JP2015122467A - Capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a porous capacitor having a structure in which occurrence of warpage can be prevented.SOLUTION: A capacitor of the present invention includes a dielectric layer, a through hole, a first outer electrode layer, a second outer electrode layer, a first inner electrode, and a second inner electrode. The dielectric layer is formed by an anodic oxidation of a metal. The through holes are a plurality of through holes which communicate a first surface of the dielectric layer and a second surface opposite to the first surface, and has a minimum hole diameter portion having a minimum hole diameter, the hole diameter gradually increasing toward the first and second surfaces from the minimum hole diameter portion. The first outer electrode layer is disposed on the first surface. The second outer electrode layer is disposed on the second surface. The first inner electrode is formed in part of the plurality of through holes and is connected to the first outer electrode layer. The second inner electrode is formed in the other part of the plurality of through holes and is connected to the second outer electrode layer.

Description

  The present invention relates to a porous capacitor.

  In recent years, a porous capacitor has been developed as a new type of capacitor. Porous capacitors use a property that a metal oxide formed on a metal surface such as aluminum forms a porous (through-hole) structure, forms an internal electrode in the porous, and uses the metal oxide as a dielectric. It is a capacitor.

  External conductors are laminated on the front surface and the back surface of the dielectric, respectively, and the internal electrode formed in the porous is connected to either the external conductor on the front surface or the external conductor on the back surface. The external conductor on the side not connected to the internal electrode is insulated by a gap or an insulating material. Thereby, an internal electrode functions as a counter electrode (a positive electrode or a negative electrode) which opposes via a dielectric.

  For example, Patent Literature 1 and Patent Literature 2 disclose a porous capacitor having such a configuration. In any of the patent documents, an internal electrode is formed in a porous body, one end of the internal electrode is connected to one conductor, and the other end is insulated from the other conductor.

Japanese Patent No. 4493686 JP 2009-76850 A

  Here, the porous capacitor has a problem of warpage that occurs in its manufacturing process. When a metal oxide having a through-hole is formed, the hole diameter of the through-hole is not uniform, and the internal electrode is filled in the inside thereof, thereby causing a difference in filling volume of the internal electrode between the front and back of the capacitor. There is a case. In this case, stress becomes nonuniform on the front and back sides of the porous capacitor, and warpage occurs.

  In view of the circumstances as described above, an object of the present invention is to provide a porous capacitor having a structure capable of preventing the occurrence of warping.

In order to achieve the above object, a capacitor according to an embodiment of the present invention includes a dielectric layer, a through hole, a first external electrode layer, a second external electrode layer, a first internal electrode, 2 internal electrodes.
The dielectric layer is formed by metal anodic oxidation.
The through hole is a through hole that communicates the first surface of the dielectric layer and the second surface opposite to the first surface, and the through hole has a minimum hole diameter that is the smallest. A plurality of through-holes having a hole diameter gradually increasing from the minimum hole diameter portion toward the first surface and the second surface.
The first external electrode layer is disposed on the first surface.
The second external electrode layer is disposed on the second surface.
The first internal electrode is formed in a part of the plurality of through holes and connected to the first external electrode layer.
The second internal electrode is formed in another part of the plurality of through holes and connected to the second external electrode layer.

1 is a perspective view of a capacitor according to an embodiment of the present invention. It is sectional drawing of the same capacitor. It is a perspective view of the dielectric material layer with which the same capacitor is provided. It is sectional drawing of the dielectric material layer with which the same capacitor | condenser is provided. It is an enlarged view of the through-hole with which the same capacitor is provided. It is an enlarged view of the through-hole with which the same capacitor is provided. It is an enlarged view of the through-hole with which the same capacitor is provided. It is an enlarged view of the through-hole with which the same capacitor is provided. It is an enlarged view of the through-hole with which the same capacitor is provided. It is sectional drawing of the capacitor | condenser which is a modification of the capacitor | condenser. It is sectional drawing of the capacitor | condenser which concerns on the comparative example of this invention. It is a schematic diagram which shows the manufacturing process of the same capacitor. It is a schematic diagram showing a manufacturing process of the capacitor It is a schematic diagram showing a manufacturing process of the capacitor It is a schematic diagram showing a manufacturing process of the capacitor It is a schematic diagram showing a manufacturing process of the capacitor It is a schematic diagram showing a manufacturing process of the capacitor

A capacitor according to an embodiment of the present invention includes a dielectric layer, a through hole, a first external electrode layer, a second external electrode layer, a first internal electrode, and a second internal electrode. It has.
The dielectric layer is formed by metal anodic oxidation.
The through hole is a through hole that communicates the first surface of the dielectric layer and the second surface opposite to the first surface, and the through hole has a minimum hole diameter that is the smallest. A plurality of through-holes having a hole diameter gradually increasing from the minimum hole diameter portion toward the first surface and the second surface.
The first external electrode layer is disposed on the first surface.
The second external electrode layer is disposed on the second surface.
The first internal electrode is formed in a part of the plurality of through holes and connected to the first external electrode layer.
The second internal electrode is formed in another part of the plurality of through holes and connected to the second external electrode layer.

  According to this configuration, the first internal electrode and the second internal electrode that face each other through the dielectric layer function as the counter electrode of the capacitor. The first internal electrode is connected to the first external electrode layer, and the second internal electrode is connected to the second external electrode layer, and is connected to the outside (connection terminal or the like) through these. Here, in the first internal electrode and the second internal electrode, the through holes filled with the electrodes are shaped so that the hole diameter gradually increases from the minimum hole diameter portion toward the first surface and the second surface. Thereby, the symmetry of the front and back of the internal electrode is improved, and the occurrence of warpage can be prevented.

  The minimum hole diameter portion may be shifted from the center of the first surface and the second surface to the first surface side or the second surface side.

  As described above, the position of the minimum hole diameter portion can be shifted to the first surface and the second surface side. For this reason, when there is a possibility of warping due to a factor other than the filling volume difference of the internal electrodes, it is possible to prevent the warping from occurring by adjusting the position of the minimum hole. Factors other than the filling volume difference include, for example, thermal stress due to sputtering when the first external electrode layer and the second external electrode layer are formed.

  The dielectric layer may be made of a material that forms a porous layer by self-organization when anodized.

  According to this configuration, a dielectric layer having a through hole (porous) can be formed by anodizing the material.

  The dielectric layer may be made of aluminum oxide formed by anodic oxidation of aluminum.

  Aluminum oxide produced when anodizing aluminum produces through-holes due to a self-organizing action during the oxidation process. That is, a dielectric layer having a through hole can be formed by anodizing aluminum.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[Configuration of capacitor]
FIG. 1 is a perspective view of a capacitor 100 according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view of the capacitor 100. As shown in these drawings, the capacitor 100 includes a dielectric layer 101, a first external electrode layer 102, a second external electrode layer 103, a first internal electrode 104, and a second internal electrode 105.

  The first external electrode layer 102, the dielectric layer 101, and the second external electrode layer 103 are laminated in this order, that is, the dielectric layer 101 is sandwiched between the first external electrode layer 102 and the second external electrode layer 103. . The first internal electrode 104 and the second internal electrode 105 are formed inside the through hole 101a in the dielectric layer 101 as shown in FIG. The capacitor 100 may be provided with a configuration other than that shown here, for example, wirings connected to the first external electrode layer 102 and the second external electrode layer 103, respectively.

The dielectric layer 101 is a layer that functions as a dielectric of the capacitor 100. The dielectric layer 101 can be made of a dielectric material capable of forming a through hole (porous), which will be described later, and is preferably a material that generates a porous layer by self-organization when anodized. is there. As such a material, aluminum oxide (Al ₂ O ₃ ) can be given. In addition, the dielectric layer 101 can be made of an oxide of valve metal (Al, Ta, Nb, Ti, Zr, Hf, Zn, W, Sb). Although the thickness of the dielectric material layer 101 is not specifically limited, For example, it can be set as several micrometers-several hundred micrometers.

FIG. 3 is a perspective view of the dielectric layer 101, and FIG. 4 is a cross-sectional view of the dielectric layer 101. As shown in these drawings, the dielectric layer 101 has a plurality of through holes 101a. When the surface parallel to the layer surface direction of the dielectric layer 101 is a first surface 101b and the opposite surface is a second surface 101c, the through hole 101a is perpendicular to the first surface 101b and the second surface 101c. The first surface 101b and the second surface 101c are formed so as to communicate with each other (in the thickness direction of the dielectric layer 101). The number and size of the through holes 101a shown in FIG. 3 and the like are for convenience, and the actual ones are smaller and more in number.

  FIG. 5 is an enlarged view showing the through hole 101a. As shown in the figure, each through hole 101a has a minimum hole diameter portion 101d having a minimum hole diameter, and the hole diameter gradually increases from the minimum hole diameter portion 101d toward the first surface 101b and the second surface 101c. Have. That is, each through-hole 101a has a tapered portion that is diverging toward the first surface 101b and a tapered portion that is diverging toward the second surface 101c. Such a shape of the through-hole 101a can be formed by a manufacturing method to be described later, but according to the manufacturing method, the minimum hole diameter portion 101d is located at an equivalent position in the thickness direction of the dielectric layer 101. A plurality of through-holes 101a are formed.

  The minimum hole diameter portion 101d in each through hole 101a may be located at the center (hereinafter referred to as the through hole center) in the extending direction of the through hole 101a (the thickness direction of the dielectric layer 101), or may be shifted from the through hole center. Good. FIG. 6 is a schematic diagram showing the position of the minimum hole diameter portion 101d. As shown in the figure, assuming that the center of the through hole is L, the position of the minimum hole diameter portion 101d may coincide with the center L of the through hole.

  7 and 8 are enlarged views showing through-holes 101a having different positions of the minimum hole diameter portion 101d. As shown in FIG. 7, the position of the minimum hole diameter portion 101d in the through hole 101a may be shifted from the through hole center L toward the first surface 101b. Further, as shown in FIG. 8, the position of the minimum hole diameter portion 101d in the through hole 101a may be shifted from the through hole center L toward the second surface 101c. The position of the minimum hole diameter portion 101d can be adjusted when the through hole 101a is formed.

  As shown in FIG. 2, the first external electrode layer 102 is disposed on the first surface 101 b of the dielectric layer 101. The first external electrode layer 102 is made of a conductive material, for example, a pure metal such as Cu, Ni, Cr, Ag, Pd, Fe, Sn, Pb, Pt, Ir, Rh, Ru, Al, Ti, or an alloy thereof. Can be. The thickness of the first external electrode layer 102 can be several tens of nm to several μm, for example. In addition, the first external electrode layer 102 may be arranged such that a plurality of conductive materials are laminated in the thickness direction (extending direction of the through hole 101a).

  The second external electrode layer 103 is disposed on the second surface 101c of the dielectric layer 101 as shown in FIG. The second external electrode layer 103 can be made of the same conductive material as the first external electrode layer 102, and the thickness thereof can be, for example, several nm to several μm. The constituent material of the second external electrode layer 103 may be the same as or different from the constituent material of the first external electrode layer 102. The second external electrode layer 103 can also be arranged such that a plurality of conductive materials are laminated in the thickness direction (extending direction of the through hole 101a).

  The first internal electrode 104 functions as one counter electrode of the capacitor 100. FIG. 9 is a sectional view showing the first internal electrode 104 and the second internal electrode 105, and is an enlarged view of FIG. As shown in the figure, the first internal electrode 104 is formed in the through hole 101 a and is connected to the first external electrode layer 102. Since the through-hole 101a has a shape in which the hole diameter gradually increases as described above, the shape of the first internal electrode 104 formed therein has a shape according to the through-hole 101a. The length of the first internal electrode (the extending direction of the first internal electrode 104) can be such that the tip 104a of the first internal electrode 104 is located on the second surface 101c side from the minimum hole diameter portion 101d. . The first internal electrode 104 is made of a conductive material such as pure metals such as In, Sn, Pb, Cd, Bi, Al, Cu, Ni, Au, Ag, Pt, Pd, Co, Cr, Fe, Zn, and the like. It can consist of alloys.

  The first internal electrode 104 is formed away from the second external electrode layer 103 and is insulated from the second external electrode layer 103. The gap between the first internal electrode 104 and the second external electrode layer 103 may be filled with an insulator (not shown). The first internal electrodes 104 and the second internal electrodes 105 shown in FIG. 2 and the like are shown alternately, but these are for convenience and may not actually exist alternately. Good.

  The second internal electrode 105 functions as one counter electrode of the capacitor 100. As shown in FIG. 9, the second internal electrode 105 is formed in the through hole 101 a and is connected to the second external electrode layer 103. Since the through hole 101a has a shape in which the hole diameter gradually increases as described above, the shape of the second internal electrode 105 formed therein has a shape according to the through hole 101a. The length of the second internal electrode (the extending direction of the second internal electrode 105) can be such that the tip 105a of the second internal electrode is located closer to the first surface 101b than the minimum hole diameter portion 101d. The second internal electrode 105 is made of a conductive material such as pure metals such as In, Sn, Pb, Cd, Bi, Al, Cu, Ni, Au, Ag, Pt, Pd, Co, Cr, Fe, Zn, and the like. It can consist of alloys.

  The capacitor 100 has the above configuration. The first internal electrode 104 and the second internal electrode 105 face each other through the dielectric layer 101 to form a capacitor. That is, the first internal electrode 104 and the second internal electrode 105 function as counter electrodes of the capacitor. Note that either the first internal electrode 104 or the second internal electrode 105 may be a positive electrode. The first internal electrode 104 is connected to the outside via a first external electrode layer 102, and the second internal electrode 105 is connected to the outside via a second external electrode layer 103, respectively.

  As described above, the minimum hole diameter portion 101d may be shifted from the through hole center L to the first surface 101b side or the second surface 101c side. FIG. 10 is a cross-sectional view showing the capacitor 100 in this case. 10A shows a case where the minimum hole diameter portion 101d is shifted from the through hole center L to the first surface 101b side. FIG. 10B shows a case where the minimum hole diameter portion 101d is from the through hole center L to the second surface 101c side. The case where it has shifted to is shown. In any case, the tip 104a of the first internal electrode is positioned on the second surface 101c side from the minimum hole diameter portion 101d, and the tip 105a of the second internal electrode is on the first surface 101b side from the minimum hole diameter portion 101d. Can be located.

[Effect of capacitor]
The effect of the capacitor 100 will be described using a comparative example. FIG. 11 is a cross-sectional view of a capacitor 200 according to a comparative example. As shown in the figure, the capacitor 200 includes a dielectric layer 201, a first external electrode layer 202, a second external electrode layer 203, a first internal electrode 204, and a second internal electrode 205.

  As shown in the figure, the dielectric layer 201 is provided with a through hole 201a communicating with the first surface 201b and the second surface 201c. The through hole 201a is divergent with respect to the first surface 201b. It has a tapered shape. This is because when the through hole is processed by anodization, a taper is formed in the through hole depending on the conditions of the circulation of the oxidizing solution.

  Thereby, a filling volume difference between the first internal electrode 204 and the second internal electrode 205 is generated. As shown in FIG. 11, a region having a certain height from the first surface 201b is L2, and a region having a height equivalent to the region L2 from the second surface 201c is L3. Here, as shown in the figure, the filling volume of the first internal electrode 204 and the second internal electrode 205 included in the region L2 is included in the first internal electrode 204 and the second internal electrode 205 included in the region L3. It becomes larger than the filling volume. This is because the through hole 201a has a tapered shape and the hole diameter on the first surface 201b side is large. As a result, the stress balance in the region L2 and the region L3 is lost, and the capacitor 200 may be warped.

  However, in the capacitor 100 according to the present invention, as shown in FIG. 2, the through-hole 101a has a tapered shape in which the through hole 101a is divergent toward the first surface 101b, and the divergent taper is in the direction toward the second surface 101c. And a portion having a shape. Thereby, the filling volume difference of the 1st internal electrode 104 and the 2nd internal electrode 105 like a comparative example does not generate | occur | produce, but generation | occurrence | production of curvature can be prevented.

  Also, as shown in FIGS. 10A and 10B, the position of the minimum hole diameter portion 101d can be shifted to the first surface 101b or the second surface 101c side. For this reason, when there is a possibility of warping due to factors other than the filling volume difference of the internal electrodes, it is possible to prevent the warping from occurring by adjusting the position of the minimum hole diameter portion 101d. Factors other than the filling volume difference include, for example, thermal stress due to sputtering when the first external electrode layer 102 and the second external electrode layer 103 are formed.

[Capacitor manufacturing method]
A method for manufacturing the capacitor 100 according to the present embodiment will be described. In addition, the manufacturing method shown below is an example and the capacitor | condenser 100 can also be manufactured with the manufacturing method different from the manufacturing method shown below. 12 to 17 are schematic views showing the manufacturing process of the capacitor 100. FIG.

  FIG. 12A shows a base material 301 that is the basis of the dielectric layer 101. When the dielectric layer 101 is made of a metal oxide (for example, aluminum oxide), the base material 301 is a metal (for example, aluminum) before the oxidation.

  As shown in FIG. 12B, regular pits P (concave portions) are formed on the front and back surfaces of the base material 301, and holes H described later can be formed using the pits P as a base point. The arrangement of the holes H can be controlled by the arrangement of the pits P.

  The pits P can be formed, for example, by pressing a mold (mold) against the base material 301. As the mold, a sword-shaped metal mold such as stainless steel having a desired pitch can be used. The sword mountain metal mold can be produced, for example, as follows.

  First, porous alumina having a desired pitch is prepared, and a Ti—Cu film is deposited on the surface thereof by sputtering to have a thickness of about 1 μm, thereby providing electrical conduction. After plating metal (Ni) in the pores of alumina, the alumina is immersed in an alkaline aqueous solution (0.1 M NaOH aqueous solution). As a result, the Ti—Cu film is dissolved, and a sword mountain metal mold is produced.

Next, using a driving stage with a position control resolution equal to or less than the pitch of the sword-shaped metal mold (for example, JBX-6300FS electron beam lithography system manufactured by JEOL) Match. Thereafter, the base material 301 is inserted between two sword-like metal molds and pressed with both molds. The press pressure is preferably 800 kgf / cm ² .

  When the base material 301 on which the pits P are formed is anodized, the base material 301 is oxidized and a base material oxide 311 is formed as shown in FIG. At this time, holes H are formed in the base material oxide 311 due to the self-organizing action of the base material oxide 311. The holes H grow in the direction of progress of oxidation, that is, in the thickness direction of the substrate 301. Here, by performing anodization from both the front and back surfaces of the substrate 301, as shown in FIG. 12C, a minimum hole diameter portion 301d is provided, and the hole diameter is directed from the minimum hole diameter portion 301d toward the front and back surfaces of the substrate oxide 311. A hole H having a gradually increasing shape is formed.

  Anodization can be performed, for example, in a treatment solution adjusted to 15 ° C. to 20 ° C. (for example, an oxalic acid (0.1 mol / l) solution) by applying a voltage with the substrate 301 as an anode. . The applied voltage can be several volts to several hundred volts, and the processing time can be several minutes to several days. For example, when the applied voltage is 40 V, a hole H having a hole diameter of 100 nm is formed. The growth rate of the base oxide 301 can be set to 4 ± 1.5 μm / h, for example. In order to perform anodic oxidation from both the front and back surfaces of the base material 301, the front and back surfaces of the base material 301 in FIG.

  Subsequently, as shown in FIG. 13A, a base material 302 is vapor-deposited on the base material oxide 311 in which the holes H are formed. The substrate 302 can be, for example, an aluminum substrate.

Specifically, the base material 302 is processed for 180 minutes under the conditions of an output 350 w, an internal pressure of 1 × 10 ⁻⁴ Pa, and a pressure of 0.35 Pa after introducing Ar gas, using a high-frequency sputtering apparatus, to form a base material oxide 311. It can be evaporated. The thickness of the base material 302 can be 700 nm, for example.

  Next, the base material 302 is anodized again. At this time, if the voltage applied to the base material 302 is increased as compared with the above-described anodic oxidation, the pitch (hole diameter and inter-hole distance) of some holes H increases as shown in FIG. Self-organization progresses. On the other hand, when the pitch of the holes H is increased, the formation of holes for the other holes H is stopped. Hereinafter, the hole H in which the formation of the hole has stopped is referred to as a hole H1, and the hole H in which the formation of the hole has been continued (the hole diameter is enlarged) is referred to as a hole H2.

  The applied voltage at this time can be several times the voltage, and the processing time can be several minutes to several tens of minutes. For example, when the applied voltage is 80 V, the hole diameter of the hole diameter H2 is expanded to 200 nm. By setting the applied voltage in the first stage of anodic oxidation shown in FIG. 12C and the applied voltage in the second stage of anodic oxidation shown in FIG. The numbers can be roughly equivalent. In addition, by setting the processing time of the voltage application at the second stage within the above range, the thickness of the base material 302 formed on the bottom by the voltage application at the second stage while the pitch conversion of the holes H2 is sufficiently completed. The thickness can be reduced. The base material 301 formed by the second-stage voltage application is preferably as thin as possible because it is removed in a later process.

  Subsequently, as shown in FIG. 13C, the non-oxidized base material 302 is removed. The substrate 302 can be removed by wet etching, for example. Hereinafter, the surface of the substrate 301 on which the holes H1 and H2 are formed is referred to as a front surface 301b, and the opposite surface is referred to as a back surface 301c.

  Subsequently, as shown in FIG. 14A, the base material oxide 311 is removed from the back surface 301c side with a predetermined thickness. This can be done by reactive ion etching (RIE). At this time, the base oxide 311 is removed so that the hole H2 communicates with the back surface 301c and the hole H1 does not communicate with the back surface 301c.

Subsequently, as shown in FIG. 14B, a first conductor layer 303 made of a conductive material is disposed on the surface 301b. The first conductor layer 303 can be disposed by any method such as sputtering or vacuum deposition.

  Subsequently, as shown in FIG. 14C, the first plating conductor M1 is embedded in the hole H2. The first first plating conductor M1 can be embedded by performing electrolytic plating on the base material oxide 311 using the first conductor layer 303 as a seed layer. Since the plating solution does not enter the hole H1, the first plating conductor M1 is not formed in the hole H1.

  Subsequently, as shown in FIG. 15A, the base material oxide 311 is removed again from the back surface 301c with a predetermined thickness. This can be removed by reactive ion etching. At this time, the base material oxide 311 is removed with such a thickness that the hole H1 communicates with the back surface 301c.

  Subsequently, as shown in FIG. 15B, the second plating conductor M2 is embedded in the hole H1, and the third plating conductor M3 is embedded in the hole H2.

  The second plating conductor M2 can be embedded by performing electrolytic plating on the base material oxide 311 using the first conductor layer 303 as a seed layer. Further, since the first plating conductor M1 is formed in the hole H2 by the previous process, the tip of the third plating conductor M3 protrudes from the tip of the second plating conductor M2. In the following description, the first plating conductor M1 and the third plating conductor M3 are referred to as a first inner conductor 304, and the second plating conductor M2 is referred to as a second inner conductor 305.

  Subsequently, as shown in FIG. 15C, the base material oxide 311 is removed again from the back surface 301c with a predetermined thickness. This can be done by mechanical polishing or the like. At this time, the base oxide 311 is removed with such a thickness that the tip of the first inner conductor 304 is exposed on the back surface 301c and the tip of the second inner conductor 305 is not exposed on the back surface 301c.

  Subsequently, as shown in FIG. 16A, a second conductor layer 306 made of a conductive material is disposed on the back surface 301c. The second conductor layer 306 can be disposed by a sputtering method, a vacuum evaporation method, or an arbitrary method.

  Subsequently, as shown in FIG. 16B, the first conductor layer 303 is removed. The first conductor layer 303 can be removed by wet etching, dry etching, ion milling, CMP (Chemical Mechanical Polishing), or the like.

  Subsequently, as shown in FIG. 16C, the base oxide 311 is subjected to electrolytic etching using the second conductor layer 306 as a seed layer. Since the first inner conductor 304 is electrically connected to the second conductor layer 306, it is etched by electrolytic etching. As a result, the first inner conductor 304 is removed in the hole H2, and a gap is formed between the surface 301b and the tip of the first inner conductor 304. On the other hand, since the second inner conductor 305 is not conductive to the second conductor layer 306, it is not etched by electrolytic etching.

  Subsequently, as shown in FIG. 17, a third conductor layer 307 made of a conductive material is formed on the surface 301b. The third conductor layer 307 can be formed by sputtering, vacuum deposition, or any method.

  As described above, the capacitor 100 can be manufactured. The base oxide 311 corresponds to the dielectric layer 101, the third conductor layer 307 corresponds to the first external electrode layer 102, and the second conductor layer 306 corresponds to the second external electrode layer 103. The second inner conductor 305 corresponds to the first inner electrode 104, and the first inner conductor 304 corresponds to the second inner electrode 105.

[How to change the position of the minimum hole diameter]
A method for changing the position of the minimum hole diameter portion 101d of the capacitor according to this embodiment will be described.

  As described above, the through-hole 101a can be formed by anodizing the base material 301 from the respective sides of the front surface and the back surface of the base material 301. At this time, the anodic oxidation treatment time from the front surface and the back surface of the substrate 301 can be shifted. Thereby, the position of the minimum hole diameter portion 101d can be shifted from the through hole center L to the front surface side or the back surface side.

  That is, if the anodic oxidation processing time from the front surface side is longer than the anodic oxidation processing time from the back surface side, the minimum hole diameter portion 101d as shown in FIG. A through-hole 101a shifted to the 101c side can be formed. On the other hand, if the treatment time for anodization from the back surface side is longer than the treatment time for anodization from the front surface side, the minimum hole diameter portion 101d as shown in FIG. A through-hole 101a shifted to the surface 101b side can be formed.

  Alternatively, only the surface of the substrate 301 may be immersed in the treatment solution and subjected to anodization, and then both front and back surfaces may be immersed in the treatment solution to perform anodization. Since the surface of the base material 301 is anodized twice while the back surface is anodized once, the minimum hole diameter portion 101d is shifted from the through hole center L to the second surface 101c side. A hole 101a can be formed. Similarly, only the back surface of the substrate 301 is immersed in the treatment solution and subjected to anodization, and then both front and back surfaces are immersed in the treatment solution and subjected to anodization so that the minimum hole diameter portion 101d is first from the through-hole center L. The through-hole 101a shifted to the surface 101b side can be formed

DESCRIPTION OF SYMBOLS 100 ... Capacitor 101 ... Dielectric layer 101a ... Through-hole 101b ... 1st surface 101c ... 2nd surface 101d ... Minimum hole diameter part 102 ... 1st external electrode layer 103 ... 2nd external electrode layer 104 ... 1st internal electrode 105 ... Second internal electrode

Claims (4)

A dielectric layer formed by metal anodization;
A through-hole communicating the first surface of the dielectric layer and the second surface opposite to the first surface, the through-hole having a minimum hole diameter portion having a minimum hole diameter; A plurality of through holes whose hole diameters gradually increase from the minimum hole diameter portion toward the first surface and the second surface;
A first external electrode layer disposed on the first surface;
A second external electrode layer disposed on the second surface;
A first internal electrode formed in a part of the plurality of through holes and connected to the first external electrode layer;
A second internal electrode formed in another part of the plurality of through holes and connected to the second external electrode layer;
A capacitor comprising: The capacitor according to claim 1,
The minimum hole diameter portion is deviated from the center of the first surface and the second surface toward the first surface or the second surface. The capacitor according to claim 2,
The dielectric layer is a capacitor made of a material that forms a porous layer by self-organization when anodized. The capacitor according to claim 3,
The dielectric layer is a capacitor made of aluminum oxide formed by anodization of aluminum.

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