Suspension capacitive sensing chip

Abstract

The application relates to a suspended capacitive sensing chip, in particular to a suspended capacitive sensing chip, and belongs to the technical field of micro-electro-mechanical systems (MEMS). The application provides a suspended capacitive sensing chip. The application comprises an upper pole plate (1) and a lower pole plate (2), and a cavity (3) is arranged between the upper pole plate (1) and the lower pole plate (2), characterized in that the cavity (3) is provided with gas (4) and / or the lower pole plate (2) is provided with a support (5).

Description

Technical Field

[0001] This invention belongs to the field of microelectromechanical systems (MEMS) technology, and particularly relates to a suspended capacitive sensing chip. Background Technology

[0002] MEMS, or Micro-Electro-Mechanical Systems, is a cutting-edge interdisciplinary field and has been listed as one of the five disruptive technologies impacting the future of manufacturing. Advanced MEMS sensors have become a strategic development area in my country. MEMS pressure sensors, a technology-intensive industry, have become indispensable key components in various sectors, widely used in consumer electronics, automotive electronics, aerospace, petrochemicals, biomedicine, and defense. The key core technology of MEMS pressure sensors is the pressure-sensitive chip. Currently, the mainstream technologies are piezoresistive and capacitive, with capacitive pressure-sensitive chips offering advantages such as good temperature characteristics, high sensitivity, low power consumption, and high accuracy. Capacitive pressure sensors have received widespread attention, application, and research in fields requiring high-precision pressure measurement.

[0003] Capacitive pressure sensors measure pressure by causing physical deformation of the sensing plates when pressure is applied, thus changing the capacitance. Currently, capacitive pressure sensors are mainly classified into non-contact and contact types. Non-contact ordinary capacitive pressure sensors typically employ a parallel-plate capacitor structure, consisting of a movable plate and a fixed plate. When pressure is applied to the movable plate, the distance between the plates changes, resulting in a change in capacitance. Pressure is measured by detecting this capacitance value. However, this type suffers from severe nonlinearity between input and output, and low overload capacity. In the 1990s, Wen H. Ko et al. proposed a contact capacitive pressure sensor structure (US Patent No.: 5,528,452). The main feature of this structure is that during operation, as the external pressure increases, the upper sensing plate contacts the dielectric layer on the lower plate. At this point, the output capacitance value exhibits an approximately linear relationship with the pressure change, thereby improving the linearity of ordinary capacitive pressure sensors to some extent. However, it suffers from low sensitivity, a small linear range, and cannot be applied to differential pressure measurement. To address the above problems, this invention designs a new structure with a working principle between contact and non-contact types, called a suspended capacitive pressure sensitive chip. Summary of the Invention

[0004] The present invention addresses the above-mentioned problems by providing a floating capacitive sensing chip.

[0005] To achieve the above objectives, the present invention adopts the following technical solution. The present invention includes an upper electrode plate (1) and a lower electrode plate (2), and a cavity (3) is formed between the upper electrode plate (1) and the lower electrode plate (2). The cavity (3) contains gas (4) and / or a support (5) is provided on the lower electrode plate (2).

[0006] As a preferred solution, the cavity (3) in the present invention is a sealed cavity.

[0007] As another preferred solution, a communication hole (10) for communicating the cavity (3) with the outside is provided on the upper electrode plate (1) or the substrate (7) in the present invention.

[0008] As another preferred solution, there are multiple supports (5) in the present invention, which are evenly distributed on the lower electrode plate (2).

[0009] As another preferred solution, the cross-section of the support (5) in the present invention is in a C shape or a square frame shape.

[0010] As another preferred solution, a groove (9) is provided on the lower electrode plate (2) in the present invention, and the side wall part of the groove serves as the support (5); when there are multiple grooves, the raised part between the grooves (9) serves as the support (5).

[0011] As another preferred solution, the gas (4) in the present invention is air or nitrogen.

[0012] As another preferred solution, the lower end of the lower electrode plate (2) in the present invention is a substrate (7).

[0013] As another preferred solution, a groove (6) is provided on the substrate (7) in the present invention, and the groove (6) and the lower electrode plate (2) form a cavity.

[0014] As another preferred solution, the cavity formed by the groove (6) and the lower electrode plate (2) in the present invention is communicated with the outside through a pressure channel.

[0015] As another preferred solution, the pressure channel in the present invention is provided on the substrate (7).

[0016] Secondly, a dielectric layer (8) is provided at the upper end of the lower electrode plate (2) in the present invention, and the support (5) is provided at the upper end of the dielectric layer (8).

[0017] In addition, the upper electrode plate (1) and the lower electrode plate (2) in the present invention are respectively connected to an external circuit through solder joints and metal leads or solder joints.

[0018] Advantages of the present invention.

[0019] There is gas (4) in the cavity (3) of the present invention and / or supports (5) are provided on the lower electrode plate (2),

[0020] providing a novel capacitive chip structure. This novel capacitive chip structure combines the advantages of non-contact and contact types, has good hysteresis, strong overload capacity, large range, and good output characteristics. Description of the drawings

[0021] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. The scope of protection of the present invention is not limited to the following description.

[0022] Figure 1 This is a schematic diagram of the structure of Embodiment 1 of the present invention.

[0023] Figure 2 This is a schematic diagram of the structure of Embodiment 2 of the present invention.

[0024] Figure 3 This is a top view of the U-shaped support provided on the lower electrode plate of the present invention.

[0025] Figure 4 This is a top view of the U-shaped support provided on the lower electrode plate of the present invention.

[0026] Figure 5 This is a cross-sectional view of the support provided in the groove on the lower electrode plate of the present invention.

[0027] Figure 6 This is a schematic diagram of the structure of Embodiment 3 of the present invention.

[0028] Figure 7 This is a schematic diagram of the gas-filled chip in the sealed cavity of the present invention.

[0029] Figure 8 This is a schematic diagram of the working process of the supporting chip on the lower electrode plate of the present invention.

[0030] Figure 9 This is a schematic diagram of the operation of the sealed cavity filled with gas and the supporting chip on the lower electrode plate of this invention.

[0031] Figure 10 This is the response characteristic curve of the capacitance and pressure relationship of this invention.

[0032] Figure 11 , 12 This is a design and construction example of a non-sealed cavity in the present invention.

[0033] Figure 13 This is a schematic diagram of the pressure channel structure of the present invention.

[0034] Explanation of reference numerals in the attached figures:

[0035] 1. Upper electrode plate, 2. Lower electrode plate, 3. Cavity, 4. Gas, 5. Support, 6. Groove below the lower electrode plate, 7. Substrate, 8. Dielectric layer, 9. Groove on the lower electrode plate, 10. Connecting hole, 11. Pressure channel. Detailed Implementation

[0036] As shown in the figure, the present invention includes an upper electrode plate (1) and a lower electrode plate (2), and a cavity (3) is formed between the upper electrode plate (1) and the lower electrode plate (2).

[0037] The cavity (3) is a sealed cavity.

[0038] The cavity (3) contains gas (4). The sealed cavity of the existing pressure-sensitive chip is a vacuum.

[0039] like Figure 1 As shown, the cavity (3) is filled with gas (4), and the upper electrode (1) is directly pressurized.

[0040] like Figure 7 As shown, the upward tension of the gas (4) inside the cavity (3) on the upper plate (1) will cause the upper plate (1) to float above the lower plate (2); when the pressure on the upper plate (1) decreases, the pressure of the gas (4) inside the cavity (3) forces the upper plate (1) to rapidly reduce its deformation, thereby reducing the hysteresis characteristics.

[0041] The first chip working principle: In this invention, the upper electrode (1) is a pressure-sensitive electrode. After sensing pressure, the upper electrode (1) deforms towards the lower electrode (2), thereby changing the capacitance value between the upper electrode (1) and the lower electrode (2), which has the advantage of non-contact operation. As the pressure on the upper electrode (1) increases, when it is about to contact the lower electrode (2), the volume of the sealed cavity (3) decreases and the internal gas pressure increases. At this time, the upward tension of the gas (4) inside the cavity (3) on the upper electrode (1) will cause the upper electrode (1) to float above the lower electrode (2), which has the advantage of contact operation. When the pressure on the upper electrode (1) decreases, the pressure of the gas (4) inside the cavity (3) forces the upper electrode (1) to quickly reduce its deformation, thereby reducing the hysteresis characteristic. The amount of gas (4) injected can be calculated based on the range, the volume of the cavity (3), the density of the gas (4), and the pressure, as shown in Figure (7).

[0042] like Figure 2 As shown, a support (5) is provided on the lower electrode plate (2).

[0043] like Figure 8 As shown, when the upper electrode plate (1) contacts the support (5) on the lower electrode plate (2), the upper electrode plate (1) is suspended above the lower electrode plate (2) and does not contact the lower electrode plate (2).

[0044] The second chip working principle is as follows: In this invention, the upper electrode plate (1) is a pressure-sensitive electrode plate. After the upper electrode plate (1) senses pressure, it deforms towards the lower electrode plate (2), thereby changing the capacitance value between the upper electrode plate (1) and the lower electrode plate (2). At this time, it has the advantage of non-contact operation. As the pressure on the upper electrode plate (1) increases, when the upper electrode plate (1) contacts the support on the lower electrode plate (2), the upper electrode plate (1) floats above the lower electrode plate (2) without contacting it. At this time, it has the advantage of contact operation, as shown in Figure (8).

[0045] The working principle of the third type of chip. In the present invention, the upper plate (1) is a pressure-sensitive plate. When the upper plate (1) senses pressure, it deforms in the direction of the lower plate (2), thereby changing the capacitance value between the upper plate (1) and the lower plate (2). At this time, it has the advantages of non-contact. As the pressure on the upper plate (1) increases, the upward tension of the gas (4) inside the cavity (3) on the upper plate (1) and the support (5) on the lower plate (2) act together, causing the upper plate (1) to float above the lower plate (2) without contacting the lower plate (2). At this time, it has the advantages of contact. When the pressure on the upper plate (1) decreases, the pressure of the gas (4) inside the cavity (3) forces the upper plate (1) to rapidly reduce its deformation, thereby reducing the hysteresis characteristic. The amount of gas (4) rushing in can be calculated based on the measuring range, the volume of the cavity (3), the density and pressure of the gas (4), as shown in Figure (9).

[0046] As Figure 9 shown, at this time, the upward tension of the gas (4) inside the cavity (3) on the upper plate (1) and the support (5) on the lower plate (2) act together, causing the upper plate (1) to float above the lower plate (2) without contacting the lower plate (2); when the pressure on the upper plate (1) decreases, the pressure of the gas (4) inside the cavity (3) forces the upper plate (1) to rapidly reduce its deformation, thereby reducing the hysteresis characteristic.

[0047] The supports (5) are multiple and are evenly distributed on the lower plate (2).

[0048] The cross-section of the support (5) is U-shaped or square-shaped.

[0049] Grooves (9) are provided on the lower plate (2), and the raised parts between the grooves (9) serve as the supports (5).

[0050] The gas (4) is air or nitrogen. The gas in the cavity (3) can be a single gas or a mixed gas.

[0051] The supports (5) on the lower plate (2) can be connected to each other (such as the support (5) with a U-shaped cross-section) or not connected (such as the support (5) with a square-shaped cross-section). When the upper plate (1) contacts the support (5), the gas between the connected supports (5) is evenly distributed, and the pressure of the gas (4) inside the entire cavity (3) is evenly distributed. When the pressure changes, the tension exerted on the upper plate (1) by the gas (4) inside the cavity (3) is uniform. When only the support can meet the performance requirements, such as for a large pressure measuring range, the support can be not connected; when high-precision measurement of small pressure is required, the support can be connected.

[0052] The lower end of the lower plate (2) is a substrate (7).

[0053] The substrate (7) has a groove (6) which forms a cavity with the lower electrode plate (2). The cavity can be sealed or connected to the outside.

[0054] like Figure 6 As shown, the present invention includes an upper electrode plate (1), a lower electrode plate (2), a cavity (3) between the upper electrode plate (1) and the lower electrode plate (2), a gas (4) filled inside the cavity (3), a support (5), a groove (6), and a substrate (7). The upper electrode plate (1) is directly pressurized. When the groove (6) is sealed, the lower electrode plate (2) can move downward with the upper electrode plate (1), improving the linearity of the output characteristics, increasing the range, and improving the overload capacity. When the groove (6) is connected to the outside, the lower electrode plate (2) and the upper electrode plate (1) simultaneously feel the same pressure, and the lower electrode plate (2) moves towards the upper electrode plate (1), improving the linearity of the output characteristics, increasing the sensitivity, increasing the range, and improving the overload capacity.

[0055] The cavity formed by the groove (6) and the lower electrode plate (2) is connected to the outside through a pressure channel.

[0056] like Figure 12 As shown, the pressure channel (11) can be disposed on the substrate (7).

[0057] A dielectric layer (8) is provided on the upper end of the lower electrode plate (2), and a support (5) is provided on the upper end of the dielectric layer (8). The support (5) can be provided on the dielectric layer (8) in various configurations. The dielectric layer (8) can be made of silicon dioxide or silicon nitride. The support (5) can be directly etched on the lower electrode plate (2), in which case the support (5) and the lower electrode plate (2) are integrated; or the required shape can be directly etched from the dielectric layer (8), in which case the dielectric layer (8) and the support (5) are integrated; or the support (5) can be made on the dielectric layer (8), depending on the size of the chip.

[0058] The upper electrode plate (1) and the lower electrode plate (2) are respectively connected to the external circuit through a pressure solder joint and a metal lead or pressure solder joint.

[0059] like Figure 11 , 12 As shown, the upper electrode plate (1) or substrate (7) is provided with a connecting hole (10) to connect the cavity (3) with the outside. The cavity (3) can also be unsealed. The unsealed cavity (3) is used in conjunction with the support (5). This structure chip can be used to measure acceleration in an accelerometer and can also be used to measure pressure in a gauge.

[0060] like Figure 10 (against Figure 8As shown in the data obtained from the structure, the pressure-sensitive chip structure with support (5) proposed in this invention is used to design an absolute pressure sensor with a range of 0-190kPa. The upper and lower plates can be annular diaphragms. The thickness of the upper plate (6) can be 3.5μm, the thickness of the lower plate (3) can be 3.5μm, the height of the cavity (3) can be 1.2μm, and the height of the support (5) can be 50nm.

[0061] The suspended capacitive pressure-sensitive chip proposed in this invention can be used for the measurement of absolute and differential pressure in various fields such as consumer electronics, automotive electronics, industrial measurement and control, medical electronics, aerospace, and national defense. This pressure-sensitive chip has advantages such as high sensitivity, good linearity, large linear range, low temperature drift, strong overload capacity, and compatibility with integrated circuit technology, making it particularly suitable for developing high-precision pressure sensors.

[0062] This invention can be applied to pressure detection, silicon microphones, accelerometers, flow meters, etc.

[0063] It is understood that the above specific description of the present invention is only for illustrating the present invention and is not limited to the technical solutions described in the embodiments of the present invention. Those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention to achieve the same technical effect; as long as the use needs are met, they are all within the protection scope of the present invention.

Claims

1. A suspended capacitive sensing chip, comprising an upper electrode (1) and a lower electrode (2), wherein a cavity (3) is located between the upper electrode (1) and the lower electrode (2), characterized in that, The cavity (3) contains gas (4), and supports (5) are provided on the lower plate (2). The cavity (3) is a sealed cavity; there are multiple supports (5), which are evenly distributed on the lower plate (2). The cross-section of the support (5) is in the shape of a U or a square with a hole in the middle. Multiple second grooves (9) are provided on the lower plate (2), and the raised parts between the second grooves (9) serve as supports (5). A dielectric layer (8) is provided at the upper end of the lower plate (2), and the support (5) is provided at the upper end of the dielectric layer (8). The dielectric layer (8) is made of silicon dioxide or silicon nitride. The support (5) is directly etched into shape from the dielectric layer (8), and the dielectric layer (8) and the support (5) are integrated; or the support (5) is formed on the dielectric layer (8). The upper plate (1) and the lower plate (2) are respectively connected to an external circuit through bonding pads and metal leads or bonding pads. The upper plate (1) is a pressure-sensing plate. When the upper plate (1) senses pressure, it deforms towards the lower plate (2), thereby changing the capacitance value between the upper plate (1) and the lower plate (2). At this time, it has the advantages of non-contact; as the pressure on the upper plate (1) increases, the upward tension of the gas (4) inside the cavity (3) on the upper plate (1) and the support (5) on the lower plate (2) work together to make the upper plate (1) float above the lower plate (2) without contacting the lower plate (2). At this time, it has the advantages of contact; when the pressure on the upper plate (.) decreases, the pressure of the gas (4) inside the cavity (3) forces the upper plate (1) to quickly reduce its deformation, thereby reducing the hysteresis characteristic; the inflow amount of the internal gas (4) is calculated based on the range, the volume of the cavity (3), the density and pressure of the gas (4). The gas (4) is nitrogen. The supports (5) on the lower plate (2) are either connected or not connected to each other; when the upper plate (1) contacts the support (5), the gas between the connected supports (5) is evenly distributed, and the pressure of the gas (4) throughout the cavity (3) is evenly distributed. When the pressure changes, the tension exerted by the gas (4) inside the cavity (3) on the upper plate (1) is uniform. The lower end of the lower plate (2) is a substrate (7). First grooves (6) are provided on the substrate (7), and the first grooves (6) and the lower plate (2) form a second cavity. The second cavity formed by the first grooves (6) and the lower plate (2) is connected to the outside through a pressure channel or the second cavity formed by the first grooves (6) and the lower plate (2) is a sealed cavity. The pressure channel (11) is provided on the substrate (7).

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