CN217276630U

CN217276630U - Low-voltage MEMS pressure sensor

Info

Publication number: CN217276630U
Application number: CN202220455601.1U
Authority: CN
Inventors: 马清杰; 李静
Original assignee: Suzhou Yuexin Micro Sensing Technology Co ltd
Current assignee: Suzhou Yuexin Micro Sensing Technology Co ltd
Priority date: 2022-03-03
Filing date: 2022-03-03
Publication date: 2022-08-23
Anticipated expiration: 2032-03-03

Abstract

The utility model discloses a low pressure MEMS pressure sensor, include: the device comprises a device layer, a first supporting layer and a second supporting layer which are connected to two opposite sides of the device layer in a bonding mode; a first cavity is etched on the surface of one side, close to the first supporting layer, of the device layer, and a second cavity is etched on the surface of one side, close to the device layer, of the second supporting layer; the device layer between the first cavity and the second cavity is used as a strain film layer; the surface of one side of the strain film layer close to the second supporting layer is provided with a pressure-sensitive component, the surface of one side of the device layer close to the second supporting layer is provided with a closed-loop second conductive strip around the periphery of the edge of the Wheatstone bridge component, the second conductive strip and the Wheatstone bridge component are spaced by a groove, and the power supply end of the Wheatstone bridge component is electrically connected with the second conductive strip. The structure reduces the influence of stress on the strain film, improves the etching precision of the first cavity, reduces the area of a chip, reduces the cost and can also ensure the uniformity of the thickness of the strain film.

Description

Low-voltage MEMS pressure sensor

Technical Field

The embodiment of the utility model provides a relate to sensor technical field, especially relate to a low pressure MEMS pressure sensor.

Background

The pressure sensor is widely applied to various industries such as national defense and military industry, automotive electronics, petrochemical industry, aerospace, medical appliances, consumer electronics and the like, and accounts for one third of the whole sensor market. Pressure sensors can be classified into piezoresistive type, capacitive type, piezoelectric type, surface acoustic wave type, hall effect type, and the like, according to their operation principle. Among them, the piezoresistive pressure sensor manufactured based on the MEMS technology is widely used with its high sensitivity and low cost.

However, most of the existing piezoresistive low-pressure sensors adopt a back cavity wet-method deep silicon etching film-forming mode, the etching depth is deep (more than 300 um), and because the wet etching is not etched in the vertical direction, a larger chip area is needed to supplement the transverse etching, the cost is increased, and the thickness uniformity and consistency of the strain film are difficult to control due to the deep etching depth; in addition, the existing piezoresistive low-pressure sensor is only bonded with a glass sheet on the back surface, and the phenomenon of unbalanced stress is easy to generate.

SUMMERY OF THE UTILITY MODEL

An embodiment of the utility model provides a low pressure MEMS pressure sensor to reduce the sculpture degree of depth, reduce the chip area, guarantee the thickness homogeneity of foil gage, realize stress balance, reduce the influence of stress to the sensor performance.

In order to achieve the above object, an embodiment of the present invention provides a low-voltage MEMS pressure sensor, including:

a first support layer, a device layer, and a second support layer; the first supporting layer and the second supporting layer are bonded and connected to two opposite sides of the device layer;

a first cavity is etched on the surface of one side, close to the first supporting layer, of the device layer, and a second cavity is etched on the surface of one side, close to the device layer, of the second supporting layer; the device layer between the first cavity and the second cavity is used as a strain film layer;

a pressure-sensitive assembly is arranged on one side surface, close to the second supporting layer, of the strain film layer, and comprises four piezoresistive components and a plurality of first conductive strips; the four piezoresistive components are distributed along the same central line of the strain film layer; a plurality of said first conductive strips for connecting four of said piezoresistive members together to form a Wheatstone bridge section;

and the device layer is close to one side surface of the second support layer, a closed-loop second conductive strip is arranged around the periphery of the edge of the Wheatstone bridge component, the second conductive strip is separated from the Wheatstone bridge component by a groove, and a power supply end of the Wheatstone bridge component is electrically connected with the second conductive strip by a metal bridge.

According to the utility model discloses an embodiment, the device layer is the silicon layer of N type light doping, first busbar is the busbar of P type heavy doping, the second busbar is the busbar of N type heavy doping, the piezo-resistor in the pressure drag part is P type light doping.

According to one embodiment of the present invention, the four piezoresistive components comprise a first piezoresistive component, a second piezoresistive component, a third piezoresistive component and a fourth piezoresistive component;

the first piezoresistive component and the fourth piezoresistive component are symmetrically distributed in the edge area of the strained thin film layer with the center of the strained thin film layer, and the second piezoresistive component and the third piezoresistive component are symmetrically distributed in the center area of the strained thin film layer with the center of the strained thin film layer.

According to the utility model discloses an embodiment, connect second pressure drag part with third pressure drag part both ends first busbar spiral distribution in the central zone of foil gage layer is connected first pressure drag part with fourth pressure drag part both ends first busbar be sharp distribution in the marginal zone of foil gage layer.

According to an embodiment of the present invention, a first power signal is input to a first end of the first piezoresistive member, and a first detection signal is output from a second end of the first piezoresistive member; the second end of the second piezoresistive component inputs the first power signal, and the first end of the second piezoresistive component outputs a second detection signal; a first end of the third piezoresistive component inputs a second power signal and a second end of the third piezoresistive component outputs the first detection signal; a second terminal of the fourth piezoresistive block inputs the second power supply signal and a first terminal of the fourth piezoresistive block outputs the second detection signal;

wherein the first end of each piezoresistive member is located on the same side of the centerline and the second end of each piezoresistive member is located on the other side of the centerline.

According to an embodiment of the present invention, the first conductive strip at the first end of the first piezoresistive member and the first conductive strip at the second end of the second piezoresistive member have a first common connection portion, which serves as a common power source terminal for inputting the first power signal;

the first conductive strip at the second end of the first piezoresistive component and the first conductive strip at the second end of the third piezoresistive component have a second common connection part, and the second common connection part is used as a first signal detection end and is used for outputting the first detection signal;

the first conductive strip at the first end of the second piezoresistive component and the first conductive strip at the first end of the fourth piezoresistive component have a third common connection part, and the third common connection part is used as a second signal detection end and is used for outputting the second detection signal;

the first conductive strip at the first end of the third piezoresistive member and the first conductive strip at the second end of the fourth piezoresistive member have a fourth common connection, and the fourth common connection serves as a common ground for inputting the second power signal.

According to an embodiment of the present invention, the first common connection portion, the second common connection portion, the fourth common connection portion and the third common connection portion are sequentially arranged around an edge of the strained thin film layer.

According to an embodiment of the present invention, a first spacing groove is provided between the first common connection portion and the second common connection portion, a second spacing groove is provided between the second common connection portion and the fourth common connection portion, and a third spacing groove is provided between the fourth common connection portion and the third common connection portion; and a fourth spacing groove is arranged between the third public connecting part and the first public connecting part.

According to an embodiment of the present invention, the fourth common connecting portion may be divided by a zeroth spacing groove to form two independent ground terminals.

According to an embodiment of the present invention, fifth spacing grooves are disposed in the first conductive strips at the two ends of the first piezoresistive component, and are close to the joint of the first piezoresistive component, and the two fifth spacing grooves are symmetrically disposed with respect to the first spacing groove; the fifth spacing groove is used for adjusting the resistance of the first conductive strips at two ends of the first piezoresistive component;

and sixth spacing grooves are formed in the first conductive strips at the two ends of the fourth piezoresistive component and close to the connection part of the fourth piezoresistive component, the two sixth spacing grooves are symmetrically arranged with the third spacing groove, and the sixth spacing grooves are used for adjusting the resistance of the first conductive strips at the two ends of the fourth piezoresistive component.

According to the utility model discloses an embodiment, each public connecting portion are kept away from a side surface of first supporting layer still is provided with metal electrode.

According to the utility model discloses an embodiment, the second supporting layer is provided with a plurality of pin holes, every it has the electric conductor to fill in the pin hole, the one end of electric conductor is connected metal electrode, other end connection pad.

According to an embodiment of the present invention, the first support layer has a first air hole therein, and the second support layer has a second air hole therein; the projection of the first air hole on the surface of one side of the device layer and the projection of the second air hole on the surface of one side of the device layer can both fall on the strain film layer.

The embodiment of the utility model provides a low pressure MEMS pressure sensor, through setting up low pressure MEMS pressure sensor into first supporting layer and the bonding of second supporting layer and connect the "sandwich" formula structure in the relative both sides of device layer, upper and lower supporting layer all plays the guard action to the device layer for stress balance about the device layer reduces the influence that stress corresponds the variable film; moreover, when the strain film layer is formed, the first cavity can be etched on the basis of the thinner device layer, and then the first supporting layer (lower supporting layer) is bonded on the back surface of the device layer, so that the mode that the center of the prior art starts etching (back cavity wet-process deep silicon etching) from the surface of one side, which is away from the piezoresistive component, of the thick silicon substrate to form a film is replaced, the etching depth of the first cavity can be shallower, the etching precision is improved, the chip area is reduced, the cost is reduced, and the uniformity of the thickness of the strain film can be further ensured. In addition, the PN junction leakage current is avoided by arranging the N-type heavily doped layer.

Drawings

Fig. 1 is a perspective view of a low-voltage MEMS pressure sensor according to an embodiment of the present invention;

FIG. 2 is a cross-sectional view of the embodiment of FIG. 1 taken along AA 1;

fig. 3 is a top view of a device layer provided by an embodiment of the present invention;

fig. 4 is a circuit diagram of a wheatstone bridge according to an embodiment of the present invention;

fig. 5 is a top view of another device layer provided by embodiments of the present invention;

fig. 6 is a top view of yet another device layer provided by an embodiment of the present invention;

fig. 7 is a flowchart of a method for manufacturing a low-voltage MEMS pressure sensor according to an embodiment of the present invention;

fig. 8 is a flowchart of another method for manufacturing a low-voltage MEMS pressure sensor according to an embodiment of the present invention;

fig. 9 is a cross-sectional view of a structure corresponding to step S101 in a method for manufacturing a low-voltage MEMS pressure sensor according to an embodiment of the present invention;

fig. 10 is a cross-sectional view of a structure corresponding to step S1021 in a method for manufacturing a low-voltage MEMS pressure sensor according to an embodiment of the present invention;

fig. 11 is a cross-sectional view of the structure corresponding to step S1022 in the method for manufacturing a low-voltage MEMS pressure sensor according to an embodiment of the present invention;

fig. 12 is a cross-sectional view of a structure corresponding to step S1023 in a method for manufacturing a low-voltage MEMS pressure sensor according to an embodiment of the present invention;

fig. 13 is a cross-sectional view of the structure corresponding to step S103 in the method for manufacturing a low-voltage MEMS pressure sensor according to an embodiment of the present invention;

fig. 14 is a cross-sectional view of a structure corresponding to step S104 in a method for manufacturing a low-voltage MEMS pressure sensor according to an embodiment of the present invention;

fig. 15 is a cross-sectional view of the structure corresponding to step S1051 in the method for manufacturing a low-voltage MEMS pressure sensor according to an embodiment of the present invention;

fig. 16 is a cross-sectional view of the structure corresponding to step S105 in the method for manufacturing a low-voltage MEMS pressure sensor according to an embodiment of the present invention;

fig. 17 is a cross-sectional view of a structure corresponding to step S106 in a method for manufacturing a low-voltage MEMS pressure sensor according to an embodiment of the present invention;

fig. 18 is a cross-sectional view of a structure corresponding to step S107 in the manufacturing method of the low-voltage MEMS pressure sensor according to the embodiment of the present invention;

fig. 19 is a cross-sectional view of the structure corresponding to step S1081 in the method for manufacturing a low-voltage MEMS pressure sensor according to an embodiment of the present invention;

fig. 20 is a cross-sectional view of a structure corresponding to step S108 in a method for manufacturing a low-voltage MEMS pressure sensor according to an embodiment of the present invention;

fig. 21 is a cross-sectional view of a structure corresponding to step S109 in a method for manufacturing a low-voltage MEMS pressure sensor according to an embodiment of the present invention.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It should be further noted that, for the convenience of description, only some of the structures related to the present invention are shown in the drawings, not all of the structures.

Fig. 1 is a perspective view of a low-voltage MEMS pressure sensor provided by an embodiment of the present invention, which is shown in fig. 1 to 3, the low-voltage MEMS pressure sensor includes:

a first support layer 10, a device layer 20, and a second support layer 30; wherein the first support layer 10 and the second support layer 30 are bonded to opposite sides of the device layer 20;

a first cavity 50 is etched on the surface of the device layer 20 close to the first support layer 10, and a second cavity 40 is etched on the surface of the second support layer 30 close to the device layer 20; the device layer 20 between the first cavity 50 and the second cavity 40 serves as a strained thin film layer 21;

the side of the strained membrane layer 21 adjacent to the second support layer 30 is provided with a pressure sensitive assembly comprising four piezoresistive members 61 and a plurality of first conductive strips 62; the four piezoresistive members 61 are distributed along the same center line of the strained thin film layer 21; a plurality of first conductive strips 62 for connecting the four piezoresistive members 61 together to form a Wheatstone bridge section 60;

on the side of the device layer 20 adjacent to the second support layer 30, a closed loop of second conductive strips 70 is disposed around the periphery of the edge of the wheatstone bridge member 60, the second conductive strips 70 are spaced apart from the wheatstone bridge member 60 by a groove 80, and a power terminal (VCC) of the wheatstone bridge member 60 is electrically connected to the second conductive strips 70 by a metal bridge 90.

It is understood that the first support layer 10, the device layer 20, and the second support layer 30 are sequentially stacked in a first direction, which is a direction in which the first support layer 10 is perpendicularly directed to the device layer 20. The device layer 20 is sandwiched between the first support layer 10 and the second support layer 30 such that the low voltage MEMS pressure sensor forms a "sandwich" structure. The first support layer 10 and the second support layer 30 both protect the device layer 20, and while one side of the device layer 20 is subjected to the interface stress of the first support layer 10, the opposite side of the device layer 20 may be subjected to the interface stress of the second support layer 30, so that the stresses on both sides of the device layer 20 may be balanced.

Wherein, the perpendicular projection of the first cavity 50 and the second cavity 40 on the strained thin film layer 21 covers the strained thin film layer 21. When the strained thin film layer 21 is deformed by pressure change, the four protruded piezoresistive members 61 of the wheatstone bridge members 60 on the upper surface of the strained thin film layer 21 are also deformed, so that the resistance value of the piezoresistive members 61 is changed. The four piezoresistive members 61 are distributed along the same center line of the strained thin film layer 21, and the piezoresistive members located at the edges of the strained thin film layer 21 and the piezoresistive members located at the center of the strained thin film layer 21 are opposite in resistance change polarity due to the opposite stress directions. According to the characteristics of the wheatstone bridge, the two output ports (Vout + and Vout-) of the wheatstone bridge component 60 output the potential difference, and the output potential difference is in direct proportion to the pressure applied to the strained thin film layer 21, so as to detect the pressure value applied to the strained thin film layer 21. The low-voltage MEMS pressure sensor is arranged into a sandwich structure in which the first supporting layer 10 and the second supporting layer 30 are connected to two opposite sides of the device layer 20 in a bonding mode, so that the stress on the upper surface and the stress on the lower surface of the device layer 20 are balanced, the influence of the stress on the strain thin film layer 21 is reduced, and the accuracy of detecting the pressure value of the strain thin film layer 21 can be improved.

Moreover, the low-voltage MEMS pressure sensor is arranged into a sandwich structure in which the first supporting layer 10 and the second supporting layer 30 are bonded and connected to two opposite sides of the device layer 20, the first cavity 50 can be etched on the basis that the device layer 20 is thin to form the strain film layer 21, and the first supporting layer 10 (the lower supporting layer) is bonded to the back of the device layer 20, so that the mode that the film is formed by etching (back cavity wet-process deep silicon etching) from the surface of one side of the thick silicon substrate, which is far away from the piezoresistive device, in the prior art is replaced, the etching depth of the first cavity 50 can be shallow, therefore, the etching precision is improved, the chip area is reduced, the cost is reduced, and the uniformity of the thickness of the strain film layer 21 can be ensured.

In addition, since the device layer 20 is in contact with the wheatstone bridge member 60, the wheatstone bridge member 60 is usually a P-type semiconductor material, and the device layer 20 is usually an N-type semiconductor material, the contact surface thereof will form a PN junction, and P to N leakage current is likely to occur during use, especially in a high temperature environment, which affects the device performance. The embodiment of the present invention provides a side surface close to the second supporting layer 30 on the device layer 20, a closed loop second conductive strip 70 is disposed around the periphery of the edge of the wheatstone bridge member 60, the second conductive strip 70 is N-type heavily doped, the second conductive strip 70 is spaced apart from the wheatstone bridge 60 by a groove, and the power source end of the wheatstone bridge member 60 is electrically connected to the second conductive strip 70 through the metal bridge 90. When the power source terminal of the wheatstone bridge component 60 is powered on, since the second conductive strip 70 is in contact with the device layer 20 and the second conductive strip 70 and the device layer 20 are both N-type, the second conductive strip 70 is electrically connected with the whole device layer 20, and therefore the potential of the device layer 20 is higher than or equal to the potential of any part in the wheatstone bridge component 60, so that when the device layer 20 and even the upper and lower support layers are at high potential, the PN junction formed by the wheatstone bridge component 60 and the device layer 20 is reversely biased (electrically insulated), thereby effectively preventing the generation of leakage current and ensuring the performance of the device.

According to an embodiment of the present invention, the device layer 20 is a lightly doped N-type silicon layer, the first conductive strip 62 is a heavily doped P-type silicon conductive strip, the second conductive strip 70 is a heavily doped N-type silicon conductive strip, and the strip-type piezoresistor 601 of the piezoresistive member 61 is a lightly doped P-type silicon piezoresistor.

The first conductive strips 62 are P-type heavily doped silicon conductive strips, and have very low resistivity; the strip piezoresistor 601 in the piezoresistive component 61 is a P-type lightly doped silicon piezoresistor, and has higher resistivity. Each piezoresistive member 61 is connected at each end to a first conductive strip 62. The line width of the piezoresistive element 61 is much smaller than the line width of the first conductive strip 62, so that the resistance of the piezoresistive element 61 is much larger than that of the first conductive strip 62, the piezoresistive element 61 has a larger resistance in the overall circuit, and the piezoresistive element 61 and the first conductive strip 62 are arranged differently.

In addition, the PN junction formed between the P-type heavily doped layer and the N-type device layer 20 is a parallel plane junction, the parasitic parameter between the raised P-type heavily doped layer and the N-type device layer 20 is smaller, and the PN junction can be regarded as an ideal PN junction.

According to one embodiment of the present invention, referring to fig. 3, the four piezoresistive components 61 include a first piezoresistive component 611, a second piezoresistive component 612, a third piezoresistive component 613, and a fourth piezoresistive component 614;

first piezoresistive component 611 and fourth piezoresistive component 614 are symmetrically distributed in the edge area of strained membrane layer 21 at the center of strained membrane layer 21, and second piezoresistive component 612 and third piezoresistive component 613 are symmetrically distributed in the center area of strained membrane layer 21 at the center of strained membrane layer 21.

It will be appreciated that since the stress is most concentrated at the edges and center of the membrane when it is compressed, the four piezoresistive members 61 are distributed on the surface of the device layer 20 along the centerline of the strained membrane layer 21, and the four piezoresistive members 61 are distributed symmetrically at the edges and center of the membrane at the midpoint.

Wherein each piezoresistive member 61 comprises a plurality of strip-shaped piezoresistors 601 and a wire part 602 for connecting the plurality of strip-shaped piezoresistors 601 in series; the line width of the strip piezoresistor 601 is far smaller than that of the lead part 602; the strip piezoresistors 601 are all parallel to the symmetry axis and are distributed in an axisymmetric manner with the symmetry axis as the central axis, and the wire portions 602 are all perpendicular to the symmetry axis. Each piezoresistive member 61 is illustratively depicted in fig. 3 as comprising two strip-shaped piezoresistors 601 and one wire portion 602 for connecting the strip-shaped piezoresistors 601 in series. The resistance of the strip-shaped piezoresistor 601 is far greater than that of the lead part 602, and the lead part 602 can be regarded as a lead, in addition, the length of the two strip-shaped piezoresistors 601 along the direction of the symmetry axis can be adjusted according to actual requirements, and the larger the resistance value of the required resistor is, the longer the length is.

In other embodiments, a plurality of strip-shaped piezoresistors 601 can be arranged in series through the wire portions 602. Each strip-shaped piezoresistor 601 is parallel to the symmetry axis, and the wire part 602 is perpendicular to the symmetry axis, so that the total resistance of the whole strip-shaped protrusion can be adjusted by the length according to actual requirements.

According to an embodiment of the present invention, referring to fig. 3, the first conductive strips 62 connected to the two ends of the second and third piezoresistive members 612 and 613 are spirally distributed in the central region of the strained thin film layer 21, and the first conductive strips 62 connected to the two ends of the first and fourth piezoresistive members 611 and 614 are linearly distributed in the edge region of the strained thin film layer 21. The four piezoresistive components are symmetrically distributed on the edge and the central area of the film in pairs at the middle points, and all the piezoresistive strips can provide piezoresistive effect and have better linearity. The first conductive strips 62 distributed in the center region of the film are spirally distributed so that the terminals of the piezoresistive members 61 in the center region can be disposed at the top corners of the strained film layer 21, with the terminals being common to the piezoresistive members 61 in the edge regions, thereby reducing the number of terminals.

According to an embodiment of the present invention, a first power signal is input to a first end of the first piezoresistive member 611 when viewed from left to right, and a first detection signal is output from a second end of the first piezoresistive member 611; a first power signal is input to a second terminal of second piezoresistive block 612, and a second detection signal is output from a first terminal of second piezoresistive block 612; a first terminal of the third piezoresistive component 613 inputs a second power signal, and a second terminal of the third piezoresistive component 613 outputs the first detection signal; the second terminal of the fourth piezoresistive block 614 inputs the second power signal and the first terminal of the fourth piezoresistive block 614 outputs the second detection signal; wherein the first ends of the piezoresistive components are located on the same side of the centerline and the second ends of the piezoresistive components are located on the other side of the centerline.

As shown in FIGS. 3 and 4, a plurality of first conductive strips 62 connect the four piezoresistive members 61 together to form a Wheatstone bridge section 60. Wherein the first piezoresistive member 611 is equivalent to the resistor R1 in the Wheatstone bridge member 60, the second piezoresistive member 612 is equivalent to the resistor R2 in the Wheatstone bridge member 60, the third piezoresistive member 613 is equivalent to the resistor R3 in the Wheatstone bridge member 60, and the fourth piezoresistive member 614 is equivalent to the resistor R4 in the Wheatstone bridge member 60. A first terminal of first piezoresistive block 611 and a second terminal of second piezoresistive block 612 input Vcc; the second end of first piezoresistive block 611 and the second end of third piezoresistive block 613 output Vout +; a first terminal of second piezoresistive component 612 and a first terminal of fourth piezoresistive component 614 output Vout-; the second end of the fourth piezoresistive component 614 and the first end of the third piezoresistive component 613 are connected to ground GND.

Wherein two terminals inputting the same signal or two terminals outputting the same signal may be connected together, thereby reducing the signal terminals of the sensor (5 signal terminals are exemplarily drawn in fig. 3).

According to an embodiment of the present invention, referring to fig. 6, the first conductive strip 62 at the first end of the first piezoresistive member 611 and the first conductive strip 62 at the second end of the second piezoresistive member 612 have a first common connection portion, which serves as a common power source terminal for inputting a first power signal;

the first conductive strip 62 at the second end of the first piezoresistive block 611 and the first conductive strip 62 at the second end of the third piezoresistive block 613 have a second common connection, which serves as a first signal detection terminal for outputting the first detection signal;

the first conductive strip 62 at the first end of the second piezoresistive member 612 and the first conductive strip 62 at the first end of the fourth piezoresistive member 614 have a third common connection, which is a second signal detecting terminal for outputting the second detecting signal;

the first conductive strip 62 at the first end of the third piezoresistive member 613 and the first conductive strip 62 at the second end of the fourth piezoresistive member 614 have a fourth common connection, which serves as a common ground for inputting the second power signal.

It is understood that the region where the common connection is located is a region where the same input signal or the same output signal is merged. After receiving a first power signal inputted from the outside, the first common connection part transmits the first power signal to the first piezoresistive member 611 through the first conductive strip 62 connected to the first end of the first piezoresistive member 611, and transmits the first power signal to the second piezoresistive member 612 through the first conductive strip 62 connected to the second end of the second piezoresistive member 612. The second common connection portion receives the first detection signals output by the first and third piezoresistive components 611 and 613 respectively through the first conductive strip 62 connected to the second end of the first piezoresistive component 611 and the first conductive strip 62 connected to the second end of the third piezoresistive component 613, and then transmits the first detection signals to the outside. The third common connection portion and the fourth common connection portion may refer to the first common connection portion and the second common connection portion, and are not described in detail here. By providing four common connections, a 4-port sensor can be realized. If one of the common connections is two separate outputs or inputs, the 5-port sensor is realized, for example, the fourth common connection can be divided by the zeroth spacing slot to form two independent grounds (as shown in fig. 3).

According to an embodiment of the present invention, referring to fig. 6 and 21, the first common connection portion, the second common connection portion, the fourth common connection portion, and the third common connection portion are sequentially disposed around the edge of the strained thin film layer 21. The second support layer 30 is provided with a plurality of lead holes 33, and each of the lead holes 33 is filled with a conductive body having one end connected to the common connection portion and the other end connected to the pad 32.

The strain film layer can be set to be rectangular, and then the first common connecting portion, the second common connecting portion, the fourth common connecting portion and the third common connecting portion can be sequentially arranged at four vertex angles of the strain film layer, so that the distance between the common connecting portions serving as signal ends is increased. This ensures, on the one hand, that the first conductive strips 62 associated with each piezoresistive member 61 have the same resistance (ensuring that the bridge is balanced in the absence of pressure) and, on the other hand, that the lead holes in the second support layer 30 are not locally too dense (this would affect the local strength and would create a high risk of chipping during processing).

In other embodiments (refer to fig. 5, 6 and 21), the surface of the common connection portion away from the first support layer 10 may be further provided with a metal electrode 620, the second support layer 30 is provided with a plurality of lead holes 33, each lead hole 33 covers the metal electrode 620, and each lead hole 33 is filled with a metal conductor 331, for example, the metal conductor 331 may be a common metal material such as Cu, Pt, Au, etc. One end of the metal conductor 331 is connected to the metal electrode 620, and the other end is connected to the pad 32. The resistance of the external electrode can be reduced, and the accuracy of pressure signal detection is improved. When voltage is applied to the bonding pad 32, the bonding pad is electrically connected with the metal electrode 620 through the conductor 331, the voltage is applied to the piezoresistive component, the resistance value of the piezoresistive component is changed, the balance of the bridge is broken, and an electric signal is output outwards through the conductor 331, so that the pressure applied to the strain film layer is detected.

According to an embodiment of the present invention, referring to fig. 6, a first spacing groove 81 is provided between the first common connection portion and the second common connection portion, a second spacing groove 82 is provided between the second common connection portion and the fourth common connection portion, and a third spacing groove 83 is provided between the fourth common connection portion and the third common connection portion; a fourth spacing groove 84 is provided between the third common connection and the first common connection. Electrical isolation of each adjacent common connection is achieved by the trenches. The two adjacent common connecting parts can be filled with a dielectric layer to realize electric insulation. Preferably, the cost of the device is reduced by electrically isolating each adjacent common connection by the trench.

According to an embodiment of the present invention, referring to fig. 3, 5 and 6, fifth spacing grooves 85 are disposed in the first conductive strips 62 at the two ends of the first piezoresistive member 611, at the joints close to the first piezoresistive member 611, and the two fifth spacing grooves 85 are symmetrically disposed with respect to the first spacing groove; the fifth spacing slot 85 is used to adjust the resistance of the first conductive strip 62 at the two ends of the first piezoresistive member 611;

in the first conductive strip 62 at both ends of the fourth piezoresistive member 614, a sixth spacing groove 86 is disposed near the connection of the fourth piezoresistive member 614, two sixth spacing grooves 86 are symmetrically disposed with a third spacing groove 83 (for fig. 3 and 5, the third spacing groove 83 refers to a groove for separating Vout-and GND), and the sixth spacing groove 86 is used for adjusting the resistance of the first conductive strip 62 at both ends of the fourth piezoresistive member 614.

According to an embodiment of the present invention, referring to fig. 2, the first support layer 10 is provided with a first air hole 11 therein, and the second support layer 30 is provided with a second air hole 31 therein; the projection of the first air hole 11 on the surface of the device layer 20 and the projection of the second air hole 31 on the surface of the device layer 20 can both fall on the strained thin film layer 21. So that the first support layer 10 and the second support layer 30 have air holes in the orthographic projection area of the strained thin film to realize differential pressure measurement.

The embodiment of the utility model provides a low pressure MEMS pressure sensor's preparation method is still provided, is applied to low pressure MEMS pressure sensor as before, as shown in figure 7, including following step:

s101, providing a substrate, where the substrate includes a first device material layer 201, a buried oxide layer 202, and a second device material layer 203 (as shown in fig. 9) stacked in sequence.

S102, piezoresistive member 61, first conductive strip 62, and second conductive strip 70 are formed on a side of first device material layer 201 away from second device material layer 203 (as shown in fig. 12).

S103, growing and etching to form a metal bridge 90 by adopting a photoetching process; a metal bridge 90 spans the trench between the common power terminal of the wheatstone bridge member 60 and the second conductive strip 70 (as shown in fig. 13).

According to an embodiment of the present invention, after the step S102 etching is performed to form the raised piezoresistive members, the P-type heavily doped first conductive strip 62, and the N-type heavily doped second conductive strip 70, the method further includes:

growing and etching to form a metal electrode by adopting a photoetching process; the metal electrode is positioned at one end of the first conductive strip for signal transmission. The growth and etching for forming the metal electrode and the growth and etching for forming the metal bridge can be synchronously carried out, so that the preparation flow of the pressure sensor is reduced, and the preparation efficiency is improved.

S104, providing a glass sheet or a silicon wafer as the second support layer 30, and etching the surface of one side of the second support layer 30 to form a second cavity 40; a second air hole 31 and a plurality of lead holes 33 are etched on the side surface of the second support layer 30 facing away from the second cavity by using a laser, sand blasting or photolithography process (as shown in fig. 14 and 15).

And S105, bonding and connecting the side, provided with the second cavity 40, of the second support layer 30 to the side, provided with the pressure-sensitive component, of the first device material layer 201 (as shown in FIG. 16).

And S106, sequentially removing the second device material layer 203 and the buried oxide layer 202 (as shown in FIG. 17).

S107, etching the first device material layer 201, and forming a first cavity 50 on one side, away from the piezoresistive component, of the first device material layer 201; the etched first device material layer 201 serves as the device layer 20 (shown in fig. 18).

And S108, providing another glass sheet or silicon wafer as the first support layer 10, and etching by using laser, sand blasting or photoetching technology to form the first air holes 11 (as shown in FIG. 19).

And S109, bonding the first support layer 10 on the surface of the device layer 20, which is far away from the second support layer 30 (as shown in FIG. 20).

According to an embodiment of the present invention, the device layer 20 is an N-type lightly doped silicon layer, the first conductive strip 62 is a P-type heavily doped silicon conductive strip, the second conductive strip 70 is an N-type heavily doped silicon conductive strip, and the piezoresistor in the piezoresistive member is a P-type lightly doped silicon piezoresistor; as shown in fig. 8, the forming S102 of the pressure sensitive element 61, the first conductive strip 62 and the second conductive strip 70 on the side of the first device material layer 201 away from the second device material layer 202 includes:

and S1021, lightly doping boron elements on the N-type lightly doped silicon layer to form a P-type lightly doped silicon layer. (As shown in FIG. 10, P-type light doping is represented by P-)

S1022, based on the mask, heavily doping the first conductive strip 62 region and the second conductive strip 70 region of the P-type lightly doped silicon layer with boron elements. (As shown in FIG. 11, the heavily doped boron in the first conductive stripe region of the P-type lightly doped silicon layer is represented by P + for the P-type heavy doping, and the heavily doped boron in the second conductive stripe region is represented by N + for the N-type heavy doping)

1023, a photoresist process is used to etch the raised piezoresistive members 61, the P-type heavily doped first conductive strips 62, and the N-type heavily doped second conductive strips 70. (As shown in FIG. 12, the P-type lightly doped silicon layer is the piezoresistive component 61)

According to an embodiment of the present invention, as shown in fig. 21, further comprising:

s110, filling a metal material into the lead hole 33 to form a conductor 331, and growing the metal material on the side of the second support layer 30 away from the device layer 20 and etching to form a plurality of bonding pads 32; one end of the conductor 331 is connected to the metal electrode 620, and the other end is connected to the corresponding pad 32. (which is a cross-sectional view along BB1 in fig. 5).

It should be noted that, the formation of the device layer 20, the etching of the first support layer 10, and the etching of the second support layer 30 are not sequential, and may be performed simultaneously, so as to shorten the time period for manufacturing the pressure sensor and improve the phase rate of the manufacturing.

The embodiment of the utility model provides a preparation method of low pressure MEMS pressure sensor sets up low pressure MEMS pressure sensor into first supporting layer and the bonding of second supporting layer and connects the "sandwich" formula structure in the relative both sides of device layer, and upper and lower supporting layer all plays the guard action to the device layer, makes the device layer stress balance from top to bottom more, reduces the influence of stress to the deformation film; moreover, when the strain film layer is formed, the first cavity can be etched on the basis of the thinner device layer, and then the first supporting layer (lower supporting layer) is bonded on the back surface of the device layer, so that the mode that the center of the prior art starts etching (back cavity wet-process deep silicon etching) from the surface of one side, which is far away from the piezoresistive component, of the thick silicon substrate to form a film is replaced, the etching depth of the first cavity can be shallower, the etching precision is improved, the chip area is reduced, the cost is reduced, and the uniformity of the thickness of the strain film can be ensured. In addition, the PN junction leakage current is avoided by arranging the N-type heavily doped layer.

It should be noted that the foregoing is only a preferred embodiment of the present invention and the technical principles applied. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious changes, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present invention has been described in greater detail with reference to the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the scope of the present invention.

Claims

1. A low pressure MEMS pressure sensor, comprising:

a pressure-sensitive assembly is arranged on one side surface, close to the second supporting layer, of the strain film layer, and comprises four piezoresistive components and a plurality of first conductive strips; the four piezoresistive components are distributed along the same central line of the strain film layer; a plurality of said first conductive strips for connecting four of said piezoresistive members together to form a Wheatstone bridge member;

and a closed loop second conductive strip is arranged around the periphery of the edge of the Wheatstone bridge component, the second conductive strip is spaced from the Wheatstone bridge component by a groove, and a power supply end of the Wheatstone bridge component is electrically connected with the second conductive strip by a metal bridge.

2. The low pressure MEMS pressure sensor of claim 1,

the device layer is an N-type lightly doped silicon layer, the first conductive strips are P-type heavily doped silicon conductive strips, the second conductive strips are N-type heavily doped silicon conductive strips, and the piezoresistors in the piezoresistive component are P-type lightly doped silicon piezoresistors.

3. The low pressure MEMS pressure sensor of claim 1,

the four piezoresistive components include a first piezoresistive component, a second piezoresistive component, a third piezoresistive component, and a fourth piezoresistive component;

4. The low pressure MEMS pressure sensor of claim 3,

the first conductive strips connected to the two ends of the second piezoresistive component and the third piezoresistive component are spirally distributed in the central area of the strained thin film layer, and the first conductive strips connected to the two ends of the first piezoresistive component and the fourth piezoresistive component are linearly distributed in the edge area of the strained thin film layer.

5. The low pressure MEMS pressure sensor of claim 4,

a first end of the first piezoresistive component inputs a first power supply signal, and a second end of the first piezoresistive component outputs a first detection signal; the second end of the second piezoresistive component inputs the first power signal, and the first end of the second piezoresistive component outputs a second detection signal; a first end of the third piezoresistive component inputs a second power signal and a second end of the third piezoresistive component outputs the first detection signal; the second end of the fourth piezoresistive block inputs the second power signal and the first end of the fourth piezoresistive block outputs the second detection signal;

6. The low pressure MEMS pressure sensor of claim 5,

the first conductive strip at the first end of the first piezoresistive component and the first conductive strip at the second end of the second piezoresistive component have a first common connection, which serves as a common power source terminal for inputting the first power signal;

7. The low pressure MEMS pressure sensor of claim 6, wherein the first, second, fourth, and third common connections are disposed sequentially around an edge of the strained thin film layer.

8. The low pressure MEMS pressure sensor of claim 6,

a first spacing groove is formed between the first public connecting part and the second public connecting part, a second spacing groove is formed between the second public connecting part and the fourth public connecting part, and a third spacing groove is formed between the fourth public connecting part and the third public connecting part; and a fourth spacing groove is arranged between the third public connecting part and the first public connecting part.

9. The low pressure MEMS pressure sensor of claim 6, wherein the fourth common connection is separable by a zero-spacing groove forming two separate grounds.

10. The low pressure MEMS pressure sensor of claim 8,

fifth spacing grooves are formed in the first conductive strips at two ends of the first piezoresistive component and close to the connection position of the first piezoresistive component, and the two fifth spacing grooves are symmetrically arranged with the first spacing groove; the fifth spacing groove is used for adjusting the resistance of the first conductive strips at two ends of the first piezoresistive component;

11. The low-voltage MEMS pressure sensor according to claim 6, wherein a side surface of each common connection portion away from the first support layer is further provided with a metal electrode.

12. The low pressure MEMS pressure sensor of claim 11, wherein the second support layer is provided with a plurality of lead holes, each of the lead holes is filled with an electrical conductor, one end of the electrical conductor is connected to the metal electrode, and the other end of the electrical conductor is connected to a pad.

13. The low pressure MEMS pressure sensor of claim 1, wherein the first support layer has a first air hole disposed therein and the second support layer has a second air hole disposed therein; the projection of the first air hole on the surface of one side of the device layer and the projection of the second air hole on the surface of one side of the device layer can fall on the strained thin film layer.