JP6690154B2 - Thin film capacitor - Google Patents

Description

  The present invention relates to thin film capacitors.

  The dielectric element has a structure in which a dielectric is provided between a plurality of conductors. A thin film capacitor is a typical example of a dielectric element. Patent Document 1 discloses a structure of a capacitor using a metal foil as a conductor. Patent Document 2 discloses, as a method of manufacturing a thin film capacitor, providing a dielectric layer on a metal foil layer and forming a metal layer on the dielectric layer. Patent Document 3 discloses that a first conductor, a dielectric on the first conductor, and a second conductor on the dielectric are provided, and the first conductor contains an additive. There is.

JP, 2001-203455, A JP, 2000-164460, A JP, 2007-194592, A

  When a voltage is applied to the thin film capacitor, mechanical strain may occur in the dielectric layer due to the electrostrictive effect, and the thin film capacitor may be displaced. As a result, when an AC voltage is applied to the thin film capacitor, vibration may occur in the thin film capacitor. If this vibration continues for a long period of time, the dielectric layer and the electrode layer of the thin film capacitor may be peeled off, resulting in a decrease in reliability. This vibration is also a cause of so-called "squealing" and may cause noise when a thin film capacitor is used in a television or an audio device.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a thin film capacitor capable of reducing the amount of displacement when a voltage is applied.

  The present invention comprises a first electrode layer, a dielectric layer provided on the first electrode layer, and a second electrode layer provided on the dielectric layer, wherein the second electrode layer is Ni, At least one conductive layer containing at least one metal selected from the group consisting of Cu and Al as a main component is included, and the conductive layer further includes atoms (Ne, A thin film capacitor containing at least one additive atom selected from (excluding Ar and Kr), and the content of each additive atom is 1 to 1000 mass ppm.

  According to the thin film capacitor, it is possible to reduce the amount of displacement and vibration when a voltage is applied.

  In the above thin film capacitor, the conductive layer contains Ni as a main component, and the added atoms are Ti, V, Cr, Mn, Fe, Co, Cu, Al, C, Si, F, N, and Cl. It can be at least one additional atom selected from more. By providing the thin film capacitor with the above configuration, the displacement when a voltage is applied can be further suppressed.

  In the thin film capacitor, the conductive layer contains Cu as a main component, and the added atoms are selected from Cr, Mn, Fe, Co, Ni, Al, C, Si, N, P, O, S, F, and Cl. It can be at least one additional atom selected from the group consisting of: By providing the thin film capacitor with the above configuration, the displacement when a voltage is applied can be further suppressed.

  In the thin film capacitor, the second electrode layer may include two or more conductive layers. By providing the thin film capacitor with the above configuration, the displacement when a voltage is applied can be further suppressed.

  According to the present invention, it is possible to provide a thin film capacitor with a reduced amount of displacement when a voltage is applied.

It is a schematic sectional drawing of the thin film capacitor which concerns on one Embodiment of this invention. It is a schematic sectional drawing of the thin film capacitor which concerns on another embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail. The present invention is not limited to the embodiments below.

  FIG. 1 is a schematic sectional view of a thin film capacitor according to an embodiment of the present invention. FIG. 2 is a schematic sectional view of a thin film capacitor according to another embodiment of the present invention. 1 and 2, the thin film capacitor 10 includes a lower electrode layer 11 (first electrode layer), a dielectric layer 12 provided on the lower electrode layer 11, and an upper electrode provided on the dielectric layer 12. And a layer 13 (second electrode layer).

(Upper electrode layer)
The upper electrode layer (second electrode layer) 13 includes at least one conductive layer. For example, in FIG. 1, the upper electrode layer (second electrode layer) 13 has one conductive layer, and in FIG. 2, the upper electrode layer 13 includes the first conductive layer 13A, the second conductive layer 13B, and the third conductive layer. It has a conductive layer 13C.

  At least one conductive layer in the upper electrode layer 13 contains any one metal selected from the group consisting of Ni, Cu, and Al as a main component, and the second to fourth periods of the periodic table. Contains at least one additive atom selected from the atoms (excluding Ne, Ar, and Kr), and the content of each additive atom is 1 to 1000 mass ppm. Hereinafter, this layer is referred to as an added conductive layer.

  In the present specification, the main component means a component that occupies 50% by mass or more of the entire layer. The metal as the main component can occupy 70% by mass or more, 80% by mass or more, 90% by mass or more, 95% by mass or more, 99% by mass or more in the layer.

  The atoms belonging to the second period (excluding Ne) are Li, Be, B, C, N, O and F, and the atoms belonging to the third period (excluding Ar) are Na, Mg, Al and Si. , P, S, Cl. The atoms belonging to the fourth period (excluding Kr) are K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Se, Br.

  The content (mass) of each added atom in the added conductive layer is 1 ppm to 1000 ppm (based on the total mass of the added conductive layer). When the content of each added atom is within the above range, the displacement amount of the thin film capacitor can be reduced to 300 nm or less, and noise can be reduced. The lower limit of the content can be 3 ppm, 5 ppm, 10 ppm, and the upper limit can be 600 ppm, 300 ppm, 100 ppm, 10 ppm. Further, the total content (mass) of the added atoms in the added conductive layer can be 1 ppm to 1500 ppm (based on the total mass of the added conductive layer). The upper limit of the total content can be 1200 ppm, 800 ppm, 500 ppm, 100 ppm.

  When the added conductive layer contains Ni as the main component, Ni is removed from the added atoms, when the added conductive layer contains Cu as the main component, Cu is removed from the added atoms, and when it contains Al as the main component, it is added. Al is removed from the atom. Further, Ne, Ar and Kr are excluded from the added atoms. This is because Ne, Ar, and Kr are inactive atoms, do not form a compound with the main component metal of the conductive layer, and do not sufficiently contribute to embrittlement of the added conductive layer due to migration.

  The added atoms belonging to the second period, particularly B, C, N, O, and F, can be inserted between the crystal lattices of Ni, Cu, or Al in the added conductive layer. This enables embrittlement of the added conductive layer.

  The added atoms belonging to the third to fourth periods, in particular Mg, Al, Si, P, Mn, Fe, Co, Ni, Cu, Zn, and Ga, are Ni, Cu, and Al in the added conductive layer. Can be substituted with a metal atom in the crystal lattice formed by to form a part of the lattice. This enables embrittlement of the added conductive layer.

  The added atoms having a high electronegativity, especially Al, C, Si, N, P, O, S, Cl, and F, tend to chemically react with metals such as Ni, Cu, Al, which are the main components. Therefore, the crystal growth of the metal in the added conductive layer tends to be suppressed. Generally, the higher the purity of a metal, the easier the crystal growth tends to be, but by suppressing the crystal growth of the metal that is the main component of the added conductive layer, the fine crystal structure is controlled, and the grain boundary region in the added conductive layer is controlled. Can be increased.

  When the main component of the added conductive layer is Ni or Cu belonging to the transition element of the fourth period, the added atom belongs to the transition element of the fourth period, for example, Ti, V, Cr, Mn, Fe, Co, Ni Or Cu, the ionization potentials of the main component and the added atom are close to each other, and they tend to form a compound such as solid solution and alloying with each other. In addition, when the main component of the added conductive layer is Al belonging to the third period and the added atom is included in the third period, for example, Si, P, S, or Cl, they form a compound with each other. It tends to be easy. In these cases, by forming a compound with a metal whose added atom is the main component, crystal growth of the added conductive layer is suppressed, and it becomes possible to increase the grain boundary region in the added conductive layer.

  When the added conductive layer contains Ni as a main component, the added atom is at least one selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Cu, Al, C, Si, F, N, and Cl. The additional atom of the seed is preferable. When the added conductive layer contains Ni and the added atoms, the displacement amount of the thin film capacitor tends to be further reduced.

  When the added conductive layer contains Cu as a main component, the added atom is selected from the group consisting of Cr, Mn, Fe, Co, Ni, Al, C, Si, N, P, O, S, F, and Cl. At least one additional atom is preferable. When the added conductive layer contains Cu and the added atoms, the displacement amount of the thin film capacitor tends to be further reduced.

  When the additive conductive layer contains Al as a main component, the additive atom is selected from the group consisting of Mg, Ti, V, Cr, Mn, Fe, Co, Cu, Al, C, Si, F, N, and Cl. At least one additional atom is preferable. When the added conductive layer contains Al and the added atoms, the displacement amount of the thin film capacitor tends to be further reduced.

  The added conductive layer can contain other atoms in addition to the main component and the above-mentioned added atoms. For example, noble metal atoms such as Pt, Pd, Ir, Ru and Rh can be contained alone or in combination. The content of noble metal atoms is less than 50 mass% based on the total amount of the added conductive layer.

  When the upper electrode layer 13 is composed of only one added conductive layer, the thickness of the added conductive layer can be appropriately selected and can be, for example, 0.1 μm to 120 μm. The thickness of the conductive layers other than the added conductive layer can be set to the same level as the added conductive layer.

  When the upper electrode layer 13 has two or more conductive layers having different compositions, the added conductive layer may be located at any position. Further, the upper electrode layer 13 may have a plurality of added conductive layers, and all the conductive layers may be added conductive layers. For example, when the upper electrode layer 13 has three conductive layers 13A, 13B, and 13C as shown in FIG. 2, at least one layer among the conductive layers 13A to 13C may be an added conductive layer, and the upper electrode layer 13 Any two of the layers may be additive conductive layers, and all three conductive layers may be additive conductive layers. Of course, the number of conductive layers in the upper electrode layer 13 may be 2 instead of 3, and may be 4 or more.

  In addition, when there are a plurality of added conductive layers, the compositions of the added conductive layers may be different from each other. For example, the types of the metal as the main component may be different from each other, the types or combinations of the added atoms may be different from each other, the concentrations of the added atoms may be different from each other, or a combination thereof may be used.

  When the upper electrode layer 13 includes a plurality of conductive layers, the thickness of each layer can be set to 0.1 μm to 20 μm, for example. The total thickness of the upper electrode layer 13 may be, for example, 0.1 μm to 120 μm. The thickness of the added conductive layer may be 0.1 μm to 100 μm. The added conductive layer containing Ni as a main component may have a thickness of 0.1 to 20 μm.

  In the upper electrode layer 13, the conductive layer that is not the additive conductive layer can contain any one metal selected from the group consisting of Ni, Cu, and Al as a main component, and Pt, Pd, Ir, Ru, Rh. It may be an alloy containing 50% or less of noble metal atoms such as singly or in combination. Of course, a conductive layer not containing Ni, Cu, or Al as a main component may be used.

  When the upper electrode layer 13 includes a conductive layer containing Ni as a main component, the conductive layer is preferably in contact with the dielectric layer 12. Ni often has a small difference in coefficient of thermal expansion from the dielectric layer 12, and tends to relatively reduce thermal strain of the thin film capacitor 10. This means that the starting point of destruction of the thin film capacitor 10 due to vibration is reduced. Therefore, since the conductive layer containing Ni as a main component is in contact with the dielectric layer 12, it is possible to prevent the reliability of the thin film capacitor 10 from being lowered. When the conductive layer is in contact with the dielectric layer 12 and contains Ni as a main component, it is preferable to further have a conductive layer containing Cu as a main component on the conductive layer. It is also possible to further have a conductive layer containing Cu having a different composition as a main component on the layer.

  When the conductive layer containing Cu as the main component is present on the conductive layer containing Ni as the main component, additional atoms may be added to the layer containing Ni as the main component, and the layer containing Cu as the main component (Cu When there are a plurality of layers containing as a main component, either or both of them may be added), an additional atom may be added, and a conductive layer containing Ni as a main component and a conductive layer containing Cu as a main component The added atom may be added to both (when there are a plurality of layers containing Cu as a main component, either or both of them may be used). Further, the added conductive layer may be located at a position not contacting the dielectric layer.

(Lower electrode layer)
The material of the lower electrode layer 11 is selected from conductive materials such as metals, metal oxides, and conductive organic materials. Examples of the lower electrode layer 11 include a conductive foil containing metal, a sintered body containing metal, and a conductive thin film formed on an arbitrary substrate. That is, the lower electrode layer 11 need not be a metal-based material as long as it has conductivity, but is preferably a metal-based material.

  Specifically, the material of the lower electrode layer 11 is preferably a metal such as Ni, Cu, or Al, or an alloy containing any of these as a main component. The material of the lower electrode layer 11 is preferably Ni, Cu, or an alloy containing any of these as a main component, because it has low electrical resistance and high mechanical strength. In addition, the lower electrode layer 11 is preferably Ni or an alloy containing Ni as a main component from the viewpoint of high temperature load reliability and humidity resistance load reliability. In particular, Ni or an alloy containing Ni as a main component is preferably in contact with the dielectric layer 12.

  Similar to the upper electrode layer 13, the lower electrode layer 11 has a total of 1 to at least one additive atom selected from atoms (excluding Ne, Ar, and Kr) belonging to the second to fourth periods of the periodic table. It is possible to have an added conductive layer made of a material containing 1000 mass ppm. In this case, the same effect as the upper electrode layer 13 can be obtained also in the lower electrode layer 11. A suitable example is the same as that of the upper electrode layer 13.

  The lower electrode layer 11 may be a foil exposed to the outside, or may be a layer that is supported on a substrate such as Si or ceramic and can be formed by sputtering or vapor deposition. As described for the upper electrode layer 13, the conductive layer containing Ni as a main component is preferable because the difference in the coefficient of thermal expansion from the dielectric layer 12 is small, and the material of the substrate is preferably the same as that of the dielectric layer 12. It is more preferable to select from materials having a small difference in expansion coefficient.

  Further, the lower electrode layer 11 may have a multilayer structure like the upper electrode layer 13. The thickness of the lower electrode layer 11 can be the same as that of the upper electrode layer 13.

(Dielectric layer)
The material of the dielectric layer 12 may be a dielectric material, but is preferably a perovskite type oxide dielectric having a large dielectric constant, and from the viewpoint of environmental protection, a barium titanate-based dielectric containing no lead. Is preferred. The barium titanate-based dielectric may be a Ba site partially substituted with an alkaline earth metal atom such as Ca or Sr, and a Ti site partially substituted with an atom such as Zr, Sn, or Hf. It may be replaced. Furthermore, rare earth atoms, atoms such as Mn, V, Nb, and Ta may be added to these dielectrics.

  The thickness of the dielectric layer 12 is preferably 1000 nm or less. When the thickness of the dielectric layer 12 is 1000 nm or less, the capacitance value per unit area tends to increase. The lower limit of the thickness of the dielectric layer 12 is not particularly limited, but it is preferably 50 nm or more from the viewpoint that the insulation resistance value does not become too small. The thickness of the dielectric layer 12 is more preferably 250 to 1000 nm in consideration of the balance between the insulation resistance value and the capacitance. The dielectric layer 12 may include defects that are stochastically difficult to avoid.

(Action effect)
The thin film capacitor according to the present embodiment provides a thin film capacitor that can reduce the amount of displacement when a voltage is applied.

  Although the reason why the above effect is obtained is not always clear, the present inventors consider that the following two are one of the factors. That is, the first reason is that the added atoms form a compound with Ni, Cu, or Al to suppress the crystal growth of the metal and form a fine crystal structure having many crystal grain boundaries in the added conductive layer. It is a point. The second reason is that the presence of the added atoms imparts brittleness to the added conductive layer.

  Since metal originally has excellent malleability and ductility, the metal-based electrode layer in the thin film capacitor follows the displacement of the dielectric layer well, and the displacement generated in the dielectric layer easily leads to the displacement of the thin film capacitor as it is. However, it is considered that the large number of crystal grain boundaries explained for the first reason can absorb the vibration generated in the dielectric layer by applying a voltage without propagating to the surroundings, and as a result, the whole thin film capacitor can be absorbed. It is conceivable that the displacement will be suppressed. It is considered that the addition of brittleness for the second reason can also prevent the added conductive layer from following the displacement of the dielectric layer, and as a result, the displacement of the thin film capacitor as a whole can be suppressed.

  When the lower electrode layer contains the above-mentioned additional atom, for example, Fe may form an alloy with Ni, but the propagation of vibration can be reduced regardless of the presence or absence of the alloy formation.

  The thin film capacitor according to the present invention is particularly useful as a dielectric element mounted on an AC circuit board.

(Production method)
Such a thin film capacitor can be manufactured as follows. First, the lower electrode layer 11 such as a metal foil is prepared. Next, the dielectric layer 12 is formed on the lower electrode layer 11 by a known method. Then, the upper electrode layer 13 is formed on the dielectric layer 12.

  The lower electrode layer 11 can be obtained by a known method. When the additional atom is contained, it can be contained in the same manner as the upper electrode layer 13 described later.

  The dielectric layer 12 is formed on the upper surface of the lower electrode layer 11 by, for example, solution coating, sputtering, vapor deposition, PLD (Pulse Laser Deposition), CVD (Chemical Vapor Deposition), or the like.

  Each conductive layer forming the upper electrode layer 13 can be formed by, for example, solution coating, sputtering, vapor deposition, PLD (Pulse Laser Deposition), CVD (Chemical Vapor Deposition), and plating.

  When the additive conductive layer in the upper electrode layer 13 is formed by sputtering, sputtering may be performed using a sputtering target having a main component metal and additional atoms, and a sputtering target of the main component metal and a sputtering target of additional atoms may be used. You may use together with and sputter simultaneously. When the added conductive layer is formed by a vapor deposition method, for example, the metal as the main component and the added atom can be deposited from different vapor deposition sources.

  Alternatively, the added conductive layer can be formed by forming a conductive layer having no added atom and then introducing the added atom into the conductive layer. Examples of the method of introducing the added atom include an ion implantation method and a solid phase diffusion method. When the additional atoms are introduced by these methods, crystal growth centering on the additional atoms occurs in the conductive layer, and the conductive layer tends to be effectively miniaturized.

  Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the following examples. In the following Examples and Comparative Examples, ppm is based on mass unless otherwise specified.

[Fabrication of thin film capacitors]
(Example 1)
A dielectric layer (BaTiO ₃ system dielectric) having a thickness of 800 nm was formed on a Ni metal foil having a size of 110 mm × 110 mm and a thickness of 30 μm by a sputtering method. Then, annealing was performed to crystallize the dielectric layer on the Ni metal foil. Using Ni with 25 ppm of Ti and Cu with 20 ppm of Fe added to the sputtering target, a Ni layer with a thickness of 0.5 μm and a first Cu layer with a thickness of 5 μm were formed in this order on the dielectric layer by the sputtering method. Formed. Next, a 13-μm-thick second Cu layer was formed on the first Cu layer by electrolytic plating. Cr was added to the second Cu layer, and the electrolytic plating solution used had a Cr content adjusted so that the Cr content in the second Cu layer was 10 ppm. As described above, the upper electrode layer including the Ni layer, the first Cu layer and the second Cu layer was formed on the dielectric layer. After forming the upper electrode layer, the upper electrode layer was patterned and then cut by a laser processing machine to obtain 100 thin film capacitors of Example 1 having a size of 20 × 20 mm. Table 1 summarizes the main component metals, the added atoms and the contents of the added atoms in the upper electrode layer.

(Examples 2 to 19 and Comparative Examples 1 to 7)
In the manufacture of the upper electrode layer, the types and contents of the added atoms of the Ni layer, the types and the contents of the added atoms of the first Cu layer, and the types and the flow rates of the added atoms of the second Cu layer are shown in Tables 1 to 3. The thin film capacitors of Examples 2 to 19 and Comparative Examples 1 to 7 were obtained in the same manner as in Example 1 except that the changes were made as described above.

(Example 20)
Using Al added with 100 ppm of Mg as a sputtering target, an Al layer having a thickness of 18.5 μm was formed on the dielectric layer by a sputtering method. The Al layer was used as the upper electrode layer. After forming the upper electrode layer, the upper electrode layer was patterned to obtain a thin film capacitor of Example 20. Table 2 collectively shows the main component metal, the added atoms, and the content of the added atoms in the upper electrode layer.

(Comparative Examples 8 to 10)
In the production of the upper electrode layer, thin film capacitors of Comparative Examples 8 to 10 were obtained in the same manner as in Example 20 except that the type and content of the added atoms of the Al layer were changed as shown in Table 3. .

[Evaluation methods]
(Capacity value)
The capacitance value (F) of 100 thin film capacitors obtained in Examples and Comparative Examples was measured by using an LCR meter (trade name: 4284A, manufactured by Agilent Technologies Co., Ltd.) at 1 kHz, 1 Vrms, and room temperature (25 ° C.). It was measured under the conditions. Tables 1 to 3 show the average values of the measured capacitance values.

(Insulation resistance value yield)
The insulation resistance value (Ω) of 100 thin film capacitors obtained in Examples and Comparative Examples was measured by using a high resistance meter (trade name: 4339B, manufactured by Agilent Technologies) at DC 4V, room temperature (25 ° C.). It was measured under the conditions. The ratio of the number of 100 whose measured insulation resistance value was higher than 5 × 10 ⁸ Ω was calculated, and the above ratio was evaluated as the insulation resistance yield. The evaluation results of the insulation resistance yield are shown in Tables 1 to 3.

(Displacement amount)
The displacement amount (nm) in the depth direction of 100 thin film capacitors obtained in Examples and Comparative Examples was measured. A laser interference displacement meter (trade name: LV-2100A, manufactured by Ono Sokki Co., Ltd.) was used for measuring the displacement amount. Further, under the conditions of room temperature (25 ° C.), AC 1 kHz, and V _O-P 5V, the distance from the midpoint of one side of the main surface of the thin film capacitor to the central portion side (inner side) of the main surface of the thin film capacitor is 0.1 mm The displacement amount (average amplitude in vibration) at a point at a distance was measured. Tables 1 to 3 show the average values of the measured displacement amounts.

  The thin-film capacitors of Examples 1 to 19 have a capacitance value similar to that of Comparative Example 1 as compared with Comparative Examples 1 to 7, but the displacement amount is sufficiently low and the insulation resistance yield is low, and It was confirmed that the squeal was reduced. The same tendency was confirmed in the comparison between Example 20 and Comparative Examples 8 to 10. In Comparative Example 1, since the upper electrode layer does not contain the above-mentioned additional atoms, it is considered that the fine structure of the upper electrode layer was not controlled and the displacement amount was large due to the large metal crystals. In addition, in Comparative Examples 2 to 5 and Comparative Example 9, since the content of the added atom is too large or the added atom other than the above is included, the added atom moves to the dielectric layer and exerts an adverse effect. It is possible. In Comparative Examples 6, 7 and 10, it is considered that the sufficient effect was not exhibited because the concentration of the added atoms was too low.

  As described above, the present inventors have confirmed through the examples and the comparative examples that the thin film capacitor obtained by carrying out the present invention has a good vibration reducing effect.

10 ... Thin film capacitor, 11 ... Lower electrode layer (first electrode layer), 12 ... Dielectric layer, 13 ... Upper electrode layer (second electrode layer).

Claims (1)

A first electrode layer, a dielectric layer provided on the first electrode layer, and a second electrode layer provided on the dielectric layer,
Wherein the second electrode layer, Ni, and at least one conductive layer mainly composed of any one metal selected from C u or Ranaru group,
The conductive layer further contains at least one additional atom selected from atoms (excluding Ne, Ar and Kr) belonging to the second to fourth periods of the periodic table,
The content of each said added atom is 1-1000 mass ppm,
Wherein the second electrode layer three or more viewing including the conductive layer,
The composition is different from each other between the conductive layers,
The conductive layer containing Ni as a main component contains at least one additive atom selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Cu, C, and Si,
The conductive layer containing Cu as a main component contains at least one additive atom selected from the group consisting of Cr, Mn, Fe, Co, Ni, C, Si, N, P, O, S, and Cl. to, thin-film capacitor.

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