Multilayer body, capacitor, electrical circuit, circuit board, apparatus, and method for producing multilayer body

Abstract

This multilayer body comprises tantalum metal and a dielectric body that has a first region and a second region. The second region is located between the tantalum metal and the first region. The first region contains tantalum oxide and tin, and is located in the surface of the dielectric body. The second region contains tantalum oxide and is covered by the first region. The content of tin in the first region is higher than the content of tin in the second region.

Description

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

[0001] The present disclosure relates to a laminate, a capacitor, an electric circuit, a circuit board, a device, and a method for manufacturing the laminate.

[0002] A material in which tantalum oxide is doped with tin is known.

[0003] For example, Non-Patent Document 1 describes that Sn-doped Ta2O5 promotes the isomerization of glucose to produce enriched 5-hydroxymethylfurfural (5-HMF). Sn-doped Ta2O5 was prepared from a white precipitate obtained by suspending and stirring tantalum ethoxide in ethanol, dissolving the resulting sol in a mixed solvent of ethanol and water, and adding SnCl4 as a dopant. This white precipitate was then ultrasonically cleaned and then treated in a hydrothermal reactor at 180°C for 6 hours to obtain a slurry. The solid fraction separated from the slurry by centrifugation and decantation was washed with ultrapure water until the supernatant pH reached 7.0, and then further washed with ethanol. The washed solid fraction was dried in an oven at 80°C for 12 hours and then calcined at 500°C for 2 hours. In this manner, Sn-doped Ta2O5 was synthesized.

[0004] Sangeeta Mahala, Senthil M. Arumugam, Sandeep Kumar, Dalwinder Singh, Shelja Sharma, Bhawana Devi, Sudesh K. Yadav, and Sasikumar Elumalai, Sn Doping on Ta2O5 Facilitates Glucose Isomerization for Enriched 5-Hydroxymethylfurfural Production and its True Response Prediction using a Neural Network Model, ChemCatChem 2021, 13, 4787-4798

[0005] The present disclosure provides a stack comprising a novel dielectric comprising tantalum oxide and tin.

[0006] A laminate according to the present disclosure comprises: metallic tantalum; and a dielectric including a first portion and a second portion, wherein the second portion is located between the metallic tantalum and the first portion, the first portion includes tantalum oxide and tin and is located on a surface of the dielectric, the second portion includes tantalum oxide and is covered by the first portion, and the tin content of the first portion is higher than the tin content of the second portion.

[0007] According to the present disclosure, a laminate can be provided that includes a novel dielectric material containing tantalum oxide and tin.

[0008] FIG. 1 is a cross-sectional view showing an example of a laminate according to the present disclosure. FIG. 2 is a cross-sectional view showing an example of a capacitor according to the present disclosure. FIG. 3 is a cross-sectional view showing another example of a capacitor according to the present disclosure. FIG. 4A is a diagram schematically showing an example of an electric circuit according to the present disclosure. FIG. 4B is a diagram schematically showing an example of a circuit board according to the present disclosure. FIG. 4C is a diagram schematically showing an example of an apparatus according to the present disclosure. FIG. 5 is a graph showing the results of X-ray photoelectron spectroscopy (XPS) measurement of the dielectric film according to Example 1. FIG. 6 is a graph showing the results of time-of-flight secondary ion mass spectroscopy (TOF-SIMS) of the dielectric film according to Example 1, showing Sn + , TaO + , and O + 7 is a graph showing the relationship between the signal intensity and the depth in the dielectric film. 8 is a graph showing the relationship between the capacitance and the frequency of the capacitors including the dielectric films according to Example 1 and Comparative Example 1.

[0009] (Findings forming the basis of the present disclosure) Tantalum oxide has a high relative dielectric constant and is therefore widely used as a dielectric material for high-performance capacitors. In recent years, with the increasing performance of electronic devices, capacitors with higher capacitance are required, and it is important to further increase the capacitance even in capacitors using a dielectric material containing tantalum oxide.

[0010] In view of these circumstances, the present inventors have conducted extensive research into additives to dielectric materials that can increase the capacitance of capacitors using dielectric materials containing tantalum oxide. As a result, the present inventors have noticed that tin is thought to be likely to cause polarization in oxide films. Further research led the present inventors to newly discover that when the tin content in a specific portion of a dielectric containing tantalum oxide is higher than the tin content in other portions, the capacitance of a capacitor using that dielectric is likely to be high. As a result, the present inventors have devised the dielectric and capacitor disclosed herein.

[0011] It is believed that tin is uniformly present throughout the Sn-doped TaO material according to the manufacturing method described in Non-Patent Document 1. Therefore, it is believed that it is difficult to adjust the tin content in a specific portion of the metal oxide material to be higher than the tin content in other portions according to the manufacturing method described in Non-Patent Document 1.

[0012] (Embodiments) Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The present disclosure is not limited to the following embodiments.

[0013] FIG. 1 is a cross-sectional view showing an example of a laminate according to the present disclosure. As shown in FIG. 1 , the laminate 100 includes a dielectric 1 and a substrate 2. The dielectric 1 includes a first portion 11 and a second portion 12. The first portion 11 contains tantalum oxide and tin, and has a surface 1a of the dielectric 1. The second portion 12 contains tantalum oxide and is covered by the first portion 11. The tin content in the first portion 11 is higher than the tin content in the second portion 12. With this configuration, even if tin is not uniformly present throughout the dielectric 1, the dielectric 1 is likely to have advantageous properties, for example, from the perspective of increasing the capacitance of the capacitor. In addition, the tin contained in the first portion 11 makes it difficult for oxygen vacancies to occur in the dielectric 1, and the dielectric 1 is likely to have advantageous properties from the perspective of increasing the durability of the capacitor.

[0014] As shown in FIG. 1 , the second portion 12 is in contact with the substrate 2. The substrate 2 is not limited to a specific substrate. The substrate 2 is, for example, a conductor. The conductor is, for example, metal tantalum. In this case, the substrate 2 can function as an electrode of a capacitor. The second portion 12 is in contact with the substrate 2 made of, for example, metal tantalum. In this case, the dielectric 1 can be formed by anodization. The substrate 2 may be a dielectric.

[0015] The shape of the dielectric 1 is not limited to a particular shape. As shown in FIG. 1 , the dielectric 1 is, for example, a film. In this case, the thickness of the dielectric 1 is not limited to a particular value. The thickness is, for example, 10 nm or more and 1000 nm or less. The thickness of the dielectric 1 may be determined based on the results of TOF-SIMS, or may be determined based on observation of a cross section of the dielectric 1 using an electron microscope such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM). The shape of the dielectric 1 may be particulate or fibrous.

[0016] 1, in the dielectric 1, for example, the first portion 11 forms a first layer 11a, and the second portion 12 forms a second layer 12a. In this case, the thickness t 11a and the thickness t of the second layer 12a 12a The relationship between the thickness t of the first layer and the thickness t of the second layer is not limited to a specific relationship. 11a is, for example, the thickness t of the first layer 11a and the thickness of the second layer t 12a Tonowa S 12 Even in such a configuration, the dielectric 1 can have advantageous characteristics from the viewpoint of increasing the capacitance of the capacitor. 11a and thickness t 12a can be determined based on the measurement results of TOF-SIMS, for example, according to the method described in the Examples.

[0017] Thickness t of the first layer 11a 11a Is, Japanese S 12 The thickness t of the first layer may be 30% or less, 25% or less, 20% or less, or 15% or less. 11a For example, the sum S 12 This is more than 5% of the total.

[0018] The distribution of the tin content in the first region 11 is not limited to a specific distribution. For example, in the first region 11, the tin content C P1 is the tin content C at the second position P2 P2 The first position P1 is a position in the first portion 11 that is a first distance away from the surface 1a in a direction perpendicular to the surface 1a. The second position P2 is a position in the first portion 11 that is a second distance away from the surface 1a in a direction perpendicular to the surface 1a. The second distance is shorter than the first distance. Even in such a configuration, the dielectric 1 can have advantageous characteristics from the viewpoint of increasing the capacitance of the capacitor.

[0019] In the dielectric 1, the tin content may decrease continuously or discontinuously with increasing distance from the surface 1a in the direction perpendicular to the surface 1a.

[0020] The tin content in the first portion 11 is not limited to a specific value. For example, in TOF-SIMS of the dielectric 1, the signal intensity of ions derived from tin is lower than the signal intensity of ions derived from tantalum oxide.

[0021] The oxidation number of tin contained in the first portion 11 is not limited to a specific value. The first portion 11 contains, for example, divalent tin. In this case, polarization caused by tin in the dielectric 1 is likely to be large, and the dielectric 1 is likely to have more advantageous characteristics from the viewpoint of increasing the capacitance of the capacitor. In addition, oxygen vacancies are less likely to occur in the dielectric 1.

[0022] The method for producing the dielectric 1 is not limited to a specific method. The method for producing the dielectric 1 includes, for example, anodizing metal tantalum in a state where the metal tantalum is brought into contact with a solution containing tin. According to such a production method, the dielectric 1 in which the tin content in the first portion 11 is higher than the tin content in the second portion 12 can be efficiently produced.

[0023] In the anodization of the above-described manufacturing method, for example, metallic tantalum is used as the anode and platinum is used as the cathode. A predetermined voltage is applied between the anode and the cathode. As a result, anions such as oxide ions attracted toward the metallic tantalum anode combine with the ionized tantalum to obtain a dielectric containing tantalum oxide. At this time, tin contained in the solution is incorporated into the dielectric. As a result, tin can be contained in the portion forming the surface of the dielectric 1. On the other hand, although oxide ions can migrate to the portion of the dielectric 1 in contact with the metallic tantalum, tin is rarely incorporated into this portion. Therefore, although this portion contains tantalum oxide, the tin content in this portion is very low.

[0024] The dielectric 1 may be manufactured by a method other than anodization, for example, sputtering, in which case the material of the substrate 2 may be other than metallic tantalum.

[0025] The dielectric 1 can be used to provide, for example, a capacitor. Fig. 2 is a cross-sectional view showing an example of a capacitor according to the present disclosure. As shown in Fig. 2, the capacitor 3a includes a first electrode 21, a second electrode 22, and a dielectric film 10. The dielectric film 10 includes the dielectric 1 and is disposed between the first electrode 21 and the second electrode 22. With this configuration, the capacitor 3a is likely to have a high capacitance.

[0026] 2 , the first electrode 21 is in contact with the second portion 12 of the dielectric film 10. In addition, the first portion 11 is disposed between the second portion 12 and the second electrode 22 in the thickness direction of the dielectric film 10.

[0027] The first electrode 21 includes, for example, metallic tantalum. In this case, the capacitor 3a can be manufactured by anodization using a solution containing tin. The first electrode 21 may be made of a conductor other than metallic tantalum.

[0028] The material of the second electrode 22 is not limited to a specific material as long as it is conductive. The second electrode 22 may include a valve metal such as aluminum, tantalum, niobium, or bismuth, a noble metal such as gold or platinum, or nickel. The second electrode 22 may also include a carbon material such as graphite.

[0029] In the capacitor 3a, the surface 1a of the dielectric 1 may be in contact with an electrolyte. In this case, the second electrode 22 may contain an electrolyte. This electrolyte is not limited to a specific electrolyte. The electrolyte may include, for example, at least one selected from the group consisting of an electrolytic solution, a solid electrolyte, and a conductive polymer. Examples of the conductive polymer include polypyrrole, polythiophene, polyaniline, and derivatives thereof. The electrolyte may also be a manganese compound such as manganese oxide.

[0030] Fig. 3 is a cross-sectional view showing another example of a capacitor according to the present disclosure. Capacitor 3b shown in Fig. 3 has the same configuration as capacitor 3a, except for portions that will be specifically described. Components of capacitor 3b that are the same as or correspond to those of capacitor 3a are designated by the same reference numerals, and detailed descriptions thereof will be omitted. The description of capacitor 3a also applies to capacitor 3b, unless technically inconsistent.

[0031] 3, in capacitor 3b, dielectric 1 and first electrode 21 form porous body 15. Second electrode 22 fills pores 15p of porous body 15. With this configuration, the area of ​​first electrode 21 is increased, and capacitor 3b is likely to have a higher capacitance.

[0032] The porous body 15 can be obtained, for example, by anodizing porous tantalum metal in a state where the porous tantalum metal is brought into contact with a solution containing tin. The porous tantalum metal can be obtained, for example, by etching a tantalum metal foil or sintering a tantalum metal powder.

[0033] In the capacitor 3b, the second electrode 22 includes, for example, an electrolyte. The electrolyte includes at least one selected from the group consisting of an electrolytic solution, a solid electrolyte, and a conductive polymer. Examples of the conductive polymer include polypyrrole, polythiophene, polyaniline, and derivatives thereof. The electrolyte may be a manganese compound such as manganese oxide.

[0034] 4A is a diagram schematically illustrating an example of an electric circuit according to the present disclosure. The electric circuit 4 includes a capacitor 3a. The electric circuit 4 may be an active circuit or a passive circuit. The electric circuit 4 may be a discharge circuit, a smoothing circuit, a decoupling circuit, or a coupling circuit. Because the electric circuit 4 includes the capacitor 3a, the electric circuit 4 is likely to exhibit the desired performance. For example, noise is likely to be reduced in the electric circuit 4. The electric circuit 4 may also include a capacitor 3b.

[0035] Fig. 4B is a diagram schematically illustrating an example of a circuit board according to the present disclosure. As shown in Fig. 4B, the circuit board 5 includes a capacitor 3a. For example, an electric circuit 4 including the capacitor 3a is formed on the circuit board 5. Since the circuit board 5 includes the capacitor 3a, the circuit board 5 is likely to exhibit the desired performance. The circuit board 5 may be an embedded board or a motherboard. The circuit board 5 may also include a capacitor 3b.

[0036] FIG. 4C is a schematic diagram illustrating an example of a device according to the present disclosure. As shown in FIG. 4C , the device 7 includes a capacitor 3a. The device 7 includes, for example, a circuit board 5 including the capacitor 3a. Because the device 7 includes the capacitor 3a, the device 7 is more likely to exhibit desired performance. The device 7 may be an electronic device, a communication device, a signal processing device, or a power supply. The device 7 may be a server, an AC adapter, an accelerator, or a flat panel display such as a liquid crystal display (LCD). The device 7 may be a USB charger, a solid-state drive (SSD), an information terminal such as a PC, a smartphone, or a tablet PC, or an Ethernet switch. The device 7 may also include a capacitor 3b.

[0037] (Additional Note) From the above description, the following techniques are disclosed.

[0038] (Technology 1) A laminate comprising: metallic tantalum; and a dielectric including a first portion and a second portion, wherein the second portion is located between the metallic tantalum and the first portion, the first portion includes tantalum oxide and tin and is located on a surface of the dielectric, the second portion includes tantalum oxide and is covered by the first portion, and the tin content in the first portion is higher than the tin content in the second portion.

[0039] (Technology 2) The laminate according to Technology 1, wherein the first portion has a first layer shape, the second portion has a second layer shape, and the thickness of the first portion is 24% or less of the sum of the thickness of the first portion and the thickness of the second portion.

[0040] (Technology 3) The laminate according to Technology 1 or 2, wherein in the first region, a tin content at a first position that is a first distance away from the surface in a direction perpendicular to the surface is lower than a tin content at a second position that is a second distance away from the surface in the same direction that is shorter than the first distance.

[0041] (Technology 4) The laminate according to any one of Technologies 1 to 3, wherein the tin contained in the first portion includes divalent tin.

[0042] (Technology 5) A capacitor comprising: a first electrode; a second electrode; and a dielectric film disposed between the first electrode and the second electrode, the dielectric film including a first portion and a second portion, wherein the first electrode includes metallic tantalum; the second portion is located between the first electrode and the first portion; the first portion includes tantalum oxide and tin and is located on a surface of the dielectric; the second portion includes tantalum oxide and is covered by the first portion; and the tin content in the first portion is higher than the tin content in the second portion.

[0043] (Technology 6) An electric circuit comprising the capacitor according to Technology 5.

[0044] (Technology 7) A circuit board comprising the capacitor according to Technology 5.

[0045] (Technology 8) A device including the capacitor according to Technology 5.

[0046] (Technology 9) A method for producing a laminate, comprising: bringing metallic tantalum into contact with a solution containing tin; and anodizing the metallic tantalum while the metallic tantalum is in contact with the solution.

[0047] The present disclosure will be described in more detail below with reference to examples. Note that the following examples are illustrative and the present disclosure is not limited to the following examples.

[0048] Example 1: A tantalum plate with a thickness of 0.1 mm was prepared as the anode. This tantalum plate had a rectangular shape with a short side of 10 mm and a long side of 50 mm in plan view. A tantalum foil with a surface area several times larger than that of the tantalum plate was prepared as the cathode. The tantalum plate and tantalum foil were ultrasonically cleaned in acetone for 10 minutes and then rinsed with water. The tantalum plate and tantalum foil were placed at a predetermined distance in an aqueous solution containing K2SnO3. The concentration of K2SnO3 in the aqueous solution was 0.1 mol / L. Next, a constant voltage was applied between the tantalum plate (anode) and the tantalum foil (cathode) using a power supply, causing an electrochemical reaction on the surface of the tantalum plate, resulting in anodization. This resulted in the formation of a dielectric film on the tantalum plate. During anodization, a DC stabilized power supply was used as the power supply, and the current value during the formation of the dielectric film was measured using a digital multimeter. The voltage during anodization was increased at a rate of 20 V / min, and after reaching 80 V, it was maintained at 80 V for 90 minutes. After the voltage was applied, the dielectric film formed on the tantalum plate was washed with running water for 15 minutes. In this way, the dielectric film according to Example 1 was obtained.

[0049] Comparative Example 1 A dielectric film according to Comparative Example 1 was obtained in the same manner as in Example 1, except that an aqueous solution containing HPO was used instead of the aqueous solution containing KSnO. The concentration of HPO in this aqueous solution was 0.0017 mol / L.

[0050] (Elemental Composition Analysis) XPS measurement was performed to analyze the composition of the dielectric film according to Example 1 using an XPS measurement device, PHI 5000 VersaProbe, manufactured by ULVAC-PHI, Inc. In this measurement, MgKα radiation (1253.6 eV) was used as the characteristic X-ray. FIG. 5 is a graph showing the results of the XPS measurement of the dielectric film according to Example 1. In FIG. 5, the vertical axis represents the photoelectron intensity, and the horizontal axis represents the binding energy. The measurement data in FIG. 5 was fitted using the least squares method to identify the peak position (486.7 eV) of the graph shown in FIG. 5. Since this peak position is close to the peak position of SnO, the oxidation number of tin contained in the dielectric film according to Example 1 is considered to be divalent, which is two lower than the highest oxidation number, tetravalent.

[0051] (Composition Analysis in the Depth Direction) A TOF-SIMS apparatus TOF.SIMS5 manufactured by ION-TOF was used to perform composition analysis of the dielectric film according to Example 1 by TOF-SIMS. In the TOF-SIMS, Bi accelerated at a voltage of 30 kV was used as an ion beam. 3+ The sputtering ion species used was Cs + The depth was determined based on the sputtering rate. FIG. 6 shows the TOF-SIMS results of the tin ions (Sn + ), tantalum oxide ions (TaO + ), and oxygen ions (O + 6 is a graph showing the relationship between the signal intensity of each ion in TOF-SIMS and the depth in the dielectric film. In FIG. 6, the vertical axis represents the signal intensity of each ion in TOF-SIMS, and the horizontal axis represents the depth in the dielectric film.

[0052] According to FIG. + and O + The signal intensity of Sn is almost constant in the depth range from 0 nm to about 160 nm, and it is understood that tantalum oxide is included in this range. + The signal intensity of decreases with increasing depth in the depth range from 0 nm to about 20 nm, and becomes very low in the depth range of about 20 nm or more. Therefore, it is understood that the dielectric film containing tantalum oxide is formed to a thickness of about 160 nm, and that tin is present in the first region about 20 nm thick from the surface of the dielectric film, but that almost no tin is present in other regions corresponding to the second region.

[0053] In FIG. + and O + The signal intensity of Sn is almost constant in the depth range from 0 nm to about 160 nm. +The signal intensity of decreases with increasing depth in the depth range of 0 nm to about 20 nm, which corresponds to the first region, and becomes very low in the depth range of about 20 nm or more, which corresponds to the second region. This indicates that the tin content in the first region is higher than the tin content in the second region.

[0054] (Dielectric Properties) AC impedance measurements were performed using the tantalum plates on which the dielectric films of Example 1 and Comparative Example 1 were formed. The measurements were performed in a phosphoric acid aqueous solution with a concentration of 1 mol / L using a potentiostat and a galvanostat. The voltage amplitude was adjusted to 100 mV, and an AC voltage was applied between a pair of electrodes including the tantalum plate in the range of 0.1 Hz to 1 MHz. Based on the AC impedance measurement results, the capacitance of the capacitor equipped with the dielectric film was calculated. The AC impedance measurements were performed in a room temperature environment.

[0055] 7 is a graph showing the relationship between the capacitance and frequency of capacitors including the dielectric films of Example 1 and Comparative Example 1. In FIG. 7, the vertical axis represents capacitance, and the horizontal axis represents the frequency of the AC voltage. As shown in FIG. 7, the capacitance of the capacitor including the dielectric of Example 1 was greater than the capacitance of the capacitor including the dielectric of Comparative Example 1. This suggests that the inclusion of tin in the surface portion of the dielectric containing tantalum oxide is advantageous in increasing the capacitance of the capacitor. As described above, the oxidation number of tin included in the dielectric is thought to be divalent, which creates structural asymmetry and makes polarization more likely to occur, and this is thought to contribute to the realization of high capacitance.

[0056] The laminate according to the present disclosure can be used in electronic components such as capacitors.

[0057] REFERENCE SIGNS LIST 1 Dielectric 1a Surface 2 Substrate 3a, 3b Capacitor 4 Electric circuit 5 Circuit board 7 Device 10 Dielectric film 11 First portion 11a First layer 12 Second portion 12a Second layer 15 Porous body 15p Hole 21 First electrode 22 Second electrode 100 Laminate

Claims

1. Tantalum metal, a dielectric including a first portion and a second portion; the second portion is located between the tantalum metal and the first portion, the first portion includes tantalum oxide and tin and is located on a surface of the dielectric; the second portion includes tantalum oxide and is covered by the first portion; The tin content in the first portion is higher than the tin content in the second portion. Laminate.

2. the first portion has a first layer shape; the second portion has a second layer shape; The thickness of the first portion is 24% or less of the sum of the thickness of the first portion and the thickness of the second portion. The laminate according to claim 1 .

3. In the first region, a tin content at a first position that is a first distance away from the surface in a direction perpendicular to the surface is lower than a tin content at a second position that is a second distance away from the surface in the same direction that is shorter than the first distance. The laminate according to claim 1 .

4. The tin contained in the first moiety includes divalent tin. The laminate according to claim 1 .

5. A first electrode; A second electrode; a dielectric film disposed between the first electrode and the second electrode, the dielectric film including a first portion and a second portion; the first electrode comprises tantalum metal; the second portion is located between the first electrode and the first portion, the first portion includes tantalum oxide and tin and is located on a surface of the dielectric; the second portion includes tantalum oxide and is covered by the first portion; The tin content in the first portion is higher than the tin content in the second portion. Capacitor.

6. A capacitor comprising: Electrical circuit.

7. A capacitor comprising: Circuit board.

8. A capacitor comprising: device.