JP2002100276A - Micro machine switch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small machine type switch and a relay having a contact with high reliability. SOLUTION: A holding electrode having the same shape as the deflection shape of a beam is provided to keep the beam's deflection shape by an electrostatic force. The contact surfaces of the contacts are made to be contacted each other with a contact angle close to 0 as much as possible for a larger contact area. Since the contact is kept by the electrostatic force of a uniformly distributed load, high quality contacts in which a stiction problem is reduced, with a lower contact resistance can be provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mechanical switch and a relay, and more particularly to a micromechanical switch capable of realizing a small and highly reliable contact in a highly integrated circuit.

[0002]

2. Description of the Related Art FIG.
This will be described with reference to FIGS. FIG. 7 shows the IEEE MTT-S
Digest 1999, p. 1923-1926
Is a microwave switch introduced in. A gold contact portion 2 is provided below the tip of the silicon cantilever 1 via an insulating layer, and a circuit terminal portion 3 forming a closed circuit by contact with the contact portion is provided on a surface facing the contact portion 2; A drive electrode 4 for applying an electrostatic force to the contact portion 2 to bend the silicon cantilever 1
Is provided. The gap between the contact part 2 and the circuit terminal part 3 is 1
The voltage is set to 0 μm or less. When a voltage of 50 V or more is applied to the drive electrode 4, the beam 1 bends and the contact portion 2 comes into contact with the circuit terminal portion 3 to close the contact.

[0003]

However, since the voltage required to close the contacts is as high as 50 V or more, it is necessary to mount a dedicated booster circuit, which hinders miniaturization of the switch element. In addition, microwaves are susceptible to capacitive coupling and inductive coupling even if there is no conduction at the contacts, and the gap between the contacts and the circuit terminals must be further expanded to improve isolation when the contacts are open. However, since the electrostatic force is inversely proportional to the square of the distance between the opposed electrodes, there has been a problem that a higher voltage is required to close the circuit.

[0004] Further, as shown in FIG. 8 (a), a contact portion may be partially contacted. In order to increase the contact area and reduce the contact resistance, an even higher voltage is applied as shown in FIG. 8 (b). It was necessary to flex the beam in the opposite direction to eliminate the gap between the contacts. At that time, the contact pressure becomes excessive only in the vicinity of the one-sided portion, and an adhesion phenomenon called stiction occurs. As shown in FIG. Without returning, the circuit could remain closed and lose control.

An object of the present invention is to provide a micromechanical switch having a simple structure and high-quality contacts in such a micromechanical switch.

[0006]

SUMMARY OF THE INVENTION In order to solve this problem, the present invention provides a substrate-side holding electrode having a shape equivalent to the shape of a beam-side holding electrode of a beam bent by applying a force. By applying an electrostatic force, it is possible to maintain the bent shape of the beam at a low voltage. In addition, the contact area and the circuit terminal section have the same shape and the contact angle between them is made as close to zero as possible to increase the contact area.In addition, the contact force is increased by the electrostatic force of the holding electrode, and the contact resistance is reduced. By uniformly distributing the pressure, the stiction problem was reduced, and it was possible to provide a high quality contact. In addition, the means for bending the beam is an electrostatic force, and by using the holding electrode as a driving electrode together,
It is possible to provide a small mechanical switch at a low voltage.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is characterized in that a working portion on which a force for bending a beam acts, a beam-side holding electrode portion for holding a bent shape of the beam by applying an electrostatic force. A beam having a contact portion functioning as a contact by bending the beam, a substrate-side holding electrode for applying an electrostatic force to the beam-side holding electrode portion, and contacting the contact portion by bending the beam. In a beam drive structure comprising a substrate having a circuit terminal portion that closes the circuit, the shape of the beam-side holding electrode portion in a closed state and the shape of the substrate-side holding electrode have the same shape, so that both are in close contact with each other. This is a micro mechanical switch characterized by the above.

According to a second aspect of the present invention, there is provided the micromechanical switch according to the first aspect, wherein the contact portion and the circuit terminal portion are in close contact with each other with no gap when the circuit is closed.

According to a third aspect of the present invention, the contact portion is provided at a portion other than the acting portion and the beam-side holding electrode portion on the beam, and is not subjected to bending due to a force acting on the acting portion. A micro mechanical switch according to claim 2.

According to a fourth aspect of the present invention, the beam-side holding electrode portion also serves as an action portion, and the force for bending the beam is an electrostatic force between the substrate-side holding electrode portion and the beam-side holding electrode portion. The micro mechanical switch according to claim 1.

According to a fifth aspect of the present invention, the shape of the substrate-side holding electrode has the same curved shape as the bent shape when an evenly distributed load is applied to the beam-side holding electrode portion. 5. The micromechanical switch according to claim 4, wherein the beam-side holding electrode unit is in close contact with no gap.

According to a sixth aspect of the present invention, there is provided the micromechanical switch according to the first aspect, wherein the driving means of the driving section is a piezoelectric body.

According to a seventh aspect of the present invention, there is provided the micromechanical switch according to the first aspect, wherein the driving means of the driving section is a bimetal.

According to an eighth aspect of the present invention, there is provided the micromechanical switch according to the first aspect, wherein the driving means of the driving section is a shape memory alloy.

According to a ninth aspect of the present invention, there is provided the micromechanical switch according to the first aspect, wherein the driving means of the driving section is a magnetostrictive element.

According to a tenth aspect of the present invention, there is provided the micromechanical switch according to the first aspect, wherein the driving means of the driving section is an optical distortion element.

According to an eleventh aspect of the present invention, there is provided the micromechanical switch according to the first aspect, wherein the driving means of the driving section is an electrostrictive polymer.

FIG. 1 shows an embodiment of the present invention.
This will be described with reference to FIG.

(Embodiment 1) FIG. 1 is a perspective view showing an outline of a micromechanical switch according to an embodiment of the present invention. The beam 1 is a U-shaped beam, and the end point is supported by the fixed portion 8. The material of the beam 1 is an insulating material or an insulating film formed on the lower surface of a conductor material.

The lower surface of the beam 1 has a distance of 0 from the fixed portion 8.
Beam-side electrodes 9a and 9b for driving and holding the beam by electrostatic force are provided between L1 and L1. The distance L2 to L
Between 3, a beam-side electrode 9c for holding the beam by electrostatic force,
9d is provided. A contact electrode 10 is provided at a position sandwiched between the beam side electrodes 9c and 9d.

FIG. 2 is a sectional view taken along the line AA ′ of FIG. 1 and FIG. 2 is a sectional view taken along the line BB ′ of the substrate 11 made of an insulator disposed below the beam 1 and supporting the beam 1 via the fixing portion 8. This will be described with reference to FIG.

In FIG. 2, a beam fixing portion 8 is provided on a substrate 11.
From 0 to L1 in the distance from the substrate side electrode 12 which drives and holds the beam by applying an electrostatic force to the beam side electrodes 9a and 9b.
a and 12 b are provided, and the surface thereof is covered with an insulating film 13. Between the distances L2 and L3, the beam-side electrodes 9c, 9
substrate-side electrode 12 for holding a beam by applying electrostatic force to d
c and 12 d are provided, and the surface thereof is covered with the insulating film 13.

In FIG. 3, a signal line 1 is provided on a substrate 11.
4 are provided, and a circuit terminal portion 15 is formed by a portion corresponding to a distance L2 to L3 from the fixing portion 8 of the beam.
A contact is constituted with the contact electrode 10 of FIG. In the section between L2 and L3, the shape of the substrate 11 is the substrate-side electrode 1 in FIG.
The surface of the signal line 14 is the same as the surface having 2c and 12d, and the thickness of the signal line 14 is equal to or slightly larger than the thickness of the insulating film 13 in FIG.

According to the above configuration, since the electrostatic force for bending the beam 1 is applied to the beam 1 itself, there is no need to provide a portion for applying the electrostatic force to the tip of the beam as shown in FIG. Can be achieved.

The surfaces of the substrate-side electrodes 12a and 12b are 0 to
It is a curved surface up to L1. Normally, when an electrostatic force is applied to the beam to bend it, as shown in FIG. 4, when the voltage is applied, the tip of the beam gradually displaces with the spring force and the electrostatic force of the beam being balanced up to the pull-in voltage Vpi. At Vpi, the beam is suddenly pulled by the electrostatic force and displaced to near the maximum displacement, and the beam comes into contact with the counter electrode. For example, in FIGS. 1 and 2, the beam is made of silicon and the Young's modulus of the beam is 150 GPa.
The width h of the beam is 40 μm, the thickness t of the beam is 2.5 μm, L1 is 400 μm, the thickness d of the insulating film 13 is 0.3 μm, the relative permittivity is 1, and the gap δmax at L1 is 6 μm.

[0026]

(Equation 1)

When the shape of the surface of the insulating film 13 in the section from 0 to L1 is represented by (Equation 1) by xy coordinates as shown in FIG.
0, that is, the surface of the insulating film 13 is flat and parallel to the beam, and Vpi is 110 V when a voltage is applied between the substrate-side electrodes 12a and 12b and the beam-side electrodes 9a and 9b. Therefore, when n = 2, that is, when the surface of the insulating film 13 is formed into a curved surface, Vpi becomes 30 V, and when the order is increased to near n = 4, Vpi becomes 10 V or less, and the beam can be bent at a low voltage.

[0028]

(Equation 2)

The amount of deflection w of the beam 1 when an equal distribution load F is applied to a range of 0 to L1 from the fixed portion 8 of the beam 1 is the same as the beam Young's modulus E and the secondary moment of area I. x-
If the y coordinate is used, it is represented by (Equation 2). Note that x>
No bending of the beam occurs at L1. Between 0 and L1, the beam-side electrode 12 has a shape substantially equivalent to the beam bending shape w (x).
If the surface of the insulating film 13 on a and 12b has
Both can be brought into close contact. For example, if the surface shape s (x) of the insulating film 13 is between (x = 0) and (L1) and the shape of (Equation 1) at n = 4 where Vpi can be reduced to 10 V or less, the w (x) of the beam is approximately Since the shape can be approximately expressed, the insulating film 13 and the beam 1 can be closely attached. The uniformly distributed load at this time is an electrostatic force F per unit area, and F is given by (Equation 3) using εr as a relative dielectric constant of the insulating film 13.

[0030]

(Equation 3)

After the contact, even if the voltage is increased, there is no displacement of the beam, but the contact pressure increases uniformly according to the above equation. Accordingly, there is no large deviation in the contact pressure between the beam between 0 and L1 and the substrate, and the problem of stiction can be reduced.

The shape of the substrate before L1 is made flat, and
1, if it is continuous with the curved surface of 0 to L1,
When a voltage is applied between the electrodes a and 12b and the beam-side electrodes 9a and 9b to bring 0 to L1 into close contact with each other, the beams and the substrate surface are also in gentle contact with L1 to L3. In order to stabilize the contact between the contact electrode 10 and the circuit terminal 15, a voltage is further applied between the substrate-side electrodes 12 c and 12 d and the beam-side electrodes 9 c and 9 d to cause electrostatic force to act on the contact electrode 10. The contact surface with the circuit terminal portion 15 contacts with a uniform contact pressure, the contact resistance is reduced, and the stiction problem is also reduced. FIG. 5 is a sectional view taken along the line AA ′ of FIG. 1 at this time.

The curved shape of the substrate 11 is, for example, when an organic material such as polyimide is used as the substrate material.
It can be formed by excimer laser processing using a halftone mask. Alternatively, a similar curved surface shape can be generated by adjusting the irradiation time of the excimer laser depending on the position of the substrate plane.

When a photosensitive organic material is used as the substrate material, a curved surface shape can be generated by controlling the exposure time depending on the position of the substrate plane.

When an insulator such as a silicon oxide film is deposited by sputtering, a curved surface can be formed by controlling the opening of the mask so that the deposition time can be adjusted depending on the position of the substrate plane.

If a material having a high relative dielectric constant, such as strontium titanate (SrTiO3), is used as the insulating film 13, it goes without saying that the beam can be driven and held at a lower voltage.

(Embodiment 2) FIG. 6 is a sectional view showing an outline of a micromechanical switch according to Embodiment 2 of the present invention. In FIG. 2 which is an explanatory view of Embodiment 1, FIG. FIG. 9 is a diagram illustrating a cross section of a micromechanical switch when a piezoelectric thin film 16 is used as a means for giving a deflection between a distance 0 and a distance L1 from 8.

The material of the piezoelectric thin film 16 is ZnO or PZ
T. etc., especially I. Kanno, et a
l., "Piezoelectric property
ies of c-axis oriented Pb
(Zr, Ti) O3 thin films ", Ap
pl. Phys. Lett. , 70 (11), p
p. 1378-1380, 1997. PZ shown in
The T thin film has a d constant as high as that of a bulk material, and is optimal for the present micromechanical switch.

Further, as an advantage over the bulk material, the piezoelectric thin film 16 has a small thickness, so that the electric field strength can be increased and the applied voltage can be reduced.

When a voltage is applied to the piezoelectric thin film 16, the piezoelectric thin film 16 extends in the longitudinal direction of the beam, and the beam 1 is deformed toward the insulating film 13 so as to absorb the distortion.
As a result, the beam side electrodes 9c and 9d and the substrate side electrodes 12c and
2d approaches or comes into contact partially with the insulating film 13 interposed therebetween. Further, the beam side electrodes 9c and 9d and the substrate side electrode 12
By applying a voltage at which an electrostatic attraction force acts between c and 12d, the adhesion between the two can be further enhanced.

It should be noted that, before the beam 1 is deformed by the action of the piezoelectric thin film 16, the beam-side electrode 9c,
The voltage when the deformation of the piezoelectric thin film 16 is used in combination can be much smaller than the voltage required for bringing the 9d and the substrate-side electrodes 12c and 12d into close contact with each other by electrostatic force. This has an effect of lowering the drive voltage of the present micromechanical switch, in combination with the lower drive voltage of the piezoelectric thin film 16, and is advantageous in applying the present micromechanical switch to mobile devices.

The beam-side electrodes 9c and 9d and the substrate-side electrode 1
Due to the close contact between 2c and 12d, the contact surface of the contact electrode 10 (not shown) with the circuit terminal portion 15 (not shown) comes into contact with a uniform contact pressure, the contact resistance is reduced, and the stiction problem occurs. Is also reduced.

In the first and second embodiments of the present invention, the means for bending the beam is an electrostatic force or a piezoelectric thin film. However, the beam may be bent to bend to open and close the contact. If possible, without being limited to electrostatic force or piezoelectric thin film, for example, bimetal, shape memory alloy, magnetostrictive element,
A photostrictive element, an electrostrictive polymer, or the like may be used.

In the first and second embodiments of the present invention, the contacts are opened and closed by the contact between the conductors. However, in order to perform the switching of the electromagnetic wave, the capacitors and the coils are moved closer to each other by bending the beams. By doing so, a structure for performing capacitive coupling or inductive coupling may be adopted.

[0045]

As described above, according to the present invention, by providing a holding electrode having the same shape as the curved surface shape of a beam bent by applying a force, the bent shape of the beam can be reduced at a low voltage. The advantageous effect of being able to hold is obtained.

According to the present invention, the contact area is enlarged by making the shape of the contact portion and the circuit terminal portion the same and making the contact angle between them as close to zero as possible. In addition, the contact resistance is reduced by increasing the contact pressure, and the contact pressure is evenly distributed, so that the stiction problem is reduced and the advantageous effect that a high quality contact can be provided can be obtained.

Further, according to the present invention, the means for imparting bending to the beam is an electrostatic force, and the holding electrode having the same shape as the curved shape of the bending of the beam is used in combination as a driving electrode.
An advantageous effect is obtained that a small mechanical switch can be provided at a low voltage.

[Brief description of the drawings]

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

FIG. 2 is a sectional view taken along the line A-A 'in FIG.

FIG. 3 is a cross-sectional view taken along a line B-B 'in FIG.

FIG. 4 is a characteristic diagram illustrating an operation of driving a beam by electrostatic force according to an embodiment of the present invention;

FIG. 5 is a cross-sectional view taken along the line AA ′ in a state where the micromechanical switch of FIG. 1 is closed.

FIG. 6 is a sectional view showing an outline of a micromechanical switch according to an embodiment of the present invention.

FIG. 7 is a top view and a cross-sectional view schematically showing a conventional micromechanical switch.

FIG. 8 is a cross-sectional view showing contact contact in a conventional micromechanical switch.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Beam 2 Contact part 3 Circuit terminal part 4 Drive electrode 5 Substrate 6 Signal line 7 Insulating film 8 Fixed part 9 Beam side electrode 10 Contact electrode 11 Substrate 12 Substrate side electrode 13 Insulating film 14 Signal line 15 Circuit terminal part 16 Piezoelectric thin film

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01H 55/00 H01H 55/00 57/00 57/00 DA H01L 41/09 H01L 41/12 41/12 41/08 U

Claims (11)

[Claims] 1. A working portion on which a force for bending a beam acts, a beam-side holding electrode portion for holding a bent shape of a beam by applying electrostatic force, and a contact portion functioning as a contact by bending the beam. And a substrate having a circuit-side holding electrode for applying an electrostatic force to the beam-side holding electrode portion, and a circuit terminal portion for closing the circuit by making contact with the contact portion by bending the beam. A micromechanical switch characterized in that in a beam driving structure, the shape of a beam-side holding electrode portion in a state where a circuit is closed and the shape of a substrate-side holding electrode have the same shape, so that both are in close contact with each other. 2. The micromechanical switch according to claim 1, wherein the contact portion and the circuit terminal portion are in close contact with each other with no gap when the circuit is closed. 3. The micromachine according to claim 2, wherein the contact portion is provided at a portion other than the acting portion and the beam-side holding electrode portion on the beam, and does not bend by a force acting on the acting portion. switch. 4. The micro-electrode according to claim 1, wherein the beam-side holding electrode portion also functions as an action portion, and the force for bending the beam is an electrostatic force between the substrate-side holding electrode portion and the beam-side holding electrode portion. Mechanical switch. 5. The substrate-side holding electrode has the same curved shape as the bending shape when an evenly distributed load is applied to the beam-side holding electrode, so that there is a gap between the substrate-side holding electrode and the beam-side holding electrode. The micromechanical switch according to claim 4, wherein the switch is in close contact with the micromechanical switch. 6. The micromechanical switch according to claim 1, wherein the driving means of the driving section is a piezoelectric body. 7. The micromechanical switch according to claim 1, wherein the driving means of the driving section is a bimetal. 8. The micromechanical switch according to claim 1, wherein the drive means of the drive section is a shape memory alloy. 9. The micromechanical switch according to claim 1, wherein the driving means of the driving section is a magnetostrictive element. 10. The micromechanical switch according to claim 1, wherein the driving means of the driving section is a photostrictive element. 11. The micromechanical switch according to claim 1, wherein the driving means of the driving section is an electrostrictive polymer.