JPWO2014080444A1 - Electrostatic actuators and variable capacitance devices - Google Patents

Abstract

Provided is an electrostatic actuator or the like capable of reliably swinging a swinging beam swinging in a direction in which the other part approaches the substrate with a simple configuration in a direction in which the other part approaches the substrate. On the silicon substrate 2 side, a swinging beam part 22 supported by a support part 21 on the silicon substrate 2 so as to be swingable in a seesaw shape and swinging by electrostatic force, and an outer portion 22a of the swinging beam part 22 with respect to the support part 21 And an electrostatic force is generated between the outer portion 22a and the end portion on the opposite side to the support portion 21 side, and the end portion on the support portion 21 side is connected to the end portion of the outer portion 22a. And a movable beam 25 fixed to the silicon substrate 2.

Description

  The present invention relates to an electrostatic actuator having an oscillating beam that oscillates by an electrostatic force, and a variable capacitance device including the same.

  2. Description of the Related Art Conventionally, there is known an electrostatic actuator that changes a capacitance by driving a variable capacitance electrode including a signal line and an electrode facing the signal line above the signal line. This electrostatic actuator includes a movable upper electrode connected to a variable capacitance electrode through an insulating layer, and a fixed lower electrode facing the upper electrode. The end of the upper electrode opposite to the variable capacitance side is connected to the anchor by a spring structure (see Patent Document 1). In addition, as an electrostatic actuator in a MEMS (Micro Electro Mechanical Systems) switch, there is an electrostatic actuator that includes an inner working member that swings like a seesaw on a substrate, and an outer working member that has a switch contact function swings like a seesaw. It has been. In this MEMS switch, the first and second pressure rods provided at both ends of the inner working member are used to press both ends of the outer working member from above so that the outer working member is rocked by the inner working member. It is designed to swing in conjunction with the movement (see Patent Document 2).

JP 2008-278634 A JP 2006-173132 A

  By the way, at the time of hot switching in which a variable capacitor is switched with an RF (Radio Frequency) voltage applied to a variable capacitor (variable capacitor), a signal line (fixed capacitor electrode) and an electrode (movable capacitor electrode) are caused by the RF voltage. ), An electrostatic force is generated between the upper electrode and the lower electrode of the electrostatic actuator (sticking). On the other hand, it is conceivable to provide the inner working member (swinging beam) that swings like a seesaw as an electrostatic actuator that drives a variable capacitance electrode. In this case, in the state where the variable capacity side portion (the other portion) of the inner working member is in contact with the lower electrode, the portion (one portion) opposite to the variable capacity side of the inner working member and the lower electrode (fixed drive electrode) By applying a voltage difference between them, the electrostatic force generated between them can be made to act as a force that separates the other part of the inner working member from the lower electrode. However, in the state where the other part of the inner working member is in contact with the lower electrode, the distance between the one part of the inner working member and the lower electrode is greatly separated, so that there is a gap between the one part of the inner working member and the lower electrode. Even if the same voltage difference is given, the electrostatic force becomes small, so it is necessary to give a larger voltage difference between them or to increase the opposing area between them.

  The present invention is provided with an electrostatic actuator capable of reliably swinging a swinging beam swinging in a direction in which the other part approaches the substrate, in a direction in which the other part approaches the substrate, with a simple configuration. An object is to provide a variable capacitance device.

  The electrostatic actuator of the present invention is supported by a support portion on a substrate so as to be able to swing in a seesaw shape, and is opposed to a swing beam swinging by electrostatic force and one portion of the swing beam with respect to the support portion on the substrate side. In addition, an electrostatic force is generated between one part and the end opposite to the support part side is connected to the end part of one part, and the end part on the support part side is fixed to the substrate. And a movable beam.

  According to this configuration, since the movable beam connected to the one end portion of the swing beam on the substrate side and connected to the end portion of the one portion is swung in the direction in which the other portion of the swing beam approaches the substrate. Even in this state, since the distance between the one part of the oscillating beam and the movable beam does not increase, a strong electrostatic force can be generated between the one part of the oscillating beam and the movable beam. In addition, since the end of the movable beam on the support portion side is fixed to the substrate, the electrostatic force generated between one part of the swinging beam and the movable beam is in a direction in which the first part approaches the substrate. The swing beam acts to swing. Therefore, a simple configuration (low drive voltage) can be achieved without applying a large potential difference between one part of the oscillating beam and the movable beam and without increasing the opposing area between the one part of the oscillating beam and the movable beam. With the small chip area), the swinging beam swinging in the direction in which the other part approaches the substrate can be reliably swung in the direction in which one part approaches the substrate.

  In this case, it is preferable to further include a fixed drive electrode provided on the substrate so as to face the movable beam and generating an electrostatic force between the movable beam and the movable beam.

  According to this configuration, even when the other portion of the swing beam with respect to the support portion swings in the direction approaching the substrate, the movable beam and the fixed drive electrode are compared with the distance between the one portion of the swing beam and the fixed drive electrode. Therefore, a strong electrostatic force can be generated between the movable beam and the fixed drive electrode. The electrostatic force generated between the movable beam and the fixed drive electrode also acts so that the oscillating beam oscillates in a direction in which one portion approaches the substrate. Therefore, the swinging beam that swings in the direction in which the other part approaches the substrate can be more efficiently swung in the direction in which the one part approaches the substrate.

  In this case, when the swinging beam swings in a direction in which one part is away from the substrate, the movable beam is deformed with elasticity, and the restoring force of the deformation causes the swinging beam to swing in a direction in which one part approaches the substrate. It is preferable to act so as to move.

  According to this configuration, not only the electrostatic force generated between one part of the oscillating beam and the movable beam, but also the one part can be oscillated in the direction approaching the substrate not only by the restoring force of the deformation of the movable beam. it can. Therefore, the force for swinging the swing beam in the direction in which one portion approaches the substrate can be further increased.

  In this case, it is preferable that the oscillating beam and the movable beam are each made of a conductor.

  In this case, at least one of the oscillating beam and the movable beam includes an insulator portion that is a main body, and a conductor layer formed on at least one of the substrate-side surface and the substrate-side surface of the insulator portion. It is preferable to have.

  Another electrostatic actuator of the present invention is supported by a support portion on a substrate so as to be swingable in a seesaw shape. The swing beam swings by electrostatic force, and one portion of the swing beam with respect to the support portion is provided on the substrate side. The end opposite to the support side is connected to the end of one part, and the end on the support side is opposed to the movable beam fixed to the substrate and the movable beam. And a fixed drive electrode that is provided on the substrate and generates an electrostatic force between the movable beam and the movable beam.

  According to this configuration, by providing the movable beam opposed to the substrate side in one part of the oscillating beam, even when the other part of the oscillating beam is oscillated in the direction approaching the substrate, Since the distance between the movable beam and the fixed drive electrode does not increase compared to the distance between the portion and the fixed drive electrode, a strong electrostatic force can be generated between the movable beam and the fixed drive electrode. In addition, since the end of the movable beam is connected to the end of one part, the electrostatic force generated between the movable beam and the fixed drive electrode causes the swinging beam to swing in the direction in which one part approaches the substrate. Act to move. Therefore, without applying a large potential difference between one part of the oscillating beam and the movable beam, and without increasing the facing area between the one part of the oscillating beam and the movable beam, the other part The rocking beam swung in the direction approaching the substrate can be reliably swung in the direction in which one portion approaches the substrate.

  Another electrostatic actuator of the present invention is supported by a support portion on a substrate so as to be able to swing in a seesaw shape, and swings by an electrostatic force, one portion of the swing beam with respect to the support portion, and the substrate. And a movable part having a plurality of movable beams connected in a folded structure to each other, the movable beam side movable beam provided on the most movable beam side among the plurality of movable beams The end on the opposite side to the support side is connected to the end of one part, and the substrate side movable beam provided on the most substrate side among the plurality of movable beams is on the side opposite to the folded portion side. The end portion is fixed to the substrate and is between at least one of a plurality of movable beams facing each other and between the movable beam side movable beam and one portion facing the movable beam side movable beam. It is characterized by generating electrostatic force.

  According to this configuration, by providing a plurality of movable beams between the one part of the oscillating beam and the substrate, even when the other part of the oscillating beam with respect to the support unit oscillates in a direction approaching the substrate, Compared to the distance between one part of the oscillating beam and the fixed drive electrode, the distance between the one part of the oscillating beam and the movable beam side movable beam and the distance between the movable beams do not increase. A strong electrostatic force can be generated between one of the portions and the movable beam. In addition, since the end of the substrate side movable beam is fixed to the substrate, an electrostatic force generated between one part of the oscillating beam and the movable beam side movable beam or between the movable beams is generated. Due to the electrostatic force, one portion can be swung in a direction approaching the substrate. Therefore, with a simple configuration, the swinging beam that swings in the direction in which the other part approaches the substrate can be reliably swung in the direction in which one part approaches the substrate.

  Another electrostatic actuator of the present invention is supported by a support portion on a substrate so as to be able to swing in a seesaw shape, and swings by an electrostatic force, one portion of the swing beam with respect to the support portion, and the substrate. And a movable part having a plurality of movable beams connected in a folded structure and a substrate-side movable beam provided on the most substrate side among the plurality of movable beams. A fixed drive electrode that generates an electrostatic force between the movable beam and the substrate side movable beam, and the movable beam side movable beam provided on the most movable beam side among the plurality of movable beams is the support portion side. The opposite end is connected to the end of one portion, and the substrate-side movable beam has an end opposite to the folded-back portion fixed to the substrate.

  According to this configuration, since the plurality of movable beams are provided between the one part of the oscillating beam and the substrate, the oscillating beam can be used even when the other part of the oscillating beam is oscillated in the direction approaching the substrate. Compared with the distance between one part of the substrate and the fixed drive electrode, the distance between the substrate-side movable beam and the fixed drive electrode does not increase, so a strong electrostatic force is generated between the substrate-side movable beam and the fixed drive electrode. be able to. In addition, since the end of the movable beam-side movable beam is connected to the end of one portion, the electrostatic force generated between the substrate-side movable beam and the fixed drive electrode is in a direction in which the first portion approaches the substrate. The swing beam acts to swing. Therefore, without applying a large potential difference between one part of the oscillating beam and the movable beam, and without increasing the facing area between the one part of the oscillating beam and the movable beam, the other part The rocking beam swung in the direction approaching the substrate can be reliably swung in the direction in which one portion approaches the substrate.

  A variable capacitance device according to the present invention includes the electrostatic actuator, a fixed capacitance electrode, and a movable capacitance electrode facing the fixed capacitance electrode and provided at the end of the other portion of the swing beam with respect to the support portion. And a variable capacitance element that varies the capacitance.

When an electrostatic force is generated between the fixed capacitance electrode and the movable capacitance electrode of the variable capacitance element, the electrostatic force is in the direction in which the other part of the oscillating beam provided with the movable capacitance electrode at the end approaches the substrate. Therefore, there is a possibility that the other part of the rocking beam may stick to an electrode or the like on the substrate facing the rocking beam.
On the other hand, according to the present configuration, an electrostatic beam capable of reliably swinging the swinging beam swinging in the direction in which the other part approaches the substrate with a simple structure in the direction in which one part approaches the substrate. By providing an actuator, even when an electrostatic force is generated between the fixed capacitor electrode and the movable capacitor electrode of the variable capacitor, it is possible to reliably swing the swing beam so that one part approaches the substrate. Can do. Therefore, it is possible to effectively prevent the other part of the oscillating beam from adhering to the electrode on the substrate opposed to the other part.
The movable capacitive electrode provided at the end of the other part of the oscillating beam means that the end of the other part of the oscillating beam is a movable capacitive electrode and the other part of the oscillating beam. It is a concept that includes both movable capacitive electrodes formed separately and connected to the end of the other portion.

  In this case, the electrostatic actuator preferably performs the swinging motion of the swinging beam in a state where a voltage is applied to the variable capacitance element.

  According to this configuration, when the variable capacitive element is switched (hot switching) by performing the swinging motion of the swing beam while a voltage is applied to the variable capacitive element, the variable capacitive element is movable with the fixed capacitive electrode. Although an electrostatic force is generated between the capacitor electrode and the capacitor electrode, in this case as well, it is possible to effectively prevent the other part of the oscillating beam from adhering to the electrode or the like facing the other part. Therefore, hot switching can be performed satisfactorily without the oscillating beam sticking.

It is sectional drawing of the variable capacitor provided with the electrostatic actuator which concerns on 1st Embodiment. It is a figure which shows rocking | fluctuation operation | movement of the electrostatic actuator in a variable capacitor. It is a figure which shows the electric potential supply pattern with respect to an electrostatic actuator. It is a figure which shows another example of the electric potential supply pattern with respect to an electrostatic actuator. It is a figure which shows the modification of an electrostatic actuator. It is a figure which shows the modification of the movable beam in an electrostatic actuator. It is sectional drawing of the electrostatic actuator which concerns on 2nd Embodiment.

  Hereinafter, an electrostatic actuator and a variable capacitance device including the same according to an embodiment of the present invention will be described with reference to the accompanying drawings. In the present embodiment, a variable capacitor is exemplified as the variable capacitance device. This variable capacitor is a MEMS device, and is configured by forming an electronic circuit and a mechanical structure on a semiconductor substrate such as a silicon substrate using a semiconductor integrated circuit manufacturing technique.

  As shown in FIGS. 1 and 2, the variable capacitor 1 includes a silicon substrate 2, a variable capacitor 3 provided on the silicon substrate 2, and both left and right sides of the variable capacitor 3 provided on the silicon substrate 2. And a pair of electrostatic actuators 4. In this variable capacitor 1, so-called hot switching is performed in which the variable capacitor 3 is driven by using the electrostatic actuator 4 as a drive source in a state where an RF voltage is applied to the variable capacitor 3, thereby changing the capacitance. Is called.

An insulating layer 5 made of, for example, SiO ₂ (silicon oxide film) is formed on the surface of the silicon substrate 2, and the variable capacitance element 3 and a pair of electrostatic actuators 4 are provided on the insulating layer 5. .

  The variable capacitance element 3 includes a fixed capacitance electrode 10 provided on the silicon substrate 2 and a movable capacitance electrode portion 13 facing the fixed capacitance electrode 10. The movable capacitive electrode portion 13 is constituted by an intermediate portion of a doubly supported beam 20 shared by a pair of electrostatic actuators 4. That is, the doubly-supported beam 20 includes an intermediate movable capacitive electrode portion 13 and oscillating beam portions 22 provided on both outer sides of the movable capacitive electrode portion 13 via the insulator 6. Then, along with the deformation of the doubly-supported beam 20 described later (the swinging motion of the swinging beam portion 22), the movable capacitive electrode portion 13 is brought into and out of contact with the fixed capacitive electrode 10 so that the electrostatic capacitance in the variable capacitive element 3 is The capacity is changed.

  The fixed capacitance electrode 10 includes a first fixed capacitance electrode 11 and a second fixed capacitance electrode 12 made of a conductor such as polysilicon. Here, the first fixed capacitance electrode 11 is an electrode through which an RF signal flows, and the second fixed capacitance electrode 12 is an electrode connected to ground, for example. The variable capacitance element 3 has a capacitance C <b> 1 between the first fixed capacitance electrode 11 and the movable capacitance electrode portion 13, and between the second fixed capacitance electrode 12 and the movable capacitance electrode portion 13. It has a capacity C2. The electrostatic capacitance C1 and the electrostatic capacitance C2 change with the change in the distance between the movable capacitance electrode portion 13 and the first fixed capacitance electrode 11 and the second fixed capacitance electrode 12. The electrostatic capacitance in the variable capacitance element 3 includes an electrostatic capacitance C1 and an electrostatic capacitance C2 connected in series between the first fixed capacitance electrode 11 and the second fixed capacitance electrode 12.

When the distance between the movable capacitive electrode section 13 and the first fixed capacitive electrode 11 or the second fixed capacitive electrode 12 varies and the capacitance of the variable capacitive element 3 varies, the first fixed capacitive electrode 11 through which the RF signal flows is changed. The potential changes, and an RF voltage corresponding to the potential is output from the first fixed capacitor electrode 11 and the second fixed capacitor electrode 12.
In the present embodiment, the fixed capacitance electrode 10 is constituted by the first fixed capacitance electrode 11 and the second fixed capacitance electrode 12, but it may be constituted by a single electrode. In this field, for example, the fixed capacitance electrode 10 is used as an electrode connected to the ground, and the movable capacitance electrode portion 13 is used as an electrode through which an RF signal flows.

Each surface of the first fixed capacitance electrode 11 and the second fixed capacitance electrode 12 is covered with an insulating film 14 made of, for example, SiO ₂ . The insulating film 14 determines the maximum capacitance value when the movable capacitance electrode portion 13 approaches the first fixed capacitance electrode 11 and the second fixed capacitance electrode 12. That is, the movable capacitance electrode portion 13 is displaced downward until it comes into contact with the insulating film 14.

  The electrostatic actuator 4 includes a support portion 21 projecting on the silicon substrate 2, a swinging beam portion 22 whose left and right substantially intermediate portions are supported by the support portion 21, and left and right outer sides of the swinging beam portion 22 with respect to the support portion 21. The outer fixed drive electrode 23 provided on the silicon substrate 2 so as to face the outer portion 22a (one portion) which is the opposite side of the variable capacitance element 3 side, and the swing beam portion 22 with respect to the support portion 21 An inner fixed drive electrode 24 provided on the silicon substrate 2 so as to face the inner portion 22b (the other portion) which is the left and right inner side (the variable capacitance element 3 side), and the outer portion 22a and the outer fixed portion of the oscillating beam portion 22. A movable beam 25 provided with a gap between each electrode and the drive electrode 23 is provided.

  The swing beam portion 22 of one electrostatic actuator 4 is integrally formed with a conductor such as polysilicon together with the swing beam portion 22 of the other electrostatic actuator 4 and constitutes a doubly supported beam 20. Yes. That is, the tips of the inner portions 22b of the oscillating beam 22 in each electrostatic actuator 4 are continuous with each other. In addition, the doubly supported beam 20 is supported by the support portions 21 of the left and right electrostatic actuators 4 at positions that are approximately ¼ length inside from the left and right ends, respectively. As described above, the intermediate portion of the both-end supported beam 20, that is, the end portion on the support portion 21 side in the inner portion 22 b of each oscillating beam portion 22 functions as the movable capacitive electrode portion 13 in the variable capacitance element 3. .

  Further, each oscillating beam portion 22 constituting the both-end supported beam 20 is supported by the support portion 21 so as to be able to oscillate in a seesaw shape. As described above, in the oscillating beam portion 22, the portion on the side opposite to the variable capacitance element 3 side from the support portion 21 is called an outer portion 22 a, and the portion on the variable capacitance element 3 side from the support portion 21 is Called the inner portion 22b.

  The inner fixed drive electrode 24 is made of a conductor such as polysilicon, and generates an electrostatic force between the inner fixed drive electrode 24 and the inner portion 22 b of the swing beam portion 22. An inner insulating film 26 is formed on the surface of the inner fixed drive electrode 24. When a voltage is applied between the inner fixed drive electrode 24 and the inner portion 22b of the swinging beam portion 22, an electrostatic force is generated therebetween. As a result, the swinging beam portion 22 swings in the direction in which the inner portion 22 b approaches the silicon substrate 2 (pull-in direction), and the inner portion 22 b comes into contact with the inner insulating film 26. Along with this, the movable capacitance electrode portion 13 which is the end portion of the inner portion 22b approaches the first fixed capacitance electrode 11 or the second fixed capacitance electrode 12 and comes into contact with the insulating film 14 (pull-in).

  On the other hand, the outer fixed drive electrode 23 is made of a conductor such as polysilicon and generates an electrostatic force between the outer fixed drive electrode 23 and the movable beam 25. An outer insulating film 27 is formed on the outer end surface of the outer fixed driving electrode 23. When a voltage is applied between the outer fixed drive electrode 23 and the movable beam 25, an electrostatic force is generated therebetween. As a result, the swinging beam portion 22 swings in the direction in which the outer portion 22 a approaches the silicon substrate 2 (pull-out direction), and the outer end portion of the movable beam 25 contacts the outer insulating film 27. Along with this, the movable capacitance electrode portion 13 moves away from the first fixed capacitance electrode 11 or the second fixed capacitance electrode 12 (pull out). As will be described later, when the movable capacitive electrode portion 13 is pulled out, the oscillating beam portion 22 swings in the pull-out direction due to electrostatic force generated between the outer portion 22a of the oscillating beam portion 22 and the movable beam 25. To do.

  Each swinging beam portion 22 is slightly elastically deformed into an arc shape protruding upward (on the opposite side to the silicon substrate 2 side) when swinging in the pull-in direction or swinging in the pull-out direction. (See FIGS. 2B and 2C).

  The support portion 21 is elastically deformed so as to bend as the swing beam portion 22 swings. That is, when the oscillating beam portion 22 oscillates in the pull-in direction, the upper end portion slightly curves inward (on the variable capacitance element 3 side). The portion is slightly curved outward (on the opposite side to the variable capacitance element 3 side).

Further, as described above, the left and right widths D of the support portion 21 are set so that the swing beam portion 22 can be deformed when the swing beam portion 22 swings. The thickness is preferably less than 1.5 times the thickness T (D <1.5 × T).
In the present embodiment, the support portion 21 is made of a material (insulator) different from the swing beam portion 22 (both supported beams 20), but is not limited thereto, and the swing beam portion is not limited thereto. The same material as 22 may be used.

  The movable beam 25 is made of a conductor such as polysilicon, and faces the outer portion 22a of the oscillating beam portion 22 on the silicon substrate 2 side, and generates an electrostatic force between the outer portion 22a. Further, the outer end of the movable beam 25 (the end opposite to the support portion 21) is connected to the end of the outer portion 22a of the swinging beam portion 22 by a connecting portion 28 made of an insulator. ing. On the other hand, the inner end portion (the end portion on the support portion 21 side) of the movable beam 25 is connected to an anchor 29 provided on the silicon substrate 2 in proximity to the outside of the support portion 21. That is, the end of the movable beam 25 on the support portion 21 side is fixed to the silicon substrate 2 via the anchor 29.

  When the swinging beam portion 22 swings in the pull-in direction, the movable beam 25 swings upward about the inner end connected to the anchor 29. In addition, the movable beam 25 is slightly elastically deformed into an arc shape that protrudes downward. At this time, the outer portion 22a of the oscillating beam portion 22 and the movable beam 25 are in a state where the left and right substantially intermediate portions are most separated. In addition, the movable beam 25 and the outer fixed drive electrode 23 are gradually spread from the inside toward the outside. In this state, when an electrostatic force is generated between the outer portion 22a of the oscillating beam portion 22 and the movable beam 25 and between the movable beam 25 and the outer fixed drive electrode 23, the movable beam 25 is moved to the oscillating beam portion. The outer fixed drive electrode 23 is attracted to the outer fixed drive electrode 23 so as to be closed like a fastener from the inner side while pulling the outer portion 22 a of the outer cover 22. Thereby, the swinging beam portion 22 swings in the pull-out direction.

  When the oscillating beam portion 22 oscillates in the pull-out direction, the movable beam 25 oscillates downward about the inner end connected to the anchor 29, and the outer end contacts the outer insulating film 27. . At this time, the movable beam 25 is slightly elastically deformed into an arc shape protruding upward.

As shown in FIG. 3A (a), the oscillating beam portion 22 and the outer fixed drive electrode 23 are each connected to a ground terminal and supplied with a ground potential (V _gnd ). On the other hand, the inner fixed drive electrode 24 is connected to the power supply circuit 31 and is selectively supplied with a pull-in potential (V _in ) and a ground potential. The movable beam 25 is connected to a power supply circuit 32, and is selectively supplied with a pull-out potential (V _out ) and a ground potential. Note that the pull-in potential and the pull-out potential may be the same or different.

  As shown in FIG. 3A (b), the electrostatic actuator 4 configured in this manner is supplied with a ground potential to the inner fixed drive electrode 24 and the movable beam 25 in a steady state. At this time, between the inner portion 22b of the swing beam portion 22 and the inner fixed drive electrode 24, between the outer portion 22a of the swing beam portion 22 and the movable beam 25, and between the movable beam 25 and the outer fixed drive electrode 23, Since no electrostatic force is generated in between, the oscillating beam portion 22 and the movable beam 25 are parallel to the surface of the silicon substrate 2 (see FIG. 2A). Needless to say, in a steady state, the swing beam portion 22, the outer fixed drive electrode 23, the inner fixed drive electrode 24, and the movable beam 25 may be at the same potential, and a potential other than the ground potential is supplied to them. May be.

  When a pull-in potential is supplied to the inner fixed drive electrode 24 in the steady state, the pull-in state is established. That is, an electrostatic force is generated between the inner portion 22b of the swing beam portion 22 and the inner fixed drive electrode 24, and the swing beam portion 22 swings in the pull-in direction (see FIG. 2B).

  In the pull-in state, when the ground potential is supplied to the inner fixed drive electrode 24 and the pull-out potential is supplied to the movable beam 25, the pull-out state is established. That is, the electrostatic force generated between the inner portion 22b of the oscillating beam portion 22 and the inner fixed drive electrode 24 is released, and the outer portion 22a of the oscillating beam portion 22 and the movable beam 25 are movable and movable. An electrostatic force is generated between the beam 25 and the outer fixed drive electrode 23, and the swing beam portion 22 swings in the pull-out direction (see FIG. 2C).

  When the ground potential is supplied to the inner fixed drive electrode 24 and the movable beam 25 in the pull-out state, the movable beam 25 and the outer fixed drive electrode are interposed between the outer portion 22a of the swing beam portion 22 and the movable beam 25. The electrostatic force between the two is released. Then, due to the restoring force (spring force) of the oscillating beam 22 and the movable beam 25, the oscillating beam 22 and the movable beam 25 become parallel to the surface of the silicon substrate 2 and return to a steady state (see FIG. 2C). .

  Thus, it is preferable that the same potential is always supplied to the outer fixed drive electrode 23 and the movable beam 25. Note that the potential supply pattern is not limited to this, and for example, as shown in FIG. 3A (c), a reverse pattern may be used.

  In the pull-in state described above, the outer portion 22a of the oscillating beam portion 22 and the outer fixed drive electrode 23 are separated from each other as compared with the steady state. Therefore, when the movable beam 25 is not provided, the outer fixed drive electrode 23 is provided. Even if the same pull-out potential is supplied, only a weak electrostatic force can be obtained. On the other hand, according to the electrostatic actuator 4 of the present embodiment, the movable beam 25 connected to the end portion of the outer portion 22a of the swing beam portion 22 is provided at the outer end portion. Since the distance between the outer portion 22a of the oscillating beam portion 22 and the movable beam 25 does not increase, a strong electrostatic force can be generated between the outer portion 22a of the oscillating beam portion 22 and the movable beam 25. it can. In particular, in the vicinity of the connection portion 28, a strong electrostatic force can be generated because the distance between the outer portion 22a of the swinging beam portion 22 and the movable beam 25 is short. Similarly, since the distance between the movable beam 25 and the outer fixed drive electrode 23 does not become larger than the distance between the outer portion 22a of the oscillating beam portion 22 and the outer fixed drive electrode 23, the movable beam 25 and the outer fixed drive electrode 23 are fixed. A strong electrostatic force can be generated between the drive electrodes 23. That is, the force (pull-out force) by which the oscillating beam portion 22 swings in the pull-out direction can be increased. Therefore, the swinging beam portion 22 in the pull-in state can be formed with a simple configuration without increasing the pull-out potential and without increasing the facing area between the outer portion 22a of the swinging beam portion 22 and the movable beam 25. It can be reliably swung in the pull-out direction.

  When the variable capacitance element 3 is hot-switched, a force for swinging the oscillating beam portion 22 in the pull-out direction so as to overcome the electrostatic force between the fixed capacitance electrode 10 and the movable capacitance electrode portion 13 of the variable capacitance element 3 is used. Although it is necessary to increase the strength, in the electrostatic actuator 4 of the present embodiment, as described above, the force by which the swing beam portion 22 swings in the pull-out direction can be increased, so that the swing beam portion 22 is pulled out. It can be reliably swung in the direction. Therefore, hot switching can be performed satisfactorily without the inner portion 22 b of the swing beam portion 22 sticking to the inner fixed drive electrode 24.

  Further, not only the electrostatic force generated between the outer portion 22 a of the swinging beam portion 22 and the movable beam 25 and the electrostatic force generated between the movable beam 25 and the outer fixed drive electrode 23, but also the movable beam 25. The deformation restoring force (spring force) also acts in the direction in which the oscillating beam portion 22 oscillates in the pull-out direction. Therefore, the force with which the oscillating beam 22 oscillates in the pull-out direction can be further increased.

  In the present embodiment, in order to oscillate the oscillating beam portion 22 in the pull-out direction, between the outer portion 22a of the oscillating beam portion 22 and the movable beam 25 and between the movable beam 25 and the outer fixed drive electrode 23. However, the electrostatic force is not generated between the outer portion 22 a of the oscillating beam portion 22 and the movable beam 25, and only between the movable beam 25 and the outer fixed drive electrode 23. It may be configured to generate an electrostatic force.

  FIG. 3B shows an example of the potential supply pattern. As a difference from the potential supply pattern shown in FIG. 3A, the connection between the outer fixed drive electrode 23 and the movable beam 25 is reversed. That is, the outer fixed drive electrode 23 is connected to the power supply circuit 32, and the movable beam 25 is connected to the ground terminal (see FIG. 3B (a)). In the pull-in state, when the ground potential is supplied to the inner fixed drive electrode 24 and the pull-out potential is supplied to the outer fixed drive electrode 23, the pull-out state is entered (see FIG. 3B (b)). The electrostatic force generated between the inner portion 22b of the oscillating beam portion 22 and the inner fixed drive electrode 24 is released, and the electrostatic force is generated between the movable beam 25 and the outer fixed drive electrode 23. The portion 22 swings in the pull-out direction In this configuration as well, the potential supply pattern is not limited to this, and for example, as shown in FIG. There may be.

  Further, in the present embodiment, the electrostatic actuator 4 is configured to include the outer fixed drive electrode 23, but may be configured to not include the outer fixed drive electrode 23 as illustrated in FIG. In this case, an inter-beam insulating film 33 is formed on the movable beam 25 on the oscillating beam portion 22 side. The inter-beam insulating film 33 may be formed on the movable beam 25 side of the outer portion 22 a of the oscillating beam portion 22. In the pull-in state of FIG. 4B, when an electrostatic force is generated between the outer portion 22a of the oscillating beam portion 22 and the movable beam 25, the outer portion 22a of the oscillating beam portion 22 is movable by the electrostatic force. The beam 25 comes into contact with the intermediate portion (see FIG. 4C). The outer portion 22a of the oscillating beam portion 22 and the movable beam 25 come into contact with each other and are integrated to be hard as a spring. That is, generally, in the case of a cantilever beam that receives a concentrated load at the free end, the spring constant is proportional to the cube of the thickness. As a result, a sufficient pull-out force is obtained, and the swing beam portion 22 swings in the pull-out direction (see FIG. 4D). Of course, even when the outer fixed drive electrode 23 is provided, the same effect can be obtained when no electrostatic force is generated between the outer fixed drive electrode 23 and the movable beam 25.

  In the present embodiment, the oscillating beam portion 22 and the movable beam 25 are all made of a conductor, but at least one of the oscillating beam portion 22 and the movable beam 25 is replaced with an insulator portion and a conductor. You may comprise with a layer. For example, as shown in FIG. 5, the movable beam 25 includes an insulator portion 25 a that forms the main body, a lower conductor layer 25 b that is formed on the lower side (silicon substrate 2 side) of the insulator portion 25 a, and an insulator. You may comprise by the upper side conductor layer 25c formed in the upper side (oscillating beam part 22 side) of the part 25a. Although not shown, the oscillating beam portion 22 can be configured in the same manner.

  Further, the lower conductor layer 25b and the upper conductor layer 25c may be connected to each other through vias. Further, only one of the lower conductor layer 25b and the upper conductor layer 25c may be provided for the insulator portion 25a. However, in order to prevent the warp of the movable beam 25 due to the internal stress of the conductor layer, it is preferable to provide both the lower conductor layer 25b and the upper conductor layer 25c. These modifications are similarly applied to the oscillating beam portion 22.

  Next, an electrostatic actuator according to a second embodiment of the present invention will be described. The electrostatic actuator of the second embodiment has substantially the same configuration as that of the first embodiment, but differs in that two movable beams are provided. Hereinafter, a description will be given focusing on differences from the first embodiment. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. Moreover, the modification applied about the component similar to 1st Embodiment is applicable similarly to this embodiment.

  As shown in FIG. 6, the electrostatic actuator 4 of the second embodiment is similar to the electrostatic actuator 4 of the first embodiment (see FIG. 1). A drive electrode 23 and an inner fixed drive electrode 24 are provided. Further, a movable portion 40 including a first movable beam 41 and a second movable beam 42 is provided between the outer portion 22 a of the oscillating beam portion 22 and the outer fixed drive electrode 23. The anchor 29 is provided on the silicon substrate 2 so as to be separated from the support portion 21 to the outside. The outer insulating film 27 is formed on the inner end surface of the outer fixed drive electrode 23.

  The first movable beam 41 provided on the side of the oscillating beam 22 is opposed to the outer portion 22a of the oscillating beam 22 and generates an electrostatic force with the outer portion 22a. Further, the outer end of the first movable beam 41 (the end opposite to the support portion 21 side) is connected to the end of the outer portion 22 a of the swinging beam portion 22 by the connection portion 28.

  On the other hand, the second movable beam 42 provided on the outer fixed drive electrode 23 side has the anchor 29 at the end (outer side) opposite to the folded portion (a connecting portion 53 described later) with the first movable beam 41. And fixed to the silicon substrate 2.

  The first movable beam 41 and the second movable beam 42 are connected in a folded structure. That is, the first movable beam 41 and the second movable beam 42 are opposed to each other, and the end portion on the inner side (the side opposite to the variable capacitance element 3 side) is connected via the connecting portion 53 made of an insulator. Are connected (connected) to each other.

  Similarly to the first embodiment, the both-end supported beam 20 (the swinging beam portion 22) is connected to the ground terminal, and the inner fixed drive electrode 24 is connected to the power supply circuit 31. On the other hand, unlike the first embodiment, the outer fixed drive electrode 23 is connected to the power supply circuit 32 and is selectively supplied with a pull-out potential and a ground potential. The first movable beam 41 is also connected to the power supply circuit 32 and selectively supplied with a pull-out potential and a ground potential. The second movable beam 42 is connected to a ground terminal and supplied with a ground potential.

  As in the first embodiment, when a pull-in potential is supplied to the inner fixed drive electrode 24 in a steady state, the swing beam portion 22 swings in the pull-in direction. In the pull-in state, when the ground potential is supplied to the inner fixed drive electrode 24 and the pull-out potential is supplied to the first movable beam 41 and the outer fixed drive electrode 23, the inner portion 22b of the swinging beam portion 22 and the inner fixed portion are fixed. The electrostatic force generated between the drive electrode 24 is released, and the outer portion 22a of the oscillating beam 22 and the first movable beam 41, and between the first movable beam 41 and the second movable beam 42. In addition, an electrostatic force is generated between the second movable beam 42 and the outer fixed drive electrode 23, and the swinging beam portion 22 swings in the pull-out direction. That is, these electrostatic forces act so that the oscillating beam portion 22 oscillates in the pull-out direction.

  Also in the electrostatic actuator 4 of the second embodiment configured as described above, the first movable member connected to the end portion of the outer portion 22a of the swinging beam portion 22 at the outer end portion as in the first embodiment. By providing the beam 41, the distance between the outer portion 22a of the oscillating beam portion 22 and the first movable beam 41 does not increase even in the pull-in state. A strong electrostatic force can be generated between the first movable beam 41 and the first movable beam 41. In addition, since the distance between the second movable beam 42 and the outer fixed drive electrode 23 does not increase, a strong electrostatic force can be generated between the second movable beam 42 and the outer fixed drive electrode 23. The electrostatic force generated between the outer portion 22a of the oscillating beam 22 and the first movable beam 41, the electrostatic force generated between the second movable beam 42 and the outer fixed drive electrode 23, The electrostatic force generated between the first movable beam 41 and the second movable beam 42 acts so that the oscillating beam portion 22 oscillates in the pull-out direction. Therefore, the swinging beam portion 22 in the pull-in state can be reliably swung in the pull-out direction with a simple configuration.

  In the second embodiment, the movable portion 40 is configured by two movable beams. However, three or more movable beams may be configured so as to form a folded structure. In the first and second embodiments described above, the variable capacitor 1 is exemplified as the variable capacitor. However, the present invention may be applied to a variable capacitor switch using the variable capacitor 3 or the like. .

  1: variable capacitor, 2: silicon substrate, 4, electrostatic actuator, 21: support portion, 22: swinging beam portion, 22a: outer portion, 25: movable beam

Claims (10)

A swing beam supported by a support portion on the substrate so as to be swingable in a seesaw shape and swinging by electrostatic force;
An electrostatic force is generated between the one portion of the swinging beam with respect to the support portion and the one portion facing the substrate portion, and an end portion on the opposite side to the support portion side is formed on the one portion. A movable beam connected to an end portion, and an end portion on the support portion side fixed to the substrate;
An electrostatic actuator comprising:   The electrostatic actuator according to claim 1, further comprising a fixed drive electrode provided on the substrate so as to face the movable beam and generating an electrostatic force between the movable beam and the movable beam.   When the swinging beam swings in a direction in which the one part moves away from the substrate, the movable beam deforms with elasticity, and the restoring force of the deformation causes the swinging beam in the direction in which the one part approaches the substrate. The electrostatic actuator according to claim 1, wherein the moving beam acts to swing.   4. The electrostatic actuator according to claim 1, wherein the swing beam and the movable beam are each made of a conductor. At least one of the rocking beam and the movable beam is
An insulator part for the main body;
A conductor layer formed on at least one of the substrate-side surface and the substrate-side surface of the insulator portion;
The electrostatic actuator according to claim 1, wherein the electrostatic actuator is provided. A swing beam supported by a support portion on the substrate so as to be swingable in a seesaw shape and swinging by electrostatic force;
The one end portion of the swing beam with respect to the support portion is opposed to the substrate side, and the end portion on the opposite side to the support portion side is connected to the end portion of the one portion, and the end portion on the support portion side Is a movable beam fixed to the substrate;
A fixed drive electrode provided on the substrate so as to face the movable beam and generating an electrostatic force between the movable beam;
An electrostatic actuator comprising: A swing beam supported by a support portion on the substrate so as to be swingable in a seesaw shape and swinging by electrostatic force;
A movable portion that is provided between one portion of the oscillating beam with respect to the support portion and the substrate, and has a plurality of movable beams connected to each other in a folded structure;
Of the plurality of movable beams, the oscillating beam side movable beam provided on the most oscillating beam side is connected to the end of the one portion at the end opposite to the support portion side,
Of the plurality of movable beams, the substrate-side movable beam provided on the most substrate side has an end opposite to the folded portion side fixed to the substrate,
An electrostatic force is generated between the plurality of movable beams facing each other and between at least one of the movable beam side movable beam and the one portion facing the movable beam side movable beam. An electrostatic actuator. A swing beam supported by a support portion on the substrate so as to be swingable in a seesaw shape and swinging by electrostatic force;
A movable part provided between one part of the swing beam with respect to the support part and the substrate, and having a plurality of movable beams connected in a folded structure to each other;
A fixed drive electrode that is provided so as to face the substrate-side movable beam provided on the most substrate side among the plurality of movable beams, and generates an electrostatic force between the substrate-side movable beam, and
Of the plurality of movable beams, the oscillating beam side movable beam provided on the most oscillating beam side is connected to the end of the one portion at the end opposite to the support portion side,
The electrostatic actuator according to claim 1, wherein the substrate-side movable beam has an end opposite to the folded portion side fixed to the substrate. An electrostatic actuator according to any one of claims 1 to 8,
A variable capacitance element having a fixed capacitance electrode and a movable capacitance electrode facing the fixed capacitance electrode and provided at an end portion of the other portion of the swing beam with respect to the support portion, wherein the capacitance is variable When,
A variable capacity device comprising:   The variable capacitance device according to claim 9, wherein the electrostatic actuator performs a swinging motion of the swinging beam in a state where a voltage is applied to the variable capacitive element.

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