Laminate, capacitor, electrical circuit, circuit board, device, and method for manufacturing laminate

Abstract

The laminate (1a) has metal tantalum (10) and a dielectric layer (20). The dielectric layer (20) is in contact with the metal tantalum (10) and contains an oxide containing tantalum and tungsten. The dielectric layer (20) has a relative dielectric constant of more than 27 and 41.7 or less at 120 Hz.

Description

Technical Field

[0001] This disclosure relates to laminates, capacitors, electrical circuits, circuit boards, devices, and methods for manufacturing laminates. Background Technology

[0002] The technique of increasing dielectric constant through anodizing has long been known.

[0003] For example, Patent Document 1 describes a high-dielectric-constant composite oxide film containing 1 to 50% by weight of the central atom of an inorganic oxyacid salt anion, made from metals selected from Group IIIA, IVA, and VA. This high-dielectric-constant composite oxide film has a relative permittivity more than twice that of the oxide of the metal. This high-dielectric-constant composite oxide film is manufactured by electrolytic anodic oxidation of a metal selected from Group IIIa, IVa, and Va metals in a non-aqueous electrolyte containing less than 5% by weight of water from the inorganic oxyacid salt.

[0004] Patent document 2 describes a method for manufacturing a solid capacitor. This method includes a step of forming a dielectric oxide film layer on the surface of a metal substrate, and a step of surface treating the dielectric oxide film layer. In the step of surface treating the dielectric oxide film layer, a portion of the dielectric oxide film layer is immersed in a surface treatment aqueous solution containing one or more of phosphotungstic acid, molybdic acid, phosphomolybdic acid, or their salts. For example, an aluminum anodic oxide film layer is immersed in phosphotungstic acid (H3(PW)2)2. 12 O 40 In an aqueous solution, an inorganic oxide film layer of P2O5WO3 is formed on the aluminum anodic oxide film layer. The metal substrate can be tantalum foil or tantalum sintered body, etc.

[0005] Patent document 3 describes a tantalum solid electrolytic capacitor. It uses fine tantalum metal powder doped with tungsten.

[0006] Patent document 4 describes a two-terminal nonlinear element. This two-terminal nonlinear element is manufactured by a method comprising a step of anodizing a first conductive film made of tantalum in a prescribed non-aqueous chemical conversion solution to form an insulating film on the surface of the first conductive film.

[0007] Non-Patent Document 1 describes the formation of an anode film on a Ta-W alloy magnetron sputtered film. The anode film consists of an outer Ta2O5 thin film that does not contain tungsten and an inner layer containing both tantalum and tungsten.

[0008] Existing technical documents

[0009] Patent documents

[0010] Patent Document 1: Japanese Patent Application Publication No. 8-134696

[0011] Patent Document 2: Japanese Patent Application Publication No. 10-154639

[0012] Patent Document 3: Japanese Patent Application Publication No. 9-293647

[0013] Patent Document 4: Japanese Patent Application Publication No. 10-275949

[0014] Non-patent literature

[0015] Non-patent document 1: Masatoshi ISHIZUKA, Etsushi TSUJI, Yoshitaka AOKI, Hiroki HABAZAKI: "Formation and Dielectric Properties of Anodic Films Formedon Ta-W Alloys at Various Formation Voltages", 81, p.840-844(2013) Summary of the Invention

[0016] The problem that the invention aims to solve

[0017] This disclosure provides a novel laminate having a defined dielectric layer on tantalum metal.

[0018] Methods for solving problems

[0019] The present disclosure discloses a laminate having a metallic tantalum and a dielectric layer in contact with the metallic tantalum, the dielectric layer containing an oxide containing tantalum and tungsten.

[0020] The dielectric layer has a relative permittivity greater than 27 and less than 41.7 at 120 Hz.

[0021] Invention Effects

[0022] According to this disclosure, a novel laminate having a specified dielectric layer on tantalum metal can be provided. Attached Figure Description

[0023] Figure 1 This is a cross-sectional view showing an example of a laminate of the present disclosure.

[0024] Figure 2 It is a potential-pH diagram showing the state of tungsten in water.

[0025] Figure 3 This is a flowchart illustrating an example manufacturing method of a laminate of the present disclosure.

[0026] Figure 4 This is a cross-sectional view showing an example capacitor of this disclosure.

[0027] Figure 5 This is a cross-sectional view showing another example of a capacitor in this disclosure.

[0028] Figure 6A This is a schematic diagram showing an example of an electrical circuit of this disclosure.

[0029] Figure 6B This is a schematic diagram showing an example of a circuit board of this disclosure.

[0030] Figure 6C This is a diagram schematically showing an example device of this disclosure.

[0031] Figure 7 This is a graph showing the relationship between the concentrations of oxygen and tungsten in the sample of Example 1 and the depth from the sample surface. Detailed Implementation

[0032] (The views that form the basis of this disclosure)

[0033] According to the technology described in Patent Document 1, in order to perform electrolytic anodic oxidation of metals and form a dielectric film in a non-aqueous electrolyte containing an inorganic oxyacid salt with an aqueous content of 5% or less, the required oxygen source is substantially limited to the oxygen contained in the oxyacid. Therefore, for example, it is difficult to oxidize tantalum metal to a state corresponding to the highest oxidation number. From the viewpoint of reducing current leakage when a voltage is applied to the dielectric, this can hardly be considered advantageous.

[0034] According to the technology described in Patent Document 2, before surface treatment using a surface treatment aqueous solution containing phosphotungstic acid or the like, it is necessary to form a dielectric oxide film layer by means of anodizing or the like.

[0035] As can be understood from the techniques described in Patent Document 3 and Non-Patent Document 1, anodizing an alloy of tantalum and tungsten creates a dielectric containing oxides of tungsten and tantalum. However, in these techniques, the tantalum and tungsten alloy is necessary, which poses a constraint from the viewpoint of mass production.

[0036] The technology described in Patent Document 4 relates to a two-terminal nonlinear element with a sufficiently small element capacity of the MIM element, wherein the relative permittivity of the MIM element in the embodiment is 17.7 to 20.5.

[0037] In view of this situation, the inventors repeatedly investigated whether it was possible to obtain a laminate containing a dielectric layer of tantalum and tungsten oxides with a specified relative permittivity on tantalum metal. Through numerous trials and errors, the inventors discovered for the first time a method for obtaining such a laminate. Based on this new insight, the inventors and others have proposed the laminate of this disclosure.

[0038] (Implementation Method)

[0039] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. The present disclosure is not limited to the following embodiments.

[0040] Figure 1 This is a cross-sectional view showing an example of a laminated body according to the present disclosure. For example... Figure 1 As shown, the laminate 1a includes a tantalum metal 10 and a dielectric layer 20. The dielectric layer 20 is in contact with the tantalum metal 10 and contains an oxide containing tantalum and tungsten. The relative permittivity of the dielectric layer 20 at 120 Hz is greater than 27 and less than 41.7. The relative permittivity of the dielectric layer formed on the tantalum metal can be determined according to the method described in the example embodiment.

[0041] Table 1 shows the relative permittivity values ​​of the metal oxides that can be formed by anodizing metals. As shown in Table 1, WO3 obtained by anodizing is amorphous and has the highest relative permittivity among the following amorphous metal oxides. Therefore, it can be expected that if the metal oxide obtained by anodizing, for example, tantalum metal contains tungsten in addition to tantalum, the relative permittivity of the dielectric layer obtained by anodizing tantalum metal will be higher.

[0042] [Table 1]

[0043]

[0044] Figure 2 This is a potential-pH diagram showing the state of tungsten in water. For example... Figure 2 As shown, tungsten exhibits water solubility at pH values ​​above the specified range of 4 to 7, depending on its concentration in water. Therefore, when anodizing metallic tantalum using an aqueous solution of a tungsten compound with a pH value above the specified range of 4 to 7, the tungsten incorporated into the dielectric layer formed by anodizing can be redissolved into the aqueous solution through a reverse reaction. For example, the technique described in Non-Patent Document 1 uses an aqueous solution of ammonium borate for the anodizing treatment of Ta-W alloys. The pH of the ammonium borate aqueous solution is typically about 8.2. Therefore, it can be considered that tungsten dissolves from the surface of the dielectric layer formed by the anodizing treatment of Ta-W alloys into the ammonium borate aqueous solution.

[0045] The laminate 1a can be manufactured, for example, by methods comprising (I) and (II) below. Figure 3 This is a flowchart illustrating an example of a method for manufacturing a laminate 1a.

[0046] (I) Contact tantalum metal with an acidic solution containing tungsten compounds.

[0047] (II) Anodizing of tantalum metal is performed while tantalum metal is in contact with the above solution.

[0048] First, in step S11, tantalum metal is brought into contact with an acidic solution containing a tungsten compound. The solution is preferably an aqueous solution with a pH below 4. This makes it difficult for tungsten to dissolve from the dielectric layer formed by the anodization of tantalum metal, and the concentration of tungsten in the dielectric layer easily increases. Therefore, the relative permittivity of the dielectric layer can be easily adjusted to the desired range. The pH of the aqueous solution can be below 3.5, below 3.0, below 2.5, below 2.0, below 1.5, or below 1.0.

[0049] The tungsten compound contained in the above solution is not limited to specific compounds. The solution may contain, for example, an electrolyte containing polytungstate or polytungstate containing two or more tungsten atoms in one molecule of anion. In this case, tungsten tends to exist stably in the solution, and the concentration of tungsten in the dielectric layer tends to be higher. Therefore, the relative permittivity of the dielectric layer can be easily adjusted to the desired range.

[0050] Polytungstates or polytungstates preferably have heteroatoms with a valence of 3 or higher. In this case, the pH of the aqueous solution tends to decrease. Examples of heteroatoms are phosphorus and silicon.

[0051] The concentration of the tungsten compound in the above solution is not limited to a specific value. For example, its concentration can be 0.5% by mass or higher. In this case, the tungsten concentration in the dielectric layer can easily be increased, making it easier to adjust the relative permittivity of the dielectric layer to the desired range.

[0052] The concentration of the tungsten compound in the above solution is preferably 1% by mass or more, more preferably 2% by mass or more, and even more preferably 2.5% by mass or more. This concentration can be 5% by mass or more, 10% by mass or more, 15% by mass or more, or 20% by mass or more. This concentration is, for example, 50% by mass or less, and can also be 45% by mass or less, 40% by mass or less, 35% by mass or less, or 30% by mass or less. This concentration is, for example, 0.5% by mass or more and 50% by mass or less, preferably 1% by mass or more and 50% by mass or less, more preferably 2% by mass or more and 50% by mass or less, and even more preferably 2.5% by mass or more and 50% by mass or less.

[0053] The above solution satisfies at least one of the conditions selected from (i) and (ii) below. In this way, the tungsten concentration of the dielectric layer can be easily increased, and the relative permittivity of the dielectric layer can be easily adjusted to the desired range. Heteropolytungstate is a polytungstate oxyacid containing elements (heteroatoms) other than Group V and Group VI elements (V, Nb, Ta, Mo, and W) in its anions as oxyacid ions.

[0054] (i) The solution contains an electrolyte containing heteropolytungstic acid or heteropolytungstate, wherein the heteropolytungstic acid and the heteropolytungstate contain two or more tungsten atoms in one molecule of the anion.

[0055] (ii) The concentration of the tungsten compound in the solution is 0.5% by mass or more.

[0056] Next, in step S12, anodic oxidation of the tantalum metal is performed while it is in contact with the solution. For example, in the solution, with the tantalum metal and the counter electrode arranged at a predetermined interval, a predetermined voltage is applied between the tantalum metal and the counter electrode to perform anodic oxidation. For example, tantalum metal is used as the anode and platinum is used as the cathode. Anions such as oxide ions attracted to the tantalum metal serving as the anode combine with the ionized tantalum to form tantalum oxide. At this time, tungsten contained in the solution is incorporated into the dielectric layer. In this way, a dielectric layer 20 containing tantalum and tungsten oxides is formed on the tantalum metal 10, resulting in a laminate 1a. In this way, the dielectric layer 20 is, for example, an anodic oxide film.

[0057] The dielectric layer 20 can also be manufactured by methods other than anodizing, such as sputtering. The dielectric layer 20 can also be a sputtered film.

[0058] The relative permittivity of the dielectric layer 20 can be, for example, 28 or 29 or more, or 40 or less.

[0059] The average tungsten concentration in the dielectric layer 20 is not limited to a specific value. For example, its average value is 0.1% by mass or more and 20% by mass or less. In this case, the dielectric layer 20 easily possesses the desired relative permittivity. Furthermore, the dielectric layer 20 is less prone to generating oxygen vacancies, and the durability of the product having the laminate 1a is easily increased. The average tungsten concentration in the dielectric layer 20 can be 0.15% by mass or more or 0.2% by mass or more, or it can be 15% by mass or less, 10% by mass or less, 5% by mass or less, 4% by mass or less, 3% by mass or less, 2% by mass or less, or 1% by mass or less. The average tungsten concentration in the dielectric layer 20 can be determined according to the method described in, for example, the embodiments.

[0060] In measurements of the dielectric layer 20 using time-of-flight secondary ion mass spectrometry (TOF-SIMS), the intensity of the ion signal from tungsten was lower than that from, for example, tantalum oxide.

[0061] The thickness of the dielectric layer 20 is not limited to a specific value. Its thickness is, for example, 10 nm or more and 1000 nm or less. The thickness of the dielectric layer 20 can be determined based on measurements such as TOF-SIMS, or based on observations of the cross-section of the dielectric layer obtained using electron microscopes such as scanning electron microscopes (SEM) and transmission electron microscopes (TEM).

[0062] The dielectric layer 20, for example, includes a portion 21. The tungsten concentration of the portion 21 is 0.15% by mass or more, and it has a thickness of 10 nm or more. In this case, the dielectric layer 20 is more likely to have the desired relative permittivity, and the durability of the product having the laminate 1a is more likely to be improved. The thickness of the portion 21 can be 20 nm or more, 50 nm or more, or 100 nm or more, or it can be less than 1000 nm, less than 500 nm, or less than 200 nm.

[0063] Regarding the concentration of tungsten in the dielectric layer 20, it may decrease continuously or discontinuously in the thickness direction of the dielectric layer 20 as the distance from the surface of the dielectric layer 20 (the surface that is not in contact with the tantalum metal 10) increases. The dielectric layer 20 may also contain regions where the concentration of tungsten increases with the distance from the surface of the dielectric layer 20.

[0064] The shape of tantalum 10 is not limited to a specific shape. Tantalum 10 can be in the form of plates or foils, particles or fibers, or porous materials.

[0065] Figure 4 This is a cross-sectional view showing an example of a capacitor according to the present disclosure. Figure 4 As shown, capacitor 2a has a first electrode 11 containing tantalum 10, a second electrode 12, and a dielectric layer 20. The dielectric layer 20 is disposed between the first electrode 11 and the second electrode 12. The dielectric layer 20 contains an oxide containing tantalum and tungsten. The relative permittivity of the dielectric layer 20 at 120 Hz is greater than 27 and less than 41.7. With this structure, capacitor 2a can easily have a high capacitance.

[0066] The capacitor 2a can be manufactured, for example, by forming or configuring a second electrode 12 on the surface of the dielectric layer 20 of the laminate 1a. Therefore, the dielectric layer 20 in the capacitor 2a can have the structure and characteristics derived from the dielectric layer 20 in the laminate 1a.

[0067] The second electrode 12 can be made of any conductive material and is not limited to a specific material. The second electrode 12 can contain valve metals such as aluminum, tantalum, niobium, and bismuth, as well as precious metals such as gold and platinum, and nickel. The second electrode 12 can also contain carbon materials such as graphite.

[0068] In capacitor 2a, the surface of dielectric layer 20 can also be in contact with the electrolyte. In this case, the second electrode 12 can also contain an electrolyte. This electrolyte is not limited to a specific electrolyte. The electrolyte contains, for example, at least one selected from electrolytes, solid electrolytes, and conductive polymers. Examples of conductive polymers include polypyrrole, polythiophene, polyaniline, and their derivatives. The electrolyte can also be a manganese compound such as manganese oxide.

[0069] Figure 5 This is a cross-sectional view showing another example of the capacitor disclosed herein. Figure 5 Except where specifically stated, capacitor 2b is constructed in the same manner as capacitor 2a. The same symbols are used to denote the constituent elements of capacitor 2b that are identical or corresponding to those of capacitor 2a, and detailed descriptions of these elements are omitted. The description of capacitor 2a also applies to capacitor 2b, provided it is not technically contradictory.

[0070] like Figure 5 As shown, in capacitor 2b, the dielectric layer 20 and the first electrode 11 form a porous body 15. The second electrode 12 fills the pores 15p of the porous body 15. With this structure, the capacitor 2b can easily have a higher electrostatic capacitance because the area of ​​the first electrode 11 is increased.

[0071] The porous body 15 is obtained, for example, by anodizing a porous tantalum metal 10 in contact with an acidic solution containing a tungsten compound. The porous tantalum metal 10 is obtained, for example, by etching a tantalum foil or sintering tantalum powder.

[0072] In capacitor 2b, the second electrode 12 contains, for example, an electrolyte. The electrolyte contains at least one selected from, for example, electrolytes, solid electrolytes, and conductive polymers. Examples of conductive polymers include polypyrrole, polythiophene, polyaniline, and their derivatives. The electrolyte may also be a manganese compound such as manganese oxide.

[0073] Figure 6AThis diagram schematically shows an example of an electrical circuit according to the present disclosure. Electrical circuit 3 is equipped with capacitor 2a. Electrical circuit 3 can be an active circuit or a passive circuit. Electrical circuit 3 can be a discharge circuit, a smoothing circuit, a decoupling circuit, or a coupling circuit. Because electrical circuit 3 includes capacitor 2a, electrical circuit 3 can easily achieve the desired performance. For example, noise can be easily reduced in electrical circuit 3. Electrical circuit 3 may also include capacitor 2b.

[0074] Figure 6B This is a schematic diagram showing an example of the circuit board of this disclosure. (As shown) Figure 6B As shown, the circuit board 5 includes a capacitor 2a. For example, an electrical circuit 3 containing a capacitor 2a is formed in the circuit board 5. Because the circuit board 5 includes a capacitor 2a, the circuit board 5 can easily achieve the desired performance. The circuit board 5 can be an embedded board or a motherboard. The circuit board 5 may also include a capacitor 2b.

[0075] Figure 6C This is a schematic diagram illustrating an example of the device disclosed herein. (As shown) Figure 6C As shown, device 7 includes capacitor 2a. Device 7 includes, for example, a circuit board 5 containing capacitor 2a. Because device 7 includes capacitor 2a, device 7 can easily achieve the desired performance. Device 7 can be an electronic device, a communication device, a signal processing device, or a power supply device. Device 7 can be a server, an AC adapter, an accelerator, a liquid crystal display (LCD), or a flat panel display. Device 7 can be a USB charger, a solid-state drive (SSD), an information terminal such as a personal computer (PC), a smartphone, or a tablet computer, or an Ethernet switch. Device 7 may also include capacitor 2b.

[0076] (Postscript)

[0077] Based on the above records, the following technology is disclosed.

[0078] (Technology 1)

[0079] A laminate having a metallic tantalum and a dielectric layer in contact with the metallic tantalum, the dielectric layer containing an oxide containing tantalum and tungsten.

[0080] The dielectric layer has a relative permittivity greater than 27 and less than 41.7 at 120 Hz.

[0081] (Technology 2)

[0082] As described in Technique 1, the average tungsten concentration in the dielectric layer is 0.1% by mass or more and 20% by mass or less.

[0083] (Technology 3)

[0084] As described in technique 1 or 2, the dielectric layer contains a portion having a tungsten concentration of 0.15% by mass or more and a thickness of 10 nm or more.

[0085] (Technology 4)

[0086] A capacitor having:

[0087] The first electrode contains tantalum metal.

[0088] The second electrode, and

[0089] A dielectric layer disposed between the first electrode and the second electrode, the dielectric layer containing an oxide containing tantalum and tungsten.

[0090] The dielectric layer has a relative permittivity greater than 27 and less than 41.7 at 120 Hz.

[0091] (Technology 5)

[0092] An electrical circuit comprising the capacitor described in Technique 4.

[0093] (Technology 6)

[0094] A circuit board having the capacitor described in Technique 4.

[0095] (Technology 7)

[0096] A device comprising the capacitor described in Technique 4.

[0097] (Technology 8)

[0098] A method for manufacturing a laminate includes the following steps:

[0099] Contacting tantalum metal with an acidic solution containing tungsten compounds, and

[0100] The tantalum metal is anodized while in contact with the solution.

[0101] (Technology 9)

[0102] In the method for manufacturing a laminate as described in Technique 8, the solution satisfies at least one condition selected from (i) and (ii).

[0103] (i) The solution contains an electrolyte containing heteropolytungstic acid or heteropolytungstate, wherein the heteropolytungstic acid and the heteropolytungstate contain two or more tungsten atoms in one molecule of the anion.

[0104] (ii) The concentration of the tungsten compound in the solution is 0.5% by mass or more.

[0105] (Technology 10)

[0106] In the method of manufacturing a laminate as described in Technique 8 or 9, the solution is an aqueous solution with a pH below 4.

[0107] (Technology 11)

[0108] In the method for manufacturing a laminate as described in any one of techniques 8 to 10, the solution satisfies the condition (i).

[0109] (Technology 12)

[0110] In the method for manufacturing a laminate as described in any one of techniques 8 to 10, the solution satisfies the condition described in (ii).

[0111] (Technology 13)

[0112] The method for manufacturing a laminate as described in any one of techniques 8 to 12, wherein the solution satisfies the conditions (i) and (ii).

[0113] (Technology 14)

[0114] The method for manufacturing a laminate as described in Technique 8, wherein the heteropolytungstate or heteropolytungstate has heteroatoms with a valence of 3 or more.

[0115] Example

[0116] The present disclosure will now be described in more detail through examples. However, the following examples are merely illustrative and the present disclosure is not limited to them.

[0117] <Example 1>

[0118] The surface of the tantalum metal was ultrasonically cleaned for 10 minutes while immersed in a container filled with acetone. Then, the acetone adhering to the tantalum metal surface was evaporated, and the surface was rinsed with pure water. Finally, the tantalum metal was allowed to dry in atmospheric air.

[0119] In H4SiW at a concentration of 100 mmol / L 12 O 40 In an aqueous solution, tantalum metal and tantalum metal as a counter electrode are arranged at specified intervals. The pH of the aqueous solution is less than 1. The H4SiW in this aqueous solution... 12 O 40The concentration was 22% by mass. A portion of the tantalum metal not immersed in the aqueous solution was connected to the positive electrode of a power supply, and a portion of the tantalum metal serving as the counter electrode was connected to the negative electrode of the power supply. Current was passed through the power supply at a constant voltage, and a voltage of 95V was applied between the tantalum metal connected to the positive electrode and the tantalum metal serving as the counter electrode for 10 hours. An electrochemical reaction occurred on the surface of the tantalum metal serving as the anode, resulting in an oxide film. The tantalum metal with the oxide film formed was removed from the aqueous solution, washed with pure water, and dried in air. This yielded the sample of Example 1, in which a dielectric film as an oxide film was formed on the surface of tantalum metal.

[0120] <Example 2>

[0121] In addition to using H3PW at a concentration of 100 mmol / L 12 O 40 Aqueous solution instead of H4SiW 12 O 40 Similar to Example 1, except for the aqueous solution, the sample of Example 2 was obtained. H3PW 12 O 40 The pH of the aqueous solution is less than 1. The H3PW in this aqueous solution... 12 O 40 The concentration was 22 by mass.

[0122] <Example 3>

[0123] In addition to H4SiW 12 O 40 Except for changing the concentration of the aqueous solution to 10 mmol / L, the sample of Example 3 was obtained in the same manner as in Example 1. In Example 3, H4SiW 12 O 40 The pH of the aqueous solution is 1.4. The H4SiW in this aqueous solution... 12 O 40 The concentration was 2.8% by mass.

[0124] <Comparative Example 1>

[0125] Besides using H3PO4 aqueous solution instead of H4SiW 12 O 40 In addition to the aqueous solution, the sample of Comparative Example 1 was obtained in the same manner as in Example 1.

[0126] (Film thickness measurement and elemental composition analysis)

[0127] The cross-sections of the samples from Examples 1, 2, and 3 were observed using a scanning electron microscope (SEM) ISM7900F manufactured by JEOL Ltd. In this observation, the cross-sections of the samples from each example were ground using an ion beam cross-section polisher, and the cross-sections were observed from a direction perpendicular to the cross-section to determine the thickness of the dielectric film. Furthermore, energy-dispersive X-ray fluorescence (EDX) analysis, an adjunct to the SEM, was performed. By averaging the tungsten concentration at four locations to smooth out errors caused by the spot position, the tungsten concentration in the dielectric film was calculated. The results are shown in Table 2. The spot diameter in the apparatus used for concentration determination was approximately 100 nm to 200 nm. Since smoothing was performed at multiple locations, it can be understood that this concentration corresponds to the average tungsten concentration in the dielectric film.

[0128] [Table 2]

[0129]

[0130] (Elemental concentration distribution determination)

[0131] GD-OES was performed on samples prepared from the surface portion of the dielectric film of the samples from Examples 1 and 2 using a GD-Profiler2 glow discharge emission spectrometry (GD-OES) apparatus manufactured by Horiba Manufacturing Co., Ltd. In GD-OES, argon gas was sputtered onto the sample under specified conditions to obtain emission spectra. The emission spectra were converted into mass concentrations using software attached to the GD-Profiler2. Since GD-OES is a semi-quantitative analytical method, the reliability of the absolute values ​​of the concentrations of the elements of interest may not be high. Therefore, the GD-OES determination results are used to evaluate the concentration distribution of the elements of interest along the thickness direction of the dielectric film in the samples of each example. The average concentration of tungsten in the dielectric film was based on the aforementioned EDX value.

[0132] Figure 7 This is a graph showing the relationship between the concentrations of oxygen and tungsten in the sample of Example 1 and the depth from the sample surface. This graph was obtained based on GD-OES analysis of the sample of Example 1. Figure 7 The upper part of the graph shows the relationship between oxygen concentration and depth from the sample surface. In this graph, the vertical axis represents oxygen concentration [mass %], and the horizontal axis represents depth from the sample surface. Figure 7 The lower section of the graph shows the relationship between tungsten concentration and depth from the sample surface. In this graph, the vertical axis represents tungsten concentration [mass %], and the horizontal axis represents depth from the sample surface.

[0133] exist Figure 7In the lower part of the figure, the portion corresponding to tungsten concentrations below 0.1% by mass is considered to be background noise caused by the similarity between the emission spectra of Ta and W. As shown in Table 2, the dielectric film thickness of the sample in Example 1 is 183 nm. Figure 7 In the figure, both oxygen and tungsten concentrations decrease sharply at depths above 180 nm. According to... Figure 7 The lower part of the figure suggests that the tungsten concentration is higher than the background noise at the depth corresponding to the dielectric film, and tungsten is present throughout the thickness direction of the dielectric film. In other words, it can be said that the dielectric film of the sample in Example 1 contains oxides containing tantalum and tungsten. Similarly, it can be considered that tungsten is present throughout the thickness direction of the dielectric films in the samples of Examples 2 and 3.

[0134] (Dielectric constant measurement)

[0135] The sample of Example 1 was immersed in sulfuric acid solution, and the dielectric properties of the dielectric films of the samples of Example 1, Example 2, Example 3 and Comparative Example 1 were evaluated by AC impedance spectroscopy with platinum as the counter electrode. The results are shown in Table 3. A Modulab XM manufactured by Solartron Analytics was used for the AC impedance measurement. In this evaluation, an AC voltage was applied to the capacitor of Example 1 with an amplitude of 10 mV to 100 mV and a frequency range of 1 MHz to 0.1 Hz, and the electrostatic capacitance C was calculated based on the complex impedance at 120 Hz. Using the calculated electrostatic capacitance C, the film thickness t calculated by SEM observation, and the dielectric constant of vacuum, i.e., the electrical constant ε0, the relative permittivity ε was calculated according to the following formula (1). In formula (1), S is the surface area of ​​the tantalum metal on which the dielectric film is formed.

[0136] ε=(C·t) / (ε0S) Formula (1)

[0137] [Table 3]

[0138]

[0139] As shown in Table 3, a comparison between Examples 1-3 and Comparative Example 1 reveals that the relative permittivity of the dielectric film increases by containing tungsten. Furthermore, Table 2 shows that the tungsten concentration in the dielectric film of Example 1 is higher than that of the sample of Example 2. Additionally, the tungsten concentration in the dielectric film of Example 2 is higher than that of the sample of Example 3. Based on the comparison between Examples 1 and 2, and between Examples 2 and 3, it is clear that a higher tungsten concentration in the dielectric film is advantageous for increasing the relative permittivity of the dielectric film.

[0140] The laminate disclosed herein is well suited for use in electronic components such as capacitors.

Claims

1. A laminate having a metal tantalum and a dielectric layer in contact with the metal tantalum, the dielectric layer containing an oxide containing tantalum and tungsten. The dielectric layer has a relative permittivity greater than 27 and less than 41.7 at 120 Hz.

2. The laminate as claimed in claim 1, wherein the average tungsten concentration in the dielectric layer is 0.1% by mass or more and 20% by mass or less.

3. The laminate as claimed in claim 1, wherein the dielectric layer contains a portion having a tungsten concentration of 0.15% by mass or more and a thickness of 10 nm or more.

4. A capacitor having: The first electrode contains tantalum metal. The second electrode, and A dielectric layer disposed between the first electrode and the second electrode, the dielectric layer containing an oxide containing tantalum and tungsten. The dielectric layer has a relative permittivity greater than 27 and less than 41.7 at 120 Hz.

5. An electrical circuit comprising the capacitor of claim 4.

6. A circuit board comprising the capacitor of claim 4.

7. An apparatus comprising the capacitor of claim 4.

8. A method for manufacturing a laminate, comprising the following steps: Contacting tantalum metal with an acidic solution containing tungsten compounds, and The tantalum metal is anodized while in contact with the solution. The solution satisfies at least one condition selected from (i) and (ii). (i) The solution contains an electrolyte containing heteropolytungstic acid or heteropolytungstate, wherein the heteropolytungstic acid and the heteropolytungstate contain two or more tungsten atoms in one molecule of the anion. (ii) The concentration of the tungsten compound in the solution is 0.5% by mass or more.

9. The method for manufacturing a laminate as described in claim 8, wherein the solution is an aqueous solution with a pH of 4 or lower.

10. The method for manufacturing a laminate as claimed in claim 8, wherein the solution satisfies the condition of (i).

11. The method for manufacturing a laminate as claimed in claim 8, wherein the solution satisfies the condition of (ii).

12. The method for manufacturing a laminate as claimed in claim 8, wherein the solution satisfies the conditions of (i) and (ii).

13. The method for manufacturing a laminate as described in claim 8, wherein the heteropolytungstate and the heteropolytungstate have heteroatoms with a valence of 3 or more.

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