MEMS micro-pressure sensing system and measuring method thereof

Abstract

The invention discloses an MEMS (Micro Electro Mechanical System) micro-pressure sensing system and a measuring method thereof, and relates to the technical field of micro electro mechanical systems. The system comprises a substrate, a vibrating diaphragm arranged on the substrate, a back polar plate which is arranged above the vibrating diaphragm and forms a capacitance gap with the vibrating diaphragm, and limiting structures which are respectively arranged between the vibrating diaphragm and the back polar plate and between the vibrating diaphragm and the substrate and are used for limiting the displacement of the vibrating diaphragm, when the external pressure exceeds the rated range, the displacement of the vibrating diaphragm in the vertical direction is restrained. At least part of the limiting structure is a structure which protrudes relative to the surface of the substrate where the limiting structure is located, and the limiting structure is used for reducing the contact area of the vibrating diaphragm during limiting contact; the limiting structures located in the vertical direction of the vibrating diaphragm have an overlapping area on a plane vertical projection taking the plane where the geometric center of the vibrating diaphragm is located as a reference, so that the vibrating diaphragm obtains a collaborative mechanical constraint state when limiting contact occurs. The device and the method are used for continuously and differentially measuring external pressure under different pressure action conditions.

Description

Technical Field

[0001] This invention relates to the field of microelectromechanical systems (MEMS) technology, and more particularly to a MEMS micro-pressure sensing system and its measurement method. Background Technology

[0002] Microelectromechanical systems (MEMS) micro-pressure sensors are widely used in gas flow detection, environmental parameter monitoring, and industrial control. Among them, capacitive micro-pressure sensing systems, which use a deformable sensitive structure as their core, measure pressure by detecting the deformation changes of the sensitive structure under external pressure. They are widely used due to their compact structure and high sensitivity.

[0003] In practical applications, micro-pressure sensing systems not only need to achieve stable and accurate measurements within their rated pressure range, but also inevitably encounter pressures exceeding their rated range. For example, during startup, shutdown, or abnormal operating conditions, transient pressure changes can cause significant deformation of the sensitive structure, adversely affecting the structural safety and long-term reliability of the device. In existing technologies, improving the structural reliability of micro-pressure sensing systems under overload pressure conditions without significantly reducing measurement sensitivity remains a pressing issue. The stress state and response characteristics of the sensitive structure in a micro-pressure sensing system may differ significantly across different pressure ranges. When the system transitions from a normal operating state to a constrained or nonlinear response state, a lack of effective differentiation and processing of these different operating states can easily lead to a decrease in the continuity and accuracy of measurement results, thus affecting the overall measurement performance of the system. Furthermore, in microscale structures, when the sensitive structure comes into contact with adjacent structures under significant deformation conditions, non-ideal contact effects may be introduced, adversely affecting the stability and repeatability of the device. Meanwhile, single-form sensing information often fails to fully reflect the actual deformation and stress state of the sensitive structure under complex working conditions, limiting further improvements in range expansion, reliability enhancement, and measurement accuracy of micro-pressure sensing systems.

[0004] Therefore, there is an urgent need for a MEMS micro-pressure sensing system and its measurement method that can balance structural reliability and measurement stability under different pressure conditions, in order to meet the ever-increasing demands for micro-pressure measurement accuracy, reliability and applicability in complex application environments. Summary of the Invention

[0005] To address the problems of insufficient structural reliability and limited measurement continuity and stability under different pressure conditions in existing MEMS micro-pressure sensing systems, a new MEMS micro-pressure sensing system and its measurement method are proposed.

[0006] The present invention aims to improve the structural safety and operational stability of the micro-pressure sensing system under pressure exceeding the rated range while ensuring the sensitivity of micro-pressure measurement, and to enable the system to maintain a stable and distinguishable measurement response under different operating conditions, thereby improving the applicability and overall performance of the MEMS micro-pressure sensing system in complex application environments.

[0007] To achieve the above objectives, the present invention employs the following technical solution: On one hand, the present invention provides a MEMS micro-pressure sensing system, including a substrate, a diaphragm disposed on the substrate, and a back electrode plate disposed above the diaphragm and forming a capacitance gap with the diaphragm. The system further includes: an upper limiting structure located between the back electrode plate and the diaphragm, used to contact the diaphragm under overload pressure exceeding the rated range to limit the maximum displacement of the diaphragm towards the back electrode plate; and a lower limiting structure located between the diaphragm and the substrate, used to contact the diaphragm under overload pressure exceeding the rated range to limit the maximum displacement of the diaphragm towards the substrate. The upper limiting structure or the lower limiting structure is a limiting protrusion structure protruding relative to the surface of the substrate, thereby reducing the contact area between the diaphragm and the corresponding structure during limiting contact and reducing the risk of adhesion failure. The upper limit structure and / or the lower limit structure have a non-zero overlap region on the vertical projection of the plane with the plane where the geometric center of the diaphragm is located as a reference, so that the diaphragm obtains a cooperative mechanical constraint state when it makes limiting contact in the vertical direction.

[0008] As a preferred embodiment of the present invention, the upper limiting structure includes at least one first limiting unit facing the diaphragm protrusion, and the lower limiting structure includes at least one second limiting unit facing the diaphragm protrusion and at least partially overlapping the first limiting unit in vertical projection; the protrusion height of the first limiting unit along the normal direction of the diaphragm is greater than the protrusion height of the second limiting unit relative to the substrate surface, such that under the overload pressure in the same direction of displacement of the diaphragm towards the back electrode plate, the diaphragm displacement gradually increases, the diaphragm preferentially contacts the first limiting unit, and enters a restricted deformation state under greater overload pressure; in the first limiting unit and the second limiting unit, the surface of the first limiting unit that contacts the diaphragm has a preset contact surface morphology different from that of the second limiting unit, the preset contact surface morphology being one or more of the following structures: micro-bump array, micro-groove structure, curved transition structure, surface roughening treatment, or anti-adhesion coating.

[0009] As a preferred embodiment of the present invention, the lower limiting structure is made of a dielectric insulating material to achieve electrical insulation during limiting contact; the dielectric insulating material is one of silicon nitride, silicon oxide or polyimide; the lower limiting structure is formed as a plurality of spaced limiting bump units, the plurality of spaced limiting bump units together constitute at least one second limiting unit, and is located between the diaphragm and the substrate.

[0010] As a preferred embodiment of the present invention, a resonant strain sensing structure is provided on the diaphragm, the resonant strain sensing structure including a mechanical resonant structure disposed on the diaphragm and mechanically coupled to the diaphragm; when the diaphragm is deformed, the inherent resonant frequency of the mechanical resonant structure changes with the mechanical strain state of the diaphragm.

[0011] In a preferred embodiment of the present invention, a resonant strain sensing unit is disposed on the diaphragm. The resonant strain sensing unit includes: a mechanical resonant structure disposed on the diaphragm; an excitation and readout circuit electrically connected to the mechanical resonant structure; the resonant strain sensing unit is configured to excite the mechanical resonant structure and detect the resonant response, and output a resonant frequency signal that changes with the mechanical strain of the diaphragm; a plurality of diaphragm region units for local detection are also defined on the diaphragm, and the plurality of diaphragm region units are respectively provided with displacement sensing structures for detecting local displacement changes of the diaphragm.

[0012] As a preferred embodiment of the present invention, the MEMS micro-pressure sensing system includes a processing unit; the processing unit is configured to determine the applied pressure based on two or more different structural state information acquired by the MEMS micro-pressure sensing system and based on a calibrated segmented mapping relationship: information on capacitance signal changes caused by contact between the diaphragm and the upper or lower limit structure and diaphragm displacement changes; information on resonant frequency changes output by the resonant strain sensing unit; and information on displacement changes acquired by the displacement sensing structure corresponding to multiple diaphragm region units.

[0013] As a preferred embodiment of the present invention, the processing unit is configured to: divide the working range of the sensor based on the capacitance signal change characteristics or contact detection signal according to whether the diaphragm contacts the upper or lower limit structure; the working range includes a working range where no limit contact occurs and a working range where limit contact occurs; and within different working ranges, switch to use a segmented calibration relationship that matches the corresponding working range to convert the acquired sensing signal into an applied pressure value.

[0014] As a preferred embodiment of the present invention, the processing unit selects segmented calibration relationships that differ in the types of input information as target calculation relationships in different working intervals; the types of input information are selected from the following group: capacitance signal change information caused by overall diaphragm deformation; resonant frequency change information caused by local strain state of the diaphragm; displacement change information generated by the diaphragm at different spatial positions.

[0015] In a preferred embodiment of the present invention, within the working range where the diaphragm contacts the upper or lower limit structure, the processing unit is configured to: generate a preliminary estimate of the applied pressure based on the resonant frequency change information, and combine the displacement distribution characteristics reflected by the displacement change information at multiple spatial locations, perform a consistency check on the preliminary estimate based on a preset consistency criterion, and when the consistency check is not satisfied, correct the preliminary estimate based on the displacement change information to determine the applied pressure. The consistency criterion includes a consistency judgment rule based on a deviation threshold between the displacement distribution characteristics and the corresponding pressure model, or a consistency judgment rule based on a residual minimization constraint.

[0016] Based on the above-described processing unit configuration, in some embodiments, the specific processing procedures of the processing unit under different pressure conditions are as follows: During the device calibration stage, when the applied pressure is within the rated range and the diaphragm does not come into contact with the upper and lower limit structures, the capacitance signal change information and resonant frequency change information at different pressure points are obtained, and a first mapping relationship is established between the applied pressure and the capacitance signal change information and resonant frequency change information.

[0017] When the applied pressure exceeds the rated range, or when the diaphragm comes into contact with the upper or lower limit structure, the resonant frequency change information at the corresponding pressure point and the displacement change information at multiple diaphragm area units are obtained, and a second mapping relationship is established between the applied pressure and the resonant frequency change information and displacement change information.

[0018] During the actual measurement process, the processing unit determines whether the diaphragm is in contact with the upper or lower limit structure based on the characteristics of the capacitance signal change or the contact detection signal, and selects the corresponding segmented mapping relationship as the current pressure calculation model accordingly.

[0019] Within the working range where the diaphragm contacts the upper or lower limit structure, the processing unit first generates a preliminary estimate of the applied pressure based on the resonant frequency change information, and then further combines the displacement change information at multiple diaphragm area units to perform a consistency check on the preliminary estimate. When the check result does not meet the preset consistency condition, the processing unit corrects the preliminary estimate based on the displacement change information to determine the applied pressure.

[0020] In this way, the MEMS micro-pressure sensing system can obtain continuous and distinguishable pressure measurement results whether the diaphragm is in a free deformation state or a restricted deformation state.

[0021] On the other hand, the present invention also provides a measurement method for a MEMS micro-pressure sensing system, applied to the aforementioned MEMS micro-pressure sensing system, comprising the following steps: S1. Under the action of external pressure, the diaphragm is deformed relative to the substrate, and a capacitance gap that changes with the deformation of the diaphragm is formed between the diaphragm and the back electrode plate. S2. When the applied pressure does not exceed the rated range, the diaphragm undergoes elastic deformation without contacting the upper limit structure and the lower limit structure. S3. When the applied pressure exceeds the rated range and forms an overload pressure, the diaphragm is displaced towards the back electrode plate or towards the substrate under the action of the overload pressure, and comes into contact with the upper limit structure located between the back electrode plate and the diaphragm or the lower limit structure located between the diaphragm and the substrate, respectively, so as to limit the maximum displacement of the diaphragm in the corresponding direction. S4. By making the upper limit structure and the lower limit structure have a non-zero overlap area on the plane with the plane where the geometric center of the diaphragm is located as a reference, and setting them symmetrically about the geometric center point of the diaphragm, the diaphragm obtains a symmetrical mechanical constraint state when limit contact occurs.

[0022] The beneficial effects of this invention are as follows: By introducing a constraint mechanism under overload conditions in the vertical direction of the diaphragm, this invention enables the diaphragm to undergo a controlled limiting response when the applied pressure exceeds the rated range. This effectively limits the maximum displacement of the diaphragm in the corresponding direction, reduces the risk of excessive deformation of the sensitive structure, and improves the structural reliability and service life of the micro-pressure sensing system under overload pressure conditions. Optimizing the contact mode of the diaphragm during limiting contact makes the actual contact behavior between the diaphragm and adjacent structures under the constrained response state more controllable, helping to reduce the impact of non-ideal contact effects on system stability and repeatability, and improving the reliability of measurement results under complex working conditions. By enabling the diaphragm to obtain a synergistic mechanical constraint state when it undergoes a constrained response in the vertical direction, it helps to improve the overall stress distribution of the diaphragm under overload conditions, reduces the adverse effects of local stress concentration on system performance, and allows the sensing system to maintain good response continuity and stability under different pressure conditions. While balancing measurement accuracy and structural reliability, this invention helps to improve the micro-pressure sensing system's ability to identify changes in applied pressure and its measurement applicability, enhancing its comprehensive applicability in various application scenarios. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein: Figure 1 This is a schematic diagram of a typical traditional MEMS capacitive micro-pressure sensor structure. Figure 2 This is a schematic diagram of the overall structure of a high-reliability MEMS micro-pressure sensing system proposed in this invention; Figure 3 In order to be in Figure 2 The diagram shows an improved structure based on the structure shown, wherein an upper limit structure and a lower limit structure are respectively set in the upper and lower directions of the diaphragm. Figure 4 In order to be in Figure 3 A schematic diagram of another improved structure based on the structure shown, wherein the upper limit structure and the lower limit structure are set as structures that protrude relative to the surface of the substrate. Figure 5 In order to be in Figure 3 A schematic diagram of a further improved structure based on the structure shown, wherein multiple connecting structures are provided between the diaphragm and the lower limiting structure; Figure 6 In order to be in Figure 5 The diagram shows an optimized structure based on the structure shown, in which the lower limiting structure and connecting structure are distributed in a gradually changing shape along the normal direction of the diaphragm. Figure 7 This is a flowchart of the method of the present invention. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention are within the scope of protection of the present invention.

[0025] It should be noted that the through-hole structures, connection structures, interlayer structures, local gap structures, and their specific forms shown in the accompanying drawings are mainly used to illustrate the hierarchical relationship, spatial layout, or manufacturing process implementation of the device, and are not intended to limit the technical solution of the present invention. Those skilled in the art can, without departing from the core technical concept of the present invention, set, adjust, or omit the above structures according to specific application requirements or manufacturing process conditions; such changes will not affect the technical problem to be solved by the present invention or its technical effects.

[0026] like Figure 2 As shown, this embodiment provides a MEMS micro-pressure sensing system, the overall structure of which is built based on the capacitive microprocessor pressure sensing principle. The system includes a substrate, a diaphragm disposed on the substrate, and a back electrode plate disposed above the diaphragm and forming a capacitive gap with the diaphragm.

[0027] In this structure, the diaphragm, as a deformable structure, displaces relative to the substrate under applied pressure. The capacitive gap formed between the diaphragm and the back electrode changes with the diaphragm displacement, thereby generating an electrical signal related to the applied pressure. The above structure and its basic working mechanism belong to the common MEMS capacitive micro-pressure sensing structures in this field.

[0028] To limit excessive displacement of the diaphragm when the applied pressure exceeds the rated range, in this embodiment, limiting structures for limiting diaphragm displacement are provided in the vertical direction of the diaphragm.

[0029] An upper limit structure is provided between the back electrode plate and the diaphragm. This upper limit structure is located between the back electrode plate and the diaphragm and is used to contact the diaphragm under overload pressure exceeding the rated range, thereby limiting the maximum displacement of the diaphragm towards the back electrode plate. When the applied pressure exceeds the rated range and causes the diaphragm to displace towards the back electrode plate, the diaphragm gradually approaches and eventually contacts the upper limit structure, thus constraining the maximum displacement of the diaphragm in that direction.

[0030] A lower limiting structure is provided between the diaphragm and the substrate. This lower limiting structure is located between the diaphragm and the substrate and is used to contact the diaphragm under overload pressure exceeding its rated range, thereby limiting the maximum displacement of the diaphragm towards the substrate. When the diaphragm displaces towards the substrate under overload pressure, the diaphragm contacts the lower limiting structure, thus limiting further displacement of the diaphragm in that direction.

[0031] like Figure 3 As shown, in this embodiment, at least a portion of the upper limit structure and / or the lower limit structure is designed as a limiting protrusion structure that protrudes relative to the surface of the substrate. This limiting protrusion structure can be achieved by forming a localized protrusion on the surface of the back electrode plate or the substrate. When the diaphragm comes into contact with the limiting structure, the diaphragm mainly contacts a localized area of ​​the limiting protrusion structure, thereby reducing the contact area between the diaphragm and the corresponding structure during limiting contact and lowering the risk of adhesion failure.

[0032] In one specific embodiment, the limiting protrusion structure can be a columnar or truncated conical protrusion, with a protrusion height in the normal direction of the diaphragm on the order of micrometers, preferably 1 μm to 5 μm, and its lateral dimension (diameter or side length) preferably 10 μm to 50 μm. The limiting protrusion structure can be made of polycrystalline silicon, silicon nitride, metal materials, or dielectric materials, and can be formed on the surface of the back electrode plate or the substrate surface by photolithography, etching, or deposition processes. With the above configuration, the diaphragm preferentially contacts the top region of the protrusion structure when limiting contact occurs, thereby effectively reducing the actual contact area and reducing the risk of adhesion failure.

[0033] Furthermore, the limiting structures located in the vertical direction of the diaphragm satisfy the following spatial arrangement: the upper limiting structure or the lower limiting structure has a non-zero overlap region on the vertical projection of a plane with the plane containing the geometric center of the diaphragm as a reference. That is, when viewed from a direction perpendicular to the plane containing the diaphragm, at least a portion of the upper limiting structure corresponds to at least a portion of the lower limiting structure on the plane projection.

[0034] In this embodiment, the overlapping regions are preferably symmetrically distributed around the geometric center of the diaphragm; the projected area of ​​the overlapping regions can account for 30% to 70% of the projected area of ​​the corresponding limiting structure, so that the diaphragm can obtain a basically symmetrical and coordinated mechanical constraint state when it makes limiting contact in the vertical direction.

[0035] In other embodiments, such as Figure 4 and Figure 5 As shown, the aforementioned non-zero overlap region can be achieved through limiting protrusion structures of different shapes. The specific shape, size, and distribution of the limiting protrusion structures can be adjusted according to actual design requirements.

[0036] In a further embodiment, such as Figure 6 As shown, by optimizing the shape of the limiting protrusion structure to make it vary in the height direction, the stress state during the limiting contact process can be improved while ensuring the limiting function.

[0037] Through the above structural design, this embodiment achieves the limitation of the vertical displacement of the diaphragm under overload pressure conditions without changing the basic working principle of capacitive micro-pressure sensing.

[0038] Based on the above embodiments, such as Figure 3 As shown, in some embodiments, the upper limit structure and the lower limit structure are further refined into mutually cooperating limit unit structures.

[0039] The upper limit structure includes at least one first limiting unit facing the diaphragm protrusion, and the lower limit structure includes at least one second limiting unit facing the diaphragm protrusion and at least partially overlapping the first limiting unit in its vertical projection. This arrangement ensures that the limiting units located in the vertical direction of the diaphragm are spatially corresponding.

[0040] In this embodiment, the protrusion height of the first limiting unit along the normal direction of the diaphragm is greater than the protrusion height of the second limiting unit relative to the substrate surface. Based on this height difference, when the applied pressure exceeds the rated range and causes the diaphragm to displace towards the back electrode plate, as the diaphragm displacement gradually increases, the diaphragm preferentially contacts the first limiting unit and enters a restricted deformation state under greater overload pressure. Through the above-mentioned limiting sequence, the diaphragm exhibits a phased restricted state at different overload stages.

[0041] In this embodiment, in the first limiting unit and the second limiting unit, the surface of the first limiting unit that contacts the diaphragm has a preset contact surface morphology that is different from that of the second limiting unit. The preset contact surface morphology can be one or more of the following combinations: micro-bump array, micro-groove structure, curved transition structure, surface roughening treatment, or anti-adhesion coating.

[0042] In one specific implementation, the bump height of the microbump array can be 0.1μm to 0.5μm, and the bump spacing can be 1μm to 5μm; the groove depth of the microgroove structure can be 0.1μm to 1μm, and the groove spacing can be 1μm to 10μm; through the above-mentioned contact surface morphology setting, the adhesion risk under the confined contact condition can be further reduced and the contact repeatability can be improved.

[0043] By setting different contact surface morphologies between the first limiting unit and the second limiting unit, the diaphragm can exhibit different contact states when it comes into contact with different limiting units, thereby meeting the structural design requirements under different limiting stages.

[0044] Based on the above embodiments, such as Figure 4 As shown, in some embodiments, the lower limit structure is further limited in terms of material and structural form.

[0045] The lower limiting structure is made of a dielectric insulating material to achieve electrical insulation during limiting contact. In this embodiment, the dielectric insulating material can be selected from silicon nitride, silicon oxide, or polyimide. By using a dielectric insulating material as the constituent material of the lower limiting structure, the formation of a conductive path can be avoided when the diaphragm comes into contact with the lower limiting structure.

[0046] Furthermore, the lower limiting structure is formed as a plurality of spaced-apart limiting protrusion units, which together constitute at least one second limiting unit and are located between the diaphragm and the substrate. By designing the lower limiting structure as a plurality of spaced-apart limiting protrusion units, the diaphragm can obtain distributed support at different positions while maintaining the limiting function.

[0047] In some embodiments, such as Figure 5 and Figure 6 As shown, the specific shape, size, and distribution of the aforementioned limiting protrusion unit can be adjusted according to actual design requirements to adapt to different device structures or manufacturing process conditions.

[0048] In one alternative embodiment, the MEMS micro-pressure sensing system can be fabricated using the following microfabrication process: depositing and patterning a sacrificial layer on a substrate; depositing a diaphragm material layer and forming a resonant structure on the diaphragm material layer; forming a lower limiting protrusion structure through photolithography and etching processes; releasing the sacrificial layer to form a capacitor gap; and subsequently setting a back electrode plate through a bonding process and forming an upper limiting protrusion structure on the surface of the back electrode plate. The above process is merely an example, and those skilled in the art can make equivalent substitutions based on the material system and equipment conditions.

[0049] Based on the above embodiments, such as Figure 1 As shown, in some embodiments, a resonant strain sensing structure is provided on the diaphragm. The resonant strain sensing structure is used to sense the mechanical strain state generated by the diaphragm during compression.

[0050] The resonant strain sensing structure includes a mechanical resonant structure disposed on the diaphragm and mechanically coupled to the diaphragm. The mechanical resonant structure can be formed on the surface of the diaphragm or integrally formed with the diaphragm through micromachining, so that it maintains a mechanical coupling relationship with the diaphragm.

[0051] In this embodiment, when the diaphragm deforms, the inherent resonant frequency of the mechanical resonant structure changes with the mechanical strain state of the diaphragm. When the diaphragm deforms under external pressure, the stress distribution inside the diaphragm changes and is transmitted to the mechanical resonant structure through mechanical coupling, thereby causing a change in its inherent resonant frequency.

[0052] By detecting changes in the resonant frequency of a mechanical resonant structure, the strain state of the diaphragm can be indirectly reflected.

[0053] In one specific embodiment, the mechanical resonant structure is a double-ended fixed beam resonant structure disposed on the diaphragm. The resonant beam can be made of silicon nitride material, with a preferred length of 50μm to 200μm, a preferred width of 2μm to 10μm, and a preferred thickness of 0.3μm to 1μm. It is mechanically coupled to the diaphragm by being fixed at both ends. The resonant beam can be excited by electrostatic means, and its resonant response can be detected by piezoresistive or capacitive means to obtain the resonant frequency signal. In other embodiments, the mechanical resonant structure can also be a ring resonator, a cantilever beam resonator, or a diaphragm resonator, as long as it can maintain coupling with the mechanical strain state of the diaphragm and output a resonant frequency signal that changes with strain.

[0054] Based on the above embodiments, such as Figure 1 As shown, in some embodiments, a resonant strain sensing unit is provided on the diaphragm for signaling the strain state of the diaphragm.

[0055] The resonant strain sensing unit includes: a mechanical resonant structure disposed on a diaphragm; and an excitation and readout circuit electrically connected to the mechanical resonant structure. The excitation and readout circuit is used to apply an excitation signal to the mechanical resonant structure and detect its resonant response.

[0056] In this embodiment, the resonant strain sensing unit is configured to excite the mechanical resonant structure and detect the resonant response, outputting a resonant frequency signal that varies with the mechanical strain of the diaphragm. The resonant frequency signal can serve as an output signal characterizing the mechanical strain state of the diaphragm.

[0057] In this embodiment, the diaphragm is further defined with multiple diaphragm region units for local detection. Each of the multiple diaphragm region units is respectively provided with a displacement sensing structure for detecting local displacement changes of the diaphragm. By setting multiple diaphragm region units at different positions of the diaphragm, displacement change information of the diaphragm at different spatial positions can be obtained, thereby reflecting the local deformation characteristics of the diaphragm.

[0058] In this embodiment, the diaphragm region unit preferably includes a diaphragm region unit located in the center region of the diaphragm and a diaphragm region located in the edge region of the diaphragm; the displacement sensing structure is preferably a piezoresistive displacement sensing structure integrated on the diaphragm, or a displacement sensing structure based on capacitance change, used to output displacement change information of the corresponding region.

[0059] Based on the above embodiments, such as Figure 1 As shown, in some embodiments, the MEMS micro-pressure sensing system includes a processing unit. The processing unit can be a signal processing module disposed inside or outside the chip.

[0060] In this embodiment, the processing unit is configured to determine the applied pressure based on two or more different structural state information acquired by the MEMS micro-pressure sensing system and based on the calibrated segmented mapping relationship.

[0061] The different structural state information may include at least two of the following: information on changes in capacitance signal caused by contact between the diaphragm and the upper or lower limit structure and changes in diaphragm displacement; information on changes in resonant frequency output by the resonant strain sensing unit; and information on changes in displacement obtained by the displacement sensing structure corresponding to multiple diaphragm region units.

[0062] The processing unit can comprehensively process the above-mentioned different structural state information according to the pre-obtained calibration relationship, thereby determining the magnitude of the applied pressure.

[0063] Based on the above embodiments, such as Figure 1 As shown, in some embodiments, the processing unit is further configured to differentiate the operating state of the sensor during the external pressure measurement process.

[0064] The processing unit is configured to divide the working range of the sensor based on the capacitance signal change characteristics or contact detection signal, depending on whether the diaphragm is in contact with the upper or lower limit structure.

[0065] In this embodiment, the processing unit can determine whether the diaphragm is in contact with the upper or lower limit structure by detecting whether the amplitude of the capacitance signal change exceeds a preset threshold or whether the slope of the capacitance signal change changes abruptly. The preset threshold can be obtained during the device calibration stage by statistically analyzing the characteristics of capacitance signal changes at different pressure points. In this embodiment, the working range includes at least two types: working ranges where no limit contact occurs and working ranges where limit contact occurs.

[0066] When the diaphragm is operating within its rated range and does not come into contact with the upper or lower limit structure, the processing unit determines the current state as the operating range where no limit contact has occurred; when the diaphragm comes into contact with the upper or lower limit structure under overload pressure, the processing unit determines the current state as the operating range where limit contact has occurred.

[0067] The processing unit is configured to switch between different working ranges and use segmented calibration relationships that match the corresponding working range to convert the acquired sensor signals into applied pressure values. In this way, the processing unit can employ appropriate calculation relationships for different working states to determine the applied pressure.

[0068] Based on the above embodiments, in some embodiments, the processing unit selects segmentation calibration relationships that are different from each other in terms of the type of input information as the target calculation relationship in different working intervals.

[0069] In this embodiment, the types of input information are selected from the following group: capacitance signal change information caused by overall diaphragm deformation; resonant frequency change information caused by local strain state of the diaphragm; displacement change information of the diaphragm at different spatial positions.

[0070] For example, in the working area where no limiting contact occurs, the processing unit can determine the applied pressure mainly based on the capacitance signal change information or the resonant frequency change information; while in the working area where limiting contact occurs, the processing unit can introduce the displacement change information generated by the diaphragm at different spatial positions as auxiliary input information to participate in the pressure calculation.

[0071] By selecting different types of input information in different working ranges, the processing unit can use a more suitable calculation method to determine the applied pressure based on the current structural state.

[0072] Based on the above embodiments, in some embodiments, within the working range where the diaphragm contacts the upper or lower limit structure, the processing unit is configured to generate a preliminary estimate of the applied pressure based on the resonant frequency change information.

[0073] The processing unit is further configured to combine the displacement distribution characteristics reflected by the displacement change information at multiple spatial locations, perform consistency verification on the preliminary estimated value based on a preset consistency criterion, and correct the preliminary estimated value based on the displacement change information when the consistency verification is not satisfied, so as to determine the applied pressure. The consistency criterion includes a consistency judgment rule based on the deviation threshold between the displacement distribution characteristics and the corresponding pressure model, or a consistency judgment rule based on the residual minimization constraint condition.

[0074] In this embodiment, the consistency criterion includes a consistency determination rule based on the deviation threshold between the displacement distribution characteristics and the corresponding pressure model, or a consistency determination rule based on the residual minimization constraint.

[0075] The deviation threshold can be obtained by statistically analyzing the displacement distribution characteristics under different applied pressure conditions during the device calibration stage, so as to ensure the feasibility and reproducibility of the consistency criterion. The processing unit can judge the degree of matching between different input information according to the above consistency criterion. When the consistency condition is met, the preliminary estimate is confirmed; when the consistency condition is not met, the preliminary estimate is corrected.

[0076] By using the above processing method, the applied pressure can be determined based on the multi-source structural state information when the diaphragm is in limited contact.

[0077] In a specific device prototype, the protrusion height of the limiting protrusion structure is 2μm and the lateral dimension is 20μm. The area of ​​the overlapping region between the upper and lower limiting structures is approximately 50%. When the applied pressure moves from the rated range to the overload pressure range, the diaphragm first makes limiting contact with the upper limiting structure and enters a restricted deformation state, limiting the maximum displacement of the diaphragm to a preset range. The processing unit can still output continuous applied pressure measurement results under the limiting contact condition through segmented calibration and consistency verification.

[0078] Based on any of the above embodiments, such as Figure 7 As shown, the present invention also provides a measurement method for a MEMS micro-pressure sensing system. The measurement method is applied to the aforementioned MEMS micro-pressure sensing system, and its specific implementation process is as follows.

[0079] S1. Under applied pressure, the diaphragm deforms relative to the substrate, forming a capacitive gap between the diaphragm and the back electrode plate that varies with the diaphragm's deformation. When applied pressure to the sensing system, the diaphragm, as a deformable structure, displaces under pressure, causing a change in the distance between it and the back electrode plate, thus creating a capacitive gap that varies with the diaphragm's deformation. This change in the capacitive gap serves as the basis for an electrical signal characterizing the overall deformation state of the diaphragm.

[0080] S2. When the applied pressure does not exceed the rated range, the diaphragm undergoes elastic deformation without contacting the upper and lower limit structures. When the applied pressure is within the rated range, the diaphragm undergoes elastic deformation without contacting the upper and lower limit structures. At this time, the deformation of the diaphragm is mainly manifested as continuous and reversible elastic displacement, and the sensing system is in the operating range without limit contact.

[0081] S3. When the applied pressure exceeds the rated range and forms an overload pressure, the diaphragm is displaced towards the back electrode plate or towards the substrate under the action of the overload pressure, and comes into contact with the upper limit structure located between the back electrode plate and the diaphragm or the lower limit structure located between the diaphragm and the substrate, respectively, so as to limit the maximum displacement of the diaphragm in the corresponding direction.

[0082] In this step, when the applied pressure exceeds the rated range and forms an overload pressure, the diaphragm continues to displace under the pressure and comes into contact with the limiting structure in the corresponding direction. By limiting the diaphragm displacement through the upper or lower limiting structure, the diaphragm enters a restricted deformation state under overload pressure conditions, thereby preventing the diaphragm from producing excessive displacement.

[0083] S4. By making the upper limit structure and the lower limit structure have a non-zero overlap area on the plane with the plane where the geometric center of the diaphragm is located as a reference, and setting them symmetrically about the geometric center point of the diaphragm, the diaphragm obtains a symmetrical mechanical constraint state when limit contact occurs.

[0084] In this step, by making the upper limit structure and the lower limit structure form a non-zero overlap area in the vertical projection direction of the plane during the structural design stage, and symmetrically arranging them around the geometric center of the diaphragm, when the diaphragm comes into contact with the limit structure under overload pressure, its stress state is symmetrically distributed in space, thereby enabling the diaphragm to obtain a symmetrical mechanical constraint state.

[0085] In summary, this invention addresses the comprehensive requirements of MEMS micro-pressure sensing systems in practical applications regarding structural reliability, measurement stability, and adaptability to complex working conditions. From a system-level perspective, it optimizes the overall design of the micro-pressure sensing system's operation under different pressure conditions. This ensures measurement sensitivity while effectively mitigating the adverse effects of overload pressure, maintaining stable and distinguishable measurement responses under various operating states. Through the combined effect of the above technical solutions, the overall performance of MEMS micro-pressure sensing systems in terms of reliability, applicability, and long-term operational stability is improved, making them more suitable for various micro-pressure detection scenarios with high requirements for measurement accuracy and reliability. Therefore, this invention has promising application prospects and significant promotional value.

[0086] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of those different embodiments or examples.

[0087] Any process or method description in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing a particular logical function or process. Furthermore, the scope of the preferred embodiments of this application includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functionality involved.

[0088] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art can easily conceive of various variations or substitutions within the technical scope disclosed in this application, and these should all be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A MEMS micro-pressure sensing system, comprising a substrate, a diaphragm disposed on the substrate, and a back electrode plate disposed above the diaphragm and forming a capacitance gap with the diaphragm, characterized in that, Also includes: An upper limit structure is located between the back electrode plate and the diaphragm, and is used to contact the diaphragm under overload pressure exceeding the rated range to limit the maximum displacement of the diaphragm towards the back electrode plate. The lower limiting structure is located between the diaphragm and the substrate, and is used to contact the diaphragm under overload pressure exceeding the rated range to limit the maximum displacement of the diaphragm towards the substrate; the upper limiting structure or the lower limiting structure is a limiting protrusion structure that is protruded relative to the surface of the substrate to reduce the contact area between the diaphragm and the corresponding structure during limiting contact, thereby reducing the risk of adhesion failure. The upper limit structure or the lower limit structure has a non-zero overlap region on the vertical projection of the plane with the plane where the geometric center of the diaphragm is located as a reference, so that the diaphragm obtains a cooperative mechanical constraint state when it makes limiting contact in the vertical direction.

2. The MEMS micro-pressure sensing system according to claim 1, characterized in that, The upper limit structure includes at least one first limiting unit facing the diaphragm protrusion, and the lower limit structure includes at least one second limiting unit facing the diaphragm protrusion and at least partially overlapping the first limiting unit in vertical projection. The protrusion height of the first limiting unit along the normal direction of the diaphragm is greater than the protrusion height of the second limiting unit relative to the substrate surface, so that under the overload pressure in the same direction that causes the diaphragm to displace towards the back electrode plate, the diaphragm displacement gradually increases, the diaphragm preferentially contacts the first limiting unit, and enters a restricted deformation state under greater overload pressure. In the first limiting unit and the second limiting unit, the surface of the first limiting unit that contacts the diaphragm has a preset contact surface morphology that is different from that of the second limiting unit. The preset contact surface morphology is one or more of the following structures: micro-bump array, micro-groove structure, curved transition structure, surface roughening treatment, or anti-adhesion coating.

3. The MEMS micro-pressure sensing system according to claim 1, characterized in that, The lower limiting structure is made of a dielectric insulating material to achieve electrical insulation during limiting contact; the dielectric insulating material is one of silicon nitride, silicon oxide or polyimide; the lower limiting structure is formed as a plurality of spaced limiting bump units, the plurality of spaced limiting bump units together constitute at least one second limiting unit, and is located between the diaphragm and the substrate.

4. The MEMS micro-pressure sensing system according to claim 1, characterized in that, The diaphragm is provided with a resonant strain sensing structure, which includes a mechanical resonant structure disposed on the diaphragm and mechanically coupled to the diaphragm; when the diaphragm is deformed, the inherent resonant frequency of the mechanical resonant structure changes with the mechanical strain state of the diaphragm.

5. A MEMS micro-pressure sensing system according to claim 4, characterized in that, The diaphragm is provided with a resonant strain sensing unit, which includes: a mechanical resonant structure disposed on the diaphragm; an excitation and readout circuit electrically connected to the mechanical resonant structure; the resonant strain sensing unit is configured to excite the mechanical resonant structure and detect the resonant response, and output a resonant frequency signal that changes with the mechanical strain of the diaphragm; the diaphragm is also defined with a plurality of diaphragm region units for local detection, and the plurality of diaphragm region units are respectively provided with displacement sensing structures for detecting local displacement changes of the diaphragm.

6. A MEMS micro-pressure sensing system according to claim 5, characterized in that, The MEMS micro-pressure sensing system includes a processing unit; the processing unit is configured to determine the applied pressure based on two or more different structural state information acquired by the MEMS micro-pressure sensing system and based on the calibrated segmented mapping relationship: information on capacitance signal changes caused by contact between the diaphragm and the upper or lower limit structure and diaphragm displacement changes; information on resonant frequency changes output by the resonant strain sensing unit; and information on displacement changes acquired by the displacement sensing structure corresponding to multiple diaphragm region units.

7. A MEMS micro-pressure sensing system according to claim 1, characterized in that, The processing unit is configured to: divide the working range of the sensor based on the capacitance signal change characteristics or contact detection signal according to whether the diaphragm is in contact with the upper or lower limit structure; the working range includes the working range where no limit contact occurs and the working range where limit contact occurs; and in different working ranges, switch to use the segmented calibration relationship that matches the corresponding working range to convert the acquired sensing signal into an applied pressure value.

8. A MEMS micro-pressure sensing system according to claim 7, characterized in that, The processing unit selects segmented calibration relationships that differ in the types of input information as target calculation relationships within different working intervals; the types of input information are selected from the following groups: capacitance signal change information caused by overall diaphragm deformation; resonant frequency change information caused by local strain state of the diaphragm; displacement change information of the diaphragm at different spatial positions.

9. A MEMS micro-pressure sensing system according to claim 8, characterized in that, Within the working range where the diaphragm contacts the upper or lower limit structure, the processing unit is configured to: generate a preliminary estimate of the applied pressure based on the resonant frequency change information, and combine the displacement distribution characteristics reflected by the displacement change information at multiple spatial locations, perform a consistency check on the preliminary estimate based on a preset consistency criterion, and if the consistency check is not satisfied, correct the preliminary estimate based on the displacement change information to determine the applied pressure. The consistency criterion includes a consistency judgment rule based on the deviation threshold between the displacement distribution characteristics and the corresponding pressure model, or a consistency judgment rule based on the residual minimization constraint condition.

10. A measurement method for a MEMS micro-pressure sensing system, applied to the MEMS micro-pressure sensing system of claim 1, characterized in that, Includes the following steps: S1. Under the action of external pressure, the diaphragm is deformed relative to the substrate, and a capacitance gap that changes with the deformation of the diaphragm is formed between the diaphragm and the back electrode plate. S2. When the applied pressure does not exceed the rated range, the diaphragm undergoes elastic deformation without contacting the upper limit structure and the lower limit structure. S3. When the applied pressure exceeds the rated range and forms an overload pressure, the diaphragm is displaced towards the back electrode plate or towards the substrate under the action of the overload pressure, and comes into contact with the upper limit structure located between the back electrode plate and the diaphragm or the lower limit structure located between the diaphragm and the substrate, respectively, so as to limit the maximum displacement of the diaphragm in the corresponding direction. S4. By making the upper limit structure and the lower limit structure have a non-zero overlap area on the plane with the plane where the geometric center of the diaphragm is located as a reference, and setting them symmetrically about the geometric center point of the diaphragm, the diaphragm obtains a symmetrical mechanical constraint state when limit contact occurs.

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