阅读说明：本技术 半导体烧结体、电气电子部件、以及半导体烧结体的制造方法 (Semiconductor sintered body, electric and electronic component, and method for producing semiconductor sintered body ) 是由 贞赖直树 于 2018-05-17 设计创作，主要内容包括：一种半导体烧结体,包括多晶体,所述多晶体包括硅或硅合金,构成所述多晶体的晶粒的平均粒径为1μm以下,所述半导体烧结体的电导率为10,000S/m以上。(A semiconductor sintered body comprising a polycrystalline body comprising silicon or a silicon alloy, crystal grains constituting the polycrystalline body having an average grain diameter of 1 μm or less, and an electrical conductivity of 10,000S/m or more.)

1. A semiconductor sintered body includes a polycrystalline body,

the polycrystalline body comprises silicon or a silicon alloy,

the average grain diameter of crystal grains constituting the polycrystalline body is 1 [ mu ] m or less,

the semiconductor sintered body has an electrical conductivity of 10,000S/m or more.

2. The sintered semiconductor body according to claim 1, wherein the sintered semiconductor body contains one or more dopants selected from phosphorus, arsenic, antimony, and bismuth.

3. The sintered semiconductor body as claimed in claim 1, wherein the sintered semiconductor body contains one or more dopants selected from boron, aluminum, gallium, indium, and thallium.

4. The sintered semiconductor body according to any one of claims 1 to 3, wherein the Seebeck coefficient of the sintered semiconductor body is-150 to 50 μ V/K.

5. An electric and electronic component comprising the semiconductor sintered body according to any one of claims 1 to 4.

6. A method for manufacturing a semiconductor sintered body, comprising:

a particle preparation step of preparing particles that include silicon or a silicon alloy and have an average particle diameter of 1 μm or less;

a film forming step of forming a film of an organic compound including a dopant element on the surface of the particles; and

and a sintering step of sintering the particles having the coating film formed on the surface thereof to obtain a semiconductor sintered body.

7. The method of manufacturing a sintered semiconductor body as claimed in claim 6, wherein the dopant element includes one or more selected from phosphorus, arsenic, antimony, and bismuth.

8. The method for manufacturing a sintered semiconductor body as claimed in claim 6, wherein the dopant element includes one or more selected from boron, aluminum, gallium, indium, and thallium.

9. The method for manufacturing a semiconductor sintered body according to any one of claims 6 to 8, wherein the sintering step is performed at a temperature of 900 ℃ or higher.

10. The manufacturing method of a semiconductor sintered body according to any one of claims 6 to 9, wherein the sintering step includes performing spark plasma sintering.

Technical Field

The present invention relates to a semiconductor sintered body, an electric and electronic component, and a method for manufacturing a semiconductor sintered body.

Background

Semiconductors are known to be used as thermoelectric materials for thermoelectric power generation because the electromotive force (seebeck coefficient) per unit temperature difference is large. Among them, silicon-based materials have attracted attention in recent years because of their low toxicity, availability at low cost, and easy control of electrical characteristics.

In order to make the thermoelectric material have higher thermoelectric performance, it is necessary to increase the electrical conductivity of the material and decrease the thermal conductivity. However, the thermoelectric performance of silicon-based materials is not sufficient due to the large thermal conductivity of silicon.

In contrast, in recent years, a technique has been known in which silicon is nanostructured by sintering nano-sized silicon particles or the like, thereby reducing thermal conductivity (patent document 1 and non-patent document 1).

< Prior Art document >

< patent document >

Patent document 1: U.S. patent application publication No. 2014/0360546 specification

< non-patent document >

Non-patent document 1: bux et al, adv.Funct.Mater.,2009,19, p.2445-2452

Disclosure of Invention

< problems to be solved by the present invention >

The thermal conductivity of the material can be reduced by the nano-structuring described in patent document 1 and non-patent document 1. However, the thermoelectric properties of silicon-based materials are not sufficient, since the electrical conductivity is also reduced by the nano-structuring.

In view of the above problems, an object of one embodiment of the present invention is to provide a semiconductor material that improves thermoelectric performance by improving electrical conductivity while having lower thermal conductivity.

< means for solving the problems >

In one embodiment of the present invention, there is provided a semiconductor sintered body including a polycrystalline body including silicon or a silicon alloy, crystal grains constituting the polycrystalline body having an average grain diameter of 1 μm or less, and an electrical conductivity of 10,000S/m or more.

< effects of the invention >

According to an embodiment of the present invention, a semiconductor material can be provided which improves thermoelectric performance by improving electrical conductivity while having lower thermal conductivity.

Detailed Description

The embodiments of the present invention will be specifically described below. However, the present invention is not limited to the embodiments described herein, and may be appropriately combined or modified within a range not departing from the technical idea of the present invention.

(semiconductor sintered body)

A semiconductor sintered body according to an embodiment of the present invention is a semiconductor sintered body including a polycrystal including silicon or a silicon alloy, crystal grains constituting the polycrystal having an average grain diameter of 1 μm or less, and an electrical conductivity of 10,000S/m or more. In addition, the semiconductor sintered body in one embodiment of the present invention is a polycrystalline body including silicon or a silicon alloy, and crystal grains constituting the polycrystalline body have an average grain diameter of 1 μm or less and an electrical conductivity of 10,000S/m or more.

When the thermoelectric performance (also referred to as thermoelectric conversion performance) of the thermoelectric material is evaluated, a dimensionless thermoelectric performance index ZT [ - ] is generally used. ZT is determined by the following equation.

ZT＝α²σT/κ (1)

In formula (1), α [ V/K ] is a Seebeck coefficient, σ [ S/m ] is an electric conductivity (in the unit "S/m", "S" is Siemens "," m "is meter), κ [ W/(mK) ] represents a thermal conductivity, and T represents an absolute temperature [ K ]. The seebeck coefficient α refers to a potential difference generated per unit temperature difference. The larger the thermoelectric performance index ZT is, the more excellent the thermoelectric conversion performance is. As can be seen from formula (1), in order to improve the thermoelectric conversion performance ZT, it is desirable that the seebeck coefficient α and the electric conductivity σ be large and the thermal conductivity κ be small.

It is known that the seebeck coefficient α of silicon is high, and according to the above configuration in the present embodiment, a semiconductor sintered body having low thermal conductivity κ and high electrical conductivity σ can be obtained, and therefore, the thermoelectric performance index ZT in formula (1) can be improved. In addition, with Bi₂Te₃Or PbTe, etc., silicon is less toxic and can be obtained at a lower cost. Therefore, by using the semiconductor sintered body in the present embodiment, an environmentally friendly thermoelectric conversion element and thermoelectric power generation device can be provided at a relatively low cost.

(constitution of polycrystal)

The semiconductor sintered body in one embodiment of the present invention is a polycrystalline body including silicon. Specifically, a silicon-based polycrystal or a silicon alloy-based polycrystal is preferable, in other words, a polycrystal containing silicon or a silicon alloy as a main crystal is preferable. The primary crystal is a crystal having the largest precipitation ratio in an XRD pattern or the like, and preferably, it is a crystal accounting for 55 mass% or more of the entire polycrystal.

In the case where the semiconductor sintered body is a polycrystalline body including a silicon alloy, it may be a solid solution, a eutectic or an intermetallic compound of silicon and an element other than silicon. Elements other than silicon contained in the silicon alloy are not particularly limited as long as they do not interfere with the effect of the present invention of improving the electrical conductivity while maintaining the low thermal conductivity of the sintered body, and include Ge, Fe, Cr, Ta, Nb, Cu, Mn, Mo, W, Ni, Ti, Zr, Hf, Co, Ir, Pt, Ru, Mg, Ba, C, Sn, and the like. One or more of these elements may be contained in the silicon alloy. The silicon alloy preferably contains 2 to 20 mass% of one or two or more elements other than silicon. The silicon alloy is preferably a silicon-germanium alloy, a silicon-tin alloy, or a silicon-lead alloy. Among them, a silicon-germanium alloy is more preferable from the viewpoint of reducing the thermal conductivity.

The semiconductor sintered body is a polycrystalline body having a so-called nanostructure in which the average grain diameter of crystal grains constituting the polycrystalline body is 1 μm or less. The average grain size of the crystal grains is preferably less than 1 μm, more preferably 800nm or less, further preferably 500nm or less, further preferably 300nm or less, and further preferably 150nm or less. By setting the grain size of the crystal grains to the above range, the size of the crystal grains is sufficiently smaller than the mean free path of phonons in the polycrystal, and therefore, the thermal conductivity can be reduced by phonon scattering at the interface.

The lower limit of the average grain size of the crystal grains is not particularly limited, and may be 1nm or more from the viewpoint of production limitations.

In the present specification, the average grain size of crystal grains refers to the median of the longest diameters of the crystal grains constituting the crystal, which are measured by direct observation using a Microscope such as a Scanning Electron Microscope (SEM) or a Transmission Electron Microscope (TEM).

The electrical conductivity of the semiconductor sintered body is 10,000S/m or more, preferably 50,000S/m, preferably 90,000S/m or more, more preferably 100,000S/m or more, and further preferably 110,000S/m or more. The above conductivity may be a value at 27 ℃. Thus, the thermoelectric performance can be improved by having an improved electrical conductivity. The upper limit of the electrical conductivity of the semiconductor sintered body may be 600,000S/m or less and 400,000S/m or less at 27 ℃. The thermoelectric performance ZT may be 0.2 or more, preferably 0.3 or more, and more preferably 0.4 or more at 527 ℃.

The thermal conductivity of the semiconductor sintered body in the present embodiment is preferably 25W/m K or less, and more preferably 10W/m K or less. The above thermal conductivity may be a value at 27 ℃. The semiconductor sintered body preferably has a Seebeck coefficient of 50 to 150 μ V/K, more preferably 80 to 120 μ V/K, in absolute value. The above value may be a value at 27 ℃.

(dopant)

The semiconductor sintered body of the present embodiment may contain an n-type or p-type dopant depending on the application. The dopant is preferably uniformly dispersed throughout the sintered body. The n-type dopant preferably contains one or a combination of phosphorus, arsenic, antimony, and bismuth, and preferably contains two or more of phosphorus, arsenic, antimony, and bismuth. The p-type dopant preferably contains one of boron, aluminum, gallium, indium, and thallium, or two or more of boron, aluminum, gallium, indium, and thallium, either alone or in combination. The conductivity type of the dopant element is exemplified, and the dopant element functions as a dopant of either n-type or p-type, and varies depending on the kind of element constituting the mother crystal, the crystal structure, and the like in the obtained sintered body.

For the dopant concentration in the sintered body, in the case of an n-type dopant, the value is [10 ]²⁰Atomic number/cm³]The unit is preferably 0.1 to 10, more preferably 0.5 to 5. In addition, the dopant concentration in the sintered body is [10 ] in the case of a p-type dopant²⁰Atomic number/cm³]The unit is preferably 0.1 to 10, more preferably 0.5 to 5. Although the thermoelectric performance ZT can be improved by increasing the dopant concentration, when the dopant concentration becomes too large, the seebeck coefficient decreases and the thermal conductivity increases, and the thermoelectric performance ZT decreases. However, by setting the dopant concentration in the above range, the thermoelectric performance ZT can be improved.

The n-type dopant is preferably contained at a concentration of-185 to-60 [ mu ] V/K in the Seebeck coefficient of the sintered semiconductor body, and the p-type dopant is preferably contained at a concentration of 60 to 185 [ mu ] V/K in the Seebeck coefficient of the sintered semiconductor body.

(electric and electronic parts)

As described above, according to the present embodiment, a semiconductor sintered body in which the electrical conductivity is improved while maintaining a low thermal conductivity can be obtained. Therefore, the thermoelectric element can be used as an electric/electronic component, particularly as a thermoelectric element. Among these, the present invention can be suitably used for a power generation device utilizing heat radiation, for example, a power generation device mounted on an engine and a heat radiation system of an automobile, a ship, or the like, a power generation device mounted on a heat radiation system of a heating furnace used in industry, or the like.

(method for producing semiconductor sintered body)

The method for manufacturing a semiconductor sintered body according to the present embodiment includes: a particle preparation step of preparing particles that include silicon or a silicon alloy and have an average particle diameter of 1 μm or less; a film forming step of forming a film of an organic compound containing a dopant element on the surface of the particles; and a sintering step of sintering the particles having the film formed on the surface thereof to obtain a semiconductor sintered body.

In the particle preparation step of preparing particles including silicon or a silicon alloy and having an average particle diameter of 1 μm or less, for example, particles (powder) having an average particle diameter of 1 μm or less can be prepared by melting a material of silicon or a silicon alloy to be a main crystal and pulverizing a cooled solid by a known pulverization method. Further, particles (powder) can be synthesized from a raw material of silicon or a silicon alloy by a known crystal growth method such as a Chemical Vapor Deposition (CVD) method.

The average particle diameter of the particles obtained in the particle preparation step is preferably less than 1 μm, more preferably 800nm, even more preferably 500nm, even more preferably 300 nm. The D90 of the particles is preferably 1 μm or less, more preferably 500nm or less, and still more preferably 200nm or less. By setting the particle size of the particles before sintering to the above range, a sintered body having crystal grains of 1 μm or less and appropriately densified can be obtained. The lower limit of the average particle diameter of the particles prepared in the particle preparation step is not particularly limited, and is preferably 10nm or more from the viewpoint of production limitations. In the present specification, the average particle diameter of the particles may be a volume-based median particle diameter value measured by a laser diffraction particle size distribution measuring apparatus.

Next, a film formation step of forming a film of an organic compound including a dopant element on the surface of the particles obtained in the particle preparation step is performed. The coating film forming step may be performed by dispersing the particles obtained in the particle preparation step in a solvent, mixing the organic compound including the dopant element, and performing a mixing treatment using a bead mill or the like. The organic compound containing the dopant element may be added to the dispersion of particles as a mixture. Thereafter, the solvent is removed by, for example, reducing the pressure, and the particles are dried to obtain particles having an organic compound film containing a dopant element formed on the surface thereof. In this case, the thickness of the coating film may be 0.5 to 5nm, and is preferably a monomolecular film of an organic compound.

The dopant element contained in the organic compound may be an n-type or p-type dopant element, depending on the application. The n-type dopant element may be one or more of phosphorus, arsenic, antimony, and bismuth. The p-type dopant element may be one or two or more of boron, aluminum, gallium, indium, and thallium.

The organic compound containing a doping element may be a polymer or a low-molecular compound. As the organic compound, hydride, oxide, oxoacid (oxoacid), or the like containing a doping element can be used.

When phosphorus is used as the n-type dopant element, examples of the organic compound include trialkyl phosphines (trialkylphosphines) such as phosphoric acid, alkyl phosphonic acids (alkylphosphonic acids), alkyl phosphinic acids (alkylphosphonic acids) and esters thereof, polyvinyl phosphonic acids (polyvinylphosphonic acids), phosphines (phosphinies), triethylphosphines (triethylphosphines), and tributylphosphines (tributylphosphines). In addition, a polymer containing phosphonic acid (phosphonic acid polymer) may be used. In the case of using arsenic as a dopant element, arsine (arsine) or the like can be used, in the case of using antimony as a dopant element, antimony trioxide or the like can be used, and in the case of using bismuth as a dopant element, bismuth acid can be used.

When boron is used as the p-type dopant element, a borane cluster (such as decaborane or orthodecaborane), boron trifluoride, or the like can be used as the organic compound. In addition, aluminum trichloride, trimethylaluminum, or the like can be used when aluminum is used as the dopant element, gallium trichloride, trimethylgallium, or the like can be used when gallium is used, indium trichloride, or the like can be used when indium is used, and thallium chloride, or the like can be used when thallium is used. The organic compounds may be used singly or in combination of two or more.

In the film-forming step, it is preferable to add 3 to 60 parts by mass of the organic compound containing the dopant element, and more preferably 10 to 30 parts by mass of the organic compound containing the dopant element, to 100 parts by mass of the particles prepared in the particle preparation step.

The Sintering step is not particularly limited as long as it can sinter the raw material particles (powder), and examples thereof include Spark Plasma Sintering (SPS), atmospheric Sintering (Two step Sintering), pressure Sintering (Hot Pressing), Hot Isostatic Pressing (HIP), and Microwave Sintering (Microwave Sintering). Among them, the spark plasma sintering method capable of obtaining smaller crystal grains is preferably used.

The sintering temperature in the sintering step may be selected depending on the composition of the main crystal of silicon or a silicon alloy, and is preferably 900 ℃ or higher, and more preferably 1000 ℃ or higher. The sintering temperature is preferably 1400 ℃ or lower, and more preferably 1300 ℃ or lower. By setting the above range, densification of the sintered body can be promoted, and the average grain size of the crystal grains of the polycrystalline body can be maintained at 1 μm or less.

In addition, the temperature rise rate in the sintering step is preferably 10 to 100 ℃/min, and more preferably 20 to 60 ℃/min. By setting the temperature increase rate to the above range, uniform sintering can be promoted, and excessively rapid grain growth can be suppressed to maintain the average grain size of the crystal grains of the polycrystalline body at 1 μm or less.

In the sintering step, pressurization is preferably performed. In this case, the pressurizing pressure is preferably 10 to 120MPa, and more preferably 30 to 100 MPa.

The semiconductor sintered body in the present embodiment is produced by preparing particles that include silicon or a silicon alloy and have an average particle diameter of 1 μm or less, forming a film of an organic compound including a dopant element on the surface of the particles, and sintering the particles having the film formed on the surface to obtain a semiconductor sintered body. The semiconductor sintered body has a high electrical conductivity while maintaining a low thermal conductivity. Therefore, a semiconductor sintered body having a higher thermoelectric performance ZT can be provided.

As described above, when the particles having the coating film containing the dopant element formed on the surface thereof are sintered, the dopant element is thermally diffused from the interface of the particles into the particles during sintering. By utilizing doping by thermal diffusion from the grain interface in this manner, the electrical conductivity of the obtained sintered body can be improved. In addition, the semiconductor sintered body obtained by the method of the present embodiment can exhibit higher electrical conductivity than a sintered body which has an equivalent dopant concentration but is not doped by thermal diffusion from the grain boundary.

As described above, in the method of the present embodiment, the coating film is doped by allowing the coating film to contain a dopant element in the coating film forming step and thermally diffusing the dopant element from the grain boundary in the sintering step. However, the coating step may be performed after the particles are doped with the dopant in advance in the step of preparing the particles. For example, in the step of melting a material of silicon or a silicon alloy as a main crystal, a dopant element simple substance or a compound thereof is mixed, and the obtained melt is cooled and pulverized to prepare particles (powder) containing a dopant. In the case of preparing particles by using a Chemical Vapor Deposition (CVD) method or the like, a raw material of silicon or a silicon alloy may be mixed with a simple substance or a compound of a dopant element in a vapor phase and coagulated to prepare particles containing a dopant.

In this way, by including the dopant in the particle preparation step and further thermally diffusing the dopant from the particle surface into the particle by the coating formation step and the firing step, higher-concentration doping can be achieved.