Thermoelectric generation device

Abstract

To provide a thermoelectric generation device that is hardly damaged and easy to handle.SOLUTION: A thermoelectric generation device comprises: a silicon substrate 100 that has a first impurity area 20 and a second impurity area 30 on a first surface 100a; a first silicon nano-wire group 10A that is provided in the first impurity area 20 and has a plurality of silicon nano-wires 10 extending in a direction intersecting the first surface 100a; a second silicon nano-wire group 10B that is provided in the second impurity area 30 and has the plurality of silicon nano-wires 10; and conductive films 510, 520 that are arranged on the first silicon nano-wire group 10A and the second silicon nano-wire group 10B, and is electrically connected with the silicon nano-wire 10.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a thermoelectric generating element. [Background technology]

[0002] Patent Document 1 discloses the structure of silicon nanowires formed using semiconductor materials such as silicon. Silicon nanowires have a very high aspect ratio, for example, a diameter of several tens of nm and a length of several μm, and low thermal conductivity, and can be used as thermoelectric elements. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2014-505998 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the configuration described in Patent Document 1, the silicon nanowires are configured with a high aspect ratio, and therefore have the problem that they are easily damaged and difficult to handle. [Means for solving the problem]

[0005] The thermoelectric power generation element comprises a silicon substrate having a first impurity region and a second impurity region on a first surface, a first silicon nanowire group provided in the first impurity region and having a plurality of silicon nanowires extending in a direction intersecting the first surface, a second silicon nanowire group provided in the second impurity region and having the plurality of silicon nanowires, and a conductive film disposed on the first silicon nanowire group and the second silicon nanowire group and electrically connected to the silicon nanowires. [Brief description of the drawings]

[0006] [Figure 1]FIG. 2 is a perspective view showing the configuration of a thermoelectric generating element. [Diagram 2] FIG. 3 is a cross-sectional view showing the configuration of a thermoelectric generating element. [Diagram 3] 3 is an enlarged cross-sectional view showing a portion A of the thermoelectric generating element shown in FIG. 2. [Figure 4] 4A to 4C are cross-sectional views showing a method for manufacturing a thermoelectric generating element. [Diagram 5] 4A to 4C are cross-sectional views showing a method for manufacturing a thermoelectric generating element. [Figure 6] 4A to 4C are cross-sectional views showing a method for manufacturing a thermoelectric generating element. [Figure 7] 4A to 4C are cross-sectional views showing a method for manufacturing a thermoelectric generating element. [Figure 8] 4A to 4C are cross-sectional views showing a method for manufacturing a thermoelectric generating element. [Figure 9] 4A to 4C are cross-sectional views showing a method for manufacturing a thermoelectric generating element. [Figure 10] 4A to 4C are cross-sectional views showing a method for manufacturing a thermoelectric generating element. [Figure 11] 4A to 4C are cross-sectional views showing a method for manufacturing a thermoelectric generating element. [Figure 12] 4A to 4C are cross-sectional views showing a method for manufacturing a thermoelectric generating element. [Figure 13] 4A to 4C are cross-sectional views showing a method for manufacturing a thermoelectric generating element. [Figure 14] 4A to 4C are cross-sectional views showing a method for manufacturing a thermoelectric generating element. [Figure 15] 4A to 4C are cross-sectional views showing a method for manufacturing a thermoelectric generating element. [Figure 16] FIG. 11 is a cross-sectional view showing the configuration of a thermoelectric generation element according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] In the following figures, the three mutually orthogonal axes are described as the X-axis, Y-axis, and Z-axis. The direction along the X-axis is the "X-direction", the direction along the Y-axis is the "Y-direction", and the direction along the Z-axis is the "Z-direction", with the arrow direction being the + direction and the direction opposite to the + direction being the - direction. The +Z direction is sometimes called "upper" or "upper side" or "front side", and the -Z direction is sometimes called "lower" or "lower side" or "rear side", and the view from the +Z direction and -Z direction is also called a planar view or planar. The surface on the +Z side is described as the "upper surface" or "front side", and the surface on the opposite side of the -Z side is described as the "lower surface" or "rear side".

[0008] First, the configuration of a thermoelectric generating element 1000 will be described with reference to FIGS.

[0009] 1 and 2, the thermoelectric generating element 1000 is an element that generates electricity by utilizing the temperature difference between, for example, the high temperature of body temperature and the low temperature of outside air, and includes a silicon substrate 100 on which a plurality of silicon nanowires 10 are formed, a heat conductive plate 200, and a heat sink 300. The thermoelectric generating element 1000 is used, for example, as a power source for a wristwatch-type portable device.

[0010] The silicon substrate 100 has a first surface 100a on the thermal conduction plate 200 side. The first surface 100a of the silicon substrate 100 has, for example, a first impurity region 20 implanted with a P-type impurity and a second impurity region 30 implanted with an N-type impurity. An example of the P-type impurity is boron (B). An example of the N-type impurity is phosphorus (P).

[0011] A P-type impurity is implanted into the first impurity region 20 of the silicon substrate 100, and a plurality of first silicon nanowires 11 extending in a direction intersecting the first surface 100a are disposed therein. An N-type impurity is implanted into the second impurity region 30 of the silicon substrate 100, and a plurality of second silicon nanowires 12 extending in a direction intersecting the first surface 100a are disposed therein.

[0012] The aggregate of the multiple first silicon nanowires 11 is referred to as a first silicon nanowire group 10A, and the aggregate of the multiple second silicon nanowires 12 is referred to as a second silicon nanowire group 10B.

[0013] The thermally conductive plate 200 is formed so that the thickness H1 of the region corresponding to the first silicon nanowire group 10A and the thickness H1 of the region corresponding to the second silicon nanowire group 10B are thicker than the thickness H2 of the other regions.

[0014] An insulating film 400 and a conductive film 500 are disposed on the silicon substrate 100 side of the thermally conductive plate 200. The insulating film 400 is preferably made of a material with good thermal conductivity, such as aluminum nitride (AlN). The conductive film 500 is, for example, aluminum (Al). The material of the conductive film 500 is not limited to aluminum, and other conductive materials may be used.

[0015] The conductive film 500 has a first conductive film 510 electrically connected to the first silicon nanowires 11 of the first silicon nanowire group 10A and a second conductive film 520 electrically connected to the second silicon nanowires 12 of the second silicon nanowire group 10B, and the first conductive film 510 and the second conductive film 520 are arranged with a gap between them. That is, the first conductive film 510 and the second conductive film 520 are insulated from each other.

[0016] As described above, by making the thicknesses H1, H2 of the thermally conductive plate 200 different, the first silicon nanowire 11 and the first conductive film 510 can be electrically connected in the region overlapping with the first impurity region 20 in a planar view. Also, the second silicon nanowire 12 and the second conductive film 520 can be electrically connected in the region overlapping with the second impurity region 30 in a planar view. In other words, electricity can be generated via the first conductive film 510 and the second conductive film 520.

[0017] The silicon substrate 100 has an outer circumferential region 40 that does not overlap the first impurity region 20 and the second impurity region 30 in a planar view. As described above, since the thicknesses H1, H2 of the thermally conductive plate 200 are made different, a gap is generated between the first surface 100a of the silicon substrate 100 and the conductive films 510, 520 in the outer circumferential region 40. An adhesive 600 for bonding the silicon substrate 100 and the conductive films 510, 520, i.e., the thermally conductive plate 200, is disposed in this gap.

[0018] Specifically, as shown in Fig. 3, the adhesive 600 has a gap material 610. The adhesive 600 is applied so as to surround the first silicon nanowire group 10A and the second silicon nanowire group 10B. This makes it possible to maintain a near-vacuum state within the space surrounded by the adhesive 600, thereby preventing the propagation of heat through the atmosphere. As a result, the efficiency of thermoelectric power generation can be improved.

[0019] Moreover, by selecting the diameter of the gap material 610, it is possible to determine the push-in amount H3 of the silicon nanowires 10 with respect to the conductive films 510 and 520. That is, it is possible to adjust the push-in amount H3. The push-in amount H3 is, for example, 0.2 μm.

[0020] In this way, by pressing the ends of the silicon nanowires 10 into the conductive films 510, 520, it is possible to reliably bring the conductive films 510, 520 into contact with the silicon nanowires 10 and establish an electrical connection even if there is variation in the length of the silicon nanowires 10, variation in the step of the heat conduction plate 200, or variation in the thickness of the insulating film 400 and the conductive films 510, 520.

[0021] In addition, the gap material 610 maintains the gap between the silicon substrate 100 and the thermally conductive plate 200, thereby allowing for appropriate contact between the silicon nanowires 10 and the conductive films 510, 520, and preventing damage to the silicon nanowires 10 due to excessive pressure on the silicon nanowires 10.

[0022] As described above, the conductive films 510, 520 electrically connected to the silicon nanowires 10, in other words, in contact with the silicon nanowires 10, are disposed on the first silicon nanowire group 10A and the second silicon nanowire group 10B, so that one end of the silicon nanowires 10 is connected to the silicon substrate 100, and the other end of the silicon nanowires 10 is connected by the conductive films 510, 520. This makes it possible to support the silicon nanowires 10, and prevents the silicon nanowires 10 from being easily damaged even if they have a high aspect ratio. That is, the thermoelectric generating element 1000 can be made easier to handle.

[0023] Moreover, since aluminum is used for the conductive films 510, 520 that contact the silicon nanowires 10, it is possible to ensure conductivity between the silicon nanowires 10 and the conductive films 510, 520. Furthermore, since the conductive films 510, 520 are relatively susceptible to plastic deformation, when they are brought into contact with the ends of the silicon nanowires 10, they can slightly bite into the silicon nanowires 10, thereby preventing the silicon nanowires 10 from being damaged.

[0024] 1, a heat sink 300 is disposed on the back surface of the silicon substrate 100 on which the silicon nanowires 10 are not provided. Note that the heat sink 300 is preferably connected to the silicon substrate 100 via a highly thermally conductive adhesive 310 as shown in FIG.

[0025] In this way, by disposing the heat sink 300 on the back surface of the silicon substrate 100, it becomes possible to actively cool the back surface of the silicon substrate 100, and it becomes possible to increase the temperature difference between the thermally conductive plate 200 and the silicon substrate 100, and it becomes possible to generate a large electromotive force. Therefore, the thermoelectric generating element 1000 can be used with high efficiency.

[0026] Next, a method for manufacturing the thermoelectric generating element 1000 will be described with reference to FIGS.

[0027] 4, a heat conductive plate 200 is prepared. Specifically, a region 50 of the heat conductive plate 200 that comes into contact with the silicon nanowires 10 is formed in a convex shape so that the thickness H1 of the region 50 is large. The manufacturing method is not particularly limited, and the heat conductive plate 200 can be formed by, for example, an etching process.

[0028] 5, an insulating film 400 made of, for example, aluminum nitride (AlN) is formed. Specifically, the insulating film 400 for insulating the heat conduction plate 200 from the conductive films 510 and 520 is formed on the surface of the heat conduction plate 200 (the lower side in FIG. 5). The insulating film 400 can be formed, for example, by sputtering. The thickness of the insulating film 400 may be, for example, 0.5 μm, as long as the insulating properties are ensured.

[0029] 6, a first conductive film 510 and a second conductive film 520 are formed on the surface of the insulating film 400. Specifically, for example, a conductive film 530 is formed on the surface of the insulating film 400 by using a sputtering method or the like. The conductive film 530 is made of, for example, aluminum. Next, the first conductive film 510 and the second conductive film 520 are patterned into a predetermined shape by using a photolithography method and a wet etching method.

[0030] Next, a method for manufacturing the silicon substrate 100 having the silicon nanowires 10 will be described.

[0031] 7, a gold film pattern 120 is formed on a substrate 110 made of silicon. Specifically, a gold (Au) film that functions as a catalyst film for MACE (metal-assisted chemical etching) is formed on the substrate 110 at a position where the silicon nanowires 10 are to be formed. Next, the gold film is patterned to form the gold film pattern 120. Note that, although a gold film is used in this embodiment, there is no particular limitation as long as it is a catalyst film that causes the MACE reaction.

[0032] 8, an aluminum film 130 is formed on the gold film pattern 120 and the substrate 110. Specifically, the aluminum film 130 is formed by using, for example, a sputtering method.

[0033] 9, pores 131 are formed in the aluminum film 130. Specifically, the pores 131 are formed in the aluminum film 130 by anodization. The diameter of the pores 131 can be controlled by, for example, the composition of the chemical solution. The density of the pores 131 can be controlled by, for example, an applied voltage.

[0034] 10, the gold film pattern 120 is etched using an aluminum anodic oxide film 132 having pores 131 as a mask. Specifically, the gold film pattern 120 is etched by a sputtering method using argon (Ar). As a result, the gold film pattern 121 reflecting the shape of the pores 131 is formed in the gold film pattern 120.

[0035] In the step shown in FIG. 11, MACE processing is performed to form silicon nanowires 10. MACE processing is a simple etching method that can be performed by simply immersing a substrate in a mixture of an appropriate amount of hydrofluoric acid and hydrogen peroxide at room temperature. The aluminum anodic oxide film 132 can be easily dissolved by the MACE chemical. The length of the silicon nanowires 10 can be easily controlled by adjusting the immersion time. In the MACE processing of this embodiment, silicon nanowires 10 are formed to a length that does not penetrate the substrate 110. In addition, when the silicon nanowires 10 are formed, a gold film pattern 122 of a similar shape is also formed.

[0036] In the step shown in FIG. 12, the gold film pattern 122 remaining on the bottom of the silicon nanowires 10 is removed by immersion in a gold dissolving solution.

[0037] 13, P-type impurities are implanted into the region surrounding the first silicon nanowire group 10A, i.e., the region that will become the first impurity region 20. Furthermore, N-type impurities are implanted into the region surrounding the second silicon nanowire group 10B, i.e., the region that will become the second impurity region 30. As a result, a silicon substrate 100 is completed in which the first silicon nanowire group 10A implanted with P-type impurities and the second silicon nanowire group 10B implanted with N-type impurities are formed on the same surface.

[0038] Alternatively, a manufacturing method may be used in which the silicon nanowires 10 are formed after the impurity is first implanted.

[0039] 14, the silicon substrate 100 and the heat conductive plate 200 are bonded together. Specifically, the silicon substrate 100 and the heat conductive plate 200 are aligned so that the first silicon nanowire group 10A contacts the first conductive film 510 and further so that the second silicon nanowire group 10B contacts the second conductive film 520. Thereafter, the silicon substrate 100 and the heat conductive plate 200 are bonded together via an adhesive 600 containing a gap material 610 that is applied to the outer circumferential region 40 of the silicon substrate 100, and the bond is cured.

[0040] In addition, since the appropriate contact force between the silicon nanowires 10 and the conductive films 510 and 520 is controlled by the diameter of the gap material 610, it is preferable to select an appropriate diameter while checking the conductivity and damage state.

[0041] 15, a heat sink 300 is bonded to the rear surface of the silicon substrate 100. Specifically, the silicon substrate 100 and the heat sink 300 are bonded via a highly thermally conductive adhesive 310. Through the above steps, the thermoelectric power generating element 1000 is completed.

[0042] As described above, the thermoelectric power generation element 1000 of this embodiment comprises a silicon substrate 100 having a first impurity region 20 and a second impurity region 30 on a first surface 100a, a first silicon nanowire group 10A provided in the first impurity region 20 and having a plurality of silicon nanowires 10 extending in a direction intersecting the first surface 100a, a second silicon nanowire group 10B provided in the second impurity region 30 and having a plurality of silicon nanowires 10, and conductive films 510, 520 disposed on the first silicon nanowire group 10A and the second silicon nanowire group 10B and electrically connected to the silicon nanowires 10.

[0043] According to this configuration, the conductive films 510, 520 electrically connected to the silicon nanowires 10, in other words, in contact with the silicon nanowires 10, are disposed on the first silicon nanowire group 10A and the second silicon nanowire group 10B, so that one side of the silicon nanowires 10 is connected to the silicon substrate 100 and the other side of the silicon nanowires 10 is connected by the conductive films 510, 520. This makes it possible to support the silicon nanowires 10, and prevents the silicon nanowires 10 from being easily damaged even if they have a high aspect ratio. In other words, the thermoelectric generating element 1000 can be made easier to handle.

[0044] Moreover, in the thermoelectric generating element 1000 of this embodiment, the conductive films 510, 520 are preferably made of aluminum. With this configuration, aluminum is used for the conductive films 510, 520 that contact the silicon nanowires 10, so that the conductivity between the silicon nanowires 10 and the conductive films 510, 520 can be ensured. Furthermore, since the conductive films 510, 520 are relatively susceptible to plastic deformation, when they are brought into contact with the ends of the silicon nanowires 10, they can be slightly embedded therein, which makes it possible to prevent the silicon nanowires 10 from being damaged.

[0045] In the thermoelectric generating element 1000 of this embodiment, it is preferable that the first impurity region 20 is doped with a P-type impurity, and the second impurity region 30 is doped with an N-type impurity. With this configuration, since the above-mentioned impurities are doped into the silicon substrate 100, a potential difference can be generated between the first impurity region 20 and the second impurity region 30. That is, the temperature difference can be efficiently converted into electricity.

[0046] Furthermore, in the thermoelectric generating element 1000 of this embodiment, the silicon substrate 100 has an outer circumferential region 40 that does not overlap the first impurity region 20 and the second impurity region 30 in a planar view, and it is preferable that an adhesive 600 having a gap material 610 that determines the amount of pressing H3 of the silicon nanowire 10 into the conductive films 510, 520 is disposed between the first surface 100a and the conductive films 510, 520 in the outer circumferential region 40. According to this configuration, since the adhesive 600 having the gap material 610 is disposed, the amount of pressing H3 of the end of the silicon nanowire 10 into the conductive films 510, 520 can be adjusted by selecting the diameter of the gap material 610.

[0047] In the thermoelectric power generating element 1000 of this embodiment, the push-in amount H3 is preferably 0.2 μm. According to this configuration, since the push-in amount H3 is set to the above amount, the silicon nanowires 10 and the conductive films 510 and 520 can be electrically connected to each other.

[0048] Modifications of the above embodiment will now be described.

[0049] As described above, the thermoelectric generating element 2000 is not limited to being configured with one thermoelectric generating element 1000, and for example, two or more thermoelectric generating elements 1000 may be connected in series to configure the thermoelectric generating element 2000. Specifically, as shown in Fig. 16, a first thermoelectric generating element 1000A and a second thermoelectric generating element 1000B are connected in series. The first thermoelectric generating element 1000A and the second thermoelectric generating element 1000B have substantially the same configuration as the thermoelectric generating element 1000 described above.

[0050] In the thermoelectric generating element 2000 of the modified example, an insulating film 400 is formed on one heat conducting plate 1200, and conductive films 540, 550, and 560 are formed on the surface of the insulating film 400. The conductive film 540 is connected to the first silicon nanowire group 10A in the first impurity region 20 of the first thermoelectric generating element 1000A. The conductive film 550 is connected to the second silicon nanowire group 10B in the second impurity region 30 of the first thermoelectric generating element 1000A, and is further connected to the first silicon nanowire group 10A in the first impurity region 20 of the second thermoelectric generating element 1000B. The conductive film 560 is connected to the second silicon nanowire group 10B in the second impurity region 30 of the second thermoelectric generating element 1000B.

[0051] According to this configuration, the two thermoelectric generating elements 1000A, 1000B are connected in series, so high voltage power generation is possible and it is easy to increase the voltage, so that this configuration is highly practical. [Explanation of symbols]

[0052] 10...silicon nanowire, 10A...first silicon nanowire group, 10B...second silicon nanowire group, 11...first silicon nanowire, 12...second silicon nanowire, 20...first impurity region, 30...second impurity region, 40...periphery region, 50...contact region, 100...silicon substrate, 100a...first surface, 110...substrate, 120, 121, 122...gold film pattern, 130...aluminum film, 131...pore, 132...aluminum anodized film, 200...thermal conductive plate, 300...heat sink, 310...highly thermally conductive adhesive, 400...insulating film, 500...conductive film, 510...first conductive film, 520...second conductive film, 530...conductive film, 540, 550, 560...conductive films, 600...adhesive, 610...gap material, 1000...thermoelectric generation element, 1000A...first thermoelectric generation element, 1000B...second thermoelectric generation element, 1200...thermal conductive plate, 2000...thermoelectric generation element, H1...thickness, H2...thickness, H3...pressing amount.

Claims

1. a silicon substrate having a first impurity region and a second impurity region on a first surface; a first silicon nanowire group including a plurality of silicon nanowires provided in the first impurity region and extending in a direction intersecting the first surface; a second silicon nanowire group provided in the second impurity region and including the plurality of silicon nanowires extending in a direction intersecting the first surface; a conductive film disposed on the first group of silicon nanowires and the second group of silicon nanowires and electrically connected to the silicon nanowires; A thermoelectric power generation element comprising:

2. The thermoelectric power generation element according to claim 1, The thermoelectric power generating element, wherein the conductive film is made of aluminum.

3. The thermoelectric power generation element according to claim 1, the first impurity region is doped with a P-type impurity, The thermoelectric power generating element, wherein the second impurity region is doped with an N-type impurity.

4. The thermoelectric power generation element according to claim 1, the silicon substrate has a peripheral region that does not overlap the first impurity region and the second impurity region in a plan view, A thermoelectric power generation element, wherein an adhesive having a gap material is disposed between the first surface and the conductive film in the outer peripheral region, the adhesive defining the amount of depression of the silicon nanowires into the conductive film.

5. The thermoelectric power generating element according to claim 4, The thermoelectric power generation element has a pressing amount of 0.2 μm.

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