JP5171407B2 - Circuit board, manufacturing method thereof, and electronic apparatus - Google Patents

Description

  The present invention relates to a circuit board in which a capacitor is incorporated on or in a circuit board, a method for manufacturing the circuit board, and an electronic device in which electronic components are mounted on the circuit board.

  Electronic devices such as personal computers, mobile phones, and mobile devices have been rapidly reduced in size and performance. In order to reduce the size of such electronic equipment, mounting electronic components can be made more dense and highly integrated by incorporating passive elements such as capacitors, resistors, inductors, antennas, and filters in or on the circuit board. It has been.

In an electronic device using a high-frequency current in the order of GHz, an increase in leakage current in the capacitor is a problem.
As a capacitor incorporated in or on a circuit board, Patent Document 1 discloses that a lower electrode formed by sputtering of chromium on a silicon wafer (base substrate) and SiO formed by plasma CVD of tetraethoxysilane. _It describes what consists of _two layers and a TiN upper electrode formed by sputtering.

Patent Document 2 describes a circuit board in which a capacitor including a first electrode layer, a dielectric film formed by an aerosol deposition method, and a second electrode layer is incorporated. As fine particle materials used for the dielectric film, oxide ceramics such as Al ₂ O ₃ and TiO ₂ and oxide ceramics having a perovskite structure are disclosed. Further, it has been proposed to add or coat aluminum compounds and lead compounds to the fine particles.
Patent Document 3 discloses that the dielectric layers are SrTiO ₃ , (Ba, Sr) TiO ₃ , BaTiO ₃ , (Pb, La) (Zr, Ti) O ₃ , Pb (Zr, Ti) O ₃ , PbTiO _3. , Pb (Mg _1/3 Nb _2/3 ) O _{3 and} other perovskite structure composite oxides, and a capacitor using a refractory metal such as chromium, titanium, nickel, tungsten, tantalum and molybdenum in the conductor layer A circuit board is described.

JP 2007-221036 A JP 2004-342831 A JP 2001-250885 A

However, in the circuit board with a built-in capacitor described in the above patent document, the withstand voltage of the capacitor is low and the leakage current is still high.
An object of the present invention is to provide a capacitor built-in circuit board having a high capacitance density, a low leakage current, and a small capacitance temperature dependency and bias voltage dependency.

  As a result of investigations to achieve the above object, the present inventor formed a metal layer made of titanium or a titanium alloy on a base substrate or an insulating layer, and formed an anode in an electrolyte containing hydrogen peroxide at a temperature of 3 ° C. or lower. The first electrode layer, the dielectric film, and the second electrode are formed in or on the circuit board by oxidizing to form an amorphous titanium dioxide layer on the surface of the metal layer and forming a metal layer on the amorphous titanium dioxide layer. When a circuit board incorporating a capacitor composed of layers was manufactured, the circuit board was found to have a high capacity, a low leakage current, and a low temperature dependence and bias voltage dependence of the capacity. As a result of further investigation based on this finding, the present invention has been completed.

That is, the present invention is as follows.
(1) A circuit board having a structure in which a base substrate and an insulating layer are laminated, and a dielectric film and a second electrode layer having a first electrode layer and an amorphous titanium dioxide layer in or on the circuit board A circuit board with a built-in capacitor.
(2) The circuit board according to (1), wherein the dielectric film further has a composite oxide layer having a perovskite structure.
(3) The circuit board according to (2), wherein the complex oxide having a perovskite structure is a complex oxide of Ti and at least one metal selected from the group consisting of Ca, Sr, and Ba.
(4) The circuit board according to any one of (1) to (3), wherein the capacitor is formed by alternately stacking a plurality of first electrode layers and second electrode layers with a dielectric film interposed therebetween. .
(5) The circuit board according to any one of (1) to (4), wherein the base board is made of a resin material.
(6) In any one of the above (1) to (4), the base substrate is made of at least one material selected from the group consisting of an epoxy resin, a polyimide resin, a polyester resin, a fluorocopolymer, and fiber glass. Circuit board as described.

(7) An electronic device comprising the circuit board according to any one of (1) to (6) and an electronic component.
(8) forming a metal layer made of titanium or a titanium alloy;
(1) including a step of anodizing in an electrolyte containing hydrogen peroxide at a temperature of 3 ° C. or less to form a surface of the metal layer into an amorphous titanium dioxide layer, and a step of forming a metal layer on the amorphous titanium dioxide layer. The manufacturing method of the circuit board as described in (6)-(6).
(9) forming a metal layer made of titanium or a titanium alloy;
A process of anodizing in an electrolyte containing hydrogen peroxide at a temperature of 3 ° C. or less to form a metal layer surface into an amorphous titanium dioxide layer;
The circuit according to any one of (1) to (6), including a step of forming a composite oxide layer having a perovskite structure on an amorphous titanium dioxide layer, and a step of forming a metal layer on the composite oxide layer having a perovskite structure. A method for manufacturing a substrate.
(10) The circuit according to (8) or (9), wherein in the step of forming the metal layer on the amorphous titanium dioxide layer or the composite oxide layer having a perovskite structure, the metal layer is made of titanium or a titanium alloy. A method for manufacturing a substrate.

  The circuit board of the present invention has a high capacity density, a low leakage current, a low temperature dependence of the capacity and a bias voltage dependence, and excellent flexibility, so that a personal computer using a high-frequency current on the order of GHz is used. It is also suitable for electronic devices such as mobile phones and mobile devices. According to the circuit board of the present invention, passive elements such as capacitors, resistors, inductors, antennas, and filters can be incorporated in or on the circuit board to achieve higher density and higher integration of the mounted electronic components.

According to the method for manufacturing a circuit board of the present invention, a large number of capacitors can be formed without exposing the board to a high temperature, and multilayering is easy. Capacitors formed on the surface can be reduced, and other elements can be arranged close to each other, so that high integration and miniaturization can be achieved.
Further, by stacking a composite oxide layer having a perovskite structure such as barium titanate on the amorphous titanium dioxide layer, the withstand voltage can be increased without substantially reducing the capacity.

  According to the present invention, electronic components such as LSI can be highly integrated and mounted on the circuit board surface. As a result, the distance between the electronic components is shortened, so that the transmission time can be shortened and high-speed operation is possible.

Next, the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view of a main part of a circuit board according to an embodiment of the present invention.
The circuit board 10 according to the present invention is formed by laminating a base substrate 11 and an insulating layer 16. In FIG. 1, the insulating layer 17 is laminated on the insulating layer 16, but the insulating layer 17 may be omitted if desired, and another insulating layer (not shown) may be formed on the insulating layer 17. 1) or more may be laminated. Further, an insulating layer may be provided on the lower side of the base substrate 11.

  The base substrate 11 is known as a conventional base substrate for circuit boards. For the base substrate, a resin material such as epoxy resin, polyimide resin, polyester resin, fluororesin, fluorocopolymer, prepreg made by impregnating a thermosetting resin into inorganic fibers or organic fibers such as fiberglass, etc. are used. . Of course, by providing an insulating layer between the base substrate 11 and the first electrode layer 12, the base substrate 11 has a single metal such as Fe, Ni, Ti, Mo, W, Al, Cu, Ag, Au or the like. A metal material made of an alloy containing can be used. When a semiconductor substrate is used as the base substrate, the circuit board of the present invention can be used as a semiconductor package.

  The insulating layer is not particularly limited as long as it is a layer made of an electrically insulating material. For example, an epoxy resin insulating layer, a polyimide resin insulating layer, a polybenzoxazole insulating layer, or the like can be used.

  A capacitor 15 is incorporated in the circuit board 10 shown in FIG. The capacitor 15 includes a first electrode layer 12, a dielectric film 13, and a second electrode layer 14, and the dielectric film 13 is sandwiched between the first electrode layer 12 and the second electrode layer 14. In FIG. 1, the capacitor is provided between the base substrate 11 and the insulating layer 16, but the capacitor may be provided between the insulating layer 16 and the insulating layer 17 or in the outermost layer of the circuit board as desired. Capacitors can be provided on both sides of the base substrate.

  The first electrode layer and the second electrode layer are not particularly limited as long as they are layers made of a conductive material. Examples of the conductive material include simple metals such as Fe, Ni, Ti, Mo, W, Al, Cu, At, Pd, Ag, Au, and alloys containing them. Of these, titanium or a titanium alloy is preferable from the viewpoint of easily forming a dielectric film to be described later. The thicknesses of the first electrode layer and the second electrode layer are preferably 0.1 μm to 100 μm, more preferably 0.5 μm to 50 μm, and particularly preferably 1 μm to 30 μm.

  The dielectric film used for the circuit board of the present invention has an amorphous titanium dioxide layer. Titanium dioxide usually has a rutile or anatase crystal structure, but amorphous titanium dioxide is used in the present invention. The amorphous titanium dioxide layer can be confirmed by observation with a transmission electron microscope. The refractive index of the amorphous titanium dioxide layer with respect to light of 632.8 nm is usually 1.90 to 2.35. The relative dielectric constant of the amorphous titanium dioxide layer is usually 30 or more.

The amorphous titanium dioxide layer is obtained by anodizing titanium or a titanium alloy.
The anodic oxidation requires that the outermost surface of the first electrode layer be formed of titanium or a titanium alloy. When the first electrode layer is formed of a metal other than titanium and a titanium alloy, for example, copper, a titanium or titanium alloy film may be formed on the metal surface using a sputtering method or the like. When the first electrode layer is formed of titanium or a titanium alloy, the next step can be performed as it is. The titanium alloy preferably contains 70 mass% or more of titanium. A preferred titanium alloy is β-titanium. If there is a natural oxide film, dirt or scratches on the surface of titanium or a titanium alloy, it is preferable to remove them by etching or the like before anodic oxidation. Examples of the etching method used for the pretreatment of the anodic oxidation include a chemical etching method using hydrofluoric acid and the like, and an electrolytic etching method. Further, a portion where anodic oxidation is not desired can be covered with a masking material. Examples of the masking material include a heat-resistant resin or a precursor thereof, a composition comprising inorganic fine particles and cellulose (for example, see JP-A-11-80596).

  Next, anodization is performed. By anodization, titanium or a titanium alloy is formed into amorphous titanium dioxide. In the present invention, it is preferable to anodize in an electrolytic solution containing hydrogen peroxide at a temperature of 3 ° C. or lower. The concentration of hydrogen peroxide in the electrolytic solution is preferably from 0.1% by weight to less than 50% by weight, more preferably from 0.1% by weight to 40% by weight, and particularly preferably from 0.2% by weight to 20% by weight. preferable. Examples of the electrolyte contained in the electrolytic solution include acids such as phosphoric acid, sulfuric acid, oxalic acid, boric acid, and adipic acid, and salts thereof. Among these, since the resistance of the generated amorphous titanium dioxide layer becomes higher, an electrolytic solution made of an aqueous solution containing phosphoric acid or a salt thereof is preferable. The electrolytic solution may further contain a small amount of an antifreezing agent. Examples of the antifreezing agent include ethylene glycol, isopropanol, ethanol, diethylene glycol and the like.

The temperature of the electrolytic solution at the time of anodization is preferably 3 ° C. or lower, more preferably 0 ° C. or lower. By setting the temperature to 3 ° C. or less, an amorphous titanium dioxide layer can be easily obtained stably. The lower limit of the electrolyte temperature is preferably −30 ° C. from the viewpoint of freezing of the electrolyte.
The current density in anodization is preferably 0.1 to 1000 mA / cm ² , more preferably 0.1 to 100 mA / cm ² . The voltage is preferably 2 to 400V, more preferably 5 to 90V. The anodic oxidation time can be appropriately selected, but is preferably 1 millisecond to 400 minutes, more preferably 1 second to 300 minutes.

The dielectric film used for the circuit board of the present invention preferably further has a composite oxide layer having a perovskite structure from the viewpoint of improving withstand voltage and reducing leakage current. As the composite oxide having a perovskite structure, SrTiO ₃ , (Ba, Sr) TiO ₃ , BaTiO ₃ , (Pb, La) (Zr, Ti) O ₃ , Pb (Zr, Ti) O ₃ , PbTiO ₃ , Pb ( Mg _1/3 Nb _2/3 ) O _{3 and the} like. Among these, a composite oxide of at least one metal selected from the group consisting of Ca, Sr and Ba and Ti is preferable. The composite oxide layer of Ti and at least one metal selected from the group consisting of Ca, Sr and Ba is, for example, at least one metal element selected from the group consisting of Ca, Sr and Ba in the titanium dioxide layer. It is obtained by reacting an aqueous solution containing 11 or more in the range of 80 ° C. to boiling point.

  The dielectric film used for the circuit board of the present invention preferably has a thickness of 1 nm to 300 nm from the viewpoint of withstand voltage, capacitance density, and the like. The thickness of the dielectric film can be controlled by adjusting the anodic oxidation conditions.

  The circuit board of the present invention may incorporate passive elements such as a resistor, an inductor, an antenna, a filter, a battery, a crystal oscillator, a varistor, and a piezoelectric element in addition to the capacitor. According to the circuit board manufacturing method of the present invention, a large number of capacitors can be formed without exposing the board to high temperatures, so that other passive elements can be arranged close to each other, and high integration and miniaturization can be achieved. It can be easily achieved. Further, an electronic device can be configured by mounting an active element such as an integrated circuit or a light emitting diode such as an LSI, VLSI, ULSI, or GSI on the circuit board, or a passive element as described above.

Next, embodiments of the present invention will be described with reference to the drawings.
[First embodiment]
FIG. 3 is a cross-sectional view illustrating a schematic configuration of an electronic device including the circuit board according to the first embodiment. The circuit board 50A includes a base substrate 51 made of a double-sided copper-clad board FR-4 substrate on which a through hole 52A and a conductor layer 52B are formed, and an insulating layer 53-1 formed on one main surface of the base substrate 51. To 53-4 and the dielectric films 54-1 to 54-3 disposed between the insulating layers 53-1 to 53-4, the lower electrode layers 56-1 to 56-3 and the upper electrode layers 58-1 to 58-3. Capacitors 53-1 to 57-3 sandwiched between 58-3 and the other main surface of the base substrate 51, the first electrode layer 66 / dielectric film 64 / second electrode layer 68 / The electronic device 50 includes a capacitor 67 formed by alternately repeating dielectric films 64, a resistance element 62 having a resistor film 61 formed on the surface of the circuit board 50A, and the electronic device 50 includes a circuit board 50A, a circuit LSI 70 mounted on the surface of substrate 50A It is constructed from.

In the electronic device 50 including the circuit board according to the present embodiment, the dielectric films 54-1 to 54-3 are amorphous titanium dioxide layers.
2A to 2H are diagrams illustrating a manufacturing process of the circuit board according to the present embodiment. First, a double-sided copper-clad plate FR-4 substrate was prepared as the base substrate 51 (FIG. 2A). The base substrate 51 is provided with through holes 52A that allow energization of the front and back surfaces, and a conductor layer 52B that serves as a wiring is provided on both sides.

  Next, epoxy resin sheets (ABF-SH-9K (Ajinomoto Co., Inc., thickness 50 μm)) as the insulating layers 53-1 and 63-1 were bonded to both surfaces of the base substrate 51 (FIG. 2B).

On the surface of the insulating layer 53-1, a desmear protective film (NIT215 manufactured by Nichigo Morton Co., Ltd.) having a film thickness of 40 μm was laminated at an adhesion roll temperature of 105 ° C. and a linear pressure of 4 kg / cm. The surface of the insulating layer 53-1 was irradiated with UV-YAG laser with an energy of 3 mW through the laminated desmear protective film, and a hole having a diameter of about 50 μm was formed. Using an oxygen plasma apparatus, treatment was performed for 5 minutes at an oxygen pressure of 0.15 mPa and an output of 500 W. Subsequently, it was immersed in a tetramethylammonium hydroxide (TMAH) 5% solution, the desmear protective film was peeled off, washed with water and dried to obtain a via hole 73.
Further, Cu made of an electroless plating method was plated on the surface of the insulating layer 53-1 on which the via hole 73 was formed to form a plating seed layer 74. A dry film resist (NIT215 manufactured by Nichigo-Morton) having a film thickness of 40 μm was laminated on the surface of the plating seed layer 74 at an adhesion roll temperature of 105 ° C. and a linear pressure of 4 kg / cm. Next, the wiring pattern was exposed using parallel light ultraviolet rays using all wavelengths, and developed by a spray method using a 1% by mass aqueous solution of sodium carbonate to obtain a resist film 75 on which the wiring pattern was formed (FIG. 2C).

  A metal layer was laminated by an electrolytic plating method. Next, the resist film 75 was peeled off, and a portion of the plating seed layer covered with the resist film 75 was removed by panel etching. As the etching solution, a mixed solution of hydrogen peroxide and sulfuric acid was used. As a result, a metal layer 56-1 'patterned by wiring was formed (FIG. 2D).

  Masking was performed in accordance with the pattern of the metal layer 56-1 ′, and titanium was laminated on the metal layer 56-1 ′ by sputtering to form a lower electrode layer (titanium layer) 56-1 (FIG. 2E). ).

  An aqueous solution containing 3% by mass hydrogen peroxide, 0.1% by mass phosphoric acid, and 25% by volume ethylene glycol was used as the electrolyte, and the surface of the lower electrode layer 56-1 was anodized at −10 ° C. and 60V. A dielectric film 54-1 was formed. The dielectric film 54-1 was an amorphous titanium dioxide layer having a thickness of about 140 nm (FIG. 2F).

  It is desirable to anodize as soon as possible after laminating titanium. This is because it is desirable that the oxide film on the titanium surface is only an amorphous anodic oxide film, so that the growth of a crystalline natural oxide film on the titanium surface is avoided as much as possible. A crystalline oxide film increases leakage current when a capacitor is formed. Usually, if the time during which the titanium surface is exposed to the air is within about 5 minutes, the performance of the capacitor to be produced is hardly affected.

  Using a mask matched to the pattern of the dielectric film 54-1, copper was vapor-deposited on the dielectric film 54-1, and an upper electrode layer 58-1 was laminated by 5 μm by electrolytic plating (FIG. 2G). A capacitor was formed by the lower electrode layer 56-1, the dielectric film 54-1, and the upper electrode layer 58-1.

  Next, an epoxy resin sheet (ABF-SH-9K (Ajinomoto Co., Inc., thickness 50 μm)) as the insulating layer 53-2 was adhered to the surface of the structure (FIG. 2H).

  By repeating the above operation, a multilayer structure in which insulating layers 53-1 to 53-4 and dielectric films 54-11 to 54-3 were alternately laminated as shown in FIG. 3 was formed. A wiring 59 such as a via is formed between each lower electrode layer 56 and upper electrode layer 58.

  On the insulating layer 63-1 formed on the other main surface of the base substrate 51, a plating seed layer (not shown) by an electroless plating method and a first electrode layer 66 by an electrolytic plating method were formed. Next, a dielectric film 64 was formed on the first electrode layer 66 in the same manner as the dielectric film 54-1. Next, a second electrode layer 68 was formed in the same manner as the first electrode layer, and a dielectric film 64 was further formed. Further, the first electrode layer 66 / dielectric film 54-1 / second electrode layer 68 / dielectric film 54-1 / first electrode layer 66 are formed, and the first electrode layers 66 or the second electrode layers 68 are formed. Vias 69A and 69B are formed to form a large-capacitance capacitor 67.

  Further, an electrode 79 was formed on the surface of the circuit board 50A. Next, the entire structure of the circuit board 50A was integrated and bonded by a vacuum lamination press. Specifically, the pressure of 60 Torr or less and the temperature of 180 ° C. and the linear pressure of 30 kg / cm for 70 minutes were used. When this was confirmed by cross-sectional observation, a good multi-layer circuit board was obtained. Furthermore, a surface overcoat layer was formed by using both screen printing and a photolithographic method. Next, electronic components such as LSI 70 were soldered to the surface of the circuit board 50A. Thus, the circuit board and electronic device according to the first example shown in FIG. 3 were formed.

  According to the present embodiment, the capacitors 57-1 to 57-3 and 67 are formed between the insulating layers, so that multilayering is easy and a large-capacity capacitor can be formed. Therefore, the number of capacitors mounted on the surface of the circuit board 50A can be reduced, the number of active elements such as the LSI 70 that can be mounted can be increased, and the circuit board can be downsized. As a result, the operation speed of the electronic device can be increased by bringing the active elements close to each other.

[Second Example]
The second embodiment is the same as the first embodiment except that the dielectric films 54-1 to 54-3 and 64 of the first embodiment are formed by laminating an amorphous titanium dioxide layer and a barium titanate layer. The same.
A dielectric film in which an amorphous titanium dioxide layer and a barium titanate layer were laminated was obtained by the following method.
First, 10 g of barium hydroxide octahydrate was dissolved in 1 L of a 20% tetramethylammonium hydroxide aqueous solution to obtain a treatment solution.
A dielectric film (amorphous titanium dioxide layer) was formed in the same manner as in the first example, and then the surface of the titanium dioxide layer was brought into contact with the treatment liquid for 4 hours. Next, barium carbonate adhering with 0.1N nitric acid was dissolved and removed, and further washed with water. After washing with water, it was dried. Barium titanate was formed from the surface of the amorphous titanium dioxide layer to an average depth of about 20 nm.

[Third embodiment]
The third example is the same as the first example except that the anodic oxidation of titanium performed in the first example is performed at 5 V and the thickness of the dielectric films 54-1 to 54-3 is set to 12 nm.

[Fourth embodiment]
The fourth embodiment is the same as the first embodiment except that the anodic oxidation of titanium performed in the first embodiment is performed at 90 V and the thickness of the dielectric films 54-1 to 54-3 is set to 210 nm.

[Fifth Example]
FIG. 4 is a cross-sectional view showing a schematic configuration of an electronic device 80 including a circuit board according to the fifth embodiment. The circuit board 80A is formed on the base substrate 80B and the base substrate 80B in which the insulating layers 81-1 to 81-4 and the prepregs 85-1 to 85-4 are alternately stacked and the through hole 86 is provided. Insulating layers 53-1 to 53-4 and a resistance element 92 formed on the surface of the circuit board 80A. Furthermore, the electronic device 80 includes a circuit board 80A and an LSI 70 mounted on the surface of the circuit board 80A.

  The capacitor 87 includes lower electrode layers 82-1 to 82-4 selectively formed on the insulating layers 81-1 to 81-4, the insulating layers 81-1 to 81-4, and the lower electrode layer 82-. Dielectric films 83-1 to 83-4 covering 1 to 82-4 and upper sides formed on the dielectric films 83-1 to 83-4 so as to face the lower electrode layers 82-1 to 82-4 It is comprised from the electrode layers 84-1 to 84-4. The lower electrode layers 82-1 to 82-4 and the upper electrode layers 84-1 to 84-4 are connected in parallel by through holes 86, respectively. The dielectric films 83-1 to 83-4 are made of amorphous titanium dioxide.

The circuit board 80A was manufactured by the following method. First, a single-sided copper-clad board FR-4 substrate on which a conductive layer for the insulating layer 81 and the lower electrode layer 82 was formed was prepared, and the lower electrode layer 82 was formed by etching the copper film on the substrate surface. Next, as in the first example, titanium was laminated on the lower electrode layer 82, and a dielectric film 83 was formed by anodic oxidation. An upper electrode layer 84 facing the lower electrode layer 82 was formed on the dielectric film 83 in the same manner as described in the first embodiment. Thus, a capacitor 87 was formed.
Four insulating layers 81 on which capacitors 87 were formed were prepared, prepregs 85 were placed between the insulating layers 81, and laminated and adhered at a heating temperature of 80 ° C. and a linear pressure of 4 kg / cm. Through holes were formed by drilling and electroplating. A base substrate for a build-up substrate in which capacitors 87 were connected in parallel was formed.

  Next, epoxy resin sheets (ABF-SH-9K manufactured by Ajinomoto Co., Inc. (thickness 50 μm)) as the insulating layers 53-1 to 53-4 are bonded to both sides of the base substrate, and the surfaces of the wirings 89 to 91 and the circuit board 80A are adhered. An electrode 79 was formed. Next, electronic components such as LSI 70 were soldered to the surface of the circuit board 80A. As a result, the electronic device 80 including the circuit board 80A according to the present embodiment shown in FIG. 4 was formed.

  According to the present embodiment, a large-capacity capacitor can be formed in the base substrate 80A. Further, since the capacitor can be formed on the base substrate 80A, the capacitance per unit area of the circuit board, that is, the so-called capacitance density can be increased as compared with the first to fourth embodiments. it can. Furthermore, the degree of freedom of the wiring formed on the base substrate 80A can be increased as compared with the first to fourth embodiments.

[Sixth embodiment]
The circuit board according to the sixth embodiment relates to a flexible board on which an insulating layer made of polyimide resin is laminated, and a capacitor formed between the insulating layers has a dielectric film having an amorphous titanium dioxide layer. .
FIG. 5 is a cross-sectional view showing a schematic configuration of the electronic device 100 including the circuit board according to the sixth embodiment. The circuit board 100A includes capacitors 105 and 115 formed between insulating layers 101-1 to 101-4 or between insulating layers 111-1 to 111-2 made of polyimide resin, and a resistance element formed on the surface of the circuit board 100A. 108 or the like. The electronic device 100 includes a circuit board 100A and an LSI 70 mounted on the surface of the circuit board 100A.

  The capacitor 105 includes lower electrode layers 102-1 to 102-3 that are selectively formed so as to cover the insulating layers 101-1 to 101-3, and the insulating layers 101-1 to 101-3 and the lower electrodes. The dielectric films 103-1 to 103-3 covering the layers 102-1 to 102-3 and the upper electrode layers 104-1 to 104-3 selectively formed on the dielectric film are formed by vias 106. Electrically connected.

The capacitor 115 includes a lower electrode layer 112 that is selectively formed so as to cover the insulating layer 111-1, a dielectric film 113 that covers the insulating layer 111 and the lower electrode layer 112, and a dielectric film 113. The upper electrode layer 114 is selectively formed on the upper electrode layer 114 and is electrically connected to other wirings by vias 116 or the like.
In the electronic device 100 including the circuit board 100A according to the present embodiment, the insulating layer is formed of polyimide resin, and the dielectric films 103-1 to 103-3 and 113 are formed of amorphous titanium dioxide.

The circuit board 100A was manufactured by the following method. 6A to 6C are views showing a part of the manufacturing process of the circuit board according to the sixth embodiment.
First, a non-photosensitive polyimide resin film 111-1 having a thickness of about 10 μm was formed on the surface of a Pyrex (registered trademark) glass process substrate PS by spin coating. As a coating method, a screen printing method, a spray method, a curtain coating method, a roll coating method, or a dip method may be used instead of the spin coating method.
The polyimide resin film formed on the process substrate was cured by drying at a temperature of 80 ° C. for 30 minutes and heating at 350 ° C. for 30 minutes to form an insulating layer 111-1. Next, the insulating layer 111-1 was polished and planarized by a CMP (Chemical Mechanical Polishing) method.
A titanium layer 112 having a thickness of 1 μm was formed on the surface of the insulating layer 111-1 by sputtering to form the lower electrode layer 102.
Immediately after the formation of the titanium layer, the surface of the lower electrode layer 112 is −10 ° C. using an aqueous solution containing 1% by mass of hydrogen peroxide, 0.3% by mass of adipic acid and 25% by volume of ethylene glycol as an electrolyte. Anodization was performed at 60 V to form an amorphous titanium dioxide layer 113 having a thickness of about 140 nm (FIG. 6A).

Next, a laminated conductor (not shown) made of Cr / Cu is formed on the dielectric film 113 by sputtering, and a Cu film (upper electrode layer) 114 having a thickness of about 5 μm is formed thereon by electrolytic plating. Formed. Further, a resist film 118 having a thickness of about 10 μm is applied to the surface of the upper electrode layer 114, a glass mask is overlaid, exposure is performed at 400 MmJ / cm ² with a mercury lamp, and the exposed portion is dissolved with a developer containing alkali. It was removed (FIG. 6 (B)).

  Using the resist film 118 as a mask, the upper electrode layer 114 was etched to form a patterned upper electrode layer 114. Thus, the capacitor 115 including the lower electrode layer 112, the upper electrode layer 114, and the dielectric film 113 sandwiched between them was formed. Next, an insulating layer 111-2 was formed (FIG. 6C). Further, the capacitor 105 having the dielectric films 103-1 to 103-3 was similarly formed by the same method.

  Via 107 in dielectric film 103 forms a resist film on dielectric film 103, patterns the resist film, and etches dielectric film 103 with hydrofluoric acid or the like to form via holes (not shown). Then, a plating seed layer was formed by the above-described electroless plating method, and then a plating film was grown on the plating seed layer by the electrolytic plating method. Note that after forming the upper electrode layer 104 and the insulating layer 101 on the dielectric film 103, via holes that expose the dielectric film through these layers may be formed in advance, and then the dielectric film 104 may be etched. . The circuit board formed as described above was peeled from Pyrex (registered trademark) glass to form a film.

  According to the present embodiment, not only can the capacitor 115 be formed directly on the process substrate PS as in the prior art, but also the capacitor 105 can be formed between the laminated insulating layers 101-1 to 101-4 made of polyimide resin. Is possible. Therefore, it is possible to form a capacitor having a larger capacity than in the conventional case. Further, even if the circuit board of this example was bent at 180 degrees with a curvature radius of 1 mm, the performance of the capacitor was not affected. This is presumably because the dielectric amorphous titanium dioxide is excellent in flexibility.

[Seventh embodiment]
The circuit board according to the seventh embodiment uses the casing of the electronic device as a base board. In this example, a casing made of epoxy resin coated magnesium was used.
FIG. 7 is a cross-sectional view showing a schematic configuration of an electronic device including a circuit board according to a seventh embodiment.
The circuit board 140A is formed on the surface of the circuit board 140A, a base board 141 that is a housing of the electronic device, a capacitor 147 formed on the base board 141, an insulating layer 145 that covers the base board 141 and the capacitor 147, and the like. It consists of a resistance element 148 and the like. The electronic device 140 includes a circuit board 140A and an LSI 70 mounted on the surface of the circuit board 140A.

The circuit board 140A was manufactured by the following method. First, a patterned metal mask was placed on the base substrate, and a titanium film having a thickness of 1.2 μm was formed using a sputtering method to form the lower electrode layer 142.
Immediately thereafter, the surface of the lower electrode layer 142 was anoded at −10 ° C. and 60 V using an aqueous solution containing 1% by mass hydrogen peroxide, 0.1% by mass phosphoric acid, and 25% by volume ethylene glycol as an electrolyte. Oxidized to form a dielectric film 143 made of amorphous titanium dioxide having a thickness of about 140 nm.
A laminated conductor (not shown) made of Cr / Cu was formed on the dielectric film 143 by sputtering, and a Cu film (upper electrode layer) 144 having a thickness of about 5 μm was formed thereon by electrolytic plating. . Further, an epoxy resin sheet (ABF-SH-9K (Ajinomoto Co., Inc., thickness: 50 μm)) as an insulating layer 145 was adhered thereon.

  A capacitor using amorphous titanium dioxide as a dielectric film 143 has high capacitance density, low leakage current, high damage strength without damaging the base substrate 141 which is a casing of the electronic device, and high reliability. A circuit can be formed. Furthermore, since the electronic device 140 including the circuit board 140A and the electronic components can be formed over the housing, the electronic device can be further reduced in size.

It is principal part sectional drawing of the circuit board which concerns on one Embodiment of this invention. (A)-(H) are figures which show the manufacturing process of the circuit board based on a 1st Example. It is principal part sectional drawing of the electronic apparatus provided with the circuit board based on the 1st Example of this invention. It is principal part sectional drawing of the electronic apparatus provided with the circuit board based on 5th 4th Example of this invention. It is principal part sectional drawing of the electronic apparatus provided with the circuit board based on 6th Example of this invention. (A)-(C) are figures which show a part of manufacturing process of the circuit board based on 6th Example. It is principal part sectional drawing of the electronic apparatus provided with the circuit board based on 7th Example of this invention.

Explanation of symbols

10, 50A, 80A, 100A, 140A: Circuit board 11: Base board 12: First electrode layer 13: Dielectric film 14: Second electrode layer 15: Capacitor 16: Insulating layer 50, 80, 100, 140: Electronic device

Claims (7)

A circuit board having a structure in which a base substrate and an insulating layer are laminated,
A first electrode layer in or on the circuit board;
An amorphous titanium dioxide layer obtained by anodization , and an aqueous solution having a pH of 11 or more containing at least one metal element selected from the group consisting of Ca, Sr and Ba are reacted in the range of 80 ° C. to boiling point. A circuit board in which a capacitor comprising a dielectric film having a complex oxide layer having a perovskite structure and a second electrode layer is incorporated. Capacitors, circuit board according to claim 1 and the first electrode layer and a second electrode layer is obtained by laminating a plurality alternately across the dielectric film. The circuit board according to claim 1 or 2 base substrate made of a resin material. Base substrate, an epoxy resin, the circuit board according to the polyimide resin, any one of a polyester resin, according to claim 1 to 3 comprising at least one material selected from the group consisting of fluorine-based copolymer and fiber glass. Electronic device that includes a circuit board and an electronic component according to any one of claims 1-4. Forming a metal layer made of titanium or a titanium alloy;
A process of anodizing in an electrolyte containing hydrogen peroxide at a temperature of 3 ° C. or less to form a metal layer surface into an amorphous titanium dioxide layer;
A complex oxide layer having a perovskite structure is formed by reacting an amorphous titanium dioxide layer with an aqueous solution having a pH of 11 or more containing at least one metal element selected from the group consisting of Ca, Sr and Ba in the range of 80 ° C. to boiling point. process, and on the complex oxide layer having a perovskite structure comprising the steps of forming a metal layer, the manufacturing method of circuit board of claim 1-4. In the step of forming a metal layer on the complex oxide layer of the perovskite structure, method of manufacturing a circuit board according to claim 6 metal layers are made of titanium or a titanium alloy.

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