Capacitive MEMS tire pressure sensor with high precision and low power consumption and manufacturing method thereof

Abstract

The invention relates to the technical field of pressure sensors, and discloses a high-precision and low-power-consumption capacitive MEMS tire pressure sensor which comprises a silicon substrate serving as a bottom electrode of the sensor. The silicon thin film is used as a pressure sensing element and is combined with the silicon substrate through a silicon-silicon direct bonding process; the vacuum cavity is positioned between the silicon thin film and the silicon substrate and is used for detecting pressure change; the upper electrode is positioned above the silicon thin film and is used for forming a capacitor structure with the silicon substrate; the insulating layer is positioned between the upper electrode and the silicon thin film and is used for preventing ohmic contact; and the capacitance detection circuit is used for detecting capacitance change and outputting a pressure signal. The pressure sensor is particularly suitable for a low-power-consumption system, due to the fact that the measurement principle of the pressure sensor is energy-saving, compared with a resistance type pressure sensor which does not need direct current bias, the pressure sensor is remarkably improved in the aspects of precision, energy efficiency and noise reduction.

Description

Technical Field

[0001] The present invention relates to the technical field of pressure sensors, and in particular to a high-precision, low-power consumption capacitive MEMS tire pressure sensor and a manufacturing method thereof. Background Art

[0002] Tire pressure monitoring system (TPMS) is an integral part of the vehicle safety system, which can monitor tire pressure and temperature in real time to ensure driving safety. Accurate monitoring of tire pressure is essential for extending tire life, reducing suspension system wear, improving fuel economy and reducing CO 2 Traditional tire pressure sensors mostly use resistive or piezoresistive sensing technology, which has problems such as high power consumption, low accuracy and high cost.

[0003] With the development of MEMS technology, capacitive pressure sensors have gradually become the mainstream choice for TPMS due to their advantages of low power consumption, high precision and low cost. However, existing capacitive MEMS sensors still have room for improvement in manufacturing process, precision and power consumption. Especially for tire pressure monitoring, the sensor needs to work stably for a long time under harsh environmental conditions, and the power consumption must be extremely low to ensure battery life. Summary of the invention

[0004] The present invention provides a holographic stereoscopic picture synchronization method, device, equipment and storage medium, which are used to improve the accuracy of holographic stereoscopic picture synchronization.

[0005] A first aspect of the present invention provides a high-precision, low-power capacitive MEMS tire pressure sensor, comprising:

[0006] A silicon substrate, which serves as the bottom electrode of the sensor;

[0007] The silicon film, as the pressure sensing element, is bonded to the silicon substrate through a silicon-silicon direct bonding process;

[0008] A vacuum chamber, located between the silicon film and the silicon substrate, is used to detect pressure changes;

[0009] An upper electrode, located above the silicon film, and used to form a capacitor structure with the silicon substrate;

[0010] An insulating layer, located between the upper electrode and the silicon film, to prevent ohmic contact;

[0011] The capacitance detection circuit is used to detect capacitance changes and output pressure signals.

[0012] Furthermore, the thickness of the silicon film is 2 microns, and the height of the vacuum chamber is 0.2 microns.

[0013] Furthermore, the sensor is manufactured using a silicon-silicon direct bonding process, and the specific steps include:

[0014] Etching a vacuum chamber on a silicon substrate;

[0015] Bonding the silicon thin film to the silicon substrate through a low-temperature direct bonding process;

[0016] removing the excess silicon layer on the silicon film to form a thin silicon film;

[0017] preparing an upper electrode and an insulating layer on the silicon film;

[0018] A bottom electrode is prepared on a silicon substrate to form a capacitor structure.

[0019] Furthermore, the operating current of the sensor is at the nanoampere level, and the measurement accuracy is ±0.01 bar (1 kPa).

[0020] Furthermore, the sensor detects capacitance changes through a capacitance detection circuit and calculates tire pressure based on the capacitance changes.

[0021] In a second aspect, the present application provides a method for manufacturing a capacitive MEMS tire pressure sensor, comprising the following steps:

[0022] Etching a vacuum chamber on a silicon substrate;

[0023] Bonding the silicon thin film to the silicon substrate through a low-temperature direct bonding process;

[0024] removing the excess silicon layer on the silicon film to form a thin silicon film;

[0025] preparing an upper electrode and an insulating layer on the silicon film;

[0026] A bottom electrode is prepared on a silicon substrate to form a capacitor structure.

[0027] Furthermore, the low temperature direct bonding process comprises the following steps:

[0028] Clean the surface of silicon substrate and silicon film;

[0029] The cleaned surface is subjected to O2 plasma activation treatment;

[0030] pre-bonding the silicon film to the silicon substrate at room temperature;

[0031] High temperature annealing is performed at 1050°C in an inert gas environment to form covalent bonds.

[0032] Furthermore, the height of the vacuum chamber is 0.2 microns, and the thickness of the silicon film is 2 microns.

[0033] In the technical solution provided by the present invention, a high-precision, low-power capacitive MEMS tire pressure sensor is provided by optimizing the CMUT structural design and manufacturing process. The sensor is capable of achieving a measurement accuracy of ±0.01 bar (1kPa) at a nanoampere operating current and has a service life of up to 10 years, and is suitable for tire pressure monitoring systems (TPMS). Utilizing the latest advances in MEMS and wafer bonding technology, the solution adopts a pressure sensor based on capacitive detection. The design combines an array cavity structure to provide accurate and reliable tire pressure monitoring. The sensor stands out for its high measurement accuracy, strong stability, fast response time and low power consumption, all of which are packaged in a compact size with excellent environmental adaptability. The system has a theoretical accuracy of ±0.01 bar (1kPa) while achieving ultra-low power consumption. Capacitive sensors are particularly suitable for low-power systems because their measurement principle is energy-efficient and has significant improvements in accuracy, energy efficiency and noise reduction compared to resistive pressure sensors that do not require DC current bias. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 FIG. 4 is a schematic diagram of the structure of a capacitive MEMS tire pressure sensor in an embodiment of the present invention. DETAILED DESCRIPTION

[0035] Embodiments of the present invention provide a holographic stereoscopic picture synchronization method, device, equipment and storage medium for improving the accuracy of holographic stereoscopic picture synchronization.

[0036] The terms "first", "second", "third", "fourth", etc. (if any) in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments described herein can be implemented in an order other than that illustrated or described herein. In addition, the terms "including" or "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0037] For ease of understanding, the specific process of the embodiment of the present invention is described below. Figure 1 In a first aspect, a high-precision, low-power capacitive MEMS tire pressure sensor is provided, comprising:

[0038] A silicon substrate, which serves as the bottom electrode of the sensor;

[0039] The silicon film, as the pressure sensing element, is bonded to the silicon substrate through a silicon-silicon direct bonding process;

[0040] A vacuum chamber, located between the silicon film and the silicon substrate, is used to detect pressure changes;

[0041] An upper electrode, located above the silicon film, and used to form a capacitor structure with the silicon substrate;

[0042] An insulating layer, located between the upper electrode and the silicon film, to prevent ohmic contact;

[0043] The capacitance detection circuit is used to detect capacitance changes and output pressure signals.

[0044] Furthermore, the thickness of the silicon film is 2 microns, and the height of the vacuum chamber is 0.2 microns.

[0045] Furthermore, the sensor is manufactured using a silicon-silicon direct bonding process, and the specific steps include:

[0046] Etching a vacuum chamber on a silicon substrate;

[0047] Bonding the silicon thin film to the silicon substrate through a low-temperature direct bonding process;

[0048] removing the excess silicon layer on the silicon film to form a thin silicon film;

[0049] preparing an upper electrode and an insulating layer on the silicon film;

[0050] A bottom electrode is prepared on a silicon substrate to form a capacitor structure.

[0051] Furthermore, the operating current of the sensor is at the nanoampere level, and the measurement accuracy is ±0.01 bar (1 kPa).

[0052] Furthermore, the sensor detects capacitance changes through a capacitance detection circuit and calculates tire pressure based on the capacitance changes.

[0053] In a second aspect, the present application provides a method for manufacturing a capacitive MEMS tire pressure sensor, comprising the following steps:

[0054] Etching a vacuum chamber on a silicon substrate;

[0055] Bonding the silicon thin film to the silicon substrate through a low-temperature direct bonding process;

[0056] removing the excess silicon layer on the silicon film to form a thin silicon film;

[0057] preparing an upper electrode and an insulating layer on the silicon film;

[0058] A bottom electrode is prepared on a silicon substrate to form a capacitor structure.

[0059] Furthermore, the low temperature direct bonding process comprises the following steps:

[0060] Clean the surface of silicon substrate and silicon film;

[0061] The cleaned surface is subjected to O2 plasma activation treatment;

[0062] pre-bonding the silicon film to the silicon substrate at room temperature;

[0063] High temperature annealing is performed at 1050°C in an inert gas environment to form covalent bonds.

[0064] The design of CMUT devices is largely influenced by the choice of membrane shape, and common geometries include square, circular, and regular hexagonal. The anisotropy of silicon wafers in wet process technology usually leads to square membrane structures because this method usually produces square cavities. Although the regular hexagonal structure has a higher drawing ratio attraction, both square and hexagonal films may lead to reduced manufacturing yield. This reduction is due to uneven stress distribution during processing, which may affect device sensitivity. In particular, square membranes are prone to stress concentration at their sharp corners, which may cause membrane rupture and thus yield loss. In order to meet these challenges, circular membrane structures are proposed as a viable alternative. The optimal CMUT unit arranged from top to bottom in this application includes an upper electrode, an insulating layer to prevent ohmic contact, a core vibrating membrane, a cavity, a peripheral support for structure and fixation, another insulating layer, a supporting substrate plane, and a lower electrode. This design method aims to minimize stress concentration, thereby improving device performance and manufacturing yield.

[0065] The manufacturing of CMUT relies on key processing technologies. One technology is called the sacrificial layer release process, which is the cornerstone of the traditional CMUT manufacturing process. The key process in the production of CMUT in this application is wafer bonding technology, a method that has improved with the advancement of MEMS technology. The sacrificial layer release process is well suited for the initial stages of CMUT manufacturing, while wafer bonding technology provides a more advanced, cleaner and more controlled method to manufacture high-quality CMUT devices.

[0066] Traditional CMUT manufacturing relies on a sacrificial layer release method. Despite its widespread adoption, it has several limitations, including complex processes, inconsistent cavity size and distribution, and a high risk of contamination during production. Wafer bonding technology solves many of the problems associated with the sacrificial layer release method. Wafer bonding not only simplifies the manufacturing process, but also produces more uniformly sized cavities and reduces contamination, making it ideal for the production of large-area CMUT two-dimensional arrays. Therefore, wafer bonding can become the preferred method for the preparation of CMUT two-dimensional arrays.

[0067] Wafer bonding techniques can be divided into direct bonding, anodic bonding, and interlayer bonding, among which low-temperature direct bonding is considered to be the most suitable for CMUT 2D array manufacturing because no interlayer is allowed when forming the CMUT cavity. Bonding options without an interlayer usually require chemical or plasma activation, which may complicate the bonding process and hinder its progress. Therefore, the simplicity and reliability of the silicon-silicon direct bonding process make it the preferred method for assembling CMUT 2D arrays.

[0068] In our design, we implemented a low-temperature direct bonding process combined with micro-capacitor micro-nanotechnology. This approach significantly improved the yield and consistency of the micro-capacitor structure while reducing the manufacturing cost. For the CMUT pressure sensor assembly, silicon (Si) was selected as the material for the pressure sensing membrane, and silicon dioxide (SiO 2 ) as the isolation and insulation layer, and aluminum (Al) as the electrode material.

[0069] The manufacturing steps of the CMUT micro-capacitor pressure sensing structure are as follows: First, a suitable SOI (silicon on insulator) wafer is selected and SiO is etched out of the silicon. 2 (Silicon dioxide) cavity, using a low-temperature direct bonding process to form an SOI bonded silicon wafer, then remove the silicon layer and oxide layer of the SOI substrate to form a thin silicon film, oxidize the insulating layer; prepare the top metal electrode; etch the isolation trench, and remove the oxide layer on the back of the silicon. Finally, the bottom electrode is manufactured to form an ohmic contact to complete the device structure. This process takes advantage of the uniformity of the SOI device layer to ensure the consistency of the sensor vibration membrane structure.

[0070] The following are the key requirements for low-temperature direct bonding: Surface cleanliness: The wafer must be free of contamination for effective bonding; Surface roughness: The roughness of the hydrophobic wafer should be less than 0.25μm, and the roughness of the hydrophilic wafer should not exceed 0.5μm; Total thickness variation (TTV): Ideally about 2μm; Surface activation: Required to increase bonding efficiency. The bonding process has two stages: pre-bonding and high-temperature annealing. During the pre-bonding process, the wafers are aligned and weakly bonded. High-temperature annealing then forms covalent bonds, ensuring a strong and permanent connection. Low-temperature direct bonding is used to bond silicon wafers to SOI, and the steps are as follows: Cleaning: The silicon and SOI wafers are cleaned with RCA standard methods to remove dust and residues that may hinder bonding; Surface activation: The cleaned surface is treated with O2 plasma to improve bonding efficiency; Pre-bonding: At room temperature, the silicon and SOI wafers are aligned and pre-bonded in a wafer bonder; High-temperature annealing: The pre-bonded wafers are annealed in an inert gas at 1050°C for 20 hours to form a strong covalent bond between silicon and SOI. This process is critical to creating a stable and reliable bond between the silicon wafer and SOI, which is critical to the structural integrity of the final device.

[0071] The present invention provides a high-precision, low-power capacitive MEMS tire pressure sensor by optimizing the CMUT structural design and manufacturing process. The sensor is capable of achieving a measurement accuracy of ±0.01 bar (1kPa) at a nanoampere operating current and has a service life of up to 10 years, making it suitable for tire pressure monitoring systems (TPMS). Taking advantage of the latest advances in MEMS and wafer bonding technology, the scheme uses a pressure sensor based on capacitive detection. The design combines an array cavity structure to provide accurate and reliable tire pressure monitoring. The sensor stands out for its high measurement accuracy, strong stability, fast response time and low power consumption, all of which are packaged in a compact size with excellent environmental adaptability. The system has a theoretical accuracy of ±0.01 bar (1kPa) while achieving ultra-low power consumption. Capacitive sensors are particularly suitable for low-power systems because their measurement principle is energy-efficient and has significant improvements in accuracy, energy efficiency and noise reduction compared to resistive pressure sensors that do not require DC current bias.

[0072] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high-precision, low-power capacitive MEMS tire pressure sensor, characterized in that: include: A silicon substrate, which serves as the bottom electrode of the sensor; The silicon film, as the pressure sensing element, is bonded to the silicon substrate through a silicon-silicon direct bonding process; A vacuum chamber, located between the silicon film and the silicon substrate, is used to detect pressure changes; An upper electrode, located above the silicon film, and used to form a capacitor structure with the silicon substrate; An insulating layer, located between the upper electrode and the silicon film, to prevent ohmic contact; The capacitance detection circuit is used to detect capacitance changes and output pressure signals.

2. A high-precision, low-power capacitive MEMS tire pressure sensor according to claim 1, characterized in that: The thickness of the silicon film is 2 microns, and the height of the vacuum chamber is 0.2 microns.

3. The high-precision, low-power capacitive MEMS tire pressure sensor according to claim 1, characterized in that: The sensor is manufactured using a silicon-silicon direct bonding process, and the specific steps include: Etching a vacuum chamber on a silicon substrate; Bonding the silicon thin film to the silicon substrate through a low-temperature direct bonding process; removing the excess silicon layer on the silicon film to form a thin silicon film; preparing an upper electrode and an insulating layer on the silicon film; A bottom electrode is prepared on a silicon substrate to form a capacitor structure.

4. The capacitive MEMS tire pressure sensor according to claim 1, characterized in that: The operating current of the sensor is in the nanoampere level and the measurement accuracy is ±0.01 bar (1 kPa).

5. The capacitive MEMS tire pressure sensor according to claim 1, characterized in that: The sensor detects capacitance changes through a capacitance detection circuit and calculates tire pressure based on the capacitance changes.

6. A method for manufacturing a capacitive MEMS tire pressure sensor, characterized in that: The following steps are involved: Etching a vacuum chamber on a silicon substrate; Bonding the silicon thin film to the silicon substrate through a low-temperature direct bonding process; removing the excess silicon layer on the silicon film to form a thin silicon film; preparing an upper electrode and an insulating layer on the silicon film; A bottom electrode is prepared on a silicon substrate to form a capacitor structure.

7. The manufacturing method according to claim 6, characterized in that: The low temperature direct bonding process comprises the following steps: Clean the surface of silicon substrate and silicon film; After cleaning, 2 Plasma activation treatment; pre-bonding the silicon film to the silicon substrate at room temperature; High temperature annealing is performed at 1050°C in an inert gas environment to form covalent bonds.

8. The manufacturing method according to claim 6, characterized in that: The height of the vacuum chamber is 0.2 micrometers, and the thickness of the silicon film is 2 micrometers.

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