Patent Publication Number: US-2023165147-A1

Title: Thermoelectric element

Description:
TECHNICAL FIELD 
     The present invention relates to a thermoelectric element, and more specifically, to a structure of an electrode disposed on a substrate. 
     BACKGROUND ART 
     A thermoelectric effect is a direct energy conversion phenomenon between heat and electricity that occurs due to the movement of electrons and holes in a material. 
     A thermoelectric element is generally referred to as an element using a thermoelectric effect and has a structure in which P-type thermoelectric materials and N-type thermoelectric materials are disposed between and bonded to metal electrodes to form PN junction pairs. 
     Thermoelectric elements may be divided into elements using a change in electrical resistance depending on a change in temperature, elements using the Seebeck effect in which an electromotive force is generated due to a difference in temperature, elements using the Peltier effect in which heat absorption or heating occurs due to a current, and the like. 
     Thermoelectric elements have been variously applied to home appliances, electronic components, communication components, and the like. As an example, thermoelectric elements may be applied to cooling apparatuses, heating apparatuses, power generation apparatuses, and the like. Therefore, the demand for the thermoelectric performance of the thermoelectric element is gradually increasing. 
     In this case, a thermoelectric element has a problem that a dielectric breakdown occurs between an electrode and a substrate. 
     DISCLOSURE 
     Technical Problem 
     The present invention is directed to providing a structure of an electrode of a thermoelectric element for improving reliability. 
     Technical Solution 
     One aspect of the present invention provides a thermoelectric element including a first insulating part, a plurality of first electrodes disposed on the first insulating part, second electrodes disposed above the first electrodes, a first conductive semiconductor structure and a second conductive semiconductor structure which are disposed apart from each other between the first electrodes and the second electrodes, and a second insulating part disposed on the second electrodes, wherein the first insulating part includes a first protruding part protruding toward the first electrodes, and the second insulating part includes a second protruding part protruding toward the second electrodes. 
     The first protruding part and the second protruding part may overlap in a vertical direction. 
     The first protruding part and the second protruding part may have the same shape based on the first conductive semiconductor structure and the second conductive semiconductor structure. 
     The first protruding part and the second protruding part may have different shapes based on the first conductive semiconductor structure and the second conductive semiconductor structure. 
     The first protruding part and the second protruding part may be disposed apart from each other in a vertical direction. 
     A height of the first protruding part may be less than or equal to 0.5 times a thickness of the first electrode. 
     A height of the first protruding part may be greater than or equal to 0.5 times a thickness of the first electrode. 
     Each of the first electrode and the second electrode may include a groove portion disposed at an edge of a surface facing a substrate adjacent thereto, and the groove portion may have a closed-loop when viewed from above. 
     Each of the first protruding part and the second protruding part may be disposed in the groove portion. 
     Each of the first electrode and the second electrode may further include a protruding electrode disposed at an edge of a lower surface of the groove portion, and a height of the protruding part in a vertical direction may be less than or equal to a height of the groove portion in the vertical direction. 
     Advantageous Effects 
     According to embodiments of the present invention, a thermoelectric element with high electrical reliability can be obtained. 
     Specifically, according to embodiments of the present invention, a thermoelectric element including a groove, which is formed along an edge of one surface disposed toward a substrate adjacent to an electrode, can be provided. 
     In addition, the thermoelectric element according to embodiments of the present invention can be applied to not only applications implemented in small types but also applications implemented in large types such as vehicles, ships, steel mills, and incinerators. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG.  1    is a perspective view illustrating a thermoelectric element according to one embodiment of the present invention. 
         FIG.  2    is a cross-sectional view illustrating the thermoelectric element according to one embodiment of the present invention. 
         FIG.  3    is a perspective view illustrating an electrode according to a first embodiment of the present invention. 
         FIG.  4    is a top view illustrating the electrode according to the first embodiment of the present invention. 
         FIG.  5    is a side view illustrating the electrode according to the first embodiment of the present invention. 
         FIG.  6    is a bottom view illustrating the electrode according to the first embodiment of the present invention. 
         FIG.  7    is a perspective view illustrating the electrode and a first protruding part according to the first embodiment of the present invention. 
         FIG.  8    is a cross-sectional view illustrating the electrode and the first protruding part according to the first embodiment of the present invention. 
         FIG.  9    is a cross-sectional view illustrating a thermoelectric element according to a second embodiment of the present invention. 
         FIG.  10    is an enlarged view illustrating portion K 1  of  FIG.  9   . 
         FIG.  11    is a view illustrating a modified embodiment of  FIG.  10   . 
         FIG.  12    is a cross-sectional view illustrating a thermoelectric element according to a third embodiment of the present invention. 
         FIG.  13    is an enlarged view illustrating portion K 2  of  FIG.  12   . 
         FIG.  14    is a view illustrating a modified embodiment of  FIG.  13   . 
         FIG.  15    is a side view illustrating an electrode and a first protruding part according to another modified embodiment. 
         FIGS.  16 A to  16 E  are views for describing a method of manufacturing the electrode according to the first embodiment. 
     
    
    
     MODES OF THE INVENTION 
     Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. 
     However, the technical spirit of the present invention is not limited to some embodiments which will be described and may be realized using various other embodiments, and at least one component of the embodiments may be selectively coupled, substituted, and used within the range of the technical spirit of the present invention. 
     In addition, unless clearly and specifically defined otherwise by context, all terms (including technical and scientific terms) used herein can be interpreted as having meanings customarily understood by those skilled in the art, and meanings of generally used terms, such as those defined in commonly used dictionaries, will be interpreted by considering contextual meanings of the related technology. 
     In addition, the terms used in the embodiments of the present invention are considered in a descriptive sense and not for limiting the present invention. 
     In the present specification, unless specifically indicated otherwise by the context, singular forms may include the plural forms thereof, and in a case in which “at least one (or one or more) among A, B, and C” is described, this may include at least one combination among all possible combinations of A, B, and C. 
     In addition, in descriptions of components of the present invention, terms such as “first,” “second,” “A,” “B,” “(a),” and “(b)” can be used. 
     The terms are only to distinguish one element from another element, and an essence, order, and the like of the element are not limited by the terms. 
     In addition, when an element is referred to as being “connected” or “coupled” to another element, such a description may include not only a case in which the element is directly connected or coupled to another element but also a case in which the element is connected or coupled to another element with still another element disposed therebetween. 
     In addition, in a case in which any one element is described as being formed or disposed “on” or “under” another element, such a description includes not only a case in which the two elements are formed or disposed in direct contact with each other but also a case in which one or more other elements are formed or disposed between the two elements. In addition, when one element is described as being disposed “on or under” another element, such a description may include a case in which the one element is disposed at an upper side or lower side with respect to another element. 
       FIG.  1    is a perspective view illustrating a thermoelectric element according to one embodiment of the present invention, and  FIG.  2    is a cross-sectional view illustrating the thermoelectric element according to one embodiment of the present invention. 
     Referring to  FIGS.  1  and  2   , a thermoelectric element  100  includes a lower substrate  110 , lower electrodes  120 , second conductive semiconductor structures  130 , first conductive semiconductor structures  140 , upper electrodes  150 , and an upper substrate  160 . 
     The lower electrodes  120  are disposed between the lower substrate  110  and lower surfaces of the second conductive semiconductor structures  130  and the first conductive semiconductor structures  140 , and the upper electrodes  150  are disposed between the upper substrate  160  and upper surfaces of the second conductive semiconductor structures  130  and the first conductive semiconductor structures  140 . Accordingly, the plurality of second conductive semiconductor structures  130  and the plurality of first conductive semiconductor structures  140  are electrically connected through the lower electrodes  120  and the upper electrodes  150 . A pair of the second conductive semiconductor structure  130  and the first conductive semiconductor structure  140  that are disposed between and electrically connected to the lower electrodes  120  and the upper electrode  150  may form a unit cell. The lower electrode  120  may be interchangeably used with a “first electrode” in the specification. In addition, the lower electrode  120  may be interchangeably used with a “second electrode” in the specification. In addition, electrodes have meanings including all the upper electrodes and the lower electrodes. In addition, the lower substrate may be interchangeably used with a “first substrate” and the upper substrate may be interchangeably used with a “second substrate.” In addition, in the present specification, a first direction (X-axis direction) may include a direction X1 from the first substrate toward the second substrate and a direction X2 opposite to the direction X1 and may be used as a “vertical direction.” In addition, the first electrode and the second electrode may be provided as the plurality of first electrodes and the plurality of second electrodes. 
     As an example, when a voltage is applied to the lower electrodes  120  and the upper electrodes  150  through lead wires  181  and  182 , due to the Peltier effect, the substrate through which a current flows from the second conductive semiconductor structure  130  to the first conductive semiconductor structure  140  may absorb heat to serve as a cooling portion, and the substrate through which a current flows from the first conductive semiconductor structure  140  to the second conductive semiconductor structure  130  may be heated to serve as a heating portion. Alternatively, when different temperatures are applied to the lower electrode  120  and the upper electrode  150 , due to the Seebeck effect, electric charges may move through the second conductive semiconductor structure  130  and the first conductive semiconductor structure  140  so that electricity may also be generated. 
     In this case, each of the second conductive semiconductor structure  130  and the first conductive semiconductor structure  140  may be a bismuth-telluride (Bi—Te)-based thermoelectric leg mainly including Bi and Te. The second conductive semiconductor structure  130  may be a Bi—Te-based thermoelectric leg including at least one among antimony (Sb), nickel (Ni), aluminum (Al), copper (Cu), silver (Ag), lead (Pb), boron (B), gallium (Ga), Te, Bi, and indium (In). As an example, the second conductive semiconductor structure  130  may include Bi—Sb—Te at 99 to 99.999 wt % as a main material and at least one material among Ni, Al, Cu, Ag, Pb, B, Ga, and In at 0.001 to 1 wt % based on a total weight of 100 wt %. The first conductive semiconductor structure  140  may be a Bi—Te-based thermoelectric leg including at least one among Se, Ni, Al, Cu, Ag, Pb, B, Ga, Te, Bi, and In. As an example, the first conductive semiconductor structure  140  may include Bi—Se—Te at 99 to 99.999 wt % as a main material and at least one material among Ni, Al, Cu, Ag, Pb, B, Ga, and In at 0.001 to 1 wt % based on a total weight of 100 wt %. 
     Each of the second conductive semiconductor structure  130  and the first conductive semiconductor structure  140  may be formed in a bulk type or stack type. Generally, the bulk type second conductive semiconductor structure  130  or the bulk type first conductive semiconductor structure  140  may be formed through a process in which a thermoelectric material is thermally treated to manufacture an ingot, the ingot is ground and strained to obtain a powder for a thermoelectric leg, the powder is sintered, and the sintered powder is cut. In this case, each of the second conductive semiconductor structure  130  and the first conductive semiconductor structure  140  may be a polycrystalline thermoelectric leg. As described above, when each of the second conductive semiconductor structure  130  and the first conductive semiconductor structure  140  is the polycrystalline thermoelectric leg, the strength of each of the second conductive semiconductor structure  130  and the first conductive semiconductor structure  140  may increase. The stacked second conductive semiconductor structure  130  or the stacked first conductive semiconductor structure  140  may be formed in a process in which a paste containing a thermoelectric material is applied on base members each having a sheet shape to form unit members, and the unit members are stacked and cut. 
     In this case, the second conductive semiconductor structure  130  and the first conductive semiconductor structure  140  provided in a pair may have the same shape and volume or may have different shapes and volumes. As an example, since electrical conduction properties of the second conductive semiconductor structure  130  and the first conductive semiconductor structure  140  are different, a height or cross-sectional area of the first conductive semiconductor structure  140  may be different from that of the second conductive semiconductor structure  130 . 
     In this case, the second conductive semiconductor structure  130  or the first conductive semiconductor structure  140  may have a cylindrical shape, a polygonal column shape, an elliptical column shape, or the like. 
     The performance of a thermoelectric element according to one embodiment of the present invention may be expressed as a thermoelectric performance figure of merit (ZT). The thermoelectric performance figure of merit (ZT) may be expressed by Equation 1. 
         ZT=α   2   ·σ·T/K   [Equation 1]
 
     Here, α denotes the Seebeck coefficient [V/K], σ denotes electrical conductivity [S/m], and α 2 ·σ denotes a power factor [W/mK 2 ]. In addition, T denotes temperature, and k denotes thermal conductivity [W/mK]. k may be expressed as a·cp·ρ, wherein a denotes thermal diffusivity [cm 2 /S], cp denotes specific heat [J/gK], and ρ denotes density [g/cm 3 ]. 
     In order to obtain the thermoelectric performance figure of merit (ZT) of a thermoelectric element, a Z value (V/K) is measured using a Z meter, and the thermoelectric performance figure of merit (ZT) may be calculated using the measured Z value. 
     In this case, each of the lower electrodes  120  disposed between the lower substrate  110  and the second conductive semiconductor structures  130  and the first conductive semiconductor structures  140  and the upper electrodes  150  disposed between the upper substrate  160  and the second conductive semiconductor structures  130  and the first conductive semiconductor structures  140  may include at least one among Cu, Ag, Al, and Ni and may have a thickness of 0.01 mm to 0.3 mm. When the thickness of the lower electrode  120  or the upper electrode  150  is less than 0.01 mm, an electrode function is degraded, and thus the electrical conductivity performance may be degraded, and when the thickness is greater than 0.3 mm, a resistance increases, and thus a conduction efficiency can be lowered. 
     In addition, the lower substrate  110  and the upper substrate  160 , which are opposite to each other, may be metal substrates, and a thickness of each of the lower substrate  110  and the upper substrate  160  may be in the range of 0.1 mm to 1.5 mm. When a thickness of the metal substrate is less than 0.1 mm or greater than 1.5 mm, since a heat radiation property or thermal conductivity may become excessively high, reliability of the thermoelectric element may be degraded. 
     In addition, when the lower substrate  110  and the upper substrate  160  are the metal substrates, a first insulating part  170   a  and a second insulating part  170   b  may be further formed between the lower substrate  110  and the lower electrode  120  and between the upper substrate  160  and the upper electrode  150 . 
     Accordingly, the thermoelectric element  100  according to the embodiment may further include insulating parts  170  including the first insulating part  170   a  and the second insulating part  170   b.    
     First, each of the first insulating part  170   a  and the second insulating part  170   b  may include materials having a thermal conductivity of 1 to 20 W/mK. In this case, each of the first insulating part  170   a  and the second insulating part  170   b  may be a resin composition including at least one of an epoxy resin and a silicon resin and an inorganic material, a layer formed of a silicon composite including silicon and an inorganic material, or an aluminum oxide layer. In this case, the inorganic material may be at least one among an oxide, a carbide, and a nitride containing aluminum, boron, silicon, or the like. 
     In addition, the insulating part  170  may be disposed between the adjacent lower electrodes  120  or the adjacent upper electrodes  150  and positioned closer to the second conductive semiconductor structure  130  or the first conductive semiconductor structure  140  than a protruding part  180  which will be described below. For example, a length of the insulating part  170  in the first direction (X-axis direction) may be greater than a length of the protruding part  180  in the first direction. 
     In addition, the insulating part  170  may be convex toward the adjacent substrate between the adjacent lower electrodes  120  or the adjacent upper electrodes  150 . For example, an upper surface of the first insulating part  170   a  may be positioned above an upper surface of the first protruding part  180   a  and may be convex toward the lower substrate  110  between the adjacent lower electrodes  120 . Alternatively, the upper surface of the first insulating part  170   a  may be concave toward the upper substrate  160 . Such contents may be equally applied to various embodiments which will be descried below. 
     In this case, sizes of the lower substrate  110  and the upper substrate  160  may also be different. That is, a volume, a thickness, or an area of one of the lower substrate  110  and the upper substrate  160  may be greater than a volume, a thickness, or an area of the other. In this case, the thickness may be a thickness in a direction from the lower substrate  110  toward the upper substrate  160 , and the area may be an area in a direction perpendicular to the direction from the substrate  110  toward the upper substrate  160 . Accordingly, the heat absorption or radiation performance of the thermoelectric element can be improved. Preferably, at least one of the volume, the thickness, and the area of the lower substrate  110  may be greater than that of the upper substrate  160 . In this case, when the lower substrate  110  is disposed in a high-temperature region for the Seebeck effect or applied as a heating region for the Peltier effect, or a sealing member for protecting the thermoelectric element, which will be described below, from an external environment is disposed on the lower substrate  110 , at least one of the volume, the thickness, and the area of the lower substrate  110  may be greater than that of the upper substrate  160 . In this case, the area of the lower substrate  110  may be formed in the range of 1.2 to 5 times the area of the upper substrate  160 . When the area of the lower substrate  110  is smaller than 1.2 times the area of the upper substrate  160 , an effect of an increase in heat transfer efficiency may not be large, and when the area of the lower substrate  110  is greater than 5 times the area of the upper substrate  160 , a heat transfer efficiency may rather be remarkably reduced, and a basic shape of the thermoelectric apparatus may not be maintained. 
     In addition, a heat radiation pattern, for example, an uneven pattern, may be formed on a surface of at least one of the lower substrate  110  and the upper substrate  160 . Accordingly, the heat radiation performance of the thermoelectric element can be improved. When the uneven pattern is formed on a surface in contact with the second conductive semiconductor structure  130  or the first conductive semiconductor structure  140 , a bonding property between the thermoelectric leg and the substrate can be improved. The thermoelectric element  100  includes the lower substrate  110 , the lower electrodes  120 , the second conductive semiconductor structures  130 , the first conductive semiconductor structures  140 , the upper electrodes  150 , and the upper substrate  160 . 
     Although not illustrated in the drawings, the sealing member may also be further disposed between the lower substrate  110  and the upper substrate  160 . The sealing member may be disposed on side surfaces of the lower electrodes  120 , the second conductive semiconductor structures  130 , the first conductive semiconductor structures  140 , and the upper electrodes  150  between the lower substrate  110  and the upper substrate  160 . Accordingly, the lower electrodes  120 , the second conductive semiconductor structures  130 , the first conductive semiconductor structures  140 , and the upper electrodes  150  can be sealed from external moisture, heat, contamination, or the like. 
     In addition, in the thermoelectric element according to the embodiment, the first insulating part  170   a  and the second insulating part  170   b  may further include a first protruding part  180   a  and a second protruding part  180   b . The first protruding part  180   a  and the second protruding part  180   b  may be disposed in groove portions, which will be described below, of the lower electrode  120  and the upper electrode  150 . For example, the first protruding part  180   a  and the second protruding part  180   b  may include the first protruding part  180   a  disposed in the groove portion of the lower electrode  120  and the second protruding part  180   b  disposed in the groove portion of the upper electrode  150 . Due to such a configuration, a problem, that the lower electrode  120  and the upper electrode  150  pass through the first insulating part  170   a  and the second insulating part  170   b  to cause dielectric breakdown so as to be electrically connected to the lower substrate  110  and the upper substrate  160 , can be prevented. This will be described below. In the present specification, the first protruding part  180   a  will be mainly described, this will be equally applied to the second protruding part  180   b , and the insulating parts  170  may include or not include the first protruding part  180   a  and the second protruding part  180   b  as elements. That is, the first insulating part  170   a  may be formed of a material different from a material of the first protruding part  180   a . Alternatively, the first insulating part  170   a  may be formed of a material which is the same as a material of the first protruding part  180   a . Accordingly, it should be understood that the first insulating part  170   a  may have or may not have a boundary surface between the first insulating part  170   a  and the first protruding part  180   a . Accordingly, the protruding part will be described as an element which is included in the insulating part or described as an element different from the insulating part. 
       FIG.  3    is a perspective view illustrating an electrode according to a first embodiment of the present invention,  FIG.  4    is a top view illustrating the electrode according to the first embodiment of the present invention,  FIG.  5    is a side view illustrating the electrode according to the first embodiment of the present invention, and  FIG.  6    is a bottom view illustrating the electrode according to the first embodiment of the present invention. 
     Referring to  FIGS.  3  to  6   , an electrode  120  or  150  according to the first embodiment includes the first electrode  120  or the second electrode  150 , and the first electrode  120  will be mainly described below. 
     The first electrode  120  may include a first surface S 1 , a second surface S 2 , and a third surface S 3 . 
     The first surface  51  may be a surface disposed at a side of a substrate (for example, a lower substrate  110 ) adjacent to the first electrode  120 . At least a part of the first surface  51  may be in contact with the adjacent substrate  110  or a first insulating part  170   a  (see  FIG.  2   ) on the substrate  110 . The first surface  51  may have a rectangular shape but also may have a polygonal or circular shape. 
     In addition, the first surface  51  may include a first edge portion E 1 , a second edge portion E 2 , a third edge portion E 3 , and a fourth edge portion E 4  which are outermost portions. 
     The first edge portion E 1  may be disposed to face the second edge portion E 2 . In addition, the third edge portion E 3  may be disposed to face the fourth edge portion E 4 . In addition, the third edge portion E 3  and the fourth edge portion E 4  may be disposed between the first edge portion E 1  and the second edge portion E 2 . 
     In addition, lengths of the first edge portion E 1  and the second edge portion E 2  in a second direction (Y-axis direction) may be different from lengths of the third edge portion E 3  and the fourth edge portion E 4  in a third direction (Z-axis direction). In this case, the second direction (Y-axis direction) and the third direction (Z-axis direction) are two perpendicular directions on a plane perpendicular to a first direction (X-axis direction). 
     As an example, the lengths of the first edge portion E 1  and the second edge portion E 2  in the second direction (Y-axis direction) may be smaller than the lengths of the third edge portion E 3  and the fourth edge portion E 4  in the third direction (Z-axis direction). 
     In addition, a groove portion G 1  may be disposed along an edge of the first surface S 1 . That is, the first surface S 1  may include the groove portion G 1 . In other words, the first surface S 1  may have a shape having a protruding structure extending from a central portion toward the adjacent substrate (for example, the lower substrate). In the present specification, the first electrode  120  and the second electrode  150  includes the groove portion G 1  and a groove portion G 2 , but, as described above, the first electrode  120  and the groove portion G 1  disposed in the first electrode  120  will be mainly described. 
     The groove portion G 1  may extend along the edge of the first surface S 1  and has a closed-loop on a plane YZ. Accordingly, the groove portion G 1  may be disposed to surround the protruding structure positioned at the central portion of the first surface S 1 . 
     On the first surface S 1 , the first edge portion E 1  to the fourth edge portion E 4  may be disposed apart from the central portion of the first surface S 1  in the first direction. That is, a lower surface GS 1   a  of the groove portion G 1  and a central surface S 1   a  of the first surface S 1  may be disposed apart from each other. Accordingly, the first surface S 1  may have a height difference due to the groove portion G 1 , and the height difference may correspond to a height H 2  of the groove portion G 1  in the first direction. 
     According to the embodiment, a ratio of the height H 2  of the groove portion G 1  to a height H 1  of the first electrode  120  may be in the range of 1:1.8 to 1:3.2. When the ratio is less than 1:1.8, there is a problem that an electric resistance of the electrode increases to degrade the performance of the thermoelectric element. In addition, when the ratio is greater than 1:3.2, there is a problem that a first protruding part  180   a  seated in the groove portion is separated from the electrode. In addition, there may be a problem that the first protruding part formed in the groove portion passes through the first insulating part  170   a  to cause dielectric breakdown on the first insulating part  170   a.    
     In addition, the first surface S 1  may include the lower surface GS 1   a  and a side surface GS 2   a  of the groove portion G 1  and the central surface Sla. 
     In addition, according to the embodiment, a ratio of a width W 1  of the groove portion G 1  to a width W 2  of the first electrode  120  may be in the range of 1:20 to 1:54.2. When the ratio is smaller than 1:20, there is a problem of degrading mechanical reliability between the electrode and the protruding part. In addition, when the ratio is greater than 1:54.2, there is a problem of increasing an electrical resistance of the electrode. 
     The second surface S 2  may be disposed to face the first surface S 1 . In addition, the second surface S 1  may be a surface disposed on a thermoelectric leg electrically connected to the first electrode  120 . At least a part of the second surface S 2  may be in contact with or electrically connected to a second conductive semiconductor structure or first conductive semiconductor structure. 
     The third surface S 3  may be disposed between the first surface S 1  and the second surface S 2 . When the first surface S 1  and the second surface S 2  are a lower surface and an upper surface of the first electrode  120 , the third surface S 3  may correspond to a side surface of the first electrode  120 . 
       FIG.  7    is a perspective view illustrating the electrode and the first protruding part according to the first embodiment of the present invention, and  FIG.  8    is a cross-sectional view illustrating the electrode and the first protruding part according to the first embodiment of the present invention. 
     Referring to  FIGS.  7  and  8   , the first protruding part  180   a  may be disposed in the groove portion G 1  of the first electrode  120 . In this case, the first protruding part  180   a  may have a shape corresponding to a shape of the groove portion G 1 . That is, each of surfaces of the first protruding part  180   a  may be coplanar with one of the first surface S 1  and the third surface S 3 . 
     In addition, the first protruding part  180   a  and the first electrode  120  may be in contact with the first insulating part  170   a  disposed under the first protruding part  180   a  and the first electrode  120  as described above. In addition, the first protruding part  180   a  and the first electrode  120  may be coupled to the lower substrate through the first insulating part  170   a.    
     In addition, according to the embodiment, the first electrode  120  includes the groove portion G 1  at an edge, the first protruding part  180   a  is seated in the groove portion G 1 , and thus a protruding electrode protruding from the first electrode (or the first surface) toward the lower substrate may not be formed. That is, the first protruding part  180   a  can prevent the protruding electrode from being formed. Accordingly, since damage to the first insulating part  170   a  due to the protruding part does not occur, electrical connection between the first electrode and the lower substrate (or between the second electrode and the upper substrate) due to a dielectric breakdown of the insulating part  170   a  (or the second insulating part  170   b ) can be prevented. That is, electrical reliability of the thermoelectric element can be improved. 
       FIG.  9    is a cross-sectional view illustrating a thermoelectric element according to a second embodiment of the present invention, and  FIG.  10    is an enlarged view illustrating portion K 1  of  FIG.  9   . 
     Referring to  FIGS.  9  to  10   , the thermoelectric element according to the second embodiment may include a lower substrate  110 , lower electrodes  120 , second conductive semiconductor structures  130 , first conductive semiconductor structures  140 , upper electrodes  150 , an upper substrate  160 , a first insulating part  170   a , and a second insulating part  170   b  as described above. The above-described contents may be equally applied except contents which will be described below. 
     According to the thermoelectric element according to the second embodiment, each of the first electrodes  120  may include a protruding electrode PR protruding toward the adjacent substrate at an outermost side of a first surface S 1 . 
     First, protruding electrodes PR may include a first protruding electrode PR 1   a  of the first electrode  120  and a second protruding electrode PR 1   b  of the second electrode  150 , and hereinafter, each of the first protruding electrode PR 1   a  and the second protruding electrode PR 1   b  will be described as the protruding electrode PR. 
     The protruding electrode PR may be disposed on a lower surface GS 1   a  of a groove portion G 1 . In addition, the protruding electrode PR may be disposed at an outermost side, that is, an edge, of the lower surface GS 1   a  of the groove portion G 1 . In addition, the protruding electrode PR may have a closed-loop on a plane YZ perpendicular to a first direction like the groove portion G 1 . Alternatively, the protruding electrode PR may have an open-loop on the plane YZ perpendicular to the first direction. 
     A height H 3  of the protruding electrode PR in the first direction may be smaller than or equal to a height H 2  of the groove portion G 1 . Due to such a configuration, the protruding electrode PR may not pass through the first insulating part  170   a  or at least a partial region. Accordingly, not only mechanical reliability of the first insulating part  170   a  is improved, but degradation of electrical reliability of the thermoelectric element due to a dielectric breakdown of the first insulating part  170   a  can also be prevented. 
     In addition, the first insulating part  170   a  may be in contact with the first electrode  120  and the lower substrate  110  and may couple the first electrode  120  and the lower substrate. In this case, the first insulating part  170   a  may extend into the groove portion G 1  in a bonding region OR in which the first insulating part  170   a  overlaps the first electrode  120 . That is, the first insulating part  170   a  may further include a first protruding part  180   a  protruding along an edge of an adjacent electrode (for example, the first electrode) in the bonding region OR. The first protruding part  180   a  may overlap the groove portion G 1  in the first direction. Shapes of the first protruding part  180   a  and a second protruding part  180   b  in the drawings may be different from shapes of the first protruding part  180   a  and the second protruding part  180   b  in other drawings due to the protruding electrode or the like, and this will be described below. 
     In addition, the first protruding part  180   a  may be in contact with both the lower surface GS 1   a  and a side surface GS 2   a  of the groove portion G 1 . Accordingly, a coupling force between the first protruding part  180   a  and the first electrode  120  can be improved, and the first protruding part  180   a  can easily support the first electrode  120 . Accordingly, reliability of the thermoelectric element according to the embodiment can be improved. The description according to the present embodiment may also be equally applied to the second protruding part and the second insulating part. 
       FIG.  11    is a view illustrating a modified embodiment of  FIG.  10   . 
     Referring to  FIG.  11   , a thermoelectric element according to the modified embodiment may include a lower substrate  110 , lower electrodes  120 , second conductive semiconductor structures  130 , first conductive semiconductor structures  140 , upper electrodes  150 , an upper substrate  160 , a first insulating part  170   a , and a second insulating part  170   b  as described above. The above-described contents may be equally applied except contents which will be described below. 
     According to the modified embodiment, each of the first electrodes  120  may include a protruding electrode PR protruding toward the adjacent substrate at an outer most side of a first surface S 1 . The above-described contents may be equally applied to the protruding electrode PR. 
     The protruding electrode PR may be disposed on a lower surface GS 1   a  of a groove portion G 1 . In addition, the protruding electrode PR may be disposed on at an outermost side, that is, an edge, of the lower surface GS 1   a  of the groove portion G 1 . In addition, the protruding electrode PR may have a closed-loop on a plane YZ perpendicular to a first direction like the groove portion G 1 . Alternatively, the protruding electrode PR may have an open-loop on the plane YZ perpendicular to the first direction. 
     A height H 3  of the protruding electrode PR in the first direction may be smaller than or equal to a height H 2  of the groove portion G 1 . Due to such a configuration, the protruding electrode PR may not pass through the first insulating part  170   a  or at least a partial region. Accordingly, not only mechanical reliability of the first insulating part  170   a  is improved, but degradation of electrical reliability of the thermoelectric element due to a dielectric breakdown of the first insulating part  170   a  can also be prevented. 
     In addition, according to the modified embodiment, the first insulating part  170   a  may be in contact with the first electrode  120  and the lower substrate  110  and may couple the first electrode  120  and the lower substrate  110 . In this case, the first insulating part  170   a  may extend into the groove portion G 1  in a bonding region OR in which the first insulating part  170   a  overlaps the first electrode  120 . The same contents may be applied to the second insulating part  170   b  and the second electrode  150 . 
     In this case, the first insulating part  170   a  may include a first protruding part  180   a  protruding along an edge of the adjacent electrode (for example, the first electrode) in the bonding region OR. According to the modified embodiment, the first protruding part  180   a  overlaps the groove portion G 1  in the first direction but may be disposed apart from the lower surface GS 1   a  of the groove portion G 1  in the first direction. A height H 4  of the first protruding part  180   a  may be smaller than a height H 2  of the groove portion G 1 . 
     In addition, at least a part of the first protruding part  180   a  may be in contact with a side surface GS 2   a  of the groove portion G 1 . Even when the first insulating part  170   a  is coupled to the lower substrate and the first electrode  120  due to heat and a pressure between the lower substrate and the first electrode  120 , the first insulating part  170   a  may not extend into the entire groove portion G 1  due to a thickness of the insulating part  170   a  or the like. Due to such a configuration, an air gap may be present between the first protruding part  180   a  and the lower surface GS 2   a  in the groove portion G 1 . The air gap may also have a closed-loop along the groove portion G 1  when viewed from above. Accordingly, a distance for electrical connection between the first electrode and the lower substrate in a predetermined region increases, and thus electrical reliability of the first electrode can be improved. 
     In addition, due to the first protruding part  180   a  and a second protruding part  180   b , contact areas between the first insulating part  170   a  and the second insulating part  170   b  and the electrodes  120  and  150  may increase to improve a coupling force. Accordingly, reliability of the thermoelectric element can be improved. 
     The above-described description may also be equally applied to the second protruding part and the second insulating part. 
       FIG.  12    is a cross-sectional view illustrating a thermoelectric element according to a third embodiment of the present invention, and  FIG.  13    is an enlarged view illustrating portion K 2  of  FIG.  12   . 
     The thermoelectric element according to the third embodiment may include a lower substrate  110 , lower electrodes  120 , second conductive semiconductor structures  130 , first conductive semiconductor structures  140 , upper electrodes  150 , an upper substrate  160 , a first insulating part  170   a , and a second insulating part  170   b  as described above. The above-described contents may be equally applied except contents which will be described below. 
     According to the thermoelectric element according to the third embodiment, each of the first electrodes  120  may include a protruding electrode PR protruding toward the adjacent substrate at an outermost side of a first surface S 1 . First, protruding electrodes PR may include a first protruding electrode PR 1   a  of the first electrode  120  and a second protruding electrode PR 1   b  of the second electrode  150 , and hereinafter, each of the first protruding electrode PR 1   a  and the second protruding electrode PR 1   b  will be described as the protruding electrode PR. 
     The protruding electrode PR may be disposed on a lower surface GS 1   a  of a groove portion G 1 . In addition, the protruding electrode PR may be disposed at an outermost side, that is, an edge, of the lower surface GS 1   a  of the groove portion G 1 . In addition, the protruding electrode PR may have a closed-loop on a plane YZ perpendicular to a first direction like the groove portion G 1 . Alternatively, the protruding electrode PR may have an open-loop on the plane YZ perpendicular to the first direction. 
     According to the third embodiment, a height H 5  of the protruding electrode PR in the first direction may be greater than a height H 2  of the groove portion G 1 . However, a height difference between the height H 5  of the protruding electrode PR in the first direction and the height H 2  of the groove portion G 1  may be smaller than a thickness H 6  of the first insulating part  170   a . Due to such a configuration, even when the protruding electrode PR passes through a partial region of the first insulating part  170   a , the protruding electrode PR may not pass through the entire first insulating part  170   a . Accordingly, electrical reliability of the thermoelectric element due to breakage of the first insulating part  170   a  can also be prevented. 
     The first insulating part  170   a  may be in contact with the first electrode  120  and the lower substrate  110  and may couple the first electrode  120  and the lower substrate  110 . In this case, the first insulating part  170   a  may extend into the groove portion G 1  in a bonding region OR in which the first insulating part  170   a  overlaps the first electrode  120 . That is, the first insulating part  170   a  may further include a first protruding part  180   a  protruding along an edge of the adjacent electrode (for example, the first electrode) in the bonding region OR. The first protruding part  180   a  may overlap the groove portion G 1  in the first direction. 
     According to the embodiment, the first protruding part  180   a  may be in contact with both the lower surface GS 1   a  and a side surface GS 2   a  of the groove portion G 1 . Accordingly, a coupling force between the first protruding part  180   a  and the first electrode  120  can be further improved, and the first protruding part  180   a  can easily support the first electrode  120 . Accordingly, reliability of the thermoelectric element according to the embodiment can be improved. 
       FIG.  14    is a view illustrating a modified embodiment of  FIG.  13   . 
     A thermoelectric element according to the modified embodiment may include a lower substrate  110 , lower electrodes  120 , second conductive semiconductor structures  130 , first conductive semiconductor structures  140 , upper electrodes  150 , an upper substrate  160 , a first insulating part  170   a , and a second insulating part  170   b  as described above. The above-described contents may be equally applied except contents which will be described below. In addition, the above-described contents may be equally applied to a protruding electrode PR, the first insulating part  170   a , and the second insulating part  170   b  except contents which will be described below. 
     According to the modified embodiment, the first insulating part  170   a  may be in contact with the first electrode  120  and the lower substrate  110  and may couple the first electrode  120  and the lower substrate. In this case, the first insulating part  170   a  may extend into the groove portion G 1  in a bonding region OR in which the first insulating part  170   a  overlaps the first electrode  120 . 
     In this case, the first insulating part  170   a  may include a first protruding part  180   a  protruding along an edge of the adjacent electrode (for example, the first electrode) in the bonding region OR. According to the modified embodiment, the first protruding part  180   a  overlaps the groove portion G 1  in a first direction, but may be disposed apart from a lower surface GS 1   a  of the groove portion G 1  in the first direction. 
     In addition, at least a part of the first protruding part  180   a  may be in contact with a side surface GS 2   a  of the groove portion G 1 . Even when the first insulating part  170   a  is coupled to the lower substrate and the first electrode  120  due to heat and a pressure between the lower substrate and the first electrode  120 , the first insulating part  170   a  may not extend into the entire groove portion G 1  due to a thickness of the first insulating part  170   a  or the like. Due to such a configuration, an air gap may be present between the first protruding part and the lower surface GS 2   a  in the groove portion G 1 . The air gap may also have a closed-loop along the groove portion G 1  when viewed from above. Accordingly, a distance for electrical connection between the first electrode and the lower substrate in a predetermined region increases, and thus electrical reliability of the first electrode can be improved. 
     In addition, due to the first protruding part  180   a , a contact area between the first insulating part  170   a  and the electrode  120  may increase to improve a coupling force. Accordingly, reliability of the thermoelectric element can be improved. 
     In addition, according to the various embodiments, the first protruding part  180   a  and a second protruding part  180   b  may overlap in a vertical direction (for example, an X-axis direction). Due to such a configuration, a supporting force due to the first protruding part  180   a  and the second protruding part  180   b  is applied to the same position in the vertical direction, and thus reliability of the thermoelectric element can be improved. 
     In addition, shapes of the first protruding part  180   a  and the second protruding part  180   b  may be the same. For example, the first protruding part  180   a  and the second protruding part  180   b  may be the same based on the first conductive semiconductor structure  140  and the second conductive semiconductor structure  130 . 
     Accordingly, shapes of the groove portion of the first electrode  120  and a shape of the second electrode  150  may be the same. In addition, the shapes of the first protruding part  180   a  and the second protruding part  180   b  seated in the groove portions may also be the same. Accordingly, since a coupling force between the first electrode  120  and the first substrate  110  through the first insulating part  170   a  is similar to a coupling force between the second electrode  150  and the second substrate  160  through the second insulating part  170   b , delamination occurring due to non-uniform coupling forces is reduced, and thus reliability can be improved. 
     In addition, shapes of the first protruding part  180   a  and the second protruding part  180   b  may be different from each other. For example, the shapes of the first protruding part  180   a  and the second protruding part  180   b  may be different from each other based on the first conductive semiconductor structure  140  and the second conductive semiconductor structure  130 . Accordingly, the coupling forces of the first insulating part  170   a  and the second insulating part  170   b  according to a positional difference between the second electrode  150  and the first electrode  120  can be uniformly maintained. For example, the second electrode  150  and the first electrode  120  may partially overlap in the vertical direction. In addition, the first protruding part  180   a  and the second protruding part  180   b  may be disposed apart from each other in the vertical direction. Accordingly, the shapes of the first protruding part  180   a  and the second protruding part  180   b  may be different in a region in which the first electrode and the second electrode do not overlap in the vertical direction. Accordingly, a delamination problem occurring due to the non-uniformity can be reduced. 
     In addition, a height of the first protruding part  180   a  may be smaller than or equal to 0.5 times a thickness of the first electrode. Accordingly, occurrence of a crack of the first insulating layer  170   a  due to the protruding electrode of the first electrode can be minimized. 
     Alternatively, the height of the first protruding part  180   a  may be greater than or equal to 0.5 times the thickness of the first electrode. Due to such a configuration, a coupling force between the first protruding part  180   a  and the first electrode  120  can be improved. 
       FIG.  15    is a side view illustrating an electrode and a first protruding part according to another modified embodiment. 
     Referring to  FIG.  15   , in the electrode according to another modified embodiment, at least one of a lower surface GS 1   a  and a side surface GS 2   a  of a groove portion G 1  may have a pattern. That is, any one or at least a partial region of the lower surface GS 1   a  and the side surface GS 2   a  of the groove portion G 1  may have an uneven pattern. For example, a roughness of a surface of the groove portion G 1  may be greater than a roughness of the other surface excluding the groove portion. Accordingly, the first protruding part  180   a  and the second protruding part  180   b  can be more easily coupled to the first electrode  120  to improve mechanical reliability. 
       FIGS.  16 A to  16 E  are views for describing a method of manufacturing the electrode according to the first embodiment. 
     A method of manufacturing the electrode, the first protruding part, and the second protruding part according to the first embodiment includes an etching process of a substrate member, a coating process of first protruding parts and second protruding parts, a lapping process of the first protruding parts and the second protruding parts to a partial region, and a separating process for each electrode. Hereinafter, the first protruding part will be mainly described. 
     First, referring to  FIGS.  16 A and  16 B , a part of a region excluding a region corresponding to a plurality of electrodes may be etched in a substrate member SB. 
     The substrate member SB may be formed of a material corresponding to a first electrode and a second electrode. Hereinafter, the first electrode and the second electrode will be described as an electrode. 
     In addition, a region excluding regions having sizes corresponding to the plurality of electrodes may be etched in the substrate member SB. Edge portions EP of the regions corresponding to the sizes of the plurality of electrodes disposed apart from each other may be etched in the substrate member SB in order for a manufacturing yield. In addition, widths d 11  of the edge portions corresponding to the adjacent electrodes may be the same. 
     Referring to  FIG.  16 C , a first protruding part  180 A may be applied on the etched substrate member SB. Accordingly, the first protruding part  180 A may be positioned at an entire region corresponding to the plurality of electrodes. In this case, a material of the first protruding part  180 A may be different from a material of an insulating part. 
     Referring to  FIG.  16 D , the first protruding part  180 A on the substrate member SB may be lapped to a predetermined region. Due to the lapping, a region excluding the edge portions EP in the region corresponding to the plurality of electrodes may be exposed. However, a lapped first protruding part  180 B may be positioned at the edge portions EP. Accordingly, the edge portions EP may not be exposed. 
     In addition, the substrate member SB may be separated into individual electrodes (for example, first electrodes and second electrodes) along the edge portions EP. That is, a dicing process may be performed. The dicing process may be performed along virtual lines SL 1  and SL 2  corresponding to a boundary line between the adjacent electrodes among the plurality of electrodes. 
     Referring to  FIG.  16 E , the substrate member may be divided into electrodes  120  and  150  through the dicing process. The electrodes  120  and  150  may have groove portions at edges through an etching process. The groove portions may correspond to the edge portions EP. 
     The thermoelectric element described in the present specification may be applied to a thermoelectric apparatus. The thermoelectric apparatus may include the thermoelectric element and a heat sink coupled to the thermoelectric element. 
     In addition, the thermoelectric apparatus can be used in a power generation apparatus or a power generation system including the power generation apparatus. For example, the power generation system may include the power generation apparatus and a fluid pipe, a fluid introduced into the fluid pipe may be a source for heat generated by an engine of a vehicle, vessel, or the like, a power plant, a steel mill, or the like. However, the present invention is not limited thereto. In addition, a temperature of the fluid discharged from the fluid pipe is lower than a temperature of the fluid introduced into the fluid pipe. For example, the temperature introduced into the fluid pipe may be higher than or equal to 100° C., preferably 200° C. or more, and more preferably in the range of 220° C. to 250° C. but is not limited thereto and may vary according to a temperature difference between a low-temperature part and a high-temperature part of the thermoelectric element. Accordingly, the thermoelectric element according the embodiment of the present invention can operate in a power generation apparatus, a cooling apparatus, a heating apparatus, or the like. 
     While the present invention has been described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that the present invention may be variously changed and modified without departing from the spirit and scope of the present invention defined by the appended claims below.