Novel capacitive MEMS pressure sensor

Abstract

The utility model discloses a novel capacitive MEMS pressure sensor, which comprises a sensitive structure layer, a bonding layer and a bottom plate layer which are sequentially arranged from top to bottom, and a closed vacuum cavity is defined by the sensitive structure layer, the middle part of the bottom plate layer and the bonding layer; the sensitive structure layer comprises a sensitive layer frame and a sensitive layer capacitance plate, and the bottom plate layer comprises a bottom layer outer frame and a bottom layer capacitance plate; the middle parts of the sensitive layer frame and the bottom layer outer frame are correspondingly provided with a sensitive layer capacitance plate and a bottom layer capacitance plate respectively; the peripheral side of the sensitive layer capacitance plate is connected with the sensitive layer frame through a sensitive layer elastic film; a capacitance gap located in the vacuum cavity is formed between the sensitive layer capacitance plate and the bottom layer capacitance plate. Deformation under the action of external pressure mainly occurs at the elastic thin film, the deformation quantity of the sensitive layer capacitance polar plate is small, the linearity between the capacitance value variation and the air pressure or pressure variation is effectively improved, and good practicability is achieved.

Description

Technical Field

[0001] The utility model belongs to the technical field of capacitive pressure sensors, and in particular relates to a novel capacitive MEMS pressure sensor. Background Art

[0002] MEMS pressure sensor is one of the typical applications of MEMS technology in the field of sensor devices. MEMS pressure sensors are widely used in the fields of automobiles, consumer electronics, industrial control, medical, etc., for the detection of information such as air pressure and hydraulic pressure. MEMS pressure sensors are currently mainly of piezoresistive, resonant, capacitive and other types. Piezoresistive MEMS pressure sensors have the advantages of low cost and simple detection circuit, but they have the disadvantages of large temperature drift and low precision. Resonant MEMS pressure sensors have extremely high precision, but their structure is complex and the cost is high. Capacitive MEMS pressure sensors combine the advantages and disadvantages of resonant and piezoresistive types, with the advantages of simple structure, high precision and simple detection circuit, and are widely used in the field of pressure measurement.

[0003] At present, capacitive MEMS pressure sensors mainly include fixed air pressure cavity, pressure sensitive film, fixed electrode and other structures. When the pressure difference on both sides of the pressure sensitive film changes, deformation occurs, thereby changing the capacitance between the fixed electrode and the sensitive film to reflect the pressure. However, the existing device design mainly has the problem of poor linearity between the capacitance change caused by the deformation of the sensitive film and the pressure change. The Chinese invention patent with announcement number CN105067178B discloses a differential capacitive MEMS pressure sensor and its manufacturing method, in which the film used to sense the pressure difference bends under pressure instead of moving horizontally, so that the detection capacitance change formed by the film and the fixed plate has a large nonlinearity. Utility Model Content

[0004] The purpose of the utility model is to provide a novel capacitive MEMS pressure sensor, aiming to solve the above-mentioned problems.

[0005] The utility model is mainly realized through the following technical solutions:

[0006] A novel capacitive MEMS pressure sensor comprises a sensitive structure layer, a bonding layer and a bottom plate layer which are arranged in sequence from top to bottom, wherein the sensitive structure layer comprises a sensitive layer frame and a sensitive layer capacitor plate, and the bottom plate layer comprises a bottom outer frame and a bottom capacitor plate; the middle parts of the sensitive layer frame and the bottom outer frame are respectively provided with a sensitive layer capacitor plate and a bottom capacitor plate, and the peripheral side of the sensitive layer capacitor plate is connected to the sensitive layer frame through a sensitive layer elastic film; a vacuum-sealed capacitor gap is provided between the sensitive layer capacitor plate and the bottom capacitor plate.

[0007] In order to better realize the utility model, further, the sensitive structure layer also includes a sensitive layer outer frame, the outer side of the sensitive layer frame is connected to the sensitive layer outer frame through an upper suspension beam, and the bottom layer outer frame is connected to the bottom layer capacitor plate through a lower suspension beam; the upper suspension beam and the lower suspension beam are respectively provided with a sensitive layer metal electrode and a bottom layer metal electrode, and the sensitive layer metal electrode and the bottom layer metal electrode are respectively electrically connected to the sensitive layer capacitor plate and the bottom layer capacitor plate.

[0008] In order to better realize the utility model, further, the thickness of the sensitive layer outer frame, the sensitive layer frame and the sensitive layer capacitor plate are the same, and the thickness of the sensitive layer capacitor plate is greater than the thickness of the sensitive layer elastic film; the thickness of the bottom layer outer frame and the bottom layer capacitor plate are the same.

[0009] In order to better realize the utility model, further, the bonding layer includes a bonding outer frame and a bonding border, the bonding border is arranged on the inner side of the bonding outer frame, a bonding outer frame is arranged between the sensitive layer outer frame and the bottom layer outer frame, and a bonding border is arranged between the sensitive layer border and the bottom layer metal electrode; the sensitive layer border, the sensitive layer elastic film, the sensitive layer capacitor plate, the bonding border and the bottom layer capacitor plate are enclosed to form a sealed vacuum cavity.

[0010] In order to better implement the utility model, further, the thickness of the capacitor gap is equal to the thickness of the bonding layer.

[0011] In order to better realize the utility model, further, the sensitive structure layer and the bottom plate layer are composed of <100> A single crystal silicon wafer with a crystalline orientation is prepared, and the bonding layer is prepared from an insulating material.

[0012] The beneficial effects of the utility model are as follows:

[0013] During the use of the utility model, when the external air pressure and the vacuum chamber air pressure change or the pressure applied to the sensitive layer capacitor plate changes, the force acting on the sensitive layer capacitor plate changes, causing the elastic film of the sensitive layer to deform, so as to change the capacitance value of the parallel plate capacitor formed between the sensitive layer capacitor plate and the bottom layer capacitor plate. The air pressure or pressure information can be obtained by measuring the capacitance value. At the same time, since the elastic film of the sensitive layer is relatively thin, the deformation under the action of external pressure mainly occurs at the elastic film, and the deformation of the sensitive layer capacitor plate is relatively small, which effectively improves the linearity between the capacitance value change and the air pressure or pressure change. Secondly, the sensitive layer frame is connected to the sensitive layer outer frame through the upper cantilever beam, and the bottom layer outer frame is connected to the bottom layer capacitor plate through the lower cantilever beam, which can isolate the stress caused by packaging and temperature, thereby improving the temperature stability and stress stability of the device, and has good practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1It is a three-dimensional structural schematic diagram of the novel capacitive MEMS pressure sensor of the utility model;

[0015] Figure 2 A top view of the novel capacitive MEMS pressure sensor of the utility model;

[0016] Figure 3 for Figure 2 Schematic diagram of the cross-sectional structure of A1-A1.

[0017] Wherein: 1-sensitive layer outer frame, 2-sensitive layer border, 3-sensitive layer elastic film, 4-sensitive layer capacitor plate, 5-sensitive layer metal electrode, 6-bottom layer outer frame, 7-bottom layer metal electrode, 8-bottom layer capacitor plate, 9-vacuum cavity, 10-bonding outer frame, 11-bonding border. DETAILED DESCRIPTION

[0018] Embodiment 1:

[0019] A new type of capacitive MEMS pressure sensor, such as Figure 1-Figure 3 As shown, it includes a sensitive structure layer, a bottom plate layer and a bonding layer, wherein the sensitive structure layer is connected to the bottom plate layer through the bonding layer, and the sensitive structure layer and the bottom plate layer are insulated and separated by the bonding layer, and a closed vacuum cavity 9 is formed between the sensitive structure layer and the bottom plate layer. A sensitive layer capacitor plate 4 is installed in the middle of the sensitive structure layer through a sensitive layer elastic film 3, and a bottom layer capacitor plate 8 is correspondingly arranged in the middle of the bottom plate layer, and a parallel plate capacitor is formed between the sensitive layer capacitor plate 4 and the bottom layer capacitor plate 8, and the sensitive layer capacitor plate 4 is displaced under the action of external pressure to cause a change in capacitance between the sensitive structure layer and the bottom plate layer.

[0020] When the external air pressure and the air pressure of the vacuum chamber 9 change or the pressure applied to the sensitive layer capacitor plate 4 changes, the force acting on the sensitive layer capacitor plate 4 changes, causing the sensitive layer elastic film 3 to deform, so as to change the capacitance value of the parallel plate capacitor formed between the sensitive layer capacitor plate 4 and the bottom capacitor plate 8. The air pressure or pressure information can be obtained by measuring the capacitance value. At the same time, since the sensitive layer elastic film 3 is relatively thin, the deformation under the action of external pressure mainly occurs at the elastic film, and the deformation of the sensitive layer capacitor plate 4 is relatively small, thereby improving the linearity between the capacitance value change and the air pressure or pressure change. The capacitive MEMS pressure sensor of the utility model can be well applied to pressure measurement applications such as air pressure detection and contact pressure measurement.

[0021] Preferably, the sensitive structural layer includes a sensitive layer capacitor plate 4 located in the middle, a sensitive layer frame 2 located in the outer area, and a sensitive layer elastic film 3 located between the capacitor plate and the frame. The sensitive layer capacitor plate 4 is connected to the sensitive layer frame 2 through the sensitive layer elastic film 3, and the thickness of the elastic film is less than the thickness of the sensitive layer capacitor plate 4. The sensitive layer frame 2 is connected to the sensitive layer outer frame 1 through a beam, and a sensitive layer metal electrode 5 is made on the cantilever beam.

[0022] Specifically: Figure 2 and Figure 3 As shown, the sensitive structure layer includes a sensitive layer outer frame 1, a sensitive layer frame 2, a sensitive layer elastic film 3, a sensitive layer capacitor plate 4 and a sensitive layer electrode. The sensitive layer outer frame 1 and the sensitive layer frame 2 are connected only by a single beam, and the sensitive layer electrode is located above the beam; the thickness of the sensitive layer outer frame 1, the sensitive layer frame 2 and the sensitive layer capacitor plate 4 are the same, which is the thickness of the wafer used to make them. The sensitive layer elastic film 3 is relatively thin, and the sensitive layer elastic film 3 is respectively connected to the sensitive layer frame 2 and the sensitive layer capacitor plate 4, and is used to deform the sensitive layer capacitor plate 4 when the sensitive layer capacitor plate 4 is subjected to force, so that the sensitive layer capacitor plate 4 is displaced; the material used for the sensitive structure layer is low-resistance single crystal silicon.

[0023] Preferably, the bottom plate layer includes a bottom capacitor plate 8 located below the sensitive layer capacitor plate 4 and aligned with the sensitive layer frame 2, and a bottom outer frame 6 located outside, wherein the bottom capacitor plate 8 is connected to the bottom outer frame 6 via a cantilever beam, and a bottom metal electrode 7 is formed on the cantilever beam. Specifically, the bottom outer frame 6 and the bottom capacitor plate 8 have the same thickness, which is the thickness of the wafer used to make them; the material used for the bottom plate layer is low-resistance single-crystal silicon.

[0024] Preferably, the bonding layer includes a bonding frame 11 and a bonding outer frame 10 located at the edge, wherein the bonding outer frame 10 is located between the bottom outer frame 6 and the sensitive layer outer frame 1, and connects the bottom outer frame 6 and the sensitive layer outer frame 1; the bonding frame 11 is located between the bottom capacitor plate 8 and the sensitive layer frame 2, and connects the sensitive layer frame 2 and the bottom capacitor plate 8. The sensitive layer frame 2, the sensitive layer elastic film 3, the sensitive layer capacitor plate 4, the bottom capacitor plate 8 and the bonding frame 11 are integrally sealed and connected to form a vacuum chamber 9. Specifically, a capacitor gap is formed between the bottom capacitor plate 8 and the sensitive layer capacitor plate 4; the thickness of the capacitor gap is the thickness of the bonding layer; and the material used for the bonding layer is insulating silicon dioxide.

[0025] Preferably, the sensitive layer electrode and the bottom layer electrode can be led out as external conductive contacts, which are respectively electrically connected to the sensitive layer capacitor plate 4 and the bottom layer capacitor plate 8. The capacitive MEMS pressure sensor of the utility model needs to lead out the electrical signals of the sensitive layer electrode and the bottom layer electrode to measure the capacitance value formed by the sensitive layer capacitor plate 4 and the bottom layer capacitor plate 8 which are electrically connected to the sensitive layer electrode and the bottom layer electrode.

[0026] Preferably, the sensitive structure layer and the bottom plate layer are <100> The bonding layer is made of insulating material and can be made of silicon dioxide material.

[0027] When the external air pressure and the air pressure of the vacuum chamber 9 change or the pressure applied to the sensitive layer capacitor plate 4 changes, the force acting on the sensitive layer capacitor plate 4 changes, causing the sensitive layer elastic film 3 to deform, thereby changing the capacitance value of the parallel plate capacitor formed between the sensitive layer capacitor plate 4 and the bottom capacitor plate 8. The air pressure or pressure information can be obtained by measuring the capacitance value.

[0028] The sensitive layer outer frame 1 of the utility model is connected to the bottom layer outer frame 6 through a bonding outer frame 10, and this part is connected to the internal sensitive layer frame 2, the sensitive layer capacitor plate 4, and the bottom layer capacitor plate 8 through two beams, which are used to isolate the stress caused by packaging and temperature. When fixing the pressure sensor of the utility model, it can be fixed at the bottom layer outer frame 6 to improve the temperature stability and stress stability of the device.

[0029] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification or equivalent changes made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A new capacitive MEMS pressure sensor, characterized in that: The invention comprises a sensitive structure layer, a bonding layer and a bottom plate layer which are arranged in sequence from top to bottom; the sensitive structure layer comprises a sensitive layer frame (2) and a sensitive layer capacitor plate (4), and the bottom plate layer comprises a bottom outer frame (6) and a bottom capacitor plate (8); the middle parts of the sensitive layer frame (2) and the bottom outer frame (6) are respectively provided with a sensitive layer capacitor plate (4) and a bottom capacitor plate (8); the peripheral side of the sensitive layer capacitor plate (4) is connected to the sensitive layer frame (2) via a sensitive layer elastic film (3); and a vacuum-sealed capacitor gap is provided between the sensitive layer capacitor plate (4) and the bottom capacitor plate (8).

2. A novel capacitive MEMS pressure sensor according to claim 1, characterized in that: The sensitive structure layer further comprises a sensitive layer outer frame (1); the outer side of the sensitive layer frame (2) is connected to the sensitive layer outer frame (1) via an upper suspension beam; the bottom layer outer frame (6) is connected to a bottom layer capacitor electrode plate (8) via a lower suspension beam; a sensitive layer metal electrode (5) and a bottom layer metal electrode (7) are respectively arranged on the upper suspension beam and the lower suspension beam; the sensitive layer metal electrode (5) and the bottom layer metal electrode (7) are respectively electrically connected to the sensitive layer capacitor electrode plate (4) and the bottom layer capacitor electrode plate (8).

3. A novel capacitive MEMS pressure sensor according to claim 2, characterized in that: The thickness of the sensitive layer outer frame (1), the sensitive layer frame (2) and the sensitive layer capacitor plate (4) are the same, and the thickness of the sensitive layer capacitor plate (4) is greater than the thickness of the sensitive layer elastic film (3); the thickness of the bottom layer outer frame (6) and the bottom layer capacitor plate (8) are the same.

4. A novel capacitive MEMS pressure sensor according to claim 2 or 3, characterized in that: The bonding layer comprises a bonding outer frame (10) and a bonding frame (11); the bonding frame (11) is arranged on the inner side of the bonding outer frame (10); the bonding outer frame (10) is arranged between the sensitive layer outer frame (1) and the bottom layer outer frame (6); and the bonding frame (11) is arranged between the sensitive layer frame (2) and the bottom layer metal electrode (7); the sensitive layer frame (2), the sensitive layer elastic film (3), the sensitive layer capacitor electrode plate (4), the bonding frame (11) and the bottom layer capacitor electrode plate (8) enclose and form a sealed vacuum cavity (9).

5. A novel capacitive MEMS pressure sensor according to claim 1, characterized in that: The thickness of the capacitor gap is equal to the thickness of the bonding layer.

6. A novel capacitive MEMS pressure sensor according to claim 1, characterized in that: The sensitive structure layer and the bottom plate layer are composed of <100> A single crystal silicon wafer with a crystalline orientation is prepared, and the bonding layer is prepared from an insulating material.

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