Capacitor

Abstract

Provided is a capacitor in which a plurality of fibrous conductive members are used and in which the bonding strength between a substrate and a composite member is high. A capacitor is provided with: a conductive substrate; a plurality of fibrous conductive members disposed on the substrate and electrically connected to the substrate; a dielectric layer covering the surface of the fibrous conductive member; and a conductor layer covering the surface of the dielectric layer, the plurality of fibrous conductive members, the dielectric layer, the conductor layer, and a space formed between the plurality of fibrous conductive members covered by the dielectric layer and the conductor layer constitute a composite member. In a cross-section along the thickness direction of the substrate, with the in-plane direction of the substrate as the width direction, the composite member has a width (W1) on the opposite side from the substrate and a width (W2) on the substrate side, and the width (W1) is smaller than the width (W2).

Description

Technical Field

[0001] The present disclosure relates to a capacitor, and more particularly, to a capacitor having a conductor-dielectric-conductor structure. Background Art

[0002] It is known that capacitors can be manufactured using fibrous members. For example, Patent Document 1 describes a method in which a fibrous member is formed on a substrate (base surface), and a lower plate (metal), an insulating layer, and an upper plate (metal) are sequentially formed on the surface of the fibrous member to form a capacitor having a metal-insulator-metal (MIM) structure.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application No. 2010-506391

[0006] Non-patent literature

[0007] Non-patent document 1: Michael FL De Volder, Sei Jin Park, Sameh H Tawfick, Daniel O Vidaud and A John Hart, "Fabrication and electrical integration of robust carbon nanotube micropillars by self-directed elastocapillarydensification", Journal of Micromechanics and Microengineering, 2011. Summary of the Invention

[0008] Problems to be solved by the invention

[0009] When the fibrous member has conductivity, by forming a dielectric layer and further forming a conductor layer on the surface of the fibrous conductive member, a capacitor having a conductor-dielectric-conductor structure can be formed.

[0010] For example, vertically aligned carbon nanotubes (VACNTs) can be used as multiple fibrous conductive members. VACNTs can be grown at high density on a substrate with a catalyst attached. Multiple VACNTs form a forest. In a capacitor, the VACNTs are covered by a dielectric layer and a conductive layer.

[0011] The forest (composite component) covered by dielectric and conductive layers primarily contacts the substrate through the dielectric layer. The substrate and dielectric layers have different thermal expansion coefficients. Therefore, if the capacitor or its precursor is heated, this difference in thermal expansion coefficients can cause delamination between the substrate and the composite component.

[0012] An object of the present disclosure is to provide a capacitor having high bonding strength between a substrate and a composite member.

[0013] Technical solutions to solve problems

[0014] According to the subject matter of the present disclosure, a capacitor can be provided, comprising:

[0015] a substrate having electrical conductivity;

[0016] a plurality of fibrous conductive members disposed on the substrate and electrically connected to the substrate;

[0017] a dielectric layer covering the surface of the fibrous conductive member; and

[0018] a conductive layer covering the surface of the dielectric layer,

[0019] The plurality of fibrous conductive members, the dielectric layer, the conductor layer, and spaces formed between the plurality of fibrous conductive members covered with the dielectric layer and the conductor layer constitute a composite member.

[0020] In a cross section along the thickness direction of the substrate,

[0021] Assuming that the in-plane direction of the substrate is a width direction, the composite member has a width W1 on the opposite side to the substrate and a width W2 on the substrate side, and the width W1 is smaller than the width W2.

[0022] Effects of the Invention

[0023] According to the present disclosure, a capacitor having high bonding strength between a substrate and a composite member can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1It is a schematic cross-sectional view of a capacitor in accordance with the first embodiment of the present disclosure.

[0025] Figure 2 yes Figure 1 Magnified view of part A.

[0026] Figure 3A yes Figure 1 Magnified view of part B.

[0027] Figure 3B yes Figure 1 A cross-sectional view of portion B along the in-plane direction of the substrate.

[0028] Figure 4 It is a schematic cross-sectional view of a capacitor in accordance with Embodiment 2 of the present disclosure.

[0029] Figure 5A yes Figure 4 Magnified view of part D.

[0030] Figure 5B yes Figure 4 A cross-sectional view of portion D along the in-plane direction of the substrate.

[0031] Figure 6 This is an optical microscope photograph showing a portion of a cross section of the composite member obtained in Production Example 1, taken along the thickness direction of the substrate.

[0032] Figure 7A This is a schematic cross-sectional view of a conventional capacitor.

[0033] Figure 7B This is a schematic cross-sectional view of a conventional capacitor, showing the state in which the composite member is peeled off.

[0034] Figure 8A This is an SEM image of a portion of the outer peripheral region of the polished XZ cross section of the composite member obtained in Production Example 1.

[0035] Figure 8B This is an SEM image of a portion of the central region of the polished XZ cross section of the composite member obtained in Production Example 1.

[0036] Figure 9A This is an SEM image of a portion of the outer peripheral region of the polished XY cross section of the composite member obtained in Production Example 1.

[0037] Figure 9B This is an SEM image of a portion of the central region of the polished XY cross section of the composite member obtained in Production Example 1. DETAILED DESCRIPTION

[0038] The following describes in detail a capacitor as one embodiment of the present disclosure through the illustrated embodiments. Note that some of the drawings are schematic and may not reflect actual dimensions or ratios. The present disclosure is not limited to these embodiments.

[0039] <Implementation Method 1>

[0040] Figure 1 This is a schematic cross-sectional view of the capacitor in the first embodiment. Figure 1 1 shows a cross section along the thickness direction of the substrate 10. Figure 1 , for convenience, the outer shapes of the substrate 10 and the composite member 20 are shown, and the fibrous conductive member 21, the dielectric layer 22, and the conductor layer 23 are omitted. Figure 2 yes Figure 1 An enlarged view of part A. Figure 2 , a fibrous conductive member 21 covered with a dielectric layer 22 and a conductor layer 23 in this order is schematically shown. Figure 3A yes Figure 1 An enlarged view of part B. Figure 3A , a fibrous conductive member 21 covered with a dielectric layer 22 and a conductor layer 23 in this order is schematically shown. Figure 3B yes Figure 1 A cross-sectional view of portion B along the in-plane direction of the substrate. Figure 3B Corresponding to Figure 3A II section. For convenience, Figure 3A 、 3B , only a portion of the substrate 10 , the fibrous conductive member 21 , the dielectric layer 22 , and the conductor layer 23 are shown.

[0041] In the figure, the thickness direction of substrate 10 is defined as the Z direction. A straight line extending along the Z direction and including the center C of substrate 10 when capacitor 1 is viewed from the Z direction is defined as the central axis AX. Center C of substrate 10 is generally coaxial with the center of capacitor 1. The direction perpendicular to the Z direction of a cross section of capacitor 1 obtained by cutting the capacitor 1 along a plane including the central axis AX and extending in the Z direction is defined as the X direction (also referred to as the width direction in an XZ cross section). The X direction is an example of a direction parallel to the in-plane direction of substrate 10. A direction perpendicular to the Z direction and the X direction is defined as the Y direction (also referred to as the width direction in a YZ cross section).

[0042] The surface obtained by cutting the capacitor 1 with a surface formed by a straight line extending in the X direction and a straight line extending in the Z direction and including the central axis AX is referred to as an XZ cross-section. The XZ cross-section is an example of a cross-section along the thickness direction of the substrate 10. The surface obtained by cutting the capacitor 1 with a surface formed by a straight line extending in the Y direction and a straight line extending in the Z direction and including the central axis AX is referred to as a YZ cross-section. The YZ cross-section is another example of a cross-section along the thickness direction of the substrate 10. The surface obtained by cutting the capacitor 1 with a surface formed by a straight line extending in the X direction and a straight line extending in the Y direction is referred to as an XY cross-section. The XY cross-section is a cross-section parallel to the in-plane direction of the substrate 10. The center C of the substrate 10 is the center of the smallest circle that includes the substrate 10 when the capacitor 1 is observed from the Z direction.

[0043] In the Z direction, the direction from the substrate 10 toward the composite member 20 is sometimes referred to as the upper direction. The so-called upper side of an element refers to the upper side of the element. In the Z direction, the direction from the composite member 20 toward the substrate 10 is sometimes referred to as the lower direction. The so-called lower side of an element refers to the lower side of the element. In an XZ cross-section, the X direction is sometimes referred to as the left-right direction. The so-called right side of an element refers to the right side of the element. The so-called left side of an element refers to the left side of the element.

[0044] (structure)

[0045] Capacitor 1 includes: a substrate 10 having conductivity; a plurality of fibrous conductive members 21 disposed on and electrically connected to substrate 10; a dielectric layer 22 covering the surface of the fibrous conductive members 21; and a conductor layer 23 covering the surface of the dielectric layer 22. Capacitor 1 may include a conductive member (not shown) in contact with conductor layer 23. The plurality of fibrous conductive members 21, the dielectric layer 22, the conductor layer 23, and the space 24 formed between the plurality of fibrous conductive members covered by the dielectric layer 22 and the conductor layer 23 constitute a composite component 20. Space 24 may also be filled with a filler such as a resin. The conductive member will be described later.

[0046] In the capacitor 1 , “on the substrate 10 ” can be more specifically referred to as the outer surface of the substrate 10 , and is a surface (surface 10 a described later) parallel to a plane (XY plane) formed by straight lines extending in the X direction and straight lines extending in the Y direction.

[0047] The dielectric layer 22 may cover, in addition to the surfaces of the fibrous conductive members 21 (excluding the region directly bonded to the substrate 10), portions of the surface 10a of the substrate 10 where the fibrous conductive members 21 are not disposed between the plurality of fibrous conductive members 21. The dielectric layer 22 may also be formed continuously with the dielectric portion 22a that covers the portions of the surface 10a of the substrate 10 where the fibrous conductive members 21 are not disposed, outside the plurality of fibrous conductive members 21. However, the composite member 20 does not include the dielectric portion 22a.

[0048] In addition to the dielectric layer 22 covering the surfaces of the fibrous conductive members 21, the conductive layer 23 may also cover the dielectric layer 22 between the plurality of fibrous conductive members 21. The portion of the conductive layer 23 covering the dielectric layer 22 between the plurality of fibrous conductive members 21 can be understood as the portion defining the bottom of the space 24 (e.g., the bottom of the groove). The conductive layer 23 may also be formed continuously with the conductive portion 23a, which covers the dielectric portion 22a on the outside of the plurality of fibrous conductive members 21. However, the composite member 20 does not include the conductive portion 23a.

[0049] The fibrous conductive member 21 is directly bonded to the substrate 10. More specifically, the fibrous conductive member 21 is directly in contact with and bonded to the substrate 10. The fibrous conductive member 21 is directly synthesized on the surface 10a of the substrate 10.

[0050] The plurality of fibrous conductive members 21 are electrically conductive (representatively, conductors) and are electrically connected to the substrate 10 so as to be at the same potential or voltage. Thus, a conductor-dielectric-conductor structure can be formed by the fibrous conductive members 21, the dielectric layer 22, and the conductor layer 23. This conductor-dielectric-conductor structure can be understood as a structure corresponding to a so-called MIM structure (metal-insulator-metal structure). Capacitor 1 having such a structure can achieve a high capacitance density due to the large specific surface area of ​​the fibrous conductive members 21.

[0051] (Composite component)

[0052] The composite member 20 is composed of a plurality of fibrous conductive members 21 (hereinafter referred to as conductive fibers 21 ), a dielectric layer 22 , a conductor layer 23 , and spaces 24 formed between the plurality of conductive fibers 21 covered by the dielectric layer 22 and the conductor layer 23 (hereinafter also referred to as covered conductive fibers 21 ).

[0053] · Method for determining the composite component 20

[0054] The composite member 20 can be determined based on a cross-section (e.g., an XZ cross-section) along the thickness direction of the capacitor 1. As described above, the composite member 20 does not include the dielectric portion 22a and the conductive portion 23a, so these can be excluded. The following description will primarily focus on the XZ cross-section as a cross-section along the thickness direction.

[0055] First, any appropriate filling resin is used to fill the spaces 24 formed between the coated conductive fibers 21. Next, the center C of the substrate 10 when the capacitor 1 is viewed from the Z direction is determined.

[0056] Polishing exposes a cross-section (herein, an XZ cross-section) of capacitor 1 in the thickness direction, including center C. The resulting XZ cross-section (No. 1) is observed using a scanning electron microscope (SEM). The SEM image of XZ cross-section (No. 1) reveals substrate 10 and a first member (not shown) disposed on surface 10a of substrate 10, comprising conductive fibers 21, dielectric layer 22 (and dielectric portion 22a, if present, the same shall apply hereinafter), conductive layer 23 (and conductive portion 23a, if present, the same shall apply hereinafter), and a filling resin (corresponding to space 24 described above). Furthermore, a conductive member may be present.

[0057] This SEM image is processed to identify the conductive fibers 21, dielectric layer 22, conductor layer 23, and filler resin (space 24) within the first member. Furthermore, the conductive members are identified and separated. Elemental analysis using energy dispersive X-ray analysis (EDX) can also be used for this identification.

[0058] In the XZ cross-section, the composite member 20 is a substantially quadrilateral. In this SEM image, the conductive fibers 21 located near each of the four corners of the composite member 20 are identified. This identification can be performed by magnifying the portion of the SEM image containing each corner to a viewing field of approximately 1 μm x 1 μm.

[0059] In this SEM image, the leftmost conductive fiber 21 of the first member, located closest to the substrate 10 and on the far left side, is identified. Next, the dielectric layer 22 and the conductive layer 23 covering the leftmost conductive fiber 21 are determined. These layers can exist continuously with the dielectric portion 22a and the conductive portion 23a, respectively. Due to the manufacturing method, the thickness of the dielectric layer 22 (and the dielectric portion 22a, hereinafter referred to as the same) covering the conductive fibers 21 is approximately uniform. Therefore, the outer edge of the dielectric layer 22 covering the leftmost conductive fiber 21 can be determined by taking into account the thickness of the dielectric layer 22 covering the other conductive fibers 21. Due to the manufacturing method, the thickness of the conductive layer 23 (and the conductive portion 23a, hereinafter referred to as the same) covering the conductive fibers 21 through the dielectric layer 22 is also approximately uniform. Therefore, the outer edge of the conductive layer 23 covering the leftmost conductive fiber 21 can be determined by taking into account the thickness of the conductive layer 23 covering the other conductive fibers 21.

[0060] Draw a first straight line L1 that is tangential to the outer edge of the determined conductive layer 23 and parallel to the central axis AX. The point of tangency between the first straight line L1 and the conductive layer 23 is the left bottom P1 of the composite member 20. The left bottom P1 is generally located on the surface 10a of the substrate 10. The first straight line L1 defines the boundary (imaginary boundary, the same applies hereinafter) between the dielectric layer 22 and the dielectric portion 22a, and the boundary between the conductive layer 23 and the conductive portion 23a. With respect to the first straight line L1, the dielectric layer 22 is located on the right, and the dielectric portion 22a is located on the left. With respect to the first straight line L1, the conductive layer 23 is located on the right, and the conductive portion 23a is located on the left. The dielectric portion 22a and the conductive portion 23a are not included in the composite member 20.

[0061] Similarly, the rightmost conductive fiber 21 of the first member, located closest to the substrate 10 and on the rightmost side, is identified. The dielectric layer 22 and the conductive layer 23 covering the rightmost conductive fiber 21 are also determined. A second straight line L2 is drawn, tangent to the outer edge of the conductive layer 23 and parallel to the central axis AX. The point of tangency between the second straight line L2 and the conductive layer 23 is the right bottom P2 of the composite member 20. The right bottom P2 generally lies on the surface 10a of the substrate 10. The second straight line L2 defines the boundary between the dielectric layer 22 and the dielectric portion 22a, and the boundary between the conductive layer 23 and the conductive portion 23a. With respect to the second straight line L2, the dielectric layer 22 is located to the left, and the dielectric portion 22a is located to the right. With respect to the second straight line L2, the conductive layer 23 is located to the left, and the conductive portion 23a is located to the right. The dielectric portion 22a and the conductive portion 23a are not included in the composite member 20.

[0062] Similarly, the conductive fibers 21 that are on the side opposite to the substrate 10 of the first member and are located at the leftmost and rightmost positions are respectively determined, and the dielectric layers 22 and the conductor layers 23 that cover these conductive fibers 21 are determined. A third straight line L3 that is tangent to the outer edge of the conductor layer 23 covering the conductive fiber 21 at the left top and is parallel to the central axis AX is drawn. The tangent point of the third straight line L3 and the above-mentioned conductor layer 23 is the left top P3 of the composite member 20. A fourth straight line L4 that is tangent to the outer edge of the conductor layer 23 covering the conductive fiber 21 at the right top and is parallel to the central axis AX is drawn. The tangent point of the fourth straight line L4 and the above-mentioned conductor layer 23 is the right top P4 of the composite member 20.

[0063] Similarly in the case where the conductor layer 23 contacts the conductive member, the outer edge of the conductor layer 23 can be determined considering the thickness of the conductor layer 23 covering other conductive fibers 21. The conductive member is not included in the composite member 20.

[0064] The composite member 20 is composed of a plurality of conductive fibers 21, dielectric layers 22, conductor layers 23, and a space 24 existing in the region sandwiched by the first straight line L1 and the second straight line L2. The quadrilateral obtained by connecting the left bottom P1, the right bottom P2, the right top P4, and the left top P3 represents the outer shape of the composite member 20.

[0065] <Widths W1, W2>

[0066] In the cross-section in the thickness direction, the composite member 20 of the present embodiment is a trapezoid in which the upper side (upper side s1) is shorter than the lower side (lower side s2). That is, in the XZ cross-section, the composite member 20 has a width W1 on the side opposite to the substrate 10 and a width W2 on the substrate 10 side, and the width W1 is smaller than the width W (W1 < W2). Further, in the composite member 20 in the XZ cross-section, the angle θ1 formed by the lower side s2 and the left side (left side s3) and the angle θ2 formed by the lower side s2 and the right side (right side s4) are both less than 90 degrees.

[0067] As Figure 7A shown, the XZ cross-section of the composite member 120 in the conventional capacitor 100 is usually a rectangle in which the upper side s101 and the lower side s102 are of substantially the same length (W2) and the four corners are approximately 90 degrees each. If the capacitor 100 or its precursor is heated and cooled, the composite member 120 will tend to shrink significantly. However, since the lower side s102 is joined to the substrate 110, it cannot shrink in the X direction, and the shrinkage stress F acts in the Z direction. In addition, the upper side s101 can shrink without limit, so its shrinkage amount is likely to become large. If the shrinkage amount of the upper side s101 becomes large, the end of the lower side s102 is further stretched in the Z direction. As a result, as Figure 7BAs shown, the composite member 120 is peeled off from the substrate 110.

[0068] In the present embodiment, the upper side s1 is shorter than the lower side s2 (W1 < W2), so the amount of shrinkage of the upper side s1 is smaller than that of the lower side s2. Further, the left side s3 and the right side s4 of the composite member 20 are inclined with respect to the Z direction, so the shrinkage stress F applied to the lower side s2 is dispersed in the Z direction and the X direction. Thus, the stress for stretching the end portion of the lower side s2 in the Z direction becomes smaller than the conventional stress. Therefore, peeling of the composite member 20 from the substrate 10 can be suppressed.

[0069] In this way, according to the present disclosure, it is possible to suppress a decrease in the performance of the capacitor 1 caused by unnecessarily thickening the dielectric layer 22 of the entire composite member 20, and it is possible to increase the strength of the composite member 20 to suppress peeling.

[0070] The precursor of the capacitor 1, for example, refers to an object including the substrate 10, a plurality of conductive fibers 21, and the dielectric layer 22 before forming the conductive layer 23.

[0071] Heating and cooling of the capacitor 1 or its precursor may occur, for example, in the drying process, firing process, and film forming process of the dielectric layer 22, in the manufacturing process and use of the capacitor 1. Hereinafter, the stress applied in the X direction toward the center of the composite member 20 is referred to as tensile stress.

[0072] The relationship of W1 < W2 only needs to be satisfied in a cross section in one thickness direction.

[0073] The relationship of W1 < W2 can also be satisfied in cross sections in a plurality of different thickness directions. The relationship of W1 < W2 can also be satisfied in cross sections in three or more different thickness directions. The relationship of W1 < W2 can also be satisfied in cross sections in all arbitrary thickness directions. In this case, the effect of alleviating the tensile stress can be further improved.

[0074] The cross sections in a plurality of different thickness directions are XZ cross sections and can be YZ cross sections. The cross sections in a plurality of different thickness directions can be obtained by rotating the XZ cross section less than 360 degrees around the central axis AX.

[0075] · Calculation method of the width W1 and the width W2

[0076] In the XZ cross-section, the width W1 is the distance in the X direction between a straight line that includes one end (the upper edge) of the upper side of the composite member 20 and extends in the Z direction and a straight line that includes the other end and extends in the Z direction. In the XZ cross-section, the width W2 is the distance in the X direction between a straight line that includes one end (the lower edge) of the lower side of the composite member 20 and extends in the Z direction and a straight line that includes the other end and extends in the Z direction.

[0077] Specifically, as Figure 1 shown, the width W2 is the distance in the X direction between the first straight line L1 and the second straight line L2. The width W1 is the distance in the X direction between the third straight line L3 and the fourth straight line L4.

[0078] The widths W1 and W2 in multiple cross-sections are calculated as follows. First, for the composite member 20 where the XZ cross-section (No. 1) is exposed, another cross-section in the other thickness direction (for example, the YZ cross-section. No. 2) is further exposed by polishing. The cross-section (No. 2) represents a part (half) of the cross-section in the thickness direction of the composite member 20. By observing the obtained cross-section (No. 2) with SEM, the bottom P11 and P21, and the top P31 and P41 of the composite member 20 that become half are determined (illustrations of P11 to P41 are omitted). Then, the distance W in the X direction between a straight line that includes the left bottom P11 and extends in the Z direction and a straight line that includes the right bottom P21 and extends in the Z direction is obtained

[0080] , , 11 , 21 and the distance W in the X direction between a straight line that includes the left top P31 and extends in the Z direction and a straight line that includes the right top P41 and extends in the Z direction 11 .

[0079] As described above, the cross-section (No. 2) represents half of the cross-section in the thickness direction of the composite member 20, but it is okay to consider that the remaining half also has the same structure. Therefore, by doubling the distance W 11 , the width W1 can be obtained. Similarly, by doubling the distance W 21 , the width W2 can be obtained. Repeat such operations and calculations for multiple cross-sections in different thickness directions as needed, whereby the widths W1 and W2 in multiple cross-sections in the thickness direction can be obtained respectively. For one cross-section in the thickness direction, one width W1 and one width W2 can be obtained respectively. It is also possible to satisfy the relationship of W1 < W2 in multiple cross-sections in the thickness direction. <00,004,04>The upper side s1 is a line segment connecting the left top P3 and the right top P4. The lower side s2 is a line segment connecting the left bottom P1 and the right bottom P2. The left side s3 is a line segment connecting the left bottom P1 and the left top P3. The right side s4 is a line segment connecting the right bottom P2 and the right top P4. The upper side s1, the lower side s2, the left side s3, and the right side s4 are the outer edges of the composite member 20. In this embodiment, the outer shape of the composite member 20 formed by connecting the above four line segments is roughly trapezoidal.

[0081] <Angles θ1, θ2>

[0082] In a cross-section taken along the thickness direction, both the internal angles θ1 and θ2 are less than 90 degrees. θ1 is the internal angle formed by the bottom side s2 and the left side s3. θ2 is the internal angle formed by the bottom side s2 and the right side s4. Angles θ1 and θ2 can be measured as follows using the SEM image of the XZ cross-section (No. 1) used to calculate widths W1 and W2. In this SEM image, bottoms P1 and P2 and tops P3 and P4 are already defined. The bottom side s2 is obtained by connecting the left bottom side P1 and the right bottom side P2. The left side s3 is obtained by connecting the left bottom side P1 and the left top P3. The right side s4 is obtained by connecting the right bottom side P2 and the right top P4. Angle θ1 is determined by measuring the internal angle formed by the bottom side s2 and the left side s3. Angle θ2 is determined by measuring the internal angle formed by the bottom side s2 and the right side s4.

[0083] The relationship θ1 and θ2 < 90 degrees can be satisfied in multiple different cross-sections in the thickness direction. The relationship θ1 and θ2 < 90 degrees can also be satisfied in three or more different cross-sections in the thickness direction. The relationship θ1 and θ2 < 90 degrees can also be satisfied in any cross-section in all thickness directions. The angles θ1 and θ2 in multiple cross-sections in the thickness direction can be measured and estimated using the YZ cross-section (No. 2) described above, for example.

[0084] <Central Region R1, Peripheral Region R2>

[0085] In a cross-section taken in the thickness direction, the composite member 20 has a central region R1 corresponding to width W1 and peripheral regions R2 on one side and the other side sandwiching central region R1. The "central region R1 corresponding to width W1" is the region sandwiched in the XZ cross-section by a straight line extending in the Z direction and including one end of the upper side (upper side) of the composite member 20, and a straight line extending in the Z direction and including the other end (the distance in the X direction between these two ends being width W1).

[0086] Specifically, if Figure 1As shown, the central region R1 is the region of the composite member 20 sandwiched between the third straight line L3 and the fourth straight line L4. The peripheral region R2 is the region of the composite member 20 outside the central region R1. Two peripheral regions R2 are arranged at both ends in the X direction, sandwiching the central region R1. The peripheral regions R2 on one side and the other side face each other across the central region R1.

[0087] In the central region R1, the conductive fibers 21 have a maximum height H max . Maximum height H max , width W1 and width W2 can also satisfy the following relationship:

[0088] W2-W1≥1.6×H max .

[0089] (W2-W1) represents the combined width of the outer peripheral regions R2 on both sides. The larger (W2-W1) is, the greater the inclination of the left side s3 and / or right side s4 relative to the central axis AX. From the perspective of alleviating tensile stress, a larger (W2-W1) is preferred.

[0090] In particular, if (W2-W1) is the maximum height H of the conductive fiber 21 max If the height H of the conductive fiber 21 is greater than 1.6 times, the tensile stress relief effect can be further exerted. (W2-W1) can also be the maximum height H of the conductive fiber 21. max More than 2.0 times of .

[0091] On the other hand, considering the outer diameter of the capacitor 1, (W2-W1) is preferably not too large. Furthermore, from the viewpoint of capacitance, it is preferable to ensure a certain maximum height H of the conductive fibers 21. max Therefore, (W2-W1) can be the maximum height H of the conductive fiber 21. max It can be less than 50 times, or less than 10 times.

[0092] W2-W1≥1.6×H max The relationship only needs to be satisfied in a cross section in one thickness direction. The above relationship can be satisfied in cross sections in multiple different thickness directions, or in cross sections in three or more different thickness directions, or in any cross sections in all thickness directions. In this case, the effect of alleviating tensile stress can be further enhanced.

[0093] The larger the contact area between the composite member 20 (particularly, the dielectric layer 22) and the substrate 10, the greater the tensile stress applied to the composite member 20, making it easier to peel. However, according to the present disclosure, when the contact area between the composite member 20 and the substrate 10 is large, for example, when the length (width W2) of the lower side is greater than the maximum height H of the conductive fiber 21, the composite member 20 may be subjected to a plurality of tensile stresses.max In the case of large (W2>H max ), it is also possible to suppress the peeling of the composite component 20.

[0094] The width W2 can be the maximum height H max Width W2 can be more than 4 times of the maximum height H, or more than 10 times. max If the width W2 is less than the maximum height H max If the capacitance is 4 times that of the composite member 20, the volume of the composite member 20 becomes too small, and thus the volume capacitance density of the capacitor 1 also becomes small.

[0095] Maximum height H max Decision method

[0096] Maximum height H max The maximum height H can be determined based on the SEM image of the XZ cross section (No. 1). The end of the conductive fiber 21 that is farthest from the surface 10a of the substrate 10 in the Z direction is determined, and the distance between the end and the surface 10a in the Z direction is the maximum height H. max .

[0097] <Width W3, W4>

[0098] From the perspective of alleviating tensile stress, it is preferable that the angles θ1 and θ2 are small, that is, the inclination of both the left side s3 and the right side s4 relative to the central axis AX is large. The greater the inclination of the left side s3 and the right side s4, the larger the width W3 of the composite member 20 in the peripheral region R2 on one side and the width W4 of the composite member 20 in the peripheral region R2 on the other side. The widths W3 and W4 may also satisfy the following relationship, for example:

[0099] W3≥0.8×H max , and W4 ≥ 0.8 × H max .

[0100] The width W3 is the length of the composite member 20 in the left outer peripheral region R2 in the X direction. The width W4 is the length of the composite member 20 in the right outer peripheral region R2 in the X direction.

[0101] W3 and W4 can both be the maximum height H of the conductive fiber 21 max From the perspective of the volume capacitance density of the capacitor 1, both W3 and W4 can be the maximum height H of the conductive fiber 21. max W3 and W4 may be the same or different.

[0102] W3 and W4 and maximum height H max The above relationship only needs to be satisfied in a cross section in one thickness direction. The above relationship can be satisfied in cross sections in different thickness directions, or in cross sections in three or more different thickness directions, or in any cross sections in all thickness directions.

[0103] Calculation method of width W3 and width W4

[0104] Widths W3 and W4 can be determined using the SEM image of the XZ cross section (No. 1) described above. Width W3 is the distance in the X direction between the first straight line L1 and the third straight line L3. Width W4 is the distance in the X direction between the second straight line L2 and the fourth straight line L4.

[0105] In this embodiment, if Figure 3A As shown, the conductive fibers 21 are inclined relative to the Z direction or bent in the X direction in the peripheral region R2 . Therefore, in the peripheral region R2 (typically the upper side thereof), at least two conductive fibers 21 can contact each other via the dielectric layer 22 or not.

[0106] In this embodiment, if the conductive fibers 21 have high strength (specifically, if the conductive fibers 21 have a higher strength than the dielectric layer 22), the plurality of conductive fibers 21 can support each other in the outer peripheral region R2 of the composite member 20, making the composite member 20 less susceptible to deformation by external forces. In other words, the lower side s2 is less likely to shrink further in the Z direction, further suppressing separation of the composite member 20 from the substrate 10. Furthermore, because the conductive fibers 21 can function as a core material, the occurrence of cracks in the composite member 20 caused by tensile stress can be suppressed.

[0107] The strength of the conductive fibers 21 is, for example, 5 MPa / (nm) 2 Above and 150GPa / (nm) 2 As a result, it is expected that the conductive fiber 21 will function as the core material of the composite member 20. The strength of the conductive fiber 21 can be 10 MPa / (nm) 2 Above, it can also be 10GPa / (nm) 2 The strength of the conductive fiber 21 can also be 100GPa / (nm) 2 the following.

[0108] As a 5Mpa / (nm) 2 Above and 150GPa / (nm) 2The conductive fibers 21 having the strength described below may be at least one selected from the group consisting of carbon nanotubes, metal nanowires, and conductive polymer wires.

[0109] <Area occupancy ratio S 11 、S 21 >

[0110] As described above, the conductive fibers 21 of this embodiment are inclined relative to the Z direction or bent in the X direction in the peripheral region R2 of the XZ cross section. Therefore, the space 24 in the peripheral region R2 is smaller than the space 24 in the central region R1. In other words, the total area occupied by the conductive fibers 21 and the dielectric layer 22 in the peripheral region R2 is 1 / 2. 21 The total area occupancy ratio S of the conductive fibers 21 and the dielectric layer 22 in the central region R1 is 11 High part.

[0111] If the space 24 is small, it becomes less susceptible to deformation due to external forces. Therefore, shrinkage of the lower side s2 in the Z direction can be suppressed. In particular, since deformation of the peripheral region R2, which serves as the starting point for peeling, is suppressed, peeling of the composite member 20 from the substrate 10 can be further suppressed.

[0112] Area occupancy ratio S 11 The area occupancy ratio S is the total area occupancy ratio of the conductive fiber 21 and the dielectric layer 22 in any part of the central region R1 of the cross section in any thickness direction. 21 = is the total area occupancy ratio of the conductive fibers 21 and the dielectric layer 22 in any portion of the outer peripheral region R2 of the same cross section as above. Even if the area occupancy ratio S is 21 Specific area occupancy ratio S 11 Even if the area of ​​the outer peripheral region R2 in the cross section is low, the area of ​​the outer peripheral region R2 in the cross section is 21 Specific area occupancy ratio S 11 Just high.

[0113] Area occupancy ratio S 11 、S 21 The above relationship only needs to be satisfied in a portion of the cross section in any thickness direction. Alternatively, in any cross section in the thickness direction, the outer peripheral region R2 on one side and the other side both contain the area occupancy ratio S 21 Specific area occupancy ratio S 11As a result, the relatively deformable central region R1 is reinforced from both sides, thereby suppressing shrinkage of the entire composite member 20 in the width direction (e.g., X direction). This further facilitates suppressing separation of the composite member 20 from the substrate 10.

[0114] Alternatively, in a plurality of different cross sections in the thickness direction, the outer peripheral region R2 may include an area occupancy ratio S 21 Specific area occupancy ratio S 11 In this case, the shrinkage in the width direction of the composite member 20 can be further suppressed. The so-called "including the high portion in the cross section in multiple thickness directions" means that the outer peripheral region R2 in at least two different cross sections in the thickness direction includes the area occupancy ratio S 21 Specific area occupancy ratio S 11 It is not required that the outer peripheral region R2 includes the area occupancy ratio S in all cross sections in the thickness direction. 21 Specific area occupancy ratio S 11 High part.

[0115] Alternatively, in at least two cross sections in different thickness directions, the outer peripheral regions R2 on one side and the outer peripheral regions R2 on the other side may both include the area occupancy ratio S 21 Specific area occupancy ratio S 11 High part.

[0116] The so-called "area occupancy ratio S 21 High", which means the area occupies a proportion of S 11 With S 21 The difference is more than 5%. 21 / S 11 ≥1.05. S 21 / S 11 It may be 1.2 or more, 2 or more, or 5 or more.

[0117] Area occupancy ratio S 11 It can be 0.1 or more, 0.15 or more, or 0.20 or more. 11 It may be 0.5 or less, 0.4 or less, or 0.35 or less.

[0118] Area occupancy ratio S 21 It can be 0.2 or more, 0.25 or more, or 0.30 or more. 21 It may be 0.7 or less, 0.5 or less, or 0.45 or less.

[0119] Area occupancy ratio S 11 、S21 Calculation method

[0120] Area occupancy ratio S 11 、S 21 The calculation can be performed as follows using the SEM image of the XZ cross-section (No. 1) described above. The SEM image clearly identifies the composite member 20, the peripheral region R2, and the central region R1. Within the composite member 20, the conductive fibers 21, the dielectric layer 22, the conductive layer 23, and the filling resin (space 24) are clearly visible.

[0121] Divide the area of ​​the conductive fibers 21 and dielectric layer 22 in the right peripheral region R2 by the area of ​​the peripheral region R2 (i.e., the total area of ​​the conductive fibers 21, dielectric layer 22, conductor layer 23, and filling resin). This allows the area occupancy ratio S of the right peripheral region R2 to be calculated. 21 Similarly, calculate the area occupancy ratio S of the outer peripheral region R2 on the left side 21 Similarly, calculate the area occupancy ratio S of the central region R1 11 .

[0122] The observation field can be large enough to observe only a portion of the central region R1. Similarly, the observation field can be large enough to observe only a portion of the peripheral region R2. For example, the observation field can be approximately 1 μm x 1 μm. This makes it easier to distinguish between the conductive fibers 21, the dielectric layer 22, the conductive layer 23, and the filling resin.

[0123] Area occupancy ratio S in multiple cross sections in the thickness direction 11 、S 21 The calculation can be performed using the same concept as that used to calculate the widths W1 and W2 in multiple thickness-direction cross sections. In other words, it can be assumed that a portion of the outer peripheral region R2 appearing in the thickness-direction cross section has the same structure as the remaining outer peripheral region R2, and that a portion of the central region R1 appearing in the thickness-direction cross section has the same structure as the remaining central region R1.

[0124] <Area occupancy ratio S 12 、S 22 >

[0125] The outer peripheral region R2 includes the conductive fibers 21, the dielectric layer 22, and the conductor layer 23, and the total area occupied by the conductive fibers 21 is S. 22 The total area occupancy ratio S of the conductive fibers 21, the dielectric layer 22, and the conductor layer 23 in the central region R1 is greater than 12 The high part. That is, satisfying S 22 / S12 ≥1.05. S 22 / S 12 It may be 1.2 or more, 2 or more, or 5 or more.

[0126] The above situation can also be said to be that the space 24 is small, so the composite member 20 becomes less likely to deform due to external force. Therefore, as described above, the area occupancy ratio S of the outer peripheral region R2 can be obtained. 21 Specific area occupancy ratio S 11 The same effect occurs in the case of the higher portion.

[0127] About the area occupancy ratio S 11 The recorded items can be read as area occupancy ratio S 12 About the area occupancy ratio S 21 The recorded items can be read as area occupancy ratio S 22 To apply.

[0128] Area occupancy ratio S 12 、S 22 Calculation method

[0129] About the area occupancy ratio S 12 、S 22 In addition to dividing the total area of ​​the conductive fiber 21, the dielectric layer 22, and the conductor layer 23 by the area of ​​the central region R1 or the peripheral region R2, the area occupation ratio S can be calculated. 11 、S 21 Calculate similarly.

[0130] <Area occupancy ratio S 13 、S 23 >

[0131] In the cross section in the thickness direction, the conductive fibers 21 in the peripheral region R2 have a width direction component. Figure 3B As shown, in the XY cross section, the cross-sectional area of ​​the coated conductive fibers 21 in the peripheral region R2 is larger than that in the central region R1. That is, in the XY cross section, similarly to the XZ cross section, the area occupied by the conductive fibers 21, the dielectric layer 22, and the conductor layer 23 in the peripheral region R2 is greater than that in the central region R1. 23 The total area occupancy ratio S of the conductive fibers 21, the dielectric layer 22, and the conductor layer 23 in the central region R1 is greater than 13 The high part. That is, satisfying S 23 / S 13 ≥1.05. S 23 / S 13 It may be 1.2 or more, 2 or more, or 5 or more.

[0132] Area occupancy ratio S 13 It can be 0.08 or more, 0.10 or more, or 0.15 or more. 13 It may be 0.50 or less, 0.40 or less, or even 0.30 or less.

[0133] Area occupancy ratio S 23 It can be 0.15 or more, 0.20 or more, or 0.25 or more. 23 It may be 0.70 or less, 0.50 or less, or even 0.40 or less.

[0134] Figure 3B Corresponding to Figure 3A The height H of the II section from the surface 10a of the substrate 10 is, for example, the maximum height H max The closer the II cross section is to the substrate 10, the larger the cross-sectional area of ​​the coated conductive fiber 21 in the peripheral region R2 can be. A single conductive fiber 21 can also be arranged to span the peripheral region R2 and the central region R1.

[0135] Area occupancy ratio S 13 、S 23 Calculation method

[0136] Area occupancy ratio S 13 、S 23 The calculation can be performed using the sample used to determine the central region R1 and the peripheral region R2 and its thickness direction cross section (XZ cross section). In the XZ cross section, the central region R1 and the peripheral region R2 have already been determined. First, the height H of the sample from the surface 10a of the substrate 10 is polished to the maximum height H. max The XY cross section at the first position is exposed at a level of less than 20% (typically less than 10%) of the dielectric portion 22a or the conductive portion 23a. In this case, the XY cross section can be obtained by cutting the dielectric portion 22a or the conductive portion 23a, or by not cutting the dielectric portion 22a or the conductive portion 23a. The obtained XY cross section shows a portion (which may be less than half) of the XY cross section of the composite member 20, but the remaining portion of the XY cross section may have the same structure as the obtained portion of the XY cross section.

[0137] The outer shape of the composite member 20 as viewed from the Z direction and the outer shape in the XY cross section may be, for example, a circle, an ellipse, or a polygon.

[0138] Next, the central region R1 and the outer peripheral region R2 determined using the XZ cross section are projected onto the obtained XY cross section, thereby determining the central region R1 and the outer peripheral region R2 in the XY cross section.

[0139] Next, the composite member 20 is divided into the conductive fibers 21, the dielectric layer 22, the conductive layer 23, and the filling resin (space 24) by image processing (EDX analysis is also used as needed, the same applies hereinafter), and the area occupancy ratio S is calculated. 11 、S 21 Similarly, calculate the area occupancy ratio S 13 、S 23 .

[0140] <Other>

[0141] Whether the SEM image of the cross section (No. 1) used above is a cross section in the thickness direction of the substrate 10 can be determined by observing the thickness and width of the substrate 10. If the thickness of the substrate 10 measured from the SEM image is greater than the original thickness of the substrate, the cross section can be determined not to be a cross section in the thickness direction. "Greater than the original thickness of the substrate" means that the thickness of the substrate 10 in the SEM image is 5% or more greater than the original thickness of the substrate 10. Furthermore, if the width of the substrate 10 measured from the SEM image is smaller than the original width of the substrate (the distance between the two intersection points of a straight line passing through the center of the substrate and the two ends of the substrate), the cross section can also be determined not to be a cross section in the thickness direction. "Smaller than the original width of the substrate" means that the width of the substrate 10 in the SEM image is 5% or more smaller than the original width of the substrate 10.

[0142] From the perspective of being able to confirm that the aforementioned SEM image is an SEM image of a cross section in the thickness direction, the field of view of the SEM observation is preferably wide enough to allow the front surface 10a, back surface 10b, and both ends of the substrate 10 to be confirmed (e.g., 5 μm x 5 μm or more). On the other hand, the field of view used for identifying and / or distinguishing components of the composite member 20 or calculating area occupancy ratios may be narrower (e.g., approximately 1 μm x 1 μm).

[0143] Whether the XY cross-sectional SEM image used above is a cross-sectional SEM image parallel to the in-plane direction of substrate 10 can be determined by looking at the cross-sectional shape of the conductive fibers 21. At the first position described above, the majority of the conductive fibers 21 extend in the Z direction, and their cross-sectional shape is generally circular. Therefore, if the cross-sectional shape of the conductive fibers 21 is flat, it can be determined that the cross-sectional shape is not an XY cross-sectional shape. "The cross-sectional shape of the conductive fibers 21 is flat" means that the ratio of the major diameter to the minor diameter (major diameter / minor diameter) of the cross-sectional shape of the conductive fibers 21 is 1.41 or greater. The major diameter is the longest diameter among the diameters passing through the center of the cross-sectional shape of the conductive fibers 21. The minor diameter is the shortest diameter among the diameters passing through the center of the cross-sectional shape of the conductive fibers 21. The center of the cross-sectional shape of the conductive fibers 21 is the center of the smallest circle that contains the cross-sectional shape of the conductive fibers 21.

[0144] Hereinafter, each component will be described.

[0145] <<Conductive Fiber>>

[0146] In the present disclosure, the conductive fibers 21 are not particularly limited as long as their longitudinal dimension (length) is (preferably significantly) larger than the maximum dimension of a cross section perpendicular to the longitudinal direction and they are roughly elongated linear.

[0147] From the perspective of increasing the capacitance density per unit area, the average length of the conductive fibers 21 can be longer. The average length of the conductive fibers 21 can be, for example, several μm or more, 20 μm or more, 50 μm or more, 100 μm or more, 500 μm or more, 750 μm or more, 1000 μm or more, or 2000 μm or more. The upper limit of the average length of the conductive fibers 21 can be appropriately selected. For example, the length of the conductive fibers 21 can be 10 mm or less, 5 mm or less, or 3 mm or less. In one embodiment, the average length of the conductive fibers 21 is 50 μm or more. The average length of the conductive fibers 21 can also be 50 μm or more and 3 mm or less.

[0148] The average length of the conductive fibers 21 can be calculated from the SEM image of the XZ cross section (No. 1) described above. The average length of the conductive fibers 21 is the average value of the lengths of at least five conductive fibers 21 .

[0149] In order to increase the capacitance density per unit area, the average number density of the conductive fibers 21 (also referred to as the "average root number density") can also be larger. For example, the average number density of the conductive fibers 21 can be 10 8 root / cm 2 The average number density of the conductive fibers 21 may be, for example, 10 13 root / cm 2 the following.

[0150] In particular, the average length of the conductive fibers 21 may be greater than 50 μm, and the average number density thereof may be 10 8 root / cm 2 As a result, in the outer peripheral region R2 , the inclined or curved conductive fibers 21 are more likely to come into contact with other conductive fibers 21 , and the strength of the composite member 20 is more likely to be improved.

[0151] Calculation method of average number density

[0152] The average number density of the conductive fibers 21 can be used to calculate the area occupancy ratio S 13 、S 23 The XY cross-sectional SEM image used for this calculation is as follows. In this SEM image, determine the outer edge of the composite member 20 in the same manner as described above. Count the number of conductive fibers 21 present in a portion of the composite member 20 determined (e.g., a 5 μm x 5 μm area) to determine the number of conductive fibers 21 per unit area (number density). Repeat this process to obtain number densities for five or more viewing fields, and take the average value of these values ​​as the average number density N of the composite member 20.

[0153] The maximum cross-sectional dimension of the conductive fibers 21 may be, for example, 0.1 nm or greater, 1 nm or greater, or 10 nm or greater. The maximum cross-sectional dimension of the conductive fibers 21 may be, for example, 1 nm or greater, or 10 nm or greater. The maximum cross-sectional dimension of the conductive fibers 21 may be less than 1000 nm, 800 nm or less, or 600 nm or less.

[0154] The maximum cross-sectional dimension of the conductive fiber 21 can be calculated based on the area occupancy ratio S 13 、S 23 The maximum cross-sectional dimension of the conductive fiber 21 is calculated based on the XY cross-sectional SEM image used when calculating the maximum cross-sectional dimension of the conductive fiber 21. The maximum cross-sectional dimension of the conductive fiber 21 is the average value of the maximum cross-sectional dimensions of at least five conductive fibers 21.

[0155] The conductive fibers 21 may also be conductive nanofibers (fibers having a maximum cross-sectional dimension on the nanometer scale (1 nm or more and less than 1000 nm)). For example, the conductive nanofibers may be conductive nanotubes (hollow, preferably cylindrical) or conductive nanorods (solid, preferably cylindrical). Nanorods that are conductive (including semiconductive) are also called nanowires.

[0156] As the conductive nanofiber that can be used in the present invention, for example, carbon nanofiber can be cited. As the conductive nanotube that can be used in the present invention, for example, metal nanotubes, organic conductive nanotubes, and inorganic conductive nanotubes can be cited. Typically, the conductive nanotubes can be carbon nanotubes or titanium dioxide carbon nanotubes. As the conductive nanorods (nanowires) that can be used in the present invention, for example, silicon nanowires, metal nanowires (especially silver nanowires), and conductive polymer wires can be cited. Preferably, the conductive nanorods have a conductivity of 5 MPa / (nm). 2 Above and 150GPa / (nm) 2 The conductive fiber 21 has the following strength.

[0157] In particular, the conductive fibers 21 may be carbon nanotubes, which have electrical and thermal conductivity.

[0158] The chirality of the carbon nanotubes is not particularly limited and may be either semiconductor or metallic, or a mixture thereof may be used. From the viewpoint of reducing the resistance value, a higher ratio of metallic carbon nanotubes is preferred.

[0159] The number of carbon nanotube layers is not particularly limited, and may be one layer of SWCNT (single-walled carbon nanotube) or two or more layers of MWCNT (multi-walled carbon nanotube).

[0160] The plurality of conductive fibers 21 may also be so-called vertically aligned carbon nanotubes (VACNTs). VACNTs have a large specific surface area. Furthermore, as will be described later, VACNTs can be grown in a vertically aligned state on the substrate 10 and thus have the advantage of being able to easily control the maximum height H. max , width W3 and width W4, etc.

[0161] <<Substrate>>

[0162] The substrate 10 has two main surfaces (a front surface 10 a and a back surface 10 b ) facing each other, and may be in the form of a plate (substrate), foil, film, block, or the like.

[0163] The material constituting substrate 10 can be selected appropriately, as long as it is conductive and can electrically connect to the plurality of conductive fibers 21. Examples include semiconductor materials such as silicon, conductive materials such as metals (copper, aluminum, nickel), insulating (or relatively low-conductive) materials such as ceramics (silicon oxide), and resins. Substrate 10 can consist of a single material, a mixture of two or more materials, or a composite of two or more materials. Metal is preferred for substrate 10 because it can easily be used as a contact point with the outside, reduces resistance, and can withstand high temperatures.

[0164] The thickness of substrate 10 is not particularly limited and may vary depending on the application of capacitor 1. Substrate 10 may also be provided with electrodes for external contact and wiring for ensuring electrical conductivity. The outer shape of substrate 10 as viewed from the Z direction may be, for example, circular, elliptical, or polygonal.

[0165] <<Dielectric layer>>

[0166] The dielectric material constituting the dielectric layer 22 can be appropriately selected. Examples include silicon dioxide, aluminum oxide, silicon nitride, tantalum oxide, hafnium oxide, barium titanate, and lead zirconate titanate. These materials may be used alone or in combination (e.g., in a stacked form).

[0167] The thickness of the dielectric layer 22 may be 10 nm or more, or 15 nm or more. By setting the thickness of the dielectric layer to 10 nm or more, the insulation can be improved and the leakage current can be reduced. The thickness of the dielectric layer 22 may be 1 μm or less, or 100 nm or less, or 70 nm or less. By setting the thickness of the dielectric layer 22 to 1 μm or less, a greater electrostatic capacitance can be obtained. In one embodiment, the thickness of the dielectric layer 22 is 10 nm or more and 1 μm or less.

[0168] The thickness of the dielectric layer 22 can be calculated based on the area occupancy ratio S 13 、S 23 The thickness of the dielectric layer 22 is calculated based on the XY cross-sectional SEM image used when the dielectric layer 22 is formed. The thickness of the dielectric layer 22 is the average value of the thickness of the dielectric layer 22 covering at least five conductive fibers 21.

[0169] Where present, the material constituting the dielectric portion 22 a and the thickness of the dielectric portion 22 a may be the same as those of the dielectric layer 22 .

[0170] <<Conductor Layer>>

[0171] Examples of conductive materials constituting the conductor layer 23 include metals and conductive polymers (polymer materials having conductivity and / or imparted conductivity, also known as organic conductive materials). These materials may be used alone or in combination of two or more. The conductor layer 23 may also be a laminate of multiple layers made of different conductive materials.

[0172] Examples of metals include silver, gold, copper, platinum, aluminum, or alloys containing at least two of these. Examples of conductive polymers include PEDOT (polyethylene dioxythiophene), PPy (polypyrrole), and PANI (polyaniline). These can be appropriately doped with organic sulfonic acid compounds such as polyvinyl sulfonic acid, polystyrene sulfonic acid, polyallyl sulfonic acid, polyacrylic sulfonic acid, polymethacrylic sulfonic acid, poly-2-acrylamide-2-methylpropane sulfonic acid, and polyisoprene sulfonic acid.

[0173] The thickness of the conductor layer 23 can be 3 nm or greater, or 10 nm or greater. By setting the thickness of the conductor layer 23 to 3 nm or greater, the resistance of the conductor layer 23 itself can be reduced. The thickness of the conductor layer 23 can be 500 nm or less, or 100 nm or less. In one embodiment, the thickness of the conductor layer 23 is 3 nm or greater and 500 nm or less.

[0174] The thickness of the conductor layer 23 can be calculated by calculating the area occupation ratio S 13 、S 23 The thickness of the conductor layer 23 is calculated based on the XY cross-sectional SEM image used when the conductive fibers 21 are coated. The thickness of the conductor layer 23 is the average value of the thickness of the conductor layer 23 covering at least five conductive fibers 21.

[0175] When present, the material constituting the conductor portion 23 a and the thickness of the conductor portion 23 a may be the same as those of the conductor layer 23 .

[0176] <<Space>>

[0177] Spaces 24 are formed between the coated conductive fibers 21. In the thickness-direction cross-section and the XY cross-section, the spaces 24 in the peripheral region R2 are smaller than those in the central region R1. Reducing the spaces 24 makes it easier to suppress deformation of the composite member 20, making it less likely to peel from the substrate 10.

[0178] <<Conductive member>>

[0179] The capacitor 1 may include a conductive member in contact with the conductive layer 23. The conductive member is electrically connected to the conductive layer 23 and serves to lead the electrodes to the outside of the capacitor 1.

[0180] The conductive member does not contact the conductive fibers 21, the dielectric layer 22, or the substrate 10. The boundary between the conductive member and the conductive layer 23 can be confirmed using a SEM image. Alternatively, the boundary between the conductive member and the conductive layer 23 can be determined by elemental analysis using EDX. Furthermore, the boundary between the conductive member and the conductive layer 23 can also be determined based on the thickness of the conductive layer 23 in the portion not in contact with the conductive member.

[0181] The conductive member is formed, for example, by applying or supplying carbon paste or a conductive polymer material to a predetermined surface or portion. Carbon paste and conductive polymer materials generally have relatively high viscosities, making them less likely to penetrate into the spaces 24 and reach deep within the spaces 24 (e.g., the surface 10a of the substrate 10). Consequently, spaces 24 are maintained between the coated conductive fibers 21.

[0182] (Manufacturing Method)

[0183] The capacitor 1 of this embodiment can be obtained by, for example, a manufacturing method including the following steps:

[0184] (a) Preparing a forest composed of a plurality of conductive fibers 21 arranged on the surface 10 a of the substrate 10 and directly bonded to the substrate 10 at one end;

[0185] (b) tilting the conductive fibers 21 on the outside of the forest toward the center;

[0186] (c) forming the dielectric layer 22 (and the dielectric portion 22a, if present; the same applies hereinafter) covering the surfaces of the plurality of conductive fibers 21 by a sol-gel method; and

[0187] (d) The conductive layer 23 (and the conductive portion 23 a , if present; the same applies hereinafter) covering the surface of the dielectric layer 22 is formed.

[0188] Hereinafter, steps (a) to (d) will be described in more detail.

[0189] Process (a)

[0190] First, a forest consisting of a plurality of vertically aligned carbon nanotubes (VACNTs) is prepared, which is disposed on a substrate 10 and directly bonded to the substrate 10 at one end.

[0191] Step (a) can be performed by applying a catalyst to the surface 10 a of the substrate 10 to grow a plurality of VACNTs from the surface 10 a (in other words, directly synthesizing them on the substrate 10 ). This is described in more detail below.

[0192] The substrate 10 may also be a synthetic substrate for growing VACNTs. Generally, the material of the synthetic substrate is not particularly limited; for example, silicon oxide, silicon, gallium arsenide, aluminum, SUS, etc. may be used. In this embodiment, a conductive substrate 10 is used as the synthetic substrate.

[0193] First, a catalyst is deposited on the surface 10a of the substrate 10. Examples of catalysts that can be used include iron, nickel, platinum, cobalt, or alloys thereof. Chemical vapor deposition (CVD), sputtering, physical vapor deposition (PVD), and atomic layer deposition (ALD) can be used to deposit the catalyst on the substrate 10. Depending on the circumstances, these techniques may be combined with photolithography, etching, and other techniques.

[0194] Next, VACNTs are grown (direct synthesis) on the substrate 10 with the catalyst attached. The method for growing VACNTs is not particularly limited; CVD or plasma-enhanced CVD under heating can be used as needed. The gas used is not particularly limited; for example, at least one selected from the group consisting of carbon monoxide, methane, ethylene, and acetylene, or a mixture of at least one of these with hydrogen and / or ammonia, can be used. If desired, moisture can be present in the atmosphere surrounding the VACNT growth. Thus, VACNTs grow on the substrate 10 with the catalyst serving as nuclei. The end of the VACNT on the side of the substrate 10 where the catalyst is attached is fixed to the substrate 10 (generally via the catalyst), while the end on the opposite side of the VACNT serves as a free end, serving as the growth point. The length and diameter of the VACNT can be varied depending on parameters such as gas concentration, gas flow rate, and temperature. In other words, by appropriately selecting these parameters, the length and diameter of the VACNT can be adjusted.

[0195] As a result, a forest of VACNTs (conductive fibers 21) can be formed on substrate 10. Strictly speaking, the length of each VACNT in the resulting forest may vary toward the free end (e.g., within-plane variation) due to factors such as differences in growth rate. When growing VACNTs on substrate 10 with a catalyst attached, there is a risk of carbon nanotubes (CNTs) pausing growth due to catalyst deactivation during VACNT synthesis. These CNTs become entangled with continuing CNTs, causing them to be stretched, causing their fixed ends to separate from substrate 10 and be pulled toward the leading end of the VACNT.

[0196] The plurality of VACNTs (conductive fibers 21 ) obtained as described above are arranged on the substrate 10 and directly bonded at one end to the substrate 10 . However, as will be understood from the above description, some CNTs may not be directly bonded to the substrate 10 .

[0197] Process (b)

[0198] Next, the VACNT at the edge of the forest is tilted toward the center. As a result, in the cross section of the resulting composite member 20 in the thickness direction, the length of the upper side (W1) becomes smaller than the length of the lower side (W2) (W1 <W2)。

[0199] By immersing the forest in a suitable solvent, VACNTs at the edges of the forest can be tilted toward the center. Immersing the forest in a suitable solvent makes it easier for VACNTs on the outer edges of the forest to clump together. Meanwhile, VACNTs near the center of the forest can more easily maintain an upright position. As a result, VACNTs at the edges tilt toward the center.

[0200] The solvent should be selected based on the wettability of the VACNTs. If the wettability of the VACNTs is too low, aggregation of the VACNTs will be difficult. On the other hand, if the wettability of the VACNTs is too high, aggregation of the VACNTs will be excessive, making it difficult to obtain a composite member 20 suitable for capacitor 1. Suitable solvents include, for example, water, ethanol, isopropyl alcohol, and acetone. Ethanol is particularly suitable.

[0201] A surfactant can also be added to the solvent. This facilitates adjusting the wettability of the VACNT. The surfactant can also be anionic. The surfactant should be selected appropriately, taking into account the charge and molecular weight of the hydrophilic group. Examples of surfactants include sodium dodecyl sulfate, cetyltrimethylammonium bromide, and sodium dodecylbenzenesulfonate. The amount of surfactant added can be appropriately adjusted based on the wettability of the VACNT.

[0202] The material of the dielectric layer 22 may be added to the solvent. In this way, the step (c) can be carried out using the bath used in the step (b) as it is.

[0203] Immersion conditions can also be set based on the wettability of the VACNTs. To prevent excessive aggregation, immersion can be performed by lowering the substrate 10 with the forest into a room temperature (23°C ± 3°C) solvent at a speed of 2 to 10 mm / s (typically 5 mm / s), such that the angle between the substrate 10 and the liquid surface is approximately 90 degrees. After immersing the forest in the solvent, the substrate is pulled up and dried. This allows the VACNTs outside the forest to be tilted or curved significantly toward the center.

[0204] The cohesion of forests is also described in Non-Patent Document 1.

[0205] Process (c)

[0206] Next, a dielectric layer 22 covering at least the surface of the VACNT is formed by a sol-gel method.

[0207] Films formed using liquid-phase film-forming methods, such as the sol-gel method, tend to contain impurities and volatile components. These impurities and volatile components are easily released by heating, which can increase the film's shrinkage and increase the tensile stress applied to the composite member 20. However, the composite member 20 of the present disclosure can suppress delamination of the dielectric layer 22 from the substrate 10 even when the dielectric layer 22 is formed using a liquid-phase film-forming method.

[0208] The thickness of the formed dielectric layer 22 can be controlled by appropriately selecting or setting the conditions for implementing the sol-gel method. For example, the composition of the liquid used in the liquid-phase film formation method, the solvent used in the preparation (e.g., water, ethanol, isopropyl alcohol, acetone), the film formation time, the stirring speed, the temperature, etc. can be appropriately selected or set.

[0209] As described above, when the material for dielectric layer 22 is added to the solvent used in step (b), steps (b) and (c) are performed simultaneously or continuously in the same bath. In other words, the VACNTs aggregate and the dielectric layer 22 material adheres simultaneously or continuously. The dielectric layer 22 material adheres to the surface of the VACNTs, making it easier to maintain an appropriate aggregated state between the VACNTs, and subsequent drying can inhibit further aggregation. From the perspective of easily controlling the aggregated state, steps (b) and (c) can also be performed simultaneously or continuously. In this case, the film formation time can be 1 to 3 hours (typically 1.5 hours), and the stirring speed can be 150 to 500 rpm (typically 300 rpm). Other conditions can be the same as the immersion conditions in step (b).

[0210] Then, the solution is dried to remove the solvent, thereby forming the dielectric layer 22 .

[0211] Process (d)

[0212] Next, the conductive layer 23 is formed to cover the surface of the dielectric layer 22 .

[0213] The film forming method of the conductive layer 23 is not particularly limited, and liquid phase film forming methods, vapor phase film forming methods, and combinations thereof may be used. Liquid phase film forming methods may include, for example, sol-gel methods and plating. Vapor phase film forming methods may include ALD, sputtering, CVD, and the like.

[0214] For example, the conductor layer 23 can be formed using a conductive polymer through a liquid-phase film-forming method. More specifically, the conductor layer 23 can be formed by applying or supplying (e.g., coating or impregnation) a liquid composition containing a conductive polymer dissolved or dispersed in an organic solvent to a predetermined surface or portion. The conductive polymer easily penetrates the spaces formed between the plurality of conductive fibers 21 covered by the dielectric layer 22, allowing the conductor layer 23 to be appropriately formed even deep within these spaces (e.g., at the bottom).

[0215] Through the above, it is possible to produce Figure 1 、 Figure 2 、 Figure 3A as well as Figure 3B Capacitor 1 is shown.

[0216] <Implementation Method 2>

[0217] Figure 4 This is a schematic cross-sectional view of a capacitor in accordance with the second embodiment. Figure 4 corresponds to Figure 1 cross-section. Figure 5A yes Figure 4 The enlarged view of part D corresponds to Figure 3A . Figure 5B yes Figure 4 A cross-sectional view of portion D along the in-plane direction of the substrate. Figure 5B Corresponding to Figure 5A For convenience, Figure 5A 、 Figure 5B , only a portion of the substrate 10 , the conductive fibers 21 , the dielectric layer 22 , and the conductor layer 23 are shown.

[0218] In the second embodiment, the outer shape of the composite member is different from that of the first embodiment. This different structure will be described below. The other structures are the same as those of the first embodiment, and the same reference numerals as those of the first embodiment are used and their description will be omitted.

[0219] <Outer edge>

[0220] like Figure 4 As shown, in capacitor 1A of Embodiment 2, composite member 20A has an outer edge portion 20a extending parallel to the width direction in outer peripheral region R2 of a cross section in the thickness direction. Outer edge portion 20a corresponds to at least a portion of outer peripheral region R2 and includes at least a portion of the outer edge of composite member 20A.

[0221] The outer edge portion 20a is different from the dielectric portion 22a and the conductor portion 23a and includes conductive fibers 21. Figure 5A 、 Figure 5B As shown, in the outer edge portion 20a of the XZ cross-section, the conductive fibers 21 include a first portion 21a extending parallel to the X-direction. In other words, in the outer edge portion 20a, the conductive fibers 21 are tilted so that at least a portion extends parallel to the X-direction. Consequently, the space 24 in the outer edge portion 20a is smaller. This makes the composite member 20A less susceptible to deformation, further preventing it from peeling off from the substrate 10.

[0222] In addition, the first portion 21a increases the contact area between the conductive fiber 21 and the substrate 10 and reduces the contact area between the dielectric layer 22 and the substrate 10, thereby reducing the influence of the difference in thermal expansion and further suppressing the delamination of the composite member 20A.

[0223] When the conductive fibers 21 have high strength, the first portion 21a effectively functions as a core material for the fibers 21, suppressing the occurrence of cracks in the composite member 20A due to tensile stress. Furthermore, the contact area between the conductive fibers 21 in the outer edge portion 20a increases, thereby increasing the mechanical strength of the composite member 20A and further enhancing the deformation suppression effect of the composite member 20A.

[0224] Although Figure 5AAlthough not shown in the figure, the coated conductive fiber 21 exists near the left top P3 of the composite member 20 , and the left top P3 is determined by the coated conductive fiber 21 .

[0225] The term "parallel" to the outer edge portion 20a refers to an acute angle θa (not shown) formed between a tangent line to the surface of the composite member 20A (i.e., the surface of the conductive layer 23) and the surface 10a of the substrate 10 being 30 degrees or less. The upper surface of the outer edge portion 20a may have fine irregularities arising from the dielectric layer 22 and / or the conductive layer 23. When observed within a viewing field of 5 μm x 5 μm or larger, if the acute angle θa is 30 degrees or less, the outer edge portion 20a may be considered to extend parallel to the width direction, disregarding these fine irregularities.

[0226] The term “parallel” in the first portion 21 a means that an acute angle θb (not shown) formed between the upper surface of the conductive fiber 21 and the surface 10 a of the substrate 10 is 30 degrees or less.

[0227] like Figure 5A As shown, the conductive fiber 21 may include a second portion 21b in addition to the first portion 21a in the outer peripheral region R2. The second portion 21b is a portion of the conductive fiber 21 that extends along the Z direction or in a direction that forms an acute angle (not shown) with the Z direction that exceeds 0 degrees and is less than 60 degrees. The second portion 21b may be disposed in the outer edge portion 20a along with the first portion 21a of the conductive fiber 21.

[0228] Length L and maximum height H of the first portion 21a max The following relationship can also be satisfied:

[0229] L≥0.8×H max .

[0230] About the maximum height H max , it is considered that it may also represent the full length of a conductive fiber 21. When more than 80% of the full length of the conductive fiber 21 extends parallel to the X direction, the contact area between the conductive fiber 21 and the substrate 10 is further increased, thereby further improving the effect of suppressing the composite member 20A from peeling off from the substrate 10. In particular, the length L and the maximum height H max It can also meet L≥1.0×H max The relationship between length L and maximum height H max It can also satisfy L≤10×H max relationship.

[0231] In the outer edge portion 20a, each of the plurality of conductive fibers 21 may have a first portion 21a. As long as the first portion 21a of at least one of the plurality of conductive fibers 21 satisfies the above relationship (L ≥ 0.8 × Hmax ) can be used.

[0232] · Decision method for Section 1, 21a

[0233] The first portion 21a can be determined as follows using an SEM image of a cross-section (e.g., XZ cross-section) in the thickness direction of the composite member 20A. First, the outer peripheral region R2 in the XZ cross-section is determined in the same manner as described above. Within the conductive fibers 21 present in the outer peripheral region R2, the acute angle θb formed between the upper surface of the conductive fibers 21 and the surface 10a of the substrate 10 is continuously measured from the outer edge of the composite member 20A toward the central axis AX. The observation field at this time only needs to be sufficient to allow the entire outer peripheral region R2 to be observed.

[0234] like Figure 5A As shown in FIG, the point where the acute angle θb first becomes less than 30 degrees is one end P7 of the first portion 21a. When P7 is near the outer edge of the peripheral region R2, one end of the first portion 21a can also be regarded as the outermost portion of the conductive fiber 21. Figure 5A In FIG. 2 , since the end portion P7 is located near the outer edge of the outer peripheral region R2 , the outermost portion of the conductive fiber 21 is regarded as one end portion of the first portion 21 a .

[0235] The point where the acute angle θb exceeds 30 degrees and no further decrease in the acute angle θb is observed is the other end P8 of the first portion 21a. The portion of the conductive fiber 21 corresponding to the region sandwiched between the one end P7 or the outer end of the conductive fiber 21 and the other end P8 is the first portion 21a.

[0236] · Method for determining the outer edge portion 20a

[0237] The outer edge portion 20a can be determined as follows based on the XZ cross-sectional SEM image used to determine the first portion 21a. In this SEM image, the acute angle θa formed between a tangent line to the surface of the composite member 20A and the surface 10a of the substrate 10 is continuously measured from the outer edge of the composite member 20A toward the central axis AX. As described above, the observation field in this case is set to be at least 5 μm × 5 μm.

[0238] like Figure 5A As shown, the point where the acute angle θa first becomes less than 30 degrees is one end P5 on the upper surface side of the outer edge portion 20a. When P5 is near the outer edge of the outer peripheral region R2, one end of the outer edge portion 20a can also be regarded as the outermost part of the outer peripheral region R2. Figure 5A In the diagram, since the end portion P5 is located near the outer edge of the outer peripheral region R2, the outermost portion of the outer peripheral region R2 is regarded as one end portion of the outer edge portion 20a.

[0239] The point where the acute angle θa exceeds 30 degrees and no further decrease in the acute angle θa is observed is the other end P6 on the upper surface side of the outer edge portion 20a. The composite member 20A corresponding to the area sandwiched between the one end P5 or one end of the outer peripheral region R2 and the other end P6 is the outer edge portion 20a.

[0240] The outer edge portion 20a only needs to be present in one cross-section in the thickness direction. The outer edge portion 20a may be present in multiple different cross-sections in the thickness direction, or in three or more different cross-sections in the thickness direction, or in any of all cross-sections in the thickness direction. In this case, the composite member 20A can be further prevented from peeling off from the substrate 10.

[0241] In a cross-section taken in the thickness direction, the outer edge portion 20a only needs to be present in at least one of the outer peripheral regions R2 on one side and the other side. The outer edge portion 20a may also be present in the outer peripheral regions R2 on both the one side and the other side. The first portion 21a of the conductive fiber 21 only needs to be disposed in a portion of the outer edge portion 20a, or may be disposed across the entire outer edge portion 20a.

[0242] The outer edge portion 20a may or may not coincide with the outer peripheral region R2. The width W5 of the outer edge portion 20a may be 30% or more and 100% or less of the width W3 or width W4 of the outer peripheral region. The width W5 of the outer edge portion 20a may or may not coincide with the outer peripheral region R2. The width W5 of the outer edge portion 20a may or may not coincide with the outer peripheral region R2.

[0243] The width W5 of the outer edge portion 20a can be determined as follows using the XZ cross-sectional SEM image used to determine the outer edge portion 20a. The distance in the X direction between a straight line extending in the Z direction and including one end P5 of the outer edge portion 20a or one end of the outer peripheral region R2 determined above, and a straight line extending in the Z direction and including the other end P6 of the outer edge portion 20a is the width W5.

[0244] How to determine the length L

[0245] The length L of the first portion 21a is the length of the first portion 21a in the X direction. The length L of the first portion 21a can be determined as follows using the XZ cross-sectional SEM image used to determine the outer edge portion 20a. The length L is the distance in the X direction between a straight line extending in the Z direction and including one end P7 of the first portion 21a, or the outer end of the conductive fiber 21, determined above, and a straight line extending in the Z direction and including the other end P8 of the first portion 21a.

[0246] like Figure 4As shown, in the XZ cross section, the outer edge portion 20a has a height H O Height H O and the maximum height H max The following relationship can also be satisfied:

[0247] H O ≤0.2×H max .

[0248] Height H O Decision method

[0249] Height H of outer edge portion 20a O It can also be the maximum height H of the conductive fiber 21 max From the perspective of capacitance, the height H of the outer edge portion 20a is less than 0.01 times. O It can also be the maximum height H of the conductive fiber 21 max More than 0.0001 times.

[0250] Height H of outer edge portion 20a O The XZ cross section used when determining the outer edge 20a can be used for measurement as follows. In this cross section, the outer edge 20a has already been determined. Calculate the distance in the Z direction from the surface 10a of the substrate 10 to any point on the upper surface of the outer edge 20a. Repeat this operation to obtain the above distances at five or more points, and the average value of these distances is set as the height H of the outer edge 20a. O .

[0251] <Area occupancy ratio S 24 >

[0252] In the cross section in the thickness direction, the outer edge portion 20a has a total area occupancy ratio S including the conductive fibers 21 and the dielectric layer 22. 24 The total area occupancy ratio S of the conductive fibers 21 and the dielectric layer 22 in the central region R1 is 11 The high part. That is, satisfying S 24 / S 11 ≥1.05. Area occupancy ratio S 24 and area occupancy ratio S 21 Calculate similarly.

[0253] Area occupancy ratio S 11 and S 24 The above relationship only needs to be satisfied in a cross section in one thickness direction. The above relationship can be satisfied in cross sections in different thickness directions, or in cross sections in three or more different thickness directions, or in any cross sections in all thickness directions.

[0254] Although two embodiments of the present disclosure have been described in detail above, the present disclosure is not limited thereto. For example, any two or more features of the above-described embodiments may be combined.

[0255] In the composite members 20 and 20A of the above embodiments, the length of the upper side s1 is equal to the width W1, and the length of the lower side s2 is equal to the width W2. However, this is not limiting. The length of the upper side s1 may be longer than the width W1, such as when the upper side s1 and the lower side s2 are not parallel.

[0256] In the composite member 20 of the above-described embodiment, the internal angle θ1 formed by the lower side s2 and the left side s3 (i.e., one end side in the width direction of the composite member 20), and the internal angle θ2 formed by the lower side s2 and the right side s4 (i.e., the other end side in the width direction of the composite member 20), are both less than 90 degrees. However, this is not limiting. Alternatively, at least one of the internal angles θ1 and θ2 may be less than 90 degrees. In particular, both internal angles θ1 and θ2 may be less than 90 degrees.

[0257] In the composite members 20 and 20A of the above-described embodiments, the outer peripheral regions R2 are disposed at two locations at both ends in the width direction, sandwiching the central region R1. However, the present invention is not limited thereto. Alternatively, in a cross-section of the composite members 20 and 20A in the thickness direction, the outer peripheral region R2 may be disposed at only one end in the X direction of the central region R1.

[0258] In the composite members 20 and 20A of the above-described embodiments, the conductive fibers 21 are directly bonded to the substrate 10, but this is not limiting. The conductive fibers 21 may also be bonded to the substrate 10 via a conductive adhesive layer. The conductive fibers 21 may be bonded to the surface of the adhesive layer or by inserting their ends into the adhesive layer. Typically, the conductive adhesive layer is formed of a metal material.

[0259] In the composite members 20 and 20A of the above-described embodiments, the conductive fibers 21 in the outer peripheral region R2 are inclined or curved, but this is not limiting. The conductive fibers 21 in the outer peripheral region R2 may also extend in the Z direction. In this case, the conductive fibers 21 in the outer peripheral region R2 are shorter than the conductive fibers 21 in the central region R1.

[0260] In the composite members 20 and 20A of the above-described embodiments, the conductive fibers 21 in the outer peripheral region R2 are in contact with each other via the dielectric layer 22 or without the dielectric layer 22. However, the present invention is not limited thereto. The plurality of conductive fibers 21 in the outer peripheral region R2 may be isolated.

[0261] In the capacitors 1 and 1A of the above-described embodiments, the conductive fibers 21 and / or the composite members 20 and 20A may be present on the surface (side surface) connecting the front surface 10 a and the back surface 10 b of the substrate 10 .

[0262] In the above embodiment, in step (a), carbon nanotubes (CNTs) are cited as the conductive fibers 21 , but the present invention is not limited thereto. The conductive fibers 21 may be conductive fibers other than CNTs.

[0263] In the above embodiment, a forest is formed on substrate 10 in step (a), but this is not limiting. Alternatively, the forest may be formed on another synthetic substrate and then transferred to substrate 10. In this case, steps (b) and subsequent steps may be performed after the transfer. An adhesive layer may also be provided on substrate 10.

[0264] In the above embodiment, in step (b), the cross-sectional shape of the forest is formed into a trapezoidal shape by tilting a portion of the conductive fibers 21. However, the present invention is not limited to this. Alternatively, in step (a), the cross-sectional shape of the forest may be formed into a trapezoidal shape by reducing the growth rate of the conductive fibers 21 forming the edge of the forest. In this case, step (b) can be omitted.

[0265] In the above embodiment, in step (b), part of the conductive fibers 21 are tilted by aggregation, but the present invention is not limited thereto. Alternatively, part of the conductive fibers 21 may be tilted by pressing the forest from the outside toward the center.

[0266] In the above embodiment, in step (c), dielectric layer 22 is formed using a sol-gel method, but the present invention is not limited to this. Dielectric layer 22 can also be formed using a vapor-phase film formation method (typically, sputtering). In this case, step (c) is performed after removing the solvent used in step (b). Dielectric layer 22 can also be formed using a liquid-phase film formation method other than the sol-gel method (typically, plating). If dielectric layer 22 contains a metal oxide, a method combining plating and surface oxidation treatment can also be used.

[0267] Example

[0268] The present invention will be described in more detail with reference to the following production examples, but the present invention is not limited thereto.

[0269] (Production Example 1)

[0270] The capacitor 1A including the composite member 20A according to the above-described embodiment was manufactured.

[0271] (1) Forest Preparation

[0272] A catalyst is applied to the surface of the Si substrate 10 and VACNT is grown, thereby obtaining a forest 200. The maximum height of the forest 200 (maximum height H max ) is 105 μm, and the outer diameter of the CNT is about 20 nm. The number density of CNTs in the forest is 3.99×10 8 root / cm 2 The number density of CNTs in the forest 200 can be considered as the average number density of the conductive fibers 21 in the composite member 20 .

[0273] (2) CNT tilt and dielectric layer formation

[0274] The substrate 10, on which the forest 200 was placed, was immersed in a raw material solution containing sodium lauryl sulfate, ammonia, 3-aminopropyltriethoxysilane, and ethanol. The immersion was performed as follows. First, the substrate 10, on which the forest 200 was placed, was placed into the raw material solution at room temperature (23°C ± 3°C), such that the angle between the substrate 10 and the liquid surface was approximately 90 degrees. The placement speed was set at 5 mm / second. The solution was stirred at 300 rpm at 25°C for 1.5 hours, and then the substrate was pulled up. Finally, the solution was dried, forming a dielectric layer 22 (SiO2) covering the surface of the multiple CNTs (conductive fibers 21) on the substrate 10.

[0275] (3) Formation of the conductor layer

[0276] Next, the substrate 10 was immersed in a dispersion containing PEDOT (polyethylene dioxythiophene) and PSS (polystyrene sulfonic acid) to form a conductive layer 23 (a PEDOT / PSS composite) on the dielectric layer 22 . In this way, the capacitor 1A was obtained.

[0277] After filling the spaces within the resulting composite member 20A of the capacitor 1A with resin, the substrate 10 was observed from the Z direction to determine the center C of the substrate 10. Next, polishing was performed to expose an XZ cross-section including the center C. The resulting cross-section was observed using a SEM. The average length of the fibrous conductive member was understood to be 50 μm or greater, and the thickness of the dielectric layer was understood to be 10 nm or greater.

[0278] A SEM image of a portion of this cross section is shown in Figure 6 .exist Figure 6 In FIG, a composite member 30 is also present on the side surface 10c of the composite member 20A. Figure 6 In FIG. 1 , for convenience, dotted lines showing the outer edges of the composite members 20A and 30 and the substrate 10 are marked.

[0279] Based on the SEM image that allows observation of the entire cross section, the left bottom P1, right bottom P2, left top P3, and right top P4 of the composite member 20A are determined in the same manner as above. Based on P1 to P4, the widths W1, W2, W3, W4, and H are obtained. max Width W1 is 4.76mm, W2 is 5.00mm, W2-W1 is 240μm, H max It can be understood that the widths W1, W2, W3, and W4 satisfy W1. <W2、W2-W1≥1.6×H max and W2>H max The relationship between W3≥0.8×H max and W4≥0.8×H max The relationship is as follows. Let the line segment formed by connecting the left bottom P1 and the right bottom P2 be the bottom side s2, the line segment formed by connecting the left bottom P1 and the left top P3 be the left side s3, and the line segment formed by connecting the right bottom P2 and the right top P4 be the right side s4. At this time, the angle θ1 of the interior angle formed by the bottom side s2 and the left side s3 is 73.6 degrees, and the angle θ2 of the interior angle formed by the bottom side s2 and the right side s4 is 54.4 degrees.

[0280] In any cross section in the thickness direction, both outer peripheral regions R2 on one side and the other side include an area occupancy ratio S 22 The area occupancy ratio S of the central region R1 12 The high part. The area occupancy ratio satisfies S 22 / S 12 ≥1.36. Therefore, it can be understood that the two outer peripheral regions R2 on one side and the other side include the area occupancy ratio S 21 The area occupancy ratio S of the central region R1 11 High part.

[0281] In at least one cross section in the in-plane direction, the outer peripheral region R2 includes an area occupancy ratio S 23 The area occupancy ratio S of the central region R1 13 The high part. The area occupancy ratio satisfies S 23 / S 13 The relationship is ≥1.53.

[0282] The maximum cross-sectional dimension of the CNT calculated from the in-plane cross section is 33 nm. The thickness of the dielectric layer 22 is 51 nm. The thickness of the conductor layer 23 is 15 nm.

[0283] Figure 8A This is an SEM image of a portion of the outer peripheral region of the polished XZ cross section of the composite member obtained in Production Example 1. Figure 8BThis is an SEM image of a portion of the central region of the polished XZ cross section of the composite member obtained in Manufacturing Example 1. Figure 8A as well as Figure 8B In FIG. 2 , the linear, whitish portions are the conductive fibers 21 covered by the dielectric layer 22 and the conductor layer 23 , and the black portions are the filling resin corresponding to the spaces 24 .

[0284] Figure 9A This is an SEM image of a portion of the outer peripheral region of the polished XY cross section of the composite member obtained in Production Example 1. Figure 9B This is an SEM image of a portion of the central region of the polished XY cross section of the composite member obtained in Manufacturing Example 1. Figure 9A as well as Figure 9B In FIG. 2 , the circular, whitish portion is the conductive fiber 21 covered by the dielectric layer 22 and the conductor layer 23 , and the black portion is the filling resin corresponding to the space 24 .

[0285] Industrial applicability

[0286] The capacitor disclosed herein can be used in any appropriate application, and can be preferably used in applications requiring high bonding strength between a substrate and a composite member.

[0287] This application claims priority based on Japanese Patent Application No. 2022-175699, filed in Japan on November 1, 2022, the entire contents of which are incorporated herein by reference.

[0288] <1>

[0289] A capacitor comprising:

[0290] a substrate having electrical conductivity;

[0291] a plurality of fibrous conductive members disposed on the substrate and electrically connected to the substrate;

[0292] a dielectric layer covering the surface of the fibrous conductive member; and

[0293] a conductive layer covering the surface of the dielectric layer,

[0294] The plurality of fibrous conductive members, the dielectric layer, the conductor layer, and spaces formed between the plurality of fibrous conductive members covered with the dielectric layer and the conductor layer constitute a composite member.

[0295] In a cross section along the thickness direction of the substrate,

[0296] Assuming that the in-plane direction of the substrate is a width direction, the composite member has a width W1 on the opposite side to the substrate and a width W2 on the substrate side, and the width W1 is smaller than the width W2.

[0297] <2>

[0298] according to <1> The capacitor, wherein

[0299] In a cross section along the thickness direction of the substrate,

[0300] The fibrous conductive member has a maximum height H in the central region corresponding to the width W1. max ,

[0301] The width W1, the width W2, and the maximum height H max The following relationship is satisfied:

[0302] W2-W1≥1.6×H max .

[0303] <3>

[0304] according to <2> The capacitor, wherein

[0305] In a cross section along the thickness direction of the substrate,

[0306] The composite member has a width W3 and a width W4 in the outer peripheral region on one side and the other side, respectively, sandwiching the central region corresponding to the width W1.

[0307] The width W3, the width W4, and the maximum height H max The following relationship is satisfied:

[0308] W3≥0.8×H max , and W4 ≥ 0.8 × H max .

[0309] <4>

[0310] according to <1> ~ <3> The capacitor according to any one of claims 1 to 5, wherein

[0311] In a cross section along the thickness direction of the substrate,

[0312] In at least one of the outer peripheral regions on one side and the other side of the composite member sandwiching the central region corresponding to the width W1,

[0313] The fibrous conductive member has a first portion extending parallel to the in-plane direction of the substrate.

[0314] <5>

[0315] according to <4> The capacitor, wherein

[0316] In a cross section along the thickness direction of the substrate,

[0317] The fibrous conductive member has a maximum height H in the central region. max ,

[0318] The length L of the first portion and the maximum height H max The following relationship is satisfied:

[0319] L≥0.8×H max .

[0320] <6>

[0321] according to <1> ~ <5> The capacitor according to any one of claims 1 to 5, wherein

[0322] In a cross section along the thickness direction of the substrate,

[0323] The total area occupancy ratio S of at least one of the outer peripheral regions on one side and the other side sandwiching the central region corresponding to the width W1, including the fibrous conductive member, the dielectric layer, and the conductor layer, is 22 The area occupancy ratio S of the total area of ​​the fibrous conductive member, the dielectric layer, and the conductor layer in the central region is greater than 12 High part.

[0324] <7>

[0325] according to <1> ~ <6> The capacitor according to any one of claims 1 to 5, wherein

[0326] In a cross section along the thickness direction of the substrate,

[0327] The total area occupancy ratio S of the outer peripheral area on one side and the outer peripheral area on the other side sandwiching the central area corresponding to the width W1, including the fibrous conductive member, the dielectric layer, and the conductor layer, is 22 The area occupancy ratio S of the total area of ​​the fibrous conductive member, the dielectric layer, and the conductor layer in the central region is greater than 12 High part.

[0328] <8>

[0329] according to <1> ~ <7> The capacitor according to any one of claims 1 to 5, wherein

[0330] In a plurality of cross sections along the thickness direction of the substrate,

[0331] The total area occupancy ratio S of at least one of the outer peripheral regions on one side and the other side sandwiching the central region corresponding to the width W1, including the fibrous conductive member, the dielectric layer, and the conductor layer, is 22 The area occupancy ratio S of the total area of ​​the fibrous conductive member, the dielectric layer, and the conductor layer in the central region is greater than 12 High part.

[0332] <9>

[0333] according to <1> ~ <8> The capacitor according to any one of claims 1 to 5, wherein

[0334] In a cross section along the in-plane direction of the substrate,

[0335] The total area occupancy ratio S of at least one of the outer peripheral regions on one side and the other side sandwiching the central region corresponding to the width W1, including the fibrous conductive member, the dielectric layer, and the conductor layer, is 23 The area occupancy ratio S of the total area of ​​the fibrous conductive member, the dielectric layer, and the conductor layer in the central region is greater than 13 High part.

[0336] <10>

[0337] according to <1> ~ <9> The capacitor according to any one of claims 1 to 5, wherein

[0338] The fibrous conductive member has a maximum height H in the central region corresponding to the width W1. max ,

[0339] The width W2 and the maximum height H max The following relationship is satisfied:

[0340] W2>H max .

[0341] <11>

[0342] according to <1> ~ <10> The capacitor according to any one of claims 1 to 5, wherein

[0343] The thickness of the dielectric layer is greater than 10 nm.

[0344] <12>

[0345] according to <1> ~ <11> The capacitor according to any one of claims 1 to 5, wherein

[0346] The average number density of the plurality of fibrous conductive members is 10 8 root / cm2 above.

[0347] <13>

[0348] according to <1> ~ <12> The capacitor according to any one of claims 1 to 5, wherein

[0349] The average length of the plurality of fibrous conductive members is 50 μm or more.

[0350] <14>

[0351] according to <1> ~ <13> The capacitor according to any one of claims 1 to 5, wherein

[0352] The fibrous conductive member is a carbon nanotube.

[0353] Description of Reference Numerals

[0354] 1. 1A: capacitor;

[0355] 10: Substrate;

[0356] 10a: surface;

[0357] 10b: back;

[0358] 10c: side view;

[0359] 20, 20A: composite member;

[0360] 20a: outer edge;

[0361] 21: fibrous conductive member (conductive fiber);

[0362] 21a: Part 1;

[0363] 21b: Part 2;

[0364] 22: dielectric layer;

[0365] 22a: dielectric part;

[0366] 23: conductor layer;

[0367] 23a: Conductor part;

[0368] 24: Space;

[0369] 30: composite member at the side;

[0370] 100: previous capacitors;

[0371] 110: substrate;

[0372] 120: composite component;

[0373] 200: Forest;

[0374] 300: SiO2 precipitation;

[0375] L1~L4: represent the edges of the composite component's shape;

[0376] P1, P2: left and right bottoms of the composite component;

[0377] P3, P4: left and right tops of the composite component;

[0378] P5, P6: ends of the outer edge;

[0379] P7, P8: the end of part 1;

[0380] C: center of substrate;

[0381] R1: central region;

[0382] R2: peripheral region.

Claims

1. A capacitor having: A substrate, which is electrically conductive; a plurality of fibrous conductive members, arranged on the substrate and electrically connected to the substrate; a dielectric layer covering the surface of the fibrous conductive member; and a conductive layer covering the surface of the dielectric layer, The plurality of fibrous conductive members, the dielectric layer, the conductor layer, and spaces formed between the plurality of fibrous conductive members covered with the dielectric layer and the conductor layer constitute a composite member. In a cross section along the thickness direction of the substrate, The in-plane direction of the substrate is defined as a width direction. The composite member has a width W1 on the opposite side to the substrate and a width W2 on the substrate side, and the width W1 is smaller than the width W2.

2. The capacitor according to claim 1, wherein: In a cross section along the thickness direction of the substrate, The fibrous conductive member has a maximum height H in the central region corresponding to the width W1. max , The width W1, the width W2 and the maximum height H max Satisfies the following relationship: W2-W1≥1.6×H max 。 3. The capacitor according to claim 2, wherein: In a cross section along the thickness direction of the substrate, The composite member has a width W3 and a width W4 in the outer peripheral region on one side and the other side sandwiching the central region corresponding to the width W1, respectively. The width W3, the width W4 and the maximum height H max Satisfies the following relationship: W3≥0.8×H max , and W4 ≥ 0.8 × H max .

4. The capacitor according to any one of claims 1 to 3, wherein: In a cross section along the thickness direction of the substrate, In at least one of the outer peripheral regions on one side and the other side of the composite member sandwiching the central region corresponding to the width W1, The fibrous conductive member has a first portion extending parallel to the in-plane direction of the substrate.

5. The capacitor according to claim 4, wherein: In a cross section along the thickness direction of the substrate, The fibrous conductive member has a maximum height H in the central region. max , The length L of the first portion and the maximum height H max Satisfies the following relationship: L≥0.8×H max 。 6. The capacitor according to any one of claims 1 to 5, wherein: In a cross section along the thickness direction of the substrate, The total area occupancy ratio S of at least one of the outer peripheral regions on one side and the other side sandwiching the central region corresponding to the width W1, including the fibrous conductive member, the dielectric layer, and the conductor layer 22 The area occupancy ratio S of the total area of ​​the fibrous conductive member, the dielectric layer, and the conductor layer in the central region is 12 High part.

7. The capacitor according to any one of claims 1 to 6, wherein: In a cross section along the thickness direction of the substrate, The total area occupancy ratio S of the outer peripheral area on one side and the outer peripheral area on the other side sandwiching the central area corresponding to the width W1 includes the fibrous conductive member, the dielectric layer, and the conductor layer. 22 The area occupancy ratio S of the total area of ​​the fibrous conductive member, the dielectric layer, and the conductor layer in the central region is 12 High part.

8. The capacitor according to any one of claims 1 to 7, wherein: In a plurality of cross sections along the thickness direction of the substrate, The total area occupancy ratio S of at least one of the outer peripheral regions on one side and the other side sandwiching the central region corresponding to the width W1, including the fibrous conductive member, the dielectric layer, and the conductor layer 22 The area occupancy ratio S of the total area of ​​the fibrous conductive member, the dielectric layer, and the conductor layer in the central region is 12 High part.

9. The capacitor according to any one of claims 1 to 8, wherein: In a cross section along the in-plane direction of the substrate, The total area occupancy ratio S of at least one of the outer peripheral regions on one side and the other side sandwiching the central region corresponding to the width W1, including the fibrous conductive member, the dielectric layer, and the conductor layer 23 The area occupancy ratio S of the total area of ​​the fibrous conductive member, the dielectric layer, and the conductor layer in the central region is 13 High part.

10. The capacitor according to any one of claims 1 to 9, wherein: The fibrous conductive member has a maximum height H in the central region corresponding to the width W1. max , The width W2 and the maximum height H max Satisfies the following relationship: W2>H max 。 11. The capacitor according to any one of claims 1 to 10, wherein: The thickness of the dielectric layer is greater than 10 nm.

12. The capacitor according to any one of claims 1 to 11, wherein: The average number density of the plurality of fibrous conductive members is 10 8 Root / cm 2 above.

13. The capacitor according to any one of claims 1 to 12, wherein: The average length of the plurality of fibrous conductive members is 50 μm or more.

14. The capacitor according to any one of claims 1 to 13, wherein: The fibrous conductive member is a carbon nanotube.

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