, the As content is preferably 0% to 30% to reduce environmental impact. More specifically, the upper limit of the As content is preferably 30% or less, 25% or less, 20% or less, 10% or less, 5% or less, or 3% or less, with substantially no As content being particularly preferred.

[0070] The resistance variable material of the present invention preferably contains substantially no Sb, Se, and As. This facilitates further reduction of environmental load.

[0071] When the content of B, C, N, F, Cl, Br and I is too much, the amorphous state tends to become unstable. In addition, weather resistance tends to decrease. Therefore, the upper limit of the content of B+C+N+F+Cl+Br+I (the total amount of B, C, N, F, Cl, Br and I) is preferably 50% or less, 45% or less, 40% or less, 35% or less, 30% or less, 25% or less, 20% or less, 15% or less, 14% or less, 12% or less, 10% or less, 8% or less, 6% or less, and particularly preferably 5% or less. In addition, the upper limit of the content of each component of B, C, N, F, Cl, Br and I is preferably 50% or less, 45% or less, 40% or less, 35% or less, 30% or less, 25% or less, 20% or less, 15% or less, 14% or less, 12% or less, 10% or less, 8% or less, 6% or less, and particularly preferably 5% or less. However, from the viewpoint of increasing the crystallization temperature, the total amount of B, C, N, F, Cl, Br and I may be contained in an amount of 0% or more, 1% or more, and particularly preferably 2% or more.

[0072] When the content of P, Cr, Mn, Ti, and Fe is too high, the amorphous state tends to become unstable. Therefore, the content of P+Cr+Mn+Ti+Fe (the total amount of P, Cr, Mn, Ti, and Fe) is preferably 0% to 10%. More specifically, the upper limit of the content of P+Cr+Mn+Ti+Fe is preferably 10% or less, 5% or less, 1% or less, less than 1%, or 0.1% or less, and it is particularly preferred that it is substantially free of these components. When the content of these components is too high, the amorphous state tends to become unstable. In addition, the content of each of P, Cr, Mn, Ti, and Fe is preferably 0% to 10%. More specifically, the upper limit of the content of each of P, Cr, Mn, Ti, and Fe is preferably 10% or less, 5% or less, 1% or less, less than 1%, or 0.1% or less, and it is particularly preferred that it is substantially free of these components.

[0073] From the viewpoint of reducing environmental load, it is preferred that Cd, Tl, and Pb are substantially not contained.

[0074] The variable resistance material of the present invention preferably contains less than 1 atomic % oxygen. More specifically, the upper limit of the oxygen content is preferably 0.8% or less, 0.5% or less, 0.3% or less, 0.1% or less, 0.09% or less, 0.05% or less, and particularly preferably 0.02% or less. When the oxygen content is too high, not only the ON current density is likely to decrease, but also the threshold voltage is likely to increase. From the perspective of raw material refining costs, the lower limit of the oxygen content is preferably 1×10 -6 % or more, 1×10 -5 % or more, 5×10 -5 % or more, 1×10 -4 % or more, particularly preferably 2×10 -4 %above.

[0075] The composition of the variable resistance material can be evaluated using methods such as energy dispersive X-ray spectroscopy (EDX), electron probe microanalyzer (EPMA), and X-ray fluorescence (XRF). EDX can be performed using TEM-EDX or SEM-EDX, both of which are attached to transmission electron microscopes (TEMs) and scanning electron microscopes (SEMs). The oxygen content can also be evaluated using methods such as inert gas fusion and infrared absorption.

[0076] The crystallization temperature Tx of the variable resistance material of the present invention is preferably 150°C or higher, 160°C or higher, and particularly preferably 170°C or higher. By ensuring that the crystallization temperature Tx satisfies this value, crystallization is less likely to occur due to heat generated during switching, making it easier to increase the number of cycles described later. The upper limit of the crystallization temperature Tx is not particularly limited; for example, it can be 500°C or lower, 450°C or lower, and particularly preferably 400°C or lower.

[0077] The crystallization temperature Tx of the resistance variable material can be evaluated using differential thermal analysis (DTA: Differential Thermal Analysis) or differential scanning calorimetry (DSC: Differential Scanning Calorimetry). In addition, the temperature dependence of the resistance can be measured in the measurement of resistance using a two-terminal method, and the temperature at which the resistance drops sharply can be evaluated as the crystallization temperature Tx. Furthermore, the obtained resistance variable material can be heat-treated at a specified temperature, and the point at which a crystallization peak is generated by XRD can be evaluated as the crystallization temperature Tx. The crystallization temperature Tx evaluated by any of the above methods preferably satisfies the preferred value of the above-mentioned crystallization temperature Tx. It is particularly preferred that the crystallization temperature Tx evaluated in the temperature dependence of the resistance satisfies the preferred value of the above-mentioned crystallization temperature Tx.

[0078] Since the variable resistance material of the present invention is in a stable amorphous state, the number of cycles can be increased when used as a switching element. That is, the ON / OFF current ratio can be maintained even when repeatedly turned on and off. Specifically, the lower limit of the number of cycles (the number of times the ON / OFF current is repeatedly switched (switched) until the ON / OFF current ratio reaches 10% of the initial measured value) is preferably 5×10 2 times or more, 1×10 3 times or more, particularly preferably 1×10 4 If the number of cycles is too small, it is difficult to use as a switching element. The upper limit of the number of cycles is not particularly limited, for example, it can be 1×10 10 Less than 1×10 9 Less than 1×10 8 times or less, especially 1×10 7 times or less.

[0079] The variable resistance material of the present invention is preferably used as a thin film (variable resistance film). This thin film (variable resistance film) is particularly suitable for use as a switching layer or a switching memory layer described below. However, the variable resistance material is not limited to a thin film.

[0080] The film thickness of the thin film (variable resistance film) is preferably 1 nm to 300 nm. More specifically, the lower limit of the thickness of the variable resistance film is preferably 1 nm or greater, 2 nm or greater, 5 nm or greater, 10 nm or greater, or 30 nm or greater, and particularly preferably greater than 50 nm. The upper limit of the thickness of the variable resistance film is preferably 300 nm or less, 200 nm or less, and particularly preferably 100 nm or less. If the film thickness is too small, the current value (OFF current) in the high-resistance state tends to increase. If the film thickness is too large, the threshold voltage tends to increase.

[0081] The switching element material of the present invention is preferably composed of the variable resistance material of the present invention. Furthermore, the switching layer of the present invention is preferably composed of the variable resistance material of the present invention. As described above, the variable resistance material of the present invention exhibits excellent OTS properties and is therefore suitable for use as a material for both the switching layer and the switching element.

[0082] The variable resistance material of the present invention can be produced, for example, as follows. First, the raw materials are mixed to achieve the desired composition. Next, the mixed raw materials are added to a heated and evacuated quartz glass ampoule, and the ampoule is sealed with an oxygen burner while evacuating the quartz glass. The sealed quartz glass ampoule is then maintained at approximately 650°C to 1000°C for 6 to 12 hours. The ampoule is then rapidly cooled to room temperature to obtain a bulk variable resistance material.

[0083] As the raw materials, elemental raw materials (Ge, Ga, Si, Te, Ag, I, etc.) or compound raw materials (GeTe4, Ga2Te3, AgI, etc.) may be used. Furthermore, these materials may be used in combination.

[0084] A thin film (variable resistance film) having the above-described composition can be formed by a PVD method (Physical Vapor Deposition) using the obtained variable resistance material as a target.

[0085] In addition, by using a multi-element sputtering method that uses a pure element M target (Ge, Te, Sb, Si, Al, Ga, Sn, Bi, Cu, Ag, Zn, Y, In, Ca and Mg), a binary alloy target or a ternary or higher alloy target as a target, and by appropriately adjusting the film forming output to adjust the composition, a thin film (resistance variable film) having the above composition can also be formed.

[0086] The thin film production method is not particularly limited. PVD methods include sputtering, vacuum evaporation, and ion plating. Other thin film production methods include CVD (Chemical Vapor Deposition) and ALD (Atomic Layer Deposition). Sputtering is particularly preferred for ease of composition and film thickness control.

[0087] Switching elements

[0088] Figure 1It is a schematic cross-sectional view of a switching element according to an embodiment of the present invention. The switching element 10 includes a first electrode 1, a second electrode 2, and a switching layer 3 arranged on the main surface of the first electrode 1. The second electrode 2 is arranged at a position opposite to the first electrode 1. In this embodiment, the switching layer 3 is arranged between the first electrode 1 and the second electrode 2. In other words, the switching element 10 according to this embodiment includes a switching layer 3 and the first electrode 1 arranged on the switching layer 3. In other words, the switching element 10 according to this embodiment preferably includes the second electrode 2 arranged at a position opposite to the first electrode 1 across the switching layer 3. At this time, the switching layer 3 is preferably composed of a resistance change material containing Te and when the current density when a voltage of 1 / 2 of the threshold voltage is applied is the OFF current density, the OFF current density is 3.1×10 2 A / cm 2 the following.

[0089] The switching element 10 of this embodiment is applicable to a cross-point memory device or a BiCS (Bit-Cost Scalable) memory device, which will be described later. In the case of a BiCS memory device, in the switching element 10 of this embodiment, the first electrode 1 is preferably arranged on the outer peripheral surface of the switching layer 3, and the second electrode 2 is preferably arranged on the inner peripheral surface of the switching layer 3.

[0090] Inorganic materials can be used for the first electrode 1 and the second electrode 2. Metal materials and ceramic materials can be used as inorganic materials. For example, the first electrode 1 and the second electrode 2 are preferably at least one selected from tungsten, titanium, copper, platinum, tungsten nitride, and titanium nitride. Tungsten, titanium, copper, and platinum are preferred as metal materials. In addition, tungsten nitride and titanium nitride are preferred as ceramic materials.

[0091] The thickness of the first electrode 1 and the second electrode 2 can be appropriately designed. For example, the upper limit of the thickness of the first electrode 1 and the second electrode 2 is preferably 200 nm or less, 100 nm or less, 80 nm or less, or 60 nm or less, and particularly preferably 50 nm or less. The smaller the thickness of the first electrode 1 and the second electrode 2, the easier it is to increase the capacity of the memory device. The lower limit of the thickness of the first electrode 1 and the second electrode 2 is preferably 1 nm or more, and particularly preferably 2 nm or more.

[0092] The upper limit of the area of ​​the first electrode 1 and the second electrode 2 is preferably 1,000,000 nm, for example. 2 Below, 562500nm 2 Below, 250000nm 2 Below, 62500nm 2 Below, 10000nm 2 Below, 6400nm 2 Below, 2500nm2 Below, particularly preferably 1600nm 2 The lower limit of the area of ​​the first electrode 1 and the second electrode 2 is not particularly limited, but from the viewpoint of production cost, each can be 1 nm. 2 Above, especially 2nm 2 The upper limit of the contact area between the first electrode 1 and the switching layer 3 or the upper limit of the contact area between the second electrode 2 and the switching layer 3 is preferably 1,000,000 nm. 2 Below, 562500nm 2 Below, 250000nm 2 Below, 62500nm 2 Below, 10000nm 2 Below, 6400nm 2 Below, 2500nm 2 Below, particularly preferably 1600nm 2 There is no particular limit on the lower limit of the contact area between the first electrode 1 and the switching layer 3 or the contact area between the second electrode 2 and the switching layer 3, but from the perspective of manufacturing cost, it can be 1 nm. 2 Above, especially 2nm 2 Regarding the contact area between the electrodes and the switching layer 3, at least one of the contact area between the first electrode 1 and the switching layer 3 and the contact area between the second electrode 2 and the switching layer 3 satisfies the above value, and more preferably, both contact areas satisfy the above value.

[0093] The switch layer 3 is formed of the resistance variable material of the present invention and exhibits OTS characteristics. More specifically, the switch layer 3 is preferably composed of a thin film (resistance variable film). The resistance state of the switch layer 3 changes according to the applied voltage. That is, when a voltage above the threshold voltage is applied, it becomes a low resistance state (ON state). In addition, when a voltage of 1 / 2 of the threshold voltage is applied, it becomes a high resistance state (OFF state). In addition, in this embodiment, the switch layer 3 is amorphous and does not cause a phase change due to the application of voltage. In other words, the switch layer 3 does not undergo a phase change to crystalline (crystalline) due to the application of voltage.

[0094] The switching layer 3 is arranged in contact with at least one electrode. In other words, the switching layer 3 is preferably arranged on the first electrode 1. More specifically, the first electrode 1 is preferably arranged on the switching layer 3. Furthermore, the second electrode 2 is preferably arranged at a position opposite the first electrode 1 across the switching layer 3.

[0095] The thickness of the switching layer 3 can be appropriately designed based on the required threshold voltage. The upper limit of the thickness of the switching layer 3 is preferably 300 nm or less, 200 nm or less, and particularly preferably 100 nm or less. Excessive thickness can easily lead to excessively high threshold voltages. The lower limit of the thickness of the switching layer 3 is preferably 1 nm or more, 2 nm or more, 5 nm or more, 10 nm or more, or 30 nm or more, and particularly preferably greater than 50 nm.

[0096] In the switching element 10, it is preferable that the ionicity of the switching layer 3 is σ ' and hybridization (hybridity) r π -1 More specifically, the ionicity of the switching layer 3 is σ ' is preferably 0.05 or more. Ionicity r σ The upper limit of ' is not particularly limited, and can be, for example, 0.30 or less, 0.25 or less, and particularly 0.20 or less. π -1 It is preferably 2.0 or less, and particularly preferably 1.9 or less. π -1 The lower limit of is not particularly limited, for example, it is preferably 1.0 or more, 1.1 or more, 1.2 or more, and particularly preferably 1.3 or more. σ ′ and hybrid r π -1 When the above values ​​are met, the OFF current density can be reduced while maintaining the stability of the amorphous state. σ ′ and hybrid r π -1 It can be calculated by the following formula 1 and formula 2 described in non-patent document 1. Here, r s and r p represents the orbital radius of s and p, n i 、n j It represents the number of atoms per unit formula of chemical species i (anion) and chemical species j (cation).

[0097]

[0098] The switching element 10 of this embodiment preferably increases the carrier activation energy as the applied voltage increases. For example, with respect to the switching element 10, when the carrier activation energy when an applied voltage of 0.15V is applied to the switching layer 3 is a (eV), and the carrier activation energy when an applied voltage of 0.30V is applied to the switching layer 3 is b (eV), it is preferred to satisfy a / b<1. By exhibiting the above characteristics, even if the applied voltage becomes larger, the OFF current density is difficult to increase, and the ON / OFF current ratio becomes larger. Here, the carrier activation energy refers to the energy required for electrons to transform into a conductive state, and can be calculated as follows. First, a voltage is applied to the switching element 10 at different temperatures, and the current value at this time is measured. The range of the temperature and the applied voltage at this time is not limited. For example, the temperature can be 30°C to 80°C, and the applied voltage can be 0V to 0.30V. Then, the carrier activation energy can be calculated using the following formula (3) based on the current value at any voltage value and the temperature at the time of measurement. Wherein, I represents the current, E represents the current, and a represents the carrier activation energy, k represents the Boltzmann constant, T represents the absolute temperature, and C represents a constant.

[0099]

[0100] The switching element 10 of this embodiment preferably exhibits a threshold voltage that increases with heating. For example, the threshold voltage of the switching element 10 at 80°C is preferably at least 1.05 times, and particularly preferably at least 1.1 times, the threshold voltage at room temperature (25°C). This characteristic prevents the OFF current density from increasing even at high temperatures, where the kinetic energy of electrons increases. This allows the ON / OFF current ratio to remain high even at high temperatures, resulting in excellent heat resistance.

[0101] The switching element 10 of this embodiment preferably has a Schottky barrier height that increases as the temperature rises. For example, the Schottky barrier height of the switching element 10 at 80°C is preferably 1.01 times or more of the Schottky barrier height at 30°C, and particularly preferably 1.02 times or more. By exhibiting the above characteristics, the movement of carriers is hindered, thereby reducing the OFF current density. Therefore, it is easy to increase the ON / OFF current ratio. In addition, the Schottky barrier height It can be calculated by the following formula (4). s represents the saturation current, A represents the contact area, A* represents the Richardson constant, q represents the elementary charge, k represents the Boltzmann constant, and T represents the absolute temperature.

[0102]

[0103] <Memory Element>

[0104] Figure 2This is a schematic cross-sectional view of a memory element according to one embodiment of the present invention. Memory element 21 includes a first electrode 11, a second electrode 12, and a switching memory layer 4 disposed on a principal surface of first electrode 11. Second electrode 12 is disposed opposite first electrode 11. In this embodiment, switching memory layer 4 is disposed between first electrode 11 and second electrode 12. In other words, memory element 21 according to this embodiment includes switching memory layer 4, first electrode 11 disposed on one principal surface of switching memory layer 4, and second electrode 12 disposed on the other principal surface of switching memory layer 4. Switching memory layer 4 is formed of a variable resistance film.

[0105] Inorganic materials can be used for the first electrode 11 and the second electrode 12. Metal materials and ceramic materials can be used as inorganic materials. Preferred metal materials include tungsten, titanium, copper, and platinum. Preferred ceramic materials include tungsten nitride and titanium nitride.

[0106] The thickness of the first electrode 11 and the second electrode 12 can be appropriately designed. For example, the thickness of the first electrode 11 and the second electrode 12 is preferably 200 nm or less, 100 nm or less, 80 nm or less, or 60 nm or less, and particularly preferably 50 nm or less. The smaller the thickness of the first electrode 11 and the second electrode 12, the easier it is to increase the capacity of the memory device. The lower limit of the thickness of the first electrode 11 and the second electrode 12 is preferably 1 nm or more, and particularly preferably 2 nm or more.

[0107] The memory element 21 is a resistance-variable memory element, including a switch memory layer 4 having both a storage function and a switch element function. For example, by applying a voltage greater than a specified voltage to the switch memory layer 4, it can be changed to a low resistance state LR1 and information can be recorded. Furthermore, when the applied voltage is reduced from the low resistance state LR1, the state becomes a high resistance state HR1 while information is recorded. Furthermore, when a read voltage is applied without performing an erase operation, the state becomes a low resistance state LR2. On the other hand, if a read voltage is applied when no information is recorded or in a high resistance state after an erase operation, the state becomes a high resistance state HR2. At this time, by making LR2 and HR2 correspond to 1 and 0, respectively, information can be recorded. In addition, the operation method is not limited to the above method. For example, after recording information, the applied voltage is set to 0, and when a read voltage is applied, it becomes LR2. On the other hand, if a read voltage is applied after an erase operation, it becomes HR2, so by making 1 and 0 correspond to it, respectively, information can be recorded.

[0108] The upper limit of the area of ​​the first electrode 11 and the second electrode 12 is preferably 1,000,000 nm, for example. 2 Below, 562500nm 2 Below, 250000nm 2Below, 62500nm 2 Below, 10000nm 2 Below, 6400nm 2 Below, 2500nm 2 Below, particularly preferably 1600nm 2 The lower limit of the area of ​​the first electrode 11 and the second electrode 12 is not particularly limited, but can be 1 nm from the viewpoint of manufacturing cost. 2 Above, especially 2nm 2 The upper limit of the contact area between the first electrode 11 and the switch memory layer 4 or the contact area between the second electrode 12 and the switch memory layer 4 is preferably 1,000,000 nm. 2 Below, 562500nm 2 Below, 250000nm 2 Below, 62500nm 2 Below, 10000nm 2 Below, 6400nm 2 Below, 2500nm 2 Below, particularly preferably 1600nm 2 There is no particular limit on the lower limit of the contact area between the first electrode 11 and the switch memory layer 4 and / or the contact area between the second electrode 12 and the switch memory layer 4. However, from the perspective of manufacturing cost, for example, 1 nm may be sufficient. 2 Above, especially 2nm 2 The contact area between the electrode and the switch storage layer 4 may be such that at least one of the contact area between the first electrode 11 and the switch storage layer 4 and the contact area between the second electrode 12 and the switch storage layer 4 satisfies the above value, and more preferably, both contact areas satisfy the above value.

[0109] Storage device

[0110] (First embodiment)

[0111] The storage device of this embodiment preferably includes a switching element, and more preferably includes a switching element and a storage element. In addition, when including a switching element and a storage element, the storage device of the present invention is preferably composed of a stacked body in which the switching element and the storage element are stacked. More specifically, the storage device of this embodiment is a storage device including a stacked body in which the switching element and the storage element are stacked, the switching element including a switching layer and a first electrode arranged on the switching layer, the switching layer being composed of a resistance variable material, and the resistance variable material having an OFF current density of 3.1×10 2 A / cm2 Hereinafter, the memory element is preferably constituted by any one of a resistance change memory element, a magnetoresistive memory element, a phase change memory element, and a ferroelectric memory element.

[0112] Figure 3 is a schematic perspective view of a storage device according to a first embodiment of the present invention. Figure 4 1 is an enlarged schematic perspective view of the storage device according to the first embodiment of the present invention. Figure 3 and Figure 4 As shown, memory device 100 includes a switching element 10, a memory element 20, a word line 30, and a bit line 40. The bit line 40 is perpendicular to the word line 30 in a plan view. The switching element 10 and the memory element 20 are arranged at the intersection of the word line 30 and the bit line 40 in a plan view. That is, memory device 100 of this embodiment is a so-called cross-point memory device.

[0113] Figure 5 This is a schematic perspective view of a modified example of the memory device of the first embodiment of the present invention. Memory device 200 includes a switching element 10, a memory element 20, a word line 30, and a bit line 40. The bit line 40 is arranged in a through-hole provided in the word line 30. The memory element 20 and the switching element 10 are arranged on the periphery of the bit line 40. In the switching element 10, the first electrode 1 is arranged on the outer peripheral surface of the switching layer 3, and the second electrode 2 is arranged on the inner peripheral surface opposite to the first electrode 1 across the switching layer 3. In other words, the memory device 200 of this modified example is a so-called BiCS-type memory device. As such, the memory device of the present invention is not limited to a cross-point memory device, but may be a variety of memory devices.

[0114] Any memory element such as a resistance change memory element, a magnetoresistive memory element, a phase change memory element, or a ferroelectric memory element can be used as the memory element 20. Preferred embodiments of each memory element will be described below.

[0115] The resistance variable memory element includes a resistance variable layer. More specifically, the resistance variable memory element preferably includes a stack of upper and lower electrodes sandwiching the resistance variable layer. The resistance variable layer is preferably composed of a metal oxide material, a metal nitride material, or a chalcogenide material. The metal oxide material is preferably selected from NiO x 、NbO x 、TiO x 、TaO x , HfO x 、ZrO x 、MoO x , WO x and Pr 1-x Ca x At least one of MnO3 (PCMO). Metal nitride materials are preferably selected from SiNx 、AlN x 、ZrN x 、NiN x 、CuN x 、CrN x The chalcogenide material is preferably at least one selected from the group consisting of Ge-Te, Sb-Te, Ge-Sb-Te, Si-Sb-Te, Ge-Ga-Te, In-Sb-Te, Ge-Se-As, and Ge-Se-As-Te. The variable resistance layer may also be composed of carbon nanotubes.

[0116] In the resistance variable memory element, the upper electrode and / or the lower electrode are preferably formed of at least one selected from tungsten, titanium, copper, platinum, tungsten nitride, and titanium nitride. Tungsten, titanium, copper, and platinum are preferred as metal materials. Tungsten nitride and titanium nitride are preferred as ceramic materials.

[0117] The magnetoresistive memory element comprises a laminate (TMR element) of an insulator layer sandwiched between ferromagnetic layers. The insulator layer is composed of an insulator, preferably at least one selected from MgO, CaO, SrO, and Al2O3. The thickness of the insulator layer is preferably 0.1 nm to 3 nm. The ferromagnetic layer is composed of a ferromagnetic material, preferably at least one selected from CoFeB, FeB, NiFe, MnIr, Fe, CoPt, CoNi, Co, Ni, Pt, Ni, and Mn.

[0118] The ferroelectric memory element includes a ferroelectric layer. More specifically, the ferroelectric memory element preferably includes a stack of upper and lower electrodes sandwiching the ferroelectric layer. The ferroelectric layer is preferably composed of a ferroelectric containing hafnium oxide, for example, preferably composed of hafnium oxide doped with at least one selected from Si, Zr, Ge, Gd, La, Y, and Yb. Alternatively, the ferroelectric layer may be composed of at least one selected from lead zirconate titanate (PZT), strontium bismuth tantalate (SBT), and bismuth ferrite (BFO).

[0119] The phase-change memory element is a memory layer composed of a phase-change material. More specifically, the phase-change memory element preferably includes a stack of upper and lower electrodes sandwiching a phase-change layer. The phase-change layer is preferably composed of a chalcogenide material. For example, the chalcogenide material is preferably at least one selected from Ge-Te, Sb-Te, Ge-Sb-Te, Si-Sb-Te, Ge-Ga-Te, In-Sb-Te, Cu-Ge-Te, Cr-Ge-Te, Mn-Te, Ge-Se-As, and Ge-Se-As-Te.

[0120] (Second embodiment)

[0121] The storage device of the present invention is not limited to a structure including a switching layer and a storage element. For example, the storage device of the present invention may also be a structure including only a switching element. In this case, the switching element can function as a switching element and a storage element. For example, the storage device of this embodiment preferably includes a resistance-variable storage element (storage element 21) having the storage function and the switching element function. In this embodiment, by using a resistance-variable storage element having the storage function and the switching element function, information can be recorded in the storage element even if a switching element is not included. Of course, in the storage device of this embodiment, any switching element may also be included.

[0122] Figure 6 : is a schematic perspective view of a storage device according to a second embodiment of the present invention. Figure 6 As shown, memory device 101 includes memory element 21, word line 30, and bit line 40. Bit line 40 is perpendicular to word line 30 in plan view. Memory element 21 is arranged at the intersection of word line 30 and bit line 40 in plan view. That is, memory device 101 of this embodiment is a so-called cross-point memory device.

[0123] Figure 7 : is a schematic perspective view of a modified example of the storage device of the second embodiment of the present invention. Figure 7 As shown, memory device 201 includes memory element 21, word line 30, and bit line 40. Bit line 40 is disposed in a through-hole provided in word line 30. Furthermore, memory element 21 is disposed on the periphery of bit line 40. In other words, memory device 201 in this embodiment is a so-called BiCS-type memory device. Thus, in this embodiment, the memory device is not limited to a cross-point memory device and may be a variety of memory devices.

[0124] Example

[0125] Hereinafter, the present invention will be described based on examples, but the present invention is not limited to these examples.

[0126] [Table 1]

[0127]

[0128] [Table 2]

[0129]

[0130] [Table 3]

[0131]

[0132] [Table 4]

[0133]

[0134] The Examples and Comparative Examples were prepared as follows. First, a quartz glass ampoule was heated and evacuated, and the raw materials were mixed to the composition shown in Table 1. The raw materials were then placed in the quartz glass ampoule. The quartz glass ampoule was then sealed with an oxygen burner. The sealed quartz glass ampoule was then placed in a melting furnace, heated at a rate of 10°C to 40°C / hour to a temperature of 650°C to 1000°C, and then held at this temperature for 6 to 12 hours. During this holding period, the quartz glass ampoule was inverted to stir the melt. Finally, the quartz glass ampoule was removed from the melting furnace and rapidly cooled to room temperature to produce a variable resistance material.

[0135] The oxygen content of the obtained resistance variable material was measured by an inert gas fusion-infrared absorption method. The results are shown in Table 1.

[0136] Next, a switching element is made using a variable resistance material as a target. First, a W electrode with a thickness of 50nm is formed (film-formed) on a Si / SiO2 substrate. Next, a SiO2 insulating layer with a thickness of 100nm is formed on the W electrode. Then, a focused ion beam device (manufactured by JEOL, JIB-4600F) is used to form a Φ500nm hole in the SiO2 insulating layer and the W electrode layer. Next, a 150nm thick film of a variable resistance material is formed in the formed hole to form a switching layer. Finally, a 150nm thick W electrode is further formed on the switching layer to make a switching element. The film formation is performed by Ar sputtering in a reduced pressure atmosphere.

[0137] The obtained switching element was used to determine the OFF current density, ON current density, ON / OFF current ratio, and threshold voltage. The results are shown in Table 2.

[0138] The OFF current density, ON current density, ON / OFF current ratio and threshold voltage are calculated as follows. First, a voltage of 0V to 10V is applied to the switching element, and the current value flowing through the switching element and the threshold voltage are measured. The voltage applied at this time is not limited to DC voltage, AC voltage, pulse voltage, etc., but from the perspective of preventing heat accumulation in the switching element, measurement is performed with a pulse voltage. The threshold voltage is the voltage value when the resistance value changes sharply from a high resistance state to a low resistance state. The OFF current density is the value obtained by dividing the current value (OFF current value) flowing when a voltage of 1 / 2 of the threshold voltage is applied by the contact area with the electrode. The ON current density is the value obtained by dividing the current value (ON current value) flowing when a voltage greater than the threshold voltage is applied by the contact area with the electrode. The ON / OFF current ratio is calculated by dividing the ON current value by the OFF current value.

[0139] The thin film sample used for carrier mobility measurement was prepared by depositing a 150 nm thick film of variable resistance material on a Si / SiO2 substrate by Ar sputtering. The carrier mobility of the resulting thin film sample was measured at 30°C using a resistivity-Hall system (ResiTest8308, manufactured by TOYO Corporation). The results are shown in Table 2.

[0140] Figure 8 The ionicity of the switching layer is plotted. σ ′ and hybrid r π -1 As shown in the figure. Figure 8 As shown, the ionicity of the switching layer of the embodiment is σ ' satisfies 0.05 or more, hybrid r π -1 Satisfy 2.0 or below.

[0141] As shown in Table 1 and Table 2, the carrier mobility of the resistance variable materials of Examples 1 to 7 is 2.6×10 - 3 cm 2 / Vs or less, the OFF current density is 2.55×10 2 A / cm 2 In addition, the logarithm of the ON / OFF current ratio x is 10 x is 4.3 to 6.6. On the other hand, the carrier mobility of Comparative Example 1 is as high as 5.1×10 -3 cm 2 / Vs, the OFF current density is as high as 3.57×10 2 A / cm 2 In addition, the logarithm of the ON / OFF current ratio x is 10 x is as small as 3.9.

[0142] Table 3 shows the change in carrier activation energy when a voltage is applied to the switching element, and Table 4 shows the relationship between the absolute temperature of the switching element and the Schottky barrier height. As shown in Table 3, in Example 2, when the carrier activation energy when a voltage of 0.15V is applied to the switching layer is set to a (eV), and when the carrier activation energy when a voltage of 0.30V is applied to the switching layer is set to b (eV), a / b < 1 is satisfied. In addition, as shown in Table 4, in Example 2, the Schottky barrier height at 80°C is Schottky barrier height at 30°C 1.04 times of that.

[0143] Industrial applicability

[0144] The variable resistance material of the present invention can be applied to switching elements that can be used in memory devices of a variable resistance type, a magnetoresistive type, a phase change type, a ferroelectric type, or the like.

[0145] Description of Reference Signs

[0146] 1.11 1st electrode

[0147] 2.12 Second electrode

[0148] 3 Switch Layer

[0149] 4 switch storage layer

[0150] 10 Switching elements

[0151] 20, 21 Storage Components

[0152] 30-character line

[0153] 40-bit line

[0154] 100, 101, 200, 201 storage devices.

Claims

1. A variable resistance material comprising Te, wherein: When the current density when a voltage of 1 / 2 of the threshold voltage is applied is defined as the OFF current density, the OFF current density is 3.1×10 2 A / cm 2 the following.

2. The resistance variable material according to claim 1, wherein: Furthermore, when the current density when a voltage higher than the threshold voltage is applied is defined as the ON current density, the ON current density is 1×10 6 A / cm 2 above.

3. The resistance variable material according to claim 1 or 2, wherein: The carrier mobility is 5×10 -3 cm 2 / Vs or less.

4. The resistance variable material according to claim 1 or 2, wherein: When the current density when a voltage greater than the threshold voltage is applied is defined as the ON current density, the ON / OFF current ratio obtained by dividing the ON current density by the OFF current density is 1×10 4 above.

5. The resistance variable material according to claim 1 or 2, wherein: The threshold voltage is in the range of 0.5V to 10V.

6. The resistance variable material according to claim 1 or 2, wherein: In terms of atomic %, it contains 0.1% to 50% of Ge and 40% to 90% of Te.

7. The resistance variable material according to claim 1 or 2, wherein: It contains 1% to 59% of Si+Al+Ga+Sn+Bi+Cu+Ag+Zn+Y+In+Ca+Mg in atomic %.

8. The resistance variable material according to claim 1 or 2, wherein: The Sb content is 0% or more and less than 5% in atomic %.

9. The resistance variable material according to claim 1 or 2, wherein: It contains virtually no Sb, Se, and As.

10. The resistance variable material according to claim 1 or 2, wherein: The oxygen content is less than 1 atomic %.

11. The resistance variable material according to claim 1 or 2, wherein: The resistance variable material is a thin film.

12. A material for a switching element, characterized in that: Composed of the resistance variable material according to claim 1 or 2.

13. A switch layer, characterized in that: Composed of the resistance variable material according to claim 1 or 2.

14. A switching element, characterized in that: include: The switch layer according to claim 13; and A first electrode is disposed on the switching layer.

15. A switching element, characterized in that: include: Switch layer; a first electrode disposed on the switch layer; and a second electrode disposed at a position opposing the first electrode across the switching layer; The switching layer is composed of a resistance variable material containing Te, and when a current density when a voltage half of a threshold voltage is applied is defined as an OFF current density, the OFF current density is 3.1×10 2 A / cm 2 the following.

16. The switching element according to claim 15, wherein: The first electrode is arranged on the outer peripheral surface of the switching layer, The second electrode is arranged on the inner peripheral surface of the switching layer.

17. The switching element according to claim 15 or 16, wherein: The first electrode and the second electrode are at least one selected from tungsten, titanium, copper, platinum, tungsten nitride, and titanium nitride.

18. The switching element according to claim 15 or 16, wherein: The ionicity of the switching layer σ ′ and hybrid r π -1 Satisfy the following values, r σ ′≥0.05， r π -1 ≤2.0。 19. The switching element according to claim 15 or 16, wherein: When the carrier activation energy when a voltage of 0.15 V is applied to the switching layer is represented by a, and the carrier activation energy when a voltage of 0.30 V is represented by b, a / b<1 is satisfied.

20. A storage device, characterized in that: The switch element according to claim 15 or 16 is included.

21. A storage device, characterized in that: include: The switching element according to claim 15 or 16; and Storage element.

22. A storage device, characterized in that: A stacked body including a switching element and a memory element, The switching element includes a switching layer and a first electrode arranged on the switching layer. The switching layer is made of a resistance variable material. When the current density when a voltage of 1 / 2 of the threshold voltage is applied is defined as the OFF current density, the OFF current density is 3.1×10 2 A / cm 2 the following, The memory element is composed of any one of a resistance change memory element, a magnetoresistive memory element, a phase change memory element, and a ferroelectric memory element.

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