A differential capacitive differential pressure sensor and method of manufacturing the same

Abstract

The application provides a differential capacitive differential pressure sensor and a manufacturing method thereof, relates to the technical field of micro electro mechanical systems (MEMS), and comprises a substrate and differential pressure sensitive capacitors; the differential pressure sensitive capacitor comprises a differential pressure sensitive film, a lower electrode plate, a through hole and a support body; the differential pressure sensitive capacitor comprises a differential pressure sensitive film, an upper electrode plate, a through hole and a support body. The differential pressure sensitive capacitor and the differential pressure sensitive capacitor form a differential capacitor structure. The manufacturing method of the application is to manufacture a differential capacitive differential pressure sensor by using two SOI substrates and MEMS processes; the two differential pressure sensitive films are manufactured by etching the silicon films of the SOI substrates, and the thicknesses and shapes of the two differential pressure sensitive films are the same, so that the consistency of the two differential pressure sensitive films is ensured, and the accuracy of the capacitor spacing is ensured by using an oxidation process.

Description

Technical Field

[0001] This invention relates to the field of microelectromechanical systems (MEMS), and in particular to a differential capacitive differential pressure sensor and its manufacturing method. Background Technology

[0002] MEMS sensors, with their advantages of small size, light weight, low power consumption, and easy integration with CMOS, are widely used in industrial control, automotive electronics, and medical devices. Existing MEMS differential pressure sensors are mainly of two types: piezoresistive and capacitive. Among them, capacitive sensors have attracted much attention due to their advantages such as high sensitivity, wide operating temperature range, and low power consumption. However, existing capacitive differential pressure sensors still face significant challenges in improving sensitivity, enhancing linearity, and reducing manufacturing costs.

[0003] The following are some typical structures and their shortcomings in the existing technology: Single-capacitor differential pressure sensor: This type of sensor contains only two electrode layers. Although it has a simple structure and low manufacturing cost, its sensitivity is extremely low and its anti-interference ability is poor, making it difficult to meet the requirements of high-precision measurement. Therefore, it has not been widely used in high-end practical products.

[0004] Traditional three-layer differential capacitive differential pressure sensors: These sensors consist of three layers of electrodes, offering high sensitivity and strong anti-interference capabilities, making them the current mainstream solution. However, their manufacturing process is extremely complex, resulting in high costs. Especially when based on SOI substrates, they require the consumption of three SOI wafers; the manufacturing process involves two support layer fabrications, two bonding operations, and two removals of the SOI silicon substrate, with extremely high alignment and bonding precision requirements, significantly increasing processing difficulty and scrap rates.

[0005] Quasi-differential capacitive pressure sensors: While these sensors consist of two layers of electrodes, solving some interference issues, they have inherent drawbacks. For example, when pressure changes, only the first capacitance changes, while the second capacitance remains constant, resulting in relatively low overall sensitivity. Furthermore, some patented products of this type do not even have the capability to measure differential pressure.

[0006] In summary, how to simplify the structure of MEMS differential pressure sensors, significantly reduce manufacturing process steps, and lower production costs while ensuring high sensitivity and good linearity is a technical challenge that urgently needs to be solved in this field. Summary of the Invention

[0007] The purpose of this invention is to provide a differential capacitive differential pressure sensor and its manufacturing method to solve the problems in the prior art.

[0008] To achieve the above objectives, the present invention provides the following technical solution: a differential capacitive differential pressure sensor and its manufacturing method, comprising a substrate, a differential pressure sensitive capacitor, and a differential pressure sensitive capacitor; The substrate includes a base, a through-hole extending through the base, and a via. The differential pressure sensitive capacitor includes a differential pressure sensitive film, a lower electrode plate, a through hole formed on the lower electrode plate, and a support body for supporting the structure; The differential pressure sensitive capacitor includes a differential pressure sensitive membrane, an upper electrode plate, a through hole formed on the differential pressure sensitive membrane, and a support body for supporting the structure. The vias are disposed in the substrate, and the pressure difference acts on both the differential pressure sensitive membrane and the differential pressure sensitive capacitor simultaneously, causing one of the differential pressure sensitive capacitors to increase in capacitance and the other to decrease in capacitance, thereby forming a differential capacitor structure.

[0009] Furthermore, the lower electrode plate and the differential pressure sensitive membrane are physically connected to form an integral structure, or the differential pressure sensitive membrane and the upper electrode plate are physically connected to form an integral structure, so as to achieve mechanical linkage.

[0010] Furthermore, an insulating layer is provided on the opposing surfaces of the lower electrode plate and the upper electrode plate. The insulating layer is made of silicon dioxide and is grown by a thermal oxidation process to prevent short circuits between the upper and lower electrode plates.

[0011] Furthermore, a reinforcing layer is provided on the non-working side of the upper electrode plate. The reinforcing layer is used to enhance the mechanical strength of the upper electrode plate during sensor packaging and use, and to prevent it from deforming.

[0012] Furthermore, the lower electrode plate and the differential pressure sensitive membrane are respectively connected to lead-out electrodes, and the lead-out electrodes are provided with metal electrodes. The metal electrodes are made of aluminum and are used to make electrical connections with external detection circuits.

[0013] Furthermore, the differential pressure sensitive membrane and the differential pressure sensitive membrane have the same thickness and the same shape; the lower electrode plate and the upper electrode plate have the same thickness and the same shape; the sensor is composed of 10 sets of identical unit arrays to improve the overall signal output strength.

[0014] Furthermore, the support is made of silicon dioxide and is formed by oxidation and selective etching on the silicon film surface of the SOI substrate. The support is used to maintain a constant spacing between the upper and lower plates after bonding.

[0015] Furthermore, this manufacturing method is based on two SOI substrates and is achieved using semiconductor manufacturing processes, specifically including the following steps: S101: The lower electrode plate, differential pressure sensitive film and via are etched on the silicon film of the first SOI substrate, and vias, vias, lower electrode plate lead-out plate and differential pressure sensitive film lead-out plate are etched on the substrate. S102: Oxidize a silicon dioxide film on the silicon film surface in step S101; etch the silicon dioxide layer, leaving the silicon dioxide as a support layer; etch away the silicon dioxide film on the electrode lead-out plate and the differential pressure sensitive film lead-out plate. S103: A layer of silicon dioxide is thermally oxidized on the substrate in step S102, and the silicon dioxide is etched to form an insulating layer that serves as the surface of the lower electrode plate.

[0016] Furthermore, it also includes the following steps: S104: Etch the differential pressure sensing film, the upper electrode plate, and the through hole on the upper electrode plate onto the second SOI substrate silicon thin film; S105: Thermally oxidize a layer of silicon dioxide on the substrate in step S104, etch the silicon dioxide, and etch out an insulating layer that serves as the surface of the upper electrode plate. S106: The substrates prepared in step S103 and step S105 are aligned and bonded together with the patterned faces to form a composite structure.

[0017] Furthermore, it also includes the following steps: S107: The silicon substrate and silicon dioxide substrate of the second SOI are etched away by plasma etching to expose the differential pressure sensitive film. S108: Sputter a layer of metallic aluminum onto the structure in step S107, and then etch out the metal electrode after alloying. S109: Etch the first SOI substrate silicon dioxide layer to form vias and complete the sensor fabrication.

[0018] Compared with the prior art, the beneficial effects of the present invention are: High sensitivity and high linearity: When the pressure difference Pl-P2 changes, it can simultaneously cause the differential pressure sensitive capacitor (200) and the differential pressure sensitive capacitor (300) to change in opposite directions (one increases and the other decreases). Through differential detection, the sensitivity of the sensor is significantly increased and the linearity of the sensor is effectively improved.

[0019] Low cost and high yield: The sensor is manufactured using a two-layer structure (requiring only two SOI substrates), which significantly reduces the sensor processing steps compared to the traditional sandwich structure (requiring three SOI substrates). Specifically, the manufacturing process only requires one support layer, one bonding, and one removal of the SOI silicon substrate. It does not employ complex alignment bonding, which significantly reduces the processing difficulty and reduces the manufacturing process and processing time by about one-third, thereby greatly reducing the manufacturing cost.

[0020] Precise and controllable structure: Using common MEMS manufacturing processes, the sensitive film in the sensor is made of silicon dioxide and silicon film in SOI substrate, which makes the thickness of the sensitive film easier to control; at the same time, the thickness of silicon dioxide thermally grown on the silicon film of SOI substrate can be precisely controlled, ensuring the accuracy of capacitor spacing. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the basic structure of the capacitive differential pressure sensor of the present invention; Figure 2 This is a schematic diagram of the differential pressure sensor provided in Embodiment 1 of the present invention; Figure 3 This is a schematic diagram of the differential pressure sensor provided in Embodiment 2 of the present invention and a processing structure diagram of step S109 in the manufacturing method; Figure 4 This is a processing structure diagram of step S101 in the differential pressure sensor manufacturing method provided in Embodiment 2 of the present invention; Figure 5 This is a processing structure diagram of step S102 in the differential pressure sensor manufacturing method provided in Embodiment 2 of the present invention; Figure 6 This is a processing structure diagram of step S103 in the differential pressure sensor manufacturing method provided in Embodiment 2 of the present invention; Figure 7 This is a processing structure diagram of step S104 in the differential pressure sensor manufacturing method provided in Embodiment 2 of the present invention; Figure 8 This is a processing structure diagram of step S105 in the differential pressure sensor manufacturing method provided in Embodiment 2 of the present invention; Figure 9 This is a processing structure diagram of step S106 in the differential pressure sensor manufacturing method provided in Embodiment 2 of the present invention; Figure 10 This is a processing structure diagram of step S107 in the differential pressure sensor manufacturing method provided in Embodiment 2 of the present invention; Figure 11 This is a processing structure diagram of step S108 in the differential pressure sensor manufacturing method provided in Embodiment 2 of the present invention; Figure 12 This is a schematic diagram of the relationship between differential pressure and differential capacitance provided in Embodiment 2 of the present invention.

[0022] In the diagram, the markings are as follows: 100-substrate; 101-silicon substrate; 102-through hole; 103-through hole; 104-silicon dioxide layer; 200-first differential pressure sensitive capacitor; 201-first differential pressure sensitive film; 202-through hole; 203-lower electrode plate; 23-support layer; 300-second differential pressure sensitive film; 301-sensitive film; 302-through hole; 303-upper electrode plate; 4-silicon dioxide layer (insulating layer); 5-reinforcing layer; 6-lower electrode plate lead-out plate; 7-differential pressure sensitive film lead-out plate; 8-metal electrode. Detailed Implementation

[0023] Example 1 like Figure 1 and Figure 2 As shown, this embodiment provides a differential capacitive pressure sensor, including a substrate 100, a differential pressure sensitive capacitor 200, and a differential pressure sensitive capacitor 300. The substrate 100 includes a base 101, a through-hole 102, and a through-hole 103. The differential pressure sensitive capacitor 200 includes a differential pressure sensitive membrane 201, a lower electrode 203, a through-hole 202, and a support 23. The differential pressure sensitive capacitor 300 includes a differential pressure sensitive membrane 301, an upper electrode 303, a through-hole 302, and a support 23.

[0024] More specifically, through-hole 202 is disposed on the lower electrode plate 203, and through-hole 302 is disposed on the differential pressure sensitive membrane 301. The pressure difference acts on both the differential pressure sensitive membrane 201 and the differential pressure sensitive membrane 301 simultaneously. In this embodiment, the lower electrode plate 203 and the differential pressure sensitive membrane 301 are connected together to form an integral structure.

[0025] In the specific structure, such as Figure 2 As shown, both the lower electrode 203 and the upper electrode 303 have an insulating layer 4 on their surfaces, which is a silicon dioxide layer. Furthermore, the upper electrode 303 has a reinforcing layer 5. The differential pressure sensitive capacitors 200 and 300 increase in size under the influence of a voltage difference, while the other decreases, forming a differential capacitor structure.

[0026] Example 2 This embodiment describes in detail the manufacturing method of the sensor of the present invention. This pressure sensor manufacturing method is based on semiconductor manufacturing processes using two SOI substrates, and the specific steps are as follows: S101: As Figure 4 As shown, a lower electrode 203, a differential pressure sensitive film 301, and a via 202 are etched on the first SOI substrate silicon film. A via 102 and a via 103, a lower electrode 203 lead-out plate 6, and a differential pressure sensitive film 301 lead-out plate 7 are etched on the substrate 100.

[0027] S102: As Figure 5As shown, a silicon dioxide film is oxidized on the silicon film surface in step S101; the silicon dioxide layer is etched, and the remaining silicon dioxide serves as the support layer 23; the silicon dioxide film on the electrode lead-out plate 6 and the differential pressure sensitive film 301 lead-out plate 7 is etched away.

[0028] S103: As Figure 6 As shown, in step S102, a layer of silicon dioxide is thermally oxidized on the substrate, and the silicon dioxide is etched to etch out the insulating layer 4, which serves as the surface of the lower electrode 203.

[0029] S104: As Figure 7 As shown, a differential pressure sensitive film 201 and an upper electrode 303, as well as a through hole 302 on the upper electrode 303, are etched on the second SOI substrate silicon thin film.

[0030] S105: As Figure 8 As shown, in step S104, a layer of silicon dioxide is thermally oxidized on the substrate, and the silicon dioxide is etched to etch out the insulating layer 4, which serves as the surface of the upper electrode 303.

[0031] S106: As Figure 9 As shown, the substrates prepared in step S103 and step S105 are aligned and bonded together with the patterned faces facing each other.

[0032] S107: As Figure 10 As shown, the silicon substrate 101 and silicon dioxide substrate 104 of the second SOI are etched away using a plasma etching method.

[0033] S108: As Figure 11 As shown, a layer of metallic aluminum is sputtered onto the structure in step S107, and then the metal electrode 8 is etched out after alloying.

[0034] S109: As Figure 3 As shown, the silicon dioxide layer of the first SOI substrate is etched to form vias 105 and 106.

[0035] The structural parameters of the sensor made by the above method are as follows: fixed upper and lower electrode plate dimensions: Φ350μm×1.5μm; moving electrode plate dimensions: Φ350μm×1.5μm; and it consists of 10 sets of sensors with the same structure.

[0036] Example 3 This embodiment verifies the performance of the sensor fabricated using the method of Embodiment Two. Simulation analysis was performed using finite element software, and the relationship curve between differential capacitance and pressure was obtained as follows: Figure 12As shown, when the sensor operates within the 0kPa to 20kPa range, the sensitivity of the sensor of this invention is approximately 0.0422pF / kPa, and the nonlinearity is 0.425%FS. In comparison, the sensitivity of a prior art sensor is approximately 0.0266pF / kPa, and the nonlinearity is 1.63%FS. Clearly, the sensor of this invention improves sensitivity by approximately 58.6% and reduces nonlinearity by approximately 73.9% compared to prior art sensors, fully demonstrating the significant advantages of this invention in improving performance and reducing costs.

[0037] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A differential capacitive differential pressure sensor and its manufacturing method, characterized in that: It includes a substrate (100), a differential pressure sensitive capacitor (200), and a differential pressure sensitive capacitor (300); The substrate (100) includes a base (101), a through hole (102) and a through hole (103) disposed through the base (101); The differential pressure sensitive capacitor (200) includes a differential pressure sensitive film (201), a lower electrode plate (203), a through hole (202) opened on the lower electrode plate (203), and a support body (23) for supporting the structure; The differential pressure sensitive capacitor (300) includes a differential pressure sensitive film (301), an upper electrode plate (303), a through hole (302) formed on the differential pressure sensitive film (301), and a support body (23) for supporting the structure; The vias (102) and (103) are disposed in the substrate (100). The pressure difference acts simultaneously on the differential pressure sensitive membrane (201) and the differential pressure sensitive membrane (301), causing one of the differential pressure sensitive capacitors (200) and (300) to increase in capacitance and the other to decrease in capacitance, thereby forming a differential capacitor structure.

2. The differential capacitive differential pressure sensor and its manufacturing method according to claim 1, characterized in that: The lower electrode plate (203) and the differential pressure sensitive membrane (301) are physically connected to form an integral structure, or the differential pressure sensitive membrane (201) and the upper electrode plate (303) are physically connected to form an integral structure to achieve mechanical linkage.

3. The differential capacitive differential pressure sensor and its manufacturing method according to claim 1, characterized in that: The lower electrode plate (203) and the upper electrode plate (303) are provided with an insulating layer (4) on their opposite surfaces. The insulating layer (4) is made of silicon dioxide and is grown by a thermal oxidation process to prevent short circuits between the upper and lower electrode plates.

4. The differential capacitive differential pressure sensor and its manufacturing method according to claim 1, characterized in that: The upper electrode plate (303) has a reinforcing layer (5) on the non-working side. The reinforcing layer (5) is used to enhance the mechanical strength of the upper electrode plate (303) during sensor packaging and use, and to prevent it from deforming.

5. A differential capacitive differential pressure sensor and its manufacturing method according to claim 1, characterized in that: The lower electrode plate (203) and the differential pressure sensitive membrane (301) are respectively connected to lead-out electrodes. The lead-out electrodes are provided with metal electrodes (8). The metal electrodes (8) are made of aluminum and are used to make electrical connections with external detection circuits.

6. The differential capacitive differential pressure sensor and its manufacturing method according to claim 1, characterized in that: The differential pressure sensitive membrane (201) and the differential pressure sensitive membrane (301) have the same thickness and the same shape; the lower electrode plate (203) and the upper electrode plate (303) have the same thickness and the same shape; the sensor is composed of 10 sets of unit arrays with the same structure to improve the overall signal output strength.

7. A differential capacitive differential pressure sensor and its manufacturing method according to claim 1, characterized in that: The support (23) is made of silicon dioxide and is formed by oxidation and selective etching on the silicon film surface of the SOI substrate. The support (23) is used to maintain a constant spacing between the upper and lower plates after bonding.

8. A differential capacitive differential pressure sensor and its manufacturing method according to any one of claims 1 to 7, characterized in that: This manufacturing method is based on two SOI substrates and is achieved using semiconductor manufacturing processes. Specifically, it includes the following steps: S101: The lower electrode plate (203) and the differential pressure sensitive film (301) and the via (202) are etched on the silicon film of the first SOI substrate, and the via (102) and via (103) and the lower electrode plate (203) lead-out plate (6) and the differential pressure sensitive film (301) lead-out plate (7) are etched on the substrate (100); S102: Oxidize a silicon dioxide film on the silicon film surface in step S101; etch the silicon dioxide layer, leaving the silicon dioxide as a support layer (23); etch away the silicon dioxide film on the electrode lead plate (6) and the differential pressure sensitive film (301) lead plate (7). S103: A layer of silicon dioxide is thermally oxidized on the substrate in step S102, and the silicon dioxide is etched to etch out an insulating layer (4) that serves as the surface of the lower electrode plate (203).

9. A differential capacitive differential pressure sensor and its manufacturing method according to claim 8, characterized in that, It also includes the following steps: S104: Etch a differential pressure sensitive film (201) and an upper electrode plate (303) and a through hole (302) on the upper electrode plate (303) on the second SOI substrate silicon thin film; S105: Thermally oxidize a layer of silicon dioxide on the substrate in step S104, etch the silicon dioxide, and etch out an insulating layer (4) that serves as the surface of the upper electrode plate (303). S106: The substrates prepared in step S103 and step S105 are aligned and bonded together with the patterned faces to form a composite structure.

10. A differential capacitive differential pressure sensor and its manufacturing method according to claim 9, characterized in that, It also includes the following steps: S107: The silicon substrate (101) and silicon dioxide substrate (104) of the second SOI are etched away by plasma etching to expose the differential pressure sensitive film (201); S108: Sputter a layer of aluminum metal onto the structure in step S107, and then etch out the metal electrode (8) after alloying. S109: Etch the silicon dioxide layer of the first SOI substrate to form vias (105) and (106), completing the fabrication of the sensor.

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