JP2003217421A - Micromachine switch - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve low power consumption and high reliability by simplifying the arrangement of a switch mechanism and efficiently shutting a high frequency signal, in a micromachine switch for switching the high frequency signal. <P>SOLUTION: This micromachine switch is provided with a signal line conductor 12 formed on a substrate, a driving short-circuiting mechanism 15 for shutting passing of the high frequency signal and a piezoelectric material 16 to be a driving means for displacing the driving short-circuiting mechanism 15 by imparting a control signal. By applying voltage as the control signal to the piezoelectric material 16, the signal line conductor 12 and a ground conductor 13 are short-circuited via a conductive layer 17 on a bottom surface of the driving short-circuiting mechanism 15 and the high frequency signal can be efficiently shut. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a micromachine switch used for switching a high frequency signal in a high frequency circuit.

[0002]

2. Description of the Related Art In recent years, due to market expansion and development promotion of various high frequency devices such as portable communication devices, the manufacture of high frequency electronic components constituting these devices has been activated.
Particularly, in a high frequency signal transmission / reception circuit incorporated in a mobile communication device, there is an increasing demand for higher performance of a switch element used for switching an input / output signal to / from an antenna. Particularly, high performance is desired for low insertion loss of high frequency signals and high isolation for preventing leakage of high frequency signals to the outside. Currently, this switch element is mechanical or PIN that uses a relay.
An electronic type using a diode or the like is generally used, but recently, with the development of a micromachining technique mainly on a silicon process originating in a semiconductor manufacturing process, the use of a micromachine switch has been studied. The advantage of the micromachine switch is that the insertion loss of a high frequency signal is smaller than that of other electronic switch elements, the cost is relatively low, and the power consumption is low.

As a micromachine switch in a conventional example, one described in Japanese Patent Laid-Open No. 2000-294104 is known. A conventional technique will be described below with reference to the drawings. FIG. 4 shows the structure of a conventional micromachine switch. The main constituent elements are driving means 42 for displacing the contact 41 based on a control signal, and control signal lines 43 and 43 for giving a control signal to the driving means 42. Is a high-frequency signal blocking means 45 that blocks the passage of high-frequency signals that are connected to the high-frequency signal lines 44a and 44b. In order to pass a high frequency signal through the high frequency signal lines 44a and 44b in this switch, a voltage is applied from the high frequency signal blocking means 45 to the driving means 42 via the control signal line 43 to charge the surface of the driving means 42, Electric charges having a polarity different from that of the surface of the driving means 42 are generated on the lower surface of the contact 41 opposed by electrostatic induction. As a result, an electrostatic attraction force is generated between both the contact 41 and the driving means 42, the contact 41 is attracted to the driving means 42, and the high-frequency signal lines 44a and 44b are connected at high frequencies via the contact 41. This structure allows high-frequency signals to pass through.

[0004]

A micromachine switch generally performs a switch operation by driving a movable structure formed on a substrate, and has a higher responsiveness and lower power consumption than a semiconductor switch. Power, reliability, and long life are required.

However, the micromachine switch described in the conventional example performs the switch operation by accumulating the electric charge in the driving means 42 and the contact 41 by using the electrostatic attraction force as the driving force, so that the time required for the electric charge accumulation is shortened and the responsiveness is improved. There is a limit to improving.

The driving means 42 has low power consumption.
The drive voltage to be applied to the device requires several tens of volts or more, which is a very large voltage with respect to the voltage of several volts required to operate other elements in the transmission / reception circuit. For this reason, there is a possibility that a high-frequency signal passing through other signal line conductors in the circuit or the characteristics of the entire circuit may be adversely affected in a transmission / reception circuit in which miniaturization is rapidly progressing. In addition, a power supply circuit used only for applying a large voltage to the micromachine switch drive may be necessary, and there are many points to be considered to realize low power drive of the electrostatic micromachine switch itself.

[0007] The electrostatic micromachine switch is often manufactured by applying a semiconductor process using a sacrificial layer with silicon as a main structural material, and there is an advantage that no assembly is required in the manufacturing process. There are few examples that have been clarified regarding the durability of the silicon movable structure as described above, and there are many unconfirmed factors regarding reliability, life, and the like.

According to the present invention, in a micromachine switch for cutting off a high frequency signal, a switch machine having a simple structure and efficiently cutting off a high frequency signal can realize a micromachine switch with low power consumption and high reliability. With the goal.

[0009]

In order to solve this problem, the present invention provides a signal line conductor formed on a substrate, and a drive short-circuit mechanism for blocking passage of a high frequency signal of the signal line conductor, A micromachine switch comprising: a drive unit that displaces the drive short-circuit mechanism by giving a control signal. In particular, the drive short-circuit mechanism has a beam shape and a piezoelectric body as a driver. Then, by deforming this mechanism, the signal line conductor and the ground conductor are short-circuited to interrupt the high-frequency signal.

In this micromachine switch, a coplanar line in which a signal line conductor and a ground conductor are arranged on the same plane is formed on a substrate, and a beam-shaped driving short-circuit mechanism is joined via a conductive support portion. It is composed of things.

It is possible to use silicon, ceramics, gallium arsenide or the like as the substrate material. The signal line conductor and the ground conductor are desirably made of a metal material having high electric conductivity,
Further, it is desirable that the metal be a metal that facilitates a bonding technique such as wire bonding when electrically connecting with another high frequency element to form a circuit.

The drive short-circuit mechanism has a laminated structure of the following members. A material having a spring characteristic that can generate a restoring force sufficient to cancel the short circuit between the signal line conductor and the ground conductor, a piezoelectric body that is a main part of the driver, and a short circuit between the signal line conductor and the ground conductor on the substrate. It is a conductive layer necessary for this.

The support portion joining the substrate and the drive short-circuiting mechanism has conductivity so as to short-circuit the high-frequency signal from the ground conductor to the signal line conductor through the drive short-circuiting circuit, and has a drive short-circuiting mechanism. Must have the necessary strength to perform repeated movements.

By joining these components, a micromachine switch having a simple switch mechanism and capable of efficiently blocking high-frequency signals passing through the signal line conductors and having low power consumption and high reliability is provided. Can be realized.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention includes a signal line conductor formed on a substrate, a drive short-circuit mechanism for blocking passage of a high-frequency signal through the signal line conductor, and a control. A drive means for displacing the drive short-circuit mechanism by giving a signal, and a micromachine switch characterized by low insertion loss of high-frequency signals compared to electronic switches, and low power consumption, and Since the switch structure can be simplified, the cost can be reduced.

The invention according to claim 2 is characterized in that the high-frequency signal passing through the signal line conductor is cut off by short-circuiting the signal line conductor and the ground conductor via a drive short-circuit mechanism. The micromachine switch according to claim 1, wherein the high-frequency signal is cut off by a physical action of a short circuit, so that the high-frequency signal does not leak outside.

The third aspect of the present invention is the micromachine switch according to the first or second aspect, wherein the drive short-circuit mechanism is in the form of both ends supported or cantilever, and the beam shape is relatively easy. Since it has a structure that can be formed, the micromachine switch itself can be easily manufactured, and the cost can be reduced.

According to a fourth aspect of the present invention, the driving means is a piezoelectric body, and the driving short circuit mechanism is operated by applying a control signal to bend the piezoelectric body. This is a switch, and it is possible to perform a stable switch operation with low voltage and low power consumption by using a piezoelectric body capable of efficiently converting electrical energy into mechanical energy as a driver. Have.

According to a fifth aspect of the invention, the piezoelectric body is Pb,
The micromachine switch according to claim 4, which is an oxide containing Zr and Ti, and has a thickness of 0.1 μm or more and 10 μm or less. 6. The micromachine switch according to claim 4, wherein at least one of the electrodes formed in is a metal containing Pt, Ir or Ru, or a conductive oxide. The piezoelectric material is an oxide containing Pb, Zr, and Ti and can be driven at a low voltage by reducing its thickness, and a thin film can be obtained by using a material containing Pt, Ir, or Ru as its electrode material. It has an effect that good piezoelectric drive can be realized even in the case of a piezoelectric body.

The invention according to claim 7 is characterized in that a conductive layer is formed on the bottom surface of the driving short-circuit mechanism having a beam shape in order to short-circuit the signal line conductor and the ground conductor. The micromachine switch described in any one of 1 to 3 above has an effect that the structure of the switch can be simplified by providing the drive short-circuit mechanism with a grounding function.

The invention according to claim 8 is the micromachine switch according to any one of claims 4 to 6, characterized in that the control signal is an applied voltage for operating the piezoelectric body. The piezoelectric body, which is the driving body, has the function of being able to control the amount of deformation by the applied voltage applied, so that the drive short-circuit mechanism is operated with a simple circuit configuration without the need for a special signal generator or the like. It has the effect that it is possible.

The invention according to claim 9 is characterized in that a material having a spring characteristic capable of generating a restoring force sufficient to release the short circuit between the signal line conductor and the ground conductor when the control signal is stopped is used as a constituent material. The micromachine switch according to any one of claims 3 to 8, further comprising a drive short-circuiting mechanism, wherein the beam shape is bent by applying an applied voltage to the piezoelectric body only when a high-frequency signal is cut off, and a high-frequency wave is generated. When a signal is passed through, the restoring force of a material having a spring characteristic is used to move the beam shape away from the signal line conductor, thereby making it possible to make a state that does not affect high frequency signal passage.

According to a tenth aspect of the present invention, the drive voltage for operating the drive short-circuit mechanism can be operated at a voltage equal to or lower than the voltage required to drive other elements of the high frequency circuit. The micromachine switch according to any one of claims 1 to 9, which does not require a high-voltage power supply circuit used only for the operation of the drive short-circuit mechanism, which simplifies the switch drive circuit and saves power. It has the effect of being able to.

FIG. 1 shows an embodiment of the present invention.
3 to FIG. 3 will be described.

(First Embodiment) FIG. 1 is a perspective view showing a micromachine switch according to the present embodiment. Figure 1
In the figure, 11 is a substrate for incorporating the constituent elements of the micromachine switch. As the substrate material, silicon, ceramics, gallium arsenide, or the like can be used. The signal line conductor 12 and the ground conductor 1 are provided on the substrate 11.
3 is formed by a sputtering method or a plating method. It is desirable that the material for forming the signal line conductor 12 and the ground conductor 13 has high electrical conductivity. Since the micromachine switch is electrically bonded to other high frequency circuit elements, it is desirable that the wiring material be easily bonded by wire bonding or the like.

On the ground conductor 13, the conductive support portion 14 for joining the drive short-circuit mechanism 15 is formed.
The support portion 14 plays a role of holding the drive short-circuit mechanism 15 at a height that does not affect the signal when the high-frequency signal passes through the signal line conductor 12, together with the shape restoring force of the drive short-circuit mechanism 15.

In order for the drive short-circuit mechanism 15 to be grounded to the signal line conductor 12 to block high-frequency signals, the height of the support portion 14 should be less than the bendable amount of the piezoelectric body constituting the drive short-circuit mechanism 15. is necessary. Since the drive short-circuit mechanism 15 in the present embodiment has a single supporting portion, it has a cantilever shape, and the drive short-circuit mechanism 15 can have a unimorph structure, which facilitates manufacture.

A cantilever having a length of 300 μm and a width of 30 μm was formed by using Pb (Zr, Ti) O 3 having a thickness of 3 μm as the piezoelectric body 16 constituting the drive section. The lower part of this beam is the conductive layer 1
A Pt electrode having a thickness of 0.1 μm was used as 7, and a Cr having a thickness of 2.5 μm was used as a material 18 having a spring characteristic on the upper part, and also had a role as an upper electrode. When a voltage of 0-5V is applied between the upper and lower electrodes, about 8
A displacement of μm occurred. By this tip displacement, the conductive layer 1
The switch can be turned on and off between 7 and the signal line conductor 12.

As for the thickness of the piezoelectric body 16, if it is thicker than 10 μm, the displacement is 5 μm or more so as to generate displacement of 10 μm or more.
It requires a voltage of V or more, and is not suitable as a micromachine switch for high frequencies. Further, when the thickness is less than 0.1 μm, the strength of the beam becomes weak and the operation becomes unstable, resulting in a sudden increase in malfunctions.

Considering the structure of the switch having the supporting portion 14 capable of holding the space where the driving short-circuit mechanism 15 does not affect the high frequency signal when the high frequency signal passes through the signal line conductor 12, one calculation As an example, the beam shape has a width of 10
A value of 0 μm, a length of 500 μm, and a height of the supporting portion 14 of 2 μm were obtained. FIG. 2 shows the relationship between the height of the support portion 14 and the passage characteristic of the high frequency signal. Support 1 as shown
If the height of 4 is 2 μm or more, the passage characteristics are not hindered, but the height of the support portion 14 should be 4 μm in consideration of the bending of the beam shape due to its own weight and the deformation due to internal stress that may occur during formation. With this, the reliability of the switch mechanism was improved. A cantilever having each dimension in this calculation example and the above Pb (Zr, Ti) O3 are used, the thickness is 3 μm, the length is 300 μm, and the width is 30 μm.
By comparing the driving voltage and the amount of deflection with the cantilever beam of No. 2, even if the cantilever shape having the dimension obtained from the calculation example is used, the switch of the present invention operates sufficiently even when viewed from RF with 5 V or less. It was possible to obtain the result.

Therefore, according to the present embodiment, it is possible to realize a micro switch which has a simple structure, can cut off high-frequency signals efficiently, has low driving voltage, consumes less power, and has high reliability.

(Second Embodiment) FIG. 3 is a perspective view showing a micromachine switch in the present embodiment.

Although the structure is almost the same as that of the first embodiment, the drive short-circuit mechanism 15 has both-end support beam shape by forming the conductive support portions 14 on both the ground conductors 13. With this shape, the mechanical strength of the drive short-circuit mechanism 15 can be improved, and the reliability of the switch can be improved.

Therefore, as in (Embodiment 1),
A micro switch that has low power consumption and high reliability can be realized.

[0035]

As described above, according to the present invention, by using the driving short-circuit mechanism in which the piezoelectric body is used as the driving body in the high-frequency signal circuit, the high-frequency signal passing through the signal line conductor has a simple switch mechanism structure. It is possible to obtain an advantageous effect that it is possible to easily manufacture a micromachine switch with low power consumption and high reliability, which can efficiently shut off the power supply.

[Brief description of drawings]

FIG. 1 is a perspective view showing a micromachine switch according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing a relationship between a height of a supporting portion 14 and a passing characteristic of a high frequency signal according to an embodiment of the present invention.

FIG. 3 is a perspective view showing a micromachine switch according to an embodiment of the present invention.

FIG. 4 is a schematic diagram showing a configuration of a conventional electrostatic micromachine switch.

[Explanation of symbols]

11 board 12 Signal line conductor 13 Ground conductor 14 Support 15 Drive short circuit 16 Piezoelectric body 17 Conductive layer 18 Materials with spring properties 41 contacts 42 Drive means 43 Control signal line 44a high frequency signal line 44b High frequency signal line 45 High-frequency blocking means

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Isaku Jinno             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. F-term (reference) 5J012 AA06

Claims (10)

[Claims] 1. A signal line conductor formed on a substrate, a drive short-circuit mechanism for blocking passage of a high-frequency signal through the signal line conductor, and drive means for displacing the drive short-circuit mechanism by giving a control signal. A micromachine switch characterized by having. 2. The micromachine according to claim 1, wherein the high-frequency signal passing through the signal line conductor is cut off by short-circuiting the signal line conductor and the ground conductor through a driving short-circuit mechanism. switch. 3. The micromachine switch according to claim 1, wherein the drive short-circuit mechanism is in the form of both ends supported or cantilevered. 4. The micromachine switch according to claim 3, wherein the driving means is a piezoelectric body, and the drive short-circuit mechanism is operated by applying a control signal to bend the piezoelectric body. 5. The micromachine switch according to claim 4, wherein the piezoelectric body is an oxide containing Pb, Zr, and Ti and has a thickness of 0.1 μm or more and 10 μm or less. 6. The piezoelectric element according to claim 4, wherein at least one of the electrodes formed on both sides of the piezoelectric body is a metal containing Pt, Ir or Ru, or a conductive oxide. Micromachine switch. 7. The micromachine according to claim 3, wherein a conductive layer is formed on the bottom surface of the driving short-circuit mechanism having a beam shape to short-circuit the signal line conductor and the ground conductor. switch. 8. The micromachine switch according to claim 4, wherein the control signal is an applied voltage for operating the piezoelectric body. 9. A drive short-circuit mechanism including, as a constituent material, a material having a spring characteristic capable of generating a restoring force sufficient to cancel a short circuit between a signal line conductor and a ground conductor when a control signal is stopped. The micromachine switch according to any one of claims 3 to 8, characterized in that: 10. The drive voltage for operating the drive short-circuit mechanism can be operated at a voltage equal to or lower than a voltage required to drive other elements of the high frequency circuit. 9. The micromachine switch according to any one of 9.