CN212322916U

CN212322916U - MEMS capacitive switch

Info

Publication number: CN212322916U
Application number: CN202020986486.1U
Authority: CN
Inventors: 孔令成; 朱雁青; 王超; 李杨
Original assignee: AAC Acoustic Technologies Shenzhen Co Ltd
Current assignee: AAC Technologies Holdings Shenzhen Co Ltd
Priority date: 2020-06-02
Filing date: 2020-06-02
Publication date: 2021-01-08
Anticipated expiration: 2030-06-02
Also published as: WO2021243745A1

Abstract

The utility model provides a MEMS capacitive switch, including the substrate and set up in switch roof beam and the effective electrode of substrate top, the switch roof beam include with substrate parallel arrangement's crossbeam portion and with crossbeam portion vertically extension, effective electrode set up in crossbeam portion with between the substrate, at least when MEMS capacitive switch is in the off-state, the roof of effective electrode with the crossbeam portion of switch roof beam is relative, the lateral wall of effective electrode with the extension of switch roof beam is relative to form the condenser. Switch overall structure simple, be one kind can realize simultaneously that high off/open-state electric capacity compares MEMS capacitive switch, compare with the traditional switch that only has variable interval dull and stereotyped electric capacity, reduced charge injection to increased the switch life-span, improved the reliability of switch, realized easily in the technology, easily make.

Description

MEMS capacitive switch

[ technical field ] A method for producing a semiconductor device

The utility model relates to an electric capacity field especially relates to a MEMS capacitive switch.

[ background of the invention ]

In the structural design of an RF MEMS (RF: radio frequency, MEMS: micro electro mechanical system) capacitive switch, the off/on capacitance ratio and the capacitance density are two important indexes for evaluating the RF performance. In a conventional RF MEMS capacitive switch, the RF capacitive area is usually a parallel plate capacitor with variable spacing, and the capacitance value of the on/off state of the switch is determined by the variation of the spacing between the upper surface of the effective electrode of the RF capacitive area and the lower surface of the metal beam under the condition that the facing area is determined during the operation of the switch. In this scheme, the on/off capacitance is limited by the spacing between the active electrode and the metal beam, and it is not easy to achieve the desired off/on capacitance ratio over a wide range.

Therefore, there is a need for an RF MEMS capacitive switch that can achieve a high off/on capacitance ratio simultaneously, while the process is relatively simple and well controlled.

[ Utility model ] content

An object of the utility model is to solve above-mentioned technical problem, provide a can realize the MEMS capacitive switch of high off/on-state capacitance ratio.

The technical scheme of the utility model as follows:

the utility model provides a MEMS capacitive switch, including the substrate and set up in switch roof beam and the effective electrode of substrate top, wherein, the switch roof beam include with substrate parallel arrangement's crossbeam portion and with crossbeam portion vertically extension, effective electrode set up in crossbeam portion with between the substrate, at least when MEMS capacitive switch is in the off-state, the roof of effective electrode with the crossbeam portion of switch roof beam is relative, the lateral wall of effective electrode with the extension of switch roof beam is relative to form the condenser.

Furthermore, the number of the effective electrodes is N, the effective electrodes are arranged at intervals along a direction parallel to the substrate, the number of the extending parts is N-1, and one extending part is arranged between every two adjacent effective electrodes.

Preferably, a surface of at least one of a top wall of the active electrode and a sidewall of the active electrode is provided with a first dielectric layer.

Furthermore, the MEMS capacitive switch also comprises a switch driving electrode arranged on the periphery of the effective electrode and an anchor point for supporting and fixing the switch beam.

Furthermore, a second dielectric layer is arranged on one side, facing the switch beam, of the substrate, and the effective electrode and the switch driving electrode are located on the second dielectric layer.

Furthermore, a third dielectric layer is arranged on the top surface of the switch driving electrode.

Preferably, the first dielectric layer, the second dielectric layer and the third dielectric layer are made of silicon oxide or silicon nitride.

The beneficial effects of the utility model reside in that:

the utility model provides a MEMS capacitive switch, through set up the extension on the switch roof beam, outside roof and the relative formation condenser of crossbeam portion of effective electrode, the extension also can form the condenser relatively with the lateral wall of effective electrode. Compared with the prior art in which a capacitor is only formed between the top wall and the beam part of the effective electrode, the utility model can realize larger off-state capacitance, thereby improving the off/on-state capacitance ratio; in addition, the utility model has the advantages of simple integral structure, easy realization in the technology, easy manufacturing.

[ description of the drawings ]

Fig. 1 is a schematic structural diagram of an MEMS capacitive switch according to an embodiment of the present invention;

fig. 2 is an exploded view of an MEMS capacitive switch in an embodiment of the present invention;

fig. 3 is a sectional view of an embodiment of the present invention along a-a direction of a MEMS capacitive switch.

Fig. 4 is an off-state diagram of a MEMS capacitive switch according to an embodiment of the present invention.

Fig. 5 is an on-state diagram of a MEMS capacitive switch according to an embodiment of the present invention.

[ detailed description ] embodiments

The present invention will be further described with reference to the accompanying drawings and embodiments.

Referring to fig. 1, the present embodiment provides a MEMS capacitive switch, which includes a substrate 1, and a switch beam 4 and an active electrode 3 disposed above the substrate 1. Wherein the switch beam 4 comprises a beam portion 42 arranged parallel to the substrate 1 and an extension portion 41 perpendicular to the beam portion 42, the active electrode 3 is arranged between the beam portion 42 and the substrate 1, at least when the MEMS capacitive switch is in an off-state, a top wall 31 of the active electrode 3 is opposite to the beam portion 42 of the switch beam 4, and a side wall 32 of the active electrode 3 is opposite to the extension portion 41 of the switch beam 4, so as to form a capacitor.

In the existing MEMS capacitive switch, a capacitance region is usually a parallel plate capacitor with a variable spacing, and a capacitance value in an on/off state is determined by a variation in the spacing between an upper surface of the capacitance region and a lower surface of a metal beam in a working process of the switch under the condition that a facing area is determined. When the distance between the upper surface and the metal beam is limited due to the requirements of product miniaturization and the like, the off/on capacitance ratio of the MEMS capacitive switch is difficult to improve.

The utility model discloses in, switch beam 4 includes crossbeam portion 42 and extension 41, is close to or keeps away from the in-process that effective electrode 3 removed at switch beam 4, and crossbeam portion 42 and the roof 31 of effective electrode are relative and form the changeable parallel plate electric capacity of an inter-electrode relative distance, and extension 41 and the lateral wall 32 of effective electrode are relative and form the changeable parallel plate condenser of an inter-electrode relative area, promptly the utility model discloses a MEMS capacitive switch comprises a variable distance parallel plate condenser and a variable area parallel plate condenser. From the basic equation of capacitance: c ═ S/(4 pi kd) (where S represents the relative area between the electrodes and d represents the distance between the electrodes), the present invention can change the value of d by the variable-pitch parallel plate capacitor and change the value of S by the variable-area parallel plate capacitor, thereby increasing the variation range of the capacitance value C without increasing the overall height of the MEMS capacitive switch, and thus increasing the off/on capacitance ratio. In addition, compare with the traditional switch that only has variable interval plate capacitor, the utility model discloses a MEMS capacitive switch has reduced the charge injection effect to increased the switch life-span, improved the reliability, realized easily in the technology, easily made.

In this embodiment, referring to fig. 1, the number of the effective electrodes 3 is preferably 3, and the effective electrodes are spaced apart from each other in a direction parallel to the substrate 1, and one of the extending portions 41 is disposed between every two adjacent effective electrodes 3, that is, the number of the extending portions is 2 in this embodiment. Of course, in other embodiments, the extension portions 41 may be disposed on both sides of the effective electrode 3 at the edge-most position, and are not limited to be disposed only on the side close to another adjacent effective electrode 3. In addition, the number of the effective electrodes 3 can be set according to actual needs to achieve the purpose of optimizing the capacitance, and the utility model discloses do not limit its quantity.

Preferably, the surface of at least one of the top wall 31 of the active electrode 3 and the side wall 32 of the active electrode is provided with a first dielectric layer 33. From the basic capacitance equation for capacitance: c ═ S/(4 pi kd) (where epsilon represents the dielectric constant of the dielectric layer) it is known that the capacitance C can be increased by using the dielectric layer. In addition, for a variable pitch capacitor, the first dielectric layer 33 may act as an insulating layer to prevent the top wall 31 of the effective electrode 3 and the switch beam 4 from being shorted.

Referring to fig. 1-2, the MEMS capacitive switch further includes a switch driving electrode 5 disposed around the effective electrode 3 and an anchor point 6 supporting and fixing the switch beam 4. When no voltage is applied to the switch driving electrode 5, the switch is in an on state. When a driving voltage is applied to the two ends of the switch driving electrode 5, an electrostatic force is generated, and the switch beam 4 moves towards the effective electrode 3 under the action of the electrostatic force, and finally the off state of the switch is formed.

Referring to fig. 1, a second dielectric layer 2 is disposed on a side of the substrate 1 facing the switch beam 4, and the effective electrode 3 and the switch driving electrode 5 are disposed on the second dielectric layer 2, so as to form a capacitor space.

Further, referring to fig. 1, the top surface of the switch driving electrode 5 is provided with a third dielectric layer 51.

Preferably, the first dielectric layer 33, the second dielectric layer 2, and the third dielectric layer 51 are made of silicon oxide or silicon nitride.

Referring to fig. 3-5, in an embodiment, the number of the effective electrodes is N, 1 extending portion 41 is disposed between every two adjacent effective electrodes 3, the top wall of the effective electrode 3 is disposed with the first dielectric layer 33, and the on/off capacitance expressions of the MEMS capacitive switch are respectively as follows:

wherein epsilon₀、ε_rThe dielectric constant in vacuum and the relative dielectric constant of the first dielectric layer are respectively; a. the₁Area of the top wall, g, which is an effective electrode₁The distance between the top wall and the beam part of the effective electrode of the variable-pitch parallel plate capacitor, the thickness of the first dielectric layer, A_2.on、A_2.offThe area g is the facing area of the side wall of the effective electrode and the extension part in the on state and the off state respectively₂The distance between the sidewall of the effective electrode and the extension part.

The utility model provides a novel MEMS capacitive switch, the switch roof beam include crossbeam portion and extension, be close to or keep away from the in-process that effective electrode removed at the switch roof beam, crossbeam portion and effective electrode's roof are relative and form the changeable parallel plate electric capacity of an inter-electrode interval, the lateral wall of extension and effective electrode is relative and form the changeable parallel plate condenser of relative area between an electrode to under the condition that does not increase switch overall height, the change scope of multiplicable capacity value, thereby increase the off/on-state capacitance ratio.

The above are only embodiments of the present invention, and it should be noted that, for those skilled in the art, modifications can be made without departing from the inventive concept, but these all fall into the protection scope of the present invention.

Claims

1. A MEMS capacitive switch comprises a substrate, a switch beam and an effective electrode, wherein the switch beam and the effective electrode are arranged above the substrate, the switch beam comprises a beam part parallel to the substrate and an extension part perpendicular to the beam part, the effective electrode is arranged between the beam part and the substrate, at least when the MEMS capacitive switch is in an off state, the top wall of the effective electrode is opposite to the beam part of the switch beam, and the side wall of the effective electrode is opposite to the extension part of the switch beam so as to form a capacitor.

2. The MEMS capacitive switch of claim 1, wherein the number of the active electrodes is N, and the active electrodes are spaced apart in a direction parallel to the substrate, and the number of the extensions is N-1, and one extension is disposed between each adjacent two of the active electrodes.

3. The MEMS capacitive switch of claim 1 wherein a surface of at least one of a top wall of the active electrode and a sidewall of the active electrode is provided with a first dielectric layer.

4. The MEMS capacitive switch of claim 3, further comprising a switch driving electrode disposed on a periphery of the active electrode and an anchor point supporting and fixing the switch beam.

5. The MEMS capacitive switch of claim 4 wherein a second dielectric layer is disposed on a side of the substrate facing the switch beam, and the active electrode and the switch drive electrode are disposed on the second dielectric layer.

6. The MEMS capacitive switch of claim 5 wherein the top surface of the switch drive electrode is provided with a third dielectric layer.

7. The MEMS capacitive switch of claim 6, wherein the first, second, and third dielectric layers are silicon oxide or silicon nitride.