CN111739731A

CN111739731A - Dielectric film, dielectric thin film, electronic component, thin film capacitor, and electronic circuit board

Info

Publication number: CN111739731A
Application number: CN202010194812.XA
Authority: CN
Inventors: 大槻史朗; 高桥和子; 原田祥典; 铃木翔太; 加贺谷康永; 加藤友彦; 石田未来
Original assignee: TDK Corp
Current assignee: TDK Corp
Priority date: 2019-03-25
Filing date: 2020-03-19
Publication date: 2020-10-02

Abstract

The present invention relates to a dielectric film. The dielectric film includes: (1) bi and Ti; (2) at least one element E1 selected from Na and K; and (3) at least one element E2 selected from Ba, Sr and Ca. The dielectric film is provided with: a main phase including an oxide including Bi, Ti, an element E1, and an element E2 and having a perovskite structure; and a secondary phase comprising Bi and having a lower oxygen concentration than the primary phase. In the cross section of the dielectric film, a ratio RS of an area of the sub-phase to a total of the area of the main phase and the area of the sub-phase is 0.03 to 0.3.

Description

Dielectric film, dielectric thin film, electronic component, thin film capacitor, and electronic circuit board

Technical Field

The invention relates to a dielectric film, a dielectric thin film, an electronic component, a thin film capacitor and an electronic circuit board.

Background

In recent years, with the miniaturization of electronic devices, the space for housing electronic components in the electronic devices has become narrow. Therefore, small and thin electronic parts are sought. A film capacitor is one of electronic components mounted on various electronic devices. (refer to Japanese patent laid-open Nos. 2000-49045, 2017/012800 pamphlet and 2006-160594.) in Japan, a film capacitor is often referred to as a film capacitor. The substrate, the insulating film, the electrode and the dielectric film of the film capacitor are thinner than those of the conventional laminated ceramic capacitor, and the thickness of the entire film capacitor is also thinner than that of the conventional laminated ceramic capacitor. Therefore, it is desired to mount a thin film capacitor in a small electronic device instead of a conventional multilayer ceramic capacitor. In recent years, a thin film capacitor embedded in an electronic circuit substrate has also been developed.

Disclosure of Invention

First invention

The thin film capacitor has a smaller capacitance than conventional multilayer ceramic capacitors. As one of methods for increasing the capacitance, there is a method of reducing the thickness of a dielectric film. However, if the thickness of the dielectric film is reduced, the strength of the dc electric field applied to the dielectric increases even if the dc voltage applied to both ends of the dielectric film is the same during actual use. Furthermore, BaTiO₃The relative permittivity of such ferroelectrics has a so-called DC bias characteristic in which the higher the DC electric field strength is, the lower the relative permittivity is, and therefore, the capacitance cannot be increased even if the film thickness is made thin.

In addition, from the viewpoint of stabilizing the capacitance generated in the dielectric film, it is also required to reduce the amount of change in the relative permittivity (capacitance) according to a temperature change, that is, to improve the temperature characteristics of the relative permittivity.

Jp 2000 a-49045 discloses that DC bias characteristics are improved by using a tungsten bronze type composite oxide containing K, Sr, Mg, and Nb for the dielectric film.

International publication No. 2017/012800 discloses a perovskite dielectric having a core-shell structure, and discloses improvement of DC bias characteristics.

The following findings were made in Japanese patent laid-open No. 2006-160594: by adding Si, Mg, Y, etc. to barium titanate, the EIA standard X5R characteristic, that is, the capacity change rate in the range of-55 to 85 ℃ is within + -15%.

However, the respective inventions described in japanese patent laid-open nos. 2000-49045, 2017/012800 pamphlet and 2006-160594 cannot achieve both improvement of the DC bias characteristic and improvement of the temperature characteristic of the relative dielectric constant.

The first invention has been made to solve the above-mentioned problems, and an object thereof is to provide a dielectric film, an electronic component, a thin-film capacitor, and an electronic circuit board, which can improve both DC bias characteristics and temperature characteristics of relative permittivity.

A dielectric film according to a first aspect of the present invention includes: (1) bi and Ti; (2) at least one element E1 selected from Na and K; and (3) a dielectric film of at least one element E2 selected from Ba, Sr, and Ca. The dielectric film includes: a main phase including an oxide including Bi, Ti, an element E1, and an element E2 and having a perovskite structure; and a secondary phase comprising Bi and having a lower oxygen concentration than the primary phase. Further, in the cross section of the dielectric film, a ratio RS of the area of the sub-phase to the total of the area of the main phase and the area of the sub-phase satisfies the expression 0.03 RS 0.3.

Here, the total number of atoms of Bi and the element E1 may be 30:70 to 90:10, based on the total number of atoms of the element E2.

In the oxide, the ratio of the number of atoms of the element E1 to the number of atoms of Bi may be 0.9 to 1.1.

In the oxide, the ratio of the number of atoms of Ti to the total number of atoms of Bi, the element E1, and the element E2 may be 0.9 to 1.1.

An electronic component according to a first aspect of the present invention includes the dielectric film.

Here, the electronic component may include an electrode, and the dielectric film may be in contact with the electrode.

A thin film capacitor according to a first aspect of the present invention includes the dielectric film.

An electronic circuit board according to a first aspect of the present invention includes the dielectric film.

An electronic circuit board according to an aspect of the first invention includes the electronic component.

An electronic circuit board according to a first aspect of the present invention includes the thin film capacitor described above.

According to the first aspect of the invention, it is possible to provide a dielectric film and the like capable of improving both DC bias characteristics and temperature characteristics of relative permittivity.

Second invention

Electronic devices incorporating thin film capacitors can be used in various environments. However, the relative permittivity of a conventional dielectric thin film is likely to change with a change in temperature. Therefore, in order to stably operate the electronic device in various environments, it is required that the change in the relative permittivity accompanying the temperature change is small. The temperature characteristics described below are properties in which the relative dielectric constant is hard to change with a change in temperature.

For example, japanese patent application laid-open No. 2006-160594 discloses: the dielectric ceramic contains at least one selected from the group consisting of Si, Mg, Mn, Y and Ca in order to improve temperature characteristics. The multilayer ceramic capacitor provided with the dielectric ceramic realizes X5R based on the EIA standard. X5R indicates that the rate of change in capacitance of the capacitor is-15% to 15% in a temperature range of-55 ℃ to 85 ℃.

The temperature characteristics of conventional dielectric thin films are not necessarily superior to those of the above-described dielectric ceramics.

A second object of the present invention is to provide a dielectric thin film having excellent temperature characteristics, an electronic component including the dielectric thin film, a thin-film capacitor, and an electronic circuit board.

A dielectric thin film according to one aspect of the second invention includes an oxide having a perovskite structure, the oxide including Bi, an element E1, an element E2, and Ti, the element E1 being at least one element selected from Na and K, the element E2 being at least one element selected from Ca, Sr, and Ba, and the oxide including a double crystal.

The content of Bi in the dielectric thin film may be represented as [ Bi ] mol%, the total content of the element E2 in the dielectric thin film may be represented as [ E2] mol%, and [ Bi ]/[ E2] may be 0.214 to 4.500.

An electronic component according to a second aspect of the present invention includes the above-described dielectric thin film.

A thin film capacitor according to a second aspect of the present invention includes the above-described dielectric thin film.

The electronic circuit board according to the second aspect of the present invention may include the above-described dielectric thin film.

The electronic circuit board according to the second aspect of the present invention may include the electronic component.

The electronic circuit board according to the second aspect of the present invention may include the thin film capacitor described above.

According to the second aspect of the present invention, a dielectric thin film having excellent temperature characteristics, an electronic component including the dielectric thin film, a thin-film capacitor, and an electronic circuit board can be provided.

Third invention

The temperature characteristics of conventional dielectric thin films are not necessarily superior to those of the above dielectric ceramics.

A third object of the present invention is to provide a dielectric thin film having excellent temperature characteristics, an electronic component including the dielectric thin film, a thin-film capacitor, and an electronic circuit board.

The dielectric thin film according to the first aspect of the present invention includes an oxide having a perovskite structure, the oxide including Bi, an element E1, an element E2, and Ti, the element E1 being at least one element selected from Na and K, the element E2 being at least one element selected from Ca, Sr, and Ba, and the dielectric thin film includes tetragonal crystals of the oxide and rhombohedral crystals of the oxide.

The dielectric thin film according to the second aspect of the third invention is a dielectric thin film containing an oxide having a perovskite structure, the oxideComprising Bi, an element E1, an element E2 and Ti, the element E1 being at least one element selected from Na and K, the element E2 being at least one element selected from Ca, Sr and Ba, the X-ray diffraction pattern of the dielectric thin film being measured by using CuK α rays as incident X-rays, the X-ray diffraction pattern comprising a peak having a diffraction angle 2 theta of 39.0 DEG to 41.2 DEG, the peak having a diffraction angle 2 theta of 39.0 DEG to 41.2 DEG being represented by the superposition of a first peak and a second peak, the diffraction angle 2 theta of the first peak being represented by the superposition of the first peak and the second peak₁Diffraction angle 2 theta to second peak₂Small, S1 is the area of the first peak, S2 is the area of the second peak, and S1/S2 is 0.02 to 55.

The dielectric thin film according to the second aspect of the third invention may include tetragonal crystals of the oxide and rhombohedral crystals of the oxide, the first peaks may be derived from the tetragonal crystals of the oxide, and the second peaks may be derived from the rhombohedral crystals of the oxide.

In the first and second aspects of the third invention, the content of Bi in the dielectric thin film may be represented as [ Bi ] mol%, the total content of the element E2 in the dielectric thin film may be represented as [ E2] mol%, and [ Bi ]/[ E2] may be 0.214 to 4.500.

An electronic component according to a third aspect of the present invention includes the dielectric thin film.

A thin film capacitor according to a third aspect of the present invention includes the above dielectric thin film.

The electronic circuit board according to the third aspect of the present invention may include the above-described dielectric thin film.

The electronic circuit board according to the third aspect of the present invention may include the electronic component.

The electronic circuit board according to the third aspect of the present invention may include the thin film capacitor described above.

According to the third aspect of the present invention, a dielectric thin film having excellent temperature characteristics, an electronic component including the dielectric thin film, a thin-film capacitor, and an electronic circuit board can be provided.

Drawings

Fig. 1 is a cross-sectional view of a dielectric film according to an embodiment of the first invention.

Fig. 2 is a schematic cross-sectional view of an electronic component (film capacitor) according to each embodiment of the first, second, and third inventions.

Fig. 3A and 3B are cross-sectional views of electronic components according to other embodiments of the first invention.

Fig. 4A is a schematic cross-sectional view of the electronic circuit substrate according to each embodiment of the first, second, and third inventions, and fig. 4B is an enlarged view of a portion 90A shown in fig. 4A.

Fig. 5 is a schematic perspective view of a unit cell of perovskite structure, relating to the second invention.

Fig. 6 is a schematic cross-sectional view of a double crystal of an oxide, relating to the second invention.

Fig. 7 is a schematic diagram of a fast fourier transform pattern of an image of a double crystal of an oxide taken by a transmission electron microscope, relating to the second invention.

Fig. 8 is a lattice image of the dielectric thin film of example 31 taken by a transmission electron microscope, and relates to a second invention.

Fig. 9A is an FFT pattern of the image shown in fig. 8, fig. 9B is an enlarged view of a point 211 shown in fig. 9A, and fig. 9A and 9B relate to the second invention.

Fig. 10 is a schematic perspective view of tetragonal crystals of an oxide having a perovskite structure, relating to the third invention.

Fig. 11 is a schematic perspective view of rhombohedral crystals of an oxide having a perovskite structure, relating to the third invention.

FIG. 12 is a peak in the X-ray diffraction pattern of example 51 of the third invention.

Fig. 13 shows a first peak and a second peak constituting the peak shown in fig. 12.

Fig. 14 is a peak represented by the superposition of the first peak and the second peak shown in fig. 13.

Fig. 15 is the peak in fig. 12 and the peak in fig. 14.

Detailed Description

Mode for carrying out the first invention

The following describes an embodiment of the first invention in detail.

(dielectric film)

The dielectric film according to the first aspect of the invention includes:

(1) bi and Ti;

(2) at least one element E1 selected from Na and K; and

(3) at least one element E2 selected from Ba, Sr and Ca. The dielectric film has: a main phase including an oxide including Bi, Ti, an element E1, and an element E2 and having a perovskite structure; and a secondary phase comprising Bi and having a lower oxygen concentration than the primary phase. Further, in the cross section of the dielectric film, a ratio RS of the area of the sub-phase to the total of the area of the main phase and the area of the sub-phase satisfies the following expression,

0.03≤RS≤0.3。

here, the total number of atoms of Bi and the element E1 is preferably 30:70 to 90:10, based on the total number of atoms of the element E2. This makes it easy to exhibit a high dielectric constant.

In the oxide, the ratio of the number of atoms of the element E1 to the number of atoms of Bi may be 0.9 to 1.1. The ratio of the number of atoms may be 0.95 to 1.05.

In the oxide, the ratio of the number of atoms of Ti to the total number of atoms of Bi, the element E1, and the element E2 may be 0.9 to 1.1 or less. The lower limit may be 0.95 and the upper limit may be 1.05 or less.

The element E1 may be at least one element selected from Na and K, and may be, for example, Na alone or K alone, or a combination of Na and K. The ratio in the case where the element E1 contains two elements is arbitrary.

The element E2 may be at least one of Ba, Sr, and Ca, and may be, for example, Ba alone, Sr alone, or Ca alone, a combination of Ba and Sr, a combination of Ba and Ca, a combination of Sr and Ca, or a combination of all of Ba, Sr, and Ca. The proportion in the case where the element E2 contains two or more elements is arbitrary.

(Structure of dielectric film)

The dielectric film has a main phase and a sub-phase. An example of a schematic cross-sectional view of dielectric film 40 is shown in fig. 1. The main phase M forms a continuous phase and the secondary phase S is dispersed within the main phase M. In the embodiment of the first invention, the secondary phase S is spatially uniformly dispersed in the cross section.

(leading photo)

The main phase contains a large amount of oxide crystals containing Bi, Ti, an element E1, and an element E2 and having a perovskite structure. The main phase may contain 90 mass% or more of the oxide crystal, 95 mass% or more of the oxide crystal, 99 mass% or more of the oxide crystal, or 100 mass%.

The perovskite structure is typically ABX₃The crystal structure shown. The cations of the A site are located at the vertices of the hexahedral lattice, the cations of the B site are located at the body center of the lattice, and the anions of the X site are located at the face center of the lattice. In the first invention, Ba²⁺、Ca²⁺、Sr²⁺、Bi³⁺、Na⁺、K⁺Isocationic (divalent or a combination of monovalent and trivalent) access to the A site, Ti⁴⁺The tetravalent cation of the ion enters the B site, O^2-Divalent anions such as ions enter the X site.

(deputy phase)

The secondary phase S contains Bi and has a lower oxygen concentration than the main phase, and is dispersed in the main phase M. The oxygen concentration is an atomic ratio (atm%) of oxygen atoms in the entire atoms constituting the phase. For example, the oxygen concentration of each phase can be obtained by energy dispersive X-ray spectrometry (STEM-EDS) using a scanning transmission electron microscope. The oxygen concentration of the main phase M is about 50 atomic%, and the oxygen concentration of the sub-phase S is usually 20 atomic% or more lower than that of the main phase M. The secondary phase S may be a metal phase substantially not containing oxygen, or may contain oxygen to some extent. Such a secondary phase S generally does not have a perovskite structure.

The equivalent circular diameter of each particle of the secondary phase S may be 1 to 30 nm. The secondary phase S may contain a metal element other than Bi.

In the first embodiment of the present invention, in the cross section of the dielectric film 40, the ratio RS of the area of the sub-phase S to the total of the area of the main phase M and the total area of the sub-phases S satisfies the following expression.

0.03≤RS≤0.3

Here, the ratio RS is a value measured over the entire cross section of the dielectric film 40. In general, the secondary phase S exists substantially uniformly in the cross section, and in this case, the ratio RS may be calculated based on a partial region in the cross section.

The lower limit of the ratio RS may be 0.05, and the upper limit may be 0.2.

The area of the dielectric film 40 other than the main phase M and the sub-phase S may be 10% or less, 5% or less, 1% or less, or 0% in the cross section.

The thickness of the dielectric film 40 is not limited, and may be, for example, 10nm to 2000nm, preferably 50nm to 1000 nm.

The thickness of the dielectric film can be measured by obtaining a thin sample of a laminate including the dielectric film by FIB (Focused Ion Beam) and then observing the thin sample by TEM (Transmission electron microscope).

Such a dielectric film is excellent in both DC bias characteristics and temperature characteristics. The reason is not clear, but the inventors consider the following.

The expression of the relative permittivity of the oxide having the perovskite type crystal structure is caused by the displacement of the ion of each element with respect to the voltage, and if the voltage is applied, the displacement of the ion is saturated, and thus, the decrease of the relative permittivity caused by the DC bias occurs. It is considered that the combination of the bonding between the ions of the a site and the B site and the oxygen ion is important for the displacement of the ions of the perovskite crystal structure, and when at least one element E2 selected from Sr, Ba and Ca is included in the perovskite crystal structure containing Bi and at least one element E1 selected from Na and K and Ti, the degree of freedom of each bond is expanded, and thereby the magnitude of DC bias for saturation of the displacement of the ions is increased.

In the first embodiment of the present invention, the dielectric film 40 has a structure including the main phase M and the sub-phase S. Since the main phase M and the sub-phase S have different thermal expansion coefficients, it is considered that both the DC bias characteristic and the temperature characteristic of the dielectric constant are improved by suppressing the phase transition of the main phase. In particular, it is considered that the phase transition accompanying the temperature change is effectively suppressed by the ratio RS of the area of the sub-phase S to the total of the area of the main phase M and the area of the sub-phase S satisfying the above expression.

If the ratio is too small as compared with RS, the above-mentioned effects are difficult to obtain. On the other hand, if it is too large as compared with RS, the dielectric constant is lowered.

The dielectric film according to the embodiment of the first invention may contain a trace amount of impurities, sub-components, and the like within the range in which the effects of the first invention are exhibited. Examples of such a component include Cr and Mo.

For example, the dielectric film may further contain at least one rare earth element selected from Sc (scandium), Y (yttrium), La (lanthanum), Ce (cerium), Pr (praseodymium), Nd (neodymium), Pm (promethium), Sm (samarium), Eu (europium), Gd (gadolinium), Tb (terbium), Dy (dysprosium), Ho (holmium), Er (erbium), Tm (thulium), Yb (ytterbium), and Lu (lutetium). The dielectric film may contain a rare earth element, thereby improving DC bias characteristics of the dielectric film.

(method for producing dielectric film)

For example, the dielectric film can be produced by the following method.

First, an oxide film having the above-described overall composition and not having the sub-phase S is formed by a known method. Examples of the film formation method include a vacuum evaporation method, a sputtering method, a Pulsed Laser Deposition (PLD), a Metal-Organic Chemical vapor Deposition (MOCVD), a Metal-Organic Decomposition (MOD), a sol-gel method, and a Chemical Solution Deposition (CSD).

Specifically, the ratio of the metal element in the raw material composition used in each film formation method may be set within the range of the entire composition of the dielectric film. In addition, although a small amount of impurities, subcomponents, and the like may be contained in the raw materials (deposition material, various target materials, organic metal material, and the like) used in film formation, there is no particular problem as long as desired dielectric characteristics can be obtained.

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

Thereafter, the obtained molded body is fired to obtain a fired body. The firing conditions may be such that the holding temperature is 900 to 1300 ℃, the temperature holding time is 1 to 10 hours, and the atmosphere is an oxidizing atmosphere such as air. Finally, the obtained sintered body may be processed into a disk shape to obtain a sputtering target material.

Next, the obtained target is sputtered to form the dielectric film as a deposited film on the base material. The sputtering conditions are not particularly limited, but high frequency (RF) sputtering is preferable, the power may be set to 100W to 300W, and the atmosphere is preferably an oxygen-containing atmosphere, among which an oxygen-containing argon atmosphere, argon (Ar)/oxygen (O) atmosphere are preferable₂) The ratio is preferably 1/1 to 5/1, and the substrate temperature is preferably set to room temperature to 200 ℃.

After the oxide film is formed by sputtering, next, Rapid Thermal Annealing (RTA) is performed in a reducing atmosphere to form a sub-phase S. An example of the reducing atmosphere is an inert gas atmosphere containing hydrogen. Examples of inert gases are argon, nitrogen. The temperature rise rate is preferably 100 ℃/min or more, the annealing time is preferably 0.5 to 120 min, and the annealing temperature is preferably 700 ℃ to 1000 ℃.

Since Bi is relatively most easily reduced among metals constituting a dielectric, the sub-phase S can be formed by this treatment. For example, the area of the secondary phase S can be adjusted by adjusting the hydrogen concentration, the annealing time, and the annealing temperature.

(film capacitor of the first embodiment)

Next, a thin film capacitor will be described with reference to fig. 2, taking as an example an electronic component having the dielectric film according to the first embodiment of the first invention.

The thin-film capacitor 100 of the first embodiment includes a substrate 10, an adhesive film 20, a lower electrode 30, a dielectric film 40, and an upper electrode 50 in this order.

(substrate)

The substrate 10 supports the adhesive film 20, the lower electrode 30, the dielectric film 40, and the upper electrode 50 formed thereon. The material of the substrate 10 is not particularly limited as long as it has mechanical strength enough to support the above layers. Examples of the substrate 10 are Si single crystal, SiGe single crystal, GaAs single crystal, InP single crystal, SrTiO single crystal₃Single crystal, MgO single crystal, LaAlO₃Single crystal, ZrO₂Single crystal, MgAl₂O₄Single crystal, NdGaO₃A single crystal substrate such as a single crystal; al (Al)₂O₃Polycrystal, ZnO polycrystal, SiO₂A ceramic polycrystalline substrate such as a polycrystal; and a metal substrate selected from the group consisting of Ni, Cu, Ti, W, Mo, Al, Pt, and alloys thereof. From the viewpoint of low cost, workability, and the like, a Si single crystal substrate is preferable.

The thickness of the substrate 10 may be, for example, 10 μm to 5000 μm. If the thickness is too small, the mechanical strength may not be ensured; if the thickness is too large, there may be a problem that it is impossible to contribute to miniaturization of electronic components.

The resistivity of the substrate 10 varies depending on the material of the substrate. When the substrate is made of a material having low resistivity, a current may leak to the substrate 10 side during operation of the thin film capacitor, and the electrical characteristics of the thin film capacitor may be affected. Therefore, when the resistivity of the substrate 10 is low, it is preferable to perform an electrical insulation treatment on the surface thereof so that the current during the capacitor operation does not flow through the substrate 10.

For example, when the substrate 10 is a Si single crystal substrate, an insulating film is preferably formed on the surface of the substrate 10. The material and thickness of the insulating film are not particularly limited as long as the insulation between the substrate 10 and the lower electrode 30 is sufficiently ensured. An example of a material constituting the insulating film is SiO₂、Al₂O₃、Si₃N_x. The thickness of the insulating film is preferably 0.01 μm or more. The insulating film is preferably an adhesion film provided on the substrate 1020 side (lower electrode 30 side). The insulating film can be formed by a known film formation method such as a thermal oxidation method or a CVD (Chemical Vapor Deposition) method.

(laminating film)

The adhesion film 20 is provided between the substrate 10 and the lower electrode 30, and improves adhesion between the substrate 10 and the lower electrode 30. The material of the adhesion film 20 is not particularly limited as long as it can sufficiently ensure adhesion between the substrate 10 and the lower electrode 30. For example, in the case where the lower electrode 30 is a Cu film, the adhesion film 20 may be a Cr film; when the lower electrode 30 is a Pt film, the adhesion film 20 may be a Ti film. The thickness of the adhesive film 20 may be set to 5 to 50nm, for example.

(lower electrode)

On the substrate 10, the lower electrode 30 is formed in a thin film shape through the adhesive film 20. 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 material constituting the lower electrode 30 is not particularly limited as long as it is a material having conductivity. For example, metals such as Pt, Ru, Rh, Pd, Ir, Au, Ag, Cu, and Ni, alloys thereof, and conductive oxides thereof are exemplified.

The thickness of the lower electrode 30 is not particularly limited as long as it functions as an electrode. The thickness of the lower electrode 30 is preferably 10nm or more, and from the viewpoint of making the film thinner, it is preferably 300nm or less.

(dielectric film)

The dielectric film 40 is the above-described dielectric film. The lower end surface of the dielectric film is in contact with the adhesive film 20, and the upper end surface is in contact with the upper electrode 50. The thickness of the dielectric film 40 may be 10nm to 2000nm, preferably 50nm to 1000 nm. The thickness of the dielectric film 40 can be measured by digging a thin film capacitor 100 including the dielectric film 40 with an FIB (focused ion beam) processing apparatus and observing the obtained cross section with an SEM (scanning electron microscope).

(Upper electrode)

On the upper surface of the dielectric film 40, the upper electrode 50 is formed in a thin film shape. The upper electrode 50 is an electrode that sandwiches the dielectric film 40 together with the lower electrode 30 and functions as a capacitor.

The material of the upper electrode 50 is not particularly limited as long as it is a material having conductivity, as in the lower electrode 30. Examples of the material include metals such as Pt, Ru, Rh, Pd, Ir, Au, Ag, Cu, and Ni, alloys thereof, and conductive oxides thereof, and may be the same as or different from the material of the lower electrode 30. The thickness of the upper electrode 50 may be set to be the same as that of the lower electrode 30.

The thin-film capacitor 100 may also include a protective film 70 for covering the side surface of the dielectric film 40 and for insulating the dielectric film 40 from the outside atmosphere. Examples of the material of the protective layer are resins such as epoxy.

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

The lower electrode 30, the dielectric film 40, and the upper electrode 50 form a capacitor portion 60 (capacitor portion). 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 embodiment of the first invention, since the dielectric film 40 is used, high DC bias characteristics and temperature characteristics can be achieved at the same time.

Further, since the dielectric film 40 having the sub-phase S having a relatively low oxygen concentration, that is, a strong metallic property, is in contact with the upper electrode 50 and the lower electrode 30, the adhesion between each electrode and the dielectric film 40 is improved, and the occurrence of cracks on the dielectric film can be suppressed.

(dielectric film of second embodiment)

Next, a film capacitor 100 according to a second embodiment of the first invention will be described with reference to fig. 3A and 3B. The thin-film capacitor 100 of the second embodiment differs from the thin-film capacitor 100 of the first embodiment in that the electrodes are not in contact with both surfaces of the dielectric film 40, the electrodes are in contact with only one surface of the dielectric film 40, and the other dielectric film 41 is formed on the other surface of the dielectric film 40.

Specifically, in fig. 3A, another dielectric film 41 is provided between the upper electrode 50 and the dielectric film 40. Another dielectric film 41 may be provided between the dielectric film 40 and the lower electrode 30. In fig. 3B, two dielectric films 40 are provided, one dielectric film 40 is in contact with the upper electrode 50, the other dielectric film 40 is in contact with the lower electrode 30, and the other dielectric film 41 is provided between the dielectric films 40.

The other dielectric film 41 is a film having the same overall composition as the dielectric film 40 but not having the sub-phase S. When a laminated dielectric including dielectric film 41 and dielectric film 40 is provided between the electrodes, ratio RS is defined for the entire laminated dielectric including all

dielectric films

41 and 40. The ratio of the thicknesses of the dielectric film 40 and the other dielectric film 41 is arbitrary.

Further, since at least one electrode is in contact with the dielectric film 40, adhesiveness to one electrode is high, adhesion between the electrode and the dielectric film 40 is improved, and generation of cracks on the dielectric film can be suppressed.

(method of manufacturing film capacitor)

Next, an example of a method for manufacturing the film capacitor 100 shown in fig. 2 will be described below.

First, the substrate 10 is prepared, and the adhesion film 20 and the lower electrode 30 are formed on the substrate 10 by a known film formation method such as a sputtering method.

After the lower electrode 30 is formed, heat treatment may be performed to improve the adhesion between the adhesive film 20 and the lower electrode 30 and to improve the stability of the lower electrode 30. The heat treatment conditions are, for example, a temperature rise rate of preferably 10 to 2000 ℃/min, more preferably 100 to 1000 ℃/min. The holding temperature at the time of the heat treatment is preferably 400 to 800 ℃ and the holding time is preferably 0.1 to 4.0 hours. When the heat treatment conditions are outside the above ranges, adhesion failure between the adhesion film 20 and the lower electrode 30 is likely to occur, and unevenness is likely to occur on the surface of the lower electrode 30. As a result, the dielectric characteristics of the dielectric film 40 are likely to be lowered.

Next, a dielectric film 40 is formed on the lower electrode 30 by the above-described method. As in the second embodiment (fig. 3A and 3B), in order to form a laminated body including a plurality of dielectric films of the dielectric film 40, the dielectric films may be laminated in order.

Next, the upper electrode 50 is formed on the dielectric film 40 by a known film formation method such as sputtering.

Through the above steps, as shown in fig. 2, a thin film capacitor 100 in which a capacitor portion (lower electrode 30, dielectric film 40, and upper electrode 50)60 is formed on a substrate 10 via a sealing film 20 can be obtained. The protective film 70 for protecting the dielectric film 40 may be formed by a known film forming method so as to cover at least the portion of the dielectric film 40 exposed to the outside.

(modification example)

As described above, the embodiment of the first invention has been described, but the first invention is not limited to the above embodiment, and may be modified in various ways within the scope of the first invention.

In the embodiment of the first invention described above, the adhesive film 20 is formed in order to improve the adhesion between the substrate 10 and the lower electrode 30, but the adhesive film 20 may be omitted when the adhesion between the substrate 10 and the lower electrode 30 can be sufficiently ensured. In the case where a metal such as Cu or Pt, an alloy thereof, or an oxide conductive material, which can be used as an electrode, is used as a material constituting the substrate 10, the adhesive film 20 and the lower electrode 30 may be omitted.

In addition, Si may be used₃N_x、SiO_x、Al₂O_x、ZrO_x、Ta₂O_xThe amorphous film or the crystalline film is provided as a buffer layer between the dielectric film 40 or the dielectric film 41 and the electrode. In this case, the temperature change of the impedance or the relative permittivity of the entire laminated body of the dielectric films including the plurality of dielectric films can be adjusted by using the characteristics of the dielectric film 40.

Examples of the first invention

Next, the first invention will be described in more detail with reference to examples and comparative examples. However, the first invention is not limited to the following embodiments.

(examples 1 to 17, comparative examples 1 to 3)

First, a sputtering target material required for forming the dielectric film 40 is prepared by a solid phase method as follows.

As raw material powder for producing a target, powder of barium carbonate, strontium carbonate, calcium carbonate, titanium oxide, bismuth oxide, potassium carbonate, and sodium carbonate was prepared. These powders were weighed so that the number of atoms of each metal became the composition shown in table 1.

The weighed raw material powders for producing the target were wet-mixed in a ball mill for 20 hours using water as a solvent. The obtained mixed powder slurry was dried at 100 ℃ to obtain a mixed powder. The obtained mixed powder was press-molded by a press to obtain a compact. The molding conditions were set to 100Pa, 25 ℃ and 3 minutes for the pressing time.

Then, the obtained molded body is fired to obtain a fired body. The firing conditions were 1100 ℃ for a holding temperature, 5 hours for a temperature holding time, and air for an atmosphere.

The obtained sintered body was processed into a diameter of 80mm and a thickness of 5mm by a surface grinder and a cylindrical grinder, to obtain a target material for sputtering for forming the dielectric film 40.

Next, the Si wafer having a thickness of 500 μm was subjected to a heat treatment in a dry atmosphere of an oxidizing gas to form SiO having a thickness of 500nm on the wafer surface₂The film is formed to produce a substrate. On the surface of the substrate, a Cr thin film as a base electrode was first formed to a thickness of 20nm by sputtering. Further, a Pt thin film was formed on the formed Cr thin film by a sputtering method so as to have a thickness of 100nm, thereby forming a lower electrode.

Next, a dielectric film was formed on the lower electrode by a sputtering method using the sputtering target prepared above to a thickness of 500 nm. Sputtering conditions were set to be Ar/O atmosphere₂3/1, pressure 1.0Pa, high frequency workThe rate was 200W, and the substrate temperature was 100 ℃.

After the dielectric film is formed, Rapid Thermal Annealing (RTA) is performed on the dielectric film under annealing conditions of a hydrogen-containing nitrogen atmosphere at a temperature rise rate of 900 ℃/min and 900 ℃ for 1 min, thereby obtaining a dielectric film 40 having a sub-phase S.

In examples 1 to 3 and comparative examples 1 to 3, the hydrogen concentration was changed to change the ratio RS of the dielectric films 40. In comparative example 1, the hydrogen concentration was set to zero, and another dielectric film other than the dielectric film 40 was obtained.

Then, on the obtained dielectric film, a Pt thin film was formed by a sputtering method using a mask so as to have a diameter of 200 μm and a thickness of 100nm, thereby forming an upper electrode. Through the above steps, a thin film capacitor having the structure shown in fig. 2 was obtained.

As a result of analyzing the cross section of the dielectric film by STEM-EDS, the dielectric film of the example had: a structure of a main phase M comprising a continuous phase having a relatively high oxygen concentration and a sub-phase S comprising a dispersed phase having a relatively low oxygen concentration. In addition, a region lower by 20 at% or more than the oxygen concentration of the main phase M is determined as the sub-phase S. The oxygen concentration of the main phase is about 50 at%, and the average oxygen concentration of the secondary phase is about 10 to 20 at%.

The main phase contains Bi, Ti, an element E1, an element E2 and oxygen, and the sub-phase mainly contains Bi and oxygen.

The crystal structure of the dielectric film was measured and analyzed by an X-ray diffraction method using an XRD apparatus (Rigaku corporation, Smartlab). As a result, it was confirmed that the main phase had a perovskite crystal structure.

Further, the metal composition of the entire dielectric film was analyzed by XRF (X-ray Fluorescence Analysis), and it was confirmed that the metal composition of the entire dielectric film was consistent with the composition described in table 1.

The relative dielectric constant of all the obtained thin film capacitors was measured by the following method when DC bias was applied.

(DC bias characteristics: relative permittivity when applying DC voltage)

The electrostatic capacity, the effective electrode area, the inter-electrode distance, and the dielectric constant in vacuum were measured at room temperature of 25 ℃ and a frequency of 1kHz and an input signal level (measurement voltage) of 1.0Vrms using a digital LCR apparatus (Hewlett-Packard Co., Ltd., 4284A) while applying a DC bias of 10V/. mu.m in the thickness direction to the thin film capacitor, and the relative dielectric constant (unitless) at the time of applying the DC bias was calculated from the measured electrostatic capacity, effective electrode area, inter-electrode distance, and dielectric constant in vacuum. The dielectric film preferably has a high relative permittivity when DC bias is applied, and preferably has a relative permittivity of 600 or more when DC bias is applied. The results are shown in Table 1.

In addition, for reference, the relative dielectric constant was also measured without applying a DC bias. The assay conditions were the same except that no DC bias was applied. The results are shown in Table 1.

(temperature characteristics of relative dielectric constant)

In terms of the temperature characteristics of the relative permittivity, the relative permittivity was measured while changing the temperature of the thin film capacitor from-55 ℃ to 85 ℃, and the rate of change in the relative permittivity (the maximum rate of change in the relative permittivity with respect to 25 ℃) was calculated. The relative permittivity (unitless) at each temperature was calculated from the capacitance, effective electrode area, inter-electrode distance, and permittivity in vacuum measured under the conditions of a frequency of 1kHz and an input signal level (measurement voltage) of 1.0 Vrms. In this example, the change rate was judged to be good within ± 15%.

As can be seen from table 1, in the dielectric satisfying the above ratio RS, improvement of the DC bias characteristic and improvement of the rate of change of the relative permittivity were found.

(example 24)

The same operation as in example 1 was carried out except that the atomic composition of the dielectric film was changed to that described in table 2, a 200nm thick dielectric film having a sub-phase S was formed by performing a rapid thermal annealing treatment in a hydrogen-containing nitrogen atmosphere, and then a 300nm thick dielectric film having no sub-phase S was formed thereon by performing a rapid thermal annealing treatment in an atmospheric atmosphere, instead of performing a rapid thermal annealing treatment in a hydrogen-containing nitrogen atmosphere to form a 500nm thick dielectric film having a sub-phase S, thereby obtaining a capacitor as in example 24. The ratio RS of all dielectric films is 0.2.

(example 25)

A thin film capacitor of example 25 was obtained in the same manner as in example 24, except that after a dielectric film having a subphase S with a thickness of 100nm was formed by rapid thermal annealing in a nitrogen atmosphere containing hydrogen, a dielectric film having no subphase S with a thickness of 300nm was formed by rapid thermal annealing in an atmospheric atmosphere, and then a dielectric film 40 having a subphase S with a thickness of 100nm was formed by rapid thermal annealing in a nitrogen atmosphere containing hydrogen. The ratio RS of all dielectric films is 0.2.

Comparative example 4

A capacitor of comparative example 4 was obtained in the same manner as in example 24, except that the dielectric film having a thickness of 500nm and no sub-phase S was formed by rapid thermal annealing in an atmospheric atmosphere.

[ crack Generation Effect by indentation test ]

In examples 24 to 25 and comparative example 4, the presence or absence of cracks in the dielectric film was evaluated by the indentation test.

The test mode is as follows: load indentation test by nanoindentation device

Loading: 2mN and 8mN

Specifically, the indenter was pressed from the upper surface of the capacitor until the load was applied, and the presence or absence of cracks in the dielectric film of the capacitor was confirmed by an optical microscope.

The depth of penetration when 8mN was penetrated was 10% of the thickness of the dielectric film.

[ Table 1]

[ Table 2]

Further, it was confirmed from the comparison of examples 24 and 25 and comparative example 4 that the occurrence of cracks can be suppressed if the dielectric film 40 is in contact with the electrode.

[ explanations of reference symbols in FIGS. 1, 2, 3A, 3B, 4A, and 4B ]

10 … substrate, 20 … sealing film, 30 … bottom electrode, 40 … dielectric film (dielectric film), 50 … top electrode, 90 … electronic circuit substrate, 91, 100 … film capacitor.

Embodiment of the second invention

Next, preferred embodiments of the second invention will be described with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals. The second invention is not limited to the following embodiments.

A thin film capacitor will be described as an example of an electronic component according to an embodiment of the second invention. However, the electronic component is not limited to the film capacitor.

(Structure of film capacitor)

Fig. 2 is a cross section of the film capacitor 100 perpendicular to the surface of the dielectric film 40. In other words, fig. 2 is a cross section of the thin film capacitor 100 parallel to the thickness direction of the dielectric thin film 40. As shown in fig. 2, a film capacitor 100 according to a second embodiment of the present invention includes: a substrate 10; a sealing film 20 overlapping the substrate 10; a lower electrode 30 overlapping the sealing film 20; a dielectric thin film 40 overlapping the lower electrode 30; an upper electrode 50 overlapping the dielectric film 40; and a protective film 70 covering the lower electrode 30, the dielectric thin film 40, and the upper electrode 50.

The capacitor portion 60 is composed of the lower electrode 30, the dielectric thin film 40, and the upper electrode 50. The lower electrode 30 and the upper electrode 50 are connected to an external circuit. By applying a voltage to the dielectric thin film 40 positioned between the lower electrode 30 and the upper electrode 50, dielectric polarization occurs in the dielectric thin film 40, and electric charges are accumulated in the capacitor portion 60.

The shape of the film capacitor 100 may be, for example, a rectangular parallelepiped. However, the shape and size of the entire film capacitor are not limited.

(dielectric film)

The dielectric thin film 40 of the second embodiment of the invention contains an oxide having a perovskite structure. The oxide contains Bi (bismuth), an element E1, an element E2, and Ti (titanium). The element E1 is at least one alkali metal element selected from Na (sodium) and K (potassium). The element E2 is at least one alkaline earth metal element selected from Ca (calcium), Sr (strontium), and Ba (barium).

The unit cell of the perovskite structure is shown in fig. 5. The unit cell uc of the perovskite structure may be composed of an element located at an a site, an element located at a B site, and oxygen (O). The element at the a site may be at least one selected from Bi, the element E1, and the element E2. The element at the B site may be Ti. A1, b1, and c1 in fig. 5 are elementary vectors of cubic crystals or tetragonal crystals constituting the perovskite structure.

The dielectric thin film 40 according to the embodiment of the second invention is superior to a conventional dielectric thin film in DC bias characteristics. The DC bias characteristic is a property that the relative permittivity is hard to decrease with an increase in the strength of the direct-current electric field applied to the dielectric thin film 40. The following description of the DC bias characteristics of the dielectric thin film 40 includes assumptions or theoretical assumptions. The reason why the DC bias characteristics of the dielectric thin film 40 are improved is not necessarily limited to the following mechanism.

The dielectric characteristics of an oxide having a perovskite structure are caused by displacement of ions of each element constituting the oxide under voltage. As the voltage increases, the displacement amount of each ion is saturated, and thus the relative dielectric constant of the oxide is easily lowered. Even if the voltage is the same in intensity, the vibration of each ion constituting the oxide is reduced by applying the dc voltage. However, in the case of the second embodiment of the present invention, the atomic radii or the ionic radii of Bi, the element E1, and the element E2 constituting the oxide are different from each other. Therefore, Bi, the element E1, and the element E2 are arranged at the a site, thereby creating a space in the perovskite structure. As a result, Ti is easily moved in the perovskite structure, the dielectric thin film 40 is easily polarized, and the DC bias characteristics of the dielectric thin film 40 are improved. In other words, the combination of Bi, the element E1, and the element E2 increases the intensity of the dc electric field in which the displacement amount of the Ti plasma is saturated. As described later, when [ Bi ]/[ E2] is 0.214 to 4.500, the DC bias characteristics are easily improved by the above mechanism.

In the case where the oxide having a perovskite structure contains Bi, the elements E1 and Ti and does not contain the element E2, the curie point of the oxide is about 300 ℃. However, since the oxide contains element E2 in addition to Bi, element E1, and Ti, the curie point of the oxide is close to room temperature. As a result, the absolute value of the relative permittivity of the oxide increases, and the relative permittivity of the oxide under a dc electric field also increases.

In order to miniaturize an electronic device on which the film capacitor 100 is mounted, it is desirable to make the dielectric film 40 thinner. In addition, in order to increase the capacitance of the film capacitor 100, it is also desirable to make the dielectric film 40 thinner. However, even if the dc voltage applied to the dielectric thin film 40 is constant, the intensity of the dc electric field reaching the dielectric thin film 40 increases as the thickness of the dielectric thin film 40 decreases. The relative permittivity of the dielectric thin film 40 is likely to decrease with an increase in the strength of the dc electric field. However, the DC bias characteristics of the dielectric thin film 40 according to the second embodiment of the present invention are superior to those of the conventional dielectric thin film. As a result, even when the thickness of the dielectric thin film 40 is thinner than that of a conventional dielectric thin film, the decrease in the relative permittivity of the dielectric thin film 40 is suppressed.

The oxide contains a double crystal. A twin crystal is a crystal composed of two or more single crystals of the same kind joined to each other at a certain angle. Each single crystal constituting the oxide twin crystal has the above perovskite structure, and each single crystal constituting the oxide twin crystal contains Bi, an element E1, an element E2, Ti, and O. An example of a double crystal of oxide is shown in fig. 6. For example, the twins tw of the oxide may be composed of the first crystal c1 and the second crystal c 2. The first crystal c1 and the second crystal c2 have plane symmetry with respect to the plane p. FIG. 6 is a cross section of a twinned tw in a direction perpendicular to first crystal plane cp1 and second crystal plane cp 2. Therefore, in fig. 6, first crystal plane cp1 and second crystal plane cp2 are indicated by line segments. The first crystal plane cp1 belonging to the first crystal c1 is oriented in the first orientation d 1. That is, the first orientation d1 is the normal direction of the first crystal plane cp 1. Second crystal plane cp2 belonging to second crystal c2 is oriented in second orientation d 2. That is, second azimuth d2 is the normal direction to second crystal plane cp 2. The first crystal plane cp1 and the second crystal plane cp2 are equivalent crystal planes in the perovskite structure, but the first orientation d1 and the second orientation d2 are not parallel to each other. The structure of the bimorph is not limited to the structure shown in fig. 6.

If the dielectric thin film 40 does not contain a double crystal of an oxide, the phase transition of the oxide is likely to occur with a temperature change. Due to the phase change, the relative permittivity of the dielectric thin film 40 is easily changed. On the other hand, the twin crystal tw of the oxide is composed of two or more single crystals of the same kind joined to each other at a certain angle, and therefore, a deformation in the crystal structure is formed in the oxide. Since the deformation in the crystal structure suppresses the progress of the phase transition of the oxide, the variation in the relative dielectric constant of the dielectric thin film 40 is suppressed. That is, the dielectric thin film 40 includes a double crystal of an oxide, and thus, the dielectric thin film 40 may have excellent temperature characteristics. However, the reason for the improvement of the temperature characteristics is not necessarily limited to the above mechanism.

Whether or not the dielectric thin film 40 contains a double crystal of an oxide can be confirmed by the following method.

The dielectric thin film 40 is processed by using a Focused Ion Beam (FIB), thereby forming a thin sheet (sample). An image of the lattice inside the wafer was taken by a Transmission Electron Microscope (TEM). The size of the field of view of the TEM may be 35nm long by 35nm wide, for example. The FFT pattern can be obtained by Fast Fourier Transform (FFT) of a lattice image within a grain photographed by TEM. An example of an FFT pattern is shown in fig. 7. 100, 200, 011, 111, and 211 in fig. 7 are indices related to the crystal orientation in the perovskite structure described above, respectively. 000 corresponds to an origin for specifying the position of each point in the FFT pattern. In the case of a bimorph assuming that the crystal grains do not contain an oxide, the FFT pattern has a plurality of dots, and one dot corresponds to one crystal orientation. On the other hand, in the case of a twin crystal in which the crystal grains contain an oxide, two or more dots corresponding to one crystal orientation appear. That is, in the case of a twin crystal in which the crystal grains contain an oxide, the dots corresponding to one crystal orientation are separated into at least two dots. Note that although the FFT pattern differs depending on the field of view observed by TEM, the FFT pattern may be other than that shown in fig. 7 as long as the dots in the FFT pattern can be confirmed.

In the case of observing the field of view at 20 spots of the sheet (sample) based on the FFT pattern, it is preferable that at least two of the 20 spots contain twins. The dimensions of each field of view are as described above. The dielectric thin film 40 may have a plurality of crystal grains including an oxide. At least a portion of the plurality of grains may include a double crystal of an oxide. The plurality of crystal grains may all comprise a double crystal of an oxide. When the crystal grain size is 150nm or more, at least two sites within the same crystal grain are preferably observed.

The content of Bi in the dielectric thin film 40 can be expressed as [ Bi ] mol%. The unit of [ Bi ] may be atomic%. The total content of the element E2 in the dielectric thin film 40 can be represented as [ E2] mol%. [E2] The unit of (c) may be atomic%. [ Bi ]/[ E2] may be 0.214 to 4.500. Since [ Bi ]/[ E2] is within the above range, the temperature characteristics and DC bias characteristics of the dielectric thin film 40 are easily improved.

The composition of the oxide contained in the dielectric thin film 40 may be represented by the following chemical formula 1a or chemical formula 1 b. X, α, β, s, t and u in chemical formula 1a and chemical formula 1b are real numbers. The unit of each of x, α, β, s, t and u is mol. Both chemical formula 1a and chemical formula 1b satisfy all inequalities 2 to 9 below.

< chemical formula 1a >

(1-x)Bi_1-α-βNa_αK_βTiO₃-xCa_sSr_tBa_uTiO₃

< chemical formula 1b >

(Bi_1-α-βNa_αK_β)_1-x(Ca_sSr_tBa_u)_xTiO₃

0<x<1 (2)

0.4<α+β<0.6 (3)

0≤α<0.6 (4)

0≤β<0.6 (5)

0.9<s+t+u≤1.1 (6)

0≤s≤1.1 (7)

0≤t≤1.1 (8)

0≤u≤1.1 (9)

The oxide may be a main component of the dielectric thin film 40. In the case where the composition of the oxide contained in the dielectric thin film 40 is represented by the above chemical formula 1a or chemical formula 1b, the content of the oxide in the dielectric thin film 40 may be 70 mol% or more and 100 mol% or less. The dielectric thin film 40 may contain other elements in addition to Bi, the element E1, the element E2, Ti, and O as long as the perovskite structure of the oxide is not damaged. That is, the dielectric thin film 40 may contain a subcomponent or a trace amount of impurities in addition to the above-described oxide. For example, the dielectric thin film 40 may further include at least one element of Cr (chromium) and Mo (molybdenum). The dielectric thin film 40 may further contain at least one rare earth element selected from Sc (scandium), Y (yttrium), La (lanthanum), Ce (cerium), Pr (praseodymium), Nd (neodymium), Pm (promethium), Sm (samarium), Eu (europium), Gd (gadolinium), Tb (terbium), Dy (dysprosium), Ho (holmium), Er (erbium), Tm (thulium), Yb (ytterbium), and Lu (lutetium). Since the dielectric thin film 40 further contains a rare earth element, the DC bias characteristics of the dielectric thin film 40 are easily improved.

The thickness of the dielectric thin film 40 may be, for example, 0.01 μm to 2 μm (10nm to 2000 nm). However, the thickness of the dielectric thin film 40 is not limited. The thickness of the dielectric thin film 40 can be measured by observing the cross section of the thin film capacitor 100 with a Scanning Electron Microscope (SEM). The cross section of the thin film capacitor 100 may be formed by excavating the thin film capacitor 100 using a Focused Ion Beam (FIB).

(substrate)

The composition of the substrate 10 is not limited as long as the substrate 10 has mechanical strength enough to support the adhesive film 20, the lower electrode 30, the dielectric thin film 40, and the upper electrode 50 formed on the substrate 10. The substrate 10 may be, for example, a single crystal substrate, a ceramic polycrystalline substrate, or a metal substrate. The single crystal substrate may be made of, for example, Si single crystal, SiGe single crystal, or GaAs single crystalInP single crystal, SrTiO₃Single crystal, MgO single crystal, LaAlO₃Single crystal, ZrO₂Single crystal, MgAl₂O₄Single crystal or NdGaO₃A single crystal. The ceramic polycrystalline substrate may be made of, for example, Al₂O₃Polycrystalline, ZnO polycrystalline or SiO₂A polycrystalline structure. The metal substrate may be made of, for example, Ni (nickel), Cu (copper), Ti (titanium), W (tungsten), Mo (molybdenum), Al (aluminum), Pt (platinum), or an alloy containing these metals. In view of low cost and easy processing, a Si single crystal is preferable. When the substrate 10 has sufficient conductivity, the dielectric thin film 40 may directly overlap with the surface of the substrate, and the substrate 10 may function as an electrode.

The thickness of the substrate 10 may be, for example, 10 μm to 5000 μm. However, the thickness of the substrate 10 is not limited. In the case where the substrate 10 is too thin, it is difficult for the substrate 10 to have sufficient mechanical strength. When the substrate 10 is too thick, the thickness of the entire thin-film capacitor 100 increases, making it difficult to mount the thin-film capacitor 100 on a small electronic component.

The resistivity of the substrate 10 varies depending on the material of the substrate 10. When the resistivity of the substrate 10 is low, a current leaks to the substrate 10 when the thin film capacitor 100 operates, and thus the electrical characteristics of the thin film capacitor 100 are impaired. For example, in the case where the substrate 10 is composed of Si single crystal, current may leak to the substrate 10. Therefore, when the resistivity of the substrate 10 is low, the surface of the substrate 10 may be covered with an insulating film, and the adhesion film 20 or the lower electrode 30 may overlap the surface of the insulating film. The insulating film suppresses leakage current. The composition and thickness of the insulating film are not limited as long as the substrate 10 and the capacitor portion 60 are insulated from each other. The insulating film may be made of, for example, SiO₂、Al₂O₃Or Si₃N_xAnd (4) forming. The thickness of the insulating film may be, for example, 0.01 μm or more and 10 μm or less. An insulating film is not necessary for the thin film capacitor 100. That is, the adhesive film 20 or the lower electrode 30 may directly overlap the surface of the substrate 10.

(laminating film)

By disposing the adhesive film 20 between the substrate 10 and the lower electrode 30, lower current can be suppressedThe pole 30 is peeled off the substrate 10. The composition of the adhesive film 20 is not limited as long as the peeling of the lower electrode 30 from the substrate 10 can be suppressed. The adhesive film 20 may contain, for example, Cr, Ti, TiO₂、SiO₂、Y₂O₃And ZrO₂At least one of (1). For the film capacitor 100, an adhesion film is not necessary. In the case where the lower electrode 30 is easily directly adhered to the substrate 10 or the insulating film, the lower electrode 30 may be directly overlapped with the substrate 10 or the insulating film.

(lower electrode)

The composition of the lower electrode 30 is not limited as long as the lower electrode 30 has sufficient conductivity. The lower electrode 30 may be, for example, Pt (platinum), Ru (ruthenium), Rh (rhodium), Pd (palladium), Ir (iridium), Au (gold), Ag (silver), Cu (copper), Ni (nickel), an alloy containing these metals, or a conductive oxide. The thickness of the lower electrode 30 is not limited as long as the lower electrode 30 functions as an electrode. The thickness of the lower electrode 30 may be, for example, 0.01 μm or more and 10 μm or less.

(Upper electrode)

The composition of the upper electrode 50 is not limited as long as the upper electrode 50 has sufficient conductivity. The upper electrode 50 may be, for example, Pt (platinum), Ru (ruthenium), Rh (rhodium), Pd (palladium), Ir (iridium), Au (gold), Ag (silver), Cu (copper), Ni (nickel), an alloy containing these metals, or a conductive oxide. The thickness of the upper electrode 50 is not limited as long as the upper electrode 50 functions as an electrode. The thickness of the upper electrode 50 may be, for example, 0.01 μm or more and 10 μm or less.

(protective layer)

The lower electrode 30, the dielectric thin film 40, and the upper electrode 50 are covered with the protective film 70, whereby the lower electrode 30, the dielectric thin film 40, and the upper electrode 50 can be isolated from the external atmosphere. As a result, oxidation of the lower electrode 30 and the upper electrode 50 and corrosion of the dielectric thin film 40 can be suppressed. In addition, the protective film 70 suppresses breakage of the thin film capacitor. As long as the protective film 70 has the above function, the composition of the protective film 70 is not limited. The protective film 70 may be made of a thermosetting resin such as an epoxy resin.

(method for producing dielectric thin film and thin film capacitor)

The dielectric thin film 40 and the thin film capacitor 100 can be manufactured by the following manufacturing method.

The adhesive film 20 is formed on the surface (main surface) of the substrate 10, and the lower electrode 30 is formed on the surface of the adhesive film 20. The bonding film 20 and the lower electrode 30 may be formed by a sputtering method, a vacuum deposition method, a printing method, a spin coating method, or a sol-gel method.

When a Si single crystal substrate is used as the substrate 10, an insulating film may be formed on the surface of the substrate 10 before the bonding film 20 and the lower electrode 30 are formed. The insulating film can be formed by, for example, a thermal oxidation method or a CVD (Chemical Vapor Deposition) method.

After the lower electrode 30 is formed, the substrate 10, the adhesive film 20, and the lower electrode 30 may be heat-treated. By the heat treatment, the adhesion between the adhesion film 20 and the lower electrode 30 is improved. The rate of temperature rise in the heat treatment may be preferably 10 ℃/min to 2000 ℃/min, more preferably 100 ℃/min to 1000 ℃/min. The temperature of the heat treatment may be preferably 400 ℃ to 800 ℃. The time for the heat treatment may be preferably 0.1 hour to 4.0 hours. When the conditions of the heat treatment are outside the above ranges, the adhesion between the adhesion film 20 and the lower electrode 30 is difficult to improve, and the surface of the lower electrode 30 is difficult to be flat. As a result, the dielectric characteristics of the dielectric thin film 40 are easily impaired.

By depositing Bi, the element E1, the element E2, Ti, and O on the surface of the lower electrode 30, the dielectric thin film 40 is formed on the surface of the lower electrode 30. The dielectric thin film 40 can be formed by, for example, a vacuum evaporation method, a sputtering method, a Pulsed Laser Deposition (PLD), a Metal-Organic Chemical Vapor Deposition (MOCVD), a Metal-Organic Deposition (MOD), a sol-gel method, a Chemical Solution Deposition (CSD), or the like. The composition of the entire raw material may be adjusted so that the composition of the entire raw material used in the above formation method substantially matches the above chemical formula 1a or chemical formula 1 b. The [ Bi ]/[ E2] can be controlled by adjusting the composition of the whole raw material. A variety of raw materials may be used. The raw material may contain a trace amount of impurities or subcomponents as long as the dielectric characteristics of the dielectric thin film 40 are not impaired.

When the dielectric thin film 40 is formed by a sputtering method, a target having a composition substantially equal to the chemical formula la or the chemical formula 1b can be manufactured. The raw material of the target is not limited as long as the whole raw material of the target contains Bi, the element E1, the element E2, and Ti. The target material can be made from a variety of raw materials. The raw material of the target material may be, for example, at least one compound selected from carbonates, oxides, and hydroxides. After weighing the powders of the respective compounds in accordance with the composition of the dielectric thin film 40, the powders of the respective compounds are mixed. The mixing method may be, for example, a ball mill. Powders of each compound may be mixed together with water or an organic solvent. The molded body can be obtained by molding the pressurized mixed powder. The molding pressure may be, for example, 10Pa to 200 Pa.

The target (sintered body) can be obtained by firing (sintering) the molded body in an oxidizing atmosphere. The firing temperature may be, for example, 900 ℃ to 1300 ℃. The firing time may be, for example, 1 hour to 10 hours. The oxidizing atmosphere may be, for example, the atmosphere. The shape and size of the target can be adjusted by processing the target. The target may be, for example, a disk.

The dielectric thin film 40 is preferably formed by a Radio-Frequency Sputtering method (Radio-Frequency Sputtering). In the high-frequency sputtering method, the substrate 10 on which the adhesion film 20 and the lower electrode 30 are laminated is set in a vacuum chamber. With Ar (argon) and O₂The mixed gas (oxygen) fills the inside of the vacuum chamber. Volume of Ar V1 and O₂The ratio of the volume V2 of (V1/V2) may preferably be 1/1 or more and 5/1 or less. The high frequency power may preferably be 150W to 1000W. The high-frequency power is power for applying an alternating voltage between the vacuum chamber (anode) and the target (cathode). Since the high-frequency power is sufficiently large, oxide twins are easily formed. When the high-frequency power is too small, it is difficult to form the oxide-containing twin dielectric thin film 40. In the high-frequency sputtering methodThe temperature of the substrate 10 may preferably be between room temperature and 200 ℃.

After the dielectric film 40 is formed, Rapid Thermal Annealing (RTA) of the dielectric film 40 may be performed. In RTA, after the temperature of the dielectric thin film 40 is raised to the annealing temperature T at the temperature rise rate Vt, the dielectric thin film 40 is continuously heated at the annealing temperature T. The temperature rise rate Vt of RTA is preferably 300 ℃/min to 3000 ℃/min. Since the temperature rise rate Vt is sufficiently high, the crystal of the oxide in the dielectric thin film 40 is likely to grow rapidly, and lattice mismatch is likely to be formed in the crystal of the oxide. As a result, oxide twins are easily formed. The annealing temperature T is preferably 700 ℃ to 1000 ℃ inclusive, because oxide twins are easily formed. Since oxide twins are easily formed, the annealing time of the dielectric thin film 40 is preferably 0.5 minutes to 5 minutes. The annealing time is a time for maintaining the temperature of the dielectric thin film 40 at the annealing temperature T. In the RTA, the dielectric thin film 40 is preferably heated in the atmosphere or an oxidizing atmosphere.

By the above method, the dielectric thin film 40 of the oxide-containing twin crystal is formed. As described above, since the high-frequency sputtering method and the RTA are performed under predetermined conditions, a twin crystal of oxide can be formed. In the conventional thick film method (sintering method), a thick film of ceramic is formed by sintering a dielectric powder, and therefore, it is difficult to control the formation of a double crystal of an oxide by the thick film method (sintering method).

After RTA, the upper electrode 50 is formed on the surface of the dielectric thin film 40. The upper electrode 50 can be formed by the same method as the lower electrode 30.

After the upper electrode 50 is formed, a protective film 70 may be formed to cover the lower electrode 30, the dielectric thin film 40, and the upper electrode 50. The method of forming the protective film 70 is not limited. For example, the protective film 70 may be formed by covering the lower electrode 30, the dielectric thin film 40, and the upper electrode 50 with an uncured thermosetting resin and then heating the thermosetting resin. The protective film 70 may be formed by covering the lower electrode 30, the dielectric thin film 40, and the upper electrode 50 with a semi-cured product of a thermosetting resin and then heating the semi-cured product.

The preferred embodiments of the second invention have been described above, but the second invention is not limited to the above embodiments. Various modifications of the second invention are possible without departing from the scope of the second invention, and these modifications are also included in the second invention.

For example, the thin film capacitor may further include another dielectric thin film laminated on the dielectric thin film 40. The other dielectric film may be, for example, Si₃N_x、SiO_x、Al₂O_x、ZrO_xOr Ta₂O_xAnd the like amorphous dielectric thin films. By laminating another dielectric thin film on the dielectric thin film 40, the impedance and temperature characteristics of the dielectric thin film 40 can be easily adjusted. As long as the thin film capacitor includes at least a pair of electrodes and a dielectric thin film 40 disposed between the pair of electrodes, the structure of the thin film capacitor is not limited to the structure shown in fig. 2.

Examples of the second invention

The second invention will be described in more detail below with reference to examples and comparative examples, but the second invention is not limited to these examples.

(example 31)

< preparation of target >

A target material, which is a raw material of the dielectric thin film, was produced by the following solid-phase method.

The mixed powder was prepared by mixing respective powders of bismuth oxide, sodium carbonate, strontium carbonate, and titanium oxide. Powders of bismuth oxide, sodium carbonate, strontium carbonate and titanium oxide were weighed so that the composition of the mixed powder was in accordance with chemical formula 1A below. That is, 1-x and x in chemical formula 1A were adjusted to values shown in Table 3 below, and [ Bi ]/[ E2] was set to values shown in Table 3 below. [ Bi ]/[ E2] is as defined above. If based on x in chemical formula 1A, [ Bi ]/[ E2] is expressed as { (1-x). times.0.5 }/x.

(1-x)Bi_0.5Na_0.5TiO₃-xSrTiO₃(1A)

BNT described below means Bi_0.5Na_0.5TiO₃. ST described below means SrTiO₃。

The above mixed powder and water were mixed for 20 hours by using a ball mill to prepare a slurry. The mixed powder was recovered by drying the slurry at 100 ℃. The mixed powder was molded by a press to obtain a molded body. The molding pressure was 100 Pa. The temperature of the mixed powder in molding was 25 ℃. The time for pressurizing the mixed powder was 3 minutes.

The molded body was fired in air to obtain a sintered body. The firing temperature is 1100 ℃. The firing time was 5 hours.

The sintered body is processed to produce a disk-shaped target material. A surface grinder and a cylindrical grinder are used for machining the sintered body. The diameter of the target material is 80mm, and the thickness of the target material is 5 mm.

< production of dielectric thin film and thin film capacitor >

As the substrate, a wafer made of a single crystal of Si is used. The thickness of the substrate was 500. mu.m. By heating the substrate in an oxidizing gas, the substrate will be made of SiO₂The insulating film is formed on the surface of the substrate. The thickness of the insulating film was adjusted to 500 nm.

An adhesion film made of Cr was formed on the surface of the substrate (insulating film) by sputtering. The thickness of the adhesive film was adjusted to 20 nm. A lower electrode made of Pt was formed on the surface of the adhesion film by a sputtering method. The thickness of the lower electrode was adjusted to 100 nm.

A dielectric thin film is formed on the surface of the lower electrode by a high-frequency sputtering method using the target. In the high-frequency sputtering method, a substrate on which an insulating film, an adhesive film, and a lower electrode are laminated is placed in a vacuum chamber. With Ar and O₂The mixed gas of (2) fills the inside of the vacuum chamber. The pressure in the vacuum chamber was maintained at 1.0 Pa. Volume of Ar V1 and O₂The volume of (2) V2 (V1/V2) was 3/1. The high frequency power was 300W. The temperature of the substrate 10 in the vacuum chamber was maintained at 100 ℃. The thickness of the dielectric thin film was adjusted to 300 nm.

After the formation of the dielectric thin film, Rapid Thermal Annealing (RTA) of the dielectric thin film is performed. In RTA, a dielectric thin film is heated in the atmosphere. In RTA, after the temperature of the dielectric thin film rises to the annealing temperature T at the temperature rise rate Vt, the dielectric thin film 40 is continuously heated at the annealing temperature T. The temperature rise rate Vt of RTA is 900 deg.C/min. The annealing temperature T was 900 ℃. The annealing time of the dielectric thin film was 1 minute.

After RTA, an upper electrode made of Pt was formed on the surface of the dielectric thin film by sputtering. A circular upper electrode is formed through a mask. The diameter of the upper electrode was adjusted to 200 μm. The thickness of the upper electrode was adjusted to 100 nm.

The dielectric thin film and the thin film capacitor of example 31 were produced by the above methods.

< analysis of dielectric thin film and thin film capacitor >

[ analysis of composition and Crystal Structure of dielectric thin film ]

The X-ray diffraction (XRD) pattern of the dielectric thin film of example 31 was measured. For the measurement of the XRD pattern, an X-ray diffraction device (SmartLab) manufactured by Rigaku K.K. was used. The XRD pattern indicates that the dielectric thin film has a perovskite structure.

The composition of the dielectric thin film of example 31 was analyzed by fluorescent X-ray Fluorescence (XRF) analysis. The analysis result showed that the composition of the dielectric thin film was consistent with the composition shown in chemical formula 1A, and that 1-x and x in chemical formula 1A were consistent with the values shown in table 3 below.

The field of view at 20 of the dielectric thin film of example 31 was photographed by a Transmission Electron Microscope (TEM). The size of each field of view photographed was 35nm in length by 35nm in width. Through the fast fourier transform of each of the 20 images, 20 FFT patterns were obtained. The fast fourier transform of each image was performed by software (GATAN Microscopy Suite) manufactured by GATAN corporation. In 5 of the 20 FFT patterns, the points corresponding to the respective crystal orientations were separated into points S1 and S2. That is, at 5 of 20, twins were detected. The lattice image of the portion where the twins are formed is shown in fig. 8. The FFT pattern corresponding to the lattice image shown in fig. 8 is shown in fig. 9A and 9B. 100, 200, 011, 111, and 211 in fig. 9A are indices related to the crystal orientation in the perovskite structure, respectively. 000 corresponds to an origin for specifying the position of each point. Fig. 9B is an enlarged view of the points S1 and S2 corresponding to 211 shown in fig. 9A.

The above analysis results show that the dielectric thin film of example 31 is an oxide represented by the above chemical formula 1A, the oxide has a perovskite structure, and the oxide contains a double crystal.

[ evaluation of DC bias characteristics ]

The capacitance C1 of the film capacitor of example 31 was measured in a state where no dc electric field was applied to the dielectric film. As an apparatus for measuring electrostatic capacity, a digital LCR (4284A) manufactured by Hewlett-Packard company was used. The measurement conditions of the capacitance C1 are as follows.

Measuring temperature: 25 deg.C

Measuring frequency: 1kHz

Input signal level (measurement voltage): 1.0Vrms

Strength of direct current electric field (DC bias): 0V/. mu.m

According to the capacitance C1, the effective area of the electrode (the area of the upper electrode), the distance between the electrodes and the vacuum dielectric constant₀The relative permittivity r1 of the dielectric thin film of example 31 was calculated. That is, the relative permittivity r1 of the dielectric thin film in a state where no dc electric field is applied to the dielectric thin film was calculated. R1 of example 31 is shown in Table 3 below. The relative dielectric constant is unitless.

The capacitance C2 of the film capacitor of example 31 was measured in a state where a dc electric field was applied to the dielectric film. The intensity of the DC electric field was 10V/. mu.m. The measurement conditions of the capacitance C2 were the same as those of the capacitance C1, except for the intensity of the dc electric field. The relative permittivity r2 of the dielectric thin film of example 31 was calculated from the capacitance C2. That is, the relative permittivity r2 of the dielectric thin film in a state where a dc electric field is applied to the dielectric thin film was calculated. Except for the capacitance, the method of calculating r2 is the same as that of r 1. R2 of example 31 is shown in Table 3 below. r2 is preferably 600 or more.

[ evaluation of temperature characteristics ]

The film capacitor of example 31 was set in a constant temperature bath. The electrostatic capacitance of the film capacitor at each temperature was continuously measured while continuously changing the temperature of the film capacitor in the thermostatic bath from-55 ℃ to 85 ℃. The measurement conditions of the electrostatic capacity at each temperature are as follows.

Measuring frequency: 1kHz

Input signal level (measurement voltage): 1.0Vrms

Strength of direct current electric field (DC bias): 0V/. mu.m

The relative dielectric constant at each temperature was calculated from the capacitance at each temperature. The method for calculating the relative permittivity at each temperature is the same as the method for calculating r1 except for the capacitance. Based on the relative permittivity at each temperature, the rate of change Δ r of the relative permittivity was calculated. Δ r is defined by the following equation a. Δ r is in%. R (25 ℃) in the formula a is a relative dielectric constant at 25 ℃. r (T) is the relative permittivity which is the largest difference from the absolute value of r (25 ℃) among all the relative permittivities measured in the above temperature range. Δ r of example 31 is shown in the following Table 3. Deltar is preferably from-15% to 15%.

Δr＝100×{r(T)-r(25℃)}/r(25℃) (a)

(examples 32 to 34)

In the production of the targets of examples 32 to 34, 1-x and x in chemical formula 1A were adjusted to values shown in Table 3 below, and [ Bi ]/[ E2] was adjusted to values shown in Table 3 below. Dielectric thin films and thin film capacitors of examples 32 to 34 were produced in the same manner as in example 31, except for the composition of the target.

The dielectric thin films and the thin film capacitors of examples 32 to 34 were analyzed by the same method as in example 31. In examples 32 to 34, the compositions of the dielectric thin films were all the same as those shown in chemical formula 1A, and 1-x and x in chemical formula 1A were all the same as values shown in Table 3 below. In examples 32 to 34, the dielectric thin films were all the oxides represented by the above chemical formula 1A, and all the oxides had a perovskite structure and all the oxides contained a twin crystal. The r1, r2 and Δ r of examples 32 to 34 are shown in Table 3 below.

Comparative example 31

The high-frequency power in the high-frequency sputtering method of comparative example 31 was 100W. The temperature rise rate Vt of the RTA of comparative example 31 is 100 ℃ C/min. The annealing time in RTA of comparative example 31 was 10 minutes. Except for these matters (method for forming dielectric thin film), the dielectric thin film and the thin film capacitor of comparative example 31 were produced in the same manner as in example 33.

The dielectric thin film and the thin film capacitor of comparative example 31 were analyzed by the same method as in example 31. The composition of the dielectric thin film of comparative example 31 was identical to that shown in chemical formula 1A, and 1-x and x in chemical formula 1A were identical to the values shown in table 3 below. The oxide of comparative example 31 had a perovskite structure. However, in the FFT pattern of comparative example 31, the dots corresponding to each crystal orientation were not separated. That is, no oxide twins were detected from the dielectric thin film of comparative example 31. R1, r2 and Δ r of comparative example 31 are shown in table 3 below.

(example 41)

The target material of example 41 was produced by the following solid phase method.

The mixed powder was prepared by mixing respective powders of bismuth oxide, sodium carbonate, barium carbonate, and titanium oxide. Powders of bismuth oxide, sodium carbonate, barium carbonate and titanium oxide were weighed so that the composition of the mixed powder was in accordance with chemical formula 1B below. That is, 1-x and x in chemical formula 1B are adjusted to values shown in Table 4, [ Bi ]]/[E2]The values are shown in Table 4 below. If based on x in chemical formula 1B, [ Bi ] will be]/[E2]BT, expressed as { (1-x) × 0.5.5 }/x, means BaTiO₃。

(1-x)Bi_0.5Na_0.5TiO₃-xBaTiO₃(1B)

A dielectric thin film and a thin film capacitor of example 41 were produced in the same manner as in example 31, except for the composition of the target.

The dielectric thin film and the thin film capacitor of example 41 were analyzed by the same method as in example 31. The composition of the dielectric thin film of example 41 was identical to that shown in chemical formula 1B, and 1-x and x in chemical formula 1B were identical to the values shown in table 4 below. The dielectric thin film of example 41 is an oxide represented by the above chemical formula 1B, the oxide having a perovskite structure, and the oxide containing a twin crystal. R1, r2 and Δ r of example 41 are shown in table 4 below.

(example 42)

The target material of example 42 was produced by the following solid phase method.

The mixed powder was prepared by mixing respective powders of bismuth oxide, sodium carbonate, calcium carbonate, and titanium oxide. Powders of each of bismuth oxide, sodium carbonate, calcium carbonate and titanium oxide were weighed so that the composition of the mixed powder was in accordance with the following chemical formula 1C. That is, 1-x and x in chemical formula 1C were adjusted to values shown in Table 4 below, [ Bi ]]/[E2]The values are shown in Table 4 below. If based on x in chemical formula 1C, [ Bi ] will be]/[E2]CT represented by { (1-x) × 0.5.5 }/x. hereinafter means CaTiO₃。

(1-x)Bi_0.5Na_0.5TiO₃-xCaTiO₃(1C)

The dielectric thin film and the thin film capacitor of example 42 were produced in the same manner as in example 31, except for the composition of the target.

The dielectric thin film and the thin film capacitor of example 42 were analyzed by the same method as in example 31. The composition of the dielectric thin film of example 42 was identical to that shown in chemical formula 1C, and 1-x and x in chemical formula 1C were identical to the values shown in table 4 below. The dielectric thin film of example 42 was an oxide represented by the above chemical formula 1C, the oxide having a perovskite structure, and the oxide including a twin crystal. R1, r2 and Δ r of example 42 are shown in Table 4 below.

(example 43)

The target material of example 43 was produced by the following solid phase method.

The mixed powder was prepared by mixing respective powders of bismuth oxide, potassium carbonate, barium carbonate, and titanium oxide. Powders of each of bismuth oxide, potassium carbonate, barium carbonate, and titanium oxide were weighed so that the composition of the mixed powder was in accordance with the following chemical formula 1D. That is, 1-x and x in chemical formula 1D were adjusted to values shown in Table 4 below, [ Bi ]]/[E2]The values are shown in Table 4 below. If based on x in chemical formula 1D, [ Bi ] will be]/[E2]Is represented by { (1)-x) × 0.5.5 }/x. BKT described below means Bi_0.5K_0.5TiO₃。

(1-x)Bi_0.5K_0.5TiO₃-xBaTiO₃(1D)

A dielectric thin film and a thin film capacitor of example 43 were produced in the same manner as in example 31, except for the composition of the target.

The dielectric thin film and the thin film capacitor of example 43 were analyzed by the same method as in example 31. The composition of the dielectric thin film of example 43 was identical to that shown in chemical formula 1D, and 1-x and x in chemical formula 1D were identical to the values shown in table 4 below. The dielectric thin film of example 43 was an oxide represented by the above chemical formula 1D, the oxide having a perovskite structure, and the oxide including a twin crystal. R1, r2 and Δ r of example 43 are shown in Table 4 below.

(example 44)

The target of example 44 was produced by the following solid phase method.

The mixed powder was prepared by mixing respective powders of bismuth oxide, potassium carbonate, strontium carbonate, and titanium oxide. Powders of each of bismuth oxide, potassium carbonate, strontium carbonate, and titanium oxide were weighed so that the composition of the mixed powder was in accordance with chemical formula 1E below. That is, 1-x and x in chemical formula 1E are adjusted to values shown in Table 4 below, and [ Bi ]/[ E2] is adjusted to values shown in Table 4 below. If based on x in chemical formula 1E, [ Bi ]/[ E2] is expressed as { (1-x). times.0.5 }/x.

(1-x)Bi_0.5K_0.5TiO₃-xSrTiO₃(1E)

The dielectric thin film and the thin film capacitor of example 44 were produced in the same manner as in example 31, except for the composition of the target.

The dielectric thin film and the thin film capacitor of example 44 were analyzed by the same method as in example 31. The composition of the dielectric thin film of example 44 was identical to that shown in chemical formula 1E, and 1-x and x in chemical formula 1E were identical to the values shown in table 4 below. The dielectric thin film of example 44 was an oxide represented by the above chemical formula 1E, the oxide having a perovskite structure, and the oxide including a twin crystal. R1, r2 and Δ r of example 44 are shown in Table 4 below.

(example 45)

The target material of example 45 was produced by the following solid phase method.

The mixed powder was prepared by mixing respective powders of bismuth oxide, potassium carbonate, calcium carbonate, and titanium oxide. Powders of each of bismuth oxide, potassium carbonate, calcium carbonate, and titanium oxide were weighed so that the composition of the mixed powder was in accordance with chemical formula 1F below. That is, 1-x and x in chemical formula 1F are adjusted to values shown in Table 4 below, and [ Bi ]/[ E2] is adjusted to values shown in Table 4 below. If based on x in chemical formula 1F, [ Bi ]/[ E2] is expressed as { (1-x). times.0.5 }/x.

(1-x)Bi_0.5K_0.5TiO₃-xCaTiO₃(1F)

The dielectric thin film and the thin film capacitor of example 45 were produced in the same manner as in example 31, except for the composition of the target.

The dielectric thin film and the thin film capacitor of example 45 were analyzed by the same method as in example 31. The composition of the dielectric thin film of example 45 was identical to that shown in chemical formula 1F, and 1-x and x in chemical formula 1F were identical to the values shown in table 4 below. The dielectric thin film of example 45 was an oxide represented by the above chemical formula 1F, the oxide having a perovskite structure, and the oxide including a twin crystal. R1, r2 and Δ r of example 45 are shown in Table 4 below.

[ Table 3]

[ Table 4]

Industrial applicability

The dielectric thin film of the second invention is used for a thin film capacitor, for example.

[ explanations of reference numerals in FIGS. 5, 6, 7, 8, 9A, and 9B ]

uc … perovskite structure unit cell, twin crystal of tw … oxide.

Embodiment of the third invention

Next, preferred embodiments of the third invention will be described with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals. The third invention is not limited to the following embodiments.

A thin film capacitor will be described as an example of an electronic component according to an embodiment of the third invention. However, the electronic component is not limited to the film capacitor.

(Structure of film capacitor)

Fig. 2 is a cross section of the film capacitor 100 perpendicular to the surface of the dielectric film 40. In other words, fig. 2 is a cross section of the thin film capacitor 100 parallel to the thickness direction of the dielectric thin film 40. As shown in fig. 2, a film capacitor 100 according to a third embodiment of the present invention includes: a substrate 10; a sealing film 20 overlapping the substrate 10; a lower electrode 30 overlapping the sealing film 20; a dielectric thin film 40 overlapping the lower electrode 30; an upper electrode 50 overlapping the dielectric film 40; and a protective film 70 covering the lower electrode 30, the dielectric thin film 40, and the upper electrode 50.

(dielectric film)

The dielectric thin film 40 of the third embodiment of the invention contains an oxide having a perovskite structure. The oxide contains Bi (bismuth), an element E1, an element E2, and Ti (titanium). The element E1 is at least one alkali metal element selected from Na (sodium) and K (potassium). The element E2 is at least one alkaline earth metal element selected from Ca (calcium), Sr (strontium), and Ba (barium).

The dielectric thin film 40 according to the third embodiment of the present invention has DC bias characteristics superior to those of conventional dielectric thin films. The DC bias characteristic is a property that the relative permittivity is hard to decrease with an increase in the strength of the direct-current electric field applied to the dielectric thin film 40. The following description of the DC bias characteristics of the dielectric thin film 40 includes assumptions or theoretical assumptions. The reason why the DC bias characteristics of the dielectric thin film 40 are improved is not necessarily limited to the following mechanism.

The dielectric characteristics of an oxide having a perovskite structure are caused by displacement of ions of each element constituting the oxide under voltage. The displacement amount of each ion is saturated with an increase in voltage, and thus the relative permittivity of the oxide is easily lowered. Even if the voltage is the same in intensity, the vibration of each ion constituting the oxide is reduced by applying the dc voltage. However, in the case of the third embodiment of the present invention, the atomic radii or the ionic radii of Bi, the element E1, and the element E2 constituting the oxide are different from each other. Therefore, since Bi, the element E1, and the element E2 are arranged at the a site, a space is created in the perovskite structure. As a result, Ti is easily moved in the perovskite structure, the dielectric thin film 40 is easily polarized, and the DC bias characteristics of the dielectric thin film 40 are improved. In other words, the combination of Bi, the element E1, and the element E2 increases the intensity of the dc electric field in which the displacement amount of the Ti plasma is saturated. As described later, when [ Bi ]/[ E2] is 0.214 to 4.500, the DC bias characteristics are easily improved by the above mechanism.

In the case where the oxide having a perovskite structure contains Bi, the elements E1 and Ti and does not contain the element E2, the curie point of the oxide is about 300 ℃. However, since the oxide contains the element E2 in addition to Bi, the element E1, and Ti, the curie point of the oxide is close to room temperature. As a result, the absolute value of the relative permittivity of the oxide increases, and the relative permittivity of the oxide under a dc electric field also increases.

In order to miniaturize an electronic device on which the film capacitor 100 is mounted, it is desirable to further reduce the thickness of the dielectric film 40. In addition, in order to increase the capacitance of the film capacitor 100, it is desirable to further reduce the thickness of the dielectric film 40. However, even if the dc voltage applied to the dielectric thin film 40 is constant, the intensity of the dc electric field reaching the dielectric thin film 40 increases as the thickness of the dielectric thin film 40 decreases. The relative permittivity of the dielectric thin film 40 is likely to decrease with an increase in the strength of the dc electric field. However, the DC bias characteristics of the dielectric thin film 40 according to the third embodiment of the present invention are superior to those of the conventional dielectric thin film. As a result, even when the thickness of the dielectric thin film 40 is thinner than that of a conventional dielectric thin film, a decrease in the relative permittivity of the dielectric thin film 40 can be suppressed.

The dielectric thin film 40 contains tetragonal crystal (tetragonal crystal) of the above oxide and rhombohedral crystal (rhombohedral crystal) of the above oxide. Substantially, the dielectric thin film 40 may be composed of only tetragonal crystals of the above-mentioned oxide and rhombohedral crystals of the above-mentioned oxide. In addition to tetragonal and rhombohedral crystals, the dielectric film 40 may also include other crystalline phases. For example, the dielectric thin film 40 may contain cubic crystals (cubic crystals) of the above-described oxide in addition to tetragonal crystals and rhombohedral crystals. In addition to the tetragonal crystal and rhombohedral crystal, the dielectric film 40 may further include a Structure Gradient Region (SGR). In general, the structure-inclined region is a region (layer) present in the vicinity of an interface where two crystal phases having different crystal structures are joined to each other. The lattice constant is gradually changed in the inclined region of the structure, thereby eliminating the lattice mismatch between two crystal phases and relaxing the stress caused by the lattice mismatch. In the embodiment of the third invention, the structure-inclined region is a region existing in the vicinity of the interface where the tetragonal crystal and the rhombohedral crystal are bonded to each other.

The tetragonal crystal of the above oxide having a perovskite structure is shown in fig. 10. The unit cell uc1 of a tetragonal crystal may be composed of an element located at an a site, an element located at a B site, and oxygen (O). The element at the a site may be at least one selected from Bi, the element E1, and the element E2. The element at the B site may be Ti. A1, b1, and c1 in fig. 10 are basic vectors constituting a tetragonal crystal. The lengths of a1, b1, and c1 are each the lattice constant of tetragonal crystals in the direction of anisotropy. The length of a1 is equal to the length of b 1. The length of c1 is greater than the length of a 1. That is, the length of c1 is greater than the length of b 1.

Rhombohedral crystals of the above oxides having a perovskite structure are shown in fig. 11. The unit cell uc2 of rhombohedral can be composed of an element located at the a site, an element located at the B site, and oxygen (O). For ease of mapping, sites B and O are omitted from fig. 11. The element at the a site may be at least one selected from Bi, the element E1, and the element E2. The element at the B site may be Ti. A2, b2, and c2 in fig. 11 are basic vectors constituting rhombohedral. c2 corresponds to the cubic rotation axis of unit cell uc 2. I.e. rhombohedral has a triple symmetry. In the case where the basic vectors of cubic crystals constituting the above-mentioned oxides are a3, b3 and c3, [111] (crystal orientation) of a3, b3 and c3 based on cubic crystals corresponds to [001] of a2, b2 and c2 based on rhombohedral crystals.

If the dielectric thin film 40 does not contain one of tetragonal crystal and rhombohedral crystal, the phase transition of the oxide is likely to occur with a temperature change. The relative dielectric constant of the dielectric thin film 40 is easily changed due to the phase change. However, since the dielectric thin film 40 includes both tetragonal crystals and rhombohedral crystals, the structurally inclined region is formed in the vicinity of the interface of the tetragonal crystals and the rhombohedral crystals. The structure-inclined region suppresses rapid progress of phase transition of the oxide. For example, a rapid phase transition from rhombohedral to tetragonal is suppressed. Alternatively, a rapid phase transition from tetragonal to rhombohedral is suppressed. Since these phase changes are suppressed, the change in the relative permittivity of the dielectric thin film 40 accompanying the temperature change is suppressed. That is, since the dielectric thin film 40 includes both tetragonal crystals and rhombohedral crystals, the dielectric thin film 40 can have excellent temperature characteristics. However, the reason for the improvement of the temperature characteristics is not necessarily limited to the above mechanism.

Whether the dielectric thin film 40 includes tetragonal crystals and rhombohedral crystals can be confirmed based on an X-ray diffraction (XRD) pattern of the dielectric thin film 40. When the XRD pattern of the dielectric thin film 40 has a peak at a diffraction angle inherent to the tetragonal crystal, the dielectric thin film 40 contains the tetragonal crystal. In the case where the XRD pattern of the dielectric thin film 40 has a peak at a diffraction angle inherent to rhombohedral crystals, the dielectric thin film 40 contains rhombohedral crystals.

As explained below, the dielectric thin film 40 of the third embodiment of the invention has characteristics with respect to its XRD pattern.

The XRD pattern of the dielectric thin film 40 was measured by using CuK α rays as incident X-rays. The unit of the intensity of the diffracted X-ray may be an arbitrary unit (arbitrary unit). The measurement of the XRD pattern of the dielectric thin film 40 may be an Out-of-Plane (Out of Plane) measurement on the surface of the dielectric thin film 40. The XRD pattern of the dielectric thin film 40 includes a peak Pexp having a diffraction angle 2 θ of 39.0 ° to 41.2 °. That is, the XRD pattern has a peak Pexp in a range where the diffraction angle 2 θ is 39.0 ° or more and 41.2 ° or less. The diffraction angle 2 θ of the peak Pexp may be 39.8 ° or more and 40.4 ° or less. An example of the peak Pexp is shown in fig. 12.

The peak Pexp is represented by a superposition of the first peak P1 and the second peak P2. In other words, the peak Pexp may be separated into the first peak P1 and the second peak P2. Diffraction angle 2 θ of first peak P1₁Diffraction angle 2 theta to the second peak P2₂Is small. Diffraction angle 2 θ of first peak P1₁About 39.4 ° or more and 40.4 ° or less. Diffraction angle 2 theta of second peak P2₂Is about 39.8 DEG to 40.8 deg. Fig. 13 shows an example of each of the first peak P1 and the second peak P2. The peak Pexp can be separated into a first peak P1 and a second peak P2 by the following method.

The first peak P1 may be approximated by a ford function (Voigt function) f 1. The second peak P2 may be approximated by another ford function f 2. Curve fitting (curve fitting) of the measured peak Pexp to f1 and f2 was performed. That is, the measured peak Pexp is approximated by f1+ f 2. The curve-fitted f1 corresponds to the first peak P1. The curve-fitted f2 corresponds to the second peak P2. The peak P1+ P2 of the first peak P1 and the second peak P2 superimposed is shown in fig. 14. As shown in fig. 15, the peak P1+ P2 obtained by curve fitting approximately coincided with the measured peak Pexp. The first peak P1 and the second peak P2 may also be approximated by Lorentzian functions (Lorentzian) instead of Forger functions, respectively. The first peak P1 and the second peak P2 may also be approximated by Gaussian functions (Gaussian) instead of the ford functions. By the above method, the measured peak Pexp was separated into the first peak P1 and the second peak P2.

The area S1 of the first peak P1 is calculated by integration of the first peak P1. The area S2 of the second peak P2 is calculated by integration of the second peak P2. S1/S2 is 0.02-55. When S1/S2 is 0.02 to 55, the temperature characteristics of the dielectric thin film 40 are improved. Since the temperature characteristics of the dielectric thin film 40 are more easily improved, S1/S2 is preferably 0.02 to 50.

The first peak P1 may be derived from the tetragonal crystal of the above oxide, and the second peak P2 may be derived from the rhombohedral crystal of the above oxide. The first peak P1 may be a peak of a (111) plane of a tetragonal crystal that diffracts X-rays. The (111) plane of the tetragonal crystal is defined based on the above-mentioned basis vectors (a1, b1, and c1) of the tetragonal crystal. The second peak P2 may be a peak of the (003) plane of rhombohedral diffraction X-ray. The (003) plane of the rhombohedral is defined based on the above-mentioned basic vectors (a2, b2, and c2) of the rhombohedral.

In the case where the first peak P1 originates from tetragonal crystal and the second peak P2 originates from rhombohedral crystal, whether or not the dielectric thin film 40 includes tetragonal crystal and rhombohedral crystal can be confirmed by separation of the peaks Pexp and calculation of S1/S2. For example, when S1 is zero and S1/S2 is zero, the dielectric thin film 40 contains not tetragonal but rhombohedral. In the case where S2 is very small, and S1/S2 diverges to infinity, the dielectric thin film 40 contains tetragonal crystals and contains substantially no rhombohedral crystals. The larger S1/S2, the more tetragonal crystals in the dielectric film 40 and the less rhombohedral crystals in the dielectric film 40. The smaller S1/S2, the less tetragonal crystals in the dielectric film 40 and the more rhombohedral crystals in the dielectric film 40.

The content of Bi in the dielectric thin film 40 can be expressed as [ Bi ] mol%. The unit of [ Bi ] may be atomic%. The total content of the element E2 in the dielectric thin film 40 can be represented as [ E2] mol%. [E2] The unit of (c) may be atomic%. [ Bi ]/[ E2] may preferably be 0.214 to 4.500. Since [ Bi ]/[ E2] is within the above range, the temperature characteristics and DC bias characteristics of the dielectric thin film 40 are easily improved.

< chemical formula 1a >

(1-x)Bi_1-α-βNa_αK_βTiO₃-xCa_sSr_tBa_uTiO₃

< chemical formula 1b >

(Bi_1-α-βNa_αK_β)_1-x(Ca_sSr_tBa_u)_xTiO₃

0<x<1 (2)

0.4<α+β<0.6 (3)

0≤α<0.6 (4)

0≤β<0.6 (5)

0.9<s+t+u≤1.1 (6)

0≤s≤1.1 (7)

0≤t≤1.1 (8)

0≤u≤1.1 (9)

(substrate)

The composition of the substrate 10 is not limited as long as the substrate 10 has mechanical strength enough to support the adhesive film 20, the lower electrode 30, the dielectric thin film 40, and the upper electrode 50 formed on the substrate 10. The substrate 10 may be, for example, a single crystal substrate, a ceramic polycrystalline substrate, or a metal substrate. The single crystal substrate may be made of, for example, Si single crystal, SiGe single crystal, GaAs single crystal, InP single crystal, SrTiO single crystal₃Single crystal, MgO single crystal, LaAlO₃Single crystal, ZrO₂Single crystal, MgAl₂O₄Single crystal or NdGaO₃A single crystal. The ceramic polycrystalline substrate may be made of, for example, Al₂O₃Polycrystalline, ZnO polycrystalline or SiO₂A polycrystalline structure. The metal substrate may be made of, for example, Ni (nickel), Cu (copper), Ti (titanium), W (tungsten), Mo (molybdenum), Al (aluminum), Pt (platinum), or an alloy containing these metals. Si single crystal is preferable in terms of low cost and easy processing. When the substrate 10 has sufficient conductivity, the dielectric thin film 40 may directly overlap with the surface of the substrate, and the substrate 10 may function as an electrode.

The resistivity of the substrate 10 varies depending on the material of the substrate 10. When the resistivity of the substrate 10 is low, a current leaks to the substrate 10 when the thin film capacitor 100 operates, and thus the electrical characteristics of the thin film capacitor 100 are impaired. For example, in the case where the substrate 10 is composed of Si single crystal, current may leak to the substrate 10. Therefore, in the case where the resistivity of the substrate 10 is low, the surface of the substrate 10 may be insulatedThe film is covered, and the adhesion film 20 or the lower electrode 30 may overlap with the surface of the insulating film. The insulating film suppresses leakage current. The composition and thickness of the insulating film are not limited as long as the substrate 10 and the capacitor portion 60 are insulated from each other. The insulating film may be made of, for example, SiO₂、Al₂O₃Or Si₃N_xAnd (4) forming. The thickness of the insulating film may be, for example, 0.01 μm or more and 10 μm or less. An insulating film is not necessary for the thin film capacitor 100. That is, the adhesive film 20 or the lower electrode 30 may directly overlap the surface of the substrate 10.

(laminating film)

By disposing the adhesive film 20 between the substrate 10 and the lower electrode 30, the lower electrode 30 can be prevented from peeling off from the substrate 10. The composition of the adhesive film 20 is not limited as long as the peeling of the lower electrode 30 from the substrate 10 can be suppressed. The adhesive film 20 may contain, for example, Cr, Ti, TiO₂、SiO₂、Y₂O₃And ZrO₂At least one of (1). For the film capacitor 100, an adhesion film is not necessary. In the case where the lower electrode 30 is easily in direct contact with the substrate 10 or the insulating film, the lower electrode 30 may directly overlap with the substrate 10 or the insulating film.

(lower electrode)

(Upper electrode)

(protective layer)

The lower electrode 30, the dielectric thin film 40, and the upper electrode 50 are covered with the protective film 70, and the lower electrode 30, the dielectric thin film 40, and the upper electrode 50 are isolated from the external atmosphere. As a result, oxidation of the lower electrode 30 and the upper electrode 50 and corrosion of the dielectric thin film 40 can be suppressed. In addition, the protective film 70 suppresses breakage of the thin film capacitor. As long as the protective film 70 has the above function, the composition of the protective film 70 is not limited. The protective film 70 may be made of a thermosetting resin such as an epoxy resin.

(method for producing dielectric thin film and thin film capacitor)

The dielectric thin films 40 and the thin film capacitor 100 can be manufactured by the following manufacturing method.

After the lower electrode 30 is formed, the substrate 10, the adhesive film 20, and the lower electrode 30 may be heat-treated. By the heat treatment, the adhesion between the adhesion film 20 and the lower electrode 30 is improved. The rate of temperature rise in the heat treatment may be preferably 10 ℃/min to 2000 ℃/min, more preferably 100 ℃/min to 1000 ℃/min. The temperature of the heat treatment may preferably be 400 ℃ to 800 ℃. The time of the heat treatment may be preferably 0.1 hour to 4.0 hours. When the conditions of the heat treatment are out of the above ranges, it is difficult to improve the adhesion between the adhesive film 20 and the lower electrode 30, and the surface of the lower electrode 30 is difficult to be flat. As a result, the dielectric characteristics of the dielectric thin film 40 are easily impaired.

By depositing Bi, the element E1, the element E2, Ti, and O on the surface of the lower electrode 30, the dielectric thin film 40 is formed on the surface of the lower electrode 30. The dielectric thin film 40 may be formed by, for example, vacuum evaporation, sputtering, Pulsed Laser Deposition (PLD), Metal-Organic Chemical Vapor Deposition (MOCVD), Metal-Organic Deposition (MOD), sol-gel, or Chemical Solution Deposition (CSD). The composition of the entire raw material may be adjusted so that the composition of the entire raw material used in the forming method substantially matches the chemical formula 1a or the chemical formula 1 b. The composition of the whole raw material may be adjusted to control the [ Bi ]/[ E2 ]. A variety of raw materials may be used. The raw material may contain a trace amount of impurities or subcomponents as long as the dielectric characteristics of the dielectric thin film 40 are not impaired.

When the dielectric thin film 40 is formed by a sputtering method, a target having a composition substantially equal to that of the chemical formula 1a or 1b can be manufactured. The raw material of the target is not limited as long as the whole raw material of the target contains Bi, the element E1, the element E2, and Ti. The target material can be made from a variety of raw materials. The raw material of the target material may be, for example, at least one compound selected from carbonates, oxides, and hydroxides. After weighing the powders of the respective compounds in accordance with the composition of the dielectric thin film 40, the powders of the respective compounds are mixed. The mixing method may be, for example, a ball mill. Powders of each compound may be mixed together with water or an organic solvent. The molded body can be obtained by molding the pressurized mixed powder. The molding pressure may be, for example, 10Pa to 200 Pa.

The dielectric thin film 40 is excellentFormed by a Radio-Frequency Sputtering method (Radio-Frequency Sputtering). In the high-frequency sputtering method, the substrate 10 on which the adhesion film 20 and the lower electrode 30 are laminated is set in a vacuum chamber. With Ar (argon) and O₂The mixed gas (oxygen) fills the inside of the vacuum chamber. Volume of Ar V1 and O₂The ratio of the volume V2 of (V1/V2) may preferably be 1/1 or more and 5/1 or less. The high frequency power may preferably be 100W to 300W. The high-frequency power is power for applying an alternating voltage between the vacuum chamber (anode) and the target (cathode). The temperature Tsub of the substrate 10 in the high-frequency sputtering method is preferably equal to or higher than room temperature and equal to or lower than 200 ℃, or preferably equal to or higher than 100 ℃ and equal to or lower than 200 ℃. When the temperature Tsub of the substrate 10 in the high-frequency sputtering method is too high, it is difficult to form tetragonal crystals of an oxide having a perovskite structure in the dielectric thin film 40, and S1/S2 is easily lower than 0.02. For example, when the temperature Tsub of the substrate 10 is 300 ℃ or higher, rhombohedral crystals of only an oxide having a perovskite structure are easily formed in the dielectric thin film 40, and S1/S2 is substantially zero.

After the dielectric film 40 is formed, Rapid Thermal Annealing (RTA) of the dielectric film 40 may be performed. In RTA, after the temperature of the dielectric thin film 40 is raised to the annealing temperature T at the temperature rise rate Vt, the dielectric thin film 40 is continuously heated at the annealing temperature T. The dielectric film 40 is heated at the annealing temperature T, and then the dielectric film 40 is cooled to room temperature at a cooling rate Vt'. The temperature rise rate Vt of RTA may be 100 ℃ C/min or more and 3000 ℃ C/min or less. The annealing temperature T may be 700 ℃ to 1000 ℃. The annealing time of the dielectric thin film 40 may be 0.5 minutes to 120 minutes. The annealing time is a time for maintaining the temperature of the dielectric thin film 40 at the annealing temperature T. The cooling rate Vt' of the RTA is preferably 600 ℃/min or more and 800 ℃/min or less. If the temperature lowering rate Vt' is too high, rhombohedral crystals of the oxide having the perovskite structure are difficult to form in the dielectric thin film 40, and S1/S2 easily becomes a value larger than 55. For example, when the temperature decrease rate Vt' is 1000 ℃/min or more, only tetragonal crystals of an oxide having a perovskite structure are easily formed in the dielectric thin film 40, and S1/S2 easily diverges to infinity. In the RTA, the dielectric thin film 40 is preferably heated in the atmosphere or an oxidizing atmosphere.

By the above method, the dielectric thin film 40 can be formed. As described above, since the high-frequency sputtering method and the RTA are performed under predetermined conditions, the tetragonal crystal and the rhombohedral crystal are formed, and S1/S2 is controlled to be in the range of 0.02 to 55. In the conventional thick film method (sintering method), since a ceramic thick film is formed by sintering a dielectric powder, it is difficult to control the crystal structure of the dielectric thin film 40 and S1/S2 by the thick film method (sintering method).

The preferred embodiments of the third invention have been described above, but the third invention is not limited to the above embodiments. Various modifications may be made to the third invention without departing from the scope of the third invention, and these modifications are also included in the third invention.

Examples of the third invention

The third invention will be described in more detail below with reference to examples and comparative examples, but the third invention is not limited to these examples.

(example 51)

< preparation of target >

The mixed powder was prepared by mixing respective powders of bismuth oxide, sodium carbonate, strontium carbonate, and titanium oxide. Powders of bismuth oxide, sodium carbonate, strontium carbonate and titanium oxide were weighed so that the composition of the mixed powder was in accordance with chemical formula 1A below. That is, 1-x and x in chemical formula 1A are adjusted to values shown in Table 5 below, and [ Bi ]/[ E2] is adjusted to values shown in Table 5 below. [ Bi ]/[ E2] is as defined above. If based on x in chemical formula 1A, [ Bi ]/[ E2] is expressed as { (1-x). times.0.5 }/x.

(1-x)Bi_0.5Na_0.5TiO₃-xSrTiO₃(1A)

The above mixed powder and water were mixed for 20 hours by using a ball mill to prepare a slurry. The mixed powder was recovered by drying the slurry at 100 ℃. The mixed powder is molded by a press to obtain a molded article. The molding pressure was 100 Pa. The temperature of the mixed powder in molding was 25 ℃. The time for pressure mixing of the powders was 3 minutes.

The sintered body can be obtained by firing the molded body in air. The firing temperature is 1100 ℃. The firing time was 5 hours.

The sintered body is processed to produce a disk-shaped target material. In the machining of the sintered body, a surface grinder and a cylindrical grinder are used. The diameter of the target material is 80mm, and the thickness of the target material is 5 mm.

< production of dielectric thin film and thin film capacitor >

A wafer composed of a single crystal of Si is used as a substrate. Thickness of the substrateThe degree was 500. mu.m. By heating the substrate in an oxidizing gas, the substrate will be made of SiO₂The insulating film is formed on the surface of the substrate. The thickness of the insulating film was adjusted to 500 nm.

A dielectric thin film is formed on the surface of the lower electrode by a high-frequency sputtering method using the target. In the high-frequency sputtering method, a substrate on which an insulating film, an adhesive film, and a lower electrode are laminated is placed in a vacuum chamber. With Ar and O₂The mixed gas of (2) fills the inside of the vacuum chamber. The pressure in the vacuum chamber was maintained at 1.0 Pa. Volume of Ar V1 and O₂The volume of (2) V2 (V1/V2) was 3/1. The high frequency power was 200W. The temperature Tsub of the substrate 10 in the vacuum chamber was maintained at the temperature shown in table 5 below. The thickness of the dielectric thin film was adjusted to 300 nm.

After the formation of the dielectric thin film, Rapid Thermal Annealing (RTA) of the dielectric thin film is performed. In RTA, a dielectric thin film is heated in the atmosphere. In RTA, the temperature of the dielectric thin film is raised to the annealing temperature T at a predetermined temperature rise rate Vt, and then the dielectric thin film 40 is continuously heated at the annealing temperature T. The dielectric film 40 is heated at an annealing temperature T, and then the dielectric film 40 is cooled from the annealing temperature T to room temperature at a cooling rate Vt'. The temperature rise rate Vt of RTA is 900 deg.C/min. The annealing temperature T was 900 ℃. The annealing time of the dielectric thin film was 1 minute. The temperature decrease rate Vt' of RTA was adjusted to the value shown in table 5 below.

After RTA, an upper electrode made of Pt was formed on the surface of the dielectric thin film by sputtering. Through the mask, a circular upper electrode is formed. The diameter of the upper electrode was adjusted to 200 μm. The thickness of the upper electrode was adjusted to 100 nm.

The dielectric thin film and the thin film capacitor of example 51 were produced by the above-described methods.

< analysis of dielectric thin film and thin film capacitor >

[ analysis of composition and Crystal Structure of dielectric thin film ]

The composition of the dielectric thin film of example 51 was analyzed by fluorescent X-ray Fluorescence (XRF) analysis. The analysis result showed that the composition of the dielectric thin film was consistent with the composition shown in chemical formula 1A, and that 1-x and x in chemical formula 1A were consistent with the values shown in table 5 below. That is, the dielectric thin film of example 51 is an oxide represented by the above chemical formula 1A.

The X-ray diffraction (XRD) pattern of the dielectric thin film of example 51 was measured. The XRD pattern uses CuK α rays as incident X-rays. For the measurement of the XRD pattern, an X-ray diffraction device (SmartLab) manufactured by Rigaku K.K. was used. The XRD pattern indicates that the dielectric thin film is an oxide having a perovskite structure.

The XRD pattern of the dielectric thin film of example 51 contained the peak Pexp having a diffraction angle 2 θ of 39.0 ° to 41.2 °. The peak Pexp was separated into a first peak P1 and a second peak P2 by the curve fitting described above. That is, the measured peak Pexp is represented by the superposition of the first peak P1 and the second peak P2. The first peak P1 is approximated by a ford function f 1. The second peak P2 is approximated by another ford function f 2. Diffraction angle 2 θ of first peak P1₁About 40.13 deg. and is the diffraction angle inherent to the tetragonal crystals of the above oxides. Diffraction angle 2 theta of second peak P2₂About 40.26 ° and is a diffraction angle inherent to rhombohedral crystals of the above-mentioned oxides. The area S1 of the first peak P1 is calculated by integration of the first peak P1. The area S2 of the second peak P2 is calculated by integration of the second peak P2. S1/S2 of example 51 is shown in Table 5 below.

The above analysis results show that the dielectric thin film of example 51 is an oxide represented by the above chemical formula 1A, the oxide has a perovskite structure, and the dielectric thin film contains tetragonal crystals and rhombohedral crystals.

[ evaluation of DC bias characteristics ]

The capacitance C1 of the film capacitor of example 51 was measured in a state where no dc electric field was applied to the dielectric film. As an apparatus for measuring electrostatic capacity, a digital LCR (4284A) manufactured by Hewlett-Packard company was used. The measurement conditions of the capacitance C1 are as follows.

Measuring temperature: 25 deg.C

Measuring frequency: 1kHz

Input signal level (measurement voltage): 1.0Vrms

Strength of direct current electric field (DC bias): 0V/. mu.m

According to the capacitance C1, the effective area of the electrode (the area of the upper electrode), the distance between the electrodes and the vacuum dielectric constant₀The relative dielectric constant r1 of the dielectric thin film of example 51 was calculated. That is, the relative permittivity r1 of the dielectric thin film in a state where no dc electric field is applied to the dielectric thin film was calculated. R1 of example 51 is shown in Table 5 below. The relative dielectric constant is unitless.

The capacitance C2 of the film capacitor of example 51 was measured in a state where a dc electric field was applied to the dielectric film. The intensity of the DC electric field was 10V/. mu.m. The measurement conditions of the capacitance C2 were the same as those of the capacitance C1, except for the intensity of the dc electric field. The relative permittivity r2 of the dielectric thin film of example 51 was calculated from the capacitance C2. That is, the relative permittivity r2 of the dielectric thin film in a state where a dc electric field is applied to the dielectric thin film was calculated. Except for the capacitance, the method of calculating r2 is the same as that of r 1. R2 of example 51 is shown in Table 5 below. r2 is preferably 600 or more. r2 is more preferably 630 or more.

[ evaluation of temperature characteristics ]

The film capacitor of example 51 was set in a constant temperature bath. The electrostatic capacitance of the film capacitor at each temperature was continuously measured while continuously changing the temperature of the film capacitor in the thermostatic bath from-55 ℃ to 85 ℃. The measurement conditions of the electrostatic capacity at each temperature are as follows.

Measuring frequency: 1kHz

Input signal level (measurement voltage): 1.0Vrms

Strength of direct current electric field (DC bias): 0V/. mu.m

The relative dielectric constant at each temperature was calculated from the capacitance at each temperature. The method for calculating the relative permittivity at each temperature is the same as the method for calculating r1 except for the capacitance. Based on the relative permittivity at each temperature, the rate of change Δ r of the relative permittivity was calculated. Δ r is defined by the following equation a. Δ r is in%. R (25 ℃) in the formula a is a relative dielectric constant at 25 ℃. r (T) is the relative permittivity which is the largest difference from the absolute value of r (25 ℃) among all the relative permittivities measured in the above temperature range. Δ r of example 51 is shown in Table 5 below. Deltar is preferably from-15% to 15%. More preferably,. DELTA.r is from-10% to 10%.

Δr＝100×{r(T)-r(25℃)}/r(25℃) (a)

(examples 52 to 54)

In the production of the targets of examples 52 to 54, 1-x and x in chemical formula 1A were adjusted to values shown in Table 5, and [ Bi ]/[ E2] was adjusted to values shown in Table 5. Dielectric thin films and thin film capacitors of examples 52 to 54 were produced in the same manner as in example 51 except for the composition of the target.

The dielectric thin films and the thin film capacitors of examples 52 to 54 were analyzed by the same method as in example 51. In examples 52 to 54, the compositions of the dielectric thin films were all the same as those shown in chemical formula 1A, and 1-x and x in chemical formula 1A were all the same as values shown in table 5 below. In examples 52 to 54, the dielectric thin films were all the oxides represented by the above chemical formula 1A, all the oxides had a perovskite structure, and all the dielectric thin films included tetragonal crystals and rhombohedral crystals. The S1/S2, r1, r2 and Δ r of examples 52 to 54 are shown in Table 5 below.

In the XRD pattern of example 51, the peak Pexp at a diffraction angle 2 θ of 39.0 ° to 41.2 ° is shown in fig. 12. P1 and P2 of example 51 are shown in FIG. 13. The peak (Pl + P2) represented by the superposition of P1 and P2 of example 51 is shown in fig. 14. Pexp and P1+ P2 for example 51 are shown in FIG. 15.

Comparative example 51

The temperature Tsub of the substrate 10 in the high-frequency sputtering method of comparative example 51 was maintained at the temperature shown in table 5 below. The temperature decrease rate Vt' of RTA of comparative example 51 was adjusted to the value shown in table 5 below. Except for these matters, the dielectric thin film and the thin film capacitor of comparative example 51 were produced in the same manner as in example 52.

The dielectric thin film and the thin film capacitor of comparative example 51 were analyzed by the same method as example 51. The composition of the dielectric thin film of comparative example 51 was identical to that shown in chemical formula 1A, and 1-x and x in chemical formula 1A were identical to the values shown in table 5 below. The oxide of comparative example 51 had a perovskite structure. However, S1 of comparative example 51 is zero, and S1/S2 of comparative example 51 is also zero. That is, the dielectric thin film of comparative example 51 contains rhombohedral crystals, but no tetragonal crystals were detected from the dielectric thin film of comparative example 51. R1, r2 and Δ r of comparative example 51 are shown in table 5 below.

Examples 55 to 57

The cooling rate Vt' of RTA in each of examples 55 to 57 was adjusted to the value shown in Table 5 below. Dielectric thin films and thin film capacitors of examples 55 to 57 were produced in the same manner as in example 52, except for the temperature decrease rate Vt' of RTA.

The dielectric thin films and the thin film capacitors of examples 55 to 57 were each analyzed by the same method as in example 51. In examples 55 to 57, the compositions of the dielectric thin films were all the same as the composition shown in chemical formula 1A, and 1-x and x in chemical formula 1A were all the same as the values shown in Table 5 below. In examples 55 to 57, the dielectric thin films were all the oxides represented by the above chemical formula 1A, all the oxides had a perovskite structure, and all the dielectric thin films included tetragonal crystals and rhombohedral crystals. Examples 55 to 57 each had S1/S2, r1, r2 and Δ r as shown in Table 5 below.

Comparative example 52

The temperature decrease rate Vt' of RTA of comparative example 52 was adjusted to the value shown in table 5 below. A dielectric thin film and a thin film capacitor of comparative example 52 were produced in the same manner as in example 52, except for the temperature decrease rate Vt' of RTA.

The dielectric thin film and the thin film capacitor of comparative example 52 were analyzed by the same method as in example 51. The composition of the dielectric thin film of comparative example 52 was identical to that shown in chemical formula 1A, and 1-x and x in chemical formula 1A were identical to the values shown in table 5 below. The oxide of comparative example 52 has a perovskite structure. However, S2 for comparative example 52 was zero, and S1/S2 for comparative example 52 diverged to infinity. That is, the dielectric thin film of comparative example 52 contains tetragonal crystals, but no rhombohedral crystals were detected from the dielectric thin film of comparative example 52. R1, r2 and Δ r of comparative example 52 are shown in table 5 below.

(example 61)

The target material of example 61 was produced by the following solid phase method.

The mixed powder was prepared by mixing respective powders of bismuth oxide, sodium carbonate, barium carbonate, and titanium oxide. Powders of bismuth oxide, sodium carbonate, barium carbonate and titanium oxide were weighed so that the composition of the mixed powder was in accordance with chemical formula 1B below. That is, 1-x and x in chemical formula 1B were adjusted to values shown in Table 6 below, [ Bi ]]/[E2]The values are shown in Table 6 below. If based on x in chemical formula 1B, [ Bi ] will be]/[E2]BT, expressed as { (1-x) × 0.5.5 }/x, means BaTiO₃。

(1-x)Bi_0.5Na_0.5TiO₃-xBaTiO₃(1B)

A dielectric thin film and a thin film capacitor of example 61 were produced in the same manner as in example 52, except for the composition of the target.

The dielectric thin film and the thin film capacitor of example 61 were analyzed by the same method as in example 51. The composition of the dielectric thin film of example 61 was identical to that shown in chemical formula 1B, and 1-x and x in chemical formula 1B were identical to the values shown in table 6 below. The dielectric thin film of example 61 was an oxide represented by the above chemical formula 1B, the oxide had a perovskite structure, and the dielectric thin film included tetragonal crystals and rhombohedral crystals. S1/S2, r1, r2 and Δ r of example 61 are shown in Table 6 below.

(example 62)

The target material of example 62 was produced by the following solid phase method.

The mixed powder was prepared by mixing respective powders of bismuth oxide, sodium carbonate, calcium carbonate, and titanium oxide. Powders of bismuth oxide, sodium carbonate, calcium carbonate and titanium oxide were weighed so that the composition of the mixed powder was the same as the following chemical formulaFormula 1C is identical. That is, 1-x and x in chemical formula 1C were adjusted to values shown in Table 6 below, [ Bi ]]/[E2]The values are shown in Table 6 below. If based on x in chemical formula 1C, [ Bi ] will be]/[E2]CT represented by { (1-x) × 0.5.5 }/x. hereinafter means CaTiO₃。

(1-x)Bi_0.5Na_0.5TiO₃-xCaTiO₃(1C)

A dielectric thin film and a thin film capacitor of example 62 were produced in the same manner as in example 52, except for the composition of the target.

The dielectric thin film and the thin film capacitor of example 62 were analyzed by the same method as in example 51. The composition of the dielectric thin film of example 62 was identical to that shown in chemical formula 1C, and 1-x and x in chemical formula 1C were identical to the values shown in table 6 below. The dielectric thin film of example 62 was an oxide represented by the above chemical formula 1C, the oxide had a perovskite structure, and the dielectric thin film included tetragonal crystals and rhombohedral crystals. S1/S2, r1, r2 and Δ r of example 62 are shown in Table 6 below.

(example 63)

The target of example 63 was produced by the following solid phase method.

The mixed powder was prepared by mixing respective powders of bismuth oxide, potassium carbonate, barium carbonate, and titanium oxide. Powders of each of bismuth oxide, potassium carbonate, barium carbonate, and titanium oxide were weighed so that the composition of the mixed powder was in accordance with the following chemical formula 1D. That is, 1-x and x in chemical formula 1D were adjusted to values shown in Table 6 below, [ Bi ]]/[E2]The values are shown in Table 6 below. If based on x in chemical formula 1D, [ Bi ] will be]/[E2]BKT expressed as { (1-x) × 0.5.5 }/x. described below means Bi_0.5K_0.5TiO₃。

(1-x)Bi_0.5K_0.5TiO₃-xBaTiO₃(1D)

A dielectric thin film and a thin film capacitor of example 63 were produced in the same manner as in example 52, except for the composition of the target.

The dielectric thin film and the thin film capacitor of example 63 were analyzed by the same method as in example 51. The composition of the dielectric thin film of example 63 was consistent with the composition shown in chemical formula 1D, and 1-x and x in chemical formula 1D were consistent with the values shown in table 6 below. The dielectric thin film of example 63 was an oxide represented by the above chemical formula 1D, the oxide had a perovskite structure, and the dielectric thin film included tetragonal crystals and rhombohedral crystals. S1/S2, r1, r2 and Δ r of example 63 are shown in Table 6 below.

(example 64)

The target material of example 64 was produced by the following solid phase method.

The mixed powder was prepared by mixing respective powders of bismuth oxide, potassium carbonate, strontium carbonate, and titanium oxide. Powders of each of bismuth oxide, potassium carbonate, strontium carbonate, and titanium oxide were weighed so that the composition of the mixed powder was in accordance with chemical formula 1E below. That is, 1-x and x in chemical formula 1E are adjusted to the values shown in Table 6 below, and [ Bi ]/[ E2] is the value shown in Table 6 below. If based on x in chemical formula 1E, [ Bi ]/[ E2] is expressed as { (1-x). times.0.5 }/x.

(1-x)Bi_0.5K_0.5TiO₃-xSrTiO₃(1E)

A dielectric thin film and a thin film capacitor of example 64 were produced in the same manner as in example 52, except for the composition of the target.

The dielectric thin film and the thin film capacitor of example 64 were analyzed by the same method as in example 51. The composition of the dielectric thin film of example 64 was identical to that shown in chemical formula 1E, and 1-x and x in chemical formula 1E were identical to the values shown in table 6 below. The dielectric thin film of example 64 is an oxide represented by the above chemical formula 1E, the oxide has a perovskite structure, and the dielectric thin film contains tetragonal crystals and rhombohedral crystals. S1/S2, r1, r2 and Δ r of example 64 are shown in Table 6 below.

(example 65)

The target material of example 65 was produced by the following solid phase method.

The mixed powder was prepared by mixing respective powders of bismuth oxide, potassium carbonate, calcium carbonate, and titanium oxide. Powders of each of bismuth oxide, potassium carbonate, calcium carbonate, and titanium oxide were weighed so that the composition of the mixed powder was in accordance with chemical formula 1F below. That is, 1-x and x in chemical formula 1F are adjusted to values shown in Table 6 below, and [ Bi ]/[ E2] is adjusted to values shown in Table 6 below. If based on x in chemical formula 1F, [ Bi ]/[ E2] is expressed as { (1-x). times.0.5 }/x.

(1-x)Bi_0.5K_0.5TiO₃-xCaTiO₃(1F)

The dielectric thin film and the thin film capacitor of example 65 were produced in the same manner as in example 52, except for the composition of the target.

The dielectric thin film and the thin film capacitor of example 65 were analyzed by the same method as example 51. The composition of the dielectric thin film of example 65 was consistent with the composition shown in chemical formula 1F, and 1-x and x in chemical formula 1F were consistent with the values shown in table 6 below. The dielectric thin film of example 65 was an oxide represented by the above chemical formula 1F, the oxide had a perovskite structure, and the dielectric thin film included tetragonal crystals and rhombohedral crystals. S1/S2, r1, r2 and Δ r of example 65 are shown in Table 6 below.

[ Table 5]

[ Table 6]

[ industrial applicability ]

The dielectric thin film of the third invention is used for a thin film capacitor, for example.

[ explanations of symbols in FIGS. 10 to 15 ]

A unit cell of uc1 … tetragonal crystal, a unit cell of uc2 … rhombohedral crystal, a peak of diffraction X-rays having a Pexp … diffraction angle 2 theta of 39.0 DEG to 41.2 DEG, a first peak of P1 …, and a second peak of P2 ….

Electronic component according to each of embodiments of the first, second, and third inventions

The dielectric thin films according to the embodiments of the first, second, and third inventions can be used in electronic components such as electronic circuit boards and piezoelectric elements, in addition to capacitors. The "dielectric thin film" described below has the same meaning as the "dielectric film".

The electronic component including the dielectric thin film 40 according to each of the embodiments of the first, second, and third inventions may be a piezoelectric element. The piezoelectric element may be, for example, a piezoelectric microphone, a harvester, an oscillator, a resonator, or an acoustic multilayer film. The piezoelectric element may be a piezoelectric actuator, for example. The piezoelectric actuator may be used for a head assembly, a head stack assembly (head stack assembly), or a hard disk drive, for example. Piezoelectric actuators may also be used in print heads or inkjet printing devices, for example. Piezoelectric actuators may also be used for piezoelectric switches. The piezoelectric element can also be a piezoelectric transducer, for example. The piezoelectric element may be a piezoelectric sensor, for example. The piezoelectric sensor may be, for example, a gyro sensor, a pressure sensor, a pulse wave sensor, an ultrasonic sensor, or a vibration sensor. The electronic component provided with the dielectric thin film 40 may be a pyroelectric element such as an infrared detector. Each of the electronic components may be a part or all of Micro Electro Mechanical Systems (MEMS).

Electronic circuit board according to each of embodiments of the first, second, and third inventions

The electronic circuit boards according to the respective embodiments of the first, second, and third inventions are the same except for the composition or crystal structure of the dielectric film (dielectric thin film). The structure and the manufacturing method of the electronic circuit board described below are common to the electronic circuit boards according to the embodiments of the first, second, and third inventions.

The electronic circuit board may include the dielectric thin film according to the first, second, or third aspect. The electronic circuit board may further include the electronic component including a dielectric thin film. 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 provided on the surface of the electronic circuit board. Electronic components such as thin film capacitors may be embedded in the electronic circuit board. Fig. 4A and 4B show an example of the electronic circuit board. The electronic circuit board 90 may include: an epoxy resin substrate 92, a resin layer 93 covering the epoxy resin substrate 92, a film capacitor 91 provided on the resin layer 93, an insulating coating layer 94 covering the resin layer 93 and the film capacitor 91, an electronic component 95 provided on the insulating coating layer 94, and a plurality of metal wirings 96. At least a part of the metal wiring 96 may be led 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 lead electrode of the thin film capacitor 91 or the electronic component 95. At least a portion of the metal wiring 96 may penetrate the electronic circuit substrate 90 in a direction from the front surface toward the back surface of the electronic circuit substrate 90.

As shown in fig. 4B, the film capacitor 91 may include: a lower electrode 30; a dielectric thin film 40 provided on the surface of the lower electrode 30; an upper electrode 50 provided on an upper surface of a part of the dielectric thin film 40; a through electrode 52 penetrating the other part of the dielectric thin film 40 and directly provided on the surface of the lower electrode 30; an insulating resin layer 58 covering the upper electrode 50, the dielectric thin film 40, and the through electrode 52; a lead electrode 54 which penetrates the insulating resin layer 58 and is directly provided on the surface of the through electrode 52; and a lead electrode 56 which penetrates the insulating resin layer 58 and is directly provided on the surface of the upper electrode 50.

The electronic circuit substrate 90 can be manufactured in the following order. 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 film capacitor 91 is disposed on the surface of the uncured resin layer so that the base electrode of the film capacitor 91 faces the uncured resin layer. By covering the uncured resin layer and the film capacitor 91 with the insulating coating layer 94, the film capacitor 91 is sandwiched between the epoxy resin substrate 92 and the insulating coating layer 94. The resin layer 93 is formed by thermal curing of the uncured resin layer. The insulating coating layer 94 is pressure-bonded to the epoxy resin substrate 92, the film capacitor 91, and the resin layer 93 by hot pressing. A plurality of through holes are formed to penetrate the laminated substrate. A metal wiring 96 is formed in each through hole. After the metal wiring 96 is formed, the electronic component 95 is provided on the surface of the insulating coating layer 94. By the above method, the electronic circuit board 90 in which the thin film capacitor 91 is embedded can be obtained. Each metal wire 96 may be made of a conductor such as Cu. The uncured resin layer may be a B-stage thermosetting resin (e.g., epoxy resin, etc.). The B-stage thermosetting resin is not completely cured at room temperature and 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.

Claims

1. A dielectric film, wherein,

the dielectric film includes:

(1) bi and Ti;

(2) at least one element E1 selected from Na and K; and

(3) at least one element E2 selected from Ba, Sr and Ca,

the dielectric film includes:

a main phase including an oxide including Bi, Ti, an element E1, and an element E2 and having a perovskite structure; and

a secondary phase comprising Bi and having a lower oxygen concentration than the primary phase,

a ratio RS of an area of the sub-phase to a total of the area of the main phase and the area of the sub-phase in a cross section of the dielectric film satisfies the following expression,

0.03≤RS≤0.3。

2. the dielectric film according to claim 1, wherein,

the total number of atoms of Bi and the element E1 is 30:70 to 90:10 in total number of atoms of the element E2.

3. The dielectric film according to claim 1, wherein,

in the oxide, the ratio of the number of atoms of the element E1 to the number of atoms of Bi is 0.9 to 1.1.

4. The dielectric film according to claim 1, wherein,

in the oxide, the ratio of the number of atoms of Ti to the total number of atoms of Bi, the element E1 and the element E2 is 0.9 to 1.1.

5. An electronic component, wherein,

a dielectric film according to any one of claims 1 to 4.

6. The electronic component of claim 5, wherein,

the dielectric film is in contact with the electrode.

7. A thin-film capacitor, wherein,

a dielectric film according to any one of claims 1 to 4.

8. An electronic circuit board, wherein,

a dielectric film according to any one of claims 1 to 4.

9. An electronic circuit board, wherein,

the electronic component according to claim 5 or 6 is provided.

10. An electronic circuit board, wherein,

a thin film capacitor according to claim 7.

11. A dielectric thin film, wherein,

comprises an oxide having a perovskite structure, and a method for producing the same,

the oxide comprises Bi, an element E1, an element E2 and Ti,

the element E1 is at least one element selected from Na and K,

the element E2 is at least one element selected from Ca, Sr and Ba,

the oxide comprises a double crystal.

12. The dielectric thin film according to claim 11,

the content of Bi in the dielectric thin film is represented by [ Bi ] mol%, the total content of the elements E2 in the dielectric thin film is represented by [ E2] mol%,

[ Bi ]/[ E2] is 0.214 to 4.500.

13. An electronic component, wherein,

a dielectric thin film according to claim 11 or 12.

14. A thin-film capacitor, wherein,

a dielectric thin film according to claim 11 or 12.

15. An electronic circuit board, wherein,

a dielectric thin film according to claim 11 or 12.

16. An electronic circuit board, wherein,

the electronic component according to claim 13 is provided.

17. An electronic circuit board, wherein,

a thin film capacitor according to claim 14.

18. A dielectric thin film, wherein,

the oxide comprises Bi, an element E1, an element E2 and Ti,

the element E1 is at least one element selected from Na and K,

the element E2 is at least one element selected from Ca, Sr and Ba,

the dielectric thin film includes tetragonal crystals of the oxide and rhombohedral crystals of the oxide.

19. A dielectric thin film, wherein,

the dielectric thin film contains an oxide having a perovskite structure,

the oxide comprises Bi, an element E1, an element E2 and Ti,

the element E1 is at least one element selected from Na and K,

the element E2 is at least one element selected from Ca, Sr and Ba,

the X-ray diffraction pattern of the dielectric thin film is measured by using CuK alpha rays as incident X-rays,

the X-ray diffraction pattern includes a peak having a diffraction angle 2 theta of 39.0 DEG to 41.2 DEG,

the peak having a diffraction angle 2 theta of 39.0 DEG to 41.2 DEG is represented by the superposition of the first peak and the second peak,

diffraction angle 2 theta of the first peak₁Diffraction angle 2 theta to the second peak₂The size of the product is small, and the product is small,

s1 is the area of the first peak,

s2 is the area of the second peak,

S1/S2 is 0.02-55.

20. The dielectric thin film of claim 19,

comprising tetragonal crystals of said oxide and rhombohedral crystals of said oxide,

the first peak is derived from the tetragonal crystals of the oxide,

the second peak is derived from rhombohedral crystals of the oxide.

21. The dielectric thin film according to any one of claims 18 to 20,

the content of Bi in the dielectric thin film is expressed as [ Bi ] mol%,

the total content of the element E2 in the dielectric thin film was represented as [ E2] mol%,

[ Bi ]/[ E2] is 0.214 to 4.500.

22. An electronic component, wherein,

a dielectric thin film comprising the dielectric thin film according to any one of claims 18 to 21.

23. A thin-film capacitor, wherein,

24. An electronic circuit board, wherein,

25. An electronic circuit board, wherein,

the electronic component according to claim 22 is provided.

26. An electronic circuit board, wherein,

a thin film capacitor according to claim 23.