Differential capacitive pressure sensor

Abstract

The utility model provides a differential capacitive pressure sensor, which relates to the technical field of microelectronics and comprises a substrate, a sensitive film, a fixed layer with an upper polar plate, a lower polar plate, a movable polar plate, a connector and a support. The connecting body is connected with the sensitive film and the movable polar plate, and the movable polar plate is positioned between the upper polar plate and the lower polar plate which are parallel and fixed to form a differential capacitor. The sensitive film is stressed to move to drive the movable pole plate to move, the movable pole plate keeps a plane state and is connected with the deformed bottom of the sensitive film, and the sensor is high in sensitivity and linearity. When absolute pressure is tested, the sensor does not need to be provided with a through hole, when differential pressure is tested, the sensor only needs to be provided with one through hole, the reliability of the sensor is improved, the service life of the sensor is prolonged, and the manufacturing cost of the sensor is reduced. According to the utility model, a universal mems manufacturing process is adopted based on the SOI substrate, so that the sensor chip is easy to manufacture, and the accuracy of the thickness of the sensitive film and the capacitance spacing is ensured.

Description

Technical Field

[0001] The utility model relates to the related field of microelectronics technology, and in particular to a differential capacitive pressure sensor. Background Art

[0002] MEMS sensors have been widely developed and applied due to their advantages such as small size, light weight, low power consumption, and easy integration with CMOS. Among them, capacitive pressure sensors are one of the main types. According to the working principle of capacitance, MEMS capacitive pressure sensors can be divided into variable-spacing type, variable-area type, and variable-dielectric type. Among them, the differential MEMS pressure sensor in the variable-spacing capacitive pressure sensor has been widely used because it has higher sensitivity, better linearity, and stronger anti-interference ability compared with the single-capacitor MEMS pressure sensor.

[0003] In the current technical solutions of differential MEMS pressure sensors, the patent document (publication number CN105067178) discloses a differential capacitive MEMS pressure sensor and its manufacturing method, and provides the following technical solution: "In order to enable the common sensitive part to sense the external pressure change and bend and deform, a plurality of etching holes are provided on the upper fixed electrode. Through these plurality of etching holes 33, the common sensitive part can be connected to the outside world"; the patent document (publication number CN104848982 B) discloses a quasi-differential capacitive MEMS pressure sensor. In order to keep the capacitance value of the reference capacitor unchanged, holes 12 communicating with the external environment are provided on the film 4b. In the above two patents, the setting of the through holes causes moisture, harmful gases, and dust in the external environment to easily enter the cavity of the capacitor through the through holes, affecting the reliability and service life of the sensor.

[0004] At the same time, the end faces of the pressure-sensitive film 22 (the movable plate of the variable capacitor) in the patent document (publication number CN105067178) and the common sensitive film 4a (the movable plate of the capacitor) in the patent document (publication number CN104848982 B) are fixed. In this way, when the sensitive film (movable plate) is stressed, it will bend and deform. The increase or decrease of the capacitance mainly occurs in the part with large central deformation. The movable plate does not give full play to its performance, reducing the sensitivity. At the same time, when the sensitive film (movable plate) is stressed, the displacement and bending of the movable plate cause changes in the capacitance value, reducing the linearity of the sensor. Summary of the Invention

[0005] The purpose of the utility model is to provide a differential capacitive pressure sensor to solve the problems in the prior art that moisture, harmful gases, and dust in the external environment easily enter the cavity of the capacitor through the through holes, affecting the reliability and service life of the sensor, and to provide a structure for improving the sensitivity and linearity of the differential capacitive pressure sensor, and at the same time make the manufacturing process of the sensor of the utility model easier to control and implement.

[0006] To solve the existing technical problems, the embodiments of the present utility model provide the following technical solutions:

[0007] This embodiment provides a differential capacitive pressure sensor, which includes a substrate, a support, a movable electrode assembly, and a fixed electrode assembly. The movable electrode assembly includes a sensitive film, a connecting body, and a movable plate. The fixed electrode assembly includes a lower plate and a fixed layer composed of an upper plate and an upper plate additional layer;

[0008] The support is disposed on the substrate. The support encloses a hollow cavity. The lower plate is disposed at the bottom of the hollow cavity and fixed on the substrate. The connecting body and the movable plate are both disposed in the hollow cavity. The fixed layer is connected to the sensitive film and disposed above the hollow cavity, and its periphery is fixed on the support;

[0009] The movable plate is connected to the sensitive film through the connecting body. The movable plate is located between the upper plate and the lower plate. The sensitive film moves under the action of pressure and drives the movable plate to move through the connecting body. The capacitance formed by the upper plate and the movable plate and the capacitance formed by the lower plate and the movable plate form a differential capacitance structure.

[0010] In some modified forms, the connecting body connects the bottom of the sensitive film that deforms under force, and the force-deformed part of the sensitive film is located in the hollow cavity.

[0011] In some modified forms, the upper plate, the movable plate, and the lower plate are arranged in parallel;

[0012] In some modified forms, insulating layers are provided on the surface of the upper plate facing the movable plate and the surface of the lower plate facing the movable plate.

[0013] In some modified forms, when the sensitive film is a semiconductor, an isolator is provided between the sensitive film and the upper plate.

[0014] In some modified forms, the isolator is a pn junction.

[0015] In some modified forms, the isolator is a groove.

[0016] In some modified forms, the sensitive film is an insulator.

[0017] In some modified forms, through holes are provided on the substrate or the support.

[0018] In some modified forms, the upper plate is provided with an upper plate lead-out electrode plate, the movable plate is provided with a movable plate lead-out electrode plate, and the lower plate is provided with a lower plate lead-out electrode plate. Metal electrodes are provided on the above-mentioned lead-out electrode plates.

[0019] The working principle of the differential capacitive pressure sensor provided by the present utility model is as follows: A movable plate is provided between a fixed upper plate and a fixed lower plate. The capacitance formed by the movable plate and the upper plate and the capacitance formed by the movable plate and the lower plate form a differential capacitance. The movable plate is connected to the bottom of the sensitive film. When the sensitive film is stressed and moves, it drives the movable plate to move, and the differential capacitance changes. The change signal of the differential capacitance is transmitted to an external measuring device through the metal electrodes of each plate, realizing the measurement of pressure by the sensor.

[0020] Through the implementation of the present utility model, the following technical effects are achieved:

[0021] (1): When measuring the absolute pressure, the capacitive sensor of the present utility model does not need to make through holes in the capacitor, which increases the reliability and service life of the product; when measuring the differential pressure, the differential capacitive sensor of the present utility model only needs to make one through hole, reducing the manufacturing cost.

[0022] (2): The movable plate is located between the parallel and fixed upper plate and lower plate to form a differential capacitance. When the sensitive film is stressed and moves, it drives the movable plate to move. When the movable plate moves, it maintains a planar state. The movable plate is connected to the bottom of the deformed sensitive film, improving the sensitivity and linearity of the differential capacitive sensor. Description of the Drawings

[0023] In order to more clearly illustrate the embodiments of the present utility model, the drawings required for use in the embodiments will be briefly introduced below.

[0024] Figure 1 It is a schematic structural diagram (A-A cross-sectional view) of the differential capacitive pressure sensor according to Embodiment 1 of the present utility model;

[0025] Figure 2 It is a schematic structural diagram of the differential capacitive pressure sensor according to Embodiment 1 of the present utility model when under pressure;

[0026] Figure 3 It is a top view of the differential capacitive pressure sensor according to Embodiment 1 of the present utility model;

[0027] Figure 4 It is a B-B cross-sectional view of the differential capacitive pressure sensor according to Embodiment 1 of the present utility model;

[0028] Figure 5 It is a layout diagram (C-C top view) of the lower plate in the pressure sensor provided by Embodiment 1;

[0029] Figure 6 It is a layout diagram (D-D top view) of the movable plate in the pressure sensor provided by Embodiment 1 of the present utility model;

[0030] Figure 7Layout diagram of the sensitive film and the upper electrode plate in the pressure sensor provided in Embodiment 1 of the present utility model; (E-E bottom view);

[0031] Figure 8 Schematic diagram of the SOI substrate structure;

[0032] Figure 9 Schematic diagram of the structure of the differential capacitive pressure sensor in Embodiment 2 of the present utility model (processing structure diagram in step S112);

[0033] Figure 10a Top view of the processing structure in step S101 in the manufacturing method of the pressure sensor provided in Embodiment 2 of the present utility model;

[0034] Figure 10b F-F cross-sectional view of the processing structure in step S101 in the manufacturing method of the pressure sensor provided in Embodiment 2 of the present utility model;

[0035] Figure 11 Processing structure diagram in step S102 in the manufacturing method of the pressure sensor provided in Embodiment 2 of the present utility model;

[0036] Figure 12 Processing structure diagram in step S103 in the manufacturing method of the pressure sensor provided in Embodiment 2 of the present utility model;

[0037] Figure 13 Processing structure diagram in step S104 in the manufacturing method of the pressure sensor provided in Embodiment 2 of the present utility model;

[0038] Figure 14 Processing structure diagram in step S105 in the manufacturing method of the pressure sensor provided in Embodiment 2 of the present utility model;

[0039] Figure 15 Processing structure diagram in step S106 in the manufacturing method of the pressure sensor provided in Embodiment 2 of the present utility model;

[0040] Figure 16 Processing structure diagram in step S107 in the manufacturing method of the pressure sensor provided in Embodiment 2 of the present utility model;

[0041] Figure 17 Processing structure diagram in step S108 in the manufacturing method of the pressure sensor provided in Embodiment 2 of the present utility model;

[0042] Figure 18 Processing structure diagram in step S109 in the manufacturing method of the pressure sensor provided in Embodiment 2 of the present utility model;

[0043] Figure 19The processing structure diagram of step S110 in the manufacturing method of the pressure sensor provided in the second embodiment of the present utility model;

[0044] Figure 20 The processing structure diagram of step S111 in the manufacturing method of the pressure sensor provided in the second embodiment of the present utility model;

[0045] Figure 21 The top view of the processing of step S113 in the manufacturing method of the pressure sensor provided in the second embodiment of the present utility model;

[0046] Figure 22 The structural schematic diagram of the differential capacitance type pressure sensor in the third embodiment of the present utility model (the processing structure diagram of step S212);

[0047] Figure 23 The processing structure diagram of step S201 in the manufacturing method of the pressure sensor provided in the third embodiment of the present utility model;

[0048] Figure 24 The processing structure diagram of step S202 in the manufacturing method of the pressure sensor provided in the third embodiment of the present utility model;

[0049] Figure 25 The processing structure diagram of step S204 in the manufacturing method of the pressure sensor provided in the third embodiment of the present utility model;

[0050] Figure 26 The processing structure diagram of step S206 in the manufacturing method of the pressure sensor provided in the third embodiment of the present utility model;

[0051] Figure 27 The processing structure diagram of step S210 in the manufacturing method of the pressure sensor provided in the third embodiment of the present utility model;

[0052] Figure 28 The processing structure diagram of step S211 in the manufacturing method of the pressure sensor provided in the third embodiment of the present utility model;

[0053] Figure 29 The top view of the processing of step S213 in the manufacturing method of the pressure sensor provided in the third embodiment of the present utility model;

[0054] Figure 30 The differential capacitance and pressure relationship curve in the manufacturing method of the pressure sensor provided in the second embodiment of the present utility model;

[0055] Figure 31 The differential capacitance and differential pressure relationship curve in the manufacturing method of the pressure sensor provided in the third embodiment of the present utility model;

[0056] In the figure: 1 - hollow cavity; 2 - silicon dioxide; 3 - window; 4 - metal electrode; 5 - isolator; 6 - n-type silicon; 11 - through hole; 100 - substrate; 101 - silicon substrate; 102 - silicon dioxide substrate; 200 - support; 201 - first support layer; 202 - second support layer; 203 - third support layer; 204 - fourth support layer; 300 - movable electrode assembly; 310 - sensitive film; 320 - connector; 321 - silicon connector; 322 - silicon dioxide connector; 330 - movable plate; 331 - movable plate lead-out electrode plate; 400 - fixed electrode assembly; 410 - lower plate; 411 - lower plate lead-out electrode; 420 - fixed layer; 421 - upper plate; 4211 - upper plate lead-out electrode; 422 - upper plate additional layer; 4221 - silicon dioxide additional layer; 4222 - semiconductor additional layer; 440 - insulating layer. Detailed implementation mode

[0057] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0058] Embodiment 1 (related to the accompanying drawings Figures 1 to 7 )

[0059] As Figure 1 shown, this embodiment provides a differential capacitive pressure sensor, including a substrate 100, a support 200, a movable electrode assembly 300, and a fixed electrode assembly 400; the movable electrode assembly 300 includes a sensitive film 310, a connector 320, and a movable plate 330; the fixed electrode assembly 400 includes a lower plate 410 and a fixed layer 420 containing an upper plate; the fixed layer 420 containing the upper plate is composed of an upper plate 421 and an upper plate additional layer 422. The support 200 is fixed on the substrate 100, and the support 200 encloses a hollow cavity; the lower plate 410 is arranged at the bottom of the hollow cavity and fixed on the substrate 100; the connector 320 and the movable plate 330 are both arranged in the hollow cavity; the fixed layer 420 is connected to the sensitive film 310 and arranged above the hollow cavity, and its periphery is fixed on the support 200.

[0060] The movable plate 330 is connected to the sensitive film 310 through the connector 320. The movable plate 330 is located between the upper plate 421 and the lower plate 410. The sensitive film 310 moves under the action of an external force and drives the movable plate 330 to move through the connector 320; the capacitance formed by the upper plate 421 and the movable plate 330 and the capacitance formed by the lower plate 410 and the movable plate 330 form a differential capacitance structure.

[0061] Further, as Figure 2 shown, the connecting body 320 is connected to the bottom of the sensitive film 310 that deforms under force, and the force-deformed part of the sensitive film 310 is located within the hollow cavity 1.

[0062] It should be noted that the number of the sensitive film 310 and the connecting body 320 can be set to one or more according to actual requirements.

[0063] Further, as Figure 5 shown, the layout of the lower electrode plate 410 is illustrated: the support body 200 is fixed on the substrate 100, the support body 200 encloses a hollow cavity, the lower electrode plate 410 and the lower electrode lead-out electrode 411 are fixed on the substrate 100, and the lower electrode lead-out electrode 411 is inserted into the support body 200.

[0064] Further, as Figure 6 shown, the layout of the moving electrode plate 330 is illustrated: the connecting body 320 is connected to the moving electrode plate 330, located within the hollow cavity enclosed by the support body 200, and the moving electrode lead-out electrode 331 is inserted into the support body 200.

[0065] Further, Figure 7 shown, the layout of the upper electrode plate 421 is illustrated: when the sensitive film 310 is a semiconductor, an isolator 5 is provided at the position where the sensitive film 310 contacts the upper electrode plate 421 and the upper electrode lead-out electrode plate 4211; in this embodiment, a pn junction is provided around the sensitive film 310 to achieve electrical isolation from the upper electrode plate 421 and the upper electrode lead-out electrode plate 4211.

[0066] Further, Figure 4 shown, the upper electrode plate 421, the moving electrode plate 330 and the lower electrode plate 410 are arranged in parallel. In Embodiment 1, the areas of the upper electrode plate 421 and the lower electrode plate 410 are the same and they are opposite in position.

[0067] Further, insulating layers 440 are provided on the surface of the upper electrode plate 421 facing the moving electrode plate 330 and the surface of the lower electrode plate 410 facing the moving electrode plate 330.

[0068] Further, the fixed layer composed of the upper electrode plate 421 and the upper electrode additional layer 422 does not deform when subjected to an external force.

[0069] It should be noted that the upper electrode additional layer 422 is a semiconductor or an insulator or a combination of a semiconductor and an insulator.

[0070] Further, as Figure 3 shown, windows 3 are opened at the positions of the lead-out electrode plate 331, the lead-out electrode 411 and the lead-out electrode 4211, and electrodes 4 are made at the windows 3;

[0071] Further, the differential capacitance change signal is transmitted to an external measuring device through the metal electrodes 4 of each electrode plate, realizing the measurement of pressure by the differential capacitive sensor.

[0072] Embodiment 2 (related to the drawings Figures 8 to 21 )

[0073] The manufacturing method of the differential capacitive pressure sensor in this embodiment is a technical method for manufacturing a differential capacitance chip based on an SOI substrate using semiconductor processes such as oxidation, photolithography, ion etching, and bonding sputtering. As Figure 8 shown is the structural diagram of the SOI substrate, which consists of a silicon substrate 101, a silicon dioxide substrate 102, and a silicon film on the silicon dioxide substrate 102.

[0074] The differential capacitive pressure sensor in this embodiment is a sensor for testing absolute pressure. The structural diagram of the sensor is as Figure 9 shown; this pressure sensor does not have a through hole 11, the number of sensitive membranes 310 is 4, the sensitive membranes 310 are semiconductors, the fixed layer 420 consists of an upper electrode plate 421 and an upper electrode plate additional layer 422, and the upper electrode plate additional layer 422 consists of a silicon dioxide additional layer 4221 and a semiconductor additional layer 4222; the support 200 is successively composed of a first support layer 201, a second support layer 202, a third support layer 203, and a fourth support layer 204; when the sensitive membrane 310 is not under pressure, the thickness of the connecting body 320 is the electrode plate distance of the capacitor formed by the moving electrode plate 330 and the upper electrode plate 421, and the thickness of the third support layer 203 is the electrode plate distance of the capacitor formed by the moving electrode plate 330 and the lower electrode plate 410; its manufacturing process steps are as follows:

[0075] S101: As Figure 10a and as Figure 10b shown, fabricate a pn junction on the silicon film of the first SOI substrate: select an SOI substrate with a p-type silicon film, and use photolithography, phosphorus ion implantation, and high-temperature annealing processes to fabricate an n-type region on the p-type silicon film. The pn junction formed by the p-type and n-type on the silicon film serves as the isolator 5 between the sensitive membrane 310, the upper electrode plate 421, and the upper electrode plate lead electrode 4211;

[0076] S102: As Figure 11 shown, oxidize a layer of silicon dioxide film 2 on the surface of the silicon film in step S101;

[0077] S103: As Figure 12 shown, use photolithography and etching processes to etch the silicon dioxide 2 on the silicon dioxide 2 layer in step S102, and the remaining silicon dioxide serves as part of the first support layer 201 and the connecting body 320;

[0078] S104: As Figure 13Thermally oxidize a layer of silicon dioxide on the substrate in step S103, etch away the silicon dioxide on the surface of the sensitive film 310, and the silicon dioxide on the surface of the upper electrode plate 421 serves as the insulating layer 440 on the surface of the upper electrode plate 421;

[0079] S105: As shown in Figure 14 the figure, etch the silicon film on the silicon film of the second SOI, and the remaining silicon film serves as the second support layer 202, the movable electrode plate 330, and the movable electrode lead-out electrode plate 331;

[0080] S106: As shown in Figure 15 the figure, align and bond the substrates made in step S104 and step S105 with the patterned faces facing each other;

[0081] S107: As shown in Figure 16 the figure, in the structure of step S106, use the plasma etching method to remove the silicon substrate 101 and the silicon dioxide substrate 102 of the second SOI;

[0082] S108: As shown in Figure 17 the figure, oxidize a layer of silicon dioxide 2 on the silicon film of the third SOI substrate;

[0083] S109: As shown in Figure 18 the figure, etch the silicon dioxide 2 in step S108, and the remaining silicon dioxide serves as the third support layer 203;

[0084] S110: As shown in Figure 19 the figure, etch the silicon film on the third SOI substrate in step S109, and the remaining silicon film serves as the fourth support layer 204, the lower electrode plate 410, and the lower electrode lead-out electrode plate 411; then thermally grow a layer of silicon dioxide on the silicon films of the lower electrode plate 410 and the lower electrode lead-out electrode plate 411, and the silicon dioxide on the surface of the lower electrode plate 410 serves as the insulating layer 440 on the surface of the lower electrode plate 410;

[0085] S111: As shown in Figure 20 the figure, align and bond the substrates made in step S107 and step S110 together with the patterned faces facing each other;

[0086] S112: As shown in Figure 9 the figure, in the structure of step S111, use the plasma etching method to etch the silicon substrate 101 of the first SOI substrate to the required thickness, and then etch out the silicon dioxide additional layer 4221, the semiconductor additional layer 4222, and the sensitive film 310;

[0087] S113: As shown in Figure 21 the figure, etch a window 3 in the structure of step S112, sputter a layer of aluminum metal, and etch out the metal electrode 4 after alloying.

[0088] The structural parameters of the sensor fabricated by the above method are as follows: The sizes of the upper and lower plates are both 200 µm × 450 µm, and the size of the middle movable plate is 380 µm × 450 µm; the sizes of the 4 sensitive membranes are all 180 µm × 160 µm × 1.5 µm; the distances between the middle movable plate 330 and the upper plate 421 and the lower plate 410 are both 0.9 µm. Compared with the sensors of the prior art, the structural parameters of the prior art differential capacitive pressure sensors are as follows: the sizes of the upper plate, the middle movable plate and the lower plate are all 570 µm × 160 µm × 1.5 µm, and the distance between the plates is 0.9 µm.

[0089] Using finite element software for simulation analysis, the relationship curve between the differential capacitance and the pressure is obtained as Figure 30 shown. When the sensor operates in the range of (20 kPa to 120 kPa), the sensitivity of the sensor of the present invention is about 0.104 pF / KPa, and the non-linearity is 1.69% FS. The sensitivity of the prior art sensor is about 0.075 pF / KPa, and the non-linearity is 3.5% FS. Obviously, the sensor of the present invention has higher sensitivity and lower non-linearity than the prior art sensor.

[0090] Example 3 (related to the drawings Figures 22 to 29 )

[0091] Example 3 is a differential capacitive pressure sensor for testing differential pressure, which is used to test the difference in pressure at different positions; the structure diagram is as Figure 22 shown. The test principle is as follows: If the pressure at one position is P H, applied to the upper surface of the sensitive membrane, and the pressure at another position is P L, applied to the lower surface of the sensitive membrane through the through hole 11, the pressure difference P H -P L causes the sensitive membrane to move, so that the difference in capacitance C H between the movable plate and the lower plate and the capacitance C L between the movable plate and the upper plate changes. The differential capacitance change signal is transmitted to the external measuring device through the metal electrodes 4 of each plate, realizing the measurement of differential pressure by the differential capacitive sensor.

[0092] Compared with the second embodiment, the sensitive film 310 of the pressure sensor is made of an insulating material, the number of sensitive films 310 is two, the substrate 100 is provided with a through hole 11, the support 200 is successively composed of a first support layer 201, a second support layer 202, a third support layer 203 and a fourth support layer 204, and the connecting body 320 is composed of a silicon connecting body 321 and a silicon dioxide connecting body 322; when the sensitive film 310 is not under pressure, the thickness of the silicon dioxide connecting body 322 is the plate distance of the capacitor formed by the moving plate 330 and the upper plate 421, and the thickness of the fourth support layer 204 is the plate distance of the capacitor formed by the moving plate 330 and the lower plate 410; the specific process steps are as follows:

[0093] S201: As shown in Figure 23 , on the first SOI substrate, a layer of silicon dioxide is oxidized by using a dry-oxygen wet-oxygen dry-oxygen alternate oxidation process, the silicon dioxide is etched, and then the silicon dioxide connecting body 322 and the second support layer 202 are etched by using photolithography and etching processes;

[0094] S202: As shown in Figure 24 , on the silicon film of the substrate in step 1, the upper plate 421 and its lead-out electrode plate 4211, the first support layer 201 and the silicon connecting body 321 are etched by using photolithography and etching processes, and at the same time, the silicon film on the sensitive film 310 is etched away;

[0095] S203: Deposit a layer of silicon nitride on the substrate in step S202, etch away the silicon nitride on the second support layer (202), and the silicon nitride on the surface of the upper plate (421) serves as the insulating layer (440);

[0096] S204: As shown in Figure 25 , on the silicon film of the second SOI, the third support layer 203, the moving plate 330 and the moving plate lead-out electrode plate 331 are etched by using photolithography and etching processes;

[0097] S205: Align and bond the substrates made in step S203 and step S204 with the patterned faces;

[0098] S206: As shown in Figure 26 , use the plasma etching method to remove the silicon substrate 101 and the silicon dioxide substrate 102 of the second SOI from the structure bonded in step S205;

[0099] S207: Take a p-type single crystal as the substrate 100, and etch a through hole 11 on the substrate 100;

[0100] S208: On the substrate 100 of the p-type single crystal in step S207, an n-type silicon 6 is formed by using an oxidation photolithography phosphorus diffusion process; then on the n-type silicon 6, a p-type silicon is formed by using an oxidation photolithography boron diffusion process, and the p-type silicon serves as the lower plate 410 and its lead-out electrode 411.

[0101] S209: Oxidize a layer of silicon dioxide 2 on the silicon surface in step S208, etch the silicon dioxide 2 to form the fourth support layer 204;

[0102] S210: Thermally grow a layer of silicon dioxide on the substrate in step S209 as the insulating layer 440 on the surface of the lower electrode 410, with a thickness of 200 nm; as Figure 27 shown, Figure 27 is the result of processing from process step S207 to process step S210;

[0103] S211: As Figure 28 shown, align and bond the products made in step S206 and step S210 together with the patterned faces;

[0104] S212: As Figure 22 shown, in the structure of step S211, remove the silicon substrate 101 of the first SOI substrate by plasma etching method;

[0105] S213: As Figure 29 shown, etch the contact window 3 in the structure of step 212, then sputter a layer of aluminum metal with a thickness of 1 µm, and etch the metal electrode 4.

[0106] The sensor structure parameters of the third embodiment are as follows: The sizes of the upper electrode and the lower electrode are both 300 µm × 350 µm, the size of the middle moving electrode is 500 µm × 350 µm, and the 2 sensitive films are insulators with sizes of: 370 µm × 160 µm × 2 µm; the distances between the middle moving electrode 330 and the upper electrode 421 and the lower electrode 410 are both 0.57 µm.

[0107] Under the above sensor structure dimensions, using finite element software for simulation analysis, the relationship curve between the output differential capacitance and the differential pressure is obtained as Figure 31 shown; when the designed sensor operates in the differential pressure range of (0 kPa to 20 kPa), the maximum capacitance output value is about 3.03 pF, the sensitivity is 152 aF / P, and the non-linearity is 0.29% FS.

[0108] The above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A differential capacitive pressure sensor, characterized in that: The invention comprises a substrate (100), a support body (200), a movable electrode assembly (300), and a fixed electrode assembly (400); the movable electrode assembly (300) comprises a sensitive film (310), a connector (320), and a movable electrode plate (330); and the fixed electrode assembly (400) comprises a lower electrode plate (410), and a fixed layer (420) composed of an upper electrode plate (421) and an upper electrode plate additional layer (422); The support body (200) is arranged on the substrate (100), the support body (200) encloses a hollow cavity (1), the lower electrode plate (410) is arranged at the bottom of the hollow cavity (1) and fixed on the substrate (100), the connector (320) and the moving electrode plate (330) are both arranged in the hollow cavity (1), and the fixed layer (420) is connected to the sensitive film (310) and arranged above the hollow cavity (1), and its periphery is fixed on the support body (200); The moving electrode plate (330) is connected to the sensitive film (310) via the connector (320); the moving electrode plate (330) is located between an upper electrode plate (421) and a lower electrode plate (410); the sensitive film (310) moves under pressure and drives the moving electrode plate (330) to move via the connector (320); a capacitor formed by the upper electrode plate (421) and the moving electrode plate (330) and a capacitor formed by the lower electrode plate (410) and the moving electrode plate (330) form a differential capacitor structure.

2. A differential capacitive pressure sensor according to claim 1, characterized in that The connector (320) is connected to the bottom of the sensitive membrane (310) that is deformed by force, and the deformed part of the sensitive membrane (310) that is deformed by force is located in the hollow cavity (1).

3. A differential capacitive pressure sensor according to claim 1, characterized in that: The upper electrode plate (421), the moving electrode plate (330) and the lower electrode plate (410) are arranged in parallel.

4. A differential capacitive pressure sensor according to claim 1, characterized in that: An insulating layer (440) is provided on the surface of the upper electrode plate (421) facing the moving electrode plate (330) and on the surface of the lower electrode plate (410) facing the moving electrode plate (330).

5. The differential capacitive pressure sensor according to claim 1, characterized in that: When the sensitive film (310) is a semiconductor, an isolator (5) is provided between the sensitive film (310) and the upper electrode plate (421), and the isolator (5) is a pn junction or a trench.

6. The differential capacitive pressure sensor according to claim 1, characterized in that: The sensitive film (310) is an insulator.

7. The differential capacitive pressure sensor according to claim 1, characterized in that: A through hole (11) is provided on the substrate (100) or the support body (200).

8. A differential capacitive pressure sensor according to claim 1, characterized in that The upper electrode plate (421) is provided with an upper electrode plate lead-out electrode plate (4211), the moving electrode plate (330) is provided with a moving electrode plate lead-out electrode plate (331), the lower electrode plate (410) is provided with a lower electrode plate lead-out electrode plate (411), and a metal electrode (4) is provided on the lead-out electrode plate.

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