High-precision differential capacitive MEMS pressure sensor

Abstract

The utility model discloses a high-precision differential capacitive MEMS pressure sensor, which comprises a top plate layer, an upper bonding layer, a sensitive structure layer, a lower bonding layer and a bottom plate layer which are sequentially arranged from top to bottom, a top layer capacitance plate, a sensitive layer capacitance plate and a bottom layer capacitance plate are correspondingly arranged in the middle of the top plate layer, the middle of the sensitive structure layer and the middle of the bottom plate layer respectively, and a plurality of through top layer air holes are formed in the top layer capacitance plate; an upper capacitance gap communicated with the top-layer air hole is formed between the top-layer capacitance plate and the sensitive-layer capacitance plate, and a vacuum-sealed lower capacitance gap is formed between the sensitive-layer capacitance plate and the bottom-layer capacitance plate; the sensitive structure layer comprises a sensitive layer frame and a sensitive layer capacitance plate, the sensitive layer capacitance plate is arranged in the middle of the sensitive layer frame, and the peripheral side of the sensitive layer capacitance plate is connected with the sensitive layer frame through a sensitive layer elastic film. According to the utility model, the suppression of common-mode signals is enhanced, and the signal-to-noise ratio of output signals is improved; and meanwhile, the linearity between the capacitance value variation and the air pressure or pressure variation is improved, and good practicability is achieved.

Description

Technical Field

[0001] The utility model belongs to the technical field of capacitive MEMS pressure sensors, and in particular relates to a high-precision differential 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 sensor is widely used in automobile, consumer electronics, industrial control, medical and other fields for air pressure, hydraulic pressure and other information detection. MEMS pressure sensors are currently mainly piezoresistive, resonant, capacitive and other types. Piezoresistive MEMS pressure sensor has the advantages of low cost and simple detection circuit, but it has the disadvantages of large temperature drift and low precision; resonant MEMS pressure sensor has extremely high precision, but its structure is complex and costly; capacitive MEMS pressure sensor combines the advantages and disadvantages of resonant and piezoresistive, has the advantages of simple structure, high precision and simple detection circuit, and is 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 metal 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 metal 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 utility model aims to provide a high-precision differential 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 high-precision differential capacitive MEMS pressure sensor comprises a top plate layer, an upper bonding layer, a sensitive structure layer, a lower bonding layer and a bottom plate layer which are arranged in sequence from top to bottom; a top capacitor plate, a sensitive layer capacitor plate and a bottom capacitor plate are respectively arranged in the middle of the top plate layer, the sensitive structure layer and the bottom plate layer, and a plurality of top pores are arranged on the top capacitor plate; an upper capacitor gap connected to the top pores is arranged between the top capacitor plate and the sensitive layer capacitor plate, and a vacuum-sealed lower capacitor gap is arranged between the sensitive layer capacitor plate and the bottom capacitor plate; the sensitive structure layer comprises a sensitive layer frame and a sensitive layer capacitor plate, a sensitive layer capacitor plate is arranged in the middle of the sensitive layer frame, and the peripheral side of the sensitive layer capacitor plate is connected to the sensitive layer frame through a sensitive layer elastic film.

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

[0008] 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 a middle suspension beam, and a top metal electrode electrically connected to the sensitive layer capacitor plate is provided on the middle suspension beam.

[0009] In order to better realize the utility model, further, the upper bonding layer includes an upper bonding frame and an upper bonding outer frame, an upper bonding outer frame is arranged between the top outer frame and the sensitive layer outer frame, and an upper bonding frame is arranged between the sensitive layer frame and the top capacitor plate; the sensitive layer frame, the sensitive layer elastic film, the sensitive layer capacitor plate, the bottom capacitor plate and the upper bonding frame are integrally enclosed to form a cavity connected to the outside world and the upper capacitor gap.

[0010] In order to better realize the utility model, further, the bottom plate layer includes a bottom outer frame, the outer side of the bottom capacitor plate is connected to the bottom outer frame through a lower suspension beam, and the lower suspension beam is provided with a bottom metal electrode electrically connected to the bottom capacitor plate.

[0011] In order to better realize the utility model, further, the lower bonding layer includes a lower bonding frame and a lower bonding outer frame, a lower bonding outer frame is arranged between the bottom layer outer frame and the sensitive layer outer frame, and a lower bonding frame is arranged between the sensitive layer frame and the bottom layer capacitor plate; the sensitive layer frame, the sensitive layer elastic film, the sensitive layer capacitor plate, the bottom layer capacitor plate and the lower bonding frame are integrally enclosed to form a vacuum sealed cavity connected to the lower capacitor gap.

[0012] In order to better realize the utility model, further, the thickness of the top outer frame is the same as that of the top capacitor plate, the thickness of the sensitive layer outer frame, the sensitive layer frame and the sensitive layer capacitor plate are the same, the thickness of the sensitive layer elastic film is less than the thickness of the sensitive layer capacitor plate; the thickness of the bottom outer frame is the same as that of the bottom capacitor plate.

[0013] In order to better implement the utility model, further, the upper capacitor gap is the same as the thickness of the upper bonding layer, and the lower capacitor gap is the same as the thickness of the lower bonding layer.

[0014] In order to better realize the utility model, further, the top plate layer, the sensitive structure layer and the bottom plate layer are respectively <100> The bonding layer is made of insulating material.

[0015] In order to better realize the utility model, further, a plurality of penetrating top-layer air holes are provided on the peripheral side of the top-layer capacitor plate above the elastic film of the sensitive layer.

[0016] The beneficial effects of the utility model are as follows:

[0017] (1) A group of parallel plate capacitors is formed between the sensitive layer capacitor plate and the top layer capacitor plate, and a group of parallel plate capacitors is formed between the sensitive layer capacitor plate and the bottom layer capacitor plate. The two groups of parallel plate capacitors form differential capacitance detection, which enhances the detection suppression of common mode signals, improves the signal-to-noise ratio of the output signal, and has good practicality;

[0018] (2) The upper capacitor gap is connected to the outside air through the top layer pores, and the lower capacitor gap is a sealed vacuum chamber. When the outside air pressure and the vacuum chamber air pressure change, the force acting on the sensitive layer capacitor plate changes, causing the sensitive layer elastic film to deform, so as to increase or decrease the capacitance value of the parallel plate capacitor formed between the sensitive layer capacitor plate and the top layer capacitor plate, and at the same time reduce or increase the capacitance value of the parallel plate capacitor formed between the sensitive layer capacitor plate and the bottom layer capacitor plate. Accurate air pressure information can be obtained by measuring the differential capacitance value. At the same time, since the sensitive layer elastic film 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, and has good practicality;

[0019] (3) The top outer frame and the top capacitor plate, the sensitive layer outer frame and the sensitive layer frame, and the bottom outer frame and the bottom capacitor plate are connected by upper cantilever beams, middle cantilever beams, and lower cantilever beams, respectively, to isolate stresses caused by packaging and temperature, thereby improving the temperature stability and stress stability of device installation and having good practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a three-dimensional structural schematic diagram of the high-precision differential capacitive MEMS pressure sensor of the utility model;

[0021] Figure 2 It is a top view of the high-precision differential capacitive MEMS pressure sensor of the utility model;

[0022] Figure 3 for Figure 2 Schematic diagram of the cross-sectional structure of A1-A1.

[0023] Wherein: 1-top outer frame, 2-top capacitor plate, 3-top pore, 4-sensitive layer outer frame, 5-sensitive layer border, 6-sensitive layer elastic film, 7-sensitive layer capacitor plate, 8-bottom outer frame, 9-bottom capacitor plate, 10-upper capacitor gap, 11-lower capacitor gap, 12-upper bonding outer frame, 13-upper bonding border, 14-lower bonding outer frame, 15-lower bonding border, 16-bottom metal electrode, 17-sensitive layer metal electrode, 18-top metal electrode. DETAILED DESCRIPTION

[0024] Embodiment 1:

[0025] A high-precision differential capacitive MEMS pressure sensor, such as Figure 1-Figure 3 As shown, it includes a top plate layer, a sensitive structure layer and a bottom plate layer arranged in sequence from top to bottom; an upper bonding layer and a lower bonding layer are respectively arranged between the top plate layer and the sensitive structure layer and between the sensitive structure layer and the bottom plate layer. The sensitive structure layer and the top plate layer and the sensitive structure layer and the bottom plate layer are insulated and separated by the upper bonding layer and the lower bonding layer, respectively, and parallel plate capacitors are formed between the sensitive layer capacitor plate 7 and the top capacitor plate 2 and between the sensitive layer capacitor plate 7 and the bottom capacitor plate 9, respectively, and the two capacitors form a differential capacitor.

[0026] Preferably, the sensitive structural layer includes a sensitive layer capacitor plate 7 located in the middle, a sensitive layer frame 5 located in the outer area, and a sensitive layer elastic film 6 located between the capacitor plate and the frame. The sensitive layer capacitor plate 7 is connected to the sensitive layer frame 5 through the sensitive layer elastic film 6, and the thickness of the elastic film is less than the thickness of the sensitive layer capacitor plate 7.

[0027] Specifically, Figure 3As shown, the sensitive structure layer includes the following structures: a sensitive layer outer frame 4, a sensitive layer frame 5, a sensitive layer elastic film 6, a sensitive layer capacitor plate 7 and a sensitive layer metal electrode 17. The sensitive layer outer frame 4 and the sensitive layer frame 5 are connected only by a single suspension beam, and the metal electrode 17 of the sensitive layer is located above the beam; the thickness of the sensitive layer outer frame 4, the sensitive layer frame 5 and the sensitive layer capacitor plate 7 is the same, which is the thickness of the wafer for making them; the sensitive layer elastic film 6 is relatively thin, connecting the sensitive layer frame 5 and the sensitive layer capacitor plate 7, and is used to deform the sensitive layer capacitor plate 7 when the sensitive layer capacitor plate 7 is subjected to force, so that the sensitive layer capacitor plate 7 is displaced; the material used for the sensitive structure layer is low-resistance single crystal silicon.

[0028] Preferably, the top plate layer includes a top capacitor plate 2 located above the sensitive layer capacitor plate 7 and aligned with the sensitive layer frame 5, a top air hole 3 penetrating the top capacitor plate 2, and a top outer frame 1 located outside the top capacitor plate 2, wherein the top capacitor plate 2 is connected to the top outer frame 1 through a cantilever beam, and the cantilever beam is provided with a top metal electrode 18. Preferably, the sensitive layer elastic film 6 region is below the top plate air hole, and the top plate air hole is connected to the upper capacitor gap 10 region, which has the same air pressure as the device's external pressure.

[0029] Specifically, Figure 2 As shown, the top outer frame 1 and the top capacitor plate 2 are connected only by a single cantilever beam, and the top metal electrode 18 is located above the beam; the top air holes 3 are distributed on the top capacitor plate 2 and penetrate the top capacitor plate 2; the thickness of the top outer frame 1 and the top capacitor plate 2 is the same, which is the thickness of the wafer for making them; the material used for the top plate layer is low-resistance single crystal silicon.

[0030] Preferably, the bottom plate layer includes a bottom capacitor plate 9 located below the sensitive layer capacitor plate 7 and aligned with the sensitive layer frame 5, and a bottom outer frame 8 located outside the bottom capacitor plate 9, wherein the bottom capacitor plate 9 is connected to the bottom outer frame 8 via a suspension beam, and the suspension beam is provided with a bottom metal electrode 16. Specifically, Figure 3 As shown, the bottom outer frame 8 and the bottom capacitor plate 9 are connected only by a single suspension beam, and the bottom metal electrode 16 is located above the beam; the bottom outer frame 8 and the bottom capacitor plate 9 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.

[0031] Preferably, the upper bonding layer includes an upper bonding frame 13 and an upper bonding outer frame 12 located at the edge, the upper bonding outer frame 12 is located between the top outer frame 1 and the sensitive layer outer frame 4, and connects the top outer frame 1 and the sensitive layer outer frame 4; the upper bonding frame 13 is located between the sensitive layer frame 5 and the top capacitor plate 2, and connects the sensitive layer frame 5 and the top capacitor plate 2, so that the sensitive layer frame 5, the sensitive layer elastic film 6, the sensitive layer capacitor plate 7, the bottom capacitor plate 9 and the upper bonding frame 13 are integrally connected to form a cavity, and the cavity is connected to the outside world through the top pore 3, and at the same time, the distance between the sensitive layer capacitor plate 7 and the top capacitor plate 2 is the bonding layer height, and an upper capacitor gap 10 is formed therebetween.

[0032] Furthermore, the lower bonding layer includes a lower bonding frame 15 and a lower bonding outer frame 14 located at the edge, the lower bonding outer frame 14 is located between the bottom outer frame 8 and the sensitive layer outer frame 4, and connects the bottom outer frame 8 and the sensitive layer outer frame 4; the lower bonding frame 15 is located between the sensitive layer frame 5 and the bottom capacitor plate 9, and connects the sensitive layer frame 5 and the bottom capacitor plate 9, so that the sensitive layer frame 5, the sensitive layer elastic film 6, the sensitive layer capacitor plate 7, the bottom capacitor plate 9 and the lower bonding frame 15 are integrally sealed and connected to form a vacuum cavity, and at the same time, the distance between the sensitive layer capacitor plate 7 and the bottom capacitor plate 9 is the bonding layer height, and a lower capacitor gap 11 is formed therebetween.

[0033] Preferably, the top metal electrode 18, the sensitive layer metal electrode 17, and the bottom metal electrode 16 can be led out as external conductive contacts, which are respectively electrically connected to the top capacitor plate 2, the sensitive layer capacitor plate 7, and the bottom capacitor plate 9. The utility model needs to lead out the electrical signals of the top metal electrode 18, the sensitive layer metal electrode 17, and the bottom metal electrode 16, so as to measure the differential capacitance value formed by the top capacitor plate 2, the sensitive layer capacitor plate 7, and the bottom capacitor plate 9 which are electrically connected to the top metal electrode 18, the sensitive layer metal electrode 17, and the bottom metal electrode 16.

[0034] Preferably, the top plate layer, the sensitive structure layer and the bottom plate layer are <00> The bonding layer is made of insulating material and can be made of silicon dioxide material.

[0035] During the use of the utility model, when the external air pressure and the vacuum chamber air pressure change, the force acting on the sensitive layer capacitor plate 7 changes, causing the sensitive layer elastic film 6 to deform, so as to change the differential capacitance value of the differential parallel plate capacitor formed by the sensitive layer capacitor plate 7 and the bottom layer capacitor plate 9 and the sensitive layer capacitor plate 7 and the top layer capacitor plate 2. The air pressure information can be obtained by measuring the differential capacitance value.

[0036] The top outer frame 1, the sensitive layer outer frame 4, and the bottom outer frame 8 of the utility model are connected through the upper bonding outer frame 12 and the lower bonding outer frame 14, and this part is connected with the internal top capacitor plate 2, the sensitive layer frame 5, the sensitive layer capacitor plate 7, and the bottom capacitor plate 9 through three beams, which are used to isolate the stress generated by packaging and temperature, so as to improve the temperature stability and stress stability of the device. At the same time, because the utility model adopts the differential capacitance detection formed by the sensitive layer capacitor plate 7 and the bottom capacitor plate 9 and the sensitive layer capacitor plate 7 and the top capacitor plate 2, the detection suppression of the common mode signal is enhanced, and the signal-to-noise ratio of the output signal is improved.

[0037] 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 high-precision differential capacitive MEMS pressure sensor, characterized in that: The invention comprises a top plate layer, an upper bonding layer, a sensitive structure layer, a lower bonding layer and a bottom plate layer which are arranged in sequence from top to bottom; a top capacitor plate (2), a sensitive layer capacitor plate (7) and a bottom capacitor plate (9) are arranged in the middle of the top plate layer, the sensitive structure layer and the bottom plate layer respectively; a plurality of top pores (3) are arranged on the top capacitor plate (2); an upper capacitor gap (10) which is connected to the top pores (3) is arranged between the top capacitor plate (2) and the sensitive layer capacitor plate (7); a vacuum-sealed lower capacitor gap (11) is arranged between the sensitive layer capacitor plate (7) and the bottom capacitor plate (9); the sensitive structure layer comprises a sensitive layer frame (5) and a sensitive layer capacitor plate (7); a sensitive layer capacitor plate (7) is arranged in the middle of the sensitive layer frame (5), and the peripheral side of the sensitive layer capacitor plate (7) is connected to the sensitive layer frame (5) through a sensitive layer elastic film (6).

2. A high-precision differential capacitive MEMS pressure sensor according to claim 1, characterized in that: The top plate layer comprises a top outer frame (1), the outer side of the top capacitor plate (2) is connected to the top outer frame (1) via an upper suspension beam, and a top metal electrode (18) electrically connected to the top capacitor plate (2) is provided on the upper suspension beam.

3. The high-precision differential capacitive MEMS pressure sensor according to claim 2, characterized in that: The sensitive structural layer further comprises a sensitive layer outer frame (4); the outer side of the sensitive layer frame (5) is connected to the sensitive layer outer frame (4) via a middle suspension beam; and a top metal electrode (18) electrically connected to the sensitive layer capacitor plate (7) is provided on the middle suspension beam.

4. The high-precision differential capacitive MEMS pressure sensor according to claim 3, characterized in that: The upper bonding layer comprises an upper bonding frame (13) and an upper bonding outer frame (12); the upper bonding outer frame (12) is arranged between the top outer frame (1) and the sensitive layer outer frame (4); and the upper bonding frame (13) is arranged between the sensitive layer frame (5) and the top capacitor electrode plate (2); the sensitive layer frame (5), the sensitive layer elastic film (6), the sensitive layer capacitor electrode plate (7), the bottom capacitor electrode plate (9) and the upper bonding frame (13) are integrally enclosed to form a cavity that is connected to the outside and the upper capacitor gap (10).

5. The high-precision differential capacitive MEMS pressure sensor according to claim 3, characterized in that: The bottom plate layer comprises a bottom outer frame (8), the outer side of the bottom capacitor plate (9) is connected to the bottom outer frame (8) via a lower suspension beam, and the lower suspension beam is provided with a bottom metal electrode (16) electrically connected to the bottom capacitor plate (9).

6. The high-precision differential capacitive MEMS pressure sensor according to claim 5, characterized in that: The lower bonding layer comprises a lower bonding frame (15) and a lower bonding outer frame (14); the lower bonding outer frame (14) is arranged between the bottom layer outer frame (8) and the sensitive layer outer frame (4); and the lower bonding frame (15) is arranged between the sensitive layer frame (5) and the bottom layer capacitor electrode plate (9); the sensitive layer frame (5), the sensitive layer elastic film (6), the sensitive layer capacitor electrode plate (7), the bottom layer capacitor electrode plate (9) and the lower bonding frame (15) are integrally enclosed to form a vacuum sealed cavity connected to the lower capacitor gap (11).

7. The high-precision differential capacitive MEMS pressure sensor according to claim 5, characterized in that: The top outer frame (1) has the same thickness as the top capacitor plate (2); the sensitive layer outer frame (4), the sensitive layer frame (5) and the sensitive layer capacitor plate (7) have the same thickness; the thickness of the sensitive layer elastic film (6) is less than the thickness of the sensitive layer capacitor plate (7); and the bottom outer frame (8) has the same thickness as the bottom capacitor plate (9).

8. A high-precision differential capacitive MEMS pressure sensor according to claim 1 or 7, characterized in that: The upper capacitor gap (10) has the same thickness as the upper bonding layer, and the lower capacitor gap (11) has the same thickness as the lower bonding layer.

9. The high-precision differential capacitive MEMS pressure sensor according to claim 1, characterized in that: The top plate layer, the sensitive structure layer and the bottom plate layer are respectively <100> The bonding layer is made of insulating material.

10. The high-precision differential capacitive MEMS pressure sensor according to claim 1, characterized in that: A plurality of penetrating top-layer air holes (3) are arranged on the peripheral side of the top-layer capacitor plate (2) above the sensitive layer elastic film (6).

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