JP2020161792A - Dielectric thin film element, electronic component and electronic circuit board - Google Patents

Abstract

To provide a dielectric thin film element, an electronic component, and an electronic circuit board in which both of DC bias characteristics and temperature characteristics are compatible with each other.SOLUTION: A dielectric thin film element 200 includes: a dielectric film 40 containing an oxide which contains (1) Bi and Ti, (2) at least one element E1 selected from the group consisting of Na and K, and (3) at least one element E2 selected from the group consisting Ba, Sr, and Ca, and has a perovskite structure; and a lower electrode 30 provided on a lower surface 40a of the dielectric film 40. The lower electrode 30 includes: a first layer 31 which is in contact with the dielectric film 40 on an upper surface 31a and made of Cu; and a second layer 32 which is in contact with a lower surface 31b of the first layer 31 and made of Ni.SELECTED DRAWING: Figure 1

Description

The present invention relates to dielectric thin film devices, electronic components and electronic circuit boards.

The mounting space for electronic components allowed in an electronic device tends to shrink as the electronic device becomes smaller. Capacitors (often referred to as "capacitors" in Japan) are electronic components that are mounted on many electronic devices, and it is essential that they be made smaller and thinner. The thin film capacitor has thinner base material, dielectric film, insulating film, etc. than the conventional laminated ceramic capacitor by the thick film method, and can be made thinner and thinner. Therefore, thin film capacitors are expected as electronic components to be mounted in a small space with a low profile. Further, capacitors embedded in electronic component boards have been developed in recent years.

Many thin-film capacitors have a smaller electrical capacity than conventional multilayer ceramic capacitors. One of the methods for improving the electric capacity is to reduce the film thickness of the dielectric layer. However, when the film thickness of the dielectric film is reduced, the DC electric field strength applied to the dielectric film increases even if the DC voltage applied to both ends of the dielectric film during actual use is the same. Since a ferroelectric substance such as BaTiO ₃ has a so-called DC bias characteristic that the relative permittivity decreases as the DC electric field strength increases, the electric capacity cannot be improved even if the film thickness is reduced.

Further, the thin film capacitor is required to have a small change in the relative permittivity (hereinafter referred to as temperature characteristic) in a wide temperature range for stable operation in various environments of electronic devices.

Patent Document 1 discloses that the DC bias characteristic is improved by using a tungsten bronze type composite oxide containing K, Sr, Mg and Nb for the dielectric film.

However, Patent Document 1 shows only the data of relatively low DC electric field strength (3 to 5 V / μm), which is higher in order to make the dielectric film thinner or increase the DC voltage. Correspondence to DC electric field strength is desired.

Patent Document 2 discloses a dielectric composition containing particles having a perovskite-type crystal structure containing Bi, Na, Sr and Ti. Further, in Patent Document 2, at least a part of the particles contained in the dielectric composition has a core-shell structure including a core portion and a shell portion, and the Bi content in the core portion and the shell portion are present. It is disclosed that the DC bias characteristic is improved by defining the ratio of the Bi content. However, in Cited Document 2, only the data of relatively low DC electric field strength (up to 8 V / μm) is shown, and it is desired to cope with higher DC electric field strength. Further, since it is difficult to form the core-shell structure shown in Cited Document 2 in a thin film, it is desired to improve the DC bias characteristic by a means different from the core-shell structure.

Patent Document 3 discloses that BaTiO ₃ satisfies the temperature characteristics (X5R characteristics of the EIA standard) by containing subcomponents such as Si, Mg, and Y. However, Patent Document 3 does not mention the decrease in the relative permittivity due to the DC voltage at all.

Japanese Unexamined Patent Publication No. 2000-49045 International release 2017/012800 Japanese Unexamined Patent Publication No. 2006-160594

In all of Patent Documents 1 to 3, the temperature characteristic and the DC bias characteristic cannot be compatible with each other.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a dielectric thin film element, an electronic component, and an electronic circuit board capable of achieving both DC bias characteristics and temperature characteristics.

The dielectric thin film element according to one embodiment of the present invention includes at least one element E1 selected from the group consisting of (1) Bi and Ti, (2) Na and K, and (3) Ba, Sr. A dielectric film containing at least one element E2 selected from the group consisting of Ca and an oxide having a perovskite structure, and a first electrode film provided on one surface of the dielectric film are provided. , The first electrode film is in contact with the dielectric film on one surface and is in contact with the first layer composed of Cu and the other surface of the first layer and has a coefficient of thermal expansion smaller than the coefficient of thermal expansion of Cu. Includes a second layer made of metal.

In the dielectric thin film device according to the other embodiment, when the thickness of the first layer is t and the thickness of the second layer is T, the relationship of 0.01 ≦ t / T ≦ 1 is satisfied.

In the dielectric thin film device according to another form, the second layer is composed of Ni.

The electronic component according to one embodiment of the present invention includes the dielectric thin film element.

The electronic circuit board according to one embodiment of the present invention includes the dielectric thin film element.

The electronic circuit board according to another form includes the above-mentioned electronic components.

According to the present invention, a dielectric thin film element, an electronic component, and an electronic circuit board capable of achieving both DC bias characteristics and temperature characteristics are provided.

FIG. 1 is a schematic cross-sectional view of a thin film capacitor according to an example of an electronic component according to the present embodiment. FIG. 2A is a schematic cross-sectional view of an electronic circuit board according to an embodiment, and FIG. 2B is an enlarged view of a portion 90A shown in FIG. 2A. Is.

Hereinafter, embodiments of the present invention will be described in detail.

(Dielectric film)
The dielectric film according to the embodiment of the present invention contains an oxide having a perovskite structure.

This oxide includes the following (1) to (3).
(1) Bi and Ti
(2) At least one element E1 selected from the group consisting of Na and K
(3) At least one element E2 selected from the group consisting of Ba, Sr, and Ca.
The oxide can be adjusted so that the total number of atoms of Bi and the element E1: the total number of atoms of the element E2 is 30:70 to 90:10.

The element E1 may be at least one element selected from the group consisting of Na and K, and may be, for example, Na alone or K only, or a combination of a plurality of elements such as a combination of Na and K. The ratio when the element E1 contains two or more kinds of elements is arbitrary.

The element E2 may be at least one of Ba, Sr, and Ca, for example, Ba only, Sr only, or Ca only, a combination of Ba and Sr, a combination of Ba and Ca, and , Sr and Ca, or all combinations of Ba, Sr, and Ca. The ratio when the element E2 contains two or more kinds of elements is arbitrary.

In the present embodiment, the above oxides have the ratios of the atomic numbers of Bi, Ba, Sr, and Ca to the total atomic numbers of Bi, Ba, Sr, and Ca, respectively, X _Bi , X _Ba , and X, respectively. _When expressed as _Sr and X _Ca , 0.2 ≦ X _Bi / (X _Ba + X _Sr + X _Ca ) ≦ 5 is satisfied. The upper limit is preferably 4.5 or less, and more preferably 4 or less.

The perovskite structure is a crystal structure generally represented by ABX ₃ . The A-site cation is located at the apex of the hexahedral unit cell, the B-site cation is located at the body center of this unit cell, and the X-site anion is located at the face center of this unit cell. In the present invention, cations (bivalent or a combination of monovalent and trivalent) such as Ba ²⁺ , Sr ²⁺ , Ca ²⁺ , Bi ³⁺ , Na ⁺ and K ⁺ are ^{contained in the A} site, and Ti ^{4+ is contained in} the B site. A tetravalent cation such as an ion enters, and a divalent anion such as an O ^2- ion enters the X site.

The oxide may occupy 70% by mass or more of the dielectric film, 80% by mass or more, 90% by mass or more, 95% by mass or more, 99% by mass or more, or 100% by mass. ..

The thickness of the dielectric film is not limited, but can be, for example, 10 nm to 2000 nm, preferably 50 nm to 1000 nm.

Such a dielectric film is excellent in DC bias characteristics. The reason for this is not clear, but the inventors think as follows.

The expression of the relative permittivity in an oxide having a perovskite-type crystal structure is due to the displacement of the ions of each element with respect to the voltage. When the voltage is strong, the displacement of the ions is saturated, and the ratio due to DC bias. The dielectric constant decreases. The combination of the A-site and B-site ions and the oxygen ion bond is important for the ion displacement of the perovskite crystal structure, and the combination of the Bi ion and oxygen ion and the Ti ion and oxygen ion bond. Therefore, it is considered that the magnitude of the DC bias that saturates the displacement of the ions is increased.

Further, the Curie point of the oxide having a perovskite structure containing Bi, Ti and Na (or K) is about 300 ° C., but by containing at least one selected from Ba, Sr, and Ca. , Bi, Ti and Na-containing perovskite-type oxides are considered to have a higher absolute value of relative permittivity and a higher relative permittivity when DC bias is applied as the Curie point approaches room temperature.

In addition to the above oxides, the dielectric film according to the present embodiment may contain trace impurities, subcomponents, and the like within the range in which the effects of the present invention are exhibited. Examples of such a component include Cr, Mo and the like. Further, the dielectric film according to the present embodiment includes Sc (scandium), Y (yttrium), La (lantern), Ce (cerium), Pr (placeodium), Nd (neodymium), Pm (promethium), Sm (samarium). ), Eu (Europium), Gd (Gadolinium), Tb (Terbium), Dy (Dysprosium), Ho (Holmium), Er (Elbium), Tm (Thulium), Yb (Yttrium) and Lu (Lutetium). It may further contain at least one rare earth element of choice. Since the dielectric film further contains rare earth elements, the DC bias characteristics of the dielectric film can be easily improved.

In the present embodiment, the above-mentioned dielectric film is a thin-film dielectric deposition film formed by a known film forming method.

(Thin film capacitor)
Subsequently, with reference to FIG. 1, a thin film capacitor will be described as an example of an electronic component having a dielectric film according to an embodiment of the present invention.

The thin film capacitor 100 according to the embodiment of the present invention has a lower electrode 30 (first electrode film), a dielectric film 40, and an upper electrode 50 in this order.

(Lower electrode)
The lower electrode 30 has a multi-layer structure, and in the present embodiment, the lower electrode 30 has a two-layer structure including a first layer 31 and a second layer 32. The lower electrode 30 is an electrode that sandwiches the dielectric film 40 together with the upper electrode 50 and functions as a capacitor. The lower electrode 30 is provided on the lower surface 40a (one side) of the dielectric film 40.

The first layer 31 is formed in a thin film shape and is in contact with the dielectric film 40 on the upper surface (one surface) 31a. The first layer 31 is made of Cu. The thickness t of the first layer 31 can be set to, for example, 0.05 to 500 μm.

One of the reasons why the first layer 31 in contact with the dielectric film 40 is made of Cu is to suppress redox generated at the interface with the dielectric film 40. By forming the first layer 31 with Cu, the metal component of the dielectric film 40 may be precipitated at the interface with the dielectric film 40, and the dielectric constant or the dielectric strength may be lowered. Conceivable.

The second layer 32 is in contact with the lower surface (the other surface) 31b of the first layer 31. Further, the second layer 32 is composed of a metal having a coefficient of thermal expansion smaller than the coefficient of thermal expansion of Cu, and examples of such a metal include metals such as Ni, Au, Pt, and Co. In this embodiment, the second layer 32 is made of Ni foil. The thickness T of the second layer 32 can be set to, for example, 5 to 500 μm.

During the high temperature operation of the thin film capacitor 100, the second layer 32 can suppress the expansion of the first layer 31 and suppress the excessive expansion of the lower electrode 30. As a result, the strain and stress generated in the dielectric film 40 in contact with the lower electrode 30 can be reduced, and the temperature characteristics of the thin film capacitor 100 can be improved.

The ratio (t / T) of the thickness t of the first layer 31 to the thickness T of the second layer 32 can be designed to satisfy 0.01 ≦ t / T ≦ 1. In this case, the temperature characteristics of the thin film capacitor 100 are further improved, and the DC bias characteristics are also further improved.

The total thickness (t + T) of the lower electrode 30 is not particularly limited as long as it functions as an electrode.

(Dielectric film)
The dielectric film 40 is the above-mentioned dielectric film. As described above, the thickness of the dielectric film 40 can be 10 nm to 2000 nm, preferably 50 nm to 1000 nm. The thickness of the dielectric film 40 can be measured by drilling a thin film capacitor 100 including the dielectric film 40 with a FIB processing device and observing the obtained cross section with an SEM (scanning electron microscope).

(Upper electrode)
The upper electrode 50 is formed in a thin film on the dielectric film 40. The upper electrode 50 is an electrode that sandwiches the dielectric film 40 together with the lower electrode 30 described above and functions as a capacitor. The upper electrode 50 is provided on the upper surface 40b of the dielectric film 40.

The material of the upper electrode 50 is not particularly limited as long as it is a conductive material. Examples of the material are metals such as Pt, Ru, Rh, Pd, Ir, Au, Ag, Cu, Ni, alloys thereof, or conductive oxides, even if they are the same as the material of the lower electrode 30. It may be good or different. The upper electrode 50 is made of Ni in this embodiment. The thickness of the upper electrode 50 can be the same as that of the lower electrode 30.

The upper electrode 50 may have a multi-layer structure. Like the lower electrode 30, the upper electrode 50 has a first layer in contact with the dielectric film 40 and made of Cu, and a second layer made of a metal having a coefficient of thermal expansion smaller than that of Cu. May include.

Further, the thin film capacitor 100 may have a protective film 70 for covering the side surface of the dielectric film 40 and the like and blocking the dielectric film 40 from the external atmosphere. An example of the material of the protective film 70 is a resin such as epoxy.

The shape of the thin film capacitor 100 is not particularly limited, but is usually a rectangular parallelepiped shape when viewed from the thickness direction. Further, the dimensions are not particularly limited, and the thickness and length may be appropriate dimensions according to the application.

The lower electrode 30, the dielectric film 40, and the upper electrode 50 form a capacitor portion 60. When the lower electrode 30 and the upper electrode 50 are connected to an external circuit and a voltage is applied between the electrodes, the dielectric film 40 exhibits a predetermined capacitance and functions as a capacitor. In particular, in the present embodiment, since the above-mentioned dielectric film 40 is used, high DC bias characteristics can be realized.

(Manufacturing method of thin film capacitor)
Next, an example of the method for manufacturing the thin film capacitor 100 shown in FIG. 1 will be described below.

First, a Ni foil to be the second layer 32 is prepared, and the first layer 31 is formed on the second layer 32 by a known film forming method such as a sputtering method. The thickness t of the first layer 31 can be adjusted by the film forming time or the like. As a result, the lower electrode 30 composed of the first layer 31 and the second layer 32 is formed.

Subsequently, the dielectric film 40 is formed on the lower electrode 30. In the present embodiment, the dielectric film 40 is formed as a deposited film by depositing the material constituting the dielectric film 40 on the lower electrode 30 in the form of a thin film by a known film forming method. Known film forming methods for forming the dielectric film 40 include, for example, a vacuum vapor deposition method, a sputtering method, a pulsed laser deposition method (PLD), and a metal-organic chemical vapor deposition method (Metal-Organic Chemical Vapor Deposition). MOCVD), Metalorganic Decomposition (MOD), Zol-Gel method, Chemical Solution Deposition (CSD) and the like are exemplified.

Specifically, the ratio of metal elements in the raw material composition used in each film forming method may be within the above range. The raw materials used for film formation (deposited materials, various target materials, organic metal materials, etc.) may contain trace amounts of impurities, subcomponents, etc. No problem.

For example, when the sputtering method is used, an oxide target having the above metal composition is first prepared. Specifically, powders of compounds containing each metal, for example, carbonates, oxides, hydroxides, etc. are prepared and mixed so that the ratio of metal elements is within the above range to obtain a mixed powder. .. Mixing is preferably carried out in water using, for example, a ball mill. Next, the mixed powder is molded to obtain a molded product. The molding pressure can be, for example, 10 to 200 Pa.

Then, the obtained molded product is fired to obtain a fired product. The firing conditions are such that the holding temperature is 900 to 1300 ° C., the temperature holding time is 1 to 10 hours, and the atmosphere is an oxidizing atmosphere such as air. Finally, the obtained fired body can be processed into a disk shape to obtain a target for sputtering.

Next, the obtained target is sputtered to form the above-mentioned dielectric film as a deposited film on the substrate. The sputtering conditions are not particularly limited, but high frequency (RF) sputtering is preferable, the electric power can be 100 W to 300 W, the atmosphere is preferably an argon gas atmosphere, and the substrate temperature can be preferably room temperature to 200 ° C. ..

It is also preferable to perform rapid thermal annealing (RTA) after forming a dielectric film by sputtering. As conditions for applying RTA, the atmosphere is preferably a nitrogen atmosphere, the heating rate is preferably 300 ° C./min or more, the annealing time is preferably 0.5 to 30 minutes, and the annealing temperature is 700. It is preferably ° C. or higher and 1000 ° C. or lower.

After forming the dielectric film 40, the above-mentioned annealing can be performed if necessary.

Next, a thin film of the material constituting the upper electrode is formed on the formed dielectric film 40 by using a known film forming method (for example, a sputtering method) to form the upper electrode 50.

Through the above steps, as shown in FIG. 1, a thin film capacitor 100 having a capacitor portion (lower electrode 30, dielectric film 40 and upper electrode 50) 60 formed on the substrate 10 via an adhesive film 20 is formed. can get. The protective film 70 that protects the dielectric film 40 may be formed by a known film forming method so as to cover at least the portion where the dielectric film 40 is exposed to the outside.

(Dielectric thin film element)
The dielectric thin film element 200 that can be used for the thin film capacitor 100 described above includes the lower electrode 30 and the dielectric film 40 described above.

(Modification example)
Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and may be modified in various ways within the scope of the present invention.

For example, the lower electrode is not limited to the two-layer structure, and may have a multi-layer structure of three or more layers including the first layer and the second layer described above.

Further, a dielectric film made of a material different from that of the dielectric film 40 may be further provided between the lower electrode 30 and the upper electrode 50. For example, a plurality of dielectrics can be obtained by forming a laminated structure of an amorphous film or a crystal film such as Si ₃ N _x , SiO _x , Al ₂ O _x , ZrO _x , Ta ₂ O _x and the above-mentioned dielectric film 40. It is possible to adjust the temperature change of impedance and relative permittivity of the entire film.

Further, the dielectric film according to the present embodiment can be used for electronic components such as piezoelectric elements in addition to capacitors.

(Electronic circuit board)
The electronic circuit board according to this embodiment may include the above-mentioned dielectric thin film element. The electronic circuit board may include the above electronic components including a dielectric thin film element. For example, the electronic circuit board may include the thin film capacitor as an electronic component. Electronic components such as thin film capacitors may be installed on the surface of the electronic circuit board. Electronic components such as thin film capacitors may be embedded in the electronic circuit board. An example of the electronic circuit board is shown in (a) in FIG. 2 and (b) in FIG. The electronic circuit board 90 includes an epoxy-based resin substrate 92, a resin layer 93 covering the epoxy-based resin substrate 92, a thin film capacitor 91 installed on the resin layer 93, and an insulating coating covering the resin layer 93 and the thin film capacitor 91. A layer 94, an electronic component 95 installed on the insulating coating layer 94, and a plurality of metal wirings 96 may be provided. At least a part of the metal wiring 96 may be drawn out to the surface of the epoxy resin substrate 92 or the insulating coating layer 94. At least a part of the metal wiring 96 may be connected to the extraction electrode of the thin film capacitor 91 or the electronic component 95. At least a part of the metal wiring 96 may penetrate the electronic circuit board 90 in the direction from the front surface to the back surface of the electronic circuit board 90.

As shown in FIG. 2B, the thin film capacitor 91 according to the present embodiment has a lower electrode 30, a dielectric film 40 provided on the surface of the lower electrode 30, and a part of the upper surface of the dielectric film 40. And the through electrode 52 provided directly on the surface of the lower electrode 30 through the other portion of the dielectric film 40 (specifically, the rest of the portion where the upper electrode is provided). The insulating resin layer 58 that covers the upper electrode 50, the dielectric film 40, and the penetrating electrode 52, the take-out electrode 54 that penetrates the insulating resin layer 58 and is directly provided on the surface of the penetrating electrode 52, and the insulating resin. A take-out electrode 56 is provided which penetrates the layer 58 and is provided directly on the surface of the upper electrode 50.

The electronic circuit board 90 may be manufactured by the following procedure. First, the surface of the epoxy resin substrate 92 is covered with an uncured resin layer. The uncured resin layer is a precursor of the resin layer 93. The thin film capacitor 91 is installed on the surface of the uncured resin layer so that the base electrode of the thin film capacitor 91 faces the uncured resin layer. By covering the uncured resin layer and the thin film capacitor 91 with the insulating coating layer 94, the thin film capacitor 91 is sandwiched between the epoxy resin substrate 92 and the insulating coating layer 94. The resin layer 93 is formed by thermosetting the uncured resin layer. The insulating coating layer 94 is pressure-bonded to the epoxy resin substrate 92, the thin film capacitor 91, and the resin layer 93 by hot pressing. A plurality of through holes penetrating the laminated substrate are formed. Metal wiring 96 is formed in each through hole. After forming the metal wiring 96, the electronic component 95 is installed on the surface of the insulating coating layer 94. By the above method, the electronic circuit board 90 embedded in the thin film capacitor 91 can be obtained. Each metal wiring 96 may be made of a conductor such as Cu. The uncured resin layer may be a B-stage thermosetting resin (for example, epoxy resin or the like). The B-stage thermosetting resin is not completely cured at room temperature, but is completely cured by heating. The insulating coating layer 94 may be formed of an epoxy resin, a polytetrafluoroethylene resin, a polyimide resin, or the like.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, the present invention is not limited to the following examples.

(Example, comparative example)
First, the target for sputtering required for forming the dielectric film was prepared by the solid phase method as follows.

As raw material powders for preparing the target, powders of barium carbonate, strontium carbonate, calcium carbonate, titanium oxide, bismuth oxide, and potassium carbonate were prepared. These powders were weighed so that the number of atoms of each metal had the composition shown in Table 1.

Wet mixing of the weighed raw material powder for target preparation was carried out in a ball mill using water as a solvent for 20 hours. The obtained mixed powder slurry was dried at 100 ° C. to obtain a mixed powder. The obtained mixed powder was press-molded by a press machine to obtain a molded product. The molding conditions were a pressure of 100 Pa, a temperature of 25 ° C., and a pressing time of 3 minutes.

Then, the obtained molded product was fired to obtain a fired product. The firing conditions were a holding temperature of 1100 ° C., a temperature holding time of 5 hours, and an atmosphere of air.

The obtained fired body was processed into a diameter of 80 mm and a thickness of 5 mm by a surface grinder and a cylindrical grinder to obtain a target for sputtering for forming a dielectric film.

Subsequently, a Ni foil having a thickness of 50 μm was prepared, and a Cu layer having a predetermined thickness was formed on the Ni foil by a sputtering method to form a lower electrode.

Further, a dielectric film having a thickness of 500 nm was formed on the lower electrode by a sputtering method using the target for sputtering prepared above. The sputtering conditions were atmosphere: Ar, pressure: 1.0 Pa, high frequency power: 200 W, and substrate temperature: 100 ° C. After forming the dielectric film, the dielectric film is subjected to rapid thermal anneal treatment (RTA) under a nitrogen atmosphere at 900 ° C. for 1 minute and at a heating rate of 900 ° C./min. gave.

Next, a Ni thin film was formed on the obtained dielectric film by a sputtering method so as to have a diameter of 200 μm and a thickness of 100 nm using a mask, and used as an upper electrode. Through the above steps, a thin film capacitor having the configuration shown in FIG. 1 was obtained.

The crystal structure of the dielectric film was measured and analyzed by an X-ray diffraction method using an XRD measuring device (Rigaku, Smartlab). As a result, it was confirmed that the dielectric film has a perovskite-type crystal structure.

In addition, the composition of the dielectric film was analyzed using XRF (X-ray Fluorescense Analysis), and it was confirmed that the composition was consistent with the composition shown in Table 1.

For all the obtained thin film capacitors, the relative permittivity when DC bias was applied was measured by the method shown below.

(Relative permittivity)
The relative permittivity when a DC bias is applied is an input at a room temperature of 25 ° C. and a frequency of 1 kHz while applying a DC bias of 10 V / μm in the thickness direction to the thin film capacitor using a digital LCR meter (Hewlet-Packard, 4284A). It was calculated from the capacitance, effective electrode area, inter-electrode distance and vacuum permittivity measured under the condition of signal level (measurement voltage) of 1.0 Vrms (no unit). As the dielectric film, it is preferable that the relative permittivity when DC bias is applied is high, and a sample having a relative permittivity of 600 or more when DC bias is applied is judged to be good. The results are shown in Table 1.

(Temperature characteristics)
The X5R characteristics of the EIA standard were evaluated as the temperature characteristics of the relative permittivity. Specifically, each sample of the thin-film capacitor is changed in temperature from -55 ° C. to 85 ° C., and the capacitance measured under the conditions of a frequency of 1 kHz and an input signal level (measurement voltage) of 1.0 Vrms is effective. Calculated from the electrode area, the distance between the electrodes, and the capacitance of the vacuum (no unit). Then, it was judged that the change within ± 15% with respect to the relative permittivity at 25 ° C. was good.

As shown in Table 1, in the comparative example in which the lower electrode is composed of only the Cu layer, the temperature characteristic does not satisfy the X5R characteristic (within ± 15% at −55 ° C. to 85 ° C.), but the lower electrode is the Cu layer and Ni. It was confirmed that all of Examples 1 to 14 composed of layers satisfy the X5R characteristics. It was also confirmed that Examples 1 to 14 had excellent DC bias characteristics in which the relative permittivity when DC bias was applied was 600 or more.

Further, Examples 2 to 5 satisfying the relationship of 0.01 ≦ t / T ≦ 1 have DC bias characteristics and temperature as compared with Examples 1 and 6 not satisfying the relationship of 0.01 ≦ t / T ≦ 1. It was confirmed that the characteristics were better.

30 ... lower electrode, 31 ... first layer, 32 ... second layer, 40 ... dielectric film, 50 ... upper electrode, 90 ... electronic circuit board, 91, 100 ... thin film capacitor, 200 ... dielectric thin film element.

Claims (6)

(1) Bi and Ti,
(2) At least one element E1 selected from the group consisting of Na and K, and
(3) At least one element E2 selected from the group consisting of Ba, Sr, and Ca.
A dielectric film containing an oxide having a perovskite structure and
It is provided with a first electrode film provided on one surface of the dielectric film.
The first electrode film is in contact with the dielectric film on one surface and is in contact with the first layer made of Cu and the other surface of the first layer and has a coefficient of thermal expansion smaller than the coefficient of thermal expansion of Cu. A dielectric thin film element comprising a second layer made of a metal having. The dielectric thin film device according to claim 1, wherein the relationship of 0.01 ≦ t / T ≦ 1 is satisfied when the thickness of the first layer is t and the thickness of the second layer is T. The dielectric thin film device according to claim 1 or 2, wherein the second layer is made of Ni. An electronic component comprising the dielectric thin film device according to any one of claims 1 to 3. An electronic circuit board comprising the dielectric thin film device according to any one of claims 1 to 3. An electronic circuit board comprising the electronic component according to claim 4.

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