Improved high-precision piezoelectric sensor and preparation method thereof
By using a preferably undoped zinc oxide film and an aluminum or platinum electrode material to form a stable ohmic contact, the problems of poor temperature stability and hysteresis of traditional piezoelectric pressure sensors in high temperature environments are solved, and the pressure sensing effect with high precision and linear output is achieved.
Patent Information
- Application Number
- CN202311683244.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-09
- Publication Date
- 2025-06-10
AI Technical Summary
Traditional piezoelectric pressure sensors have poor temperature stability and hysteresis problems in high temperature environments, which limits their application scope, especially in petrochemicals, mining and metallurgy, new energy, transportation and aerospace, and the weapons industry.
The preferred undoped zinc oxide is used as the piezoelectric material, and its preparation process is controlled, so that the material texture is a c-axis texture, the oxygen vacancies concentration is reduced, and a piezoelectric active film arranged in a large range of electrical dipoles is obtained, and an ohmic contact is formed with electrode materials such as aluminum or platinum to ensure the linear sensing process.
It realizes piezoelectrically active devices without significant thermal degradation in high temperature environments, outputs linear signals, improves sensing accuracy and industrial process efficiency, and is suitable for large-scale applications of pressure sensing in a variety of high temperature environments.
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Figure CN120121187A_ABST
Abstract
Description
Technical Field
[0001] Piezoelectric sensors are an important branch in the field of sensors. Relying on the piezoelectric effect to achieve electromechanical coupling, they can realize the mutual conversion between mechanical signals such as pressure, displacement and electrical signals, and are basic tools for monitoring basic physical quantities. However, piezoelectric sensors generally have problems of poor temperature stability and hysteresis during use, which limits their application in high-temperature environments.
[0002] In the field of piezoelectric sensors, high-temperature piezoelectric pressure sensors are an important research direction and one of the high-precision and advanced technologies that countries around the world compete to master. Such sensors can withstand special working conditions, so they have broad application prospects in fields such as petrochemical, mining and metallurgy, new energy, transportation, aerospace and the ordnance industry.
[0003] Currently, commercially available piezoelectric pressure sensors mainly use lead zirconate titanate (PZT) ferroelectric ceramics as piezoelectric active materials. However, the Curie point of PZT ferroelectric ceramics is about 300 °C, and the conventional operating temperature is less than 200 °C, and the lead element in PZT will cause serious environmental pollution.
[0004] In addition, when ferroelectric materials perform pressure detection tasks, due to the existence of ferroelectric hysteresis and creep phenomena, their responses are not single-valued and linear. This hysteresis characteristic leads to the need to build models or develop calibration algorithms to correct it, and its accuracy depends to a large extent on factors such as the model, algorithm and the response of the material itself. In application scenarios that require fast and accurate responses, the errors caused by hysteresis cannot be ignored.
[0005] The level of accuracy is the main indicator for evaluating the performance of sensors. In industrial applications, accurate piezoelectric sensors can ensure accurate data for the monitoring and control of the production process, thereby improving production efficiency and reducing the scrap rate. In the medical field, precise measurements can help doctors make more accurate diagnoses and ensure that patients receive the correct treatment. In the aerospace field, accuracy is a key factor for flight safety, so the accuracy of sensors is crucial for the performance and safety of aircraft. Moreover, the manufacturing of current new electronic devices is becoming more miniaturized and integrated, which also requires piezoelectric materials to have better performance.
[0006] In fields with high requirements for the reliability and accuracy of high-temperature environments, the accuracy and high-temperature resistance characteristics of piezoelectric pressure sensors not only concern the performance of the sensors themselves, but also directly determine the efficiency, reliability and safety of key process procedures.
[0007] In addition, high-temperature resistant pressure sensors are devices widely used in petrochemical, mining and metallurgy, new energy, transportation, aerospace, and ordnance industries. Therefore, cost and quality control are particularly important. Compared with one-dimensional and zero-dimensional nanomaterials such as nanowires and quantum dots, thin films, as two-dimensional nanomaterials, have simple processes, more controllable preparation processes, and low requirements for preparation conditions. For example, methods such as magnetron sputtering can be used for large-scale production and application.
[0008] In view of this, it is necessary to propose a high-temperature resistant piezoelectric ultra-high precision pressure sensor and its large-scale preparation method to solve the problems of poor high-temperature stability and measurement accuracy of traditional piezoelectric pressure sensors and promote the upgrading of the intelligent manufacturing industry. Summary of the Invention
[0009] To solve the above problems, the present invention mainly provides a high-temperature resistant piezoelectric ultra-high precision pressure sensor and its preparation method.
[0010] The purpose of the present invention is to break through the problem that the operating temperature of traditional ferroelectric piezoelectric pressure sensors is limited by the Curie point, provide a piezoelectric active device without obvious thermal degradation, and adapt to large-scale pressure sensing applications in various high-temperature environments such as petrochemical, mining and metallurgy, new energy, transportation, aerospace, and ordnance industries.
[0011] Moreover, the purpose of the present invention is to solve the problems of non-linearity and low precision of the output signal of traditional ferroelectric piezoelectric pressure sensors, provide a sensor that linearly converts the input pressure signal into an output voltage signal, and improve the sensing accuracy and industrial process efficiency.
[0012] The main contents of the present invention mainly include the following technical solutions:
[0013] Preferably, undoped zinc oxide is used as the piezoelectric material, and the preparation method is adjusted to make the texture of the material a c-axis texture, and the oxygen vacancy concentration is reduced to a specific limit, obtaining a large-range electric dipole arrangement composed of positive and negative ion sublattices, and its spontaneous piezoelectric polarization is more stable than the multi-domain polarization of ferroelectric materials.
[0014] Regulate the preparation process of undoped zinc oxide thin film materials, including regulating the oxygen atmosphere during the preparation of the piezoelectric active thin film, reducing the oxygen vacancy defects in the piezoelectric active thin film, improving the film quality, and enhancing the high-temperature resistance and polarity stability of the material.
[0015] Regulate the magnetron sputtering power and heating temperature during the preparation of undoped zinc oxide thin film materials to improve the film quality and piezoelectric performance stability.
[0016] Preferably, the upper and lower electrode materials are selected to make the electrode materials form an ohmic contact with undoped zinc oxide, eliminate interference with the linear sensing process, and reduce the electrode resistivity to improve the sensing efficiency.
[0017] Adjust the preparation process of the upper and lower electrode materials to form a stable chemical interface between the electrode materials and undoped zinc oxide, and eliminate the problem that impurities diffuse into the piezoelectric active film under high-temperature environment, resulting in the failure of the linear piezoelectric output characteristics.
[0018] Adjust the thickness of the upper and lower electrode materials and the three-layer film of the sensor, and consider the thermal expansion coefficient matching between the electrode materials and undoped zinc oxide to prevent the failure of the three-layer film structure of the device under high-temperature environment, resulting in the breakdown of the sensor.
[0019] Select a preferably matched piezoelectric performance test method, use the input of triangular waveform pressure signal to replace the input of three-point and stepped pressure signals, detect and verify the linear output characteristics of the sensor, and complete the on-line test on a high-temperature stage to verify the high-temperature resistance characteristics of the sensor. Brief Description of the Drawings
[0020] Figure 1 It is a schematic structural diagram of the main body of the present invention - a high-temperature resistant and ultra-high precision piezoelectric pressure sensor, and the piezoelectric active material is high-quality undoped zinc oxide;
[0021] Figure 2 It is a schematic structural diagram of a ferroelectric type pressure sensor as a reference sample, and the piezoelectric active material is vanadium-doped zinc oxide;
[0022] Figure 3 It is the lattice orientation of the sensor thin film material reflected by the high-resolution X-ray diffraction pattern;
[0023] Figure 4 It is the triangular waveform pressure input used to test the characteristics of the sensor;
[0024] Figure 5 The high-temperature resistant and ultra-high precision piezoelectric pressure sensor under Figure 4 The triangular waveform voltage signal output under the shown input signal;
[0025] Figure 6 The ferroelectric type vanadium-doped zinc oxide pressure sensor under Figure 4 The non-linear sail-shaped voltage signal output under the shown input signal;
[0026] Figure 7 It is the input voltage-output voltage diagram of the high-temperature resistant and ultra-high precision piezoelectric pressure sensor;
[0027] Figure 8 It is the input voltage-output voltage diagram of the ferroelectric type vanadium-doped zinc oxide pressure sensor;
[0028] Figure 9 It is the triangular waveform voltage signal output by the high-temperature resistant and ultra-high precision piezoelectric pressure sensor measured at 450 °C under Figure 4 The shown input signal; Detailed Description of the Invention
[0029] The present invention will be described in detail below with reference to the accompanying drawings in the following specific embodiments.
[0030] Example 1
[0031] A magnetron sputtering method is used to prepare high-quality undoped zinc oxide thin films, as Figure 1 shown. An undoped zinc oxide target with a purity of more than 99.99% and a polished silicon wafer after ultrasonic cleaning are used as the substrate. High-purity oxygen with a purity of more than 99.999% and high-purity argon are used as the gas sources. The ultimate vacuum degree of the coating chamber of the magnetron sputtering equipment is below 5E-5 Pa. A mixed gas of oxygen and argon with appropriate pressure and ratio is introduced into the chamber. The substrate is heated to a high temperature above 400 degrees Celsius, the working pressure of the chamber is adjusted to 0.5 - 5 Pa, and a high-quality undoped zinc oxide thin film is deposited using an appropriate magnetron sputtering power. The thickness of the thin film is between 30 nanometers and 10 micrometers.
[0032] Using this preparation method, high-quality undoped zinc oxide thin films can be obtained. Its crystallographic texture is a fiber texture along the c-axis, and its high-resolution X-ray diffraction pattern is dominated by the ZnO(002) diffraction peak, and the intensity of the remaining diffraction peaks is lower than 10% of the intensity of the ZnO(002) diffraction peak, as Figure 3 shown. Its oxygen vacancy defect concentration is lower than 10 20 per cubic centimeter. It is composed of complete grains inside, the surface is uniform and dense, and its surface roughness Rq is lower than 5 nm.
[0033] Aluminum-doped zinc oxide thin films are used as the upper and lower electrode materials to form an ohmic contact. The lower electrode thin film layer is first deposited on the silicon substrate. After depositing the undoped zinc oxide thin film, the upper electrode thin film layer is deposited again. When preparing the aluminum-doped zinc oxide electrode thin film layer, argon with a purity of more than 99.999% is introduced into the chamber, and the substrate needs to be heated to a high temperature above 500 degrees Celsius. Other process conditions are selected as appropriate, and the thickness of the electrode thin film is between 100 nanometers and 10 micrometers. Except when introducing the working gas, the pressure in the coating chamber is below 5E-5 Pa, and the vacuum condition of the chamber is not damaged to complete the preparation of the three-layer thin film.
[0034] Using this preparation method, a thin film electrode with a resistivity below 1E-4 ohm-cm can be obtained, and the interface between the thin film electrode layer and the undoped zinc oxide piezoelectric active layer is clean and neat. I-V electrical tests show that it is an ohmic contact, and its chemical properties remain stable in a high-temperature environment without obvious diffusion phenomenon.
[0035] The high-quality undoped zinc oxide thin film obtained by the above preparation method and the aluminum-doped zinc oxide electrode layer form the main body of the present invention - a high-temperature and ultra-high-precision piezoelectric pressure sensor. This method has the characteristics of low cost and scalable production. Subsequently, only by cutting the large sensor or using the template method, the micro pressure sensor can be integrated into the chip. The innovation of this pressure sensor is reflected as follows:
[0036] Due to the use of a high-quality undoped zinc oxide thin film, it has a large-range electric dipole arrangement composed of positive and negative ion sublattices, has spontaneous piezoelectric polarization and is irreversible under an external electric field condition, and is more stable than ferroelectric materials. With the addition of an electrode material that forms a stable ohmic contact, this pressure sensor can output a linear signal and work stably at high temperatures.
[0037] First, when inputting Figure 4 the triangular waveform pressure signal shown, the voltage signal output by this pressure sensor is a similar triangular waveform, as Figure 5 shown, and the output signal corresponds one-to-one with the input signal. Plotting the input pressure and the output voltage, we can obtain Figure 7 It can be seen that the output voltage and the input pressure are linearly corresponding within a specific working range. The non-linear range at low pressure is caused by the test method.
[0038] Placing this pressure sensor on a high-temperature heating table with the surface temperature of the heating table being 150, 300, and 450 degrees Celsius, when inputting Figure 4 the triangular waveform pressure signal shown, this pressure sensor can still continuously output a voltage signal similar to a triangular waveform and has a linear working range similar to that at room temperature. The test results at 450 degrees Celsius are as Figure 9 shown. Due to the temperature affecting the accuracy of the test process, there is weak background noise in the test signal.
[0039] Example 2
[0040] This example is a reference example, and the obtained result is a ferroelectric pressure sensor, aiming to verify the serious degradation of the linear characteristics and high-temperature resistance characteristics of the sensor when using a non-high-quality undoped zinc oxide thin film.
[0041] Prepare a vanadium-doped zinc oxide thin film by magnetron sputtering method, as Figure 2As shown in the figure. A vanadium-doped zinc oxide target with a purity of more than 99.99% and a polished silicon wafer after ultrasonic cleaning are used as the substrate. High-purity argon with a purity of more than 99.999% is used as the gas source. The ultimate vacuum degree of the coating chamber of the magnetron sputtering equipment is below 5E-4 Pa. Argon with a suitable pressure is introduced into the chamber. The substrate is heated to a high temperature above 400 °C, the working pressure of the chamber is adjusted to 0.5 - 5 Pa, and a vanadium-doped zinc oxide thin film is deposited using a suitable magnetron sputtering power. The thickness of the thin film is between 30 nanometers and 10 micrometers. Under these process conditions, the vanadium-doped zinc oxide thin film has a fibrous texture along the c-axis, and its high-resolution X-ray diffraction pattern is dominated by the ZnO(002) diffraction peak, and the intensity of the remaining diffraction peaks is lower than 10% of the intensity of the ZnO(002) diffraction peak, as Figure 3 shown. The vanadium / zinc atomic ratio in the thin film is about 2.2%, and the defects are mainly impurity defects composed of vanadium atoms.
[0042] Using the same aluminum-doped zinc oxide electrode material and preparation process as in Example 1, a pressure sensor with a three-layer thin film structure is fabricated. I-V electrical tests show that it is an ohmic contact. The sensing characteristics and high-temperature characteristics of this pressure sensor are tested as follows:
[0043] When inputting the triangular waveform pressure signal shown in Figure 4 , the voltage signal output by this pressure sensor is sail-shaped, as Figure 6 shown. Plotting the input pressure and the output voltage, we can obtain Figure 8 , it can be seen that each input pressure corresponds to two output voltages, and the signal magnitude is related to the dynamic process of pressure loading and unloading. Considering the complexity of the loading and unloading processes in the actual process, each input pressure can correspond to multiple output voltages, making it difficult for this sensor to perform precise pressure sensing.
[0044] Placing this pressure sensor on a high-temperature heating stage with the surface temperature of the heating stage being 150 °C, when inputting the triangular waveform pressure signal shown in Figure 4 , the sail-shaped signal output by this pressure sensor undergoes obvious thermal degradation, and the noise amplitude exceeds the effective signal amplitude. Raising the surface temperature of the heating stage to 300 °C, this pressure sensor can only output a background noise signal, and its pressure detection characteristics disappear.
[0045] Comparing with Example 1, it can be seen that the ferroelectric pressure sensor based on vanadium-doped zinc oxide cannot perform precise detection of pressure signals at room temperature; and there is an obvious thermal degradation phenomenon at high temperatures, which cannot meet the detection requirements in high-temperature environments.
[0046] Example 3
[0047] This embodiment aims to prove that the selection of electrode materials in the present invention is relatively diverse, and the following prerequisites need to be met when making the selection: 1. Ensure that the undoped zinc oxide thin film has high quality, including fiber texture along the c-axis, the oxygen vacancy defect concentration is lower than 10 20 per cubic centimeter, the surface is uniform and dense, and the surface roughness Rq is lower than 5 nm; 2. Form a clean and flat interface with the undoped zinc oxide thin film, and show ohmic contact electrically; 3. There is no thermal failure phenomenon caused by atomic diffusion. This embodiment uses a platinum electrode.
[0048] The same undoped zinc oxide thin film and preparation process as in Example 1 are used.
[0049] Platinum thin film is used as the upper and lower electrode materials to form ohmic contact. The lower electrode thin film layer is first deposited on the silicon substrate. After depositing the undoped zinc oxide thin film, the upper electrode thin film layer is deposited again. When preparing the platinum electrode thin film layer, argon with a purity of more than 99.999% is introduced into the cavity, and the substrate can be selectively heated to a high temperature of about 300 degrees Celsius. Other process conditions are selected as appropriate, and the thickness of the electrode thin film is between 100 nanometers and 10 micrometers. Except when introducing the working gas, the pressure in the coating cavity is below 5E-5 Pa, and the vacuum condition of the cavity is not damaged, and the preparation of the three-layer thin film is completed.
[0050] Under these process conditions, the resistivity of the obtained thin film electrode is below 1E-6 ohm-cm, and the interface between the thin film electrode layer and the undoped zinc oxide piezoelectric active layer is clean and neat. I-V electrical tests show that it is ohmic contact, and its chemical properties remain stable in a high-temperature environment without obvious diffusion phenomenon.
[0051] A high-temperature and ultra-high-precision piezoelectric pressure sensor can be obtained by using the above method.
[0052] The described embodiments are only a part of the embodiments of the invention, not all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention without creative efforts shall fall within the protection scope of the present invention.
Claims
1. A high-temperature resistant piezoelectric ultra-high precision pressure sensor and its preparation method, Characterized in that, When the sensor detects pressure, a linearly corresponding voltage signal is generated and remains stable in a high-temperature environment.
2. A high-temperature resistant piezoelectric ultra-high precision pressure sensor and its preparation method, Characterized in that, The sensor includes an upper electrode layer / piezoelectric active material layer / lower electrode layer / substrate, and the three thin film materials are sequentially prepared on the substrate, where: The substrate is used to support the device and serve as a chip integration matrix, generally a silicon wafer; The lower electrode layer is mainly used to lead out the sensor voltage signal and serve as a buffer layer for the preparation of the piezoelectric active material layer; The piezoelectric active material layer is mainly used to convert the pressure signal into a voltage signal; The upper electrode layer is mainly used to lead out the sensor voltage signal and serve as a protective layer for the piezoelectric active material.
3. The pressure sensor and its preparation method according to claim 1, Characterized by, Undoped zinc oxide (ZnO) is used as the piezoelectric active material, and the preparation method is adjusted to obtain high-quality materials and interfaces, realizing the linear correspondence between the output voltage signal and the input pressure signal. Compared with materials such as lead titanate piezoelectric ceramics (PZT) and bismuth titanate (BT), it has the characteristics of no hysteresis, no creep, low cost and no pollution.
4. The pressure sensor preparation method according to claim 1, Characterized by, The upper and lower electrode materials used can form an ohmic contact with undoped zinc oxide, including but not limited to doped zinc oxide and noble metal composite materials, such as aluminum-doped zinc oxide (AZO), indium-gallium-doped zinc oxide (IGZO), platinum (Pt), gold (Au), chromium-gold composite materials (Cr / Au), etc.
5. The pressure sensor and its preparation method according to claim 1, Characterized by, Undoped zinc oxide material is used, the upper and lower electrode materials are preferably selected, and the preparation process of the materials is adjusted to obtain a stable material structure and interface structure at high temperatures, meeting the pressure sensing requirements at 450 degrees Celsius.
6. The pressure sensor and its preparation method according to claim 3, Characterized by, The preparation process is adjusted to make the undoped zinc oxide material have a lattice orientation along (002) (also marked as (0002)), and the material structure includes but not limited to single crystal texture and fiber texture.
7. The pressure sensor preparation method according to claim 3, Characterized by, The undoped zinc oxide material is prepared using a specific atmosphere, including but not limited to oxygen and argon with a partial pressure of 0.1 - 10 Pa, such that the oxygen vacancy concentration of the undoped zinc oxide is lower than 10 20 per cubic centimeter.
8. The pressure sensor according to claim 1, Characterized by, The sensor structure is a three-layer film structure of upper electrode layer / ZnO / lower electrode layer. Compared with two-dimensional nanowires and zero-dimensional quantum dots with poor repeatability, the quality control of the three-layer thin film structure is simple and suitable for large-scale low-cost production.
9. The three-layer film sensor structure according to claim 8, Characterized by, The selected materials and the preparation method of the device structure are adapted to low-cost, large-scale industrial production methods, including but not limited to magnetron sputtering coating, sol-gel coating, etc.
10. The pressure sensor according to claim 1, Characterized by, The sensor can output a voltage signal in a high-temperature environment from room temperature to 450 °C.
11. The pressure sensor according to claim 1, Characterized by, The output voltage of the sensor and the input pressure maintain a one-to-one correspondence relationship in the room temperature environment to the high temperature environment of 450°C.
12. The pressure sensor according to claim 1, characterized in that, in the room temperature environment to the high temperature environment of 450°C, the linearity between the sensor output signal and the input signal is less than or equal to 23.3%.
13. The pressure sensor according to claim 1, characterized in that, the detection sensitivity of the sensor is greater than or equal to 1.68 mV / kPa.