JP2006294460A - Micro mechanical switch - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a micro switch that can be driven at a low voltage and at a high speed. <P>SOLUTION: Because of having a pair of electrodes that drive a movable part with a contact by static electricity, and furthermore, because of having two pairs of the electrodes for limiting movement in a direction vertical to the driving direction, switching operation can be carried out at low voltage and at high speed by basically making the movable part float from a structure, and by making force from outside as small as possible. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a micromechanical switch used in a high frequency band mainly used for mobile communication and the like.

In mobile communication, higher communication wavelengths are being promoted to support multimedia. For example, a higher frequency region than a conventionally used high frequency band such as 10 GHz is required. In such a high frequency region, an element using a conventional semiconductor has a large insertion loss and insufficient isolation, so that practically sufficient performance cannot be obtained. For this reason, development of a high-frequency switch using a micromachine technology capable of obtaining sufficient performance in terms of insertion loss and isolation is being promoted. As one of the methods, there has been proposed a method in which a switching plate-like electrode is brought into contact with a bending signal line by static electricity or the like as shown in [Patent Document 1]. In addition, a large potential of about 24 V may be required. Further, when such a large voltage is applied, a large force is applied when the switching electrode contacts the signal line, which causes a problem in terms of reliability. A switch for improving this is proposed in [Non-Patent Document 1]. In this case, the movable part basically floats from the structure. Since the upper and lower electrodes operate in a push-pull manner, a large force can be prevented from being applied from the outside and can be driven at a low voltage, but the movable part can be turned into a supporting column by external acceleration other than the movable direction. There was a drawback of being subjected to frictional force due to contact.
JP 2002-260498 SWITCH DEVICE 2005 Spring Proceedings of the 65th Joint Conference on Applied Physics

The present invention has been made in view of the above problems, and the object of the present invention is to make the movable part structured in a direction other than the direction of movement of the other movable part by the acceleration applied from the outside when the movable part is floated in the air. It is to prevent contact with the body.

Having a pair of electrodes that drive a movable part having a contact by static electricity, and further having two pairs of electrodes to restrict movement perpendicular to the driving direction, the movable part is basically floated from the structure. To reduce the external force as much as possible.

With the structure according to the present invention, unnecessary force is not applied to the movable part, so that the movable part can be driven at a low voltage and at a high speed. In addition, since it is mechanical switching, there are no unnecessary parasitic capacitances and current leaking parts, so that characteristics such as insertion loss and isolation are good. Further, since the plate thickness of the movable part does not use elastic deformation, it can be sufficiently thick within an appropriate range, so that the reliability can be improved. Further, when an electrostatic force is applied to the movable part, the damage at the moment of contact with the signal line can be reduced if this force can be appropriately controlled. Thereby, reliability can be further improved.

A micromechanical switch characterized in that, in a switch using static electricity as a driving source, part or all of a substantially plate-like movable portion having an electrode serving as a contact is floated from another structure by static electricity.

Embodiments of the present invention will be described below with reference to the accompanying drawings. However, the drawings are for explanation only and do not limit the technical scope of the present invention.

FIG. FIG. 2 is a structural diagram reported to the Japan Society of Applied Physics. For the sake of explanation, FIG. 2 shows FIG. 1 broken down into three parts. Driving electrodes 2 and 4 are arranged on the substrate at locations facing each other via the driving electrodes 1 and 3 and the movable portion 5. Here, when the movable part is charged to 3 V, the drive electrodes 1 and 2 are set to the ground potential, and the drive electrodes 3 and 4 are set to 3 V, the movable part 5 comes into contact with the tilt drive electrodes 1 and 2 to drive the drive electrode. 2, the A signal line 7 is short-circuited and the B signal line 8 is opened. When the drive electrodes 1 and 2 are set to 3 V and the drive electrodes 3 and 4 are set to the ground potential, the A signal line 7 is opened and the B signal line 8 is short-circuited. At this time, the movement of the movable part in the planar direction is restricted by contacting the support part 6.

FIG. FIG. 3 is a structural diagram of a switch according to the present invention. For the purpose of explanation, FIG. Shown in First, the driving electrode 11 and the movable part position limiting electrode 14 are provided on the substrate. The movable part is fitted in this, and the upper driving electrode 12 covers them. Actually, the assembled shape is as shown in FIG. When the movable part 13 is in contact with the upper electrode, a potential of 3 V is applied from the voltage supply part 16, and when it is in contact with the lower electrode, a potential of 3 V is applied from the signal line 15 itself. The signal line 15 is always biased to 3 V separately from the signal, and the signal line 15 is supplied to the signal line 15 via an electrostatic capacity. As a result, the movable portion 13 is always charged to about 3V. Further, the signal line 15 and the voltage supply unit 16 protrude from the lower electrode 11 and the upper electrode 12 toward the movable unit 13, so that the movable unit 13 contacts other than the signal line 15 and the voltage supply unit 16 except when the movable unit moves. I try not to. The signal line 15 is separated at the center, and is conductive only when the movable part 13 is in contact therewith.

To explain the operation, when the upper electrode 12 is 3 V and the lower electrode 11 is ground, the movable part is in contact with the lower electrode, the signal line 15 provided with an open part at the center is short-circuited, and the switch is turned on. On the other hand, when the upper electrode 12 is set to the ground potential and the lower electrode 11 is set to 3 V, the movable part is in contact with the upper electrode, the signal line 15 is opened, and the switch is turned off. At this time, a concavo-convex shape is provided around the movable portion 13, which repels against the electrode on the concavo-convex portion of the movable portion position limiting electrode 14 provided in opposition, and is perpendicular to the movable direction of the movable portion 13. Restricts movement in the direction. Assuming the case where gravity perpendicular to the movable direction is applied from the outside, in this design, when the structure is nickel, the gap between the movable portion 13 and the movable portion position limiting electrode 14 is about 3 μm at the minimum, and is in contact. Can hinder. Therefore, the switch according to the present invention can perform the switching operation without touching the movable portion 13 to the structure of the signal line 15 and the structure at any angle.

An example of the manufacturing process will be described with reference to FIG. The materials and structures are illustrative and do not limit the technical scope of the present invention. For example, a Cr / Ti pattern is formed on a glass substrate by a lift-off method. This is applied to the pattern of the upper drive electrode 11, the signal line 15, and the movable part position limiting electrode 14. Here, a part of the signal line 15 or the movable part position limiting electrode 14 is made thicker by gold plating than the other part as shown in FIG. 5a. In order to provide a gap below the movable portion, the mold of the movable portion position limiting electrode 14 is formed of a resist having a thickness of 5 μm or a metal that can be easily dissolved by alkali. The movable part limiting electrode 14 is formed by filling the nickel plating here. This is shown in FIG. The movable portion 13 and the movable portion position limiting electrode 14 are formed by nickel plating in the same manner as the movable position portion limiting electrode is formed thereon. This is shown in FIG. Further, the upper electrode 12 formed on another substrate by the same method as the lower electrode 11 is completed by bonding by anodic bonding. This is shown in FIG.

Thus, the high frequency switch according to the present invention can be formed. In such a structure, there is no force such as friction caused by contact or bending stress on the movable part, so that switching can be performed at low voltage and high speed and high reliability can be obtained. Can

The most promising application of the present invention is a high-frequency switch for a mobile communication device such as a mobile phone. At present, solid-state switches made of semiconductors are the mainstream, but it is considered that both the insertion loss and the isolation will cause problems in the further higher frequency expected in the future. Since the present invention uses a metal contact, the insertion loss is extremely small, and since the contact is spatially separated, the isolation is good. Furthermore, since the force applied to the movable part can be minimized, high-speed switching with high reliability is possible. In addition, when the contact is made, the movable part floats when contacting, so the impact is mitigated and the damage resistance is considered to be high, and it has extremely excellent characteristics. Can be expected.

It is an overhead view of the switch for high frequency by the conventional micromachine. FIG. It is the figure which decomposed | disassembled the switch of into three elements. It is an overhead view of the switch for high frequency by this invention. FIG. It is the figure which decomposed | disassembled the switch of into three elements. It is a figure which shows the manufacturing process of the lower electrode of the switch by this invention. It is a figure which shows the manufacturing process which adds the electrode for a movable part position limitation of the switch by this invention. It is a figure which shows the manufacturing process which adds the movable part of the switch by this invention. FIG. 5 shows a manufacturing process for adding an electrode on top of a switch according to the invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 3 Lower drive electrode 2, 4 Upper drive electrode 5 Movable part 6 Support part 7 A signal line 8 B signal line 11 Lower electrode 12 Upper electrode 13 Movable part 14 Movable part position limiting electrode 15 Signal line 16 Voltage supply Part

Claims (2)

In a switch using static electricity as a drive source, the electrostatic force that moves the movable part in the myromechanical switch is characterized in that a part or all of the substantially plate-like movable part having the contact electrode floats from another structure due to static electricity. A micromechanical switch comprising an electrode for generating an electrostatic force for limiting movement of a movable part in a direction perpendicular to the movable direction in addition to the generated electrode. 2. The micromechanical switch according to claim 1, further comprising an electrode for supplying a potential to the movable part itself by contacting the movable part.