JPH1079324A - Capacitance-variable-element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a capacitance-variable-element which can be downsized and can vary electrostatic capacity at a low voltage. SOLUTION: A fixed electrode 3 is formed on a support substrate 2, and a cantilever 5 is formed over the fixed electrode 3 via a gap oppositely to the fixed electrode 3. A movable electrode 4 is formed on a face opposite to the fixed electrode of the cantilever 5. The movable electrode 4 and the cantilever 5 reduce in width D as coming from a supporting end toward a tip. By applying voltage between the fixed electrode 3 and the movable electrode 4, Coulomb force is developed between the fixed electrode 3 and the movable electrode 4, whereby the cantilever 5 is elastically displaced and the electrostatic capacibty between the fixed electrode 3 and the movable electrode 4 varies.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art A variable-capacitance element is constituted, for example, by having two electrodes facing each other with a gap therebetween, and the distance between these electrodes and the area of a portion where these electrodes face each other are determined in advance. It is possible to vary the capacitance between the electrodes by varying the capacitance by the above method.

Such a variable capacitance element is incorporated as a variable capacitance capacitor in an oscillation circuit, a modulation circuit, or the like, and is used by variably setting the capacitance of the variable capacitance capacitor so as to obtain a desired circuit output. . Or, if the capacitance of the variable capacitance element becomes small, it becomes very difficult for high-frequency current to flow through the variable capacitance element, and conversely,
Utilizing the characteristic of a variable capacitance element that makes it easier for high-frequency current to flow when the capacitance increases, the variable capacitance element is incorporated as a switch element in a high-frequency circuit that drives the circuit at high frequency, and by increasing the capacitance It is used as a switching element such that the variable capacitance element is switched on and the capacitance variable element is switched off by reducing the capacitance.

[0004] As the variable capacitance element, a variable condenser, FIG.
(See JP-A-5-74655)
It has been known. As is well known, a variable condenser has a rotating mechanism such as a motor, and varies the facing area of electrodes facing each other by this rotating mechanism, thereby varying the capacitance between the electrodes.

The device shown in FIG. 10 has a fixed electrode 23 formed on the bottom surface 22 of the concave portion of the substrate 20 and a movable electrode 24 which bridges the opening of the concave portion 21 and faces the fixed electrode 23. ,
Voltage applying means connected to the fixed electrode 23 and the movable electrode 24
By applying a voltage between the fixed electrode 23 and the movable electrode 24 from 25, a Coulomb force acts between the fixed electrode 23 and the movable electrode 24, and the movable electrode 24 bends and fluctuates as shown by a chain line in FIG. The capacitance between the fixed electrode 23 and the movable electrode 24 is varied by changing the distance between the electrode 23 and the movable electrode 24.

[0006]

However, the variable condenser has a complicated structure, and it is difficult to reduce the size of a rotating mechanism which is indispensable for changing the capacitance. There is a problem that it is difficult to achieve. In addition, since both ends of the movable electrode 24 of the element shown in FIG. 10 are fixed, there is a problem that a high voltage is required to bend and change the central portion of the movable electrode 24.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has as its object the purpose of being able to reduce the size with a simple structure, to be able to change the capacitance at a low voltage, and to have a high accuracy. It is an object to provide a variable capacitance element which can function as a variable capacitance capacitor or a switching element.

[0008]

Means for Solving the Problems To achieve the above object, the present invention has the following structure to solve the above problems.

According to a first aspect of the present invention, there is provided a support substrate, a fixed electrode fixedly formed on the support substrate, and a cantilever-shaped support supported by the support substrate and disposed opposite to the fixed electrode via a gap. Having a movable electrode formed on the fixed electrode facing surface of the cantilever so as to face the fixed electrode,
The above-mentioned cantilever has a configuration in which the width on the tip side is narrower than the width on the support end side, and is a means for solving the above-mentioned problem.

According to a second aspect of the present invention, the fixed electrode constituting the first aspect of the present invention is separated and divided into first and second fixed electrodes, and the first and second fixed electrodes are provided on the support end side of the cantilever. The fixed electrode on the support end side of the cantilever forms a drive electrode for bending and changing the cantilever, and the fixed electrode on the other side is movable. Means for solving the above-mentioned problem are constituted by forming a detection electrode for detecting a capacitance between the electrode and the electrode.

According to a third aspect of the present invention, the movable electrode constituting the first or second aspect is separated and divided into first and second movable electrodes, and the first and second movable electrodes are of a cantilever type. The movable electrode on the support end side of the cantilever is arranged on the surface facing the fixed electrode with a gap in the direction from the support end side to the tip side, and the movable electrode on the support end side of the cantilever flexures and changes the cantilever. An electrode is formed, and the movable electrode on the other side is configured as a detection reference electrode for detecting the capacitance between the movable electrode and the fixed electrode.

A fourth invention is directed to the first, second, or third aspect.
The cantilever beam according to the present invention has a configuration in which the width of the beam is reduced continuously or stepwise from the support end side to the distal end side as means for solving the above problem.

According to a fifth aspect of the present invention, there is provided a support substrate, a drive electrode fixedly formed on the support substrate, detection electrodes arrayed and formed on the support substrate via a gap between the drive electrode, and the drive electrode and the detection electrode. The drive electrode and the detection electrode are extended and formed with the drive electrode side in the arrangement direction in the arrangement direction, and the drive electrode and the detection electrode have a cantilever that is disposed opposite to each other with a gap therebetween. A width-deformed beam portion that is opposed to and has a width on the distal end side smaller than the width on the support end side, and is formed by a detection portion that is provided at the distal end side of the width-deformed beam portion and faces the detection electrode,
The detection unit is formed on the tip side of the width-deformed beam, and a drive reference electrode for bending and changing the cantilever is provided on the drive electrode facing surface of the width-deformed beam. A detection reference electrode for detecting the capacitance between the detection electrode and the detection electrode is provided on the detection electrode facing surface, and the drive reference electrode and the detection reference electrode are separately formed via a gap. The configuration is a means for solving the above problem.

According to a sixth aspect, in the fifth aspect, the width of the cantilever beam is reduced continuously or stepwise from the support end toward the distal end. Is a means for solving the above problem.

According to a seventh aspect of the present invention, there is provided a liquid crystal display device comprising the above-described one of the first to sixth aspects, wherein a protective film for protecting the electrodes is formed on a surface of at least one of the electrodes. Is a means to solve.

In the present invention having the above structure, for example, when a voltage is applied between the fixed electrode and the movable electrode, a Coulomb force acts between the fixed electrode and the movable electrode, and the coulomb force causes the cantilever to bend and deform. The distance between the fixed electrode and the movable electrode changes, and the capacitance between the fixed electrode and the movable electrode changes.

Since the movable electrode is formed in a cantilever beam, the cantilever is largely bent and fluctuated with a small Coulomb force, that is, a low voltage, as compared with a case where the movable electrode is formed in a cantilever beam. It is possible to do. In addition, since the width of the beam at the tip end of the cantilever is narrower than that at the support end, the force in the bending direction on the beam tip side received from the fixed electrode side is also small, and as a result, the tip side of the cantilever becomes excessive. Deflected into contact with the support substrate, resulting in a capacitive element (capacitor)
This avoids the possibility that the function cannot be performed.

[0018]

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

FIG. 1A is a perspective view showing the variable capacitance element according to the first embodiment, and FIG. 1B is a perspective view showing the X-axis of the variable capacitance element shown in FIG. X sectional views are respectively shown. The variable capacitance element according to this embodiment can function as a variable capacitance capacitor or a switching element as described above.
, A movable electrode 4, and a cantilever 5.

As shown in FIGS. 1A and 1B, a fixed electrode 3 is fixedly formed on the upper surface of a support substrate 2, and the fixed electrode 3 is provided above the fixed electrode 3 with a gap 11 therebetween. An opposing cantilever 5 is provided supported by the support substrate 2,
A movable electrode 4 facing the fixed electrode 3 is formed on a lower surface (a fixed electrode facing surface) of the cantilever 5.

As shown in FIG. 1A, the beam width D of the cantilever 5 continuously decreases from the support end to the tip. Similarly to the shape of the cantilever 5, the movable electrode 4 also becomes narrower in width from the support end side of the cantilever 5 to the distal end side.

On the upper surface of the support substrate 2, a fixed extraction electrode 7 connected to the fixed electrode 3 and formed outside the tip end of the cantilever 5, and a single extraction electrode 7 connected to the movable electrode 4. A movable extraction electrode 8 is formed so as to be drawn out of the support end side of the holding beam 5.

The input-side lead conductor for externally introducing a drive voltage signal for applying a voltage between the fixed electrode 3 and the movable electrode 4 to apply a Coulomb force to the fixed-side lead electrode 7 and the movable-side lead electrode 8. (Not shown) are connected to each other, and an outgoing lead conductor (not shown) for guiding a detection voltage signal corresponding to the capacitance between the fixed electrode 3 and the movable electrode 4 to the outside is connected to each other. The variable capacitance element shown in FIG. 1 is incorporated in a predetermined circuit and functions as a variable capacitance capacitor or a switching element.

The support substrate 2 is made of an insulating substrate such as glass or ceramics, or silicon or gallium arsenide coated with a coating film (eg, a silicon oxide film, a silicon nitride film, a resin film, etc.).
The fixed electrode 3 and the movable electrode 4 are formed of a semiconductor substrate such as germanium or a metal substrate covered with a coating film.
The fixed-side extraction electrode 7 and the movable-side extraction electrode 8 are doped with a metal such as aluminum, gold, titanium, chromium, silver, copper, palladium, platinum, nickel, or nichrome, or an impurity such as boron, arsenic, phosphorus, or antimony. The cantilever 5 is formed of silicon oxide, silicon nitride, silicon, or the like.

The variable capacitance element of this embodiment is configured as described above. For example, when the variable capacitance element is incorporated in a circuit such as an oscillation circuit or a modulation circuit as a variable capacitance capacitor, the fixed electrode 3 and the movable electrode A drive voltage signal is applied to the fixed electrode 3 and the movable electrode 4 via the input-side lead conductor so that the capacitance between the fixed electrodes 3 and 4 becomes a predetermined capacitance suitable for the above-described circuit. A Coulomb force is applied between the electrode 3 and the movable electrode 4, and the cantilever 5 is flexed and changed by the Coulomb force to change an interval between the fixed electrode 3 and the movable electrode 4. The capacitance is variably set to a capacitance suitable for the above circuit, and a detection voltage signal corresponding to the capacitance is output via the lead conductor on the output side.

When the switching element is incorporated in a high-frequency circuit or the like, the driving voltage signal is fixed via the input-side lead conductor so as to have a capacitance greater than a predetermined switch-on capacitance. By applying the capacitance between the fixed electrode 3 and the movable electrode 4 to the electrode 3 and the movable electrode 4 so as to be equal to or larger than the above-mentioned switch-on capacitance, the variable-capacitance element is switched on to correspond to the capacitance The detected voltage signal (current) flows to the outside via the lead conductor on the outgoing side. At other times, the variable capacitance element is switched off and no detected voltage signal is output. As described above, the variable capacitance element having the above configuration is used as a switch element.

As described above, the fixed electrode 3 is
And a function of a drive electrode for causing the cantilever 5 to bend and fluctuate by applying a Coulomb force between the two, and a function of a detection electrode for detecting a capacitance between the movable electrode 4 and Further, the movable electrode 4 detects a function of a reference electrode for driving to bend and fluctuate the cantilever by applying Coulomb force between the movable electrode 4 and the fixed electrode 3, and detects a capacitance between the movable electrode 4 and the fixed electrode 3. And also functions as a reference electrode for detection.

Hereinafter, an example of a method of manufacturing the variable capacitance element having the above configuration will be briefly described with reference to FIG. First, a film of an electrode material is formed on the entire upper surface of the support substrate 2 by using a film forming technique such as evaporation, sputtering, CVD, or printing, and the fixed electrode 3 and the fixed-side extraction electrode 7 are formed on the upper surface of the film. Is formed by photolithography or the like. Thereafter, the film of the electrode material other than the portion where the resist pattern is formed is removed by etching or the like. Then, the resist pattern is removed, and FIG.
As shown in (a) of FIG.
Then, the fixed-side extraction electrode 7 connected to the fixed electrode 3 is formed.

Next, as shown in FIG. 2B, a sacrificial layer (for example,
Silicon oxide, phosphorus glass, ZnO) 10 is formed by vapor deposition, sputtering, CVD, or the like. Then, as shown in FIG. 2C, the movable electrode 4 is provided on the upper surface of the sacrifice layer 10 so as to be located at the position facing the fixed electrode 3, and the movable electrode 4 is provided on the upper surface of the support substrate 2. The movable side lead-out electrodes 8 are formed by vapor deposition, sputtering, CVD or the like.

Thereafter, a film of a material for forming the cantilever 5 is formed on the movable electrode 4 and the movable side extraction electrode 8 by vapor deposition, sputtering, CVD, or the like, and the cantilever 5 is formed on the film. A resist pattern defining a position is formed by photolithography or the like. Then, the material film of the cantilever 5 other than the resist pattern is removed by etching, and thereafter, the resist pattern is removed to form the cantilever 5 as shown in FIG.

Finally, the sacrificial layer 10 is removed by etching, and as shown in FIG. 2E, a gap 11 is formed between the fixed electrode 3 and the movable electrode 4 to complete the variable capacitance element.

According to this embodiment, since the movable electrode 4 is formed on the cantilever 5, a smaller distance between the fixed electrode 3 and the movable electrode 4 than in the case where the movable electrode 4 is formed on the double-supported beam. It is possible to flex and fluctuate the cantilever 5 only by applying Coulomb force, that is, at a low voltage. Therefore, the distance between the fixed electrode 3 and the movable electrode 4 can be changed at a low voltage, and the capacitance between the fixed electrode 3 and the movable electrode 4 can be changed.

Further, since the variable capacitance element of this embodiment has a simple structure, it is easy to reduce the size. Further, since the manufacturing process is simple, the manufacturing cost can be reduced.

By the way, as shown in FIG.
When the drive voltage signal is applied to the fixed electrode 3 and the movable electrode 4, when the drive voltage signal is applied to the fixed electrode 3 and the movable electrode 4, the tip of the cantilever 5 becomes excessively close to the support substrate 2. To bend.

That is, the fixed electrode 3 and the movable electrode 4
Due to the Coulomb force generated on the support end side of the cantilever 5 when a voltage is applied therebetween, the support end side of the cantilever 5 changes to the support substrate 2 side, and the support end side of the cantilever 5 The tip side of the cantilever 5 inevitably bends and fluctuates with the fluctuation, and the interval between the support substrate 2 and the cantilever 5 (the interval between the fixed electrode 3 and the movable electrode 4) is the supporting end side of the cantilever 5. The tip side becomes narrower than that. The Coulomb force attracting the cantilever 5 toward the support substrate 2 also acts on the tip side of the cantilever 5 with the magnitude F according to the following equation (1), so that the tip side of the cantilever 5 further flexes and fluctuates.

F = −q · (V _d / d) · S (1)

Here, q in the above equation (1) represents a predetermined amount of electric charge per unit electrode area, V _d represents a voltage applied between the electrodes, d represents a distance between the electrodes,
S represents an electrode facing area.

In the cantilever 5 (movable electrode 4) having the same width as shown in FIG. 8, q, V _d , and S shown in the above equation (1) are equal on the supporting end side and the tip end side. Since d is smaller on the tip side than on the support end side, the magnitude F of the Coulomb force between the support substrate 2 and the cantilever 5 (between the fixed electrode 3 and the movable electrode 4) is
As can be seen from the above equation (1), the front end side of the cantilever 5 is much larger than the support end side, and the front end side of the cantilever 5 is excessively bent and fluctuates.

For this reason, for example, a driving voltage signal is applied to the fixed electrode 3 and the movable electrode 4 to slightly deflect the support end side of the cantilever 5 toward the support substrate 2 to change the cantilever 5. The tip side is excessively bent and the tip side of the cantilever 5 (movable electrode 4
(The tip side) comes into contact with the fixed electrode 3 in many cases. In such a case, since the fixed electrode 3 and the movable electrode 4 are in a short-circuit state, even if the voltage level of the driving voltage signal is increased, the capacitance between the fixed electrode 3 and the movable electrode 4 can be changed in a direction to increase. I can't. That is, there is a problem that the control voltage range of the drive voltage signal for variably controlling the capacitance is very narrow, and it is difficult to variably control the capacitance.

On the other hand, in this embodiment, since the width D of the movable electrode 4 and the cantilever 5 decreases from the support end to the distal end, the width of the fixed electrode 3 and the movable electrode 4 is reduced. Since the opposing area S is smaller at the tip end side than at the support end side of the cantilever 5, the opposing area S decreases when the tip end side also bends due to a change in the deflection of the support end side of the cantilever 5. As a result, it is possible to prevent the magnitude F of the Coulomb force acting between the fixed electrode 3 and the movable electrode 4 from becoming much larger on the tip end side than on the support end side of the cantilever 5, and the Coulomb force can be prevented. Can be made uniform from the support end side to the distal end side of the cantilever 5, and the distal end side of the cantilever 5 can be prevented from being excessively bent.

Accordingly, the cantilever 5 having the same width as shown in FIG.
Fixed electrode 3 and movable electrode 4
This makes it possible to widen the control voltage range for variably controlling the capacitance between them, facilitate the variable control of the capacitance, and perform the variable control of the capacitance with high accuracy.

In this embodiment, as described above, since the width D of the cantilever 5 decreases from the support end toward the distal end, the cantilever 5 has the same width as shown in FIG. If the condition other than the condition of the width D is equal to that of the beam 5, the resonance frequency of the cantilever 5 shown in this embodiment is higher than the resonance frequency of the cantilever 5 having the same width.
When the resonance frequency is increased in this manner, the resonance frequency of the cantilever 5 is far from the frequency of the vibration noise. Therefore, the output signal of the variable capacitance element having a frequency corresponding to the resonance frequency of the cantilever 5 ( No vibration noise is added to the detection voltage signal, and the SN of the output signal of the variable capacitance element is reduced.
It is possible to improve the ratio.

Hereinafter, a second embodiment will be described.
This embodiment is different from the first embodiment in that, as shown in FIG. 3, the fixed electrode 3 is composed of a detection electrode 3a as a first fixed electrode and a second fixed electrode. This is because it is separated and divided into a certain drive electrode 3b, and the configuration is such that the capacitance can be largely varied with a smaller change in deflection of the cantilever 5. The other configuration is the same as that of the first embodiment, and the description thereof will not be repeated.

In this embodiment, when the bending of the cantilever 5 is changed using the Coulomb force, the amount of the bending change is equal to the entire area from the support end side to the tip end side of the cantilever 5. Paying attention to the fact that the tip side of the cantilever 5 is larger than the support end side of the average value, only the capacitance of the tip side of the cantilever 5 is detected. By doing so, it is possible to obtain a larger amount of capacitance variation with a small deflection variation of the cantilever 5.

In this embodiment, the fixed electrode 3 and the drive electrode 3a are located at the positions facing the movable electrode.
The detection electrode 3a and the drive electrode 3b are arranged on the upper surface of the support substrate 2 with the drive electrode 3b in the direction from the support end side of the cantilever 5 to the tip end side. A gap is provided between the detection electrode 3a and the drive electrode 3b so that the detection electrode 3a and the drive electrode 3b do not directly conduct.

Although not shown in FIG. 3, on the upper surface of the support substrate 2 are formed fixed-side extraction electrodes which are respectively drawn out from the detection electrode 3a and the drive electrode 3b to the outside. An output lead conductor for outputting the above-mentioned detection voltage signal to the outside is connected to the fixed-side extraction electrode, and an input for introducing the driving voltage signal from the outside to the fixed-side extraction electrode on the drive electrode 3b side. Side lead conductor is connected.

The variable capacitance element of this embodiment is configured as described above, and generates a Coulomb force between the drive electrode 3b and the movable electrode 4 by applying a drive voltage signal to the drive electrode 3b and the movable electrode 4. The Coulomb force causes the cantilever 5
Of the cantilever 5 by bending the supporting end side of the
Also bends and fluctuates. A detection voltage signal corresponding to the capacitance between the detection electrode 3a on the tip side of the cantilever 5 and the movable electrode 4 is output to the outside via the fixed-side extraction electrode.

According to this embodiment, the same excellent effects as those of the first embodiment can be obtained. In addition, the fixed electrode 3 is separated and divided into the detection electrode 3a and the drive electrode 3b, and the drive is performed. Since the electrode 3b is formed on the support substrate 2 on the support end side of the cantilever 5, the support end side of the cantilever 5 is flexibly changed by utilizing the Coulomb force between the drive electrode 3b and the movable electrode 4. In addition, the tip end of the cantilever 5 can be flexed and changed more than the support end. Since the detection electrode 3a is formed on the support substrate 2 on the distal end side of the cantilever 5 which largely bends and fluctuates, only the capacitance on the distal end side of the cantilever 5 can be detected. The variable amount of the capacitance between the detection electrode 3a on the tip side of the beam 5 and the movable electrode 4 is
If the amount of deflection fluctuation of the entire cantilever 5 is the same as the variable amount of the capacitance between the fixed electrode 3 and the movable electrode 4 shown in the first embodiment, the first embodiment Therefore, the variation rate of the detected capacitance with respect to the deflection variation of the entire cantilever 5 can be made larger than that of the first embodiment.

Further, in this embodiment, since the fixed electrode 3 is divided into the detection electrode 3a and the drive electrode 3b as described above, the Coulomb force for bending and changing the cantilever 5 is used. Can be generated only on the support end side, and as described above, it is possible to avoid the problem that the tip side of the cantilever 5 is excessively bent and contacts the support substrate 2 due to the Coulomb force. As in the first embodiment, the voltage control range for variably controlling the capacitance can be widened, the variability of the capacitance can be easily controlled, and the variability of the capacitance can be accurately controlled. It can be performed.

Hereinafter, a third embodiment will be described. The feature of this embodiment different from the first embodiment is that, as shown in FIG. 4, the movable electrode 4 is a detection reference electrode 4a which is a first movable electrode and a second movable electrode. Is divided and divided into the drive reference electrode 4b,
As in the case of the first embodiment, the configuration is such that the capacitance can be largely varied with less deflection fluctuation of the cantilever 5. The other configuration is the same as that of the first embodiment, and the description thereof will not be repeated.

As described above, in this embodiment, the movable electrode 4 is separated and divided by the detection reference electrode 4a and the drive reference electrode 4b.
b is arranged in the fixed electrode facing region on the lower surface of the cantilever 5 in a direction from the support end side of the cantilever 5 to the tip end side with the drive reference electrode 4b as the support end side.
A gap is provided between a and the driving reference electrode 4b so that the detection reference electrode 4a and the driving reference electrode 4b do not directly conduct.

Although not shown in FIG. 4, a terminal portion is provided on the detection reference electrode 4a, and the detection reference electrode 4a corresponds to the capacitance between the detection reference electrode 4a and the fixed electrode 3 via this terminal portion. The driving reference electrode 4b generates a Coulomb force by applying a voltage between the driving reference electrode 4b and the fixed electrode 3 via the movable-side extraction electrode 8 to connect the detection voltage signal to the outside. Connected to a lead conductor on the input side for introducing a drive voltage signal for causing the drive voltage signal from the outside.

In this embodiment, the fixed electrode 3
A coulomb force for bending and changing the cantilever 5 is generated between the drive reference electrode 4b and the driving reference electrode 4b, and the cantilever 5 is bent and changed by the Coulomb force, and the fixed electrode 3 is detected by the change in bending of the cantilever. The capacitance between the reference electrodes 4b varies. A detection voltage signal corresponding to the capacitance between the fixed electrode 3 and the detection reference electrode 4b is detected and output.

According to this embodiment, the same excellent effects as those of the first embodiment can be obtained, and the movable electrode 4 is connected to the detection reference electrode 4a and the drive reference electrode 4b. Since the detection reference electrode 4a is formed on the tip side of the cantilever 5 and the drive reference electrode 4b is formed on the support end side of the cantilever 5, the fixed reference electrode 4a is separated from the fixed electrode 3 on the tip side of the cantilever 5. Only the capacitance between the detection reference electrodes 4a can be detected, and the same excellent effects as in the second embodiment can be obtained. Further, similarly to the second embodiment, it is possible to generate a Coulomb force for bending and changing the cantilever 5 only on the supporting end side of the cantilever 5, and to provide the tip of the cantilever 5. It is possible to prevent the side from flexing and fluctuating excessively, and it is possible to widen the variable control range of the voltage for variably controlling the capacitance.

Hereinafter, a fourth embodiment will be described.
What is characteristic in this embodiment is that, as shown in FIG. 5, the fixed electrode 3 is divided and divided into a detection electrode 3a and a drive electrode 3b as shown in the second embodiment.
Further, as shown in the third embodiment, the movable electrode 4 is divided into the detection reference electrode 4a and the drive reference electrode 4b so that the drive voltage signal for bending and changing the cantilever 5 is provided. And the detection voltage signal corresponding to the capacitance is completely separated to improve the SN ratio of the detection voltage signal. Other configurations are the same as those of the above-described embodiments, and the description thereof will not be repeated.

In a configuration in which one or both of the fixed electrode 3 and the movable electrode 4 are used for both driving and detecting,
There is a case where the noise of the drive voltage signal is superimposed on the detection voltage signal, and when the noise of the drive voltage signal is large, there is a possibility that the SN ratio of the detection voltage signal is deteriorated. This embodiment is configured to reliably avoid the above-mentioned problem.

As described above, the fixed electrode 3 is formed separately from the detection electrode 3a and the drive electrode 3b, the movable electrode 4 is formed separately from the detection reference electrode 4a and the drive reference electrode 4b, and the detection electrode 3a and the detection reference electrode 4a are formed. , The drive electrode 3b and the drive reference electrode 4b face each other.

In this embodiment, a coulomb force is generated between the drive electrode 3b and the drive reference electrode 4b to generate the cantilever 5
And outputs a detection voltage signal corresponding to the capacitance between the detection electrode 3a and the detection reference electrode 4b.

According to this embodiment, excellent effects similar to those of the above-described embodiments can be obtained, and the fixed electrode 3 and the movable electrode 4 are separately formed for driving and detection. In addition, the drive voltage signal for driving the cantilever 5 and the detection voltage signal corresponding to the capacitance can flow through a completely separated path, and the detection voltage signal is not affected by the noise of the drive voltage signal. Of the detection voltage signal
The N ratio can be further improved.

Hereinafter, a fifth embodiment will be described. What is characteristic in this embodiment is that FIG.
As shown in the figure, the cantilever 5 has a width-deformed beam portion 12 having a width D decreasing from the support end side to the tip end side, and a width-deformed beam connected to the tip end side of the width-deformation beam portion 12. Detector that is wider than the width of the tip side of section 12
13 (a) of FIG.
As shown in FIG. 6B, which is a cross-sectional view taken along the line YY in FIG. 6A, a drive reference electrode 4b is provided on the surface of the width-deformed beam portion 12 facing the support substrate. A detection reference electrode 4a is formed on the support substrate facing surface of the detection unit 13, and a detection electrode 3a facing the detection reference electrode 4a and a drive electrode facing the drive reference electrode 4b are formed on the upper surface of the support substrate 2. The electrode 3b is formed. Configurations other than those described above are the same as those of the above-described embodiments, and the description thereof will not be repeated.

By the way, the movable electrode 4 and the cantilever 5 are formed so that the width D becomes narrower from the support end side to the distal end side. 4 has a smaller facing area. The capacitance between the fixed electrode 3 and the movable electrode 4 decreases as the facing area decreases.

Therefore, in this embodiment, as described above, the detection section 13 having a wide surface is continuously provided on the distal end side of the width-deformed beam section 12, and the detection reference electrode 4a is formed on the detection section 13 to support it. A detection electrode 3a opposed to the detection reference electrode 4a is formed on the upper surface of the substrate 2 so that the facing area between the detection electrode 3a and the detection reference electrode 4a is wider than that shown in each of the above embodiments. Is possible. By doing so, the facing area between the detection electrode 3a and the detection reference electrode 4a can be increased so as to obtain a capacitance suitable for a circuit incorporating the variable capacitance element, and a desired capacitance can be obtained. In addition, the capacitance can be variably set to be large or small so that the voltage level of the detection voltage signal can be increased.

In this embodiment, as in the case of the fourth embodiment, the fixed electrode 3 comprises the detection electrode 3a and the drive electrode 3a.
b, and the movable electrode 4 is separated and divided into a detection reference electrode 4a and a drive reference electrode 4b, and a Coulomb force is applied between the drive electrode 3b and the drive reference electrode 4b as in the fourth embodiment. The Coulomb force causes the cantilever 5 to bend and fluctuate, and the detection electrode 3a and the detection reference electrode 4b
It detects and outputs the capacitance between them.

According to this embodiment, the fixed electrode 3 and the movable electrode 4 are separately divided for driving and detection, respectively, as in the fourth embodiment, so that the deflection variation of the cantilever 5 Since it is possible to increase the variability of the detection capacitance with respect to and to completely separate the conduction path between the drive voltage signal and the detection voltage signal, noise of the detection voltage signal is reduced. Can be reduced. Moreover,
In this embodiment, the detection electrode 3a and the detection reference electrode 4
a can be made wider than that of the configuration shown in each of the above-described embodiments.
a and the detection electrode 3a
a and the capacitance between the detection reference electrode 4a can be increased, whereby the voltage level of the detection voltage signal can be increased and the SN ratio of the detection voltage signal can be further improved.

In this embodiment, the width D of the drive reference electrode 4b and the width-deformable beam portion 12 decreases from the support end side of the cantilever 5 toward the tip end. The opposing area of the drive reference electrode 4b is smaller on the tip end side than on the support end side, and as described in the first embodiment, the Coulomb force acting between the drive electrode 3b and the drive reference electrode 4b is reduced. This makes it possible to equalize from the support end side to the tip end side, and the tip end side is excessively bent so that the detection reference electrode 4a comes into contact with the detection electrode 3a, so that the variable voltage control range of the capacitance becomes very narrow. Problems can be prevented.

Further, as described above, the detection section 13 having a wide surface that protrudes from the front end side of the width-deformed beam section 12 is continuously provided on the front end side of the width-deformation beam section 12, so that each of the above-described embodiments can be used. Compared with the configuration, the facing area between the detection electrode 3a and the detection reference electrode 4a shown in FIG. 6A can be increased. From this, it is easy to variably set the capacitance to be large or small according to the circuit in which the variable capacitance element is incorporated.
Of course, if a desired capacitance can be obtained without providing the wide-area detection unit 13 and increasing the facing area between the detection electrode 3a and the detection reference electrode 4a, the wide-area detection unit 13
May not be provided.

The present invention is not limited to the above-described embodiments, but can adopt various embodiments.
For example, in each of the above embodiments, the movable electrode 4 (the detection reference electrode 4a and the drive reference electrode 4b) is formed on the lower surface of the cantilever 5, but the upper surface of the cantilever 5 which is the fixed electrode facing surface. May be formed.

In each of the above embodiments, the surfaces of all the electrodes are exposed, but a protective film may be formed on the surface of one or more of the electrodes. In this case, the electrode can be protected by the protective film.

In the first and second embodiments, the cantilever 5 is made of a material having low conductivity such as silicon oxide. However, the cantilever 5 is made of metal such as aluminum, gold, titanium and chromium. And the cantilever itself may function as a movable electrode. In this case, since the manufacturing process of the movable electrode 4 described in each of the above embodiments can be omitted, the manufacturing process can be simplified. Further, the cantilever 5 is made of silicon oxide, silicon nitride,
Some of various materials such as silicon, aluminum, gold, titanium, and chromium may be stacked and formed.

Further, in each of the above embodiments, the cantilever 5 is flexed and varied using Coulomb force. However, the cantilever 5 may be flexed and varied using a piezoelectric element and a magnetic force. Good. For example, when using piezoelectric, FIG.
As shown in (1), a first piezoelectric drive electrode 14, a piezoelectric element 15, and a second piezoelectric drive electrode 16 are sequentially laminated on the upper surface of the cantilever 5. When a voltage is applied to the first and second piezoelectric drive electrodes 14 and 15, the piezoelectric element 15 expands and contracts in accordance with the magnitude of the voltage, and the cantilever 5 changes in accordance with the expansion and contraction of the piezoelectric element 15. Deflection fluctuates, and the distance between the fixed electrode 3 and the movable electrode 4 changes. The capacitance between the fixed electrode 3 and the movable electrode 4 changes due to the change in the distance between the electrodes. The capacitance between the fixed electrode 3 and the movable electrode 4 is detected and output.

Further, in the fifth embodiment, the wide surface of the detecting section 13 is rectangular, but it is formed in a shape other than rectangular, such as a circle, a triangle, or a polygon having five or more angles. You may.

Furthermore, in the first to fourth embodiments, the surface of the cantilever 5 is formed in a trapezoidal shape.
(A), the shape may be triangular. Also, the cantilever 5 shown in the first to fourth embodiments, the fifth
In the width-deformed beam portion 12 of the cantilever 5 shown in the embodiment of the present invention, the width D is continuously narrowed from the support end side to the distal end side, but as shown in FIG. Alternatively, the width D may be gradually reduced from the support end toward the distal end.

Further, in each of the above-described embodiments, an example is shown in which the present invention is incorporated in a high-frequency AC circuit, but it may be incorporated in a DC circuit. However, when incorporated in a DC circuit as a switch element, for example, when the movable electrode 4 comes into contact with the fixed electrode 3, the switch is turned on, and otherwise, the switch is turned off.

[0074]

According to the present invention, the use of a cantilever makes it easier to flex and fluctuate the cantilever at a lower voltage than in the case of using a cantilever. Is formed with a movable electrode (reference electrode for detection and reference electrode for drive) opposed to a fixed electrode (detection electrode, drive electrode). , And the capacitance between the movable electrode and the fixed electrode can be varied at a low voltage. Also,
Since the variable capacitance element of the present invention has a simple structure,
It is easy to reduce the size and it can be manufactured by a simple manufacturing method, so that the manufacturing cost can be reduced.

Further, when the variable capacitance element of the present invention is used by being incorporated in a high-frequency circuit, the resonance frequency of the cantilever may be changed from the support end side to the tip end side under the same conditions except for the width of the beam. Since the width of the cantilever beam whose tip end side is narrower than that of the support end side as in the present invention is higher than that of the cantilever beam in the same width state, the resonance frequency of the cantilever beam in the present invention Deviates from the frequency of the vibration noise in a higher direction. As a result, the output signal of the variable capacitance element having a frequency corresponding to the resonance frequency of the cantilever does not include the vibration noise, and the output of the variable capacitance element The SN ratio of the signal can be improved.

Further, by making the width of the cantilever narrower at the tip end side than the support end side and making the width of the movable electrode narrower at the tip end side than the support end side, the cantilever flexure changes due to Coulomb force. Then, it is possible to avoid the problem that the Coulomb force strongly acts on the tip side of the cantilever and the tip side of the cantilever is excessively bent. From this,
The variable control range of the voltage level for variably controlling the capacitance can be expanded, the variable control of the capacitance can be easily performed, and the variable control of the capacitance can be performed with high accuracy.

Either the fixed electrode or the movable electrode is separated and divided for detection and driving, and the driving is disposed on the support end side of the cantilever and the detection is disposed on the tip side of the cantilever. In accordance with the above, the tip of the cantilever is inevitably bent and fluctuated with the variation of the support end of the cantilever, and only the capacitance between the electrodes on the tip of the cantilever is detected and output. Therefore, the capacitance to be detected can be largely varied only by slightly changing the support end side of the cantilever.

Further, since the Coulomb force for bending and changing the cantilever can be generated only on the support end side of the cantilever, the Coulomb force strongly acts on the tip side of the cantilever, and excessively. There is no bending, the voltage level variable range for variably controlling the capacitance can be expanded, and the variable control of the capacitance becomes easy.

Further, when both the fixed electrode and the movable electrode are separately divided for detection and driving, the driving voltage signal for bending and changing the cantilever and the detection voltage signal for capacitance are completely converted. Since the current can flow through the divided paths, noise of the detection voltage signal can be reduced, and the SN ratio of the detection voltage signal can be improved.

In the case where the cantilever is formed by the width-deformed beam portion and the detection portion formed on the tip side of the width-deformed beam portion, the opposing area between the detection reference electrode and the detection electrode is set. Can be expanded. As a result, it is possible to increase the capacitance between the detection reference electrode and the detection electrode,
It becomes easy to obtain a desired capacitance suitable for a circuit incorporating the variable capacitance element. Further, since the voltage level of the detection voltage signal corresponding to the capacitance can be increased, the SN ratio of the detection voltage signal can be further improved.

The invention in which the width of the cantilever is reduced continuously or stepwise from the support end to the tip end, or the width of the width-deformed beam portion of the cantilever is continuously increased from the support end to the tip end In the invention in which the resonance frequency of the cantilever is shifted in a direction higher than the frequency of the vibration noise, the S / N ratio of the output signal of the variable capacitance element is further improved. Is possible. Also,
It is easy to make the magnitude of the Coulomb force acting between the fixed electrode and the movable electrode uniform from the support end side to the tip end side of the cantilever, and the variable control of the capacitance can be performed more accurately.

In the case where the protective film is formed on the electrode,
Since the protective film is formed on the surface of the electrode, the surface of the electrode can be protected by the protective film.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a first embodiment.

FIG. 2 is an explanatory view showing an example of a method of manufacturing the variable capacitance element shown in FIG.

FIG. 3 is an explanatory diagram showing a second embodiment.

FIG. 4 is an explanatory diagram showing a third embodiment.

FIG. 5 is an explanatory diagram showing a fourth embodiment.

FIG. 6 is an explanatory diagram showing a fifth embodiment.

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

FIG. 8 is an explanatory diagram showing an example of a cantilever having a uniform width.

FIG. 9 is an explanatory diagram showing another embodiment.

FIG. 10 is an explanatory diagram showing a conventional example.

[Explanation of symbols]

 2 Support substrate 3 Fixed electrode 3a Detection electrode 3b Driving electrode 4 Movable electrode 4a Detection reference electrode 4b Driving reference electrode 11 Void 12 Width deformed beam 13 Detection section

Claims (7)

[Claims] 1. A support substrate, a fixed electrode fixedly formed on the support substrate, and a cantilever supported by the support substrate in a cantilever shape and disposed opposite to the fixed electrode via a gap, The cantilever has a movable electrode formed on the fixed electrode-facing surface of the cantilever so as to face the fixed electrode, and the cantilever has a width on the tip side smaller than the width on the support end side. Characteristic variable capacitance element. 2. The fixed electrode is separated and divided into first and second fixed electrodes, and the first and second fixed electrodes are supported via a gap in a direction from a support end side of the cantilever to a tip end side. The fixed electrode on the support end side of the cantilever is arranged on the substrate and forms a drive electrode for bending and changing the cantilever, and the fixed electrode on the other side is for detecting the capacitance between the movable electrode and the movable electrode. 2. A structure as described in claim 1, wherein said detecting electrode is formed.
The variable capacitance element according to the above. 3. The movable electrode is divided into a first movable electrode and a second movable electrode. The first and second movable electrodes are separated from each other by a gap in a direction from the support end side of the cantilever to the distal end side. The movable electrode on the support end side of the cantilever is a drive reference electrode for bending and changing the cantilever, and the movable electrode on the other side is in contact with the fixed electrode. 3. The variable capacitance element according to claim 1, wherein the variable capacitance element is configured to form a detection reference electrode for detecting a capacitance between the capacitances. 4. The cantilever according to claim 1, wherein the width of the cantilever is reduced continuously or stepwise from the support end toward the distal end. Variable capacitance element. 5. A support substrate, a drive electrode fixedly formed on the support substrate, detection electrodes arrayed on the support substrate with a gap between the drive electrode, and a drive electrode and a detection electrode arranged in a direction in which the drive electrode and the detection electrode are arranged. A drive electrode extending from the drive electrode side to the support end side, the drive electrode and the detection electrode having a cantilever disposed opposite to the drive electrode via a gap, and the cantilever is opposed to the drive electrode and has a distal end. Is formed by a width-deformed beam portion having a width smaller than the width of the support end side, and a detection portion that is provided continuously to the tip side of the width-deformation beam portion and faces the detection electrode. A drive reference electrode is formed on the tip side of the width-deformed beam portion, and a drive electrode facing the drive electrode of the width-deformed beam portion is provided with a drive reference electrode for bending and changing the cantilever. Is provided with a reference electrode for detection to detect the capacitance between it and the detection electrode. Wherein the driving and detecting reference electrodes are formed separately with a gap therebetween. 6. The variable-capacitance element according to claim 5, wherein the width of the cantilever beam is reduced continuously or stepwise from the support end toward the distal end. . 7. A structure in which a protective film for protecting an electrode is formed on a surface of at least one electrode, wherein the protective film is formed on the surface of at least one of the electrodes. The variable capacitance element according to claim 5 or 6.