CN215217896U

CN215217896U - Pressure sensor

Info

Publication number: CN215217896U
Application number: CN202121312093.3U
Authority: CN
Inventors: 许克宇; 武斌
Original assignee: Shenzhen Meisi Xianrui Electronic Co ltd
Current assignee: Shenzhen Meisi Xianrui Electronic Co ltd
Priority date: 2021-06-11
Filing date: 2021-06-11
Publication date: 2021-12-17
Anticipated expiration: 2031-06-11

Abstract

The utility model provides a pressure sensor, which comprises a glass base and a silicon strain diaphragm positioned on the glass base, wherein one side of the glass base is provided with a concave cavity, and the silicon strain diaphragm comprises an insulating medium layer positioned on the front side and a silicon substrate covered by the insulating medium layer; a fishbone-shaped cross beam membrane piece is arranged on the front surface of the silicon strain membrane facing the cavity, each end of the cross beam membrane piece is provided with a group of piezoresistors, a group of heavily doped contact regions and a pair of metal leads, the piezoresistors are connected with the heavily doped contact regions in series, the metal leads are led out from the heavily doped contact regions at two ends, the metal leads and the heavily doped contact regions form ohmic contact on the front surface of the silicon strain membrane, and a Wheatstone bridge is formed between the piezoresistors; the cost is reduced, the efficiency is improved, the performance of the sensor can be adjusted, and the sensor is suitable for different measuring ranges; the anti-interference performance is strong, and the rigidity, the ultimate yield bending moment and the restoring force characteristics are excellent.

Description

Pressure sensor

Technical Field

The utility model relates to a sensor technical field especially relates to a pressure sensor.

Background

The piezoresistive pressure sensor converts the external pressure change into corresponding electric signals based on the monocrystalline silicon piezoresistive effect, and the external pressure is measured by a Wheatstone bridge formed by four equivalent resistors. The piezoresistive pressure sensor is mainly applied to the relevant fields of industrial control, automotive electronics, consumer electronics, medical electronics, aerospace and the like. The piezoresistive pressure sensor is designed and developed by adopting technology, and the piezoresistive pressure sensor is internally composed of a silicon diaphragm obtained by adopting a silicon wafer as a force sensitive element, four equivalent resistors manufactured by doping, etching and other processes, a low-resistance interconnecting wire, an evaporation deposited metal lead wire and other multi-functional layer integrated by various materials.

The piezoresistive pressure sensor mainly adopts a flat membrane type and a beam membrane type, in order to pursue the performance requirement of high sensitivity, the strain membrane of a pressure sensor chip of the flat membrane structure is designed to be thinner and thinner, and the thinner strain membrane can cause larger membrane deflection, so that the maximum displacement value of the membrane exceeds the general design standard (the beam membrane thickness is one fifth of the principle), thereby causing the linearity reduction of the sensor and the poor shock resistance; although the beam-film structure pressure sensor has excellent linearity, deep silicon etching is involved in the manufacturing process of the flow sheet, and the radial depth error of the large-size deep silicon etching is larger (+/-10 percent) at present, so that the thickness uniformity of a flat film layer after the front beam film etching is not guaranteed, and the risk of breaking a strain diaphragm of the sensor is increased; for the piezoresistive pressure sensor, the thickness of the strain diaphragm is the most critical, the performance difference of the same sensor is larger due to the uneven thickness, the difficulty of subsequent debugging and compensation is increased, and the manufacturing cost is increased.

SUMMERY OF THE UTILITY MODEL

An object of the utility model is to provide a pressure sensor, it can overcome the uneven, the sensor of above-mentioned flat membrane layer thickness and meet an emergency risk of diaphragm fragment, follow-up be difficult to debugging compensation and intelligence and cause this increase scheduling problem.

To achieve the above object, the solution of the present invention is:

a pressure sensor comprises a glass base and a silicon strain diaphragm positioned on the glass base, wherein a concave cavity is formed in one surface of the glass base, and the silicon strain diaphragm comprises an insulating medium layer positioned on the front surface and a silicon substrate covered by the insulating medium layer;

the front face of the silicon strain diaphragm is provided with a fishbone-shaped cross beam diaphragm facing the cavity, each end of the cross beam diaphragm is provided with a group of piezoresistors, a group of heavily doped contact regions and a pair of metal leads, the piezoresistors are connected with the heavily doped contact regions in series, the metal leads are led out from the heavily doped contact regions at two ends, the metal leads and the heavily doped contact regions form ohmic contact on the front face of the silicon strain diaphragm, and a Wheatstone bridge is formed between the piezoresistors.

Further, the membrane piece of the cross beam comprises island-shaped beam blocks which are arranged at equal intervals or non-equal intervals and fishbone strips used between two sections of the island-shaped beam blocks, and the number of the island-shaped beam blocks on each beam of the membrane piece of the cross beam is equal.

Further, the cross beam membrane piece at the joint of the cross beam membrane piece and the edge membrane area is in a straight strip shape or is gradually deformed linearly.

Further, each group of piezoresistors comprises a plurality of piezoresistor strips.

Further, the island-shaped beam block is one or more of rectangular, triangular, oval, rhombic and circular.

After the technical scheme is adopted, the fishbone-shaped cross beam membrane piece not only ensures the sensitivity of the pressure sensor, but also improves the linearity of the sensor; the cost is reduced, and the risk of breaking the strain diaphragm caused by large radial depth error of large-size deep silicon etching is reduced; the efficiency is improved, the risk caused by uneven thickness of the flat membrane is reduced, the difficulty of subsequent debugging and compensation is reduced, and the manufacturing cost is reduced; the performance of the sensor can be adjusted, and the sensor is suitable for different measuring ranges; the anti-interference performance is strong, and the rigidity, the ultimate yield bending moment and the restoring force characteristics are excellent.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to these drawings without creative efforts.

Fig. 1 is a schematic structural diagram of a pressure sensor according to an embodiment of the present invention;

fig. 2 is a partial cross-sectional view of a pressure sensor according to an embodiment of the present invention;

fig. 3 is a top view of a pressure sensor according to an embodiment of the present invention;

FIGS. 4A-4C are schematic front views of silicon strained diaphragms in various configurations;

fig. 5A-5B are schematic front views of various configurations of a cross-beam membrane.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

As shown in fig. 1, a pressure sensor, which is an MEMS piezoresistive pressure sensor designed and developed by using an MEMS technology, includes a glass base 1 and a silicon strain diaphragm 2 located on the glass base 1, where the silicon strain diaphragm 2 is a silicon film having a front beam film and a back cavity structure and formed by an SOI wafer/silicon wafer through front etching and back cavity etching processes;

as shown in fig. 1 or fig. 2, a recessed cavity is formed in one surface of the glass base 1, the Silicon strain diaphragm 2 includes an insulating medium layer located On the front surface and a Silicon substrate covered by the insulating medium layer, wherein the Silicon substrate is an N-type <100> crystal face SOI (Silicon-On-Insulator) Silicon wafer or an N-type Silicon wafer, and the Silicon strain diaphragm 2 and the glass base 1 with the recessed cavity adopt an anodic bonding method, so that a non-bonding surface of the Silicon wafer can be thinned, and since the cavity is formed in the glass base 1, the thinned thickness is not affected by the cavity, so that the thickness and other dimensions of the chip can be reduced, and the cost of the chip can be reduced; and because the silicon glass anodic bonding process is adopted, the glass plays a role in buffering stress on the silicon strain diaphragm 2, the stability of the sensor in subsequent packaging and testing is improved, and the silicon glass anodic bonding method has a wide application prospect.

As shown in fig. 1, a fishbone-shaped cross beam membrane 3 is arranged on the front surface of the silicon strain membrane 2 facing the cavity, and the cross beam membrane 3 is arranged at the center of the silicon strain membrane 2, so that large deformation of the silicon strain membrane 2 is inhibited, and the pressure sensor has high linearity;

as shown in fig. 1 or fig. 3, specifically, the cross beam film 3 has four end portions, and each end portion is provided with a group of piezoresistors 4, a group of heavily doped contact regions 5 and a pair of metal leads 6, the piezoresistors 4 and the heavily doped contact regions 5 at each end portion are connected in series, two ends are led out from the heavily doped contact regions 5 by the metal leads 6, the metal leads 6 and the heavily doped contact regions 5 form ohmic contacts on the front surface of the silicon strained membrane 2, and a wheatstone bridge is formed between the piezoresistors 4.

As shown in fig. 1, further, the cross beam membrane 3 is island-shaped beam blocks 31 arranged at equal intervals or at non-equal intervals, the island-shaped beam blocks 31 are connected in series through fishbone strips, and the cross beam membrane 3 in a fishbone-like shape is adopted, so that the cost can be reduced, and the risk of breaking the strain membrane caused by a large radial depth error of large-size deep silicon etching can be reduced;

and the number of the island-shaped beam blocks 31 on each beam of the cross beam membrane part 3 is the same, so that the risk caused by uneven thickness of the flat membrane can be reduced, the difficulty of subsequent debugging and compensation is reduced, the thickness of each island-shaped beam block 31 can be adjusted, the performance of the sensor can be adjusted, and the cross beam membrane part is suitable for different measuring ranges.

In addition, the cross beam membrane 3 adopting the fishbone-like structure has strong anti-interference performance, and the fishbone-like structure has excellent rigidity, ultimate yield bending moment and restoring force characteristics and is impact-resistant.

Further, the cross beam membrane piece 3 at the connection part of the cross beam membrane piece 3 and the edge membrane area is in a straight strip shape or linear gradual change shape, and in the embodiment, the straight strip shape is adopted, so that the whole is more stable, and the anti-interference performance is strong.

As shown in fig. 1 or fig. 3, further, each group of the piezoresistors 4 includes a plurality of piezoresistors 4, specifically, the piezoresistors 4 including four groups are symmetrically distributed at the end of the cross beam membrane 3, and each group of the piezoresistors 4 is not limited to the number of the piezoresistors 4, and is generally 2-4, and 4 are adopted in this embodiment.

Further, the island-shaped beam blocks 31 are one or more of rectangular, triangular, oval, rhombic and circular, specifically, in the embodiment, the rectangular island-shaped beam blocks 31 are adopted and are arranged on the beams of the cross beam at equal intervals, the island-shaped beam blocks 31 on the beams are connected through the fishbone strips 32, and the fishbone strips 32 and the island-shaped beam blocks 31 are of an integral structure, so that the integral structure is more stable, the plasticity and the flexibility are better, and the island-shaped beam blocks are suitable for different measuring ranges; referring to fig. 5A, the island-shaped beam block 31 is triangular, so that the structure is more stable; referring to fig. 5B, the island-shaped beam blocks 31 are oval, and the island-shaped beam blocks 31 are arranged at equal intervals, so that the overall plasticity and flexibility are better.

As shown in fig. 4A, the end of the cross beam membrane 3 in the scheme can also adopt a square boss structure, so that the overall sensitivity and linearity can be improved; as shown in fig. 4B, the cross beam membrane 3 in this solution has a wider central portion and better stability; as shown in fig. 4C, the end of the cross beam membrane 3 in this solution is in an arc structure, so that the whole is more stable and is suitable for different ranges.

Specifically, the metal lead 6 may be made of Al, Cr/Au, Ti/Au, or the like, and in this embodiment, Cr/Au is used as the metal lead to prevent oxygen generated by anodic bonding from oxidizing the metal lead.

The above description is only exemplary of the present invention and should not be construed as limiting the present invention, and any modification, equivalent replacement or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. The pressure sensor is characterized by comprising a glass base (1) and a silicon strain diaphragm (2) positioned on the glass base (1), wherein a concave cavity is formed in one surface of the glass base (1), and the silicon strain diaphragm (2) comprises an insulating medium layer positioned on the front surface and a silicon substrate covered by the insulating medium layer;

the front face of the silicon strain membrane (2) faces the cavity and is provided with a fishbone-shaped cross beam membrane (3), each end of the cross beam membrane (3) is provided with a group of piezoresistors (4), a group of heavily doped contact regions (5) and a pair of metal leads (6), the piezoresistors (4) are connected with the heavily doped contact regions (5) in series, two ends of each piezoresistor are led out from the heavily doped contact regions (5) through the metal leads (6), the metal leads (6) and the heavily doped contact regions (5) are in ohmic contact with the front face of the silicon strain membrane (2), and a Wheatstone bridge is formed between the piezoresistors (4).

2. A pressure sensor according to claim 1, wherein the cross beam membrane (3) comprises equally or unequally spaced island beam blocks (31) and fishbone strips (32) connecting the island beam blocks (31); the number of the island-shaped beam blocks (31) on each beam of the cross beam membrane (3) is equal.

3. A pressure sensor according to claim 2, characterized in that the cross beam membrane (3) where the cross beam membrane (3) is connected to the edge membrane area is straight or linearly tapered.

4. A pressure sensor according to claim 3, characterized in that each group of said piezoresistors (4) comprises a plurality of piezoresistors (4).

5. A pressure sensor according to claim 4, wherein the island-like beam pieces (31) are one or more of rectangular, triangular, oval, diamond-shaped, circular.