CN110567619A - A high-sensitivity pressure sensor and its manufacturing method - Google Patents

Abstract

The invention relates to a high-sensitivity pressure sensor and a manufacturing method thereof. A new integrated design process is adopted to obtain a designed high-sensitivity pressure sensor through a series of etching operations, which can form a stress concentration area while ensuring linearity and improving pressure detection. Sensitivity, wherein, through the longitudinal arrangement of four piezoresistive bodies (4), 4 sensitive resistors are formed to form a Huishitong bridge, of which two at the edge bear compressive stress and two in the middle bear tensile stress, due to the four sensitive resistors The arrangement is exactly the same, and the initial resistance is the same, so in practical applications, it has a nearly perfect zero point output, which greatly improves the inspection accuracy of the pressure sensor.

Description

A high-sensitivity pressure sensor and its manufacturing method

technical field

The invention relates to a high-sensitivity pressure sensor and a manufacturing method thereof, belonging to the technical field of micro-electromechanical systems.

Background technique

Compared with traditional machinery, the size of MEMS devices is smaller, generally on the order of microns to millimeters. It is based on the semiconductor integrated circuit (IC) manufacturing process, and can make large-scale, low-cost production by utilizing mature technologies and processes in IC production. Compared with the traditional "mechanical" manufacturing technology, the cost performance is greatly improved; in the existing pressure sensor, the four piezoresistive bodies are respectively arranged on the four sides, and the stress concentration area is not used, resulting in low sensitivity and linearity. The degree is not good.

Contents of the invention

The technical problem to be solved by the present invention is to provide a high-sensitivity pressure sensor that can form a stress concentration area while ensuring linearity and improving the sensitivity of pressure detection.

In order to solve the above technical problems, the present invention adopts the following technical solutions: the present invention designs a high-sensitivity pressure sensor, including a box body, a partition, a substrate, and four piezoresistive bodies; wherein, the top surface of the box body is provided with a concave cavity , the partition is fixedly arranged on the top surface of the box body along the edge of the concave cavity; the substrate is a polygonal ring structure, and all parts of the substrate are in the same plane, the substrate is fixed on the upper surface of the partition, and the substrate is of a polygonal ring structure The position of the middle area corresponds to the position of the concave cavity on the top surface of the box body, and the cavity inside the concave cavity on the top surface of the box body is in a vacuum state;

The structures of the four piezoresistive bodies are identical to each other, and each piezoresistive body includes at least two piezoresistive strips, and the lengths of the piezoresistive strips are equal to each other; in each piezoresistive body, the piezoresistive strips are parallel to each other and coplanar. Adjacent piezoresistive strips are connected in series to form a curved structure, and the straight line parallel to the piezoresistive strips and the middle position between the outermost piezoresistive strips on both sides is taken as the axis, and the curved structure is axisymmetric;

The two ends of each piezoresistive curved structure pass through wires and are fixedly connected to the inner side of the polygonal ring structure of the substrate. Fixed on the upper surface of the separator; the faces of the piezoresistive bodies are coplanar with each other, and the straight lines parallel to the symmetry axes of the piezoresistive strips on each piezoresistive body are collinear, and the collinear cross-substrate polygonal ring structures are opposite to each other. At the midpoint of the side, adjacent piezoresistive bodies are axisymmetric to each other;

The upper surface of the substrate is provided with pads connected to the wires respectively. By supplying power to each pad, power is supplied to each piezoresistive body through the wires. Among them, the two piezoresistive bodies on both sides bear compressive stress, and the two piezoresistive bodies in the middle A piezoresistive body is subjected to tensile stress.

As a preferred technical solution of the present invention: the substrate is a rectangular ring structure, and the two ends of the piezoresistive curve structures are respectively connected to the two inner sides of the rectangular ring structure of the docking substrate through wires and opposite to each other. The overall structure of the piezoresistive body and the wires connected at its two ends is axisymmetric with its axis of symmetry parallel to the piezoresistive strip.

As a preferred technical solution of the present invention: the box body, the partition, and the substrate are all made of silicon material, and the piezoresistive strips and wires are formed by ion implantation of the silicon material.

Corresponding to the above, the technical problem to be solved by the present invention is to provide a manufacturing method for a high-sensitivity pressure sensor, adopt a new integrated design process, and obtain the designed high-sensitivity pressure sensor through a series of etching operations, which can form Stress concentration areas, while ensuring linearity, improve the sensitivity of pressure detection.

In order to solve the above-mentioned technical problems, the present invention adopts the following technical solutions: the present invention designs a method for manufacturing a high-sensitivity pressure sensor, and uses two silicon wafers to realize the production of a high-sensitivity pressure sensor, including the following steps:

Step A. performing oxidation treatment on the upper surface of the first silicon wafer to obtain an oxide layer located on the upper surface of the first silicon wafer;

Step B. patterning the oxide layer on the upper surface of the first silicon wafer, and etching to obtain a recessed cavity located on the upper surface of the first silicon wafer;

Step C. performing oxidation treatment on the lower surface of the second silicon wafer to obtain an oxide layer located on the lower surface of the second silicon wafer;

Step D. In a vacuum environment, bonding the oxide layer on the lower surface of the second silicon wafer to the upper surface of the first silicon wafer, and covering the concave cavity on the upper surface of the first silicon wafer by the second silicon wafer;

Step E. Thinning the second silicon wafer to a preset thickness from the upper surface of the second silicon wafer, and then performing oxidation treatment on the upper surface of the second silicon wafer to obtain an oxide layer on the upper surface of the second silicon wafer ;

Step F. patterning the oxide layer on the upper surface of the second silicon wafer, and etching the oxide layer to obtain injection ports corresponding to each piezoresistive strip and each wire;

Step G. Carry out ion implantation for each injection port on the oxide layer on the upper surface of the second silicon wafer, and each ion implantation position constitutes each piezoresistive strip and each wire;

Step H. For patterning the upper surface of the second silicon wafer, etch the preset thickness for each piezoresistive strip and the surrounding area of each wire, and the etching depth is higher than the lower bottom surface of the second silicon wafer, thereby forming a surrounding area. A polygonal annular structure substrate for each piezoresistive strip and each wire;

Step 1. For the surface of each piezoresistive strip, the surface of each wire, and the middle area of the substrate polygonal ring structure, deposit a layer of insulating layer;

Step J. Patterning the oxide layer on the upper surface of the second silicon wafer, opening windows, and depositing metal materials to form each pad.

As a preferred technical solution of the present invention: in the step A, the upper surface of the first silicon chip is firstly polished, and then oxidized; in the step C, the lower surface of the second silicon chip is firstly treated Polishing treatment followed by oxidation treatment.

As a preferred technical solution of the present invention: if the pressure sensor is a differential pressure sensor, step K is also included, and step K is entered after step J is performed;

Step K. Patterning the lower surface of the first silicon wafer to form a hollow structure on the lower surface of the first silicon wafer.

A high-sensitivity pressure sensor and its manufacturing method described in the present invention, compared with the prior art by adopting the above technical scheme, has the following technical effects:

The high-sensitivity pressure sensor designed in the present invention and its manufacturing method adopt a new integrated design process and obtain the designed high-sensitivity pressure sensor through a series of etching operations, which can form a stress concentration area while ensuring linearity and improving pressure detection. Sensitivity, wherein, through the longitudinal arrangement of four piezoresistive bodies, four sensitive resistors are formed to form a Huishitong bridge, of which two on the edge bear compressive stress, and two in the middle bear tensile stress. Since the four sensitive resistors are arranged exactly the same, And the initial resistance is the same, in practical application, it has a nearly perfect zero point output, which greatly improves the inspection accuracy of the pressure sensor.

Description of drawings

Fig. 1 is a schematic top view of Embodiment 1 of designing a high-sensitivity pressure sensor in the present invention;

Fig. 2 is a three-dimensional schematic diagram of Embodiment 2 of the present invention designing a high-sensitivity pressure sensor;

Fig. 3 is the schematic diagram of the results of step A in the method for manufacturing a high-sensitivity pressure sensor of the present invention;

Fig. 4 is the schematic diagram of the results of step B in the method for manufacturing a high-sensitivity pressure sensor designed in the present invention;

Fig. 5 is a schematic diagram of the results of step D in the method for manufacturing a high-sensitivity pressure sensor designed in the present invention;

Fig. 6 is a schematic diagram of the results of step E in the method for manufacturing a high-sensitivity pressure sensor designed in the present invention;

Fig. 7 is a schematic diagram of the results of step F in the method for manufacturing a high-sensitivity pressure sensor designed in the present invention;

Fig. 8 is a schematic diagram of the results of step H in the method for designing a high-sensitivity pressure sensor of the present invention;

Fig. 9 is a schematic diagram of the results of step I in the method for manufacturing a high-sensitivity pressure sensor designed in the present invention;

Fig. 10 is a schematic diagram of the result of step J in the method for manufacturing a high-sensitivity pressure sensor designed in the present invention;

Fig. 11 is a schematic diagram of the stress distribution in the direction of the lead wire in the implementation of the design of the high-sensitivity pressure sensor of the present invention.

Among them, 1. box body, 2. partition, 3. substrate, 4. piezoresistive body, 5. recessed cavity, 6. wire, 7. welding pad, 8. first silicon wafer, 9. oxide layer, 10. Second silicon wafer, 11. Insulation layer, 12. Metal material.

Detailed ways

The specific implementation manners of the present invention will be further described in detail below in conjunction with the accompanying drawings.

The present invention designs a high-sensitivity pressure sensor. In practical applications, as shown in Figure 1 and Figure 2, it includes a box body 1, a partition plate 2, a substrate 3 and four piezoresistive bodies 4; wherein, the box body 1 The top surface is provided with a concave cavity 5, and the partition plate 2 is fixedly arranged on the top surface of the box body 1 along the edge of the concave cavity 5; the substrate 3 is a polygonal ring structure, and all parts of the substrate 3 are coplanar, and the substrate 3 is fixed On the upper surface of the partition plate 2, the position of the middle region of the polygonal ring structure of the substrate 3 corresponds to the position of the recessed cavity 5 on the top surface of the box body 1, and the interior of the recessed cavity 5 on the top surface of the box body 1 is in a vacuum state.

The structures of the four piezoresistive bodies 4 are identical to each other, each piezoresistive body 4 includes at least two piezoresistive strips, and the lengths of each piezoresistive strip are equal to each other; in each piezoresistive body 4, each piezoresistive strip is parallel to each other On the surface, adjacent piezoresistive strips are connected in series to form a curved structure, and the straight line parallel to the piezoresistive strips and passing through the middle position between the outermost piezoresistive strips on both sides is taken as the axis, and the curved structure is axisymmetric.

The two ends of the curved structure of each piezoresistive body 4 are respectively passed through the wire 6 and fixedly connected to the inner side of the polygonal ring structure of the substrate 3, and each piezoresistive body 4 and each wire 6 are located in the middle area of the polygonal ring structure of the substrate 3, and each The piezoresistive bodies 4 and the wires 6 are fixed on the upper surface of the partition plate 2; the faces of the piezoresistive bodies 4 are coplanar with each other, and the straight lines parallel to the symmetry axes of the piezoresistive strips on the piezoresistive bodies 4 are collinear, and the common The lines pass through the midpoints of the inner sides of the polygonal ring structures of the substrate 3 opposite to each other, and the adjacent piezoresistive bodies 4 are axially symmetrical to each other.

In the actual product design, the box body 1, the partition plate 2, and the substrate 3 are all made of silicon material, and the piezoresistive strips and the wires 6 are formed by ion implantation for the silicon material; the substrate 3 is rectangular Ring structure, the two ends of each piezoresistive body 4 curve structure pass through the wire 6 and the two inner sides of the rectangular ring structure of the fixed docking substrate 3 respectively. The overall structure is axisymmetric with its axis of symmetry parallel to the piezoresistive strip.

The upper surface of the substrate 3 is provided with each pad 7 connected to each wire 6 respectively, and by supplying power to each pad 7, power is supplied to each piezoresistive body 4 through the wire 6, wherein the two piezoresistive bodies 4 on both sides Under compressive stress, the two piezoresistive bodies 4 in the middle bear tensile stress.

Based on the above technical solution, the high-sensitivity pressure sensor shown in Fig. 1 or Fig. 2 is finally constructed.

Aiming at the high-sensitivity pressure sensor designed above in the technical solution, the present invention further designs its manufacturing method. In practical application, two silicon wafers are specifically used to realize the manufacturing of the high-sensitivity pressure sensor, including the following steps.

Step A. Perform polishing treatment on the upper surface of the first silicon wafer 8 first, and then perform oxidation treatment to obtain an oxide layer 9 located on the upper surface of the first silicon wafer 8, as shown in FIG. 3 .

Step B. Patterning the oxide layer 9 on the upper surface of the first silicon wafer 8, and etching to obtain a recessed cavity 5 located on the upper surface of the first silicon wafer 8, as shown in FIG. 4 .

Step C. Perform polishing treatment on the lower surface of the second silicon wafer 10 first, and then perform oxidation treatment to obtain the oxide layer 9 located on the lower surface of the second silicon wafer 10 .

Step D. In a vacuum environment, the oxide layer 9 on the lower surface of the second silicon wafer 10 is bonded to the upper surface of the first silicon wafer 8, and the concave cavity 5 on the upper surface of the first silicon wafer 8 is formed by the second silicon wafer 10 To achieve coverage, as shown in Figure 5.

Step E. Thinning the second silicon wafer 10 to a predetermined thickness from the upper surface of the second silicon wafer 10, and then performing oxidation treatment on the upper surface of the second silicon wafer 10 to obtain The oxide layer 9 on the surface is shown in FIG. 6 .

Step F. Patterning the oxide layer 9 on the upper surface of the second silicon wafer 10, and etching the oxide layer 9 to obtain injection ports corresponding to each piezoresistive strip and each wire 6, as shown in FIG. 7 .

Step G. Carry out ion implantation for each injection port on the oxide layer 9 on the upper surface of the second silicon wafer 10, and form each piezoresistive strip and each wire 6 by each ion implantation position. In practical applications, in this step The ion implantation can be designed to use multiple implants to make the wire have smaller resistivity.

Step H. For patterning the upper surface of the second silicon wafer 10, etch the preset thickness for each piezoresistive strip and the surrounding area of each wire 6, and the etching depth is higher than the lower bottom surface of the second silicon wafer 10, by This constitutes a polygonal annular structure substrate 3 surrounding each piezoresistive strip and each wire 6 , as shown in FIG. 8 .

Step I. Deposit a layer of insulating layer 11 on the surface of each piezoresistive strip, the surface of each wire 6, and the middle area of the polygonal ring structure of the substrate 3, as shown in FIG. 9 .

Step J. Pattern the oxide layer on the upper surface of the second silicon wafer 10, open a window, and then deposit metal material 12 to form each pad 7, as shown in FIG. 10 .

In a specific practical application, if the pressure sensor is a differential pressure sensor, step K is also included, and step K is entered after step J is performed.

Step K. Patterning the lower surface of the first silicon wafer 8 to form a hollow structure on the lower surface of the first silicon wafer 8 .

The high-sensitivity pressure sensor and manufacturing method designed by the above technical solution, in practical application, adopts a new integrated design process, and obtains the designed high-sensitivity pressure sensor through a series of etching operations, which can form a stress concentration area while ensuring linearity , to improve the sensitivity of pressure detection, wherein, through the longitudinal arrangement of four piezoresistive bodies 4, four sensitive resistors are formed to form a Huishitong bridge, in which two of the edges bear compressive stress, and the middle two bear tensile stress. The sensitive resistors are arranged exactly the same, and the initial resistance is the same, so in practical applications, it has a nearly perfect zero output, which greatly improves the inspection accuracy of the pressure sensor.

And in a specific practical implementation, as shown in FIG. 11 , the stress distribution in the X direction of the lead wire under pressure. Since the stress in this direction has tensile stress and compressive stress, most of the resistance changes produced by it can cancel each other out, and the influence of the remaining part on the sensitivity can be ignored.

The embodiments of the present invention have been described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments, and can also be made without departing from the gist of the present invention within the scope of knowledge possessed by those of ordinary skill in the art. Variations.

Claims (6)

1. a high sensitivity pressure sensor, characterized by: comprises a box body (1), a clapboard (2), a substrate (3) and four piezoresistive bodies (4); wherein, the top surface of the box body (1) is provided with a concave cavity (5), and the clapboard (2) is fixedly arranged on the periphery of the edge of the concave cavity (5) on the top surface of the box body (1); the substrate (3) is of a polygonal annular structure, all parts of the substrate (3) are coplanar, the substrate (3) is fixedly arranged on the upper surface of the partition plate (2), the position of the middle area of the polygonal annular structure of the substrate (3) corresponds to the position of the concave cavity (5) on the top surface of the box body (1), and the interior of the concave cavity (5) on the top surface of the box body (1) is in a vacuum state;

the four piezoresistive bodies (4) have the same structure, each piezoresistive body (4) comprises at least two piezoresistive strips, and the lengths of the piezoresistive strips are equal to each other; in each piezoresistive body (4), each piezoresistive strip is parallel and coplanar, adjacent piezoresistive strips are connected in series to form a curve structure, a straight line which is parallel to the piezoresistive strips and passes through the middle position between the outermost piezoresistive strips at two sides is taken as an axis, and the curve structure is axisymmetric;

Two ends of the curve structure of each piezoresistive body (4) are fixedly butted with the inner side edge of the polygonal annular structure of the substrate (3) through a conducting wire (6), each piezoresistive body (4) and each conducting wire (6) are positioned in the middle area of the polygonal annular structure of the substrate (3), and each piezoresistive body (4) and each conducting wire (6) are fixed on the upper surface of the partition plate (2); the surfaces of the piezoresistive bodies (4) are coplanar, the straight lines on the piezoresistive bodies (4) parallel to the symmetry axis of the piezoresistive strips are collinear, the collinear lines pass through the middle points of two opposite inner side edges of the polygonal annular structure of the substrate (3), and the adjacent piezoresistive bodies (4) are axisymmetric;

the upper surface of the substrate (3) is provided with each bonding pad (7) which is respectively connected with each lead (6), and power is supplied to each bonding pad (7) and each piezoresistive body (4) through the leads (6), wherein two piezoresistive bodies (4) on two sides bear compressive stress, and two piezoresistive bodies (4) in the middle bear tensile stress.

2. A high sensitivity pressure sensor as claimed in claim 1, wherein: the substrate (3) is of a rectangular annular structure, two ends of the curve structure of each piezoresistive body (4) are fixedly connected with two opposite inner side edges of the rectangular annular structure of the substrate (3) through a conducting wire (6), and the integral structure of each piezoresistive body (4) and the conducting wires (6) connected with the two ends of the piezoresistive body is axisymmetric with a symmetry axis parallel to the piezoresistive strips.

3. A high sensitivity pressure sensor as claimed in claim 1, wherein: the box body (1), the partition plate (2) and the substrate (3) are all made of silicon materials, and each piezoresistive strip and each lead (6) are formed by ion implantation of the silicon materials.

4. a method for manufacturing a high-sensitivity pressure sensor according to any one of claims 1 to 3, wherein two silicon wafers are used to realize the manufacture of the high-sensitivity pressure sensor, comprising the following steps:

Step A, carrying out oxidation treatment on the upper surface of a first silicon wafer (8) to obtain an oxidation layer (9) positioned on the upper surface of the first silicon wafer (8);

B, patterning an oxide layer (9) on the upper surface of the first silicon wafer (8), and etching to obtain a recessed cavity (5) on the upper surface of the first silicon wafer (8);

C, carrying out oxidation treatment on the lower surface of the second silicon wafer (10) to obtain an oxidation layer (9) positioned on the lower surface of the second silicon wafer (10);

Step D, bonding the oxide layer (9) on the lower surface of the second silicon wafer (10) with the upper surface of the first silicon wafer (8) in a vacuum environment, and covering the sunken cavity (5) on the upper surface of the first silicon wafer (8) by the second silicon wafer (10);

E, thinning the second silicon wafer (10) to a preset thickness from the upper surface of the second silicon wafer (10), and then oxidizing the upper surface of the second silicon wafer (10) to obtain an oxide layer (9) on the upper surface of the second silicon wafer (10);

f, patterning the oxide layer (9) on the upper surface of the second silicon wafer (10), and etching the oxide layer (9) to obtain injection ports respectively corresponding to each pressure barrier strip and each lead (6);

g, respectively injecting ions into each injection hole on the oxide layer (9) on the upper surface of the second silicon wafer (10), and respectively forming each pressure barrier and each lead (6) by each ion injection position;

Step H, patterning the upper surface of the second silicon wafer (10), and etching the surrounding areas of each pressure barrier strip and each lead (6) to a preset thickness, wherein the etching depth is higher than the lower bottom surface of the second silicon wafer (10), so that a substrate (3) with a polygonal annular structure surrounding each pressure barrier strip and each lead (6) is formed;

I, depositing an insulating layer (11) aiming at the surfaces of the pressure resistance strips, the surfaces of the leads (6) and the middle area of the polygonal annular structure of the substrate (3);

And J, patterning the oxide layer on the upper surface of the second silicon wafer (10), windowing, and depositing a metal material (12) to form each bonding pad (7).

5. The method of claim 4, wherein the method further comprises: in the step A, polishing treatment is firstly carried out on the upper surface of the first silicon wafer (8), and then oxidation treatment is carried out; and in the step C, polishing treatment is firstly carried out on the lower surface of the second silicon wafer (10), and then oxidation treatment is carried out.

6. the method of claim 4, wherein the method further comprises: if the pressure sensor is a differential pressure sensor, the method also comprises a step K, and after the step J is executed, the step K is executed;

and K, patterning the lower surface of the first silicon chip (8) to form a hollow structure of the lower surface of the first silicon chip (8).