JP4604939B2 - Dielectric thin film, thin film dielectric element and manufacturing method thereof - Google Patents

Description

  The present invention relates to a dielectric thin film, a thin film dielectric element, and a manufacturing method thereof, and more particularly, to a dielectric thin film, a thin film dielectric element, and a manufacturing method thereof that have a high dielectric constant and can reduce a leakage current.

  In recent years, in the field of electronic components, with the increase in density and integration of electronic circuits, there has been a demand for further downsizing, thinning, and large capacity of capacitors, which are essential circuit elements for various electronic circuits. .

In order to reduce the size, thickness and capacity of the capacitor, a dielectric material having a high relative dielectric constant is used. As such a dielectric material, lead titanate (PbTiO ₃ ), lead zirconate titanate Examples thereof include perovskite oxides such as (PZT), barium titanate (BaTiO ₃ : BT), strontium titanate (SrTiO ₃ : ST), and barium strontium titanate (BaSrTiO ₃ : BST).

  Among these, barium titanate (BT), strontium titanate (ST), and barium strontium titanate (BST) have a high relative dielectric constant, a long life, and excellent characteristics. In particular, barium strontium titanate (BST), which is a solid solution of barium titanate (BT) and strontium titanate (ST), can adjust the Curie temperature by changing the ratio of BT and ST. It is possible to obtain a paraelectric material having a high dielectric constant even at room temperature.

  In such a capacitor, for example, a capacitor element used as an essential circuit element in various electronic circuits needs to be a thin film element. Therefore, it is necessary to reduce the thickness of BT, ST and BST used as the dielectric layer of the capacitor element to form a dielectric thin film. Thus, when the dielectric material is a dielectric thin film, it is desired to have a high dielectric constant and a small leakage current.

  However, it is generally difficult for such a dielectric thin film to achieve both high dielectric constant and low leakage current. In order to solve this problem, a method of doping an additive into BST has been performed. For example, Patent Document 1 proposes an Er-doped BST in which BST is doped with erbium (Er). However, when the dielectric material such as BT, ST or BST is thinned to about 500 nm or less as in the invention described in this document, it is difficult to uniformly add the additive Er, and the distribution of the additive Since variations occur, it is difficult to obtain stable characteristics.

Patent Document 2 discloses a dielectric thin film that is a perovskite oxide represented by the chemical formula of (Ba, Sr) _y TiO ₃ and has a composition of 1.00 <y ≦ 1.20. Therefore, high dielectric constant and low leakage current are achieved. In the example of this document, the composition of BST constituting the dielectric thin film is (Ba _0.5 , Sr _0.5 ) _y TiO ₃ with an equivalent ratio of barium to strontium, and the value of y is 1. .00 <y ≦ 1.20. However, when the BST composition is within the above composition range, it is still not sufficient to achieve both a high dielectric constant and a low leakage current. In particular, when the dielectric thin film is further thinned (for example, 100 nm) In the case of the following, it cannot be said that both the dielectric constant and the low leakage current characteristic are sufficient.

Japanese Patent Laid-Open No. 8-198669 JP 7-17713 A

  An object of the present invention is to provide a dielectric thin film having a high relative dielectric constant, a small leakage current, and stable physical characteristics and electrical characteristics. Another object of the present invention is to provide a thin film dielectric element such as a thin film capacitor having a high capacity and high reliability using such a dielectric thin film, and a manufacturing method thereof.

The inventors of the present invention, in a dielectric thin film containing an oxide whose composition formula is represented by (Ba _x Sr _(1-x) ) _a TiO ₃ , limits the composition ratio, thereby other than the oxides described above. The present inventors have found that the above object can be achieved without using any additive, and have completed the present invention.

That is, the dielectric thin film according to the present invention is
A dielectric thin film containing an oxide represented by _a composition formula (Ba _x Sr _(1-x) ) _a TiO ₃ , for example, barium strontium titanate (BST),
Symbols x and a indicating the composition ratio are
0.5 <x ≦ 1.0,
0.96 <a ≦ 1.00,
The thickness is 500 nm or less.

The present invention provides a dielectric thin film containing an oxide represented by (Ba _x Sr _(1-x) ) _a TiO ₃ , wherein the thickness of the dielectric thin film is 500 nm or less, and the composition has more barium than strontium. The composition is characterized in that the amount of elements constituting the A site is the same as or slightly smaller than the amount of elements constituting the B site. By setting the composition in such a composition range, a dielectric thin film having a high relative dielectric constant, a small leakage current, and stable physical and electrical characteristics can be obtained.

Further, in the present invention, since additives other than the above-described composition are not substantially used, problems such as variations in the distribution of additives that are likely to occur when the additives are used do not substantially occur. In this specification, (Ba _x Sr _(1-x) ) _a TiO ₃ (0.5 <x ≦ 1.0, 0.96 <a ≦ 1.00) is a strict stoichiometric composition. The amount of oxygen (O) may be slightly deviated from the stoichiometric composition of the above formula.

The dielectric thin film according to the present invention preferably has a leak current density of 1 × 10 ⁻⁶ A / cm ² or less when the relative dielectric constant is 450 or more and the applied electric field strength is 100 kV / cm.

  In the dielectric thin film according to the present invention, the symbol a indicating the composition ratio is preferably 0.96 <a <1.00, and more preferably 0.98 ≦ a <1.00.

The thin film dielectric element according to the present invention is
A lower electrode, a dielectric thin film, and an upper electrode are sequentially formed on the substrate.
The dielectric thin film is the above-described dielectric thin film according to the present invention.

Alternatively, the thin film dielectric element of the present invention is
A plurality of dielectric thin films and internal electrode thin films are alternately laminated on the substrate,
The dielectric thin film is the above-described dielectric thin film according to the present invention.

  Specific examples of the thin film dielectric element are not particularly limited, and examples thereof include a thin film capacitor, a multilayer thin film capacitor, an inorganic EL element, and a DRAM capacitor. In addition, the thin film dielectric element of the present invention may be a thin film dielectric element formed directly on a semiconductor substrate and mounted on the substrate.

  The thin film dielectric element of the present invention can be a single layer element or a multilayer element. A single-layer element is configured by sequentially forming a lower electrode, a dielectric thin film, and an upper electrode on a substrate. On the other hand, a multilayer element is formed by forming a lower electrode on a substrate, laminating a plurality of dielectric thin films and internal electrode thin films alternately on the lower electrode, and forming an upper electrode thereon. The

The manufacturing method of the thin film dielectric element of the present invention is as follows:
It includes a step of forming the above-described dielectric thin film of the present invention on a conductive electrode by a sputtering method.

  Here, the conductive electrode means the lower electrode or the internal electrode thin film. In the method for manufacturing a thin film dielectric element of the present invention, the formation of the dielectric thin film is performed by a sputtering method, so that the composition control is good and the physical characteristics and electrical characteristics of a large area substrate can be obtained at high speed. A stable dielectric thin film can be formed.

The method of manufacturing a thin film dielectric element according to the present invention is preferably
The sputtering method is performed in an oxidizing gas atmosphere in which argon gas and oxygen gas are mixed,
The ratio of oxygen gas in the oxidizing gas is more than 0% by volume and 50% by volume or less.

  In the present invention, it is preferable to perform the sputtering method in an oxidizing gas atmosphere. By doing so, it is possible to effectively prevent the generation of oxygen vacancies from the crystal structure of an oxide such as BST.

  The method for manufacturing a thin film dielectric element according to the present invention preferably further includes a step of annealing the dielectric thin film in an oxidizing gas atmosphere.

According to the present invention, in the oxide whose composition formula is represented by (Ba _x Sr _(1-x) ) _a TiO ₃ , the relative dielectric constant is high by limiting the composition ratio and setting the thickness to 500 nm or less. Further, it is possible to provide a dielectric thin film and a thin film dielectric element having a small leakage current and stable physical characteristics and electrical characteristics.

  Furthermore, according to the method for manufacturing a thin film dielectric element of the present invention, since the dielectric thin film of the present invention is formed by a sputtering method, it is possible to provide a thin film dielectric element such as a thin film capacitor having a high capacity and high reliability. it can.

Hereinafter, the present invention will be described based on embodiments shown in the drawings.
FIG. 1 is a sectional view of a thin film dielectric device according to an embodiment of the present invention.
FIG. 2 is a sectional view of a thin film dielectric device according to an embodiment of the present invention.
FIG. 3 is a graph showing the relationship between the value of a in the composition formula (Ba _x Sr _(1-x) ) _a TiO ₃ and the relative dielectric constant;
FIG. 4 is a graph showing the relationship between the value of a in the composition formula (Ba _x Sr _(1-x) ) _a TiO ₃ and the leakage current density.

  In the present embodiment, a thin film dielectric element 1 in which the dielectric thin film of the present invention is formed as a single layer will be described as an example.

Thin film dielectric element 1
As shown in FIG. 1, a thin film dielectric element 1 according to an embodiment of the present invention includes an insulating film 3, a lower electrode 4, a dielectric thin film 5, and an upper electrode 6 that are sequentially formed on a substrate 2. ,It is configured.

  The substrate 2 is a substrate that supports the lower electrode, the dielectric thin film, and the upper electrode, and may be any substrate that has high chemical stability and generates less stress, and is made of ceramic, glass, silicon, or the like. In the present embodiment, the substrate 2 is composed of a silicon single crystal substrate.

The insulating film 3 is a silicon oxide film (SiO ₂ ), and is formed by thermally oxidizing a silicon single crystal substrate.

The material for forming the lower electrode 4 is not particularly limited as long as it is a conductive material. For example, platinum (Pt), gold (Au), silver (Ag), iridium (Ir), ruthenium ( Ru), cobalt (Co), nickel (Ni), iron (Fe), copper (Cu), aluminum (Al) and other metals or their alloys, gallium arsenide (GaAs), gallium phosphide (GaP), Conductive semiconductors such as indium phosphorus (InP) and silicon carbide (SiC), indium tin oxide (ITO), zinc oxide (ZnO), tin oxide (SnO ₂ ), indium oxide (In ₂ O ₃ ), iridium dioxide _(IrO 2), ruthenium dioxide _(RuO 2), trioxide rhenium _{(ReO 3), LSCO (La} 0.5 Sr 0.5 CoO 3) metal oxide conductive such as There can be used. Although the thickness of the lower electrode 4 is not specifically limited, Preferably it is 10-1000 nm, More preferably, it is about 50-800 nm.

In order to ensure adhesion between the substrate 2 and the lower electrode 4, a buffer layer may be provided between the insulating film 3 formed on the substrate 2 and the lower electrode 4. Examples of the buffer layer include TiO _x / Si, TiO _x / SiO ₂ / Si, TaN / Si, and the like. “/ Si” means the substrate side. A method for forming the adhesion layer can be performed by a vapor deposition method such as a physical vapor deposition method (PVD method) or a chemical vapor deposition method (CVD method), and may be appropriately selected depending on a deposition material.

  The upper electrode 6 can be made of the same material as that of the lower electrode 4. The thickness may be the same.

The dielectric thin film 5 contains an oxide represented by (Ba _x Sr _(1-x) ) _a TiO ₃ , for example, barium strontium titanate (BST). BST is an all solid solution in which barium and strontium occupy the A site of the perovskite structure and form a solid solution with all compositions of 0 ≦ x ≦ 1.0.

  The symbol x indicating the composition ratio in the above formula is 0.5 <x ≦ 1.0, preferably 0.6 ≦ x ≦ 0.9, and more preferably 0.65 ≦ x ≦ 0.85. . That is, in the present invention, the barium ratio in the composition formula is set to be larger than the strontium ratio. Here, when x is too small, it becomes close to the properties of strontium titanate and the relative dielectric constant tends to decrease.

  The symbol a indicating the composition ratio in the above formula is 0.96 <a ≦ 1.00, preferably 0.96 <a <1.00, and more preferably 0.98 ≦ a <1.00. It is. If a is too large, the leakage current density tends to increase, and if it is too small, the relative permittivity tends to decrease.

  The thickness of the dielectric thin film 5 is 500 nm or less, preferably 300 nm or less, more preferably 100 nm or less. If the dielectric thin film 5 is too thick, it tends to be difficult to reduce the size of the element. The lower limit of the thickness is not particularly limited, but is usually about 40 nm in consideration of ensuring the minimum grain size, the smoothness of the substrate, and the in-plane uniformity of the film thickness.

As a feature of the present invention, a dielectric thin film containing an oxide represented by (Ba _x Sr _(1-x) ) _a TiO ₃ , for example, barium strontium titanate (BST), the thickness of the dielectric thin film Is 500 nm or less, and the composition formula (Ba _x Sr _(1-x) ) _a TiO ₃ symbols x and a are within the above range. That is, the present invention is characterized in that the above composition is a composition having more barium than strontium, and the amount of elements constituting the A site is the same as or slightly less than the amount of elements constituting the B site. And By doing so, it is possible to obtain a dielectric thin film having a high relative dielectric constant, a small leakage current, and a stable physical property and electrical property.

The relative dielectric constant of the dielectric thin film 5 is preferably 450 or more, more preferably 480 or more, and the leakage current density when the applied electric field strength is 100 kV / cm is 1 × 10 ⁻⁶ A / cm ² or less. It is preferably 1.5 × 10 ⁻⁷ A / cm ² or less. In this embodiment, since the dielectric thin film of the present invention is used as the dielectric thin film 5, a high dielectric constant and a low leakage current can be achieved.

  The thin film dielectric element 1 of this embodiment is manufactured by sequentially forming a lower electrode, a dielectric thin film, and an upper electrode on a silicon single crystal substrate that has been subjected to a thermal oxidation process by a sputtering method. Hereinafter, the manufacturing method will be specifically described.

Method for Manufacturing Thin Film Dielectric Element 1 First, a silicon single crystal substrate is used as the substrate 2, and the silicon single crystal substrate is thermally oxidized to form an insulating film 3 (silicon oxide film: SiO ₂ ) on the surface of the silicon single crystal substrate. To do. The method of thermal oxidation treatment is not particularly limited, but there are dry oxidation performed on a silicon single crystal substrate in an oxidizing gas atmosphere such as oxygen gas and nitrous oxide gas at high temperature, and wet oxidation performed in a steam atmosphere. Can be mentioned.

  Next, a lower electrode 4 is formed on a silicon single crystal substrate on which a silicon oxide film is formed by thermal oxidation treatment, and a stacked body in which the lower electrode is formed is manufactured. In the present embodiment, the above-described conductive material can be used as the material constituting the lower electrode 4. The lower electrode 4 is preferably formed by a sputtering method. Specifically, the lower electrode 4 is formed by sputtering using the above-described conductive material as a target.

  Next, the dielectric thin film 5 is formed on the lower electrode 4 of the laminated body in which the lower electrode is formed, and the laminated body in which the dielectric thin film is formed is manufactured. In this embodiment, as a method of forming the dielectric thin film 5, BST is formed by forming a film by a sputtering method.

In the sputtering method, the stacked body in which the lower electrode is formed is heated, and preferably an oxide represented by (Ba _x Sr _(1-x) ) _a TiO ₃ under reduced pressure in an oxidizing gas atmosphere, for example, BST The target is used and sputtering is performed.

In this embodiment, the formation of the dielectric thin film 5 on the lower electrode 4 is performed by the sputtering method. Therefore, a perovskite structure (Ba _x) having excellent composition controllability at a high speed on a large-area substrate. A dielectric thin film of Sr _(1-x) ) _a TiO ₃ can be grown.

  The substrate heating temperature when forming a film by the sputtering method is preferably 400 to 800 ° C, more preferably 450 to 750 ° C. If the heating temperature is too low, the density and uniformity of the dielectric thin film to be formed tend to decrease, and if it is too high, crystal growth tends to occur non-uniformly.

  The film formation rate is preferably 1 to 10 nm / min, and more preferably 2 to 8 nm / min. The deposition rate can be controlled by the input power and deposition pressure, etc. If the deposition rate is too fast, the leakage current density tends to increase. If it is too slow, the production time becomes longer and the production efficiency decreases. Tend to.

As other conditions for forming a film by sputtering, the film forming pressure is preferably 0.1 to 10 Pa, more preferably 0.3 to 5 Pa, and the input power is 0.5 to 5 W / cm. It is preferable that it is ² , More preferably, it is 1.0-5 W / cm < ² >.

  Sputtering is preferably performed in an oxidizing gas atmosphere, and the oxidizing gas is preferably a gas in which argon gas and oxygen gas are mixed. In the oxidizing gas, the oxygen gas ratio is preferably more than 0% by volume and 50% by volume or less, and more preferably 10% by volume or more and 35% by volume or less. When sputtering is performed in an oxidizing gas atmosphere in this manner, growth of an oxide, for example, BST, occurs in an oxidizing atmosphere, so that oxygen vacancies from the crystal structure of the oxide can be effectively prevented.

When the dielectric thin film 5 containing the oxide is formed by a sputtering method, a BST target to be used has a desired composition (Ba _x Sr _(1-x) ) _a TiO ₃ target or BaTiO ₃ in advance. A target in which components are separated into a target and a SrTiO ₃ target can be used. When using a target in which components are separated into a BaTiO ₃ target and a SrTiO ₃ target, it is preferable to sputter both targets at the same time, and it is preferable to adjust the ratio of both targets so as to obtain a desired composition.

  In the present embodiment, it is preferable that after the dielectric thin film 5 is formed by the sputtering method, the laminated body on which the dielectric thin film is formed is annealed in an oxidizing gas atmosphere. By performing the annealing process, the oxide in the dielectric thin film formed by sputtering, for example, BST grows and the crystallization progresses in the substrate surface direction, so that the relative dielectric constant can be improved. In the present embodiment, the annealing treatment is preferably performed in an oxidizing atmosphere, and by performing the annealing treatment in the oxidizing atmosphere as described above, oxygen from the crystal structure of the oxide is obtained. Defects can be effectively prevented.

  The annealing temperature is not particularly limited as long as it is higher than the temperature at which sputtering is performed, but is preferably 600 to 1000 ° C, more preferably 800 to 1000 ° C. The temperature holding time when annealing is preferably 10 to 120 minutes, and more preferably 30 to 60 minutes.

Next, an upper electrode layer is formed on the dielectric thin film 5 of the laminate on which the dielectric thin film is formed. In the present embodiment, the upper electrode 6 is preferably formed by sputtering using the above-described metal or alloy, conductive semiconductor, or metal oxide conductor as a target, similarly to the lower electrode. In the present embodiment, as shown in FIG. 1, the upper electrode 6 is formed on the entire upper surface of the dielectric thin film 5.
Thus, the thin film dielectric element 1 of this embodiment is manufactured.

  The present invention is not limited to the above-described embodiment, and can be variously modified within the scope of the present invention.

  For example, in the above-described embodiment, the thin-film dielectric element 1 shown in FIG. 1 is illustrated as the thin-film dielectric element according to the present invention. However, the thin-film dielectric element according to the present invention is not limited to the above-described form. Any material having a dielectric thin film can be used. Specific examples of the thin film dielectric element described above include a thin film capacitor.

  In the embodiment described above, the upper electrode 6 is formed on the entire upper surface of the dielectric thin film 5 as shown in FIG. 1, but is formed on a part of the upper surface of the dielectric thin film 5a as shown in FIG. You may do it. As a method for forming the upper electrode in a pattern on the upper surface of the dielectric thin film 5a as shown in FIG. 2, for example, a method using a shielding mask can be cited. As a method of using a shielding mask, a method of patterning using a movable metal mask, a method of forming a mask with an etching resist, and patterning by etching can be used.

  In the above-described embodiment, the thin film dielectric element in which the dielectric thin film is formed as a single layer is exemplified. However, a plurality of dielectric thin films and internal electrode thin films can be alternately stacked to form a multilayer structure. . A thin film dielectric element having a multilayer structure is formed by forming a lower electrode on a substrate, laminating a plurality of dielectric thin films and internal electrode thin films alternately on the lower electrode, and forming an upper electrode thereon. Consists of. The internal electrode thin film can be made of the same material as the above-described upper electrode and lower electrode, and the thickness may be the same.

  In the above-described embodiment, the thin film dielectric element is illustrated as a single element. However, a thin film dielectric element necessary for an integrated semiconductor circuit is formed directly on a semiconductor substrate and mounted on the substrate. Is also possible.

  Hereinafter, although this invention is demonstrated based on a more detailed Example, this invention is not limited to these Examples.

First, a silicon single crystal substrate was prepared as a substrate, the silicon single crystal substrate was thermally oxidized, and a silicon oxide film (SiO ₂ ) was formed on the surface of the silicon single crystal substrate.

  Next, a platinum lower electrode was formed on the silicon single crystal substrate subjected to the thermal oxidation treatment. The platinum lower electrode was formed by sputtering using platinum (Pt) as a target. It was 200 nm when the thickness of the formed platinum lower electrode was measured by SEM observation.

Next, a dielectric thin film was formed by sputtering using a BST target as a target on the lower electrode of the laminate in which the lower electrode was formed as described above. The composition of the BST target at the time of sputtering was adjusted so that x and a in the formula had the composition shown in Table 1 in the composition formula (Ba _x Sr _(1-x) ) _a TiO ₃ . As sputtering conditions, the heating temperature was 550 ° C., the input power was 1.3 to 1.8 W / cm ² , the atmosphere was in a volume ratio of Ar: O ₂ = 9: 1 or 3: 1, and the film formation pressure was set to 0.00. The film formation time was set to 3 to 4.0 Pa and 20 to 30 minutes. The thickness of the dielectric thin film of each sample was measured by SEM observation. Table 1 shows the film thickness of each sample. The composition ratio of the formed dielectric thin film was analyzed by fluorescent X-ray analysis.

  Next, the laminated body on which the dielectric thin film was formed was annealed. The annealing conditions were an oxygen stream, a holding temperature of 900 ° C., and a temperature holding time of 30 minutes.

  Finally, the platinum upper electrode was formed on the dielectric thin film of the laminated body subjected to the annealing treatment as described above, thereby obtaining thin film capacitor samples 1 to 9 shown in FIG. The platinum upper electrode was formed by sputtering using platinum (Pt) as a target, and the pattern was formed by a method using a metal mask. It was 200 nm when the thickness of the formed platinum lower electrode was measured by SEM observation. In addition, each capacitor sample has a plurality of upper electrodes in a range of 10 × 10 mm to form a plurality of thin film capacitor samples, and the relative permittivity and leakage current density of each sample are measured, and the average value of the measurement results Evaluation was performed by asking.

The relative permittivity and leakage current density of the thin film capacitor sample were measured. The relative dielectric constant (no unit) is the capacitance measured for a thin film capacitor sample using a digital LCR meter (YHP 4194A) at room temperature (25 ° C.) and measurement frequency 1 kHz (AC 1 Vrms). It was calculated from the electrode area and film thickness of the thin film capacitor sample. The leakage current density (unit: A / cm ² ) was measured under the condition of applied electric field strength of 100 kV / cm. Table 1 shows the measurement results of the relative dielectric constant and leakage current density of each sample.

As shown in Table 1, in the composition formula (Ba _x Sr _(1-x) ) _a TiO ₃ , the value of a increases in samples 1 to 5 in which the value of x is 0.71 to 0.73. It was confirmed that the relative dielectric constant increased according to This is also apparent from FIG. 3 in which the relationship between the value of a and the relative dielectric constant is graphed for Samples 1 to 5. Further, Sample 1 of the comparative example in which a = 0.96 has a low relative dielectric constant of less than 300. From this result, it was confirmed that a> 0.96 is desirable in order to increase the relative dielectric constant.

Regarding the leakage current density, Samples 1 to 4 having a value of a of 1.00 or less had a low value of 2.0 × 10 ⁻⁷ A / cm ² or less. On the other hand, the comparative sample 5 having a value of 1.03 has a large leakage current density of 4.5 × 10 ⁻⁶ A / cm ^2, which is about 100 times the leakage current density of sample 3. . From this result, it was confirmed that a ≦ 1.00 is desirable in order to keep the leakage current density low.

From the measurement results of the relative dielectric constant and the leakage current density for Samples 1 to 5, in the composition formula (Ba _x Sr _(1-x) ) _a TiO ₃ , the value of x is 0.5 <x ≦ 1.0. In a composition having more barium than strontium, the value of a is desirably 0.96 <a ≦ 1.00, and preferably 0.96 <a <1.00.

  Moreover, the samples 6 and 7 of the comparative example which set x <= 0.5 are respectively a = 1.00 and a = 1.07, Compared with the samples 2-4 of the Example of this invention, The relative dielectric constant was low, and the leakage current density was high. That is, when x ≦ 0.5, which is outside the scope of the present invention, it is impossible to achieve both a high relative dielectric constant and a low leakage current density regardless of the value of a. Furthermore, although x = 1.0, the sample 8 of the comparative example in which a = 0.96 has a lower relative dielectric constant than the samples 2 to 4 of the example of the present invention. On the other hand, sample 9 of the example in which x = 1.0 and a = 0.98 had a high relative dielectric constant as in samples 2 to 4 of the example of the present invention. That is, when x = 1.0, which is within the scope of the present invention, only a high relative dielectric constant and a low leakage current density can be achieved only when the value of a is 0.96 <a. did it. From this result, in order to achieve a high dielectric constant and a low leakage current density, x is set to 0.5 <x ≦ 1.0 and 0.96 <a ≦ 1.00, that is, the composition of BST is It was confirmed that it is desirable to have a composition with more barium than strontium.

FIG. 1 is a cross-sectional view of a thin film dielectric device according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of a thin film dielectric device according to an embodiment of the present invention. FIG. 3 is a graph showing the relationship between the value of a in the composition formula (Ba _x Sr _(1-x) ) _a TiO ₃ and the relative dielectric constant. FIG. 4 is a graph showing the relationship between the value of a in the composition formula (Ba _x Sr _(1-x) ) _a TiO ₃ and the leakage current density.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Thin film dielectric element 2 ... Substrate 3 ... Insulating film 4 ... Lower electrode 5 ... Dielectric thin film 6 ... Upper electrode 1a ... Thin film dielectric element 2a ... Silicon substrate 3a ... Silicon oxide film 4a ... Platinum lower electrode 5a ... Dielectric Thin film 6a ... Platinum top electrode

Claims (6)

A dielectric thin film containing an oxide whose composition formula is represented by (Ba _x Sr _(1-x) ) _a TiO ₃ ,
Symbols x and a indicating the composition ratio are
0.5 < x <1.0 ,
0.96 < a <1.00 ,
Thickness Ri der less than 500nm,
An oxidizing gas atmosphere, the dielectric thin film characterized Rukoto produced by annealing at 800 to 1000 ° C.. ^2. The dielectric thin film according to claim 1, wherein the leakage current density is 1 × 10 ⁻⁶ A / cm ² or less when the relative dielectric constant is 450 or more and the applied electric field strength is 100 kV / cm. 3. The dielectric thin film according to claim 1, wherein a symbol x indicating the composition ratio is 0.6 ≦ x ≦ 0.9. A thin film dielectric element in which a lower electrode, a dielectric thin film, and an upper electrode are sequentially formed on a substrate,
A thin film dielectric element, wherein the dielectric thin film is the dielectric thin film according to claim 1. A thin film dielectric element in which a plurality of dielectric thin films and internal electrode thin films are alternately laminated on a substrate,
A thin film dielectric element, wherein the dielectric thin film is the dielectric thin film according to claim 1.   A method for manufacturing a thin film dielectric element, comprising: forming the dielectric thin film according to claim 1 on a conductive electrode; and annealing the dielectric thin film in an oxidizing gas atmosphere.

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