CN212031528U

CN212031528U - Capacitive MEMS accelerometer

Info

Publication number: CN212031528U
Application number: CN202021037658.7U
Authority: CN
Inventors: 张广平; 白龙; 刘杨; 陈首任; 万育彰
Original assignee: Chengdu Huatuo Weina Intelligent Sensor Technology Co ltd
Current assignee: Chengdu Huatuo Weina Intelligent Sensor Technology Co ltd
Priority date: 2020-06-09
Filing date: 2020-06-09
Publication date: 2020-11-27
Anticipated expiration: 2030-06-09

Abstract

The utility model discloses a capacitive MEMS accelerometer, which comprises a first fixed part, a second fixed part, a mass block, a supporting beam and a fixed frame; a plurality of first fixed polar plates and a plurality of second fixed polar plates which are respectively arranged on the first fixed part and the second fixed part are arranged in parallel and in a cross way with movable polar plates arranged on the mass block; the first fixed polar plate and the movable polar plate form a capacitor C1, and the second fixed polar plate and the movable polar plate form a capacitor C2; etching holes are formed in the first fixed polar plate, the second fixed polar plate and the movable polar plate; the right end of the mass block is connected with the fixed frame through the supporting beam. The utility model discloses a design a series of etching holes on accelerometer electric capacity polar plate, make the electric capacity polar plate form the truss structure, to a great extent has improved polar plate rigidity, has reduced the polar plate because sharp acceleration signal and the risk of adhesion or damage, has extremely low mechanical noise, wide use prospect.

Description

Capacitive MEMS accelerometer

Technical Field

The utility model relates to an inertial sensor technical field, concretely relates to capacitanc MEMS accelerometer.

Background

With the development of MEMS technology, inertial sensors have become one of the most widely used MEMS devices, and micro-accelerometers are an outstanding representative of inertial sensors. It relates to various subjects and technologies such as electronics, machinery, materials, physics, chemistry and the like, and has wide application prospect. The capacitive micro accelerometer has the advantages of high precision, low temperature sensitivity coefficient, low power consumption, wide dynamic range, micro mechanical structure and the like, so that the capacitive micro accelerometer becomes a research hotspot at home and abroad at present.

The basic principle of the capacitive micro-accelerometer is to use a capacitor as a detection interface to detect the micro-displacement of the mass block caused by the action of inertia force. The mass block is supported and connected on the base body by the elastic micro-beams. When a series of parallel plate electrodes are formed on the mass, which plates are interdigitated with corresponding plates of the fixed part to form interdigital electrodes, the interdigital electrodes constituting the capacitors can be simultaneously used to measure the displacement of the mass in the direction of acceleration by measuring the variation of the capacitance, and at the same time the mass can be restored to its original position by applying an electrostatic force in each capacitor, which electrostatic force is obtained by applying a feedback voltage by means of a feedback capacitance module therein. The electrostatic restoring force is determined by the previous capacitance displacement.

For such accelerometers based on MEMS technology, the person skilled in the art is usually faced with noise superimposed on the measurement signal. It has been demonstrated that in the case of an accelerometer structure with a series of interdigitated electrodes, part of the noise originates from the vibrations in the horizontal direction of each pair of plates. In addition, the noise is more likely to originate from the outside, and its spectrum covers the vibration frequency of the pole plate. Another consideration is that the plates become fragile when bent. Whether they are resonant or only subjected to sharp external accelerations, these plates are prone to sticking and even damage from bending, limiting the lifetime of such devices.

It is well known that during operation of inertial MEMS devices, when micro-surfaces, such as capacitive plates, touch and permanently adhere to each other, MEMS failure is caused, the so-called pull-in phenomenon. One solution to reduce the likelihood of adhesion of inertial MEMS devices is to increase the restoring force of the springs by increasing the spring rate. However, a higher spring rate means a larger spring, which reduces the compactness of the inertial MEMS device, and likewise, if the spring rate is increased, the sensitivity and signal-to-noise ratio (or SNR) of the inertial MEMS device may also be reduced. The second solution consists in reducing the static friction by applying a suitable coating (so-called "anti-adhesion layer") on the surface of the conductive plates that is liable to come into contact, but the surface coating requires a surface treatment process that has well-known drawbacks: the process is complex and the cost is high.

SUMMERY OF THE UTILITY MODEL

To the above problem, the utility model provides a capacitanc MEMS accelerometer through designing a series of through-holes on the electric capacity polar plate, makes the electric capacity polar plate form truss structure, has improved polar plate rigidity greatly, has reduced the polar plate because the risk of sharp acceleration signal adhesion or damage.

The utility model adopts the following technical proposal:

a capacitive MEMS accelerometer comprises a first fixing part, a second fixing part, a mass block, a supporting beam and a fixing frame;

a plurality of first fixed polar plates and a plurality of second fixed polar plates which are respectively arranged on the first fixing part and the second fixing part are arranged in parallel and in a cross way with a plurality of movable polar plates which are arranged on the mass block; the first fixed polar plate and the movable polar plate form a capacitor C1, and the second fixed polar plate and the movable polar plate form a capacitor C2;

etching holes are formed in the first fixed polar plate, the second fixed polar plate and the movable polar plate, so that the capacitor polar plate forms a truss structure, the rigidity and the bending resistance of the polar plate are improved, and the risk of damage to a device caused by the bow effect of the polar plate is reduced;

the right end of the mass block is connected with the fixed frame through the supporting beam.

Preferably, the pole plate backstop is arranged on the end faces, facing the movable pole plate, of the first fixed pole plate and the second fixed pole plate, so that the sticking phenomenon between the first fixed pole plate and the movable pole plate and between the second fixed pole plate and the movable pole plate are avoided.

Preferably, the pole plate stopper protrudes out of the first fixed pole plate, and the end face of the second fixed pole plate is 0.5-1 μm.

Preferably, the left side and the right side of the support beam are both provided with vertical through grooves.

Preferably, the lower end of the through groove on the left side of the supporting beam and the upper end of the through groove on the right side are both provided with arc chamfers, so that stress release is facilitated, and the influence of stress concentration caused by the vertical connection of the supporting beam 10 and the mass block 5 on capacitance detection is eliminated.

Preferably, the lower end of the through groove on the right side of the support beam is provided with a stop, so that the mass block 5 is prevented from colliding with the fixed frame 11 or even being adhered together to cause device failure when the acceleration signal is too large.

Preferably, the number of the support beams is 1-3, and the acting force of the mass block 5 on the fixed frame 11 can be buffered.

The utility model has the advantages that:

1. the utility model discloses a design a series of etching holes on accelerometer electric capacity polar plate, make the electric capacity polar plate form the truss structure, to a great extent has improved polar plate rigidity, combines the polar plate backstop structure of polar plate side, has reduced the polar plate because sharp acceleration signal and the risk of adhesion or damage, has improved the holistic quality factor of device and SNR.

2. The utility model discloses have extremely low mechanical noise, high figure of merit makes this product obvious in seismic signal pickup and energy exploration signal measurement aspect advantage, has wide use prospect.

Drawings

In order to illustrate the technical solutions of the embodiments of the present invention more clearly, the drawings of the embodiments will be briefly described below, and it is obvious that the drawings in the following description only relate to some embodiments of the present invention, and are not intended to limit the present invention.

FIG. 1 is a schematic perspective view of the present invention;

FIG. 2 is a front view of the present invention;

FIG. 3 is an enlarged schematic view of FIG. 2A according to the present invention;

fig. 4 is an enlarged schematic view of fig. 2B according to the present invention;

shown in the drawings

1-a first fixed polar plate, 2-a second fixed polar plate, 3-a first fixed part, 4-a second fixed part, 5-a mass block, 6-a movable polar plate, 7-an etching hole, 8-a stop, 9-a polar plate stop, 10-a supporting beam, 11-a fixed frame, 12-a through groove;

Detailed Description

In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the drawings of the embodiments of the present invention are combined below to clearly and completely describe the technical solution of the embodiments of the present invention. It is to be understood that the embodiments described are only some of the embodiments of the present invention, and not all of them. All other embodiments, which can be obtained by a person skilled in the art without any inventive work based on the described embodiments of the present invention, belong to the protection scope of the present invention.

Unless otherwise defined, technical or scientific terms used herein shall have the ordinary meaning as understood by one of ordinary skill in the art to which this disclosure belongs. The use of the word "comprising" or "comprises", and the like, in this disclosure is intended to mean that the elements or items listed before that word, include the elements or items listed after that word, and their equivalents, without excluding other elements or items. "upper", "lower", "left", "right", and the like are used merely to indicate relative positional relationships, and when the absolute position of the object being described is changed, the relative positional relationships may also be changed accordingly.

The present invention will be further explained with reference to the drawings and examples.

As shown in fig. 1 to 4, a capacitive MEMS accelerometer includes a first fixing portion 3, a second fixing portion 4, a mass 5, a support beam 10 and a fixing frame 11;

the first fixed part 3 is provided with a plurality of first fixed polar plates 1, the second fixed part 4 is provided with a plurality of second fixed polar plates 2, the mass block 5 is provided with a plurality of movable polar plates 6, the first fixed polar plates 1 and the second fixed polar plates 2 are arranged in parallel and in a crossed manner with the movable polar plates 6, and the first fixed polar plates 1 and the second fixed polar plates 2 are electrically insulated from the movable polar plates 6;

the parallel and crossed arrangement sequence between the first fixed polar plate 1 and the movable polar plate 6 is opposite to the parallel and crossed arrangement sequence between the second fixed polar plate 2 and the movable polar plate 6; as shown in fig. 2, the first fixed polar plate 1 and the movable polar plate 6 are arranged in a cross manner from left to right, that is, the movable polar plate 6 is arranged first and then the first fixed polar plate 1 is arranged in a cross manner, and the second fixed polar plate 2 is arranged between the second fixed polar plate 2 and the movable polar plate 6 from left to right, that is, the second fixed polar plate 2 is arranged first and then the movable polar plate 6 is arranged in a cross;

first fixed polar plate 1 and first fixed part 3, second fixed polar plate 2 and second fixed part 4, movable polar plate 6 all set up the arc chamfer with the junction of quality piece 5, are favorable to stress release, have eliminated first fixed polar plate 1 and first fixed part 3, and second fixed polar plate 2 and second fixed part 4, movable polar plate 6 is connected the influence to the electric capacity detection with the quality piece 5 perpendicular stress concentration that arouses.

The first fixed polar plate 1 and the movable polar plate 6 form a capacitor C1, and the second fixed polar plate 2 and the movable polar plate 6 form a capacitor C2;

when the mass 5 is displaced with respect to the first and

second fixing portions

3, 4, the values of the capacitor C1 and the capacitor C2 change in opposite directions. This makes it possible to measure the relative position of the mass 5. Further, in the present embodiment, applying a voltage across the terminals of the capacitor C2 generates an electrostatic force that brings the second fixed plate 2 and the movable plate 6 close to each other, thereby moving the mass 5 in the opposite direction. The mass 5 is returned to its initial position by applying a suitable voltage across capacitor C2.

The first and second

fixed plates

1, 2 and the movable plate 6 are all connected to an external circuit that can be adjusted by time-division multiplexing of clocks and measures the capacitance across each capacitor by successive periodic voltages (differential measurement of two adjacent capacitances). The duration of the measurement voltage application (load duration) is much less than the resonance period of the system.

Etching holes 7 are formed in the first fixed polar plate 1, the second fixed polar plate 2 and the movable polar plate 6, the etching holes 7 are trapezoidal or triangular, the capacitor polar plates form a truss structure, the rigidity and the bending resistance of the polar plates are improved, so that the accelerometer cannot bend and swing greatly when subjected to rapid external acceleration, and the risk of damage to devices caused by bending deformation of the polar plates is reduced. The mechanical noise reaches 40ng/√ Hz, and the accelerometer has extremely high quality factor (more than 30000).

The end faces, facing one end of the movable polar plate 6, of the first fixed polar plate 1 and the second fixed polar plate 2 are provided with polar plate backstops 9, so that the sticking phenomenon between the first fixed polar plate 1 and the movable polar plate 6 and between the second fixed polar plate 2 and the movable polar plate 6 is avoided.

The polar plate backstop 9 protrudes out of the first fixed polar plate 1, and the end surface of the second fixed polar plate 2 is 0.5-1 μm.

The right end of the mass block 5 is connected with a fixed frame 11 through a support beam 10;

vertical through grooves 12 are formed in the left side and the right side of the supporting beam 10, and arc chamfers are arranged at the lower end of the through groove 12 in the left side of the supporting beam 10 and the upper end of the through groove 12 in the right side of the supporting beam 10, so that stress release is facilitated, and the influence of stress concentration caused by the vertical connection of the supporting beam 10 and the mass block 5 on capacitance detection is eliminated;

the lower end of the through groove 12 on the right side of the supporting beam 10 is bent, and the stopping blocks 8 are arranged in the horizontal direction and the vertical direction of the bent position, so that the device failure caused by collision and even adhesion of the mass block 5 and the fixed frame 11 when the acceleration signal is too large is prevented.

The number of the support beams 10 is 1-3, and when the number of the support beams 10 is multiple, the acting force of the mass block 5 on the fixed frame 11 can be buffered.

The utility model discloses an at least a pair of electrode (first fixed polar plate 1 is decided polar plate 2 and movable polar plate 6 with movable polar plate 6 or second) when contacting, in the scheduled time, applys feedback voltage on a pair of or more pairs of electrode to produce the electrostatic force, this electrostatic force can make the quality piece take place the displacement, and the orientation is belonged to the electrostatic force, realizes breaking away from each other of adhesion polar plate (first fixed polar plate 1 and movable polar plate 6 or second fixed polar plate 2 and movable polar plate 6). In addition, in at least one of the electrode pairs, the one or more plate stops are attached to one of the electrodes of the at least one electrode pair, and the "bow effect" between the capacitor plates is optimized, reducing the likelihood of complete adhesion between the electrodes and facilitating the de-adhesion process. Also, the plate stops have very low conductivity, which avoids a complete short circuit of a pair of plates when the plates are stuck.

The above description is only a preferred embodiment of the present invention, and the present invention is not limited to the above description, and although the present invention has been disclosed with the preferred embodiment, it is not limited to the present invention, and any skilled person in the art can make some modifications or equivalent embodiments without departing from the scope of the present invention, but all the technical matters of the present invention are within the scope of the present invention.

Claims

1. A capacitive MEMS accelerometer is characterized by comprising a first fixing part (3), a second fixing part (4), a mass block (5), a supporting beam (10) and a fixing frame (11);

a plurality of first fixed polar plates (1) and a plurality of second fixed polar plates (2) which are respectively arranged on the first fixing part (3) and the second fixing part (4) are arranged in parallel and in a cross way with a plurality of movable polar plates (6) which are arranged on the mass block (5);

etching holes (7) are formed in the first fixed polar plate (1), the second fixed polar plate (2) and the movable polar plate (6);

the right end of the mass block (5) is connected with the fixed frame (11) through a supporting beam (10).

2. A capacitive MEMS accelerometer according to claim 1, wherein the first (1) and second (2) fixed plates are provided with plate stops (9) on their end faces facing the movable plate (6).

3. A capacitive MEMS accelerometer according to claim 2, wherein the plate stop (9) protrudes beyond the first fixed plate (1) and the second fixed plate (2) has an end surface of 0.5-1 μm.

4. A capacitive MEMS accelerometer according to claim 1, wherein the support beam (10) is provided with vertical through slots (12) on both left and right sides.

5. A capacitive MEMS accelerometer according to claim 4, wherein the support beam (10) has curved chamfers at the lower end of the left side channel (12) and at the upper end of the right side channel (12).

6. A capacitive MEMS accelerometer according to claim 5, wherein the lower end of the through slot (12) at the right side of the support beam (10) is provided with a stop (8).

7. A capacitive MEMS accelerometer according to claim 6, wherein the number of support beams (10) is 1-3.