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 a stable switching action. This resistance change material contains, in atomic%, 40-90% of Te, more than 0% but not more than 40% of Ge, and more than 0% but not more than 40% of Ga, and in an XPS spectrum measured by X-ray photoelectron spectroscopy, the apex of an XPS peak Px1 caused by the Te3d5 / 2 orbital is shifted toward the lower energy side than the apex of an XPS peak Px1GT caused by the Te3d5 / 2 orbital of amorphous GeTe5.

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 intersect orthogonally with the word lines when viewed from above, and memory elements and switching elements arranged at the intersection of the two when viewed from above. Conventional technology uses triodes (transistors) and diodes 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 Summary of the Invention

[0008] Technical problem to be solved by the invention

[0009] 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.

[0010] 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 capable of obtaining a stable switching action.

[0011] Technical means for solving technical problems

[0012] Each embodiment of a variable resistance material, a switching element material, a switching layer, a switching element, and a memory device for solving the above-mentioned technical problems will be described.

[0013] The resistance variable material of embodiment 1 is characterized by containing, in atomic percent, 40% to 90% Te, greater than 0% and less than 40% Ge, and greater than 0% and less than 40% Ga. In an XPS spectrum measured by X-ray photoelectron spectroscopy, the apex of the XPS peak Px1 due to the Te 3d 5 / 2 orbital is shifted toward a lower energy side compared to the apex of the XPS peak Px1GT due to the Te 3d 5 / 2 orbital of amorphous GeTe 5 . The term "amorphous GeTe 5 " in the present invention refers to GeTe 5 produced by high-frequency magnetron sputtering using Ar gas.

[0014] In the resistance variable material of embodiment 2, in embodiment 1, the top of the XPS peak Px1 is preferably shifted toward the lower energy side by 0.05 eV or more from the top of the XPS peak Px1GT.

[0015] In the resistance variable material of embodiment 3, in embodiment 1 or embodiment 2, it is preferable that the half-value width Px1hw of the XPS peak Px1 is larger than the half-value width Px1GThw of the XPS peak Px1GT.

[0016] In the variable resistance material of embodiment 4, in embodiment 3, the ratio of the half-value width Px1hw of the XPS peak Px1 to the half-value width Px1GThw of the XPS peak Px1GT (Px1hw / Px1GThw) is preferably 1.01 or more.

[0017] In any one of modes 1 to 4, the resistance change material of mode 5 preferably has a half-value width Px2hw of the XPS peak Px2 caused by the Ge3d orbital in the XPS energy spectrum that is larger than the half-value width Px2GThw of the XPS peak Px2GT caused by the Ge3d orbital of the amorphous GeTe5.

[0018] In the resistance variable material of embodiment 6, in embodiment 5, the ratio of the half-value width Px2hw of the XPS peak Px2 to the half-value width Px2GThw of the XPS peak Px2GT (Px2hw / Px2GThw) is preferably 1.01 or more.

[0019] The resistance variable material of method 7 is characterized in that it contains 40% to 90% Te and greater than 0% and less than or equal to 40% Ge in atomic %, and in the XPS energy spectrum measured by X-ray photoelectron spectroscopy, it has at least 3 peak vertices in the binding energy range of 15eV to 44eV.

[0020] The resistance variable material of embodiment 8 is characterized by containing, in atomic percent, 40% to 90% Te, greater than 0% and less than 40% Ge, and greater than 0% and less than 40% Ga, and having a Raman spectrum measured by Raman spectroscopy, a peak Pr1 formed by overlapping Raman peaks due to Ge-Te bonds and Te-Te bonds, at a wave number of 118 cm -1 ~130cm -1 In the range of , the half-value width Pr1hw of the Raman peak Pr1 is larger than the half-value width Pr1GThw of the Raman peak Pr1GT of amorphous GeTe5.

[0021] In the resistance variable material of aspect 9, in aspect 8, the ratio of the half-value width Pr1hw of the Raman peak Pr1 to the half-value width Pr1GThw of the Raman peak Pr1GT (Pr1hw / Pr1GThw) is preferably 1.05 or more.

[0022] In the resistance variable material of embodiment 10, it is preferable that, in embodiment 8 or embodiment 9, the apex of the Raman peak Pr1 is shifted toward a higher wave number side than the apex of the Raman peak Pr1GT.

[0023] The resistance variable material of embodiment 11 is preferably such that, in embodiment 10, the apex of the Raman peak Pr1 is shifted to the higher wave number side by 0.1 cm relative to the apex of the Raman peak Pr1GT. -1 above.

[0024] The resistance variable material of embodiment 12 is preferably such that, in any one of embodiments 8 to 11, the apex of the Raman peak Pr2 due to the Te-Te bond is at a wave number of 135 cm -1 ~145cm -1 In the range of , the apex of the Raman peak Pr2 is shifted to the higher wavenumber side compared with the apex of the Raman peak Pr2GT caused by the Te-Te bond of amorphous GeTe5.

[0025] The resistance variable material of embodiment 13 is preferably such that, in embodiment 12, the apex of the Raman peak Pr2 is shifted by 0.1 cm toward the higher wave number side compared to the apex of the Raman peak Pr2GT. -1 above.

[0026] The resistance variable material of mode 14 is characterized in that it contains 40% to 90% Te and greater than 0% and less than or equal to 40% Ge in atomic %, and the activation energy Ea during crystallization of the amorphous thin film composed of the resistance variable material is greater than 240 kJ / mol.

[0027] The resistance variable material of embodiment 15 is preferably such that, in any of embodiments 1 to 14, the number of cycles is 5×10 2 times or more.

[0028] The resistance variable material of embodiment 16 is preferably such that, in any of embodiments 1 to 15, the number of cycles x (times) and the activation energy Ea (kJ / mol) satisfy the relationship of the following formula (1).

[0029] log 10 x≥0.011Ea+0.1...Formula (1)

[0030] The resistance variable material of embodiment 17 preferably contains 0 to 20 atomic % of Sb in any of embodiments 1 to 16.

[0031] The resistance variable material of embodiment 18 preferably contains substantially no Sb, Se, or As in any of embodiments 1 to 17.

[0032] The resistance variable material of embodiment 19 is preferably a thin film in any of embodiments 1 to 18.

[0033] The switching element material according to aspect 20 is characterized by being composed of the resistance variable material according to any one of aspects 1 to 19.

[0034] The switching layer of aspect 21 is characterized by being composed of the resistance variable material according to any one of aspects 1 to 19.

[0035] The switching element of aspect 22 is characterized by including a first electrode and the switching layer of aspect 21 arranged on the first electrode.

[0036] In the switching element of aspect 23, it is preferable that the switching element according to aspect 22 include a second electrode disposed at a position opposing the first electrode with the switching layer interposed therebetween.

[0037] A storage device of mode 24 is characterized by including a switching element and a storage element of mode 22 or mode 23.

[0038] Effects of the Invention

[0039] According to the present invention, a resistance variable material, a switching element material, a switching layer, a switching element, and a memory device capable of achieving a stable switching action can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is a schematic cross-sectional view of a switching element according to one embodiment of the present invention.

[0041] Figure 2 is a schematic cross-sectional view of a memory element according to one embodiment of the present invention.

[0042] Figure 3 This is a schematic perspective view of a storage device according to the first embodiment of the present invention.

[0043] Figure 4 This is a schematic enlarged perspective view of the storage device according to the first embodiment of the present invention.

[0044] 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.

[0045] Figure 6 It is a schematic perspective view of a storage device according to a second embodiment of the present invention.

[0046] Figure 7 It is a schematic perspective view of a modified example of the storage device according to the second embodiment of the present invention.

[0047] Figure 8 Graphs showing the XPS spectra of Te 3d 5 / 2 orbitals of the resistance variable materials of Examples and Comparative Examples.

[0048] Figure 9 Graphs showing the XPS spectra of Ge 3d orbitals in the resistance variable materials of Examples and Comparative Examples.

[0049] Figure 10 Graphs showing the XPS spectra of Te 4d orbitals of the resistance variable materials of Examples and Comparative Examples.

[0050] Figure 11 Graphs showing the XPS spectra of Ga 3d orbitals in the resistance variable materials of Examples and Comparative Examples.

[0051] Figure 12 Graphs showing Raman spectra of variable resistance materials of Examples and Comparative Examples.

[0052] Figure 13 This is a graph showing the relationship between activation energy and cycle number for variable resistance materials and switching elements in Examples and Comparative Examples. DETAILED DESCRIPTION

[0053] Hereinafter, preferred embodiments will be described. However, the following embodiments are merely examples, and the present invention is not limited to the following embodiments.

[0054] <Resistance Variable Materials>

[0055] [XPS spectrum]

[0056] (First Invention)

[0057] In a broad aspect of the variable resistance material of the present invention, it is characterized by containing, in atomic %, 40% to 90% Te, greater than 0% and less than 40% Ge, and greater than 0% and less than 40% Ga, and in an XPS spectrum measured by X-ray photoelectron spectroscopy (XPS), the apex of the XPS peak Px1 due to the Te3d5 / 2 orbital is shifted to the lower energy side compared to the apex of the XPS peak Px1GT due to the Te3d5 / 2 orbital of amorphous GeTe5 (first invention). The electron density around Te in the variable resistance material having this structure is high. Therefore, the covalent bond of the Te bond is higher than that of GeTe5, and the stability of the amorphous state is high. Therefore, the variable resistance material of the present invention does not undergo phase transformation into a crystalline state (crystalline) in response to an applied voltage, and a stable switching action can be obtained. In addition, in the present invention, the switching action refers to the characteristic that the resistance changes according to the applied voltage. In the following description, the switching action may also be described as a switching characteristic or an OTS characteristic. The values ​​of the binding energy of the XPS spectrum mentioned below are values ​​corrected using the XPS peak Px1C due to the C1s orbital. In the present invention, "C" refers to hydrocarbons.

[0058] The peak of the XPS peak Px1 due to the Te3d5 / 2 orbital is within the binding energy range of 570 eV to 580 eV. More specifically, the peak of the XPS peak Px1 is preferably 570 eV or higher, particularly preferably 571 eV or higher, and preferably 580 eV or lower, 578 eV or lower, 576 eV or lower, and particularly preferably 574 eV or lower.

[0059] The apex of the XPS peak Px1 is preferably shifted toward the lower energy side by 0.05 eV or more, 0.06 eV or more, 0.08 eV or more, and particularly preferably by 0.10 eV or more, relative to the apex of the XPS peak Px1GT. By shifting the apex of the XPS peak Px1 toward the lower energy side, the covalent bond of the Te bond is further improved, and the stability of the amorphous state is further improved. The upper limit of the shift is not particularly limited, and for example, it can be 0.3 eV or less.

[0060] The half-value width Px1hw of the XPS peak Px1 is preferably larger than the half-value width Px1GThw of the XPS peak Px1GT. With this structure, the electron distribution around Te is broadened, and the overlap of electrons between orbitals is increased. This enhances covalent bonding and further improves the stability of the amorphous state. Consequently, a more stable switching action is achieved.

[0061] The half-value width ratio (Px1hw / Px1GThw) is preferably 1.01 or greater, 1.02 or greater, 1.04 or greater, 1.06 or greater, 1.08 or greater, or 1.10 or greater, and particularly preferably 1.12 or greater. By increasing the half-value width Px1hw, the covalent bonding property of the Te bond is further improved, and the stability of the amorphous state is further improved. The upper limit of the half-value width ratio is not particularly limited, and for example, it can be 1.20 or less.

[0062] The variable resistance material of the present invention preferably contains, in atomic percentages, 40% to 90% Te, greater than 0% and less than 40% Ge, and greater than 0% and less than 40% Ga. In an XPS spectrum measured using X-ray photoelectron spectroscopy (XPS), the energy difference |Px1-Px1C| between the apex of the XPS peak Px1 due to the Te 3d5 / 2 orbital and the apex of the XPS peak Px1C due to the C1s orbital is preferably smaller than the energy difference |Px1GT-Px1C| between the apex of the XPS peak Px1GT due to the Te 3d5 / 2 orbital and the apex of the XPS peak Px1C in amorphous GeTe5. In a variable resistance material having this structure, the covalent nature of the Te bond is higher than that of GeTe5, resulting in greater stability in the amorphous state. Consequently, a more stable switching action can be achieved.

[0063] The peak of the XPS peak Px1C due to the C1s orbital is within the binding energy range of 279 to 294 eV. More specifically, the peak of the XPS peak Px1C is preferably at or above 281 eV, particularly preferably at or above 282 eV, and preferably at or below 288 eV, particularly preferably at or below 286 eV.

[0064] The energy difference ratio |Px1-Px1C| / |Px1GT-Px1C| is preferably 0.9999 or less, 0.9998 or less, and particularly preferably 0.9997 or less. By satisfying the above energy difference ratio, the stability of the amorphous state is further improved. The lower limit of the energy difference ratio is not particularly limited, and for example, it can be 0.98 or greater.

[0065] In the XPS spectrum of the variable resistance material of the present invention, the half-value width Px2hw of the XPS peak Px2 due to the Ge 3d orbital is preferably greater than the half-value width Px2GThw of the peak Px2GT due to the Ge 3d orbital in the amorphous GeTe5. With this structure, the electron distribution around Ge is broadened, and the overlap of electrons between orbitals is enhanced. As a result, the covalent bonding of Ge bonds is enhanced, further improving the stability of the amorphous state. Consequently, a more stable switching action can be achieved.

[0066] The peak of the XPS peak Px2 due to the Ge 3d orbital is within the binding energy range of 25 to 37 eV. More specifically, the peak of the XPS peak Px2 is preferably 25 eV or higher, 27 eV or higher, and particularly preferably 29 eV or higher, and preferably 35 eV or lower, 33 eV or lower, and particularly preferably 31 eV or lower.

[0067] The half-value width ratio (Px2hw / Px2GThw) is preferably 1.01 or greater, 1.015 or greater, and particularly preferably 1.02 or greater. By increasing the half-value width Px2hw, the covalent bonding of the Ge bond is further enhanced, and the stability of the amorphous state is further improved. The upper limit of the half-value width ratio is not particularly limited, and for example, it can be 1.20 or less.

[0068] In the XPS spectrum of the variable resistance material of the present invention, the apex of the XPS peak Px3 due to the Te 4d5 / 2 orbital is preferably shifted toward a lower energy level compared to the apex of the XPS peak Px3GT due to the Te 4d5 / 2 orbital in the amorphous GeTe5. The variable resistance material having this structure has a high electron density around Te. Consequently, the covalent nature of the Te bond is higher than that of GeTe5, resulting in greater stability in the amorphous state. Consequently, a more stable switching action can be achieved.

[0069] The binding energy at the top of the XPS peak Px3 due to the Te4d5 / 2 orbital is within the range of 35 to 44 eV. More specifically, the top of the XPS peak Px3 is preferably 35 eV or higher, 37 eV or higher, and particularly preferably 39 eV or higher, and preferably 44 eV or lower, 43 eV or lower, and particularly preferably 42 eV or lower. Within the binding energy range of 35 to 44 eV, an XPS peak due to the Te4d3 / 2 orbital exists at a higher energy than the peak due to the Te4d5 / 2 orbital.

[0070] The apex of the XPS peak Px3 is preferably offset to the low energy side by 0.05 eV or more, 0.06 eV or more, 0.08 eV or more, 0.10 eV or more, and particularly preferably 0.11 eV or more than the apex of the XPS peak Px3GT. By shifting the apex of the XPS peak Px3 to the low energy side, the covalent bond of the Te bond is further improved, and the stability of the amorphous state is further improved. The upper limit of the offset is not particularly limited, for example, it can be 0.3 eV or less.

[0071] The variable resistance material of the present invention further preferably has an XPS peak Px3 half-value width (Px3hw) due to the Te4d5 / 2 orbital that is larger than the half-value width (Px3GThw) of the peak Px3GT due to the Te4d5 / 2 orbital in the amorphous GeTe5. This structure broadens the electron distribution around Te in the variable resistance material, increasing the overlap of electrons between orbitals. This enhances covalent bonding and further improves the stability of the amorphous state, resulting in a more stable switching action.

[0072] The half-value width ratio (Px3hw / Px3GThw) is preferably 1.01 or more, 1.02 or more, 1.04 or more, 1.06 or more, 1.08 or more, 1.10 or more, 1.12 or more, and particularly preferably 1.15 or more. By increasing the half-value width Px3hw, the covalent bonding property of the Te bond is further improved, and the stability of the amorphous state is further improved. The upper limit of the half-value width ratio is not particularly limited, and for example, it can be 1.25 or less.

[0073] In the variable resistance material of the present invention, the peak of the XPS peak Px4a due to the Ga 3d orbital in the XPS spectrum is preferably shifted toward a lower energy level compared to the peak of the XPS peak Px4b due to the Ga 3d orbital in a variable resistance material that does not contain Ag. The electron density around Ga in a variable resistance material with this structure is high. Consequently, the covalent bonding strength of the Ga bond is higher than that of a variable resistance material that does not contain Ag, resulting in a more stable amorphous state. Consequently, a more stable switching action can be achieved.

[0074] The binding energy at the top of the XPS peak Px4a due to the Ga3d orbital is in the range of 15 to 25 eV. More specifically, the top of the XPS peak Px4a is preferably 15 eV or higher, 17 eV or higher, and particularly preferably 18 eV or higher, and is preferably 25 eV or lower, 23 eV or lower, 21 eV or lower, and particularly preferably 20 eV or lower.

[0075] The top of XPS peak Px4a is preferably more than 0.05eV, more than 0.06eV, particularly preferably more than 0.08eV to the low energy side than the top of XPS peak Px4b. By shifting the top of XPS peak Px4a to the low energy side, the covalent bond of Ga bond is further improved, and the stability of amorphous state is further improved. The upper limit of the offset is not particularly limited, for example, can be less than 0.3eV.

[0076] (Second Invention)

[0077] Another broad aspect of the variable resistance material of the present invention is characterized by containing, in atomic percent, 40% to 90% Te and greater than 0% to 40% Ge, and having at least three peaks within the binding energy range of 15 eV to 44 eV in an XPS spectrum measured using X-ray photoelectron spectroscopy (XPS) (Second Invention). A variable resistance material having peaks within this binding energy range not only increases the electron density around Te and Ge, but also broadens the electron distribution and increases the overlap of electrons between orbitals. Consequently, covalent bonding is enhanced, and the stability of the amorphous state is improved. Consequently, a stable switching action can be achieved.

[0078] As peaks observed in the range of binding energy 15eV to 44eV, the XPS peak Px2 (binding energy 25eV to 35eV) caused by the Ge3d orbital, the XPS peak Px3 (binding energy 35eV to 44eV) caused by the Te4d orbital, and the XPS peak Px4a (binding energy 15eV to 25eV) caused by the Ga3d orbital are preferred. However, the resistance variable material may also include XPS peaks caused by orbitals other than the above-mentioned orbitals in the XPS energy spectrum within the range of binding energy 15eV to 44eV. In addition, in any element, due to the spin-orbit interaction, the electron orbital is sometimes split into two peaks, but in this case, the number of peaks is counted as one. For example, the Te4d orbital is split into two peaks, the Te4d5 / 2 orbital and the Te4d3 / 2 orbital, but the number of peaks is counted as one.

[0079] [Raman spectroscopy]

[0080] (Third Invention)

[0081] Another broad aspect of the variable resistance material of the present invention is characterized in that, in terms of atomic %, the material contains 40% to 90% Te, greater than 0% and less than 40% Ge, and greater than 0% and less than 40% Ga. In a Raman spectrum measured by Raman spectroscopy, the peak of a Raman peak Pr1, which is a superposition of Raman peaks due to Ge-Te and Te-Te bonds, is at a wavenumber of 118 cm. -1 ~130cm -1 Within the range of , the half-value width Pr1hw of the Raman peak Pr1 is greater than the half-value width Pr1GThw of the Raman peak Pr1GT of the amorphous GeTe5 (the third invention). The covalent bonding property of the Te-Te bond in the resistance variable material having this structure is improved, and the stability of the amorphous state is improved. Therefore, a stable switching action can be obtained. In addition, the Raman peaks caused by the Ge-Te bond and the Te-Te bond overlap, making it difficult to separate the peaks. Therefore, the Raman peak Pr1 is treated as a peak caused by both the Ge-Te bond and the Te-Te bond.

[0082] The apex of the Raman peak Pr1 is at wave number 118 cm -1 ~130cm -1 More specifically, the apex of the Raman peak Pr1 is preferably at 118 cm -1 Above, 120cm -1 Above, particularly preferably at 123cm -1 Above, preferably at 130cm -1 Below, 128cm -1 Below, particularly preferably at 126cm -1 the following.

[0083] The half-value width ratio (Pr1hw / Pr1GThw) is preferably 1.01 or greater, 1.05 or greater, 1.10 or greater, or 1.15 or greater, and particularly preferably 1.20 or greater. As the half-value width Pr1hw increases, the covalent bonding property of the Te-Te bond is further enhanced, and the stability of the amorphous state is further improved. The upper limit of the half-value width ratio is not particularly limited, and for example, it can be 1.40 or less.

[0084] The variable resistance material of the present invention preferably has the apex of the Raman peak Pr1 shifted toward higher wavenumbers compared to the apex of the Raman peak Pr1GT. This structure of the variable resistance material exhibits a higher covalent Te-Te bond than GeTe5, resulting in a more stable amorphous state. Consequently, a more stable switching action can be achieved.

[0085] The apex of the Raman peak Pr1 is preferably shifted to the higher wave number side by 0.1 cm compared to the apex of the Raman peak Pr1GT. -1 Above, 0.4cm -1 Above, 0.7cm -1 More than, particularly preferably 1cm -1 By shifting the apex of the Raman peak Pr1 to the high wave number side, the covalent bond of the Te-Te bond is further improved, and the stability of the amorphous state is further improved. The upper limit of the shift amount is not particularly limited, for example, it can be 2 cm -1 the following.

[0086] The resistance variable material of the present invention preferably has a peak of the Raman peak Pr2 caused by the Te-Te bond at a wave number of 135 cm -1 ~145cm -1 Within the range of , the apex of the Raman peak Pr2 shifts toward higher wavenumbers compared to the apex of the Raman peak Pr2GT caused by Te-Te bonds in amorphous GeTe5. The covalent nature of the Te-Te bonds in a variable resistance material with this structure is higher than that of GeTe5, and the amorphous state is more stable. Consequently, a more stable switching action is achieved.

[0087] The apex of the Raman peak Pr2GT is preferably shifted to the higher wave number side by 0.1 cm -1 Above, 0.4cm -1 Above, 0.7cm -1 More than, particularly preferably 1cm -1 By shifting the apex of the Raman peak Pr1 to the high wave number side, the covalent bond of the Te-Te bond is further improved, and the stability of the amorphous state is further improved. The upper limit of the shift amount is not particularly limited, for example, it can be 3.5 cm -1 the following.

[0088] [Activation energy Ea]

[0089] (Fourth Invention)

[0090] Another broad aspect of the resistance change material of the present invention is characterized in that it contains 40% to 90% Te and greater than 0% and less than or equal to 40% Ge in atomic %, and the activation energy Ea during crystallization of the amorphous thin film composed of the resistance change material is greater than 240 kJ / mol (the fourth invention).

[0091] The activation energy Ea can be obtained using the Kissinger method. The details are as follows. First, an amorphous film with a thickness of 150 nm made of a resistance variable material is prepared. Then, while heating the amorphous film by changing the heating rate in the range of 5°C / min to 15°C / min, the resistance is measured using a two-terminal method. Then, the temperature at which the resistance drops sharply is taken as the crystallization temperature (crystallization temperature), and the activation energy during crystallization is calculated using the following formula (2). Among them, the measurement can be carried out not only in an inactive atmosphere such as argon and nitrogen, but also in an atmospheric atmosphere. Here, α represents the heating rate of the sample, Tx represents the crystallization temperature, R represents the gas constant, and C represents the constant.

[0092] ln(α / Tx 2 )=-(Ea / RTx)+C……Formula (2)

[0093] The lower limit of the activation energy Ea is 240 kJ / mol or more, preferably 250 kJ / mol or more, 270 kJ / mol or more, 285 kJ / mol or more, 300 kJ / mol or more, 330 kJ / mol or more, 350 kJ / mol or more, and particularly preferably 360 kJ / mol or more. The resistance variable material that meets the above activation energy has high activation energy when crystallized and high stability in the amorphous state. Therefore, from the viewpoint of further improving the cycle characteristics, the resistance variable material having the above activation energy is particularly useful. The upper limit of the activation energy Ea is not particularly limited, for example, it can be 500 kJ / mol or less, and particularly preferably 450 kJ / mol or less.

[0094] The first to fourth inventions described above can be implemented independently. However, the first to fourth inventions can also be implemented in combination with one another in part or in whole. Hereinafter, the first to fourth inventions may be collectively referred to as the present invention.

[0095] 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 (on / off current ratio) can be maintained even when repeatedly switched on and off. Specifically, the lower limit of the number of cycles (the number of times ON / OFF switching is repeated 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, particularly preferably 1×10 7 times or less.

[0096] In addition, the threshold voltage refers to the voltage value when the resistance value of the resistance variable material changes sharply from a high resistance state to a low resistance state. The voltage applied at this time (applied voltage) is not limited to a DC voltage, an AC voltage, a pulse voltage, etc., but from the viewpoint of preventing heat storage of the switching element, a pulse voltage is preferably used. The ON current value refers to the current value (ON current value) flowing when a voltage above the threshold voltage is applied. The OFF current value refers to the current value (OFF current value) flowing when a voltage of 1 / 2 of the threshold voltage is applied. The ON / OFF current ratio refers to the value obtained by dividing the ON current value by the OFF current value. The upper limit of the threshold voltage is preferably less than 10V, less than 8V, less than 6V, and particularly preferably less than 5V. By making the threshold voltage within the above range, it is possible to drive with less energy. The lower limit of the threshold voltage is not particularly limited and can be more than 0.5V, more than 1V, and particularly preferably more than 1.5V.

[0097] The variable resistance material of the present invention preferably satisfies the following relationship (1) when the number of cycles is x (times) and the activation energy is Ea (kJ / mol). A variable resistance material satisfying this relationship is particularly suitable as a switching element.

[0098] log 10 x≥0.011Ea+0.1...Formula (1)

[0099] The resistance variable material of the present invention contains 40% to 90% Te and greater than 0% and less than or equal to 40% Ge in atomic %. In particular, the resistance variable materials of the first invention and the third invention contain 40% to 90% Te, greater than 0% and less than or equal to 40% Ge, and greater than 0% and less than or equal to 40% Ga in atomic %. In addition, the resistance variable materials of the second invention and the fourth invention may contain greater than 0% and less than or equal to 40% Ga, or may not contain Ga. The reasons for specifying the composition in this way and the content of each component (component) are explained below. In addition, in the following description, "%" refers to "atomic %" unless otherwise specified. In addition, in the present invention, "x+y+z+······" refers to the total content of each component. Here, each component may not necessarily be contained as an essential component, and there may 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+······” and “x=0%, y=0%, A% to B% of z+······”.

[0100] The resistance variable material of the present invention contains at least Te. Te is a component that constitutes the resistance variable material and is used to obtain a switching effect. The Te content is 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 a switching effect. When the Te content is too high, the amorphous state tends to become unstable. In addition, the OFF current density tends to increase.

[0101] Ge is a component that stabilizes the amorphous state of the resistance variable material. The Ge content is greater than 0% to 40%. More specifically, the lower limit of the Ge content is preferably greater than 0%, greater than 0.1%, greater than 1%, greater than 3%, greater than 5%, greater than 7%, greater than 10%, greater than 11%, and particularly preferably greater than 13%. The upper limit of the Ge content is preferably less than 40%, less than 30%, and particularly preferably less than 20%. 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 a switching effect. In addition, the manufacturing cost tends to increase.

[0102] The lower limit of the Ge+Te content (the total amount of Ge and Te) is preferably greater than 40%, greater than 41%, greater than 45%, greater than 50%, greater than 60%, greater than 65%, greater than 70%, greater than 75%, and particularly preferably greater than 80%. The upper limit of the Ge+Te content is preferably less than 99%, less than 98%, less than 97%, and particularly preferably less than 95%. If the Ge+Te content is too low, the amorphous state tends to become unstable. In addition, it is difficult to obtain a switching effect. If the Ge+Te content is too high, it is difficult to obtain a switching effect.

[0103] Ga is a component that easily increases the electron density around Te by being introduced into the glass network. Therefore, it can reduce the OFF current and can particularly contribute to the improvement of the ON / OFF current ratio. The lower limit of the Ga content is preferably 0% or more, more than 0%, 1% or more, 2% or more, 3% or more, and particularly preferably 5% or more. The upper limit of the Ga 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, and particularly preferably 10% or less. When the Ga content is too much, the amorphous state tends to become unstable.

[0104] Ag is a component that particularly stabilizes the amorphous state, easily increases activation energy, and helps to increase the number of cycles. The lower limit of the Ag content is preferably 0% or more, more than 0%, 1% or more, 2% or more, 3% or more, 5% or more, and particularly preferably 6% or more. The upper limit of the 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, 11% or less, and particularly preferably 10% or less. When the Ag content is too high, the amorphous state tends to become unstable.

[0105] From the viewpoint of further stabilizing the amorphous state, the lower limit of the Ga+Ag content (the total amount of Ga and Ag) is preferably above 0%, more than 0%, above 0.1%, above 0.5%, above 1%, above 2%, above 3%, and particularly preferably above 5%. The upper limit of the Ga+Ag content is preferably below 59%, below 58%, below 55%, below 50%, below 45%, below 40%, below 35%, below 30%, below 25%, below 20%, below 15%, below 14%, below 13%, below 10%, and particularly preferably below 9%.

[0106] From the perspective of further reducing the OFF current value, 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.

[0107] From the perspective of further increasing the number of cycles, 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.

[0108] The resistance variable material of the present invention may contain the following components in addition to the above components.

[0109] Si, Al, Sn, Bi, Cu, Zn, Y, In, Ca, and Mg are components that tend to stabilize the amorphous state of the variable resistance material and improve the number of cycles. In the present invention, the number of cycles refers to 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. Furthermore, they are components that tend to increase the ON / OFF current ratio by reducing the OFF current. Therefore, the variable resistance material of the present invention preferably has a Si+Al+Sn+Bi+Cu+Zn+Y+In+Ca+Mg content (the total amount of Si, Al, Sn, Bi, Cu, Zn, Y, In, Ca, and Mg) of 0 to 59%. More specifically, the lower limit of the Si+Al+Sn+Bi+Cu+Zn+Y+In+Ca+Mg content is preferably 0% or more, 1% or more, and particularly preferably 2% or more. The upper limit of the Si+Al+Sn+Bi+Cu+Zn+Y+In+Ca+Mg 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, or 10% or less, and particularly preferably 9% or less. The above-mentioned content can also be translated as containing one or more components selected from Si, Al, Sn, Bi, Cu, Zn, Y, In, Ca, and Mg. If the content of these components is too low, the above-mentioned effects are difficult to achieve. If the content of these components is too high, the amorphous state tends to become unstable. In addition, it is difficult to achieve a switching effect. Furthermore, the lower limit of the content of each of Si, Al, Sn, Bi, Cu, 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 component of Si, Al, Sn, Bi, Cu, 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.

[0110] Sb is a component that easily destabilizes the amorphous state at high temperatures. Therefore, the Sb content is preferably 0% to 20%. More specifically, the upper limit of the Sb content is preferably 20% or less, 15% or less, 10% or less, 9% or less, less than 5%, 4% or less, 3% or less, or 2% or less, and it is particularly preferably substantially free of Sb. In this specification, "substantially free of Sb" means that the raw material is intentionally free of Sb, and does not exclude the inclusion of impurities. Objectively, it means that the content of each component is less than 0.1%.

[0111] 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.

[0112] 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.

[0113] The resistance variable material of the present invention preferably contains substantially no Sb, Se, and As. This facilitates further reduction of environmental load.

[0114] 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, B, C, N, F, Cl, Br and I may be contained in a total amount of 0% or more, 1% or more, and particularly 2% or more.

[0115] If 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 absent. Furthermore, 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 absent.

[0116] From the viewpoint of reducing environmental load, it is preferred that Cd, Tl, and Pb are substantially not contained.

[0117] 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 also be evaluated using TEM-EDX or SEM-EDX, which are attached to transmission electron microscopes (TEMs) or scanning electron microscopes (SEMs).

[0118] The resistance variable material of the present invention has a large ON / OFF current ratio and exhibits a stable switching action. Specifically, the ON / OFF current ratio is preferably 1×10 4 Above, 1×10 5 More than 1×10 6 By satisfying the above values, more excellent OTS characteristics can be obtained.

[0119] 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, facilitating a further increase in the number of cycles. The upper limit of the crystallization temperature Tx is not particularly limited, but can be, for example, 500°C or lower, 450°C or lower, and particularly preferably 400°C or lower.

[0120] 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.

[0121] 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.

[0122] 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.

[0123] 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 switching performance and can be suitably used as a material for the switching layer and a switching element having the switching layer.

[0124] 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.

[0125] 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.

[0126] By using the obtained variable resistance material as a target, a thin film (variable resistance film) having the above-mentioned composition can be formed.

[0127] 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.

[0128] The thin film production method is not particularly limited. PVD methods include sputtering, vacuum evaporation, and ion plating. Alternatively, methods such as CVD (Chemical Vapor Deposition) and ALD (Atomic Layer Deposition) can be used. Sputtering is particularly preferred for ease of composition and film thickness control.

[0129] Switching elements

[0130] Figure 1 This is a schematic cross-sectional view of a switching element according to one embodiment of the present invention. The switching element 10 includes a first electrode 1, a second electrode 2, and a switching layer 3 disposed on the principal surface of the first electrode 1. The second electrode 2 is disposed opposite the first electrode 1. In this embodiment, the switching layer 3 is disposed between the first and second electrodes 1 and 2. In other words, the switching element 10 according to this embodiment includes the switching layer 3, the first electrode 1 disposed on one principal surface of the switching layer 3, and the second electrode 2 disposed on the other principal surface of the switching layer 3.

[0131] The switching element 10 of the present invention is applicable to cross-point memory devices and BiCS (Bit-Cost Scalable) memory devices, which will be described later. In the case of BiCS memory devices, in the switching element 10 of the present invention, the first electrode 1 is preferably disposed on the outer peripheral surface of the switching layer 3, and the second electrode 2 is disposed on the inner peripheral surface of the switching layer 3.

[0132] 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.

[0133] The thickness of the first electrode 1 and the second electrode 2 can be appropriately designed. For example, the upper limits of the thickness of the first electrode 1 and the second electrode 2 are preferably 200 nm or less, 100 nm or less, 80 nm or less, or 60 nm or less, respectively, 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 limits of the thickness of the first electrode 1 and the second electrode 2 are preferably 1 nm or more, and particularly preferably 2 nm or more, respectively.

[0134] The switch layer 3 is composed 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 the present invention, the switch layer 3 is amorphous and does not undergo phase change due to voltage application. In other words, the switch layer 3 does not undergo phase change to crystalline (crystalline) due to voltage application.

[0135] 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. In other words, the first electrode 1 is preferably arranged on the switching layer 3. In addition, the second electrode 2 is preferably arranged at a position opposite the first electrode 1 with the switching layer 3 interposed therebetween.

[0136] 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.

[0137] <Memory Element>

[0138] 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 the 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 composed of a variable resistance film.

[0139] 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.

[0140] 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 are preferably 200 nm or less, 100 nm or less, 80 nm or less, or 60 nm or less, respectively, 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, particularly preferably 2 nm or more.

[0141] The memory element 21 is a resistance-variable memory element and includes a switch memory layer 4 having both a storage function and a switching element function. For example, by applying a voltage greater than a specified voltage to the switch memory layer 4, the switch memory layer 4 can be changed to a low resistance state LR1, thereby recording information. 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 while information is not 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. 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, the state becomes LR2. On the other hand, if a read voltage is applied after an erase operation, the state becomes HR2, so by making 1 and 0 correspond to each other, information can be recorded.

[0142] Storage device

[0143] (First embodiment)

[0144] The memory device of this embodiment preferably includes a switching element and a memory element.

[0145] 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.

[0146] 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.

[0147] 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.

[0148] 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 SiN x 、AlN x 、ZrN x 、NiN x 、CuNx 、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.

[0149] 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.

[0150] 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.

[0151] 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.

[0152] The ferroelectric memory element includes a ferroelectric layer. More specifically, the ferroelectric memory element preferably includes a laminated body sandwiching the ferroelectric layer between an upper electrode and a lower electrode. 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).

[0153] (Second embodiment)

[0154] The storage device of the present invention is not limited to a configuration that includes a switching layer and a storage element respectively. For example, the storage device of the present invention may also be a structure that includes 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 above-mentioned storage function and switching element function. In this embodiment, by using a resistance-variable storage element having a storage function and a 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.

[0155] 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.

[0156] 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.

[0157] Example

[0158] Hereinafter, the present invention will be described based on examples, but the present invention is not limited to these examples.

[0159] (First to third inventions) [Table 1]

[0160]

[0161] [Table 2]

[0162]

[0163] The sample was 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 and 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 obtain a variable resistance material.

[0164] Next, the produced variable resistance material is used as a target, and a variable resistance material as an amorphous thin film is obtained by high-frequency magnetron sputtering.

[0165] [XPS measurement]

[0166] To remove the oxide layer on the surface of the resulting amorphous thin film variable resistance material, approximately 20 nm of the sample surface was etched under the following conditions. After etching, XPS measurements were performed under the following conditions. The specific measurement conditions are as follows.

[0167] [Dry etching conditions]

[0168] Ion type: Ar +

[0169] Accelerating voltage: 4 kV

[0170] Etching time: 0.4 minutes

[0171] Grating range: 2×2mm

[0172] [XPS measurement conditions]

[0173] Measuring device: PHI 5000 Versa Probe III (manufactured by ULVAC-PHI)

[0174] Excitation X-rays: Al Kα1,2 rays (monochromatized X-rays, 1486.6 eV)

[0175] X-ray source power: 25W (15kV)

[0176] Pass energy: 69eV

[0177] Measurement step: 0.05eV

[0178] Analysis area (beam diameter): 100 μm in diameter

[0179] Photoelectron intake angle (detector tilt relative to the sample surface): 45°

[0180] Charge neutralization: using a dual beam of electrons and Ar ions

[0181] Peak shift correction: After etching the sample surface, the C in the sample measurement section was used to correct the peak shift by setting the C1s main peak (CHx, CC) to 284.6 eV.

[0182] Smoothing: 9-point smoothing was performed using analysis software Multi Pak (manufactured by ULVAC-PHI).

[0183] The peak shift corrected spectrum was normalized by intensity, and the peak and half-value width of the XPS peak were obtained. The results are shown in Table 2 and Figures 8 to 11 .

[0184] The half-value width of the energy spectrum obtained by XPS is obtained by drawing a tangent line at the point where the first differential value of the shoulder of the normalized energy spectrum peak becomes maximum and taking the width of the binding energy at which the energy spectrum intensity becomes 1 / 2 (0.5).

[0185] [Raman measurement]

[0186] Raman spectroscopy was performed on the resulting amorphous thin film variable resistance material. Specific measurement conditions are described below. However, the measurement is not limited to these conditions; any conditions that ensure the variable resistance material is not degraded by the laser and that a sufficient S / N ratio is achieved will suffice.

[0187] [Raman measurement conditions]

[0188] Measurement device: Laser Raman microscope RAMAN

[0189] touch (manufactured by Nanophoton Corporation)

[0190] Laser wavelength: 532nm

[0191] Entrance slit width of the beam splitter: 50 μm

[0192] Diffraction grating line count: 1200gr / mm

[0193] Laser output: 300W / cm 2

[0194] Ratio of the light intensity after attenuation by the N / D filter to the maximum laser intensity: 144 / 255 Smoothing: Moving average method

[0195] Regarding the laser wave number, the spectrum of silicon of the standard sample is measured at 520 cm -1The peak of the Raman peak was corrected. The intensity of the Raman spectrum obtained from the resistance variable material was normalized to obtain the top and half-value width of the Raman peak. The results are shown in Table 2 and Figure 12 .

[0196] The half-value width of the spectrum obtained by laser Raman microscopy was determined by plotting a tangent line at the point where the first differential value of the shoulder of the standardized spectrum peak was the largest, and defining it as the width of the wave number at which the spectrum intensity was 1 / 2 (0.5).

[0197] [XPS measurement results]

[0198] like Figure 8 As shown in Table 2, XPS peaks Px1 and Px1GT attributed to Te 3d5 / 2 orbitals were observed around 573 eV in Examples 1-1, 1-2, and Comparative Example 1. More specifically, the peak of the XPS peak Px1 was observed in the range of 572.79 to 572.80 eV. Furthermore, the peaks of the XPS peaks Px1 in Examples 1-1 and 1-2 were shifted to the lower energy side by more than 0.10 eV compared to the peak of peak Px1GT in Comparative Example 1.

[0199] like Figure 9 As shown in Table 2, in Examples 1-1 and 1-2, the half-value width Px2hw of the XPS peak due to the Ge3d orbital is 1.25 eV or more, which is larger than the half-value width Px2GThw of Comparative Example 1. At this time, the ratio of the half-value width of the XPS peak of Examples 1-1 and 1-2 to the half-value width of the XPS peak of Comparative Example 1 (Px2hw / Px2GThw) is 1.02 or more.

[0200] like Figure 10 As shown in Table 2, in Examples 1-1, 1-2 and Comparative Example 1, XPS peaks due to the Te4d orbital can be confirmed near 40eV and 42eV. More specifically, the XPS peak Px3 due to the Te4d5 / 2 orbital can be confirmed in the range of 40.28 to 40.32eV. In addition, the XPS peak due to the Te4d3 / 2 orbital can be confirmed near 42eV. The apex of the XPS peak Px3 due to the Te4d3 / 2 orbital of Examples 1-1 and 1-2 is shifted to the low energy side by more than 0.13eV compared to the apex of the peak Px3GT of Comparative Example 1. Furthermore, the half-value width Px3hw of the XPS peak of Examples 1-1 and 1-2 is 1.22eV, which is larger than that of Comparative Example 1. At this time, the ratio of the half-value widths of the XPS peaks of Examples 1-1 and 1-2 to the half-value width of the XPS peak of Comparative Example 1 (Px3hw / Px3GThw) was 1.184.

[0201] like Figure 11As shown in Table 2, XPS peaks Px4a and Px4b attributed to Ga 3d orbitals were observed around 19.5 eV in Examples 1-1 and 1-2. More specifically, the apexes of XPS peaks Px4a and Px4b were observed in the 19.44-19.53 eV range. Furthermore, the apex of XPS peak Px4a in Example 1-2 was shifted to a lower energy side of 0.09 eV compared to the apex of peak Px4b in Example 1-1.

[0202] [Raman measurement results]

[0203] like Figure 12 As shown in Table 2, in Examples 1-1, 1-2 and Comparative Example 1, it can be confirmed that -1 The Raman peaks Pr1 and Pr1GT are formed by the overlap of the Raman peaks caused by Ge-Te and Te-Te bonds. More specifically, at 124.99 cm -1 The peak of the Raman peak Pr1 can be confirmed. In Examples 1-1 and 1-2, the half-value width Pr1hw of the Raman peak is 15.8 cm -1 The above is larger than the half-value width Pr1GThw1 of Comparative Example 1. In Examples 1-1, 1-2, and Comparative Example 1, at 136 cm -1 Raman peaks Pr2 and Pr2GT due to Te-Te bonds can be observed near the 136.50-137.55 cm -1 The apex of the Raman peak Pr2 can be confirmed. At this time, the apex of the Raman peak Pr2 of Examples 1-1 and 1-2 is shifted to the high wave number side by 1.04 cm compared to the apex of the Raman peak Pr2GT of Comparative Example 1. -1 above.

[0204] [Switching element]

[0205] Next, a switching element was fabricated using a variable resistance material as a target. First, a 50nm thick W electrode was formed on a Si / SiO2 substrate. Next, a 100nm thick SiO2 insulating layer was formed on the W electrode. Then, a focused ion beam device (JEOL, JIB-4600F) was used to form a 100nm thick SiO2 insulating layer between the SiO2 insulating layer and the W electrode layer. A 150nm thick film of variable resistance material was then formed in the resulting hole to form the switching layer. Finally, a 150nm thick W electrode was formed on the switching layer (i.e., a W electrode film was formed), thus fabricating the switching element. This film formation was performed using Ar sputtering in a reduced pressure atmosphere.

[0206] Using the obtained switching element, the ON / OFF current ratio was measured. The ON / OFF current ratio was calculated as follows. First, a voltage of 0V to 10V was applied to the switching element, and the current value flowing through the switching element and the threshold voltage were 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, the measurement was performed with a pulse voltage. Next, the ON / OFF current ratio was calculated by dividing the ON current value by the OFF current value. The ON current value is the current value that flows when a voltage greater than the threshold voltage is applied. The OFF current value is the current value that flows when a voltage of 1 / 2 of the threshold voltage is applied. The results are shown in Table 2.

[0207] As shown in Table 2, the ON / OFF current ratio of Examples 1-1 and 1-2 is 1×10 5.1 As described above, it is larger than that of Comparative Example 1.

[0208] (Fourth Invention)

[0209] [Table 3]

[0210]

[0211] [Table 4]

[0212]

[0213] The sample is prepared in the same manner as in the first to third inventions. Specifically, it is prepared as follows. First, after heating a quartz glass ampoule container while performing vacuum exhaust, the raw materials are mixed to obtain the composition shown in Table 3, and the raw materials are placed in a quartz glass ampoule container. Next, the quartz glass ampoule container is sealed with an oxygen burner. Next, the sealed quartz glass ampoule container is placed in a melting furnace, heated to 650°C to 1000°C at a rate of 10°C to 40°C / hour, and then maintained for 6 to 12 hours. During the holding time, the quartz glass ampoule container is turned upside down to stir the melt. Finally, the quartz glass ampoule container is removed from the melting furnace and rapidly cooled to room temperature, thereby obtaining a resistance variable material.

[0214] Next, the produced variable resistance material was used as a target to obtain an amorphous thin film of the variable resistance material by high-frequency magnetron sputtering.

[0215] The crystallization temperature Tx of the variable resistance material is the temperature at which the resistance drops sharply when the resistance material is heated. Specifically, a 150nm thick amorphous thin film of the variable resistance material was formed. The film was then heated at a rate of 10°C / min while the resistance was measured using a two-terminal method. Measurements were performed in an air atmosphere. The temperature at which the resistance drops sharply is the temperature at which the first differential value of the resistance with respect to temperature reaches its maximum.

[0216] [activation energy]

[0217] For the obtained resistance variable material, the activation energy Ea was calculated using the Kissinger method. Specifically, after making an amorphous film with a thickness of 150nm using the resistance variable material, the amorphous film was heated while changing the heating rate in the range of 5℃ / min to 15℃ / min, and the resistance was measured using the two-terminal method. The temperature at which the resistance dropped sharply was taken as the crystallization temperature, and the activation energy during crystallization was calculated using the following formula (2). The measurement was carried out in an atmospheric atmosphere. Here, α represents the heating rate of the sample, Tx represents the crystallization temperature, R represents the gas constant, and C represents the constant. The results are shown in Tables 4 and Figure 13 .

[0218] ln(α / Tx 2 )=-(Ea / RTx)+C……Formula (2)

[0219] [Switching element]

[0220] Next, a switching element is made by the same method as the first to third inventions. The details are as follows. First, a W electrode with a thickness of 50 nm is formed (film-formed) on a Si / SiO2 substrate. Next, a SiO2 insulating layer with a thickness of 100 nm is formed on the W electrode. Then, a focused ion beam device (manufactured by JEOL, JIB-4600F) is used to form a W electrode layer between the SiO2 insulating layer and the W electrode layer. A 150nm thick film of variable resistance material was then deposited into the resulting hole to form the switching layer. Finally, a 150nm thick W electrode was deposited on the switching layer to create the switching element. This film deposition was performed using Ar sputtering in a reduced pressure atmosphere.

[0221] The number of cycles was measured using the obtained switching element. First, a voltage of 0V to 10V was applied to the switching element, and the current value and threshold voltage flowing through the switching element were measured. From the viewpoint of preventing heat accumulation in the switching element, the applied voltage was measured as 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 current value flowing when a voltage of 1 / 2 of the threshold voltage is applied is set as the OFF current, and the current value flowing when a voltage above the threshold voltage is applied is set as the ON current. The ON current is measured by applying a trapezoidal pulse voltage of 3μs, and the OFF current is measured by applying a trapezoidal pulse voltage of 22μs. The number of cycles is the number of times the ON / OFF current conversion (switching) is repeated until the ON / OFF current ratio becomes 10% of the initial measured value. The results are shown in Table 4.

[0222] like Figure 13As shown in Table 4, the activation energies of Examples 2-1 to 2-6 are as high as 251 kJ / mol or more. In addition, the number of cycles of the switching elements made using the resistance variable materials of Examples 2-1 to 2-6 is as high as 8×10 2 At this time, if Figure 13 As shown, the resistance variable materials of Examples 2-1 to 2-6 satisfy log 10 The relationship is x≥0.011Ea+0.1.

[0223] Industrial applicability

[0224] The resistance variable material of the present invention can be applied to a switching element, and the switching element can be used in a resistance variable type, phase change type, or other memory device.

[0225] Description of Reference Signs

[0226] 1.11 1st electrode

[0227] 2.12 Second electrode

[0228] 3 Switch Layer

[0229] 4 Switch Storage Layer

[0230] 10 Switching elements

[0231] 20, 21 Storage Components

[0232] 30-character line

[0233] 40-bit line

[0234] 100, 101, 200, 201 storage devices.

Claims

1. A resistance variable material, characterized in that: Contains, in atomic %, 40% to 90% of Te, greater than 0% and less than 40% of Ge, and greater than 0% and less than 40% of Ga, In the XPS spectrum measured by X-ray photoelectron spectroscopy, the top of the XPS peak Px1 due to the Te 3d 5 / 2 orbital is shifted to the lower energy side compared with the top of the XPS peak Px1GT due to the Te 3d 5 / 2 orbital of amorphous GeTe 5 .

2. The resistance variable material according to claim 1, wherein: The top of the XPS peak Px1 is shifted toward the lower energy side by 0.05 eV or more than the top of the XPS peak Px1GT.

3. The resistance variable material according to claim 1 or 2, wherein: The half-value width Px1hw of the XPS peak Px1 is larger than the half-value width Px1GThw of the XPS peak Px1GT.

4. The resistance variable material according to claim 3, wherein: The ratio of the half-value width Px1hw of the XPS peak Px1 to the half-value width Px1GThw of the XPS peak Px1GT, that is, Px1hw / Px1GThw, is 1.01 or more.

5. The resistance variable material according to claim 1 or 2, wherein: In the XPS energy spectrum, the half-value width Px2hw of the XPS peak Px2 caused by the Ge3d orbit is larger than the half-value width Px2GThw of the XPS peak Px2GT caused by the Ge3d orbit of the amorphous GeTe5.

6. The resistance variable material according to claim 5, wherein: The ratio of the half-value width Px2hw of the XPS peak Px2 to the half-value width Px2GThw of the XPS peak Px2GT, that is, Px2hw / Px2GThw, is 1.01 or more.

7. A resistance variable material, characterized in that: Contains 40% to 90% Te and more than 0% and less than or equal to 40% Ge in atomic %, In an XPS spectrum measured by X-ray photoelectron spectroscopy, there are at least three peak tops within a binding energy range of 15 eV to 44 eV.

8. A resistance variable material, characterized in that: Contains, in atomic %, 40% to 90% of Te, greater than 0% and less than 40% of Ge, and greater than 0% and less than 40% of Ga, In the Raman spectrum measured by Raman spectroscopy, the peak of the Raman peak Pr1, which is formed by the overlap of the Raman peaks caused by the Ge-Te bond and the Te-Te bond, is at a wave number of 118 cm -1 ~130cm -1 within the scope of The half-value width Pr1hw of the Raman peak Pr1 is larger than the half-value width Pr1GThw of the Raman peak Pr1GT of amorphous GeTe5.

9. The resistance variable material according to claim 8, wherein: The ratio of the half-value width Pr1hw of the Raman peak Pr1 to the half-value width Pr1GThw of the Raman peak Pr1GT, that is, Pr1hw / Pr1GThw, is 1.05 or more.

10. The resistance variable material according to claim 8 or 9, wherein: The apex of the Raman peak Pr1 is shifted toward a higher wave number side compared to the apex of the Raman peak Pr1GT.

11. The resistance variable material according to claim 10, wherein: The apex of the Raman peak Pr1 is shifted by 0.1 cm toward the higher wave number side compared to the apex of the Raman peak Pr1GT. -1 above.

12. The resistance variable material according to claim 8 or 9, wherein: Furthermore, the apex of the Raman peak Pr2 caused by the Te-Te bond is at a wave number of 135 cm -1 ~145cm -1 In the range of , the apex of the Raman peak Pr2 is shifted to the high wave number side compared with the apex of the Raman peak Pr2GT caused by the Te-Te bond of amorphous GeTe5.

13. The resistance variable material according to claim 12, wherein: The apex of the Raman peak Pr2 is shifted by 0.1 cm to the higher wave number side compared to the apex of the Raman peak Pr2GT. -1 above.

14. A resistance variable material, characterized in that: Contains 40% to 90% Te and more than 0% and less than or equal to 40% Ge in atomic %, The activation energy Ea during crystallization of the amorphous thin film composed of the variable resistance material is 240 kJ / mol or more.

15. The resistance variable material according to claim 14, wherein: The number of cycles was 5×10 2 times or more.

16. The resistance variable material according to claim 14 or 15, wherein: The number of cycles x and the activation energy Ea satisfy the relationship of the following formula (1), wherein the unit of the number of cycles x is times, and the unit of the activation energy Ea is kJ / mol. log 10 x≥0.011Ea+0.1...Equation (1).

17. The resistance variable material according to claim 1, 7, 8 or 14, wherein: Contains 0% to 20% of Sb in atomic %.

18. The resistance variable material according to claim 1, 7, 8 or 14, wherein: The resistance variable material does not substantially contain Sb, Se, and As.

19. The resistance variable material according to claim 1, 7, 8 or 14, wherein: The resistance variable material is a thin film.

20. A material for a switching element, characterized in that: Composed of the resistance variable material according to claim 1, 7, 8 or 14.

21. A switch layer, characterized in that: Composed of the resistance variable material according to claim 1, 7, 8 or 14.

22. A switching element, characterized in that: include: 1st electrode; and The switching layer according to claim 21 is arranged on the first electrode.

23. The switching element according to claim 22, wherein: A second electrode is provided, which is arranged at a position facing the first electrode with the switching layer interposed therebetween.

24. A storage device, characterized in that: include: The switching element according to claim 23; and Storage element.

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