MEMS plate capacitance type differential pressure sensor

Abstract

The invention relates to the technical field of sensors, in particular to an MEMS plate capacitance type differential pressure sensor, which comprises an outer frame used as a bearing structure and used for mounting a double-layer film and a plate electrode; the plate electrode is fixedly mounted in the middle of the outer frame; the double-layer films are arranged in the outer frame and are respectively arranged on two sides of the plate electrode, and the change of pressure is reflected by measuring the change of capacitance between the films and the plate capacitor; and the rigid connecting body is positioned between the two layers of films and is used for conducting pressure of the two layers of films and balancing the pressure on the two sides. Through the fixed plate electrode and the thin film structures on the two sides of the plate electrode, differential measurement is achieved, and the sensitivity is improved while errors are reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of sensors, and in particular to a MEMS flat plate capacitive differential pressure sensor. Background Art

[0002] Existing MEMS pressure gauges generally make a thin film structure first, apply pressure to the film to cause it to deform, and measure the change in pressure by the change in the film. The measurement method is usually to add a bridge structure to the film, and reflect the change in pressure by measuring the change in resistance. Another measurement method is to set a flat plate capacitor near the film, and detect the change in pressure by measuring the change in capacitance between the film and the flat plate capacitor. The problem with the above measurement methods is that they all rely on unilateral deformation of the film, resulting in large errors. In addition, Chinese patent CN102445298A discloses a structure in which the film changes in the middle, and the double-sided plates are fixed and perforated. The problem with this structure is that the pressure medium acts on the middle pressure-sensitive film through the small holes, and the response speed during measurement is slow. Summary of the invention

[0003] The object of the present invention is to provide a MEMS flat plate capacitive differential pressure sensor to solve the problems raised in the above background technology.

[0004] To achieve the above object, the present invention provides the following technical solutions:

[0005] A MEMS flat plate capacitive differential pressure sensor comprises: an outer frame (1) used as a bearing structure; a flat plate electrode (4) fixedly arranged in the outer frame (1); a first film (2) and a second film (3) installed in the outer frame (1) and respectively located on both sides of the flat plate electrode (4), and configured to reflect the change of pressure by measuring the change of capacitance between the film and the flat plate electrode (4); and a rigid connector (5) located between the first film (2) and the second film (3) and used to conduct the pressure of the first film (2) and the second film (3).

[0006] Optionally, the first film (2) is used to be applied with a measured pressure, and the second film (3) is used to be applied with a fixed pressure.

[0007] Optionally, the flat plate electrode (4) is arranged around the rigid connector (5).

[0008] Optionally, the flat electrode (4) is a continuous whole structure, two half structures, or four quarter structures.

[0009] Optionally, the rigid connector (5) is single and located at the center of the first film (2) or the second film (3); or the rigid connector (5) is multiple and arranged in an array.

[0010] Optionally, in the outer frame (1), an insulating layer (7) is provided between the first film (2) and the flat electrode (4).

[0011] Optionally, the material of the first film (2) and / or the second film (3) is silicon, and the material of the insulating layer (7) is silicon oxide.

[0012] Optionally, the distance between the first film (2) and the flat electrode (4) is a first spacing, and the range of the first spacing is 1 μm to 10 μm; the distance between the second film (3) and the flat electrode (4) is a second spacing, and the range of the second spacing is 1 μm to 10 μm.

[0013] Optionally, the first spacing is equal to the second spacing.

[0014] Optionally, the rigid connector (5) comprises a first surface and a second surface opposite to the first surface, wherein the first surface is in contact with and fixed to the first film (2), and the second surface is in contact with and fixed to the second film (3).

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention realizes differential measurement of pressure through a fixed flat electrode and thin film structures on both sides of the flat electrode, thereby reducing errors and improving sensitivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic cross-sectional view of the sensor of the present invention.

[0017] Figure 2 This is a schematic diagram of the internal structure of the sensor of the present invention after removing the upper film.

[0018] Figure 3 It is an enlarged schematic diagram of the sensor side of the present invention.

[0019] Figure 4 It is a schematic diagram of the pressure acting on the double-layer film of the sensor of the present invention.

[0020] In the figure: 1-outer frame, 2-first film, 3-second film, 4-flat electrode, 5-rigid connector, 7-insulating layer. DETAILED DESCRIPTION

[0021] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] In the description of the present invention, it should be noted that the terms "upper / lower end", "inner", "outer", "front end", "rear end", "two ends", "one end", "the other end" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0023] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "setting / sleeving", "sleeve connection", "connection", etc. should be understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0024] See also Figure 1-4 , the present invention provides a technical solution:

[0025] A MEMS flat plate capacitive differential pressure sensor comprises: an outer frame 1, used as a bearing structure, specifically, the outer frame 1 is used to install a double-layer film, a flat plate electrode 4 and a rigid connector 5; the flat plate electrode 4 is installed in the middle of the outer frame 1; it also includes a double-layer film, which is installed in the outer frame 1 and on both sides of the flat plate electrode 4, respectively, and reflects the change of pressure by measuring the change of capacitance between the film and the flat plate electrode 4; the rigid connector 5 is located between the double-layer film, and is used for conducting pressure of the double-layer film and balancing the pressure on both sides.

[0026] The double-layer film is respectively a first film 2 and a second film 3. Specifically, in this embodiment, the first film 2 is located above the flat electrode 4, that is, the upper film, and the second film 3 is located below the flat electrode 4, that is, the lower film. Among them, the first film 2 is arranged on one side of the flat electrode 4, and the second film 3 is arranged on the other side of the flat electrode 4, that is, the flat electrode 4 is arranged between the first film 2 and the second film 3. Specifically, the first film 2 and the flat electrode 4 are spaced and arranged oppositely, and the distance between the first film 2 and the flat electrode 4 is a first spacing, and the range of the first spacing can be 1μm to 10μm; the second film 3 and the flat electrode 4 are spaced and arranged oppositely, and the distance between the second film 3 and the flat electrode 4 is a second spacing, and the second spacing can be 1μm to 10μm. In some embodiments, the first spacing is equal to the second spacing.

[0027] The first film 2 and the second film 3 need to have good mechanical properties, chemical stability and specific electrical properties. The material of the first film 2 and the second film 3 can be silicon or silicon compounds, or metal. The thickness of the first film 2 and the second film 3 can be 1 μm to 100 μm, for example, 5 μm to 50 μm.

[0028] After being packaged into an actual pressure sensor, the film on one side, such as the first film 2, is connected to the pressure to be measured, and the measured pressure will be applied to the first film 2. The film on the other side, such as the second film 3, is packaged to make a fixed pressure (differential pressure sensor) or vacuum (absolute pressure sensor).

[0029] During normal measurement, the first film 2, the second film 3 and the plate electrode 4 are insulated from each other. In some embodiments, in order to achieve electrical insulation, especially to maintain insulation at the outer frame 1, an insulating layer 7 may be provided between the first film 2 and the plate electrode 4 in the outer frame 1, so that the first film 2 and the plate electrode 4 are isolated at the outer frame 1; similarly, an insulating layer 7 may be provided between the second film 3 and the plate electrode 4, so that the second film 3 and the plate electrode 4 are isolated at the outer frame 1. The material of the insulating layer 7 may be selected from insulating oxides and nitrides, such as silicon oxide and silicon nitride.

[0030] In this embodiment, since the pressure acts directly on the surfaces of the first film 2 and the second film 3, the pressure medium does not need to flow into or out of the chip, thereby improving the response speed of the pressure sensor.

[0031] The flat plate electrode 4 is disposed between the first film 2 and the second film 3. The flat plate electrode 4 may be a continuous integral structure or two or more discrete structures. When the flat plate electrode 4 is a discrete structure, the shapes of the discrete structures may be substantially the same, such as two half structures, four quarter structures, etc. The flat plate electrode 4 is fixed to the outer frame 1 structure around the sensor. When the first film 2 and / or the second film 3 are subjected to force, the flat plate electrode 4 will not be deformed or displaced.

[0032] The rigid connector 5 is located between the first film 2 and the second film 3, and is used to conduct the pressure on the first film 2 and the second film 3 to balance the pressure on both sides. The rigid connector 5 includes a first surface and a second surface opposite to the first surface, wherein the first surface faces the first film 2, and the second surface faces the second film 3. Specifically, the first surface contacts and is fixed to the first film 2, and the second surface contacts and is fixed to the second film 3. In some embodiments, the first surface of the rigid connector 5 is bonded to the first film 2, and the second surface is bonded to the second film 3. In some embodiments, as Figure 2 As shown, the rigid connector 5 is a columnar structure, located at the center of the first film 2 or the second film 3. It can be understood that the rigid connector 5 can also be other shapes; the number of rigid connectors 5 can be one or more than one, and multiple rigid connectors 5 can be arranged in an array.

[0033] Differential pressure sensor is relative to absolute pressure sensor. Differential pressure refers to the difference between any two pressures. Differential pressure sensor is mainly used to measure the relative difference between two different pressures. Absolute pressure is a pressure expression method based on absolute vacuum. Absolute pressure sensor directly measures absolute pressure. The present invention utilizes a double-sided membrane structure. A rigid connector 5 is provided between the two membranes. A fixed flat electrode 4 is provided around the rigid connector 5. The flat electrode 4 is used to measure the capacitance change between the membrane and the flat electrode 4. There is a vacuum or a fixed pressure value between the two membranes. The two membranes are deformed under the pressure on both sides, resulting in a change in the capacitance between the membrane and the middle flat electrode 4.

[0034] like Figure 4As shown, pressure A acts on the first film 2, and pressure B acts on the second film 3. The first film 2 and the second film 3 transmit pressure through the rigid connector 5 in the middle and balance the pressure on both sides. If pressure A is greater than pressure B, the first film 2 moves downward, and the gap with the middle flat electrode 4 is reduced, resulting in an increase in capacitance between the first film 2 and the flat electrode 4; the second film 3 also moves downward, and the gap between the second film 3 and the middle flat electrode 4 increases, resulting in a decrease in capacitance between the second film 3 and the flat electrode 4. By differentially calculating the capacitance change, the differential pressure value between pressure A and pressure B can be measured. The middle flat electrode 4 is fixed to the outer frame 1 structure around the sensor without deformation or displacement.

[0035] Compared with the prior art, the present invention uses a double-sided membrane and a flat electrode structure disposed in the middle thereof, and eliminates measurement errors by differential means, thereby being able to reduce errors and improve sensitivity at the same time.

[0036] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A MEMS flat plate capacitive differential pressure sensor, characterized in that: include: An outer frame (1) is used as a bearing structure; A flat plate electrode (4) fixedly arranged in the outer frame (1); The first film (2) and the second film (3) are installed in the outer frame (1) and are respectively located on both sides of the flat electrode (4), and are configured to reflect the change of pressure by measuring the change of capacitance between the film and the flat electrode (4); The rigid connector (5) is located between the first film (2) and the second film (3) and is used to transmit the pressure of the first film (2) and the second film (3).

2. The MEMS flat plate capacitive differential pressure sensor according to claim 1, characterized in that: The first film (2) is used to be applied with a measured pressure, and the second film (3) is used to be applied with a fixed pressure.

3. The MEMS flat plate capacitive differential pressure sensor according to claim 1, characterized in that: The flat plate electrode (4) is arranged around the rigid connector (5).

4. The MEMS flat plate capacitive differential pressure sensor according to claim 1, characterized in that: The flat plate electrode (4) is a continuous whole structure, two half structures, or four quarter structures.

5. The MEMS flat plate capacitive differential pressure sensor according to claim 1, characterized in that: The rigid connector (5) is single and located at the center of the first film (2) or the second film (3); or the rigid connector (5) is multiple and arranged in an array.

6. The MEMS flat plate capacitive differential pressure sensor according to any one of claims 1 to 5, characterized in that: In the outer frame (1), an insulating layer (7) is provided between the first film (2) and the flat electrode (4).

7. The MEMS flat plate capacitive differential pressure sensor according to claim 6, characterized in that: The material of the first film (2) and / or the second film (3) is silicon, and the material of the insulating layer (7) is silicon oxide.

8. The MEMS flat plate capacitive differential pressure sensor according to claim 1, characterized in that: The distance between the first film (2) and the flat electrode (4) is a first spacing, and the range of the first spacing is 1 μm to 10 μm; the distance between the second film (3) and the flat electrode (4) is a second spacing, and the range of the second spacing is 1 μm to 10 μm.

9. The MEMS flat plate capacitive differential pressure sensor according to claim 8, characterized in that: The first interval is equal to the second interval.

10. The MEMS flat plate capacitive differential pressure sensor according to claim 1, characterized in that: The rigid connector (5) comprises a first surface and a second surface opposite to the first surface, wherein the first surface is in contact with and fixed to the first film (2), and the second surface is in contact with and fixed to the second film (3).

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