MEMS chip and sensor module

Abstract

The invention provides an MEMS (Micro Electro Mechanical System) chip and a sensor module, the MEMS chip comprises a support base, and a vibrating diaphragm and a back polar plate which are arranged on the support base, and the vibrating diaphragm and the back polar plate form a capacitor structure; a porous filtering assembly is arranged on one side, far away from the vibrating diaphragm, of the back polar plate; the porous filtering assembly is used for screening vibration signals entering the capacitor structure; and the vibrating diaphragm generates displacement according to a vibration signal entering the capacitor structure so as to convert the vibration signal into an electric signal. According to the invention, the accuracy of detecting the target signal by the chip can be improved.

Description

Technical Field

[0001] The present invention relates to the field of sensor technology, and more specifically, to a MEMS chip and a sensor module. Background Art

[0002] With the progress of society and the development of technology, in recent years, the size of electronic products such as mobile phones, computers, and wearable devices has been continuously reduced, and people have higher and higher performance requirements for these portable electronic products, which also requires the size of the electronic parts that match them to be continuously reduced, and the performance and consistency to be continuously improved. MEMS products integrated by MEMS (Micro-Electro-Mechanical-System, referred to as MEMS) technology have begun to be applied in batches to such electronic products, and their packaging volume is smaller than that of traditional electronic devices, for example, MEMS chips favored by most manufacturers.

[0003] At present, the main structural parts of conventional acoustic MEMS include the diaphragm and back plate that form the capacitor. The sound vibration signal is collected and analyzed by monitoring the electrical signal generated by the change in the capacitance of the capacitor caused by the deformation of the diaphragm under different sound pressures. When such MEMS devices are used in gas sensors based on the acousto-optic theory, the vibration signal generated by the excitation of the target gas molecules is received and converted into an electrical signal, thereby completing the detection of the target gas molecule concentration based on the analysis of the electrical signal. However, conventional MEMS designs have no ability to distinguish vibration signals of different frequency bands, and the vibration signals generated by the excitation of non-target gas molecules will interfere with the detection accuracy of the target gas concentration.

[0004] Therefore, there is an urgent need for a MEMS chip that can screen vibration signals of different frequencies and improve the accuracy of detecting different target gas concentrations. Summary of the invention

[0005] In view of the above problems, the purpose of the present invention is to provide a MEMS chip and a sensor module to solve the problem that existing MEMS products have no ability to distinguish vibration signals of different frequency bands, thereby affecting the accuracy of target gas concentration detection.

[0006] The MEMS chip provided by the present invention comprises a supporting base, and a diaphragm and a back plate arranged on the supporting base, wherein the diaphragm and the back plate form a capacitor structure; wherein:

[0007] A porous filter component is provided on a side of the back plate away from the diaphragm;

[0008] The porous filter assembly is used to filter the vibration signal entering the capacitor structure;

[0009] The diaphragm is displaced according to the vibration signal entering the capacitor structure to convert the vibration signal into an electrical signal.

[0010] In addition, an optional technical solution is that the porous filtration component includes at least one layer of porous membrane;

[0011] When the porous membrane is provided with at least two layers, each layer of the porous membrane is spaced apart by an insulating layer.

[0012] In addition, an optional technical solution is that the pores on the porous membrane are circular, elliptical or polygonal.

[0013] In addition, an optional technical solution is that when the porous membranes are provided in at least two groups, in a direction perpendicular to the porous membranes, the positions of the pores on two adjacent layers of the porous membranes are distributed correspondingly or staggeredly.

[0014] In addition, an optional technical solution is that a through hole is provided on the back plate; and an anti-adsorption protrusion structure is provided on a side of the back plate close to the diaphragm to avoid the distribution of the through hole.

[0015] In addition, an optional technical solution is that the porous filter component covers all the through holes on the back plate and is spaced apart from the back plate.

[0016] In addition, an optional technical solution is to provide at least one air leakage hole on the diaphragm.

[0017] In addition, an optional technical solution is to further include a first pad and a second pad exposed from the back plate; wherein the first pad is connected and conducted with the electrode layer of the back plate, and the second pad is connected and conducted with the diaphragm.

[0018] In addition, an optional technical solution is that the porous filter component is an integrally formed silicon compound.

[0019] On the other hand, the present invention further provides a sensor module, comprising a substrate and a shell forming a packaging structure with the substrate; the above-mentioned MEMS chip is arranged in the packaging structure.

[0020] By utilizing the above-mentioned MEMS chip and sensor module, a porous filter component is arranged on the side of the back plate away from the diaphragm. The vibration signal entering the capacitor structure can be screened through the porous filter component. The diaphragm is displaced according to the vibration signal entering the capacitor structure to convert the vibration signal into an electrical signal. The porous filter component can enable the sound signal of the target frequency to be picked up by the capacitor structure, thereby improving the accuracy of the chip in detecting the concentration of target molecules and reducing the difficulty of designing the back-end processing circuit.

[0021] In order to achieve the above and related purposes, one or more aspects of the present invention include the features that will be described in detail later. The following description and the accompanying drawings describe some exemplary aspects of the present invention in detail. However, these aspects indicate only some of the various ways in which the principles of the present invention can be used. In addition, the present invention is intended to include all these aspects and their equivalents. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] By referring to the following description in conjunction with the accompanying drawings, and with a more comprehensive understanding of the present invention, other objects and results of the present invention will become more apparent and easy to understand. In the accompanying drawings:

[0023] Figure 1 is a top view of a MEMS chip according to an embodiment of the present invention;

[0024] Figure 2 for Figure 1 Sectional view along line AB;

[0025] Figure 3 is a cross-sectional view of a MEMS chip according to another embodiment of the present invention;

[0026] Figure 4 is a schematic structural diagram of a porous membrane according to an embodiment of the present invention;

[0027] Figure 5 is a schematic structural diagram of a porous membrane according to another embodiment of the present invention;

[0028] Figure 6 FIG. 4 is a partial schematic structure of a porous membrane according to an embodiment of the present invention.

[0029] The accompanying drawings are marked with the following: support base 1, diaphragm 2, air leakage hole 21, back plate 3, anti-adsorption protrusion structure 4, first welding pad 51, second welding pad 52, porous filter component 6, pores 61, insulating layer 62, support layer 7.

[0030] The same reference numerals throughout the drawings indicate similar or corresponding features or functions. DETAILED DESCRIPTION

[0031] In the following description, for the purpose of illustration, in order to provide a comprehensive understanding of one or more embodiments, many specific details are set forth. However, it is apparent that these embodiments may also be implemented without these specific details. In other examples, for ease of describing one or more embodiments, known structures and devices are shown in the form of block diagrams.

[0032] In the description of the present invention, it is to be understood that the terms “center”, “longitudinal”, “lateral”, “length”, “width”, “thickness”, “up”, “down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside”, “outside”, “clockwise”, “counterclockwise”, “axial”, “radial”, “circumferential”, etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0033] It will be understood by those skilled in the art that, unless otherwise stated, the singular forms "a", "an", "said" and "the" used herein may also include plural forms. It should be further understood that the term "comprising" used in the specification of the present invention refers to the presence of the features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof. It should be understood that the term "and / or" used herein includes any unit and all combinations of one or more associated listed items.

[0034] It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as those generally understood by those skilled in the art in the art to which the present invention belongs. It should also be understood that terms such as those defined in common dictionaries should be understood to have meanings consistent with the meanings in the context of the prior art, and will not be interpreted with idealized or overly formal meanings unless defined as herein.

[0035] To describe the MEMS chip and sensor module in the present invention in detail, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0036] Figure 1 and Figure 2 The schematic structure of the MEMS chip according to the embodiment of the present invention is shown from different angles.

[0037] like Figure 1 and Figure 2As shown together, the MEMS chip of an embodiment of the present invention includes a support base 1 and a diaphragm 2 and a back plate 3 which are arranged on the support base 1 at intervals, the support base 1 includes a substrate and a support layer 7 located on the substrate, the edges of the diaphragm 2 and the back plate 3 are limited in the support layer 7 to form a parallel plate capacitor structure; wherein, a porous filter component 6 is arranged on the side of the back plate 3 away from the diaphragm 2, the porous filter component 6 can screen and filter the vibration signal entering the capacitor, so that the target signal enters the capacitor and is picked up by the diaphragm 2, the diaphragm 2 is displaced according to the vibration signal entering the capacitor structure, the displacement causes the distance between the diaphragm 2 and the back plate 3 to change, thereby converting the vibration signal into an electrical signal output, thereby completing the detection of the target signal.

[0038] Among them, the target signal can be a detection signal in various forms. For example, when the MEMS chip is used in a gas sensor based on the acousto-optic theory, the target signal can be a target gas molecule. The gas molecule is excited by external light and its temperature rises after absorbing light energy, thereby generating a vibration signal. The vibration signal can be picked up by the capacitor structure, thereby completing the detection of the concentration of the target gas molecules through the corresponding electrical signal. The porous filter component 6 is set to distinguish vibration signals of different frequency bands, thereby realizing the screening of vibration signals of different frequencies and improving the accuracy of detecting the target gas concentration.

[0039] Specifically, the porous filter assembly 6 includes at least one layer of porous membrane, and at least one layer of porous membrane can be arranged on the upper side of the back plate 3 through an isolation layer. When the porous membrane is provided with at least two layers, each layer of porous membrane can also be spaced apart by an insulating layer 62. In other words, the porous filter assembly 6 can include a plurality of porous membranes that are parallel to each other and spaced apart, and the porous membranes close to the back plate 3 are also spaced apart from the back plate 3 to avoid mutual adsorption interference between the two and affect the detection accuracy. Among them, Figure 3 The schematic structure of a layer of porous membrane according to an embodiment of the present invention is shown. In this embodiment, the porous membrane can be set on the back plate 3 by various methods such as pasting or welding after being formed.

[0040] In addition, the porous filter component 6 can be integrally formed using a silicon compound, such as silicon nitride or other silicides. Silicon oxide can be deposited between the multi-layer porous membranes for support, and the silicon oxide can be removed by etching later to form a multi-layer three-dimensional structure; wherein the spacing between the porous membranes can be adjusted according to the actual needs of the chip, and the pores 61 provided on the porous membranes can be set to be circular, elliptical or polygonal, and the pores 61 can be regular or irregular in shape, wherein, Figure 4 and Figure 5The schematic structures of the porous membranes according to the embodiments of the present invention are shown respectively, wherein the pores 61 can be set to be prototypes or regular hexagons. In addition, according to the force difference of the multilayer membrane at different positions, pores 61 with different densities or shapes can be set at different positions, thereby improving the signal filtering quality of the porous membrane.

[0041] It should be noted that the setting size, number and arrangement rules of the pores 61 located on the porous membrane can be adjusted according to actual needs. For example, the relevant parameters of the porous membrane pores 61 can be adjusted according to the frequency of the vibration signal emitted by the target gas molecules to be detected, so as to utilize the sound absorption effect of the porous membrane structure to absorb the external sound signal of non-target frequency, and only retain the vibration signal of the target frequency (the frequency of the target signal) to enter the capacitor structure to stimulate the vibration of the diaphragm 2, thereby improving the accuracy of the target signal detection.

[0042] In the MEMS chip of the present invention, the absorption effect of the pores (micropores) on the porous membrane on the vibration signals of different frequency bands is mainly due to the radial velocity gradient of the vibration signal in the gap. The relative motion under different velocity gradients generates friction resistance, which causes the viscous loss of the vibration signal. Figure 6 It can be seen that it is mainly affected by the following parameters:

[0043] 1. Pore opening size d: The vibration signal is subject to viscous resistance when propagating in the micropores. The smaller the pore size, the greater the viscous resistance the vibration signal is subject to. When the micropore size is close to the wavelength λ of the vibration signal, the scattering and refraction of the vibration signal in the pore is most obvious, the energy loss caused is also greater, and the intensity of the vibration signal near this wavelength is more obviously attenuated; the irregular opening shape will make the propagation path of the vibration signal in the pore more complicated, and its ability to attenuate the vibration signal will also increase;

[0044] 2. Micropore depth t: The depth of the micropore affects the propagation path of the vibration signal in the micropore and the interaction time between the vibration signal and the side wall of the pore. Increasing t can cause longer wavelength signals to produce effective energy loss in the micropore structure, that is, the effective absorption frequency is shifted forward, thereby increasing the frequency bandwidth of the affected vibration signal.

[0045] 3. Cavity depth D: The air layer below the surface porous membrane is equivalent to increasing the effective thickness of the porous membrane-air composite structure. The vibration signal is reflected and interfered between the back plate and the porous membrane, so that the vibration signal of some frequency bands can re-enter the surface porous structure, thereby improving the absorption effect of the frequency signal in this frequency band.

[0046] Among them, when there are at least two groups of porous membranes, in the direction perpendicular to the porous membrane, the positions of the pores 61 on the two adjacent layers of porous membranes can be one-to-one corresponding to each other, or can be staggered. The multiple groups of porous membranes are in series relationship with each other. By adjusting the parameters, the absorption effect of different frequency bands can be more conveniently adjusted to increase the affected frequency bandwidth; among them, when the positions of the multiple layers of pores 61 correspond to each other up and down, the filtering intensity of non-target signals can be enhanced, which can be used to effectively intercept non-target signals that play a major interfering role; and when the positions of the multiple layers of pores 61 are staggered, multi-frequency non-target signals can be filtered, and the specific setting method can be flexibly set according to the application scenario and detection requirements.

[0047] As a specific example, in the MEMS chip of an embodiment of the present invention, when a group of porous membranes is provided, the pore parameters of the porous membrane can be set to d=1mm, t=1mm, D=30mm. Under this parameter, the porous filter assembly can have an obvious absorption effect on 800Hz signals; when two groups of porous membranes are provided, the parameters of the upper porous membrane are d=1mm, t=1mm, D=30mm, and the parameters of the lower porous membrane are d=1mm, t=1mm, D=20mm. Under this parameter, the porous filter assembly can have an obvious absorption effect on 500Hz and 1280Hz signals, and also has a greater absorption effect on vibration signals in the intermediate frequency band.

[0048] In the MEMS chip of the embodiment of the present invention, a plurality of through holes are further arranged on the back plate 3. During the assembly process of the porous filter component 6, it can cover all the through holes on the back plate 3 and be distributed with intervals from the back plate 3. In addition, an anti-adsorption protrusion structure 4 is arranged on the side of the back plate 3 close to the diaphragm 2 to avoid the distribution of the through holes. The anti-adsorption protrusion structure 4 can prevent the diaphragm 2 from being adsorbed together with the back plate 3 during vibration. The density and size of the anti-adsorption protrusion structure 4 can be set according to the size of the chip.

[0049] In addition, the MEMS chip of the embodiment of the present invention may also be provided with at least one air leakage hole 21 on the diaphragm 2, and the air leakage hole 21 can prevent the diaphragm 2 from breaking during large-scale vibration; in addition, the MEMS chip may also include a first solder pad 51 and a second solder pad 52 exposed from the back plate 3; wherein the first solder pad 51 is connected and conductively connected to the electrode layer of the back plate 3, and the second solder pad 52 is connected and conductively connected to the diaphragm 2, and the signal transmission between the MEMS chip and the outside world can be realized through the first solder pad 51 and the second solder pad 52.

[0050] Corresponding to the above-mentioned MEMS chip, the present invention further provides a sensor module, which may include a substrate and a shell forming a packaging structure with the substrate, and the above-mentioned MEMS chip is arranged in the packaging structure.

[0051] It should be noted that the embodiments of the above-mentioned sensor module can refer to the embodiments of the MEMS chip, which will not be described one by one here.

[0052] According to the above-mentioned MEMS chip and sensor module of the present invention, a porous filter component is arranged on the side of the back plate away from the diaphragm, and the vibration signal entering the capacitor structure is screened by at least one porous membrane in the porous filter component. Vibration signals of different frequency bands can be distinguished, thereby realizing the screening of vibration signals of different frequencies, improving the accuracy of the chip in detecting the concentration of target molecules, and reducing the design difficulty of the back-end processing circuit.

[0053] The MEMS chip and sensor module according to the present invention are described as examples with reference to the accompanying drawings. However, those skilled in the art should understand that various improvements can be made to the MEMS chip and sensor module proposed by the present invention without departing from the content of the present invention. Therefore, the protection scope of the present invention should be determined by the content of the attached claims.

Claims

1. A MEMS chip, characterized in that: It includes a supporting base, a diaphragm and a back plate arranged on the supporting base, wherein the diaphragm and the back plate form a capacitor structure; wherein, A porous filter component is provided on a side of the back plate away from the diaphragm; The porous filter assembly is used to filter the vibration signal entering the capacitor structure; The diaphragm is displaced according to the vibration signal entering the capacitor structure to convert the vibration signal into an electrical signal.

2. The MEMS chip according to claim 1, characterized in that: The porous filtration component includes at least one layer of porous membrane; When the porous membrane is provided with at least two layers, each layer of the porous membrane is spaced apart by an insulating layer.

3. The MEMS chip according to claim 2, characterized in that: The pores on the porous membrane are circular, elliptical or polygonal.

4. The MEMS chip according to claim 2, characterized in that: When at least two groups of the porous membranes are provided, in a direction perpendicular to the porous membranes, positions of the pores on two adjacent layers of the porous membranes are distributed correspondingly or staggeredly.

5. The MEMS chip according to claim 1, characterized in that: A through hole is provided on the back plate; and An anti-adsorption protrusion structure is arranged on one side of the back plate close to the diaphragm to avoid the distribution of the through holes.

6. The MEMS chip according to claim 5, characterized in that: The porous filter assembly covers all through holes on the back plate and is spaced apart from the back plate.

7. The MEMS chip according to claim 1, characterized in that: At least one air leakage hole is arranged on the diaphragm.

8. The MEMS chip according to claim 1, characterized in that: It also includes a first pad and a second pad exposed from the back plate; wherein, The first pad is connected to the electrode layer of the back plate, and the second pad is connected to the diaphragm.

9. The MEMS chip according to claim 1, characterized in that: The porous filter component is an integrally formed silicon compound.

10. A sensor module, comprising a substrate and a housing forming a packaging structure with the substrate; characterized in that: The MEMS chip according to any one of claims 1 to 9 is arranged in the packaging structure.

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