JP4500201B2 - Micromachine switch - Google Patents

Description

  The present invention belongs to a technical field of a micromachine that realizes an extremely fine mechanical mechanism using a semiconductor microfabrication technology, and particularly relates to a micromachine switch that controls switching between conduction / non-conduction of a signal line extending on a substrate. is there.

  As shown in FIGS. 18 and 19, this type of micromachine switch is configured by bringing a working electrode (80) into contact with or separating from a signal line (20) formed on the surface of a glass substrate (10). In this case, the conduction / non-conduction of the signal line (20) is controlled (see Patent Document 1).

The micromachine switch includes a pair of left and right silicon support portions (50) and (50) provided on both sides of the signal line (20) on the substrate (10), and the support portions (50) and (50). A pair of left and right silicon arms (70) and (70) extending in a direction approaching each other, and a pair of left and right silicon upper electrodes (40) provided at the distal ends of the arms (70) and (70) ( 40) and an insulating member (60a) laid across the back surfaces of both upper electrodes (40) and (40), and a silicon reinforcing portion (30) at the center of the surface of the insulating member (60a). ) And the working electrode (80) is formed at the center of the back surface of the insulating member (60a) so as to face the disconnection portion of the signal line (20).
On the other hand, a pair of left and right lower electrodes (90) and (90) are formed on the surface of the substrate (10) at positions facing the pair of left and right upper electrodes (40) and (40).

  In the micromachine switch, by generating an electrostatic force between the upper electrodes (40) (40) and the lower electrodes (90) (90), as shown in FIG. 20, a pair of left and right arms (70) (70) ) Is elastically deformed, and the working electrode (80) comes into contact with the signal line (20). Further, by eliminating the electrostatic force, as shown in FIG. 19, the first arm portions (70) (70) are elastically restored and the working electrode (80) is separated from the signal line (20).

  FIG. 17A shows a configuration of a micromachine switch formed on one side of the signal line (20). In the micromachine switch, an arm part (70) protrudes from the support part (50), and an insulating member (60) is connected to the tip of the arm part (70), and the insulating member (60 ) Are formed with an upper electrode (40) and a working electrode (80).

In the micromachine switch, when the working electrode (80) contacts the signal line (20) by generating an electrostatic force between the upper electrode (40) and the lower electrode (90), the signal line (20) is in a conductive state. Thus, for example, a high-frequency signal up to several hundred GHz band flows through the signal line (20).
Here, since the contact resistance R exists between the working electrode (80) and the signal line (20), the switch-on state can be expressed by an equivalent circuit shown in FIG. At this time, the amount of attenuation of the signal by the resistor R is constant regardless of the frequency of the signal, as shown in FIG.

  Further, the micromachine switch shown in FIG. 8 increases the capacitance component between the signal line (20) and the working electrode (80) by bringing the working electrode (80) closer to the signal line (20). This is a so-called shunt switch that cuts off the signal flowing through the signal line (20), and a working electrode (80) is formed on the back surface of the conductive member (63) at a position facing the signal line (20). The working electrode (80) is covered with an insulating layer (61).

In the micromachine switch, by generating an electrostatic force between the upper electrode (40) and the lower electrode (90), the insulating layer (61) contacts the signal line (20), and the signal line (20) and the working electrode When (80) approaches each other, the capacitance component between the signal line (20) and the working electrode (80) increases, and this state is as shown in FIG. The capacitance component can be represented by an equivalent circuit connected thereto.
Therefore, the attenuation amount of the signal flowing through the signal line (20) increases as the signal frequency increases as shown in FIG. 8 (c), and a signal having a high frequency is accompanied by a large attenuation. Will be blocked.
Japanese Patent No. 3538109

However, in the micromachine switch shown in FIG. 8 (a), the signal attenuation gradually increases as the frequency increases as shown in FIG. 8 (c), so the frequency f of the signal flowing through the signal line (20) is If it is relatively low, there is a problem that a sufficiently large attenuation amount cannot be obtained when the switch is turned off and the signal cutoff characteristic (isolation characteristic) is deteriorated.
Further, in the micromachine switch shown in FIG. 17A, when the contact resistance R between the signal line (20) and the working electrode (80) is large, there is a problem that the high frequency signal passing characteristic is deteriorated. In particular, the contact resistance increased when the switch was used for a long time.

Accordingly, a first object of the present invention is to provide a micromachine switch having a good signal cutoff characteristic capable of obtaining a sufficiently large attenuation amount for a signal flowing through a signal line when the switch is turned off.
A second object of the present invention is to provide a micromachine switch having a good signal passing characteristic capable of sufficiently suppressing an attenuation amount of a signal flowing through a signal line when the switch is turned on.

In the first micromachine switch according to the present invention, the working electrode (8) is brought close to the signal line (2) extending on the substrate (1), so that the signal line (2) and the working electrode (8) are connected. By increasing the capacitance component, the signal flowing through the signal line (2) is blocked,
A support portion (5) disposed on the surface of the substrate (1), and an arm portion that protrudes from the support portion (5) and extends from the surface of the substrate (1) along the substrate (1) ( 7), an upper electrode (4) provided at the distal end portion of the arm portion (7), and a working electrode (provided near the upper electrode (4) at the distal end portion of the arm portion (7)). 8) and a lower electrode (9) disposed on the surface of the substrate (1) so as to face the upper electrode (4), and at least a part of the arm portion (7) is made of a conductive material. The shape of the arm portion (7) has a predetermined inductance component, and the resonance frequency determined by the inductance component and the capacitance component matches or approximates the frequency of the signal passing through the signal line (2). Is stipulated.

In the first micromachine switch, when the switch is off, an electrostatic force is generated between the upper electrode (4) and the lower electrode (9), so that the arm portion (7) is elastically deformed and the signal line (2) , The working electrode (8) approaches and the capacitance component between the signal line (2) and the working electrode (8) increases.
Then, an inductance component constituted by the arm portion (7) is connected in series to the capacitance component, and as a result, an LC circuit comprising the inductance component and the capacitance component with respect to the signal line (2). An electrical state in which the (trap circuit) is connected is realized.
Therefore, a large amount of attenuation can be obtained at the resonance frequency of the LC circuit, and the shape and dimensions of the arm portion (7) are defined so that the resonance frequency matches the frequency of the signal flowing through the signal line (2). In the configuration, the signal flowing through the signal line (2) is prevented from passing through the signal line (2) with great attenuation.

When the switch is turned on, by eliminating the electrostatic force, the arm (7) is elastically restored, the working electrode (8) is separated from the signal line (2), and the signal line (2) and the working electrode (8). The capacitance component between is reduced.
As a result, the electrical state in which the LC circuit is connected to the signal line (2) is canceled, and the signal flowing through the signal line (2) passes through the signal line (2) with almost no attenuation.

Further, the second micromachine switch according to the present invention is configured by bringing the working electrode (8) into contact with the opposite ends of the two signal lines (2a) and (2b) extending on the substrate (1). The two signal lines (2a) and (2b) are connected to each other,
A support portion (5) disposed on the surface of the substrate (1), and an arm portion that protrudes from the support portion (5) and extends from the surface of the substrate (1) along the substrate (1) ( 71), an upper electrode (41) provided at the tip of the arm part (71), and a working electrode provided in the vicinity of the upper electrode (41) at the tip of the arm part (71) ( 81) and a lower electrode (91) disposed on the surface of the substrate (1) so as to face the upper electrode (41), and at the ends of the two signal lines (2a) and (2b) Each of the electrode pieces (21a) and (21a) protrudes, and the arm portion (71) is provided with a counter electrode (82) opposite to both electrode pieces (21a) and (21b), thereby providing a working electrode (81). In addition, a capacitance component is formed in parallel with the resistance component R of the signal lines (2a) and (2b).

In the second micromachine switch, when the switch is turned on, an electrostatic force is generated between the upper electrode (41) and the lower electrode (9), whereby the arm portion (71) is elastically deformed and the signal line (2a) The working electrode (81) comes into contact with (2b), and a contact resistance is generated between the signal lines (2a) (2b) and the working electrode (81).
Further, with the elastic deformation of the arm portion (71), the counter electrode (82) approaches the electrode pieces (21a) (21b), and between the counter electrode (82) and the electrode pieces (21a) (21b). The capacitance component will increase.
As a result, an electrical state is realized in which the RC circuit formed by connecting the capacitance component in parallel to the resistor is connected to the signal lines (2a) and (2b).
Therefore, when the frequency of the signal flowing through the signal lines (2a) and (2b) is low, there is a large attenuation by the resistance, but when the signal frequency rises above a certain value, the signal lines (2a) and (2b) Since the flowing signal passes through the capacitance component, the amount of attenuation decreases and passes through the signal lines (2a) and (2b) with almost no attenuation.

  At the time of switch-off, by eliminating the electrostatic force, the arm part (71) is elastically restored, the working electrode (81) is separated from the signal line (2a) (2b), and the signal line (2a) (2b) Will be cut off and the signal will be blocked.

According to the first micromachine switch of the present invention, a sufficiently large attenuation can be obtained for the signal flowing through the signal line when the switch is turned off, and a good signal cutoff characteristic can be obtained.
Further, according to the second micromachine switch of the present invention, the attenuation amount of the signal flowing through the signal line can be sufficiently suppressed when the switch is turned on, and a good signal passing characteristic can be obtained.

Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings.
First Embodiment In the micromachine switch of the present embodiment, as shown in FIGS. 1 (a), 2, 3, and 4, a material obtained by injecting boron into silicon on the surface of a glass substrate (1) is used. A support portion (5) is formed using the support portion (5), which is connected to the ground potential portion on the substrate (1) and grounded.
An arm portion (7) extending from the surface of the substrate (1) is formed on the support portion (5) using a material in which boron is injected into silicon, and the tip portion of the arm portion (7) is formed. An electrically conductive member (6) is connected to the base.
The arm portion (7) is designed to have a shape and dimension having a predetermined inductance component as will be described later.

On the back surface of the conductive member (6), an upper electrode (4) is formed on the arm portion (7) side, and a working electrode (8) is formed on the tip side of the conductive member (6). The tip of the arm (7) and the working electrode (8) are electrically connected in series with each other.
On the other hand, a lower electrode (9) is formed on the surface of the substrate (1) at a position facing the upper electrode (4), and the lower electrode (9) is covered with an insulating layer (62). Further, the signal line (2) on the substrate (1) is covered with an insulating layer (61) in a region facing the working electrode (8).

  In the micromachine switch of the present invention, an electrostatic force is generated between the upper electrode (4) and the lower electrode (9) when the switch is turned off. As a result, as shown in FIGS. 5, 6, and 7, the arm portion (7) is elastically deformed so that the upper electrode (4) is in contact with the insulating layer (62) covering the lower electrode (9), The working electrode (8) contacts the insulating layer (61) covering the signal line (2). As a result, the capacitance component between the working electrode (8) and the signal line (2) increases.

  In this state, an inductance component constituted by the arm portion (7) is connected in series to the capacitance component. As a result, as shown in an equivalent circuit shown in FIG. ), An electrical state in which an LC circuit (trap circuit) composed of the inductance component and the capacitance component is connected is realized. Accordingly, as shown in FIG. 1C, a large attenuation can be obtained at the resonance frequency of the LC circuit.

  Here, the shape and dimensions of the arm portion (7) that constitutes the inductance component are defined so that the resonance frequency of the LC circuit matches the frequency f of the signal flowing through the signal line (2). As a result, the signal flowing through the signal line (2) is blocked from passing through the signal line (2) with great attenuation.

When the switch is turned on, the electrostatic force between the upper electrode (4) and the lower electrode (9) is lost. As a result, as shown in FIGS. 2, 3 and 4, the arm portion (7) is elastically restored, the working electrode (8) is separated from the signal line (2), and the signal line (2) and the working electrode (8) are separated. ) Capacitance component decreases.
As a result, the electrical state in which the LC circuit is connected to the signal line (2) is canceled, and the signal flowing through the signal line (2) passes through the signal line (2) with almost no attenuation.

FIG. 9 shows a model for examining the characteristics of the micromachine switch of this embodiment by computer simulation.
In the model, a pair of support portions (5) and (5) are formed on both sides of the signal line (2) as shown in the figure, and the left and right sides of the support portions (5) and (5) are parallel to the signal line (2). A pair of arm portions (7) and (7) extend away from the substrate (1), and a pair of left and right upper electrodes (4) and (4) are provided at the distal ends of both arm portions (7) and (7). Is formed.
Each arm portion (7) is formed to have a width W, a thickness, and a length L that will exhibit a predetermined inductance component as described above.

Furthermore, a pair of left and right second arm portions (6a) (6a) extending in a direction perpendicular to the signal line (2) and approaching each other is formed on both upper electrodes (4), (4). And the reinforcement part (3) is connected with the front-end | tip part of both arm parts (6a) (6a), and the working electrode (8) is formed in the back surface side of this reinforcement part (3).
On the other hand, a pair of left and right lower electrodes (9) and (9) are formed on the surface of the substrate (1) so as to face the pair of left and right upper electrodes (4) and (4).

  In the above micromachine switch model, the first arm portion (7) is bent at an angle of 90 degrees with respect to the second arm portion (6a). This constitutes a cantilever whose part can be freely displaced. Therefore, the spring constant involved in the on / off operation of the micromachine switch is small. As a result, the elastic restoring force acting on the first arm portion (7) in the switch-on state becomes small, and the control power for switching on / off can be greatly reduced.

  In the computer simulation using the above model, the width W of the arm portion 7 formed of silicon was 5 μm, the thickness was 5 μm, and the length L was 150 μm. As a result, the inductance L of the arm portion (7) becomes approximately 0.06 nH. The signal line (2) is made of gold and has a thickness of 2 μm and a width of 200 μm. The upper electrode (4) was 200 μm × 200 μm in size. The working electrode (8) was 200 μm × 50 μm in size. As a result, the capacitance C between the working electrode (8) and the signal line (2) is approximately 5 pF.

FIG. 10 shows the result of electromagnetic field simulation when the switch is off, and FIG. 11 shows the result of circuit simulation. In any result, the frequency resonates at about 8 to 9 GHz, and a large attenuation is obtained at the resonance frequency.
Therefore, in a configuration in which the frequency of the signal passing through the signal line (2) matches the resonance frequency, good isolation characteristics can be obtained.

Second Embodiment In the micromachine switch of the present embodiment, as shown in FIGS. 12A and 13 to 16, a silicon support portion (5) is formed on the surface of a glass substrate (1). The support part (5) is provided with a silicon arm part (71) extending from a position spaced from the surface of the substrate (1), and the tip of the arm part (7) is insulative. The member (69) is connected.

  On the back surface of the insulating member (69), an upper electrode (41) is formed at the end on the arm portion (71) side, and the upper electrode (41) is covered with an insulating layer (65). A working electrode (81) is formed on the back surface of the insulating member (69) on the tip side of the insulating member (69). Furthermore, a counter electrode (82) is formed on the back surface of the insulating member (69) between the upper electrode (41) and the working electrode (81), and the counter electrode (82) is covered with an insulating layer (64). It has been broken.

On the other hand, a lower electrode (91) is formed on the surface of the substrate (1) at a position facing the upper electrode (41).
In addition, the two signal lines (2a) (2b) formed on the surface of the substrate (1) have two electrode pieces (21a, 21a) facing the upper electrode (41), respectively. And both electrode pieces (21a) and (21a) are opposed to both ends of the counter electrode (82).

In the micromachine switch of this embodiment, an electrostatic force is generated between the upper electrode (41) and the lower electrode (91) when the switch is turned on. As a result, the arm portion (71) is elastically deformed, the working electrode (81) comes into contact with the signal lines (2a) and (2b), and the signal lines (2a) and (2b) are conducted. However, a contact resistance is generated between the signal lines (2a) (2b) and the working electrode (81).
Further, with the elastic deformation of the arm portion (71), the insulating layer (64) covering the counter electrode (82) comes into contact with the two electrode pieces (21a) (21b), and the counter electrode (82) and the two electrodes The capacitance component between the electrode pieces (21a) and (21b) increases.
As a result, as in the equivalent circuit shown in FIG. 12B, an RC circuit is configured in which the resistor is interposed in the signal lines (2a) and (2b) and the capacitance component is connected in parallel to the resistor. Will be.

FIG. 12 (c) shows frequency characteristics in the configuration in which the RC circuit is connected to the signal lines (2a) and (2b). When the frequency of the signal flowing through the signal lines (2a) and (2b) is low, The resistance causes a certain amount of attenuation, but when the frequency of the signal rises beyond a certain value, the capacitance component becomes dominant and the attenuation of the signal is greatly reduced.
Therefore, the signal flowing through the signal lines (2a) and (2b) passes through the signal lines (2a) and (2b) with almost no attenuation.

  When the switch is turned off, the electrostatic force is lost. As a result, as shown in FIGS. 13 to 16, the arm portion (71) is elastically restored, the working electrode (81) is separated from the signal lines (2a) and (2b), and the signal lines (2a) and (2b) are separated. Disconnected. As a result, the signal flowing through the signal lines (2a) and (2b) is cut off.

  In addition, each part structure of this invention is not restricted to the said embodiment, A various deformation | transformation is possible within the technical scope as described in a claim. For example, in the micromachine switch of the first embodiment shown in FIG. 1, as the shape of the arm portion (7), various shapes such as a belt shape, a C shape, an S shape, a spiral shape, etc. that can obtain a desired inductance are adopted. I can do it.

It is a figure which shows planar view (a) of the micromachine switch of 1st Example of this invention, an equivalent circuit (b), and a frequency characteristic (c). It is sectional drawing which follows the AA line of FIG. 1 at the time of switch-on. It is sectional drawing which follows the BB line of FIG. 1 at the time of switch-on. It is sectional drawing which follows the DD line | wire of FIG. 1 at the time of switch-on. It is sectional drawing which follows the AA line of FIG. 1 at the time of switch-off. It is sectional drawing which follows the BB line of FIG. 1 at the time of switch-off. It is sectional drawing which follows the DD line | wire of FIG. 1 at the time of switch-off. It is a figure which shows planar view (a) of the conventional micromachine switch corresponding to 1st Example, an equivalent circuit (b), and a frequency characteristic (c). It is a top view which shows the model of the micromachine switch of 1st Example. It is a graph showing the result of the electromagnetic field simulation at the time of switch-off in this model. It is a graph showing the result of the circuit simulation at the time of switch-off in this model. It is a figure which shows planar view (a) of the micromachine switch of 2nd Example of this invention, an equivalent circuit (b), and a frequency characteristic (c). It is sectional drawing which follows the EE line | wire of FIG. 12 at the time of switch-off. It is sectional drawing which follows the FF line | wire of FIG. 12 at the time of switch-off. It is sectional drawing which follows the GG line | wire of FIG. 12 at the time of switch-off. It is sectional drawing which follows the HH line | wire of FIG. 12 at the time of switch-off. It is a figure which shows the planar view (a) of the conventional micromachine switch corresponding to 2nd Example, an equivalent circuit (b), and a frequency characteristic (c). It is a top view of the conventional common micromachine switch. It is sectional drawing which follows the DD line | wire of FIG. 18 at the time of switch-off. It is sectional drawing which follows the DD line | wire of FIG. 18 at the time of switch-on.

Explanation of symbols

(1) Board
(2) Signal line
(2a) Signal line
(2b) Signal line
(21a) Electrode piece
(21b) Electrode piece
(4) Upper electrode
(41) Upper electrode
(5) Support part
(6) Conductive member
(69) Insulating material
(7) Arm part
(71) Arm
(8) Working electrode
(81) Working electrode
(82) Counter electrode
(9) Lower electrode
(91) Lower electrode

Claims (2)

By bringing the working electrode (8) closer to the signal line (2) extending on the substrate (1) and increasing the capacitance component between the signal line (2) and the working electrode (8), the signal line In the micromachine switch that cuts off the signal flowing through (2),
A conductive support portion (5) disposed on the surface of the substrate (1) and connected to a ground potential portion on the substrate (1), and a protrusion of the support portion (5) is provided on the substrate (1). A conductive arm portion (7) extending along the substrate (1) at a position separated from the surface, a conductive member (6) connected to the tip of the arm portion (7), and the conductive member ( 6) the upper electrode (4) formed on the back surface , the working electrode (8) provided in close proximity to the upper electrode (4) on the back surface of the conductive member (6), and the substrate (1). A lower electrode (9) disposed on the surface of the upper electrode (4) so as to face the upper electrode (4) and capable of generating an electrostatic force between the upper electrode (4) and
At least a part of the arm portion (7) has a predetermined inductance component,
When the upper electrode (4) is attracted to the lower electrode (9) by the electrostatic force, the working electrode (8) approaches the signal line (2) and the capacitor component increases. The shape dimension of the arm portion (7) is defined so that the resonance frequency determined by a predetermined inductance component and the increased capacitance component matches or approximates the frequency of the signal passing through the signal line (2). Features a micromachine switch. The two signal lines (2a) and (2b) are brought into contact with the working electrode (8) across the opposing ends of the two signal lines (2a) and (2b) extending on the substrate (1). In the micromachine switch for connecting the two to each other, a conductive support portion (5) disposed on the surface of the substrate (1) and connected to the ground potential portion on the substrate (1) , and protruding from the support portion (5) And a conductive arm portion (71) extending along the substrate (1) at a position separated from the surface of the substrate (1), and a conductive member (6) connected to the tip of the arm portion (71 ). An upper electrode (41) formed on the back surface of the conductive member (6), and a working electrode (81) provided on the back surface of the conductive member (6) in the vicinity of the upper electrode (41). And a lower electrode (91) disposed on the surface of the substrate (1) so as to face the upper electrode (41) and capable of generating an electrostatic force between the upper electrode (4) and the lower electrode (91). ,
As the upper electrode (4) is attracted to the lower electrode (9) by the electrostatic force, the working electrode (8) contacts the opposite ends of the signal lines (2a) and (2b). And
Electrode pieces (21a) and (21a) project from the end portions of the two signal lines (2a) and (2b) , respectively, and the arm portions (71) and both electrode pieces (21a and 21b) A micromachine switch characterized in that a capacitance component is formed in parallel with the resistance component R of the working electrode (81) and the signal lines (2a) and (2b) by providing a counter electrode (82) facing each other.

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