JP2015099871A - Capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a porous capacitor that does not float in plating solution and allows properly plating internal electrodes.SOLUTION: A capacitor according to the present invention includes a dielectric layer, a first external electrode layer, a second external electrode layer, a lining film, first internal electrodes, and second internal electrodes. The dielectric layer includes a first surface, a second surface on the opposite side of the first surface, and a plurality of through holes communicating with the first surface and the second surface, and is composed of a first dielectric material. The first external electrode layer is disposed on the first surface. The second external electrode layer is disposed on the second surface. The lining film is composed of a second dielectric material having higher specific gravity than the first dielectric material, and is disposed on inner peripheral surfaces of the plurality of through holes. The first internal electrodes are formed in a part of the plurality of through holes and are connected to the first external electrode layer. The second internal electrodes are formed in the other part of the through holes and are connected to the second external 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 structure. In any of the patent documents, an internal electrode is formed in the porous by electrolytic plating or the like, 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

However, Al ₂ O ₃ that is an oxide of aluminum can easily form a porous structure, but has a relatively low specific gravity. Therefore, when immersed in a plating solution for forming the internal electrode, it floats on the plating solution and it is difficult to appropriately plate the internal electrode.

  In view of the circumstances as described above, an object of the present invention is to provide a porous capacitor capable of appropriately plating an internal electrode without floating on a plating solution.

In order to achieve the above object, a capacitor according to an embodiment of the present invention includes a dielectric layer, a first external electrode layer, a second external electrode layer, a lining film, a first internal electrode, 2 internal electrodes.
The dielectric layer includes a first surface, a second surface opposite to the first surface, a plurality of through holes communicating with the first surface and the second surface, 1 dielectric material.
The first external electrode layer is disposed on the first surface.
The second external electrode layer is disposed on the second surface.
The lining film is made of a second dielectric material having a specific gravity higher than that of the first dielectric material, and is disposed on inner peripheral surfaces of the plurality of through holes.
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.

It is a perspective view of the capacitor concerning one 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. FIG. 3 is an enlarged view of FIG. 2 showing a lining film, a first internal electrode, and a second internal electrode included in the capacitor. It is the expanded sectional view of the same capacitor seen from the direction perpendicular to the layer surface direction of the dielectric layer with which the same capacitor is provided. It is a schematic diagram which shows the manufacturing process of the same capacitor. It is a schematic diagram which shows the manufacturing process of the same capacitor. It is a schematic diagram which shows the manufacturing process of the same capacitor. It is a schematic diagram which shows the manufacturing process of the same capacitor. It is a schematic diagram which shows the manufacturing process of the same capacitor. It is a schematic diagram for demonstrating the electrolytic plating process of the said manufacturing process. It is a table | surface which shows the relationship between the dielectric constant and dielectric breakdown electric field strength of each dielectric material, and a horizontal axis shows a dielectric constant and a vertical axis | shaft shows a dielectric breakdown electric field strength. (Source: P. Jain, E. J. Rymaszewski, "Embedded thin film capacitors-theoretical limits", IEEE Transactions on Advanced Packaging, August 2002, Vol. 25, pp.454)

A capacitor according to an embodiment of the present invention includes a dielectric layer, a first external electrode layer, a second external electrode layer, a lining film, a first internal electrode, and a second internal electrode. It has.
The dielectric layer includes a first surface, a second surface opposite to the first surface, a plurality of through holes communicating with the first surface and the second surface, 1 dielectric material.
The first external electrode layer is disposed on the first surface.
The second external electrode layer is disposed on the second surface.
The lining film is made of a second dielectric material having a specific gravity higher than that of the first dielectric material, and is disposed on inner peripheral surfaces of the plurality of through holes.
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 lining film made of the second dielectric material having a specific gravity higher than that of the first dielectric material is disposed in the through hole. As a result, when the first internal electrode and the second internal electrode are formed by electrolytic plating, they do not float in the plating solution, and plating defects can be prevented. Therefore, the porous capacitor can be manufactured more stably.

  The second dielectric material may have a dielectric constant higher than that of the first dielectric material.

  According to this configuration, two kinds of layers, that is, a dielectric layer made of the first dielectric material and a lining film made of the second dielectric material, sandwiched between the first internal electrode and the second internal electrode. A unit capacitance is generated by the dielectric. These are connected in parallel via the first external electrode and the second external electrode, whereby the element capacity of the capacitor is determined. That is, by using the second dielectric material, the unit capacitance can be increased and the element capacitance of the capacitor can be increased.

  The second dielectric material may have a product value of a dielectric constant and a breakdown electric field strength larger than that of the first dielectric material.

  According to this configuration, the withstand voltage can be maintained even when the thickness of the dielectric layer and the lining film sandwiched between the first internal electrode and the second internal electrode is reduced. Therefore, even when the element size of the capacitor is reduced, it is possible to increase the element capacitance while preventing problems.

  The lining film may be formed by an atomic layer growth method.

  According to this configuration, a thin and uniform lining film can be formed even if the inner peripheral surface of the through hole is uneven.

  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 lining film 104, a first internal electrode 105, and a second internal electrode 106.

  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 105 and the second internal electrode 106 are formed inside a through hole 101a formed 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 and is made of a first dielectric material. The first dielectric material can be made of a material capable of forming a through-hole (porous), which will be described later, and is particularly 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 first dielectric material can be made of an oxide of valve metal (Al, Ta, Nb, Ti, Zr, Hf, Zn, W, Sb). The thickness of the dielectric layer 101 in the vertical direction in FIG. 1 is not particularly limited, but can be, for example, several μm to several hundred μm.

  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). Note that the number, size, and shape of the through-holes 101a shown in FIG. 3 and the like are for convenience, the actual ones are smaller, many, and the shapes are various.

  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 can be a conductive material, for example, a pure metal such as Cu, Ni, Ag, Sn, Pb, Zn, or an alloy thereof (including solder and lead-free solder). The thickness of the first external electrode layer 102 can be several tens of nm to several μm, for example. Further, the first external electrode layer 102 may be disposed so that a plurality of layers of conductive materials are laminated.

  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 so that a plurality of layers of conductive materials are laminated.

  5 is an enlarged view of FIG. 2 showing the lining film 104, the first internal electrode 105, and the second internal electrode 106. FIG. 6 shows the capacitor 100 viewed from a direction perpendicular to the layer surface direction of the dielectric layer 101. FIG. FIG. 6 indicates the thickness of the dielectric layer between the first internal electrode 105 and the second internal electrode 106, and t2 indicates the thickness of the lining film.

The lining film | membrane 104 is arrange | positioned by the internal peripheral surface of the several through-hole 101a, for example, is formed in the cylinder shape which coat | covers the internal peripheral surface of the several through-hole 101a. The thickness t2 of the lining film 104 can be appropriately set in view of the thickness t1 of the dielectric layer 101 and the like, and can be set to several nm to several tens of nm, for example. The lining film 104 is a dielectric material having a specific gravity higher than that of the first dielectric material, for example, TaO _X , ZrO ₂ , TiO _X / TaO _X , STO (SrTiO ₃ ), BST ((Ba _x , Sr _{(1-X )} TiO ₃ ), etc. Such a lining film 104 may be formed by, for example, ALD (atomic layer growth method), hereinafter, a constituent material of the lining film 104 is a second dielectric. The details of the second dielectric material will be described later.

  The first internal electrode 105 functions as one counter electrode of the capacitor 100. As shown in FIGS. 5 and 6, the first internal electrode 105 is formed in the plurality of through holes 101 a in which the lining film 104 is disposed. The first internal electrode 105 may be a pure metal such as Cu, Ni, Ag, Sn, Pb, Zn, or an alloy thereof (including Cu, solder, lead-free solder), for example. In addition, the first internal electrode 105 may be formed by laminating a plurality of conductive materials in the thickness direction (the depth direction of the through hole 101a).

  The first internal electrode 105 is connected to the first external electrode layer 102 as shown in FIG. On the other hand, the first internal electrode 105 is formed away from the second external electrode layer 103 and is insulated from the second external electrode layer 103. Further, the gap between the first internal electrode 105 and the second external electrode layer 103 may be filled with an insulator (not shown). The first internal electrodes 105 and the second internal electrodes 106 shown in FIG. 2 and the like are shown alternately every other, but these are for convenience and may not actually exist alternately. Good.

  The second internal electrode 106 functions as the other counter electrode of the capacitor 100. As shown in FIGS. 5 and 6, the second internal electrode 106 is formed in the through hole 101 a in which the lining film 104 is disposed. The constituent material of the second internal electrode 106 may be the same as or different from the constituent material of the first internal electrode 105. The second internal electrode 106 can also be formed by laminating a plurality of conductive materials in the thickness direction (the depth direction of the through hole 101a).

  The second internal electrode 106 is connected to the second external electrode layer 103 as shown in FIG. On the other hand, the second internal electrode 106 is formed apart from the first external electrode layer 102 and is insulated from the first external electrode layer 102. Further, the gap between the second internal electrode 106 and the first external electrode layer 102 may be filled with an insulator (not shown).

  The capacitor 100 having the above-described configuration includes a dielectric layer 101 made of the first dielectric material and a lining film 104 made of the second dielectric material between the first internal electrode 105 and the second internal electrode 106. Two types of dielectrics are sandwiched to form one capacitor unit. Either the first internal electrode 105 or the second internal electrode 106 that functions as a counter electrode (positive electrode or negative electrode) may be a positive electrode. Further, the plurality of unit units included in the capacitor 100 are connected in parallel via the first external electrode layer 102 and the second external electrode layer 103. The first internal electrode 105 is connected to an external wiring, a terminal, and the like via the first external electrode layer 102 and the second internal electrode 106 via the second external electrode layer 103, respectively.

[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. 7 to 11 are schematic views showing the manufacturing process of the capacitor 100. FIG.

  FIG. 7A 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.

  For example, when a voltage is applied with the substrate 301 as an anode in an oxalic acid (0.1 mol / l) solution adjusted to 15 ° C. to 20 ° C., the substrate 301 is oxidized (anodized) as shown in FIG. ) To form a base oxide 302. At this time, holes H are formed in the base material oxide 302 by the self-organizing action of the base material oxide 302. The holes H grow in the direction of progress of oxidation, that is, in the thickness direction of the substrate 301.

  Note that regular pits (concave portions) may be formed in the base material 301 before the anodic oxidation, and the holes H may be grown using the pits as base points. The arrangement of the holes H can be controlled by the arrangement of the pits. The pit can be formed, for example, by pressing a mold (mold) against the base material 301.

  After a predetermined time has elapsed from the start of anodization, the voltage applied to the substrate 301 is increased. Since the pitch of the holes H formed by the self-organization is determined by the magnitude of the applied voltage, the self-organization proceeds so that the pitch of the holes H increases. Thereby, as shown in FIG.7 (c), while forming a hole about some holes H, a hole diameter expands. 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 (enlarged) is referred to as a hole H2.

  The anodizing conditions can be set as appropriate. For example, the applied voltage of the first stage anodizing shown in FIG. 7B can be set to several volts to several hundred volts, and the processing time can be set to several minutes to several days. . With the applied voltage of the second stage of anodic oxidation shown in FIG. 7C, the voltage value can be several times that of the first stage, and the processing time can be set to several minutes to several tens of minutes.

  For example, by setting the applied voltage at the first stage to 40V, holes H with a hole pitch of 100 nm are formed, and by setting the applied voltage at the second stage to 80V, the pitch of the holes H2 is expanded to 150 nm. By setting the voltage value of the second stage within the above-described range, the number of holes H1 and holes H2 can be made substantially equal. Further, by setting the processing time of the second stage voltage application within the above-mentioned range, the base oxide 302 formed on the bottom by the second stage voltage application while the pitch conversion of the holes H2 is sufficiently completed. Can be reduced in thickness. Since the base material oxide 302 formed by the voltage application in the second stage is removed in a later process, it is preferable that the base material oxide 302 be as thin as possible.

  Further, as shown in FIG. 8A, the non-oxidized base material 301 is removed. The substrate 301 can be removed by wet etching, for example. Hereinafter, the surface of the base oxide 302 on which the holes H1 and H2 are formed is referred to as a front surface 302a, and the opposite surface is referred to as a back surface 302b.

Subsequently, as shown in FIG. 8B, the inner diameters of the holes H1 and H2 are further enlarged, and a lining film 303 is formed on the inner peripheral surfaces of the enlarged holes H1 and H2. First, expansion of the inner diameters of the hole H1 and the hole H2 can be performed by a wet etching method using an acid or an alkali. For example, when the substrate oxide 302 is formed of Al ₂ O ₃ , the inner diameter is increased by about 10 nm by immersing the substrate oxide 302 in a phosphoric acid solution at 30 ° C. and 5 wt% for 10 minutes. Can do.

The lining film 303 can be formed by ALD, CVD, sol-gel method or the like, but ALD is suitable in this embodiment. ALD is a film forming method in which molecules as film forming materials are adsorbed and reacted for each monolayer in a vacuum atmosphere. ALD makes it possible to form a film having a uniform thickness on the inner peripheral surfaces of the holes H1 and H2 having fine irregularities. When the lining film 303 made of TaO _X is formed, for example, the lining film 303 having a thickness of 15 nm can be obtained by repeatedly performing the film formation process of atomic layer deposition using tantalum ethoxide as a raw material.

  Note that if the desired hole diameter can be secured even after the lining film 303 is formed, the step of expanding the inner diameters of the holes H1 and H2 may not be performed.

  Subsequently, as shown in FIG. 8C, the base material oxide 302 is removed from the back surface 302b side with a predetermined thickness. This can be performed by reactive ion etching (RIE). At this time, the base oxide 302 is removed so that the hole H2 communicates with the back surface 302b and the hole H1 does not communicate with the back surface 302b.

  Subsequently, as shown in FIG. 9A, a first conductor layer 304 made of a conductive material is formed on the surface 302a. The first conductor layer 304 can be formed by any method such as a plating method such as a barrel plating method, a sputtering method, or a vacuum evaporation method.

Subsequently, electrolytic plating is performed on the base oxide 302 using the first conductor layer 304 as a seed layer. As conditions for electrolytic plating, for example, the current density can be set to about 0.1 to 20 A / dm ² , and the temperature can be set to room temperature to about 80 ° C. As a result, as shown in FIG. 9B, a plating conductor M1 having a predetermined thickness (length) in the hole H2 is formed. 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. 9C, the base material oxide 302 is removed again from the back surface 302b with a predetermined thickness. This can be done by reactive ion etching. At this time, the base oxide 302 is removed with a thickness that allows the hole H1 to communicate with the back surface 302b.

  Subsequently, electrolytic plating is performed again on the base oxide 302 using the first conductor layer 304 as a seed layer. The electrolytic plating conditions at this time may be the same as or different from the conditions for forming the plated conductor M1. As a result, as shown in FIG. 10A, a plating conductor M2 having a predetermined thickness (length) is formed in the hole H1 and the hole H2. The thickness of the plating conductor M2 is set to a thickness that can fill most of the hole H2. Since the plated conductor M1 is not formed in the hole H1, the termination position is different between the plated conductor M2 filled in the hole H1 and the plated conductor M2 filled in the hole H2. The plated conductor M2 may be the same type of metal material as the plated conductor M1, or may be a different type of metal material.

  In the following description, the plated conductor M2 filled in the hole H1 is referred to as a first internal conductor 305, and the plated conductor M1 and the plated conductor M2 filled in the hole H2 are referred to as a second internal conductor 306 (see FIG. 10B). ).

  Subsequently, as shown in FIG. 10B, the base material oxide 302 is removed again from the back surface 302b with a predetermined thickness. This can be done by mechanical polishing or the like. At this time, the base material oxide 302 is removed with such a thickness that the second inner conductor 306 is exposed on the back surface 302b and the first inner conductor 305 is not exposed on the back surface 302b.

  Subsequently, as shown in FIG. 10C, a second conductor layer 307 made of a conductive material is formed on the back surface 302b. The second conductor layer 307 can be formed by any method such as plating, sputtering, or vacuum deposition.

  Subsequently, as shown in FIG. 11A, the first conductor layer 304 is removed. The first conductor layer 304 can be removed by wet etching, dry etching, ion milling, CMP (Chemical Mechanical Polishing), or the like.

  Subsequently, as shown in FIG. 11B, electrolytic etching is performed on the base material oxide 302 using the second conductor layer 307 as a seed layer. Since the second inner conductor 306 is electrically connected to the second conductor layer 307, it is etched by electrolytic etching. As a result, a gap is formed by removing the second inner conductor 306 in the hole H2. On the other hand, since the first inner conductor 305 is not electrically connected to the second conductor layer 307, it is not etched by electrolytic etching.

  Subsequently, as shown in FIG. 11C, a third conductor layer 308 made of a conductive material is formed on the surface 302a. The third conductor layer 308 can be formed by any method such as plating, sputtering, or vacuum deposition.

  As described above, the capacitor 100 can be manufactured. The base oxide 302 corresponds to the dielectric layer 101, the third conductor layer 308 corresponds to the first external electrode layer 102, and the second conductor layer 307 corresponds to the second external electrode layer 103. The lining film 303 corresponds to the lining film 104, the first internal conductor 305 corresponds to the first internal electrode 105, and the second internal conductor 306 corresponds to the second internal electrode 106. An insulating material (not shown) may be filled between the first inner conductor 305 and the third conductor layer 308 and between the second inner conductor 306 and the second conductor layer 307.

[Lining film material (second dielectric material)]
Based on the above configuration and manufacturing method, the material of the lining film 104 will be described in detail. In the following description, the same names and symbols as those used in FIGS. 7 to 11 are used for each component at the time of manufacture.

(specific gravity)
As described above, the lining film 104 is made of the second dielectric material having a specific gravity higher than that of the first dielectric material. By using such a second dielectric material as the lining film 104, the plated conductor M1 and the plated conductor M2 (corresponding to the first internal electrode 105 and the second internal electrode 106) described in the above manufacturing process are formed. In the step of performing the electrolytic plating (see FIGS. 9B and 10A), the following operational effects are obtained.

  FIG. 12 is a schematic diagram for explaining the function and effect of the present embodiment in the electrolytic plating process according to FIG. 9B. FIG. 12A shows the structure 309 to be plated subjected to the above process. An example is shown, and FIG. 12B shows an example in which the above-described process is performed on the structure 310 to be plated. The structure to be plated 309 includes the first conductor layer 304 and the base oxide 302 having the holes H1 and H2, but the lining film 303 is not formed. On the other hand, the structure 310 to be plated corresponds to the present embodiment, and includes a first conductor layer 304, a base oxide 302 having holes H1 and H2, and a lining film 303.

  As shown in FIG. 12, the electrolytic plating process is performed by a barrel plating method. For example, the barrel container C in which the anode electrode E1 and the negative electrode wire E2 are disposed is immersed in the plating solution S. On the negative electrode side of the barrel container C, the structure to be plated (the structure to be plated 309 or the structure to be plated 310) is accommodated together with the conductive medium M. As shown in the arrow in the figure, the barrel container C rotates to contact the negative electrode line E2 while mixing the conductive medium M and the structure to be plated. It progresses when a current flows through one conductor layer 304. That is, plating proceeds using the first conductor layer 304 as a seed layer. The plating solution S is made of, for example, a copper sulfate solution, and the specific gravity can be about 1.3, for example. In FIG. 12, the same reference numerals as those used in FIGS. 7 to 11 for explaining the manufacturing process are used.

As shown in FIG. 12A, the structure to be plated 309 does not have a liner dielectric film, and the substrate oxide 302 occupies most of the structure. The base oxide 302 is made of Al ₂ O ₃ or the like having a relatively low specific gravity in addition to having a large number of holes H1 and holes H2. For these reasons, the structure to be plated 309 easily floats in the plating solution S when the barrel container C rotates, and does not supply current to the seed layer (first conductor layer 304), so that the plated conductor M1 is sufficiently formed. I can't. That is, when the liner dielectric film is not formed, a capacitor having insufficient conduction between the internal electrode and the external electrode layer is produced due to poor plating, and the yield is lowered.

  On the other hand, as shown in FIG. 12B, the structure to be plated 310 includes a lining film 303 made of a second dielectric material. The second dielectric material has a higher specific gravity than the first dielectric material constituting the base oxide 302. As a result, the structure 310 to be plated has a higher specific gravity than the structure 309 to be plated, and the plating conductor M1 can be formed without floating in the plating solution S.

For example, the density of a capacitor manufactured from the structure to be plated 309 is about 2 to ³ g / cm ³ . That is, if the density of the capacitor 100 manufactured from the structure to be plated 310 is 3 g / cm ³ or more, the plating solution S does not float and plating defects can be prevented. Here, the specific gravity refers to the ratio between the density of a certain dielectric material and the density of water at 4 ° C. (about 1.0 g / cm ³ ) as a reference substance, and is handled as the same value as the density. Shall.

  Table 1 below shows the density value of each dielectric material. The second dielectric material will be described more specifically with reference to Table 1.

When Al ₂ O ₃ is used as the first dielectric material, TaO _X , ZrO ₂ , TiO _X / TaO _X , STO, BST, and TiO ₂ shown in Table 1 are all higher than the specific gravity of Al ₂ O _3. . Therefore, by forming the lining film 104 using a material such as TaO _X , ZrO ₂ , TiO _X / TaO _X , STO, BST, and TiO ₂ as the second dielectric material, the specific gravity of the capacitor 100 is set to 3 or more and plating failure Can be prevented.

  In addition to the above-mentioned dielectric material, a so-called perovskite material such as STO or BST can be applied as the second dielectric material. As will be described later, such a material has a very high dielectric constant, and can increase the capacitance as a capacitor. In addition, when using such a perovskite material, it should just use it paying attention to bias dependence, temperature dependence, etc.

(Dielectric constant)
The second dielectric material may be a material having a dielectric constant higher than that of the first dielectric material. Thereby, the element capacity of the capacitor 100 can be increased.

  As described above, the unit capacitance is generated by the two types of dielectrics of the dielectric layer 101 made of the first dielectric material and the lining film 104 made of the second dielectric material. Furthermore, the unit capacity of the entire capacitor 100 is determined by connecting a plurality of unit units included in the capacitor 100 in parallel (see FIG. 6). Therefore, it is possible to increase the element capacity of the capacitor 100 by increasing the dielectric constant of the second dielectric material.

Table 2 below is a table showing the dielectric constant (ε) of main dielectric materials and the Fbd and CV products described later. As shown in the table, when Al ₂ O ₃ is used as the first dielectric material, TaO _X , ZrO ₂ , TiO _X / TaO _X , STO, BST, TiO having a dielectric constant higher than that of Al ₂ O _{3. 2} or the like can be used as the second dielectric material.

  On the other hand, it is possible to increase the element capacitance while maintaining the size of the capacitor 100 by reducing the distance between the adjacent first internal electrode 105 and second internal electrode 106. That is, the element capacitance can be increased by reducing the sum of the thickness t1 of the dielectric layer and the thickness t2 of the lining film shown in FIG. However, in this case, dielectric breakdown is likely to occur, and a malfunction as a capacitor may occur. Therefore, in the present embodiment, the second dielectric material can be determined in consideration of the dielectric breakdown electric field strength in addition to the dielectric constant.

(Product of dielectric constant and dielectric breakdown field strength)
Even if the second dielectric material is a material having a larger product (hereinafter referred to as CV product) value of dielectric constant and dielectric breakdown electric field strength (hereinafter referred to as Fbd) than that of the first dielectric material. Good. As a result, the withstand voltage can be secured while increasing the element capacity of the capacitor 100, and the capacitor 100 can be downsized.

FIG. 13 is a table showing the relationship between the dielectric constant and dielectric breakdown field strength of each dielectric material, where the horizontal axis represents the dielectric constant and the vertical axis represents the dielectric breakdown field strength. Moreover, the black circle in the figure shows the material shown in Table 2, and the white circle shows other materials. As shown in the figure, the dielectric constant and Fbd generally have a trade-off relationship. For example, when Al ₂ O ₃ that can be used as the first dielectric material is used as a reference, although SiO ₂ has a smaller dielectric constant, Fbd is larger. On the other hand, TaO ₂ , ZrO _2, etc. have a higher dielectric constant and a smaller Fbd.

That is, if the dielectric constant is increased to increase the capacitance of the capacitor 100 while maintaining the element size, the possibility of dielectric breakdown increases. Therefore, by using a material having a CV product value higher than that of Al ₂ O ₃ as the second insulating material, it is possible to maintain the element capacity of the capacitor 100 and to ensure the withstand voltage. Furthermore, by using a material having a CV product of 50 or more as the second insulating material, it is possible to secure a sufficient withstand voltage while increasing the element capacity of the capacitor 100.

Table 2 shows the values of the Fbd and CV products in addition to the dielectric constant. As shown in the table, examples of the material having a CV product value higher than that of Al ₂ O ₃ include SiN, TaO _x , ZrO ₂ , TiO _x / TaO _x , STO, and BST. Among these materials, materials having a CV product of 50 or more include TaO _X , ZrO ₂ , TiO _X / TaO _X , STO, and BST. That is, the second dielectric _material, TaO _X, it is possible to use _{ZrO 2, TiO X / TaO X} , suitably STO, the BST.

  Various capacitors were produced, and the specific gravity, plating failure rate, capacitor capacity, and withstand voltage were confirmed by experiments. Table 3 is a table showing the structures and experimental results of the capacitors according to Examples and Comparative Examples.

  Table 3 shows the first dielectric material of the dielectric layer, the second dielectric material of the lining film, the first internal electrode 105 and the second internal electrode 106 of each of the capacitors according to Examples 1 and 2 and the comparative example. The dielectric layer thickness t1 (see FIG. 6) and the two-layer lining film thickness t2 × 2 (see FIG. 6) between the first internal electrode 105 and the second internal electrode 106 are shown. The sizes of the capacitors according to Examples 1 and 2 and the comparative example are all 1005 × thickness 0.1 mm, and the pitch between the adjacent first internal electrode 105 and second internal electrode 106 is 100 nm.

In Table 3, the capacitors according to Example 1 and Example 2 have the structure described in the above embodiment. In other words, the through hole has a structure including a lining film made of the second dielectric material having a specific gravity higher than that of the first dielectric material. More specifically, as described in FIG. 8A, the inner diameter of the through hole of the dielectric layer was etched by 10 nm, and a lining film made of TaO _X was formed by ALD. The thickness t2 of the lining film is 15 nm in Example 1 and 35 nm in Example 2. On the other hand, the capacitor according to the comparative example has a configuration without a lining film.

As shown in Table 3, the capacitors according to Examples 1 and 2 have a higher specific gravity than the capacitor according to the comparative example. Thus, it was confirmed that the specific gravity of the entire capacitor can be increased by using TaO _X having a specific gravity higher than that of Al ₂ O ₃ forming the dielectric layer as a lining film (see Table 1). Furthermore, as described with reference to FIG. 12, the capacitors according to Examples 1 and 2 were able to eliminate plating defects in the electrolytic plating process.

Further, comparing Example 1 and the comparative example, TaO _X having a dielectric constant higher than that of Al ₂ O ₃ forming the dielectric layer is used as the lining film (see Table 2), thereby increasing the capacitance of the capacitor. I was able to. In addition, by using TaO _X having a CV product value larger than that of Al ₂ O ₃ forming the dielectric layer (see Table 2), it is possible to maintain the same withstand voltage as in the comparative example despite the high dielectric constant. It was. Therefore, even when the element size is reduced, it has been confirmed that a desired capacitance can be realized while preventing dielectric breakdown.

  In Example 2, the dielectric breakdown voltage could be improved by forming the lining film thicker than Example 1. It was also found that the same capacity as in the comparative example can be maintained despite the large distance between the first internal electrode and the second internal electrode. Therefore, it is considered that the capacity or withstand voltage, or both can be improved by adjusting the thickness of the lining film.

DESCRIPTION OF SYMBOLS 100 ... Capacitor 101 ... Dielectric layer 101a ... Through-hole 101b ... 1st surface 101c ... 2nd surface 102 ... 1st external electrode layer 103 ... 2nd external electrode layer 104 ... Lining film 105 ... 1st internal electrode 106 ... Second internal electrode

Claims (4)

A first surface; a second surface opposite to the first surface; and a plurality of through holes communicating with the first surface and the second surface; A dielectric layer comprising:
A first external electrode layer disposed on the first surface;
A second external electrode layer disposed on the second surface;
A lining film made of a second dielectric material having a specific gravity higher than that of the first dielectric material and disposed on the inner peripheral surfaces of the plurality of through holes;
A first internal electrode formed in a part of the plurality of through holes and connected to the first external electrode layer;
And a second internal electrode formed in another part of the plurality of through holes and connected to the second external electrode layer. The capacitor according to claim 1,
The second dielectric material has a higher dielectric constant than the first dielectric material. The capacitor according to claim 1 or 2,
The second dielectric material is a capacitor in which a product of a dielectric constant and a breakdown electric field strength is larger than that of the first dielectric material. The capacitor according to any one of claims 1 to 3,
The lining film is a capacitor formed by an atomic layer growth method.

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