A static pressure compensation silicon resonant micro differential pressure sensor and a preparation method thereof

Abstract

The application provides a static pressure compensation silicon resonance micro differential pressure sensor and a preparation method thereof. The sensor comprises a composite diaphragm, which comprises, from top to bottom, a packaging layer, a resonator layer and a pressure sensitive membrane layer. The resonator layer comprises a pressure sensitive resistor and two resonators, which are respectively located in the middle region and the edge region of the sensitive membrane layer. The pressure sensitive resistor is located at the edge of the pressure sensitive membrane layer and is connected with the packaging layer. The pressure sensitive resistor is used for detecting the size of static pressure. In order to realize differential pressure measurement, the pressure membrane, the resonator layer and the packaging layer are combined to form a buried resonator composite diaphragm. The pressure difference on both sides of the diaphragm causes the deformation of the diaphragm, and the stress is transmitted to the resonator buried in the diaphragm, so as to be converted into the frequency change of the resonator. The frequency deviation of the resonator caused by the static pressure is compensated by hardware or software, so as to expand the measurement range and the range ratio of the sensor and finally improve the measurement accuracy of the sensor.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of MEMS micro-sensors, in particular to a static pressure compensated silicon resonant micro-differential pressure sensor and a preparation method thereof. BACKGROUND

[0002] The development of unmanned aerial vehicles, hypersonic vehicles and other technologies has higher requirements for the precision of sensors. When the vehicle works in low-speed, low-pressure and other environments, it needs to accurately measure its flight parameters to meet the needs of high-precision attitude control. Silicon resonant pressure sensors have been widely used in the aerospace field due to their good stability and high measurement accuracy. However, the complex resonator structure of silicon resonant pressure sensors and the special requirements of vacuum packaging make their design and preparation extremely difficult. Currently, the differential pressure sensors developed by foreign countries have achieved a high level of precision, and have advantages in static pressure compensation. For example, the differential pressure sensor based on surface silicon technology developed by Yokogawa Corporation of Japan can achieve an accuracy of 0.2% FS under a static pressure of 12 MPa. However, domestic research is relatively less, and there is a lack of mature high-precision products with independent intellectual property rights.

[0003] In the design of silicon resonant micro-differential pressure sensors, the thick packaging structure resulting from the need for vacuum packaging of the resonator with certain structural size requirements limits the improvement of sensor sensitivity. In addition, the actual working environment of the sensor has large changes in static pressure. For example, the working pressure of aircraft such as unmanned aerial vehicles and aerostats can vary from 100 kPa to below 2 kPa. The cavity structure required for the operation of the resonator results in a certain static pressure sensitivity of the resonator, making it difficult to achieve high precision in complex working environments.

[0004] In terms of preparation process, the preparation process required for silicon resonant micro-differential pressure sensors is complex and difficult to meet the requirements simultaneously. To improve the sensitivity of the differential pressure sensor, a self-aligned selective silicon epitaxial growth process is used to locally package the resonator. This method has problems such as resonator release adhesion, poor release side drilling control accuracy, and high preparation difficulty. The cited technologies of CN461438A, CN579147B, CN114993520A, etc. use glass or silicon to seal and package the resonator, with a packaging layer thickness of more than 10 μm. This makes it difficult for the resonator to be close to the surface, limiting the improvement of sensitivity and making it difficult to meet the requirements of micro-differential pressure measurement.

[0005] Therefore, in view of the application requirements of silicon resonant micro-differential pressure, it is necessary to design a new high-sensitivity micro-differential pressure sensor with static pressure compensation capability and to study its preparation method. SUMMARY

[0006] To address the aforementioned technical problems, this invention proposes a static pressure compensated silicon resonant differential pressure sensor and its fabrication method, thereby resolving the aforementioned technical issues.

[0007] The first aspect of this invention discloses a static pressure compensated silicon resonant differential pressure sensor, comprising a composite diaphragm. The composite diaphragm includes an encapsulation layer, a resonator layer, and a pressure-sensitive diaphragm layer arranged sequentially from top to bottom. The resonator layer includes a piezoresistor and two resonators, which are respectively located in the middle region and the edge region of the pressure-sensitive diaphragm layer. The piezoresistor is located at the edge of the pressure-sensitive diaphragm layer and is connected to the encapsulation layer. The piezoresistor is used to detect the static pressure magnitude.

[0008] Optionally, the resonator layer includes a filling structure that surrounds and spaced apart from the resonator and varistor. The upper and lower sides of the filling structure are connected to the encapsulation layer and the pressure-sensitive film layer, respectively, to seal the resonator.

[0009] Alternatively, the resonator is located on one side close to the upper surface of the composite diaphragm.

[0010] Optionally, the pressure-sensitive membrane layer includes an insulating layer, which is in contact with the resonator layer, and the insulating layer is made of silicon oxide; the movable part of the resonator is suspended.

[0011] Optionally, the pressure-sensitive membrane layer includes a pressure-sensitive membrane located in a thin film region below the insulating layer. The thin film region corresponds to the region where the resonator and varistor are located. The pressure-sensitive membrane is used to transfer stress to the resonator under pressure deformation.

[0012] Optionally, the encapsulation layer includes an oxide layer formed on the lower surface of the encapsulation layer; the oxide layer includes two resonator grooves; the resonator grooves correspond to the resonator beam of the resonator layer and are used to provide space for the resonator beam to vibrate.

[0013] Optionally, the oxide layer also includes a getter groove containing a getter, the getter groove corresponding to the resonator layer filling structure and communicating with the resonator groove.

[0014] Optionally, the encapsulation layer includes a support layer formed on the upper surface of the encapsulation layer to support the oxide layer; the support layer has a hollow structure in the corresponding area of ​​the composite film to provide space for the deformation of the composite film; the support layer has lead through holes at the corresponding positions of the lead electrodes of the resonator layer for lead interconnection.

[0015] Optionally, the sensor further comprises: an upper cover layer located above the packaging layer for conducting and sealing the measured air pressure, having a gas guide hole and a gas guide groove, and communicating with the hollowed area of the support layer; a lower cover layer located above the pressure sensitive membrane layer for conducting and sealing the measured air pressure, comprising: a gas guide groove, a first air hole and a second air hole; the gas guide groove communicates with the area where the pressure sensitive membrane is located; the first air hole penetrates through the lower cover layer and communicates with the gas guide groove; the second air hole penetrates through the lower cover layer, the pressure sensitive membrane layer, the resonator layer and the packaging layer, and corresponds to the gas guide hole of the upper cover layer.

[0016] The second aspect of the present application provides a preparation method of a static pressure compensated silicon resonant micro differential pressure sensor, comprising the following steps:

[0017] S1, using dry etching to etch an SOI wafer to form a pressure sensitive membrane on an SOI base layer, and etching a resonator layer structure on an SOI device layer;

[0018] S2, releasing the resonator to form a movable part of the resonator and form a resonator layer;

[0019] S3, double-side oxidizing a first silicon wafer with an oxidation thickness of 3-5 μm, patterning and etching the oxide layer to form a resonator groove and a getter groove;

[0020] S4, patterning a Cr / Au layer on the surface of the oxide layer, and depositing a getter in the getter groove;

[0021] S5, bonding the oxide wafer with the SOI under vacuum conditions;

[0022] S6, using dry / wet etching to etch / etch the corresponding area of the pressure sensitive membrane and the lead electrode on the support layer, retaining a thin oxide layer to form a buried resonator composite membrane;

[0023] S7, drilling the bonded wafer at the position of the gas guide hole of the upper cover layer;

[0024] S8, double-side oxidizing a second silicon wafer, patterning the oxide layer, forming a gas guide hole and a gas guide groove by dry etching technology, and drilling the gas guide hole to prepare a lower cover layer;

[0025] S9, depositing a layer of Cr / Au metal on the surface of the lower cover layer and bonding with the SOI base layer to seal and package the pressure sensitive membrane;

[0026] S10, double-side oxidizing a third silicon wafer, patterning the oxide layer, forming a gas guide hole and a gas guide groove by dry etching technology to prepare an upper cover layer;

[0027] S11, depositing a layer of Cr / Au metal on the surface of the upper cover layer and bonding with the packaging layer of the bonded wafer to seal the packaging layer and form a micro differential pressure sensor chip.

[0028] In summary, the present application proposes a resonant differential pressure sensor structure with high sensitivity. To realize differential pressure measurement, the buried resonator composite diaphragm is composed of pressure diaphragm, resonator layer and packaging layer. The pressure difference on both sides makes the diaphragm deform and transmits stress to the resonator buried in the diaphragm, thereby converting into resonator frequency change. To reduce the influence of static pressure on resonator frequency, the sensor is provided with a pressure-sensitive resistor, which compensates for the frequency offset caused by static pressure through hardware or software, thereby expanding the measurement range of the sensor and improving the measurement accuracy. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the drawings needed to be used in the specific embodiments or prior art description will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0030] Figure 1 The sensor stack structure according to the embodiment of the present application is shown in the figure.

[0031] Figure 2 The resonator layer structure according to the embodiment of the present application is shown in the figure.

[0032] Figure 3 The buried resonator composite diaphragm structure according to the embodiment of the present application is shown in the figure.

[0033] Figure 4 The process flow chart of the preparation method of the static pressure compensation silicon resonant differential pressure sensor according to the embodiment of the present application is shown in the figure.

[0034] In the figure: 100 - upper cover layer; 210 - packaging layer; 211 - support layer; 212 - oxide layer; 213 - resonator groove; 220 - resonator layer; 221 - resonator; 222 - piezoresistor; 223 - filling structure; 224 - resonator layer vent hole; 230 - pressure sensitive membrane layer; 232 - pressure sensitive membrane; 233 - insulating layer; 240 - composite diaphragm; 300 - lower cover layer; 310 - air guide groove; 320 - first vent hole; 330 - second vent hole. DETAILED DESCRIPTION

[0035] In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0036] Referring to Figures 1 to 3 The first aspect of the present application discloses a static pressure compensation silicon resonant micro differential pressure sensor, comprising a composite diaphragm 240, the composite diaphragm 240 comprising a packaging layer 210, a resonator layer 220 and a pressure sensitive membrane layer 230 arranged from top to bottom in sequence, the resonator layer 220 comprising a pressure sensitive resistor 222 and two resonators 221, the two resonators 221 being located at the middle region and the edge region of the sensitive membrane layer 230 respectively; the pressure sensitive resistor 222 is located at the edge of the pressure sensitive membrane layer 230 and the pressure sensitive resistor 222 is connected with the packaging layer 210, and the structure of the pressure sensitive resistor 222 is in a suspended state for detecting the size of the static pressure.

[0037] Further, the resonator layer 220 comprises a filling structure 223, the filling structure 223 surrounds the resonator 221 and the pressure sensitive resistor 222 and maintains a small spacing with them. The upper and lower sides of the filling structure 223 are connected with the packaging layer 210 and the pressure sensitive membrane layer 230 respectively for supporting the oxide film to realize the sealing of the resonator.

[0038] Further, the resonator 221 is located on the side close to the upper surface of the composite diaphragm 240.

[0039] Further, the pressure sensitive membrane layer 230 comprises an insulating layer 233, the insulating layer 233 is connected with the resonator layer 220, and the manufacturing material of the insulating layer 233 comprises silicon oxide; the movable part of the resonator 221 is suspended.

[0040] Further, the pressure sensitive membrane layer 230 comprises a pressure sensitive membrane 232, the pressure sensitive membrane 232 is located in a thin film region below the insulating layer 233, the thin film region corresponds to the regions where the resonator 221 and the pressure sensitive resistor 222 are located, and the pressure sensitive membrane 232 is used for deforming under pressure to transmit stress to the resonator 221.

[0041] Further, the packaging layer 210 comprises an oxide layer 212 formed on the lower surface of the packaging layer 210; the oxide layer 212 comprises two resonator grooves; the resonator grooves correspond to the resonator beams of the resonator layer 220, and are used for providing vibration space for the resonator beams.

[0042] Further, the oxide layer 212 further comprises a getter groove, the getter groove is provided with a getter, the getter groove corresponds to the filling structure of the resonator layer and is communicated with the resonator grooves.

[0043] Further, the packaging layer 210 includes a support layer 211 formed on the upper surface of the packaging layer 210 for supporting the oxidation layer 212; the support layer 211 is a hollow structure in the area corresponding to the composite diaphragm 240, providing the space required for the deformation of the composite diaphragm 240; the support layer 211 has lead through holes at the positions corresponding to the lead electrodes of the resonator layer 220 for lead interconnection.

[0044] Further, the sensor further includes: an upper cover layer 100 located above the packaging layer for conducting and sealing the measured gas pressure, having a gas guide hole and a gas guide groove thereon, and communicating with the hollow area of the support layer 211;

[0045] A lower cover layer 300 is located above the pressure sensitive membrane layer 230 for conducting and sealing the measured gas pressure, including: a gas guide groove 310, a first air hole 320 and a second air hole 330; the gas guide groove 310 communicates with the area where the pressure sensitive membrane 232 is located; the first air hole 320 penetrates through the lower cover layer 300 and communicates with the gas guide groove 310; the second air hole 330 penetrates through the lower cover layer 300, the pressure sensitive membrane layer 230, the resonator layer 220 and the packaging layer 210, and corresponds to the gas guide hole of the upper cover layer 100.

[0046] More specifically, the sensor chip is composed of the upper cover layer 100, the packaging layer 210, the resonator layer 220, the pressure sensitive membrane layer 230 and the lower cover layer 300 from top to bottom. Among them, the upper cover layer 100 is made of silicon, composed of a gas guide groove and an electrode groove.

[0047] The packaging layer 210 is composed of the support layer 211, the oxidation layer 212 made of silicon oxide, the getter, the resonator groove 213, the packaging layer gas guide hole.

[0048] The resonator layer 220 is composed of the resonator 221, the pressure sensitive resistor 222, the filling structure 223, the resonator layer air hole 224 and the isolation groove.

[0049] The pressure sensitive membrane layer 230 includes a combined layer 231 of silicon oxide and silicon. The pressure sensitive membrane 232 is formed on the pressure sensitive membrane layer 230 and located below the resonator 221 and the pressure sensitive resistor structure.

[0050] The pressure-sensitive resistor structure is located at the edge of the pressure-sensitive membrane 232, and the deformation of the pressure-sensitive membrane 232 has no effect on the pressure-sensitive resistor 222. On the pressure-sensitive membrane layer 230, there is no silicon oxide under the resonator beam and the pressure-sensitive resistor structure, which is used to provide space for the vibration and deformation of the resonator beam. The pressure-sensitive resistor structure is in direct contact with the oxide layer 212, and the static pressure can cause the pressure-sensitive resistor structure to deform towards the pressure-sensitive membrane 232, thereby changing the resistance and thus sensing the static pressure. Further, the resonator 221, the filling structure 223, the oxide layer 212 and the pressure-sensitive membrane 232 constitute a composite diaphragm 240 of the buried resonator, and the resonator is close to the upper surface of the composite diaphragm 240, which can maximize the differential pressure sensitivity. The lower cover layer 300 is composed of a gas guide groove 310, a first vent hole 320 and a second vent hole 330. The first vent hole 320 penetrates the lower cover layer 300, and the second vent hole 330 penetrates the lower cover layer 300, the pressure-sensitive membrane layer 230, the resonator layer 220 and the packaging layer 210, and is in communication with the gas guide groove of the upper cover layer. The first vent hole 320 and the second vent hole 330 are respectively in communication with the pressure to be detected, so that the pressure to be measured is transmitted to the two surfaces of the composite diaphragm 240 of the buried resonator, and isolation with the electrode structure is achieved.

[0051] The present application adopts a double resonator structure, which is respectively a first resonator and a second resonator. When the pressure on the upper surface of the composite diaphragm is greater than that on the lower surface, the first resonator is subjected to compressive stress and the second resonator is subjected to tensile stress, and their frequencies respectively decrease and increase, and the frequency difference is negative. When the pressure on the upper surface of the composite diaphragm is less than that on the lower surface, the first resonator is subjected to tensile stress and the second resonator is subjected to compressive stress, and their frequencies respectively increase and decrease, and the frequency difference is positive. Therefore, the frequency difference can be used to represent the differential pressure, and the sign of the frequency difference represents the direction of the differential pressure, and bidirectional differential pressure measurement can be achieved.

[0052] Because there is a gap between the resonator 221 and the packaging shell, the pressure applied on the packaging layer 210 will inevitably cause the silicon oxide to deform and transmit stress to the two resonators 221, thereby generating an additional frequency difference and further affecting the measurement accuracy. Therefore, the present application provides a piezoresistive structure. Because the piezoresistive structure is in contact with the silicon oxide packaging layer and is suspended. The static pressure applied on the upper surface causes the silicon oxide packaging layer to deform towards the resonator layer, thereby causing the piezoresistive structure to deform and causing the piezoresistive change. The resistance value can represent the size of the applied pressure. The resistance change is compensated for the two-way frequency through software or hardware circuit, thereby suppressing the influence of static pressure. It should be noted that, in order to make the resonator 221 tend to the surface of the composite diaphragm as much as possible. At the same time, in order to improve the effect of static pressure compensation and improve the surface piezoresistive effect, the resonator layer should be as thin as possible, generally 3-5 μm.

[0053] In other embodiments, the silicon oxide packaging layer includes but is not limited to thin layer materials of equivalent stiffness of silicon, silicon nitride, glass and the like.

[0054] In other embodiments, the piezoresistor can also use an external commercial piezoresistor, or other piezoresistive material as an alternative solution;

[0055] In other embodiments, Au-Si bonding is only used as an embodiment, and other alternative stack bonding technologies include but are not limited to silicon-silicon bonding, silicon glass bonding, solder bonding, etc.

[0056] In order to solve the problems of packaging vacuum and sensitivity, the sensor is packaged by a silicon oxide thin layer, so that the resonator can be as close as possible to the surface of the composite diaphragm, and the sensitivity is improved. In order to improve the static pressure resistance of the sensor, the structures of the resonator layer are isolated by a small gap, so as to prevent the silicon oxide packaging layer from breaking. In order to reduce the influence of static pressure on the frequency of the resonator, the sensor is provided with a piezoresistor, and the frequency deviation caused by the static pressure is compensated by hardware or software, so as to expand the measurement range of the sensor and improve the measurement accuracy. In order to avoid the influence of the measurement medium, humidity and the like on the sensor electrode, the upper and lower cover layers are designed, so that the measurement medium is isolated from the sensor electrode, the reliability of the sensor chip is improved, and the measurement demand of gas and non-corrosive liquid can be met.

[0057] In summary, the resonator is prepared by using a thin SOI layer, and a silicon oxide thin layer is used as a packaging layer, so that the resonator tends to the surface of the composite diaphragm, and the sensitivity of the sensor to differential pressure is effectively improved. By the structural design of the multi-layer stack bonding, the measured gas medium is sealed in the channels on both sides of the diaphragm, so as to avoid the medium corrosion of the lead electrode and the like, and better medium compatibility is achieved. The piezoresistor is formed in the resonator layer, the resistance value changes due to the static pressure of the diaphragm, and the static pressure error compensation of the micro-differential pressure sensor can be used to improve the comprehensive accuracy; the micro-differential pressure is represented by the frequency of the double resonator, and the bidirectional differential pressure measurement can be realized, so as to meet various application scenarios of the gauge pressure and the differential pressure.

[0058] The second aspect of the present application discloses a preparation method of a static pressure compensation silicon resonant micro-differential pressure sensor, which is used for manufacturing the static pressure compensation silicon resonant micro-differential pressure sensor of the first aspect of the present application, and the preparation method comprises the following steps:

[0059] S1, using dry etching SOI wafer to form a pressure sensitive film on the SOI substrate layer, and etching to form a resonator layer structure on the SOI device layer;

[0060] S2, releasing the resonator to form a resonator movable part and form a resonator layer;

[0061] S3, double-side oxidizing the first silicon wafer with an oxidation thickness of 3-5 μm, patterning and etching the silicon oxide layer to form a resonator groove and a getter groove;

[0062] S4, patterning a Cr / Au layer on the surface of the oxidation layer, and depositing a getter in the getter groove;

[0063] S5, bonding the silicon oxide wafer with the SOI under vacuum condition;

[0064] S6, etching / etching the corresponding area of the support laminated pressure sensitive membrane and lead electrode by dry / wet etching, retaining the silicon oxide thin layer, and forming a buried resonator composite wafer;

[0065] S7, drilling holes in the bonding wafer at the position of the gas guide hole of the upper cover layer;

[0066] S8, double-sided oxidation of the second silicon wafer, patterning the oxide layer, forming gas guide holes and gas guide grooves by dry etching technology, and drilling holes in the gas guide holes to prepare the lower cover layer;

[0067] S9, depositing a layer of Cr / Au metal on the surface of the lower cover layer and bonding with the SOI base layer to seal and package the pressure sensitive membrane;

[0068] S10, double-sided oxidation of the third silicon wafer, patterning the silicon oxide layer, forming gas guide holes and gas guide grooves by dry etching technology to prepare the upper cover layer;

[0069] S11, depositing a layer of Cr / Au metal on the surface of the upper cover layer and bonding with the packaging layer of the bonding wafer to seal the packaging layer and form a micro differential pressure sensor chip.

[0070] Referring to Figure 4 More specifically, the preparation process is divided into four aspects, including the upper cover layer, the lower cover layer, the packaging layer and the resonator layer, and the specific steps are as follows:

[0071] First, in terms of the resonator layer, SOI is selected as the processing substrate to simplify the process. The specific processing steps include:

[0072] Photolithography is performed on the back of the SOI, and pressure sensitive membrane is prepared by dry etching;

[0073] Photolithography is performed on the front of the SOI, and resonator, piezoresistance and other structures are prepared by dry etching;

[0074] Release the resonator beam and piezoresistance structure, etch and remove the silicon oxide under the resonator beam and piezoresistance to form a movable structure;

[0075] Second, in terms of the packaging layer, a silicon wafer is selected for processing, and the specific steps include:

[0076] Single-sided oxidation of the lower surface of the silicon wafer, with an oxidation thickness of 3-5 μm;

[0077] Sputtering Cr / Au metal layer on the lower surface and patterning to form bonding area;

[0078] The lower surface is patterned by photolithography and etched to form resonator grooves and getter grooves;

[0079] Vacuum encapsulation is achieved by depositing getter in a getter tank and bonding the encapsulation layer to the SOI resonator layer under vacuum conditions.

[0080] The upper surface of the encapsulation layer is etched until the silicon oxide self-stops, forming a buried layer resonator composite film.

[0081] Drilling is performed on the bonding sheet to form a gas guide hole 1, forming the main body of the differential pressure sensor chip;

[0082] Secondly, regarding the top capping layer, silicon wafers are used for processing, and the specific steps include:

[0083] The upper capping silicon wafer is subjected to double-sided oxidation, and the lower surface silicon oxide is patterned;

[0084] The exposed silicon on the lower surface is etched to form a gas channel.

[0085] Electrode grooves are formed by using laser etching or sandblasting processes to create grooves in silicon wafers;

[0086] A Cr / Au layer is deposited on the lower surface of the upper capping silicon wafer.

[0087] Finally, for the lower capping layer, silicon wafers are used for processing, and the specific steps include:

[0088] The lower capping silicon wafer is subjected to double-sided oxidation, and the upper surface silicon oxide is patterned;

[0089] The exposed silicon on the upper surface is etched to form a gas guide groove;

[0090] The silicon wafer is drilled using laser etching or sandblasting processes to form the first vent hole and the second vent hole;

[0091] A Cr / Au layer is deposited on the upper surface of the lower capping silicon wafer.

[0092] The upper capping layer, the chip body, and the lower capping layer are aligned and bonded in sequence to form a stacked bonded chip.

[0093] The silicon oxide of the encapsulation layer electrode portion is removed, and an AL metal layer is deposited in the lead hole for lead interconnection.

[0094] The application is to realize differential pressure measurement, through the pressure diaphragm, resonator layer, packaging layer to form the buried resonator composite diaphragm, the pressure difference of two sides makes the diaphragm deformation, and the stress is transmitted to the resonator buried in the diaphragm, thereby converting into the resonator frequency change. In order to reduce the influence of static pressure on the resonator frequency, the sensor is provided with a pressure-sensitive resistor, and the resonator frequency offset caused by static pressure is compensated through hardware or software, thereby expanding the measurement range and range ratio of the sensor and finally improving the measurement accuracy of the sensor.

[0095] Please note that the technical features of the above embodiments can be combined in any way. In order to make the description simple, all possible combinations of the technical features in the above embodiments are not described, however, as long as the combination of the technical features does not exist contradictory, it should be considered as the scope of the description. The above embodiments only express several embodiments of the application, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of the patent. It should be pointed out that for those skilled in the art, without departing from the concept of the application, a number of modifications and improvements can be made, which are all within the scope of the application. Therefore, the scope of the patent of the application should be subject to the appended claims.

Claims

1. A static pressure compensated silicon resonant micro differential pressure sensor, comprising a composite diaphragm (240) comprising, from top to bottom, a packaging layer (210), a resonator layer (220), and a pressure sensitive membrane layer (230), characterized in that: the resonator layer (220) comprises a pressure sensitive resistor (222) and two resonators (221), the two resonators (221) being located at the middle region and the edge region of the pressure sensitive membrane layer (230) respectively; the pressure sensitive resistor (222) is located at the edge of the pressure sensitive membrane layer (230) and interfaces with the packaging layer (210), and is used for detecting the size of static pressure; the resonator layer (220) comprises a filling structure (223) surrounding and spaced apart from the resonators (221) and the pressure sensitive resistor (222), and the upper and lower sides of the filling structure (223) are connected with the packaging layer (210) and the pressure sensitive membrane layer (230) respectively to seal the resonators; the resonators (221) are located on one side close to the upper surface of the composite diaphragm (240); the pressure sensitive membrane layer (230) comprises an insulating layer (233) interfacing with the resonator layer (220), and the manufacturing material of the insulating layer (233) comprises silicon oxide; and the movable part of the resonator (221) is suspended; the pressure sensitive membrane layer (230) comprises a pressure sensitive membrane (232) located in a thin film region below the insulating layer (233), the thin film region corresponding to the regions where the resonators (221) and the pressure sensitive resistor (222) are located, and the pressure sensitive membrane (232) is used for transmitting stress to the resonators (221) by deforming under pressure; the packaging layer (210) comprises an oxidation layer (212) formed on the lower surface of the packaging layer (210); the oxidation layer (212) comprises two resonator grooves corresponding to the resonator beams of the resonator layer (220) for providing vibration space for the resonator beams.

2. The static pressure-compensated silicon resonant micro differential pressure sensor according to claim 1, characterized in that, The oxidation layer (212) further comprises a getter groove containing a getter, the getter groove corresponding to the filling structure of the resonator layer and communicating with the resonator grooves.

3. The static pressure compensated silicon resonant micro differential pressure sensor according to claim 2, characterized in that, The packaging layer (210) comprises a support layer (211) formed on the upper surface of the packaging layer (210) for supporting the oxidation layer (212); the support layer (211) is a hollow structure in the corresponding region of the composite diaphragm (240) to provide space required for deformation of the composite diaphragm (240); and the support layer (211) has lead through holes at positions corresponding to the lead electrodes of the resonator layer (220) for lead interconnection.

4. The static pressure compensated silicon resonant micro differential pressure sensor according to claim 3, characterized in that, wherein, the sensor further comprises: an upper cover layer (100) located above the packaging layer for conducting and sealing the measured gas pressure, having a gas guide hole and a gas guide groove, and communicating with the hollow region of the support layer (211); The lower cover layer (300) is located above the pressure sensitive membrane layer (230) and is used for conducting and sealing the pressure to be measured, and comprises a gas guide groove (310), a first air hole (320) and a second air hole (330); the gas guide groove (310) is communicated with the area where the pressure sensitive membrane (232) is located; the first air hole (320) penetrates the lower cover layer (300) and is communicated with the gas guide groove (310); the second air hole (330) penetrates the lower cover layer (300), the pressure sensitive membrane layer (230), the resonator layer (220) and the packaging layer (210) and corresponds to the gas guide hole of the upper cover layer (100).

5. A method for manufacturing a hydrostatically compensated silicon resonant micro differential pressure sensor according to any one of claims 1 to 4, characterized in that The method comprises the following steps: S1, using dry etching to etch the SOI wafer to form the pressure sensitive membrane (232) on the SOI base layer and to form the resonator layer structure on the SOI device layer; S2, releasing the resonator (221) to form the resonator movable part and form the resonator layer (220); S3, double-side oxidizing the first silicon wafer with an oxidation thickness of 3-5 μm, patterning and etching the oxide layer to form the resonator groove and the getter groove; S4, patterning the Cr / Au layer on the surface of the oxide layer and depositing the getter in the getter groove; S5, bonding the oxide wafer with the SOI under vacuum condition; S6, using dry / wet etching to etch / etch the corresponding area of the support layer pressure sensitive membrane (232) and the lead electrode, retaining the thin oxide layer to form the buried resonator composite diaphragm; S7, drilling the bonding wafer at the position of the upper cover layer gas guide hole; S8, double-side oxidizing the second silicon wafer, patterning the oxide layer, forming the gas guide hole and the gas guide groove (310) by using dry etching technology, drilling the gas guide hole and preparing the lower cover layer (300); S9, depositing a layer of Cr / Au metal on the surface of the lower cover layer and bonding with the SOI base layer to seal and package the pressure sensitive membrane (232); S10, double-side oxidizing the third silicon wafer, patterning the oxide layer, forming the gas guide hole and the gas guide groove by using dry etching technology and preparing the upper cover layer; S11, depositing a layer of Cr / Au metal on the surface of the upper cover layer and bonding with the packaging layer of the bonding wafer to seal the packaging layer (210) and form the micro differential pressure sensor chip.

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