Capacitor

Abstract

To provide a capacitor capable of suppressing changes in capacitance due to frequency change while increasing the capacitance.SOLUTION: A capacitor 1 includes an anode 3, a laminated film 2, and a cathode 4 laminated in this order. The laminated film 2 includes: a first insulator layer 211 in contact with the anode 3; a conductive layer 22; and a second insulator layer 212 in contact with the cathode 4 laminated in this order. The conductive layer 22 and both the anode 3 and the cathode 4 are electrically insulated.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a capacitor, and more particularly to a capacitor having two electrodes and an insulator between the two electrodes.

Background Art

[0002] Non-Patent Document 1 discloses a laminated structure having two electrodes and a laminated film in which a layer made of HfO2 and a layer made of ZnO are alternately laminated between the two electrodes.

Prior Art Documents

Non-Patent Documents

[0003]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present disclosure is to provide a capacitor in which the capacitance is increased and the change in capacitance accompanying a change in frequency is suppressed.

Means for Solving the Problems

[0005] A capacitor according to one aspect of the present disclosure includes an anode, a laminated film, and a cathode, laminated in this order. The laminated film includes a first insulator layer in contact with the anode, a conductor layer, and a second insulator layer in contact with the cathode, laminated in this order. The conductor layer is electrically insulated from both the anode and the cathode. [Effects of the Invention]

[0006] According to this disclosure, it is possible to provide a capacitor in which capacitance can be increased while suppressing changes in capacitance due to frequency changes. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1A is a schematic cross-sectional view showing an example of a capacitor according to one embodiment of the present disclosure. Figure 1B is a schematic cross-sectional view showing an example of a capacitor according to another embodiment of the present disclosure. [Figure 2] Figure 2A is a schematic cross-sectional view showing the steps of a capacitor manufacturing method according to one embodiment of the present disclosure. Figure 2B is a schematic cross-sectional view showing the steps of a capacitor manufacturing method following the manufacturing method in Figure 2A. [Figure 3] Figure 3A is a schematic cross-sectional view showing the steps of a capacitor manufacturing method according to one embodiment of the present disclosure. Figure 3B is a schematic cross-sectional view showing the steps of a capacitor manufacturing method following the manufacturing method in Figure 3A. Figure 3C is a schematic cross-sectional view showing the steps of a capacitor manufacturing method following the manufacturing method in Figure 3B. Figure 3D is a schematic cross-sectional view showing the steps of a capacitor manufacturing method following the manufacturing method in Figure 3C. [Figure 4] Figure 4 is a schematic cross-sectional view showing the steps of a capacitor manufacturing method according to one embodiment of the present disclosure. [Figure 5] Figure 5 is a schematic cross-sectional view showing the steps of a capacitor manufacturing method according to one embodiment of the present disclosure. [Figure 6] Figure 6 is a schematic cross-sectional view showing an evaluation circuit including a capacitor according to one embodiment of the present disclosure. [Figure 7] Figure 7A is a schematic cross-sectional view showing a capacitor according to a modified example of the present disclosure. Figure 7B is a schematic cross-sectional view showing the multilayer film provided by the capacitor according to a modified example of the present disclosure. [Figure 8] Figure 8 is a graph showing the relationship between the capacitance of a capacitor and the measurement frequency according to one embodiment of this disclosure. [Figure 9]Figure 9 is a graph showing the relationship between the capacitance of a capacitor and the measurement frequency according to another embodiment of this disclosure. [Figure 10] Figure 10 is a graph showing the relationship between the capacitance of a capacitor and the measurement frequency according to another embodiment of this disclosure. [Modes for carrying out the invention]

[0008] (1) Overview We will now explain the process that led to capacitor 1 in this disclosure.

[0009] A laminated structure is known that has two electrodes and a laminated film between the two electrodes in which an insulating layer containing an insulating material such as HfO2 and a semiconductor layer containing a semiconductor material such as ZnO are alternately stacked. This laminated structure has an increased capacitance due to the presence of the laminated film in which the insulating layer and semiconductor layer are alternately stacked as described above.

[0010] According to the inventor's research, there is a problem in that, with respect to the laminated structure in which an insulating layer and a semiconductor layer are stacked as described above, it is difficult to increase the capacitance while suppressing the change in capacitance due to frequency changes.

[0011] Therefore, the inventors diligently conducted research to obtain a laminated structure in which capacitance can be increased while suppressing changes in capacitance due to frequency changes, which led to this disclosure.

[0012] Embodiments and modifications will be described with reference to Figures 1A to 10, but the embodiments and modifications described below are only a part of the various embodiments of this disclosure. Furthermore, the embodiments and modifications described below can be modified in various ways depending on the design, etc., as long as the objectives of this disclosure are achieved. Moreover, it is possible to combine the configurations of the modifications as appropriate. Note that the figures referenced below are all schematic diagrams, and the dimensional ratios of the components in the figures do not necessarily reflect the actual dimensional ratios.

[0013] (2) Embodiment (2.1) Summary First, the general structure of the capacitor 1 will be described while referring to FIG. 1A. As shown in FIG. 1A, the capacitor 1 includes an anode 3 and a cathode 4 as electrodes, and a laminated film 2 is provided between the anode 3 and the cathode 4. That is, the capacitor 1 includes the anode 3, the laminated film 2, and the cathode 4, laminated in this order.

[0014] The laminated film 2 includes an insulator layer 21. More specifically, the laminated film 2 includes a first insulator layer 211 and a second insulator layer 212. In other words, in the laminated film 2, the insulator layer 21 in contact with the anode 3 is the first insulator layer 211, and the insulator layer 21 in contact with the cathode 4 is the second insulator layer 212. Thus, by including the laminated film 2 in which the insulator layers 21 are laminated, the capacitance of the capacitor 1 can be increased.

[0015] Also, the laminated film 2 includes the first insulator layer 211 in contact with the anode 3, a conductor layer 22, and the second insulator layer 212 in contact with the cathode 4, laminated in this order. That is, the conductor layer 22 is interposed between the first insulator layer 211 and the second insulator layer 212. Since the conductor layer 22 is interposed between the first insulator layer 211 and the second insulator layer 212 as described above, the conductor layer 22 does not directly contact both the anode 3 and the cathode 4. That is, the conductor layer 22 is electrically insulated from both the anode 3 and the cathode 4. In other words, the conductor layer 22 is in a so-called electrically floating state. In the present disclosure, "being in an electrically floating state" means that the object is not grounded and is electrically insulated from other members.

[0016] In this embodiment, the presence of the conductive layer 22 in the laminated film 2 ensures an enhanced capacitance. Specifically, the presence of the conductive layer 22 in the laminated film 2 makes it less likely for the capacitance of the capacitor 1 to change with frequency when an AC voltage is applied. Therefore, when the capacitor 1 is connected to a DC power supply and installed in a circuit, the AC component (voltage noise) generated from the DC power supply is removed, thereby stabilizing the voltage supplied from the power supply. In other words, the capacitor 1 is suitably used as a bypass capacitor installed in a circuit to remove voltage noise. However, the applications of the capacitor 1 are not limited to that of a bypass capacitor. The capacitor 1 can be applied to a variety of applications.

[0017] (2.2) Details Let's explain the details of capacitor 1.

[0018] (Anode / Cathode) As described above, capacitor 1 comprises an anode 3 and a cathode 4 as electrodes. In other words, when capacitor 1 is installed in a circuit, the anode 3 of capacitor 1 is electrically connected to the positive terminal of the power supply, and the cathode 4 is electrically connected to the negative terminal of the power supply or to ground 7.

[0019] Furthermore, the capacitor 1 may have external connection terminals so that it can be connected to, for example, the positive and negative terminals of a power supply. Preferably, such external connection terminals are installed on the anode 3 and cathode 4, in which case the capacitor 1 can be installed in the circuit such that the external connection terminal installed on anode 3 is connected to the positive terminal of the power supply, and the external connection terminal installed on cathode 4 is connected to the negative terminal of the power supply.

[0020] Furthermore, it is preferable that the two electrodes of capacitor 1 be distinguished so that it is possible to determine which is the anode 3 and which is the cathode 4. There are no particular restrictions on the method of distinguishing between anode 3 and cathode 4. For example, anode 3 and cathode 4 can be distinguished by marking capacitor 1 to indicate the distinction between anode 3 and cathode 4, by making the shapes of anode 3 and cathode 4 different, or by defining the positional relationship between anode 3 and cathode 4 in capacitor 1.

[0021] At least one of the anode 3 and cathode 4 includes at least one selected from the group consisting of, for example, Ti, Pt, Al, Ni, TiN, Ta, TaN, and Au. In this case, the capacitance of capacitor 1 can be increased. Furthermore, it is preferable that at least one of the anode 3 and cathode 4 includes at least one of Ti, Pt, and Al. In this case, the capacitance of capacitor 1 can be increased even further.

[0022] At least one of the anode 3 and cathode 4 can be fabricated, for example, by electron beam deposition. In this case, the thickness of both the anode 3 and the cathode 4 can be easily adjusted as needed. Furthermore, in capacitor 1, at least one of the thicknesses of the anode 3 and cathode 4 is, for example, 0.01 μm or more and 1 mm or less.

[0023] Furthermore, at least one of the anode 3 and cathode 4 may be, for example, a metal foil. The surface of the metal foil may also be roughened. This increases the surface area of ​​the metal foil, and thus increases the area of ​​the laminated film 2 in contact with the metal foil, which tends to increase the capacitance of the capacitor 1. The method of roughening the surface is not particularly limited; for example, etching can be used. Moreover, at least one of the anode 3 and cathode 4 may be a porous material. In other words, the metal contained in at least one of the anode 3 and cathode 4 may be a porous metal. In this case, the capacitance of the capacitor 1 may increase.

[0024] At least one of the anode 3 and cathode 4 may contain, for example, a conductive polymer. The conductive polymer may contain one or more components selected from the group consisting of, for example, polypyrrole, polythiophene, polyaniline, and derivatives thereof.

[0025] (Laminated film) <Insulating layer> As described above, the laminated film 2 comprises an insulating layer 21, which is in contact with the anode 3, and a second insulating layer 212, which is in contact with the cathode 4.

[0026] It is preferable that at least one of the first insulating layer 211 and the second insulating layer 212 contains a compound of at least one metal selected from the group consisting of Al, Si, Ta, and Hf. More specifically, it is preferable that at least one of the first insulating layer 211 and the second insulating layer 212 contains at least one metal oxide selected from the group consisting of Al2O3, SiO2, Ta2O5, and HfO2. In this case, the capacitance of capacitor 1 may be increased. It is even more preferable that at least one of the first insulating layer 211 and the second insulating layer 212 contains Al2O3. In this case, the capacitance of capacitor 1 may be increased even further. Furthermore, it is particularly preferable that both the first insulating layer 211 and the second insulating layer 212 contain Al2O3. In this case, the capacitance of capacitor 1 may be particularly increased. Note that the metal compound contained in at least one of the first insulating layer 211 and the second insulating layer 212 may be only one type or two or more types.

[0027] Alternatively, a metal having an oxide film may be produced by oxidizing the surface of a metal that can become anode 3 using an anodic oxidation method, and the oxide film portion may be used as the first insulator layer 211. In this case, the unoxidized portion can be used as anode 3. Furthermore, a metal having an oxide film may be produced by oxidizing the surface of a metal that can become cathode 4 using an anodic oxidation method, and the oxide film portion may be used as the second insulator layer 212. In this case, the unoxidized portion can be used as cathode 4.

[0028] The thickness of the insulating layer 21 is preferably adjusted to a specific range. Specifically, it is preferable that at least one of the thicknesses of the first insulating layer 211 and the second insulating layer 212 is between 5.0 nm and 20.0 nm. In this case, with respect to the capacitor 1, leakage current generation can be suppressed while changes in capacitance due to frequency changes can be suppressed. Furthermore, if both the thickness of the first insulating layer 211 and the thickness of the second insulating layer 212 are between 5.0 nm and 20.0 nm, leakage current generation can be further suppressed while changes in capacitance due to frequency changes can be further suppressed with respect to the capacitor 1.

[0029] Furthermore, when at least one of the thicknesses of the first insulator layer 211 and the second insulator layer 212 is between 5.0 nm and 20.0 nm, the cutoff frequency of capacitor 1 tends to increase while the capacitance of capacitor 1 increases. When both the thickness of the first insulator layer 211 and the second insulator layer 212 are between 5.0 nm and 20.0 nm, the cutoff frequency of capacitor 1 tends to increase even further while the capacitance of capacitor 1 increases even further. In this disclosure, the cutoff frequency refers to the frequency at which the capacitance decreases to 95% of the capacitance at 100 Hz.

[0030] Furthermore, in this embodiment, the thickness of the first insulating layer 211 and the thickness of the second insulating layer 212 may be the same or different. In other words, it is preferable that the thickness of the first insulating layer 211 and the thickness of the second insulating layer 212 be adjusted as appropriate so that the capacitance of the capacitor 1 can be increased, or so that changes in capacitance due to frequency changes can be suppressed with respect to the capacitor 1.

[0031] The thickness of the first insulating layer 211 and the thickness of the second insulating layer 212 can be measured using a TEM (transmission electron microscope). More specifically, the thickness of the first insulating layer 211 and the thickness of the second insulating layer 212 can be determined by measuring the thickness at five or more arbitrarily selected points using a TEM and taking the average value of those five or more measurements.

[0032] <Conductor layer> As described above, the laminated film 2 comprises a conductive layer 22.

[0033] The conductive layer 22 can be made from, for example, a conductive material. Examples of conductive materials include metals such as transition metals or alloys of these metals. More specifically, it is preferable that the conductive layer 22 contains at least one of Ti, Pt, Au, and Al. In this case, the change in capacitance with respect to the capacitor 1 can be further suppressed with respect to frequency changes.

[0034] Furthermore, in this embodiment, the presence of a conductive layer 22 in the laminated film 2 tends to increase the cutoff frequency of the capacitor 1. More specifically, a capacitor 1 with a conductive layer 22 tends to have a higher cutoff frequency than a capacitor with a semiconductor layer made from a semiconductor material instead of a conductive layer 22. As a result, the change in capacitance with respect to frequency changes tends to be suppressed for the capacitor 1. In addition, a capacitor 1 with a conductive layer 22 containing at least one of Ti, Pt, Au, and Al tends to have an even higher cutoff frequency.

[0035] The thickness of the conductor layer 22 is preferably adjusted to a specific numerical range. Specifically, the thickness of the conductor layer 22 is preferably 20.0 nm or more and 100.0 nm or less. In this case, the change in capacitance with respect to the capacitor 1 due to frequency changes can be further suppressed. Also, when the thickness of the conductor layer 22 is an appropriate thickness of 20.0 nm or more, it can become a continuous and uniform film.

[0036] The thickness of the conductor layer 22 can be measured in the same way as in the case of the first insulator layer 211 and the second insulator layer 212.

[0037] As described above, the conductor layer 22 is interposed between the first insulator layer 211 and the second insulator layer 212. For example, as shown in Figure 1A, if the surface of the conductor layer 22 in contact with the first insulator layer 211 is the upper surface and the surface of the conductor layer 22 in contact with the second insulator layer 212 is the lower surface, then in the capacitor 1, the conductor layer 22 is arranged such that its upper and lower surfaces are in contact with the first insulator layer 211 and the second insulator layer 212, respectively, and the surfaces (sides) of the conductor layer 22 that are different from the upper or lower surface do not need to be covered by the first insulator layer 211 or the second insulator layer 212. Alternatively, as shown in Figure 1B, the conductor layer 22 may be arranged such that its lower surface is in contact with the second insulator layer 212, and the area other than the lower surface is covered by the first insulator layer 211.

[0038] Furthermore, as described above, the conductor layer 22 is in an electrically floating state. To explain this in more detail, the conductor layer 22 is not in direct contact with either the anode 3 or the cathode 4, nor is it connected to any components such as the external connection terminals of the capacitor 1. Also, when the capacitor 1 is installed in a circuit, that is, when it is used as an element of the circuit, the conductor layer 22 is not electrically connected to any other elements in the circuit, nor is it grounded.

[0039] (2.3) Manufacturing method The method for manufacturing capacitor 1 will be explained with reference to Figures 2A-2B, 3A-3D, 4, and 5. Note that the method for manufacturing capacitor 1 described below is just one example. In other words, the manufacturing method for capacitor 1 can be adapted to the intended use and purpose of the capacitor 1.

[0040] In the method for manufacturing capacitor 1, the cathode 4, the multilayer film 2, and the anode 3 are sequentially fabricated on the substrate 5 (see Figures 2A to 5). In other words, the method for manufacturing capacitor 1 includes a cathode fabrication step, a multilayer film fabrication step, an anode fabrication step, and an etching step. These steps will be explained in detail below.

[0041] <Cathode fabrication process> In the cathode fabrication process, first, a substrate 5 is prepared (see Figure 2A). For example, a Si substrate is used as the substrate 5. Next, the substrate 5 is cleaned with an etching agent to remove organic matter and other contaminants adhering to the surface of the substrate 5. Buffered hydrofluoric acid (a mixture of hydrofluoric acid and ammonium fluoride) is preferably used as the etching agent.

[0042] Then, a cathode 4 is fabricated on the cleaned substrate 5 (see Figure 2B). One method for fabricating the cathode 4 is to continuously deposit a thin film containing a deposition material using electron beam evaporation, thereby fabricating a cathode 4 containing an appropriate metal. Electron beam evaporation is a method of fabricating a thin film by irradiating a deposition material with an electron beam in a vacuum, heating and evaporating it, and depositing the deposition material onto the substrate 5. In this disclosure, the deposition material used to fabricate the cathode 4 includes, for example, one selected from the group consisting of Ti, Pt, Al, Ni, TiN, Ta, TaN, and Au.

[0043] <Laminated film fabrication process> First, a second insulating layer 212 is fabricated on the cathode 4 (see Figures 3A and 3B). Next, a conductive layer 22 is fabricated on the second insulating layer 212 fabricated on the cathode 4 (see Figure 3C). Then, a first insulating layer 211 is fabricated on the conductive layer 22 (see Figure 3D). The laminated film 2 is fabricated by this procedure. When fabricating the first insulating layer 211 on the conductive layer 22, as described above, the first insulating layer 211 may be fabricated so as to cover the entire surface of the conductive layer 22 (see Figure 3D), or only the upper surface of the conductive layer 22 may be covered by the first insulating layer 211, and the sides may not be covered by the first insulating layer 211.

[0044] One method for producing the first insulating layer 211 and the second insulating layer 212 is the atomic layer deposition (ALD) method. Atomic layer deposition is a film formation method that uses an atomic layer deposition apparatus (ALD apparatus) to alternately supply a metal-containing raw material gas and an oxidizing agent to a reaction chamber in which the object is placed, thereby creating a layer containing metal oxides on the surface of the object. In atomic layer deposition, a self-stopping action is in operation, so the metal is deposited on the surface of the object in atomic layer units. Therefore, one cycle consists of adsorption of metal raw materials by supplying raw material gas, removal of excess raw materials by exhausting (purging) the raw material gas, oxidation of the metal raw materials by supplying the oxidizing agent, and exhausting (purging) the oxidizing agent, and the thickness of the layer produced can be controlled by the number of cycles. As the raw material gas, a gaseous organometallic compound is preferably used. Furthermore, it is preferable to create the laminated film 2 in a reduced-pressure atmosphere in the reaction chamber before film formation. Specifically, the pressure in the reaction chamber is reduced to, for example, 26.7 Pa or less.

[0045] Regarding film deposition, for example, the process is carried out while an inert gas is flowed through the reaction chamber at a constant flow rate. Examples of inert gases used include N2 and Ar. The flow rate of the inert gas is, for example, 4.39 × 10⁻⁶. -1 Pa·m 3 It is / s.

[0046] The supply time for adsorbing the metal raw material is, for example, 0.12 seconds to 0.14 seconds. Excess raw material gas is purged by flowing inert gas. N2, Ar, etc., are used as inert gases. The flow rate of the inert gas when purging the excess raw material gas is, for example, 4.39 × 10⁻⁶ as described above. -1 Pa·m 3 The time for purging excess raw material gas is, for example, between 10 and 20 seconds.

[0047] The time for supplying the oxidizing agent to oxidize the adsorbed metal raw material is, for example, 0.06 seconds to 0.07 seconds. As the oxidizing agent, for example, H2O, O2 plasma, O3, etc., can be used, but among these, H2O is preferred. Excess oxidizing agent is purged by flowing inert gas. N2, Ar, etc., can be used as the inert gas. The flow rate of the inert gas when purging the excess oxidizing agent can be the same as the flow rate of the inert gas when purging the excess raw material gas. The time for purging the excess oxidizing agent is, for example, 10 seconds to 20 seconds.

[0048] Furthermore, when depositing layers using atomic layer deposition, the deposition temperature can be set to, for example, 150°C. This makes it easier to control the chemical reactions that occur when the first insulating layer 211 and the second insulating layer 212 are fabricated, enabling the stable deposition of the first insulating layer 211 and the second insulating layer 212.

[0049] The raw material gas used to produce the first insulating layer 211 and the second insulating layer 212 includes, for example, a compound of at least one metal selected from the group consisting of Al, Si, Ta, and Hf. In other words, the raw material gas used to produce the first insulating layer 211 and the second insulating layer 212 includes, for example, at least one selected from the group consisting of an organometallic compound containing Al, an organometallic compound containing Si, an organometallic compound containing Ta, and an organometallic compound containing Hf.

[0050] Examples of organometallic compounds containing Al include trimethylaluminum (TMA, (CH3)3Al). When an organometallic compound containing Al is used, a first insulating layer 211 and a second insulating layer 212 containing Al2O3 of adjusted thickness can be fabricated.

[0051] Examples of organometallic compounds containing Si include tris(dimethylamino)silane (3DMAS, HSi[N(CH3)2]3). When an organometallic compound containing Si is used, a first insulating layer 211 and a second insulating layer 212 containing SiO2 of adjusted thickness can be fabricated.

[0052] Examples of organometallic compounds containing Ta include (t-butylimide)tris(ethylmethylamino)tantalum(V) (TBTEMT, (CH3)3CNTa[N(C2H5)CH3]3). When an organometallic compound containing Ta is used, a first insulating layer 211 and a second insulating layer 212 containing Ta2O5 of adjusted thickness can be prepared.

[0053] Examples of organometallic compounds containing Hf include tetrakis(ethylmethylamino)hafnium (TEMAH, Hf[N(C2H5)CH3]4). When an organometallic compound containing Hf is used, a first insulating layer 211 and a second insulating layer 212 containing HfO2 of adjusted thickness can be fabricated.

[0054] As a method for fabricating the conductive layer 22, for example, an electron beam evaporation method can be employed, similar to the method for fabricating the cathode 4. More specifically, a conductive layer 22 containing an appropriate metal can be fabricated by continuously depositing a thin film containing a deposition material such as a metal using an electron beam evaporation method. The deposition material used to fabricate the conductive layer 22 includes, for example, at least one selected from the group consisting of Ti, Pt, Au, and Al. When an electron beam evaporation method is employed to fabricate the conductive layer 22, the thickness of the fabricated conductive layer 22 can be adjusted to an appropriate value.

[0055] <Anode fabrication process> An anode 3 is fabricated on the first insulating layer 211 (see Figure 4). The same method used to fabricate the cathode 4 can be applied to fabricate the anode 3; for example, an anode 3 containing an appropriate metal can be fabricated by electron beam deposition. Alternatively, the same deposition material used to fabricate the cathode 4 can be used to fabricate the anode 3.

[0056] The anode 3 is fabricated, for example, by partially covering the anode 3 side of the first insulating layer 211 (see Figure 4). This makes it easier to remove the portion of the laminated film 2 that is not sandwiched between the anode 3 and the cathode 4 in the etching process described later.

[0057] <Etching process> A portion of the laminated film 2 is removed by etching (see Figure 5). This exposes a portion of the cathode 4, and as a result, the exposed portion of the cathode 4 can be electrically connected to the negative electrode or ground 7 of the power supply. In Figure 5, a portion of the first insulator layer 211 and a portion of the second insulator layer 212 are removed to expose a portion of the cathode 4. However, for example, etching may be performed using the anode 3 as a mask to remove a portion of the first insulator layer 211, a portion of the conductor layer 22, and a portion of the second insulator layer 212. Furthermore, to protect the anode 3 and the interface between the anode 3 and the first insulator layer 211 from damage during etching, the anode 3 and its surrounding area may be protected with a resist or the like before etching.

[0058] Capacitor 1 is manufactured according to the procedure described above. Note that when manufacturing capacitor 1, the procedure is not limited to sequentially manufacturing the cathode 4, multilayer film 2, and anode 3 on the substrate 5 as described above. Alternatively, a method of sequentially manufacturing the anode 3, multilayer film 2, and cathode 4 on the substrate 5 may also be employed.

[0059] (2.4) Performance Let's explain the performance of capacitor 1.

[0060] As described above, capacitor 1 includes a laminated film 2 containing a conductor layer 22 between a first insulator layer 211 and a second insulator layer 212. This allows capacitor 1 to achieve a capacitance higher than the theoretical capacitance C represented by the following equation (1). Furthermore, capacitor 1 can achieve a capacitance higher than the theoretical capacitance C represented by the following equation (1) when the measurement frequency is 1 MHz or less, an even higher capacitance higher than the theoretical capacitance C represented by the following equation (1) can be achieved when the measurement frequency is 1 MHz or less, and a particularly high capacitance higher than the theoretical capacitance C represented by the following equation (1) can be achieved when the measurement frequency is 1 MHz or less.

[0061]

number

[0062] In equation (1) above, C1 is the capacitance between anode 3 and cathode 4 when only the first insulating layer 211 is interposed between anode 3 and cathode 4. C2 is the capacitance between anode 3 and cathode 4 when only the second insulating layer 212 is interposed between anode 3 and cathode 4.

[0063] In addition, the values ​​of C1 and C2 in the above formula (1) are calculated based on the area of ​​the parts where the anode 3 and cathode 4 face each other. More specifically, the area of ​​the parts where the anode 3 and cathode 4 face each other is the area of ​​the electrode on the cathode 4 side of the anode 3 that faces the cathode 4, and also the area of ​​the electrode on the anode 3 side of the cathode 4 that faces the anode 3.

[0064] Furthermore, capacitor 1 shows a tendency for its capacitance to improve as the measurement frequency decreases. Specifically, the capacitance of capacitor 1 tends to improve at measurement frequencies of 1 MHz or less, improves even more at measurement frequencies of 10,000 Hz or less, and improves even further at measurement frequencies of 1,000 Hz or less. Capacitor 1 shows a particularly high capacitance improvement at a measurement frequency of 100 Hz, and can achieve a capacitance higher than the theoretical capacitance C represented by the above equation (1).

[0065] Furthermore, the capacitor 1 of this disclosure exhibits a remarkable effect in suppressing changes in capacitance due to frequency changes in a specific measurement frequency range. More specifically, because the laminated film 2 of the capacitor 1 includes a conductor layer 22, it exhibits a remarkable effect in suppressing changes in capacitance due to frequency changes in the measurement frequency range of 100 Hz to 1 MHz. As a result, the capacitor 1 can potentially improve its ability to remove voltage noise generated in the measurement frequency range of 100 Hz to 1 MHz. In addition, because the laminated film 2 of the capacitor 1 includes a conductor layer 22, it tends to suppress changes in capacitance due to frequency changes in the measurement frequency range of 100 Hz to 1 MHz compared to a capacitor 1 having a laminated film 2 that includes a semiconductor layer containing a semiconductor material such as ZnO instead of the conductor layer 22. Furthermore, with respect to capacitor 1, the effect of suppressing capacitance changes is more pronounced in the measurement frequency range of 1,000 Hz to 1 MHz, the effect of suppressing capacitance changes is even more pronounced in the measurement frequency range of 10,000 Hz to 1 MHz, and the effect of suppressing capacitance changes is particularly pronounced at a measurement frequency of 1 MHz.

[0066] Regarding capacitor 1, the capacitance between anode 3 and cathode 4 at measurement frequencies from 100 Hz to 1 MHz is a measurement obtained using impedance analyzer 6 (product name: Impedance Analyzer 4294A, distributor: Keysight Technologies). More specifically, an evaluation circuit 10 (see Figure 6) including capacitor 1 and impedance analyzer 6 is constructed, and an AC voltage of 500 mV is applied between anode 3 and cathode 4. The capacitance at each frequency can be confirmed from the measured capacitance obtained when the measurement frequency is set from 100 Hz to 1 MHz. Furthermore, the evaluation circuit 10 is constructed so that the impedance analyzer 6 is connected to anode 3 and cathode 4 of capacitor 1, and cathode 4 is also connected to ground 7.

[0067] Furthermore, the cutoff frequency of capacitor 1 can also be measured using the evaluation circuit 10, which includes capacitor 1 and impedance analyzer 6.

[0068] (3) Variant Modified versions of capacitor 1 will be described with reference to Figures 7A and 7B. Note that the modified versions are examples of variations in which the configuration of the embodiment is partially changed, added, or deleted. Furthermore, with respect to the modified versions, components similar to those of capacitor 1 in the embodiment are denoted by the same reference numerals and their description is omitted.

[0069] In the modified example, the anode 3 is a porous body having pores 31, and a portion of the cathode 4 is embedded within the pores 31 of the anode 3 (see Figure 7A). A laminated film 2 (see Figure 7B) is interposed between the inner surface of the pores 31 and the portion of the cathode 4 embedded within the pores 31. Because the cathode 4 is embedded within the pores 31, the surface area between the anode 3 and the cathode 4 can be increased. As a result, the capacitance of the capacitor 1 can be increased. Alternatively, the cathode 4 can be a porous body having pores 31, and a portion of the anode 3 can be embedded within the cathode 4.

[0070] Furthermore, in the modified version, the capacitor 1 can be fitted with appropriate materials for its electrodes. For example, the anode 3 may contain Al, and the cathode 4 may contain a conductive polymer. In other words, the capacitor 1 comprises, in this order, an anode 3 containing Al, a laminated film 2 in which an insulating layer 21 and a conductive layer 22 are laminated, and a cathode 4 containing a conductive polymer. In this case, the capacitor 1 has high capacitance because porous Al is used as the anode 3, and a conductive polymer can be used as the cathode 4. This allows the capacitor 1 to be used as a conductive polymer aluminum electrolytic capacitor. In this case, the laminated film 2 may be located between the anode 3 and the cathode 4 and may be a dielectric film covering the cathode 4. It is also preferable that the laminated film 2 of the capacitor 1 contains an oxide film. In other words, it is preferable that at least one of the first insulating layer 211 and the second insulating layer 212 contains Al2O3.

[0071] In addition, even when the anode 3 is a porous material, a laminated film 2 with a three-layer structure, in which the first insulating layer 211, the conductive layer 22, and the second insulating layer 212 are stacked, can be fabricated by atomic layer deposition to create the first insulating layer 211 and the second insulating layer 212, and by electron beam deposition to create the conductive layer 22. Furthermore, the anode 3 may have an anodic oxide coating on its surface. In other words, the first insulating layer 211 may be fabricated by oxidizing a part of the anode 3 using an anodic oxidation method. Then, the laminated film 2 may be fabricated by creating the conductive layer 22 on the first insulating layer 211, which is the anodic oxide coating, using electron beam deposition, and subsequently creating the second insulating layer 212 using atomic layer deposition.

[0072] Furthermore, the cathode 4 may contain both a conductive polymer and an electrode containing a metal, or it may not contain a conductive polymer. In other words, in the modified example, the capacitor 1 may have a configuration in which the cathode 4 does not contain a conductive polymer, and a layer containing a conductive polymer is laminated between the second insulating layer 212 and the cathode 4 containing a metal such as Al or Ag.

[0073] In a modified example, with respect to the capacitor 1, one of the anode 3 and cathode 4 may contain Al, while the other may contain a conductive polymer. That is, the capacitor 1 can have a configuration in which the anode 3 contains Al and the cathode 4 contains a conductive polymer, or, for example, the cathode 4 contains Al and the anode 3 contains a conductive polymer. In this case, the capacitor 1 can have a high capacitance because porous Al is used as the cathode 4, while also being able to use a conductive polymer as the anode 3.

[0074] Furthermore, in the modified example, the capacitor 1 may have a configuration in which both the anode 3 and cathode 4 contain Al. Specifically, the capacitor 1 can employ a configuration in which an anode 3 containing Al, a laminated film 2 which is a dielectric film, a layer containing a conductive polymer, and a cathode 4 containing Al are stacked in this order. In this case, it is preferable that the laminated film 2 which is a dielectric film contains an oxide film containing Al2O3. In other words, it is preferable that at least one of the first insulating layer 211 and the second insulating layer 212 of the laminated film 2 contains Al2O3. A capacitor 1 having such a configuration can have a high capacitance. [Examples]

[0075] 1. Capacitor Evaluation 1 1.1 Method for fabricating the evaluation circuit Capacitors 1 for Examples 1 and 2 and Comparative Example 1 were fabricated according to the following procedure, and an evaluation circuit 10 including these capacitors 1 was constructed (see Figure 6).

[0076] <Making Capacitors> Capacitor 1 was fabricated using the following method.

[0077] First, a substrate 5 (made of silicon) was prepared and washed with buffered hydrofluoric acid. A cathode 4 containing Ti was then fabricated on the washed substrate 5 using electron beam evaporation.

[0078] Then, the substrate 5 on which the cathode 4 was stacked was cleaned using ultrasound while immersed in an organic solvent such as acetone or isopropyl alcohol.

[0079] Next, a second insulating layer 212 containing Al2O3 was fabricated on cathode 4 by atomic layer deposition, consisting of one cycle of supplying trimethylaluminum gas, exhausting trimethylaluminum gas, supplying H2O gas, and exhausting H2O gas, and this cycle was repeated sequentially.

[0080] Next, for capacitor 1 of Examples 1 and 2, a Ti-containing layer (conductor layer 22) was fabricated on the second insulator layer 212 by electron beam deposition. Then, a first insulator layer 211 containing Al2O3 was fabricated on the conductor layer 22 following the same procedure as the fabrication of the second insulator layer 212.

[0081] Furthermore, with respect to capacitor 1 of Comparative Example 1, a ZnO-containing layer (semiconductor layer) was fabricated on the second insulator layer 212 using the same procedure as the fabrication of the second insulator layer 212, except that the trimethylaluminum gas was replaced with diethylzinc gas. Then, on that semiconductor layer, a first insulator layer 211 containing Al2O3 was fabricated using the same procedure as the fabrication of the second insulator layer 212. In other words, compared to capacitors 1 of Examples 1 and 2, capacitor 1 of Comparative Example 1 has a semiconductor layer instead of a conductor layer 22.

[0082] Next, for each of Examples 1 and 2 and Comparative Example 1, an anode 3 containing Ti was fabricated on the first insulating layer 211 by electron beam deposition. Then, the laminated film 2 on the anode 3 side of the cathode 4 that was not facing the anode 3 was removed by etching, and a part of the cathode 4 was exposed to fabricate a capacitor 1.

[0083] In the fabrication of capacitor 1 in Examples 1 and 2 and Comparative Example 1, the thickness of the anode 3, cathode 4, the first insulating layer 211, the second insulating layer 212, the conductor layer 22, and the semiconductor layer were each adjusted to the values ​​shown in Table 1.

[0084] Furthermore, as described above, the first insulating layer 211 and the second insulating layer 212 in capacitors 1 of Examples 1-2 and Comparative Example 1, and the semiconductor layer in capacitor 1 of Comparative Example 1 were fabricated by atomic layer deposition using an atomic layer deposition apparatus (product name: Fiji F200, distributor: Cambridge Nanotech). The film deposition conditions per cycle when the first insulating layer 211, the second insulating layer 212, and the semiconductor layer were fabricated by atomic layer deposition were as follows.

[0085] <Insulating layer> Film forming temperature: 150℃ Supply time of raw material gas for adsorption of metal raw materials: 0.12 seconds Time to purge excess raw material gas: 10 seconds Supply time of oxidizing agent for oxidizing metal raw materials: 0.06 seconds Oxidizer removal (purging) time: 10 seconds <Semiconductor layer> Film forming temperature: 150℃ Supply time of raw material gas for adsorption of metal raw materials: 0.14 seconds Time to purge excess raw material gas: 20 seconds Supply time of oxidizing agent for oxidizing metal raw materials: 0.07 seconds Oxidizer removal (purging) time: 20 seconds During film deposition, Ar was used as the inert gas, and the inert gas was flowed at a constant flow rate. The inert gas flow rate was 4.39 × 10⁻⁶. -1 Pa·m 3 The flow rate was set to / s. In other words, the supply of the oxidizing agent for oxidizing the metal raw material and the exhaust (purging) of the oxidizing agent for removal were carried out at the aforementioned flow rate. Furthermore, regarding the number of cycles during film formation in atomic layer deposition, the thickness of the first insulating layer 211, the thickness of the second insulating layer 212, and the thickness of the semiconductor layer were adjusted to the values ​​listed in Table 1.

[0086] <Fabrication of evaluation circuit used for measuring capacitance and cutoff frequency> For capacitor 1 in Examples 1 and 2 and Comparative Example 1, an evaluation circuit 10 was fabricated by connecting the anode 3 and a portion of the exposed cathode 4 to an impedance analyzer 6, and further connecting the cathode 4 to ground 7 (see Figure 6). The impedance analyzer 6 used was an impedance analyzer 4294A (manufactured by Keysight Technologies).

[0087] 1.2 Evaluation Results <Capacitance> For the evaluation circuit 10 including capacitor 1 of Examples 1-2 and Comparative Example 1, the capacitance of capacitor 1 of Examples 1-2 and Comparative Example 1 was measured by applying an AC voltage of 500mV between anode 3 and cathode 4 in a frequency band from 100Hz to 1MHz. The relationship between the measurement frequency and capacitance for capacitor 1 of Examples 1-2 and Comparative Example 1 is shown in Figure 8. The measurement results of capacitance obtained at measurement frequencies of 100Hz and 1MHz are listed in Table 1. The theoretical capacitance of capacitor 1 of Examples 1-2 and Comparative Example 1 is the value calculated according to formula (1) described in "(2.4) Performance".

[0088] <Cutoff frequency> The capacitance was measured for each frequency in the frequency band from 100 Hz to 1 MHz according to the method described in "Capacitance". The cutoff frequency was defined as the frequency at which the capacitance decreased to 95% of the capacitance at 100 Hz. The measurement results obtained for each of the capacitors 1 in Examples 1 and 2 and Comparative Example 1 are shown in Table 1.

[0089] [Table 1]

[0090] The capacitors 1 of Examples 1 and 2, which are equipped with a conductor layer 22, were shown to have a larger difference between their capacitance and theoretical capacitance at measurement frequencies from 100 Hz to 1 MHz compared to the capacitor 1 of Comparative Example 1, which is equipped with a semiconductor layer instead of a conductor layer 22.

[0091] The capacitors 1 of Examples 1 and 2, which are equipped with a conductive layer 22, were shown to have a higher capacitance at a measurement frequency of 1 MHz compared to the capacitor 1 of Comparative Example 1, which is equipped with a semiconductor layer instead of a conductive layer 22.

[0092] It was shown that the capacitors 1 of Examples 1 and 2, which are equipped with a conductive layer 22, show a smaller difference between the capacitance at a measurement frequency of 100 Hz and the capacitance at a measurement frequency of 1 MHz compared to the capacitor 1 of Comparative Example 1, which is equipped with a semiconductor layer instead of a conductive layer 22.

[0093] The capacitors 1 of Examples 1 and 2, which are equipped with a conductive layer 22, were shown to have a higher cutoff frequency compared to the capacitor 1 of Comparative Example 1, which is equipped with a semiconductor layer instead of a conductive layer 22.

[0094] 2. Capacitor Evaluation 2 2.1 Method for fabricating the evaluation circuit Except for changing the metal used to fabricate the conductor layer 22 of capacitor 1 in Example 2 from Ti to Pt, capacitor 1 of Example 3 and evaluation circuit 10 (see Figure 6) including capacitor 1 and impedance analyzer 6 were fabricated using the same procedure as the procedure for fabricating the capacitor of Example 2 described in "1. Capacitor Evaluation 1 1.1 Method for Fabricating Evaluation Circuit".

[0095] 2.2 Evaluation Results The capacitance and cutoff frequency of capacitor 1 in Example 3 were measured according to the method described in "1. Capacitor Evaluation 1 1.2 Evaluation Results". Figure 9 shows the relationship between the measurement frequency and capacitance for capacitor 1 in Example 3. Table 2 shows the measurement results for capacitance and cutoff frequency obtained for capacitor 1 in Example 3 at measurement frequencies of 100 Hz and 1 MHz.

[0096] For comparison with Example 3, Figure 9 shows the relationship between the measurement frequency and capacitance of capacitor 1 of Example 2 obtained in "1. Capacitor Evaluation 1," and Table 2 shows the measurement results of capacitance and cutoff frequency obtained at measurement frequencies of 100 Hz and 1 MHz.

[0097] [Table 2]

[0098] The evaluation results of capacitor 1 in Example 3 and Example 2 showed that by changing the metal contained in the conductor layer 22 from Ti to Pt, the difference between the capacitance and the theoretical capacitance at measurement frequencies from 100 Hz to 1 MHz can be increased.

[0099] Furthermore, the evaluation results of capacitor 1 in Example 3 and Example 2 showed that, not limited to Ti, even when other metals such as Pt are used, capacitor 1 equipped with a conductive layer 22 can increase the difference between capacitance and theoretical capacitance at measurement frequencies from 100 Hz to 1 MHz, and can also increase the cutoff frequency, compared to capacitor 1 in Comparative Example 1 which is equipped with a semiconductor layer instead of a conductive layer 22.

[0100] 3. Capacitor Evaluation 3 3.1 Method for fabricating the evaluation circuit Except for changing the thickness of the first insulating layer 211 and the thickness of the second insulating layer 212 of the capacitor in Example 2 to the values ​​shown in Table 3, capacitors 1 of Examples 4 and 5, and evaluation circuits 10 (see Figure 6) including each capacitor 1 and an impedance analyzer 6 were fabricated using the same procedure as the procedure for fabricating the capacitor in Example 2 described in "1. Capacitor Evaluation 1 1.1 Method for Fabricating Evaluation Circuit".

[0101] 3.2 Evaluation Results The capacitance and cutoff frequency of capacitor 1 in Examples 4 and 5 were measured according to the method described in "1. Capacitor Evaluation 1 1.2 Evaluation Results". Figure 10 shows the relationship between the measurement frequency and capacitance for capacitor 1 in Examples 4 and 5. Table 3 shows the measurement results of capacitance and cutoff frequency obtained for capacitor 1 in Examples 4 and 5 at measurement frequencies of 100 Hz and 1 MHz.

[0102] For comparison with Examples 4 and 5, Figure 10 shows the relationship between the measurement frequency and capacitance of capacitor 1 of Example 2 obtained in "1. Capacitor Evaluation 1," and Table 3 shows the measurement results of capacitance and cutoff frequency obtained at measurement frequencies of 100 Hz and 1 MHz.

[0103] [Table 3]

[0104] The evaluation results of capacitor 1 in Examples 4-5 and Example 2 show that the capacitance at measurement frequencies of 100Hz to 1MHz can be increased by reducing the thickness of the first insulating layer 211 and the second insulating layer 212.

[0105] (summary) As is evident from the embodiments described above, this disclosure includes the following aspects. Hereafter, reference numerals are enclosed in parentheses solely to indicate their correspondence with the embodiments.

[0106] A capacitor (1) according to a first aspect of the present disclosure comprises an anode (3), a multilayer film (2), and a cathode (4) stacked in this order. The multilayer film (2) comprises a first insulating layer (211) in contact with the anode (3), a conductor layer (22), and a second insulating layer (212) in contact with the cathode (4) stacked in this order. The conductor layer (22) is electrically insulated from both the anode (3) and the cathode (4).

[0107] According to the first embodiment, it is possible to provide a capacitor (1) in which capacitance can be increased while suppressing changes in capacitance due to frequency changes.

[0108] In the first embodiment, the capacitor (1) according to a second aspect of the present disclosure comprises at least one of the first insulating layer (211) and the second insulating layer (212) containing Al2O3.

[0109] According to the second embodiment, the capacitance of capacitor (1) can be increased.

[0110] In the capacitor (1) according to a third aspect of the present disclosure, in the first or second aspect, at least one of the thickness of the first insulating layer (211) and the thickness of the second insulating layer (212) is 5.0 nm or more and 20.0 nm or less.

[0111] According to the third embodiment, with respect to capacitor (1), the generation of leakage current can be suppressed, and the change in capacitance due to frequency changes can also be suppressed. Furthermore, the cutoff frequency of capacitor (1) tends to increase, and the capacitance of capacitor (1) tends to increase as well.

[0112] In any one of the first to third embodiments, the capacitor (1) according to the fourth aspect of the present disclosure has a capacitance between the anode (3) and cathode (4) at a measurement frequency of 100 Hz that is greater than the theoretical capacitance represented by the following formula (1).

[0113]

number

[0114] According to the fourth embodiment, the capacitance of capacitor (1) at a measurement frequency of 100 Hz can be particularly increased.

[0115] A capacitor (1) according to a fifth aspect of the present disclosure, in any one of the first to fourth aspects, comprises a conductor layer (22) containing at least one of Ti, Pt, Au, and Al.

[0116] According to the fifth embodiment, the change in capacitance of capacitor (1) with respect to frequency changes can be further suppressed. In addition, capacitor (1) tends to have a higher cutoff frequency.

[0117] In the sixth aspect of the present disclosure, the capacitor (1) has a thickness of 20.0 nm or more and 100.0 nm or less in any one of the first to fifth aspects.

[0118] According to the sixth aspect, with respect to capacitor (1), the change in capacitance due to frequency changes can be further suppressed.

[0119] In any one of the first to sixth embodiments, the capacitor (1) of the seventh aspect of the present disclosure comprises at least one of Ti, Pt, and Al as the anode (3) and cathode (4).

[0120] According to the seventh embodiment, the capacitance of capacitor (1) can be increased.

[0121] The capacitor (1) according to the eighth aspect of the present disclosure, in any one of the first to seventh aspects, comprises an anode (3) and a cathode (4), one of which contains Al and the other contains a conductive polymer.

[0122] According to the eighth aspect, the capacitor (1) may be a conductive polymer aluminum electrolytic capacitor. [Explanation of symbols]

[0123] 1 Capacitor 2. Multilayer film 3 Anode 4 cathode 21 Insulator layer 211 First insulating layer 212 Second insulating layer 22 Conductor layer 31 pores

Claims

1. The anode, the multilayer film, and the cathode are arranged in this order. The laminated film comprises a first insulating layer in contact with the anode, a conductive layer, and a second insulating layer in contact with the cathode, laminated in this order. The conductor layer is electrically insulated from both the anode and the cathode. At a measurement frequency of 100 Hz, the capacitance between the anode and the cathode is greater than the theoretical capacitance represented by the following formula (1). Capacitor. [Math 1] C: Theoretical capacitance C1: Capacitance between the anode and the cathode when only the first insulating layer is interposed between the anode and the cathode. C2: Capacitance between the anode and the cathode when only the second insulating layer is interposed between the anode and the cathode.

2. The anode, the laminated film, and the cathode are stacked in this order, The laminated film comprises a first insulating layer in contact with the anode, a conductive layer, and a second insulating layer in contact with the cathode, laminated in this order. The conductor layer is electrically insulated from both the anode and the cathode. Of the anode and the cathode, one contains Al and the other contains a conductive polymer. Capacitor.

3. At least one of the first insulating layer and the second insulating layer comprises Al₂O₃ The capacitor according to claim 1 or 2.

4. At least one of the thickness of the first insulating layer and the thickness of the second insulating layer is 5.0 nm or more and 20.0 nm or less. The capacitor according to claim 1 or 2.

5. The conductor layer includes at least one of Ti, Pt, Au, and Al. The capacitor according to claim 1 or 2.

6. The thickness of the conductor layer is 20.0 nm or more and 100.0 nm or less. The capacitor according to claim 1 or 2.

7. At least one of the anode and the cathode includes at least one of Ti, Pt, and Al. The capacitor according to claim 1 or 2.

8. Of the anode and the cathode, one contains Al and the other contains a conductive polymer. The capacitor according to claim 1.

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