JP5224181B2 - Variable capacitor parts - Google Patents

Description

  The present invention relates to a variable-capacitance capacitor component that can be manufactured at a low cost and used for a tuning circuit or the like.

  Conventionally, a varicap diode, which is a variable capacitor section made of a semiconductor, is used in an AM / FM tuning circuit or the like. For example, as shown in FIG. 5, in order to construct a tuning circuit composed of an inductor L0 and a variable capacitor C0 connected in parallel, a tuning circuit is formed using a varicap diode 1 as shown in FIG. It is composed.

  In this circuit, when a control voltage is applied from the power supply V, a pair of decoupling inductor component 2, bypass capacitor component 3, and coupling capacitor component 4 must be connected to varicap diode 1 for noise countermeasures and the like. . That is, a decoupling inductor is required so that a high frequency does not flow into the direct current side, and a coupling capacitor is required so that a direct current does not flow into the high frequency side. These are all mounted on the circuit board as discrete components.

  In the above tuning circuit, it is necessary to mount at least five discrete components except for the inductor portion L0, which increases the mounting area and component cost, and also increases the stray capacitance component. In the case of the varicap capacitor 1, it is difficult to incorporate a coupling capacitor. For this reason, there is a demand for downsizing and cost reduction of circuits including capacitors.

  For example, as a technology for integrating and miniaturizing capacitors, Patent Document 1 conventionally includes a metal oxide layer mounted on a silicon substrate or a glass substrate and provided between metal layers formed on these substrates. An electronic component with a built-in capacitor in which a capacitor having a small ESL (equivalent series inductance) is built in by electrodes formed in metal layers adjacent to the upper and lower sides has been proposed.

JP 2007-158164 A (Claims)

The following problems remain in the conventional technology.
That is, with the technique described in Patent Document 1, it is difficult to produce a capacitor having a small capacitance (variable capacitance capacitor) and a large capacitor (coupling capacitor) necessary for a tuning circuit or the like on the substrate. In addition, a large number of laminated structures are required to form a plurality of capacitors and inductors. For this reason, the manufacturing process becomes complicated, leading to an increase in manufacturing cost. Further, in order to integrate and mount the varicap diode as a variable capacitor, a semiconductor layer is required, and there is a problem that the layer structure and the manufacturing process are complicated.

  The present invention has been made in view of the above problems, and an object thereof is to provide a low-capacitance variable-capacitance capacitor component having a coupling capacitor and a variable-capacitance capacitor with a small layer structure without using a varicap diode. And

  The present invention employs the following configuration in order to solve the above problems. That is, the variable capacitor part of the present invention includes an insulating substrate, a pair of lower electrodes patterned on the insulating substrate, and a ferroelectric material patterned on the insulating substrate and the lower electrode. A thin film, a pair of terminal electrodes which are patterned on the ferroelectric thin film and directly above the pair of lower electrodes and constitute a pair of coupling capacitors, and are disposed across both of the pair of lower electrodes. An upper electrode patterned on the ferroelectric thin film to constitute a variable capacitor, and a pair of control voltage electrodes patterned on the ferroelectric thin film or on the insulating substrate and connected to the pair of lower electrodes And.

In this variable capacitor component, a pair of lower electrodes on an insulative substrate, a pair of control voltage electrodes connected to these lower electrodes, and a ferroelectric thin film disposed over both of the pair of lower electrodes A capacitor formed between a pair of coupling capacitors, by connecting a power source to the control voltage electrode and applying a control voltage to change the dielectric constant of the ferroelectric thin film. Can be a variable capacitor. That is, a coupling capacitor and a variable capacitor having greatly different capacities can be integrated on the insulating substrate through the same ferroelectric thin film, and a band-pass filter can be configured.
Therefore, the stray capacitance component can be minimized by integration with a small layer structure. In addition, since the semiconductor device is configured with a small layer structure and does not use a semiconductor layer, it can be integrated with a smaller area, the manufacturing process can be simplified, and the device cost can be reduced.
Furthermore, when a conventional varicap diode is used, there is polarity and mounting in consideration of the polarity is necessary. On the other hand, since the variable capacitor part of the present invention has no polarity, confirm the polarity in mounting. Etc. become unnecessary.

Further, the variable capacitor part of the present invention is formed on the insulating substrate so as to be covered with the ferroelectric thin film, and has one end connected to the control voltage electrode and the other end to the lower electrode. A pair of inductor wiring portions that are connected to form a decoupling inductor are provided.
That is, in this variable capacitor component, a pattern is formed on an insulating substrate covered with a ferroelectric thin film, and one end is connected to the control voltage electrode and the other end is connected to the lower electrode, thereby decoupling inductor. Since the ferroelectric thin film can provide a high capacity and inductance, it can be integrated including a decoupling inductor.

In the variable capacitor part of the present invention, a power source for applying a control voltage is connected to a pair of the control voltage electrodes, and the variable capacitor of the tuning circuit configured by an inductor unit and a variable capacitor unit connected in parallel It is a capacitor part.
That is, in this variable capacitor part, a power source for applying a control voltage is connected to a pair of control voltage electrodes, and a variable capacitor part of a tuning circuit composed of an inductor part and a variable capacitor part connected in parallel is formed. Therefore, a tuning circuit can be configured at a low cost.

In the variable capacitor part of the present invention, it is preferable that the ferroelectric thin film is a voltage nonlinear ferroelectric thin film capable of obtaining a nonlinear dielectric characteristic by applying an electric field.
That is, in this variable capacitor component, the ferroelectric thin film is a voltage nonlinear ferroelectric thin film that can obtain a nonlinear dielectric characteristic by applying an electric field, so that it greatly increases depending on the voltage application (electric field application) due to the nonlinear dielectric characteristic. The dielectric constant can be changed, and a variable capacitor having a large capacitance variation can be obtained.

The present invention has the following effects.
That is, according to the variable capacitor component according to the present invention, the pair of lower electrodes on the insulating substrate, the pair of control voltage electrodes connected to the lower electrodes, and the pair of lower electrodes are directly straddled. Since the upper electrode on the arranged ferroelectric thin film is provided, the stray capacitance component can be minimized and the manufacturing process can be simplified.
Conventionally, in order to construct a tuning circuit, it was basically necessary to mount five discrete components. However, according to the present invention, it is only necessary to mount one capacitance variable capacitor component. Reduction of the mounting area, space saving and device cost reduction.

1 is a plan view showing one embodiment of a variable capacitor component according to the present invention. It is the sectional view on the AA line of FIG. 1, and the BB sectional drawing. In this embodiment, it is an equivalent circuit diagram which shows a variable capacitor part. In this embodiment, it is an equivalent circuit diagram which shows the tuning circuit using a variable capacitor part. It is a circuit diagram which shows the tuning circuit which uses a variable capacitor. FIG. 6 is an equivalent circuit diagram showing a case where a variable capacitor circuit is configured with discrete components including a varicap diode in the tuning circuit shown in FIG. 5.

  Hereinafter, an embodiment of a variable capacitor component according to the present invention will be described with reference to FIGS. In each drawing used for the following description, the scale is appropriately changed in order to make each member recognizable or easily recognizable.

As shown in FIG. 5, the variable capacitor part 10 of this embodiment is a capacitor part used for the variable capacitor part C0 of the tuning circuit composed of the inductor part L0 and the variable capacitor part C0 connected in parallel. It is.
Examples of the tuning circuit include an AM / FM tuning circuit used for car navigation, audio components, etc., an FM transmitter used for transceivers, business radios, etc., an FM tuner IC used for mobile phones, portable audio devices, etc. Various circuits such as a TV circuit, a TV tuner used in a TV or a video recorder, a VCO (Voltage Controlled Oscillator) used in a mobile phone, a wireless LAN, and the like are applicable.

  As shown in FIGS. 1 to 3, the variable capacitor component 10 includes an insulating substrate 11, a pair of lower electrodes 12 patterned on the insulating substrate 11 and adjacent to each other, and an insulating substrate 11. A ferroelectric thin film 13 patterned on the upper and lower electrodes 12, and a pair of terminal electrodes 14 that are patterned directly on the ferroelectric thin film 13 and on the ferroelectric thin film 13 to constitute a pair of coupling capacitors C1. The upper electrode 15 which is arranged over the pair of lower electrodes 12 and patterned on the ferroelectric thin film 13 to form the variable capacitor C2, and the pair of patterned electrodes formed on the ferroelectric thin film 13. A pair of control voltage electrodes 16 connected to the lower electrode 12.

  In addition, the variable capacitor component 10 is a pattern formed by covering the insulating substrate 11 with the ferroelectric thin film 13 and having one end formed on the ferroelectric thin film 13 via the via connection portion 17. 16 and a pair of inductor wiring portions 18 that constitute the decoupling inductor L1 and the capacitor C3 with the other end connected to the lower electrode 12. The inductor wiring portions 18 are formed in a spiral shape.

The insulating substrate 11 is an alumina substrate, for example.
The lower electrode 12, the control voltage electrode 16, the upper electrode 15, and the terminal electrode 14 are made of Pt, Ti, Ir, or the like by sputtering or the like.
The ferroelectric thin film 13 is a thin film having a high dielectric constant and a dielectric constant that changes in accordance with an applied voltage. In particular, the ferroelectric thin film 13 can obtain a nonlinear dielectric characteristic by applying an electric field (voltage application). A dielectric thin film is preferred. For example, a (Ba _1-x , Sr _x ) TiO ₃ thin film formed by sputtering or the like can be used as the ferroelectric thin film 13. This (Ba _1-x , Sr _x ) TiO ₃ thin film is a voltage nonlinear ferroelectric thin film in which a remarkable nonlinear dielectric characteristic can be obtained by applying an electric field.

The decoupling inductor L1 and the capacitor C3 constitute a parallel resonance circuit, and are composed of an inductor component and a capacitor component by the inductor wiring portion 18 patterned in a spiral shape.
The pair of coupling capacitors C <b> 1 includes a pair of lower electrodes 12 and a pair of terminal electrodes 14 that sandwich the ferroelectric thin film 13. That is, the coupling capacitor C1 has a high capacitance due to the ferroelectric thin film 13 having a high dielectric constant.

The decoupling inductor L1 prevents a high frequency from the terminal electrode 14 from entering a control voltage electrode 16 that is a terminal to which a DC voltage is applied.
The capacitor C3 is a capacitor for setting the frequency band of the high-frequency circuit as a stop band, and a greater attenuation is obtained than when only the decoupling inductor L1 is used. In the case of decoupling in a wide band, only the decoupling inductor L1 is better. In this case, the shape pattern of the inductor wiring portion 18 may be changed so as not to constitute the capacitor C3 as much as possible.
The coupling capacitor C1 prevents a DC voltage from flowing into a high-frequency circuit connected to the terminal electrode 14.

The variable capacitor C2 is configured by a pair of lower electrodes 12 sandwiching a ferroelectric thin film 13 to which a control voltage is applied by a power source V via a control voltage electrode 16 via an upper electrode 15 that is a float electrode. The That is, the ferroelectric thin film 13 is sandwiched between one of the pair of lower electrodes 12 and the upper electrode 15, and the ferroelectric thin film 13 is sandwiched between the other of the pair of lower electrodes 12 and the upper electrode 15. A variable capacitor C2 is obtained.
For example, the variable capacitor C2 is about 100 pF, and the pair of coupling capacitors C1 is 10 to 1000 times the variable capacitor C2, that is, about 1 μF to about 100 μF.

Therefore, an equivalent circuit of the variable capacitor part 10 is configured as shown in FIG.
As shown in FIG. 4, the variable capacitor component 10 includes a power supply V for applying a control voltage to a pair of control voltage electrodes 16, and includes an inductor L0 and a variable capacitor C0 connected in parallel. The variable capacitor portion C0 of the tuning circuit.

That is, when a control voltage is applied to the ferroelectric thin film 13 by the power source V via the pair of control voltage electrodes 16, the dielectric constant of the ferroelectric thin film 13 changes according to the control voltage. For this reason, when the dielectric constant of the ferroelectric thin film 13 sandwiched between the pair of lower electrodes 12 via the upper electrode 15 changes, the capacitance of the variable capacitor C2 changes according to the control voltage.
Reference numeral 19 in the figure is an analog GND (ground), and reference numeral 20 is a digital GND (ground).

  Thus, the variable capacitor part 10 of this embodiment includes both the pair of lower electrodes 12 on the insulating substrate 11, the pair of control voltage electrodes 16 connected to the lower electrodes 12, and the pair of lower electrodes 12. And the upper electrode 15 on the ferroelectric thin film 13 disposed so as to straddle the upper portion of the ferroelectric thin film 13. By connecting the power source V to the control voltage electrode 16 and applying the control voltage, the ferroelectric thin film 13 The dielectric constant changes, and the capacitor formed between the pair of coupling capacitors C1 can be used as the variable capacitor C2. That is, the coupling capacitor C1 and the variable capacitor C2 having greatly different capacities can be integrated on the insulating substrate 11 through the same ferroelectric thin film 13, and a band-pass filter can be configured.

Therefore, the stray capacitance component can be minimized by the layer structure in which peripheral circuits including the variable capacitor C2 are integrated at a time. In addition, since the semiconductor device is configured with a small layer structure and does not use a semiconductor layer, it can be integrated with a smaller area, the manufacturing process can be simplified, and the device cost can be reduced.
Further, when using the conventional varicap diode, since there is polarity, it is necessary to mount in consideration of the polarity. On the other hand, in the variable capacitor part 10 of this embodiment, since there is no polarity, Checking the polarity is unnecessary.

  Further, a pattern is formed on the insulating substrate 11 by being covered with a ferroelectric thin film 13, and one end is connected to the control voltage electrode 16 and the other end is connected to the lower electrode 12. Since the pair of inductor wiring portions 18 constituting C3 is provided, high capacitance and inductance can be obtained by the ferroelectric thin film 13, and the decoupling inductor L1 and the capacitor C3 can be integrated.

  Further, since the ferroelectric thin film 13 is a voltage nonlinear ferroelectric thin film that can obtain a nonlinear dielectric characteristic by applying an electric field, the dielectric constant can be greatly changed according to the voltage application (electric field application) by the nonlinear dielectric characteristic. Thus, a variable capacitor C2 having a large capacitance change amount can be obtained.

  As described above, in the variable capacitor part 10, the power supply V for applying the control voltage is connected to the pair of control voltage electrodes 16, and the tuning circuit is configured by the inductor part L0 and the variable capacitor part C0 connected in parallel. Therefore, the tuning circuit can be configured at low cost.

  The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

For example, in the above embodiment, the control voltage electrode 16 connected to the inductor wiring part 18 via the via connection part 17 penetrating the ferroelectric thin film 13 is formed on the ferroelectric thin film 13. The electrode 16 may be formed on the insulating substrate 11 so as to be directly connected to the inductor wiring portion 18.
Further, as another application of the variable capacitor component 10 of the present embodiment, it can be applied as a variable capacitor used in a phase shifter, a filter, an antenna, and the like.

  DESCRIPTION OF SYMBOLS 10 ... Variable capacitor component, 11 ... Insulating substrate, 12 ... Lower electrode, 13 ... Ferroelectric thin film, 14 ... Terminal electrode, 15 ... Upper electrode, 16 ... Control voltage electrode, 17 ... Via connection part, 18 ... Inductor Wiring part, C0 ... variable capacitor part, C1 ... coupling capacitor, C2 ... variable capacitor, C3 ... capacitor, L0 ... inductor part, L1 ... decoupling inductor, V ... power source

Claims (4)

An insulating substrate;
A pair of lower electrodes patterned on the insulating substrate;
A ferroelectric thin film patterned on the insulating substrate and the lower electrode;
A pair of terminal electrodes patterned directly on the ferroelectric thin film and directly above the pair of lower electrodes;
An upper electrode which is patterned on the ferroelectric thin film is disposed across right above both of the pair of the lower electrode,
A pair of control voltage electrodes patterned on the ferroelectric thin film or the insulating substrate and connected to the pair of lower electrodes ,
A pair of coupling capacitors is constituted by the pair of lower electrodes and the pair of terminal electrodes sandwiching the dielectric thin film,
A variable capacitor is configured between the pair of lower electrodes sandwiching the ferroelectric thin film via the upper electrode,
The variable capacitor part, wherein the coupling capacitor and the variable capacitor are integrated on the insulating substrate via the same ferroelectric thin film . In the variable capacitor part according to claim 1,
A pattern is formed on the insulating substrate so as to be covered with the ferroelectric thin film, and one end is connected to the control voltage electrode and the other end is connected to the lower electrode to form a decoupling inductor. A variable capacitor component comprising an inductor wiring portion. In the variable capacitor part according to claim 1 or 2,
A power supply for applying a control voltage is connected to the pair of control voltage electrodes, and the power supply is used for the variable capacitor part of a tuning circuit including an inductor part and a variable capacitor part connected in parallel. Variable capacitor parts. In the variable capacitor part according to any one of claims 1 to 3,
A variable capacitance capacitor component, wherein the ferroelectric thin film is a voltage nonlinear ferroelectric thin film capable of obtaining a nonlinear dielectric characteristic by applying an electric field.

Images