Preparation method of pressure sensor based on flip-chip bonding process and pressure sensor

Abstract

The invention is applicable to the technical field of semiconductor devices, and provides a preparation method of a pressure sensor based on a flip-chip bonding process and the pressure sensor, and the method comprises the steps: growing an oxide layer on a substrate; a sensitive film layer is arranged on the oxide layer; the sensitive film layer is provided with a piezoresistor; arranging a wiring layer on the sensitive film layer; a silicon cover sheet layer is arranged on the wiring layer; the cavity of the silicon cover sheet layer is provided with stop structures with different heights and different positions; the silicon cover sheet layer, the sensitive film layer and the wiring layer enclose a closed cavity structure; the stop structure is enclosed in the closed cavity structure; etching a silicon through hole in the silicon cover sheet layer, and connecting the silicon through hole and the wiring layer by applying a redistribution layer process; a solder mask layer is arranged on the silicon cover sheet layer; and etching the back surface of the substrate to form a pressure sensitive cavity. According to the protection method, the component structure can be effectively protected, the response frequency and sensitivity can be kept or improved, and the requirement for high dynamic performance is met.

Description

Technical Field

[0001] The present application belongs to the technical field of semiconductor devices, and in particular, relates to a method for preparing a pressure sensor based on a flip-chip bonding process and a pressure sensor. Background Art

[0002] In related technologies, MEMS (micro-electromechanical system) pressure sensors have been widely used to protect component structures from external influences, especially for application scenarios requiring miniaturization and high precision. MEMS pressure sensors are high-precision, miniaturized pressure measurement devices manufactured based on microelectronics technology. They use micromechanical structures to sense external pressure changes and convert them into electrical signal outputs.

[0003] In the design of MEMS pressure sensors, in order to enable the MEMS pressure sensors to be used under high dynamic pressure, one method is to design a larger dynamic range to cope with a wider range of pressure changes, but this method may cause the accuracy and stability of the sensor to decrease within a specific pressure range. Another method is to seal the chip in oil and wrap it with a stainless steel film. Although this method may provide certain mechanical protection and stability, under high dynamic pressure and large pressure changes, the deformation of the membrane structure is large, and it is easy to overload and cause damage to the membrane structure, affecting the response frequency and sensitivity of the sensor. Therefore, the above method cannot enable MEMS pressure sensors to be applied to the response field of high dynamic signals, limiting its scope of application.

[0004] In summary, how to find a protection method in the design of MEMS pressure sensors that can effectively protect the component structure while maintaining or improving the response frequency and sensitivity to meet the needs of high dynamic performance. Summary of the invention

[0005] In order to overcome the problems existing in the related art, the embodiment of the present application provides a method for preparing a pressure sensor based on a flip-chip welding process and a pressure sensor, which can find a protection method that can effectively protect the component structure and maintain or improve the response frequency and sensitivity to meet the needs of high dynamic performance.

[0006] This application is implemented through the following technical solutions: In a first aspect, an embodiment of the present application provides a method for preparing a pressure sensor based on a flip-chip bonding process, comprising: growing an oxide layer on the substrate; A sensitive film layer is arranged on the oxide layer; the sensitive film layer is provided with a varistor; Disposing a wiring layer on the sensitive film layer; A silicon cover layer is arranged on the wiring layer; stopper structures with different heights and positions are arranged on the cavity of the silicon cover layer; the silicon cover layer, the sensitive film layer and the wiring layer form a closed cavity structure; the stopper structure is surrounded in the closed cavity structure; Etching through silicon vias in the silicon cap layer and applying a redistribution layer process to connect the through silicon vias and the wiring layer; Disposing a solder resist layer on the silicon cover layer; The back side of the substrate is etched to form a pressure sensitive cavity.

[0007] In one embodiment, the wiring layer includes an insulating layer, a wiring and bonding dielectric layer; A wiring layer is arranged on the sensitive film layer, including: Depositing an insulating layer of a second preset pattern on the upper surface of the sensitive thin film layer; reserving a partial cavity in the center of the insulating layer; A wiring and bonding dielectric layer are arranged on the insulating layer; the wiring is used to connect the sensitive film layer and the silicon cover layer; a partial cavity is reserved in the center of the silicon cover layer; and the bonding dielectric layer is used to bond the insulating layer and the silicon cover layer.

[0008] In one embodiment, a silicon cover layer is provided on the wiring layer, comprising: Determining a preset position of the stop structure according to the deformation degree of different areas of the sensitive film layer; Through the self-alignment process, the silicon cover layer is etched step by step at the preset position to form stopper structures of different heights to match the deformation degree of different areas of the sensitive film layer; The silicon cover layer having the stopper structure is bonded to the wiring layer.

[0009] In one embodiment, the height range of the stop structure satisfies that the upper surface of the stop structure is in the maximum movable position range of the sensitive film layer and is in a movable position range smaller than the Von Mise stress of the sensitive film layer.

[0010] In one embodiment, after etching the through silicon via on the silicon cover layer and before providing the solder mask on the silicon cover layer, the method for preparing the pressure sensor based on the flip chip bonding process further includes: Electroplating the through silicon vias in the silicon cover layer to form a metal layer; A dielectric filling of a third preset pattern is performed on the metal layer and the silicon cover layer to form an isolation layer.

[0011] In one embodiment, a sensitive thin film layer is provided on the oxide layer, comprising: Growing a sensitive film on the oxide layer; Etching a groove of a first preset pattern on the sensitive film; The varistor is arranged in the groove of the first preset pattern to form a sensitive film layer.

[0012] In one embodiment, the method for preparing a pressure sensor based on a flip chip bonding process further includes: Design dedicated grounding holes to connect the inversion layer of the substrate and the silicon cover layer.

[0013] In one embodiment, the oxide layer is grounded.

[0014] In one embodiment, the internal pressure of the closed cavity structure is less than one atmosphere.

[0015] In a second aspect, the present application provides a pressure sensor based on a flip-chip process, which is prepared by the method for preparing a pressure sensor based on a flip-chip process as in the first aspect, and includes, from bottom to top, a substrate, an oxide layer, a sensitive film layer, a wiring layer, a silicon cover layer, and a solder resist layer; Among them, the sensitive film layer is provided with a varistor; the cavity of the silicon cover layer is provided with stop structures of different heights and positions; the silicon cover layer, the sensitive film layer and the wiring layer form a closed cavity structure; the stop structure is surrounded by the closed cavity structure; a through silicon via is provided in the silicon cover layer, and the through silicon via is connected to the wiring layer; and a pressure sensitive cavity is provided on the back side of the substrate.

[0016] Compared with the prior art, the embodiments of the present invention have the following beneficial effects: In the embodiment of the present application, a stop structure is provided on the cavity of the silicon cover layer, and together with the sensitive film layer and the wiring layer, a closed cavity structure is formed, so that the sensitive film layer can directly face the external environment without the need for an additional protective layer or dielectric layer. Direct exposure of the silicon film to the external environment reduces dielectric obstruction during signal transmission, thereby improving the response frequency of the sensor.

[0017] In the application scenarios of dynamic pressure sensors, the sensors often need to withstand greater pressure and vibration. Traditional sensor designs are often unable to withstand these extreme conditions and are prone to structural damage or failure. The preparation method, by adding a stop structure and setting stop structures of different heights and positions, can also achieve effective support and protection for the sensitive film layer under different pressure conditions. When the sensor is subjected to excessive pressure or resonance, the stop structure can absorb part of the energy, reduce the impact and damage to the silicon membrane, and significantly improve the sensor's pressure resistance and anti-resonance ability, thereby avoiding the risk of structural damage and failure.

[0018] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present specification. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0020] Figure 1 It is a schematic flow chart of a method for preparing a pressure sensor based on a flip chip bonding process provided in one embodiment of the present application; Figure 2 is a schematic structural diagram of a pressure sensor based on a flip-chip bonding process provided by an embodiment of the present application; Figure 3 is a schematic structural diagram of another pressure sensor based on a flip-chip bonding process provided by an embodiment of the present application; Figure 4 is a cross-sectional schematic diagram of a stop structure provided in one embodiment of the present application; Figure 4 (a) is the loop stop structure, Figure 4 (b) is a breakpoint type loop stop structure; Figure 5 It is a schematic structural diagram of another pressure sensor based on the flip chip bonding process provided in an embodiment of the present application. DETAILED DESCRIPTION

[0021] In the following description, specific details such as specific system structures, technologies, etc. are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present application. However, it should be clear to those skilled in the art that the present application may also be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to prevent unnecessary details from obstructing the description of the present application.

[0022] It should be understood that when used in the present specification and the appended claims, the term "comprising" indicates the presence of described features, wholes, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or combinations thereof.

[0023] It should also be understood that the term “and / or” used in the specification and appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0024] As used in the specification and appended claims of this application, the term "if" can be interpreted as "when" or "uponce" or "in response to determining" or "in response to detecting", depending on the context. Similarly, the phrase "if it is determined" or "if [described condition or event] is detected" can be interpreted as meaning "uponce it is determined" or "in response to determining" or "uponce [described condition or event] is detected" or "in response to detecting [described condition or event]", depending on the context.

[0025] In addition, in the description of the present application specification and the appended claims, the terms "first", "second", "third", etc. are only used to distinguish the descriptions and cannot be understood as indicating or implying relative importance.

[0026] References to "one embodiment" or "some embodiments" etc. described in the specification of this application mean that one or more embodiments of the present application include specific features, structures or characteristics described in conjunction with the embodiment. Therefore, the statements "in one embodiment", "in some embodiments", "in some other embodiments", "in some other embodiments", etc. that appear in different places in this specification do not necessarily refer to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized in other ways. The terms "including", "comprising", "having" and their variations all mean "including but not limited to", unless otherwise specifically emphasized in other ways.

[0027] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0028] Figure 1 is a schematic flow chart of a method for preparing a pressure sensor based on a flip chip bonding process provided in an embodiment of the present application, Figure 2 Schematic diagram of the structure of a pressure sensor based on flip chip bonding process provided by an embodiment of the present application. Figure 1 and Figure 2 , the preparation method of the pressure sensor based on the flip chip bonding process is described in detail as follows: A method for preparing a pressure sensor based on a flip chip bonding process, comprising: Step 101: growing an oxide layer on a substrate.

[0029] For example, a silicon dioxide layer of uniform thickness and good quality is usually grown on the surface of a clean substrate (such as a silicon wafer) by thermal oxidation or chemical vapor deposition (CVD) and other methods. The oxide layer serves as an isolation layer between the sensitive film layer and the substrate, which can prevent impurities in the substrate from diffusing into the sensitive film layer, while providing a certain insulation performance to ensure the stability and reliability of the sensor.

[0030] Step 102: Disposing a sensitive thin film layer on the oxide layer.

[0031] Wherein, the sensitive film layer is provided with a varistor.

[0032] Exemplarily, step 102 includes: growing a sensitive film on the oxide layer; etching a groove of a first preset pattern on the sensitive film; and disposing a varistor in the groove of the first preset pattern to form a sensitive film layer.

[0033] For example, the sensitive film layer is usually deposited on the oxide layer by sputtering, evaporation or chemical vapor deposition, and a thin film material with piezoresistive effect, such as silicon, germanium or their alloys, is deposited. In this thin film, a varistor is specially designed and made. The sensitive film layer is the core part of the sensor, which can convert external pressure changes into changes in resistance value, thereby realizing pressure measurement. The varistor is the key component in this conversion process.

[0034] Step 103: Disposing a wiring layer on the sensitive thin film layer.

[0035] Exemplarily, the wiring layer is formed by metal deposition and patterning processes, and is responsible for connecting the varistor in the sensitive film layer to the external circuit. The wiring layer usually uses metals with good conductivity such as copper, aluminum or gold. The wiring layer provides electrical connections between the internal circuit of the sensor and the external circuit, so that the sensor can work normally and transmit the measurement signal.

[0036] Step 104: Dispose a silicon cover layer on the wiring layer.

[0037] Among them, stop structures with different heights and positions are arranged on the cavity of the silicon cover layer; the silicon cover layer, the sensitive film layer and the wiring layer form a closed cavity structure; and the stop structure is surrounded in the closed cavity structure.

[0038] Exemplarily, the silicon cover layer is formed on polysilicon material by chemical vapor deposition and other methods, and has a certain thickness and strength. Stop structures of different heights and positions are specially designed and manufactured on the cavity of the silicon cover layer. The silicon cover layer not only provides protection for the sensor, but also realizes precise control of the internal space of the sensor through the stop structure thereon. The closed cavity structure enables the sensor to respond more sensitively to external pressure changes.

[0039] Step 105 , etching through silicon vias in the silicon cap layer, and applying a redistribution layer process to connect the through silicon vias and the wiring layer.

[0040] For example, a through silicon via (TSV) is first fabricated on the silicon cover layer by an etching process, and then an electrical connection is formed between the through silicon via and the wiring layer by a redistribution layer (RDL) process. The through silicon via and RDL processes enable the circuit inside the sensor to be more flexibly connected to the external circuit.

[0041] Step 106, providing a solder resist layer on the silicon cover layer.

[0042] Exemplarily, the solder mask layer is typically formed by coating and curing a layer of solder mask ink, which covers the silicon cover layer and leaves necessary openings for external connections, thereby protecting the circuit inside the sensor from corrosion and interference from the external environment while providing reliable external connection points.

[0043] Step 107, etching the back side of the substrate to form a pressure sensitive cavity.

[0044] For example, a pressure-sensitive cavity of a certain shape and size is produced on the back of the substrate through an etching process. This cavity is connected to the closed cavity structure inside the sensor, so that the sensor can sense the change of external pressure more directly.

[0045] In this embodiment, a stopper structure is provided on the cavity of the silicon cover layer, and together with the sensitive film layer and the wiring layer, a closed cavity structure is formed, so that the sensitive film layer can directly face the external environment without the need for an additional protective layer or dielectric layer. Direct exposure of the silicon film to the external environment reduces dielectric obstruction during signal transmission, thereby improving the response frequency of the sensor.

[0046] In the application scenarios of dynamic pressure sensors, the sensors often need to withstand greater pressure and vibration. Traditional sensor designs are often unable to withstand these extreme conditions and are prone to structural damage or failure. The present preparation method, by adding a stop structure and setting stop structures at different heights and positions, can also achieve effective support and protection for the sensitive film layer under different pressure conditions.

[0047] In one embodiment, see Figure 3 The wiring layer includes an insulating layer, a wiring layer and a bonding dielectric layer. The process of setting the wiring layer on the sensitive film layer is specifically introduced. Step 103 includes: First, an insulating layer of a second preset pattern is deposited on the upper surface of the sensitive thin film layer, wherein a partial cavity is reserved in the center of the insulating layer.

[0048] Then, wiring and bonding dielectric layers are arranged on the insulating layer, wherein the wiring is used to connect the sensitive film layer and the silicon cover layer; a partial cavity is reserved in the center of the silicon cover layer; and the bonding dielectric layer is used to bond the insulating layer and the silicon cover layer.

[0049] In one embodiment, the process of setting a silicon cover layer on the wiring layer is specifically described. Step 104 includes: Firstly, the preset position of the stop structure is determined according to the deformation degree of different regions of the sensitive film layer.

[0050] Exemplarily, the deformation degree of different regions of the sensitive film layer is different. Since the two sides of different regions of the sensitive film layer are fixed, the deformation degree in the middle of the sensitive film layer is larger, and the deformation degree on both sides is smaller. However, the vibration frequency on both sides is higher, which is easy to produce resonance or resonance in high dynamic pressure application scenarios, increase the deformation amount, and cause overload to damage the membrane structure. Therefore, according to the deformation degree of different regions of the sensitive film layer, in order to enable the stop structure to absorb vibration energy more easily and prevent the deformation amount of the membrane structure from being too large, the height of the stop structure set in the middle region is less than the height of the stop structure set on both sides. Among them, the number of stop structures of different heights and different positions is not limited to a specific number, and can be set according to actual conditions, for example, it can be 3-5. Here, this embodiment is a stop structure designed for the resonance of the membrane structure in a piezoresistive pressure sensor, and is not used to fix and support the device.

[0051] Considering that the size of the closed cavity structure is not the same in different sensors, the specific height of the stop structure cannot be determined, but the position of the upper surface of the stop structure in contact with the sensitive film layer can be limited to better achieve resonance protection. Therefore, the height range of the stop structure satisfies: the upper surface of the stop structure is in the maximum movable position range of the sensitive film layer, and is in a movable position range that is less than the Von Mise stress of the sensitive film layer. The Von Mise stress criterion is: when the equivalent stress strain of the stress-strain state at a certain point reaches a certain constant related to the stress-strain state, the material yields.

[0052] For example, considering that the sensor needs to adapt to different pressure ranges, the stopper structure shape design can be designed as a loop stopper structure or a breakpoint loop stopper structure, and accurate measurement of different pressure ranges can be achieved by adjusting the size and shape of the stopper structure. Figure 4 As shown, Figure 4 (a) is the loop stop structure, Figure 4 (b) is a breakpoint loop stop structure, and the number of breakpoints is not limited. In addition, the ring-shaped or end-point ring-shaped stop structure can better guide the pressure distribution, so that the pressure can act more evenly on the sensitive film layer, reduce stress concentration, and avoid damage to the sensitive film layer due to excessive stress. At the same time, by optimizing the shape and size of the stop structure, unnecessary material use is reduced, thereby reducing the overall weight of the sensor.

[0053] Then, through a self-alignment process, the silicon cover layer is etched step by step at preset positions to form stop structures of different heights to match the deformation degree of different areas of the sensitive thin film layer.

[0054] Finally, the silicon cover layer with the stopper structure is bonded to the wiring layer.

[0055] In one embodiment, see Figure 5 After etching the through silicon vias on the silicon cover layer and before providing a solder resist layer on the silicon cover layer, the method for preparing a pressure sensor based on a flip chip bonding process further includes: Electroplating the through silicon vias in the silicon cover layer to form a metal layer; filling the metal layer and the silicon cover layer with a dielectric of a third preset pattern to form an isolation layer.

[0056] For example, the metal layer formed by electroplating can ensure the electrical connection of the silicon via in the internal circuit of the sensor, and at the same time enhance the mechanical strength of the silicon via, making it more able to withstand the influence of environmental factors such as external pressure and vibration, thereby improving the overall reliability of the sensor. The metal layer formed by electroplating can also protect the silicon via from damage such as oxidation and corrosion, thereby extending the service life of the sensor.

[0057] The isolation layer formed by dielectric filling can isolate the through silicon via and the metal layer from the external environment, preventing deformation, cracking and other problems caused by changes in environmental factors such as temperature and humidity. At the same time, the isolation layer can also protect the circuit inside the sensor to prevent failures caused by short circuits, leakage and other problems. The isolation layer formed by dielectric filling can provide a flat and uniform base for subsequent processing steps such as solder mask setting and packaging.

[0058] In one embodiment, the method for preparing a pressure sensor based on a flip chip bonding process further includes: Design a dedicated grounding hole to connect the inversion layer (heavily doped N-type) of the substrate and the silicon cover layer. The inversion layer and the silicon cover layer wrap the varistor into the equipotential area to avoid external interference.

[0059] In one embodiment, the oxide layer can be grounded. The oxide layer above the varistor serves as a shielding layer, and the shielding layer is grounded to reduce interference of the external environment on the pressure signal.

[0060] In one embodiment, the internal pressure of the closed cavity structure is less than one atmosphere, and is between 1 Pa and several hundred Pa. The natural frequency of the closed cavity structure is closely related to its internal pressure. When the internal pressure decreases, the stiffness of the cavity structure may change, thereby causing a change in its natural frequency, which helps to make the natural frequency of the cavity structure no longer match the frequency of the external excitation, thereby reducing the probability of resonance.

[0061] The method for preparing a pressure sensor based on a flip-chip welding process in an embodiment of the present application sets a stop structure on the cavity of the silicon cover layer to form a closed cavity structure together with the sensitive film layer and the wiring layer, so that the sensitive film layer can directly face the external environment without the need for an additional protective layer or dielectric layer. Directly exposing the silicon film to the external environment reduces dielectric obstruction during signal transmission, thereby improving the response frequency of the sensor.

[0062] In the application scenarios of dynamic pressure sensors, the sensors often need to withstand greater pressure and vibration. Traditional sensor designs are often unable to withstand these extreme conditions and are prone to structural damage or failure. The preparation method, by adding a stop structure and setting stop structures of different heights and positions, can also achieve effective support and protection for the sensitive film layer under different pressure conditions. When the sensor is subjected to excessive pressure or resonance, the stop structure can absorb part of the energy, reduce the impact and damage to the silicon membrane, and significantly improve the sensor's pressure resistance and anti-resonance ability, thereby avoiding the risk of structural damage and failure.

[0063] See also Figures 2 to 5 An embodiment of the present application provides a pressure sensor based on a flip-chip process, which is prepared using the method for preparing a pressure sensor based on a flip-chip process as in the above embodiment, and includes, from bottom to top, a substrate, an oxide layer, a sensitive film layer, a wiring layer, a silicon cover layer and a solder resist layer.

[0064] Among them, the sensitive film layer is provided with a varistor; the cavity of the silicon cover layer is provided with stop structures of different heights and positions; the silicon cover layer, the sensitive film layer and the wiring layer form a closed cavity structure; the stop structure is surrounded by the closed cavity structure; a through silicon via is provided in the silicon cover layer, and the through silicon via is connected to the wiring layer; and a pressure sensitive cavity is provided on the back side of the substrate.

[0065] Exemplarily, the shape design of the stop structure can be designed as a loop stop structure or a breakpoint loop stop structure.

[0066] Exemplarily, the pressure sensor based on the flip chip process further includes a metal layer and an isolation layer.

[0067] Electroplating the through silicon vias in the silicon cover layer to form a metal layer, and filling the metal layer and the silicon cover layer with a dielectric of a third preset pattern to form an isolation layer.

[0068] For the beneficial effects of the pressure sensor based on the flip-chip bonding process, refer to the beneficial effects of the method for preparing the pressure sensor based on the flip-chip bonding process in the above embodiment.

[0069] It should be understood that the size of the serial numbers of the steps in the above embodiments does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0070] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A method for preparing a pressure sensor based on a flip chip bonding process, characterized in that: include: growing an oxide layer on the substrate; Disposing a sensitive thin film layer on the oxide layer; The sensitive film layer is provided with a varistor; Disposing a wiring layer on the sensitive film layer; A silicon cover layer is arranged on the wiring layer; and stopper structures with different heights and positions are arranged on the cavity of the silicon cover layer; The silicon cover layer, the sensitive film layer and the wiring layer form a closed cavity structure; the stopper structure is surrounded by the closed cavity structure; Etching a through silicon via in the silicon cover layer, and applying a redistribution layer process to connect the through silicon via and the wiring layer; Disposing a solder resist layer on the silicon cover layer; The back side of the substrate is etched to form a pressure sensitive cavity.

2. The method for preparing a pressure sensor based on flip chip bonding process according to claim 1, characterized in that: The wiring layer includes an insulating layer, a wiring layer and a bonding dielectric layer; The step of providing a wiring layer on the sensitive film layer comprises: Depositing an insulating layer of a second preset pattern on the upper surface of the sensitive thin film layer; a partial cavity is reserved in the center of the insulating layer; A wiring and a bonding dielectric layer are arranged on the insulating layer; the wiring is used to connect the sensitive film layer and the silicon cover layer; a partial cavity is reserved in the center of the silicon cover layer; and the bonding dielectric layer is used to bond the insulating layer and the silicon cover layer.

3. The method for preparing a pressure sensor based on flip chip bonding process according to claim 1, characterized in that: The step of providing a silicon cover layer on the wiring layer comprises: Determining a preset position of the stop structure according to the deformation degree of different areas of the sensitive film layer; The silicon cover layer is etched step by step at the preset position through a self-alignment process to form stopper structures of different heights to match the deformation degrees of different areas of the sensitive film layer; The silicon cover layer having the stopper structure is bonded to the wiring layer.

4. The method for preparing a pressure sensor based on flip chip bonding process according to claim 1, characterized in that: The height range of the stop structure satisfies that the upper surface of the stop structure is in the maximum movable position range of the sensitive film layer and is in a movable position range smaller than the Von Mise stress of the sensitive film layer.

5. The method for preparing a pressure sensor based on flip chip bonding process according to claim 1, characterized in that: After etching the through silicon vias on the silicon cover layer and before providing a solder resist layer on the silicon cover layer, the method for preparing the pressure sensor based on the flip chip bonding process further includes: Electroplating the through silicon vias in the silicon cover layer to form a metal layer; A dielectric filling of a third preset pattern is performed on the metal layer and the silicon cover layer to form an isolation layer.

6. The method for preparing a pressure sensor based on flip chip bonding process according to claim 1, characterized in that: The step of providing a sensitive thin film layer on the oxide layer comprises: growing a sensitive thin film on the oxide layer; Etching a groove of a first preset pattern on the sensitive film; The varistor is arranged in the groove of the first preset pattern to form a sensitive film layer.

7. The method for preparing a pressure sensor based on flip chip bonding process according to claim 1, characterized in that: Also includes: A dedicated grounding hole is designed to connect the inversion layer of the substrate and the silicon cover layer.

8. The method for preparing a pressure sensor based on flip chip bonding process according to claim 1, characterized in that: The oxide layer is grounded.

9. The method for preparing a pressure sensor based on flip chip bonding process according to claim 1, characterized in that: The internal pressure of the closed cavity structure is less than one atmosphere.

10. A pressure sensor based on flip chip bonding process, characterized in that: The pressure sensor is prepared by the method for preparing a pressure sensor based on a flip chip process as described in any one of claims 1 to 9, and comprises, from bottom to top, a substrate, an oxide layer, a sensitive film layer, a wiring layer, a silicon cover layer and a solder resist layer; Among them, the sensitive film layer is provided with a varistor; the cavity of the silicon cover layer is provided with stop structures of different heights and positions; the silicon cover layer, the sensitive film layer and the wiring layer form a closed cavity structure; the stop structure is surrounded by the closed cavity structure; a silicon through hole is provided in the silicon cover layer, and the silicon through hole is connected to the wiring layer; and a pressure-sensitive cavity is provided on the back side of the substrate.

Images