CN219751919U

CN219751919U - Capacitive MEMS device

Info

Publication number: CN219751919U
Application number: CN202320216680.5U
Authority: CN
Inventors: 威特·弗雷克; 威廉姆斯·凯特; 黄莉
Original assignee: Meixin Semiconductor Tianjin Co ltd
Current assignee: Meixin Semiconductor Tianjin Co ltd
Priority date: 2022-12-30
Filing date: 2023-02-14
Publication date: 2023-09-26
Anticipated expiration: 2033-02-14
Also published as: CN116143067A

Abstract

The present utility model provides a capacitive MEMS device comprising: a MEMS device comprising a detection capacitance comprising a first electrode, a second electrode, and a mass; a detection circuit; a first switching circuit coupled to the first electrode; and a second switching circuit coupled to the second electrode. In a first stage of self-inspection, the first switch circuit couples the first electrode to the first power terminal, and the second switch circuit couples the second electrode to the second power terminal; in a second stage of self-checking, a first switch circuit couples a first electrode to a first input end of the detection circuit, a second switch circuit couples a second electrode to a second input end of the detection circuit, and the detection circuit detects signals of the first electrode and the second electrode and outputs a self-checking response signal, and whether the MEMS device is normal or not is determined based on the self-checking response signal. Thus, the self-test can be completed without adding an additional self-test electrode.

Description

Capacitive MEMS device

[ field of technology ]

The utility model relates to the field of MEMS (Micro-Electro-Mechanical System, micro-electromechanical system) devices, in particular to a capacitive MEMS device.

[ background Art ]

To ensure proper system of the MEMS device, the MEMS device typically includes a self-test system. In the prior art, self-inspection of MEMS devices is accomplished by using a pair of additional self-inspection electrodes and applying a voltage to the self-inspection electrodes to create an electrostatic force. The additionally arranged self-checking electrode brings about the increase of the circuit area and improves the production cost. In addition, existing MEMS devices also require separate self-test circuitry, which also increases cost.

Therefore, a new solution is needed to solve the above problems.

[ utility model ]

It is an object of the present utility model to provide a capacitive MEMS device with multiplexing electrodes, which can complete self-inspection of the MEMS device without adding any additional electrodes, thereby avoiding the increase of circuit area caused by adding additional electrodes.

To solve the above problems, according to one aspect of the present utility model, the present utility model provides a capacitive MEMS device, comprising: a MEMS device comprising a detection capacitance comprising a first electrode, a second electrode, and a mass; the detection circuit comprises a first input end, a second input end and an output end; a first switch circuit coupled to the first electrode for selectively coupling the first electrode to a first input terminal or a first power terminal of the detection circuit; a second switching circuit coupled to the second electrode for selectively coupling the second electrode to a second input terminal or a second power supply terminal of the detection circuit; in the first stage of self-checking, the first switch circuit is controlled to couple the first electrode to the first power end, and the second switch circuit is controlled to couple the second electrode to the second power end; in a second stage of self-checking, the first switch circuit is controlled to couple the first electrode to the first input end of the detection circuit, the second switch circuit is controlled to couple the second electrode to the second input end of the detection circuit, the detection circuit detects signals of the first electrode and the second electrode and outputs self-checking response signals, and whether the MEMS device is normal or not is determined based on the self-checking response signals.

Compared with the prior art, the self-checking device and the self-checking method have the advantages that the electrode of the detection capacitor is multiplexed, and the self-checking is carried out through the electrode of the detection capacitor, so that the self-checking of the MEMS device can be finished without adding any additional electrode, and the increase of circuit area caused by adding the additional electrode is avoided. In addition, the sensitivity of the MEMS device can be improved.

[ description of the drawings ]

In order to more clearly illustrate the technical solutions of the embodiments of the present utility model, the drawings that are needed in the description of the embodiments will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present utility model, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art. Wherein:

FIG. 1 is a schematic diagram of a capacitive MEMS device in one embodiment of the utility model;

FIG. 2 is a schematic diagram of a capacitive MEMS device according to the present utility model in a first stage of self-inspection;

FIG. 3 is a schematic diagram of a capacitive MEMS device according to the present utility model in a second phase of self-test;

FIG. 4 is a schematic diagram of a self-test response signal meeting predetermined conditions obtained during self-test of the capacitive MEMS device according to the present utility model.

[ detailed description ] of the utility model

In order that the above-recited objects, features and advantages of the present utility model will become more readily apparent, a more particular description of the utility model will be rendered by reference to the appended drawings and appended detailed description.

Reference herein to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic may be included in at least one implementation of the utility model. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments.

In the present utility model, unless specifically stated otherwise, the terms connected, coupled, and the like, herein, mean either directly or indirectly electrically connected. For example, a is connected to B, which may be a direct connection or an indirect connection through an intermediate medium, where the intermediate medium may be a basic electrical element (resistor, capacitor, inductor, switch, transistor, etc.), or may be a resistor having a certain function, such as a filter, an amplifier, etc. The specific meaning of the above terms in the present utility model can be understood by those of ordinary skill in the art according to the specific circumstances.

The utility model provides a capacitance MEMS device with multiplexing electrodes, which can complete self-inspection of the MEMS device without adding any additional electrodes, and avoids the increase of circuit area caused by adding the additional electrodes.

FIG. 1 is a schematic diagram of a capacitive MEMS device 100 in one embodiment of the utility model. As shown in fig. 1, the capacitive MEMS apparatus 100 includes a MEMS device 110 and a circuit portion 120.

The MEMS device 110 comprises a detection capacitance comprising a first electrode P, a second electrode n and a mass 113. The circuit part 120 includes a first switching circuit 121 coupled to the first electrode P, a second switching circuit 122 coupled to the second electrode N, and a detection circuit 123. The detection circuit 123 includes a first input terminal SWP, a second input terminal SWN, and an output terminal out. The first switch circuit 121 selectively couples the first electrode P to the first input terminal or the first power terminal of the detection circuit 123, and the second switch circuit 122 selectively couples the second electrode P to the second input terminal or the second power terminal of the detection circuit 123.

Specifically, the first power supply terminal is coupled to one of the power supply voltage AVDD or the ground terminal GND, and the second power supply terminal is coupled to the other of the power supply voltage AVDD or the ground terminal GND. In the example shown in fig. 1, the first power supply terminal is coupled to the power supply voltage AVDD, and the second power supply terminal is coupled to the ground terminal GND. In another embodiment, the first power terminal may be coupled to the ground terminal GND, and the second power terminal may be coupled to the power voltage AVDD. Of course, other connections for the first power source terminal and the second power source terminal are also possible.

The detection capacitor may comprise a capacitor or a differential capacitor pair. In each of the figures, the detection capacitance is described by way of example as comprising a differential capacitance pair. In addition, it should be noted that fig. 1 only schematically illustrates the principle structure of the MEMS device 110, and the detailed structure of the MEMS device 110 is designed and implemented according to the design, and this is not repeated herein because this is not an important point of the present utility model.

As shown in fig. 1, the detection capacitor further includes a first capacitor plate 111 coupled to the first electrode P, a second capacitor plate 112 coupled to the second electrode N, and a third electrode APM coupled to the mass 113. The mass block 113 and the first capacitor plate 111 form a first differential capacitor Cp, the mass block 113 and the second capacitor plate 112 form a second differential capacitor Cn, and the first differential capacitor Cp and the second differential capacitor Cn form the differential capacitor pair. As the mass 113 moves, one of the capacitance values of the first differential capacitance Cp and the second differential capacitance Cn increases, while the other decreases. In general, the capacitance value of the differential capacitor pair is the difference between the capacitance values of the first differential capacitor Cp and the second differential capacitor Cn, and when the mass 113 is in the equilibrium position, the capacitance value of the differential capacitor pair is 0, and the further the mass 113 is deviated from the equilibrium position, the larger the absolute value of the capacitance value of the differential capacitor pair is. The direction of displacement of the mass 113 may be represented by the positive and negative values of the capacitance of the differential capacitance pair.

In normal operation of the capacitive MEMS device 100, the first switch circuit 121 couples the first electrode P to the first input terminal of the detection circuit 123, and the second switch circuit 122 couples the second electrode P to the second input terminal of the detection circuit 123.

The self-test principle of the capacitive MEMS device is described below. In the present utility model, the self-test includes two stages. FIG. 2 is a schematic diagram of a capacitive MEMS device according to the present utility model in a first stage of self-inspection. FIG. 3 is a schematic diagram of a capacitive MEMS device according to the present utility model in a second stage of self-inspection.

The capacitive MEMS device 100 also includes a third switching circuit (not shown) coupled with the third electrode APM.

As shown in fig. 2, during the first stage of the self-test, the first switch circuit 121 is controlled to couple the first electrode P to the first power terminal, the second switch circuit 122 is controlled to couple the second electrode N to the second power terminal, as shown in fig. 1, wherein the first power terminal is coupled to the power voltage AVDD and the second power terminal is coupled to the ground GND. In addition, in the first stage of the self-test, the third switch circuit is controlled to couple the third electrode APM to one of the power voltage AVDD or the ground GND, as shown in fig. 1, when the third electrode APM is coupled to the power voltage AVDD. In the first stage of self-test, the mass 113 moves to deviate from the equilibrium position under the influence of an electric field. Specifically, the mass 113 moves toward the second capacitive plate 112. The capacitances of the first differential capacitor Cp and the second differential capacitor Cn change inversely, i.e. the capacitance of Cn increases, and the capacitance of Cp decreases, i.e. the absolute value of the capacitance of the differential capacitor pair increases gradually from 0. For a certain period of time in the first phase.

As shown in fig. 3, in the second phase of the self-test, the first switch circuit 121 is controlled to couple the first electrode P to the first input terminal of the detection circuit 123, the second switch circuit 122 is controlled to couple the second electrode N to the second input terminal of the detection circuit 123, and the third switch circuit is controlled to couple the third electrode APM to the ac driving signal, which is the same as the ac driving signal to which the third electrode APM is coupled during normal operation of the MEMS device. At this time, the mass 113 returns to the equilibrium position, and the signals of the first electrode P and the second electrode N reflect the capacitance changes of the first differential capacitance and the second differential capacitance, thereby reflecting the position of the mass 113. That is, in theory, the absolute value of the capacitance value of the differential capacitor pair gradually decays from a larger value to 0 in the second phase.

As shown in fig. 3, in the second stage of the self-test, the detection circuit 123 detects the signals of the first electrode P and the second electrode N and outputs a self-test response signal, and determines whether the MEMS device 110 functions normally based on the self-test response signal. The detection circuit 123 includes an analog-to-digital converter ADC and a filter. The first input of the analog-to-digital converter is coupled to the first input of the detection circuit 123, the second input of the analog-to-digital converter is coupled to the second input of the detection circuit 123, the output of the analog-to-digital converter is coupled to the input of the filter, and the output of the filter is coupled to the output of the detection circuit 123. The filter may be a low pass filter. The detection circuit 123 may further comprise a signal amplifier located before the analog-to-digital converter ADC.

In one embodiment, the MEMS device is considered to function properly and self-test passes if the self-test response signal satisfies a predetermined condition. And if the self-checking response signal does not meet the preset condition, the MEMS device is considered to be abnormal, and the self-checking is failed. Fig. 4 is a schematic diagram of a self-checking response signal meeting a predetermined condition obtained by the capacitive MEMS device 100 according to the present utility model during self-checking. As shown in fig. 4, the ordinate represents the absolute value of the capacitance value of the differential capacitance pair, and the abscissa represents time, the absolute value of the capacitance value of the differential capacitance pair gradually decays from a larger value to 0. If the self-checking response signal is continuously a fixed value, or cannot reach a preset maximum value, or cannot return to 0, etc., the MEMS device is considered to be abnormal, and the self-checking is failed.

In an alternative embodiment, the third switching circuit may be controlled to couple the third electrode APM to a dc voltage signal during the second phase of the self-test when the MEMS device is used in a gyroscope application, where the dc voltage signal is the same as the dc voltage signal to which the third electrode APM is coupled during normal operation of the MEMS device.

In another alternative embodiment, the detection capacitor includes only one capacitor, and then the detection capacitor includes only the first electrode P and the second electrode N, and does not include the third electrode, and the mass 113 may be one of the first capacitor plate 111 and the second capacitor plate 112.

According to the utility model, the electrode of the detection capacitor is multiplexed, and self-detection is carried out through the electrode of the detection capacitor, so that the self-detection of the MEMS device can be completed without adding any additional electrode, and the increase of circuit area caused by adding the additional electrode is avoided. In addition, the sensitivity of the MEMS device can be improved.

According to another aspect of the present utility model, the present utility model proposes a self-test method based on the capacitive MEMS device 100 described above.

The self-checking method comprises the following steps:

step one: in the first stage of self-checking, the first switch circuit is controlled to couple the first electrode to the first power end, the second switch circuit is controlled to couple the second electrode to the second power end, and the mass block moves to deviate from the balance position under the action of an electric field;

step two: in the second stage of self-checking, the first switch circuit is controlled to couple the first electrode to the first input end of the detection circuit, the second switch circuit is controlled to couple the second electrode to the second input end of the detection circuit, the mass block returns to the balance position, and the signals of the first electrode and the second electrode reflect the position of the mass block. The detection circuit detects signals of the first electrode and the second electrode and outputs a self-checking response signal, and whether the MEMS device is normal or not is determined based on the self-checking response signal.

In one embodiment, the first power terminal is coupled to one of a power supply voltage or a ground terminal, and the second power terminal is coupled to the other of the power supply voltage or the ground terminal. And if the self-checking response signal meets the preset condition, the MEMS device is considered to be normal in function, the self-checking is passed, and if the self-checking response signal does not meet the preset condition, the MEMS device is considered to be abnormal, and the self-checking is not passed.

For more details of the self-test method, please refer to the related description of the capacitive MEMS device 100, which is not repeated here.

In the description of the present specification, a description referring to terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present utility model. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Further, one skilled in the art may combine and combine the different embodiments or examples described in this specification.

While embodiments of the present utility model have been shown and described above, it will be understood that the above embodiments are illustrative and not to be construed as limiting the utility model, and that variations, modifications and alternatives to the above embodiments may be made by those skilled in the art within the scope of the utility model.

Claims

1. A capacitive MEMS device, comprising:

a MEMS device comprising a detection capacitance comprising a first electrode, a second electrode, and a mass;

the detection circuit comprises a first input end, a second input end and an output end;

a first switch circuit coupled to the first electrode for selectively coupling the first electrode to a first input terminal or a first power terminal of the detection circuit;

a second switching circuit coupled to the second electrode for selectively coupling the second electrode to a second input terminal or a second power supply terminal of the detection circuit;

in the first stage of self-checking, the first switch circuit is controlled to couple the first electrode to the first power end, and the second switch circuit is controlled to couple the second electrode to the second power end;

in a second stage of self-checking, the first switch circuit is controlled to couple the first electrode to the first input end of the detection circuit, the second switch circuit is controlled to couple the second electrode to the second input end of the detection circuit, the detection circuit detects signals of the first electrode and the second electrode and outputs self-checking response signals, and whether the MEMS device is normal or not is determined based on the self-checking response signals.

2. The capacitive MEMS device of claim 1, wherein,

the first power terminal is coupled to one of a power supply voltage or a ground terminal, the second power terminal is coupled to the other of the power supply voltage or the ground terminal,

in the first stage of self-checking, the mass moves to deviate from the balance position under the action of an electric field;

in the second phase of self-test, the mass is returned to the equilibrium position, and the signals of the first electrode and the second electrode reflect the position of the mass.

3. The capacitive MEMS device, as recited in claim 1, wherein if the self-test response signal satisfies a predetermined condition, the MEMS device is deemed to function properly, the self-test passes,

and if the self-checking response signal does not meet the preset condition, the MEMS device is considered to be abnormal, and the self-checking is failed.

4. The capacitive MEMS device of claim 1, wherein,

the detection capacitor comprises a first capacitor plate coupled with the first electrode, a second capacitor plate coupled with the second electrode and a third electrode coupled with the mass block, the mass block and the first capacitor plate form a first differential capacitor, the mass block and the second capacitor plate form a second differential capacitor, the first differential capacitor and the second differential capacitor form a differential capacitor pair,

in the first stage of self-checking, the mass block moves to deviate from the balance position under the action of an electric field, and the capacitance of the first differential capacitor and the capacitance of the second differential capacitor are inversely changed;

and in the second stage of self-detection, the mass block returns to the balance position, and the signals of the first electrode and the second electrode reflect the capacitance changes of the first differential capacitor and the second differential capacitor so as to reflect the position of the mass block.

5. The capacitive MEMS device of claim 4, further comprising a third switching circuit coupled to the third electrode,

in the first stage of self-test, the third switch circuit is controlled to couple the third electrode to one of the power voltage or the ground terminal,

in the second phase of self-inspection, the third switch circuit is controlled to couple the third electrode to the AC driving signal or the DC voltage signal.

6. The capacitive MEMS device of claim 4, wherein the detection circuit comprises an analog-to-digital converter and a filter,

the first input end of the analog-to-digital converter is coupled to the first input end of the detection circuit, the second input end of the analog-to-digital converter is coupled to the second input end of the detection circuit, the output end of the analog-to-digital converter is coupled to the input end of the filter, the output end of the filter is coupled to the output end of the detection circuit,

the capacitance value of the differential capacitor pair is the difference between the capacitance values of the first differential capacitor and the second differential capacitor, when the mass block is positioned at the balance position, the capacitance value of the differential capacitor pair is 0, and the farther the mass block is deviated from the balance position, the larger the absolute value of the capacitance value of the differential capacitor pair is.