Silicon carbide-based strain temperature micro-nano sensor and preparation and detection method thereof

Abstract

A silicon carbide-based strain-temperature micro / nano sensor is provided, comprising a silicon carbide substrate, on which an N-type buffer layer and a P-type functional layer are grown to form a strain-sensitive substrate; the P-type functional layer is precisely processed using NLD etching, and the remaining area forms four interconnected piezoresistive blocks; in a designated area on the four piezoresistive blocks, Ti thin films, Ni thin films, and Pt thin films are sequentially sputtered using magnetron sputtering to form four metal electrodes, and the four piezoresistive blocks form a four-resistance bridge to achieve high-sensitivity strain measurement, thereby forming a strain sensor; on the back side of the silicon carbide substrate, a strip-shaped, tortuous, hollowed-out area is defined, and an alumina barrier layer and a platinum Pt thin film layer are sequentially sputtered and deposited using magnetron sputtering to form a strip-shaped, tortuous, tortuous temperature sensing strip, the temperature sensing strip including two ends for external electrical connection; the present invention also provides its preparation method and detection method.

Description

Technical Field

[0001] This invention belongs to the field of microelectromechanical systems (MEMS) strain sensor manufacturing technology, specifically relating to a high-temperature resistant, high-precision silicon carbide-based strain-temperature dual-parameter micro / nano sensor and its fabrication method. More specifically, it is a high-temperature resistant, high-precision strain-temperature dual-parameter micro / nano sensor based on a silicon carbide substrate, along with its fabrication and detection methods, suitable for monitoring multimodal physical quantities under extreme environments. Background Technology

[0002] With the rapid development of industrial automation and intelligent manufacturing, the demand for sensors capable of reliable operation in extreme environments is increasing, especially for monitoring tasks under harsh conditions such as high temperature and high pressure. In critical fields such as nuclear reactors, aircraft engines, and semiconductor manufacturing, real-time monitoring of internal strain and temperature is crucial for structural optimization, fault diagnosis, and safe operation. However, traditional sensor technologies face significant challenges: silicon-based pressure sensors experience a sharp drop in sensitivity at high temperatures, have limited detection temperature ranges, and are complex to manufacture; metal-based sensors have short lifespans in corrosive environments, while semiconductor-based sensors, although corrosion-resistant, lack sufficient high-temperature performance to meet the requirements for long-term stable operation. Furthermore, existing sensors often use single-parameter detection, failing to simultaneously capture strain and temperature changes, resulting in poor data correlation under complex conditions, affecting monitoring accuracy and system reliability. Silicon carbide (SiC) materials, due to their high melting point, high thermal conductivity, radiation resistance, and corrosion resistance, have become an ideal choice for high-temperature sensors. However, existing SiC sensor technology still has limitations; for example, the vertical structural design makes it difficult to reduce size, resulting in low integration, and changes in bulk resistance at high temperatures affect linearity, restricting its application in compact devices. Therefore, developing a highly integrated, high-temperature resistant, and dual-parameter SiC-based sensor capable of simultaneously measuring strain and temperature is of great practical significance for improving the monitoring capabilities of extreme environments. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a high-temperature resistant, high-precision strain-temperature dual-parameter micro / nano sensor based on a silicon carbide substrate, as well as its fabrication and detection methods.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention for the high-temperature resistant, high-precision strain-temperature dual-parameter micro / nano sensor based on a silicon carbide substrate is as follows:

[0005] A silicon carbide-based strain-temperature micro / nano sensor is a high-temperature resistant, high-precision dual-parameter strain-temperature sensor based on a silicon carbide substrate. It includes a silicon carbide substrate and is characterized by the sequential upward growth of an N-type buffer layer and a P-type functional layer on the front side of the silicon carbide substrate, completely covering the front side to form a strain-sensitive substrate. The P-type functional layer is precisely fabricated using an NLD etching process, with the remaining area forming four interconnected piezoresistive blocks. This structure maximizes the detection sensitivity. In designated areas on the four piezoresistive blocks, Ti thin films and N-type buffer layers are sequentially sputtered using a magnetron sputtering process. Four metal electrodes, consisting of an i-thin film and a Pt thin film, are formed. High-temperature annealing achieves ohmic contact on the upper surface, and a silver paste sintering process is used to weld leads for external electrical connection. These four piezoresistive blocks form a four-resistance bridge, enabling high-sensitivity strain measurement by detecting voltage changes, thus forming a strain sensor on the front side of the silicon carbide substrate. On the back side of the silicon carbide substrate, a strip-shaped, zigzag-like hollow area is centrally located. An alumina barrier layer and a platinum (Pt) thin film layer are sequentially sputtered and deposited using magnetron sputtering to form a strip-shaped, zigzag-like temperature sensing strip. This temperature sensing strip includes two ends for external electrical connection.

[0006] The following are further solutions for the chip and its heat dissipation structure of the present invention:

[0007] Each piezoresistive block includes a large rectangle extending from one of the four corners of the N-type buffer layer toward the center, a small rectangle extending toward the center integrally connected to the large rectangle, and an interconnecting area extending from the small rectangle to the two adjacent piezoresistive blocks in a meandering manner; there are four large rectangles, four small rectangles, and four interconnecting areas, wherein the large rectangles and four small rectangles are independently owned by each other, and the interconnecting areas are shared by every two adjacent piezoresistive blocks.

[0008] The designated areas on the four piezoresistive blocks are rectangular, forming four rectangular metal electrodes with areas smaller than the large rectangles of the piezoresistive blocks.

[0009] The two ends are arranged in a spaced-together configuration in the same orientation.

[0010] A 4-inch double-sided polished and standard-cleaned 4H-SiC single crystal was selected as the material for sensor fabrication. The 4H-SiC single crystal was 350±25μm thick and had a crystal orientation of <11-20> offset by 4°. It was placed in a low-pressure hot-wall chemical vapor deposition system with H2 as the carrier gas.First, the reaction chamber was evacuated, then the temperature was raised to 1600℃ and the pressure was adjusted to 100 mbar. Next, SiH4, C3H8, and N2 were introduced as reaction gases, with N2 serving as the nitrogen dopant source, to epitaxially grow an N-type buffer layer on a silicon carbide substrate. After the N-type buffer layer was grown, the reaction chamber temperature was kept constant at 1600℃ and the pressure at 100 mbar, and the epitaxial gases were switched to SiH4, C3H8, and (CH3)3Al, with (CH3)3Al serving as the aluminum dopant source, to continue epitaxially growing a highly doped P-type epitaxial layer on the N-type buffer layer (3). During the growth process, the flow rate of each gas and the growth time were precisely controlled to finally obtain the desired 4H-SiC epitaxial layer. The substrate consists of a 2µm thick N-type buffer layer and a 3µm thick P-type functional layer, forming a strain-sensitive substrate. The top layer employs a novel NLD etching process: magnetic neutral line plasma dry etching, achieving radial density uniformity through magnetic field confinement. The main RF power is 800-1200W, the bias RF power is 50-150W, the chamber pressure is 10mTorr, and the ion bombardment energy is controlled. In an SF6 and O2 atmosphere, 4H-SiC is etched using plasma dry etching. The piezoresistive block distribution structure is precisely fabricated using a Ni metal mask. Photolithography is performed using a 4H-SiC metal pad mask after spin-coating a negative photoresist. Magnetron sputtering is then performed sequentially using titanium, nickel, and platinum targets under vacuum. At a pressure of 1×10⁻⁵ Pa and a power of 100W, Ti, Ni, and Pt metal thin films with thicknesses of 50nm, 50nm, and 200nm were sputtered, respectively. The Ti, Ni, and Pt metal thin films were then stripped with acetone to obtain a substrate with metal pads. Activated ohmic contacts were obtained through rapid RTP thermal annealing at 1000℃ for three minutes. Leads were then soldered using silver paste sintering technology, enabling the silicon carbide-based strain temperature micro / nano sensor to achieve high-sensitivity strain measurement by detecting voltage changes. On the back side of the silicon carbide substrate, a layer of aluminum oxide and a layer of platinum were sputtered in the cutout area using a metal hard mask. An RF power supply was first used at a sputtering power of 100W and a working pressure of 1... Under conditions of 0.3 Pa and a substrate temperature of 26°C, a 200 nm thick layer of alumina (Al2O3) was sputtered as an insulating layer. Then, by switching to DC power, sputtering power of 100 W, working pressure of 1.3 Pa, and substrate temperature of 26°C, a 500 nm thick platinum (Pt) layer was sputtered as a temperature sensing strip. The alumina layer effectively prevents platinum atoms from diffusing into the silicon carbide substrate. At the same time, its excellent high-temperature adhesion stability avoids the problem of traditional adhesive layers easily falling off under high-temperature conditions. In addition, the alumina insulating layer effectively isolates the back temperature sensing strip from the front strain sensor, avoiding signal interference. The platinum (Pt) temperature sensing strip utilizes the characteristic of its resistance changing with temperature to achieve high-precision temperature measurement.

[0011] A nonlinear temperature-compensated strain-temperature acquisition system is employed. This system converts the output voltage at different temperatures into an output voltage at a fixed room temperature. To avoid the influence of different temperatures on the voltage, its value is corrected at a standard temperature. Finally, using a temperature drift calibration coefficient, the compensated voltage is converted into an equivalent corrected strain value. Simultaneously, within a high strain range, all output voltages of the sensor are easily distinguishable, achieving high voltage resolution. The error between compensated strains is corrected for temperature drift, successfully achieving temperature independence. This method does not require complex data processing or additional standard equipment; only a few parameters from the calibration experiment are needed to achieve high-precision data acquisition. To achieve real-time temperature compensation, a platinum (Pt) resistor is integrated as a temperature sensing strip with a silicon carbide substrate to obtain real-time changes in ambient temperature.

[0012] To solve the above-mentioned technical problems, the technical solution adopted in the fabrication method of the silicon carbide-based strain temperature micro / nano sensor of the present invention is as follows:

[0013] The method for fabricating the silicon carbide-based strain temperature micro / nano sensor described above is characterized by comprising the following steps:

[0014] Step (a): A 4-inch double-sided polished and standard-cleaned 4H-SiC single crystal wafer was selected as the material for sensor fabrication. The thickness of the 4H-SiC single crystal wafer was 350±25μm, and the crystal orientation <11-20> was offset by 4°.

[0015] Step (b) involves using the Si surface of a 4H-SiC single wafer as a silicon carbide substrate and placing it in a low-pressure hot-wall chemical vapor deposition system with H2 as the carrier gas. First, the reaction chamber is evacuated, then the temperature is raised to 1600°C and the pressure is adjusted to 100 mbar. Next, SiH4, C3H8, and N2 are introduced as reaction gases, with N2 serving as the nitrogen doping source, to epitaxially grow an N-type buffer layer on the silicon carbide substrate. After the N-type buffer layer is grown, the reaction chamber temperature is kept constant at 1600°C and the pressure at 100 mbar. The epitaxial gases are then switched to SiH4, C3H8, and (CH3)3Al, with (CH3)3Al serving as the aluminum doping source, to continue epitaxially growing a highly doped P-type epitaxial layer 3 on the N-type buffer layer. During the growth process, the flow rate of each gas and the growth time are precisely controlled to finally obtain the desired 4H-SiC epitaxial wafer.

[0016] Step (c): A Ni metal mask covering the front side of the P-type silicon carbide is prepared on the epitaxial surface of the 4H-SiC epitaxial wafer using a magnetron sputtering process;

[0017] Step (d): Spin-coat 10µm positive photoresist on the top surface of the Ni mask; after photolithography to form the pattern of the silicon carbide serpentine piezoresistive full bridge, develop it, and then perform wet etching to remove the Ni mask to obtain the silicon carbide serpentine piezoresistive full bridge Ni metal mask.

[0018] Step (e) uses magnetic neutral line (NLD) plasma dry etching to achieve radial density uniformity through magnetic field confinement. The main RF power is 800-1200W, the bias RF power is 50-150W, the chamber pressure is 10mTorr, and the ion bombardment energy is controlled. In an atmosphere of SF6 and O2, 4H-SiC is etched by plasma dry etching. After etching, a serpentine piezoresistive interconnect resistor strip and metal trench structure 3 are formed.

[0019] Step (f): After etching, the mask is removed by wet etching with aqua regia to obtain the etched substrate;

[0020] Step (g): Spin-coat negative photoresist and perform photolithography using a mask with 4H-SiC metal pads; sequentially use titanium, nickel, and platinum targets for magnetron sputtering at a vacuum of 1×10⁻⁵ Pa and a power of 100 W to sputter Ti, Ni, and Pt metal films with thicknesses of 50 nm, 50 nm, and 200 nm, respectively; use acetone to strip the Ti, Ni, and Pt metal films; obtain a substrate with metal pads.

[0021] Step (h) involves performing RTP rapid thermal annealing on the 4H-SiC varistor chip under N2 airflow at a temperature of 1000℃ for 3 minutes to obtain a substrate with activated ohmic contact areas. The wafer is then separated by laser cleaving and polished to achieve efficient wafer splitting.

[0022] In step (I), a layer of aluminum oxide and a layer of platinum are sputtered on the back of the device using a metal hard mask in the cutout area. First, an aluminum oxide (Al2O3) layer is sputtered as an insulating layer under the conditions of 100W sputtering power, 1.3Pa working pressure, and 26℃ substrate temperature using an RF power supply. Then, the power supply is switched to DC, and platinum (Pt) is sputtered as a temperature sensing strip under the conditions of 100W sputtering power, 1.3Pa working pressure, and 26℃ substrate temperature. The aluminum oxide insulating layer effectively isolates the back temperature sensing strip from the front strain sensor, avoiding signal interference. The Pt temperature sensing strip utilizes the characteristic of its resistance changing with temperature to achieve high-precision temperature measurement.

[0023] To solve the above-mentioned technical problems, the technical solution adopted by the strain detection method of the present invention is as follows:

[0024] A strain detection method is characterized by using the aforementioned silicon carbide-based strain-temperature micro / nano sensor. During detection, the strain sensor is connected to an external circuit and firmly fixed to the object being tested. The silicon carbide resistive strain sensing layer is connected to an external current source via one pair of pad leads, providing excitation current to one pair of opposite ends of a four-resistance bridge circuit. The silicon carbide resistive deformation sensing layer is connected to an external voltage detection circuit via another pair of pad leads. When the object being tested is subjected to an external impact and deforms, the other pair of opposite ends of the four-resistance bridge circuit will output a voltage signal proportional to the strain.

[0025] The following is a further embodiment of the strain detection method of the present invention:

[0026] Let the resistances of the four resistor bridge formed by the four piezoresistive blocks be respectively , , , When the strain sensor undergoes lateral deformation, its components... and Some long, straight, highly doped piezoresistive bars will undergo corresponding deformation and widen, thus reducing their resistance value. Similarly, and The two long, straight strips of highly doped resistors will be elongated accordingly. According to the piezoresistive effect theory, due to the relative deformation caused by their elongation ( )and , The relative deformation value of the widening that occurs in some parts ( Since the resistance values ​​are equal, the resistance value will increase. ; , , , It is a varistor. As a constant input current source, The output voltage of the full-bridge circuit is as shown in the circuit diagram. Figure 6 Output voltage Expressed as:

[0027]

[0028] Ideally Therefore, when the silicon carbide strain gauge is not subjected to stress or temperature loading, the output voltage is zero. According to the piezoresistive effect, when stress is applied to the silicon carbide strain gauge, the resistivity of the piezoresistor changes, and the corresponding resistance value changes. When stress is applied to the silicon carbide strain gauge, assuming... and When in the normal stress region, the resistance becomes and ; and When in the negative stress region, the resistance becomes and ;

[0029] The expression for the output voltage under stress is:

[0030]

[0031] As can be seen from the above formula, the output voltage of the silicon carbide strain gauge is proportional to the relative change in resistance. Under stress, the silicon carbide strain gauge generates strain, causing the resistance of the piezoresistor to change proportionally. The relative change in resistance is then converted into a voltage output through a full-bridge circuit, thereby indirectly realizing the test of stress and strain. Temperature sensing strip: The temperature sensing layer is connected to an external temperature detection circuit through a pair of pads on it, and outputs an instantaneous temperature signal.

[0032] According to temperature sensing theory, when the temperature increases, the resistance of platinum (Pt) increases by a certain proportion, and the relationship is as follows: In the formula, For temperature The resistance value at that time; For temperature ,generally = Resistance value at 0℃; α is the temperature coefficient;

[0033] Strain sensors require temperature compensation primarily because the resistivity of strain sensors changes with temperature, and changes in thermal stress at the interface can cause mechanical strain, affecting the measurement accuracy and stability of the sensor. Through temperature compensation algorithms, strain sensors can maintain measurement accuracy and stability under different temperature environments.

[0034] Furthermore, the temperature acquisition module S1 is used to calculate the temperature in the following manner:

[0035] Connect the temperature sensor strip leads to the data acquisition circuit to calibrate the temperature value in real time, and calculate the temperature using the following method.

[0036] Where T is temperature. The temperature correction coefficient is used; the voltage acquisition module S2 is used to connect the silicon carbide serpentine full-bridge resistive strain sensing layer to an external current source via one pair of pad leads, providing excitation current to one pair of opposite ends of the four-resistance bridge of the resistive strain sensing layer; the silicon carbide resistive deformation sensing layer is connected to an external voltage detection circuit via another pair of pad leads; when the object being detected is subjected to external impact and deforms, the other pair of opposite ends of the four-resistance bridge will output a voltage signal that is proportional to the strain.

[0037] The temperature drift correction factor calculation module S3 is used to calculate the following:

[0038] By applying strain to the strain sensor at different temperatures and sampling the voltage, a series of output voltage values ​​as a function of temperature under different strains can be obtained, thereby obtaining the zero-point temperature drift correction coefficient and the sensitivity temperature drift correction coefficient.

[0039] The zero-point temperature drift formula is: Where T is temperature. This is the zero-point temperature drift correction factor. This is the zero-point drift output voltage; the sensitivity temperature drift formula is... Where T is temperature. This is the sensitivity temperature drift correction factor. The output voltage represents the sensitivity drift; the temperature drift correction coefficient calculation module S4 is used to calculate it in the following way; the zero-point temperature drift correction formula is... , This is the original output voltage value. This is the zero-point drift correction voltage value; the sensitivity drift correction formula is... , The voltage value is used to correct for zero-point temperature drift. The voltage value is used to correct for sensitivity temperature drift; the acquisition method of the strain-temperature dual-parameter acquisition system with nonlinear temperature compensation algorithm includes:

[0040] Step S5: Execute the calibration procedure and collect temperature values. During the system startup time, the calibration procedure is executed first. The temperature value of the environment where the sensor chip is located is collected in real time through the temperature sensor strip, providing basic data for subsequent temperature compensation. This step ensures the accuracy and timeliness of the acquired temperature data and is the starting point of the entire temperature compensation process.

[0041] Step S6: Voltage sampling is performed on the strain of the sensor chip. While acquiring the temperature value, the voltage signal generated by the strain of the sensor chip is sampled in real time. This voltage signal reflects the strain experienced by the sensor, but due to the influence of temperature drift, this original voltage signal has errors and needs further processing.

[0042] Step S7: Calculate the temperature drift correction coefficient for the sensor chip, based on the pre-established temperature-drift characteristic model, i.e., the zero-point drift temperature compensation matrix. The sensitivity temperature drift temperature compensation matrix is: Combined with the collected current temperature value, the temperature drift correction coefficient of the sensor chip at that temperature is calculated. This correction coefficient is used to measure the degree of influence of temperature change on the sensor output and is a key parameter for accurate compensation.

[0043] Step S8: Calculate the sensor chip voltage correction value. The original voltage sampling value of the sensor chip is collected and the calculated temperature drift correction coefficient is used to obtain the voltage correction value after temperature compensation. This step effectively eliminates the influence of temperature change on the original voltage signal, so that the voltage value can more accurately reflect the actual pressure on the sensor.

[0044] Step S9: Calculate the strain value corresponding to the voltage. Finally, based on the voltage-strain conversion relationship of the sensor, convert the temperature-compensated voltage correction value into the corresponding strain value. This strain value is the measurement result that accurately reflects the strain experienced by the sensor after temperature compensation.

[0045] This invention discloses a high-precision high-temperature strain and temperature composite sensor based on a silicon carbide substrate. Addressing the technical challenges of decreased sensitivity, structural failure, and inability to simultaneously measure strain and temperature in traditional sensors under extreme environments, this invention achieves high-precision monitoring of two parameters through innovative structural design based on Micro-Electro-Mechanical System (MEMS) technology.

[0046] This invention has significant advantages. Compared with the prior art, the silicon carbide-based strain temperature micro / nano sensor proposed in this invention has the following significant advantages:

[0047] 1) A silicon carbide substrate and an aluminum oxide layer are used to achieve high-temperature stability and anti-diffusion capability.

[0048] 2) A Wheatstone bridge structure is adopted to achieve high sensitivity strain capability.

[0049] 3) Dual-parameter synchronous measurement avoids signal interference and improves monitoring accuracy under complex working conditions.

[0050] 4) It has a compact structure and high integration, making it suitable for extreme environments such as aerospace and nuclear energy equipment.

[0051] This invention achieves high-sensitivity strain measurement in high-temperature environments by using an epitaxial structure of an N-type buffer layer and a P-type functional layer on the front side of a silicon carbide substrate, combined with a serpentine piezoresistive full-bridge fabricated using NLD etching. The resistance change rate is more than four times higher than that of traditional structures, and long-term stability is significantly enhanced. On the back side of the substrate, a temperature strip area is cut out using a metal hard mask, and aluminum oxide (Al2O3) and platinum (Pt) films are sequentially deposited by magnetron sputtering to form a dual-functional composite sensor. Overall, this invention advances research in the field of high-temperature sensors, avoids the instability of strain and temperature measurements in high-temperature sensors, and proposes a research scheme for a high-stability, high-temperature-range, and high-precision dual-parameter MEMS high-temperature sensor. A strain-temperature acquisition system based on a nonlinear temperature compensation algorithm is proposed. This algorithm does not require additional high-performance devices or a strict standard environment, making it a simple and low-cost method for achieving high-precision data acquisition. Using this algorithm, the output voltage at different temperatures can be converted to the output voltage at a fixed room temperature. This method successfully avoids the influence of different temperatures on the voltage and corrects its value at a standard temperature. Finally, using a temperature drift calibration coefficient, the compensated voltage is converted into an equivalent corrected strain value. Meanwhile, within a high strain range, all output voltages of the sensor are easily distinguishable, and high voltage resolution can be achieved. The error between compensating strains is well corrected for temperature drift of the experimental pressure values, successfully achieving independence from temperature changes. This method does not require complex data processing or additional standard equipment; high-precision data acquisition can be achieved with only a few parameters from the calibration experiment. To achieve real-time temperature compensation, a platinum (Pt) resistance thermometer is integrated with a silicon carbide substrate as a temperature sensor to obtain real-time changes in ambient temperature.

[0052] The implementation of the technical solution of this invention not only promotes the development of high temperature sensor technology, but also provides new possibilities for applications in fields such as industrial automation and intelligent manufacturing, and environmental monitoring. It has important scientific research significance and broad market application prospects. Attached Figure Description

[0053] Figure 1 This is a three-dimensional front view of the silicon carbide-based strain temperature micro / nano sensor of the present invention.

[0054] Figure 2 This is a three-dimensional schematic diagram of the bottom surface of the silicon carbide-based strain temperature micro / nano sensor of the present invention.

[0055] Figure 3 This is a three-dimensional schematic diagram of the state changes during the fabrication process of the silicon carbide-based strain temperature micro / nano sensor of the present invention.

[0056] Figure 4 This is a schematic diagram of the state changes during the fabrication process of the silicon carbide-based strain temperature micro / nano sensor of the present invention.

[0057] Figure 5 This is a schematic diagram of the silicon carbide-based strain temperature micro / nano sensor circuit of the present invention.

[0058] Figure 6 This is a schematic diagram of the temperature compensation correction calculation process for the silicon carbide-based strain temperature micro / nano sensor of the present invention.

[0059] Figure 7 This is a schematic diagram of the temperature compensation correction calculation process of the silicon carbide-based strain temperature micro / nano sensor of the present invention using a nonlinear temperature compensation algorithm.

[0060] The parts indicated by the numbers in each figure are: 1. Silicon carbide substrate; 2. N-type buffer layer; 3. P-type functional layer; 4. Piezoresistive block; 5. Metal electrode; 6. Temperature sensing strip; 7. End; 8. Large rectangle; 9. Small rectangle; 10. Interconnection area; 11. Ni metal mask. Detailed Implementation

[0061] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0062] The present invention relates to a silicon carbide-based strain-temperature micro / nano sensor, which is a high-temperature resistant, high-precision strain-temperature dual-parameter micro / nano sensor based on a silicon carbide substrate 1.

[0063] like Figure 1 As shown, the silicon carbide-based strain-temperature micro / nano sensor of the present invention includes a silicon carbide substrate 1. An N-type buffer layer 2 and a P-type functional layer 3 are sequentially grown upward on the front side of the silicon carbide substrate 1, completely covering the front side of the silicon carbide substrate 1 to form a strain-sensitive substrate. The P-type functional layer 3 is precisely processed using NLD etching technology, and the remaining area forms four interconnected piezoresistive blocks 4. This structure maximizes the detection sensitivity. In the designated area on the four piezoresistive blocks 4, Ti thin films, Ni thin films, and Pt thin films are sequentially sputtered using magnetron sputtering technology to form four metal electrodes 5. Ohmic contact is achieved on the upper surface through high-temperature annealing, and leads are soldered using silver paste sintering technology for external electrical connection. Thus, the four piezoresistive blocks 4 form a four-resistance bridge, and high-sensitivity strain measurement is achieved by detecting voltage changes, thereby forming a strain sensor on the front side of the silicon carbide substrate 1.

[0064] like Figure 1 or Figure 3As shown in diagram d, each piezoresistive block includes a large rectangle 8 extending from near one of the four corners of the N-type buffer layer 2 towards the center, a small rectangle 9 integrally connected to the large rectangle 8 extending towards the center, and interconnecting regions 10 extending from the small rectangle 9 in a meandering manner towards the two adjacent piezoresistive blocks. There are four large rectangles 8, four small rectangles 9, and four interconnecting regions 10. The large rectangles 8 and four small rectangles 9 are each independently owned, while the interconnecting regions 10 are shared by every two adjacent piezoresistive blocks. The designated areas on the four piezoresistive blocks 4 are rectangular, forming four rectangular metal electrodes 5 with an area smaller than the large rectangle 8 of the piezoresistive blocks.

[0065] like Figure 2 As shown, a strip-shaped, tortuous, hollowed-out area is set in the center of the back side of the silicon carbide substrate 1. An alumina barrier layer and a platinum (Pt) thin film layer are sequentially sputtered and deposited using a magnetron sputtering process to form a strip-shaped, tortuous, tortuous temperature sensing strip 6. The temperature sensing strip 6 includes two ends 7 for external electrical connection. The two ends 7 are arranged in the same orientation and are spaced apart and adjacent to each other.

[0066] A 4-inch double-sided polished and standard-cleaned 4H-SiC single crystal was selected as the material for sensor fabrication. The 4H-SiC single crystal was 350±25μm thick and had a crystal orientation of <11-20> offset by 4°. It was placed in a low-pressure hot-wall chemical vapor deposition system with H2 as the carrier gas.First, the reaction chamber was evacuated, then the temperature was raised to 1600℃ and the pressure was adjusted to 100 mbar. Next, SiH4, C3H8, and N2 were introduced as reaction gases, with N2 serving as the nitrogen dopant source, to epitaxially grow an N-type buffer layer 2 on the silicon carbide substrate 1. After the N-type buffer layer growth was completed, the reaction chamber temperature was kept constant at 1600℃ and the pressure at 100 mbar, and the epitaxial gases were switched to SiH4, C3H8, and (CH3)3Al, with (CH3)3Al serving as the aluminum dopant source, to continue epitaxially growing a highly doped P-type epitaxial layer 3 on the N-type buffer layer. During the growth process, the flow rate of each gas and the growth time were precisely controlled to finally obtain the desired 4H-SiC epitaxial layer. The substrate consists of an N-type buffer layer (2µm thick) and a P-type functional layer (3µm thick), forming a strain-sensitive substrate. The top layer employs a novel NLD etching process: magnetic neutral line plasma dry etching, achieving radial density uniformity through magnetic field confinement. The main RF power is 800-1200W, the bias RF power is 50-150W, the chamber pressure is 10mTorr, and the ion bombardment energy is controlled. In an atmosphere of SF6 and O2, 4H-SiC is etched using plasma dry etching. A piezoresistive block 4 distribution structure is precisely fabricated using a Ni metal mask. Photolithography is performed using a 4H-SiC metal pad mask after spin-coating a negative photoresist. Magnetron sputtering is then performed sequentially using titanium, nickel, and platinum targets. With a porosity of 1×10⁻⁵ Pa and a power of 100 W, Ti, Ni, and Pt metal thin films with thicknesses of 50 nm, 50 nm, and 200 nm were sputtered, respectively. The Ti, Ni, and Pt metal thin films were then stripped with acetone to obtain a substrate with metal pads. Activated ohmic contacts were obtained through rapid RTP thermal annealing at 1000 °C for three minutes. Leads were then soldered using silver paste sintering technology, enabling the silicon carbide-based strain temperature micro / nano sensor to achieve high-sensitivity strain measurement by detecting voltage changes. On the back side of the silicon carbide substrate 1, a layer of aluminum oxide and a layer of platinum were sputtered in the cutout area using a metal hard mask. An RF power supply was used with a sputtering power of 100 W and a working pressure of 1.3 P. a. Under the condition of a substrate temperature of 26℃, a layer of aluminum oxide (Al2O3) with a thickness of 200nm is sputtered as an insulating layer. Then, under the condition of switching to DC power, sputtering power of 100W, working gas pressure of 1.3Pa, and substrate temperature of 26℃, a layer of platinum (Pt) with a thickness of 500nm is sputtered as a temperature sensing strip 6. The aluminum oxide layer effectively prevents platinum atoms from diffusing into the silicon carbide substrate 1. At the same time, due to its excellent high-temperature adhesion stability, it avoids the problem of traditional adhesive layers easily falling off under high-temperature conditions. Meanwhile, the aluminum oxide insulating layer effectively isolates the back temperature sensing strip 6 from the front strain sensor, avoiding signal interference. The platinum (Pt) temperature sensing strip 6 utilizes the characteristic of its resistance changing with temperature to achieve high-precision temperature measurement.

[0067] A nonlinear temperature-compensated strain-temperature acquisition system is employed. This system converts the output voltage at different temperatures into an output voltage at a fixed room temperature. To avoid the influence of different temperatures on the voltage, its value is corrected at a standard temperature. Finally, using a temperature drift calibration coefficient, the compensated voltage is converted into an equivalent corrected strain value. Simultaneously, within a high-range strain, all output voltages of the sensor are easily distinguishable, achieving high voltage resolution. The error between compensated strains is corrected for temperature drift, successfully achieving temperature independence. This method does not require complex data processing or additional standard equipment; only a few parameters from the calibration experiment are needed to achieve high-precision data acquisition. To achieve real-time temperature compensation, a platinum Pt resistor is integrated as a temperature sensing strip 6 with a silicon carbide substrate 1 to obtain real-time changes in ambient temperature.

[0068] The above methods for fabricating silicon carbide-based strain temperature micro / nano sensors, such as... Figure 3 , Figure 4 As shown, it includes the following steps:

[0069] Step (a) uses a 4-inch double-sided polished and standard-cleaned 4H-SiC single crystal wafer as the material for sensor fabrication. The 4H-SiC single crystal wafer has a thickness of 350±25μm and a crystal orientation <11-20> offset of 4°. Figure 3 a or Figure 4 As shown in a;

[0070] Step (b) involves using the Si surface of a 4H-SiC single wafer as the silicon carbide substrate 1, placing it in a low-pressure hot-wall chemical vapor deposition system with H2 as the carrier gas. First, the reaction chamber is evacuated, then the temperature is raised to 1600°C and the pressure adjusted to 100 mbar. Next, SiH4, C3H8, and N2 are introduced as reaction gases, with N2 serving as the nitrogen doping source, to epitaxially grow an N-type buffer layer 2 on the silicon carbide substrate 1. After the N-type buffer layer growth is complete, the reaction chamber temperature is kept constant at 1600°C and the pressure at 100 mbar. The epitaxial gases are switched to SiH4, C3H8, and (CH3)3Al, with (CH3)3Al serving as the aluminum doping source, to continue epitaxially growing a P-type highly doped epitaxial layer 3 on the N-type buffer layer. During the growth process, the flow rate of each gas and the growth time are precisely controlled to finally obtain the desired 4H-SiC epitaxial wafer, as shown below. Figure 3 b or Figure 4 As shown in b;

[0071] Step (c) involves fabricating a Ni metal mask 11 covering the front side of a P-type silicon carbide wafer using magnetron sputtering on the epitaxial surface of the 4H-SiC epitaxial wafer, as shown below. Figure 4 As shown in c;

[0072] Step (d): Spin-coat 10µm positive photoresist onto the top surface of the Ni mask; after photolithography to create the pattern of a silicon carbide serpentine piezoresistive full bridge, develop the image, and then perform wet etching to remove the Ni mask, obtaining the silicon carbide serpentine piezoresistive full bridge Ni metal mask 11, as shown. Figure 4 As shown in d;

[0073] Step (e) involves dry etching using magnetic neutral line (NLD) plasma. Radial density uniformity is achieved through magnetic field confinement. The main RF power is 800-1200W, the bias RF power is 50-150W, and the chamber pressure is 10 mTorr. Ion bombardment energy is controlled, and 4H-SiC is dry-etched using plasma in an SF6 and O2 atmosphere. After etching, a serpentine piezoresistive interconnect resistor strip and a metal trench structure are formed. Figure 4 As shown in e;

[0074] Step (f) involves removing the mask after etching using aqua regia wet etching to obtain the etched substrate, as shown below. Figure 4 As shown in f;

[0075] Step (g): Spin-coat negative photoresist and perform photolithography using a mask with 4H-SiC metal pads; sequentially perform magnetron sputtering using titanium, nickel, and platinum targets at a vacuum of 1×10⁻⁵ Pa and a power of 100 W to sputter Ti, Ni, and Pt metal films with thicknesses of 50 nm, 50 nm, and 200 nm, respectively; strip the Ti, Ni, and Pt metal films with acetone; obtain a substrate with metal pads, as shown below. Figure 4 As shown in g;

[0076] Step (h) involves performing RTP rapid thermal annealing on the 4H-SiC varistor chip under N2 gas flow at a temperature of 1000℃ for 3 minutes to obtain a substrate with activated ohmic contact regions. The wafer is then separated using laser dicing and polished to achieve efficient wafer dicing. Figure 4 As shown in h;

[0077] Step (I) involves sputtering a layer of aluminum oxide and a layer of platinum metal into the cutout area on the back of the device using a hard metal mask, such as... Figure 3 As shown in Figure I, an aluminum oxide (Al2O3) layer is first sputtered as an insulating layer using an RF power supply at a sputtering power of 100W, a working pressure of 1.3Pa, and a substrate temperature of 26℃. Then, the power supply is switched to DC, and platinum (Pt) is sputtered as a temperature sensing strip 6 at a sputtering power of 100W, a working pressure of 1.3Pa, and a substrate temperature of 26℃. The aluminum oxide insulating layer effectively isolates the back temperature sensing strip 6 from the front strain sensor, avoiding signal interference. The Pt temperature sensing strip 6 utilizes the characteristic of its resistance changing with temperature to achieve high-precision temperature measurement.

[0078] The strain detection method of this invention uses the above-mentioned silicon carbide-based strain-temperature micro / nano sensor. During detection, the strain sensor is connected to an external circuit and firmly fixed to the object being tested. The silicon carbide resistive strain sensing layer is connected to an external current source via one pair of pad leads, providing excitation current to one pair of opposite ends of a four-resistance bridge circuit of the resistive strain sensing layer. The silicon carbide resistive deformation sensing layer is connected to an external voltage detection circuit via another pair of pad leads. When the object being tested is subjected to an external impact and deforms, the other pair of opposite ends of the four-resistance bridge circuit will output a voltage signal that is directly proportional to the strain.

[0079] Let the resistances of the four resistor bridge formed by the four piezoresistive blocks be respectively , , , ,like Figure 5 As shown, when the strain sensor undergoes lateral deformation, its... and Some long, straight, highly doped piezoresistive bars will undergo corresponding deformation and widen, thus reducing their resistance value. Similarly, and The two long, straight strips of highly doped resistors will be elongated accordingly. According to the piezoresistive effect theory, due to the relative deformation caused by their elongation ( )and , The relative deformation value of the widening that occurs in some parts ( Since the resistance values ​​are equal, the resistance value will increase. ; , , , It is a varistor. As a constant input current source, The output voltage of the full-bridge circuit is as shown in the circuit diagram. Figure 6 Output voltage Expressed as:

[0080]

[0081] Ideally Therefore, when the silicon carbide strain gauge is not subjected to stress or temperature loading, the output voltage is zero. According to the piezoresistive effect, when stress is applied to the silicon carbide strain gauge, the resistivity of the piezoresistor changes, and the corresponding resistance value changes. When stress is applied to the silicon carbide strain gauge, assuming... and When in the normal stress region, the resistance becomes and ; and When in the negative stress region, the resistance becomes and ;

[0082] The expression for the output voltage under stress is:

[0083]

[0084] As can be seen from the above formula, the output voltage of the silicon carbide strain gauge is proportional to the relative change in resistance. Under stress, the silicon carbide strain gauge generates strain, causing the resistance of the piezoresistor to change proportionally. The relative change in resistance is then converted into a voltage output through a full-bridge circuit, thereby indirectly realizing the test of stress and strain. Temperature sensing strip 6: The temperature sensing layer is connected to an external temperature detection circuit through a pair of pads on it, and outputs an instantaneous temperature signal.

[0085] According to temperature sensing theory, when the temperature increases, the resistance of platinum (Pt) increases by a certain proportion, and the relationship is as follows: In the formula, For temperature The resistance value at that time; For temperature ,generally = Resistance value at 0℃; α is the temperature coefficient;

[0086] Strain sensors require temperature compensation primarily because their resistivity changes with temperature, and variations in thermal stress at the interface can induce mechanical strain, affecting the sensor's measurement accuracy and stability. Through temperature compensation algorithms, strain sensors can maintain measurement accuracy and stability under varying temperature conditions. Figure 6 As shown.

[0087] Furthermore, the temperature acquisition module S1 is used to calculate the temperature in the following manner:

[0088] Connect the temperature sensor strip 6 lead to the acquisition circuit to calibrate the temperature value in real time, and calculate the temperature using the following method.

[0089] Where T is temperature. The temperature correction coefficient is used; the voltage acquisition module S2 is used to connect the silicon carbide serpentine full-bridge resistive strain sensing layer to an external current source via one pair of pad leads, providing excitation current to one pair of opposite ends of the four-resistance bridge of the resistive strain sensing layer; the silicon carbide resistive deformation sensing layer is connected to an external voltage detection circuit via another pair of pad leads; when the object being detected is subjected to external impact and deforms, the other pair of opposite ends of the four-resistance bridge will output a voltage signal that is proportional to the strain.

[0090] The temperature drift correction factor calculation module S3 is used to calculate the following:

[0091] By applying strain to the strain sensor at different temperatures and sampling the voltage, a series of output voltage values ​​as a function of temperature under different strains can be obtained, thereby obtaining the zero-point temperature drift correction coefficient and the sensitivity temperature drift correction coefficient.

[0092] The zero-point temperature drift formula is: Where T is temperature. This is the zero-point temperature drift correction factor. This is the zero-point drift output voltage; the sensitivity temperature drift formula is... Where T is temperature. This is the sensitivity temperature drift correction factor. The output voltage represents the sensitivity drift; the temperature drift correction coefficient calculation module S4 is used to calculate it in the following way; the zero-point temperature drift correction formula is... , This is the original output voltage value. This is the zero-point drift correction voltage value; the sensitivity drift correction formula is... , The voltage value is used to correct for zero-point temperature drift. The voltage value is used to correct for sensitivity temperature drift.

[0093] like Figure 7 As shown, the acquisition method of the strain-temperature dual-parameter acquisition system of the nonlinear temperature compensation algorithm includes:

[0094] Step S5: Execute the calibration procedure and collect temperature values. During the system startup time, the calibration procedure is executed first. The temperature value of the environment where the sensor chip is located is collected in real time through the temperature sensor strip 6, providing basic data for subsequent temperature compensation. This step ensures the accuracy and timeliness of the acquired temperature data and is the starting point of the entire temperature compensation process.

[0095] Step S6: Voltage sampling is performed on the strain of the sensor chip. While acquiring the temperature value, the voltage signal generated by the strain of the sensor chip is sampled in real time. This voltage signal reflects the strain experienced by the sensor, but due to the influence of temperature drift, this original voltage signal has errors and needs further processing.

[0096] Step S7: Calculate the temperature drift correction coefficient for the sensor chip, based on the pre-established temperature-drift characteristic model, i.e., the zero-point drift temperature compensation matrix. The sensitivity temperature drift temperature compensation matrix is: Combined with the collected current temperature value, the temperature drift correction coefficient of the sensor chip at that temperature is calculated. This correction coefficient is used to measure the degree of influence of temperature change on the sensor output and is a key parameter for accurate compensation.

[0097] Step S8: Calculate the sensor chip voltage correction value. The original voltage sampling value of the sensor chip is collected and the calculated temperature drift correction coefficient is used to obtain the voltage correction value after temperature compensation. This step effectively eliminates the influence of temperature change on the original voltage signal, so that the voltage value can more accurately reflect the actual pressure on the sensor.

[0098] Step S9: Calculate the strain value corresponding to the voltage. Finally, based on the voltage-strain conversion relationship of the sensor, convert the temperature-compensated voltage correction value into the corresponding strain value. This strain value is the measurement result that accurately reflects the strain experienced by the sensor after temperature compensation.

Claims

1. A silicon carbide-based strain-temperature micro / nano sensor, which is a high-temperature resistant, high-precision strain-temperature dual-parameter micro / nano sensor based on a silicon carbide substrate (1), comprising a silicon carbide substrate (1), characterized in that, An N-type buffer layer (2) and a P-type functional layer (3) are grown sequentially upwards on the front side of a silicon carbide substrate (1), completely covering the front side of the silicon carbide substrate (1) to form a strain-sensitive substrate. The P-type functional layer (3) is precisely processed using NLD etching, and the remaining area forms four interconnected piezoresistive blocks (4). In the designated area on the four piezoresistive blocks (4), Ti thin films, Ni thin films, and Pt thin films are sequentially sputtered using magnetron sputtering to form four metal electrodes (5). Ohmic contact on the upper surface is achieved by high-temperature annealing. Leads are soldered out using silver paste sintering process for external electrical connection. Thus, four piezoresistive blocks (4) form a four-resistance bridge. High-sensitivity strain measurement is achieved by detecting voltage changes, thereby forming a strain sensor on the front side of the silicon carbide substrate (1). At the center of the back side of the silicon carbide substrate (1), a strip-shaped, tortuous, hollow area is set. An alumina barrier layer and a platinum Pt thin film layer are sequentially sputtered and deposited using magnetron sputtering process to form a strip-shaped, tortuous, tortuous temperature sensing strip (6). The temperature sensing strip (6) includes two ends (7) for external electrical connection.

2. The silicon carbide-based strain temperature micro / nano sensor as described in claim 1, characterized in that, Each piezoresistive block includes a large rectangle (8) extending from one of the four corners of the N-type buffer layer (2) toward the center, a small rectangle (9) extending toward the center in an integral connection with the large rectangle (8), and an interconnection area (10) extending from the small rectangle (9) to the two adjacent piezoresistive blocks in a meandering manner; there are four large rectangles (8), four small rectangles (9), and four interconnection areas (10), of which the large rectangles (8) and the small rectangles (9) are owned independently by each other, and the interconnection areas (10) are shared by every two adjacent piezoresistive blocks.

3. The silicon carbide-based strain temperature micro / nano sensor as described in claim 2, characterized in that, The set area on the four piezoresistive blocks (4) is rectangular, forming four rectangular metal electrodes (5) with an area smaller than that of the piezoresistive blocks (8).

4. The silicon carbide-based strain temperature micro / nano sensor as described in claim 1, characterized in that, The two ends (7) are arranged in the same direction and are adjacent to each other.

5. The silicon carbide-based strain temperature micro / nano sensor as described in claim 1, characterized in that, A 4-inch double-sided polished and standard-cleaned 4H-SiC single crystal was selected as the material for sensor fabrication. The 4H-SiC single crystal was 350±25μm thick and had a crystal orientation of <11-20> offset by 4°. It was placed in a low-pressure hot-wall chemical vapor deposition system with H2 as the carrier gas. First, the reaction chamber was evacuated, and then the temperature of the reaction chamber was raised to 1600℃ and the pressure was adjusted to 100mbar. Next, SiH4, C3H8 and N2 were introduced as reaction gases, with N2 as the nitrogen doping source, and an N-type buffer layer (2) was epitaxially grown on the silicon carbide substrate (1). After the N-type buffer layer was grown, the reaction chamber temperature was kept constant at 1600℃ and the pressure at 100mbar. The epitaxial gases were switched to SiH4, C3H8 and (CH3)3Al, with (CH3)3Al as the aluminum doping source, and a P-type highly doped epitaxial layer (3) was continued to be epitaxially grown on the N-type buffer layer. During the growth process, the flow rate of each gas and the growth time were precisely controlled, and the required 4H-SiC epitaxial wafer was finally obtained. The thickness of the N-type buffer layer (2) was 2um and the thickness of the P-type functional layer (3) was 3um, forming a strain-sensitive substrate. The top layer adopts a novel NLD etching process: magnetic neutral line plasma dry etching, radial density uniformity is achieved by magnetic field confinement, main RF power is 800-1200W, bias RF power is 50-150W, chamber pressure is 10mTorr, ion bombardment energy is controlled, 4H-SiC is etched by plasma dry etching in SF6 and O2 atmosphere, the distribution structure of the piezoresistive block (4) is precisely processed by Ni metal mask (11); negative photoresist is spin-coated, and photolithography is performed using the mask of 4H-SiC metal pad; Ti, Ni, and Pt metal thin films (4) with thicknesses of 50nm, 50nm, and 200nm are sputtered sequentially using titanium, nickel, and platinum targets, vacuum degree is 1×10-5Pa, power is 100W, and Ti, Ni, and Pt metal thin films (4) with thicknesses of 50nm, 50nm, and 200nm are sputtered respectively; Ti, Ni, and Pt are sputtered with acetone. The metal film is peeled off; a substrate with metal pads is obtained; an activated ohmic contact is obtained by rapid thermal annealing at 1000°C for three minutes using RTP; leads are soldered using silver paste sintering technology, so that the silicon carbide-based strain temperature micro / nano sensor can achieve high-sensitivity strain measurement by detecting voltage changes; on the back side of the silicon carbide substrate (1), a layer of aluminum oxide and a layer of platinum are sputtered in the hollow area using a metal hard mask. First, an aluminum oxide Al2O3 layer with a thickness of 200nm is sputtered as an insulating layer under the conditions of 100W sputtering power, 1.3Pa working pressure and 26°C substrate temperature using an RF power supply. Then, a platinum Pt layer with a thickness of 500nm is sputtered as a temperature sensing strip (6) under the conditions of 100W sputtering power, 1.3Pa working pressure and 26°C substrate temperature using a DC power supply.

6. The silicon carbide-based strain temperature micro / nano sensor as described in claim 5, characterized in that, A nonlinear temperature-compensated strain-temperature acquisition system is adopted. Using this system, the output voltage at different temperatures is converted into the output voltage at a fixed room temperature. In order to avoid the influence of different temperatures on the voltage, its value is corrected at a standard temperature. Finally, the compensated voltage is converted into an equivalent corrected strain value using a temperature drift calibration coefficient. At the same time, in the high-range strain range, all output voltages of the sensor are easily distinguishable, and high voltage resolution is obtained. The error between the compensated strains is corrected as the experimental pressure value drifts with temperature. This method does not require complex data processing and additional standard devices. Only a few parameters of the calibration experiment are needed to achieve high-precision data acquisition. In order to achieve real-time temperature compensation, a platinum Pt resistor is integrated with a silicon carbide substrate (1) as a temperature sensing strip (6) to obtain the real-time change of ambient temperature.

7. The method for fabricating a silicon carbide-based strain temperature micro / nano sensor as described in any one of claims 1 to 6, characterized in that, Includes the following steps: Step (a): A 4-inch double-sided polished and standard-cleaned 4H-SiC single crystal wafer was selected as the material for sensor fabrication. The thickness of the 4H-SiC single crystal wafer is 350±25μm, and the crystal orientation <11-20> is offset by 4°, as shown in Figure 4a. Step (b): The Si surface of the 4H-SiC single wafer is used as the silicon carbide substrate (1), and it is placed in a low-pressure hot-wall chemical vapor deposition system with H2 as the carrier gas. First, the reaction chamber is evacuated, and then the temperature of the reaction chamber is raised to 1600℃ and the pressure is adjusted to 100mbar. Then, SiH4, C3H8 and N2 are introduced as reaction gases, with N2 as the nitrogen doping source, and an N-type buffer layer (2) is epitaxially grown on the silicon carbide substrate (1). After the N-type buffer layer is grown, the reaction chamber temperature is kept constant at 1600℃ and the pressure is kept constant at 100mbar. The epitaxial gases are switched to SiH4, C3H8 and (CH3)3Al, with (CH3)3Al as the aluminum doping source, and a P-type highly doped epitaxial layer (3) is continued to be epitaxially grown on the N-type buffer layer. During the growth process, the flow rate of each gas and the growth time are precisely controlled, and the required 4H-SiC epitaxial wafer is finally obtained, as shown in Figure 4b. Step (c): A Ni metal mask (11) covering the front side of the P-type silicon carbide is prepared on the epitaxial surface of the 4H-SiC epitaxial wafer using a magnetron sputtering process, as shown in Figure 4c. Step (d): Spin-coat 10µm of positive photoresist onto the top surface of the Ni mask; After photolithography to create the pattern of the silicon carbide serpentine piezoresistive full bridge, development is performed, followed by wet etching to remove the Ni mask, resulting in the silicon carbide serpentine piezoresistive full bridge Ni metal mask (11), as shown in Figure 4d. Step (e) uses magnetic neutral line (NLD) plasma dry etching to achieve radial density uniformity through magnetic field confinement. The main RF power is 800-1200W, the bias RF power is 50-150W, the chamber pressure is 10mTorr, and the ion bombardment energy is controlled. In an atmosphere of SF6 and O2, 4H-SiC is etched by plasma dry etching. After etching, a serpentine piezoresistive interconnect resistor strip and metal trench structure are formed (3), as shown in Figure 4e. Step (f): After etching, the mask is removed by wet etching with aqua regia to obtain the etched substrate, as shown in Figure 4f. Step (g): Spin-coat negative photoresist and perform photolithography using a mask with 4H-SiC metal pads; then perform magnetron sputtering sequentially using titanium, nickel, and platinum targets at a vacuum level of 1×10⁻⁶. -5 Pa, with a power of 100W, sputtered Ti, Ni, and Pt metal films with thicknesses of 50nm, 50nm, and 200nm respectively (4); the Ti, Ni, and Pt metal films were stripped with acetone; a substrate with metal pads was obtained, as shown in Figure 4g; Step (h) involves performing RTP rapid thermal annealing on the 4H-SiC varistor chip under N2 gas flow at a temperature of 1000℃ for 3 minutes to obtain a substrate with activated ohmic contact regions. The wafer is then separated by laser cleaving and polished to achieve efficient wafer splitting; as shown in Figure 4h. Step (I): On the back of the device, a layer of aluminum oxide and a layer of platinum are sputtered in the cutout area using a metal hard mask, as shown in Figure 3I. First, an aluminum oxide (Al2O3) layer is sputtered as an insulating layer using an RF power supply with a sputtering power of 100W, a working pressure of 1.3Pa, and a substrate temperature of 26℃. Then, the power supply is switched to DC, and platinum (Pt) is sputtered as a temperature sensing strip (6) with a sputtering power of 100W, a working pressure of 1.3Pa, and a substrate temperature of 26℃. The aluminum oxide insulating layer effectively isolates the back temperature sensing strip (6) from the front strain sensor, avoiding signal interference. The Pt temperature sensing strip (6) utilizes the characteristic of its resistance changing with temperature to achieve high-precision temperature measurement.

8. A strain detection method, characterized in that, When using the silicon carbide-based strain-temperature micro / nano sensor as described in any one of claims 1 to 6, during detection, the strain sensor is connected to an external circuit and firmly fixed to the object being tested. The silicon carbide resistive strain sensing layer is connected to an external current source via one pair of pad leads, providing excitation current to one pair of opposite ends of the four-resistance bridge of the resistive strain sensing layer. The silicon carbide resistive deformation sensing layer is connected to an external voltage detection circuit via another pair of pad leads. When the object being tested is subjected to an external impact and deforms, the other pair of opposite ends of the four-resistance bridge will output a voltage signal that is proportional to the strain.

9. The strain detection method as described in claim 8, characterized in that, ... The resistances of the four resistor bridge formed by the four piezoresistive blocks (4) are respectively , , , When the strain sensor undergoes lateral deformation, its components... and Some long, straight, highly doped piezoresistive bars will undergo corresponding deformation and widen, thus reducing their resistance value. Similarly, and The two long, straight strips of highly doped resistors will be elongated accordingly. According to the piezoresistive effect theory, due to the relative deformation caused by their elongation ( )and , The relative deformation value of the widening that occurs in some parts ( Since the resistance values ​​are equal, the resistance value will increase. ; , , , It is a varistor. As a constant input current source, The output voltage of the full-bridge circuit is shown in Figure 6. Expressed as:

10. Ideally Therefore, when the silicon carbide strain gauge is not subjected to stress or temperature loading, the output voltage is zero. According to the piezoresistive effect, when stress is applied to the silicon carbide strain gauge, the resistivity of the piezoresistor changes, and the corresponding resistance value changes. When stress is applied to the silicon carbide strain gauge, assuming... and When in the normal stress region, the resistance becomes and ; and When in the negative stress region, the resistance becomes and ; The expression for the output voltage under stress is:

11. As can be seen from the above formula, the output voltage of the silicon carbide strain gauge is proportional to the relative change in resistance; under stress, the silicon carbide strain gauge generates strain, causing the resistance of the pressure-sensitive resistor to change proportionally; then the relative change in resistance is converted into voltage output through the full-bridge circuit, thereby indirectly realizing the stress and strain test; temperature sensing strip (6): the temperature sensing layer is connected to the external temperature detection circuit through a pair of solder pads on it, and outputs the instantaneous temperature signal; According to temperature sensing theory, when the temperature increases, the resistance of platinum (Pt) increases by a certain proportion, and the relationship is as follows: In the formula, For temperature The resistance value at that time; For temperature ,generally = Resistance value at 0℃; α is the temperature coefficient; Strain sensors require temperature compensation primarily because the resistivity of strain sensors changes with temperature, and changes in thermal stress at the interface can cause mechanical strain, which can affect the measurement accuracy and stability of the sensor. Through temperature compensation algorithms, strain sensors can maintain measurement accuracy and stability under different temperature environments, as shown in Figure 8.

12. The strain detection method as described in claim 9, characterized in that, Using temperature acquisition module S1, the temperature is calculated in the following manner: Connect the temperature sensor strip (6) lead to the acquisition circuit to calibrate the temperature value in real time, and calculate the temperature using the following method. Where T is temperature. The temperature correction coefficient is used; the voltage acquisition module S2 is used to connect the silicon carbide serpentine full-bridge resistive strain sensing layer to an external current source via one pair of pad leads, providing excitation current to one pair of opposite ends of the four-resistance bridge of the resistive strain sensing layer; the silicon carbide resistive deformation sensing layer is connected to an external voltage detection circuit via another pair of pad leads; when the object being detected is subjected to external impact and deforms, the other pair of opposite ends of the four-resistance bridge will output a voltage signal that is proportional to the strain. The temperature drift correction factor calculation module S3 is used to calculate the following: By applying strain to the strain sensor at different temperatures and sampling the voltage, a series of output voltage values ​​as a function of temperature under different strains can be obtained, thereby obtaining the zero-point temperature drift correction coefficient and the sensitivity temperature drift correction coefficient. The zero-point temperature drift formula is: Where T is temperature. This is the zero-point temperature drift correction factor. This is the zero-point drift output voltage; the sensitivity temperature drift formula is... Where T is temperature. This is the sensitivity temperature drift correction factor. The output voltage represents the sensitivity drift; the temperature drift correction coefficient calculation module S4 is used to calculate it in the following way; the zero-point temperature drift correction formula is... , This is the original output voltage value. Correct the voltage value for zero-point drift; The sensitivity drift correction formula is: , The voltage value is used to correct for zero-point temperature drift. The voltage value is used to correct for sensitivity temperature drift. The acquisition method of the strain-temperature dual-parameter acquisition system based on the nonlinear temperature compensation algorithm includes: Step S5: Execute the calibration procedure and collect temperature values. During the system startup time, the calibration procedure is executed first. The temperature value of the environment where the sensor chip is located is collected in real time through the temperature sensor strip (6) to provide basic data for subsequent temperature compensation. This step ensures the accuracy and timeliness of the acquired temperature data and is the starting point of the entire temperature compensation process. Step S6: Voltage sampling is performed on the strain of the sensor chip. While acquiring the temperature value, the voltage signal generated by the strain of the sensor chip is sampled in real time. This voltage signal reflects the strain experienced by the sensor, but due to the influence of temperature drift, this original voltage signal has errors and needs further processing. Step S7: Calculate the temperature drift correction coefficient for the sensor chip, based on the pre-established temperature-drift characteristic model, i.e., the zero-point drift temperature compensation matrix. The sensitivity temperature drift temperature compensation matrix is: Combined with the collected current temperature value, the temperature drift correction coefficient of the sensor chip at that temperature is calculated. This correction coefficient is used to measure the degree of influence of temperature change on the sensor output and is a key parameter for accurate compensation. Step S8: Calculate the sensor chip voltage correction value. The original voltage sampling value of the sensor chip is collected and the calculated temperature drift correction coefficient is used to obtain the voltage correction value after temperature compensation. This step effectively eliminates the influence of temperature change on the original voltage signal, so that the voltage value can more accurately reflect the actual pressure on the sensor. Step S9: Calculate the strain value corresponding to the voltage. Finally, based on the voltage-strain conversion relationship of the sensor, convert the temperature-compensated voltage correction value into the corresponding strain value. This strain value is the measurement result that accurately reflects the strain experienced by the sensor after temperature compensation.

Images