CN108426658B

CN108426658B - Ring contact high-range capacitance type micro-pressure sensor

Info

Publication number: CN108426658B
Application number: CN201810253660.9A
Authority: CN
Inventors: 李凯; 彭志辉
Original assignee: Wenzhou University
Current assignee: Wenzhou University
Priority date: 2018-03-26
Filing date: 2018-03-26
Publication date: 2020-05-19
Anticipated expiration: 2038-03-26
Also published as: CN108426658A

Abstract

A ring contact high range capacitive micro pressure sensor. The device comprises a substrate, a fixed electrode, a thin film and a movable electrode, wherein the fixed electrode is positioned on the substrate, the movable electrode is positioned on the thin film, a stop ring is arranged on the substrate in a chamber formed by closing the substrate and the thin film, a distance is reserved between the stop ring and the thin film in a non-working state, the thin film is only in ring contact with the stop ring except for the initial stage of measuring range in a normal working state, and the thin film has the characteristic of step-shaped non-uniform thickness. The invention replaces the insulating layer in the traditional contact mode capacitance type micro-pressure sensor with the stop ring, thereby inhibiting the over-low sensitivity caused by capacitance saturation and the hysteresis error caused by friction force and Van der Waals force, and replaces the equal-thickness film in the traditional contact or non-contact mode micro-pressure sensor with the unequal-thickness step-shaped film, which is beneficial to reducing the bending stress.

Description

Ring contact high-range capacitance type micro-pressure sensor

Technical Field

The invention relates to the field of micro electro mechanical systems, in particular to a ring contact high-range capacitive micro pressure sensor.

Background

The pressure sensor is widely applied to the fields of industry, military, aviation, daily life and the like. According to the working principle, the micro-pressure sensor can be divided into a capacitance type, a piezoresistive type, a piezoelectric type and the like, wherein the capacitance type has the advantages of high sensitivity, small temperature drift and the like, so the development is rapid. The range of a conventional capacitive micro-pressure sensor is mainly affected by two factors: the maximum flexibility value of the film (including the moving electrode) allowed by preventing the short circuit of the moving electrode and the fixed electrode, namely the initial gap of the moving electrode and the fixed electrode, and the bearing capacity of the film. In the traditional capacitance type micro pressure sensor, the maximum deflection position is always positioned at the center of the film, and once the deflection of the position reaches the initial gap value of the movable electrode and the fixed electrode, the measured pressure exceeds the range. In addition, in the conventional capacitive micro pressure sensor, the load bearing capacity of the membrane depends only on the bending stiffness and material properties of the membrane.

Based on the search of the prior art documents, Wen h.ko in US patent publication No. US005528452, "Capacitive absolute pressure sensor", proposes a contact-mode-based high-range Capacitive micro-pressure sensor, whose principle is: the insulating layer is covered on the fixed electrode, so that the movable electrode and the fixed electrode can not be short-circuited, the movable electrode is continuously deformed after contacting the insulating layer, the measuring range is not limited by the initial gap of the movable electrode and the fixed electrode, and meanwhile, the insulating layer provides support for the deformed film, so that the bearing capacity of the film is improved, and the measuring range of the capacitive micro-pressure sensor is greatly expanded. The patent and the related research results of the inventor of the patent still obtain wide attention and application in foreign countries and China, but a plurality of scholars including the inventor of the patent indicate that the invention has the defect of capacitance saturation in related papers, namely, as the contact area of a moving electrode and an insulating layer is increased, the area of the residual deformable area of the film is smaller and smaller, the rigidity is larger and larger, and the deformation of the film is more and more difficult along with the increase of the measured pressure, so that the capacitance change is smaller and smaller, and the sensitivity of the sensor gradually tends to zero. In addition, in the process of changing the contact area, van der waals (intermolecular) force and friction force exist between the thin film (including the moving electrode) and the insulating layer on the fixed electrode, and hysteresis error (return error) occurs in the sensor.

Disclosure of Invention

In order to solve the problems of over-low sensitivity caused by capacitance saturation, hysteresis errors caused by friction force and van der waals force and limitation of measuring range caused by uniform thickness of a film in the traditional contact mode and non-contact mode capacitive micro-pressure sensors in the background art, the invention provides a loop-contact high-measuring-range capacitive micro-pressure sensor.

The technical scheme adopted by the invention for solving the technical problems is as follows: a loop-contact high-range capacitive micro-pressure sensor, comprising: the device comprises a substrate, a fixed electrode, a film and a moving electrode, wherein the fixed electrode and the film are positioned on the substrate, the moving electrode is positioned on the film, a cavity is formed after the substrate and the film are bonded, a stop ring is arranged on the substrate in the cavity, an initial gap exists between the stop ring and the film, and when the device is in a working state, the film and the stop ring are in ring contact except for a range starting stage.

The width of the stop ring is less than one twentieth of the radius of the movable electrode and the fixed electrode.

The deformable part (not connected with the substrate) of the thin film is circular, and the movable electrode on the thin film and the fixed electrode on the substrate are correspondingly circular.

The membrane has a stepped non-uniform thickness feature with an edge thickness greater than a center portion thickness.

The fixed electrode is covered with an insulating layer, and the thickness of the insulating layer is smaller than the height of the stop ring (2).

The stop ring does not close.

The invention has the beneficial effects that: the contact between the moving electrode and the stop ring is ring contact, the area of a region on the film (including the moving electrode) directly blocked by the stop ring is very small, and the region on the film, which deforms and increases along with the increase of the measured pressure, almost keeps the area unchanged, so that the phenomenon of capacitor saturation can be effectively prevented; the contact area between the thin film and the stopper ring is almost kept constant and its area is very small, so that it can be considered that there are no frictional force due to the change in the contact area and van der waals force due to close contact between the objects, and thus there is no sensor hysteresis error due to the frictional force and van der waals force; the deformable part (not connected with the substrate) of the film (including the moving electrode) has a ladder shape, the thickness close to the edge is larger than that of other parts, and the bending moment of the film is the largest at the edge, so that the ladder structure is designed to be beneficial to reducing the maximum bending stress on the film, improve the strength of the film and better meet the requirement of high-range measurement.

Description of the drawings:

fig. 1 is a schematic view of the overall structure of an embodiment of the present invention (in order to clearly reflect the structure of the device, the ratio of the dimensions in the height direction in the figure is greatly different from the actual situation, and the following is the same).

Fig. 2 is a perspective cross-sectional view of the present invention.

Fig. 3 shows a substrate, an insulating layer (covered with a fixed electrode), a stop ring (etched from the substrate and integrated with the substrate), and an opening thereof.

FIG. 4 shows the substrate, the fixed electrode, the stop ring and the opening thereof.

Fig. 5 shows a membrane and a moving electrode.

Detailed Description

The embodiments of the invention will be further described with reference to the accompanying drawings in which:

in an embodiment of the present invention, a ring contact high-range capacitive micro pressure sensor includes: the pressure measuring device comprises a substrate 1, a fixed electrode 3 positioned on the substrate 1, an insulating layer 4 covering the fixed electrode 3, a film 5 and a moving electrode 6 positioned on the film 5, wherein the central part of the substrate 1 is sunken downwards to form a chamber after being bonded with the film 5, the substrate 1 is provided with a stop ring 2 integrally arranged with the substrate 1, the fixed electrode 3 and the moving electrode 6 form a variable capacitor, the measured pressure acts on the film 5, when the measured pressure reaches a certain value, the film 5 only contacts with the stop ring 2, so that the pressure measuring device works in a contact mode, and the insulating layer 4 is only used for preventing the fixed electrode 6 and the fixed electrode 3 from contacting with each other to cause short circuit when the measured pressure exceeds a range.

The contact between the film (including the moving electrode) and the stop ring is ring contact, most of the film (including the moving electrode) does not contact the stop structure and thus the deformation of the film is not directly blocked, the film (including the moving electrode) keeps continuously deforming along with the increase of the measured pressure, the capacitance saturation phenomenon can be effectively prevented, the contact area between the film (including the moving electrode) and the stop ring is almost kept unchanged, the contact area is very small, and therefore, the friction force caused by the change of the contact area and the van der waals force caused by the close contact between objects do not exist, and the sensor hysteresis error caused by the friction force and the van der waals force does not exist.

The stop rings are all obtained by etching the substrate, and the higher the stop rings are, the larger the measuring range of the pressure sensor is. The stop ring 2 is provided with a small opening 7 through which a lead connecting the inner and outer fixed electrodes of the stop ring passes to prevent the fixed electrode 3 from being divided into two parts separated from each other by the stop ring. The inner diameter, the outer diameter and the opening width of the stop ring are determined by the size of a graph on a mask plate, and finite element simulation calculation software ANSYS verifies that the deformation and the stress of the film are hardly influenced when the opening width on the stop ring occupies less than 1/50 of the circumference of the stop ring.

The deformable part (not the part connected with the substrate) of the film 5 adopts a non-uniform thickness ladder-shaped structure, the height of the deformable part close to the edge is larger than that of other parts, the structure is processed by an etching process, and the bending moment of the film is the largest at the edge, so the design of the ladder-shaped structure is beneficial to reducing the maximum bending stress on the film, improving the strength of the ladder-shaped structure and better meeting the requirement of high-range measurement.

The fixed electrode 3 and the movable electrode 6 are respectively positioned on the substrate 1 and the film 5 and form a variable capacitor. The two electrodes can be processed by sputtering, evaporation and other processes.

The insulating layer 4 is positioned on the fixed electrode 3 or the moving electrode 6, the thickness of the insulating layer 4 is far smaller than the height of the stop ring 2, the insulating layer only has the function of preventing the short circuit of the fixed electrode when the measured pressure exceeds the range, so the precision requirement on the thickness of the insulating layer is far lower than that of the traditional contact mode micro-pressure sensor, the requirements on the compactness of the insulating layer, the bonding strength between the insulating layer and a substrate and the like are also lower, and the insulating layer can be manufactured by processes such as sputtering, evaporation and the like, and can also be manufactured by a mode with lower precision and lower cost such as whirl coating and the like due to the lower requirement on the processing precision.

The skilled person should understand that: although the invention has been described in terms of the above specific embodiments, the inventive concept is not limited thereto and any modification applying the inventive concept is intended to be included within the scope of the patent claims.

Claims

1. A loop-contact high-range capacitive micro-pressure sensor, comprising: the utility model provides a fixed electrode (3), film (5) on base (1), be located moving electrode (6) on film (5), its characterized in that: the utility model discloses a little pressure sensor, including base (1), diaphragm (5), but the deformation part of diaphragm (5) is in the middle of the range initial stage, base (1) with form the cavity behind the bonding of diaphragm (5) in the cavity, be equipped with backstop ring (2) on base (1), the deformable part of diaphragm (5) has the unequal thickness characteristic of echelonment, the deformable part of diaphragm (5) be on diaphragm (5) non with the base connecting portion, its edge thickness is greater than central thickness, decide electrode (3) coats and is stamped insulating layer (4), when little pressure sensor is in non-operating condition, have the clearance between backstop ring (2) and diaphragm (5), when being operating condition, except range initial stage, the ring contact takes place for diaphragm (5) and backstop ring (2).

2. The loop-contact high-range capacitive micro pressure sensor of claim 1, wherein: the width of the stop ring (2) is less than one twentieth of the radius of the movable electrode (6) and the fixed electrode (3).

3. The loop-contact high-range capacitive micro pressure sensor of claim 1, wherein: the deformable part of the film (5) is circular, and the moving electrode (6) on the film and the fixed electrode (3) on the substrate (1) are correspondingly circular.

4. The loop-contact high-range capacitive micro pressure sensor according to claim 1, 2 or 3, wherein: the thickness of the insulating layer (4) is smaller than the height of the stop ring (2).

5. The ring-contact high-range capacitive micro-pressure sensor according to claim 1 or 2, wherein: the stop ring (2) is not closed.