JP7348192B2 - semiconductor element - Google Patents

Description

The present invention relates to semiconductor devices.

Traditionally, semiconductor devices have been used as thermoelectric conversion elements to directly convert thermal energy and electrical energy, using thermoelectric conversion modules that have thermoelectric effects such as the Seebeck effect and Peltier effect, as an effective means of energy utilization. There is a device designed to do this.
Among these, the configuration of a so-called π-type thermoelectric conversion element is known as the thermoelectric conversion element. In the π-type, a pair of electrodes, which are spaced apart from each other, is usually provided on the substrate. The upper surfaces of both thermoelectric elements are connected to the electrodes of the opposing substrate. Furthermore, the use of so-called in-plane type thermoelectric conversion elements is known. In the in-plane type, a plurality of thermoelectric elements are usually arranged so that N-type thermoelectric elements and P-type thermoelectric elements are arranged alternately. For example, the lower electrodes of the thermoelectric elements or the upper electrodes of the thermoelectric elements are connected in series. It consists of connecting.

In recent years, there has been a demand for improved thermoelectric performance, including thinner thermoelectric conversion elements and higher integration. Patent Document 1 discloses a method of directly forming a pattern of a thermoelectric element layer by screen printing or the like using a thermoelectric semiconductor composition containing resin etc., including the viewpoint of thinning the thermoelectric element layer by thinning the layer. There is.

International Publication No. 2016/104615

However, as in Patent Document 1, a method in which a thermoelectric semiconductor composition made of a thermoelectric semiconductor material, a heat-resistant resin, etc. is directly formed as a pattern layer on an electrode or a substrate using a screen printing method, etc., cannot be obtained. The shape controllability of the thermoelectric element layer is not sufficient, and bleeding may occur at the end of the thermoelectric element layer at the electrode interface or the substrate interface, resulting in the thermoelectric element layer losing its shape. For example, when forming a thermoelectric element layer with the intention of forming it in a rectangular parallelepiped shape (including a cubic shape) from the viewpoint of thermoelectric performance and ease of manufacture, the actual cross-sectional shape is approximately semi-elliptic (as described later). , see FIG. 3(a)), which not only makes it impossible to obtain the desired thickness but also makes it impossible to control the upper surface area of the thermoelectric element layer to be uniformly flat. For this reason, when constructing the aforementioned π-type thermoelectric conversion element, the area of the junction between the upper surface of the obtained thermoelectric element layer and the opposing electrode cannot be secured sufficiently, resulting in an increase in interfacial resistance and thermal resistance. , the thermoelectric performance deteriorates, and the thermoelectric performance inherent in the thermoelectric element layer may not be fully brought out. Furthermore, when configuring an in-plane type thermoelectric element, the cross-sectional area of the thermoelectric element layer becomes smaller, which increases electrical resistance, which may lead to a decrease in thermoelectric performance. As described above, when forming a thermoelectric element layer, it is important to improve the shape controllability of each thermoelectric element layer from the viewpoint of improving thermoelectric performance and increasing integration.

In view of the above, an object of the present invention is to provide a thermoelectric conversion element having a thermoelectric element layer with a controlled cross-sectional shape and having excellent thermoelectric performance when a semiconductor element is used as a thermoelectric conversion element.

In order to solve the above problems, the present invention provides the following (1) to (7).
(1) A semiconductor element including a semiconductor element layer made of a semiconductor composition containing a semiconductor material on a substrate, where the area of a vertical cross section including the central part of the semiconductor element layer is S (μm 2 ), and the thickness of the vertical cross section is S (μm ² ). When the maximum value of the thickness in the width direction is Dmax (μm) and the maximum value of the length in the width direction of the vertical section is Xmax (μm), the vertical cross section of the semiconductor element layer satisfies the following condition (A). A semiconductor device that satisfies (B) and (B).
(A) 0.75≦S/(Dmax×Xmax)≦1.00
(B) Dmax≧10μm, or (Dmax/Xmax)≧0.03
Here, the maximum value Dmax of the thickness in the thickness direction of the vertical section is the upper and lower ends of the thickness in the thickness direction of the vertical section when a perpendicular line is drawn on the substrate in the vertical section of the semiconductor element layer. means the maximum distance (thickness) between two points of intersection obtained when Sometimes it means the maximum distance (length) between two intersections obtained when the left and right ends of the length in the width direction of the longitudinal section intersect with the parallel line.
(2) A thermoelectric conversion element using the semiconductor element according to (1) above, wherein the semiconductor material is a thermoelectric semiconductor material, and the semiconductor element includes a thermoelectric element layer made of a thermoelectric semiconductor composition containing the thermoelectric semiconductor material. .
(3) The thermoelectric conversion element according to (2) above, wherein the thermoelectric semiconductor composition further contains a heat-resistant resin.
(4) The above (2) or (3), wherein the thermoelectric semiconductor material is a bismuth-tellurium thermoelectric semiconductor material, a telluride thermoelectric semiconductor material, an antimony-tellurium thermoelectric semiconductor material, or a bismuth selenide thermoelectric semiconductor material. The thermoelectric conversion element described in .
(5) The thermoelectric conversion element according to any one of (2) to (4) above, wherein the heat-resistant resin is a polyimide resin, a polyamide resin, a polyamideimide resin, or an epoxy resin.
(6) The thermoelectric conversion element according to any one of (2) to (5) above, wherein the thermoelectric semiconductor composition further contains an ionic liquid and/or an inorganic ionic compound.
(7) The condition (A) is 0.83≦S/(Dmax×Xmax)≦1.00, and the condition (B) is Dmax≧50 μm or (Dmax/Xmax)≧0.08. , the thermoelectric conversion element according to any one of (1) to (6) above.

According to the present invention, when a semiconductor element is used as a thermoelectric conversion element, it is possible to provide a thermoelectric conversion element having excellent thermoelectric performance and having a thermoelectric element layer with a controlled cross-sectional shape.

Equipped with a thermoelectric element layer with a controlled longitudinal cross-sectional shape.
FIG. 1 is a cross-sectional configuration diagram showing an example of a thermoelectric conversion element including a thermoelectric element layer with a controlled longitudinal cross-sectional shape according to the present invention. FIG. 3 is a diagram for explaining the definition of a longitudinal section of a thermoelectric element layer when the semiconductor element of the present invention is used as a thermoelectric conversion element. FIG. 2 is a cross-sectional view for explaining a longitudinal section of a thermoelectric element layer used in a thermoelectric conversion element of an example or a comparative example of the present invention. FIG. 3 is an explanatory diagram showing, in order of steps, an example of a method for manufacturing a thermoelectric element layer by a pattern frame arrangement/peeling method used in the present invention. FIG. 3 is an explanatory diagram showing, in order of steps, an example of a method for manufacturing a thermoelectric conversion element using a patterned layer arrangement method used in the present invention.

[Thermoelectric conversion element]
The semiconductor element of the present invention is a semiconductor element including a semiconductor element layer made of a semiconductor composition containing a semiconductor material on a substrate, and the area of a vertical cross section including the central part of the semiconductor element layer is S (μm ² ), If the maximum value of the thickness in the thickness direction of the longitudinal section is Dmax (μm), and the maximum value of the length in the width direction of the longitudinal section is Xmax (μm), the longitudinal section of the semiconductor element layer is as follows. It is characterized by satisfying conditions (A) and (B).
(A) 0.75≦S/(Dmax×Xmax)≦1.00
(B) Dmax≧10μm, or (Dmax/Xmax)≧0.03
Here, the maximum value Dmax of the thickness in the thickness direction of the vertical section is the upper and lower ends of the thickness in the thickness direction of the vertical section when a perpendicular line is drawn on the substrate in the vertical section of the semiconductor element layer. means the maximum distance (thickness) between two points of intersection obtained when Sometimes it means the maximum distance (length) between two intersections obtained when the left and right ends of the length in the width direction of the longitudinal section intersect with the parallel line.
By satisfying the above-mentioned conditions (A) and (B), the vertical cross section of the semiconductor element layer constituting the semiconductor element of the present invention tends to have a substantially rectangular shape, and the shape of the semiconductor element layer is This makes it easier to control the shape into a substantially rectangular parallelepiped shape (including a substantially cubic shape), which is preferable from the viewpoint of performance improvement and high integration.
It is preferable that the semiconductor material is a thermoelectric semiconductor material, and the semiconductor element is a thermoelectric conversion element using the semiconductor element, including a thermoelectric element layer made of a thermoelectric semiconductor composition containing the thermoelectric semiconductor material.
When the semiconductor element layer satisfying the above conditions (A) and (B) is used as a thermoelectric element layer, it is preferable from the viewpoint of thermoelectric performance and ease of manufacture. In addition to being able to obtain the desired thickness, the upper surface of the thermoelectric element layer tends to be a flat surface, and the area of the junction between the upper surface of the thermoelectric element layer and the opposing electrode is sufficient, which reduces the interfacial resistance and thermal resistance. When configuring a π-type thermoelectric conversion element or an in-plane type thermoelectric conversion element, the increase in the thermoelectric conversion element is suppressed, and the thermoelectric conversion element originally possessed by the thermoelectric element layer This leads to sufficient performance, and as a result, thermoelectric performance improves. In addition, since the vertical cross-sectional area becomes larger, the electrical resistance of the thermoelectric element layer decreases, so when forming an in-plane type thermoelectric conversion element, thermoelectric performance is improved.

In this specification, the definition of "a vertical section including the central portion of a semiconductor element layer" will be explained using FIG. 2. FIG. 2 is a diagram for explaining a longitudinal cross section of a thermoelectric element layer when the semiconductor element of the present invention is used as a thermoelectric conversion element, and (a) is a plan view of the thermoelectric element layer 4, and FIG. The layer 4 has a length X in the width direction and a length Y in the depth direction, and (b) is a longitudinal section of the thermoelectric element layer 4, and the longitudinal section includes the central portion C of (a). , means the shaded part (rectangular in the figure) having length X and thickness D obtained when cutting between AA' in the width direction.
Furthermore, in this specification, "the vertical cross section of the thermoelectric element layer tends to be substantially square" means that it tends to have a rectangular shape, such as a rectangle or a square, including a trapezoid.

FIG. 1 is a cross-sectional configuration diagram showing an example of a thermoelectric conversion element including a thermoelectric element layer with a controlled longitudinal cross-sectional shape according to the present invention. It is provided with an element layer 4a and a P-type thermoelectric element layer 4b, and further provided with a counter electrode substrate having electrodes 3b on the substrate 2b on the upper surfaces of the N-type thermoelectric element layer 4a and the P-type thermoelectric element layer 4b. Adjacent N-type thermoelectric element layer 4a and P-type thermoelectric element layer 4b are arranged so as to be electrically connected in series with intervening electrode 3b on substrate 2b, and are configured as a π-type thermoelectric conversion element.

(Thermoelectric element layer)
The thermoelectric element layer (hereinafter sometimes referred to as "thermoelectric element layer thin film") constituting the thermoelectric conversion element of the present invention is made of a thermoelectric semiconductor composition containing a thermoelectric semiconductor material on a substrate. From the viewpoint of shape stability of the thermoelectric element layer, it is preferable that the thermoelectric semiconductor material contains a heat-resistant resin, and from the viewpoint of thermoelectric performance, it is more preferable that the thermoelectric semiconductor material (hereinafter sometimes referred to as "thermoelectric semiconductor fine particles") ), a heat-resistant resin, and a thermoelectric semiconductor composition containing an ionic liquid and/or an inorganic ionic compound.

<Longitudinal cross section of thermoelectric element layer>
A longitudinal section of the thermoelectric element layer used in the present invention will be explained using the drawings.

FIG. 3 is a cross-sectional view for explaining a longitudinal section of a thermoelectric element layer used in a thermoelectric conversion element of an example of the present invention or a comparative example, and (a) is a sectional view of the thermoelectric element layer 4s used in comparative example 1. The thermoelectric element layer 4s has a longitudinal section (cross-sectional area S) having a maximum length Xmax in the width direction and a maximum thickness Dmax in the thickness direction, and the longitudinal section is approximately half It is oval. In addition, (b) is a vertical cross section of the thermoelectric element layer 4t used in Example 1, and the vertical cross section of the thermoelectric element layer 4t has a maximum length Xmax in the width direction and a maximum thickness in the thickness direction. It has a vertical cross section (cross-sectional area S) having a value Dmax, and the vertical cross section is approximately square (approximately trapezoidal). Further, (c) is a longitudinal section of the thermoelectric element layer 4u used in Example 2, and has a maximum length Xmax in the width direction and a maximum thickness Dmax in the thickness direction (cross-sectional area S), and the vertical cross section is approximately square (rectangular).

In a longitudinal section including the central part of the thermoelectric element layer constituting the thermoelectric conversion element included in the semiconductor element of the present invention, the area of the longitudinal section is S (μm ² ), and the maximum value of the thickness in the thickness direction of the longitudinal section is S (μm 2 ). Dmax (μm), and when the maximum value of the length in the width direction of the longitudinal section is Xmax (μm), the longitudinal section of the thermoelectric element layer needs to satisfy the following conditions (A) and (B). .
(A) 0.75≦S/(Dmax×Xmax)≦1.00
(B) Tmax≧10μm, or (Dmax/Xmax)≧0.03

Condition (A) requires that S/(Dmax×Xmax) be 0.75≦S/(Dmax×Xmax)≦1.00. When S/(Dmax×Xmax) is less than 0.75, the longitudinal cross section of the thermoelectric element layer tends to become a semi-ellipse and becomes less likely to become a substantially square shape. Regarding the shape of the thermoelectric element layer, it becomes difficult to form a substantially rectangular parallelepiped shape (including a substantially cubic shape), the desired constant thickness cannot be obtained, and the area on the top surface of the thermoelectric element layer that is a flat surface becomes small. . In addition, the area of the longitudinal section becomes smaller. S/(Dmax×Xmax) is preferably 0.78 or more, more preferably 0.83 or more, still more preferably 0.90 or more, particularly preferably 0.95 or more.

Condition (B) requires that Dmax≧10 μm or (Dmax/Xmax)≧0.03.
If Dmax is less than 10 μm or Dmax/Xmax is less than 0.03, the vertical cross section will be difficult to form a semi-ellipse in coating methods such as screen printing and stencil printing, and the shape of the thermoelectric element layer will not be suitable. However, when used as a thermoelectric element layer, problems such as a decrease in efficiency of thermoelectric performance and a decrease in integration may occur.
When Dmax is 10 μm or more, or Dmax/Xmax is 0.03 or more, the vertical cross section tends to be semi-elliptical in coating methods such as screen printing and stencil printing, and the shape of the thermoelectric element layer is almost rectangular. (including a substantially cubic shape) becomes difficult to control.
Dmax is preferably 50 μm or more, more preferably 100 μm or more, even more preferably 150 μm or more. Further, Dmax/Xmax is preferably 0.05 or more, more preferably 0.08 or more, even more preferably 0.08 to 3.00, particularly preferably 0.09 to 1.50, most preferably 0.10 to It is 1.00. If Dmax or Dmax / This leads to higher efficiency and higher integration of thermoelectric performance.

When the longitudinal section of the thermoelectric element layer constituting the thermoelectric conversion element falls within the range of conditions (A) and (B) above, the longitudinal section of the thermoelectric element layer tends to be approximately square, and the shape of the thermoelectric element layer In this case, it is easier to control the shape into a substantially rectangular parallelepiped (including a substantially cubic shape), and the desired constant thickness can be obtained. The area of the joint between the upper surface of the electrode and the opposing electrode is sufficient, and an increase in interfacial resistance and thermal resistance is suppressed. In addition, since the vertical cross-sectional area becomes larger, the electrical resistance of the thermoelectric element layer decreases. In either case, thermoelectric performance is improved.

(thermoelectric semiconductor material)
The thermoelectric semiconductor material used in the present invention, that is, the thermoelectric semiconductor material included in the thermoelectric element layer, is not particularly limited as long as it is a material that can generate a thermoelectromotive force by applying a temperature difference, for example, Bismuth-tellurium thermoelectric semiconductor materials such as P-type bismuth telluride and N-type bismuth telluride; Telluride thermoelectric semiconductor materials such as GeTe and PbTe; Antimony-tellurium thermoelectric semiconductor materials; ZnSb, Zn ₃ Sb _2, Zn ₄ Sb _3, etc. zinc-antimony thermoelectric semiconductor materials; silicon-germanium thermoelectric semiconductor materials such as SiGe; bismuth selenide thermoelectric semiconductor materials such as Bi ₂ Se ₃ ; β-FeSi ₂ , CrSi ₂ , MnSi _1.73 , Mg ₂ Si Silicide-based thermoelectric semiconductor materials such as; oxide-based thermoelectric semiconductor materials; Heusler materials such as FeVAl, FeVAlSi, and FeVTiAl; sulfide-based thermoelectric semiconductor materials such as TiS2 _; etc. are used.
Among these, bismuth-tellurium thermoelectric semiconductor materials, telluride thermoelectric semiconductor materials, antimony-tellurium thermoelectric semiconductor materials, or bismuth selenide thermoelectric semiconductor materials are preferred.

Furthermore, from the viewpoint of thermoelectric performance, a bismuth-tellurium-based thermoelectric semiconductor material such as P-type bismuth telluride or N-type bismuth telluride is more preferable.
The P-type bismuth telluride has holes as carriers and a positive Seebeck coefficient, and is preferably represented by, for example, Bi _X Te ₃ Sb _2-X . In this case, X preferably satisfies 0<X≦0.8, more preferably 0.4≦X≦0.6. When X is greater than 0 and less than or equal to 0.8, the Seebeck coefficient and electrical conductivity increase, and the characteristics as a P-type thermoelectric element are maintained, which is preferable.
Further, the N-type bismuth telluride has an electron as a carrier and a negative Seebeck coefficient, and for example, one represented by Bi ₂ Te _3-Y Se _Y is preferably used. In this case, Y preferably satisfies 0≦Y≦3 (when Y=0: Bi ₂ Te ₃ ), more preferably 0<Y≦2.7. It is preferable that Y is 0 or more and 3 or less because the Seebeck coefficient and electrical conductivity become large and the characteristics as an N-type thermoelectric element are maintained.

The thermoelectric semiconductor fine particles used in the thermoelectric semiconductor composition are obtained by pulverizing the above-mentioned thermoelectric semiconductor material to a predetermined size using a pulverizer or the like.

The blending amount of the thermoelectric semiconductor fine particles in the thermoelectric semiconductor composition is preferably 30 to 99% by mass. More preferably, it is 50 to 96% by mass, and even more preferably 70 to 95% by mass. If the blending amount of the thermoelectric semiconductor fine particles is within the above range, the Seebeck coefficient (absolute value of the Peltier coefficient) is large, and the decrease in electrical conductivity is suppressed, and only the thermal conductivity decreases, resulting in high thermoelectric performance. At the same time, a film having sufficient film strength and flexibility can be obtained, which is preferable.

The average particle size of the thermoelectric semiconductor fine particles is preferably 10 nm to 200 μm, more preferably 10 nm to 30 μm, even more preferably 50 nm to 10 μm, particularly preferably 1 to 6 μm. Within the above range, uniform dispersion becomes easy and electrical conductivity can be increased.
The method for obtaining thermoelectric semiconductor fine particles by pulverizing the thermoelectric semiconductor material is not particularly limited, and may be pulverized to a predetermined size using a known pulverizer such as a jet mill, ball mill, bead mill, colloid mill, roller mill, etc. .
The average particle size of the thermoelectric semiconductor fine particles was obtained by measuring with a laser diffraction particle size analyzer (Mastersizer 3000, manufactured by Malvern), and was taken as the median of the particle size distribution.

Further, the thermoelectric semiconductor fine particles are preferably heat-treated in advance (the "heat treatment" here is different from the "annealing treatment" performed in the annealing treatment step of the present invention). By performing heat treatment, the crystallinity of the thermoelectric semiconductor particles improves, and the surface oxide film of the thermoelectric semiconductor particles is removed, so the Seebeck coefficient or Peltier coefficient of the thermoelectric conversion material increases, further improving the thermoelectric figure of merit. can be improved. Heat treatment is not particularly limited, but before preparing the thermoelectric semiconductor composition, the heat treatment may be carried out under an inert gas atmosphere such as nitrogen or argon, with a controlled gas flow rate so as not to adversely affect the thermoelectric semiconductor fine particles. It is preferable to carry out under a reducing gas atmosphere such as hydrogen or under vacuum conditions, and it is more preferable to carry out under a mixed gas atmosphere of an inert gas and a reducing gas. The specific temperature conditions depend on the thermoelectric semiconductor fine particles used, but it is usually preferable to carry out the reaction at a temperature below the melting point of the fine particles and at 100 to 1500° C. for several minutes to several tens of hours.

(Heat-resistant resin)
In the thermoelectric semiconductor composition used in the present invention, it is preferable to use a heat-resistant resin from the viewpoint of annealing the thermoelectric semiconductor material at a high temperature after forming the thermoelectric element layer. It acts as a binder between thermoelectric semiconductor materials (thermoelectric semiconductor fine particles), making it possible to increase the flexibility of the thermoelectric conversion module and making it easier to form a thin film by coating or the like. The heat-resistant resin is not particularly limited, but it has various properties such as mechanical strength and thermal conductivity as a resin when crystal-growing thermoelectric semiconductor fine particles by annealing a thin film made of a thermoelectric semiconductor composition. A heat-resistant resin whose physical properties are maintained without impairment is preferred.
The heat-resistant resin is preferably a polyamide resin, a polyamide-imide resin, a polyimide resin, or an epoxy resin because it has higher heat resistance and does not adversely affect the crystal growth of the thermoelectric semiconductor fine particles in the thin film, and has excellent flexibility. From this point of view, polyamide resin, polyamideimide resin, and polyimide resin are more preferable. When a polyimide film is used as the substrate to be described later, polyimide resin is more preferable as the heat-resistant resin in terms of adhesion with the polyimide film. Note that in the present invention, polyimide resin is a general term for polyimide and its precursor.

It is preferable that the heat-resistant resin has a decomposition temperature of 300° C. or higher. If the decomposition temperature is within the above range, even when a thin film made of the thermoelectric semiconductor composition is annealed, it will not lose its function as a binder and will maintain its flexibility, as will be described later.

Further, the heat-resistant resin preferably has a mass reduction rate at 300°C measured by thermogravimetry (TG) of 10% or less, more preferably 5% or less, and even more preferably 1% or less. . If the mass reduction rate is within the above range, even when a thin film made of a thermoelectric semiconductor composition is annealed, the flexibility of the thermoelectric element layer can be maintained without losing its function as a binder, as will be described later. .

The blending amount of the heat-resistant resin in the thermoelectric semiconductor composition is 0.1 to 40% by mass, preferably 0.5 to 20% by mass, more preferably 1 to 20% by mass, and even more preferably 2 to 15% by mass. Mass%. When the amount of the heat-resistant resin is within the above range, it functions as a binder for the thermoelectric semiconductor material, facilitates the formation of a thin film, and provides a film that has both high thermoelectric performance and film strength.

(ionic liquid)
The ionic liquid used in the present invention is a molten salt consisting of a combination of a cation and an anion, and refers to a salt that can exist in liquid form in any temperature range of -50 to 500°C. Ionic liquids have characteristics such as extremely low vapor pressure, non-volatility, excellent thermal stability and electrochemical stability, low viscosity, and high ionic conductivity. Therefore, as a conductivity auxiliary agent, it is possible to effectively suppress reduction in electrical conductivity between thermoelectric semiconductor fine particles. Further, the ionic liquid exhibits high polarity based on its aprotic ionic structure and has excellent compatibility with the heat-resistant resin, so that the electrical conductivity of the thermoelectric element layer can be made uniform.

Known or commercially available ionic liquids can be used. For example, nitrogen-containing cyclic cation compounds such as pyridinium, pyrimidinium, pyrazolium, pyrrolidinium, piperidinium, and imidazolium and derivatives thereof; amine cations of tetraalkylammonium and derivatives thereof; phosphines such as phosphonium, trialkylsulfonium, and tetraalkylphosphonium Cation components such as lithium cations and derivatives thereof, chloride ions such as Cl ⁻ , AlCl ₄ ⁻ , Al ₂ Cl ₇ ⁻ , ClO ₄ ⁻ , bromide ions such as Br ^−, I ^−, etc. iodide ions such as BF ₄ ^- , fluoride ions such as PF ₆ ^- , halide anions such as F(HF) _n ^- , NO ₃ ^- , CH ₃ COO ^- , CF ₃ COO ^- , CH ₃ SO ₃ ^- , CF ₃ SO ₃ ^- , (FSO ₂ ) ₂ N ^- , (CF ₃ SO ₂ ) ₂ N ^- , (CF ₃ SO ₂ ) ₃ C ^- , AsF ₆ -, SbF ₆ ^- , NbF ₆ ^{- ,} TaF ₆ ^- , F(HF)n ^- , (CN) ₂ N ^- , C ₄ F ₉ SO ₃ ^- , (C ₂ F ₅ SO ₂ ) ₂ N ^- , C ₃ F ₇ COO ^- , (CF ₃ SO ₂ ) (CF ₃ Examples include those composed of an anion component such as CO)N ^- .

Among the above-mentioned ionic liquids, from the viewpoint of high temperature stability, compatibility with thermoelectric semiconductor particles and resin, and suppression of decrease in electrical conductivity between thermoelectric semiconductor particles, the cation component of the ionic liquid is pyridinium cation and its derivatives. , imidazolium cations and derivatives thereof. The anion component of the ionic liquid preferably contains a halide anion, more preferably at least one selected from Cl ^- , Br ^- and I ^- .

Specific examples of ionic liquids whose cation components include pyridinium cations and derivatives thereof include 4-methyl-butylpyridinium chloride, 3-methyl-butylpyridinium chloride, 4-methyl-hexylpyridinium chloride, and 3-methyl-hexylpyridinium. Chloride, 4-methyl-octylpyridinium chloride, 3-methyl-octylpyridinium chloride, 3,4-dimethyl-butylpyridinium chloride, 3,5-dimethyl-butylpyridinium chloride, 4-methyl-butylpyridinium tetrafluoroborate, 4- Examples include methyl-butylpyridinium hexafluorophosphate, 1-butyl-4-methylpyridinium bromide, 1-butyl-4-methylpyridinium hexafluorophosphate, and 1-butyl-4-methylpyridinium iodide. Among these, 1-butyl-4-methylpyridinium bromide, 1-butyl-4-methylpyridinium hexafluorophosphate, and 1-butyl-4-methylpyridinium iodide are preferred.

Further, as specific examples of ionic liquids in which the cation component contains imidazolium cations and derivatives thereof, [1-butyl-3-(2-hydroxyethyl)imidazolium bromide], [1-butyl-3-(2-hydroxyethyl)imidazolium bromide], [1-butyl-3-(2-hydroxyethyl)imidazolium bromide], -hydroxyethyl)imidazolium tetrafluoroborate], 1-ethyl-3-methylimidazolium chloride, 1-ethyl-3-methylimidazolium bromide, 1-butyl-3-methylimidazolium chloride, 1-hexyl-3 -Methylimidazolium chloride, 1-octyl-3-methylimidazolium chloride, 1-decyl-3-methylimidazolium chloride, 1-decyl-3-methylimidazolium bromide, 1-dodecyl-3-methylimidazolium chloride, 1-Tetradecyl-3-methylimidazolium chloride, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium tetrafluoroborate, 1-hexyl-3-methylimidazolium tetrafluoride Oroborate, 1-ethyl-3-methylimidazolium hexafluorophosphate, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-methyl-3-butylimidazolium methyl sulfate, 1,3-dibutylimidazolium methyl Examples include sulfate. Among these, [1-butyl-3-(2-hydroxyethyl)imidazolium bromide] and [1-butyl-3-(2-hydroxyethyl)imidazolium tetrafluoroborate] are preferred.

The above ionic liquid preferably has an electrical conductivity of 10 ⁻⁷ S/cm or more, more preferably 10 ⁻⁶ S/cm or more. When the electrical conductivity is within the above range, the electrical conductivity aid can effectively suppress reduction in electrical conductivity between thermoelectric semiconductor fine particles.

Moreover, it is preferable that the above ionic liquid has a decomposition temperature of 300° C. or higher. If the decomposition temperature is within the above range, the effect as a conductive auxiliary agent can be maintained even when the thin film of the thermoelectric element layer made of the thermoelectric semiconductor composition is annealed, as will be described later.

Furthermore, the mass loss rate of the above ionic liquid at 300°C measured by thermogravimetry (TG) is preferably 10% or less, more preferably 5% or less, and even more preferably 1% or less. . If the mass reduction rate is within the above range, the effect as a conductive auxiliary agent can be maintained even when the thin film of the thermoelectric element layer made of the thermoelectric semiconductor composition is annealed, as will be described later.

The content of the ionic liquid in the thermoelectric semiconductor composition is preferably 0.01 to 50% by mass, more preferably 0.5 to 30% by mass, and even more preferably 1.0 to 20% by mass. When the amount of the ionic liquid is within the above range, a decrease in electrical conductivity is effectively suppressed, and a membrane having high thermoelectric performance can be obtained.

(Inorganic ionic compound)
The inorganic ionic compound used in the present invention is a compound composed of at least a cation and an anion. Inorganic ionic compounds are solid at room temperature, have a melting point somewhere in the temperature range of 400 to 900°C, and have high ionic conductivity, so they can be used as conductive aids. A reduction in electrical conductivity between thermoelectric semiconductor fine particles can be suppressed.

A metal cation is used as the cation.
Examples of metal cations include alkali metal cations, alkaline earth metal cations, typical metal cations, and transition metal cations, with alkali metal cations and alkaline earth metal cations being more preferred.
Examples of the alkali metal cation include Li ⁺ , Na ⁺ , K ⁺ , Rb ⁺ , Cs ⁺ and Fr ⁺ .
Examples of the alkaline earth metal cation include Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Ba ²⁺ .

Examples of anions include F ⁻ , Cl ⁻ , Br ⁻ , I ⁻ , OH ⁻ , CN ⁻ , NO ₃ ⁻ , NO ₂ ⁻ , ClO ⁻ , ClO ₂ − , ClO ₃ ^{− ,} ClO ₄ ⁻ , CrO ₄ ^{2 -} , HSO ₄ ^- , SCN ^- , BF ₄ ^- , PF ₆ ^- and the like.

Known or commercially available inorganic ionic compounds can be used. For example, cationic components such as potassium cations, sodium cations, or lithium cations, chloride ions such as Cl ⁻ , AlCl ₄ ⁻ , Al ₂ Cl ₇ ⁻ , ClO ₄ ⁻ , bromide ions such as Br ⁻ , I ^−, etc. Examples include those composed of iodide ions, fluoride ions such as BF ₄ ^- and PF ₆ ^- , halide anions such as F(HF) _n ^-, and anion components such as NO ₃ ^- , OH ^- , and CN ^- . It will be done.

Among the above-mentioned inorganic ionic compounds, the cation component of the inorganic ionic compound is potassium, from the viewpoint of high temperature stability, compatibility with thermoelectric semiconductor particles and resin, and suppression of decrease in electrical conductivity between thermoelectric semiconductor particles. , sodium, and lithium. Further, the anion component of the inorganic ionic compound preferably contains a halide anion, and more preferably contains at least one selected from Cl ⁻ , Br ⁻ , and I ⁻ .

Specific examples of inorganic ionic compounds whose cation components include potassium cations include KBr, KI, KCl, KF, KOH, K ₂ CO ₃ and the like. Among these, KBr and KI are preferred.
Specific examples of inorganic ionic compounds whose cation components include sodium cations include NaBr, NaI, NaOH, NaF, Na ₂ CO ₃ and the like. Among these, NaBr and NaI are preferred.
Specific examples of inorganic ionic compounds whose cation components include lithium cations include LiF, LiOH, LiNO ₃ and the like. Among these, LiF and LiOH are preferred.

The above-mentioned inorganic ionic compound preferably has an electrical conductivity of 10 ⁻⁷ S/cm or more, more preferably 10 ⁻⁶ S/cm or more. When the electrical conductivity is within the above range, the conductivity aid can effectively suppress reduction in electrical conductivity between thermoelectric semiconductor fine particles.

Moreover, it is preferable that the above-mentioned inorganic ionic compound has a decomposition temperature of 400° C. or higher. If the decomposition temperature is within the above range, the effect as a conductive auxiliary agent can be maintained even when the thin film of the thermoelectric element layer made of the thermoelectric semiconductor composition is annealed, as will be described later.

Furthermore, the mass loss rate of the above-mentioned inorganic ionic compound at 400°C measured by thermogravimetry (TG) is preferably 10% or less, more preferably 5% or less, and preferably 1% or less. More preferred. If the mass reduction rate is within the above range, the effect as a conductive auxiliary agent can be maintained even when the thin film of the thermoelectric element layer made of the thermoelectric semiconductor composition is annealed, as will be described later.

The amount of the inorganic ionic compound in the thermoelectric semiconductor composition is preferably 0.01 to 50% by mass, more preferably 0.5 to 30% by mass, and even more preferably 1.0 to 10% by mass. . When the amount of the inorganic ionic compound is within the above range, a decrease in electrical conductivity can be effectively suppressed, and as a result, a membrane with improved thermoelectric performance can be obtained.
In addition, when an inorganic ionic compound and an ionic liquid are used together, the total content of the inorganic ionic compound and the ionic liquid in the thermoelectric semiconductor composition is preferably 0.01 to 50% by mass, or more. The amount is preferably 0.5 to 30% by weight, more preferably 1.0 to 10% by weight.

(Other additives)
In addition to the components other than those listed above, the thermoelectric semiconductor composition used in the present invention may optionally further include a dispersant, a film-forming aid, a light stabilizer, an antioxidant, a tackifier, a plasticizer, a colorant, Other additives such as resin stabilizers, fillers, pigments, conductive fillers, conductive polymers, and curing agents may also be included. These additives can be used alone or in combination of two or more.

(Method for preparing thermoelectric semiconductor composition)
The method for preparing the thermoelectric semiconductor composition used in the present invention is not particularly limited, and the thermoelectric semiconductor fine particles, the heat-resistant resin, etc. , the ionic liquid and/or the inorganic ionic compound, the other additives as necessary, and a solvent may be added and mixed and dispersed to prepare the thermoelectric semiconductor composition.
Examples of the solvent include toluene, ethyl acetate, methyl ethyl ketone, alcohol, tetrahydrofuran, methylpyrrolidone, and ethyl cellosolve. These solvents may be used alone or in combination of two or more. The solid content concentration of the thermoelectric semiconductor composition is not particularly limited as long as the composition has a viscosity suitable for coating.

<Method for manufacturing thermoelectric element layer>
In the present invention, the thermoelectric element layer is formed on the substrate or the electrode using a coating liquid or the like made of the thermoelectric semiconductor composition.
Examples of the method for manufacturing the thermoelectric element layer that satisfies the conditions (A) and (B) constituting the thermoelectric conversion element of the present invention include the methods shown in (P), (Q), or (R) below.
(P) Multilayer printing method (Q) Pattern frame arrangement/peeling method (R) Pattern layer arrangement method

(Multilayer printing method)
The multilayer printing method is a screen printing method, a stencil printing method using a coating liquid made of a thermoelectric semiconductor composition, etc., and a screen plate or stencil plate having a desired pattern on the same position on the substrate or electrode. This is a method of forming a thick thermoelectric element layer in which a plurality of thin films of thermoelectric element layers are laminated by repeating printing multiple times using a printing method or the like.
Specifically, first, a coating film that is a thin film of the first thermoelectric element layer is formed, and the obtained coating film is dried to form a thin film of the first thermoelectric element layer. Next, in the same way as the first layer, a coating film that will become the thin film of the second thermoelectric element layer is formed on the thin film of the thermoelectric element layer obtained in the first layer, and the obtained coating film is dried. By doing so, a thin film of the second thermoelectric element layer is formed. For the third and subsequent layers, similarly, a coating film that will become the thin film of the thermoelectric element layer of the third and subsequent layers is formed on the thin film of the thermoelectric element layer obtained immediately before, and the obtained coating film is dried. By doing so, thin films of the third and subsequent thermoelectric element layers are formed. By repeating this process a desired number of times, a thick thermoelectric element layer in which a plurality of thin films of thermoelectric element layers are laminated can be obtained.
As the drying method, conventionally known drying methods such as hot air drying, hot roll drying, and infrared irradiation can be used. The heating temperature is usually 80 to 150°C, and the heating time varies depending on the heating method, but is usually from several seconds to several tens of minutes.
Furthermore, when a solvent is used in preparing the thermoelectric semiconductor composition, the heating temperature is not particularly limited as long as it is within a temperature range that can dry the used solvent.
By using a multilayer printing method, a thermoelectric element layer that satisfies the conditions (A) and (B) can be obtained.

(Pattern frame arrangement/peeling method)
The pattern frame arrangement/peeling method is to provide a pattern frame having spaced apart openings on a substrate, fill the openings with a thermoelectric semiconductor composition, dry it, and peel the pattern frame from the substrate. This is a method of forming a thermoelectric element layer that reflects the shape of the opening of the pattern frame and has excellent shape controllability.
The manufacturing process includes a step of providing a pattern frame having an opening on a substrate, a step of filling the opening with the thermoelectric semiconductor composition, drying the thermoelectric semiconductor composition filled in the opening, and forming a thermoelectric element. The method includes a step of forming a layer, and a step of peeling off the pattern frame from the substrate.
An example of a method for manufacturing a thermoelectric element layer using a pattern frame placement/peeling method will be specifically described using figures.
FIG. 4 is an explanatory diagram showing, in order of steps, an example of a method for manufacturing a thermoelectric element layer by the pattern frame arrangement/peeling method used in the present invention.
(a) is a sectional view showing a mode in which the pattern frame is opposed to the substrate, and the pattern frame is made of stainless steel 12' and has an opening 13s, an opening 13, and an opening depth (pattern frame thickness) 13d. 12 is prepared and made to face the substrate 11;
(b) is a sectional view after the pattern frame is provided on the substrate, and the pattern frame 12 is provided on the substrate 11;
(c) is a cross-sectional view after filling the openings of the pattern frame with a thermoelectric element layer. A thermoelectric semiconductor composition containing a thermoelectric semiconductor material and a thermoelectric semiconductor composition containing an N-type thermoelectric semiconductor material are respectively filled in predetermined openings 13, and a thermoelectric semiconductor composition containing a P-type thermoelectric semiconductor material filled in the opening 13. drying the thermoelectric semiconductor composition containing the material and the N-type thermoelectric semiconductor material to form a P-type thermoelectric element layer 14b and an N-type thermoelectric element layer 14a;
(d) is a sectional view showing a mode in which only the thermoelectric element layer is obtained by peeling off the pattern frame from the filled thermoelectric element layer, in which the pattern frame 12 is separated from the formed P-type thermoelectric element layer 14b and the N-type thermoelectric element layer. The layer 14a is peeled off to obtain a P-type thermoelectric element layer 14b and an N-type thermoelectric element layer 14a as self-supporting layers.
The drying method and the case where a solvent is used in preparing the thermoelectric semiconductor composition are the same as the multilayer printing method described above.
Through the above process, a thermoelectric element layer used for a thermoelectric conversion element can be obtained.
In this way, by using the pattern frame placement/peeling method, a thermoelectric element layer that satisfies the conditions (A) and (B) can be easily obtained.

(Pattern layer arrangement method)
The patterned layer arrangement method is to provide a patterned layer made of a resin-containing layer having spaced apart openings on the electrodes of a substrate, fill the openings with a thermoelectric semiconductor composition, and dry it to remove the openings in the patterned layer. This is a method for forming a thermoelectric element layer with excellent shape controllability that reflects the shape of the part.
For example, in the case of configuring a π-type thermoelectric conversion element, the manufacturing process includes a step of forming a pattern layer having spaced apart openings on the electrode, and a thermoelectric semiconductor composition containing a P-type thermoelectric semiconductor material in the spaced apart openings. filling the spaced-apart openings with a thermoelectric semiconductor composition containing a thermoelectric semiconductor material and an N-type thermoelectric semiconductor material; The method includes a step of drying the thermoelectric semiconductor composition to obtain a P-type thermoelectric element layer and an N-type thermoelectric element layer.
An example of a method for manufacturing a thermoelectric conversion element using a patterned layer arrangement method will be specifically explained using figures.
FIG. 5 is an explanatory diagram showing, in order of steps, an example of a method for manufacturing a thermoelectric conversion element using the patterned layer arrangement method used in the present invention.
(a) is a cross-sectional view after forming an electrode on a substrate, in which an electrode 23a is formed on a substrate 22a;
(b) is a cross-sectional view after forming a layer containing resin on the electrode, in which a layer 24' containing resin is formed on the electrode 23a;
(c) is a plan view of the pattern layer after processing the resin-containing layer (the electrode part is not shown), and (c') is the pattern layer when cut between A-A' in (c). is a cross-sectional view of , in which a layer 24' containing resin is processed to form a patterned layer 24 having openings 25s and openings 25 spaced apart on the electrode;
(d) is a cross-sectional view after the opening of the pattern layer is filled with a thermoelectric element layer, and the opening 25 of the pattern layer 24 contains a thermoelectric semiconductor composition containing a P-type thermoelectric semiconductor material and an N-type thermoelectric semiconductor material. Filling and drying the thermoelectric semiconductor compositions respectively to form an N-type thermoelectric element layer 26a and a P-type thermoelectric element layer 26b;
(e) is a cross-sectional view showing a mode in which the upper surface of the thermoelectric element layer obtained in (d) and the electrode on the substrate opposite thereto are faced and joined, and has the upper surface of the thermoelectric element layer and the electrode 23b. A counter electrode substrate consisting of the substrate 22b is bonded.
The drying method and the case where a solvent is used in the preparation of the thermoelectric semiconductor composition are the same as those for the multilayer printing method and pattern frame arrangement/peeling method described above.
Through the above process, a π-type thermoelectric conversion element can be obtained.
In this way, by using the patterned layer arrangement method, it is possible to easily obtain a π-type thermoelectric conversion element having a thermoelectric element layer that satisfies the conditions (A) and (B).

Among the above, it is more preferable to use the pattern frame arrangement/peeling method or the pattern layer arrangement method from the viewpoint of obtaining a high filling rate, and from the viewpoint of easily controlling the vertical cross section to a substantially rectangular parallelepiped shape. It is more preferable to use a peeling method.

The viscosity of the coating liquid made of the thermoelectric semiconductor composition is appropriately adjusted by the blending amount of the thermoelectric semiconductor material, the thickness of the thermoelectric element layer, and the dimensions of the pattern, but from the viewpoint of shape controllability of the thermoelectric element layer, for example, , 25°C, 5s ^-1 under the conditions of 1 Pa s to 1000 Pa s, preferably 5 Pa s to 500 Pa s, more preferably 10 Pa s to 300 Pa s, even more preferably 30 Pa s to 200 Pa s. be.
Further, when used as a π-type thermoelectric conversion element, the thickness of the thin film of the thermoelectric element layer made of the thermoelectric semiconductor composition is 50 μm or more and 1 mm or less, from the viewpoint of use of screen printing method, stencil printing method, etc. Preferably it is 80 μm or more and 1 mm or less, more preferably 100 μm or more and 700 μm or less, and even more preferably 150 μm or more and 500 μm or less.
On the other hand, when used as an in-plane type thermoelectric conversion element, the thickness of the thin film of the thermoelectric element layer made of the thermoelectric semiconductor composition is 10 μm or more and 300 μm or less, preferably 10 μm or more, from the viewpoint of flexibility. It is 200 μm or less, more preferably 10 μm or more and 100 μm or less.

(annealing treatment)
In the present invention, it is preferable to perform an annealing treatment after forming the thermoelectric element layer. By performing the annealing treatment, the thermoelectric performance can be stabilized, and the thermoelectric semiconductor fine particles in the thermoelectric element layer can be crystal-grown, so that the thermoelectric performance can be further improved.
Although not particularly limited, the annealing treatment is usually performed under an inert gas atmosphere such as nitrogen or argon, under a reducing gas atmosphere, or under vacuum conditions with a controlled gas flow rate. Although it depends on the inorganic ionic compound etc., the temperature of the annealing treatment is usually 100 to 600°C for several minutes to several tens of hours, preferably 150 to 600°C for several minutes to several tens of hours, more preferably 250 to several tens of hours. It is carried out at 600°C for several minutes to several tens of hours, more preferably at 250 to 550°C for several minutes to several tens of hours.

(substrate)
In the thermoelectric conversion element of the present invention, as the substrate, although not particularly limited, from the viewpoint of thinness and flexibility, it is possible to use a resin film that does not affect the decrease in electrical conductivity or increase in thermal conductivity of the thermoelectric element layer. can. Among these, it has excellent flexibility, and even when the thin film of the thermoelectric element layer made of a thermoelectric semiconductor composition is annealed, the performance of the thermoelectric element layer can be maintained without thermal deformation of the substrate, and the heat resistance and size are improved. A polyimide film, a polyamide film, a polyetherimide film, a polyaramid film, or a polyamideimide film is preferable in terms of high stability, and a polyimide film is particularly preferable in terms of high versatility.

The thickness of the resin film is preferably 1 to 1000 μm, more preferably 5 to 500 μm, and even more preferably 10 to 100 μm, from the viewpoints of flexibility, heat resistance, and dimensional stability.
Further, the resin film preferably has a 5% weight loss temperature of 300°C or higher, more preferably 400°C or higher, as measured by thermogravimetric analysis. The heating dimensional change rate measured at 200° C. in accordance with JIS K7133 (1999) is preferably 0.5% or less, more preferably 0.3% or less. The coefficient of linear expansion in the plane direction measured in accordance with JIS K7197 (2012) is 0.1 ppm・℃ ^-1 to 50 ppm・℃ ^-1 , and 0.1 ppm・℃ ^-1 to 30 ppm・℃ ^-1. is more preferable.

Further, as the substrate used in the present invention, an insulating material such as glass or ceramic may be used. The thickness of the substrate is preferably 100 to 1200 μm, more preferably 200 to 800 μm, and even more preferably 400 to 700 μm, from the viewpoint of process and dimensional stability.

(electrode)
Examples of the metal material for the electrode of the thermoelectric conversion element used in the present invention include copper, gold, nickel, aluminum, rhodium, platinum, chromium, palladium, stainless steel, molybdenum, tin, and alloys containing any of these metals. It will be done.
The thickness of the electrode layer is preferably 10 nm to 200 μm, more preferably 30 nm to 150 μm, even more preferably 50 nm to 120 μm. If the thickness of the electrode layer is within the above range, the electrical conductivity will be high and the resistance will be low, and sufficient strength as an electrode will be obtained.

The electrodes are formed using the metal material described above.
The method for forming the electrode is to provide an electrode without a pattern on a resin film, and then to form a predetermined shape using known physical or chemical processing mainly based on photolithography, or a combination thereof. Examples include a method of processing the electrode into a pattern shape, and a method of directly forming an electrode pattern by a screen printing method, an inkjet method, or the like.
Methods for forming electrodes without a pattern include PVD (physical vapor deposition) such as vacuum evaporation, sputtering, and ion plating, or CVD (chemical vapor deposition) such as thermal CVD and atomic layer deposition (ALD). Dry processes such as vapor phase growth (vapor phase growth), various coatings such as dip coating, spin coating, spray coating, gravure coating, die coating, and doctor blade methods, wet processes such as electrodeposition, and silver salt methods. , electrolytic plating method, electroless plating method, lamination of metal foil, etc., which are appropriately selected depending on the material of the electrode.
Since the electrode used in the present invention is required to have high electrical conductivity and high thermal conductivity from the viewpoint of maintaining thermoelectric performance, it is preferable to use an electrode formed by a plating method or a vacuum film forming method. Vacuum film forming methods such as vacuum evaporation and sputtering, electrolytic plating, and electroless plating are preferred because they can easily achieve high electrical conductivity and high thermal conductivity. Depending on the dimensions of the pattern to be formed and the requirements for dimensional accuracy, the pattern can be easily formed using a hard mask such as a metal mask.

(Joining material layer)
In the thermoelectric conversion element used in the present invention, a bonding material layer can be used to bond the thermoelectric element layer and the electrode.
Examples of bonding materials used in the bonding material layer include solder materials, conductive adhesives, sintered bonding agents, etc. In this order, the bonding materials are used as solder layers, conductive adhesive layers, sintered bonding layers, etc. Preferably, it is formed on the top. In this specification, conductivity refers to electrical resistivity of less than 1×10 ⁶ Ω·m.

The solder material constituting the solder layer may be appropriately selected in consideration of the heat resistance temperature of the material constituting the thermoelectric conversion element, as well as the electrical conductivity and thermal conductivity of the solder layer, such as Sn, Sn/Pb. Alloy, Sn/Ag alloy, Sn/Cu alloy, Sn/Sb alloy, Sn/In alloy, Sn/Zn alloy, Sn/In/Bi alloy, Sn/In/Bi/Zn alloy, Sn/Bi/Pb/Cd Alloy, Sn/Bi/Pb alloy, Sn/Bi/Cd alloy, Bi/Pb alloy, Sn/Bi/Zn alloy, Sn/Bi alloy, Sn/Bi/Pb alloy, Sn/Pb/Cd alloy, Sn/Cd Examples include known materials such as alloys. From the viewpoint of lead-free and/or cadmium-free, melting point, electrical conductivity, and thermal conductivity, 43Sn/57Bi alloy, 42Sn/58Bi alloy, 40Sn/56Bi/4Zn alloy, 48Sn/52In alloy, 39.8Sn/52In/7Bi/ Alloys such as 1.2Zn alloy are preferred.
Commercially available solder materials include the following: For example, 42Sn/58Bi alloy (manufactured by Tamura Manufacturing Co., Ltd., product name: SAM10-401-27), 41Sn/58Bi/Ag alloy (manufactured by Nihon Handa Co., Ltd., product name: PF141-LT7HO), etc. can be used.
The thickness of the solder layer (after heating and cooling) is preferably 10 to 200 μm, more preferably 20 to 150 μm, even more preferably 30 to 130 μm, particularly preferably 40 to 120 μm. When the thickness of the solder layer is within this range, it becomes easier to obtain adhesiveness with the chips and electrodes of the thermoelectric conversion material.
Methods for applying the solder material include known methods such as stencil printing, screen printing, and dispensing methods. The heating temperature varies depending on the solder material, resin film, etc. used, but it is usually performed at 150 to 280°C for 3 to 20 minutes.

The conductive adhesive constituting the conductive adhesive layer is not particularly limited, but includes conductive paste and the like. Examples of the conductive paste include copper paste, silver paste, and nickel paste, and when using a binder, examples include epoxy resin, acrylic resin, urethane resin, and the like.
Methods for applying the conductive adhesive include known methods such as screen printing and dispensing.
The thickness of the conductive adhesive layer is preferably 10 to 200 μm, more preferably 20 to 150 μm, even more preferably 30 to 130 μm, particularly preferably 40 to 120 μm.

The sintering bonding agent constituting the sintering bonding agent layer is not particularly limited, and examples thereof include sintering paste and the like. The sintering paste is made of, for example, micron-sized metal powder and nano-sized metal particles, and unlike the conductive adhesive, it directly joins metals by sintering. It may also contain a binder such as a resin.
Examples of the sintering paste include silver sintering paste and copper sintering paste.
Methods for applying the sintered bonding agent layer include known methods such as screen printing, stencil printing, and dispensing methods. Sintering conditions vary depending on the metal material used, but are usually 100 to 300°C for 30 to 120 minutes.
Commercial products of sintering bonding agents include, for example, silver sintering paste, sintering paste (manufactured by Kyocera Corporation, product name: CT2700R7S), sintering type metal bonding material (manufactured by Nihon Handa Corporation, product name: MAX102), etc. Can be used.
The thickness of the sintered bonding agent layer is preferably 10 to 200 μm, more preferably 20 to 150 μm, even more preferably 30 to 130 μm, particularly preferably 40 to 120 μm.

When the semiconductor element of the present invention is used as a thermoelectric conversion element, the longitudinal section of the obtained thermoelectric element layer satisfies conditions (A) and (B), thereby obtaining a thermoelectric conversion element having excellent thermoelectric performance. be able to. Further, it can lead to realizing high integration of the thermoelectric element layer.

Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to these examples in any way.

Evaluation of the electrical resistance value and filling rate of the thermoelectric conversion elements produced in Examples and Comparative Examples were performed by the following method.
(a) Electrical resistance value evaluation The electric resistance value between the lead-out electrode parts of the thermoelectric element layer of the obtained thermoelectric conversion element was measured using a digital high tester (manufactured by Hioki Electric Co., Ltd., model name: 3801-50) at 25℃ Measured under an environment of %RH.
(b) Filling rate evaluation A longitudinal section including the center part of the thermoelectric element layer of the obtained thermoelectric conversion element was observed using a digital microscope (manufactured by Keyence Corporation, model name "VHX-5000"), and the area of the longitudinal section was S (μm ² ), the maximum value Dmax (μm) of the thickness in the thickness direction of the longitudinal section, and the maximum value Xmax (μm) of the length in the width direction of the longitudinal section, and the filling rate [S/(Dmax× Xmax)] was calculated and evaluated.

(Example 1)
The thermoelectric semiconductor material constituting the thermoelectric semiconductor composition is used as thermoelectric semiconductor fine particles.
(Preparation of thermoelectric semiconductor fine particles)
P-type bismuth telluride Bi _0.4 Te ₃ Sb _1.6 (manufactured by Kojundo Kagaku Kenkyusho, particle size: 180 μm), which is a bismuth-tellurium based thermoelectric semiconductor material, was processed using a planetary ball mill (manufactured by Fritsch Japan, Premium line P). Thermoelectric semiconductor fine particles T1 having an average particle size of 1.2 μm were produced by pulverizing the thermoelectric semiconductor particles T1 using the following method: -7) in a nitrogen gas atmosphere. The particle size distribution of the thermoelectric semiconductor fine particles obtained by pulverization was measured using a laser diffraction particle size analyzer (Mastersizer 3000, manufactured by Malvern).
In addition, N-type bismuth telluride Bi ₂ Te ₃ (manufactured by Kojundo Kagaku Kenkyusho, particle size: 180 μm), which is a bismuth-tellurium based thermoelectric semiconductor material, was crushed in the same manner as above to obtain thermoelectric semiconductor fine particles with an average particle size of 1.4 μm. T2 was produced.

(Preparation of coating liquid)
Coating liquid (P)
90 parts by mass of the obtained fine particles T1 of the P-type bismuth-tellurium thermoelectric semiconductor material, polyamic acid which is a polyimide precursor (manufactured by Sigma-Aldrich Co., Ltd., poly(pyromellitic dianhydride-co-4,4) '-oxydianiline) amic acid solution, solvent: N-methylpyrrolidone, solid content concentration: 15% by mass) 5 parts by mass, and as an ionic liquid [1-butyl-3-(2-hydroxyethyl)imidazolium bromide] A coating liquid (P) consisting of a thermoelectric semiconductor composition mixed and dispersed in 5 parts by mass was prepared. The viscosity of the coating liquid (P) was 170 Pa·s.
Coating liquid (N)
90 parts by mass of the obtained fine particles T2 of the N-type bismuth-tellurium thermoelectric semiconductor material, polyamic acid which is a polyimide precursor (manufactured by Sigma-Aldrich, poly(pyromellitic dianhydride-co-4,4) as a heat-resistant resin) '-oxydianiline) amic acid solution, solvent: N-methylpyrrolidone, solid content concentration: 15% by mass) 5 parts by mass, and as an ionic liquid [1-butyl-3-(2-hydroxyethyl)imidazolium bromide] A coating liquid (N) consisting of a thermoelectric semiconductor composition mixed and dispersed in 5 parts by mass was prepared. The viscosity of the coating liquid (N) was 190 Pa·s.

<Formation of thermoelectric element layer>
The above-mentioned coating was applied onto the electrode (4.0 mm long x 1.5 mm wide x 10 μm thick) provided on the lower polyimide film substrate (manufactured by DuPont Toray, Kapton 200H, 100 mm x 100 mm, thickness: 50 μm). The liquid (P) was applied in three parts by the stencil printing method as follows (multilayer printing method).
First, using the coating liquid (P), a first stencil plate having a plate thickness of 30 μm was printed at a predetermined position and dried. Next, a third stencil plate with a thickness of 80 μm was printed on the printing layer formed with the first stencil plate with a thickness of 30 μm, and dried. Further, a fifth stencil plate with a thickness of 150 μm was printed on the printing layer formed with the third stencil plate with a thickness of 80 μm, and dried. Thereafter, by performing an annealing treatment, 100 P-type thermoelectric element layers of the same size of 1.5 mm x 1.5 mm were provided, in which P-type thermoelectric element layers obtained by overprinting three layers were arranged.
Note that drying after application of the coating solution was performed at a temperature of 150°C for 10 minutes in an argon atmosphere, and the annealing treatment for the obtained thin film of the thermoelectric element layer was performed using a mixed gas of hydrogen and argon (hydrogen: argon = 3 volumes). %: 97 volume %) atmosphere, the temperature was raised at a heating rate of 5 K/min and held at 325° C. for 1 hour to cause crystal growth of fine particles of the thermoelectric semiconductor material to form a P-type thermoelectric element layer.
Similarly, the upper polyimide film substrate (the lower polyimide film substrate has the same specifications except for the electrode arrangement, and the electrode arrangement is such that 100 pairs of P-type thermoelectric element layers and N-type thermoelectric element layers are arranged alternately in series, The coating solution (N) was used to print and dry at predetermined positions with a second stencil plate having a thickness of 30 μm. Next, a fourth stencil plate with a thickness of 80 μm was printed on the printing layer formed with the second stencil plate with a thickness of 30 μm, and dried. Further, a sixth stencil plate with a thickness of 150 μm was printed on the printing layer formed with the fourth stencil plate with a thickness of 80 μm, and dried. Thereafter, by performing an annealing treatment, 100 N-type thermoelectric element layers of the same size of 1.5 mm x 1.5 mm were provided, in which N-type thermoelectric element layers obtained by overprinting three layers were arranged.
The thicknesses of the P-type thermoelectric element layer and the N-type thermoelectric element layer were all 160 μm.

Next, a solder material (manufactured by Nihon Handa Co., Ltd., PF141-LT7HO F=10) was provided on the upper surface of the P-type thermoelectric element layer and the electrodes of the lower polyimide film substrate, and then the N-type thermoelectric element layer and the electrodes of the upper polyimide film substrate were applied. By providing the above-mentioned solder material on the upper surface and joining the thermoelectric element layers and electrodes, 100 pairs of P-type thermoelectric element layers and N-type thermoelectric element layers are arranged alternately in series, and electrically We fabricated series-connected π-type thermoelectric conversion elements (Peltier cooling elements).
The distance between the centers of the P-type thermoelectric element layer and the N-type thermoelectric element layer formed on the electrode of the lower polyimide film substrate is 2.5 mm, and the distance between the centers of the P-type thermoelectric element layer and the N-type thermoelectric element layer formed on the electrode of the upper polyimide film substrate is 2.5 mm. The distance between the centers of each layer and the N-type thermoelectric element layer was 2.5 mm.

(Example 2)
A thermoelectric conversion element (π-type thermoelectric conversion element) of Example 2 was produced in the same manner as in Example 1, except that the thermoelectric element layer was formed by the following pattern frame arrangement/peeling method. .
<Pattern frame arrangement/formation of thermoelectric element layer by peeling method>
A lower polyimide film substrate (manufactured by DuPont Toray, Kapton 200H, 100 mm × 100 mm, thickness: 50 μm) was designed to have spaced apart openings on the electrode (opening: 1.5 mm × 1.5 mm, Number of openings: 200, distance between centers of openings corresponding to formation of a pair of P-type thermoelectric element layer and N-type thermoelectric element layer: 2.5 mm) A pattern frame with a plate thickness of 200 μm was provided, and the openings were By filling the above-mentioned coating liquids (P) and (N) into the substrate, drying, and peeling off the pattern frame from the substrate, a P-type thermoelectric element layer and an N-type thermoelectric element layer of 1.5 mm x 1.5 mm are formed. A total of 100 pairs of element layers were provided. The thickness of the thermoelectric element layer after the annealing treatment was all 160 μm.

(Example 3)
A thermoelectric conversion element (π-type thermoelectric conversion element) of Example 3 was produced in the same manner as in Example 1, except that the thermoelectric element layer was formed by the following pattern layer arrangement method.
<Formation of thermoelectric element layer by patterned layer arrangement method>
A lower polyimide film substrate (manufactured by DuPont Toray, Kapton 200H, 100 mm × 100 mm, thickness: 50 μm) was designed to have spaced apart openings on the electrode (opening: 1.5 mm × 1.5 mm, Number of openings: 200, distance between centers of openings corresponding to formation of a pair of P-type thermoelectric element layer and N-type thermoelectric element layer: 2.5 mm) Pattern layer consisting of a polyimide resin layer with a layer thickness of 250 μm. By filling the above-mentioned opening with the coating liquids (P) and (N) and drying, a pair of a P-type thermoelectric element layer and an N-type thermoelectric element layer of 1.5 mm x 1.5 mm is formed. A total of 100 pairs were set up. The thickness of the thermoelectric element layer after the annealing treatment was all 160 μm.

(Example 4)
The thermoelectric generator of Example 4 was prepared in the same manner as in Example 2, except that the viscosity of the coating liquid (P) and coating liquid (N) was adjusted to 70 Pa·s by adding N-methylpyrrolidone. A conversion element (π-type thermoelectric conversion element) was manufactured. The thickness of the thermoelectric element layer after the annealing treatment was all 160 μm.

(Example 5)
In Example 1, the thermoelectric element layer of Example 5 was formed in the same manner as in Example 1, except that the thermoelectric element layer was formed by the following pattern frame arrangement/peeling method, and the thermoelectric conversion element was in an in-plane shape. A conversion element (in-plane type thermoelectric conversion element) was manufactured.
<Pattern frame arrangement/formation of thermoelectric element layer by peeling method>
A polyimide film substrate (manufactured by DuPont Toray, Kapton 200H, 100 mm x 100 mm, thickness: 50 μm) has spaced apart openings on the electrode (1.0 mm long x 6.0 mm wide x 10 μm thick). : 1.0 mm x 1.0 mm, number of openings: 200, distance between the centers of the openings corresponding to the formation of a pair of P-type thermoelectric element layer and N-type thermoelectric element layer: 2.0 mm) Plate thickness A 80 μm pattern frame is provided, the openings are filled with the aforementioned coating liquids (P) and (N), dried, and the pattern frame is peeled off from the substrate to form a 1.0 mm x 1.0 mm pattern. A total of 100 pairs of P-type thermoelectric element layers and N-type thermoelectric element layers were provided.
Note that drying after filling the coating liquid was performed at a temperature of 150°C for 10 minutes in an argon atmosphere, and the annealing treatment for the obtained thin film of the thermoelectric element layer was performed using a mixed gas of hydrogen and argon (hydrogen: argon = 3 volumes). %: 97 volume %) in an atmosphere at a heating rate of 5 K/min and held at 325° C. for 1 hour to grow crystals of fine particles of thermoelectric semiconductor material, forming a P-type thermoelectric element layer and an N-type thermoelectric element layer. And so. The thickness of the thermoelectric element layer after the annealing treatment was all 60 μm.

(Comparative example 1)
A thermoelectric conversion element of Comparative Example 1 was produced in the same manner as in Example 1, except that only one thermoelectric element layer was formed using a stencil plate with a thickness of 235 μm when forming the thermoelectric element layer. The thickness of the thermoelectric element layer after the annealing treatment was all 160 μm.

(Comparative example 2)
Comparative Example 2 was prepared in the same manner as in Comparative Example 1, except that the viscosity of the coating liquids (P) and (N) was adjusted to 70 Pa·s by adding N-methylpyrrolidone. A thermoelectric conversion element was fabricated.

(Comparative example 3)
In Example 5, the thermoelectric conversion element of Comparative Example 3 (in-plane type A thermoelectric conversion element) was fabricated. The thickness of the thermoelectric element layer after the annealing treatment was all 60 μm.

The electrical resistance values and filling rates of the thermoelectric conversion elements obtained in Examples 1 to 5 and Comparative Examples 1 to 3 were evaluated. The evaluation results are shown in Table 1.

It is clear from Table 1 that when comparing the configurations of π-type thermoelectric conversion elements, the thermoelectric conversion elements of Examples 1 to 4, which have thermoelectric element layers having a vertical cross section that satisfies conditions (A) and (B), , compared to the thermoelectric conversion elements of Comparative Examples 1 and 2, each of which has a thermoelectric element layer having a vertical cross section that does not satisfy the provisions of condition (A), the electricity between the electrode portions at both ends of the thermoelectric element layer constituting the thermoelectric conversion element is It can be seen that the resistance value is low and high thermoelectric performance can be obtained. Similarly, when comparing the configurations of in-plane type thermoelectric conversion elements, when comparing Example 5 and Comparative Example 3, it is clear that Example 5 has a lower electrical resistance value between electrode parts and can obtain higher thermoelectric performance. I understand that.

According to the thermoelectric conversion element included in the semiconductor element of the present invention, the thermoelectric conversion element includes a thermoelectric element layer having a vertical cross section that satisfies conditions (A) and (B), the thermoelectric element layer has a substantially rectangular shape. Since the shape can be easily controlled, the bonding between the thermoelectric element layer and the electrode is excellent, and since the electrical resistance value of the thermoelectric element layer can be controlled to be small, improvement in thermoelectric performance can be expected. Furthermore, since the thermoelectric conversion element of the present invention has excellent shape controllability of the thermoelectric element layer, it can be expected to achieve high integration.
By using the above thermoelectric conversion elements as modules, power generation is achieved by converting waste heat from various combustion furnaces such as factories, waste combustion furnaces, cement combustion furnaces, combustion gas exhaust heat from automobiles, and exhaust heat from electronic devices into electricity. It can be considered to be applied to various uses. In the field of electronic equipment, cooling applications include, for example, CPUs (Central Processing Units) used in smartphones, various computers, etc., CMOS (Complementary Metal Oxide Semiconductor Image Sensors), and CCDs (Charge Sensors). Image sensors such as e-Coupled Devices Furthermore, it is possible to apply the present invention to temperature control of various sensors such as MEMS (Micro Electro Mechanical Systems) and other light receiving elements.

1: Thermoelectric conversion element 2a: Substrate 2b: Substrate 3a: Electrode 3b: Electrodes 4, 4s, 4t, 4u: Thermoelectric element layer 4a: N-type thermoelectric element layer 4b: P-type thermoelectric element layer 11: Substrate 12: Pattern frame 12 ': Stainless steel 13s: Opening 13d: Opening depth (pattern frame thickness)
13: Opening 14a: N-type thermoelectric element layer 14b: P-type thermoelectric element layer 22a, 22b: Substrates 23a, 23b: Electrode 24: Pattern layer 24': Layer containing resin 25: Opening 25s: Opening 26a: N-type Thermoelectric element layer 26b: P-type thermoelectric element layer X: Length (width direction)
Xmax: Maximum length in the width direction (longitudinal section)
Y: Length (depth direction)
D: Thickness (thickness direction)
Dmax: Maximum thickness in the thickness direction (longitudinal section)
S: Area of vertical section

Claims (4)

A thermoelectric conversion element comprising a thermoelectric element layer made of a thermoelectric semiconductor composition containing a thermoelectric semiconductor material on a substrate,
The thermoelectric semiconductor composition further includes a heat-resistant resin, an ionic liquid and/or an inorganic ionic compound,
The area of the longitudinal section including the central part of the thermoelectric element layer is S (μm ² ), the maximum thickness in the thickness direction of the longitudinal section is Dmax (μm), and the maximum length of the longitudinal section in the width direction is A thermoelectric conversion element in which the longitudinal section of the thermoelectric element layer satisfies the following conditions (A) and (B), where Xmax (μm).
(A) 0.75≦S/(Dmax×Xmax)≦1.00
(B) Dmax≧ 150 μm and (Dmax/Xmax)≧0.03
Here, the maximum value Dmax of the thickness in the thickness direction of the longitudinal section is the upper and lower ends of the thickness in the thickness direction of the longitudinal section when a perpendicular line is drawn on the substrate in the longitudinal section of the thermoelectric element layer. means the maximum distance (thickness) between two points of intersection obtained when Sometimes it means the maximum distance (length) between two intersections obtained when the left and right ends of the length in the width direction of the longitudinal section intersect with the parallel line. The thermoelectric conversion element according to claim 1 , wherein the thermoelectric semiconductor material is a bismuth-tellurium thermoelectric semiconductor material, a telluride thermoelectric semiconductor material, an antimony-tellurium thermoelectric semiconductor material, or a bismuth selenide thermoelectric semiconductor material. The thermoelectric conversion element according to claim 1 , wherein the heat-resistant resin is a polyimide resin, a polyamide resin, a polyamideimide resin, or an epoxy resin. The condition (A) is 0.83≦S/(Dmax×Xmax)≦1.00, and the condition (B) is Dmax≧ 150 μm and (Dmax/Xmax)≧0.08. The thermoelectric conversion element according to any one of Items 1 to 3 .

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