CN111928981A

CN111928981A - MEMS pressure sensor

Info

Publication number: CN111928981A
Application number: CN202010945962.XA
Authority: CN
Inventors: 桑新文; 高洪连; 盛云
Original assignee: Suzhou Novosense Microelectronics Co ltd
Current assignee: Suzhou Novosense Microelectronics Co ltd
Priority date: 2020-09-10
Filing date: 2020-09-10
Publication date: 2020-11-13

Abstract

The invention provides a MEMS pressure sensor, which comprises a device plate, a first electrode, a second electrode and a first electrode, wherein the device plate is provided with a first surface and a second surface which are oppositely arranged; the device board comprises a device board and is characterized in that an island structure, a fixed support structure surrounding the island structure and four beam structures connected between the island structure and the fixed support structure are arranged on the first surface of the device board, and a membrane structure formed by surrounding the fixed support structure, the island structure and the beam structures is also arranged on the first surface; still be provided with the resistance device of branch on four beam structures of locating on the first surface of device board, arbitrary resistance device all includes at least one and is rectangular resistance, resistance is equallyd divide and is extended along the extending direction who is on a parallel with respective beam structure respectively.

Description

MEMS pressure sensor

Technical Field

The invention relates to the field of sensors, in particular to an MEMS pressure sensor.

Background

The MEMS pressure sensor is a process of processing a mechanical structure such as a sensitive membrane for sensing pressure and a wheatstone bridge circuit on a semiconductor substrate by using a semiconductor process. The processes adopted include, for example: film growth, ion implantation, metal sputtering, dry etching, wet etching, wafer bonding process, thinning, grinding and polishing and the like. The MEMS pressure sensor can convert pressure signals into electrical signals which are easy to identify and process, so that the MEMS pressure sensor is widely applied to the fields of consumer electronics, medical electronics, automotive electronics, industrial control, petrochemical industry and the like.

In the prior art, a MEMS pressure sensor generally uses a flat-mode structure as a sensing membrane to sense a pressure to be measured, and a wheatstone bridge circuit is used to convert a pressure signal into an electrical signal; typically, the flat membrane structure comprises a flat membrane and a support structure; the core components of the Wheatstone bridge circuit are resistors R1, R2, R3 and R4 which are positioned at the center of four sides of a flat membrane, wherein R1 and R3 are perpendicular to the membrane side, R2 and R4 are parallel to the membrane side, and R1 and R3 are parallel to R2 and R4. When pressure acts on the flat membrane structure, the flat membrane deforms to generate stress, wherein the maximum stress is positioned at the centers of four sides of the flat membrane, namely the resistors R1, R2, R3 and R4; the resistances of the resistors R1, R2, R3 and R4 change due to stress, wherein R1 and R3 increase or decrease, and R2 and R4 correspondingly decrease or increase, the wheatstone bridge is unbalanced to generate a voltage output, which is the working principle of the MEMS pressure sensor.

The MEMS pressure sensor with the structure can obtain excellent performance for medium and high measuring ranges; but for small scale. For example, for MEMS pressure sensors less than 10kpa, a flat membrane is required to be large and thin in order to achieve a certain sensitivity. Such flat membrane structures have the following disadvantages: firstly, a thin and large flat membrane structure shows great nonlinearity due to excessive central deformation, so that the measurement accuracy of the MEMS pressure sensor is poor; secondly, the area of the MEMS pressure sensor chip is larger due to the thin and large flat membrane structure, the wafer chip density is small, and the utilization rate is low; thirdly, the thin and large flat membrane structure makes the MEMS pressure sensor chip susceptible to package stress, thereby increasing the packaging difficulty.

In another prior art, a flat membrane structure is processed into an island beam membrane structure, wherein the island beam membrane structure includes a central island and a beam connecting the central island and a support structure; but wherein the resistors R1, R2, R3 and R4 are laid out in the same manner as the above-described flat film structure.

In the island beam membrane structure, the central island limits the deformation of the membrane structure, thereby improving the nonlinearity of the sensor. And the beam can concentrate stress generated by phase change of the membrane structure, so that the sensitivity of the sensor is improved, wherein the narrower the width of the beam is, the better the stress concentration effect is. Since the resistors R1, R3 are perpendicular to the membrane edge, R2, R4 are parallel to the membrane edge, and R1, R3 are parallel to R2, R4, the width of the beam is limited by the length of R2 and R4. Since the resistance of the wheatstone bridge constituting the MEMS pressure sensor is usually 5k Ω, the width of the resistance is 10um, and the square resistance is about 350 Ω, the length of the resistance is usually 100um or more. In addition, the resistor needs to be led out by a lead and the beam width is added, so that the actually required beam width can reach about 200um, the beam width is limited, and the improvement on the sensor sensitivity is not favorable.

In addition, due to the existence of the beam structure, the resistor layout mode causes inconsistency of lead wires led out from the resistors R1, R2, R3 and R4 which induce stress, so that the resistances of the resistors R1 and R3 are unequal to the resistances of the resistors R2 and R4, the output of the sensor is not zero under zero pressure, and the performance of the sensor is influenced.

Therefore, a new MEMS pressure sensor must be designed.

Disclosure of Invention

In order to solve one of the above problems, the present invention provides a MEMS pressure sensor, including a device board having a first surface and a second surface oppositely disposed;

the device board comprises a device board and is characterized in that an island structure, a fixed support structure surrounding the island structure and four beam structures connected between the island structure and the fixed support structure are arranged on the first surface of the device board, and a membrane structure formed by surrounding the fixed support structure, the island structure and the beam structures is also arranged on the first surface;

still be provided with the resistance device of branch on four beam structures of locating on the first surface of device board, arbitrary resistance device all includes at least one and is rectangular resistance, resistance is equallyd divide and is extended along the extending direction who is on a parallel with respective beam structure respectively.

As a further improvement of the present invention, the resistance device includes a first resistance device, a second resistance device, a third resistance device and a fourth resistance device, and the first resistance device, the second resistance device, the third resistance device and the fourth resistance device are respectively located on the central line position of the respective beam structures and respectively extend along the central line direction of the respective beam structures.

As a further improvement of the present invention, the first resistance device, the second resistance device, the third resistance device and the fourth resistance device each include one resistance.

As a further improvement of the present invention, the first resistance device, the second resistance device, the third resistance device and the fourth resistance device each include at least two resistances.

As a further improvement of the present invention, the resistances of the first resistance means, the second resistance means, the third resistance means and the fourth resistance means are each symmetrically distributed along the center line of the respective beam structure.

As a further improvement of the present invention, one end of each of the first resistor device and the third resistor device is located at a joint of the beam structure and the clamped structure; and one end of each of the second resistor device and the fourth resistor device is positioned at the joint of the beam structure and the island structure.

As a further improvement of the present invention, the resistances of the first resistance device, the second resistance device, the third resistance device and the fourth resistance device are all distributed along the central line of the respective beam structures.

As a further improvement of the present invention, one end of each of the first resistor device, the second resistor device, the third resistor device, and the fourth resistor device is located at a joint of the respective beam structure and the clamped structure, and the other end is located at a joint of the respective beam structure and the island structure.

As a further improvement of the present invention, the resistors of the first resistor device, the second resistor device, the third resistor device and the fourth resistor device are respectively connected in series or in parallel to form a single wheatstone bridge.

As a further improvement of the present invention, the resistors on the first resistor device, the second resistor device, the third resistor device and the fourth resistor device are connected to each other to form at least two groups of wheatstone bridges.

Compared with the prior art, the resistors in the MEMS pressure sensor respectively extend along the extension direction parallel to the beam structures, the beam structures can concentrate stress generated by phase change of the membrane structures, the width of the beam structures is not limited by the length of the resistor device any more, the beam width same as that of the resistor device can be realized, the stress is concentrated, and the sensitivity of the sensor is further improved. In addition, the layout mode of the resistor device can flexibly lead out and wire the resistor device, ensures the consistency of the resistor device and lead-out wires of the resistor device, and further reduces zero point errors, temperature mismatch and the like.

Drawings

FIG. 1 is a schematic circuit diagram of a Wheatstone bridge of a pressure sensor according to the present invention;

FIG. 2 is a schematic structural diagram of a first embodiment of the pressure sensor of the present invention;

FIG. 3 is a schematic structural diagram of a second embodiment of the pressure sensor of the present invention;

fig. 4 is a schematic structural diagram of a third embodiment of the pressure sensor of the present invention.

DETAILED DESCRIPTION OF EMBODIMENT (S) OF INVENTION

In order to make those skilled in the art better understand the technical solution of the present invention, the technical solution in the embodiment of the present invention will be clearly and completely described below with reference to the drawings in the embodiment of the present invention, and it is obvious that the described embodiment is only a part of the embodiment of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

As shown in fig. 1 to 4, the present invention provides a MEMS pressure sensor, which includes a device board 100, the device board 100 having a first surface and a second surface disposed oppositely;

the device board 100 is characterized in that an island structure 1, a support structure 2 surrounding the island structure 1, and four beam structures 3 connected between the island structure 1 and the support structure 2 are arranged on a first surface of the device board 100, and a membrane structure 4 formed by surrounding the support structure 2, the island structure 1, and the beam structures 3 is further arranged on the first surface. Since the MEMS pressure sensor can be formed by etching, the clamped structure 2, the island structure 1 and the beam structure 3 each protrude the membrane structure 4 on the first surface, i.e. the membrane structure 4 is recessed on the first surface with respect to the clamped structure 2, the island structure 1 and the beam structure 3.

The first surface of the device board 100 is further provided with resistor devices respectively arranged on the four beam structures 3, and any resistor device includes at least one rectangular resistor, and the resistors extend along the extending direction parallel to the respective beam structures 3.

Similarly to the prior art, the resistor devices are four and are respectively arranged on the four beam structures 3, and the resistors in the resistor devices are all arranged in a rectangular shape. However, unlike the prior art, two of the resistor devices extend along the extension direction of the respective beam structures 3, and the other two resistor devices are perpendicular to the extension direction of the respective beam structures 3, which limits the width of the beams and is disadvantageous to the improvement of the sensor sensitivity.

Therefore, the resistors in the MEMS pressure sensor of the present invention each extend in parallel to the extending direction of the respective beam structure 3, the beam structure 3 can concentrate the stress generated by the phase change of the membrane structure 4, the width of the beam structure 3 is not limited by the length of the resistor, and the beam width equal to the width of the resistor can be realized, so that the stress is more concentrated, and the sensitivity of the sensor is further improved. In addition, the layout mode of the resistor device can flexibly lead out and wire the resistor device, ensures the consistency of the resistor device and lead-out wires of the resistor device, and further reduces zero point errors, temperature mismatch and the like.

In particular, as shown in fig. 2, the resistance means comprise a first resistance means R1, a second resistance means R2, a third resistance means R3 and a fourth resistance means R4, said first resistance means R1, second resistance means R2, third resistance means R3 and fourth resistance means R4 being respectively located at the position of the middle line of the respective beam structure 3 and respectively extending in the direction of the middle line of the respective beam structure 3.

Thus, in the embodiment of the invention, the resistances on the four resistance devices extend not only in a direction parallel to the extension direction of the respective beam structure 3, but also in a direction along the middle line of the respective beam structure 3. Thereby, a larger space can be provided for the width of the beam structure 3.

Furthermore, since the beam structure 3 is distributed in a cross shape, the center line of the beam structure 3 where the first resistor R1 is located and the center line of the beam structure 3 where the third resistor R3 is located are on the same straight line, and the center line of the beam structure 3 where the second resistor R2 is located and the center line of the beam structure 3 where the fourth resistor R4 is located are also on the same straight line and perpendicular to each other. That is, the resistances of the first R1 and third R3 resistive devices are perpendicular to the resistances of the second R2 and fourth R4 resistive devices.

Further, as shown in fig. 1, the circuit connection condition of the first resistor device R1 to the fourth resistor device R4 of the present invention is shown when they form a wheatstone bridge. Specifically, a first resistor device R1 and a second resistor device R2 are connected in series, a third resistor device R3 and a fourth resistor device R4 are connected in series, and both ends of the first resistor device R1 and the second resistor device R2 are connected to the high voltage level VDD and the ground terminal GND respectively, one end of the output level Vout is located between the first resistor device R1 and the second resistor device R2, and the other end of the output level Vout is located between the third resistor device R3 and the fourth resistor device R4. When the MEMS pressure sensor senses a pressure, the membrane structure 4 generates a stress, and the resistances of the first resistor device R1 to the fourth resistor device R4 change due to the stress, wherein the resistances of the first resistor device R1 and the third resistor device R3 increase or decrease, the resistances of the second resistor device R2 and the fourth resistor device R4 correspondingly decrease or increase, the wheatstone bridge is unbalanced, and a voltage output is generated, which is a working principle of the MEMS pressure sensor.

Specifically, in the first embodiment of the present invention, as shown in fig. 2, the first resistor device R1, the second resistor device R2, the third resistor device R3 and the fourth resistor device R4 each include one resistor. Thus, the first through fourth resistor means R1-R4 may be connected in the manner described above to form a single wheatstone bridge configuration.

And, as shown in fig. 2, one end of each of said first R1 and third R3 resistance means is located at the junction of the respective beam structure 3 and the clamped structure 2; one end of each of the second R2 and fourth R4 resistor means is located at the junction of the respective beam structure 3 and island structure 1.

Since the first resistor means R1 to the fourth resistor means R4 each comprise a resistor which, although rectangular, has a length shorter than the length of the beam structure 3. Thus, in this embodiment, only one end of the resistors in the first resistor arrangement R1 and the third resistor arrangement R3 is located at the junction of the respective beam structure 3 and the clamped structure 2, while one end of the resistors in the second resistor arrangement R2 and the fourth resistor arrangement R4 is located at the junction of the respective beam structure 3 and the island structure 1. Therefore, when the MEMS sensor senses pressure, the difference between the stresses sensed by the resistors of the first resistor device R1 to the fourth resistor device R4 is large, and the corresponding resistance values are different, so that the sensitivity can be increased.

Alternatively, the first resistor device R1, the second resistor device R2, the third resistor device R3 and the fourth resistor device R4 may each include at least two resistors. If the number of the resistors in the resistor device is multiple, the resistors in the resistor device may have different arrangements.

For example, as shown in fig. 3, the resistances of the first, second, third and fourth resistive devices R1, R2, R3 and R4, respectively, are symmetrically distributed along the midline of the respective beam structure 3.

That is, the resistance not only extends in the direction of the center line of the beam structure 3, but also is symmetrically distributed along the center line of the beam structure 3. As shown in fig. 3, each resistor device comprises two resistors, and the length direction of the two resistors is parallel to the center line direction of the respective beam structure 3, and the two resistors are respectively located at two sides of the center line of the beam structure 3. Similarly, if each resistor device includes other even number of resistors, the even number of resistors are respectively and uniformly distributed on two sides of the center line of the beam structure 3. If each resistor device comprises an odd number of resistors, a central line of one resistor is necessarily located on the central line of the beam structure 3, and the rest resistors are also respectively and uniformly distributed on two sides of the central line of the beam structure 3.

In this embodiment, the resistors included in the resistor devices may be connected in series or in parallel, and the first resistor device R1 to the fourth resistor device R4 may be connected to each other in the above manner to form a single wheatstone bridge.

Similarly, in the second embodiment, one end of each of the first resistance device R1 and the third resistance device R3 is located at the junction of the respective beam structure 3 and the supporting structure 2; one end of each of the second R2 and fourth R4 resistor means is located at the junction of the respective beam structure 3 and island structure 1.

Although the first to fourth resistor devices R1 to R4 each include at least two resistors in the second embodiment, the resistors in each of the beam structures 3 are arranged and distributed in the width direction of the beam structure 3, and thus the distribution length of the resistors in each of the resistor devices is smaller than the length of the beam structure 3. Therefore, when the MEMS sensor senses pressure, the difference between the stresses sensed by the resistors of the first resistor device R1 to the fourth resistor device R4 is large, and the corresponding resistance values are different, so that the sensitivity can be increased.

In a third embodiment of the invention, as shown in fig. 4, the resistances of the first R1, second R2, third R3 and fourth R4 resistance devices are all arranged along the central line of the respective beam structure 3.

In this embodiment, the resistors in the first resistor device R1 to the fourth resistor device R4 are distributed along the center line of the beam structure 3, so that a resistor array can be formed on the beam structure 3. As shown in fig. 4, the resistance means on each beam structure 3 in this embodiment comprises two resistors, and the two resistors are distributed along the central line until the length direction of the beam structure 3 is full. Of course, there may be three or more resistors on each of the beam structures 3.

In this embodiment, one end of each of the first resistor device R1, the second resistor device R2, the third resistor device R3 and the fourth resistor device R4 is located at the junction of the respective beam structure 3 and the supporting structure 2, and the other end is located at the junction of the respective beam structure 3 and the island structure 1. The resistors on the resistor device are arranged and distributed in a queue shape and are fully distributed in the length direction of the beam structure 3.

In this embodiment, since the resistors have a certain interval therebetween, different wheatstone bridges can be formed by different connection methods.

Specifically, in the first embodiment, the resistors of the first resistor device R1, the second resistor device R2, the third resistor device R3, and the fourth resistor device R4 are connected in series or in parallel, respectively, to form a single wheatstone bridge.

That is, in the present embodiment, the resistors on the resistor means on each of the beam structures 3 are connected in series or in parallel. For example, in fig. 4, when the resistors R11 and R12 of the first resistor device R1 are connected in series or in parallel, the resistors R21 and R22 of the second resistor device R2 are connected in series or in parallel, the resistors R31 and R32 of the third resistor device R3 are connected in series or in parallel, and the resistors R41 and R42 of the fourth resistor device R4 are connected in series or in parallel, a single wheatstone bridge is formed as the first resistor device R1, the second resistor device R2, the third resistor device R3, and the fourth resistor device R4, respectively.

Alternatively, in the second embodiment, the resistors of the first resistor device R1, the second resistor device R2, the third resistor device R3 and the fourth resistor device R4 are connected to each other to form at least two groups of wheatstone bridges.

That is, in the present embodiment, the resistors on the resistor arrangement on each beam structure 3 are each connected in series or in parallel, respectively. For example, in fig. 4, a resistor R11 in the first resistor device R1, a resistor R21 in the second resistor device R2, a resistor R31 in the third resistor device R3, and a resistor R41 in the fourth resistor device R4 are connected to form a set of wheatstone bridges; and then a resistor R12 in the first resistor device R1, a resistor R22 in the second resistor device R2, a resistor R32 in the third resistor device R3 and a resistor R42 in the fourth resistor device R4 are connected to form another group of Wheatstone bridges. Thus, the resistive connection in the second example of the third embodiment may be such that two sets of wheatstone bridges are formed. Of course, other connection modes can be adopted, for example, the resistors R11, R22, R31 and R42 form a group of wheatstone bridges, and the resistors R12, R21, R32 and R41 form another group of wheatstone bridges. Alternatively, if each resistor device includes three or more resistors, three or more groups of wheatstone bridges may be formed by interconnection.

Therefore, in summary, the resistors in the MEMS pressure sensor of the present invention each extend in parallel to the extending direction of the respective beam structure 3, the beam structure 3 can concentrate the stress generated by the phase change of the membrane structure 4, the width of the beam structure 3 is not limited by the length of the resistor, and the beam width equal to the width of the resistor can be realized, so that the stress is more concentrated, and the sensitivity of the sensor is further improved. In addition, the layout mode of the resistor device can flexibly lead out and wire the resistor device, ensures the consistency of the resistor device and lead-out wires of the resistor device, and further reduces zero point errors, temperature mismatch and the like. In addition, a plurality of groups of Wheatstone bridges can be formed through interconnection of resistors to form a complementary mode, so that zero point errors are further reduced, and the measurement accuracy and stability are improved.

Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should make the description as a whole, and the embodiments may be appropriately combined to form other embodiments understood by those skilled in the art.

The above-listed detailed description is only a specific description of a possible embodiment of the present invention and is not intended to limit the scope of the present invention, and equivalent embodiments or modifications made without departing from the technical spirit of the present invention are included in the scope of the present invention.

Claims

1. A MEMS pressure sensor comprising a device plate having first and second oppositely disposed surfaces;

2. The pressure sensor of claim 1, wherein the resistive means includes first, second, third and fourth resistive means, each of the first, second, third and fourth resistive means being located at a centerline of the respective beam structure and each extending along the centerline of the respective beam structure.

3. The pressure sensor of claim 2, wherein the first, second, third, and fourth resistance means each comprise a resistor.

4. The pressure sensor of claim 2, wherein the first, second, third, and fourth resistive means each comprise at least two resistors.

5. A pressure sensor according to claim 4, wherein the resistances of the first, second, third and fourth resistance means are each symmetrically distributed along the centre line of the respective beam structure.

6. A pressure sensor according to claim 3 or claim 5, wherein one end of each of the first and third resistance means is located at the junction of the respective beam structure and the clamped structure; and one end of each of the second resistor device and the fourth resistor device is positioned at the joint of the beam structure and the island structure.

7. A pressure sensor according to claim 4, wherein the resistances of the first, second, third and fourth resistance means are each arranged along the centreline of the respective beam structure.

8. The pressure sensor of claim 7, wherein the first, second, third and fourth resistor means are each positioned at one end at the junction of the respective beam structure and the anchor structure and at the other end at the junction of the respective beam structure and the island structure.

9. The pressure sensor of claim 7, wherein the resistors of the first, second, third and fourth resistor means are connected in series or in parallel to form a single Wheatstone bridge.

10. The pressure sensor of claim 7, wherein the resistors of the first, second, third and fourth resistor means are interconnected to form at least two sets of wheatstone bridges.