JPWO2008133243A1 - BST-based dielectric layer, capacitor layer forming material including the BST-based dielectric layer, capacitor layer constituent member with electrode circuit, and printed wiring board including a built-in capacitor circuit - Google Patents

Abstract

An object of the present invention is to provide a dielectric layer having a small change in capacitance density even when there is a temperature change due to heat generation. In order to achieve this object, in the BST type dielectric layer used for manufacturing the capacitor circuit, the BST type dielectric layer has a composition balance of barium and strontium satisfying the relationship of BaXSr1-XTiO3 (0.8 ≦ X <1). A BST-based dielectric layer having a thickness of 0.3 μm to 0.7 μm is employed. Also provided is a capacitor layer forming material for a printed wiring board having a lower electrode forming layer on one side of the BST-based dielectric layer and an upper electrode forming layer on the other side.

Description

  The invention according to the present application relates to a BST-based dielectric layer, a capacitor layer forming material including the BST-based dielectric layer, a capacitor layer constituent member with an electrode circuit, and a printed wiring board including a built-in capacitor circuit.

  Dielectric layers that can be used to form capacitors are formed in a variety of ways. For example, the chemical vapor phase reaction method (CVD method) disclosed in Patent Document 1, the sputtering vapor deposition method disclosed in Patent Document 2, the sol-gel method disclosed in Patent Document 3, and the like are used.

Examples of the material constituting the dielectric layer include lithium niobate LiNbO ₃ , lithium borate Li ₂ B ₄ O ₇ , PbZrTiO ₃ , BaTiO ₃ , SrTiO ₃ , PbLaZrTiO ₃ , PbCaZrTiO ₃ , LiTaO ₃ , ZnO, An oxide dielectric material such as ₂ O ₅ is used.

  The dielectric layer as described above may be supplied to the market in the state of a capacitor layer forming material in which conductive layers are provided on both surfaces of the dielectric layer, as described in Patent Document 3. In this case, the capacitor layer forming material is used to form a capacitor circuit by processing the conductive layer into a desired shape by etching or the like, and to constitute a built-in capacitor layer of a printed wiring board.

  The printed wiring board is also required to be downsized due to the recent demand for downsizing electronic devices and electrical products. At this time, there is a problem of heat generation from an electronic component or the like mounted on a printed wiring board if an attempt is made to increase the functionality and speed of electronic devices and electrical products simultaneously with downsizing. That is, it is natural that the electronic component is required to have a performance that does not change even if the temperature changes due to heat generation.

Patent Document 4 discloses that a dielectric thin film having a high relative dielectric constant, a small leakage current, a stable physical property and electrical property, and a thin film dielectric such as a thin film capacitor having a high capacity and high reliability. An element and a method for manufacturing the element are disclosed. Specifically, the content of this patent document 5 is expressed by the formula (Ba _x Sr _(1-x) ) _a TiO ₃ (0.5 <x ≦ 1.0, 0.96 <a ≦ 1.00). A dielectric thin film containing an oxide represented by, for example, barium strontium titanate and having a thickness of 500 nm or less, and a step of annealing in an oxidizing gas atmosphere after forming the dielectric thin film on a conductive electrode Is a manufacturing method of a thin film dielectric element including

JP 2001-358303 A JP 07-294862 A JP 2002-539634 Gazette JP 2006-140136 A

  However, as a property of the dielectric layer, there is a case where a change in electric capacity or the like is large due to a change in the atmospheric temperature and lacks in temperature characteristics. The built-in capacitor of the printed wiring board is used to save electric power and ensure operational stability. Therefore, if the capacitance of the built-in capacitor of the printed wiring board changes due to the rise in ambient temperature, not only will the electrical and electronic products not perform as designed, but the power consumption will exceed the guaranteed power consumption. It is not preferable. Accordingly, there has been a demand in the market for improving the temperature characteristics of oxide dielectric layers.

  Accordingly, as a result of intensive studies, the inventors of the present invention have come up with the idea that the BST-based dielectric layer can solve the above-mentioned problems with the contents of the invention described below.

BST-based dielectric layer according to the present invention: The BST-based dielectric layer according to the present invention is a BST-based dielectric layer used for manufacturing a capacitor circuit. The BST-based dielectric layer has a composition balance of barium and strontium as shown in the following chemical formula 2 The thickness is 0.3 μm to 0.7 μm.

Capacitor layer forming material according to the present invention: The capacitor layer forming material according to the present invention comprises a lower electrode forming layer on one side of the BST-based dielectric layer and an upper electrode forming layer on the other side. is there.

  The lower electrode forming layer of the capacitor layer forming material according to the present invention is preferably a nickel layer or a nickel alloy layer having a thickness of 1 μm to 100 μm.

  The upper electrode forming layer of the capacitor layer forming material according to the present invention is preferably made of copper, nickel, gold, or an alloy thereof having a thickness of 100 nm to 50 μm.

  The capacitor layer forming material according to the present invention described above is preferably used for the configuration of the built-in capacitor layer of the printed wiring board.

Capacitor layer constituent member with electrode circuit according to the present invention: The capacitor layer constituent member with electrode circuit according to the present invention is formed by etching at least one of the lower electrode forming layer and the upper electrode forming layer on the other surface side of the capacitor layer forming material. The capacitor electrode circuit is formed by processing.

Printed wiring board according to the present invention: The printed wiring board according to the present invention is characterized in that the capacitor layer constituent member with electrode circuit is used as a built-in capacitor layer of the printed wiring board.

The BST-based dielectric layer according to the present invention has a composition balance of Ba _X Sr _1-X TiO ₃ (0.8 ≦ X <1), and a level that has not been obtained by controlling the thickness thereof. Temperature characteristic, and the rate of change in capacitance is small. That is, even when the temperature of the environment in which the BST dielectric layer is used rises to around 100 ° C., it exhibits extremely good temperature characteristics as compared with a BST dielectric layer having a composition conventionally used. Therefore, the capacitor layer forming material including the BST-based dielectric layer according to the present invention has good temperature characteristics. Further, by including a resin component in the BST-based dielectric layer, occurrence of short circuit failure between the upper electrode and the lower electrode can be reduced, leakage current can be reduced, and capacitor characteristics can be improved. Then, by using the capacitor layer forming material including the BST-based dielectric layer according to the present invention, it is possible to provide a capacitor layer constituting member with an electrode circuit in which a capacitor circuit shape is formed. Furthermore, by using this capacitor layer constituent member with an electrode circuit, it is possible to provide a printed wiring board incorporating a capacitor circuit having good temperature characteristics.

BST-based dielectric layer according to the present invention: The BST-based dielectric layer according to the present invention is a BST-based dielectric layer used for manufacturing a capacitor circuit, and the BST-based dielectric layer has a composition balance of barium and strontium, Ba _X Sr _{1 -X} TiO ₃ (0.8 ≦ X <1) is satisfied, and the thickness is 0.3 μm to 0.7 μm.

The BST-based dielectric layer is preferably Ba _X Sr _1-X TiO ₃ (0.8 ≦ X <1). Here, the composition of BaTiO ₃ is excluded. It should be noted that in the stoichiometric composition of BaTiO _{3 mentioned} here, the ratio of the A site element (Ba, Sr) to the B site element (Ti) and the composition of oxygen (O) are as follows. It may vary within a certain range. In general, the BST-based dielectric layer is expressed as Ba _X Sr _1-X TiO ₃ (0 ≦ X ≦ 1). However, the composition actually used is a composition in the range of 0 ≦ X <0.8 and a BaTiO ₃ composition when X = 1. That is, the composition in the range of 0.8 ≦ X <1 is hardly used. However, as a result of the study by the present inventors, for a specific dielectric layer thickness, the composition in the range of 0.8 ≦ X <1 becomes a BST-based dielectric layer having the most excellent balance between temperature characteristics and capacitance density. It has been found. Here, when the composition ratio of barium (Ba) and strontium (Sr) is Ba _X Sr _1-X TiO ₃ where X <0.8, the temperature characteristics fluctuate greatly, and the dielectric layer It is not preferable for practical use. When X = 1, the dielectric layer has a composition of BaTiO _3. This composition is not preferable because the capacitance density at room temperature tends to decrease. In consideration of the balance between temperature characteristics and electric capacity, the range of 0.85 ≦ X ≦ 0.95 is more preferable, and the range of 0.88 ≦ X ≦ 0.93 is more preferable. The BST-based dielectric layer may be formed using any manufacturing method as long as the composition of Ba _X Sr _1-X TiO ₃ (0.8 ≦ X <1) can be achieved. For example, a sol-gel method, a chemical vapor reaction method, a physical vapor deposition method, or the like can be used.

  The BST-based dielectric layer according to the present invention needs to have a thickness of 0.3 μm to 0.7 μm. In order to exhibit more stable temperature characteristics, in particular, 0.4 μm to 0.7 μm. It is preferable that When the thickness of the BST-based dielectric layer is 0.4 μm or more, the absolute value of the leakage current when the same voltage is applied is critically smaller than that of the BST-based dielectric layer having a thickness of less than 0.4 μm. This is because the reliability as the dielectric layer is greatly improved. This film thickness dependence is listed in Table 1. In Table 1, five types of dielectric layers having a Ba / Sr (mol ratio) of 90/10 and a film thickness of 165 to 835 nm were formed.

  As can be understood from Table 1, if the thickness of the BST-based dielectric layer does not satisfy the above thickness range, even if the above composition is satisfied, the characteristics as a stable capacitor layer forming material may not be exhibited. Understandable. For example, in Table 1, No. As is clear from the contents of the sample No. 1, when the thickness of the BST-based dielectric layer is less than 0.3 μm, the production yield is remarkably lowered even if the capacitance is increased. On the other hand, no. As is clear from the contents of the sample No. 5, when the thickness of the BST-based dielectric layer exceeds 0.7 μm, the dielectric layer becomes thick, so that a good electric capacity cannot be obtained and the capacitance density is small. At the same time, the rate of change in capacity density with increasing temperature increases. The thickness of the BST-based dielectric layer (0.3 μm to 0.7 μm) mentioned here indicates an allowable width of the average value of the film thickness, and the thinnest part and the thickest part. It is clearly stated that it does not indicate the allowable range.

  In addition, the BST-based dielectric layer contains one or more selected from manganese, silicon, nickel, aluminum, lanthanum, niobium, magnesium, and tin, and segregates at the crystal grain boundary, thereby reducing the leakage current flow path. Blocking is also preferred. Among these, it is preferable to use manganese. An additive such as manganese exists as manganese oxide or the like inside the BST-based dielectric layer, segregates at the crystal grain boundary of the BST-based dielectric layer, and blocks the leakage current flow path. The amount of an additive such as manganese contained in the BST-based dielectric layer is preferably 0.01 mol% to 5.00 mol%. When the amount of the additive such as manganese is less than 0.01 mol%, the segregation of the additive component on the crystal grain boundary of the BST-based dielectric layer is insufficient, and a good leakage current blocking effect cannot be obtained. On the other hand, when the amount of the additive such as manganese exceeds 5.00 mol%, the segregation of the additive to the crystal grain boundary of the BST dielectric layer becomes excessive, the BST dielectric layer becomes brittle, and the upper part is etched. Problems such as destruction of the BST-based dielectric layer are likely to occur due to an etchant shower or the like when processing the electrode shape or the like. Moreover, when the amount of additives such as manganese is excessive, the growth of the crystal structure of the BST-based dielectric layer tends to be suppressed. Therefore, by adopting a composition containing an additive such as manganese in the above-described range, the leakage current as a capacitor is further reduced and a long life is achieved. More preferably, the amount of additive such as manganese contained in the oxide dielectric film is 0.25 mol% to 1.50 mol%. This is to more reliably reduce the quality variation of the BST-based dielectric layer.

  Furthermore, it is also preferable to reduce the leakage current by impregnating the BST-based dielectric layer according to the present invention with resin. Here, the resin component impregnated in the BST-based dielectric layer will be described. As the resin component impregnated in the BST dielectric layer, a resin composition using an epoxy resin as a main component is used. Among them, the epoxy resin contains 40 wt% to 70 wt% of epoxy resin, 20 wt% to 50 wt% of polyvinyl acetal resin, 0.1 wt% to 20 wt% of melamine resin or urethane resin, and the epoxy resin. A resin composition in which 5 to 80% by weight of the resin is a rubber-modified epoxy resin is preferable.

  As an epoxy resin said here, if it is marketed for the shaping | molding of a laminated board and an electronic component, it can be especially used without a restriction | limiting. Specifically, bisphenol A type epoxy resin, bisphenol F type epoxy resin, novolac type epoxy resin, o-cresol novolac type epoxy resin, triglycidyl isocyanurate, glycidylamine compounds such as N, N-diglycidylaniline, tetrahydro Examples thereof include glycidyl ester compounds such as diglycidyl phthalate and brominated epoxy resins such as tetrabromobisphenol A diglycidyl ether. These epoxy resins are preferably used alone or in combination. Moreover, the polymerization degree and epoxy equivalent as an epoxy resin are not specifically limited.

  The “curing agent” of the epoxy resin includes dicyandiamide, organic hydrazide, imidazoles, amines such as aromatic amines, phenols such as bisphenol A and brominated bisphenol A, phenol novolac resins and cresol novolac resins. And novolaks and acid anhydrides such as phthalic anhydride. Moreover, a hardening | curing agent may use 1 type, or may mix and use 2 or more types. Since the addition amount of the curing agent with respect to the epoxy resin is naturally derived from the respective equivalents, it is considered that there is no need to specify the mixing ratio strictly strictly. Therefore, the addition amount of the curing agent is not particularly limited here.

  In addition, there is a curing accelerator to be added in an appropriate amount as necessary. As the curing accelerator, tertiary amine, imidazole-based, urea-based curing accelerator or the like can be used. In the present invention, the mixing ratio of the curing accelerator is not particularly limited. This is because the amount of addition of the curing accelerator may be determined arbitrarily and selectively by the manufacturer in consideration of the production conditions in the manufacturing process of the BST dielectric layer.

  It is preferable that the compounding quantity of the epoxy resin mix | blended with this resin composition is 40 to 70 weight% of the resin component total amount. If the blending amount is less than 40% by weight, the insulating properties and heat resistance as electrical characteristics deteriorate. On the other hand, if it exceeds 70% by weight, the resin flow during curing increases, and the resin component tends to be unevenly distributed in the BST-based dielectric layer.

  And it is preferable to use a rubber-modified epoxy resin as a part of the epoxy resin composition. The rubber-modified epoxy resin can be used without particular limitation as long as it is a product marketed for adhesives or paints. For example, “EPICLON TSR-960” (trade name, manufactured by Dainippon Ink & Co.), “EPOTOOHTO YR-102” (trade name, manufactured by Toto Kasei), “Sumiepoxy ESC-500” (trade name) , Manufactured by Sumitomo Chemical Co., Ltd.), “EPOMIK VSR 3531” (trade name, manufactured by Mitsui Petrochemical Co., Ltd.), and the like. These rubber-modified epoxy resins may be used alone or in combination of two or more. The blending amount of the rubber-modified epoxy resin here is 5% by weight to 80% by weight of the total amount of the epoxy resin. When a rubber-modified epoxy resin is used, the resin component can be easily fixed in the BST-based dielectric layer. Therefore, when the blending amount of the rubber-modified epoxy resin is less than 5% by weight, the effect of promoting fixing in the BST-based dielectric layer cannot be obtained. On the other hand, when the compounding amount of the rubber-modified epoxy resin exceeds 80% by weight, the heat resistance of the cured resin is lowered.

  And the polyvinyl acetal resin used for the said epoxy resin composition is synthesize | combined by reaction of polyvinyl alcohol and aldehydes. Currently, as a polyvinyl acetal resin, a reaction product of polyvinyl alcohol having various degrees of polymerization and one or more aldehydes is commercially available for coatings and adhesives. Regardless of the degree of acetalization, it can be used without particular limitation. Moreover, the polymerization degree of the raw material polyvinyl alcohol is not particularly limited, but considering the heat resistance as a cured resin and the solubility in a solvent, it is desirable to use a product synthesized from polyvinyl alcohol having a polymerization degree of 2000 to 3500. Further, a modified polyvinyl acetal resin having a carboxyl group or the like introduced in the molecule is also commercially available, but can be used without particular limitation as long as there is no problem in compatibility with the combined epoxy resin. As a compounding quantity of the polyvinyl acetal resin mix | blended with an insulating layer, it is 20 weight%-50 weight% of the resin composition total amount. If the blending amount is less than 20% by weight, the effect of improving the fluidity as a resin cannot be obtained. On the other hand, if the blending amount exceeds 50% by weight, the water absorption rate of the insulating layer after curing becomes high, which is not suitable as a constituent material for the BST-based dielectric layer.

  In addition to the above components, the resin composition used in the present invention preferably contains a melamine resin or a urethane resin as a crosslinking agent for the polyvinyl acetal resin. As the melamine resin used here, an alkylated melamine resin commercially available for coatings can be used. Specific examples include a methylated melamine resin, an n-butylated melamine resin, an iso-butylated melamine resin, and a mixed alkylated melamine resin thereof. At this time, it can be used without any particular limitation regardless of the molecular weight or the degree of alkylation as the melamine resin.

  As the urethane resin, a resin containing an isocyanate group in a molecule marketed for an adhesive or a paint can be used. Specific examples include reaction products of polyisocyanate compounds such as tolylene diisocyanate, diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate and polyols such as trimethylolpropane, polyether polyol, and polyester polyol. These compounds have high reactivity as a resin and may be polymerized with moisture in the atmosphere. Therefore, in the present invention, it is preferable to use a urethane resin called a blocked isocyanate obtained by stabilizing these resins with phenols or oximes so as not to cause unintended polymerization.

  The compounding quantity of the melamine resin or urethane resin added to the resin composition in this invention is 0.1 weight%-20 weight% of the resin composition total amount. When the blending amount is less than 0.1% by weight, the crosslinking effect of the polyvinyl acetal resin becomes insufficient, and the heat resistance of the insulating layer is lowered. On the other hand, when it exceeds 20% by weight, the fixing property of the resin component in the BST-based dielectric layer is deteriorated.

  In addition to the above essential components, additives such as inorganic fillers typified by talc and aluminum hydroxide, antifoaming agents, leveling agents, coupling agents and the like can also be used in this resin composition as desired. These improve the permeability of the resin component to the BST-based dielectric layer, and are effective in improving flame retardancy and reducing costs.

  The resin composition described above is used as a dilute resin varnish whose solid content is controlled within a certain range using a solvent so that the BST-based dielectric layer can be easily impregnated. In this resin varnish, the above resin composition is dissolved using an organic solvent to obtain a dilute resin varnish having a solid content of 0.1 wt% to 1.0 wt%. Here, when the solid content is less than 0.1 wt%, the viscosity is too low, the organic component does not remain in the dielectric layer, and the significance of resin impregnation is lost. On the other hand, when the solid content exceeds 1.0 wt%, the coating process tends to vary. For example, when an excessive amount of resin is applied by a spin coater, the viscosity is too high so that the resin does not penetrate into the BST dielectric layer, and a resin film is formed on the BST dielectric layer. Since it falls, it is not preferable. When the cross section of the BST dielectric layer is observed by FIB-SIM, the resin component impregnated inside the BST dielectric layer can be observed as black dots.

  Therefore, it is preferable that the organic solvent used for the adjustment of the resin varnish is, for example, any one of ethyl methyl ketone and cyclopentanone or a mixed solvent thereof. Ethyl methyl ketone and cyclopentanone can be easily volatilized and removed efficiently by heating at about 190 ° C., and the volatile gas can be easily purified. Moreover, it is easy to adjust the viscosity of the resin solution to a viscosity most suitable for impregnation of the BST dielectric layer. And the mixing ratio in the case of setting it as a mixed solvent is not specifically limited. When cyclopentanone is used as one component of the mixed solvent, it is preferable to use ethyl methyl ketone as a coexisting solvent in view of the volatilization removal rate. However, in addition to the solvents specifically mentioned here, any solvent can be used as long as it can dissolve all the resin components used in the present invention.

  Various methods can be used to apply this resin varnish to the surface of the BST dielectric layer. However, since the solid content of the resin varnish is extremely dilute as compared with a normal resin varnish, it is preferable to apply the resin varnish to the BST-based dielectric layer and impregnate it uniformly by using a spin coating method. The BST dielectric layer according to the present invention has excellent leakage characteristics as well as improved temperature characteristics by incorporating the above-mentioned additives into the BST dielectric layer or impregnating the resin component with the BST dielectric layer. A good dielectric layer.

Form of capacitor layer forming material according to the present invention: The capacitor layer forming material according to the present invention comprises a lower electrode forming layer on one side of the BST-based dielectric layer and an upper electrode forming layer on the other side. Is. Accordingly, the method for forming the lower electrode forming layer and the upper electrode forming layer on the surface of the capacitor layer forming material is not particularly limited. As a result, it is only necessary to achieve the layer configuration as shown in FIG. FIG. 1 is a schematic cross-sectional view of a capacitor layer forming material 1 composed of a BST-based dielectric layer 2, a lower electrode forming layer 3, and an upper electrode forming layer 4.

  Therefore, it is preferable that the manufacturing method of the capacitor layer forming material according to the present invention employs one of the following two types of manufacturing methods. In one manufacturing method, a BST-based dielectric layer is manufactured in advance, and one of the lower electrode forming layer and the upper electrode forming layer, which is a conductive metal layer, is formed on one side thereof, and the other electrode forming layer is formed on the other side. It is a method of forming. In such a case, since the BST-based dielectric layer is thin, for example, as shown in FIG. 2A, the BST-based dielectric layer 2 is formed on a base material 5 such as a glass substrate in advance. Then, as shown in FIG. 2B, either the lower electrode forming layer 3 or the upper electrode forming layer 4 is formed on the formed BST-based dielectric layer 2 using a physical vapor deposition method or the like. Thereafter, the substrate 5 is removed as shown in FIG. Then, the other electrode forming layer is formed on the surface of the BST-based dielectric layer 2 that has been in contact with the base material, as shown in FIG. The method of using the capacitor layer forming material 1 can be employed.

  In another manufacturing method, for example, as shown in FIG. 3A, a metal foil (or metal layer) constituting the lower electrode forming layer 3 is prepared. And as shown in FIG.3 (b), the BST type dielectric layer 2 is formed in the surface of the metal foil using a sol-gel method, MO-CVD method, a physical vapor deposition method, etc. FIG. Then, the other upper electrode forming layer 4 is formed on the formed BST-based dielectric layer 2 by laminating a physical vapor deposition method or a metal foil, and the capacitor layer forming material 1 shown in FIG. And Generally speaking, the latter manufacturing method has an advantage that various methods can be selected as a method for forming the BST-based dielectric layer 2.

  Various metals can be selectively used as the metal of the lower electrode forming layer as a base when forming the BST-based dielectric layer by using a sol-gel method, MOCVD method, physical vapor deposition method or the like. . That is, various conductive materials such as copper, nickel, cobalt, gold, and platinum can be used. However, the amount of heat applied differs depending on whether the sol-gel method, the MOCVD method, or the sputtering deposition method is employed to form the BST dielectric layer. Therefore, it is necessary to select a lower electrode formation layer as a base for forming the BST-based dielectric layer in consideration of the applied heat.

  For example, when a dielectric layer is formed using a sol-gel method, a high temperature is applied, and therefore it is preferable to employ a nickel layer or a nickel alloy layer as the lower electrode forming layer among the heat resistant metals. This is because even when a high temperature exceeding 600 ° C. is applied, oxidation, deformation, and the like are small.

  The nickel layer or nickel alloy layer here is mainly intended to use a metal foil. That is, a pure nickel foil having a so-called purity of 97%, more preferably 99% (other unavoidable impurities) or more is used for the nickel layer. The nickel alloy layer is a layer formed using, for example, a nickel-phosphorus alloy. The phosphorus content of the nickel-phosphorus alloy mentioned here is 0.1 wt% to 11 wt%, more preferably 0.2 wt% to 3 wt%, and still more preferably 0.25 wt% to 1 wt%. The phosphorus component of the nickel-phosphorus alloy layer diffuses into the dielectric layer when it is subjected to high-temperature loading in the production process of the capacitor layer forming material and the ordinary printed wiring board production process, and deteriorates the adhesion with the dielectric layer, It is thought that the dielectric constant is also changed. However, a nickel-phosphorus alloy layer having an appropriate phosphorus content improves the electrical characteristics as a capacitor. When the phosphorus content is less than 0.1 wt%, the meaning of alloying is lost because it is the same as when pure nickel is used. On the other hand, if the phosphorus content exceeds 11 wt%, phosphorus is segregated at the interface of the dielectric layer, the adhesiveness with the dielectric layer is deteriorated, and the interface peels easily, which is not preferable. The phosphorus content in the present invention is a value converted as [P component weight] / [Ni component weight] × 100 (wt%).

  When nickel foil and nickel alloy foil are used, all of those obtained by a rolling method, an electrolytic method and the like are included. And the thing of composite foil provided with nickel or a nickel alloy layer in the outermost layer of metal foil is also included. For example, a composite material having a nickel layer or a nickel alloy layer on the surface of a copper foil.

  At this time, the nickel layer or the nickel alloy layer preferably has a thickness of 1 μm to 100 μm. If the thickness is less than 1 μm, the reliability as an electrode when the capacitor circuit is formed is remarkably lacking, and it is extremely difficult to form a dielectric layer on the surface. On the other hand, even if the thickness exceeds 100 μm, there is almost no practical requirement. In the case of nickel foil and nickel alloy foil having a thickness of less than 3 μm, it is preferable to use nickel foil with carrier foil or nickel alloy foil with carrier foil. This is because handling becomes difficult. In such a case, it is preferable to use a nickel foil with a carrier foil or a nickel alloy foil with a carrier foil in a state where a carrier foil and a nickel foil or a nickel alloy foil are bonded together. And after providing a BST type dielectric layer and an upper electrode formation layer one by one on the surface of these nickel foil or nickel alloy foil side, a capacitor layer formation material provided with a thin lower electrode formation layer easily by removing carrier foil Is obtained.

  The crystal structure of the nickel layer and nickel alloy layer described above is preferably one in which the crystal grains are made as fine as possible to improve the strength. More specifically, it is preferable that the material is refined to an average crystal grain size of 0.5 μm or less and has high mechanical strength.

  Moreover, when using copper for a lower electrode formation layer, it is also preferable to provide a zinc-containing layer on the surface in contact with the dielectric layer. The presence of this zinc-containing layer suppresses copper oxidation due to heating when a dielectric layer is formed on the surface by a sol-gel method, and ensures good adhesion between the lower electrode formation layer and the dielectric layer. At the same time, the diffusion of the copper component into the dielectric layer due to heat during the heating and firing is suppressed, and stable dielectric characteristics are exhibited as a capacitor layer forming material. The zinc-containing layer referred to here is preferably provided with a zinc oxide layer on the outermost surface and a brass layer on the lower layer. The brass layer functions as a diffusion barrier to the dielectric layer side of the copper component constituting the lower electrode forming layer.

The zinc-containing layer in such a case preferably contains 50 mg / m ^{2 to} 1000 mg / m ² of zinc per unit area. This weight thickness is used as an alternative index of the thickness of the zinc-containing layer, and indicates a range necessary for maintaining good adhesion between the dielectric layer and the lower electrode forming layer. When the amount of zinc per unit area is less than 50 mg / m ² , the surface of the lower electrode formation layer (copper) cannot be uniformly coated, and the adhesion between the dielectric layer and the lower electrode formation layer varies. On the other hand, if the amount of zinc per unit area exceeds 1000 mg / m ² , the tendency of decreasing the electric capacity when forming a capacitor circuit becomes prominent and the value of dielectric loss tends to increase. If the amount of zinc exceeds the upper limit, a thick brass layer will be formed, and the electrical resistance will increase compared to copper, so the speed of the capacitor circuit operation will be slow and it will not be possible to follow high-speed signals. .

The zinc-containing layer preferably has 50 mg / m ² or more of zinc in a region from the outermost surface to a depth of 0.5 μm. That is, since the minimum necessary amount of zinc per unit area of the zinc-containing layer is 50 mg / m ² , the value of this zinc amount is used as a reference. The presence of a certain amount or more of zinc near the surface can sufficiently exhibit the effect of providing the zinc-containing layer. Here, when the zinc in the region from the outermost surface of the zinc amount to the depth of 0.5 μm is less than 50 mg / m ² , the adhesion between the dielectric layer and the lower electrode forming layer tends to vary. The depth referred to here is a glow discharge optical emission spectrometer, which analyzes the depth profile of zinc from the surface of the copper foil provided with the zinc-containing layer until the zinc signal disappears. Is obtained as an actual measurement value measured with a roughness meter.

  Further, it is preferable that 80 atomic% or more of zinc on the surface in contact with the dielectric layer of the zinc-containing layer is zinc oxide from the viewpoint of increasing the capacitance density as a capacitor. Further, in order to enhance the effect of preventing oxidation of the copper layer by providing the zinc-containing layer, the value of [zinc (atomic%)] / [copper (atomic%)] in the surface portion of the zinc-containing layer is 5 or more. It is preferable to do.

  Next, the upper electrode forming layer of the capacitor layer forming material according to the present invention is preferably made of copper, nickel, gold, or an alloy thereof having a thickness of 100 nm to 50 μm. This upper electrode forming layer is formed by a method such as laminating using a metal foil on a BST-based dielectric layer, a method of forming a conductive layer by a plating method, a method such as sputtering deposition, and is usually 500 nm to A thickness of about 50 μm is employed. When the capacitor layer forming material according to the present invention is used for forming the capacitor layer of the printed wiring board, the upper electrode forming layer is etched to form the upper electrode circuit. In such a case, when the thickness of the upper electrode forming layer is less than 100 nm, the upper electrode circuit is deformed by the press pressure even if the hot press molding conditions for processing into a multilayer printed wiring board are sufficiently controlled. In some cases, reliability as an electrode after hot press molding is lacking.

Form of capacitor layer constituent member with electrode circuit according to the present invention: The capacitor layer constituent member with electrode circuit according to the present invention is an etching process of at least one of the lower electrode forming layer and the upper electrode forming layer of the capacitor layer forming material. Thus, a capacitor electrode circuit is formed. That is, a method for forming an upper electrode circuit using the capacitor layer forming material shown in FIG. 1 will be described as an example. As shown in FIG. 4A, an etching resist layer 6 is formed on the upper electrode forming layer 4 of the capacitor layer forming material 1. Next, as shown in FIG. 4B, the etching resist pattern 6 is exposed and developed on the etching resist layer 6 to form an etching resist pattern 7. Then, the upper electrode circuit forming layer 4 is etched, the etching resist pattern 7 is peeled off, and the upper electrode circuit 8 is formed as shown in FIG. This is the capacitor layer constituting member 10 with an electrode circuit when the lower electrode forming layer is not etched. Furthermore, the dielectric layer 2 exposed between the upper electrode circuit 8 and the upper electrode circuit 8 can be removed using a wet blast method or the like. As a result, as shown in FIG. 4D, a capacitor layer constituting member 10 'with an electrode circuit having no dielectric layer between the upper electrode circuit 8 and the upper electrode circuit 8 is obtained. Therefore, the capacitor layer constituent member with an electrode circuit according to the present invention includes the form shown in FIG.

  If the steps of FIGS. 4A to 4C are performed simultaneously on the lower electrode formation layer and the upper electrode formation layer, as shown in FIG. 5, the upper electrode circuit 8 and the lower electrode circuit 9 are processed. The capacitor layer constituting member 10 with an electrode circuit is provided. Which form of these capacitor layer constituent members with electrode circuit is adopted depends on the design of the printed wiring board.

  Moreover, it is also possible to manufacture the capacitor layer constituting member 10 with an electrode circuit without going through the capacitor layer forming material. For example, as shown in FIG. 6A, the upper electrode circuit 8 is directly formed by the mask method without providing the upper electrode forming layer 8 in a state where the lower electrode forming layer 4 exists on one surface of the dielectric layer 2. It is. That is, as shown in FIG. 6B, the vapor deposition mask 11 is placed on the dielectric layer 2, and the upper electrode circuit 8 is directly formed by a physical vapor deposition technique such as sputtering vapor deposition. Thereafter, when the evaporation mask 11 is removed, the capacitor layer constituting member 10 with electrode circuit is obtained as shown in FIG. Furthermore, even in the case of this mask method, the dielectric layer 2 exposed between the upper electrode circuit 8 and the upper electrode circuit 8 can also be removed using a wet blast method or the like. As a result, as shown in FIG. 6D, the electrode layer-equipped capacitor layer constituting member 10 ′ without a dielectric layer is obtained between the upper electrode circuit 8 and the upper electrode circuit 8.

Printed wiring board according to the present invention: The printed wiring board according to the present invention uses the capacitor layer constituent member with electrode circuit as a built-in capacitor layer of a multilayer printed wiring board. There is no special limitation regarding the manufacturing method of the multilayer printed wiring board at this time. Since the printed wiring board according to the present invention uses the capacitor layer constituent member with an electrode circuit, and the dielectric layer has a good temperature characteristic, the capacitor performance can be obtained even in a temperature atmosphere exceeding 80 ° C. It is possible to keep the design quality of the printed wiring board from being minimized.

Metal foil for lower electrode formation layer: In this example, nickel foil having a thickness of 50 μm manufactured by a rolling method was used for the lower electrode formation layer. In addition, the thickness of the nickel foil manufactured by the rolling method is shown as a gauge thickness.

Formation of dielectric layer: Then, a dielectric layer was formed on the surface of the nickel foil using a sol-gel method. The nickel foil before forming the dielectric layer by the sol-gel method was heated at 250 ° C. for 15 minutes as a pretreatment and irradiated with ultraviolet rays for 1 minute. The dielectric layer was formed by the following procedures (a) to (c).

(A) First, a sol-gel solution used in the sol-gel method was prepared. Here, using a sol-gel solution prepared so as to obtain a dielectric film having a composition range of Ba _X Sr _1-X TiO ₃ (0.8 ≦ X <1), the Ba / Sr (mol ratio) is 95. Four dielectric layers of / 5, 90/10, 85/15, and 80/20 were formed.

(B) The above sol-gel solution is applied to the surface of the nickel foil using a spin coater, dried in an oxygen-containing atmosphere (air atmosphere) at 150 ° C. × 2 minutes, and then in an air atmosphere at 330 ° C. × 15 minutes. A series of steps for performing thermal decomposition was taken as one unit step, and one unit step was repeated 12 times to adjust the film thickness. And between the first unit process and the second one unit process, between the third unit process and the fourth one unit process, between the sixth one unit process and the seventh unit process. Crystallization was performed halfway at 650 ° C. for 15 minutes in the nitrogen substitution atmosphere between the first unit process and the ninth one unit process and the tenth one unit process.

(C) Finally, a baking treatment was performed in a nitrogen substitution atmosphere at 800 ° C. for 30 minutes to form a 600 nm-thick dielectric layer having four compositions on the lower electrode formation layer.

Formation of Upper Electrode Circuit: When the dielectric layer is formed as described above, it is as shown in FIG. Then, the upper electrode circuit 8 was directly formed by a mask method. That is, as shown in FIG. 5B, the deposition mask 11 was placed on the dielectric layer 2, and the upper electrode circuit 8 was directly formed by the sputtering deposition method. Thereafter, the evaporation mask 11 was removed to obtain a capacitor layer constituting member 10 with an electrode circuit including an upper electrode circuit 8 having an upper electrode area of 1 mm × 1 mm size as shown in FIG. At this time, the capacitor layer constituting member with electrode circuit includes three types of capacitor layer constituting members with first electrode circuit (Ba / Sr (mol ratio) = 95/5, hereinafter referred to as “sample 1”), the second electrode. Capacitor layer constituting member with circuit (Ba / Sr (mol ratio) = 90/10, hereinafter referred to as “sample 2”) Capacitor layer constituting member with third electrode circuit (Ba / Sr (mol ratio) = 85/15, (Hereinafter referred to as “Sample 3”), a capacitor layer constituting member with a fourth electrode circuit (Ba / Sr (mol ratio) = 80/20, hereinafter referred to as “Sample 4”) was obtained.

  The capacitor layer constituent member with the first electrode circuit (Ba / Sr (mol ratio) = 95/5), the capacitor layer constituent member with the second electrode circuit (Ba / Sr (mol ratio) = 90/10), the third Using each of the capacitor layer constituent member with electrode circuit (Ba / Sr (mol ratio) = 85/15) and the capacitor layer constituent member with fourth electrode circuit (Ba / Sr (mol ratio) = 80/20), 25 The capacity density was evaluated at 0 ° C., 90 ° C., and 125 ° C., and the change rate of the capacity density was obtained. The capacity density change rate at 90 ° C. is obtained by a formula of [(90 ° C. capacity density) − (25 ° C. capacity density)] / (25 ° C. capacity density), and the capacity density change rate at 125 ° C. is [( 125 ° C. capacity density) − (25 ° C. capacity density)] / (25 ° C. capacity density). The capacity density was measured with a Hioki 3532 LCR Hi-Tester manufactured by Hioki Electric Co., Ltd. The results are summarized in Table 2 so that the comparison with the comparative example is easy.

Comparative example

In this comparative example, in preparing the sol-gel solution used in the sol-gel method of the example, a dielectric film having a composition range of Ba _X Sr _1-X TiO ₃ (0 ≦ X ≦ 1.0) can be obtained. Three types of dielectric layers having Ba / Sr (mol ratio) of 70/30, 50/50, and 100/0 were formed using the prepared sol-gel solution. In addition, in the same manner as in the examples, three types of samples for comparison, capacitor layer-constituting member A with electrode circuit (Ba / Sr (mol ratio) = 70/30, hereinafter referred to as “sample A”), electrode circuit. Capacitor layer constituent member B (Ba / Sr (mol ratio) = 50/50, hereinafter referred to as “sample B”), Capacitor layer constituent member B with electrode circuit (Ba / Sr (mol ratio) = 100/0, (Hereinafter referred to as “Sample C”).

  Then, similarly to the examples, the capacity density at 25 ° C., 90 ° C., and 125 ° C. was evaluated, and the capacity density change rate was obtained. The results are summarized in Table 2 so that the comparison with Examples is easy.

As can be seen from Table 2, Sample 1 to Sample 4 of the example having a dielectric layer having a composition range of Ba _X Sr _1-X TiO ₃ (0.8 ≦ X <1) have the lowest capacity density at 25 ° C. The value is 1164.3, and the capacity density change rate at 125 ° C. is within 40% for each sample. On the other hand, Sample A, Sample B, and Sample C of the comparative example have a maximum capacity density of 112.4 at 25 ° C., and the capacity density change rate exceeds 40%, and there is a sample in which the capacity density change is large. It can be seen. Therefore, it can be said that the example is more excellent in balance than the comparative example in that the capacity density at 25 ° C. is kept high and the capacity density change rate at high temperature is kept low.

The BST-based dielectric layer according to the present invention has a composition balance of Ba _X Sr _1-X TiO ₃ (0.8 ≦ X <1). The rate of change in capacity density is reduced. Therefore, even if the temperature rises due to high temperature atmosphere or self-heating, a stable capacity density is exhibited. In particular, it is suitable for use as a BST-based dielectric layer of a capacitor layer forming material of a printed wiring board in which the operation speed and clock frequency are in a high frequency region, and it is possible to provide a printed wiring board incorporating a high-quality capacitor circuit. .

It is a schematic cross section for showing the layer composition of the capacitor layer forming material concerning the present invention. It is a typical manufacturing flowchart for showing the manufacturing process of the capacitor layer forming material which concerns on this invention. It is a typical manufacturing flowchart for showing the manufacturing process of the capacitor layer forming material which concerns on this invention. It is a typical manufacturing flow figure for showing a manufacturing process of a capacitor layer constituent member with an electrode circuit concerning the present invention. It is a cross-sectional schematic diagram of the capacitor layer constituent member with an electrode circuit provided with the upper electrode circuit and the lower electrode circuit simultaneously. It is a typical manufacturing flow figure for showing a manufacturing process of a capacitor layer constituent member with an electrode circuit concerning the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Capacitor layer forming material 2 BST type dielectric layer 3 Lower electrode forming layer 4 Upper electrode forming layer 5 Base material 6 Etching resist layer 7 Etching resist pattern 8 Upper electrode circuit 9 Lower electrode circuit 10 Capacitor layer constituent member 11 with electrode circuit mask

Claims (7)

In a BST-based dielectric layer used for manufacturing a capacitor circuit,
The BST-based dielectric layer is characterized in that the composition balance of barium and strontium satisfies the following chemical formula 1 and has a thickness of 0.3 μm to 0.7 μm.

A capacitor layer forming material comprising a lower electrode forming layer on one side of the BST-based dielectric layer according to claim 1 and an upper electrode forming layer on the other side. The capacitor layer forming material according to claim 2, wherein the lower electrode forming layer is a nickel layer or a nickel alloy layer having a thickness of 1 μm to 100 μm. 4. The capacitor layer forming material according to claim 2, wherein the upper electrode forming layer is made of copper, nickel, gold, or an alloy thereof having a thickness of 100 nm to 50 μm. The capacitor layer forming material according to any one of claims 2 to 4, which is used for forming a built-in capacitor layer of a printed wiring board. A capacitor electrode circuit is formed by etching at least one of the lower electrode forming layer and the upper electrode forming layer on the other surface side of the capacitor layer forming material according to claim 2. Capacitor layer constituent member with electrode circuit. A printed wiring board comprising a built-in capacitor circuit, wherein the capacitor layer constituting member with electrode circuit according to claim 6 is used as a built-in capacitor layer of the printed wiring board.

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