JP2020152635A - Dielectric composition and electronic parts - Google Patents

Abstract

To provide: a dielectric composition which has a high quality factor Q value in a high frequency region, a low absolute value of volume temperature coefficient Tcc in a predetermined temperature ange, a dielectric constant which is in a predetermined range or equal to or more than a predetermined value, and a good high temperature acceleration life; and electronic parts having the dielectric composition.SOLUTION: Provided is a dielectric composition comprising a composite oxide represented by a compositional formula BixZnyNbzO1.75+δ, where x, y, and z satisfy relationships, x+y+z=1.00, x<0.20, 0.20≤y≤0.50, and 0.25≤x/z. Also provided is a dielectric composition comprising a composite oxide represented by a compositional formula BixZnyNbzO1.75+δ, where x, y, and z satisfy relationships, x+y+z=1.00, 0.20≤y≤0.50, 1.5<x/z≤3.0, and z<0.25.SELECTED DRAWING: Figure 1

Description

The present invention relates to dielectric compositions and electronic components.

There is a high demand for higher performance of mobile communication devices such as smartphones, and for example, the number of frequency domains used is increasing in order to enable high-speed, large-capacity communication. The frequency domain used is a high frequency region such as the GHz band. Among high-frequency components such as baluns, couplers, filters, or duplexers and diplexers combined with filters that operate in such a high-frequency region, there are some that use a dielectric material as a resonator. Such a dielectric material is required to have a small dielectric loss and good frequency selectivity in a high frequency region.

Such mobile communication devices are exposed to temperature changes due to the usage environment, heat generation of parts used in the devices, and the like. On the other hand, since the capacitance of the high-frequency component changes with temperature, the high-frequency component is required to have a small temperature dependence of capacitance, that is, a small capacitance temperature coefficient in a predetermined temperature range.

Therefore, the dielectric material applied to high frequency components is required to have a small dielectric loss and a small temperature coefficient of capacitance. Since the reciprocal of the dielectric loss can be expressed as a quality coefficient Q value, in other words, a dielectric material having a high quality coefficient Q value in the high frequency region and a small capacitance temperature coefficient in a predetermined temperature range is desired. ..

In addition, in order to analyze vehicle information and driving information, and to support autonomous driving, etc., a connected car having a function of always connecting to the Internet is being developed. The in-vehicle communication device mounted on such a connected car is also a kind of mobile communication device, and is required to be capable of high-speed and large-capacity communication. Further, since the in-vehicle communication device may be arranged in or near the engine room where the temperature becomes high, the in-vehicle communication device is particularly required to have reliability at a high temperature. Therefore, high-frequency components mounted on in-vehicle communication devices are also required to be reliable at high temperatures.

In addition, as the performance of mobile communication devices and in-vehicle communication devices has improved, the number of electronic components mounted on one communication device tends to increase, and in order to maintain the size of these communication devices, electronic components are required. At the same time, miniaturization of parts is also required. In order to reduce the size of high-frequency components that use a dielectric material, it is necessary to reduce the electrode area. Therefore, in order to compensate for the decrease in capacitance due to this, the relative permittivity of the dielectric material is high in the high-frequency region. Desired.

By the way, the capacitance of a high-frequency component using a dielectric material changes depending on the relative permittivity of the dielectric material, the electrode area, and the distance between electrodes. In other words, by changing these, the capacitance of the high frequency component can be adjusted. On the other hand, when changing the performance of a high-frequency component that uses a dielectric material according to the application of the communication equipment to be mounted, the relative permittivity of the dielectric material should be adjusted without changing the mounting area of the high-frequency component. Therefore, it may be required to respond to changes in the performance of high-frequency components. In this case, it is preferable that the dielectric material having the same composition system exhibits the relative permittivity according to the performance of the high-frequency component, rather than changing the composition system of the dielectric material according to the required relative permittivity.

That is, in order to meet various needs for high-frequency components, the dielectric properties required for dielectric materials are also diversifying.

Conventionally, a Bi-Zn-Nb-O oxide is known as a material having a predetermined dielectric property in a high frequency region. For example, Patent Document 1 discloses a mixture of Bi ₃ NbO ₇ phase and Bi ₂ (Zn _2/3 Nb _4/3 ) O ₇ phase. Further, Patent Document 2 discloses a sintered body obtained by mixing Bi ₂ O ₃ , Zn O and Nb ₂ O ₅ at a predetermined ratio and firing them.

Special Table 2009-537444 Japanese Unexamined Patent Publication No. 4-285046

However, in Patent Document 1, the absolute value of the temperature coefficient of the dielectric constant of a mixture of Bi ₃ NbO ₇ phase and Bi ₂ (Zn _2/3 Nb _4/3 ) O ₇ phase mixed at a ratio of 1: 1 is 10 ppm or less. It is stated that there is. However, since the relative permittivity of the mixture is smaller than 100 and the dielectric quality coefficient Q at 1 GHz is about 1000, the dielectric property in the high frequency region is not sufficient from the viewpoint of promoting miniaturization of high frequency components.

Further, from the viewpoint of not changing the mounting area of the high-frequency component, the dielectric constant of the mixture is too large. Therefore, when the high-frequency component is manufactured in the same shape, the capacitance is adjusted by adjusting the electrode area and the thickness of the dielectric material. However, it cannot be adjusted completely, and a low capacitance cannot be realized in the same composition system.

Further, Patent Document 2 describes that the absolute value of the temperature coefficient of the dielectric constant of a sintered body obtained by mixing Bi ₂ O ₃ , Zn O and Nb ₂ O ₅ at a predetermined ratio and firing them is 100 ppm or less. Has been done. However, since the no-load Q value of the sintered body at 1 GHz is 400 or less, the dielectric characteristics in the high frequency region are not sufficient.

The present invention is a dielectric having a high quality coefficient Q value in a high frequency region, a small absolute value of the capacitance temperature coefficient Tcc in a predetermined temperature range, a relative permittivity εr within a predetermined range, and high reliability at high temperatures. A first object is to provide a composition and an electronic component having the dielectric composition.

Further, a dielectric composition in which the relative permittivity εr and the quality coefficient Q value are equal to or higher than a predetermined value in a high frequency region, the absolute value of the capacitance temperature coefficient Tcc is small in a predetermined temperature range, and the dielectric composition is highly reliable at high temperatures. A second object is to provide an electronic component having the dielectric composition.

In order to achieve the first object, the present invention
[1] A dielectric composition having a composite oxide containing bismuth, zinc and niobium.
When the composite oxide is represented by the composition formula Bi _x Zn _y Nb _z O _{1.75 + δ} , x, y and z are x + y + z = 1.00, x <0.20, 0.20 ≦ y ≦ 0.50. , 0.25 ≦ x / z, which is a dielectric composition satisfying the relationship.

In order to achieve the second object, the present invention
[2] A dielectric composition having a composite oxide containing bismuth, zinc and niobium.
When the composite oxide is represented by the composition formula Bi _x Zn _y Nb _z O _{1.75 + δ} , x, y and z are x + y + z = 1.00, 0.20 ≦ y ≦ 0.50, 1.5 <x. A dielectric composition that satisfies the relationship of / z ≦ 3.0 and z <0.25.

[3] An electronic component including a dielectric layer containing the dielectric composition according to [1] or [2].

According to the present invention, the quality coefficient Q value is high in the high frequency region, the absolute value of the capacitance temperature coefficient Tcc is small in a predetermined temperature range, the relative permittivity εr is within a predetermined range, and the reliability at high temperature is high. A dielectric composition and an electronic component having the dielectric composition can be provided.

Further, according to the present invention, the relative permittivity εr and the quality coefficient Q value are equal to or higher than a predetermined value in a high frequency region, the absolute value of the capacitance temperature coefficient Tcc is small in a predetermined temperature range, and the reliability at high temperature is high. A dielectric composition and an electronic component having the dielectric composition can be provided.

FIG. 1 is a schematic cross-sectional view of a thin film capacitor as an example of an electronic component according to the present embodiment.

Hereinafter, the present invention will be described in detail in the following order based on specific embodiments.
1. 1. Thin film capacitor 1.1. Overall configuration of thin film capacitors 1.2. Dielectric film 1.2.1. Dielectric composition 1.2.2. First composite oxide 1.2.3. Second composite oxide 1.3. Substrate 1.4. Lower electrode 1.5. Upper electrode 2. Manufacturing method of thin film capacitor 3. Summary of this embodiment 4. Modification example

(1. Thin film capacitor)
First, the electronic component according to the present embodiment is an electronic component (high frequency component) used in the high frequency region. As a high-frequency component, a thin film capacitor in which the dielectric layer is composed of a thin-film dielectric film will be described.

(1.1. Overall configuration of thin film capacitor)
As shown in FIG. 1, the thin film capacitor 10 as an example of the electronic component according to the present embodiment has a configuration in which a substrate 1, a lower electrode 3, a dielectric film 5, and an upper electrode 4 are laminated in this order. have. The lower electrode 3, the dielectric film 5, and the upper electrode 4 form a capacitor portion, and when the lower electrode 3 and the upper electrode 4 are connected to an external circuit and a voltage is applied, the capacitor portion becomes a predetermined capacitance. It shows the capacitance and can function as a capacitor. A detailed description of each component will be described later.

Further, in the present embodiment, a base layer 2 is formed between the substrate 1 and the lower electrode 3 in order to improve the adhesion between the substrate 1 and the lower electrode 3. The material constituting the base layer 2 is not particularly limited as long as the material can sufficiently secure the adhesion between the substrate 1 and the lower electrode 3. For example, when the lower electrode 3 is made of Cu, the base layer 2 is made of Cr, and when the lower electrode 3 is made of Pt, the base layer 2 can be made of Ti.

Further, in the thin film capacitor 10 shown in FIG. 1, a protective film for blocking the dielectric film 5 from the external atmosphere may be formed.

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

(1.2. Dielectric film)
The dielectric film 5 is composed of the dielectric composition (first dielectric composition and second dielectric composition) according to the present embodiment described later. Further, in the present embodiment, the dielectric film 5 is preferably a thin film-like dielectric deposited film formed on the substrate by a known film forming method.

The thin film capacitor having the dielectric film 5 composed of the first dielectric composition exhibits a high Q value (for example, 1000 or more) even in a high frequency region (for example, 2 GHz) and is good. It can exhibit a capacitive temperature coefficient (eg, the absolute value of the temperature coefficient of capacitance is within 50 ppm / ° C.) and a good high temperature acceleration life (eg, an insulation resistance (IR) life at 180 ° C. of 15.0 h or more). Further, the thin film capacitor can exhibit a relative permittivity εr within a predetermined range.

A thin film capacitor having a dielectric film 5 composed of a second dielectric composition has a high relative permittivity εr (eg 100 or more) and a high Q value (eg 100) even in the high frequency region (eg 2 GHz). , 1000 or more), and has a good temperature coefficient of capacitance (for example, the absolute value of the temperature coefficient of capacitance is within 50 ppm / ° C.) and a good high temperature acceleration life (for example, an insulation resistance (IR) life at 180 ° C. of 15). .0h or more) can be shown.

The thickness of the dielectric film 5 is preferably 10 nm to 2000 nm, more preferably 50 nm to 1000 nm. If the thickness of the dielectric film 5 is too thin, the dielectric breakdown of the dielectric film 5 tends to occur easily. If dielectric breakdown occurs, it cannot function as a capacitor. On the other hand, if the thickness of the dielectric film 5 is too thick, it is necessary to increase the electrode area in order to increase the capacitance of the capacitor, and it may be difficult to reduce the size and height depending on the design of the electronic component. is there.

It is generally known that the Q value tends to decrease as the thickness of the dielectric decreases. Therefore, in order to obtain a high Q value, it is necessary to use a dielectric having a certain thickness, that is, a bulk-shaped dielectric. However, as described above, the dielectric film composed of the dielectric composition according to the present embodiment can obtain a high Q value even when the thickness is very thin.

The thickness of the dielectric film 5 is measured by excavating a thin film capacitor containing the dielectric film 5 with a FIB (focused ion beam) processing device and observing the obtained cross section with a SEM (scanning electron microscope). be able to.

(1.2.1. Dielectric composition)
The dielectric composition according to the present embodiment contains a composite oxide (Bi-Zn-Nb-O-based oxide) containing bismuth (Bi), zinc (Zn) and niobium (Nb) as a main component. .. In the present embodiment, the main component is a component that accounts for 90% by mass or more with respect to 100% by mass of the dielectric composition.

The composite oxide is represented by the general formula A ₂ B ₂ O ₇ and has a pyrochlore phase. In the composite oxide according to the present embodiment, oxygen is coordinated 8 to the element occupying A site (A site element), and oxygen is coordinated 6 to the element occupying B site (B site element). Then, the BO ₆ octahedron in which the B-site element is located at the center of the octahedron composed of oxygen constitutes a three-dimensional network in which the vertices of each other are shared, and the A-site element is located in the gap of this network and A. The site element is located in the center of a hexahedron composed of oxygen. When the crystallinity of such a structure is high, the structure is a pyrochlore type crystal structure.

In the present embodiment, the general formula A ₂ B ₂ O ₇ can be represented by the composition formula Bi _x Zn _y Nb _z O _{1.75 + δ} . That is, the above composite oxide is represented by the composition formula Bi _x Zn _y Nb _z O _{1.75 + δ} . In this composition formula, "x", "y" and "z" are x + y + z = 1.00.

Further, in the composite oxide, the amount of oxygen (O) may be a stoichiometric ratio or may be slightly deviated from the stoichiometric ratio. The amount of deviation from the stoichiometric ratio varies depending on the type of element to be substituted and the amount of substitution thereof, and is represented by "δ" in the above composition formula.

Therefore, "x" indicates the content ratio of Bi among the metal elements in the composition formula of the above composite oxide, and "y" is the content of Zn among the metal elements in the composition formula of the above composite oxide. The ratio is shown, and "z" indicates the content ratio of Nb among the metal elements in the composition formula of the above composite oxide.

In the above general formula, Bi occupies the A site and Nb occupies the B site. On the other hand, Zn can occupy both A site and B site in the above general formula. Therefore, in the above composite oxide, in addition to the hexahedron in which oxygen is coordinated to Bi and the octahedron in which oxygen is coordinated to Nb, the hexahedron in which oxygen is coordinated to Zn and oxygen is coordinated to Zn. There is a coordinated octahedron.

In the present embodiment, the composite oxide having the above structural characteristics will be described separately as a first composite oxide and a second composite oxide.

(1.2.2. First composite oxide)
In the first composite oxide containing Bi, Zn and Nb, the proportion of the polyhedron in which oxygen is coordinated to Zn affects the stability of the structure. In the present embodiment, "y" indicating the Zn content ratio is 0.20 or more and 0.50 or less. Further, "y" is preferably 0.30 or more.

By setting "y" to the above range, the proportions of the hexahedron in which oxygen is coordinated to Zn by 8 and the octahedron in which oxygen is coordinated to Zn by 6 are increased in the first composite oxide, and the crystal structure The variation of the polyhedral structure in the above is suppressed, and the structural change due to the temperature change is less likely to occur. As a result, even if the temperature changes, the capacitance tends to be kept constant, so that the absolute value (| Tcc |) of the capacitance temperature coefficient Tcc can be set within a predetermined range.

If "y" is too small, the proportion of the hexahedron in which oxygen is 8-coordinated to Bi and the octahedron in which oxygen is 6-coordinated to Nb increases in the first composite oxide, and the variation in the polyhedral structure becomes large. Since the structure tends to change easily, the capacitance temperature coefficient Tcc tends to deteriorate. On the other hand, if "y" is too large, it tends to deviate from the range of the appropriate relative permittivity εr specified in the present embodiment.

In the first composite oxide, the Bi content ratio (“x”) is less than 0.20. Further, "x / z" indicating the content ratio ("x") of Bi with respect to the content ratio ("z") of Nb is 0.25 or more. By setting "x" and "x / z" within the above ranges, structural disorder (disorder) occurs at the B site within an appropriate range, so that a good quality coefficient Q value can be obtained.

Further, by setting "x" within the above range, the ratio of Nb in the first composite oxide becomes higher than the ratio of Bi. The difference in electronegativity between oxygen and Nb is greater than the difference in electronegativity between oxygen and Bi. Therefore, in the first composite oxide, the ionic bond between the metal element and oxygen is strengthened, so that oxygen defects are less likely to occur and the accelerated life at high temperature is improved.

In the first composite oxide, by setting "x", "y" and "z" within the above ranges, the quality coefficient Q value, the capacitance temperature coefficient Tcc, and the high temperature acceleration life are improved. Can be done. Further, it becomes easy to keep the relative permittivity εr within a predetermined range.

(1.2.3. Second composite oxide)
In the second composite oxide containing Bi, Zn and Nb, the ratio of the polyhedron in which oxygen is coordinated to Zn affects the stability of the structure. In the present embodiment, "y" indicating the Zn content ratio is 0.20 or more and 0.50 or less. Further, "y" is preferably 0.30 or more.

If "y" is too small, the proportion of the hexahedron in which oxygen is 8-coordinated to Bi and the octahedron in which oxygen is 6-coordinated to Nb increases in the second composite oxide, and the variation in the polyhedral structure becomes large. Since the structure tends to change easily, the capacitance temperature coefficient Tcc tends to deteriorate. On the other hand, if "y" is too large, the proportion of the polyhedron in which oxygen is coordinated to Zn becomes too large, and the component contributing to the relative permittivity in the second composite oxide decreases, so that the relative permittivity εr deteriorates. Tend to do.

In the second composite oxide, "x / z" indicating the Bi content ratio ("x") with respect to the Nb content ratio ("z") is larger than 1.50 and 3.00 or less. By setting "x" and "x / z" within the above range, the atomic arrangement disorder (disorder) occurs at the A site of the second composite oxide within an appropriate range, so that the quality coefficient Q value The relative permittivity εr can be made good due to this disorder while maintaining good.

Further, in the second composite oxide, the content ratio of Nb (“z”) is less than 0.25. If "z" is too large, the quality coefficient Q value tends to deteriorate. "Z" is preferably 0.15 or more.

Further, by setting "z" to the above range, the ratio of Bi in the second composite oxide becomes higher than the ratio of Nb, and the ratio of the hexahedron in which oxygen is coordinated to Bi becomes large. As a result, oxygen defects are less likely to occur, and the accelerated life at high temperatures is improved.

By setting "x", "y" and "z" in the above range in the second composite oxide, the relative permittivity εr, the quality coefficient Q value, the capacitance temperature coefficient Tcc, and the high temperature accelerated life And can be good.

The above-mentioned first dielectric composition has a first composite oxide as a main component, and the above-mentioned second dielectric composition has a second composite oxide as a main component. Further, the dielectric composition according to the present embodiment (the first dielectric composition and the second dielectric composition) contains a trace amount of impurities, subcomponents, etc. within the range in which the effect of the present invention is exhibited. You may. Examples of such a component include Mn, Ca, and Ba.

(1.3. Substrate)
The substrate 1 shown in FIG. 1 is not particularly limited as long as it is made of a material having mechanical strength sufficient to support the base layer 2, the lower electrode 3, the dielectric film 5, and the upper electrode 4 formed on the substrate 1. .. For example, from Si single crystal, SiGe single crystal, GaAs single crystal, InP single crystal, SrTIO ₃ single crystal, MgO single crystal, LaAlO ₃ single crystal, ZrO ₂ single crystal, MgAl ₂ O ₄ single crystal, NdGaO ₃ single crystal, etc. Single crystal substrate composed; Ceramic polycrystal substrate composed of Al ₂ O ₃ polycrystal, ZnO polycrystal, SiO ₂ polycrystal, etc .; Metals such as Ni, Cu, Ti, W, Mo, Al, Pt, etc. A metal substrate or the like made of an alloy of In the present embodiment, a Si single crystal is used as a substrate from the viewpoint of low cost, workability, and the like.

The thickness of the substrate 1 is set to, for example, 10 μm to 5000 μm. If the thickness is too small, mechanical strength may not be ensured, and if the thickness is too large, there may be a problem that it cannot contribute to the miniaturization of electronic components.

The resistivity of the above-mentioned substrate 1 differs depending on the material of the substrate. When the substrate is made of a material having a low resistivity, a current leak to the substrate side when the thin film capacitor is operated, which may affect the electrical characteristics of the thin film capacitor. Therefore, when the resistivity of the substrate 1 is low, it is preferable to insulate the surface thereof so that the current when the capacitor operates does not flow to the substrate 1.

For example, when a Si single crystal is used as the substrate 1, it is preferable that an insulating layer is formed on the surface of the substrate 1. As long as sufficient insulation between the substrate 1 and the capacitor portion is ensured, the material constituting the insulating layer and its thickness are not particularly limited. In this embodiment, SiO ₂ , Al ₂ O ₃ , Si _{3 Nx and the} like are exemplified as the material constituting the insulating layer. The thickness of the insulating layer is preferably 0.01 μm or more.

(1.4. Lower electrode)
As shown in FIG. 1, the lower electrode 3 is formed in a thin film on the substrate 1 via the base layer 2. The lower electrode 3 is an electrode for sandwiching the dielectric film 5 together with the upper electrode 4 described later and functioning as a capacitor. The material constituting the lower electrode 3 is not particularly limited as long as it is a conductive material. For example, metals such as Pt, Ru, Rh, Pd, Ir, Au, Ag, Cu, alloys thereof, or conductive oxides are exemplified.

The thickness of the lower electrode 3 is not particularly limited as long as it functions as an electrode. In the present embodiment, the thickness is preferably 0.01 μm or more.

(1.5. Upper electrode)
As shown in FIG. 1, the upper electrode 4 is formed in a thin film on the surface of the dielectric film 5. The upper electrode 4 is an electrode that sandwiches the dielectric film 5 together with the lower electrode 3 described above and functions as a capacitor. Therefore, the upper electrode 4 has a polarity different from that of the lower electrode 3.

The material constituting the upper electrode 4 is not particularly limited as long as it is a conductive material like the lower electrode 3. For example, metals such as Pt, Ru, Rh, Pd, Ir, Au, Ag, Cu, alloys thereof, conductive oxides and the like are exemplified.

(2. Manufacturing method of thin film capacitor)
Next, an example of a method for manufacturing the thin film capacitor 10 shown in FIG. 1 will be described below.

First, the substrate 1 is prepared. When, for example, a Si single crystal substrate is used as the substrate 1, an insulating layer is formed on one main surface of the substrate. As a method for forming the insulating layer, a known film forming method such as a thermal oxidation method or a CVD (Chemical Vapor Deposition) method may be used.

Subsequently, a thin film of the material constituting the base layer is formed on the formed insulating layer by using a known film forming method to form the base layer 2.

After the base layer 2 is formed, a thin film of the material constituting the lower electrode is formed on the base layer 2 by using a known film forming method to form the lower electrode 3.

Subsequently, the dielectric film 5 is formed on the lower electrode 3. In the present embodiment, the dielectric film 5 is formed as a deposited film by depositing the material constituting the dielectric film 5 on the lower electrode 3 in the form of a thin film by a known film forming method.

Known film forming methods include, for example, vacuum vapor deposition method, sputtering method, PLD (pulse laser vapor deposition method), MO-CVD (organic metal chemical vapor phase growth method), MOD (organic metal decomposition method), sol-gel method, and CSD. (Chemical solution deposition method) and the like are exemplified. The raw materials used for film formation (deposited materials, various target materials, organic metal materials, etc.) may contain trace amounts of impurities, auxiliary components, etc., but especially if desired dielectric properties can be obtained. No problem.

For example, when the PLD method is used, a dielectric thin film 5 is formed on the lower electrode 3 using a target having a desired composition. In the present embodiment, the film forming conditions are preferably as follows. The oxygen pressure is preferably 0.1 to 10 Pa. Further, the film formation is preferably performed at room temperature. The power of the laser is preferably ³ to 5 J / cm ² , and the pulse frequency is preferably 1 to 20 Hz.

In the present embodiment, after the dielectric film is formed, the dielectric film is subjected to Rapid Thermal Anneal (RTA). In the present embodiment, as a condition for applying RTA, the atmosphere is preferably an oxygen atmosphere, the temperature rising rate is preferably 1000 ° C./min or more, and the annealing time is preferably 1 to 30 minutes. The temperature is preferably 300 ° C. or higher and 750 ° C. or lower.

Next, a thin film of the material constituting the upper electrode is formed on the formed dielectric film 5 by using a known film forming method to form the upper electrode 4.

Through the above steps, as shown in FIG. 1, a thin film capacitor 10 having a capacitor portion (lower electrode 3, dielectric film 5 and upper electrode 4) formed on the substrate 1 is obtained. The protective film that protects the dielectric film 5 may be formed by a known film forming method so as to cover at least the portion where the dielectric film 5 is exposed to the outside.

(3. Summary of this embodiment)
In this embodiment, attention is paid to Bi-Zn-Nb-O-based oxides. The Bi-Zn-Nb-O-based oxide is a composite oxide represented by the general formula A ₂ B ₂ O ₇ . In this composite oxide, Zn can occupy both A and B sites, forming two types of polyhedra. The present inventors have found that by increasing the ratio of these two types of polyhedra, the structure of the Bi-Zn-Nb-O-based oxide is stabilized, and structural changes due to temperature changes are less likely to occur. Therefore, in the present embodiment, the capacitance temperature coefficient Tcc is improved by setting the content ratio of Zn in the Bi-Zn-Nb-O-based oxide within the above range.

Further, the present inventors control the Bi-Zn-Nb-O-based oxide by controlling the Bi content ratio occupying the A site and the Bi content ratio with respect to the Nb content ratio occupying the B site. It was also found that the defects in the above were reduced, and as a result, the quality coefficient Q value and the high temperature acceleration life were improved. Therefore, in the present embodiment, a high quality coefficient Q value and a good high temperature acceleration life are obtained by setting the above ratio within the above range.

Specifically, the above-mentioned first dielectric composition exhibits a high quality coefficient Q value of 1000 or more even in a high frequency region of 2 GHz or more, and has an absolute value of the capacitance temperature coefficient Tcc of 50 ppm / ° C. or less. The insulation resistance (IR) life at 180 ° C. can be set to 15.0 h or more.

Further, the present inventors control the content ratio of Nb occupying the B site and the content ratio of Bi occupying the A site with respect to the content ratio of Nb to obtain the quality coefficient Q value and the relative permittivity εr. It was also found that the high temperature acceleration life is improved. Therefore, in the present embodiment, by setting the above ratio within the above range, a high relative permittivity εr, a high quality coefficient Q value, and a good high temperature acceleration life are obtained.

Specifically, the above-mentioned second dielectric composition exhibits a high relative permittivity εr of 100 or more and a high quality coefficient Q value of 1000 or more even in a high frequency region of 2 GHz or more. The absolute value of the capacitance temperature coefficient Tcc can be 50 ppm / ° C. or less, and the insulation resistance (IR) life at 180 ° C. can be 15.0 h or more.

(4. Modification example)
In the above-described embodiment, the case where the dielectric film is composed of only the dielectric composition according to the present embodiment has been described, but the dielectric film is different from the dielectric film composed of the dielectric composition according to the present embodiment. It may be an electronic component having a laminated structure in which a film composed of a body composition is combined. For example, the impedance and ratio of the dielectric film 5 can be increased by forming a laminated structure with an existing amorphous dielectric film such as Si ₃ N _x , SiO _x , Al ₂ O _x , ZrO _x , Ta ₂ O _x, or a crystal film. It is possible to adjust the temperature change of the dielectric constant.

Further, it may be a multilayer capacitor having a plurality of dielectric films composed of the dielectric composition according to the present embodiment.

In the above-described embodiment, the base layer is formed in order to improve the adhesion between the substrate and the lower electrode, but the base layer is omitted when the adhesion between the substrate and the lower electrode can be sufficiently secured. be able to. Further, when a metal such as Cu or Pt that can be used as an electrode, an alloy thereof, an oxide conductive material, or the like is used as the material constituting the substrate, the base layer and the lower electrode can be omitted.

Further, in the above-described embodiment, the dielectric layer is a dielectric deposition film formed by a known film forming method, but the dielectric layer is used to fire a molded product obtained by molding the raw material powder of the dielectric composition. It may be composed of the obtained sintered body.

The electronic component having a dielectric layer composed of such a sintered body may be a single-layer capacitor in which the dielectric layer is a single layer, or a laminated capacitor in which a plurality of dielectric layers are laminated.

The single-layer capacitor has a configuration in which electrodes are formed on the facing surfaces of the dielectric composition. Further, the laminated capacitor has a laminated body having a structure in which a plurality of dielectric layers composed of a dielectric composition and internal electrode layers are alternately laminated. A pair of terminal electrodes conducting with the internal electrode layer are formed at both ends of the laminated body.

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

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

(Experimental Example 1)
First, the target required for forming the dielectric film was prepared as follows.

As raw material powders for target preparation, powders of Bi ₂ O ₃ , ZnO, and Nb ₂ O ₅ were prepared. These powders were weighed to the final composition of the samples of Examples 1-9 and Comparative Examples 1-6 shown in Table 1. The weighed raw material powder, water, and ZrO ₂ beads having a diameter of ₂ mm were placed in a polypropylene wide-mouthed pot having a volume of 1 L and wet-mixed for 20 hours. Then, the mixed powder slurry was dried at 100 ° C. for 20 hours, the obtained mixed powder was placed in an Al ₂ O ₃ crucible, and calcined under the firing conditions of holding at 800 ° C. in the air for 5 hours to obtain a calcined powder. It was.

The obtained calcined powder is placed in a mortar, and a PVA (polyvinyl alcohol) aqueous solution having a concentration of 6 wt% is added as a binder so as to be 4 wt% with respect to the calcined powder, and a granulated powder is prepared using a pestle. did. The produced granulated powder was put into a mold having a diameter of 20 mm so as to have a thickness of about 5 mm, and pressure molding was performed using a uniaxial pressure press to obtain a molded product. The molding conditions, 2.0 × ¹⁰ 8 Pa pressure, the temperature was room temperature.

Then, the obtained molded product was subjected to a binder removal treatment in a normal pressure atmosphere with a temperature rising rate of 100 ° C./hour, a holding temperature of 400 ° C., and a temperature holding time of 4 hours. Subsequently, the temperature rising rate was 200 ° C./hour, the holding temperature was 1000 ° C. to 1200 ° C., and the temperature holding time was 12 hours, and firing was performed in the atmosphere at normal pressure to obtain a sintered body.

Both sides were polished with a cylindrical grinder so that the thickness of the obtained sintered body was 4 mm, and a target for forming a dielectric film was obtained.

Subsequently, a 10 mm × 10 mm square substrate provided with SiO ₂ as a 0.5 μm-thick insulating layer on the surface of a 350 μm-thick Si single crystal substrate was prepared. A Ti thin film as a base layer was formed on the surface of this substrate by a sputtering method so as to have a thickness of 20 nm.

Next, a Pt thin film as a lower electrode was formed on the Ti thin film formed above by a sputtering method so as to have a thickness of 4 μm.

A dielectric film was formed on the above Ti / Pt thin film. In this example, using the target prepared above, a dielectric film was formed on the lower electrode by the PLD method so as to have a thickness of 400 nm. The film forming conditions by the PLD method were an oxygen pressure of 1 Pa, a laser power of 3 J / cm ² , a laser pulse frequency of 10 Hz, and a film forming temperature of room temperature. Further, in order to expose a part of the lower electrode, a metal mask was used to form a region where the dielectric film was not formed. After forming the dielectric film, the dielectric film was subjected to a rapid thermal anneal treatment (RTA) in which the temperature rising rate was 1000 ° C./min and the temperature was maintained at 550 ° C. for 1 minute in an oxygen atmosphere.

Next, an Ag thin film, which is an upper electrode, was formed on the obtained dielectric film using a thin-film deposition apparatus. By forming the shape of the upper electrode so as to have a diameter of 100 μm and a thickness of 100 nm using a metal mask, a sample of a thin film capacitor having the configuration shown in FIG. 1 (Examples 1 to 9 and Comparative Examples 1 to 6). ) Was obtained.

The composition of the dielectric film is shown in Table 1 after analyzing all the samples at room temperature using a WD-XRF (wavelength dispersive fluorescent X-ray element analysis) device (ZSX-100e manufactured by Rigaku Corporation). It was confirmed that the composition was consistent with that of. The thickness of the dielectric film was measured by excavating a thin film capacitor with a FIB and observing the obtained cross section with a SEM (scanning electron microscope).

For all the obtained thin film capacitor samples, the relative permittivity εr, the Q value, the temperature coefficient Tcc of the capacitance, and the high temperature accelerated life were measured by the methods shown below.

(Q value and relative permittivity)
The Q value and relative permittivity are the conditions for a thin film capacitor sample at a reference temperature of 25 ° C., an RF impedance / material analyzer (4991A manufactured by Agent), a frequency of 2 GHz, and an input signal level (measured voltage) of 0.5 Vrms. It was calculated from the capacitance measured below and the thickness of the dielectric film obtained above. In this example, a higher Q value is preferable, and a sample having a Q value of 1000 or more is judged to be good. Further, in this example, a sample having a relative permittivity of 50 or more and less than 80 was judged to be good. The results are shown in Table 1.

(Temperature coefficient of capacitance (Tcc))
The temperature coefficient of the capacitance is the same as above, except that the capacitance is measured by changing the measurement temperature from -55 ° C to 125 ° C every 25 ° C using a constant temperature bath. Then, it was calculated as the rate of change with respect to the capacitance at the reference temperature of 25 ° C. (unit: ppm / ° C.). Further, it is preferable that the temperature coefficient of the capacitance is small, and a sample having an absolute value (| Tcc |) of the temperature coefficient of the capacitance within 50 ppm / ° C. is judged to be good. The results are shown in Table 1.

(High temperature acceleration life)
The insulation resistance life was measured as the high temperature acceleration life. At 180 ° C., a DC voltage of 16 V / μm was applied to the dielectric film obtained above, and the change over time in the insulation resistance from before the application of the DC voltage was measured. Insulation resistance of the dielectric film and the life time until the following 10 ⁵ Omega, the lifetime for 20 samples was measured and the average value thereof insulation resistance (IR) life. A long IR life is preferable, and a sample having an IR life of 15.0 h or more is judged to be good. The results are shown in Table 1.

From Table 1, in the composite oxide containing Bi, Zn and Nb, the sample in which the relationship of “x”, “y” and “z” is within the above-mentioned range has a high quality coefficient Q in the high frequency region (2 GHz). Confirmed that it has a value (1000 or more), good temperature characteristics (| Tcc | ≤50 ppm / ° C), and good IR life (15.0 h or more), and the relative permittivity εr is within a predetermined range. did it.

(Experimental Example 2)
In the composite oxide containing Bi, Zn and Nb, a dielectric film was formed by the same method as in Experimental Example 1 except that the values of "x", "y" and "z" were set to the values shown in Table 2. , Samples of thin film capacitors (Examples 11-19 and Comparative Examples 11-16) were obtained. The same evaluation as in Experimental Example 1 was performed on the obtained thin film capacitor sample. The results are shown in Table 2. In the evaluation of the relative permittivity, a sample having a relative permittivity of 100 or more was judged to be good.

From Table 2, in the composite oxide containing Bi, Zn and Nb, the sample in which the relationship of “x”, “y” and “z” is within the above-mentioned range has a high relative permittivity in the high frequency region (2 GHz). Confirmed to have εr (100 or more), high quality coefficient Q value (1000 or more), good temperature characteristics (| Tcc | ≤50 ppm / ° C), and good IR life (15.0 h or more). did it.

According to the present invention, it is possible to obtain a dielectric composition having a high Q value in a high frequency region, a small capacitance temperature coefficient in a predetermined temperature range, and a good high temperature acceleration life. Such a dielectric composition is suitable as a thin-film dielectric film, and is suitable for high-frequency electronic components such as baluns, couplers, filters, duplexers and diplexers in which filters are combined.

10 ... Thin film capacitor 1 ... Substrate 2 ... Underlayer 3 ... Lower electrode 4 ... Upper electrode 5 ... Dielectric film

Claims (3)

A dielectric composition having a composite oxide containing bismuth, zinc and niobium.
When the composite oxide is represented by the composition formula Bi _x Zn _y Nb _z O _{1.75 + δ} , the x, y and z are x + y + z = 1.00, x <0.20, 0.20 ≦ y ≦ 0. A dielectric composition that satisfies the relationship of .50, 0.25 ≦ x / z. A dielectric composition having a composite oxide containing bismuth, zinc and niobium.
When the composite oxide is represented by the composition formula Bi _x Zn _y Nb _z O _{1.75 + δ} , the x, y and z are x + y + z = 1.00, 0.20 ≦ y ≦ 0.50, 1.5. A dielectric composition that satisfies the relationship <x / z ≦ 3.0 and z <0.25. An electronic component comprising a dielectric layer comprising the dielectric composition according to claim 1 or 2.

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