JP7226747B2 - Dielectric film, capacitor using the same, and method for manufacturing dielectric film - Google Patents

Description

The present invention relates to a dielectric film, a capacitor using the same, and a method for manufacturing such a dielectric film.

Conventionally, single crystals having a composition represented by the general formula A ₂ B ₂ O ₇ (for example, Sr ₂ Ta ₂ O ₇ , Sr ₂ Nb ₂ O _{7 ,} etc.) grown by the floating zone method (this is distinguished from thin films) (also called "bulk single crystal") has been reported to exhibit dielectric properties (see Non-Patent Document 1). Related to this report, there is also a report that the crystal structure of Sr ₂ Ta ₂ O ₇ obtained by the floating zone method is a perovskite slab structure, similar to the crystal structure of Sr ₂ Nb ₂ O ₇ (non-patent Reference 2).

Furthermore, a dielectric film having a pyrochlore-type crystal structure and a composition represented by the general formula A ₂ B ₂ O ₇ (for example, Sr ₂ Ta ₂ O ₇ etc.) was disposed between the two electrodes. A capacitor (thin film capacitor) is known (see Patent Document 1). Patent Document 1 describes that when a dielectric film made of Sr ₂ Ta ₂ O ₇ , which is a pyrochlore compound, was formed by the CVD method at a substrate temperature of 400° C., it exhibited a dielectric constant of 600.

Also, a layered perovskite material having a composition represented by (Sr ₂ Ta ₂ O ₇ ) _100−x (La ₂ Ti ₂ O ₇ ) _x (where 0≦x≦5), wherein the corresponding metal oxide A pellet (12 or 18 mm in diameter, 0.5 mm in thickness) produced by a two-step solid-phase reaction using a raw material powder is also known (see Non-Patent Document 3). It has been reported that the dielectric constant of this material changes greatly in the temperature range of 20 to 300° C. (see FIG. 7 of Non-Patent Document 3).

JP-A-10-178153

S. Nanamatsu, et al., "Crystallographic and Dielectric Properties of Ferroelectric A2B2O7 (A=Sr, B=Ta, Nb) Crystals and Their Solid Solutions", Journal of the Physical Society of Japan, 1975, Vol. 38, pp. 817-824 N. Ishizawa, et al., "Compounds with Perovskite-Type Slabs. II. The Crystal Structure of Sr2Ta207", Acta Crystallographica, 1976, Section B Vol. 32, pp.2564-2566 F. Marlec, et al., "Ferroelectricity and high tunability in novel strontium and tantalum based layered perovskite materials", Journal of the European Ceramic Society, 2018, Vol. 38, pp. 2526-2533

Capacitors used in electronic parts and the like exhibit stable electrical characteristics over a wide temperature range, for example, from room temperature or room temperature of about 20°C to relatively high temperatures of about 150°C, preferably to high temperatures of about 300°C. Above all, it is desirable to stably maintain a high dielectric constant over such a temperature range. However, research by the present inventors has revealed that the above-described conventional capacitors and materials cannot stably maintain a high dielectric constant over such a temperature range.

The present invention provides a dielectric film that can stably maintain a high dielectric constant over a wide temperature range (eg, 20 to 150° C.), a capacitor using the dielectric film, and a method for producing such a dielectric film. for the purpose.

The present inventors obtained a unique idea of controlling the orientation plane of a dielectric film having a composition represented by the general formula A ₂ B ₂ O ₇ . Arrived.

According to one aspect of the present invention, a dielectric film having a pyrochlore-type or layered perovskite-type crystal structure,
General formula A ₂ B ₂ O ₇ (wherein A is Mg, Ca, Sr, Ba, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, each one of which includes A ¹ and A ² different from each other, and B is selected from Ti, Zr, Hf, V, Nb and Ta one or more elements selected from the group consisting of ^B1 as one element),
Of all the combinations of A ₂ B ₂ O ₇ stoichiometrically obtained by selecting one element each from A and B present in the dielectric film, the main constituent of the crystal structure of the dielectric film for A ¹ ₂ B ¹ ₂ O ₇ forming A dielectric film is provided having at least one oriented plane.

According to another aspect of the present invention, there is provided a capacitor comprising an electrode and the above dielectric film of the present invention disposed over the electrode.

According to yet another aspect of the present invention, there is provided a method for producing a dielectric film having a pyrochlore or layered perovskite crystal structure, comprising:
(a) A compound of the general formula A ₂ B ₂ O ₇ (wherein A is Mg, Ca, Sr, Ba, La, Ce, Pr, Nd, Pm , Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, two or more elements A ¹ and A ² different from each other as one element among them and B is one or more elements selected from the group consisting of Ti, Zr, Hf, V, Nb and Ta, one of which includes B ¹ ). (b) heat-treating the substrate on which the precursor film is formed at a temperature of 850 to 1050° C. in an atmosphere containing oxygen to obtain the precursor film provides a manufacturing method comprising obtaining a dielectric film having a pyrochlore-type or layered perovskite-type crystal structure and having the aforementioned composition.

According to the present invention, in a dielectric film having a pyrochlore-type or layered perovskite-type crystal structure, at least two A-site elements having a composition represented by the general formula A ₂ B ₂ O ₇ are present, and With respect to A ¹ ₂ B ¹ ₂ O ₇ which forms the main part of the crystal structure of the dielectric film, the (h00), (0k0), (00l), (h0l) and (0kl) planes (h, k and l are 0 is an integer except ), by having at least one orientation plane, a dielectric film that can stably maintain a high dielectric constant over a wide temperature range (for example, 20 to 150 ° C.) is provided. be. Furthermore, according to the present invention, a capacitor using such a dielectric film and a method for manufacturing such a dielectric film are also provided.

1 is a schematic cross-sectional view showing one exemplary aspect of a capacitor in one embodiment of the invention; FIG. 2 shows a two-dimensional X-ray diffraction image of the dielectric film of Example 1. FIG. (a) schematically shows the integration direction (χ direction) when converting the two-dimensional X-ray diffraction image of the dielectric film of Example 1 into an X-ray diffraction pattern (one-dimensional profile); , shows the resulting X-ray diffraction pattern (one-dimensional profile). 4 shows measurement data of the X-ray diffraction pattern (one-dimensional profile) of the dielectric film of Example 1 and data obtained by fitting the same with a Gaussian function. (a) schematically shows the direction of integration (2θ direction) when the two-dimensional X-ray diffraction image of the dielectric film of Example 1 is converted into a one-dimensional profile with respect to the spot on the orientation surface; 1 shows measurement data of a one-dimensional profile of spots on the orientation surface of the dielectric film of Example 1 and data obtained by fitting the same with a Gaussian function. 4 is a graph showing evaluation of electrical properties of the dielectric film of Example 1. FIG. 2 shows a two-dimensional X-ray diffraction image of the dielectric film of Example 2. FIG. 4 is a graph showing evaluation of electrical properties of the dielectric film of Example 2. FIG. 2 shows a two-dimensional X-ray diffraction image of the dielectric film of Comparative Example 1. FIG. 2 shows a two-dimensional X-ray diffraction image of the dielectric film of Comparative Example 2. FIG. 2 shows a two-dimensional X-ray diffraction image of the dielectric film of Comparative Example 3. FIG. 5 is a graph showing evaluation of electrical properties at room temperature of dielectric films in Comparative Examples 1 to 3 and their modified examples. (a) shows the two-dimensional X-ray diffraction image of the dielectric film of Comparative Example 4, and (b) shows the X-ray diffraction patterns of Comparative Example 4 (shown at "900° C.") and its modification (1 dimensional profile). 10 is a graph showing the evaluation of the electrical properties of the dielectric film of Comparative Example 4. FIG. (a) shows the two-dimensional X-ray diffraction image of the dielectric film of Comparative Example 5, and (b) shows the X-ray diffraction patterns of Comparative Example 5 (shown at “900° C.”) and its modification (1 dimensional profile). 10 is a graph showing evaluation of electrical properties of the dielectric film of Comparative Example 5. FIG. (a) shows the two-dimensional X-ray diffraction image of the dielectric film of Comparative Example 6, and (b) shows the X-ray diffraction patterns of Comparative Example 6 (shown at "900° C.") and its modification (1 dimensional profile). (a) shows the two-dimensional X-ray diffraction image of the dielectric film of Comparative Example 7, and (b) shows the X-ray diffraction patterns of Comparative Example 7 (shown at "900° C.") and its modification (1 dimensional profile). 10 shows an X-ray diffraction pattern (one-dimensional profile) of the dielectric film of Comparative Example 8. FIG. 10 shows an X-ray diffraction pattern (one-dimensional profile) of the dielectric film of Comparative Example 9. FIG.

(Embodiment 1: Dielectric film and its manufacturing method)
According to one embodiment of the present invention, a dielectric film and method of making the same are provided.

The dielectric film of this embodiment is
having a pyrochlore-type or layered perovskite-type crystal structure,
General formula A ₂ B ₂ O ₇ (wherein A is Mg, Ca, Sr, Ba, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, each one of which includes A ¹ and A ² different from each other, and B is selected from Ti, Zr, Hf, V, Nb and Ta one or more elements selected from the group consisting of ^B1 as one element),
Of all the combinations of A ₂ B ₂ O ₇ stoichiometrically obtained by selecting one element each from A and B present in the dielectric film, the main constituent of the crystal structure of the dielectric film for A ¹ ₂ B ¹ ₂ O ₇ forming It has at least one orientation plane.

The crystal structure of an oxide having a composition represented by the general formula A ₂ B ₂ O ₇ can usually be a pyrochlore type or a layered perovskite type (also called a perovskite slab) (these polymorphs can be including cases). However, the crystal structure of the oxide may vary depending on its specific composition, manufacturing method, etc., and may also change depending on conditions such as temperature and pressure to which the oxide is exposed (for example, phase changes and/or transitions between polymorphs). Therefore, in the present invention, the "pyrochlore-type or layered perovskite-type crystal structure" means either one or both of these crystal structures, and should not be construed as being limited to either one.

The dielectric film of this embodiment has a composition represented by the general formula A ₂ B ₂ O ₇ . A and B are symbols that denote (or collectively) elements that occupy the A and B sites, respectively, in a pyrochlore-type or layered perovskite-type crystal structure.

A is two or more selected from the group consisting of Mg, Ca, Sr, Ba, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu contains the elements of Preferably, A contains two or more elements selected from the group consisting of Sr, Ba, La and Nd. There are two or more specific elements corresponding to A, and these are denoted as A ¹ and A ² (which are different from each other).

B contains one or more elements selected from the group consisting of Ti, Zr, Hf, V, Nb and Ta. Preferably B contains one or more elements selected from the group consisting of Ti, Nb and Ta. There is one or more specific elements that correspond to B, and this is represented as ^B1 ( ^B2 , which will be described later, is also a specific element that corresponds to B, but ^B2 is the same as ^B1 . may or may not be the same).

A ₂ B ₂ O ₇ is stoichiometrically defined, for example, when A is a trivalent element and B is a tetravalent element (that is, A(III) ₂ B(IV) ₂ O ₇ type), where A is a divalent element and B is a pentavalent element (that is, A(II) ₂ B(V) ₂ O ₇ type), and a case where these are mixed.

Among all combinations of A ₂ B ₂ O ₇ stoichiometrically obtained (or conceivable) by selecting each one of A and B elements present in the dielectric film, The A ¹ ₂ B ¹ ₂ O ₇ that forms the main part of the crystal structure is identified, thereby specifically determining each element of A ¹ and B ¹ . That is, in the dielectric film of the present embodiment, it can be understood that A ¹ ₂ B ¹ ₂ O ₇ constitutes the main part of the crystal structure, and A ² and other elements that may be present are dissolved therein. .

In the present invention, A ¹ ₂ B ¹ ₂ O ₇ “mainly forms the crystal structure” of the dielectric film means that A ¹ ₂ B ¹ ₂ O ₇ mainly bears the crystal structure of the dielectric film. means. Of all the combinations of A ₂ B ₂ O ₇ , which one is the A ¹ ₂ B ¹ ₂ O ₇ that “dominates the crystal structure” can be determined based on the X-ray diffraction pattern obtained from the dielectric film. It is determined as the crystal structure that is closest to the crystal structure of the dielectric film.

For example, in the case of a dielectric film in which A ₂ B ₂ O ₇ is (Sr _x La _1-x ) ₂ (T _x Ti _1-x ) ₂ O ₇ (where 0<x<1), A All combinations stoichiometrically obtained by selecting one each from Sr and La corresponding to B and Ta and Ti corresponding to B are Sr ₂ Ta ₂ O ₇ and La ₂ Ti ₂ O ₇ ( Note that these elements (valences) are Sr(II), La(III), Ta(V), Ti(IV)). Which one of these Sr ₂ Ta ₂ O ₇ and La ₂ Ti ₂ O ₇ “forms the main part of the crystal structure” depends on the X-ray diffraction pattern obtained from the dielectric film and the Sr ₂ Ta ₂ O ₇ and La ₂ By comparing the known powder X-ray diffraction data for each of the Ti ₂ O ₇ , the one corresponding to the powder X-ray diffraction data closest to the X-ray diffraction pattern of the dielectric film (e.g. Sr ₂ Ta ₂ O ₇ ) is identified. , as A ¹ ₂ B ¹ ₂ O ₇ (eg, A ¹ is Sr and B ¹ is Ta), which forms the main body of the crystal structure.

Known powder X-ray diffraction data can be obtained from a database provided by, for example, ICDD (International Center for Diffraction Data) and used. The X-ray diffraction pattern of the dielectric film is obtained by converting a two-dimensional X-ray diffraction image obtained using a two-dimensional detector into a one-dimensional profile (a region with a detection angle χ = 38° is circularly integrated in the χ direction. ) may be used, and for identification, a substance other than the dielectric film (for example, a substance underlying the dielectric film; ) should be ignored, and it is preferable to consider the orientation plane, which will be described later. These descriptions apply similarly to the following description unless otherwise specified.

In the present invention, the "orientation plane" of the dielectric film means a plane parallel to the surface of the dielectric film and having high orientation or crystallinity. It is a plane observed in the form of a spot in an image, and its plane index (Miller index) is determined with respect to A ¹ ₂ B ¹ ₂ O ₇ which constitutes the main constituent of the crystal structure. _The dielectric film _of the present embodiment may have ^one _or more such ^orientation planes. It has at least one orientation plane other than the (0k0), (00l), (h0l) and (0kl) planes (where h, k and l are integers other than 0).

For example, when A ¹ ₂ B ¹ ₂ O ₇ that forms the main part of the crystal structure is Sr ₂ Ta ₂ O ₇ , one or two or more observed in the two-dimensional X-ray diffraction image of the dielectric film Measure the diffraction angle (2θ) of a good spot and in which plane in the known powder X-ray diffraction data for Sr ₂ Ta ₂ O ₇ where the diffraction angle (2θ) of the spot is A ¹ ₂ B ¹ ₂ O ₇ By checking for a match, the plane index of one or more orientation planes observed as the spot is determined. ( _h00 ) ^, (0k0) _, ( _00l ) _, ( _h0l ⁾ _and Any surface other than the (0kl) plane (h, k, and l are integers other than 0) is acceptable. The diffraction angle (2θ) of the spot uses a one-dimensional profile obtained by converting a two-dimensional X-ray diffraction image (it is preferable to convert the area with a detection angle χ = 38° by performing arc integration in the χ direction). may be measured based on the peak corresponding to the spot.

The dielectric film ^of this embodiment _has ^planes ₍ h _, k and l are integers excluding 0), and have at least one orientation plane. This means that the b-axis direction of the crystal forming the dielectric film is not perpendicular to the surface of the dielectric film, but is inclined.

Since the dielectric film of the present embodiment has the orientation surface as described above, it stably maintains a high dielectric constant over a wide temperature range (for example, 20 to 150° C., preferably 20 to 300° C.). That is, it becomes possible to maintain a small rate of change. Although the present invention is not bound by any theory, the reason may be as follows. A dielectric film having a pyrochlore-type or layered perovskite-type crystal structure has a temperature range of 20 to 150° C., more broadly a temperature range of 20 to 300° C., in each of the a-axis direction, the b-axis direction, and the c-axis direction. The magnitude and temperature dependence of the relative permittivity are different. More specifically, although it depends on the composition of the dielectric film, in this temperature range, the dielectric constants in the a-axis direction and the c-axis direction are higher than the dielectric constant in the b-axis direction, and tend to increase slightly and stably. However, the Curie temperatures in the a-axis direction and the c-axis direction (the temperatures at which the non-dielectric constant rises sharply and shows a peak) are in high temperature regions that are considerably distant from such temperature ranges. The Curie temperature of is in a low temperature range close to such temperature range. From this, by inclining the b-axis direction of the crystal with respect to the surface of the dielectric film, the relative permittivity of the a-axis direction and the c-axis direction can be can be combined with the stability of It is considered that such a combination effect can be remarkably produced when two or more elements are used in the A site. Therefore, the number of elements in the A site is two or more, A ² and possibly other elements are dissolved in A ¹ ₂ B ¹ ₂ O ₇ that forms the main part of the crystal structure, and the surface of the dielectric film is By inclining the b-axis direction of the crystal with the use of a polarizer, it is possible to obtain a higher and more stable dielectric constant in the temperature range of 20 to 150.degree. C., preferably 20 to 300.degree.

The at least one orientation plane of _the dielectric film of the present embodiment is (h00), ( ^0k0 ), _{( 00l} ), ( ^h0l ) and (0 kl) planes. Such at least one orientation plane is for example (111), (131), (151), (1 15 1), (192), (153), (157), (110), (150), (212) , (172) and (1 13 0), but not limited thereto. In this specification, when h, k and l are all single-digit integers, they are represented according to the notation (hkl), but when at least one of them is an integer of two or more digits, between integers is shown with a space.

Furthermore, the at least one orientation plane of the dielectric film of the present embodiment is a plane (hk0) other than the above-mentioned planes with respect to A ¹ ₂ B ¹ ₂ O ₇ forming the main part of the crystal structure, and the plane (h, k and l are integers other than 0). Thereby, the b-axis direction of the crystal can be tilted more appropriately with respect to the surface of the dielectric film. Such at least one orientation plane is any of, for example, (111), (131), (151), (1 15 1), (192), (153), (157), (212) and (172). It may be one or two or more, but is not limited to this.

The degree of orientation of the at least one orientation plane is preferably 0.5 or more and 1 or less, more preferably 0.8 or more and 1 or less. As a result, the dielectric film can be oriented on this orientation plane at a high rate.

In the present invention, the "degree of orientation" of a given orientation plane is defined by the Lotgering factor f(-). The Lotgering factor f is calculated by the following formula (1) using the intensity of X-rays diffracted from a predetermined orientation plane (denoted as (xyz) for convenience).
f=(pp ₀ )/(1-p ₀ ) (1)
In formula (1), p ₀ is a value based on known powder X-ray diffraction data for A ¹ ₂ B ¹ ₂ O ₇ identified as the main constituent of the crystal structure, and p is the X-ray It is a value based on a diffraction pattern and obtained by the following equations (2) and (3), respectively.
p ₀ =I ₀ (xyz)/ΣI ₀ (hkl) (2)
p=I(xyz)/ΣI(hkl) (3)
In formulas (2) and (3), h, k, and l are integers including zero.
In formula (2), ΣI ₀ (hkl) is the diffraction intensity of the peaks of all planes obtained from known powder X-ray diffraction data for A ¹ ₂ B ¹ ₂ O ₇ (usually, the largest intensity is set to 100 relative intensity), and I ₀ (xyz) is the diffraction intensity (same as above) of the peak in a given orientation plane (xyz) _obtained from known powder X-ray _diffraction data for A ¹² B ¹² O ₇ means value.
In formula (3), ΣI(hkl) means the sum of diffraction intensities of peaks of all planes obtained from the X-ray diffraction pattern of the dielectric film, and I(xyz) is the X-ray diffraction pattern of the dielectric film. means the diffraction intensity value of the peak of a given orientation plane (xyz) obtained from The X-ray diffraction pattern of the dielectric film used in Equation (3) is obtained by converting a two-dimensional X-ray diffraction image obtained using a two-dimensional detector into a one-dimensional profile (for a region with a detection angle χ = 38 ° It is preferable to convert by arc integration in the χ direction), and each peak of the obtained one-dimensional profile (excluding peaks due to substances other than the dielectric film) is fitted with a Gaussian function. , as the sum of the diffraction intensities of the peaks in all planes, apply the sum of the diffraction intensity areas of all the peaks after fitting, and as the value of the diffraction intensity of the peaks in a given orientation plane (xyz), a given after fitting Apply the value of the diffraction intensity area of the peak in the orientation plane (xyz).

In addition, the at least one orientation plane preferably has a variation in inclination of the crystal axis of 10° or less, more preferably 1° or less. As a result, the dielectric film can be oriented with high crystallinity on this orientation plane.

In the present invention, the "variation in the inclination of the crystallographic axis" of a predetermined orientation plane is the half width (° ). The X-ray diffraction pattern of the dielectric film used here is a two-dimensional X-ray diffraction image obtained using a two-dimensional detector, and the portion corresponding to the predetermined orientation plane (xyz) is converted into a one-dimensional profile. (It is preferable to integrate and convert the circular arc region containing the spot on the predetermined orientation plane (xyz) in the 2θ direction), and the peak of the predetermined orientation plane (xyz) of the obtained one-dimensional profile was fitted with a Gaussian function. is used to measure the half width (°) of the peak of a predetermined orientation plane (xyz) after fitting.

In the dielectric film of this embodiment, the content of ^A1 with respect to the total amount of A may be less than 50 atomic %. Although A ¹ is an element that constitutes the main constituent of the crystal structure, the upper limit of its content can be less than 50 atomic %, preferably 40 atomic % or less, more preferably 30 atomic % or less, and still more preferably It has been found by the studies of the present inventors that it is 20 atomic % or less. The lower limit of the content of ^A1 can be 5 atomic % or more, preferably 10 atomic % or more, since it forms the main constituent of the crystal structure.

In the dielectric film of this embodiment, the content of ^A2 with respect to the total amount of A may be 50 atomic % or more. Although A ² is an element that does not form the main part of the crystal structure and is dissolved in A ¹ ₂ B ¹ ₂ O ₇ , the lower limit of the content ratio can be 50 atomic % or more, which is preferable. is 60 atomic % or more, more preferably 70 atomic % or more, and still more preferably 80 atomic % or more. The upper limit of the content of A ² can be 95 atomic % or less, preferably 90 atomic % or less, so that it can dissolve in A ¹ ₂ B ¹ ₂ O ₇ .

The content ratio of each element in the dielectric film can be measured by fluorescent X-ray analysis and/or photoelectron spectroscopy.

According to the studies of the present inventors, it has been found that two or more elements at the A site of A ₂ B ₂ O ₇ are important for controlling the orientation plane of the dielectric film. In contrast, the number of B-site elements has less or substantially no effect on the control of the orientation plane of the dielectric film.

The two A-site elements, A ¹ and A ² , preferably have different valences. It is believed that the presence of two elements with different valences can remarkably control the orientation plane of the dielectric film.

For example, A ¹ may be a divalent element, typically Sr, and A ² may be a trivalent element, typically La, but are not limited to such combinations.

The dielectric film of the present embodiment can stably maintain a high dielectric constant, that is, with a small rate of change over a wide temperature range (for example, 20 to 150° C., preferably 20 to 300° C.). The relative dielectric constant of the dielectric film of the present embodiment is 20 to 150° C., preferably 20 to 300° C., the relative dielectric constant of the bulk single crystal of the same composition (more specifically, the bulk single crystal of the same composition (relative permittivity in the a, b, and c crystal axes)), for example, 70 or more, more preferably 80 or more, particularly preferably 100 or more, and the upper limit is not particularly limited, but for example, 400 can be: The rate of change of the dielectric constant of the dielectric film of the present embodiment can be, for example, 10% or less over the range of 20 to 150° C., preferably 20 to 300° C., based on the dielectric constant at 20° C., preferably can be 5% or less.

The dielectric film of this embodiment may be of any suitable thickness, but may be a thin film. The thickness of the dielectric film of this embodiment can be, for example, 3 nm or more and 1 μm or less. The lower limit is preferably 10 nm or more, and more preferably 50 nm or more, from the viewpoint of ensuring insulation (for example, effectively preventing the generation of pinholes). The upper limit may be 10 μm or less, but practically it may be 1 μm or less, preferably 500 nm or less.

The dielectric film of this embodiment may be manufactured by any appropriate method, and can be manufactured, for example, by the following method.

The method for producing a dielectric film according to the present embodiment is a method for producing a dielectric film having a pyrochlore-type or layered perovskite-type crystal structure,
(a) A compound of the general formula A ₂ B ₂ O ₇ (wherein A is Mg, Ca, Sr, Ba, La, Ce, Pr, Nd, Pm , Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, two or more elements A ¹ and A ² different from each other as one element among them and B is one or more elements selected from the group consisting of Ti, Zr, Hf, V, Nb and Ta, one of which includes B ¹ ). (b) heat-treating the substrate on which the precursor film is formed at a temperature of 850 to 1050° C. in an atmosphere containing oxygen to obtain the precursor film to obtain a dielectric film having a pyrochlore-type or layered perovskite-type crystal structure and having the above composition.

According to the studies of the present inventors, in order to bring about a crystal structure in the dielectric film and control its orientation plane, the temperature at which the substrate is heated in the above step (a) (hereinafter simply referred to as "substrate temperature") , and the temperature at which the substrate on which the precursor is formed in the above step (b) is heat-treated (hereinafter simply referred to as “PDA temperature” (PDA: Post Deposition Annealing)) is important (for dielectric films It is believed that crystallization proceeds not only in step (a) but also in step (b)). According to the method for producing a dielectric film of the present embodiment, the substrate is heated at a temperature of 350 to 600° C., preferably at 400 to 500° C. in the step (a), and the precursor is formed in the step (b). By heat-treating the substrate at 850 to 1050° C., preferably at 850 to 950° C., the dielectric film of the present embodiment having the orientation plane as described above can be obtained.

In step (a) of the dielectric film manufacturing method of the present embodiment, the material and structure of the substrate are not particularly limited, and can be appropriately selected according to the use of the dielectric film. For example, the substrate may consist of a single material. Alternatively, for example, the substrate may have a conductive member (which may be used as an electrode, but is not limited to this) on its surface in advance, and a precursor film may be formed on the conductive member of the substrate by vapor deposition. good. When the substrate and/or the conductive member, etc. in contact with the dielectric film are made of a crystalline material, their surfaces are preferably (111) or (001) planes. Thereby, the dielectric constant of the dielectric film can be maintained high and stably.

In step (a) above, vapor phase deposition is more specifically sputtering (e.g., radio frequency (RF) sputtering, pulsed DC sputtering), electron beam evaporation, physical vapor deposition including ion plating, etc., and/or organometallic vapor deposition. A growth method (so-called MOCVD, including, for example, atomic layer deposition (ALD)) can be applied, but the method is not limited to this.

In step (a) above, A ₂ B ₂ O ₇ is represented by A ¹ ₂ B ¹ ₂ O ₇ and A ² ₂ B ² ₂ O ₇ , wherein A ¹ , A ² and B ¹ are as defined above. , B ² is one element of Ti, Zr, Hf, V, Nb and Ta, which is the same as or different from B ¹ , preferably different from B ¹ ), and A ¹ _{It is preferred that 2B12O7 has} ^{a lower} crystallization ^temperature _{than A222B22O7 .} Since _the crystallization ^{temperature of A12B12O7} _is ^lower than ^the crystallization temperature _{of A22B22O7 , in the} obtained dielectric ^film _, ^A12B12O7 is the main crystal structure _. can be formed.

In the present invention, the "crystallization temperature" of an oxide represented by the general formula A ₂ B ₂ O ₇ and having a given composition means the temperature of a conductive substrate made of a crystalline material heated to a certain temperature T ( 111) A precursor film having the predetermined composition is formed on the surface by vapor phase deposition, and the substrate on which the precursor film is formed is subjected to oxygen gas at a flow rate of 0.5 L/min under atmospheric pressure. A dielectric film is obtained from the precursor film by heat treatment at a temperature of 900° C. for 5 minutes while flowing at The lowest temperature T at which at least one spot or ring is observed in the line diffraction pattern shall be referred to. The observation of spots in the two-dimensional X-ray diffraction image indicates the presence of a single crystal or a highly oriented crystal structure, and the observation of rings in the two-dimensional X-ray diffraction image indicates a polycrystalline state. It shows what is going on.

In the study of the present inventors, the crystallization temperatures of representative oxides represented by the general formula A ₂ B ₂ O ₇ and having one element each at the A site and one element at the B site were examined according to the above results. are shown in Table 1.

The dielectric films of La ₂ Zr ₂ O ₇ and Sr ₂ Nb ₂ O ₇ shown in Table 1 were crystallized when the precursor films were formed by vapor phase deposition, so they were subjected to heat treatment at 900 ° C. was omitted and the crystallization temperature was investigated.

In step (a) above, one or more sources (which may also be referred to as deposition sources, targets, etc., and so on) may be used to form the precursor film. When two or more raw materials are used, the material composition of each raw material may be the same or different from each other.

For example, the vapor phase deposition in step (a) above is performed using a first source material having a composition of A ¹ ₂ B ¹ ₂ O ₇ and a second source material having a composition of A ² ₂ B ² ₂ O ₇ may be implemented. In this case, different vapor deposition conditions can be applied to the first source and the second source. Thereby, for example, the abundance ratio of ^A1 and ^A2 in the dielectric film, the content ratio of ^A1 to the total amount of A, and the content ratio of ^A2 to the total amount of A can be controlled. It should be noted that in this case there may or may not be _an additional raw material with a composition _{of A2B2O7} .

Preferably, the vapor phase deposition is performed under the condition that the growth rate of A ² ₂ B ² ₂ O ₇ from the second source is higher than the growth rate of A ¹ ₂ B ¹ ₂ O ₇ from the first source. be able to. As a result, for example, it is possible to control the abundance ratio of A ¹ /A ² in the dielectric film to be small, the content ratio of A ¹ to the total amount of A to be small, and the content ratio of A ² to the total amount of A to be large.

More specifically, when the vapor phase deposition is performed by high-frequency sputtering, by applying a condition in which the output applied to the second source is greater than the output applied to the first source, A The growth rate of ^A _{2 2} B ² ₂ O ₇ from the second raw material can be made higher than the growth rate of 1 ² _B ¹ ₂ O ₇ .

The output (power) ratio applied to the first raw material of A ¹ ₂ B ¹ ₂ O ₇ and the second raw material of A ² ₂ B ² ₂ O ₇ can be appropriately selected depending on the raw material composition.

When two or more raw materials having different raw material compositions are used in step (a) above, the vapor phase deposition of raw materials from these raw materials onto the surface of the substrate can be carried out in any appropriate manner. For example, the precursor film may be formed in the form of a comixed film by simultaneously vapor-depositing the raw materials from these raw materials onto the surface of the substrate. In addition, for example, materials are deposited asynchronously on the surface of the substrate from these materials (the vapor phase deposition period from each material may or may not partially overlap, and may be repeated regularly or irregularly). may be vapor deposited (eg, layered) to form the precursor in the form of a coalesced film that fuses these materials together. Fusion can occur spontaneously without further application of external energy because crystal growth and elemental diffusion are brought about by thermal energy transferred from the substrate, kinetic energy applied to the raw material during vapor phase deposition, and the like.

It is believed that the heat treatment of the precursor film in the step (b) of the method for producing a dielectric film of the present embodiment causes further crystallization in the film (the crystallization in the step (b) is interpreted as “additional crystallization”).

In the above step (b), the heat treatment is preferably performed in a gas atmosphere containing oxygen. The gas containing oxygen is not particularly limited, and air may be conveniently used under atmospheric pressure, or oxygen gas substantially composed of oxygen (for example, oxygen concentration of 99% or more) may be used. . The oxygen-containing gas does not have to flow during the heat treatment, but it is more preferable to flow, and in the latter case the flow rate can be 0.1 to 1 L/min. The heat treatment time can be selected as appropriate, and can be, for example, 2 minutes or more and 60 minutes or less.

The method for manufacturing the dielectric film of this embodiment has been described in detail above, but the dielectric film of this embodiment is not limited to that obtained by such a manufacturing method, and can be obtained by any other suitable manufacturing method. It can be anything. For example, the precursor film may be formed by a sol-gel method instead of the vapor phase deposition method.

(Embodiment 2: Capacitor and manufacturing method thereof)
According to another embodiment of the invention, a capacitor and method of manufacturing the same are provided.

The capacitor of this embodiment includes an electrode and the dielectric film described in detail in the first embodiment arranged on the electrode. Such capacitors may be so-called thin film capacitors.

The capacitor of the present embodiment may have any appropriate configuration, and is not particularly limited, as long as it includes an electrode and a dielectric film disposed on the electrode. For example, as shown in FIG. 1, a capacitor 10 may be configured by sandwiching a dielectric film 5 between two electrodes 3 and 7 (in the embodiment (parallel plate type) shown in FIG. 1, the electrodes 3 and 7 are , can be individually connected to lead wires at suitable points in the depth direction (not shown). Further, for example, a capacitor may be configured by providing a dielectric film over two electrodes that are separated from each other.

The capacitor manufacturing method of the present embodiment may be manufactured by any appropriate method, but typically includes the dielectric film manufacturing method described in detail in the first embodiment. For example, in the embodiment shown in FIG. 1, the capacitor 10 may be manufactured by sequentially laminating the lower electrode 3, the dielectric film 5, and the upper electrode 7 on the surface of the substrate 1. FIG. Alternatively, for example, two electrodes may be formed on the surface of the substrate so as to be spaced apart from each other, and a dielectric film may be formed so as to straddle them to manufacture the capacitor. The method of forming the dielectric film corresponds to the manufacturing method described in detail in the first embodiment, and the method of forming the electrode can apply any known appropriate method.

Conductive materials constituting the electrodes are, for example, Pt, Ti, W, Al, Ni, Ag, Au, Pd, Ir, Rh, TiC, TaC, TiN, Ag ₂ O, Ru, Ru ₂ O, SrRuO ₃ , Nb. It may be additive SrTiO ₃ or the like, and may be, for example, a laminate of one or more layers. The material forming the substrate is not particularly limited, but may be, for example, oxide single crystals such as Si and SrTiO ₃ . Any suitable material layer may be present between the substrate and the electrode, for example a _SiO2 layer.

The capacitor of this embodiment has the same effect as the dielectric film described in detail in the first embodiment.

In the capacitor of this embodiment, the surface of the electrode in contact with the dielectric film is preferably a (111) or (001) plane, for example. More specifically, if the electrode is made of a crystalline material, the preferred orientation exhibited by the surface may differ depending on the crystal structure of the crystalline material. For example, the crystalline material is at least selected from the group consisting of cubic materials (e.g., Pt, W, Al, Ni, Ag, Au, Pd, Ir, Rh, TiC, TaC, TiN, _Ag2O , etc.). 1 type), a tetragonal system material (e.g., Ru ₂ O, etc.), or a perovskite-type oxide (cubic system) (e.g., SrRuO ₃ , Nb-added SrTiO _{3 ,} etc.), the surface is ( 111) orientation is preferred, and in the case of hexagonal materials (eg Ti, Ru), the surface is preferably (001) orientation. Thereby, the dielectric constant of the dielectric film can be maintained high and stably.

(Example 1)
This example relates to a dielectric film having a composition represented by (Sr _x La _1-x ) ₂ (T _x Ti _1-x ) ₂ O ₇ and a capacitor comprising such a dielectric film.

Manufacturing procedure: Formation of lower electrode A Si (100) substrate with a _SiO2 film with a thickness of about 300 nm on the surface was prepared, and a Ti layer with a thickness of about 10 nm and a Ti layer with a thickness of about 100 nm were formed on the surface by DC sputtering. Pt layers were sequentially stacked to form a lower electrode composed of these layers. In the DC sputtering, the temperature of the substrate was room temperature (about 20° C.). The Ti layer was provided as a relatively thin layer to improve adhesion between the _SiO2 film and the Pt layer. The Pt layer was the body portion of the bottom electrode, which formed the (111) plane electrode surface.

Step (a): Formation of Precursor Film The substrate on which the lower electrode is formed as described above is heated to 400° C. (i.e., the substrate temperature is 400° C.), and a (Sr _x La _{1− x} ) ₂ (Tax _{Ti 1-x} ) ₂ O ₇ was formed (note that a part (edge) of the lower electrode did not have the precursor formed thereon). left exposed). RF sputtering uses a target of Sr ₂ Ta ₂ O ₇ raw material and a target of La ₂ Ti ₂ O ₇ raw material as deposition sources, and the RF power ratio of Sr ₂ Ta ₂ O ₇ raw material:La ₂ Ti ₂ O ₇ raw material is 20 W: 60 W were vapor-deposited at the same time. The oxygen concentration in the atmosphere surrounding the substrate was 5%.

Step (b): Formation of Dielectric Film by Heat Treatment The substrate on which the precursor film was formed as described above was subjected to heat treatment at 900° C. for 5 minutes while oxygen gas was flowed at 0.5 L/min. (that is, the PDA temperature is 900° C.), a dielectric film having a composition represented by (Sr _x La _1-x ) ₂ (T _x Ti _1-x ) ₂ O ₇ is formed from the precursor film. bottom. The thickness of the obtained dielectric film was about 200 nm.

Formation of Upper Electrode On the dielectric film formed as described above, a Pt layer with a thickness of about 150 nm was formed as an upper electrode in a substantially circular shape with a diameter of about 110 nm by DC sputtering. In the DC sputtering, the temperature of the substrate was room temperature (about 20° C.). As a result, a capacitor was obtained in which the dielectric film was arranged between the lower electrode and the upper electrode.

- Analysis and Evaluation Composition The content ratio of each element in the dielectric film was examined by photoelectron spectroscopy. As a result, the dielectric film was found to have a composition of (Sr _x La _1-x ) ₂ (T _x Ti _1-x ) ₂ O ₇ , where x=0.35.

Main Crystal Structure and Orientation Plane Using a two-dimensional detector, a two-dimensional X-ray diffraction image of this dielectric film was obtained (characteristic X-ray: CuKα=1.5418 Å, the same below). The results are shown in FIG. 2 (FIG. 2 exemplifies a case where 2θ is a low angle of about 50° or less, but a case where 2θ is a high angle of about 50° to 80° (not shown) was also obtained. The same applies below). Furthermore, this two-dimensional X-ray diffraction image is circularly integrated in the dotted line area schematically shown in FIG. An X-ray diffraction pattern of the dielectric film was obtained. The results are shown in FIG. 3(b). In FIG. 3(b), the symbol “*” indicates a peak attributed to substances other than the dielectric film (Pt, Ti, SiO ₂ and Si) and is ignored because it does not constitute the dielectric film (described later). 13(b), 15(b), 17(b), 19(b), 21 and 22, the peak near 2θ=40° is due to Pt). From these results, the dielectric film of this example was compared with the known powder X-ray diffraction data (ICDD) of Sr ₂ Ta ₂ O ₇ and La ₂ Ti ₂ O ₇ (Examples and Comparative Examples below). The known data used in is selected appropriately depending on the raw material used for the evaporation source), it was determined that Sr ₂ Ta ₂ O ₇ forms the main part of the crystal structure. Furthermore, from the fact that a spot was observed near 2θ=28° in the two-dimensional X-ray diffraction image shown in FIG. (In FIG. 2, the spots near 2θ=40° are due to Pt).

Degree of Orientation of Orientation Plane Each peak (peaks due to substances other than the dielectric film are excluded) was fitted with a Gaussian function from the obtained X-ray diffraction pattern (one-dimensional profile) of the dielectric film. The results are shown in FIG. 4 (in the figure, the solid line indicates the measured data of the one-dimensional profile, and the dotted line indicates the data obtained by fitting this with a Gaussian function). From this fitting, the ratio of the diffraction intensity area of the peak of the orientation plane (111) to the sum of the diffraction intensity areas of all the peaks was found to calculate p. In addition, from each known powder X-ray diffraction data (ICDD) of Sr ₂ Ta ₂ O ₇ (the known data used in the following examples and comparative examples are appropriately selected according to the composition that constitutes the main constituent of the crystal structure. p ₀ was calculated by calculating the ratio of the diffraction intensity of the peak of the plane (111) (same as above) to the sum of the diffraction intensities of the peaks of all planes (usually, the relative intensity with the highest intensity being 100). . From these p and _p0 , the Lotgering factor f was calculated as the degree of orientation of the orientation plane (111) of the dielectric film. These calculation results were as follows.
p = 0.519
_p0 = 0.028
f = 0.506

Variation in Inclination of Crystallographic Axis of Oriented Plane Next, the circular arc region including the spot on the oriented plane (111) of the two-dimensional X-ray diffraction image is shown in the 2θ direction, and in the dotted line region schematically shown in FIG. A one-dimensional profile was obtained by integration, and the peak of the orientation plane (111) was fitted with a Gaussian function. The results are shown in FIG. 5(b) (in the figure, the solid line indicates the measurement data of the one-dimensional profile, and the dotted line indicates the data (including the background) fitted with the Gaussian function). From this fitting, the half width (°) of the peak of the orientation plane (111) was measured to be 6.42°.

Evaluation of Electrical Properties The electrical properties of the dielectric film of this example were evaluated. More specifically, a DC voltage of 3 V is applied between the upper electrode and the lower electrode of the capacitor manufactured as described above, and the dielectric constant (-), dielectric loss (-) and Current density (A/cm ² ) was measured. The results are shown in FIG. As can be seen from FIG. 6, the dielectric film of this example exhibits a high dielectric constant exceeding 100 over 20 to 300° C., and the rate of change is based on the dielectric constant at 20° C. , was less than 5%. In addition, the dielectric film of this example exhibited a two-digit current density increase rate over a temperature range of 20 to 300° C., but exhibited a dielectric loss of less than 0.1 and functioned as a dielectric.

(Example 2)
This example relates to a dielectric film having a composition represented by (Sr _x La _1-x ) ₂ (Nb _x Ti _1-x ) ₂ O ₇ and a capacitor comprising such a dielectric film. Unless otherwise specified, the same explanation as in Example 1 applies (the same applies to the examples and comparative examples described herein).

- Manufacturing procedure In step (a) _, the substrate was heated to 500°C (that _is , the substrate _temperature was ₅₀₀ ° _{C )} . (Sr _x La _{1 - x} ) 2 ₍ Nb _{x Ti 1} - _x ) ₂ (Nb _x Ti _1- (Sr _x La _1-x ) ₂ (Nb _x Ti _1-x ) 2 O ₇ in the same manner as in Example 1, _except that a precursor _film having a composition represented by x ) ₂ O ₇ was formed. A capacitor was obtained by forming a dielectric film having a composition represented by (the PDA temperature was set to 900° C. as in Example 1). The thickness of the obtained dielectric film was about 200 nm.

Analysis and Evaluation Composition The dielectric film of this example has a composition of (Sr _x La _1-x ) ₂ (Nb _x Ti _1-x ) ₂ O ₇ , where x=5.0. It has been found.

Main Crystal Structure and Orientation Planes A two-dimensional X-ray diffraction image of this dielectric film is shown in FIG. It was determined from the X-ray diffraction pattern of the dielectric film of this example that Sr ₂ Nb ₂ O ₇ constitutes the main crystal structure. Further, in the dielectric film of this example, a spot was observed near 2θ=28° in the two-dimensional X-ray diffraction image shown in FIG. Also, a peak was present near 2θ=28°, so it was found to have a (150) orientation plane.

Orientation Degree of Orientation Surface The orientation degree of the orientation surface (150) of this dielectric film was 0.68.

Variation in Inclination of Crystallographic Axis of Oriented Plane The half width of the peak of the oriented plane (150) was 3.8°.

Evaluation of Electrical Characteristics FIG. 8 shows the results of evaluating the electrical characteristics of the dielectric film of this example. As can be seen from FIG. 8, the dielectric film of this example exhibits a high dielectric constant exceeding 100 over 20 to 150° C., and the rate of change is based on the dielectric constant at 20° C. , was less than 5%. Further, the dielectric film of this example exhibited a high insulation property with a current density of 1×10 ⁻⁷ A/cm ² or less and a dielectric loss of 0.05 or less. The dielectric film of this example had a large leakage current at temperatures exceeding 160° C., and was not subjected to electrical property evaluation.

(Comparative Examples 1 to 3)
This comparative example relates to a dielectric film having a composition represented by (Sr _x La _1-x ) ₂ (T _x Ti _1-x ) ₂ O ₇ and a capacitor provided with such a dielectric film.

・Manufacturing procedure The substrate heating temperature (substrate temperature) in step (a), the RF power ratio of Sr ₂ Ta ₂ O ₇ raw material: La ₂ Ti ₂ O ₇ raw material, and the heat treatment temperature (PDA temperature) in step (b) are shown. A dielectric film having a composition represented by (Sr _x La _1-x ) ₂ (T _x Ti _1-x ) ₂ O ₇ was prepared in the same manner as in Example 1 except that the composition was changed as shown in 2 was formed to obtain a capacitor. Table 2 also shows the thickness of the obtained dielectric film.

・Analysis and Evaluation Composition The dielectric film of this comparative example has a composition of (Sr _x La _1-x ) ₂ (Nb _x Ti _1-x ) ₂ O ₇ , where x=0 in Comparative Example 1. .66, Comparative Example 2 was found to be x=0.56, and Comparative Example 3 was found to be x=0.36.

Main Crystal Structure and Orientation Planes Two-dimensional X-ray diffraction images of the dielectric films of Comparative Examples 1 to 3 are shown in FIGS. 9 to 11, respectively. It was determined that the dielectric films of Comparative Examples 1 to 3 were mainly composed of Sr ₂ Ta ₂ O ₇ . Furthermore, in the dielectric film of Comparative Example 1, spots were observed near 2θ=20° in the two-dimensional X-ray diffraction image shown in FIG. Also, a peak was present near 2θ=20°, so it was found to have a (041) orientation plane. In the dielectric film of Comparative Example 2, a plurality of peaks were observed in the X-ray diffraction pattern (one-dimensional profile) (not shown). (compared to the (0 10 0) plane near =33°). However, since no spots were observed in the two-dimensional X-ray diffraction image shown in FIG. 10, the dielectric film of Comparative Example 2 does not have an orientation plane (in other words, the (080) plane is not an orientation plane). . In the dielectric film of Comparative Example 3, a plurality of peaks were observed in the X-ray diffraction pattern (one-dimensional profile) (not shown), and the peak intensity was particularly large in the (111) plane near 2θ=28°. However, since no spots were observed in the two-dimensional X-ray diffraction image shown in FIG. 11, the dielectric film of Comparative Example 2 does not have an orientation plane (in other words, the (111) plane is not an orientation plane). . Therefore, in the dielectric film of this comparative example, the Sr ₂ Ta ₂ O ₇ that forms the main part of the crystal structure has an orientation plane other than the (h00), (0k0), (00l), (h0l), and (0kl) planes. does not have

Orientation Degree of Orientation Surface The orientation degree of the orientation surface (041) of the dielectric film of Comparative Example 1 was 0.66. Although the dielectric film of Comparative Example 2 was not an oriented plane, the degree of orientation of (080) was 0.065 and the degree of orientation of (0 10 0) was 0.22. The dielectric film of Comparative Example 3 had a degree of (111) orientation of 0.30, although it was not an oriented plane.

Variation in Inclination of Crystallographic Axis of Oriented Plane The half width of the peak of the (041) oriented plane of the dielectric film of Comparative Example 1 was 3.1°. In the dielectric film of Comparative Example 2, the half-value width of the (080) peak was 9.3° although the plane was not oriented. In the dielectric film of Comparative Example 3, the half-value width of the (111) peak was 15.9° although the plane was not oriented.

Electrical Characteristic Evaluation The dielectric film of Comparative Example 1 exhibited a dielectric constant of about 45 and a dielectric loss of about 0.05 at room temperature (about 20° C.). The dielectric film of Comparative Example 2 exhibited a dielectric constant of about 30 and a dielectric loss of about 0.05 at room temperature (about 20°C). The dielectric film of Comparative Example 3 exhibited a dielectric constant of about 600 and a dielectric loss of about 0.05 at room temperature (about 20°C). For reference, Comparative Examples 1 to 3 were modified (various distances from the two evaporation sources, etc.) to form (Sr _x La _1-x ) ₂ (T _x Ti _1-x ) ₂ O ₇ Dielectric films and capacitors with different x in the formula were obtained for the dielectric films having the compositions represented, and the results of evaluating their electrical characteristics at room temperature (about 20° C.) are shown in FIG. “xSr ₂ Ta ₂ O ₇ -(1-x)La ₂ Ti ₂ O ₇ ” shown is notation based on raw materials, but (Sr _x La _1-x ) ₂ ( _Tax Ti _1-x ) ₂ is synonymous with _O7 ). In both cases, the low dielectric constant of less than 70 was obtained.

(Comparative Example 4)
This comparative example relates to a dielectric film having a composition represented by Sr ₂ Ta ₂ O ₇ and a capacitor comprising such a dielectric film.

- Manufacturing procedure In step (a), RF sputtering is performed using a target of Sr ₂ Ta ₂ O ₇ raw material as a deposition source, and the RF power of Sr ₂ Ta ₂ O ₇ raw material is 50 W to deposit Sr ₂ Ta ₂ O A dielectric film having a composition represented by Sr ₂ Ta ₂ O ₇ was formed in the same manner as in Example 1 except that a precursor film having a composition represented by ₇ was formed to obtain a capacitor. (As in Example 1, the substrate temperature was 500° C. and the PDA temperature was 900° C.). The thickness of the obtained dielectric film was about 200 nm.

Analysis and Evaluation Composition The dielectric film of this comparative example has a composition of Sr ₂ Ta ₂ O ₇ and the A element is only Sr.

Main Crystal Structure and Orientation Planes A two-dimensional X-ray diffraction image and an X-ray diffraction pattern of this dielectric film are shown in FIGS. pattern). In the dielectric film of this comparative example, Sr ₂ Ta ₂ O ₇ constitutes the main crystal structure. In the dielectric film of this comparative example, spots were observed near 2θ=23° and 46° in the two-dimensional X-ray diffraction image shown in FIG. In the X-ray diffraction pattern (one-dimensional profile) shown in , there were peaks near 2θ = 23 ° and 46 °, so it was found to have (110) and (200) orientation planes. (However, it was found that the spot of (200) was slightly extended in a ring shape compared to (110)). For reference, FIG. 13(b) also shows the X-ray diffraction pattern of the film obtained by modifying this comparative example. After forming, it is the X-ray diffraction pattern of the film before being subjected to the step (b). It is an X-ray diffraction pattern of the obtained dielectric film. From FIG. 13(b), it can be seen that a PDA temperature of 900° C. is required to bring about (110) and (200) oriented planes by crystallization in this dielectric film.

Orientation Degree of Orientation Surface The orientation degree of the orientation surface (110) of the dielectric film of this comparative example was 0.81, and the orientation degree of the orientation surface (200) was 0.08.

Variation in inclination of crystal axis of orientation plane The half-value width of the peak of the orientation plane (110) of the dielectric film of Comparative Example 1 is 2.1°, and the half-value width of the peak of the orientation plane (200) is 1.9°. Met.

Evaluation of Electrical Characteristics FIG. 14 shows the results of evaluating the electrical characteristics of the dielectric film of this comparative example. As understood from FIG. 14, the dielectric film of this comparative example exhibited a low dielectric constant of about 45 to 55 over a temperature range of 20 to 300.degree.

(Comparative Example 5)
This comparative example relates to a dielectric film having a composition represented by Sr ₂ Nb ₂ O ₇ and a capacitor comprising such a dielectric film.

- Manufacturing procedure In step (a), RF sputtering is performed using _a target of _Sr2Nb2O7 raw material as a deposition source, and the RF _power of _Sr2Nb2O7 raw material _is 50 W to _{deposit Sr2Nb2O .} A dielectric film having a composition represented by Sr ₂ Nb ₂ O ₇ was formed in the same manner as in Example ₁ except that a precursor film having a composition represented by 7 was formed to obtain a capacitor. (As in Example 1, the substrate temperature was 500° C. and the PDA temperature was 900° C.). The thickness of the obtained dielectric film was about 200 nm.

Analysis and Evaluation Composition The dielectric film of this comparative example has a composition of Sr ₂ Nb ₂ O ₇ and the element A is Sr only.

Main Crystal Structure and Orientation Planes A two-dimensional X-ray diffraction image and an X-ray diffraction pattern of this dielectric film are shown in FIGS. pattern). In the dielectric film of this comparative example, Sr ₂ Nb ₂ O ₇ constitutes the main crystal structure. The dielectric film of this comparative example has a plurality of peaks in the X-ray diffraction pattern (one-dimensional profile) shown at "900° C." in FIG. Relatively large peaks were observed in the plane and the (150) plane near 2θ=28°. However, no spots were observed in the two-dimensional X-ray diffraction image shown in FIG. 150) plane is not an orientation plane). For reference, FIG. 15(b) also shows the X-ray diffraction pattern of the film obtained by modifying this comparative example. After forming, it is the X-ray diffraction pattern of the film before being subjected to the step (b). It is an X-ray diffraction pattern of the obtained dielectric film.

Degree of Orientation of Oriented Surface Although the dielectric film of this comparative example was not an oriented surface, the degree of orientation of (131) was 0.52 and the degree of orientation of (150) was 0.30.

Variation in Inclination of Crystallographic Axis of Oriented Plane Although the dielectric film of this comparative example is not an oriented plane, the half-value width of the (131) peak is 21.4°, and the half-value width of the (150) peak is 20°. .8°.

Evaluation of Electrical Characteristics FIG. 16 shows the results of evaluating the electrical characteristics of the dielectric film of this comparative example. As understood from FIG. 16, the dielectric film of this comparative example exhibited a low dielectric constant of about 40 to 60 over a temperature range of 20 to 300.degree.

(Comparative Example 6)
This comparative example relates to a dielectric film having a composition represented by La ₂ Ti ₂ O ₇ and a capacitor comprising such a dielectric film.

-Manufacturing procedure In step (a), RF sputtering is performed using a La ₂ Ti ₂ O ₇ raw material target as a deposition source, and the La ₂ Ti ₂ O ₇ raw material is vapor-deposited at an RF power of 50 W to deposit La ₂ Ti ₂ O. A dielectric film having a composition represented by La 2 Ti 2 O 7 was formed in the same manner as in Example ₁ except that a precursor film having a composition represented by La ₂ Ti ₂ O ₇ was formed to obtain a capacitor. (As in Example 1, the substrate temperature was 500° C. and the PDA temperature was 900° C.). The thickness of the obtained dielectric film was about 80 nm.

Analysis and Evaluation Composition The dielectric film of this comparative example has a composition of La ₂ Ti ₂ O ₇ and only La is present as the element A.

Main Crystal Structure and Orientation Planes A two-dimensional X-ray diffraction image and an X-ray diffraction pattern of this dielectric film are shown in FIGS. pattern). In the dielectric film of this comparative example, La ₂ Ti ₂ O ₇ constitutes the main crystal structure. The dielectric film of this comparative example has a plurality of peaks in the X-ray diffraction pattern (one-dimensional profile) shown at "900° C." in FIG. A relatively large peak was observed on the surface. However, no spots were observed in the two-dimensional X-ray diffraction image shown in FIG. face). For reference, FIG. 17(b) also shows the X-ray diffraction pattern of the film obtained by modifying this comparative example. After forming, it is the X-ray diffraction pattern of the film before being subjected to the step (b). It is an X-ray diffraction pattern of the obtained dielectric film.

Degree of Orientation of Oriented Surface Although the dielectric film of this comparative example was not an oriented surface, the degree of orientation of (400) was 0.534.

Variation in Inclination of Crystallographic Axis of Oriented Plane Although the dielectric film of this comparative example was not an oriented plane, the half width of the (400) peak was 23.8°.

Evaluation of electrical properties When the electrical properties of the dielectric film of this comparative example were evaluated, it was found that at room temperature (about 20°C), the dielectric constant was about 43, the dielectric loss was about 0.05, and the dielectric loss was about 3 × 10 ^-7 A/. cm ² current density was indicated. In the system in which the element of A is only La as in this comparative example, the leakage current tends to be large. I couldn't do it.

(Comparative Example 7)
This comparative example relates to a dielectric film having a composition represented by La ₂ Zr ₂ O ₇ and a capacitor comprising such a dielectric film.

- Manufacturing procedure In step (a), RF sputtering is performed using _a target of _La2Zr2O7 raw material as a vapor deposition source, and RF _power of _La2Zr2O7 raw material _is set to 50 W to _{deposit La2Zr2O .} A dielectric film having a composition represented by La ₂ Zr ₂ O ₇ was formed in the same manner as in Example ₁ except that a precursor film having a composition represented by 7 was formed to obtain a capacitor. (As in Example 1, the substrate temperature was 500° C. and the PDA temperature was 900° C.). The thickness of the obtained dielectric film was about 60 nm.

Analysis and Evaluation Composition The dielectric film of this comparative example has a composition of La ₂ Zr ₂ O ₇ and only La is present as the element A.

Main Crystal Structure and Orientation Planes A two-dimensional X-ray diffraction image and an X-ray diffraction pattern of this dielectric film are shown in FIGS. pattern). In the dielectric film of this comparative example, La ₂ Zr ₂ O ₇ constitutes the main crystal structure. The dielectric film of this comparative example has a plurality of peaks in the X-ray diffraction pattern (one-dimensional profile) shown at “900° C.” in FIG. Relatively large peaks were observed on the plane and the (444) plane near 2θ=59°. However, in the two-dimensional X-ray diffraction image shown in FIG. 17A, spots were observed near 2θ=29°, and no spots were observed elsewhere. 222) orientation plane (in other words, the (444) plane is not an orientation plane). For reference, FIG. 18(b) also shows the X-ray diffraction pattern of the film obtained by modifying this comparative example, and “after film formation” means the precursor film in step (a). After forming, it is the X-ray diffraction pattern of the film before being subjected to the step (b). It is an X-ray diffraction pattern of the obtained dielectric film.

Orientation Degree of Orientation Surface In the dielectric film of this comparative example, the orientation degree of the orientation surface (222) was 0.97.

Variation in Inclination of Crystallographic Axis of Oriented Plane In the dielectric film of this comparative example, the half width of the peak of the oriented plane (222) was 4.3°.

Evaluation of electrical properties When the electrical properties of the dielectric film of this comparative example were evaluated, at room temperature (about 20°C), the dielectric constant was about 45, the dielectric loss was about 0.1, and the dielectric loss was about 2 × 10 ^-2 A/ cm ² current density was indicated. In the system in which the element of A is only La as in this comparative example, the leakage current tends to be large. I couldn't do it.

(Comparative Example 8)
This comparative example relates to a dielectric film having a composition represented by Sr ₂ ( _{TaxNb 1-x} ) ₂ O ₇ and a capacitor comprising such a dielectric film.

Manufacturing procedure In step (a), RF sputtering uses a Sr ₂ Ta ₂ O ₇ raw material target and a Sr ₂ Nb ₂ O ₇ raw material target as deposition sources, Sr ₂ Ta ₂ O ₇ raw material: Sr ₂ Nb The RF power ratio of _{the 2O7 raw} material was 50W:50W, and the aperture areas were alternately deposited via a controllable shutter mechanism to obtain a composition represented by _Sr2 ( _{TaxNb1 -x} ) _{2O7 .} A dielectric film having a composition represented by Sr ₂ (Ta _x Nb _1-x ) ₂ O ₇ was formed in the same manner as in Example 1, except that a precursor film having (As in Example 1, the substrate temperature was 500° C. and the PDA temperature was 900° C.). The thickness of the obtained dielectric film was about 70 nm.

・Analysis and Evaluation Composition The dielectric film of this comparative example has a composition represented by Sr ₂ (Ta _x Nb _1-x ) ₂ O ₇ , where x= 0, 0.2, 0.4, 0.6, 0.8 and 1.0. By _alternately evaporating from two deposition sources while controlling the opening area of the shutter, _{a compositional} gradient can be produced in the dielectric film. The regions became Sr ₂ Ta ₂ O ₇ rich and the regions close to the Sr ₂ Nb ₂ O ₇ source became Sr ₂ Nb ₂ O ₇ rich.

FIG. 19 shows the X-ray diffraction pattern (one-dimensional profile) of each region where x=0, 0.2, 0.4, 0.6, 0.8 and 1.0 in this dielectric film (Fig. "xSr ₂ Ta ₂ O ₇ -(1-x)Sr ₂ Nb ₂ O ₇ " shown in No. 19 is notation based on raw materials, but is synonymous with Sr ₂ ( _Tax Nb _1-x ) ₂ O ₇ . is). When x=0, as in the dielectric film of Comparative Example 5, there was no orientation plane. In the case of x=1.0, like the dielectric film of Comparative Example 4, it had an orientation plane (110). In any case of x = 0, 0.2, 0.4, 0.6, 0.8 and 1.0, the dielectric constant at room temperature (25 ° C.) is 60 or less, and the dielectric constant is high was not obtained.

(Comparative Example 9)
This comparative example relates to a dielectric film having a composition represented by La ₂ (Zr _x Ti _1-x ) ₂ O ₇ and a capacitor comprising such a dielectric film.

- Manufacturing procedure In step (a) _{, the} substrate was heated to ₅₅₀ °C (that is, the substrate _temperature was ₅₅₀ ° _C ). Using a target, the RF power ratio of La ₂ Zr ₂ O ₇ raw material:La ₂ Ti ₂ O ₇ raw material is 50 W: 50 W, and the opening area is alternately vapor-deposited through a controllable shutter mechanism to obtain La ₂ ( La ₂ (Zr _x Ti _1-x ) ₂ O ₇ was prepared in the same manner as in Example 1 except that a precursor film having a composition represented by Zr _x Ti _1-x ) ₂ O ₇ was formed. A dielectric film having a composition was formed to obtain a capacitor (the PDA temperature was set to 900° C. in the same manner as in Example 1). The thickness of the obtained dielectric film was about 70 nm.

・Analysis and Evaluation Composition The dielectric film of this comparative example has a composition represented by La ₂ (Zr _x Ti _1-x ) ₂ O ₇ , where x= 0, 0.2, 0.4, 0.6, 0.8 and 1.0. By alternately vapor-depositing _from two vapor deposition sources while controlling the opening area of the shutter, _{a compositional} gradient can be produced in the dielectric film. The regions became La ₂ Zr ₂ O ₇ rich and the regions close to the La ₂ Ti ₂ O ₇ source became La ₂ Ti ₂ O ₇ rich.

FIG. 20 shows the X-ray diffraction pattern (one-dimensional profile) of each region where x=0, 0.2, 0.4, 0.6, 0.8 and 1.0 in this dielectric film (Fig. “xLa ₂ Zr ₂ O ₇ -(1-x)La ₂ Ti ₂ O ₇ ” shown in 20 is a notation based on raw materials, but is synonymous with La ₂ (Zr _x Ti _1-x ) ₂ O ₇ is). When x=0, there was no orientation plane as in the dielectric film of Comparative Example 6. In the case of x=1.0, like the dielectric film of Comparative Example 7, it had an orientation plane (222). (Note that in Comparative Examples 6 and 7, the substrate temperature was 500° C., unlike this Comparative Example.) x=0, 0.2, 0.4, 0.6, 0.8 and 1. 0.0, the dielectric constant at room temperature (25° C.) was 50 or less, and a high dielectric constant was not obtained. Moreover, in any of these cases, the leakage current exceeded 1 mA at 50° C. or higher, and the electrical characteristics could not be evaluated.

The dielectric film of the present invention is suitably used as a dielectric film in capacitors (especially thin film capacitors), and such capacitors can be used in various electronic components, but the dielectric film of the present invention is not limited to such uses. .

This application claims priority based on Japanese Patent Application No. 2019-105680 filed in Japan on June 5, 2019, the entire contents of which are incorporated herein by reference.

1 substrate 3 electrode (lower electrode)
5 dielectric film 7 electrode (upper electrode)
10 capacitor

Claims (11)

A dielectric film having a pyrochlore-type or layered perovskite-type crystal structure,
(Sr _x La _1-x ) ₂ (Tax _{Ti 1-x} ) ₂ O ₇ (where x=0.35) ,
Regarding Sr ₂ Ta ₂ O ₇ which forms the main part of the crystal structure of the dielectric film, the (h00), (0k0), (00l), (h0l) and (0kl) planes (h, k and l exclude 0 is an integer), has a (111) orientation plane,
The dielectric film, wherein the (111) orientation plane has an orientation degree of 0.506 . A dielectric film having a pyrochlore-type or layered perovskite-type crystal structure,
(Sr _x La _1-x ) ₂ (Tax _{Ti 1-x} ) ₂ O ₇ (where x=0.35) ,
Regarding Sr ₂ Ta ₂ O ₇ which forms the main part of the crystal structure of the dielectric film, the (h00), (0k0), (00l), (h0l) and (0kl) planes (h, k and l exclude 0 is an integer), has a (111) orientation plane,
The dielectric film, wherein the (111) -orientation plane has a tilt variation of 6.42° . 3. The dielectric film according to claim 1, having a thickness of 3 nm or more and 1 μm or less. A capacitor comprising an electrode and the dielectric film according to any one of claims 1 to 3 disposed over the electrode. 5. The capacitor according to claim 4 , wherein the surface of said electrode in contact with said dielectric film is a (111) or (001) plane. A method for producing a dielectric film having a pyrochlore-type or layered perovskite-type crystal structure, comprising:
(a) A composition of (Sr _x La _1-x ) ₂ (T _x Ti _1-x ) ₂ O ₇ (where x = 0.35) was deposited on the surface of a substrate heated to a temperature of 350 to 600°C. and (b) heat-treating the substrate on which the precursor film is formed at a temperature of 850 to 1050° C. in an atmosphere containing oxygen to form the precursor A manufacturing method, comprising obtaining a dielectric film having a pyrochlore-type or layered perovskite-type crystal structure and having the composition from the film. In (a) above, _the vapor _deposition is performed using _a first _source material having a _composition of Sr2Ta2O7 and _a second source material having a composition of La2Ti2O7 , 7. The method of manufacturing a dielectric film according to claim 6 . 8. The vapor phase deposition according to claim 7 , wherein the growth rate of La ₂ Ti ₂ O ₇ from the second source material is higher than the growth rate of Sr ₂ Ta ₂ O ₇ from the first source material. A method for manufacturing a dielectric film of 9. The method of manufacturing a dielectric film according to claim 8 , wherein said vapor phase deposition is performed by high frequency sputtering under the condition that the power applied to the second source material is higher than the power applied to the first source material. 10. The method of manufacturing a dielectric film according to claim 6, wherein in said (b), said heat treatment is performed in a gas atmosphere containing oxygen. 11. The method according to any one of claims 6 to 10, wherein in (a), the substrate has a conductive member in advance on its surface, and the precursor film is formed on the conductive member of the substrate by vapor deposition. A method for producing a dielectric film according to any one of the above.

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