Resonant high pressure sensor based on beam film sensitivity and body compression sensitivity

Abstract

The present invention proposes a resonant high-pressure sensor based on beam-film sensitivity and body compression sensitivity. The composite pressure-sensitive principle is adopted in the structural design, that is, the advantages of high sensitivity of the beam-film sensitivity principle and high compressive strength of the body compression sensitivity principle are utilized to achieve the effect of sensor pressure sensitivity enhancement and range expansion. The present invention adopts two miniaturized resonant cavity structures, the pressure resistance is greatly improved, and the uniform axial stress distribution on the resonant beam at the center of the resonant cavity can improve the stability of the resonant frequency; in addition, the resonant cavity structures of different widths can achieve positive and negative sensitivity matching of the dual resonators. Under the premise of meeting high sensitivity and high pressure resistance, the temperature in-situ self-compensation can be further realized through differentiation, and the sensitivity and linearity can be improved.

Description

Technical Field

[0001] The invention relates to the field of MEMS microsensors, and in particular to a resonant high-pressure sensor based on beam-film sensitivity and body compression sensitivity. Background Art

[0002] Pressure sensors are widely used in many fields such as intelligent manufacturing, consumer electronics, and biomedicine. However, when it comes to aerospace, marine development, oil extraction, hydraulic transmission, and other applications, conventional pressure sensors with high accuracy and range no longer meet the application requirements. For example, monitoring and health assessment of equipment operating status in harsh environments with high temperature and high pressure such as rocket engines, aircraft engines, and heavy gas turbines, providing data support in underground oil extraction, detecting tsunamis and tides in marine science, and accurately positioning underwater operation robots all place higher requirements on the range and measurement accuracy of pressure sensors.

[0003] Resonant MEMS sensors have the advantages of high precision, small size, light weight, low power consumption, fast dynamic response, strong anti-interference ability, stable performance, and easy miniaturization and integration, which is conducive to maintaining high performance when measuring a large range of pressure. In order to achieve high-performance high-pressure sensors, the structural design must not only ensure the structural strength of the sensor under high-pressure full-scale measurement, but also make it have appropriate sensitivity and linearity. At present, most resonant pressure sensors adopt the beam-film integration theory, that is, the stress on the beam is consistent with the stress on the sensitive membrane, such as Chinese patent application CN113091984A (a resonant high-pressure sensor and its manufacturing method) and Chinese patent application CN114593846A (a silicon resonant high-pressure sensor with a high Q value and its manufacturing method). However, it is very difficult to expand the range of the sensor based only on the beam-film integration theory, and it is difficult to take into account both high sensitivity and pressure resistance at the same time. In order to improve the sensitivity, a dual-beam differential is used. Due to the uneven stress on the stress sensitive membrane and the narrow compressive stress area, the resonant beam The stress distribution on the sensor is also uneven and prone to large deviations, and the sensor will have a mismatch between positive and negative sensitivities; Yokogawa of Japan has adopted the body compression sensitivity principle when implementing a resonant high-pressure sensor in the published paper "High Pressure Resistance of Silicon Resonant Pressure Sensors", but the resonant beam is prone to buckling failure when under pressure. In order to achieve high-pressure measurement, Yokogawa has developed a groove diffusion method to bring a higher positive strain to the resonant beam, so that the resonant beam has an initial strain to avoid buckling under high pressure, but based on this principle, the process is complicated, and it is impossible to achieve differential pressure positive sensitivity, making it difficult to take into account both high sensitivity and high linearity. Because the various performances of resonant pressure sensors are contradictory when achieving high-pressure measurements, it is difficult to take into account both at the same time. There is no mature research and product of ultra-high-range resonant high-pressure sensors in China.

[0004] When designing the structure of a resonant high-pressure sensor, if it is based only on the beam-diaphragm integration theory, the range expansion is difficult, the sensitivity is low, and the differential sensitivity does not match. If it is based only on the body compression sensitivity principle, the process is complex and it is difficult to balance sensitivity and linearity. Summary of the invention

[0005] In view of the limitations of the performance of existing resonant high-pressure sensors, the present invention proposes a resonant high-pressure sensor based on beam-film sensitivity and body compression sensitivity. The composite pressure-sensitive principle is adopted in the structural design, that is, the beam-film theory and the body compression principle are taken into account at the same time, which can improve / expand the pressure sensitivity and range of the resonant pressure sensor, while maintaining uniform stress distribution on the resonant beam and improving the stability of the resonant frequency. The present invention achieves high sensitivity and high linearity while meeting the high withstand voltage requirement, providing technical support for the realization of high-precision high-range pressure sensors.

[0006] In order to achieve the above object, the present invention adopts the following technical scheme:

[0007] A resonant high-voltage sensor based on beam film sensitivity and body compression sensitivity, comprising an SOI wafer and a silicon cover plate, wherein the SOI wafer comprises a substrate layer, a buried oxide layer, and a device layer, and the device layer is provided with a driving electrode terminal, a bias voltage terminal, a detection electrode terminal, and an electrical isolation groove; the buried oxide layer is located between the substrate layer and the device layer; the driving electrode terminal is internally connected to a driving electrode for providing an AC drive to the resonant beam; the bias voltage terminal is internally connected to the resonant beam to provide a DC bias voltage; the detection electrode terminal is internally connected to a detection electrode for detecting the vibration frequency of the resonant beam; the driving electrode terminal, the bias voltage terminal, and the detection electrode terminal are connected to the ... The voltage terminals and the detection electrode terminals are both connected to the circuit with external metal leads; the electrical isolation grooves are located around each electrode to achieve electrical isolation; the device layer is used to design a sensitive structure, which is a resonant beam; the silicon cover plate and the SOI wafer are bonded and packaged to form a full-silicon structure sensor, and two resonant cavities of different widths are arranged on the silicon cover plate, namely a narrow resonant cavity and a wide resonant cavity, and two air suction cavities are arranged, and getters are deposited in all resonant cavities and air suction cavities; in order to achieve electrical isolation, an isolation groove is arranged on the silicon cover plate corresponding to the electrical isolation groove on the device layer, and all chambers are connected through the connecting groove to provide a single environment inside the sensor.

[0008] Furthermore, a double-ended fixed single beam is adopted, including a resonance beam I, a resonance beam II and an anchor point, and the excitation detection method is electrostatic excitation / capacitance detection; the resonance beam I and the resonance beam II are respectively fixed on the pressure sensitive membrane I and the pressure sensitive membrane II through the anchor point, and are located in the middle of the corresponding pressure sensitive membrane, and driving electrodes and detection electrodes are arranged on both sides of the resonance beam I and the resonance beam II to form a driving capacitor and a detection capacitor; the pressure sensitive membrane I and the pressure sensitive membrane II correspond to a narrow resonant cavity and a wide resonant cavity respectively, and the resonance beam I and the resonance beam II are respectively placed in the center of the narrow resonant cavity and the wide resonant cavity, and the stress states of the resonance beam I and the resonance beam II on the same horizontal plane are consistent; the deformation of the resonance beam in the wide resonant cavity caused by bending on the pressure sensing membrane II is dominant, and the resonance beam II presents tensile stress, and the resonance frequency is positive pressure sensitivity; the deformation caused by volume compression in the narrow resonant cavity is dominant, and the resonance beam I presents compressive stress, and the resonance frequency is negative pressure sensitivity; the resonator frequency changes in the narrow resonant cavity and the wide resonant cavity are opposite.

[0009] Furthermore, through holes are etched on the substrate layer at positions corresponding to the respective connection terminals to form lead holes. In order to pressure-weld the gold wires, metal electrodes are made in the lead holes, and ohmic contact is achieved through annealing.

[0010] Furthermore, it also includes a stress isolation layer, which is made of silicon wafers and has patterns etched on the upper and lower surfaces. The upper surface is four rectangular bosses that are bonded to the entire sensor, and the lower surface is a square groove that is fixed to the base by gluing.

[0011] Furthermore, the sensor, the resonant cavity and the pressure sensitive membrane are in the shape of a square, a rectangle, a circle or a polygon.

[0012] Furthermore, the resonant beam is a single beam, a tuning fork beam or an H-shaped beam.

[0013] Furthermore, the packaging bonding method of the silicon cover plate and the SOI wafer is silicon-silicon bonding or eutectic bonding.

[0014] Furthermore, the SOI sheet, silicon cover plate and stress isolation layer are made of silicon material, and the silicon material is one or a combination of SOI, single crystal silicon and polycrystalline silicon.

[0015] Beneficial effects:

[0016] (1) The present invention adopts the composite pressure sensitive principle. Compared with the existing beam-membrane integration theory and body compression principle, it can achieve high sensitivity and high linearity while ensuring high pressure resistance, and the process is simple;

[0017] (2) The resonant beam is placed in the middle of the resonant cavity. The stress at each point on the same horizontal plane of the resonant beam is basically the same. The stress average can improve the frequency stability, improve the measurement accuracy, and increase the process tolerance.

[0018] (3) The present invention realizes dual resonator design by designing resonant cavities with different widths. The differential of the positive and negative pressure sensitivity dual beams can further improve the pressure sensitivity and linearity, and at the same time can reduce the temperature characteristics and improve the anti-interference ability of the sensor;

[0019] (4) The present invention adopts a small cavity structure, which is beneficial to improving pressure resistance and integration, low cost and high manufacturing efficiency;

[0020] (5) The present invention uses bonding to realize a pure silicon sensitive core and a stress isolation layer, the mechanical properties of the materials are matched, the thermal stress is small when the temperature changes, and the accuracy and stability of the sensor pressure measurement can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the sensitive unit and its principle; the left figure is a schematic diagram of the structure and position of the resonant beam, anchor point and resonant cavity, and the right figure is a curve diagram of the relationship between the stress state on the resonant beam and the width of the resonant cavity;

[0022] Figure 2 It is a three-dimensional schematic diagram of the sensitive core;

[0023] Figure 3 This is the front view of SOI;

[0024] Figure 4 This is the overall structure diagram of the sensor.

[0025] In the figure, 1-resonance beam; 2-resonance cavity; 3-anchor point; 100-SOI sheet; 110-substrate layer; 120-buried oxide layer; 130-device layer; 140-driving electrode terminal; 150-bias voltage terminal; 160-detection electrode terminal; 170-electrical isolation groove; 200-silicon cover plate; 210-narrow resonant cavity; 220-wide resonant cavity; 230-intake cavity; 240-getter; 250-isolation groove; 260-connection groove; 300-pressure sensitive membrane I; 310-resonance beam I; 320-resonance beam II; 330-pressure sensitive membrane II; 340-SOI sheet anchor point; 350-driving electrode; 360-detection electrode; 111-lead hole; 112-metal electrode; 400-stress isolation layer. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0027] Since the resonant pressure sensor needs to provide a vacuum cavity for the resonant beam, but the cavity will reduce the pressure resistance of the sensor, in order to achieve high-range measurement, the cavity size should be as small as possible and within the pressure resistance limit size. In order to design the sensor, the present invention proposes a resonant high-pressure sensor based on beam film sensitivity and body compression sensitivity, which adopts a composite pressure sensitivity principle, such as Figure 1 As shown, a resonant high-pressure sensor based on beam film sensitivity and body compression sensitivity of the present invention includes a sensitive unit, and the sensitive unit mainly includes a resonant beam 1, a resonant cavity 2 and an anchor point 3. In order to achieve stress averaging, the resonant beam 1 is placed in the middle of the resonant cavity 2. The size of the resonant beam 1 is determined according to the fundamental frequency and process tolerance. The length of the resonant cavity 2 can be determined after considering the size of the anchor point 3. The width of the resonant cavity 2 can be deduced to the maximum limit size according to the pressure resistance requirements.

[0028] When the sensor is subjected to pressure as a whole, the deformation of the resonance beam 1 can be decomposed into membrane deformation and body compression. The corresponding position of the resonance cavity 2 is the pressure-sensitive membrane. Since the resonance beam 1 is anchored on the pressure-sensitive membrane, only considering the bending of the pressure-sensitive membrane under force will cause the resonance beam 1 to produce tensile deformation, and at this time, positive stress will appear on the resonance beam 1; when only considering body compression, the resonance beam 1 will produce extrusion deformation, and negative stress will appear on the resonance beam 1. The membrane deformation is related to the size of the resonance cavity 2, and the body compression is mainly related to the material characteristics of each component of the sensor. Figure 1 As shown in the right figure, when the width of the resonant cavity 2 increases, the positive stress on the resonant beam 1 caused by the membrane deformation continues to increase, while the negative stress on the resonant beam 1 caused by the body compression remains basically unchanged. Due to the different changing trends of positive and negative stresses, when the resonant cavity 2 increases within the allowable size range, the resultant stress on the resonant beam 1 can change from negative to positive, and when the resonant cavity 2 is at a certain width, the stress distribution on the resonant beam 1 is basically the same everywhere. Based on this composite sensitive principle, the resonant high-pressure sensor of the present invention can be extended to a range of 100MPa or even higher.

[0029] like Figure 2As shown, the sensitive core refers to the entire sensor chip, which mainly includes an SOI sheet 100 and a silicon cover plate 200, wherein the SOI sheet 100 includes a substrate layer 110, a buried oxide layer 120 and a device layer 130; wherein the buried oxide layer 120 is located between the substrate layer 110 and the device layer 130. The device layer 130 is mainly used to design a sensitive structure, and the sensitive structure refers to a resonant beam. In addition to two sensitive units, a driving electrode terminal 140, a bias voltage terminal 150, a detection electrode terminal 160 and an electrical isolation groove 170 are also provided. The sensitive unit includes a resonant beam, an anchor point and a resonant cavity. The driving electrode terminal 140 is internally connected to a driving electrode to provide an AC drive to the resonant beam. The bias voltage terminal 150 is internally connected to the resonant beam to provide a DC bias voltage. The detection electrode terminal 160 is internally connected to a detection electrode to detect the vibration frequency of the resonant beam. All three terminals are externally connected to metal leads and connected to the circuit, and the electrical isolation groove 170 is located around each electrode to achieve electrical isolation.

[0030] The silicon cover plate 200 and the SOI wafer 100 are bonded and packaged to form an all-silicon structure sensor. The same material has low thermal stress, which is conducive to improving the temperature characteristics of the sensor. In order to achieve different sensitivities for the two sensitive units, two resonant cavities of different widths are set on the silicon cover plate 200 to achieve positive and negative pressure sensitivity, which are equal in size. After differentiation, the sensitivity and linearity can be improved, including a narrow resonant cavity 210 and a wide resonant cavity 220. In order to reduce the mutual interference of the stress states inside the two resonant cavities, the positions of the two resonant cavities are as far away from each other as possible while ensuring good sealing, and on the other hand, they do not cross in the axial direction of the resonant beam. Since the small cavity structure may cause insufficient vacuum due to insufficient getter area, two additional getter cavities 230 are set, and getters 240 are deposited in all resonant cavities and getter cavities. In order to achieve electrical isolation, the isolation groove 250 is designed to correspond to the electrical isolation groove 170 on the device layer 130. In addition, all chambers are connected through the connection groove 260 to provide a single environment inside the sensor.

[0031] like Figure 3As shown, it is a front view of the SOI sheet 100, which more clearly shows the two sensitive units. In order to reduce the influence of the resonator structure on the stress in the cavity, the present invention adopts a double-end fixed single beam, including a resonant beam I 310, a resonant beam II 320 and an SOI sheet anchor point 340, and the excitation detection method selects electrostatic excitation / capacitive detection, including a driving electrode 350 and a detection electrode 360. The resonant beam I 310 and the resonant beam II 320 are respectively fixed on the pressure sensitive film I 300 and the pressure sensitive film II 330 through the anchor point 340, and are located in the middle of the corresponding sensitive film. The resonant beam I 310 and the resonant beam II 320 are both provided with a driving electrode 350 and a detection electrode 360 ​​on both sides to form a driving capacitor and a detection capacitor. The double resonator design is adopted. The pressure sensitive membrane I300 and the pressure sensitive membrane II330 correspond to the narrow resonant cavity 210 and the wide resonant cavity 220 respectively. The resonant beam I310 and the resonant beam II320 are respectively placed in the center of the two resonant cavities. The stress states of the two resonant beams are consistent at all locations on the same horizontal plane. The deformation of the resonant beam in the wide resonant cavity 220 caused by bending on the pressure sensitive membrane II330 is dominant, and the resonant beam II320 presents tensile stress, and the resonant frequency is positive pressure sensitivity; the deformation caused by overall compression in the narrow resonant cavity 210 is dominant, and the resonant beam I310 presents compressive stress, and the resonant frequency is negative pressure sensitivity. The resonator frequencies in the two cavities with different widths change in opposite directions. The difference frequency characterization of pressure can improve sensitivity and linearity. At the same time, since the dual beams have the same size and similar temperature sensitivity, the difference can also reduce the temperature sensitivity, which is beneficial to temperature compensation.

[0032] like Figure 4 As shown, in order to achieve electrical connection, through holes need to be etched on the substrate layer 110 at the corresponding positions of each terminal to form lead holes 111. At the same time, in order to press-weld the gold wire, metal electrodes 112 need to be made in the holes, and ohmic contact is achieved through annealing. The sensor needs to be assembled when it is put into practical application. However, due to the large difference in thermal expansion coefficients between the shell material and the sensitive core material, direct assembly will introduce thermal stress, and a greatly increased temperature coefficient will reduce the measurement accuracy of the sensor. Therefore, in addition to the sensitive core, the overall structure also includes a stress isolation layer 400. The silicon wafer is used to etch patterns on the upper and lower surfaces. The upper surface is four rectangular bosses, which are bonded to the sensitive core, and the lower surface is a square groove, which is fixed to the base by gluing and other methods. To a large extent, the thermal stress caused by assembly can be isolated to ensure high accuracy of sensor measurement.

[0033] Preferably, the shapes of the overall sensitive core, the resonant cavity and the pressure sensitive membrane include but are not limited to square, rectangular, circular and polygonal;

[0034] Preferably, the form of the resonant beam includes but is not limited to a single beam, a tuning fork beam, an H-beam, etc., and the driving detection method may adopt other principles;

[0035] Preferably, the number, size and position of the resonant beam, the resonant cavity and the air suction cavity can be adjusted within a reasonable range;

[0036] Preferably, the packaging bonding method between the silicon cover plate 200 and the SOI wafer 100 includes but is not limited to silicon-silicon bonding, eutectic bonding, etc.;

[0037] Preferably, the SOI sheet 100, the silicon cover plate 200 and the stress isolation layer 400 are made of silicon material, and the silicon material includes one or a combination of SOI, single crystal silicon and polycrystalline silicon;

[0038] Preferably, the presence or absence and form of the stress isolation layer 400 are preferred options and can be adjusted within a reasonable range.

[0039] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A resonant high-pressure sensor based on beam-film sensitivity and body compression sensitivity, characterized in that: The invention comprises an SOI sheet and a silicon cover plate, wherein the SOI sheet comprises a substrate layer, a buried oxide layer and a device layer, and the device layer is provided with a driving electrode terminal, a bias voltage terminal, a detection electrode terminal and an electrical isolation groove; the buried oxide layer is located between the substrate layer and the device layer; the driving electrode terminal is internally connected to a driving electrode for providing an AC drive to a resonance beam; the bias voltage terminal is internally connected to a resonance beam for providing a DC bias voltage; the detection electrode terminal is internally connected to a detection electrode for detecting the vibration frequency of the resonance beam; the driving electrode terminal, the bias voltage terminal, the detection electrode terminal are connected to the detection electrode terminal, and the detection electrode terminal is connected to the detection electrode terminal. The wire terminals are all connected to the circuit with external metal leads; the electrical isolation grooves are located around each electrode to achieve electrical isolation; the device layer is used to design a sensitive structure, which is a resonant beam; the silicon cover plate is bonded and packaged with the SOI wafer to form a full silicon structure sensor, and two resonant cavities of different widths are arranged on the silicon cover plate, namely a narrow resonant cavity and a wide resonant cavity, and two air suction cavities are arranged, and getters are deposited in all resonant cavities and air suction cavities; in order to achieve electrical isolation, an isolation groove is arranged on the silicon cover plate corresponding to the electrical isolation groove on the device layer, and all chambers are connected through the connecting groove so that the inside of the sensor has a single environment; A double-ended fixed single beam is adopted, including a resonant beam I, a resonant beam II and an anchor point, and an excitation detection method is selected as electrostatic excitation / capacitive detection; the resonant beam I and the resonant beam II are respectively fixed on the pressure sensitive membrane I and the pressure sensitive membrane II through the anchor point, and are located in the middle of the corresponding pressure sensitive membrane, and driving electrodes and detection electrodes are arranged on both sides of the resonant beam I and the resonant beam II for forming a driving capacitor and a detection capacitor; the pressure sensitive membrane I and the pressure sensitive membrane II correspond to a narrow resonant cavity and a wide resonant cavity respectively, and the resonant beam I and the resonant beam II are respectively placed in the center of the narrow resonant cavity and the wide resonant cavity, and the stress states of the resonant beam I and the resonant beam II on the same horizontal plane are consistent; the deformation of the resonant beam in the wide resonant cavity caused by bending on the pressure sensing membrane II is dominant, and the resonant beam II presents tensile stress, and the resonant frequency is positive pressure sensitivity; the deformation caused by volume compression in the narrow resonant cavity is dominant, and the resonant beam I presents compressive stress, and the resonant frequency is negative pressure sensitivity; the resonator frequency changes in the narrow resonant cavity and the wide resonant cavity are opposite.

2. A resonant high-pressure sensor based on beam-film sensitivity and body-compression sensitivity according to claim 1, characterized in that: Through holes are etched on the substrate layer at positions corresponding to the various connection terminals to form lead holes. In order to press-weld the gold wires, metal electrodes are made in the lead holes, and ohmic contact is achieved through annealing.

3. A resonant high-pressure sensor based on beam-film sensitivity and body-compression sensitivity according to claim 1, characterized in that: It also includes a stress isolation layer, which uses a silicon wafer to etch patterns on the upper and lower surfaces. The upper surface is four rectangular bosses that are bonded to the entire sensor, and the lower surface is a square groove that is fixed to the base by gluing.

4. A resonant high-pressure sensor based on beam-film sensitivity and body-compression sensitivity according to claim 1, characterized in that: The shape of the sensor, the resonant cavity and the pressure sensitive membrane is square, rectangular, circular or polygonal.

5. The resonant high-pressure sensor based on beam-film sensitivity and body-compression sensitivity according to claim 1, characterized in that: The resonant beam is a single beam, a tuning fork beam or an H-beam.

6. The resonant high-pressure sensor based on beam-film sensitivity and body-compression sensitivity according to claim 1, characterized in that: The packaging bonding method of the silicon cover plate and the SOI wafer is silicon-silicon bonding or eutectic bonding.

7. The resonant high-pressure sensor based on beam-film sensitivity and body-compression sensitivity according to claim 1, characterized in that: The SOI sheet, silicon cover plate and stress isolation layer are made of silicon material, and the silicon material is single crystal silicon, polycrystalline silicon or a combination of several thereof.

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