JP3492853B2 - Circuit board with capacitive element - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit board with a capacitive element mounted on a communication device such as a cellular phone or a satellite communication. 2. Description of the Related Art Hitherto, a circuit board with a capacitance element has been used as a part of a component constituting a transmission / reception circuit of an electric signal in communication equipment such as a cellular phone and satellite communication. In general, such a circuit board with a capacitor is prepared by preparing an insulating substrate having a predetermined pattern of circuit wiring on the upper surface thereof.
It is formed by mounting a chip capacitor on the insulating substrate and electrically connecting its terminals to circuit wiring via solder or the like. However, recently, communication devices such as cellular phones and satellite communications have rapidly become smaller and lighter, and circuit wiring is formed by a thick film forming technique such as the Mo-Mn method in a conventional circuit board with a capacitor. Since the width of each circuit wiring and the gap between adjacent circuit wirings are wide, the shape of the chip capacitor is large and the whole is large, There has been a demand for a circuit board with a capacitive element. Therefore, it has been proposed to newly form a circuit board with a capacitor by attaching a circuit wiring and a capacitor to the insulating substrate by a thin film forming technique and electrically connecting the capacitor to the circuit wiring. ing. In such a circuit board with a capacitance element, the circuit wiring and the capacitance element are formed by a thin film forming technique, so that the line width of the circuit wiring and the space between adjacent lines are narrowed, and the shape of the capacitance element is small. It can be used for communication devices such as mobile phones and satellite communications whose weights are rapidly decreasing. [0007] The circuit board with a capacitor is formed by adopting a thin film forming technique such as a sputtering method or a vapor deposition method on a substrate whose circuit wiring is made of an electrically insulating material such as an aluminum oxide sintered body. A metal material such as tantalum, tungsten, titanium, chromium, etc. is applied to a predetermined thickness and then processed into a predetermined pattern by a photolithography technique. The thin film capacitor is first formed on a substrate made of an electrically insulating material. A lower electrode layer is formed by applying α-tantalum (tantalum nitride) to a predetermined thickness by a thin film forming technique such as a sputtering method, and then a dielectric made of tantalum oxynitride or the like is formed on the surface of the lower electrode layer; A metal material such as titanium-gold or nichrome-gold is deposited by a thin film forming technique such as a sputtering method or a vapor deposition method. Processed into a predetermined pattern by etching, it is formed by a dielectric layer and an upper electrode layer. [0008] However, in this conventional circuit board with a capacitor, when a dielectric material is deposited on the surface of the lower electrode layer of the capacitor by a thin film forming technique such as a sputtering method, Dielectric material cannot be deposited to a predetermined thickness on the corners between the upper surface and the side surfaces of the lower electrode layer, and as a result, the upper electrode layer and the lower electrode layer are electrically short-circuited,
The drawback was that the function as a capacitive element could not be exhibited. SUMMARY OF THE INVENTION The present invention has been devised in view of the above-mentioned drawbacks, and has as its object to provide a small-sized and light-weight capacitance element having a capacitance element having a predetermined capacitance value. It is to provide a circuit board. The present invention is a circuit board with a capacitance element formed by forming a thin film circuit wiring and a thin film capacitance element on an insulating substrate, wherein the thin film capacitance element is provided on a lower electrode layer and a surface of the lower electrode layer. A first dielectric layer applied, a first upper electrode layer applied on an upper surface of the first dielectric layer, and a second dielectric layer applied from the upper surface to the side surface of the first dielectric layer And being applied to the surface of the second dielectric layer and the first upper electrode layer,
A part is formed by a second upper electrode layer connected to the first upper electrode layer, and the second dielectric layer is formed by anodic oxidation of the first upper electrode layer. Things. According to the circuit board with the capacitance element of the present invention,
Since the circuit wiring and the capacitor are formed by adopting the thin film forming technology on the insulating substrate, the line width and the adjacent distance of the circuit wiring are reduced, and the shape of the capacitor is reduced. Can be mounted on communication devices such as mobile phones, which are rapidly progressing. Further, according to the circuit board with a capacitor of the present invention, the thin film capacitor includes a lower electrode layer, a first dielectric layer attached to a surface of the lower electrode layer, and a first dielectric layer. A first upper electrode layer applied on the upper surface, a second dielectric layer applied from the upper surface to the side surface of the first dielectric layer, and a surface of the second dielectric layer and the first upper electrode layer. A first dielectric layer formed of a second upper electrode layer that is applied and partially connected to the first upper electrode layer, and that is applied to a corner between an upper surface and a side surface of the lower electrode layer; Is thin and the second electrode layer is interposed between the lower electrode layer and the second upper electrode layer even if the lower electrode layer and the second upper electrode layer are electrically short-circuited. Therefore, the function as a thin-film capacitive element can be sufficiently exhibited. Further, according to the circuit board with the capacitance element of the present invention, the capacitance of the thin film capacitance element is obtained by electrically connecting the lower electrode layer and the second upper electrode layer with the first dielectric layer interposed therebetween. Since the relative dielectric constant of the second dielectric layer does not greatly affect the capacitance of the capacitor, the capacitance of the thin film capacitor greatly varies depending on the second dielectric layer. It can be set to a predetermined value without any problem. Next, the present invention will be described in detail with reference to the accompanying drawings. 1 and 2 show an embodiment of a circuit board with a capacitance element according to the present invention, wherein 1 is an insulating substrate, 2 is a thin film circuit wiring, and 3a and 3b are thin film capacitance elements. The insulating substrate 1 is made of an electrically insulating material such as an aluminum oxide sintered body, a mullite sintered body, a silicon carbide sintered body, an aluminum nitride sintered body, a glass ceramic sintered body, etc. In the case of a sintered body made of aluminum oxide, a suitable organic solvent and a solvent are added to raw material powders such as aluminum oxide, silicon oxide, magnesium oxide and calcium oxide to form a slurry, which is then mixed with a conventionally known doctor. A ceramic green sheet (ceramic green sheet) is obtained by forming into a sheet shape by a blade method, a calendar roll method, or the like. Thereafter, the ceramic green sheet is subjected to an appropriate punching process to form a predetermined shape, and at a temperature of about 1600 ° C. It is manufactured by firing. The insulating substrate 1 functions as a support member for supporting the thin film circuit wiring 2 and the thin film capacitance elements 3a, 3b, etc., and has on its upper surface a thin film circuit wiring 2 of a predetermined pattern and two thin film capacitors of a predetermined capacitance value. The elements 3a and 3b are formed by attachment. The thin film circuit wiring 2 formed on the upper surface of the insulating substrate 1 is used to connect the thin film capacitive elements 3a and 3b to other electronic components mounted on the upper surface of the insulating substrate 1, for example, the semiconductor element 4 or the like. Connected or thin film capacitive elements 3a, 3b
And the function of electrically connecting the semiconductor element 4 to an external electric circuit. The thin-film circuit wiring 2 includes an adhesion layer made of, for example, titanium, chromium, nickel-chromium alloy, a barrier layer made of nickel, palladium, platinum, etc., and a main conductor layer made of gold, copper, etc. It has a three-layer structure, and the above metals are sequentially deposited on the upper surface of the insulating substrate 1 by a thin film forming technique such as an ion plating method, a sputtering method, a plating method, and a vapor deposition method. Each layer thus formed is processed into a predetermined pattern by a photolithography technique so as to be formed on the insulating substrate 1 in a predetermined pattern. Further, since the thin film circuit wiring 2 is formed on the insulating substrate 1 by employing a thin film forming technique, the line width and the adjacent distance of the thin film circuit wiring 2 are extremely narrow, and the thin film circuit wiring 2 is formed on the insulating substrate 1 with high density. As a result, the insulating substrate 1 on which the thin film circuit wiring 2 is formed can be reduced in size. Further, two thin film capacitors 3a and 3b are formed on the upper surface of the insulating substrate 1, and the two thin film capacitors 3a and 3b are, as shown in FIG. A first dielectric layer 6 deposited on a surface of the lower electrode layer 5, a first upper electrode layer 7 deposited on an upper surface of the first dielectric layer 6, and a first dielectric layer 6; A second dielectric layer 8 applied from the upper surface to the side surface of the first and second dielectric layers 8 and the surface of the first upper electrode layer 7, and a part of the second dielectric layer 8 is connected to the first upper electrode layer 7. The first dielectric layer is formed between the lower electrode layer 5 and the first upper electrode layer 7 to which the second upper electrode layer 8 is electrically connected. A constant capacitance determined by the relative dielectric constant of No. 6 is formed. The lower electrode layer 5 of the two thin film capacitors 3a and 3b is connected to, for example, the thin film circuit wiring 2, and the upper electrode layer 7 is formed of an electrode of the semiconductor element 4 or another thin film circuit wiring 2
Connected directly or via a bonding wire, thereby connecting to a predetermined electric circuit. To form the two thin film capacitors 3 a and 3 b on the upper surface of the insulating substrate 1, first, the lower electrode layer 5 is formed on the insulating substrate 1. This lower electrode layer 5 is, for example,
It is made of α-tantalum (tantalum nitride), and the α-tantalum is deposited on the insulating substrate 1 to a predetermined thickness (250 Å to 10000 Å) by employing a thin film forming technique such as a sputtering method or an ion plating method. Thereafter, this is formed on the insulating substrate 1 by processing it into a predetermined pattern by photolithography. If the thickness of the lower electrode layer 5 made of α-tantalum is less than 250 angstroms, it becomes difficult to firmly join the lower electrode layer 5 to the insulating substrate 1, and if the thickness exceeds 10,000 angstroms, When the electrode layer 5 is applied on the insulating substrate 1, a large stress is present inside the lower electrode layer 5, and the intrinsic stress tends to cause the lower electrode layer 5 to be easily separated from the insulating substrate 1. Therefore, it is preferable that the lower electrode layer 5 made of α-tantalum has a thickness in the range of 250 Å to 10000 Å. Next, the first dielectric layer 6 is formed by subjecting a part of the surface of the lower electrode layer 5 to anodizing treatment and converting a part to tantalum oxynitride. The first dielectric layer 6 functions to form a predetermined capacitance between the lower electrode layer 5 and a first upper electrode layer 7 to which a second upper electrode layer 8 described later is electrically connected. , A lower electrode layer 5 made of α-tantalum (tantalum nitride) is immersed together with a platinum plate in an electrolytic solution such as citric acid, and then the lower electrode layer 5 is connected to an anode, and the platinum plate is connected to a cathode. Is formed by applying a voltage of 290 V to 500 V to the substrate. The first dielectric layer 6 has a thickness of 2000
The thickness can be made as thin as about Angstroms to about 10000 Angstroms, whereby the capacitance element can be made small and the capacitance can be made as large as about 400 pF / mm ² . Next, the first dielectric 6 is placed on the upper surface of the first dielectric 6.
A second dielectric layer 8 is applied to the upper electrode layer 7 from the upper surface to the side surface of the first dielectric layer 6. The first upper electrode layer 7 has a function of forming a predetermined capacitance determined by the relative dielectric constant of the first dielectric layer 6 disposed between the first upper electrode layer 7 and the lower electrode layer 5. It is made of aluminum or the like, and is deposited on the surface of the first dielectric layer 6 by a thin film forming technique such as an ion plating method, a sputtering method, or a vapor deposition method, and then is processed into a predetermined pattern by a photolithography technique. The first dielectric layer 6 is formed on the upper surface of the first dielectric layer 6 to a thickness of 1000 Å to 5000 Å. Further, the second dielectric layer 8 comprises a first dielectric layer 6
Is thin, the lower electrode layer 5 and a second upper electrode layer 9 to be described later are formed at the corners of the upper surface and side surfaces of the lower electrode layer 5.
An electric short circuit occurs between them, and effectively prevents loss of the function as a thin film capacitor, for example,
When the first upper electrode layer 7 made of aluminum or the like and made of aluminum is formed on the upper surface of the first dielectric layer 6, aluminum is simultaneously formed on the upper surface of the first dielectric layer 6 from the side surface. After that, this is anodically oxidized and converted to aluminum oxide, whereby the first dielectric layer 6 is deposited from the upper surface to the side surface. The second dielectric layer 8 has a thickness of 1000
If the thickness is less than Å, the electrical insulation of the second dielectric layer 8 tends to deteriorate. Therefore, it is preferable that the thickness of the second dielectric layer 8 be 1000 Å or more. Finally, the second upper electrode layer 9 is partially formed on the surfaces of the second dielectric layer 8 and the first upper electrode layer 7 so as to be electrically connected to the first upper electrode layer 7. Is adhered. The second upper electrode layer 9 comprises a first upper electrode layer 7
Is connected to an external electric circuit, and is made of a low-resistance metal material such as aluminum, copper, or gold. The second upper electrode layer 9 is made of aluminum, copper, gold, or the like by employing a thin film forming technique such as an ion plating method, a sputtering method, or a vapor deposition method. 7 and the surface of the insulating substrate 1, and thereafter, this is processed into a predetermined pattern by a photolithography technique, so that the surface of the second dielectric layer 8, the first upper electrode layer 7 and the surface of the insulating substrate 1
It is deposited to a predetermined thickness of Angstroms to 5000 Angstroms. The second upper electrode layer 9 has a thickness of 2
If the thickness is less than 50 angstroms, it tends to be difficult to firmly join the second upper electrode layer 9 to the second dielectric layer 8 and the first upper electrode layer 7. The second upper electrode layer 9 tends to be easily separated from the second dielectric layer 8 and the first upper electrode layer 7 due to the internal stress generated when the layer 9 is formed. Therefore, the second upper electrode layer 9 has a thickness of 250
It is preferable that the thickness be in the range of Angstroms to 5000 Angstroms. Since the second upper electrode layer 9 has the second dielectric layer 8 disposed under the second upper electrode layer 9, the thickness of the first dielectric layer 6 is small at the corners of the upper surface and side surfaces of the lower electrode layer 5. , The electrical short circuit is effectively prevented by the second dielectric layer 8, and as a result, each of the thin film capacitive elements 3a and 3b serves as a capacitive element. Can exhibit a predetermined function. Since the relative permittivity of the second dielectric layer 8 has little effect on the capacitance of the thin film capacitors 3a and 3b, the capacitance of the thin film capacitors 3a and 3b is reduced by the second dielectric layer. There is no large variation due to the body layer 8, and the capacitance of the thin film capacitive elements 3a and 3b can be set to a predetermined value. Thus, according to the circuit board with the capacitance element of the present invention, the semiconductor element 4 and other resistors are mounted and connected to the thin film circuit wiring 2 provided on the insulating substrate 1, and the lower electrodes of the thin film capacitance elements 3a and 3b are connected. If the layer 5 and the upper electrode layer 7 are connected to predetermined thin film circuit wirings 2 and electrodes of the semiconductor element 5 directly or via bonding wires, an electric circuit board mounted on a communication device such as a mobile phone or satellite communication It becomes. It should be noted that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. Although two thin film capacitors 3a and 3b are formed in the first embodiment, three or more thin film capacitors may be provided.
a, 3b lower electrode layer 5, dielectric layer 6, and upper electrode layer 7
May be formed of another material.
The lower electrode layers 5a and 3b may be formed of the same material as the thin film circuit wiring 2. According to the circuit board with the capacitive element of the present invention, since the circuit wiring and the capacitive element are formed by adopting the thin film forming technique on the insulating substrate, the line width and the adjacent distance of the circuit wiring are obtained. In addition, the size of the capacitor can be reduced, and the shape of the capacitor element can be reduced. Further, according to the circuit board with the capacitor element of the present invention, the thin film capacitor element has the lower electrode layer, the first dielectric layer adhered on the surface of the lower electrode layer, and the first dielectric layer. A first upper electrode layer applied to the upper surface, a second dielectric layer applied from the upper surface to the side surface of the first dielectric layer,
A second upper electrode layer formed on the dielectric layer and a surface of the first upper electrode layer, the second upper electrode layer being partially connected to the first upper electrode layer; Since the electrode layer is formed by anodic oxidation, the thickness of the first dielectric layer applied to the corner between the upper surface and the side surface of the lower electrode layer is small, and the lower electrode layer and the second upper electrode layer are electrically connected. The electrical short circuit is effectively prevented because the second dielectric layer is interposed between the lower electrode layer and the second upper electrode layer, and as a result, the function as a thin film capacitor is prevented. It can be fully demonstrated. Further, according to the circuit board with the capacitance element of the present invention, the capacitance of the thin film capacitance element is obtained by electrically connecting the lower electrode layer and the second upper electrode layer sandwiching the first dielectric layer. Since the relative permittivity of the second dielectric layer does not significantly affect the capacitance of the capacitor, the capacitance of the thin film capacitor greatly varies depending on the second dielectric layer. It can be set to a predetermined value without any problem.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view showing one embodiment of a circuit board with a capacitance element of the present invention. FIG. 2 is an enlarged cross-sectional view for explaining the thin film capacitor shown in FIG. [Description of Signs] 1 ... Insulating substrate 2 ... Thin film circuit wiring 3a, 3b ... Thin film capacitive element 5 ... Lower electrode layer 6 ... 1 dielectric layer 7 first upper electrode layer 8 second dielectric layer 9 second upper electrode layer

Claims (1)

(57) Claims 1. A circuit board with a capacitance element formed by forming a thin film circuit wiring and a thin film capacitance element on an insulating substrate, wherein the thin film capacitance element has a lower electrode layer, A first dielectric layer deposited on the surface of the lower electrode layer, a first upper electrode layer deposited on the upper surface of the first dielectric layer, and a first dielectric layer deposited on the upper surface of the first dielectric layer from the side surface; The second dielectric layer, and the second dielectric layer and the surface of the first upper electrode layer.
A second upper electrode layer connected to the upper electrode layer , wherein the second dielectric layer is formed of anodic acid of the first upper electrode layer.
A circuit board with a capacitive element, characterized by being formed by lithography.