JP2010278346A - Method of manufacturing thin film capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a thin film capacitor for achieving the manufacturing of a thin film capacitor with a dielectric thin film having a columnar structure which is large in capacity, and which is high in an insulating resistance value and its reliability at low costs. <P>SOLUTION: The method of manufacturing the thin film capacitor includes: a lamination step of carrying out the temporary burning of the coating film of metallic solution by at least one time on an electrode, and for laminating one or more precursor layers on the electrode; a primary burning step of primarily burning one or more precursor layers in vacuum, and for forming a dielectric layer on the electrode; and a thin film formation step of alternately carrying out the lamination step and the primary burning step at least two times, and for forming a dielectric thin film on the electrode. Metallic solution contains elements A (at least any of Ba, Sr, Ca or Pb) and elements B (at least any of Ti, Zr, Hf or Sn), and the rate M<SB>A</SB>/M<SB>B</SB>of the total M<SB>A</SB>of the number of mols of the elements A to the total M<SB>B</SB>of the number of mols of the elements B is set to less than 1, and the mass per unit area of one dielectric layer is set to 10 to 50 μg/cm<SP>2</SP>. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a thin film capacitor.

  In recent years, along with the multifunction and miniaturization of electronic devices and electronic circuit boards, miniaturization of capacitors mounted thereon has been required. Conventionally, as a small capacitor, a multilayer ceramic capacitor having a very small size such as 0603 (0.6 × 0.3 mm) size or 0402 (0.4 × 0.2 mm) size has been developed.

  Furthermore, in order to improve the function as an electronic circuit board, studies for embedding passive components in the board have recently been activated. In the production of these electronic circuit boards, when embedding conventional monolithic ceramic capacitors in the board, cracks occur in the capacitors due to the stress generated during the embedding process due to the brittleness caused by the capacitor thickness and ceramic properties. And there is a problem that the embedded portion of the substrate is deformed. These problems have been difficult to solve even when a very small multilayer ceramic capacitor is used. Therefore, a low-profile capacitor having a thickness smaller than that of the multilayer ceramic capacitor is desired as a capacitor for embedding in a substrate. Conventionally, as a low-profile capacitor, a thin film capacitor including a dielectric thin film and electrodes facing each other with the dielectric thin film interposed therebetween is known (see Patent Documents 1 and 2 below).

Japanese Patent Laid-Open No. 11-177051 Japanese Patent Laid-Open No. 5-342912

  On the other hand, in the above thin film capacitor, it is required to increase the capacity as in the conventional multilayer ceramic capacitor. Methods for increasing the capacity of thin film capacitors include reducing the dielectric thickness, increasing the effective area of the capacitor, further optimizing the dielectric composition, and controlling the microstructure of the dielectric thin film. Thus, there is a method for improving the denseness of the film.

As a method for optimizing the composition of the dielectric thin film, a method of selecting BaTiO ₃ having a relatively high relative dielectric constant among dielectric ceramic compositions is generally employed.

  As a method for controlling the fine structure of the dielectric thin film, there is a technique of epitaxially growing the crystal of the dielectric thin film, orienting it, or growing it regularly in a certain direction without orientation. For example, Patent Document 1 discloses that a dielectric thin film having a multilayer structure in which a columnar structure (columnar crystal structure) of a perovskite oxide and a granular structure are stacked is formed on a substrate by a CVD method. A method for increasing the relative permittivity of is disclosed. However, the method disclosed in Patent Document 1 requires an expensive CVD apparatus for forming the dielectric thin film, which raises a problem that the manufacturing cost of the thin film capacitor increases. In the method of Patent Document 1, the substrate is heated at 550 ° C. when the dielectric thin film is formed by the CVD method. Therefore, when the substrate is a base metal, the substrate may be oxidized. Furthermore, in the method of Patent Document 1, it may be difficult to control the composition of the dielectric thin film due to various factors such as the atmosphere during CVD, the state of the raw material, and the substrate temperature.

  As another method for controlling the fine structure of the dielectric thin film, Patent Document 2 discloses a method of forming a dielectric thin film having crystal orientation on a single crystal substrate by using a sol-gel method. However, since the method of Patent Document 2 requires an expensive single crystal substrate such as sapphire or MgO, there is a problem that the manufacturing cost of the thin film capacitor is increased.

  As described above, when manufacturing a thin film capacitor having a columnar structure and a dielectric thin film having a high relative dielectric constant, the manufacturing cost is high and it is difficult to control the composition of the dielectric thin film. It was a problem. Therefore, conventionally, it has been difficult to control the microstructure and composition of the dielectric thin film using a low-cost method, increase the relative dielectric constant of the dielectric thin film, and increase the capacity of the thin film capacitor.

  Thin film capacitors are required not only to have the same capacitance as conventional multilayer ceramic capacitors, but also to have insulation resistance values and reliability as capacitors. Here, “reliability” as a capacitor means a characteristic in which an insulation resistance value is not easily lowered when a voltage is continuously applied to a thin film capacitor in a high temperature and high humidity environment. However, the thinner the thin film capacitor, the easier it is for the insulation resistance value to decrease and the reliability as the capacitor to decrease.

  Accordingly, the present invention has been made in view of the above problems, and includes a dielectric thin film having a columnar structure, a thin film having a larger capacity, a higher insulation resistance value, and a higher reliability as a capacitor. It is an object of the present invention to provide a method for manufacturing a thin film capacitor that makes it possible to form a capacitor at low cost.

In order to achieve the above object, a method of manufacturing a thin film capacitor according to the present invention includes stacking one or more precursor layers on an electrode by performing temporary firing of a coating film formed from a metal solution once or more on the electrode. Laminating step, one or more precursor layers laminated on the electrode are main-fired in a vacuum atmosphere, and a main-firing step of forming a single dielectric layer on the electrode, a laminating step and a main-firing step. A thin film forming step of forming a dielectric thin film on the electrode by laminating a plurality of dielectric layers on the electrode alternately and twice or more, and the metal solution contains Ba, Sr, Ca and Pb. and at least one element a selected from the group consisting of, Ti, Zr, wherein the at least one element B selected from the group consisting of Hf and Sn, moles of element a to the total M _B of the number of moles of element B The ratio of the total number M _A M _A / A M _B was adjusted to less than 1, to adjust the further mass per unit area of the dielectric layer formed in a single main baking step to 10-50 / cm ^2. In the present invention, “unit area of the dielectric layer” means a unit area of the dielectric layer in a plane perpendicular to the stacking direction of the electrode and the dielectric layer.

  In the present invention, a thin film capacitor having a dielectric thin film having a columnar structure and having a larger capacity, higher insulation resistance value, and higher reliability as a capacitor can be formed at low cost. .

In the said invention, it is preferable that a metal solution further contains Mn. Thereby, it becomes easy to improve the insulation resistance value and reliability of the dielectric thin film. The content of Mn in the metal _solution, to the A y BO ₃ dielectric 100 moles (where _{y = M A / M B)} , is preferably 0.05 to 0.45 mol.

  According to the present invention, a thin film including a dielectric thin film having a columnar structure and capable of forming a thin film capacitor having a larger capacity, a higher insulation resistance value, and a higher reliability as a capacitor at a low cost. It is possible to provide a method for manufacturing a capacitor.

It is a schematic diagram which shows a part of manufacturing method of the thin film capacitor which concerns on 1st embodiment of this invention. It is a schematic diagram which shows a part of manufacturing method of the thin film capacitor which concerns on 1st embodiment of this invention. It is a schematic sectional drawing of the thin film capacitor which concerns on 1st embodiment of this invention. It is a schematic diagram which shows a part of manufacturing method of the thin film capacitor which concerns on 2nd embodiment of this invention. It is a schematic sectional drawing of the thin film capacitor which concerns on 2nd embodiment of this invention.

  Hereinafter, preferred embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments. In addition, the same code | symbol is attached | subjected about the same or equivalent element. In addition, although the positional relationship between the top, bottom, left and right is as shown in the drawing, the ratio of dimensions is not limited to that shown in the drawing. Further, when the description overlaps, the description is omitted. Note that the number of dielectric layers included in the thin film capacitor described later is not limited to one or two layers, and three or more dielectric layers may be stacked in the thin film capacitor.

[First embodiment]
(Thin film capacitor manufacturing method)
The manufacturing method of the thin film capacitor according to the first embodiment includes a stacking step of stacking two precursor layers on an electrode by performing preliminary firing of a coating film formed from a metal solution twice on the electrode, And a main firing step in which the two precursor layers stacked on the substrate are fired in a vacuum atmosphere to form a single dielectric layer on the electrode. That is, in the first embodiment, the dielectric layer is formed on the base electrode using the chemical solution method. In the first embodiment, in the thin film formation step, the dielectric layer having the columnar structure is formed on the electrode by alternately laminating the main layer and the main baking step twice to laminate the two dielectric layers. Form. Next, an upper electrode is formed on the dielectric thin film to obtain a thin film capacitor. Below, each process is demonstrated using FIG. 1, FIG. 1 and 2 are schematic cross-sectional views in the stacking direction of an electrode, a coating film, a precursor layer, a dielectric layer, or a dielectric thin film.

  In the thin film formation step of the first embodiment, the following first lamination step, first main baking step, second lamination step, and second main baking step are performed.

<First lamination process>
In the first lamination step, first, the base electrode 6 is prepared. If necessary, the surface of the base electrode 6 may be polished by a method such as CMP (Chemical Mechanical Polishing), electrolytic polishing, or buffing.

  The base electrode 6 may be a base metal or a noble metal, but preferably contains Ni as a main component. Ni is preferable in that it is easy to process by CMP or the like and is cheaper than noble metals. The purity of Ni constituting the base electrode 6 is preferably as high as possible, and is preferably 99.99% by weight or more. Note that the base electrode 6 may contain a small amount of impurities as long as the effects of the present invention are not impaired.

The base electrode 6 may be a metal foil or a metal thin film formed on a substrate such as Si, glass, or ceramic. When the base electrode 6 is a metal foil, the thickness of the base electrode 6 is preferably 5 to 100 μm, and more preferably 20 to 70 μm. When the thickness of the base electrode 6 is too thin, it tends to be difficult to hand link the base electrode 6 when manufacturing the thin film capacitor. When the base electrode 6 is a metal thin film formed on a substrate, the thickness of the base electrode 6 is preferably 50 nm or more. In addition, before forming a metal thin film on a board | substrate, in order to improve the adhesiveness of a board | substrate and a metal thin film, you may form an adhesion layer on a board | substrate. The area of the base electrode 6 is, for example, about 100 × 100 mm ² .

  As shown in FIG. 1A, a metal solution is applied to the entire surface of the base electrode 6 to form a first coating film 20a. The metal solution may be applied by spin coating. What is necessary is just to adjust the thickness of the 1st coating film 20a with the rotation rate of spin coating, application | coating time, or each content rate of the following elements A and B in a metal solution.

In the first embodiment, the metal solution includes at least one element A selected from the group consisting of Ba, Sr, Ca and Pb, and at least one element B selected from the group consisting of Ti, Zr, Hf and Sn, including. Further, in the first embodiment, adjusting the ratio M _{A /} M _B of the total M _A mole number of the element A to the total M _B of the number of moles of element B to less than 1. As a result, the finally obtained dielectric thin film can be composed of a perovskite complex oxide having a composition represented by the following chemical formula (1).

A _y BO ₃ (1)
In the above chemical formula (1), A represents at least one element selected from the group consisting of Ba, Sr, Ca and Pb, B represents at least one selected from the group consisting of Ti, Zr, Hf and Sn, y <1. That is, in the first embodiment, M _A / M _B = y <1.

If M _A / _{M B} is 1 or more, and y ≧ 1 in the above formula (1). When y ≧ 1, the reliability of the insulation resistance of the dielectric thin film under a high temperature and high humidity load environment is lowered. In the first embodiment, by adjusting the M A _/ M _B less than 1, by a y <1, as compared with the case where M A _/ M _B is one or more, insulation of a high-temperature and high-humidity load environment It becomes possible to improve the reliability of resistance. In the first embodiment, it is preferable to adjust M _A / M _B to 0.97 or more. When M _A / M _B is less than 0.97, y <0.97 in the above chemical formula (1). When y <0.97, the insulation resistance value of the dielectric thin film and its reliability tend to be lower than when 0.97 ≦ y. In the first embodiment, the ratio _M A / _{M B} is adjusted to 0.97 or higher, by a 0.97 ≦ y, it is possible to suppress such a tendency.

In the first embodiment, it is preferable that the metal solution further contains Mn. Thereby, Mn can be contained in the dielectric thin film finally obtained. When the dielectric thin film contains Mn, it becomes easier to improve the insulation resistance value and the reliability of the dielectric thin film than when the dielectric thin film does not contain Mn. The content of Mn in the metal _solution, with respect to A y BO ₃ dielectric 100 moles (where _{y = M A / M B)} , preferably adjusted to 0.05 mol to 0.45 mol . When the Mn content in the metal solution is greater than 0.45 mol, the reliability of the insulation resistance of the dielectric thin film in a high-temperature and high-humidity load environment is higher than when the Mn content is 0.45 mol or less. Tends to decrease. In the first embodiment, such a tendency can be suppressed by adjusting the Mn content to 0.45 mol or less.

  As a specific example of the metal solution, for example, a liquid obtained by dissolving the organic acid salts of the elements A and B in an organic solvent such as alcohol may be used. Examples of the organic acid salt include octylate, neodecanoate, stearate, or naphthenate. If necessary, an organic acid salt of Mn may be added to the metal solution.

  By temporarily firing the first coating film 20a formed on the base electrode 6, the organic components in the first coating film 20a are thermally decomposed, and the elements A and B in the first coating film 20a are oxidized. As a result, the first precursor layer 20b is formed on the base electrode 6 as shown in FIG.

In the first embodiment, it is preferable that the first coating film 20a is temporarily fired in an oxidizing atmosphere such as air. Thus, in the single firing step described later, the generation of crystals of A _y BO ₃ having a columnar structure is promoted. In the first embodiment, the first coating film 20a is preferably calcined at 340 to 600 ° C, more preferably calcined at 400 to 480 ° C, and particularly preferably calcined at 400 to 440 ° C. preferable. When the pre-baking temperature is too low, a part of the organic component in the first coating film 20a tends to remain in the first precursor layer 20a without being thermally decomposed. When the main firing step is performed on the first precursor layer 20a in which a large amount of organic components remain, the obtained dielectric layer becomes porous, and the density of the dielectric layer is lowered. As a result, the effect of the present invention to improve the capacity of the thin film capacitor is reduced. If the pre-baking temperature is too high, the base electrode 6 tends to be oxidized. Although the time of temporary baking should just be adjusted suitably according to the thickness of the 1st coating film 20a, an area, etc., what is necessary is just to be about 5 to 30 minutes.

  After the formation of the first precursor layer 20b, as shown in FIG. 1C, a metal solution is applied to the entire surface of the first precursor layer 20b to form a second coating film 22a. Next, as shown in FIG. 1 (D), the second precursor 22a formed on the first precursor layer 20b is pre-fired by the same method as that for the first coat 20a. Layer 22b is formed on first precursor layer 20b.

  As described above, in the first laminating step, the first precursor layer 20b and the second precursor layer 22b are placed on the base electrode 6 by performing preliminary firing of the coating film formed from the metal solution twice on the base electrode. Laminate to.

<First main firing step>
In the first main baking step, the first precursor layer 20b and the second precursor layer 22b laminated on the base electrode 6 are main-fired. By this firing, crystal growth and sintering of A _y BO ₃ having a columnar structure proceeds in the first precursor layer 20b and the second precursor layer 22b, and the first precursor layer 20b and the second precursor layer 22b. Are integrated. As a result, the first dielectric layer 10 shown in FIG. 1 (E) is formed on the base electrode 6.

In the first embodiment, the average mass per unit area of the first dielectric layer 10 formed in the first main firing step is adjusted to 10 to 50 μg / cm ² . When the average mass per unit area of the first dielectric layer 10 is less than 10 [mu] g / cm ^2, as compared with the case where 10 [mu] g / cm ² or more, lamination step required to obtain a dielectric thin film of desired thickness In addition, since the number of repetitions of the main firing process increases, it is difficult to manufacture a dielectric thin film having a columnar structure at a low cost.

In addition, when the average mass per unit area of the first dielectric layer 10 is less than 10 μg / cm ² , even if a columnar structure crystal is formed on the base electrode 6, a part of the base electrode 6 may be on the island. As a result, crystals are formed and the first dielectric layer 10 becomes thick, and crystals are difficult to form in other portions, and the first dielectric layer 10 tends to be thin. Therefore, the surface shape of the first dielectric layer 10 is uneven. When a dielectric thin film is formed by laminating another dielectric layer on the first dielectric layer 10 having an uneven surface in the thin film forming step described later, the dielectric on the side opposite to the first dielectric layer 10 On the surface of the thin film, the uneven shape caused by the surface of the first dielectric layer 10 remains without being completely eliminated. This is because, in the thin film forming process, crystal growth proceeds from the convex portion (crystal on the island) on the surface of the first dielectric layer 10, so that the surface of the finally obtained dielectric thin film is also uneven. is there. For this reason, the surface roughness of the dielectric thin film is increased as compared with the case where there is no island-like crystal on the base electrode 6. Then, the thickness of the dielectric thin film becomes thinner in the recesses on the surface of the dielectric thin film than in other places, and the insulation resistance value is lower than in other places. For these reasons, when the average mass per unit area of the first dielectric layer 10 is less than 10 [mu] g / cm ^2, as compared with the case where 10 [mu] g / cm ² or more, the insulation resistance of the dielectric thin film is decreased .

When the average mass per unit area of the first dielectric layer 10 is larger than 50 μg / cm ² , a dielectric thin film having a granular structure is formed instead of a columnar structure. The effect of the present invention to improve the property cannot be obtained.

On the other hand, in the first embodiment, the above problems are prevented by adjusting the average mass per unit area of the first dielectric layer 10 and the second dielectric layer 12 described later to 10 to 50 μg / cm ^2. be able to. In the first embodiment, it is possible to form a dielectric thin film having a dense columnar structure as compared with the case where the average mass per unit area of each dielectric layer is less than 10 μg / cm ² . In addition, when forming a dielectric thin film with a thickness of 100 nm or more, it is preferable to adjust the average mass per unit area of the first dielectric layer 10 to 20 μg / cm ² or more.

  The mass per unit area of the first dielectric layer 10 may be measured by fluorescent X-ray analysis (XRF). Further, the mass per unit area of the first dielectric layer 10 is the respective contents of the elements A, B and Mn in the metal solution and the thicknesses of the first coating film 20a and the second coating film 22a formed from the metal solution. It may be adjusted depending on the situation.

In the first embodiment, the first precursor layer 20a and the second precursor layer 22b are baked in a vacuum atmosphere. Thereby, it becomes possible to grow a crystal of A _y BO ₃ having a columnar structure while suppressing oxidation of the base electrode 6. The vacuum atmosphere is, for example, an atmosphere having a total pressure of about 1.0 × 10 ^{−3 to} 1.0 × 10 ¹ Pa and an oxygen partial pressure of about 2.0 × 10 ⁻⁴ to 2.0 Pa. is there. The firing time may be about 5 minutes to 2 hours. If the first precursor layer 20a and the second precursor layer 22b are baked in a reducing atmosphere, the fine structure of the obtained dielectric thin film becomes a granular structure, and the baking is performed in a vacuum atmosphere. In comparison, the capacitance of the thin film capacitor is reduced, and the insulation resistance value of the thin film capacitor and its reliability are also reduced. In 1st embodiment, such a malfunction can be prevented by performing this baking in a vacuum atmosphere. Note that the reducing atmosphere means, for example, an atmosphere in which the oxygen partial pressure is lower than 2.0 × 10 ⁻¹⁰ Pa and the partial pressure of a reducing gas such as H ₂ is high.

The firing temperature is preferably 600 to 1000 ° C. When the main baking temperature is less than 600 ° C., the crystal growth and sintering of A _y BO ₃ become insufficient, and the effect of the present invention to improve the capacity, the insulation resistance value, and the reliability as a capacitor tends to be reduced. There is. On the other hand, when the temperature of the main baking is higher than 1000 ° C., a part of the base electrode 6 such as Ni evaporates or the base electrode 6 is deformed and its surface becomes uneven. And the effect of this invention of improving the reliability as a capacitor | condenser tends to become small. These tendencies can be suppressed by setting the main baking temperature to 600 to 1000 ° C.

<Second lamination step>
In the second laminating step, as shown in FIG. 2A, a metal solution is applied to the entire surface of the first dielectric layer 10 to form a third coating film 30a by the same method as in the first laminating step. . Next, the third coating film 30a formed on the first dielectric layer 10 is temporarily fired by the same method as in the first lamination step. As a result, the third precursor layer 30b is formed on the first dielectric layer 10 as shown in FIG. And as shown in FIG.2 (C), a metal solution is apply | coated to the whole surface of the 3rd precursor layer 30b by the method similar to a 1st lamination process, and the 4th coating film 32a is formed. Next, the fourth coating film 32a formed on the third precursor layer 30b is temporarily fired by the same method as in the first lamination step. Thereby, as shown in FIG. 2D, the fourth precursor layer 32b is formed on the third precursor layer 30b.

<Second main firing step>
In the second main baking step, the third precursor layer 30a and the second precursor layer 32b laminated on the first dielectric layer 10 are main-fired by the same method as in the first main baking step. By this firing, crystal growth and sintering of A _y BO ₃ having a columnar structure proceeds in the third precursor layer 30b and the second precursor layer 22b, and the third precursor layer 30b and the second precursor layer 22b. Are integrated. As a result, as shown in FIG. 2E, the second dielectric layer 12 is formed on the first dielectric layer 10, and the dielectric thin film 4 including the first dielectric layer 10 and the second dielectric layer 12 is provided. Is obtained. Then, by forming the upper electrode 8 on the dielectric thin film 4, the thin film capacitor 2a is completed in FIG. The upper electrode 8 may be formed by sputtering or the like. A thin film capacitor element for embedding is produced by further patterning the upper electrode from here.

In the first embodiment, for the same reason as the first dielectric layer 10, the mass per unit area of the second dielectric layer 12 formed in the second main firing step is adjusted to 10 to 50 μg / cm ² . The mass per unit area of the second dielectric layer 12 depends on the contents of the elements A, B, and Mn in the metal solution and the thicknesses of the third coating film 30a and the fourth coating film 32a formed from the metal solution. Adjust it.

  The upper electrode 8 may be a base metal, a noble metal, or a compound or alloy of a base metal and a noble metal. As the base metal, Ni or Cu is preferable. Examples of the noble metal include Pt, Rh, Pd, Re, Ir, and Ru. The upper electrode 8 may contain a small amount of impurities as long as the effects of the present invention are not impaired.

  The thickness of the dielectric thin film 4 may be 200 to 1000 nm, for example. The thickness of the dielectric thin film 4 may be adjusted according to the thickness of each dielectric layer. The thickness of each dielectric layer may be adjusted according to the thickness of each precursor layer. What is necessary is just to adjust the thickness of each precursor layer with the thickness of each coating film.

In the first embodiment, a dielectric thin film is formed by forming a coating film using a solution method and alternately performing a lamination process and a main baking process twice. Therefore, in the first manufacturing method, as in the conventional manufacturing method, an expensive apparatus or dielectric required for performing a film forming method such as a plasma CVD method, an electron cyclotron (ECR) plasma CVD method, or a plasma sputtering method. A single crystal substrate for forming the layer is not necessary. Moreover, in the first embodiment, in order to obtain a dielectric thin film having a desired thickness by adjusting the mass per unit area of the first dielectric layer 10 and the second dielectric layer 12 to 10 μg / cm ² or more. It is possible to reduce the number of repetitions of the lamination process and the main baking process required for the process. For the above reasons, in the first embodiment, the thin film capacitor 2a including the dielectric thin film 4 having a dense columnar structure can be manufactured at a low cost as compared with the prior art. Further, according to the first embodiment, it is possible to reduce the thickness of the thin film capacitor 2a without impairing the capacitance, the insulation resistance value, and the reliability thereof.

  In the first embodiment, every time the first, second, third, and fourth coating films are formed, each coating film may be individually temporarily fired and then fired. That is, you may perform this baking process as many times as the number of coating films (4 times).

(Thin film capacitor)
As shown in FIG. 3, the thin film capacitor 2a of the first embodiment includes a dielectric thin film 4 and electrodes (base electrode 6 and upper electrode 8) opposed in parallel with the dielectric thin film 4 interposed therebetween. . The dielectric thin film 4 includes a first dielectric layer 10 and a second dielectric layer 12. FIG. 3 is a cross-sectional view of the thin film capacitor 2 a in the stacking direction of the base electrode 6, the dielectric thin film 4 and the upper electrode 8.

  The dielectric thin film 4 is comprised from the dielectric composition represented by following Chemical formula (1).

A _y BO ₃ (1)
In the above chemical formula (1), A represents at least one element selected from the group consisting of Ba, Sr, Ca and Pb, B represents at least one selected from the group consisting of Ti, Zr, Hf and Sn, y <1. The dielectric thin film 4 may contain Mn as an acceptor.

  The first dielectric layer 10 has a columnar structure. That is, the first dielectric layer 10 includes a plurality of columnar crystals that have crystal grain boundaries 15 extending in the stacking direction and extend in a direction intersecting the base electrode 6 (a direction substantially orthogonal). The average particle diameter of the columnar crystals (diameter in a cross section parallel to the surface of the base electrode 6) is about 30 to 300 nm. In addition, this average particle diameter is calculated by the following code method, for example.

  In the code method, the surface of the object is observed with an optical microscope, a straight line L is arbitrarily drawn on the observation surface, the number N of intersections of the straight line L and the grain boundary is counted, and as shown in the following formula (A), This is a method in which L is divided by N, and the average length l between grain boundaries is calculated and multiplied by a certain statistical numerical value k and l to obtain an average particle diameter D (reference: “Character of ceramics” "Catalization Technology" Japan Ceramics Association, page 7).

D = k × (L / N) (A)
In the above formula (A), L / N = 1.

  In this embodiment, k = 1.7776 is used as the statistical numerical value k.

  Similar to the first dielectric layer 10, the second dielectric layer 12 has a columner structure. In other words, the second dielectric layer 12 has a plurality of columnar crystals which have crystal grain boundaries 17 extending in the stacking direction of the dielectric layers and which extend in a direction intersecting (substantially orthogonal to) the base electrode 6. Consists of. The average grain size of the columnar crystals (diameter in a cross section parallel to the surface of the base electrode 6) is 30 to 300 nm.

  In the first embodiment, since the dielectric thin film 4 is composed of the first dielectric layer 10 and the second dielectric layer 12 having a columnar structure, the dielectric film is more dielectric than the case where each dielectric layer has a granular structure. The relative dielectric constant of the thin body film 4 can be increased, the capacity of the thin film capacitor 2a can be increased, and the insulation resistance value of the dielectric thin film 4 and the reliability as a capacitor can be increased.

  In the first embodiment, as shown in FIG. 3, the columnar crystals constituting the first dielectric layer 10 and the columnar crystals constituting the second dielectric layer 12 are the first dielectric layer 10 and the second dielectric layer. It is preferable that the interface of the body layer 12 is discontinuous. That is, the first dielectric layer 10 and the second dielectric layer 12 are preferably composed of different columnar crystals. Furthermore, the crystal grain boundary 15 of the first dielectric layer 10 and the crystal grain boundary 17 of the second dielectric layer 12 are discontinuous at the interface between the first dielectric layer 10 and the second dielectric layer 12. It is preferable. Thereby, it becomes easy to improve the insulation resistance value of the dielectric thin film 4 and its reliability.

  The thickness of the first dielectric layer 10 is, for example, 10 to 500 nm. The thickness of the second dielectric layer 12 is, for example, 10 to 500 nm.

[Second Embodiment]
Below, description is abbreviate | omitted about the common matter of 1st embodiment and 2nd embodiment, and only those differences are demonstrated.

(Thin film capacitor manufacturing method)
In the first embodiment, two laminated precursor layers are fired at a time to form one dielectric layer. In the second embodiment, one precursor layer is fired to produce one dielectric layer. A body layer is formed.

  That is, the thin film capacitor manufacturing method according to the second embodiment is a lamination process of laminating one precursor layer on the base electrode by performing temporary firing of the coating film formed from the metal solution once on the base electrode. And a main firing step of firing one precursor layer laminated on the base electrode to form one dielectric layer on the base electrode, and alternately performing the lamination step and the main firing step twice. A thin film forming step of laminating the first dielectric layer and the second dielectric layer to form a dielectric thin film on the base electrode. A thin film capacitor is obtained by forming an upper electrode on the dielectric thin film. Hereinafter, each process is demonstrated using FIG.

  In the thin film formation step of the second embodiment, the following first lamination step, first main baking step, second lamination step, and second main baking step are performed.

<First lamination process>
In the first lamination step, as shown in FIG. 4A, a metal solution is applied to the entire surface of the base electrode 6 to form a first coating film 10a. And the 1st precursor layer 10b is formed on the base electrode 6 as shown in FIG.4 (B) by temporarily baking the 1st coating film 10a formed on the base electrode 6. FIG.

<First main firing step>
In the first main baking step, the first precursor layer 10b laminated on the base electrode 6 is main-baked. Thereby, the first dielectric layer 10 c shown in FIG. 4C is formed on the base electrode 6.

<Second lamination step>
As shown in FIG. 4D, a metal solution is applied to the entire surface of the first dielectric layer 10c to form a second coating film 12a. Next, as shown in FIG. 4E, the second precursor layer 12a is formed by temporarily firing the second coating film 12a formed on the first dielectric layer 10c in the same manner as in the first lamination step. 12b is formed on the first dielectric layer 10c.

<Second main firing step>
In the second main firing step, the first dielectric layer 10c laminated by subjecting the second precursor layer 12b laminated on the first dielectric layer 10c to main firing in the same manner as in the first main firing step. And a dielectric thin film 4 c having the second dielectric layer 12 c are formed on the base electrode 6. Then, by forming the upper electrode 8 on the dielectric thin film 4c, the thin film capacitor 2b shown in FIG. 5 is completed. A thin film capacitor element for embedding is produced by further patterning the upper electrode from here.

(Thin film capacitor)
In the thin film capacitor 2b shown in FIG. 5, since the first dielectric layer 10c and the second dielectric layer 12c are integrated by sintering, the dielectric thin film 4c includes the first dielectric layer 10c and the second dielectric layer 10c. It consists of a plurality of columnar crystals in which crystal grain boundaries 15 are continuous in the stacking direction of the body layer 12c.

  Also in the thin film capacitor 2b, the effect of the present invention can be achieved as in the case of the first embodiment.

  The preferred embodiment of the method for manufacturing a thin film capacitor according to the present invention has been described above, but the present invention is not necessarily limited to the above-described embodiment.

  For example, in the laminating process, three or more precursor layers may be laminated on the base electrode, and the laminating process and the main firing process are alternately performed three times or more, and the dielectric is formed from the laminated three or more dielectric layers. A body thin film may be formed. Also in these cases, the effects of the present invention can be achieved. In any case, the thickness of the dielectric thin film 4 can be controlled by appropriately setting the thickness of each dielectric layer or the number of laminated dielectric layers. The thickness of each dielectric layer can be controlled by the thickness of each precursor layer or the number of stacked precursor layers. The thickness of each precursor layer can be controlled by the thickness of each coating film or the content of each organic acid salt in the metal solution.

  The thin film capacitor may be a multilayer thin film capacitor having a plurality of internal electrodes laminated via a plurality of dielectric thin films. When manufacturing such a thin film capacitor, after forming the dielectric thin film on the base electrode, the process of forming the internal electrode on the dielectric thin film and the process of forming the thin film on the internal electrode can be repeated alternately several times. That's fine. By repeating this, a structure in which internal electrodes and dielectric thin films are alternately laminated can be formed. In this stacked structure, when the base electrode is expressed as the first layer electrode, the internal electrodes correspond to the odd layer electrode and the even layer electrode, respectively. Are connected by metal wiring, the electrodes of even layers are similarly connected by metal wiring, and each is taken out as a terminal to complete a capacitor in which a plurality of internal electrodes and dielectric thin films are laminated. I can do it.

  EXAMPLES Hereinafter, although an Example demonstrates this invention still in detail, this invention is not limited to these Examples.

(Sample 2)
An Ni foil whose surface was flattened by CMP was prepared as a base electrode. The thickness of the Ni foil after the surface was flattened was 50 μm. The dimensions of the Ni foil were 100 mm long × 100 mm wide. A butanol solution in which octylates of Ba, Ti and Mn were dissolved was prepared as a metal solution used in the chemical solution method for forming the dielectric thin film. The molar ratio of Ba, Ti, and Mn in the metal solution was adjusted so as to obtain a desired dielectric thin film composition to be described later.

<Lamination process>
In the laminating step, a metal solution was applied to the entire surface of the Ni foil by spin coating to form one coating film. And the precursor layer was formed on Ni foil by pre-baking the coating film in the atmosphere of 400 degreeC, and thermally decomposing the organic compound in a coating film. In the laminating step, each octyl in the metal solution is set so that the mass per unit area of one dielectric layer formed by subjecting the coating film to main firing in the main firing step described later is 10 μg / cm ^2. The concentration of the acid salt and the thickness of the coating film (coating amount of the metal solution) were adjusted.

<Main firing process>
In the main firing step, the precursor layer laminated on the Ni foil is placed in an infrared heating furnace, the pressure inside the furnace is reduced using a vacuum pump, and the pressure in the furnace measured by an ionization vacuum gauge at room temperature is 0.01 Pa. The oxygen partial pressure in the furnace was adjusted to about 0.002 Pa. And the temperature in a furnace was heated up to 900 degreeC, continuing the pressure_reduction | reduced_pressure by a vacuum pump. In this way, the precursor layer laminated on the Ni foil was subjected to main firing in a state where the inside of the furnace was maintained in a vacuum and the temperature in the furnace was maintained at 900 ° C., and the precursor layer was crystallized. As a result, a single dielectric layer was formed on the Ni foil.

<Thin film formation process>
In the thin film forming step, the above-described one laminating step and one main firing step were alternately performed 36 times, thereby laminating 36 dielectric layers on the Ni foil. That is, a cycle composed of one laminating step and one main firing step following the laminating step (hereinafter referred to as “crystallization cycle”) was repeated 36 times. As a result, a dielectric thin film having 36 dielectric layers stacked and having a thickness of 600 nm was formed on the Ni foil. Then, a Cu electrode was formed on the dielectric thin film as the upper electrode, and a thin film capacitor of Sample 2 was obtained. The thickness of the dielectric thin film was measured with an optical film thickness meter. The upper electrode was formed by sputtering using a metal mask. The thickness of the Cu electrode was 1 μm. The shape of the Cu electrode was a circular shape having a diameter of 2 mmφ.

In parallel with the preparation of Sample 2, the average mass per unit area (hereinafter abbreviated as “M / C”) of one dielectric layer formed in one crystallization cycle is calculated from the analysis result by XRF. An experiment to calculate was performed. As a result, it was confirmed that the M / C of each crystallization cycle was controlled to 10 μg / cm ² . As a result of analysis by XRF, it was confirmed that the dielectric thin film composition of Sample 2 contained 0.2 mol of Mn with respect to 100 mol of Ba _0.99 TiO ₃ .

(Sample 1, 3-8)
In the production of each of the thin film capacitors of Samples 1 and 3-8, the crystallization cycle was repeated the number of times shown in Table 1. In the production of each thin film capacitor of Samples 1 and 3-8, the M / C of each crystallization cycle was controlled to the value shown in Table 1 by adjusting the concentration of each octylate in the metal solution. Except for the above items, the thin film capacitors of Samples 1 and 3 to 8 were manufactured under the same conditions as in Sample 2. The composition of each dielectric thin film of Samples 1 and 3-7 was confirmed to contain 0.2 mol of Mn with respect to 100 mol of Ba _0.99 TiO ₃ , as with Sample 2. It was done. The thickness of each dielectric thin film of Samples 1 and 3 to 8 was 600 nm.

(Samples 9 to 14)
In manufacturing the thin film capacitors of Samples 9 to 14, each precursor layer was subjected to main firing in a reducing atmosphere in the main firing step. Note that the reducing atmosphere is an atmosphere made of water vapor and a mixed gas of H ₂ and N ₂ and having an oxygen partial pressure of about 1.0 × 10 ⁻²⁰ Pa. That is, the reducing atmosphere is an atmosphere in which the oxygen partial pressure is lower than that of the vacuum atmosphere in the case of Sample 2 and the Ni foil is difficult to oxidize. Moreover, in preparation of each thin film capacitor of Samples 9 to 14, the crystallization cycle was repeated the number of times shown in Table 2. Furthermore, in the production of each thin film capacitor of Samples 9 to 14, the M / C of each crystallization cycle was controlled to the value shown in Table 2 by adjusting the concentration of each octylate in the metal solution. Except for the above items, the thin film capacitors of Samples 9 to 14 were manufactured under the same conditions as in Sample 2. The composition of each dielectric thin film of Samples 9 to 14 was confirmed to contain 0.2 mol of Mn with respect to 100 mol of Ba _0.99 TiO ₃ as in Sample 2. . The thickness of each dielectric thin film of Samples 9 to 14 was 600 nm.

(Sample 15)
In the production of the thin film capacitor of Sample 15, two precursor layers were laminated on the Ni foil by alternately repeating the formation of the coating film and temporary baking twice in a single lamination step. Then, by repeating this laminating step and the main firing step eight times, eight dielectric layers formed from two precursor layers were laminated in a Ni foil shape. That is, in the production of the thin film capacitor of Sample 15, a crystallization cycle composed of one stacking step and one subsequent main firing step is repeated eight times to obtain a dielectric thin film composed of eight dielectric layers. It formed on Ni foil. The total thickness of the dielectric thin film was 600 nm. In the production of the thin film capacitor of Sample 15, the M / C of each crystallization cycle was controlled to the value shown in Table 3 by adjusting the concentration of each octylate in the metal solution. Except for the above, a thin film capacitor of Sample 15 was fabricated under the same conditions as in Sample 2. The composition of the dielectric thin film of Sample 15 was confirmed to contain 0.2 mol of Mn with respect to 100 mol of Ba _0.99 TiO ₃ , as with Sample 2.

(Samples 16 and 17)
In the production of each thin film capacitor of Samples 16 and 17, the crystallization cycle was repeated the number of times shown in Table 3. In the production of the thin film capacitors of Samples 16 and 17, the M / C of each crystallization cycle was controlled to the value shown in Table 3 by adjusting the concentration of each octylate in the metal solution. Except for the above items, the thin film capacitors of Samples 16 and 17 were manufactured under the same conditions as in Sample 15. The composition of each dielectric thin film of Samples 16 and 17 was also confirmed to be 0.2 mol of Mn with respect to 100 mol of Ba _0.99 TiO ₃ , as with Sample 15. . The thickness of each dielectric thin film of Samples 16 and 17 was 600 nm.

(Samples 18-20)
In making each thin film capacitor of Samples 18-20, the crystallization cycle was repeated the number of times shown in Table 4. In the production of each thin film capacitor of Samples 18 to 20, the M / C of each crystallization cycle was controlled to the value shown in Table 4 by adjusting the concentration of each octylate in the metal solution.

In the production of each thin film capacitor of Samples 4 and 19, the ratio M _Ba / M _Ti of the total number M _Ba of moles of Ba to the total number M _Ti of moles of Ti in the metal solution was adjusted to 0.99. A dielectric thin film having the composition shown below was formed.

In the production of each thin film capacitor of Samples 18 and 20, M _Ba / M _Ti was adjusted to 1, and a dielectric thin film having the composition shown in Table 4 was formed.

  In the production of each of the thin film capacitors of Samples 19 and 20, Mn octylate was not contained in the metal solution.

  Except for the above items, the thin film capacitors of Samples 18 to 20 were manufactured under the same conditions as in Sample 2. The thickness of each dielectric thin film of Samples 18 to 20 was 600 nm.

[Identification of microstructure of dielectric thin film]
Each thin film capacitor of Samples 1 to 20 was cut in the stacking direction, and each cross section was observed with a transmission electron microscope (TEM) to identify the microstructure of the dielectric thin film included in each thin film capacitor. The results are shown in Tables 1-4.

[Measurement of capacitance and insulation resistance]
The capacity | capacitance and insulation resistance value of each thin film capacitor of the samples 1-20 before implementing the high temperature / humidity load test mentioned later were measured. The results are shown in Tables 1-4. In measuring the capacitance, an alternating voltage of 1 kHz was applied to each thin film capacitor installed in a room temperature environment. The effective value of the AC voltage was 1 Vrms. In the measurement of the insulation resistance value, a voltage of DC 4 V was applied to each thin film capacitor installed in a room temperature environment.

[High temperature and high humidity load test]
A high-temperature and high-humidity load test was performed on each thin film capacitor of Samples 1-20. The high temperature and high humidity load test is a test for evaluating deterioration of the insulation resistance value of the thin film capacitor by holding the thin film capacitor in a high temperature and high humidity environment and continuously applying a constant voltage load to the thin film capacitor for a certain period of time. Specifically, the thin film capacitor is held for 100 hours in an atmosphere of 130 ° C. and 85% RH with a DC 3.5 V bias (5.83 V / μm electric field) applied to the dielectric thin film included in each thin film capacitor. did. Each thin film capacitor after 100 hours was installed in a room temperature environment, and the capacity and insulation resistance value of each thin film capacitor after the high temperature and high humidity load test were measured by the above method. The results are shown in Tables 1-4. The higher the insulation resistance value after the high temperature and high humidity load test, the higher the reliability as a capacitor. In Tables 1 to 4, “zE + 0n” (z is an arbitrary positive real number and n is an arbitrary natural number) means “z × 10 ⁿ ”. Further, in the samples described as “short” in Tables 1 to 4, a short circuit occurred during the high-temperature and high-humidity test, which means that the reliability as a capacitor was low.

As shown in Table 1, in producing Sample 1 having an M / C of less than 10 μg / cm ² , a dielectric thin film can be obtained as compared with Samples 2 to 6 having an M / C of 10 to 50 μg / cm ^2. Therefore, the number of crystallization cycles was twice or more, and it was confirmed that the production cost was high.

In Samples 7 and 8 where M / C was larger than 50 μg / cm ^2, it was confirmed that the dielectric thin film had a granular structure and a smaller capacity than Samples 2 to 6. In addition, it was confirmed that samples 7 and 8 have lower reliability as capacitors during the high-temperature and high-humidity load test than samples 2 to 6.

On the other hand, in Samples 2 to 6 where M / C is 10 to 50 μg / cm ² , the dielectric thin film has a columnar structure, and the capacity is about twice that of Samples 7 and 8, compared to Sample 1. It was confirmed that the insulation resistance value was high and the reliability as a capacitor was higher than those of Samples 7 and 8.

As shown in Table 2, in Samples 9 to 14 in which the precursor layer was calcined in a reducing atmosphere, the capacity was small compared to Samples 2 to 6 in Table 1 in which the precursor layer was calcined in a vacuum atmosphere. It was confirmed that the insulation resistance value and the reliability as a capacitor were low. Further, from the results of Table 2, even if M / C is 10 to 50 μg / cm ² , the fine structure of the dielectric thin film becomes a granular structure when the precursor layer is finally fired in a reducing atmosphere. confirmed.

As shown in Table 3, M / C is controlled within a range of 10 to 50 μg / cm ² among samples 15 to 17 in which coating film formation and temporary baking are alternately repeated twice in one laminating process. It was confirmed that the obtained sample 15 had a large capacity, and had a high insulation resistance value and high reliability, similar to the samples 2 to 6 in Table 1. On the other hand, it was confirmed that Samples 16 and 17 having M / C larger than 50 μg / cm ² had a smaller capacity and lower reliability as a capacitor than Sample 15.

As shown in Table 4, not only the M / C is controlled within the range of 10 to 50 μg / cm ² from the comparison between the sample 4 and the sample 18 and the comparison between the sample 19 and the sample 20, but also M _Ba / It was confirmed that the capacitance increased and the insulation resistance value and its reliability were improved only by adjusting M _Ti to less than 1. In addition, it was confirmed that the samples 18 to 20 before the test have a capacity equal to or greater than that of the sample 14.

  From the comparison between sample 4 and sample 19, it was confirmed that the dielectric thin film contains Mn, thereby improving the insulation resistance value and its reliability.

  2a, 2c: thin film capacitor, 4, 4c: dielectric thin film, 6: base electrode, 8: upper electrode, 10, 10c, 12, 12c: dielectric layer, 10a, 12a, 20a, 22a, 30a, 32a ... coating film, 10b, 12b, 20b, 22b, 30b, 32b ... precursor layer.

Claims (2)

A lamination step of laminating one or more precursor layers on the electrode by performing temporary firing of the coating film formed from the metal solution once or more on the electrode;
A main baking step in which one or more of the precursor layers laminated on the electrode are main-fired in a vacuum atmosphere to form a single dielectric layer on the electrode;
A thin film forming step of forming a dielectric thin film on the electrode by laminating a plurality of the dielectric layers on the electrode by alternately performing the laminating step and the main baking step twice or more. ,
The metal solution is
At least one element A selected from the group consisting of Ba, Sr, Ca and Pb;
At least one element B selected from the group consisting of Ti, Zr, Hf and Sn;
Including
Adjust the ratio _M A / _{M B} of the total _{M A} mole number of the element A to the total _{M B} of the number of moles of the element B to less than 1,
Adjusting the mass per unit area of the dielectric layer of one layer formed in one main firing step to 10 to 50 μg / cm ² ;
A method of manufacturing a thin film capacitor element. The metal solution further comprises Mn,
The manufacturing method of the thin film capacitor of Claim 1.

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