1. The multi-range integrated composite membrane type MEMS pressure sensor is characterized by comprising a silicon substrate layer (2), wherein a third etching cavity (13) is etched at the lower end of the silicon substrate layer (2), and a second etching cavity (11) is etched at the upper end of the silicon substrate layer (2); the second etching cavity (11) is smaller than the third etching cavity (13);

a silicon device layer (3) is further arranged on the silicon substrate layer (2), and a first etching cavity (9) is etched at the position, located in the second etching cavity (11), of the bottom of the silicon device layer (3); the first etching cavity (9) is smaller than the second etching cavity (11);

a first range sensitive membrane (8), a second range sensitive membrane (10) and a third range sensitive membrane (12) are respectively and correspondingly arranged on the first etching cavity (9), the second etching cavity (11) and the third etching cavity (13);

twelve groups of piezoresistor strips (4) are arranged on the upper layer of the silicon device layer (3), three groups of Wheatstone bridge circuits are formed from inside to outside, and each group of Wheatstone bridge circuits comprises four piezoresistor strips (4);

the innermost group of Wheatstone bridge circuits is correspondingly connected with the first range sensitive membrane (8) in the first etching cavity (9) through a metal lead (5);

the centered group of Wheatstone bridge circuits is correspondingly connected with a second range sensitive membrane (10) in a second etching cavity (11) through a metal lead (5);

a group of Wheatstone bridge circuits at the outermost side are correspondingly connected with a third range sensitive membrane (12) in a third etching cavity (13) through a metal lead (5);

the first etching cavity (9), the second etching cavity (11) and the third etching cavity (13) are symmetrically distributed by taking the central point of the silicon device layer (3) as an axis;

the first etching cavity (9) is of a trapezoid cavity structure with an opening facing downwards, the first range sensitive membrane (8) is arranged on the upper top surface of the first etching cavity (9), and the four piezoresistor strips (4) of the innermost Wheatstone bridge circuit are arranged on the silicon device layer (3) at positions corresponding to the edge of the first range sensitive membrane (8).

2. A multi-range integrated composite membrane chip MEMS pressure sensor according to claim 1, characterized in that a glass substrate (1) is further provided under the silicon substrate layer (2).

3. A multi-range integrated composite membrane MEMS pressure sensor as claimed in claim 1, characterized in that between three sets of wheatstone bridge circuits, PN diodes (7) are arranged, with the piezo-resistive strips (4) being isolated by PN diodes (7).

4. A multi-range integrated composite membrane type MEMS pressure sensor according to claim 3, wherein a plurality of voltage sources are provided, and 8 metal pads (6) are provided at the connection terminals of the three sets of wheatstone bridge circuits, and are respectively connected and closed with the corresponding voltage sources through the metal pads (6).

5. A multi-range integrated composite membrane chip MEMS pressure sensor according to any of claims 1-4, characterized in that four of the piezo-resistive strips (4) in a group of Wheatstone bridge circuits are uniformly distributed in four directions on the silicon device layer (3).

6. A multi-range integrated composite membrane type MEMS pressure sensor according to claim 1, wherein the third etching cavity (13) is a trapezoidal cavity structure with an opening facing downward, the third range sensitive membrane (12) is disposed on the top surface of the third etching cavity (13), and the four piezoresistive strips (4) of the outermost wheatstone bridge circuit are disposed on the silicon device layer (3) at positions corresponding to the edges of the third range sensitive membrane (12).

7. The multi-range integrated composite membrane type MEMS pressure sensor according to claim 1, wherein the second etching cavity (11) is a trapezoid cavity structure with an upward opening, the second range sensitive membrane (10) is disposed on a bottom surface of the second etching cavity (11), and the four piezoresistive strips (4) of the wheatstone bridge circuit located at the middle side are disposed on the silicon device layer (3) at positions corresponding to edges of the second range sensitive membrane (10).

Background

With the development of micro-electromechanical technology, due to the piezoresistive effect of the second generation semiconductor material monocrystalline silicon and the good mechanical structure characteristics thereof, the MEMS silicon piezoresistive pressure sensor manufactured by the micro-electromechanical technology gradually becomes the mainstream of the market. The device has the advantages of small volume, high precision, low cost and strong stability, and can be widely applied to the fields of aerospace, petroleum, electric power and the like. The silicon piezoresistive pressure sensor mainly comprises a sensitive diaphragm and piezoresistor strips, and has the working principle that the sensitive diaphragm is subjected to flexural deformation under the action of external pressure, the piezoresistor on the diaphragm changes the resistivity per se through the piezoresistive effect under the action of the flexural stress of the diaphragm, and a Wheatstone bridge circuit consisting of the four piezoresistor strips converts the resistivity change into the change of output voltage.

The traditional MEMS pressure sensor is provided with a sensitive diaphragm formed by deep cavity etching and 2 pairs of piezoresistors formed on the sensitive diaphragm through diffusion or ion implantation process, and the Wheatstone bridge connection is formed through metal deposition process. For the traditional silicon piezoresistive pressure sensor, the measurement range and the structural sensitivity are closely related, and in structural design, the film thickness and the area of a sensitive membrane need to be changed in order to increase the measurement range or reduce the measurement range, so that the traditional pressure sensor chip is used for measuring multiple pressure ranges, a large-range chip is often adopted to replace a small-range chip so as to detect the small-range pressure range, or the pressure chips with different structures are reprocessed through an MEMS (micro electro mechanical system) process to ensure the small-range pressure range. On the one hand, the sensitivity of the whole sensor is very low when the pressure chip with a large measuring range measures the tiny pressure, the burden of a rear-end interface circuit is increased, in addition, the development cost is greatly increased due to the fact that a front-end process flow sheet and the structural design are carried out again, on the other hand, for the rear-end packaging test, the size of the packaging tube shell is changed due to the fact that the structural sizes of different chips are different, and adverse effects are caused on the consistency and the universality replacement of subsequent products.

Disclosure of Invention

Aiming at the defects and requirements in the prior art, the invention provides a multi-range integrated composite membrane type MEMS pressure sensor, which integrates a plurality of modules with different ranges in one sensor, realizes the adaptability measurement of objects with different ranges and different sizes, and simultaneously improves the measurement consistency.

The specific implementation content of the invention is as follows:

the invention provides a multi-range integrated composite membrane type MEMS pressure sensor, which comprises a silicon substrate layer, wherein a third etching cavity is etched at the lower end of the silicon substrate layer, and a second etching cavity is etched at the upper end of the silicon substrate layer; the second etching cavity is smaller than the third etching cavity;

a silicon device layer is further arranged on the silicon substrate layer, and a first etching cavity is etched at the position, located in the second etching cavity, of the bottom of the silicon device layer; the first etching cavity is smaller than the second etching cavity;

a first range sensitive membrane, a second range sensitive membrane and a third range sensitive membrane are respectively and correspondingly arranged on the first etching cavity, the second etching cavity and the third etching cavity;

twelve groups of piezoresistor strips are arranged on the upper layer of the silicon device layer, three groups of Wheatstone bridge circuits are formed from inside to outside, and each group of Wheatstone bridge circuit comprises four piezoresistor strips;

the innermost group of Wheatstone bridge circuits is correspondingly connected with the first measuring range sensitive membrane in the first etching cavity through a metal lead;

the centered group of Wheatstone bridge circuits is correspondingly connected with the second measuring range sensitive membrane in the second etching cavity through a metal lead;

a group of Wheatstone bridge circuits on the outermost side is correspondingly connected with a third range sensitive membrane in a third etching cavity through a metal lead;

the first etching cavity, the second etching cavity and the third etching cavity are symmetrically distributed by taking the central point of the silicon device layer as an axis.

In order to better implement the invention, further, a glass substrate is arranged below the silicon substrate layer.

In order to better implement the invention, further, PN diodes are arranged among the three groups of Wheatstone bridge circuits, and the piezoresistor strips are separated by the PN diodes.

In order to better implement the invention, a plurality of voltage sources are further provided, and 8 metal pads are provided at the connection ends of the three groups of Wheatstone bridge circuits, and are respectively connected with and closed to the corresponding voltage sources through the metal pads.

In order to better implement the invention, four piezoresistor strips in a group of Wheatstone bridge circuits are uniformly distributed on the silicon device layer in four directions.

In order to better implement the present invention, further, the third etching cavity is a trapezoidal cavity structure with an opening facing downward, the third range sensitive membrane is disposed on the upper top surface of the third etching cavity, and the four piezoresistive strips of the outermost wheatstone bridge circuit are disposed on the silicon device layer at positions corresponding to the edges of the third range sensitive membrane.

In order to better implement the present invention, further, the second etching cavity is a trapezoid cavity structure with an upward opening, the second range sensitive membrane is disposed on a lower bottom surface of the second etching cavity, and the four piezoresistive strips of the wheatstone bridge circuit located on the middle side are disposed on the silicon device layer at positions corresponding to edges of the second range sensitive membrane.

In order to better implement the present invention, further, the first etching cavity is a trapezoidal cavity structure with an opening facing downward, the first range sensitive membrane is disposed on the upper top surface of the first etching cavity, and the four piezoresistor strips of the innermost wheatstone bridge circuit are disposed on the silicon device layer at positions corresponding to the edges of the first range sensitive membrane.

Compared with the prior art, the invention has the following advantages and beneficial effects:

the invention can simultaneously measure three or more pressure ranges by adopting the composite diaphragm structure, greatly reduces the size area of a chip, improves the integration level of the sensor, simultaneously meets the sensitivity and the measuring range during low-pressure measurement, and has the process flow communicated with the traditional MEMS process, compatible with the integrated circuit process and easy integration.

Drawings

FIG. 1 is a schematic cross-sectional view of the present invention;

FIG. 2 is a schematic top view of the present invention;

FIG. 3 is a schematic diagram of a circuit in which all of the varistor strips are connected for use in accordance with the present invention;

FIG. 4 is a schematic diagram of a circuit in which eight piezo-resistive strips are connected for use under relatively low pressure in accordance with the present invention;

FIG. 5 is a schematic diagram of a circuit for use with six piezo-resistor strips in communication under the action of medium pressure in the present invention;

FIG. 6 is a schematic diagram of a circuit in which four piezo-resistive strips are connected for use under relatively high pressure in accordance with the present invention;

FIG. 7 is a schematic view of a measurement performed with a small applied pressure;

FIG. 8 is a schematic illustration of measurements made with moderate pressure;

fig. 9 is a schematic view of a measurement performed with a large pressure applied.

Wherein: 1. the device comprises a glass substrate, 2 a silicon substrate layer, 3 a silicon device layer, 4 a piezoresistor strip, 5 a metal lead, 6 a metal Pad, 7 a PN junction diode, 8 a first range sensitive membrane, 9 a first etching cavity, 10 a second range sensitive membrane, 11 a second etching cavity, 12 a third range sensitive membrane, 13 and a third etching cavity.

Detailed Description

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments, and therefore should not be considered as a limitation to the scope of protection. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.

In the description of the present invention, it is to be noted that, unless otherwise explicitly specified or limited, the terms "disposed," "connected," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

Example 1:

the embodiment provides a multi-range integrated composite membrane type MEMS pressure sensor, which comprises a silicon substrate layer 2, wherein a third etching cavity 13 is etched at the lower end of the silicon substrate layer 2, and a second etching cavity 11 is etched at the upper end of the silicon substrate layer 2; the second etching cavity 11 is smaller than the third etching cavity 13;

a silicon device layer 3 is further arranged on the silicon substrate layer 2, and a first etching cavity 9 is etched at the position, located in the second etching cavity 11, of the bottom of the silicon device layer 3; the first etching cavity 9 is smaller than the second etching cavity 11;

a first range sensitive membrane 8, a second range sensitive membrane 10 and a third range sensitive membrane 12 are respectively and correspondingly arranged on the first etching cavity 9, the second etching cavity 11 and the third etching cavity 13;

twelve groups of piezoresistor strips 4 are arranged on the upper layer of the silicon device layer 3, three groups of Wheatstone bridge circuits are formed from inside to outside, and each group of Wheatstone bridge circuits comprises four piezoresistor strips 4;

the innermost group of Wheatstone bridge circuits is correspondingly connected with the first range sensitive membrane 8 in the first etching cavity 9 through the metal lead 5;

the centered group of Wheatstone bridge circuits is correspondingly connected with a second range sensitive membrane 10 in a second etching cavity 11 through a metal lead 5;

a group of Wheatstone bridge circuits at the outermost side are correspondingly connected with a third range sensitive membrane 12 in a third etching cavity 13 through a metal lead 5;

the first etching cavity 9, the second etching cavity 11 and the third etching cavity 13 are symmetrically distributed by taking the central point of the silicon device layer 3 as an axis.

Further, a glass substrate 1 is also arranged below the silicon substrate layer 2.

Further, four varistor strips 4 in a group of wheatstone bridge circuits are uniformly distributed on the silicon device layer 3 in four directions.

The working principle is as follows: as shown in fig. 1 and 2, it is characterized in that: the glass substrate 1 is used as a chip substrate structure, a silicon substrate layer 2 is arranged on the glass substrate 1, cavities with different sizes are etched on the silicon substrate layer 2 and are respectively called a second etching cavity 11 and a third etching cavity 13, so that a second-range sensitive membrane 10 and a third-range sensitive membrane 12 are respectively formed, a silicon device layer 3 is arranged on the silicon substrate layer 2, a small etching cavity 9 is etched at the bottom of the silicon device layer 3 to form a first-range sensitive membrane 8, twelve piezoresistor strips 4 on the silicon device layer 3 are respectively corresponding to Wheatstone bridge circuits of small, medium and large three-range pressure sensors, the three Wheatstone bridge circuits have different voltage sources, the respective voltage sources are switched on according to different measuring ranges, and when the measuring is carried out in different measuring ranges, only the corresponding Wheatstone bridge circuit has corresponding voltage output.

Example 2:

in this embodiment, in order to better implement the present invention based on embodiment 1 described above, as shown in fig. 3, 4, 5, 6, 7, 8, and 9, PN diodes 7 are provided between three sets of wheatstone bridge circuits, and the varistor strips 4 are isolated by the PN diodes 7.

In order to better implement the invention, a plurality of voltage sources are further provided, and 8 metal pads 6 are arranged at the connection ends of the three groups of Wheatstone bridge circuits, and are respectively connected with and closed to the corresponding voltage sources through metal pads 6.

The working principle is as follows: twelve piezoresistor strips 4 on the silicon device layer 3 form a Wheatstone bridge circuit of the small, medium and large three-range pressure sensor, the Wheatstone bridge circuits with different ranges correspond to different voltage sources, the respective voltage sources are switched on according to different measuring ranges, and the Wheatstone bridge circuits formed by the twelve piezoresistor strips are respectively isolated through diodes, so that when the pressure sensors are measured in different ranges, only the corresponding Wheatstone bridge circuits have corresponding voltage outputs. The overall circuit schematic is shown in fig. 3. Fig. 4 is a schematic diagram of a wheatstone bridge circuit formed by eight piezoresistors with small range, fig. 5 is a schematic diagram of a wheatstone bridge circuit formed by six piezoresistors with medium range, and fig. 6 is a schematic diagram of a wheatstone bridge circuit formed by four piezoresistors with large range.

Fig. 7 is a schematic diagram of a stress of the pressure sensor under a small pressure, in which only a small-range diaphragm of the overall structure undergoes flexural deformation, the corresponding wheatstone bridge is shown in fig. 4, fig. 8 is a schematic diagram of a stress of the pressure sensor under a medium pressure, both the medium-sized diaphragm and the small-sized diaphragm of the overall structure undergo flexural deformation, the corresponding wheatstone bridge is shown in fig. 5 due to a single-end conduction effect of the diode, fig. 9 is a schematic diagram of a stress of the pressure sensor under a large pressure, all three diaphragms of the overall structure undergo flexural deformation, and the corresponding wheatstone bridge is shown in fig. 6.

Other parts of this embodiment are the same as those of embodiment 1, and thus are not described again.

Example 3:

in this embodiment, on the basis of any one of the above embodiments 1-2, in order to better implement the present invention, as shown in fig. 1, further, the third etching cavity 13 is a trapezoidal cavity structure with an opening facing downward, the third range-sensitive membrane 12 is disposed on the upper top surface of the third etching cavity 13, and the four piezoresistive strips 4 of the outermost wheatstone bridge circuit are disposed on the silicon device layer 3 at positions corresponding to the edges of the third range-sensitive membrane 12.

The second etching cavity 11 is a trapezoid cavity structure with an upward opening, the second-range sensitive membrane 10 is arranged on the lower bottom surface of the second etching cavity 11, and the four piezoresistor strips 4 of the wheatstone bridge circuit positioned on the middle side are arranged on the silicon device layer 3 at positions corresponding to the edges of the second-range sensitive membrane 10.

The first etching cavity 9 is a trapezoid cavity structure with a downward opening, the first range sensitive membrane 8 is arranged on the upper top surface of the first etching cavity 9, and the four piezoresistor strips 4 of the innermost Wheatstone bridge circuit are arranged on the silicon device layer 3 at positions corresponding to the edge of the first range sensitive membrane 8.

The working principle is as follows: the stress can be more uniform by corresponding to the uniform setting, so that the measuring result is more accurate.

Other parts of this embodiment are the same as any of embodiments 1-2 described above, and thus are not described again.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way, and all simple modifications and equivalent variations of the above embodiments according to the technical spirit of the present invention are included in the scope of the present invention.