JP4451751B2 - Thermoelectric generator - Google Patents

Description

  The present invention relates to a small thermoelectric power generation element composed of a fine thermocouple.

  Technological development is progressing on power supplies for supplying power to portable devices and micro sensors. Conventional small batteries such as button batteries are larger than the required dimensions and are not suitable for downsizing, and therefore, use of a small power source utilizing changes in the environment has been studied. For example, a technique is being studied in which a physical quantity such as vibration, heat, and weight is used as energy and converted into electricity. With this technology, for example, it is possible to construct a sensor network in which a plurality of ultra-small ubiquitous devices that do not require external power supply are arranged around us.

  As a power generation element for the small device described above, a thermoelectric power generation element 900 as shown in FIG. 9 has been proposed (see Non-Patent Document 1). The thermoelectric generator 900 includes about 100 pairs of thermocouples 901 made of n-BiTe and p-BiTe formed on a prism having a bottom surface of 80 μm × 80 μm and a height of 600 μm. In FIG. 9, wiring is omitted. The thermoelectric power generation element 900 can generate an electromotive force of 20 mV with a temperature difference of 1 ° C. due to the Seebeck effect generated at the contact point between n-BiTe and p-BiTe. The thermoelectric power generation element is incorporated in, for example, a wristwatch, and an example of operating with body temperature as an energy source is realized. However, in the thermoelectric power generation element shown in Non-Patent Document 1, it is difficult to miniaturize more than the above-mentioned dimensions due to the characteristics of the material constituting the thermocouple, and the size can be further reduced. Absent.

  As a thermoelectric power generation element that enables further miniaturization, a thermoelectric power generation element having a configuration shown in FIG. 10 has been proposed (see Non-Patent Document 2). The thermoelectric power generation element shown in Non-Patent Document 2 is a device in which a thermocouple 1004 including a polysilicon part 1002 and a metal part 1003 made of gold is disposed on a silicon substrate 1001. The thermocouple 1004 is formed in a beam shape having a length of about 1000 μm and cantilevered by an insulating support portion 1010, and a contact portion 1005 supported by the insulating support portion 1010 and a contact spaced apart on the silicon substrate 1001. Part 1006.

  In this thermoelectric power generation element, the contact portion 1006 is separated from the silicon substrate 1001 by the warp of the material constituting the thermocouple 1004 to be higher than the height of the insulating support portion 1010. With this configuration, in the thermoelectric power generation element shown in Non-Patent Document 2, the contact portion 1005 connected to the silicon substrate 1001 by the insulating support portion 1010 and the contact portion 1006 separated from the silicon substrate 1001 A temperature difference is provided between the two. In the thermoelectric generator of Non-Patent Document 2, an output voltage of 110 μV is obtained at 307 K with the above configuration.

  Further, a thermoelectric generator having a configuration as shown in the sectional view of FIG. 11 has also been proposed (see Non-Patent Document 3). The thermoelectric generator shown in Non-Patent Document 3 includes a wiring 1102 made of p-type polysilicon and a wiring 1103 made of n-type polysilicon on a silicon substrate 1101, and the wiring 1102 and the wiring 1103 are connected to a metal wiring. The contact portion 1104 and the contact portion 1105 are connected to each other to form a thermocouple. The dimension of one set of thermocouples is about 5 μm, and the wiring 1102 and the wiring 1103 are arranged on an insulating layer 1111 having a thick part and a thin part formed on the silicon substrate 1101. A space 1112 is provided below the thick portion of the insulating layer 1111.

  The contact portion 1104 disposed on the thick portion of the insulating layer 1111 has a higher structure than the contact portion 1105. Therefore, the upper end portion of the contact portion 1104 is closer to the upper surface of the insulating layer 1113 formed so as to cover the contact portion 1104 and the contact portion 1105. In addition, a lower portion of the contact portion 1104 includes a thick portion of the insulating layer 1111 and a space 1112 below the thick portion. Therefore, heat from the upper surface of the insulating layer 1113 is easily conducted to the contact portion 1104, and heat from the silicon substrate 1101 side is easily conducted to the contact portion 1105. With this configuration, in the thermoelectric power generation element of Non-Patent Document 3, a temperature difference is provided between the contact portion 1104 and the contact portion 1105, and a chip size of 6 mm square is 100 to 200 mV / K. Is realized.

The applicant has not yet found prior art documents related to the present invention by the time of filing other than the prior art documents specified by the prior art document information described in this specification.
M. Kishi et al ,. "Micro-thermoelectric modules and their application to wristwatches as an energy source", IEEE International Conference on Thermoelectrics (ICT), pp. 301-307, 1999. T. Toriyama et al., "Thermoelectric micro power generator utilizin self-standing polysilicon-metal thermopile", IEEE International Conference on Micro Electro Mechanical System (MEMS), pp.562-565, 2001. M. Strasser et al., "Miniaturized thermoelectric generator based on poly-Si and poly-SiGe surface micromachining", Sens. Actuators A, vol. 97-98, pp.535-542, 2002.

  As described above, the above-described conventional thermoelectric power generation element can be miniaturized, but it is difficult to obtain a large temperature difference at the contact portion of the thermocouple, and it is difficult to obtain high power generation efficiency. It has been difficult to apply to ultra-small ubiquitous devices due to problems such as performance degradation.

  For example, in the thermoelectric element of Non-Patent Document 2, the contact portion 1005 connected to the substrate 1001 via the insulating support portion 1010 has a small thermal resistance with the substrate 1001, but is surrounded by atmospheric air. The contact part 1006 has a large thermal resistance with the surroundings. Here, when the substrate 1001 is heated, the temperature of the contact portion 1005 rises in a shorter time, and a temperature difference can be formed between the contact portion 1006 and the contact portion 1006 that is far from the substrate 1001. However, in any case, the contact portion 1006 also rises to the same temperature, and the efficiency of heat dissipation with respect to the surroundings is low, so the temperature difference with the contact portion 1005 becomes small. Thus, in the thermoelectric element of Non-Patent Document 2, it is very difficult to ensure a continuous temperature difference.

  Further, in the thermoelectric element of Non-Patent Document 3, one set of thermocouples is as small as about 5 μm, and it is difficult to form a large temperature difference between the contact part 1104 and the contact part 1105. Since the contact portion 1105 is disposed on the silicon substrate 1101 through a thin portion of the insulating layer 1111, the temperature of the contact portion 1105 can be controlled by controlling the temperature of the silicon substrate 1101 that is a highly thermally conductive material. . However, since the contact portion 1104 in which the space 1112 and the thick portion of the insulating layer 1111 exist between the silicon substrate 1101 and the metal wiring portion are covered with the insulating film (oxide film) 1113, the contact portion 1104 is selectively used. It is difficult to heat and cool.

  In addition, signals such as voltage and current generated by thermoelectric elements are not directly affected by the influence of the external environment and situation, so circuits that rectify and amplify the generated voltage and charge and discharge electric charges A secondary battery or the like is required. In the above-described conventional technique, the circuit and the secondary battery described above are not formed integrally with the power generation element, and thus there is a problem that the size is increased in the conventional form. For example, a conventional thermoelectric generator combined with a control circuit and a secondary battery has a large size, making it difficult to arrange a plurality of modules in an ultra-small ubiquitous device. Further, the parasitic capacitance and resistance in the wiring connecting the power generation element and the circuit are large, and the efficiency of power generation is reduced in the conventional form.

As described above, the conventional thermoelectric generator has a problem that the entire apparatus including the circuit becomes large and the efficiency cannot be increased. In addition, although it is possible to produce a fine thermoelectric power generation element using a microfabrication technique, it is not easy to form a large temperature difference at a contact point of a thermocouple with a conventional fine thermoelectric power generation element. The desired high power generation efficiency and power generation performance cannot be obtained. For these reasons, for example, there is a problem that it is difficult to realize an ultra-small ubiquitous device that can operate without power supply from the outside.
The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a thermoelectric power generation element composed of a thermocouple capable of obtaining a thermoelectromotive force more efficiently.

A thermoelectric power generation element according to the present invention includes a first wiring made of a first conductive material formed so as to be in contact with an insulating substrate and extending in the planar direction of the substrate, and extending in the planar direction of the substrate. A second wiring made of a second conductive material having a different thermoelectricity from the first conductive material, a contact connecting one end of the first wiring and one end of the second wiring, and a contact on the contact a first thermal conductive material that disposed in made of the first material of any of the state of the three states of matter, first heat conduction are arranged on and in contact with the other ends of and the second wiring of the first wiring At least a second heat conductive material made of a second material in a state different from the material, wherein one of the first material and the second material is a liquid, and the other of the first material and the second material is a gas or a solid The thermocouple is configured by the first wiring, the second wiring, and the contacts. .
Accordingly, the contact portion constituting the thermocouple, the other end of the first wiring, and the other end of the second wiring are arranged in contact with each other on the same substrate, and the upper surfaces have different heat conduction states. It is said that.

In the thermoelectric power generation element, the third wiring is composed of a first conductive material connected to the other end of the second wiring, and the second conductive material is connected to the third wiring on a different side from the second wiring. A fourth wiring, and a third thermal conductor made of the first material in the same state as the first thermal conductor, disposed in contact with the contact point connecting the third wiring and the fourth wiring. May be.

Further , the second substance may be a liquid or a gas . Also, the first material is a liquid, the second material may be a gas or a solid. Note that the first conductive material may be a semiconductor into which impurities are introduced, and the second conductive material may be a metal.

  As described above, according to the present invention, the first thermal conductor is disposed on the contact point between one end of the first wiring and the one end of the second wiring constituting the thermocouple, and the other end of the first wiring. Since the second thermal conductor is disposed on the other end of the second wiring, the heat conduction state is different between the contact and the other end of the wiring, and a thermoelectromotive force is generated due to a larger temperature difference. Thus, it is possible to provide an excellent effect that it is possible to provide a thermoelectric power generation element including a thermocouple that can obtain a thermoelectromotive force more efficiently.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view (a) and a plan view (b) showing a configuration example of a thermoelectric power generation element according to an embodiment of the present invention. In the thermoelectric power generation element shown in FIG. 1, a wiring 104 made of a semiconductor such as n-type single crystal silicon and a metal wiring 105 made of gold, for example, are connected by a contact 106 on an insulating layer 102 which is an insulating substrate. A plurality of thermocouples 103 are provided. The plurality of thermocouples 103 are connected by a contact 107. The metal wiring 105 is formed through an adhesion layer (not shown) made of titanium. An electromotive force of about 0.45 mV / K is obtained by the pair of thermocouples 103.

  The insulating layer 102 is disposed on the silicon substrate portion 101. By using a well-known SOI (Silicon on Insulator) substrate, the configuration of the silicon substrate portion 101, the insulating layer 102, and the wiring 104 is obtained. It is done. In addition, an insulating layer 109 is formed over the insulating layer 102 so as to fill a side portion of the wiring 104, and the upper surface of the insulating layer 109 and the wiring 104 is flat so as to form one plane. Yes. As described above, the metal wiring 105 is formed on the insulating layer 109 in a flat state.

  In addition, the thermoelectric power generation element shown in FIG. 1 includes a solid structure (first thermal conductor) 108 in contact with the contact 106, and the contact 107 is a space. As described above, in the thermoelectric power generation element of FIG. 1, on the insulating layer 102, the wiring 104 and the metal wiring 105 made of a conductive material having a different thermoelectric power are connected to each other by the contact 106 at one end. 103, a solid structure 108 made of a solid metal is disposed on the thermocouple 103, and a gas (second heat conductor) is disposed on the other end of the wiring 104 and the metal wiring 105. Is placed.

  As described above, in the thermoelectric generator shown in FIG. 1, the contact 106 and the contact 107 constituting the thermocouple are formed on the insulating layer 102 in the same state, and the upper surface of the contact 106 and the upper surface of the contact 107 are formed. Are in different states of thermal conductivity. In the case of the embodiment shown in FIG. 1, the upper surface of the contact 106 is disposed in contact with the upper surface of the contact 106, so that the upper surface of the contact 106 and the upper surface of the contact 107 have different thermal conductivities. Therefore, the contact 106 is more easily radiated than the contact 107. For this reason, when heated from the silicon substrate 101 side, the contact 106 is in a lower temperature state than the contact 107.

  Further, as shown in the cross-sectional view of FIG. 2, the metal plate 200 may be disposed in contact with the back surface of the silicon substrate portion 101, and the plate member 201 in contact with the plurality of solid structures 108 may be disposed. . The plate member 201 may be a silicon substrate in which an oxide film is formed on the surface in contact with the solid structure 108. For example, the metal plate 200 and the plate member 201 may be attached with an adhesive or an adhesive film having high thermal conductivity. By configuring as described above, for example, by heating the plate member 201 and cooling the metal plate 200, it is easy to obtain a state in which the contact 106 has a higher temperature than the contact 107. It is done.

  By heating the plate member 201, this heat is conducted to the solid structure 108 in contact with the plate member 201, and the contact portion 106 is heated. On the other hand, the contact 107 that is not in contact with the plate member 201 is difficult to conduct heat directly from the plate member 201, and the heat of the plate member 201 is contact portion 106 → metal wiring 105 or contact portion 106 → metal wiring 105. → Conducted to the contact 107 through the path of the wiring 104. In the thermoelectric power generation element shown in FIGS. 1 and 2, since the wiring constituting the thermocouple extends in the direction parallel to the substrate surface, the wiring length can be increased, so that the heat from the contact portion 106 to the contact portion 107 is increased. Is in a state where it is difficult to conduct.

  In addition to the above, the cooled metal plate 200 is in contact with the back surface of the silicon substrate portion 101. It is taken away by the metal plate 200 through the silicon substrate portion 101. Therefore, almost no heat from the heated plate member 201 is conducted to the contact 107. Thus, according to this thermoelectric power generation element, it is possible to selectively heat the portion of the contact 106, and the difference between the temperature of the contact 106 and the temperature of the contact 107 can be easily increased. The solid structure (first thermal conductor) 108 is not limited to a metal, and may be made of a material having high thermal conductivity such as silicon.

  As described above, according to the thermoelectric power generation element shown in FIG. 1, the thermocouple 103 composed of the wiring 104, the metal wiring 105, and the contact 106 is formed on the insulating layer 102 in the same state. In this state, the solid structure 108 is placed in contact with the contact 106, so that a non-solid gas is present on the contact 107 which is the other end of the wiring 104 and the metal wiring 105. By arranging the air in the state, the upper surface of the contact 106 and the upper surface of the contact 107 constituting the formed thermocouple are in different states of thermal conductivity. As a result, according to the thermoelectric generator shown in FIG. 1, as described above, a large temperature difference can be easily formed between the contact 106 and the contact 107.

Next, an example of a method for manufacturing the thermoelectric generator described above will be described. First, as shown in FIG. 3A, an SOI substrate is prepared in which an SOI layer 303 is formed on a silicon substrate portion 301 via a buried insulating layer 302 having a thickness of about 0.5 μm. The SOI layer 303 is a layer having a thickness of about 20 μm made of single crystal silicon into which an n-type impurity is introduced at about 10 ¹⁹ cm ⁻³ . Note that an integrated circuit including a plurality of elements such as MOS transistors may be formed in advance in a region (not shown) of the SOI layer 303. The region where the integrated circuit is formed may be protected by a protective film or the like. When such an SOI substrate is prepared, a resist pattern 304 is formed at a predetermined position of the SOI layer 303. The resist pattern 304 is arranged in a region where the wiring 104 shown in FIG. 1 is formed.

  Next, the SOI layer 303 is processed by anisotropic dry etching using the resist pattern 304 as a mask, so that the wiring portion 305 is formed on the buried insulating layer 302 as shown in FIG. A part of the formed wiring portion 305 is connected to the integrated circuit described above, for example. Next, after removing the resist pattern 304, a photosensitive resin (positive type) based on polybenzoxazole is spin-coated on the SOI substrate to form a photosensitive resin film. After the formed photosensitive resin film is subjected to a heat treatment (pre-bake) at about 100 ° C., the upper portion of the already formed wiring portion 305 is selectively exposed and developed to remove the exposed portion. And

  Thus, after patterning the photosensitive resin film by photolithography, the photosensitive resin film is heated to about 310 ° C. to be thermally cured. As a result, as shown in FIG. 3C, the insulating layer 306 is formed on the buried insulating layer 302 so that the side portion of the wiring portion 305 is buried, and the insulating layer 306 and the wiring portion 305 are separated from each other. A flattened state is formed such that the upper surface forms one plane.

  Next, a titanium film having a thickness of about 0.1 μm is formed on the upper surfaces of the above-described planarized wiring portion 305 and insulating layer 306 by, for example, vapor deposition, and a gold film is further formed to a thickness of about 0.1 μm. As shown in FIG. 3D, a metal layer 307 composed of these is formed. Next, a resist pattern 308 having an opening 308a is formed on the metal layer 307, and a gold plating film is formed on the metal layer 307 exposed at the bottom of the opening 308a by a plating method. As shown in e), a solid structure 309 having a height of about 20 μm is formed. Note that the solid structure 309 may be composed of a gold wire formed by a stud bump method after a wiring portion 305 and a metal wiring portion 311 described below are formed.

  Next, after removing the resist pattern 308, as shown in FIG. 3F, a resist pattern 310 is formed. The resist pattern 310 is formed in the same planar shape as the metal wiring 105 shown in FIG. 1B, and is formed in a state where the solid structure 309 is covered. With the resist pattern 310 as a mask, the metal layer 307 is selectively removed by etching, and then the resist pattern 310 is removed, so that the metal wiring portion 311 is formed as shown in FIG. In the etching of the metal layer 307, the gold film may be etched with an etchant composed of iodine, ammonium iodide, water, and ethanol, and the titanium film may be etched with an HF-based etchant. A part of the formed metal wiring part 311 is connected to the integrated circuit described above, for example.

  The thermoelectric power generation element shown in FIG. 1 can be formed by the manufacturing method described above. The embedded insulating layer 302, the wiring part 305, the insulating layer 306, the solid structure 309, and the metal wiring part 311 shown in FIG. 3 are respectively the insulating layer 102, the wiring 104, the insulating layer 109, the solid structure 108, It corresponds to the metal wiring 105. As shown in FIG. 4, a protective film 401 made of an insulating material such as silicon oxide is formed so as to cover the upper surfaces of the wiring 104, the insulating layer 109, the solid structure 108, and the metal wiring 105. May be. By providing the protective film 401, an electrical short circuit between the wiring 104 and the metal wiring 105 can be suppressed by an aqueous solution or a foreign substance attached due to an external factor.

  Further, as shown in FIG. 5A, an opening 101a may be formed in the lower portion of the region where the solid structure 108 of the silicon substrate portion 101 is disposed. By providing the opening 101a, when the metal plate 200 is provided as shown in FIG. 5 (b), the heat conduction between the metal plate 200 and the formation part of the solid structure 108 is suppressed. Good. In addition, as shown in FIG. 6, the same applies even if a groove portion 200 a is formed at a location corresponding to a region where the solid structure 108 of the metal plate 200 is disposed. By these things, the temperature fall in the contact part of the solid structure 108 by the cooled metal plate 200 can be suppressed now.

  Further, as shown in FIG. 6, the groove 201 a is provided in the plate member 201, and the distance between the plate member 201 and the region other than the area where the solid structure 108 is arranged is separated from the location of the solid structure 108. You may do it. The groove 201a only needs to be formed to face the region where the contact 107 shown in FIG. 1 is formed. Thereby, in the formation area of the groove part 201a, the influence of the heat from the plate member 201 is reduced, and the temperature rise in the area other than where the solid structure 108 is disposed can be suppressed. In other words, the groove 201a can further suppress the temperature rise at the contact 107 portion shown in FIG. 1, and the temperature difference between the contact 106 and the contact 107 can be further increased.

  Further, as shown in FIG. 1B, the wiring 104 and the metal wiring 105 constituting the pair of thermocouples 103 do not need to be arranged on a straight line. For example, as shown in the plan view of FIG. 7, a metal wiring 705 and a wiring 704 whose ends are bent perpendicularly to the center are arranged in a direction perpendicular to the extending direction of the wiring 704. These thermocouples may be composed of adjacent wiring 704 and metal wiring 705.

  By the way, in the above description, the solid structure 108 is disposed in contact with the contact 106, and a gas (air) that is in a state different from that of the solid structure 108 is disposed on the contact 107. The top of 106 and the top of contact 107 are in different heat conduction states, but are not limited to these configurations. For example, as shown in FIG. 8, a liquid 802 such as water is disposed on the contact 106 and a resin layer 801 in a solid state that is different from the liquid 802 is disposed on the contact 107. It may be arranged. The resin layer 801 may be further in a porous state such as a polystyrene foam. Since the porous resin layer 801 can have a lower thermal conductivity than the liquid 802, a large temperature difference is formed between the contact 106 and the contact 107 as in the thermoelectric power generation element shown in FIG. Is possible.

  In addition, for example, the upper part of the contact 106 is in a hydrophilic state and the other region is in a hydrophobic state, and water is brought into contact with these so that the upper part of the contact 106 is heated by a liquid such as water. A conductive material is disposed in contact with each other, and a heat conductive material in a gaseous state such as air can be disposed on the contact 107. Even in this case, the upper surface of the contact 106 and the upper surface of the contact 107 can be in different states of thermal conductivity. Further, as a matter of course, in each of the configurations shown in FIGS. 1, 2, 4, 4, and 6, a solid structure 108 is disposed on the contact 106 and is disposed on the contact 107. Needless to say, the same effects as described above can be obtained even when the liquid is disposed.

It is sectional drawing (a) and the top view (b) which show the structural example of the thermoelectric power generation element in embodiment of this invention. It is sectional drawing which shows the structural example of the thermoelectric power generation element in embodiment of this invention. It is process drawing explaining the example of the manufacturing method of the thermoelectric power generation element in embodiment of this invention. It is sectional drawing which shows the other structural example of the thermoelectric power generation element in embodiment of this invention. It is sectional drawing (a) and top view (b) which show the other structural example of the thermoelectric power generation element in embodiment of this invention. It is a top view which shows the other structural example of the thermoelectric power generation element in embodiment of this invention. It is sectional drawing which shows the other structural example of the thermoelectric power generation element in embodiment of this invention. It is sectional drawing which shows the other structural example of the thermoelectric power generation element in embodiment of this invention. It is a perspective view which shows the structure of the conventional thermoelectric power generation element. It is a perspective view which shows the structure of the conventional thermoelectric power generation element. It is sectional drawing which shows the structure of the conventional thermoelectric power generation element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 ... Silicon substrate part, 102 ... Insulating layer, 103 ... Thermocouple, 104 ... Wiring, 105 ... Metal wiring, 106, 107 ... Contact, 108 ... Solid structure (1st heat conductor), 109 ... Insulating layer.

Claims (4)

A first wiring made of a first conductive material in contact with an insulating substrate and extending in a plane direction of the substrate;
A second wiring made of a second conductive material extending in a plane direction of the substrate and having a thermoelectric power different from that of the first conductive material;
A contact point connecting one end of the first wiring and one end of the second wiring;
A first thermal conductor made of a first substance in any one of three states of the substance disposed on and in contact with the contact;
Wherein at least a second thermal conductive material comprising a second material different states from the first other end and said first thermal conductive material is disposed in contact on the other end of said second wire wiring,
One of the first substance and the second substance is a liquid;
The other of the first substance and the second substance is a gas or a solid,
A thermoelectric power generation element, wherein a thermocouple is constituted by the first wiring, the second wiring, and the contact. The thermoelectric power generation element according to claim 1,
A third wiring composed of the first conductive material connected to the other end of the second wiring;
A fourth wiring composed of the second conductive material connected to the third wiring on a different side from the second wiring;
A third thermal conductor made of the first material in contact with the third wiring and the fourth wiring, the first thermal conductor being in the same state as the first thermal conductor. Thermoelectric power generation element. The thermoelectric power generation element according to claim 1 or 2,
The first material is a metal der solid state is, thermoelectric power generation element, wherein the second material is a liquid. The thermoelectric power generation element according to any one of claims 1 to 3 ,
The first conductive material is a semiconductor into which an impurity is introduced, and the second conductive material is a metal.

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