JPH10149951A - Variable capacitance capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a variable capacitance capacitor, the capacitance change of which can be controlled with high accuracy. SOLUTION: Leg sections 2a and 2b are formed on a substrate 1 at an interval, and beam sections 4a and 4b are respectively extended from the sections 2a and 2b and connected to a common moving piece 5. The sections 4a and 4b and piece 5 are oppositely faced to the substrate 1 with gaps 10 in between, and reference substrates 8 are formed on the surfaces of the sections 4a and 4b and piece 5 facing the substrate 1. Then, drive electrodes 6a and 6b respectively faced to the sections 4a and 4b and a detecting electrode 7 faced to the piece 5 are formed on the substrate 1. The widths D of the beams of the sections 4a and 4b become narrower toward the piece 5 from their base end sections. When the sections 4a and 4b are deformed by bending the sections 4a and 4b toward the substrate 1, the interval between the reference electrode on the piece 5 and the detecting electrode 7 changes, and the change of the capacitance between the electrodes 7 and 8 can be controlled with accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable capacitor capable of changing the capacitance.

[0002]

2. Description of the Related Art Variable capacitors and varactor diodes are known as variable capacitance capacitors. As is well known, the variable condenser has electrodes facing each other and a rotating mechanism such as a motor, and varies the facing area of the electrodes facing each other by the rotating mechanism to reduce the capacitance between the electrodes. It is variable. The varactor diode can vary the parasitic capacitance according to the magnitude of the voltage applied from the outside.

[0003] Such a variable capacitor is incorporated in an oscillation circuit, a modulation circuit, or the like. For example, when a high-frequency signal is applied, the variable capacitor outputs an output voltage signal corresponding to the capacitance of the variable capacitor. Then, the capacitance (parasitic capacitance) of the variable capacitor is used variably so that the oscillation circuit or the modulation circuit incorporating the variable capacitor can obtain a desired circuit output.

[0004]

However, the structure of the variable condenser is complicated, and it is difficult to reduce the size of the rotating mechanism which is indispensable for changing the capacitance.
There is a problem that it is difficult to reduce the size of the variable condenser.

Since the varactor diode can be formed by a single element, it is easy to reduce the size. However, the internal resistance r must be increased in order to increase the withstand voltage. The following problem arises due to the increase in r.

The Q value of the output voltage signal of the varactor diode can be expressed by the following equation (1).

Q = 1 / (2πfcr) (1)

Here, f in the above equation (1) is the frequency of the high-frequency signal applied to the varactor diode, c indicates the parasitic capacitance of the varactor diode, and r indicates the internal resistance of the varactor diode.

As described above, when the internal resistance r is increased in order to improve the withstand voltage of the varactor diode, the Q value is greatly reduced as shown in the above equation (1). For this reason, the carrier noise of the output voltage signal increases and the SN ratio of the output voltage signal deteriorates. As described above, when the internal resistance r is increased in order to improve the withstand voltage of the varactor diode, there arises a problem that the output performance of the varactor diode deteriorates.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to make it easy to reduce the size and to perform variable control of the capacitance with high accuracy.
An object of the present invention is to provide a variable capacitor capable of improving the Q value of an output voltage signal and improving the output performance of the variable capacitor.

[0011]

Means for Solving the Problems To achieve the above object, the present invention has the following structure to solve the above problems. That is, a first aspect of the present invention includes a substrate,
A plurality of legs fixedly formed on the substrate and disposed with a gap therebetween; a beam formed to extend from each of the legs and disposed to face the substrate with a gap therebetween; A movable piece commonly connected to the distal end side and disposed opposite to the substrate via a gap; a movable electrode formed on the substrate facing surface of the movable piece and the substrate facing surface of the beam portion; and a movable electrode formed on the substrate. Means for solving the above-mentioned problem, comprising a movable electrode and a fixed electrode disposed opposite to each other with a gap interposed therebetween, wherein the beam portion has a configuration in which the width of the beam on the distal end side is narrower than that on the base end side. And

According to a second aspect of the present invention, in the first aspect, the fixed electrode includes a movable piece facing electrode facing the substrate facing surface of the movable piece and a beam facing electrode facing the substrate facing surface of the beam. Separately formed, the movable piece counter electrode forms a detection electrode for detecting capacitance between the movable piece and the movable electrode, and the beam portion counter electrode forms a drive electrode for bending and deforming the beam portion. With such a configuration, the above-mentioned problem is solved.

According to a third aspect of the present invention, in the first or second aspect, the movable electrode includes a movable electrode formed on a substrate facing surface of a movable piece and a movable electrode formed on a substrate facing surface of a beam. The movable electrode of the movable piece forms a detection reference electrode for detecting the capacitance between the fixed electrode and the movable electrode,
The movable electrode of the beam part serves as a means for solving the above problem by having a configuration in which the movable electrode serves as a reference electrode for driving for bending and deforming the beam part.

According to a fourth aspect of the invention, there is provided a substrate, a plurality of legs fixedly formed on the substrate and disposed with a gap therebetween, and extended from each of the legs and opposed to the substrate with a gap therebetween. A beam portion to be provided, and a movable piece commonly connected to the distal end side of each of these beam portions and disposed to face the substrate with a gap therebetween,
A movable electrode formed on the substrate-facing surface of the movable piece and the substrate-facing surface of the beam, and a fixed electrode formed on the substrate and opposed to the movable electrode via a gap; The piece is formed as a means that solves the above-mentioned problem with a configuration in which the piece is formed so as to protrude beyond the width of the front end side of the beam portion and to have a wide surface.

A fifth aspect of the present invention is a means for solving the above-mentioned problem with a configuration in which the beam portion constituting the fourth aspect has a configuration in which the width of the beam on the distal end side is smaller than that on the base end side.

According to a sixth aspect of the present invention, in the fourth or fifth aspect, the fixed electrode comprises a movable piece facing electrode facing the substrate facing surface of the movable piece and a beam facing the beam facing the substrate facing surface of the beam. The movable piece counter electrode is formed as a detection electrode for detecting the capacitance between the movable piece and the movable electrode, and the beam portion counter electrode is a drive electrode for bending and deforming the beam portion. The above configuration is a means for solving the above problem.

According to a seventh aspect of the present invention, there is provided the fourth, fifth or sixth aspect.
The movable electrode which constitutes the invention of the above is separately formed into a movable electrode formed on the substrate facing surface of the movable piece and a movable electrode formed on the substrate facing surface of the beam, and the movable electrode of the movable piece is a fixed electrode. The above object is achieved by a configuration in which the movable electrode of the beam portion is configured as a reference electrode for driving for bending and deforming the beam portion. It is a means to solve.

In the invention having the above structure, for example, the movable electrode and the fixed electrode of the variable capacitor are respectively connected to predetermined connection portions of a circuit such as an oscillation circuit and a modulation circuit, and are incorporated in the circuit. A voltage applying means for applying a bias voltage between the movable electrode and the fixed electrode is connected to the movable electrode and the fixed electrode. When a DC bias voltage is applied between the movable electrode and the fixed electrode from the voltage applying means, Coulomb force acts between the movable electrode and the fixed electrode, the movable electrode is attracted to the fixed electrode, and the beam portion is positioned on the substrate side. The movable piece is displaced toward the substrate side. Due to the displacement of the beam portion and the movable piece toward the substrate, the distance between the movable electrode and the fixed electrode is changed, and the capacitance between the movable electrode and the fixed electrode is changed.

In this state, when a high-frequency signal is externally applied between the movable electrode and the fixed electrode, an output voltage signal corresponding to the magnitude of the capacitance between the movable electrode and the fixed electrode is output to the outside. You.

As described above, by changing the distance between the movable electrode and the fixed electrode, the capacitance between the movable electrode and the fixed electrode is changed, and the variable control of the distance between the movable electrode and the fixed electrode is performed with high precision. Therefore, the variable control of the capacitance between the movable electrode and the fixed electrode is performed with high accuracy. Further, since the variable capacitor of the present invention has a simple structure and can be manufactured using the surface micromachining technology, it is easy to reduce the size of the variable capacitor.

Since the width of each beam portion is made smaller at the distal end side than at the proximal end side, the facing area between each beam portion and the fixed electrode is reduced at the distal end side than at the base end side of each beam portion. Due to the decrease in the facing area, the magnitude of the Coulomb force generated between the movable electrode and the fixed electrode formed on the substrate facing surface of each beam can be made uniform over the entire facing area. .

[0022]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1A shows a variable capacitor according to the first embodiment, and FIG. 1B shows an AA portion of the variable capacitor shown in FIG. 1A. Is shown. The variable capacitor of this embodiment includes a substrate 1, legs 2a and 2b, a doubly supported beam 3, drive electrodes 6a and 6b serving as beam counter electrodes, and a detection electrode 7 serving as a movable piece counter electrode. A reference electrode 8 that is a movable electrode;
It has lead electrodes 11, 12, 13, and 14.

As shown in FIGS. 1 (a) and 1 (b), a leg 2a and a leg 2b are arranged on a substrate 1 with a gap therebetween, and are extended over the legs 2a and 2b. Doubly supported beam 3
Are disposed opposite to the substrate surface with a gap 10 therebetween. In this doubly supported beam 3, the width D of the beam is continuously narrowed from the fixed ends on both ends toward the central region. A movable electrode 8 is formed on the substrate facing surface of the doubly supported beam 3, and drive electrodes 6 a and 6 b and a detection electrode 7 which are disposed to face the reference electrode 8 via a gap 10 are formed on the substrate 1. ing.

The drive electrodes 6a and 6b and the detection electrode 7 are arranged in the direction in which the doubly supported beam 3 extends with a gap therebetween. The drive electrode 6a is formed on the side closer to the leg 2a. Are formed on the side closer to the leg 2 b, and the detection electrode 7 is disposed opposite to the central region of the doubly supported beam 3. These drive electrodes 6a and 6b and the detection electrode 7 form a fixed electrode.

In this embodiment, the part of the doubly supported beam 3 facing the drive electrode 6a via the gap 10 is the beam portion 4a.
The portion of the doubly supported beam 3 facing the drive electrode 6b via the gap 10 constitutes a beam portion 4b, and the central region of the doubly supported beam 3 facing the detection electrode 7 via the gap 10 is a movable piece. 5
Is composed.

Further, extraction electrodes 11, 12, 13, and 14 extracted from the driving electrode 6a, the detection electrode 7, the driving electrode 6b, and the reference electrode 8, respectively, are formed on the substrate 1.

The substrate 1 may be an insulating substrate such as glass or ceramics, or a silicon substrate, a gallium arsenide substrate, or a metal coated with a coating film (for example, silicon oxide, silicon nitride, resin). It is formed of a substrate or the like. The cantilever 3 (beams 4a, 4b, movable piece 5) is formed of silicon oxide, silicon nitride, silicon, or the like, and includes drive electrodes 6a, 6b, a detection electrode 7, a reference electrode 8, an extraction electrode 11, 12,1
3, 14 are aluminum, gold, titanium, chromium, silver,
It is formed of a metal such as copper, palladium, platinum, nickel, and nichrome, or a semiconductor such as silicon doped with impurities such as boron, arsenic, phosphorus, and antimony.

The variable capacitor of this embodiment is configured as described above. When the variable capacitor of this embodiment is incorporated in an oscillation circuit, a modulation circuit, or the like, for example, the extraction electrode 12, 14 are connected to predetermined connection portions of the circuit, and voltage applying means (not shown) is connected to the lead electrodes 11, 13, and 14.

For example, a current is applied from the voltage applying means to the drive electrodes 6a, 6b and the reference electrode 8 via the extraction electrodes 11, 13, 14 so that the drive electrode 6a and the drive electrode 6
When a DC bias voltage is applied between the reference electrode 8 in the beam portion 4a opposing the driving electrode 6a and between the driving electrode 6b and the reference electrode 8 in the beam portion 4b opposing the driving electrode 6b, the driving electrode 6a Between the reference electrode 8 at the beam 4a and the drive electrode 6
A Coulomb force acts between the reference electrode 8 at the point b and the beam 4b.

The Coulomb force attracts the reference electrode 8 at the beam 4a to the drive electrode 6a and the reference electrode 8 at the beam 4b to the drive electrode 6b.
Both a and 4b bend and deform toward the substrate 1 side. This beam part 4
The movable piece 5 is displaced toward the substrate 1 in accordance with the bending deformations a and 4b toward the substrate 1, and the distance between the detection electrode 7 and the reference electrode 8 of the movable piece 5 facing the detection electrode 7 is reduced. The capacitance between the detection electrode 7 and the reference electrode 8 in the movable piece 5 increases.

On the other hand, when a high-frequency signal is applied between the detection electrode 7 and the reference electrode 8 of the movable piece 5 via the extraction electrode 14 from the outside, static electricity between the detection electrode 7 and the reference electrode 8 of the movable piece 5 is obtained. An output voltage signal corresponding to the capacitance is output to the outside via the extraction electrode 12.

As described above, this variable capacitor uses the Coulomb force to bend and deform the beam portions 4a and 4b, displaces the movable piece 5, and moves the movable electrode 5 between the detection electrode 7 and the reference electrode 8 in the movable element 5 portion. And the capacitance between the detection electrode 7 and the reference electrode 8 of the movable piece 5 can be varied.

Hereinafter, an example of a method of manufacturing the variable capacitor having the above configuration will be briefly described with reference to FIG. FIG. 2 schematically shows a cross section taken along the line AA shown in FIG.

First, the drive electrodes 6a, 6b
And a conductor film forming the detection electrode 7 and the extraction electrodes 11, 12, and 13 is formed by a film formation technique such as vapor deposition, sputtering, CVD, or printing. The drive electrode 6 is provided on the upper side of the conductive film.
a, 6b, the detection electrode 7, and the extraction electrodes 11, 12, 13
Is formed by a technique such as photolithography. The conductor film other than the resist pattern portion is removed by etching, and then the resist pattern is removed, as shown in FIG.
The drive electrodes 6a and 6b, the detection electrode 7, and the extraction electrode 11,
12 and 13 are formed on the substrate 1.

Next, as shown in FIG. 2B, a sacrifice layer (for example, a layer of phosphorus glass or ZnO) 15 is formed on a predetermined surface region of the substrate 1 by vapor deposition, sputtering, CVD, or the like. I do. Then, on the substrate 1 on which the sacrificial layer 15 is formed, a conductor film forming the reference electrode 8 and the lead electrode 14 is formed by a film formation technique such as vapor deposition, sputtering, CVD, or printing. Thereafter, a resist pattern for defining the formation region of the reference electrode 8 and the lead electrode 14 is formed by photolithography or the like, and thereafter, the excess conductor film other than the resist pattern portion is removed by etching.
After the etching of the excess conductive film, the resist pattern is removed, and the reference electrode 8 and the lead electrode 14 are formed.

Further, on the upper side of the conductor film, the legs 2a,
2b and a leg / beam forming film forming the doubly supported beam 3 are formed,
On the upper side, a resist pattern that defines the formation regions of the legs 2a and 2b and the doubly supported beam 3 is formed by photolithography or the like, and extra legs other than the resist pattern are formed.
The beam forming film is removed by etching. Then, the resist pattern is removed to form the legs 2a, 2b and the double-supported beam 3, as shown in FIG.

Finally, the sacrificial layer 15 is removed by etching, and as shown in FIG. 2D, a gap 10 is formed between the substrate 1 and the cantilever 3 to complete a variable capacitor.

According to the embodiment, the leg 2 is attached to the substrate 1.
a, 2b are provided, and are bridged between the legs 2a, 2b to form a doubly supported beam 3. A reference electrode 8 is provided on the substrate facing surface of the doubly supported beam 3 and a gap 10 is provided between the reference electrode 8 and the gap 10. Since the drive electrodes 6a and 6b and the detection electrode 7 disposed opposite to each other are provided on the substrate 1 to form a variable capacitance capacitor, the structure is simple and can be manufactured by the surface micromachining technology. It is easy to reduce the size of the variable capacitor.

In this embodiment, the fixed electrodes are separately formed into the drive electrodes 6a and 6b and the detection electrode 7, and the drive electrodes 6a and 6b are disposed opposite to the beams 4a and 4b, respectively. By applying a Coulomb force between the electrode 6a and the reference electrode 8 at the beam 4a and between the drive electrode 6b and the reference electrode 8 at the beam 4b, the beams 4a and 4b can be bent and deformed.

The movable piece 5 is displaced toward the substrate along with the bending deformation of the beams 4a and 4b, and the displacement of the movable piece 5 is larger than the bending deformation (displacement) of the beams 4a and 4b. In this embodiment, since the detection electrode 7 is provided in a region facing the movable piece 5 whose displacement amount is large, the beam portions 4a, 4b can be formed at a low voltage.
Is slightly bent and deformed, the detection electrode 7 and the movable piece 5
The distance between the reference electrodes 8 in the portion can be greatly varied, and the capacitance between the detection electrode 7 and the reference electrode 8 in the movable piece 5 can be greatly varied.

Further, in this embodiment, as described above, the doubly supported beam 3 is configured such that the width of the beam is continuously narrowed from the fixed ends on both ends toward the central region. Effects can be achieved.

For example, as shown in FIG. 3, the width of the doubly supported beam 3 is equal from the fixed ends at both ends to the central region.
That is, in the case of a rectangular configuration, if a Coulomb force is generated by applying a bias voltage between the reference electrode 8 and the fixed electrodes 6a and 6b, the central region (the movable piece 5 ) May be excessively displaced toward the substrate 1 and the reference electrode 8 of the movable piece 5 may come into close contact with the detection electrode 7. In this embodiment, the above problem is avoided for the following reasons. It is possible.

The reference electrode 8 and the driving electrode 6 shown in FIG.
When a bias voltage is applied between the driving electrodes 6a and 6b, the size according to the following equation (2) is obtained between the driving electrode 6a and the reference electrode 8 at the beam portion 4a and between the driving electrode 6b and the reference electrode 8 at the beam portion 4b. A coulomb force is generated by the force F, and the beam portions 4a and 4b of the doubly supported beam 3 bend and deform toward the substrate 1 due to the Coulomb force. The movable piece 5 is inevitably displaced toward the substrate 1, and the distance between the doubly supported beam 3 and the substrate 1 becomes narrower from the fixed end of the doubly supported beam 3 toward the central region.

F = −q · (Vd / d) · S (2)

Here, q in the above equation (2) represents a predetermined charge amount per unit electrode area, Vd represents a voltage applied between the electrodes, d represents a distance between the electrodes, and S represents
Represents an electrode facing area.

In the configuration shown in FIG. 3, q, Vd, and S shown in the above equation (2) are in the same state from the fixed end side of the doubly supported beam 3 to the central region, and the beam portions 4a and 4b are bent and deformed. In some cases, as described above, the distance between the doubly supported beam 3 and the substrate 1 becomes narrower from the fixed end of the doubly supported beam 3 toward the central region, so that the beam portions 4a and 4b of the doubly supported beam 3 and the driving electrode In each of the opposing regions 6a and 6b, the interval on the distal end side is smaller than that on the proximal end side. Therefore, the beam portion 4 of the doubly supported beam 3
The Coulomb force acting between the reference electrode 8 and the drive electrodes 6a, 6b in the portions a, 4b is the beam portion 4a, 4b of the doubly supported beam 3.
In each of the opposing regions of the portion and the drive electrodes 6a and 6b, the front end side is significantly larger than the base end side, and the movable piece 5 of the double-supported beam 3 is excessively displaced toward the substrate 1.

Therefore, for example, the biasing voltage is applied between the reference electrode 8 and the driving electrodes 6a, 6b to slightly deform the beam portions 4a, 4b of the doubly supported beam 3 to move the doubly supported beam 3. The piece 5 may be excessively displaced toward the substrate 1, and the reference electrode 8 in the movable piece 5 may be in close contact with the detection electrode 7.

On the other hand, in this embodiment, as described above, since the width of the doubly supported beam 3 becomes narrower from the fixed end toward the central region, the reference electrode 8 of the beam portion 4a is formed. And the opposing area of the driving electrode 6a and the opposing area of the reference electrode 8 and the driving electrode 6b in the beam portion 4b become narrower from the fixed end side of the doubly supported beam 3 toward the central region. The reference electrode 8 and the drive electrode 6b between the reference electrode 8 and the drive electrode 6a at the beam 4a, and between the reference electrode 8 and the drive electrode 6b at the beam 4b.
The magnitude of the Coulomb force generated therebetween is made uniform over the entire area of the opposing areas between the reference electrode 8 and the drive electrode 6a at the beam 4a and between the reference electrode 8 and the drive electrode 6b at the beam 4b. Thus, it is possible to avoid the problem that the Coulomb force excessively acts on the movable piece 5 of the doubly supported beam 3 and the reference electrode 8 of the movable piece 5 comes into close contact with the detection electrode 7.

Further, the variable control of the distance between the reference electrode 8 and the detection electrode 7 on the movable piece 5 can be accurately performed, and the capacitance between the reference electrode 8 and the detection electrode 7 on the movable piece 5 can be increased. Accurate variable control becomes possible.

In the configuration shown in FIG. 3, as described above, the movable piece 5 is excessively displaced toward the substrate 1 just by slightly bending and deforming the beam portions 4a and 4b, so that the reference electrode of the movable piece 5 is formed. In some cases, even if the level of the bias voltage applied between the reference electrode 8 and the detection electrode 7 is increased, the reference electrode 8 and the detection electrode 7 are short-circuited. The reference electrode 8 and the detection electrode 7
The capacitance between them cannot be largely varied.

In other words, there is a problem that the control voltage range of the bias voltage for variably controlling the capacitance is very narrow and it is difficult to variably control the capacitance. However, in this embodiment, as described above, the movable piece Since the problem of excessive displacement of 5 can be avoided, the variable region of the bias voltage for variably controlling the capacitance between the reference electrode 8 and the detection electrode 7 in the movable piece 5 can be widened. Accordingly, the variable control of the capacitance can be facilitated, and the variable control of the capacitance can be performed with high accuracy.

Further, the variable capacitor of this embodiment has a simple structure and can be formed by using the surface micromachining technology, so that the miniaturization is easy.

Further, as described above, the beam width D of the doubly supported beam 3 increases from the fixed end of the doubly supported beam 3 toward the central region.
, The resonance frequency of the doubly supported beam 3 becomes higher than that in the case where the doubly supported beam 3 has the same width as shown in FIG. When the resonance frequency is increased in this manner, the resonance frequency of the doubly supported beam 3 is far from the frequency of the vibration noise, and the output voltage signal of the variable capacitor having a frequency corresponding to the resonance frequency of the doubly supported beam 3 is generated. Vibration noise does not occur, and the S / N ratio of the output voltage signal of the variable capacitor can be improved.

Further, since the movable piece 5 is supported by the plurality of beams of the beam portions 4a and 4b, the distance between the movable piece 5 and the substrate 1 is set to the entire area of the opposing area of the movable piece 5 and the substrate 1. Crossing,
The distance between the reference electrode 8 and the detection electrode 7 in the movable piece 5 can be easily controlled.
The variable control of the capacitance between the reference electrode 8 and the detection electrode 7 in the portion can be performed with high accuracy.

Further, the electric path of the signal conduction path until the high frequency signal applied from the outside is output to the outside as an output voltage signal corresponding to the capacitance between the reference electrode 8 and the detection electrode 7 of the movable piece 5 is output. Although the resistance increases in accordance with the length of the current path of the signal, in this embodiment, the length of the current path of the signal is short, and the electric resistance of the current path is small.
As a result, the Q value of the output voltage signal can be significantly improved. Further, the frequency of the output voltage signal is stabilized due to the improvement of the Q value of the output voltage signal,
Carrier noise of the output voltage signal can be reduced.

In this embodiment, a high-frequency signal is applied between the reference electrode 8 and the detection electrode 7 of the movable piece 5 via the extraction electrode 14, and the high-frequency signal is applied between the reference electrode 8 and the detection electrode 7 of the movable piece 5. Output voltage signal corresponding to the capacitance of the extraction electrode 12 was output from the extraction electrode 12 to the outside.
2, a high-frequency signal is applied between the reference electrode 8 and the detection electrode 7 of the movable piece 5 and an output voltage signal is extracted from the extraction electrode 14.
May be output to the outside via the.

Further, in this embodiment, the width of the doubly supported beam 3 is continuously narrowed from the fixed end toward the central region. However, as shown in FIG. The width of the beam may be gradually reduced from the fixed end toward the central region.

Further, in this embodiment, the fixed electrodes are formed separately from the drive electrodes 6a and 6b and the detection electrode 7. However, the fixed electrodes are disposed opposite to the reference electrode 8 so that the functions of the drive electrodes 6a and 6b and the detection electrode 7 are changed. May be provided.

In this case, the fixed electrode and the reference electrode 8
Coulomb force acts to bend and deform the doubly supported beam 3 over the entire region of the opposing region, but since the width of the beam of the doubly supported beam 3 decreases from the fixed end toward the central region. The opposed area between the fixed electrode and the reference electrode 8 decreases from the fixed end of the doubly supported beam 3 toward the central region, and the Coulomb force is fixed due to the decrease in the opposed area between the fixed electrode and the reference electrode 8. It is possible to make it uniform over the entire area of the opposing area of the electrode and the reference electrode 8, and it is possible to avoid the problem of excessive bending deformation of the central area of the doubly supported beam 3.

Further, when manufacturing the above-mentioned variable capacitor, for example, a conductor film constituting the drive electrodes 6a, 6b, etc. is formed on the substrate 1, and the drive electrodes 6a, 6b, etc. are formed on the upper side of the conductor film. A resist pattern for defining a region is formed to remove an excess conductor film other than the resist pattern.
The components of the variable capacitor were manufactured by the die-cutting method such that the a, 6b and the like were completed. For example, a mask pattern for regulating the formation regions of the drive electrodes 6a and 6b on the substrate 1 was formed. A conductive film forming the drive electrodes 6a, 6b, etc. is formed on the upper side of the substrate 1 on which the mask pattern has been formed, and then the mask pattern is removed to complete the drive electrodes 6a, 6b, etc. Each component of the variable capacitor may be manufactured by a technique.

Hereinafter, a second embodiment will be described. The feature of this embodiment is that, as shown in FIG. 5, the movable piece 5 commonly connected to the distal ends of the beams 4a and 4b is larger than the width D of the distal ends of the beams 4a and 4b. That is, it was formed on a protruding wide surface. The other configuration is the same as that of the first embodiment. The same reference numerals are given to the same components as those of the first embodiment, and the duplicated description will be omitted.

In this embodiment, the movable piece 5 commonly connected to the distal ends of the beams 4a and 4b is formed wider than the width D of the distal ends of the beams 4a and 4b. , On the substrate facing surfaces of the beams 4a, 4b and the movable piece 5,
As in the case of the first embodiment, the reference electrode 8 is formed. A detection electrode 7 is provided in a region of the movable piece 5 facing the reference electrode 8, and a drive electrode 6a, 6b is provided in a region of the beam portion 4a, 4b facing the reference electrode 8. Will be arranged.

The beams from the base end (leg side) to the distal end of each of the beam portions 4a and 4b are formed to have the same length. When the beam portions 4a and 4b are flexed and deformed, the movable piece 5 can be displaced while the substrate facing surface of the movable piece 5 is kept parallel to the substrate 1, and the movable piece 5
The variable control of the capacitance between the reference electrode 8 and the detection electrode 7 in the portion can be performed with high accuracy.

According to this embodiment, the same effects as those of the first embodiment can be obtained, and the movable piece 5 is formed on a wide surface. In comparison, the opposing area between the reference electrode 8 and the detection electrode 7 in the movable piece 5 can be increased. From this, the reference electrode 8 and the detection electrode 7 of the movable piece 5 are so formed as to obtain an electrostatic capacity suitable for a circuit incorporating a variable capacitor.
Can be variably set to be large or small, and a desired capacitance can be easily obtained.

In addition, as described above, the capacitance between the reference electrode 8 and the detection electrode 7 in the movable piece 5 can be increased.
The voltage level of the output voltage signal can be increased, and the S / N ratio of the output voltage signal can be further improved.

In this embodiment, the beams 4a, 4a
As for b, the width D of the beam was continuously narrowed from the base end side to the tip end side, but as shown in FIG.
The width of the beam 4b may be gradually reduced. Although the movable piece 5 has a rectangular shape, the movable piece 5 may have a circular shape, as shown in FIGS. 7A and 7B, a triangular shape, a polygonal shape such as a pentagon or more. It may be formed in a shape other than the shape.

Hereinafter, a third embodiment will be described. The feature of this embodiment is that, as shown in FIGS. 9, 10 and 11, the movable piece 5 has three or more beams 4 (four in the examples shown in FIGS. 9, 10 and 11). Beams 4a, 4
b, 4c, 4d). Other configurations are the same as those of the above-described embodiments, and the same reference numerals are assigned to the same names as those of the above-described embodiments, and the duplicated description thereof will be omitted.

In this embodiment, three or more legs are formed on the substrate 1 with a gap therebetween, and the beam 4 is directed from each of these legs toward the center of the region surrounded by the plurality of legs. Each of the beam portions 4 is connected to a common movable piece 5 at the distal end thereof. The beam portion 4 and the movable piece 5 are disposed to face the substrate 1 with a gap 10 therebetween. Each of the beam portions 4 is formed so that the length of the beam from the base end to the tip end is equal.

A reference electrode 8 is formed on the surface of each beam 4 and the movable piece 5 facing the substrate.
A drive electrode 6 is provided to face the substrate facing surface of the movable piece 5 via the gap 10, and a detection electrode 7 is provided to face the substrate facing surface of the movable piece 5 via the gap 10. Further, the extraction electrodes (not shown) extracted from the respective drive electrodes 6, the detection electrodes 7, and the reference electrodes 8 are connected to the substrate 1 respectively.
Formed.

The variable capacitor of this embodiment is configured as described above, and connects the extraction electrode of the detection electrode 7 and the extraction electrode of the reference electrode 8 to a predetermined connection of a circuit such as an oscillation circuit or a modulation circuit. By connecting the variable capacitance capacitor to the circuit, the extraction electrode of each drive electrode 6 and the extraction electrode of the reference electrode 8 are connected to voltage application means. When a DC bias voltage is applied between the reference electrode 8 and the drive electrode 6, a Coulomb force acts between the electrodes,
The reference electrode 8 at each beam portion 4 is attracted to the drive electrode 6 side, and each beam portion 4 bends and deforms toward the substrate.

The movable piece 5 is moved with the bending deformation of each beam 4.
Is displaced toward the substrate, the distance between the reference electrode 8 and the detection electrode 7 on the movable piece 5 is changed, and the capacitance between the reference electrode 8 and the detection electrode 7 on the movable piece 5 can be changed.

According to this embodiment, the same effects as those of the above-described embodiments can be obtained.
Since it is configured to be supported by the four or more beams 4, it is possible to significantly reduce the displacement of the movable piece 5 due to vibration. When the beam portion 4 is flexed and deformed, the movable piece 5 can be displaced toward the substrate while maintaining the parallel state with the substrate surface, and the movable piece 5 can be displaced toward the substrate. The distance between the movable piece 5 and the substrate 1 can be made more uniform over the entire area of the opposing area.

From this, the reference electrode 8 of the movable piece 5
The variable control of the interval between the sensor electrode 7 and the detection electrode 7 can be performed with higher accuracy, and the accuracy of the variable control of the capacitance between the reference electrode 8 and the detection electrode 7 of the movable piece 5 can be further improved. it can.

In the examples shown in FIGS. 9, 10 and 11, the movable piece 5 is supported by the four beams 4,
As shown in FIGS. 3 (a) and 3 (b), the movable piece 5 may be supported by three beams 4, or the movable piece 5 may be supported by five or more beams 4.
May be supported.

Hereinafter, a fourth embodiment will be described. The characteristic feature of the fourth embodiment is that, as shown in FIG. 14, the reference electrode 8 is connected to the reference electrode 8 (8a, 8b) of the beam portion 4 (4a, 4b) and the reference electrode 8 (8a, 8b) of the movable piece 5. Electrode 8
(17). Other configurations are the same as those of the above-described embodiments. In this embodiment, the same reference numerals are given to the same components as those of the above-described embodiments, and the description thereof will not be repeated.

In this embodiment, as described above, the reference electrode 8 is separately formed into the reference electrode 8 (8a, 8b) of the beam portion 4 and the reference electrode 8 (17) of the movable piece 5 portion. The reference electrode 8 (8a, 8b) of the beam portion 4 is disposed to face the drive electrode 6 with a gap 10 interposed therebetween, and a Coulomb force acts between the reference electrode 8 and the drive electrode 6 to bend and deform the beam portion 4. This serves as a reference electrode for driving.

The reference electrode 8 (17) of the movable part 5 is disposed to face the detection electrode 7 via the gap 10, and is a detection reference electrode for detecting the capacitance between the detection electrode 7 and the detection electrode 7. And The drive reference electrodes (8a, 8b) and the detection reference electrode 17 are provided with a gap therebetween.
It is in an insulated state.

Extraction electrodes respectively extracted from the respective driving reference electrodes (8a, 8b) are formed on the substrate 1, and the detection reference electrode 17 is provided with a terminal portion. A lead conductor for applying a high-frequency signal to the reference electrode 17 for detection from the outside or outputting an output voltage signal from the reference electrode 17 for detection is connected to the portion.

The variable capacitor of this embodiment is constructed as described above, and is connected to the reference electrodes (8a, 8b) for driving and the extraction electrodes respectively extracted from the driving electrodes 6 by voltage application means. , And a bias voltage is applied between the drive reference electrodes (8a, 8b) and the drive electrode 6 to thereby control the drive reference electrodes (8a, 8b).
b) and a coulomb force is applied between the drive electrode 6 and the beam portion 4 is flexed and deformed by the Coulomb force to change the distance between the detection electrode 7 and the reference electrode 17 for detection. The capacitance between the detection reference electrodes 17 can be varied.

For example, when a high-frequency signal is externally applied between the detection electrode 7 and the detection reference electrode 17 via an extraction electrode drawn out of the detection electrode 7, the detection electrode 7 and the detection reference electrode 17 are applied. An output voltage signal corresponding to the capacitance between the electrodes 17 is output from the terminal of the reference electrode 17 for detection to the outside.

According to this embodiment, the same effects as those of the above embodiments can be obtained, and the reference electrode 8 is formed separately for the drive reference electrode and the detection reference electrode. To separate the DC bias voltage applied between the reference electrodes (8a, 8b) and the drive electrode 6 from the output voltage signal corresponding to the capacitance between the detection electrode 7 and the reference electrode 17 for detection. it can. Accordingly, the noise of the DC bias voltage is not superimposed on the output voltage signal, and the noise of the output voltage signal can be further reduced.

Note that the present invention is not limited to the above embodiments, but can take various embodiments. For example, in each of the above embodiments, the reference electrode 8 is formed by forming a conductor film on the insulating substrate forming the beam 4 and the movable piece 5. However, the beam 4 and the movable piece 5 are formed of a conductor. Forming
The beam portion 4 and the movable piece 5 may be configured to function as the reference electrode 8. Further, the beam portion 4 and the movable piece 5 may be formed by laminating some of various materials such as silicon oxide, silicon nitride, silicon, aluminum, gold, titanium, and chromium.

Further, the shapes of the beam portion 4 and the movable piece 5 are not limited to those of the above-described embodiments.
12 and may be formed in various shapes.

Further, in each of the above embodiments, the electrode surfaces such as the drive electrode 6, the detection electrode 7, and the reference electrode 8 are exposed, but a protective film is formed on one or more of the electrodes. It may be formed. In this case, the electrode surface can be protected by the protective film. Further, in each of the above embodiments, the beam portion 4 is bent and deformed using Coulomb force, but the beam portion 4 is deformed using a piezoelectric element or a magnetic force.
May be bent and deformed.

[0086]

According to the present invention, the legs formed on the substrate, the beams extending from the legs, and the movable portion commonly connected to the distal ends of the beams are formed. A movable electrode is formed on the substrate facing surface of each of the beam portions and the movable piece, and a fixed electrode disposed to face each of the beam portion and the movable piece is formed on the substrate. By doing so, the distance between the movable electrode and the fixed electrode can be changed, and the capacitance between the movable electrode and the fixed electrode can be changed.

The output of a signal until a high-frequency signal is externally applied between the movable electrode and the fixed electrode and an output voltage signal corresponding to the magnitude of the capacitance between the movable electrode and the fixed electrode is output to the outside. The electric resistance of the path is small, which can improve the Q value of the output voltage signal. Further, with the improvement of the Q value of the output voltage signal, the carrier noise of the output voltage signal can be reduced, the SN ratio of the output voltage signal can be improved, and the reliability of the output performance of the variable capacitor can be improved. Can be enhanced.

Further, since the variable capacitor of the present invention has a simple structure and can be manufactured by the surface micromachining technology, it is easy to reduce the size of the variable capacitor.

Further, since the width of the beam of the beam portion is configured to be smaller at the distal end side than at the proximal end side of the beam portion, the width of the beam portion is equal from the base end side to the distal end side as compared with the case where the beam width is equal. Since the resonance frequency of the beam portion becomes higher and the resonance frequency of the beam portion is further away from the frequency of the vibration noise, the vibration noise does not get on the output voltage signal having the frequency corresponding to the resonance frequency of the beam portion. , The output voltage signal S
The N ratio can be improved.

Further, the beam portion is bent and deformed by applying Coulomb force between the movable electrode and the fixed electrode, and the distance between the movable electrode and the fixed electrode is varied to change the capacitance between the movable electrode and the fixed electrode. In such a case, by making the width of the beam narrower at the distal end side than at the proximal end side of the beam portion as described above, the opposing area where the movable electrode and the fixed electrode of the beam portion oppose each other is smaller than the proximal end side of the beam portion. It is also possible to make the tip side narrower, and by reducing the facing area, when a Coulomb force is applied between the movable electrode and the fixed electrode in the beam portion, the entire area of the facing area between the electrodes is reduced. The magnitude of the Coulomb force can be made uniform.

Thus, it is possible to prevent the distal end side (movable piece) of the beam portion from being excessively displaced by the Coulomb force and coming into close contact with the substrate to cause a short circuit between the movable electrode and the fixed electrode. Further, as described above, since the problem that the movable electrode is in close contact with the fixed electrode can be avoided, the variable range of the bias voltage level for variably controlling the capacitance between the movable electrode and the fixed electrode can be increased. This makes it easy to variably control the capacitance, and variably controls the capacitance with higher accuracy.

In the case where the movable piece is formed on a wide surface so as to protrude beyond the width on the tip side of the beam portion, the tip side (movable piece) of the beam portion is excessively displaced by the Coulomb force and moves on the substrate. It is possible to prevent the movable electrode and the fixed electrode from being brought into close contact with each other and to be in a short-circuit state, and it is possible to enlarge the facing area of the movable piece portion where the movable electrode and the fixed electrode face each other. The opposing area of the movable electrode and the fixed electrode of the portion can be variably set to be large and small, and it is easy to obtain a desired capacitance suitable for a circuit incorporating a variable capacitor.

Further, as described above, since the facing area between the movable electrode and the fixed electrode of the movable piece can be increased, the capacitance between the movable electrode and the fixed electrode of the movable piece can be increased. Since the voltage level of the output voltage signal can be increased, the S / N ratio of the output voltage signal can be further improved.

In the case where the fixed electrode is formed separately into a movable piece counter electrode and a beam portion counter electrode, or when the movable electrode is formed separately into a movable electrode in a movable piece portion and a movable electrode in a beam portion, the movable electrode When the beam is flexed and deformed by applying a Coulomb force between the beam and the fixed electrode, the displacement of the movable piece is larger than the flexural deformation (displacement) of the beam, and the displacement is detected in a region facing the movable piece. Since the electrodes are present, the gap between the detection electrode and the reference electrode of the movable piece changes greatly, and the gap between the detection electrode and the reference electrode of the movable piece is greatly changed only by slightly bending and deforming the beam at a low voltage. Can be greatly varied.

In the case where the fixed electrode is formed separately in the movable piece counter electrode and the beam counter electrode, and the movable electrode is formed separately in the movable piece portion movable electrode and the beam portion portion movable electrode,
The bias voltage applied to the variable capacitor for bending the beam portion does not overlap with the output voltage signal corresponding to the capacitance, and the noise of the bias voltage is superimposed on the output voltage signal. Can be prevented, and the S / N ratio of the output voltage signal can be further improved.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a variable capacitor according to a first embodiment;

FIG. 2 is an explanatory view showing an example of a method for manufacturing the variable capacitor of FIG. 1;

FIG. 3 is an explanatory diagram illustrating an example of a doubly supported beam having an equal width.

FIG. 4 is an explanatory view showing another example of the shape of the beam portion.

FIG. 5 is an explanatory view showing a variable capacitor according to a second embodiment.

FIG. 6 is an explanatory view showing still another example of the shape of the beam.

FIG. 7 is an explanatory view showing another example of the shape of the movable piece.

FIG. 8 is an explanatory view showing still another example of the shape of the movable piece.

FIG. 9 is an explanatory diagram showing a third embodiment.

FIG. 10 is an explanatory diagram showing an embodiment of a variable capacitor provided with four beams.

FIG. 11 is an explanatory diagram showing an embodiment of a variable capacitor further provided with four beam portions.

FIG. 12 is an explanatory view showing another example of the shape of the beam portion and the movable piece.

FIG. 13 is an explanatory diagram showing an example of an embodiment of a variable capacitor provided with three beams.

FIG. 14 is an explanatory diagram showing a fourth embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2a, 2b Leg 4,4a, 4b, 4c, 4d Beam 5 Movable piece 6,6a, 6b, 6c, 6d Driving electrode 7 Detecting electrode 8,8a, 8b Reference electrode 17 Reference electrode for detection

Claims (7)

[Claims] 1. A substrate, a plurality of legs fixedly formed on the substrate and disposed with a gap therebetween, and a beam extended from each of the legs and disposed opposite to the substrate with a gap therebetween. Part, a movable piece commonly connected to the distal end side of each of these beam parts and disposed to face the substrate via a gap, and formed on the substrate facing surface of the movable piece and the substrate facing surface of the beam part. A movable electrode, and a fixed electrode formed on the substrate and opposed to the movable electrode with a gap therebetween, wherein the beam is formed such that the width of the beam on the distal end side is narrower than that on the base end side. A variable capacitor having a configuration. 2. The fixed electrode is formed separately into a movable piece facing electrode facing the substrate facing surface of the movable piece and a beam facing electrode facing the substrate facing surface of the beam. The movable piece facing electrode is a movable electrode. And a detection electrode for detecting a capacitance between the first and second beams, and the beam-facing electrode serves as a drive electrode for bending and deforming the beam. A variable capacitor as described. 3. The movable electrode is formed separately from a movable electrode formed on a substrate facing surface of a movable piece and a movable electrode formed on a substrate facing surface of a beam. And a movable reference electrode for detecting a capacitance between the movable portion and the movable electrode of the beam portion serves as a drive reference electrode for bending and deforming the beam portion. The variable capacitor according to claim 1 or 2, wherein 4. A substrate, a plurality of legs fixedly formed on the substrate and disposed with a gap therebetween, and a beam extended from each of the legs and opposed to the substrate with a gap therebetween. Part, a movable piece commonly connected to the distal end side of each of these beam parts and disposed to face the substrate via a gap, and formed on the substrate facing surface of the movable piece and the substrate facing surface of the beam part. A movable electrode, and a fixed electrode formed on the substrate and disposed to face the movable electrode with a gap therebetween, wherein the movable piece is formed to have a wider surface that protrudes beyond the width of the tip end side of the beam portion. A variable capacitor characterized by having a configuration as described above. 5. The beam portion has a configuration in which the width of the beam at the distal end side is smaller than that at the base end side.
A variable capacitor as described. 6. The fixed electrode is formed separately into a movable piece facing electrode facing the substrate facing surface of the movable piece and a beam facing electrode facing the substrate facing surface of the beam, and the movable piece facing electrode is a movable electrode. And a detection electrode for detecting a capacitance between the first and second beams, and the beam-facing electrode serves as a drive electrode for bending and deforming the beam. Or the variable capacitor according to claim 5. 7. The movable electrode is formed separately from a movable electrode formed on the substrate facing surface of the movable piece and a movable electrode formed on the substrate facing surface of the beam. And a movable reference electrode for detecting a capacitance between the movable portion and the movable electrode of the beam portion serves as a drive reference electrode for bending and deforming the beam portion. 7. The variable capacitor according to claim 4, wherein the capacitor is a variable capacitor.