WO2011158620A1 - Variable capacitance device - Google Patents

Abstract

Provided is a variable capacitance device which can prevent a failure of a MEMS, caused due to an electrostatic charge, and can easily maintain a constant correlation between a drive capacitance and a radio frequency (RF) capacitance. A variable capacitance device (1) is provided with a support plate (2), a movable beam (3), drive capacitance units (C2A, C2B), RF capacitance units (C1A, C1B), a stopper unit (12), and unipotential electrodes (9A, 9B). The movable beam (3) has a cantilever beam structure parallel to the main surface of the support plate (2). The stopper unit (12) is provided so that the longitudinal direction thereof is along the main axis direction of the movable beam, on the area of a dielectric film (8) opposite to the drive capacitance electrodes (7A, 7B) constituting the drive capacitance units (C2A, C2B), via a gap. The unipotential electrodes (9A, 9B) are opposite to the area on which the stopper unit (12) is provided, via the dielectric film (8), and are connected to the drive capacitance electrodes (7A, 7B) at the same potential.

Description

Variable capacity device

The present invention relates to a variable capacity device capable of changing an RF (Radio Frequency) capacity using a MEMS driven by an electrostatic force.

In recent years, MEMS driven by electrostatic force is sometimes used for variable capacitance devices (see Patent Documents 1 and 2).

FIG. 1 is a diagram illustrating a configuration example of a conventional variable capacitance device.
The variable capacity device 101 includes movable beams 102 and 103. The movable beams 102 and 103 each have a doubly supported beam structure and are made of a conductive material. The movable beam 102 and the movable beam 103 are arranged at a distance from each other. The movable beam 103 has a convex surface facing the movable beam 102 and includes a dielectric layer 104 on the surface. Due to the driving capacity generated by applying a driving DC voltage between the movable beams 102 and 103, the distance between the movable beams 102 and 103 is narrowed, and the convex tip end region of the movable beam 103 is passed through the dielectric layer 104 to the movable beam 102. The RF capacity of the variable capacitance device 101 changes continuously according to the contact area.

Japanese Patent Laid-Open No. 2006-210843 JP 2008-182134 A

In the conventional variable capacitance device, since the driving DC voltage and the RF signal are applied to the common electrode, a resistor and a capacitor for separating the direct current component and the alternating current component are required for the driving circuit. Since insertion of a resistor or a capacitor causes a complicated circuit configuration and an increase in insertion loss, the applicant of the present application has developed a variable capacitance device that does not require such a resistor or capacitor. 2A is a plan view showing a configuration example of the variable capacitance device 201, and FIG. 2B is a side sectional view thereof.
The variable capacity device 201 includes a support plate 202 and a movable beam 203. The movable beam 203 has a cantilever structure that is supported in parallel to the support plate 202. The support plate 202 is provided with two linear line-shaped electrodes 204 in parallel along the main axis direction of the movable beam 203, and the U-shaped line-shaped electrodes 205 are disposed between both ends of the support plate 202. In addition, dielectric films 208A and 208B are provided so as to cover the electrodes 204 and 205, respectively. The movable beam 203 includes one rectangular electrode 206 (shown in FIG. 2B) facing the two electrodes 204 and a U-shaped electrode 207 facing the electrode 205 (FIG. 2). (Illustrated in (B)). The electrode 204 and the electrode 206 are opposed to each other via the dielectric film 208A and function as an RF capacitor portion, and the electrode 205 and the electrode 207 are opposed to each other via the dielectric film 208B and function as a drive capacitor portion. The drive capacity unit deforms the movable beam 203 so that the contact area between the electrode 207 and the dielectric film 208B is continuously changed by electrostatic attraction by the drive capacity generated by applying the drive DC voltage. The RF capacitor unit is used as an RF capacitor whose capacitance can be continuously changed by connecting the electrode 204 to a high frequency circuit. As described above, the variable capacitance device 201 has a structure in which the electrodes 205 and 207 to which the driving DC voltage is applied and the electrodes 204 and 206 to which the RF signal is applied are structurally separated.

In the variable capacitance device configured as described above, when the RF capacitance is controlled by applying the drive DC voltage to the drive capacitance section, the electrodes constituting the drive capacitance section and the dielectric film are in contact with each other. Then, the drive DC voltage is directly applied to the dielectric film, and the dielectric film is charged (hereinafter, this phenomenon is referred to as charge-up). Depending on the charge amount of this charge-up, a sticking phenomenon may occur in which the movable beam sticks to the support plate and the MEMS operation cannot be performed properly.

Further, in the variable capacitance device configured as described above, since the drive capacitor unit and the RF capacitor unit are separated, the capacitance change of the RF capacitor unit is likely to be unstable with respect to the capacitance change of the drive capacitor unit, In order to keep the correlation between the driving capacity and the RF capacity constant, it is necessary to configure the variable capacity device with extremely high shape accuracy.

Therefore, an object of the present invention is to provide a variable capacitance device that can prevent malfunction of the MEMS due to charge-up and that can easily keep the correlation between the drive capacitance and the RF capacitance constant.

The variable capacitance device of the present invention includes a support plate, a movable beam, a drive capacitance portion, an RF capacitance portion, a stopper portion, and an equipotential electrode portion. The movable beam is supported in parallel to the main surface of the support plate. The drive capacitor unit includes a pair of drive capacitor electrodes provided to be opposed to each other on the movable beam and the support plate along the main axis direction of the movable beam, and a dielectric film laminated on at least one of the drive capacitor electrodes, Consists of. The drive capacity unit deforms the movable beam based on the drive capacity generated between the pair of drive capacity electrodes. The RF capacitor unit includes a pair of RF capacitor electrodes provided in a long manner along the main axis direction of the movable beam so as to face the movable beam and the support plate, and a dielectric film laminated on at least one of the RF capacitor electrodes; Consists of. The RF capacitor unit propagates an RF signal through an RF capacitor generated between a pair of RF capacitor electrodes. The stopper portion is provided so as to protrude into the gap space between the drive capacitor electrode and the dielectric film in the drive capacitor portion. The stopper portion is provided along the main axis direction of the movable beam. The equipotential electrode portion is provided along the principal axis direction of the movable beam at a position facing the stopper portion,
It is connected to the same potential as the opposing drive capacitor electrode through the gap space.

In this configuration, a gap space is secured between the drive capacitor electrode and the dielectric film in the drive capacitor portion even when the movable beam and the support plate are in the proximity state by the stopper portion. For this reason, even if the movable beam and the support plate are close to each other, the dielectric film is sandwiched between the pair of drive capacitance electrodes via the gap space or the stopper portion. Since the gap space has a sufficiently low dielectric constant, and the stopper portion is sandwiched between the drive capacitance electrode and the same potential electrode portion having the same potential, the charge amount of the dielectric film is reduced.
In addition, the stopper portion and the same potential electrode are provided along the main axis direction of the movable beam. As a result, the distance between the drive capacitor electrode and the dielectric film through the gap space in the proximity state can be made uniform in the principal axis direction of the movable beam, and the correlation between the drive capacitor and the RF capacitor is constant. Easy to keep in.

The stopper portion of the present invention is preferably provided only at a position where the drive capacitor electrode and the same potential electrode portion face each other.
In this configuration, the stopper portion is not interposed between the drive capacitance electrodes, and charging of the dielectric film in the drive capacitance portion can be prevented more reliably.

The thickness of the dielectric film in the RF capacitor portion of the present invention may be equal to the sum of the thickness of the dielectric film in the drive capacitor portion and the thickness of the stopper portion. In this case, when the movable beam and the support plate are in the proximity state, there is no gap space in the RF capacitor portion, and the RF capacitor electrode and the dielectric film are reliably in contact with each other. For this reason, it is easy to increase the capacitance value in the RF capacitor section, and a desired RF capacitor can be secured even with a small chip area.

The thickness of the dielectric film in the RF capacitor portion of the present invention may be equal to the thickness of the dielectric film in the drive capacitor portion. In this case, the same forming process can be adopted for forming the dielectric film in the RF capacitor unit and the drive capacitor unit, and the thickness of the dielectric film can be matched without being affected by the process accuracy. For this reason, it becomes easy to keep the correlation between the drive capacity and the RF capacity constant.

In this case, if the RF capacitor portion is also provided with a stopper portion, the distance from the dielectric film through the gap space can be almost completely matched between the RF capacitor portion and the drive capacitor portion. Therefore, it becomes easier to keep the correlation between the drive capacity and the RF capacity constant.

The stopper portion of the present invention may be made of the same material as the dielectric film. In this case, the dielectric film may be partially thickened and the protruding portion may be used as the stopper portion. Alternatively, a dielectric film may be formed with a uniform thickness, and a protruding portion due to the thickness of the same potential electrode may be used as a stopper portion. In this case, the manufacturing equipment used for the process for forming the stopper portion can be made common with the manufacturing equipment used for the process for forming the dielectric film, and the manufacturing equipment can be simplified.

The stopper portion of the present invention may be made of a conductive material. In that case, the stopper portion may be stacked on the dielectric film and connected to the same potential electrode and the same potential, and the dielectric film is not formed on the non-formed portion of the dielectric film. A projecting portion may be used as a stopper portion by laminating conductive materials. In this case, charging of the dielectric film in the drive capacitor unit can be prevented more reliably.

According to the present invention, since the gap portion is secured between the drive capacitor electrode and the dielectric film in the drive capacitor portion even when the movable beam and the support plate are close to each other by the stopper portion, the movable beam and the support plate The dielectric film is sandwiched between the pair of drive capacitance electrodes via the gap space or the stopper portion. The gap space has a sufficiently low dielectric constant, and the stopper portion is sandwiched between the drive capacitance electrode and the same potential electrode portion having the same potential, so that the charge amount of the dielectric film can be reduced and the charge can be increased. Occurrence of the sticking phenomenon based on this can be prevented.
Further, the stopper portion and the equipotential electrode are provided along the principal axis direction of the movable beam, so that the distance between the drive capacitor electrode and the dielectric film through the gap space in the proximity state of the movable beam and the support plate is It can be made uniform in the main axis direction of the movable beam, and it becomes easy to keep the correlation between the drive capacity and the RF capacity constant.

It is a figure explaining the structural example of the conventional variable capacitance apparatus. It is a figure explaining the structural example of another variable capacity apparatus. It is a figure explaining the example of composition of the variable capacity device concerning a 1st embodiment of the present invention. It is a figure explaining the operation | movement at the time of the drive of the variable capacitance apparatus which concerns on the 1st Embodiment of this invention. It is a figure explaining the structural example of the variable capacitance apparatus which concerns on the 2nd Embodiment of this invention. It is a figure explaining the structural example of the variable capacitance apparatus which concerns on the 3rd Embodiment of this invention. It is a figure explaining the structural example of the variable capacitance apparatus which concerns on the 4th Embodiment of this invention. It is a figure explaining the structural example of the variable capacitance apparatus which concerns on the 5th Embodiment of this invention. It is a figure explaining the structural example of the variable capacitance apparatus which concerns on the 6th Embodiment of this invention.

A configuration example of a variable capacitance device according to an embodiment of the present invention will be described with reference to the drawings. In each figure, an orthogonal coordinate XYZ axis is attached, the thickness direction of the movable beam is the Z-axis direction, the principal axis direction is the X-axis direction, and the width direction is the Y-axis direction.

<< First Embodiment >>
FIG. 3A is an XY plane plan view of the variable capacitance device 1 according to the first embodiment. FIG. 3B is a cross-sectional view of the variable capacitance device 1 taken along the XZ plane. FIG. 3C is a YZ plane cross-sectional view of the variable capacitance device 1.

The variable capacitance device 1 includes a support plate 2, a movable beam 3, an upper RF capacitive electrode 6, lower RF capacitive electrodes 4A and 4B, upper drive capacitive electrodes 7A and 7B, and lower drive capacitive electrodes 5A and 5B. And a dielectric film 8 and equipotential electrodes 9A and 9B.

The support plate 2 is made of a rectangular glass substrate in plan view.
The movable beam 3 is made of a high-resistance silicon substrate (insulating material) having a thickness of about 20 to 30 μm, and includes two connecting portions 3B, a movable portion 3C, a support portion 3A, and a ladder portion 3D, as viewed from the XZ plane. It is a substantially L-shaped cantilever structure. The support portion 3A is long in the Y-axis direction, has a columnar shape standing from the support plate 2 in the Z-axis direction, and is provided at the end portion of the movable beam 3 in the X-axis negative direction. 3C is supported in a state of being separated from the support plate 2. The movable portion 3C has a flat plate shape that is long in the X-axis direction when viewed from the XY plane, and is provided at the end portion of the movable beam 3 in the X-axis positive direction. Each of the two connecting portions 3B has a meander line shape meandering with respect to the X axis, and is erected in the X axis direction from both ends of the Y axis direction of the support portion 3A to connect the support portion 3A and the movable portion 3C. Then, the support end of the movable beam 3 is supported as a rotation end instead of a fixed end.
The movable portion 3C is partitioned into three regions arranged in the Y-axis direction by two ladder portions 3D, and each region has a flat plate shape elongated in the X-axis direction. The ladder portion 3D includes a plurality of openings arranged along the X axis.

The lower RF capacitive electrodes 4A and 4B and the lower drive capacitive electrodes 5A and 5B are line-like electrodes that are formed on the upper surface of the support plate 2 with a thickness of 2000 nm and are long in the X-axis direction. The lower drive capacitance electrodes 5A and 5B are arranged on both sides of the electrodes 4A and 4B in the Y-axis direction. The equipotential electrodes 9A and 9B have both arms (9A1, 9A2) and (9B1, 9B2), respectively, and have a U-shape that opens in the negative X-axis direction. Each arm portion 9A1, 9A2, 9B1, 9B2 has a long line shape in the X-axis direction, and the lower drive capacitance electrodes 5A, 5B are both arm portions (9A1, 9A2), (9B1, 9B2) is formed on the upper surface of the support plate 2 with a thickness of 2000 nm so as to be sandwiched between them. The upper RF capacitive electrode 6 and the upper drive capacitive electrodes 7A and 7B are line-like electrodes that are formed on the lower surface of the movable beam 3 with a thickness of 200 nm and are long in the X-axis direction. Opposite to the RF capacitive electrodes 4A and 4B, the upper drive capacitive electrodes 7A and 7B are provided to face the lower drive capacitive electrodes 5A and 5B. The dielectric film 8 is made of Ta ₂ O ₅ having a thickness of 150 nm to 200 nm and covers the lower RF capacitor electrodes 4A and 4B, the lower drive capacitor electrodes 5A and 5B, and the same potential electrodes 9A and 9B. Are stacked on the upper surface region.

The lower RF capacitive electrode 4A is connected to an RF signal input terminal (or output terminal), and the lower RF capacitive electrode 4B is connected to an RF signal output terminal (or input terminal). The lower drive capacitance electrodes 5A and 5B are connected to the drive DC voltage terminal. The upper drive capacitance electrodes 7A and 7B are connected to the ground GND. The equipotential electrodes 9A and 9B are connected to the ground GND. Due to such a connection form, the lower RF capacitive electrodes 4A and 4B constitute RF capacitive portions C1A and C1B together with the opposing regions of the upper RF capacitive electrode 6 and the dielectric film 8, respectively. The lower drive capacitance electrodes 5A and 5B constitute drive capacitance portions C2A and C2B together with the opposing regions of the upper drive capacitance electrodes 7A and 7B and the dielectric film 8, respectively.

The drive capacitors C2A and C2B serve as drive capacitors that attract the movable beam 3 to the support plate 2 side by the electrostatic attractive force and bring the movable beam 3 close to the dielectric film 8 from the tip (end on the X axis positive direction side). Function. FIG. 4 is a diagram showing a change in the area close to the dielectric film 8 in the movable beam 3 due to the drive DC voltage. The higher the driving DC voltage, the larger the proximity area between the movable beam 3 and the dielectric film 8. On the other hand, the RF capacitors C1A and C1B are used in a high-frequency circuit of several hundred MHz to several GHz, and function as an RF capacitor whose capacitance value changes according to the proximity area between the movable beam 3 and the dielectric film 8. .

The dielectric film 8 of the present embodiment includes a dividing groove 11 (see FIG. 3C) at the boundary between the lower drive capacitance electrodes 5A and 5B and the same potential electrodes 9A and 9B. The body is divided into body division regions 8A to 8E (see FIG. 3C). The dielectric division region 8A is provided so as to cover the lower RF capacitive electrodes 4A and 4B and the arm portions 9A1 and 9B1. The dielectric division regions 8B and 8C are provided so as to cover the lower drive capacitance electrodes 5A and 5B, respectively. The dielectric division regions 8D and 8E are provided so as to cover the arm portions 9A2 and 9B2, respectively. By dividing the dielectric film 8 by the dividing grooves 11 in this manner, capacitive coupling between the lower drive capacitance electrodes 5A and 5B and the same potential electrodes 9A and 9B is suppressed.

Further, the dielectric film 8 includes a stopper portion 12 on the surface of the region covering each arm portion 9A1, 9A2, 9B1, 9B2. Each stopper portion 12 is a portion that protrudes approximately 20 nm to 50 nm from the surface of the dielectric film 8 along the X-axis, and includes a portion on the lower drive capacitance electrodes 5A and 5B and the upper drive capacitance. It is provided to ensure a gap space between the electrodes 7A and 7B. The thickness of the dielectric film 8 in the region where the stopper portion 12 is formed is equal to the region where the RF capacitor portions C1A and C1B are formed, and is thicker than the region where the drive capacitor portions C2A and C2B are formed.

In this configuration, the dielectric division regions 8B and 8C have a gap space between the upper drive capacitance electrodes 7A and 7B and the lower drive capacitance electrodes 5A and 5B even when the movable beam 3 and the support plate 2 are in proximity to each other. Will be sandwiched through. Since the dielectric constant of the gap space is sufficiently low, the charge amount of the dielectric divided regions 8B and 8C is extremely reduced.
Further, the dielectric division regions 8D and 8E come into contact with the upper drive capacitance electrodes 7A and 7B through the stopper portion 12 when the movable beam 3 and the support plate 2 are brought into proximity. However, the electric field does not act between the upper drive capacitance electrodes 7A, 7B and the same potential electrodes 9A, 9B because they are at the same potential, and the dielectric division regions 8D, 8E are not charged.
Further, when the movable beam 3 and the support plate 2 are in the proximity state, the dielectric division region 8A comes into contact with the upper drive capacitor electrodes 7A and 7B via the stopper portion 12. However, the same potential electrodes 9A and 9B are provided at positions facing the upper drive capacitance electrodes 7A and 7B. Since the upper drive capacitance electrodes 7A and 7B and the same potential electrodes 9A and 9B are at the same potential, an electric field is generated. It does not act, and the dielectric division region 8A is hardly charged.
As described above, in the drive capacitor portions C2A and C2B, the dielectric film 8 is hardly charged, and sticking due to charging can be prevented from occurring. On the other hand, since the upper RF capacitive electrode 6 and the lower RF capacitive electrodes 4A and 4B are opposed to each other through only the dielectric division region 8A without a gap space, a large RF capacitance is provided in the RF capacitive portions C1A and C1B. Obtainable.

Further, the stopper portion 12 and the equipotential electrodes 9A and 9B are provided in parallel with the lower drive capacitance electrodes 5A and 5B with the main axis direction of the movable beam 3 as the longitudinal direction, and the height of the stopper portion 12 is uniform. Has been. As a result, the distance between the upper drive capacitance electrodes 7A, 7B and the dielectric film 8 through the gap space when the movable beam 3 and the support plate 2 are close to each other is made uniform in the main axis direction of the movable beam 3. This makes it easy to keep the correlation between the drive capacity and the RF capacity constant.

<< Second Embodiment >>
FIG. 5A is an XY plane plan view of the variable capacitance device 21 according to the second embodiment of the present invention. In addition, in the same figure, illustration of the movable beam 3 is omitted. FIG. 5B is a YZ plane cross-sectional view of the variable capacitance device 21.
The variable capacitance device 21 includes a dielectric film 28 having a shape different from that of the variable capacitance device 1 described above. As in the first embodiment, the dielectric film 28 is divided into dielectric division regions 28A to 28E by the division groove 11, and the stopper portion 12 is provided at a position facing the same potential electrodes 9A and 9B. In the present embodiment, the stopper portion 22 is provided at a position facing the lower RF capacitive electrodes 4A and 4B in the dielectric division region 28A. The stopper portion 22 has the same thickness as the stopper portion 12 and protrudes from the upper surface of the dielectric film 28 with the X-axis direction as the longitudinal direction. Therefore, in the RF capacitor portions C1A and C1B, the upper RF capacitor electrode 6 and the lower RF capacitor electrodes 4A and 4B are in contact with each other via the stopper portion 22 of the dielectric division region 28A.

Even with this configuration, the same effects as those of the first embodiment can be obtained. The dielectric film 28 is formed by forming a Ta ₂ O ₅ film by a film formation process by sputtering, providing stopper portions 12 and 22 by a primary RIE etching process, and providing a dividing groove 11 by a secondary RIE etching process. Can be formed. When such a process is adopted, the etching amount may deviate from the assumption in the primary RIE etching process, but in this configuration, the deviation does not cause a variation in the correlation between the RF capacitance and the drive capacitance, and the RF A high correlation between the capacity and the drive capacity can be stably obtained.

<< Third Embodiment >>
FIG. 6A is an XY plane plan view of the variable capacitance device 31 according to the third embodiment of the present invention. In addition, in the same figure, illustration of the movable beam 3 is omitted. 6B is a cross-sectional view of the variable capacitance device 31 taken along the YZ plane.
The variable capacitance device 31 includes a dielectric film 38 having a shape different from that of the variable capacitance device 1 described above. As in the first embodiment, the dielectric film 38 is divided into dielectric division regions 38A to 38E by the division groove 11, and the stopper portion 12 is provided at a position facing the same potential electrodes 9A and 9B. In the present embodiment, a plurality of circular stopper portions 32 are provided in the dielectric division regions 38B and 38C. These stopper portions 32 have the same thickness as the stopper portion 12 and protrude from the upper surface of the dielectric film 38.

In the variable capacitance device 31, when a high drive DC voltage is applied to the drive capacitor portions C2A and C2B, the position between the arm portions (9A1, 9A2) and (9B1, 9B2) of the movable beam 3 is in contact with each other. An electrostatic attractive force that bends toward the support plate 2 side acts on the portion. In this configuration, the electrostatic attracting force is supported by the stopper portion 32 to prevent the movable beam 3 from being bent. As a result, the drive capacity maintains an appropriate capacity value, and a high correlation between the RF capacity and the drive capacity can be stably obtained.

<< Fourth Embodiment >>
FIG. 7 is a schematic diagram for explaining an arrangement configuration example of stopper portions and equipotential electrodes in the variable capacitance device of the present invention.
The variable capacitance device 41A illustrated in FIG. 7A has a configuration in which the stopper portion 42A is disposed not on both sides of the lower drive capacitance electrodes 5A and 5B constituting the drive capacitance portion but on one side. In this case, the same potential electrode (not shown) is preferably provided at the same position as the stopper portion 42A.
In the variable capacitance device 41B illustrated in FIG. 7B, the stopper portion 42B is not a single long shape but a shorter strip shape, and a plurality of stopper portions 42B are arranged in the longitudinal direction of the movable beam. It is a configuration. In this case, the equipotential electrode (not shown) is preferably a single elongated shape as in the above-described embodiment.
A variable capacitance device 41C illustrated in FIG. 7C has a configuration in which the lower drive capacitance electrode is divided into two regions (5A1, 5A2) and (5B1, 5B2), and a stopper portion 42C is disposed therebetween. In this case, the equipotential electrode (not shown) is preferably a single elongated shape as in the above-described embodiment.
In the variable capacitance device 41D illustrated in FIG. 7D, the stopper portion 42D is also disposed between the two lower RF capacitance electrodes 4A and 4B constituting the RF capacitance portion, and the plurality of stopper portions 42D are equally spaced. It is the structure arranged by. By setting it as such an arrangement | positioning, it becomes possible to reduce the bending of a movable beam extremely. In this case, in the stopper portion 42D between the lower RF capacitive electrodes 4A and 4B, the equipotential electrode may not be provided at the opposing position.
As described above, the stopper portion can have various arrangement configurations.

<< Fifth Embodiment >>
Next, in the present invention, a configuration example in the case where the movable beam of the variable capacitance device has a double-supported beam structure will be described.

FIG. 8A is an XY plane plan view of a variable capacitance device 51A according to the fifth embodiment of the present invention. In addition, in the same figure, illustration of the ladder part is omitted.
The variable capacitance device 51A includes a movable beam 53 having a doubly supported beam structure, and is provided between the lower RF capacitive electrode 4A and the lower drive capacitive electrode 5A, and between the lower RF capacitive electrode 4B and the lower drive capacitive electrode 5B. The stopper portion 52 is provided at the position, and the same potential electrode (not shown) is provided at the position overlapping the stopper portion 52. Even in such a configuration, the lower drive capacitance electrodes 5A and 5B and the upper drive capacitance electrodes 7A and 7B (not shown) constituting the drive capacitance portion are formed by the stopper portion 52 as in the above-described embodiment. A gap space can be secured between them.

FIG. 8B is an XY plane plan view of a variable capacitance device 51B according to the fifth embodiment of the present invention. In the figure, the ladder part and the dielectric film are not shown.
This variable capacity device 51B is configured to support the end of the movable beam 53 in the positive X-axis direction on the support plate 2 by means of a meander-shaped connecting part 53A. The spring constant of the connecting part 53A is connected to the connecting part in the X-axis negative direction. The spring constant is significantly smaller than 3B, so that the movable beam 53 comes into contact with the dielectric film from the end in the positive direction of the X axis.
In this variable capacitance device 51B as well as the variable capacitance device 51A, between the lower RF capacitance electrode 4A and the lower drive capacitance electrode 5A and between the lower RF capacitance electrode 4B and the lower drive capacitance electrode 5B. A stopper portion 52 is provided at a position, and the same potential electrode (not shown) is provided at a position overlapping the stopper portion 52.

FIG. 8C is an XY plane plan view of a variable capacitance device 51C according to the fifth embodiment of the present invention. In the figure, the ladder part and the dielectric film are not shown.
The variable capacity device 51C connects the connecting portion 53B to the end portion of the movable beam 53 in the positive direction of the X axis and draws the connecting portion 53B to the vicinity of the end portion of the movable beam 53 in the negative direction of the X axis. It is configured to connect to a common support portion 3A, and the spring constant of the connecting portion 53B is made significantly smaller than the spring constant of the connecting portion 3B in the negative X-axis direction, whereby the movable beam 53 is the end portion in the positive X-axis direction. In this configuration, the dielectric film is in contact with the dielectric film.
Also in this variable capacitance device 51C, similarly to the variable capacitance devices 51A and 51B, between the lower RF capacitance electrode 4A and the lower drive capacitance electrode 5A and between the lower RF capacitance electrode 4B and the lower drive capacitance electrode 5B. A stopper portion 52 is provided at a position therebetween, and the same potential electrode (not shown) is provided at a position overlapping the stopper portion 52.

<< Sixth Embodiment >>
Next, a configuration example of a cross-sectional structure of the variable capacitance device of the present invention will be described.

FIG. 9A is an XY plane plan view of a variable capacitance device 61A according to the sixth embodiment of the present invention.
The variable capacitance device 61A includes an equipotential electrode 69A having an electrode thickness thicker than the electrode thicknesses of the lower RF capacitance electrodes 4A and 4B and the lower drive capacitance electrodes 5A and 5B. In this configuration, the height of the stopper portion can be adjusted by adjusting the thickness of the equipotential electrode 69A. If the equipotential electrode 69A is formed using a deposition process and a lift-off process by vapor deposition, the height of the equipotential electrode 69A is increased. Therefore, the height of the stopper portion can be adjusted with high accuracy.

FIG. 9B is an XY plane plan view of the variable capacitance device 61B according to the sixth embodiment of the present invention.
The variable capacitance device 61B has a configuration in which the same potential electrode 69B is formed so as to protrude from the dielectric film 8. In this configuration, since the stopper portion is composed of the equipotential electrode 69B, when the equipotential electrode 69B is formed by employing a deposition process and a lift-off process, the height of the stopper portion can be adjusted with high accuracy. Can do. Furthermore, the dielectric film 8 does not come into contact with the upper drive capacitor electrodes 7A and 7B in the drive capacitor portion, and reliable charging prevention can be achieved.

FIG. 9C is an XY plane plan view of a variable capacitance device 61C according to the sixth embodiment of the present invention.
The variable capacitance device 61C includes a stopper portion 62 made of a conductive material, and is configured to connect the stopper portion 62 to the same potential as the same potential electrodes 9A and 9B and the upper drive capacitance electrodes 7A and 7B. In this configuration, since the stopper portion is made of a conductive material, the dielectric film 8 does not come into contact with the upper drive capacitance electrodes 7A and 7B in the drive capacitance portion, and reliable charging prevention can be achieved.

FIG. 9D is an XY plane plan view of the variable capacitance device 61D according to the sixth embodiment of the present invention.
The variable capacitance device 61D includes the circular stopper portion 32 described in the third embodiment, and also includes a stopper portion 62 made of a conductive material. The stopper portion 62 includes the same potential electrodes 9A and 9B and the upper drive capacitance electrode. 7A and 7B are connected to the same potential. Even in this configuration, since the stopper portion is made of a conductive material, the dielectric film 8 does not come into contact with the upper drive capacitance electrodes 7A and 7B in the drive capacitance portion, so that reliable charging prevention can be achieved.

In the case where the stopper portion made of the conductive material as described above is provided, the dielectric film is charged with plasma when a process using plasma such as a RIE etching process or a film formation process by sputtering is employed. Even if this occurs, the presence of the stopper portion makes it less likely to be adversely affected by charging, and process accuracy can be improved.

The present invention is not limited to the description of the above-described embodiment, and the scope of the present invention is defined by the scope of claims, and includes meanings equivalent to the scope of claims and all modifications within the scope. Is intended.

C1A, C1B... RF capacitors C2A, C2B... Drive capacitors 1, 21, 31, 41A to 41D, 51A to 51C, 61A to 61D ... Variable capacitor device 2 ... Support plate 3, 53 ... Movable beam 3A ... Support portion 3B , 53A, 53B ... connecting part 3C ... movable part 3D ... ladder part 4A, 4B ... lower RF capacitive electrodes 4A, 4B
5A, 5B ... Lower drive capacitance electrode 6 ... Upper RF capacitance electrode 7A, 7B ... Upper drive capacitance electrodes 8, 28, 38 ... Dielectric films 8A-8E, 28A-28E, 38A-38E ... Dielectric divided region 9A, 9B, 69A, 69B ... equipotential electrodes 9A1, 9A2, 9B1, 9B2 ... arm 11 ... dividing grooves 12, 22, 32, 42A to 42D, 52, 62 ... stoppers

Claims (9)

1. A support plate;
   A movable beam supported parallel to the main surface of the support plate;
   A pair of drive capacitor electrodes provided to be opposed to each other on the movable beam and the support plate along the main axis direction of the movable beam, and a dielectric film laminated on at least one of the drive capacitor electrodes. A drive capacity unit that deforms the movable beam based on a drive capacity generated between the pair of drive capacity electrodes;
   A pair of RF capacitive electrodes provided to be opposed to each other on the movable beam and the support plate along the main axis direction of the movable beam, and a dielectric film laminated on at least one of the RF capacitive electrodes. An RF capacitor unit for propagating an RF signal through an RF capacitor generated between the pair of RF capacitor electrodes;
   A stopper that protrudes into the gap space between the drive capacitor electrode and the dielectric film in the drive capacitor, and is provided along the principal axis direction of the movable beam;
   An equipotential electrode portion provided at a position facing the stopper portion along the principal axis direction of the movable beam and connected to the same potential as the drive capacitor electrode facing the gap space;
   A variable capacity device.
2. The variable capacitance device according to claim 1, wherein the stopper portion is provided only at a position where the drive capacitance electrode and the equipotential electrode portion face each other.
3. The variable capacitance device according to claim 1 or 2, wherein a thickness of the dielectric film in the RF capacitor section is equal to a sum of a thickness of the dielectric film in the drive capacitor section and a thickness of the stopper section.
4. The variable capacitance device according to claim 1 or 2, wherein a thickness of the dielectric film in the RF capacitor section is equal to a thickness of the dielectric film in the drive capacitor section.
5. 3. The variable capacitance device according to claim 1, wherein a thickness of the dielectric film in the RF capacitor unit is equal to a thickness of the dielectric film in the drive capacitor unit, and a stopper unit is provided in the RF capacitor unit.
6. 5. The variable capacitance device according to claim 1, wherein the stopper portion is a protruding portion obtained by partially thickening the dielectric film.
7. 5. The variable capacitance device according to claim 1, wherein the stopper portion is a portion where the dielectric film is laminated on the equipotential electrode portion and protrudes.
8. 5. The variable capacitance device according to claim 1, wherein the stopper portion is a protruding portion of the same potential electrode portion thicker than the dielectric film from the dielectric film.
9. 5. The variable capacitance device according to claim 1, wherein the stopper portion is an electrode laminated on the dielectric film laminated on the equipotential electrode portion.

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