WO2021243745A1

WO2021243745A1 - Mems capacitive switch

Info

Publication number: WO2021243745A1
Application number: PCT/CN2020/095628
Authority: WO
Inventors: 孔令成; 朱雁青; 王超; 李杨
Original assignee: 瑞声声学科技(深圳)有限公司
Priority date: 2020-06-02
Filing date: 2020-06-11
Publication date: 2021-12-09
Also published as: CN212322916U

Abstract

Disclosed is a MEMS capacitive switch, comprising a substrate (1), and a switch beam (4) and an effective electrode (3) which are arranged above the substrate (1). The switch beam (4) comprises a cross beam portion (42) arranged in parallel with the substrate (1) and an extension portion (41) perpendicular to the cross beam portion (42). The effective electrode (3) is arranged between the cross 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 effective electrode (3) is opposite the cross beam portion (42) of the switch beam (4), and a side wall (32) of the effective electrode (3) is opposite the extension portion (41) of the switch beam (4), so as to form a capacitor. The switch has a simple overall structure, and is a MEMS capacitive switch capable of achieving high on/off state capacitance ratios at the same time. Compared with a traditional switch only having a variable-pitch plate capacitor, charge injection is reduced, such that the service life of the switch is prolonged, the reliability of the switch is improved, and the switch is readily achieved in a process and is easy to manufacture.

Description

A MEMS capacitive switch

Technical field

The utility model relates to the field of capacitance, in particular to a MEMS capacitive switch.

Background technique

In the structural design of RF MEMS (RF: Radio Frequency, MEMS: Micro Electro Mechanical System) capacitive switches, the off/on capacitance ratio and capacitance density are two important indicators for evaluating its RF performance. In traditional RF MEMS capacitive switches, the RF capacitor area is usually a parallel plate capacitor with variable spacing. During the operation of the switch, when the facing area is determined, it passes through the upper surface of the effective electrode of the RF capacitor area and the lower surface of the metal beam. The pitch changes to determine the capacitance value of the on/off state. In this solution, the capacitance value in the on/off state is limited by the distance between the effective electrode and the metal beam, and it is not easy to achieve an ideal off/on capacitance ratio in a large range.

Therefore, it is necessary to provide an RF MEMS capacitive switch that can simultaneously achieve a high off/on capacitance ratio on the basis of a relatively simple processing process and better control.

technical problem

The purpose of the present invention is to solve the above technical problems and provide a MEMS capacitive switch capable of achieving a high off/on capacitance ratio.

Technical solutions

The technical scheme of the utility model is as follows:

The utility model provides a MEMS capacitive switch, which includes a substrate, a switch beam and an effective electrode arranged above the substrate, wherein the switch beam includes a beam part arranged in parallel with the substrate and The vertical extension portion of the beam portion, the effective electrode is arranged between the beam portion and the substrate, at least when the MEMS capacitive switch is in the off state, the top wall of the effective electrode and the switch The cross-beam part of the beam is opposite, and the side wall of the effective electrode is opposite to the extension part of the switch beam to form a capacitor.

Further, the number of the effective electrodes is N, and they are arranged at intervals in a direction parallel to the substrate, the number of the extension portions is N-1, and the number of the effective electrodes is N-1. There is one such extension part.

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

Further, the MEMS capacitive switch further includes a switch drive electrode arranged on the peripheral side of the effective electrode and an anchor point for supporting and fixing the switch beam.

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

Further, a third dielectric layer is provided 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.

Beneficial effect

The beneficial effects of the utility model are:

The utility model provides a MEMS capacitive switch. By arranging an extension part on the switch beam, the top wall of the effective electrode and the cross beam part are opposed to form a capacitor, and the extension part and the side wall of the effective electrode can also form a capacitor opposite to each other. Compared with the prior art only forming a capacitor between the top wall of the effective electrode and the beam portion, the utility model can achieve a larger off-state capacitance, thereby improving the off/on-state capacitance ratio; in addition, the whole of the utility model The structure is simple, the process is easy to realize, and the manufacturing is easy.

Description of the drawings

Figure 1 is a schematic diagram of the structure of a MEMS capacitive switch in an embodiment of the utility model;

Figure 2 is an exploded view of the MEMS capacitive switch in the embodiment of the utility model;

Fig. 3 is a cross-sectional view of the MEMS capacitive switch in the A-A direction in the embodiment of the utility model.

FIG. 4 is a schematic diagram of the off state of the MEMS capacitive switch in the embodiment of the utility model.

FIG. 5 is a schematic diagram of the open state of the MEMS capacitive switch in the embodiment of the utility model.

Embodiments of the present invention

In the following, the utility model will be further explained in conjunction with the drawings and embodiments.

Please refer to FIG. 1, this embodiment provides a MEMS capacitive switch, which includes a substrate 1, a switch beam 4 and an effective electrode 3 disposed on the substrate 1. Wherein, the switch beam 4 includes a beam portion 42 arranged in parallel with the substrate 1 and an extension portion 41 perpendicular to the beam portion 42, and the effective electrode 3 is provided on the beam portion 42 and the substrate. 1, at least when the MEMS capacitive switch is in the off state, the top wall 31 of the effective electrode 3 is opposite to the beam portion 42 of the switch beam 4, and the side wall 32 of the effective electrode 3 is opposite to the The extension 41 of the switch beam 4 is opposed to each other to form a capacitor.

In existing MEMS capacitive switches, the capacitance area is usually a parallel plate capacitor with variable spacing. During the operation of the switch, when the facing area is determined, it is determined by the change in the distance between the upper surface of the capacitance area and the lower surface of the metal beam. Capacitance value in on/off state. When the distance between the upper surface and the metal beam is limited due to requirements such as product miniaturization, it is difficult to increase the off/on capacitance ratio of this MEMS capacitive switch.

In the present utility model, the switch beam 4 includes a cross beam portion 42 and an extension portion 41. When the switch beam 4 moves closer to or away from the effective electrode 3, the cross beam portion 42 and the top wall 31 of the effective electrode face each other to form a gap between the electrodes. Variable parallel plate capacitance. The extension 41 and the side wall 32 of the effective electrode are opposed to form a parallel plate capacitor with a variable relative area between the electrodes. That is, the MEMS capacitive switch of the present invention consists of a variable pitch parallel plate capacitor and a variable distance parallel plate capacitor. The area is composed of parallel plate capacitors. According to the basic formula of capacitance: C=εS/(4πkd) (where S represents the relative area between the electrodes, and d represents the distance between the electrodes), it can be seen that the present utility model can change the value of d through the variable-pitch parallel plate capacitor, and by changing the area The parallel plate capacitor changes the value of S, so that the variation range of the capacitance C can be increased without increasing the overall height of the MEMS capacitive switch, thereby increasing the off/on capacitance ratio. In addition, compared with the traditional switch with only variable-pitch flat capacitors, the MEMS capacitive switch of the present invention reduces the charge injection effect, thereby increasing the switch life and improving the reliability, and is easy to realize in process and easy to manufacture.

In this embodiment, further referring to FIG. 1, the number of the effective electrodes 3 is preferably three, and they are arranged at intervals in a direction parallel to the substrate 1, and every two adjacent effective electrodes 3 sub-electrodes There is one extension 41 in between, that is, there are two extensions in this embodiment. Of course, in other embodiments, the extending portions 41 may be provided on both sides of the effective electrode 3 at the most edge position, and it is not limited to only being provided on the side close to the other adjacent effective electrode 3. In addition, the number of effective electrodes 3 can be set according to actual needs to achieve the purpose of optimizing capacitance, and the present invention does not limit the number.

Preferably, the surface of at least one of the top wall 31 of the effective electrode 3 and the side wall 32 of the effective electrode is provided with a first dielectric layer 33. From the basic capacitance formula of the capacitor: C=εS/(4πkd) (where ε represents the dielectric constant of the dielectric layer), it can be known that the use of a dielectric layer can increase the capacitance C. In addition, for variable pitch capacitors, the first dielectric layer 33 can be used as an insulating layer to prevent the top wall 31 of the effective electrode 3 and the switch beam 4 from short-circuiting.

Please further refer to FIGS. 1-2. The MEMS capacitive switch further includes a switch driving electrode 5 arranged on the peripheral side of the effective electrode 3 and an anchor 6 supporting and fixing the switch beam 4. When no voltage is applied to the switch driving electrode 5, the switch is in an open state. When a driving voltage is applied to both ends of the switch driving electrode 5, an electrostatic force will be generated, and the switch beam 4 will move toward the effective electrode 3 under the electrostatic force, and finally the switch will be in an off state.

Referring to FIG. 1, the substrate 1 is provided with a second dielectric layer 2 on the side facing the switch beam 4, and the effective electrode 3 and the switch driving electrode 5 are located on the second dielectric layer 2 to This constitutes a capacitor space.

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

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 FIGS. 3-5, in an embodiment, the number of effective electrodes is N, an extension 41 is provided between every two adjacent effective electrodes 3, and the top wall of the effective electrode 3 is provided with a first dielectric layer 33 , The on/off state capacitance value expressions of MEMS capacitive switches are as follows:

Among them, ε ₀ and ε _r are the dielectric constant in the vacuum and the relative dielectric constant of the first dielectric layer; A ₁ is the area of the top wall of the effective electrode, g ¹ is the top wall and the top wall of the effective electrode of the variable-pitch parallel plate capacitor The distance between the beams, d the thickness of the first dielectric layer, A _2.on and A _2.off are the area of the side wall of the effective electrode and the extension in the on state and off state, respectively, and g ² is the side of the effective electrode The distance between the wall and the extension.

The utility model proposes a new type of MEMS capacitive switch. The switch beam includes a beam part and an extension part. When the switch beam moves closer to or away from the effective electrode, the beam part and the top wall of the effective electrode face each other to form an inter-electrode distance. Variable parallel plate capacitors. The extensions and the side walls of the effective electrodes are opposed to form a parallel plate capacitor with a variable relative area between the electrodes. This can increase the range of capacitance without increasing the overall height of the switch. Increase the off/on capacitance ratio.

The above are only the embodiments of the present utility model. It should be pointed out here that for those of ordinary skill in the art, improvements can be made without departing from the inventive concept of the present utility model, but these all belong to the present utility model. New scope of protection.

Claims

A MEMS capacitive switch includes a substrate, a switch beam and an effective electrode arranged above the substrate, and is characterized in that the switch beam includes a beam part arranged parallel to the substrate and a beam part connected to the beam part. Vertical extension, the effective electrode is arranged between the beam portion and the substrate, at least when the MEMS capacitive switch is in the off state, the top wall of the effective electrode and the beam of the switch beam The sidewalls of the effective electrode are opposite to the extension part of the switch beam to form a capacitor.
The MEMS capacitive switch according to claim 1, wherein the number of the effective electrodes is N, and they are arranged at intervals in a direction parallel to the substrate, and the number of the extensions is N-1 , An extension part is provided between every two adjacent effective electrodes.
The MEMS capacitive switch according to claim 1, wherein the surface of at least one of the top wall of the effective electrode and the side wall of the effective electrode is provided with a first dielectric layer.
3. The MEMS capacitive switch according to claim 3, wherein the MEMS capacitive switch further comprises a switch drive electrode arranged on the peripheral side of the effective electrode and an anchor point for supporting and fixing the switch beam.
The MEMS capacitive switch according to claim 4, wherein a second dielectric layer is provided on the side of the substrate facing the switch beam, and the effective electrode and the switch driving electrode are located in the second dielectric layer. On the dielectric layer.
The MEMS capacitive switch according to claim 5, wherein a third dielectric layer is provided on the top surface of the switch driving electrode.
The MEMS capacitive switch according to claim 6, wherein the first dielectric layer, the second dielectric layer, and the third dielectric layer are made of silicon oxide or silicon nitride.