MEMS differential pressure sensor and preparation method thereof

Abstract

The invention belongs to the technical field of sensors, and particularly relates to an MEMS differential pressure sensor and a preparation method thereof. The MEMS differential pressure sensor comprises a substrate, a vibrating diaphragm part, a back pole part and a supporting part, a back hole structure is arranged in the substrate, the vibrating diaphragm part is arranged on one side of the substrate and seals the back hole structure, the back pole part is arranged on one side, away from the substrate, of the vibrating diaphragm part and is connected with the vibrating diaphragm part, the vibrating diaphragm part is connected with the substrate through the supporting part, and an air leakage channel is arranged in the supporting part. The air leakage channel is communicated with the back hole structure and the outside of the base. According to the MEMS differential pressure sensor provided by the embodiment of the invention, the air leakage channel is arranged in the supporting part instead of forming an air leakage hole in the vibrating diaphragm, so that external pollutants are prevented from directly entering the gap area through the air leakage hole, and the MEMS differential pressure sensor is prevented from losing efficacy due to the external pollutants in the gap area. Meanwhile, the air leakage channel is communicated with the back hole structure and the outside of the base, so that good air leakage performance can be maintained.

Description

Technical Field

[0001] The invention belongs to the technical field of sensors, and in particular relates to a MEMS differential pressure sensor and a preparation method thereof. Background Art

[0002] MEMS (micro-electromechanical system) differential pressure sensors are widely used in various applications. Their basic structure is mainly composed of a diaphragm and a back electrode. The diaphragm is used to sense the pressure changes in the external environment and output signals through changes in capacitance. In traditional MEMS differential pressure sensors, the venting structure is usually designed on the diaphragm. Although this design is simple in process and has a direct venting effect, it has obvious defects.

[0003] The main function of the vent structure is to balance the air pressure inside and outside the sensor, preventing the diaphragm from breaking when the pressure changes too much, thereby enhancing the reliability of the sensor. In addition, the vent structure is also used to perform electrical testing of the sensor at the wafer level. However, the vent structure designed on the diaphragm makes it easy for pollutants in the external environment to enter the gap (gap area) between the diaphragm and the back pole through the vent hole. The entry of pollutants can cause the sensor to fail, reducing its reliability and service life. In order to reduce the risk of pollutants entering, the size of the vent hole is usually reduced, but this will also significantly reduce the venting capacity and affect the performance of the sensor. Summary of the invention

[0004] The purpose of the present invention is to solve the problem that external pollutants easily enter the gap area through the air leakage hole, causing the MEMS differential pressure sensor to fail, at least under the premise of ensuring good air leakage. This purpose is achieved through the following technical solutions:

[0005] A first aspect of the present invention provides a MEMS differential pressure sensor, comprising:

[0006] A substrate, wherein a back hole structure is provided in the substrate;

[0007] A diaphragm portion, the diaphragm portion is arranged on one side of the substrate, and the diaphragm portion closes the back hole structure;

[0008] a back pole portion, the back pole portion being arranged on a side of the diaphragm portion away from the substrate and connected to the diaphragm portion;

[0009] The diaphragm part is connected to the base through the supporting part, and an air leakage channel is arranged in the supporting part, and the air leakage channel is connected to the back hole structure and the outside of the base respectively.

[0010] According to the MEMS differential pressure sensor of the present invention, an air leakage channel is provided in the support part instead of opening an air leakage hole on the diaphragm, so as to prevent external pollutants from directly entering the gap area through the air leakage hole, and prevent the MEMS differential pressure sensor from failing due to external pollutants in the gap area. At the same time, since the air leakage channel connects the back hole structure and the outside of the substrate, it is possible to maintain good air leakage performance. In general, the present invention effectively solves the problem in the prior art that external pollutants easily enter the gap area and cause sensor failure, while ensuring the air leakage capacity and structural stability.

[0011] In addition, the MEMS differential pressure sensor according to the present invention may also have the following additional technical features:

[0012] In some embodiments of the present invention, the support portion and the base are an integrally formed structure.

[0013] In some embodiments of the present invention, the support portion is an oxide layer.

[0014] In some embodiments of the present invention, a thickness of the air leakage channel along a first direction is greater than or equal to 0.1 μm, and the first direction is a direction from the substrate to the diaphragm portion.

[0015] In some embodiments of the present invention, the width of the air leakage channel in a cross section is greater than or equal to 0.1 μm, and the cross section is a plane perpendicular to the first direction.

[0016] In some embodiments of the present invention, the air leakage channel is arranged in a straight line in the direction of the cross section.

[0017] In some embodiments of the present invention, within the direction of the cross section, the air leakage channel has at least one bending structure.

[0018] In some embodiments of the present invention, the number of the air leakage channels is at least two, and the at least two air leakage channels are arranged at intervals along the circumference of the back hole structure.

[0019] A second aspect of the present invention provides a method for preparing a MEMS differential pressure sensor, which is used to prepare the above-mentioned MEMS differential pressure sensor, comprising the following steps:

[0020] Etching a gas release channel on the upper surface of the substrate to form a support portion;

[0021] Depositing an oxide layer on the upper surface of the substrate, and grinding the oxide layer to be flat;

[0022] Growing a thin film layer on the oxide layer in sequence and etching out a diaphragm portion and a back pole portion in sequence;

[0023] etching the substrate to form a back hole structure;

[0024] The substrate, the support portion, the diaphragm portion and the back pole portion are wet-etched.

[0025] A third aspect of the present invention provides a method for preparing a MEMS differential pressure sensor, which is used to prepare the above-mentioned MEMS differential pressure sensor, comprising the following steps:

[0026] Depositing an oxide layer on the upper surface of the substrate and etching the oxide layer to form a gas leakage channel to form a support portion;

[0027] Growing a thin film layer on the oxide layer in sequence and etching out a diaphragm portion and a back pole portion in sequence;

[0028] etching the substrate to form a back hole structure;

[0029] The substrate, the support portion, the diaphragm portion and the back pole portion are wet-etched. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Moreover, the same reference numerals are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0031] Figure 1 The structure diagram of the first embodiment of the MEMS differential pressure sensor according to the embodiment of the present invention is schematically shown;

[0032] Figure 2 The structure diagram of the second embodiment of the MEMS differential pressure sensor according to the embodiment of the present invention is schematically shown;

[0033] Figure 3 for Figure 1 A cross-sectional view of the first embodiment taken along plane BB;

[0034] Figure 4 for Figure 1 A cross-sectional view of the second embodiment taken along plane BB;

[0035] Figure 5 for Figure 1 A cross-sectional view of the third embodiment taken along plane BB;

[0036] Figure 6 A method flow chart of a method for preparing a MEMS differential pressure sensor according to a first embodiment of an implementation mode of the present invention;

[0037] Figure 7This is a flow chart of a method for preparing a MEMS differential pressure sensor according to a second embodiment of an implementation of the present invention.

[0038] The reference numerals are as follows:

[0039] 10. Base; 11. Back hole structure; 20. Diaphragm part; 30. Back pole part; 31. Back pole supporting area; 32. Back pole structure; 40. Support part; 41. Air leakage channel; 101. Gap area. DETAILED DESCRIPTION

[0040] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0041] It should be understood that the terms used herein are only for the purpose of describing specific example embodiments and are not intended to be limiting. Unless the context clearly indicates otherwise, the singular forms "one", "an" and "said" as used herein may also be meant to include plural forms. The terms "include", "comprise", "contain", and "have" are inclusive, and therefore specify the existence of stated features, steps, operations, elements and / or parts, but do not exclude the existence or addition of one or more other features, steps, operations, elements, parts, and / or combinations thereof. The method steps, processes, and operations described herein are not interpreted as necessarily requiring them to be performed in the specific order described or illustrated, unless the execution order is clearly indicated. It should also be understood that additional or alternative steps may be used.

[0042] Although the terms first, second, third, etc. can be used in the text to describe multiple elements, components, regions, layers and / or sections, these elements, components, regions, layers and / or sections should not be limited by these terms. These terms can only be used to distinguish an element, component, region, layer or section from another region, layer or section. Unless the context clearly indicates, terms such as "first", "second" and other numerical terms do not imply order or sequence when used in the text. Therefore, the first element, component, region, layer or section discussed below can be referred to as the second element, component, region, layer or section without departing from the teaching of the example embodiments.

[0043] For ease of description, spatial relative terms may be used herein to describe the relationship of one element or feature relative to another element or feature as shown in the figure, such as "inside", "outside", "inner side", "outer side", "below", "below", "above", "above", etc. Such spatial relative terms are intended to include different orientations of the device in use or operation in addition to the orientation depicted in the figure. For example, if the device in the figure is turned over, then the elements described as "below other elements or features" or "below other elements or features" will subsequently be oriented as "above other elements or features" or "above other elements or features". Therefore, the example term "below..." can include both above and below orientations.

[0044] like Figures 1 to 5 As shown, according to an embodiment of the present invention, a MEMS differential pressure sensor is proposed, including a substrate 10, a diaphragm portion 20, a back pole portion 30 and a support portion 40, wherein a back hole structure 11 is provided in the substrate 10, the diaphragm portion 20 is provided on one side of the substrate 10, the diaphragm portion 20 closes the back hole structure 11, the back pole portion 30 is provided on the side of the diaphragm portion 20 away from the substrate 10 and is connected to the diaphragm portion 20, the diaphragm portion 20 is connected to the substrate 10 through the support portion 40, and an air leakage channel 41 is provided in the support portion 40, and the air leakage channel 41 respectively connects the back hole structure 11 and the outside of the substrate 10.

[0045] According to the MEMS differential pressure sensor of this embodiment, an air leakage channel 41 is provided in the support portion 40 instead of opening an air leakage hole on the diaphragm, so as to prevent external pollutants from directly entering the gap area 101 through the air leakage hole, and prevent the MEMS differential pressure sensor from failing due to external pollutants in the gap area 101. At the same time, since the air leakage channel 41 connects the back hole structure 11 and the outside of the substrate 10, good air leakage performance can be maintained. In general, the present invention effectively solves the problem in the prior art that external pollutants easily enter the gap area 101 and cause sensor failure, while ensuring the air leakage capacity and structural stability. In addition, the setting of the air leakage channel 41 can be compatible with the existing MEMS manufacturing process, and does not require additional complex process steps, thereby maintaining the simplicity of the manufacturing process and the rationality of the cost.

[0046] like Figure 1As shown, in some embodiments, the support portion 40 and the substrate 10 are an integrally formed structure. The support portion 40 and the substrate 10 are an integrally formed structure, providing mechanical support for the diaphragm portion 20. The integrally formed substrate 10 and support portion 40 eliminate the weaknesses of multi-component connections and improve the mechanical strength and stability of the overall structure. Through a precise etching process, the shape and size consistency of the air leakage channel 41 is ensured, mechanical stress concentration is reduced, and the impact and vibration resistance are improved. At the same time, the one-piece molding design reduces multiple manufacturing steps and assembly processes, simplifies the overall process flow, and reduces manufacturing complexity. The high-precision etching process makes the formation of the air leakage channel 41 more consistent and reliable, and improves manufacturing efficiency and yield rate. In addition, etching the air leakage channel 41 directly on the substrate 10 reduces material and assembly costs, improves production efficiency, and reduces total production costs. The simplified manufacturing process and high yield rate further improve production efficiency and enhance economic benefits.

[0047] Specifically, a circular area is etched in the middle of the substrate 10 as a barrier layer for subsequent deep silicon etching. By setting a pre-etched circular area, it is ensured that the deep silicon etching stops at a predetermined depth, thereby preventing over-etching and protecting the diaphragm part 20 from damage. The above-mentioned predetermined depth can be 0.1μm. The technical effects of this embodiment are as follows: first, by setting a circular area larger than the maximum expected diameter of the back hole, it is ensured that the back hole structure 11 can be accurately formed, thereby improving manufacturing accuracy. In addition, it prevents errors in the etching process and damage to the diaphragm part 20 caused by over-etching, thereby improving the reliability and stability of the overall structure of the sensor. Finally, a uniform and consistent etching endpoint is provided to improve the stability of the etching process and reduce the impact of process fluctuations on device performance.

[0048] Specifically, a layer of oxide is deposited on the upper surface of the substrate 10 where the gas leakage channel 41 is etched, and the gas leakage channel 41 and the deep silicon etching barrier layer are filled, and the thickness of the oxide layer is not less than the etching depth of the gas leakage channel 41. The thickness of the oxide layer is not less than the etching depth of the gas leakage channel 41, ensuring that the subsequent etching process can be stopped accurately to prevent over-etching. The filled oxide layer provides a stable etching endpoint, which improves the accuracy and consistency of the etching process.

[0049] It can be understood that the deep silicon etching barrier layer mentioned above is a thin film layer used to limit and control the etching depth of silicon materials during deep silicon etching (Deep Reactive Ion Etching, DRIE). It is usually made of a material with excellent etching resistance, and can provide a clear termination surface during the etching process to ensure that the etching stops at a predetermined depth. It can provide a clear etching endpoint to ensure that the depth of the silicon material during the etching process is accurately controlled to prevent over-etching. At the same time, it protects the underlying sensitive structure from being damaged by deep silicon etching in a multi-layer structure.

[0050] Furthermore, the oxide surface is polished flat by physical and chemical polishing (Chemical Mechanical Polishing, CMP) and stops on the upper surface of the substrate 10. Through the CMP process, the oxide surface is polished to make it consistent with the surface flatness of the substrate 10, eliminating surface unevenness. A flat surface helps to reduce defects in subsequent processes and improve the quality and reliability of the overall device. The flat oxide layer provides uniform mechanical support to ensure the stability and reliability of the diaphragm part 20 and other structures during use. By flattening the surface, stress concentration caused by surface unevenness is reduced and the service life of the device is extended. In addition, a flat surface helps to ensure the consistency of electrical properties, reduce fluctuations in capacitance and other electrical parameters, and improve the accuracy and reliability of the sensor. The flat surface after the CMP process is conducive to the deposition and electrical contact of metal pads, and improves the efficiency and stability of signal transmission.

[0051] Furthermore, a layer of nitride is deposited on the upper surface of the above-mentioned polished and flattened substrate 10 as a release isolation layer (also as the first film layer of the diaphragm), with a thickness of not less than 0.1 μm. First, the nitride layer serves as a release isolation layer to protect the conductive layer of the diaphragm part 20 from damage during the release process. Nitride materials have excellent chemical stability and mechanical strength, which increases the durability and corrosion resistance of the surface. At the same time, as the first film layer, the nitride layer can effectively alleviate the stress concentration of the diaphragm part 20, reduce the generation of cracks and defects, and improve the mechanical properties and reliability. Provide additional mechanical support to ensure that the diaphragm remains stable during pressure changes. Finally, the nitride layer has good insulation properties, reduces parasitic capacitance and leakage current, and improves the electrical characteristics of the MEMS differential pressure sensor. As the first film layer of the diaphragm, the nitride layer helps to form a stable capacitor structure and improve the sensitivity and accuracy of signal detection.

[0052] Furthermore, other structures of the MEMS differential pressure sensor are deposited and etched above the nitride layer, including but not limited to the diaphragm portion 20, the back pole support area 31, the back pole structure 32, the metal pad, etc. First, the formation step of the diaphragm portion 20 is to deposit a layer of polysilicon (Poly-Si) on the nitride layer as the diaphragm material, and the thickness is determined according to the design requirements. The pattern of the diaphragm portion 20 is defined on the polysilicon layer using photolithography technology, and a mask is formed by coating photoresist, exposing and developing. The polysilicon layer is etched through a photolithography mask using a reactive ion etching (RIE) process to form the desired diaphragm structure. The formation step of the back pole support area 31 is to deposit a layer of silicon oxide (SiO) or silicon nitride (SiN) on the polysilicon layer as an insulating layer to provide back pole support. The pattern of the back pole support area 31 is defined on the insulating layer using photolithography technology, and a mask is formed by coating photoresist, exposing and developing. The back electrode support area 31 is formed by etching the insulating layer through a photolithography mask using dry etching or wet etching. The back electrode structure 32 is at least a two-layer structure, one of which is a conductive layer and serves as a back electrode, which cooperates with the diaphragm part 20 to sense the pressure difference. The conductive layer is usually composed of polysilicon or other metal materials. The other layer is an insulating layer, which is used for electrical insulation, isolation of different functional areas and improvement of structural strength. The material of the insulating layer can be nitride or other non-conductive materials. The step of forming a metal pad includes depositing a layer of metal, such as aluminum or gold, on the back electrode structure 32 as a pad material, and the thickness is determined according to the design requirements. The pattern of the metal pad is defined on the metal layer using photolithography technology, and a mask is formed by coating photoresist, exposing and developing. The metal layer is etched through a photolithography mask using dry etching or wet etching to form the desired metal pad structure.

[0053] It is understandable that the diaphragm portion 20 and the back pole structure 32 form a capacitor, and the diaphragm of the diaphragm portion 20 usually serves as one electrode of the capacitor. When the external pressure changes, the diaphragm will deform, resulting in a change in the gap (gap area 101) between the other electrode. The back pole structure 32, as another electrode of the capacitor, is fixed on the substrate 10 and usually remains stationary. The gap (gap area 101) between the diaphragm and the back pole is an important component of the capacitor. As the diaphragm is deformed, the size of the gap area 101 changes, resulting in a change in the capacitance value. The gap area 101 is usually filled with air or maintained in a vacuum to ensure sensitive capacitance changes.

[0054] Further, the lower surface of the substrate 10 is thinned to the target thickness of the MEMS differential pressure sensor and the back hole structure 11 is etched, stopping at the above-mentioned oxide layer as the deep silicon etching barrier. Photolithography is performed on the thinned surface of the substrate 10 to define the pattern of the back hole structure 11. An etching mask is formed by coating a photoresist, exposing and developing. A deep reactive ion etching process is used to etch the back hole structure 11 on the substrate 10 through a photolithography mask. The etching process stops on the deep silicon etching barrier layer (oxide layer) to ensure precise control of the etching depth. After etching, an appropriate cleaning agent is used to remove the photoresist residue and clean the etched area to ensure that the back hole area is clean and free of pollution. By thinning the substrate 10 to the target thickness of the MEMS differential pressure sensor, it is ensured that the mechanical and electrical properties of the sensor meet the design requirements. Accurate thickness control and a complete back hole structure 11 design enhance the sensitivity of the diaphragm and improve the sensor's responsiveness to changes in pressure differentials. By strictly controlling the etching depth and surface treatment, defects and stress concentration introduced during the manufacturing process are reduced, extending the service life of the MEMS differential pressure sensor.

[0055] Furthermore, wet etching is used to cleanly etch the oxide in the gap area, the deep silicon etching barrier layer, and the gas leakage channel 41, thereby forming a gas leakage channel 41 connecting the back hole area and the outside of the substrate 10 on the substrate 10 structure, the entrance of the gas leakage channel 41 is in the back hole area, and the outlet of the gas leakage channel 41 is outside the substrate 10. Among them, a suitable wet etching agent, such as hydrogen fluoride (HF) solution, is selected to remove the oxide layer. HF solution can effectively etch silicon oxide, but has little effect on silicon itself. During the etching process, ensure that the untreated area is protected to prevent the corrosive agent from damaging other structures. The final wet etching step completely removes the oxide in the gap, the deep silicon etching barrier layer, and the gas leakage channel 41, and successfully forms the gas leakage channel 41 connecting the back hole area and the outside of the substrate 10. This technical implementation not only improves the performance and reliability of the MEMS differential pressure sensor, but also optimizes the production process and enhances manufacturing efficiency and economy.

[0056] like Figure 2As shown, in other embodiments, the support portion 40 is an oxide layer, which provides mechanical support for the diaphragm portion 20. The oxide layer is generally silicon oxide or other suitable oxide materials deposited on the substrate 10. An air leakage channel 41 is provided in the support portion 40, and the air leakage channel 41 connects the back hole structure 11 and the outside of the substrate 10 respectively. The air leakage channel 41 is formed in the oxide layer, and the channel is etched in the oxide layer by an etching process. The air leakage channel 41 connects the back hole structure 11 to the outside of the substrate 10, which is used to balance the internal and external air pressures and prevent the diaphragm from being damaged when the pressure changes too much. The oxide layer has high mechanical strength and stability, can provide reliable mechanical support, and ensure the stability of the diaphragm portion 20. The oxide material has excellent thermal stability, can maintain stable performance in a high temperature environment, and improves the adaptability of the sensor in various working environments. At the same time, the dense structure of the oxide layer gives it good sealing, which can effectively prevent external pollutants from entering the gap area 101 through the air leakage channel 41. In addition, the surface of the oxide layer is flat, which reduces the chance of pollutant adhesion and further improves the reliability of the sensor. In addition, the shape and size of the air leakage channel 41 in the oxide layer are precisely controlled through an etching process to ensure the performance consistency of the air leakage channel 41. The optimized air leakage channel 41 maintains good air leakage capacity while ensuring protection from pollutants, achieves internal pressure balance, and protects the diaphragm part 20 from damage due to excessive pressure changes. Finally, the oxide layer can be deposited and etched on the substrate 10 through standard semiconductor processes, which simplifies the manufacturing process and reduces manufacturing costs. By using existing mature etching processes, production efficiency and product consistency are improved, and defects in the manufacturing process are reduced.

[0057] like Figure 1 As shown, it can be understood that the first direction is the direction from the substrate 10 to the diaphragm portion 20. Figure 1 As shown by arrow a, the cross section is a horizontal plane perpendicular to the first direction. Figure 1 The cross-sectional view of the BB plane is shown.

[0058] Furthermore, along the first direction, the thickness of the air leakage channel 41 is greater than 0.1 μm, which ensures that the channel is deep enough to achieve effective air pressure balance and prevent the diaphragm from being damaged when the pressure changes too much.

[0059] Furthermore, the width of the gas leakage channel 41 in the cross section is greater than or equal to 0.1 μm. The width of the gas leakage channel 41 is greater than or equal to 0.1 μm, which provides a sufficient channel width to ensure that the gas can pass smoothly, thereby achieving a rapid gas leakage effect.

[0060] like Figure 3As shown, it can be understood that in the direction of the cross section, the air leakage channel 41 is arranged in a straight line. The straight channel provides a lower flow resistance, allowing the gas to pass through the air leakage channel 41 more smoothly, thereby improving the air leakage efficiency. The effective air leakage capacity speeds up the pressure balance process and improves the response speed and sensitivity of the MEMS differential pressure sensor. At the same time, the straight channel design reduces the dead corners and accumulation points that may appear in complex shapes, reducing the risk of contaminant accumulation. The straight channel is easier to clean during manufacturing and maintenance, further improving the reliability and service life of the sensor.

[0061] like Figure 4 As shown, it can be understood that in the direction of the cross section, the air leakage channel 41 has at least one bending structure. The bending structure increases the difficulty for pollutants to enter the air leakage channel 41, plays an additional filtering role, and reduces the risk of external pollutants entering the gap area 101. At the same time, the bending structure can adjust the speed and direction of the air flow, optimize the gas flow path, and make the air pressure balance faster. In addition, the bending design helps to evenly distribute the pressure during the air leakage process, reduce the phenomenon of excessive or low local pressure, and ensure the stable operation of the sensor.

[0062] like Figure 5 As shown, further, the path of the air leakage channel 41 in the support portion 40 is extended. The extended path of the air leakage channel 41 increases the difficulty for pollutants to enter the channel, and further blocks the possibility of pollutants reaching the gap area 101. The extended path provides a multi-stage filtering effect. Even if some pollutants enter the channel, the multiple turns and extended paths along the way will capture and block more pollutants. At the same time, the extended path of the air leakage channel 41 effectively slows down the air flow speed and reduces the air flow noise through multiple bends and turns, thereby improving the comfort of the sensor. The complex structure of the air leakage channel 41 has a certain noise shielding effect, making the MEMS differential pressure sensor quieter when working.

[0063] like Figures 3 to 5As shown, further, the number of the air leakage channels 41 is at least two, and at least two air leakage channels 41 are arranged at intervals along the circumference of the back hole structure 11. The design of at least two air leakage channels 41 significantly improves the air leakage capacity of the sensor, and can balance the internal and external pressure changes more quickly. Multiple air leakage channels 41 provide redundant paths. Even if one channel is blocked, other air leakage channels 41 can still work normally, ensuring the continuous reliability of the air leakage function. At the same time, multiple air leakage channels 41 help to distribute and dissipate heat more evenly, improve the thermal management ability of the sensor, and improve its performance in high temperature environments. The multi-channel design increases the path and area of ​​the air flow, improves the cooling effect, and ensures the stable operation of the sensor under high temperature conditions. In general, by increasing the number of air leakage channels 41 to at least two, the technical solution significantly improves the air leakage capacity, contaminant protection ability, mechanical properties and thermal management ability of the MEMS differential pressure sensor. The design of multiple air leakage channels 41 not only enhances the overall performance and reliability of the sensor, but also optimizes the manufacturing process, improves production efficiency and product consistency. This design meets the needs of more demanding applications and ensures the long-term stable operation of the MEMS differential pressure sensor in various complex working environments.

[0064] It is understandable that the back pole support area 31 is used to support the back pole structure 32 and provide the necessary mechanical strength and stability. It is usually directly connected to the substrate 10 to form a stable platform. The back pole structure 32 is an electrode of a capacitor, and together with the diaphragm forms a capacitor structure. It detects the displacement of the diaphragm and measures the pressure change by the change in capacitance. The back pole support area 31 provides mechanical support for the back pole structure 32, and forms a stable mechanical connection by physical contact or deposition on the back pole support area 31. The back pole support area 31 is usually an insulating material to ensure electrical isolation between the back pole structure 32 and other non-conductive parts, and the back pole structure 32 is connected to the external circuit through a conductive material.

[0065] It can be understood that the diaphragm portion 20 includes a diaphragm bottom layer (Bottom Layer), a diaphragm conductive layer (ConductiveLayer), a diaphragm top layer (Top Layer), a Dimple structure (Dimple Structures), a gap area (Gap Area) and a release layer structure (Release Layer Structure, RLS).

[0066] like Figure 6 As shown, in the first embodiment of this implementation mode, a method for preparing a MEMS differential pressure sensor is also proposed, which is used to prepare the above-mentioned MEMS differential pressure sensor, and includes the following steps:

[0067] A gas release channel 41 is etched on the upper surface of the substrate 10 to form a support portion 40;

[0068] Depositing an oxide layer on the upper surface of the substrate 10, and grinding the oxide layer to be flat;

[0069] A thin film is grown on the oxide layer in sequence and a diaphragm portion 20 and a back pole portion 30 are etched in sequence;

[0070] The substrate 10 is etched to form a back hole structure 11;

[0071] The substrate 10 , the support portion 40 , the diaphragm portion 20 and the back pole portion 30 are wet-etched.

[0072] Specifically, the above preparation method includes the following process steps:

[0073] 1. Etching the gas leakage channel 41 pattern and the deep silicon etching barrier layer area

[0074] The patterns of the gas leakage channel 41 and the deep silicon etching barrier layer are defined on the silicon substrate 10 (Si sub) by using photolithography technology, a mask is formed by coating photoresist, exposing and developing, and the gas leakage channel 41 pattern and the deep silicon etching barrier layer area are etched out by dry etching process.

[0075] 2. Fill the gas leakage channel 41 and the deep silicon etching stop layer area with an oxide layer

[0076] A layer of oxide (such as SiO) is deposited in the etched gas leakage channel 41 and the deep silicon etching stop layer area to fill these areas and ensure the integrity of the structure.

[0077] 3. Grind the surface flat and stop on the upper surface of Si sub

[0078] The surface oxide layer is polished by a chemical mechanical polishing (CMP) process until the surface of the Si substrate 10 is exposed, ensuring flatness and smoothness.

[0079] 4. Diaphragm bottom (bottom) nitride layer

[0080] A layer of nitride (such as SiN) is deposited on the polished surface of the substrate 10 as the bottom layer of the diaphragm to provide mechanical support and insulation effect.

[0081] 5. Diaphragm conductive layer

[0082] A layer of polysilicon or other conductive material is deposited on the nitride layer as a conductive layer of the diaphragm for capacitance detection.

[0083] 6. Diaphragm top (top layer) nitride layer

[0084] Another layer of nitride is deposited on top of the conductive layer to form the top layer of the diaphragm, providing protection and support.

[0085] 7. Oxide Deposition and Patterning

[0086] A top oxide layer is grown to form a gap area, and a Dimple (a tiny groove or protrusion structure) is etched on the oxide to improve the reliability of the MEMS differential pressure sensor.

[0087] 8. RLS barrier wall etching in gap area

[0088] An RLS (Release, wet release) barrier is etched in the gap area through photolithography and etching processes for protection in the subsequent release process.

[0089] 9. Dimple, RLS barrier wall, back electrode bottom nitride layer

[0090] Above the Dimple and RLS barrier wall structures, a bottom nitride layer of the back electrode is deposited for mechanical support and insulation of the back electrode.

[0091] 10.Via etching (through hole)

[0092] Via holes are etched in the back electrode structure 32 by photolithography and dry etching processes for electrical connection of subsequent metal layers.

[0093] 11. Back conductive layer

[0094] A layer of polysilicon or other conductive material (such as aluminum, titanium or chromium) is deposited in the via hole and on the back electrode structure 32 as a conductive layer of the back electrode to ensure the function of the capacitor is realized.

[0095] 12. Back electrode top nitride layer

[0096] A layer of nitride is deposited on the back electrode conductive layer to form the top layer of the back electrode, providing mechanical protection and insulation.

[0097] 13. Sound hole etching

[0098] A sound hole is etched in the back electrode structure 32 by photolithography and dry etching process for pressure sensing and air release functions.

[0099] 14. Open the metal pad position

[0100] Through photolithography and dry etching processes, the location of the metal pad is etched on the top nitride layer to ensure electrical connection.

[0101] 15.Metal pad

[0102] A metal layer (such as aluminum or gold) is deposited at the etched pad location to form a metal pad for external electrical connection.

[0103] 16. Back hole area etching

[0104] A deep reactive ion etching (DRIE) process is used to etch a back hole region on the lower surface of the substrate 10 , ensuring that the etching depth is accurate and stops on the deep silicon etching barrier layer.

[0105] 17. Gap area and air release channel 41 wet release

[0106] Finally, wet etching technology is used to remove oxides in the gap area, the deep silicon etching barrier layer and the gas leakage channel 41 to form a complete structure of the gas leakage channel 41. Through cleaning and inspection, the smooth flow and structural integrity of the gas leakage channel 41 are ensured.

[0107] like Figure 7 As shown, in the second embodiment of this implementation mode, a method for preparing a MEMS differential pressure sensor is also proposed, which is used to prepare the above-mentioned MEMS differential pressure sensor, and includes the following steps:

[0108] An oxide layer is deposited on the upper surface of the substrate 10 and the oxide layer is etched to form a gas leakage channel 41 to form a support portion 40;

[0109] A thin film is grown on the oxide layer in sequence and a diaphragm portion 20 and a back pole portion 30 are etched in sequence;

[0110] The substrate 10 is etched to form a back hole structure 11;

[0111] The substrate 10 , the support portion 40 , the diaphragm portion 20 and the back pole portion 30 are wet-etched.

[0112] Specifically, the above preparation method includes the following process steps:

[0113] 1. Etching out the pattern of the exhaust channel 41

[0114] The oxide layer deposited on the substrate 10 using photolithography technology defines the pattern of the gas leakage channel 41, and a mask is formed by coating photoresist, exposing and developing. The gas leakage channel 41 pattern is etched using a dry etching process (such as reactive ion etching, RIE) to ensure that the shape and depth of the gas leakage channel 41 meet the design requirements.

[0115] 2. Etch RLS barrier walls along both sides of the air leakage channel 41 and deposit a nitride layer at the bottom of the diaphragm. Etch RLS barrier walls on both sides of the air leakage channel 41 to provide support and protection. Deposit a layer of nitride (such as SiN) as the bottom layer of the diaphragm to provide mechanical support and isolation.

[0116] 3. Deposition of diaphragm conductive layer

[0117] A layer of polysilicon or other conductive material is deposited on the nitride layer at the bottom of the diaphragm to form a conductive layer of the diaphragm for capacitance detection.

[0118] 4. Deposition of diaphragm top nitride layer

[0119] A layer of nitride is deposited on top of the conductive layer to form the top layer of the diaphragm to provide protection and support.

[0120] 5. Oxide Deposition and Patterning

[0121] A top oxide layer is grown to form a gap area, and a Dimple (a tiny groove or protrusion structure) is etched on the oxide to improve the reliability of the MEMS differential pressure sensor.

[0122] 6. RLS barrier wall etching in the gap area

[0123] An RLS (Release, wet release) barrier is etched in the gap area through photolithography and etching processes for protection in the subsequent release process.

[0124] 7. Deposition of Dimple, RLS barrier wall, and bottom nitride layer

[0125] A bottom nitride layer of the back electrode is deposited above the Dimple and RLS barrier wall structures for mechanical support and insulation of the back electrode.

[0126] 8.Via Etching

[0127] Via holes are etched in the back electrode structure 32 by photolithography and dry etching processes for electrical connection of subsequent metal layers.

[0128] 9. Deposition of back-conductive layer

[0129] A layer of polysilicon or other conductive material (such as aluminum, titanium or chromium) is deposited in the via hole and on the back electrode structure 32 as a conductive layer of the back electrode to ensure the function of the capacitor is realized.

[0130] 10. Deposition of the back electrode top nitride layer

[0131] A layer of nitride is deposited on the back electrode conductive layer to form the top layer of the back electrode to provide mechanical protection and insulation.

[0132] 11. Sound hole etching

[0133] A sound hole is etched in the back electrode structure 32 by photolithography and dry etching process for pressure sensing and air release functions.

[0134] 12. Open the metal pad position

[0135] Through photolithography and dry etching processes, the location of the metal pad is etched on the top nitride layer to ensure electrical connection.

[0136] 13. Depositing metal pads

[0137] A metal layer (such as aluminum or gold) is deposited at the etched pad location to form a metal pad for external electrical connection.

[0138] 14. Back hole area etching

[0139] A deep reactive ion etching (DRIE) process is used to etch a back hole region on the lower surface of the substrate 10 , ensuring that the etching depth is accurate and stops on the deep silicon etching barrier layer.

[0140] 15. Gap and air release channel 41 wet release

[0141] Finally, the wet etching technology is used to remove the oxides in the gap, the deep silicon etching barrier layer and the gas leakage channel 41 to form a complete gas leakage channel 41 structure.

[0142] By cleaning and inspecting, the unblocking and structural integrity of the air leakage passage 41 are ensured.

[0143] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A MEMS differential pressure sensor, characterized in that: include: A substrate, wherein a back hole structure is provided in the substrate; A diaphragm portion, the diaphragm portion is arranged on one side of the substrate, and the diaphragm portion closes the back hole structure; a back pole portion, the back pole portion being arranged on a side of the diaphragm portion away from the substrate and connected to the diaphragm portion; The diaphragm part is connected to the base through the supporting part, and an air leakage channel is arranged in the supporting part, and the air leakage channel is connected to the back hole structure and the outside of the base respectively.

2. The MEMS differential pressure sensor according to claim 1, characterized in that: The support portion and the base are an integrally formed structure.

3. The MEMS differential pressure sensor according to claim 1, characterized in that: The supporting portion is an oxide layer.

4. The MEMS differential pressure sensor according to any one of claims 1 to 3, characterized in that: The thickness of the air leakage channel along a first direction is greater than or equal to 0.1 μm, and the first direction is a direction from the substrate to the diaphragm portion.

5. The MEMS differential pressure sensor according to claim 4, characterized in that: The width of the air leakage channel in a cross section is greater than or equal to 0.1 μm, and the cross section is a plane perpendicular to the first direction.

6. The MEMS differential pressure sensor according to claim 5, characterized in that: In the direction of the cross section, the air leakage channel is arranged in a straight line.

7. The MEMS differential pressure sensor according to claim 5, characterized in that: In the direction of the cross section, the air leakage channel has at least one bending structure.

8. The MEMS differential pressure sensor according to any one of claims 1 to 3, characterized in that: The number of the air leakage channels is at least two, and at least two of the air leakage channels are arranged at intervals along the circumference of the back hole structure.

9. A method for preparing a MEMS differential pressure sensor, characterized in that: The method for preparing the MEMS differential pressure sensor according to any one of claims 1 to 8 comprises the following steps: Etching a gas release channel on the upper surface of the substrate to form a support portion; Depositing an oxide layer on the upper surface of the substrate, and grinding the oxide layer to be flat; Growing a thin film layer on the oxide layer in sequence and etching out a diaphragm portion and a back pole portion in sequence; etching the substrate to form a back hole structure; The substrate, the support portion, the diaphragm portion and the back pole portion are wet-etched.

10. A method for preparing a MEMS differential pressure sensor, characterized in that: The method for preparing the MEMS differential pressure sensor according to any one of claims 1 to 8 comprises the following steps: Depositing an oxide layer on the upper surface of the substrate and etching the oxide layer to form a gas leakage channel to form a support portion; Growing a thin film layer on the oxide layer in sequence and etching out a diaphragm portion and a back pole portion in sequence; etching the substrate to form a back hole structure; The substrate, the support portion, the diaphragm portion and the back pole portion are wet-etched.

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