Capacitive MEMS tire pressure sensor with high precision and low power consumption
By optimizing the CMUT structure design and manufacturing process of the capacitive MEMS tire pressure sensor, and adopting silicon-silicon direct bonding process and wafer bonding technology, the shortcomings of traditional sensors in terms of accuracy and power consumption are solved, and high-precision, low-power tire pressure monitoring effect is achieved.
Patent Information
- Application Number
- CN202520199754.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-08
- Publication Date
- 2026-02-13
- Estimated Expiration
- 2035-02-08
AI Technical Summary
Existing tire pressure sensors are inadequate in terms of accuracy and power consumption, especially when working in harsh environments for extended periods. Traditional resistive or piezoresistive sensors have high power consumption and low accuracy, which cannot meet the needs of tire pressure monitoring.
A high-precision, low-power capacitive MEMS tire pressure sensor manufactured using silicon-to-silicon direct bonding technology includes a silicon substrate, a silicon thin film, a vacuum cavity, an upper electrode, and an insulating layer. It detects capacitance changes through a capacitance detection circuit and optimizes the manufacturing process using wafer bonding technology to form a circular thin film structure to reduce stress concentration.
It achieves high measurement accuracy of ±0.01 bar (1 kPa) at nanoampere operating current, has a 10-year service life and low power consumption, is suitable for tire pressure monitoring systems, provides accurate and reliable tire pressure monitoring, and reduces noise and energy consumption.
Smart Images
Figure CN223910379U_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The utility model relates to pressure sensor technical field especially relates to a high accuracy, low power consumption's capacitive MEMS tire pressure sensor. BACKGROUND
[0002] Tire pressure monitoring system (TPMS) is an indispensable part of automobile safety system, can monitor the pressure and temperature of tire in real time, ensure driving safety. The accurate monitoring of tire pressure has important significance for prolonging tire life, reducing suspension system wear, improving fuel economy and reducing CO2 emissions. The traditional tire pressure sensor adopts resistance or piezoresistive sensing technology, and has the problems of high power consumption, low precision and high cost.
[0003] With the development of MEMS technology, capacitive pressure sensors gradually become the mainstream choice of TPMS due to their low power consumption, high precision and low cost. However, the 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 in harsh environmental conditions, and the power consumption must be extremely low to ensure the battery life. SUMMARY
[0004] The utility model provides a kind of holographic stereogram synchronization method, device, equipment and storage medium, for improving the accuracy of holographic stereogram synchronization.
[0005] The utility model provides a kind of high accuracy, low power consumption's capacitive MEMS tire pressure sensor in the first aspect, including:
[0006] Silicon substrate, as the bottom electrode of sensor;
[0007] Silicon film, as pressure sensing element, is combined with silicon substrate by silicon-silicon direct bonding process;
[0008] Vacuum cavity, located between silicon film and silicon substrate, for detecting pressure change;
[0009] Upper electrode, located above silicon film, for forming capacitive structure with silicon substrate;
[0010] Insulating layer, located between upper electrode and silicon film, prevents ohmic contact;
[0011] Capacitance detection circuit, for detecting capacitance change and outputting pressure signal.
[0012] Further, the thickness of the silicon film is 2 microns, and the height of the vacuum cavity is 0.2 microns.
[0013] Further, the sensor is manufactured by silicon-silicon direct bonding process, and the specific steps include:
[0014] etching a vacuum cavity on the silicon substrate;
[0015] bonding the silicon thin film to the silicon substrate by a low-temperature direct bonding process;
[0016] removing the excess silicon layer above the silicon thin film to form a thin silicon film;
[0017] preparing an upper electrode and an insulating layer on the silicon thin film;
[0018] preparing a bottom electrode on the silicon substrate to form a capacitor structure.
[0019] Further, the working current of the sensor is in nanoscale, and the measurement accuracy is ±0.01 bar (1 kPa).
[0020] Further, the sensor detects the capacitance change through a capacitance detection circuit, and calculates the tire pressure according to the capacitance change.
[0021] In a second aspect, the application provides a manufacturing method of a capacitive MEMS tire pressure sensor, comprising the following steps:
[0022] etching a vacuum cavity on the silicon substrate;
[0023] bonding the silicon thin film to the silicon substrate by a low-temperature direct bonding process;
[0024] removing the excess silicon layer above the silicon thin film to form a thin silicon film;
[0025] preparing an upper electrode and an insulating layer on the silicon thin film;
[0026] preparing a bottom electrode on the silicon substrate to form a capacitor structure.
[0027] Further, the low-temperature direct bonding process comprises the following steps:
[0028] cleaning the surfaces of the silicon substrate and the silicon thin film;
[0029] performing O2 plasma activation treatment on the cleaned surfaces;
[0030] pre-bonding the silicon thin film to the silicon substrate at room temperature;
[0031] performing high-temperature annealing in an inert gas environment at 1050°C to form covalent bonds.
[0032] Further, the height of the vacuum cavity is 0.2 microns, and the thickness of the silicon thin film is 2 microns.
[0033] The technical scheme provided by the utility model discloses a high-precision, low-power capacitive MEMS tire pressure sensor through optimizing CMUT structure design and manufacturing process. The sensor can realize the measurement accuracy of ±0.01 bar (1 kPa) under the working current of nano ampere level, has the service life of 10 years, and is suitable for a tire pressure monitoring system (TPMS). The capacitive pressure sensor based on the latest progress of MEMS and wafer bonding technology is adopted. The design combines the array cavity structure and provides accurate and reliable tire pressure monitoring. The sensor is outstanding in high measurement accuracy, strong stability, fast response time and low power consumption, all of which are packaged in a compact size and have excellent environmental adaptability. The theoretical accuracy of the system is ±0.01 bar (1 kPa), and ultra-low power consumption is realized. The capacitive sensor is particularly suitable for low-power systems because its measurement principle is energy-saving, and compared with a resistance pressure sensor without direct current current bias, there is significant improvement in accuracy, energy efficiency and noise reduction. BRIEF DESCRIPTION OF DRAWINGS
[0034] Figure 1 The utility model discloses a capacitive MEMS tire pressure sensor structure schematic diagram in the embodiment. DETAILED DESCRIPTION
[0035] The utility model embodiment provides a holographic stereogram synchronization method, device and equipment and storage medium for improving the accuracy of holographic stereogram synchronization.
[0036] The terms "first", "second", "third", "fourth" and the like in the description and claims of the utility model and the above drawings (if any) are used to distinguish similar objects, and do not have to be used to describe a particular order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances, so that the embodiments described herein can be implemented in an order other than that illustrated or described herein. In addition, the term "includes" or "has" and any variation thereof is intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not have to be limited to the clearly listed steps or units, but can include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.
[0037] For the convenience of understanding, the specific process of the utility model embodiment is described below. Please refer to Figure 1 , the first aspect, the first aspect provides a kind of high-precision, low-power capacitive MEMS tire pressure sensor, comprising:
[0038] Silicon substrate, as the bottom electrode of sensor;
[0039] A silicon thin film, as a pressure sensing element, is combined with a silicon substrate through a silicon-silicon direct bonding process;
[0040] A vacuum cavity is located between the silicon thin film and the silicon substrate for detecting pressure changes;
[0041] An upper electrode is located above the silicon thin film for forming a capacitor structure with the silicon substrate;
[0042] An insulating layer is located between the upper electrode and the silicon thin film to prevent ohmic contact;
[0043] A capacitance detection circuit is used to detect capacitance changes and output pressure signals.
[0044] Further, the thickness of the silicon thin film is 2 microns, and the height of the vacuum cavity is 0.2 microns.
[0045] Further, the sensor is manufactured using a silicon-silicon direct bonding process, and the specific steps include:
[0046] Etching a vacuum cavity on a silicon substrate;
[0047] Combining the silicon thin film with the silicon substrate through a low-temperature direct bonding process;
[0048] Removing the excess silicon layer above the silicon thin film to form a thin silicon film;
[0049] Preparing an upper electrode and an insulating layer on the silicon thin film;
[0050] Preparing a bottom electrode on the silicon substrate to form a capacitor structure.
[0051] Further, the working current of the sensor is in the order of nanoamperes, and the measurement accuracy is ±0.01 bar (1 kPa).
[0052] Further, the sensor detects capacitance changes through a capacitance detection circuit and calculates the tire pressure according to the capacitance changes.
[0053] In a second aspect, the application provides a manufacturing method for a capacitive MEMS tire pressure sensor, including the following steps:
[0054] Etching a vacuum cavity on a silicon substrate;
[0055] Combining the silicon thin film with the silicon substrate through a low-temperature direct bonding process;
[0056] Removing the excess silicon layer above the silicon thin film to form a thin silicon film;
[0057] Preparing an upper electrode and an insulating layer on the silicon thin film;
[0058] Preparing a bottom electrode on the silicon substrate to form a capacitor structure.
[0059] Further, the low temperature direct bonding process comprises the following steps:
[0060] cleaning the silicon substrate and the silicon thin film surface;
[0061] O2 plasma activation treatment on the cleaned surface;
[0062] pre-bonding the silicon thin film and the silicon substrate at room temperature;
[0063] high temperature annealing in inert gas environment at 1050 °C to form covalent bonds.
[0064] The design of CMUT devices is greatly influenced by the choice of membrane shape, with common geometries including square, circular, and hexagonal. Anisotropy in wet processing techniques often results in square membrane structures, as this method typically produces square cavities. Although hexagonal structures have a higher appeal for drawing ratios, both square and hexagonal thin films can result in reduced manufacturing yield. This reduction is due to uneven stress distribution during processing, which can affect device sensitivity. Square membranes, in particular, are prone to stress concentration at their sharp corners, which can lead to membrane rupture and thus yield loss. To address these challenges, circular thin film structures are proposed as a viable alternative. The top-down arrangement of the optimal CMUT cell of the present 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 support substrate plane, and a lower electrode. This design approach aims to minimize stress concentration, thereby improving device performance and manufacturing yield.
[0065] The fabrication of CMUTs relies on key processing techniques. One technique, known as the sacrificial layer release process, is the cornerstone of traditional CMUT fabrication processes. The key process in the production of CMUTs in the present application is wafer bonding technology, a method that has been improved with the advancement of MEMS technology. The sacrificial layer release process is well-suited for the initial stages of CMUT fabrication, while wafer bonding technology offers a more advanced, cleaner, and more controlled method for producing high-quality CMUT devices.
[0066] Traditional CMUT fabrication relies on the sacrificial layer release method. Despite its widespread adoption, it has several limitations, including process complexity, inconsistent cavity size and distribution, and high risk of contamination during production. Wafer bonding technology addresses many of the issues associated with the sacrificial layer release method. Wafer bonding not only simplifies the manufacturing process but also produces more uniformly sized cavities, reducing contamination, making it an ideal choice for the production of large-area CMUT two-dimensional arrays. Therefore, wafer bonding can become the method of choice for the preparation of CMUT two-dimensional arrays.
[0067] Wafer bonding techniques can be divided into direct bonding, anodic bonding, and intermediate layer bonding, among which low-temperature direct bonding is considered the most suitable for CMUT two-dimensional array manufacturing because it does not allow for an intermediate layer when forming the CMUT cavity. Bonding options without an intermediate layer often require chemical or plasma activation, which can 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 two-dimensional arrays.
[0068] In our design, we implemented a low-temperature direct bonding process combined with microcapacitor micro-nanotechnology. This approach significantly improves the yield and consistency of the microcapacitor structure while reducing manufacturing costs. For CMUT pressure sensor assembly, silicon (Si) was chosen as the material for the pressure sensing membrane, silicon dioxide (SiO2) as the isolation and insulation layer, and aluminum (Al) as the electrode material.
[0069] The manufacturing steps of the CMUT microcapacitor pressure sensor structure are as follows: First, select a suitable SOI (Silicon on Insulator) wafer and etch SiO2 (Silicon Dioxide) cavities in the silicon. Use a low-temperature direct bonding process to form an SOI bonded silicon wafer. Next, remove the silicon layer and oxide layer of the SOI substrate to form a thin silicon membrane and an oxide insulation layer. Prepare the top metal electrode. Etch the isolation trench and remove the oxide layer on the back of the silicon. Finally, manufacture the bottom electrode to form an ohmic contact and complete the device structure. This process takes advantage of the uniformity of the SOI device layer to ensure the consistency of the sensor vibrating membrane structure.
[0070] The following are the key requirements for low-temperature direct bonding: Surface cleanliness: The wafers must be free of contamination for effective bonding; Surface roughness: The roughness of hydrophobic wafers should be less than 0.25 µm, and the roughness of hydrophilic wafers should not exceed 0.5 µm; Total thickness variation (TTV): Ideally about 2 µm; Surface activation: Requires to improve the bonding success rate. The bonding process has two stages: pre-bonding and high-temperature annealing. During pre-bonding, 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 with SOI, with the following steps: Cleaning: Clean the silicon and SOI wafers with the RCA standard method to remove dust and residues that may hinder bonding; Surface activation: Treat the cleaned surface with O2 plasma to improve the bonding success rate; Pre-bonding: At room temperature, the silicon and SOI wafers are aligned and pre-bonded in a wafer bonder; High-temperature annealing: Pre-bonded wafers are annealed in an inert gas at 1050°C for 20 hours to form strong covalent bonds between silicon and SOI. This process is crucial for creating a stable and reliable bond between the silicon wafer and the SOI, which is essential for the structural integrity of the final device.
[0071] The utility model discloses a kind of high-precision, low-power capacitive MEMS tire pressure sensors by optimizing CMUT structure design and manufacturing process. The sensor can achieve the measurement accuracy of ±0.01 bar (1 kPa) under nano-ampere level working current, and has a service life of up to 10 years, suitable for tire pressure monitoring system (TPMS). With the latest progress of MEMS and wafer bonding technology, the scheme adopts a pressure sensor based on capacitance detection. The design combines array cavity structure, providing accurate and reliable tire pressure monitoring. The sensor stands out with 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 theoretical accuracy of the system is ±0.01 bar (1 kPa), while achieving ultra-low power consumption. Capacitive sensors are particularly suitable for low-power systems because their measurement principle is energy-efficient, and compared to resistance pressure sensors that do not require direct current bias, there are significant improvements in accuracy, energy efficiency and noise reduction.
[0072] The above-described and above-embodied examples are only used to illustrate the technical solutions of the present application, but not to limit the same; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions recorded in the foregoing examples can still be modified, or some technical features thereof can be replaced equivalently; and such modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present application.
Claims
1. A high-precision, low-power consumption capacitive MEMS tire pressure sensor, characterized by, The application relates to a sensor for detecting tire pressure, comprising: a silicon substrate as a bottom electrode of the sensor; a silicon film as a pressure sensing element, which is combined with the silicon substrate through a silicon-silicon direct bonding process; a vacuum cavity located between the silicon film and the silicon substrate, which is used for detecting pressure changes; an upper electrode located above the silicon film, which is used for forming a capacitor structure with the silicon substrate; an insulating layer located between the upper electrode and the silicon film, which prevents ohmic contact; and a capacitance detection circuit, which is used for detecting capacitance changes and outputting a pressure signal. The thickness of the silicon film is 2 microns, and the height of the vacuum cavity is 0.2 microns. The working current of the sensor is in the order of nanoamperes, and the measurement accuracy is + / -0.01 bar. The sensor detects capacitance changes through the capacitance detection circuit, and calculates the tire pressure according to the capacitance changes. 2. The high-precision, low-power consumption capacitive MEMS tire pressure sensor according to claim 1, characterized in that, 3. The capacitive MEMS tire pressure sensor of claim 1, wherein, 4. The capacitive MEMS tire pressure sensor of claim 1, wherein,