Nitride insulating material, its manufacturing method, and heat flow switching element and thermoelectric conversion element

Abstract

To provide a nitride insulator material having low lattice thermal conductivity, a method for manufacturing the same, a heat flow switching element and a thermoelectric conversion element.SOLUTION: A nitride insulator material according to the present invention is a metal nitride represented by M-Si-N-Te (provided that M represents at least one of Ta and Hf; and Te represents an optional metal) or nanocrystals. A heat flow switching element according to the present invention is provided with an N-type semiconductor layer 3, an insulator layer 4 stacked on the N-type semiconductor layer, and a P-type semiconductor layer 5 stacked on the insulator layer, wherein the insulator layer is made of the nitride insulator material.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a nitride insulating material having low lattice thermal conductivity, a method for producing the same, and a heat flow switching element and a thermoelectric conversion element. [Background technology]

[0002] Conventionally, as a heat flow switch that actively changes the thermal conductivity by bias voltage, for example, Non-Patent Document 1 describes a device in which an electrically insulating polyimide tape is placed between two sheets of semiconductor material: Ag2S 0.6 Se 0.4 A heat flow switching element has been proposed in which the thermal conductivity is changed by applying an electric field to a material sandwiched between two electrodes. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Takuya Matsunaga and four others, "Fabrication of a heat flow switching element operated by bias voltage," 15th Annual Meeting of the Thermoelectric Society of Japan, September 13, 2018 Summary of the Invention [Problem to be solved by the invention]

[0004] The above conventional techniques still have the following problems. In the technology described in Non-Patent Document 1, applying a voltage generates thermally conductive charges at the interface between a semiconductor material and an insulating material, and these charges can transport heat. This allows for an immediate transition to a changed thermal conductivity state, resulting in relatively good thermal response. However, in order to change the thermal conductivity at the material interface in response to this external electric field (external voltage) and increase the change in thermal conductivity of the entire device, it is necessary to reduce the inherent thermal conductivity of the materials that make up the device at zero bias. Thermal conductivity is a function proportional to the square of the thermal effusivity, so it is necessary to reduce the inherent thermal effusivity of the materials that make up the device at zero bias. The inherent thermal conductivity of a material at zero bias is expressed as the sum (addition) of the lattice thermal conductivity and the electronic thermal conductivity. Thermal conductivity = lattice thermal conductivity + electronic thermal conductivity

[0005] Lattice thermal conduction is heat conduction due to vibrations (phonons, lattice vibrations) that propagate between crystal lattices. Electronic thermal conduction is heat conduction due to conduction electrons, and generally, electronic thermal conductivity tends to increase as electrical conductivity increases. Regarding the electronic thermal conductivity of semiconductors, in order to maintain the semiconductor's electrical conductivity, the material's inherent electronic thermal conductivity at zero bias must be adjusted to an appropriate value without increasing the total thermal conduction. Insulating materials do not exhibit electronic thermal conduction. On the other hand, a lower lattice thermal conductivity is preferable. Materials with low lattice thermal conductivity can reduce the overall thermal conductivity of the device at zero bias, thereby increasing the rate of change in interface-induced thermal conductivity in response to an external electric field and improving the overall heat flow switching performance of the device. Therefore, there is a demand for the use of low thermal conductivity (low thermal permeability) semiconductor and insulator materials due to their low lattice thermal conductivity. Furthermore, the use of nitride materials as constituent materials is desirable to improve the heat resistance of heat flow switching devices. Furthermore, in a thermoelectric conversion element, it is desirable to use an insulating material with low lattice thermal conductivity and high thermal insulation performance in order to suppress heat release from the surface of the thermoelectric conversion part and ensure a sufficient temperature difference between the high-temperature side and the low-temperature side.

[0006] The present invention has been made in view of the above-mentioned problems, and has as its object to provide a nitride insulator material having low lattice thermal conductivity, a method for producing the same, and a heat flow switching element and a thermoelectric conversion element. [Means for solving the problem]

[0007] The present invention employs the following configuration to solve the above problems: Namely, the nitride insulator material according to the first invention is a metal nitride represented by M-Si-N-Te (wherein M represents at least one of Ta and Hf, and Te is an optional element), and is characterized by being a nanocrystal. This nitride insulator material is a metal nitride represented by the formula M-Si-N-Te (where M represents at least one of Ta and Hf, and Te is an optional element), and is a nanocrystal, so it has insulating properties and low lattice thermal conductivity, resulting in low thermal conductivity and low thermal effusivity. Therefore, the nitride insulator material of the present invention is suitable as an electrical and thermal barrier material. Among the constituent elements, M (at least one of Ta and Hf) and Si are nanocrystallized (crystal size is 5 nm or less, including amorphous), which reduces the lattice thermal conductivity and makes it possible to reduce the thermal effusivity. Furthermore, the content of N among the constituent elements provides insulation. Furthermore, Te among the constituent elements has the effect of further reducing the thermal effusivity. The expression "Te is an optional element" indicates that the inclusion of Te (tellurium) is optional. In other words, it indicates that Te may or may not be included. In other words, it is M-Si-N or M-Si-N-Te (where M represents at least one transition metal element).

[0008] The nitride insulating material according to the second invention is the nitride insulating material according to the first invention, which has a thermal effusivity of 2000 Ws 0.5 / m 2 K or less. That is, this nitride insulating material has a thermal effusivity of 2000Ws 0.5 / m 2K, it has a lower thermal conductivity than HfO2. In addition, the thermal effusivity is 100Ws 0.5 / m 2 It is preferable that the temperature is K or higher.

[0009] The nitride insulating material according to the third invention is the nitride insulating material according to the second invention, which has a thermal effusivity of 1700 Ws 0.5 / m 2 K or less. That is, this nitride insulating material has a thermal effusivity of 1700Ws 0.5 / m 2 Since its temperature is less than 1000K, it has a lower thermal conductivity than HfO2 or SiN. This nitride insulator material exhibits lower thermal conductivity, i.e., higher thermal insulation, making it more suitable for use as an insulator layer in a heat flow switching element and as an insulator layer in a thermoelectric conversion element.

[0010] The nitride insulating material according to the fourth invention is any one of the first to third inventions, and has an electrical resistivity of 10 8 It is characterized by being Ωcm or more. That is, this nitride insulating material has an electrical resistivity of 10 8 Ωcm or more, so for a nitride insulator material with a film thickness of 100 nm, applying a voltage of 10 V in the film thickness direction will result in a current of 100 μA / mm 2 This provides insulation that allows current to flow less than this.

[0011] A nitride insulating material according to a fifth invention is characterized in that, in any one of the first to fourth inventions, it is used as a low thermal conductive material. That is, this nitride insulating material has a low thermal effusivity and is therefore suitable as a low thermal conductive insulating material for use in heat flow switching elements, thermoelectric conversion elements, and the like.

[0012] A heat flow switching element according to a sixth aspect of the present invention comprises an N-type semiconductor layer, an insulator layer stacked on the N-type semiconductor layer, and a P-type semiconductor layer stacked on the insulator layer, wherein the insulator layer is formed from any one of the nitride insulator materials according to the first to fifth aspects of the present invention. That is, this heat flow switching element comprises an N-type semiconductor layer, an insulator layer stacked on the N-type semiconductor layer, and a P-type semiconductor layer stacked on the insulator layer, so when an external voltage is applied to the N-type semiconductor layer and the P-type semiconductor layer, electric charges are induced mainly at the interfaces between the P-type semiconductor layer and the N-type semiconductor layer and the insulator layer, and these electric charges carry heat, causing a change in thermal conductivity. In particular, since the insulator layer is formed from any of the nitride insulator materials of the first to third inventions, the insulating layer has low lattice thermal conductivity, resulting in low lattice thermal conductivity and low thermal effusivity, and the rate of change of thermal conductivity can be increased by an external electric field (external voltage). Furthermore, when the N-type semiconductor layer and the P-type semiconductor layer are made of nitride, the insulator layer is also made of nitride, which improves the bonding strength at the interfaces between the P-type semiconductor layer and the N-type semiconductor layer and the insulator layer.

[0013] The rate of increase Δk in thermal conductivity after voltage application, which is the performance of the heat flow switch, is evaluated by the following formula: Δk=k(V) / k(0)-1 Δk=b(V) 2 / b(0) 2 -1 k(V): Thermal conductivity when voltage is applied (W / mK) k(0): Thermal conductivity without voltage applied (W / mK) b(V): Thermal effusivity when voltage is applied (Ws 0.5 / m 2 K) b(0): Thermal effusivity without voltage application (Ws 0.5 / m 2 K) The thermal conductivity due to the interface, which changes with the above external voltage, is defined as the "third thermal conductivity," and for convenience, is distinguished from the thermal conductivity inherent to the material (the sum of the lattice thermal conductivity and the electronic thermal conductivity), which does not change with external voltage.

[0014] k(V) = Electronic thermal conductivity of semiconductor + Lattice thermal conductivity of semiconductor + Lattice thermal conductivity of insulator + Tertiary thermal conductivity k(0) = electronic thermal conductivity of semiconductor + lattice thermal conductivity of semiconductor + lattice thermal conductivity of insulator Therefore, to improve the performance of a heat flow switch, it is preferable to select a material with low electronic and lattice thermal conductivities. Regarding the electronic thermal conduction of a semiconductor, in order to maintain the conductivity of the semiconductor, the material's inherent electronic thermal conductivity at zero bias must be adjusted to an appropriate value without increasing the total thermal conduction. On the other hand, regarding lattice thermal conductivity, a material with low lattice thermal conductivity can reduce k(0) and lower the thermal conductivity of the entire element at zero bias. Therefore, the lower the lattice thermal conductivity, the greater the contribution of electronic thermal conductivity in response to an external electric field from zero bias. This increases the rate of change of thermal conductivity in response to an external electric field, improving heat flow switch performance.

[0015] Furthermore, because charges are generated both at and near the interface between the N-type semiconductor layer and the insulator layer, and at and near the interface between the P-type semiconductor layer and the insulator layer, a large amount of charges is generated, resulting in a large change in thermal conductivity and high thermal responsiveness. Furthermore, because this is a mechanism that physically changes thermal conductivity without using a chemical reaction mechanism, the thermal conductivity can be immediately changed, resulting in good thermal responsiveness. Furthermore, since the amount of charge induced at the interface varies depending on the magnitude of the external voltage, it is possible to adjust the thermal conductivity by adjusting the external voltage, making it possible to actively control the heat flow through this element. Furthermore, since the insulating layer is an insulator and no current is generated when a voltage is applied, no Joule heat is generated, making it possible to actively control the heat flow without self-heating.

[0016] The heat flow switching element of the seventh invention is the sixth invention, characterized in that it comprises an upper high thermal conductivity portion provided on the top surface, a lower high thermal conductivity portion provided on the bottom surface, and a peripheral heat insulation portion provided to cover the outer edges of the N-type semiconductor layer, the insulator layer, and the P-type semiconductor layer, and the peripheral heat insulation portion is formed from the nitride insulator material having lower thermal conductivity than the upper high thermal conductivity portion and the lower high thermal conductivity portion. In other words, in this heat flow switching element, the peripheral heat insulating portion is formed of the nitride insulator material, which has lower thermal conductivity than the upper high thermal conductivity portion and the lower high thermal conductivity portion, so that the heat flow in the in-plane direction can be suppressed and heat flow switching can be achieved in the stacking direction. In particular, when an N-side electrode and a P-side electrode are disposed on the periphery of each layer, the peripheral heat insulating portion, which has low thermal conductivity, can minimize the flow of heat into these electrodes.

[0017] A thermoelectric conversion element according to an eighth aspect of the present invention comprises an insulating base material, a P-type thermoelectric conversion unit and an N-type thermoelectric conversion unit formed on the insulating base material, a connection electrode unit connecting the P-type thermoelectric conversion unit and the N-type thermoelectric conversion unit, and an insulator covering surfaces of the P-type thermoelectric conversion unit and the N-type thermoelectric conversion unit, wherein the insulator is formed from a nitride insulator material according to any one of claims 1 to 5. In other words, in this thermoelectric conversion element, the insulator is formed from any of the nitride insulator materials of the first to fifth inventions, and since the surface of the thermoelectric conversion unit is covered with an insulator made of a nitride insulator material with low thermal conductivity, heat release from the surface of the thermoelectric conversion unit is suppressed, and a sufficient temperature difference between the high-temperature side and the low-temperature side can be ensured. Furthermore, when the P-type thermoelectric conversion section and the N-type thermoelectric conversion section are nitrides, the insulator is also nitride, which improves the bonding strength at the interfaces between the P-type semiconductor layer and the N-type semiconductor layer and the insulator layer.

[0018] A thermoelectric conversion element according to a ninth invention is the thermoelectric conversion element of the eighth invention, characterized in that the P-type thermoelectric conversion portion, the N-type thermoelectric conversion portion, and the insulator are in the form of films. That is, in this thermoelectric conversion element, the P-type thermoelectric conversion portion, the N-type thermoelectric conversion portion, and the insulator are in the form of films, so that the entire element can be made thinner.

[0019] A tenth aspect of the present invention is a method for producing a nitride insulator material according to any one of the first to fifth aspects of the present invention, characterized in that a film is formed by reactive sputtering in a nitrogen-containing atmosphere using an M-Si-Te sputtering target (wherein M represents at least one of Ta and Hf, and Te is an optional element). In other words, in this method for manufacturing a nitride insulator material, a M-Si-Te sputtering target (where M represents at least one of Ta and Hf, and Te is an optional element) is used to form a film by reactive sputtering in a nitrogen-containing atmosphere, making it possible to obtain a metal nitride represented by M-Si-N-Te (where M represents at least one of Ta and Hf, and Te is an optional element), a nanocrystalline nitride insulator layer or nitride insulator film with low surface roughness. [Effects of the Invention]

[0020] According to the present invention, the following effects are achieved. That is, the nitride insulator material of the present invention is a metal nitride represented by M-Si-N-Te (where M represents at least one of Ta and Hf, and Te is an optional element), and is a nanocrystal, so that it has insulating properties and low lattice thermal conductivity, resulting in low thermal conductivity with low thermal effusivity. Therefore, the nitride insulator material of the present invention is suitable as an electrical and thermal barrier material (insulating material and heat insulating material). Furthermore, in the heat flow switching element of the present invention, the insulating layer is formed from the nitride insulator material of the present invention, and the insulating layer has low lattice thermal conductivity, which increases the rate of change of thermal conductivity in response to an external electric field, thereby improving heat flow switching performance. Furthermore, in the thermoelectric conversion element of the present invention, the insulator is formed from the nitride insulator material of the present invention, and the insulator has low lattice thermal conductivity, which suppresses heat release from the surface of the thermoelectric conversion part, thereby ensuring a sufficient temperature difference between the high-temperature side and the low-temperature side. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a perspective view showing a heat flow switching element in a first embodiment of a nitride insulator material, a manufacturing method thereof, and a heat flow switching element according to the present invention.

[0023] FIG. [Figure 2] FIG. 2 is a conceptual diagram for explaining the principle of the heat flow switching element in the first embodiment. [Figure 3] FIG. 2 is a cross-sectional view showing a heat flow switching element in a second embodiment of the nitride insulator material, its manufacturing method, and heat flow switching element according to the present invention. [Figure 4] FIG. 10 is a perspective view showing a thermoelectric conversion element in a third embodiment of the nitride insulator material, the manufacturing method thereof, and the thermoelectric conversion element according to the present invention. [Figure 5] FIG. 10 is a cross-sectional view showing a thermoelectric conversion element in a fourth embodiment of the nitride insulator material, the method for producing the same, and the thermoelectric conversion element according to the present invention. [Figure 6] FIG. 1 is an explanatory diagram showing the layout of an insulation evaluation test in an embodiment of a nitride insulator material and a manufacturing method thereof, as well as a heat flow switching element and a thermoelectric conversion element according to the present invention. [Figure 7] 1 is a graph showing an XRD pattern in an example according to the present invention. [Figure 8] 1 is a cross-sectional SEM image in an embodiment according to the present invention. [Figure 9] 1A and 1B are cross-sectional SEM images showing Example 7(a) and Example 25(b) in examples according to the present invention. [Figure 10] 1 shows TEM images of Example 7(a) and Example 25(b) in examples according to the present invention. [Figure 11]10A and 10B are diffraction pattern images showing Example 7(a) and Example 25(b) in examples according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0022] A first embodiment of a nitride insulator material, a manufacturing method thereof, a heat flow switching element, and a thermoelectric conversion element according to the present invention will be described below with reference to Figures 1 and 2. Note that in the drawings used in the following description, the scale has been appropriately changed as necessary to make each part recognizable or easily recognizable.

[0023] As shown in Figures 1 and 2, the heat flow switching element 1 of this embodiment includes an N-type semiconductor layer 3, an insulator layer 4 stacked on the N-type semiconductor layer 3, and a P-type semiconductor layer 5 stacked on the insulator layer 4. Furthermore, the heat flow switching element 1 of this embodiment includes an N-side electrode 6 connected to the N-type semiconductor layer 3 and a P-side electrode 7 connected to the P-type semiconductor layer 5.

[0024] The insulator layer 4 is a nitride insulator material with low thermal conductivity, a metal nitride represented by M-Si-N-Te (wherein M represents at least one of Ta and Hf, and Te is an optional element), and is a nanocrystal. In this specification, if the crystal size is 5 nm or less, it is called nanocrystal, including amorphous materials. The above crystal size was calculated by randomly selecting 10 crystals in a cross-sectional TEM image and averaging their equivalent circle diameters.

[0025] The insulator layer 4 is a metal nitride represented by M-Si-N-Te (wherein M represents at least one of Ta and Hf, and Te is an optional element), and the metal nitride is Ta-Si-N, Hf-Si-N, Ta-Hf-Si-N, or Ta-Si-N-Te. Furthermore, the N-type semiconductor layer 3 and the P-type semiconductor layer 5 are made of a nitride semiconductor material with low thermal conductivity, for example, a metal nitride represented by A-Si-N-Te (where A represents at least one transition metal element, and Te is an optional element), and are nanocrystals. That is, the above metal nitrides include Cr-Si-N, Mn-Si-N, Ni-Si-N, Mo-Si-N, W-Si-N, Cr-W-Si-N, Cr-Si-N-Te, and W-Si-N-Te.

[0026] These films are formed by various methods such as sputtering and molecular beam epitaxy (MBE). In the sputtering method, the above metal nitride can be deposited in a sputtering apparatus using targets of various composition ratios in an atmosphere of a mixed gas of Ar gas and nitrogen gas, while varying the sputtering gas pressure, nitrogen gas partial pressure, etc. In this embodiment, an M-Si-Te sputtering target (wherein M represents at least one of Ta and Hf, and Te is an optional element) is used to perform reactive sputtering in a nitrogen-containing atmosphere to form an insulator layer 4 made of a nitride semiconductor material. It is acceptable for the film to contain a small amount of O (oxygen) as an unavoidable impurity during film formation. Furthermore, if a voltage can be applied directly to the N-type semiconductor layer 3 and the P-type semiconductor layer 5, the N-side electrode 6 and the P-side electrode 7 are not necessary.

[0027] The heat flow switching element 1 of this embodiment also includes an insulating substrate 2, on which an N-side electrode 6 is formed. That is, the N-side electrode 6, the N-type semiconductor layer 3, the insulator layer 4, the P-type semiconductor layer 5, and the P-side electrode 7 are stacked in this order on the substrate 2. The stacking order on the substrate 2 may be reversed. The substrate 2 itself may also serve as the P-side electrode 7 or the N-side electrode 6.

[0028] An external power source V is connected to apply a voltage to the N-side electrode 6 and the P-side electrode 7. The arrows in Fig. 1 indicate the direction in which the voltage (electric field) is applied. The N-type semiconductor layer 3 and the P-type semiconductor layer 5 are formed as thin films with a thickness of less than 1 μm. In particular, since the charges e (positive charges, negative charges) generated at the interface with the insulator layer 4 and in the vicinity thereof are mainly accumulated in a thickness range of 5 to 10 nm, it is more preferable that the N-type semiconductor layer 3 and the P-type semiconductor layer 5 be formed with a film thickness of 100 nm or less. It is preferable that the N-type semiconductor layer 3 and the P-type semiconductor layer 5 have a film thickness of 5 nm or more. The insulator layer 4 preferably has a thickness of 40 nm or more, which is set to a thickness that does not cause dielectric breakdown. However, if the insulator layer 4 is too thick, it becomes difficult to transport the charge e, so the thickness is preferably less than 1 μm.

[0029] In Figure 2, the type of charge e generated at the interface between the N-type semiconductor layer 3 and the insulator layer 4 and in the vicinity thereof is an electron, represented by a white circle. The type of charge e generated at the interface between the P-type semiconductor layer 5 and the insulator layer 4 and in the vicinity thereof is a hole, represented by a black circle. (A hole is a hole created by a lack of electrons in the valence band of the semiconductor, and appears to have a relatively positive charge.) The N-type and P-type of the N-type semiconductor layer 3 and the P-type semiconductor layer 5 are determined by the content of N (nitrogen). Note that the N-type and P-type can also be set by adding a metal element that indicates the N-type or P-type as a dopant to the nitride insulator material. The base material 2 may be, for example, a glass substrate. The N-side electrode 6 and the P-side electrode 7 are made of a metal such as Mo or Al.

[0030] As shown in FIG. 2, the heat flow switching element 1 of this embodiment generates thermally conductive charges e at and near the interface between the N-type semiconductor layer 3 and the insulator layer 4 when an electric field (voltage) is applied, and the generated charges e carry heat, changing the thermal conductivity.

[0031] In order to obtain a larger change in thermal conductivity due to the charges generated at the interface and its vicinity by the application of an electric field (voltage), a material with low lattice thermal conductivity is suitable, and the nitride insulator material of this embodiment is a material with low lattice thermal conductivity, i.e., low thermal conductivity. Moreover, the third thermal conductivity defined above increases in accordance with the amount of electric charge e generated in response to the applied external electric field (voltage). Since electric charges e are generated at the interfaces between the N-type semiconductor layer 3 and the P-type semiconductor layer 5 and the insulator layer 4, the amount of electric charges e generated can be increased by increasing the total area of ​​the interfaces.

[0032] The thermal conductivity is measured, for example, by the pulsed light heating thermoreflectance method, which involves instantaneously heating a thin film sample formed on a substrate with a pulsed laser and measuring the rate of surface temperature increase or decrease due to thermal diffusion into the thin film to determine the thermal diffusivity or thermal effusivity of the thin film in the film thickness direction. Among the pulsed light heating thermoreflectance methods, the method of directly measuring thermal diffusivity (rear heating / surface temperature measurement (RF) method) requires the use of a transparent substrate through which the pulsed laser can pass. Therefore, for non-transparent substrates, the thermal conductivity is measured using the surface heating / temperature measurement (FF) method, which measures the thermal effusivity and converts it into thermal conductivity. This measurement requires a metal film, such as Mo or Al. In this embodiment, the thermal effusivity is measured by the surface heating / temperature measurement (FF) method.

[0033] In the heat flow switching element 1 of this embodiment, charge e is generated both at and near the interface between the N-type semiconductor layer 3 and the insulator layer 4, and at and near the interface between the P-type semiconductor layer 5 and the insulator layer 4, so a large amount of charge is generated, resulting in a large change in thermal conductivity and high thermal responsiveness. Furthermore, because the mechanism does not use a chemical reaction mechanism but instead physically changes the thermal conductivity, the element can immediately transition to a changed state, resulting in good thermal responsiveness.

[0034] Furthermore, since the amount of charge induced at the interface varies depending on the magnitude of the external voltage, it is possible to adjust the thermal conductivity by adjusting the external voltage, making it possible to actively control the heat flow through this element. Since the insulating layer 4 is an insulator and no current is generated when a voltage is applied, no Joule heat is generated, making it possible to actively control the heat flow without self-heating. Furthermore, when the N-type semiconductor layer 3 and the P-type semiconductor layer 5 are made of nitride, the insulator layer 4 is also made of nitride, which improves the bonding strength at the interfaces between the P-type and N-type semiconductor layers and the insulator layer.

[0035] As described above, the nitride insulator material (insulator layer 4) of this embodiment is a metal nitride represented by M-Si-N-Te (where M represents at least one of Ta and Hf, and Te is an optional element), and is a nanocrystal, so it has insulating properties and low lattice thermal conductivity, resulting in low thermal conductivity and low thermal effusivity. Therefore, the insulator layer 4 of this embodiment functions as both an electrical and thermal barrier layer. Among the constituent elements, M (at least one of Ta and Hf) and Si are nanocrystallized (crystal size is 5 nm, including amorphous), which reduces the lattice thermal conductivity and makes it possible to reduce the thermal effusivity. Furthermore, the content of N among the constituent elements provides insulation. Furthermore, Te among the constituent elements has the effect of further reducing the thermal effusivity.

[0036] In particular, the nitride insulating material of this embodiment has a thermal effusivity of 2000 Ws 0.5 / m 2 K and electrical resistivity 10 8 Therefore, the nitride insulator material of this embodiment has a thermal conductivity lower than that of HfO2, and exhibits a thermal conductivity of 100 μA / mm 2 This provides insulation that allows current to flow less than this. Furthermore, the nitride insulating material of this embodiment has a thermal effusivity of 1700 Ws 0.5 / m 2 K and electrical resistivity 10 8 Therefore, such nitride insulator materials have a lower thermal conductivity than HfO2 or SiN, and can achieve a thermal conductivity of 100 μA / mm when a voltage of 10 V is applied. 2The nitride insulator material of this embodiment exhibits lower thermal conductivity, i.e., higher thermal insulation, and is therefore more suitable as an insulator layer constituting a heat flow switching element and as an insulator layer constituting a thermoelectric conversion element.

[0037] The heat flow switching element 1 of this embodiment comprises an N-type semiconductor layer 3, an insulator layer 4 stacked on the N-type semiconductor layer 3, and a P-type semiconductor layer 5 stacked on the insulator layer 4. When an external voltage is applied to the N-type semiconductor layer 3 and the P-type semiconductor layer 5, electric charges e are induced mainly at the interfaces between the P-type semiconductor layer 5 and the N-type semiconductor layer 3 and the insulator layer 4, and these electric charges e carry heat, causing a change in thermal conductivity.

[0038] In particular, since the insulator layer 4 is formed of the above-mentioned nitride insulator material, low thermal conductivity is obtained, exhibiting low lattice thermal conductivity and low thermal effusivity at zero bias, and the rate of change of thermal conductivity can be increased by an external electric field (external voltage). In other words, the lower the lattice thermal conductivity, the greater the contribution of thermal conductivity due to the interface in response to an external electric field from zero bias, and the greater the rate of change of thermal conductivity in response to an external electric field, improving the heat flow switching performance.

[0039] In the manufacturing method of the nitride insulator material (insulator layer 4) of this embodiment, a M-Si-Te sputtering target (where M represents at least one of Ta and Hf, and Te is an optional element) is used to form a film by reactive sputtering in a nitrogen-containing atmosphere, so that it is possible to obtain a metal nitride represented by M-Si-N-Te (where M represents at least one of Ta and Hf, and Te is an optional element), a nanocrystalline nitride insulator layer or nitride insulator film with low surface roughness.

[0040] Next, second and third embodiments of the nitride insulator material and its manufacturing method, as well as the heat flow switching element and thermoelectric conversion element according to the present invention will be described below with reference to Figures 3 and 4. In the following description of each embodiment, the same components as those described in the above embodiments will be denoted by the same reference numerals, and their description will be omitted.

[0041] The second embodiment differs from the first embodiment in that, in the first embodiment, one N-type semiconductor layer 3, one insulator layer 4, and one P-type semiconductor layer 5 are stacked, whereas in the heat flow switching element 21 of the second embodiment, multiple N-type semiconductor layers 23 and multiple P-type semiconductor layers 25 are stacked alternately with an insulator layer 24 sandwiched between them, as shown in FIG. 3. That is, in the second embodiment, an insulator layer 24 is first formed on a substrate 22, and then N-type semiconductor layers 23 and P-type semiconductor layers 25 are repeatedly stacked on top of the insulator layer 24 in this order with the insulator layer 24 interposed therebetween, thereby forming a stack of three N-type semiconductor layers 23, three P-type semiconductor layers 25, and seven insulator layers 24.

[0042] Each N-type semiconductor layer 23 is connected to an N-side connecting portion 23a provided at the base end, and an N-side electrode 26 is formed on a part of the N-side connecting portion 23a. Each P-type semiconductor layer 25 is connected to a P-side connecting portion 25a provided at the base end, and a P-side electrode 27 is formed on a part of the P-side connecting portion 25a. Each of the above layers is patterned using a metal mask. By forming the layers with the metal masks shifted in position, multiple N-type semiconductor layers 23, P-type semiconductor layers 25, and insulating layers 24 are stacked. Further, lead wires 26a and 27a are connected to the N-side electrode 26 and the P-side electrode 27, respectively.

[0043] In this way, in the heat flow switching element 21 of the second embodiment, the N-type semiconductor layers 23 and the P-type semiconductor layers 25 are stacked alternately with the insulator layers 24 sandwiched between them, so that when an external voltage is applied, the electric charge e generated in response to the increased number of interfaces due to the stacking also increases, resulting in a larger change in thermal conductivity and high thermal responsiveness.

[0044] Furthermore, the heat flow switching element 21 of the second embodiment comprises an upper high thermal conductivity portion 28 provided on the top surface, a substrate 22 which is a lower high thermal conductivity portion provided on the bottom surface, and a peripheral heat insulating portion 29 which is provided to cover the outer edges of the N-type semiconductor layer 23, the insulator layer 24 and the P-type semiconductor layer 25, and the peripheral heat insulating portion 29 is formed from the above-mentioned nitride insulator material which has lower thermal conductivity than the upper high thermal conductivity portion 28 and the substrate 22 which is the lower high thermal conductivity portion.

[0045] That is, the peripheral heat insulating portion 29 is a metal nitride represented by M-Si-N-Te (wherein M represents at least one of Ta and Hf, and Te is an optional element), and is a nanocrystal. Like the peripheral insulation portion 29, the insulator layer 24 is also a metal nitride represented by M-Si-N-Te (wherein M represents at least one of Ta and Hf, and Te is an optional element), and is preferably a nanocrystal. In addition, the upper high thermal conductivity portion 28 is formed from a high thermal conductivity material such as silicon-based resin (silicone), and the base material 22, which is the lower high thermal conductivity portion, is a high thermal conductivity substrate formed from alumina or the like.

[0046] The peripheral heat insulating portion 29 covers the periphery of the uppermost insulating layer 24 while leaving the uppermost insulating layer 24 exposed, and the upper high thermal conductivity portion 28 is formed on top so as to contact the exposed uppermost insulating layer 24. The outer peripheral heat insulating portion 29 is also formed to cover the N-side electrode 26 and the P-side electrode 27 that are disposed on the outer periphery of each layer and connected to the lead wires 26a and 27a.

[0047] In the second embodiment, the heat flow direction is the stacking direction (the direction of the arrow in FIG. 3), and for example, the upper high thermal conductivity section 28 side is the high temperature side, and the lower high thermal conductivity section, or base material 22 side, is the low temperature side. As long as the heat flow direction is the stacking direction, the upper high thermal conductivity section 28 side may be the low temperature side, and the lower high thermal conductivity section, or base material 22 side, may be the high temperature side. As described above, in the heat flow switching element 21 of the second embodiment, the peripheral insulation portion 29 is formed of a nitride insulator material having lower thermal conductivity than the upper high thermal conductivity portion 28 on the top surface and the lower high thermal conductivity portion on the bottom surface of the substrate 22. Therefore, while the entire N-type semiconductor layer 23, insulator layer 24, and P-type semiconductor layer 25 serve as the heat flow path, heat can be prevented from flowing via the peripheral insulation portion 29, whose thermal conductivity does not change, thereby achieving heat flow switching properties in the stacking direction.

[0048] Next, the third embodiment differs from the second embodiment in that the second embodiment is a heat flow switching element, whereas the third embodiment is a thermoelectric conversion element 31 as shown in FIG. That is, the thermoelectric conversion element 31 of the third embodiment comprises an insulating base material 32, a P-type thin-film thermoelectric conversion unit 33p and an N-type thin-film thermoelectric conversion unit 33n formed on the insulating base material 32, a connection electrode unit 34 connecting the P-type thin-film thermoelectric conversion unit 33p and the N-type thin-film thermoelectric conversion unit 33n, a pair of electrode terminal units 35 formed at the ends of the connected P-type thin-film thermoelectric conversion unit 33p and N-type thin-film thermoelectric conversion unit 33n, and an insulator film 39 covering the surfaces of the insulating base material 32, the P-type thin-film thermoelectric conversion unit 33p, the N-type thin-film thermoelectric conversion unit 33n, and the connection electrode unit 34.

[0049] The insulator film 39 is made of the same nitride insulator material as in the first embodiment. That is, the insulator film 39 is a metal nitride represented by M-Si-N-Te (where M represents at least one of Ta and Hf, and Te is an optional element), and is a nanocrystalline film.

[0050] At least one of the P-type thin-film thermoelectric converter 33p and the N-type thin-film thermoelectric converter 33n is made of a nitride thermoelectric conversion material. For example, the nitride thermoelectric conversion material may be represented by the general formula: (Cr 1-x M x ) 1-y N y(where M represents at least one of Ti, V, Mn, Fe, Co, Ni, Cu, Zr, Nb, Mo, Hf, Ta, W, Si, Al, B, and Y; 0≦x<1.0, 0.40≦y<0.54), and has a cubic NaCl-type crystal structure (space group Fm-3m (No. 225)), with either P-type or N-type thermoelectric properties.

[0051] In this embodiment, both the P-type thin-film thermoelectric conversion unit 33p and the N-type thin-film thermoelectric conversion unit 33n are formed from the above-mentioned nitride thermoelectric conversion material, but the P-type thin-film thermoelectric conversion unit may be formed from an organic thermoelectric material (printed material), and the N-type thin-film thermoelectric conversion unit 33n may be formed from the above-mentioned nitride thermoelectric conversion material.

[0052] The P-type thin-film thermoelectric conversion units 33p and the N-type thin-film thermoelectric conversion units 33n are formed in the shape of multiple lines or strips, extend parallel to each other, and are arranged alternately. Furthermore, the ends of adjacent P-type thin-film thermoelectric conversion units 33p and N-type thin-film thermoelectric conversion units 33n are connected by connecting electrode units 34, and the entire unit forms a single thin-film thermoelectric conversion unit that is folded back multiple times, and a pair of electrode terminal units 35 are formed at both ends.

[0053] The connection electrode portion 34 and the electrode terminal portion 35 are patterned and made of Ag, an Ag alloy, or the like. Lead wires 36 are connected to the pair of electrode terminals 35 , and the lead wires 36 are connected to a power source 37 .

[0054] The insulating base material 32 is preferably formed from a material with low thermal conductivity, and may be, for example, an insulating film or glass. The insulating film may be, for example, a polyimide resin sheet. Other insulating films may also be used, such as liquid crystal polymer (LCP), polyethylene terephthalate (PET), or polyethylene naphthalate (PEN). The glass substrate may be, for example, alkali-free glass, an alkali glass plate, or a glass film.

[0055] When an insulating film is used for the insulating substrate 32, the thermoelectric conversion element 31 becomes a sheet-type thermoelectric conversion element. For example, the thermoelectric conversion element 31 can be a sheet-type Peltier element (cooling element) that converts electrical energy into thermal energy and transports heat, a sheet-type Seebeck element (thermoelectric power generation element) that converts thermal energy into electrical energy and generates power from a temperature difference, or a sheet-type thermopile that serves as an infrared sensor that applies the principle of a thermocouple.

[0056] As described above, in the thermoelectric conversion element 31 of the third embodiment, the insulator film 39 is formed from the above-mentioned nitride insulator material. Therefore, since the surface is covered with the insulator film 39 made of a nitride insulator material having low thermal conductivity, heat release from the surfaces of the P-type thin-film thermoelectric conversion section 33p and the N-type thin-film thermoelectric conversion section 33n is suppressed, and a sufficient temperature difference between the high-temperature side and the low-temperature side can be ensured. Furthermore, when the P-type thin-film thermoelectric conversion unit 33p and the N-type thin-film thermoelectric conversion unit 33n are nitrides, the insulator film 39 is also a nitride, and therefore the bonding strength at the interfaces between the P-type thin-film thermoelectric conversion unit 33p and the N-type thin-film thermoelectric conversion unit 33n and the insulator film 39 is increased.

[0057] Next, the difference between the fourth embodiment and the third embodiment is that the P-type thin-film thermoelectric conversion unit 33p, the N-type thin-film thermoelectric conversion unit 33n, and the insulator film 39 are all film-like, whereas in the thermoelectric conversion elements 41A and 41B of the fourth embodiment, the P-type thermoelectric conversion unit 43p, the N-type thermoelectric conversion unit 43n, and the insulator 49 are all bulk rather than film-like, as shown in Figures 5(a) and (b).

[0058] In addition, in the third embodiment, the ends of adjacent P-type thin-film thermoelectric conversion units 33p and N-type thin-film thermoelectric conversion units 33n are connected by connecting electrode units 34 on the same plane, and the entire unit forms a single thin-film thermoelectric conversion unit that is folded over multiple times, whereas in the fourth embodiment, the ends of adjacent bulk P-type thermoelectric conversion units 43p and N-type thermoelectric conversion units 43n are connected by upper and lower connecting electrode units 44, and the entire unit forms a continuous thermoelectric conversion unit that is folded over multiple times on the vertical cross section.

[0059] In this embodiment, a bulk insulator 49 made of the above-mentioned nitride insulator material is bonded to both side surfaces of the P-type thermoelectric conversion unit 43p and the N-type thermoelectric conversion unit 43n, covering the side surfaces (surfaces). The P-type thermoelectric converter 43p, the N-type thermoelectric converter 43n, the insulator 49, and the connection electrode 44 are sandwiched between insulating substrates 42A and 42B.

[0060] In the thermoelectric conversion element 41A shown in Fig. 5(a), the insulator 49 joined to the side surface of the P-type thermoelectric conversion unit 43p and the insulator 49 joined to the side surface of the N-type thermoelectric conversion unit 43n are in contact with each other. In contrast, in the thermoelectric conversion element 41B shown in Fig. 5(b), the insulator 49 joined to the side surface of the P-type thermoelectric conversion unit 43p and the insulator 49 joined to the side surface of the N-type thermoelectric conversion unit 43n are spaced apart and do not contact each other.

[0061] In this way, in the thermoelectric conversion elements 41, 41B of the fourth embodiment, the insulator 49 is formed from the above-mentioned nitride insulator material. Therefore, since the surface (side surface) is covered with the insulator 49 made of a nitride insulator material with low thermal conductivity, even if the element is constructed in bulk, heat release from the surface is suppressed, and a sufficient temperature difference between the high-temperature side and the low-temperature side can be ensured. [Example]

[0062] Based on the first embodiment, the materials (Ta-Si-N, Hf-Si-N, Ta-Si-N-Te) listed in Tables 2 and 3 below were deposited on glass substrates by reactive sputtering in a nitrogen-containing atmosphere to measure the crystal structure, thermal effusivity, and electrical resistivity of the samples. The results of the crystal structure and thermal effusivity are shown in Tables 2 and 3. The composition of each example was set by changing the nitrogen fraction (N2 / (Ar+N2)) and the Si / (M+Si) ratio. The composition was analyzed by elemental analysis using X-ray photoelectron spectroscopy (XPS). XPS quantitative analysis was performed on the sputtered surface at a depth of 20 nm from the outermost surface using Ar sputtering. The quantitative accuracy of N / (M+Si+N) was ±2%, and that of Si / (M+Si) was ±1%.

[0063] As comparative examples, the thermal effusivity and electrical resistivity of Al-N, HfO2, Ta-Si, Hf-Si, and Si-N films were also measured. The results of the crystal structure and thermal effusivity are also shown in Table 1. A magnetron sputtering device was used for sputtering, and a nitride insulating material film was formed to a thickness of 200 nm on a glass substrate (20 x 20 x 0.5 mm) by RF method, and Mo was sputtered to a thickness of 100 nm on the obtained film to form a device. The surface roughness Ra of each of the nitride insulating material films after sputtering was small, less than 2 nm. The surface roughness Ra was evaluated using X-ray reflectivity measurement.

[0064] The thermal effusivity was measured by the FF method (surface heating / surface temperature measurement) of the pulsed light heating thermoreflectance method (using a thin film thermal property measuring device: PicoTherm PicoTR). The measurement was carried out at room temperature. The thermal conductivity is calculated from the thermal effusivity using the following formula: Thermal conductivity k = (thermal effusivity b) 2 / volumetric heat capacity =(thermal effusivity b) 2 / (specific heat x density)

[0065] [Table 1] [Table 2] [Table 3]

[0066] From these results, it can be seen that the thermal effusivity of each example of the present invention is 2000Ws 0.5 / m2 The comparative examples all had a thermal effusivity of 2000Ws 0.5 / m 2 K or more, whereas in the examples of the present invention, Hf-Si-N, Ta-Si-N-Te, and Ta-Si-N containing 17.9 at% or more of Ta in particular, have a thermal effusivity of 1700 Ws 0.5 / m 2 It is a low thermal conductivity material below K. In Ta-Si-N, increasing the Ta content tends to decrease the thermal effusivity and increase the volumetric heat capacity. When the Ta content is 17.9 at% or more, the thermal effusivity of 1Ws 0.5 / m 2 This allows for the production of highly insulating materials with low thermal conductivity below 1000K. Furthermore, the thermal effusivity of Example 35 (Ta-Si-N-Te) containing Te was 250 Ws 0.5 / m 2 In Example 35, the thermal effusivity was significantly smaller than in Examples 1 to 34, reaching 1000 Ws 0.5 / m 2 The low thermal conductivity material was less than K. Example 35 exhibits very low thermal conductivity, i.e., very high thermal insulation, and is therefore more suitable as an insulator layer constituting a heat flow switching element and an insulator layer constituting a thermoelectric conversion element. The electrical resistivity of each example of the present invention is 10 8 The electrical resistivity of Comparative Examples 3 and 4 was 10 Ωcm or more, indicating high insulation. The metal compounds in Comparative Examples 3 and 4 did not contain nitrogen, and all of them had an electrical resistivity of less than 10 Ωcm. The electrical resistivity of Comparative Examples 1, 2, and 5 was 10 8 Ωcm or more, showing high insulation properties, but the thermal effusivity of both was 2000Ws 0.5 / m 2 It is a material with high thermal conductivity of over K. The M-Si-N-Te of the example (wherein M represents at least one of Ta and Hf, and Te is an optional element) and the Si-N of the comparative example 5 both have an electrical resistivity of 10 8Although the thermal conductivity was Ωcm or more, the examples contain heavy metal elements such as Ta or Hf, which results in a smaller lattice thermal conductivity than Si-N, and a smaller thermal effusivity. The electrical resistivity measurement (insulation evaluation test) was performed using the arrangement shown in Figure 6. The measurement was performed at room temperature. Specifically, a 100 mm M-Si-N-Te thin film (12) (where M represents at least one of Ta and Hf, and Te is an optional element) nitride insulator material of the present invention was formed on a Si substrate 11. A 50 nm Mo electrode 13 was then formed on the thin film. A voltage was applied between the Si substrate 11 and the Mo electrode 13 using a high-voltage source meter, and the electrical resistivity was determined based on the current value. The M-Si-N-Te thin film (100 mm) 12 had an area 100 times larger than that of the Mo electrode 13, and the Mo electrode 13 was positioned approximately at the center of the M-Si-N-Te thin film (100 mm) 12, thereby suppressing the flow of surface current to the periphery of the M-Si-N-Te thin film 12 and enabling measurement of the electrical resistivity of the film itself.

[0067] As can be seen from Tables 2 and 3, the crystal structure of each of the examples of the present invention was nanocrystalline, whereas the Al-N Comparative Example 1 was columnar. The thermal effusivity of the Al-N columnar crystal of Comparative Example 1 was 2000 Ws 0.5 / m 2 The values ​​were significantly higher than K. Comparative Example 2 of HfO2, Comparative Example 3 of Ta-Si, Comparative Example 4 of Hf-Si, and Comparative Example 5 of Si-N all had nanocrystalline crystal structures, but the thermal effusivity was less than 2000 Ws 0.5 / m 2 In particular, Ta-Si Comparative Example 3 and Hf-Si Comparative Example 4 are metal compounds that do not contain nitrogen, and 0.5 / m 2 The thermal effusivity was high at over K.

[0068] Next, for Example 5 in Table 2, an XRD pattern (taken using a fully automated multipurpose X-ray diffractometer (SmartLab: manufactured by RIGAKU)) is shown in FIG. 7, and a cross-sectional SEM image (45-degree oblique field of view, 200,000x magnification) is shown in FIG. 8. This cross-sectional SEM image was taken from a substrate that had been cleaved. FIG. 8 shows both the cross-sectional structure and surface structure of the Ta-Si-N film. It can be seen that Example 5 of the present invention has high surface smoothness, is dense, and has high density. Thin-film XRD was performed using grazing incidence X-ray diffraction (thin-film XRD) under conditions of a Cu tube and an incident angle of 1 degree. No sharp peaks indicating long-period crystallinity, which would suggest a relatively large crystal size, were detected.

[0069] FIG. 9 shows cross-sectional SEM images (45-degree oblique field of view, 50,000x magnification) of Examples 7 and 25 of the present invention. This cross-sectional SEM image was taken from a substrate that had been cleaved. FIG. 9 also shows the cross-sectional and surface structures of the Ta-Si-N film and Hf-Si-N film. It can be seen that Examples 7 and 25 of the present invention have high surface smoothness, are dense, and have high density. Furthermore, Fig. 10 shows cross-sectional TEM (HAADF-STEM) images (high-angle annular dark-field scanning transmission microscopy) for Examples 7 and 25. The magnification of this TEM image is 1,050,000 times. As can be seen from these images, the crystalline structures of Examples 7 and 25 of the present invention are dense nanocrystals with a crystal size of 5 nm or less. Note that in this specification, the term "nanocrystal" refers to any material with a crystal size of 5 nm or less, including amorphous materials.

[0070] Next, detailed analysis of the cross-sectional structures of Ta-Si-N and Hf-Si-N was performed using a TEM. Electron diffraction images of the cross sections of the films of Examples 7 and 25 are shown in Figure 11. Neither of the electron diffraction images showed long-period crystallinity, which would suggest a relatively large crystal size, indicating that the crystal size was very small or that the nanocrystals were amorphous. The TEM images show that the examples have dense nanocrystals with crystal sizes of 5 nm or less. Furthermore, these images show that the diffraction rings are clearer in Example 25 than in Example 7, indicating that nanocrystals with smaller crystal sizes were obtained in Example 7 (Ta-Si-N) than in Example 25 (Hf-Si-N). Grazing incidence X-ray diffraction (thin film XRD) was also performed, and peaks indicating a crystallized film were observed for the columnar crystal material of the comparative example, but no sharp peaks indicating long-period crystallinity, which would suggest a relatively large crystal size, were detected for the example. The results of XRD, SEM, and TEM indicate that the example is made of very small or amorphous nanocrystals with a crystal size of 5 nm or less.

[0071] Furthermore, it is clear that the nanocrystal films of the examples have high surface smoothness (surface roughness Ra of less than 2 nm), and are dense and high density. In other words, the low thermal conductivity (high thermal insulation) is not due to low density such as voids, but rather indicates that the nitride material itself has low thermal conductivity. These results indicate that nanocrystalline crystal size reduces heat conduction due to vibrations (phonons, lattice vibrations) that travel between crystal lattices, reducing lattice thermal conduction and achieving a thermal effusivity of 2000 Ws 0.5 / m 2 This shows that low thermal conductivity semiconductor materials with a thermal effusivity of less than 1700 Ws were obtained. Furthermore, among the examples of the present invention, Hf-Si-N, Ta-Si-N-Te, and Ta-Si-N containing 17.9 at% or more of Ta in particular exhibited a thermal effusivity of 1700 Ws 0.5 / m 2 It showed low thermal conductivity of less than K. The thermal effusivity of Example 35 (Ta-Si-N-Te) containing Te was 250 Ws 0.5 / m 2 K, and the thermal effusivity is 1000Ws 0.5 / m 2 It was a very low thermal conductivity material with less than 1000 K. XRD, SEM, and TEM of Example 35 confirmed that it was a nanocrystalline film with a crystal size of 5 nm or less. Furthermore, Example 35 was found to have high surface smoothness (surface roughness Ra less than 2 nm), a dense structure, and a high density. That is, even in Example 35 (Ta-Si-N-Te) containing Te, the low thermal conductivity (high thermal insulation) is not due to low density such as voids, but rather indicates that the nitride material containing Te itself has low thermal conductivity. Because it exhibits very low thermal conductivity, i.e., very high thermal insulation, it is more suitable as an insulator layer constituting a heat flow switching element and an insulator layer constituting a thermoelectric conversion element. The composition ranges of each element in M-Si-N-Te in Examples 1 to 35 were M 5.9 to 37.9 at%, Si 8.0 to 44.1 at%, N 42.6 to 59.0 at%, and Te 0 to 8.4%, with the total of each element being 100 at%, and Si / (M+Si) being 17.4 to 87.2 at%.

[0072] The technical scope of the present invention is not limited to the above-described embodiments and examples, and various modifications can be made without departing from the spirit of the present invention. [Explanation of symbols]

[0073] 1,21...heat flow switching element, 3,23...N-type semiconductor layer, 4,24...insulating layer, 5,25...P-type semiconductor layer, 22...substrate (lower high thermal conductivity portion), 28...upper high thermal conductivity portion, 29...periphery heat insulating portion, 31,41A,41B...thermoelectric conversion element, 32...insulating substrate, 33p...P-type thin-film thermoelectric conversion portion, 43p...P-type thermoelectric conversion portion, 33n...N-type thin-film thermoelectric conversion portion, 43n...N-type thermoelectric conversion portion, 34,44...connecting electrode portion, 39...insulating film, 49...insulating body

Claims

1. A nitride insulating material is a metal nitride represented by M-Si-N-Te (wherein M represents at least one of Ta and Hf), and is characterized by being a nanocrystal.

2. The nitride insulating material according to claim 1 , Heat effusivity 2000Ws ０．５ / m ２ 2. A nitride insulating material having a temperature of less than 1000K.

3. The nitride insulating material according to claim 2, Heat effusivity 1700Ws ０．５ / m ２ 2. A nitride insulating material having a temperature of less than 1000K.

4. The nitride insulating material according to any one of claims 1 to 3, Electrical resistivity 10 ８ A nitride insulating material characterized by a resistivity of Ωcm or more.

5. The nitride insulating material according to any one of claims 1 to 4, A nitride insulating material characterized by being used as a low thermal conductive material.

6. an N-type semiconductor layer; an insulator layer stacked on the N-type semiconductor layer; a P-type semiconductor layer stacked on the insulator layer, A thermal flow switching element, wherein the insulating layer is formed from the nitride insulating material according to claim 1 .

7. 7. The thermal flow switching element according to claim 6, an upper high thermal conductivity portion provided on the top surface; a lower high thermal conductivity portion provided on the bottom surface; a peripheral heat insulating portion provided to cover peripheral edges of the N-type semiconductor layer, the insulator layer, and the P-type semiconductor layer, A heat flow switching element, wherein the outer peripheral heat insulating portion is formed of the nitride insulating material having lower thermal conductivity than the upper high thermal conductivity portion and the lower high thermal conductivity portion.

8. an insulating substrate; a P-type thermoelectric conversion section and an N-type thermoelectric conversion section formed on the insulating substrate; a connection electrode portion that connects the P-type thermoelectric conversion portion and the N-type thermoelectric conversion portion; an insulator covering surfaces of the P-type thermoelectric conversion unit and the N-type thermoelectric conversion unit; A thermoelectric conversion element, characterized in that the insulator is formed from the nitride insulator material according to any one of claims 1 to 5.

9. The thermoelectric conversion element according to claim 8, The thermoelectric conversion element is characterized in that the P-type thermoelectric conversion portion, the N-type thermoelectric conversion portion, and the insulator are in the form of a film.

10. A method for producing the nitride insulating material according to any one of claims 1 to 5, comprising the steps of: A method for producing a nitride insulating material, characterized by forming a film by reactive sputtering in a nitrogen-containing atmosphere using an M-Si-Te sputtering target (where M represents at least one of Ta and Hf).

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