MEMS magnetic field sensor and manufacturing method thereof

Abstract

The invention discloses an MEMS magnetic field sensor and a manufacturing method thereof, and relates to the technical field of MEMS magnetic field sensors, the MEMS magnetic field sensor comprises a substrate and a coupled resonator, the substrate is provided with a cavity, and a suspension plate is formed; the coupled resonator comprises an electrode assembly and a magnetoelectric composite film, the electrode assembly comprises a bottom electrode layer, the bottom electrode layer is attached to the substrate, anchor point beams are arranged at the two ends of the suspension plate, and the anchor point beams are connected with the bottom electrode layer so that the suspension plate can be suspended on the cavity; the magnetoelectric composite film is attached to the bottom electrode layer, and a stress release hole is formed in the coupled resonator and communicated with the cavity. After the stress is applied, the stress is redistributed, and the stress originally concentrated in a certain area is dispersed into surrounding materials, so that the local maximum stress value is reduced, the stress concentration phenomenon is reduced, the residual stress can be effectively released, the residual stress of the MEMS magnetic field sensor is easier to release, and the reliability of the MEMS magnetic field sensor is improved. And the coupling manufacturing yield of the MEMS magnetic field sensor is greatly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of MEMS magnetic field sensors, and in particular to a MEMS magnetic field sensor and a manufacturing method thereof. Background Art

[0002] Existing MEMS magnetic field sensors induce stress or strain on piezoelectric materials through the magnetostriction of magnetostrictive materials in magnetoelectric composite films under the action of an external magnetic field. The piezoelectric material produces a certain electrical effect under the action of this stress, and ultimately uses magnetic signals to generate and output measurable electrical signals, thereby achieving the coupling of magnetic effect and piezoelectric effect to detect the magnetic field.

[0003] At present, the detection sensitivity of MEMS magnetic field sensors based on magnetoelectric composite films is low, and there is a large gap from the theoretical detection limit. The main optimization direction lies in the coupling material system, coupling thickness and resonant structure of the coupling resonator. However, optimization through the above method may cause the MEMS magnetic field sensor to face the problem of difficulty in stress release, resulting in a low coupling manufacturing yield of the MEMS magnetic field sensor.

[0004] Therefore, it is necessary to provide a new MEMS magnetic field sensor and a manufacturing method thereof to solve the above technical problems. Summary of the invention

[0005] The main purpose of the present invention is to provide a MEMS magnetic field sensor and a manufacturing method thereof, aiming to improve the technical problem of difficulty in stress release of MEMS magnetic field sensors in the prior art.

[0006] To achieve the above object, according to one aspect of the present invention, the MEMS magnetic field sensor provided by the present invention includes:

[0007] A substrate, wherein the substrate is formed with a cavity and forms a suspension plate;

[0008] A coupled resonator, the coupled resonator comprising an electrode assembly and a magnetoelectric composite film; the electrode assembly comprising a bottom electrode layer, the bottom electrode layer being adhered to the substrate, anchor beams being provided at both ends of the suspension plate, the anchor beams being connected to the bottom electrode layer so that the suspension plate is suspended over the cavity; the magnetoelectric composite film being adhered to the bottom electrode layer; the coupled resonator being formed with a stress release hole, the stress release hole being connected to the cavity.

[0009] In one embodiment, the electrode assembly further includes a top electrode layer, the magnetoelectric composite film includes a piezoelectric film layer and a magnetostrictive film layer laminated in sequence, the piezoelectric film layer is laminated to the bottom electrode layer, and the top electrode layer is laminated to the magnetostrictive film layer.

[0010] In one embodiment, the electrode assembly further includes a top electrode layer, the magnetoelectric composite film includes a piezoelectric film layer and a magnetostrictive film layer, the piezoelectric film layer is adhered to the bottom electrode layer, and two sides of the top electrode layer are respectively adhered to the piezoelectric film layer and the magnetostrictive film layer.

[0011] In one embodiment, the number of the stress release holes is two, and the two stress release holes are arranged at intervals along the width direction of the coupled resonator.

[0012] In one embodiment, the stress relief hole is a square hole and extends along the length direction of the coupled resonator.

[0013] In one embodiment, there are multiple coupling resonators, and the multiple coupling resonators are arranged at intervals.

[0014] In one embodiment, the thickness of the suspension plate ranges from 500 nm to 20 μm, the thickness of the piezoelectric film layer ranges from 500 nm to 2 μm, the thickness of the magnetostrictive film layer ranges from 500 nm to 2 μm, and the ratio of the thickness of the piezoelectric film layer to the thickness of the magnetostrictive film layer ranges from 0.8 to 1.2.

[0015] In one embodiment, the material of the piezoelectric film layer is AlN, AlSc x N or lead zirconate titanate, wherein x is in the range of 0.40 to 0.45.

[0016] According to another aspect of the present invention, the present invention further provides a method for manufacturing a MEMS magnetic field sensor, the method for manufacturing a MEMS magnetic field sensor is applied to the MEMS magnetic field sensor as described above, and the method for manufacturing a MEMS magnetic field sensor comprises the following steps:

[0017] Processing and forming a coupled resonator on a substrate;

[0018] A mask is fabricated on the coupled resonator by photolithography patterning, and a pattern is etched on the coupled resonator by a front dry method to form a stress release hole;

[0019] A mask is fabricated on the back side of the substrate by photolithography patterning, a cavity is formed on the substrate by a back side deep dry method, and a suspended plate is formed on the coupled resonator.

[0020] In one embodiment, the step of depositing a coupled resonator on a substrate comprises:

[0021] Depositing a bottom electrode layer on the substrate;

[0022] Depositing a piezoelectric thin film layer on the bottom electrode layer, making a mask on the bottom electrode layer by photolithography, and then patterning the piezoelectric thin film layer by wet etching or dry etching process;

[0023] Patterning the bottom electrode layer by wet etching or dry etching process;

[0024] A mask is made on the piezoelectric film layer by photolithography patterning, and a magnetostrictive film layer is deposited on the piezoelectric film layer, and then the magnetostrictive film layer is patterned by a lift-off process;

[0025] A mask is made on the magnetostrictive film layer by photolithography and patterning, and a top electrode layer is deposited on the magnetostrictive film layer, and then the top electrode layer is patterned by a lift-off process.

[0026] In the above scheme, the MEMS magnetic field sensor includes a substrate and a coupled resonator, the substrate is formed with a cavity and forms a suspension plate; the coupled resonator includes an electrode assembly and a magneto-electric composite film, the electrode assembly includes a bottom electrode layer, the bottom electrode layer is adhered to the substrate, anchor beams are provided at both ends of the suspension plate, and the anchor beams are connected to the bottom electrode layer so that the suspension plate is suspended on the cavity; the magneto-electric composite film is adhered to the bottom electrode layer, and the coupled resonator is formed with a stress release hole, which connects the cavity. Single crystal silicon or other suitable materials are used as substrates, and a cavity is formed on the substrate by deep dry etching on the back side, providing a space for free movement of the suspended structure in the cavity. The bottom electrode layer is attached to the substrate, and the bottom electrode layer is used to apply voltage and collect signals. The suspension board is suspended above the cavity, and the two ends of the suspension board are connected to the bottom electrode layer through anchor beams. The anchor beams are used to support and fix the suspension board to ensure that the suspension board can vibrate freely without excessive deformation when subjected to force. The suspension board is usually composed of one or more layers of materials, such as silicon or metal. The suspension board provides a free vibration platform so that the magnetoelectric composite film can respond to changes in the external magnetic field. The magnetoelectric composite film is attached to the bottom electrode layer, has piezoelectric effect and magnetostrictive effect, can generate electrical signals under strain, and can deform under magnetic field. The bottom electrode layer is used to apply voltage and collect signals, and then a stress release hole is formed on the upper coupling resonator, and the stress release hole is connected to the cavity. The stress release hole formed by processing in this way provides a free deformation space by changing the stress distribution, inhibits crack propagation, and smoothes the stress gradient, thereby effectively releasing residual stress; when using When using a MEMS magnetic field sensor, when the external magnetic field changes, the magneto-electric composite film will deform, generate strain, and generate electrical signals. The electrical signals generated by the magneto-electric composite film can be collected through the bottom electrode layer. After these electrical signals are amplified and processed, the changes in the external magnetic field can be measured. In the present invention, stress release holes are formed on the coupled resonator. After stress is applied, the stress release holes introduce local discontinuity geometry in the stress concentration area, which will redistribute the stress and disperse the stress originally concentrated in a certain area to the surrounding materials, thereby reducing the local maximum stress value and reducing the stress concentration phenomenon. Free boundaries are formed around the stress release holes. These boundaries allow the material to deform freely when subjected to stress instead of being constrained in a fixed area, so that elastic deformation can occur more easily. Then, it is ensured that the stress release holes are connected to the cavity, which provides more free deformation space and stress release path, so that the residual stress can be effectively released, and the residual stress of the MEMS magnetic field sensor is easier to release, thereby greatly improving the coupling manufacturing yield of the MEMS magnetic field sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0028] Figure 1 A top view of the MEMS magnetic field sensor provided by the present invention;

[0029] Figure 2 A top view of the piezoelectric film layer provided by the present invention;

[0030] Figure 3 A top view of the bottom electrode layer provided by the present invention;

[0031] Figure 4 A top view of the magnetostrictive film layer and the top electrode layer provided by the present invention;

[0032] Figure 5 A cross-sectional view of a MEMS magnetic field sensor provided by the present invention;

[0033] Figure 6 A schematic flow chart of a first embodiment of a method for manufacturing a MEMS magnetic field sensor provided by the present invention;

[0034] Figure 7 This is a schematic flow chart of a second embodiment of a method for manufacturing a MEMS magnetic field sensor provided by the present invention.

[0035] Description of Figure Numbers:

[0036] 100. MEMS magnetic field sensor; 1. substrate; 11. cavity; 12. suspension plate; 121. anchor beam; 2. coupled resonator; 21. electrode assembly; 211. top electrode layer; 212. bottom electrode layer; 22. magnetoelectric composite film; 221. piezoelectric film layer; 222. magnetostrictive film layer; 23. stress release hole.

[0037] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture. If the specific posture changes, the directional indication will also change accordingly.

[0040] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features limited to "first" and "second" may explicitly or implicitly include at least one of the features. In addition, if "and / or" or "and / or" appears in the full text, its meaning includes three parallel solutions. Taking "A and / or B" as an example, it includes solution A, solution B, or solutions that satisfy both A and B. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in this field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0041] MEMS magnetic field sensors induce stress or strain on piezoelectric materials through the magnetostriction of magnetostrictive materials in magnetoelectric composite films under the action of an external magnetic field. The piezoelectric material produces a certain electrical effect under the action of this stress, and ultimately uses magnetic signals to generate and output measurable electrical signals, thereby achieving the coupling of magnetic effect and piezoelectric effect to detect magnetic fields.

[0042] At present, the detection sensitivity of MEMS magnetic field sensors based on magnetoelectric composite films is low, and there is a large gap from the theoretical detection limit. The main optimization direction lies in the coupling material system, coupling thickness and resonant structure of the coupling resonator. However, optimization through the above method may cause the MEMS magnetic field sensor to face the problem of difficulty in stress release, resulting in a low coupling manufacturing yield of the MEMS magnetic field sensor.

[0043] See also Figures 1 to 5According to one aspect of the present invention, the present invention proposes a MEMS magnetic field sensor, including a substrate 1 and a coupled resonator 2, wherein the substrate 1 is formed with a cavity 11 and a suspended plate 12; the coupled resonator 2 includes an electrode assembly 21 and a magneto-electric composite film 22, the electrode assembly 21 includes a bottom electrode layer 212, the bottom electrode layer 212 is attached to the substrate 1, anchor beams 121 are provided at both ends of the suspended plate 12, the anchor beams 121 are connected to the bottom electrode layer 212, so that the suspended plate 12 is suspended on the cavity 11, the magneto-electric composite film 22 is attached to the bottom electrode layer 212, and the coupled resonator 2 is formed with a stress release hole 23, and the stress release hole 23 is connected to the cavity 11.A single crystal silicon or other suitable material is used as the substrate 1, and a cavity 11 is formed on the substrate 1 by deep dry etching on the back side, providing a space for the suspension structure in the cavity 11 to move freely. A bottom electrode layer 212 is attached to the substrate 1, and the bottom electrode layer 212 is used to apply voltage and collect signals. The suspension board 12 is suspended above the cavity 11, and both ends of the suspension board 12 are connected to the bottom electrode layer 212 through anchor beams 121. The anchor beams 121 are used to support and fix the suspension board 12 to ensure that the suspension board 12 can vibrate freely without excessive deformation when subjected to force. The suspension board 12 is usually composed of one or more layers of materials, such as Silicon or metal, the suspension plate 12 provides a free vibration platform, so that the magnetoelectric composite film 22 can respond to changes in the external magnetic field, has a piezoelectric effect, can generate electrical signals under the action of strain, and has a magnetostrictive effect, can deform under the action of a magnetic field, the bottom electrode layer 212 can also be used to apply voltage and collect signals, and then the upper coupling resonator 2 is processed to form a stress release hole 23, and the stress release hole 23 is interconnected with the cavity 11, so that the stress release hole 23 is processed to form a stress release hole 23, by changing the stress distribution, providing a free deformation space, inhibiting crack propagation, smoothing the stress gradient, thereby Effectively release residual stress; when using the MEMS magnetic field sensor, when the external magnetic field changes, the magneto-electric composite film 22 will deform, generate strain, and generate electrical signals. The electrical signals generated by the magneto-electric composite film 22 can be collected through the bottom electrode layer 212. After these electrical signals are amplified and processed, the changes in the external magnetic field can be measured; in the present invention, a stress release hole 23 is formed on the coupled resonator 2. After stress is applied, the stress release hole 23 introduces a local discontinuity geometry in the stress concentration area, which will redistribute the stress, and disperse the stress originally concentrated in a certain area to the surrounding materials, thereby reducing the local maximum stress value and reducing the stress concentration phenomenon. Free boundaries are formed around the stress release hole 23. These boundaries allow the material to deform freely when subjected to stress, rather than being constrained in a fixed area, so that elastic deformation can occur more easily. Then, ensure that the stress release hole 23 is connected to the cavity 11, which provides more free deformation space and stress release path, so that the residual stress can be effectively released, and the residual stress of the MEMS magnetic field sensor is easier to release, thereby greatly improving the coupling manufacturing yield of the MEMS magnetic field sensor.

[0044] In one embodiment, the electrode assembly 21 also includes a top electrode layer 211, and the magnetoelectric composite film 22 includes a piezoelectric film layer 221 and a magnetostrictive film layer 222 laminated in sequence, the piezoelectric film layer 221 is laminated to the bottom electrode layer 212, and the top electrode layer 211 is laminated to the magnetostrictive film layer 222. The magnetoelectric composite film 22 can respond to changes in the external magnetic field, the piezoelectric film layer 221 is laminated to the bottom electrode layer 212, has a piezoelectric effect, can generate electrical signals under strain, and provides a flat substrate for depositing the piezoelectric film layer 221, which is also very important for maintaining the stability and integrity of the entire film structure; the magnetostrictive film layer 222 is laminated to the piezoelectric film layer 221, has a magnetostrictive effect, and can be deformed under the action of a magnetic field, and then the top electrode layer 211 is laminated to the magnetostrictive film layer 222 for applying voltage and collecting signals, which is used when using MEMS magnetic field sensing. When the external magnetic field changes, the magnetostrictive film layer 222 will be deformed and generate strain. This strain is transmitted to the piezoelectric film layer 221, causing the piezoelectric film layer 221 to generate an electrical signal. The electrical signals generated by the piezoelectric film layer 221 can be collected through the top electrode layer 211. After amplification and processing, these electrical signals can be measured to obtain changes in the external magnetic field. The top electrode layer 211 is responsible for collecting electrical signals generated by the piezoelectric effect, or applying voltage to the piezoelectric film layer 221 to cause it to deform, while the bottom electrode layer 212 helps to transmit these electrical signals to the external circuit for processing or recording.

[0045] In one embodiment, the electrode assembly 21 also includes a top electrode layer 211, and the magnetoelectric composite film 22 includes a piezoelectric film layer 221 and a magnetostrictive film layer 222, the piezoelectric film layer 221 is bonded to the bottom electrode layer 212, and the two sides of the top electrode layer 211 are respectively bonded to the piezoelectric film layer 221 and the magnetostrictive film layer 222. The magnetoelectric composite film 22 can respond to changes in the external magnetic field. The piezoelectric film layer 221 is attached to the bottom electrode layer 212, has a piezoelectric effect, can generate electrical signals under strain, and provides a flat substrate to deposit the piezoelectric film layer 221, which is also very important for maintaining the stability and integrity of the entire film structure; the magnetostrictive film layer 222 is attached to the piezoelectric film layer 221, has a magnetostrictive effect, and can be deformed under the action of a magnetic field, and then the two sides of the top electrode layer 211 are respectively attached to the piezoelectric film layer 221 and the magnetostrictive film layer 222. When using the MEMS magnetic field sensor, when the external magnetic field changes, the magnetostrictive film layer 222 will deform and generate strain. This strain is transmitted to the piezoelectric film layer 221, causing the piezoelectric film layer 221 to generate an electrical signal. The bottom electrode layer 212 provides a stable electrical connection to ensure that the external circuit can provide electrical signals to the piezoelectric film layer. 221 applies voltage or collects electrical signals from the piezoelectric film layer 221, and the top electrode layer 211 provides electrical connection between the piezoelectric film layer 221 and the magnetostrictive film layer 222 to ensure that the electrical signals can be transmitted efficiently. At the same time, the top electrode layer 211 can collect the charges generated by the piezoelectric film layer 221 and transmit them to the external circuit; the top electrode layer 211 not only provides electrical connection, but also plays a role in mechanical coupling to ensure that the deformation of the magnetostrictive film layer 222 can be effectively transmitted to the piezoelectric film layer 221, thereby improving the magnetoelectric coupling efficiency; the top electrode layer 211 forms a stable intermediate layer between the piezoelectric film layer 221 and the magnetostrictive film layer 222, which helps to maintain the integrity and reliability of the entire structure and prevent interlayer peeling or damage; by selecting appropriate materials and thicknesses, the top electrode layer 211 can optimize the electric field distribution and mechanical stress transmission, thereby further improving the overall performance of the magnetoelectric composite film 22.

[0046] See also Figures 1 to 5 In one embodiment, the number of stress release holes 23 is two, and the two stress release holes 23 are spaced apart along the width direction of the coupled resonator 2. When the number of stress release holes 23 increases from one to two, and the two holes are spaced apart along the width direction of the coupled resonator 2, the stress can be more evenly distributed throughout the structure, further reducing the possibility of local stress concentration, which is very important for maintaining the physical shape stability and electrical performance consistency of the coupled resonator 2. By improving the stress distribution, the risk of material fatigue and crack propagation due to stress can be reduced, and the residual stress can be further released more easily, thereby improving the long-term reliability and service life of the coupled resonator 2.

[0047] See also Figures 1 to 5 In one embodiment, the stress release hole 23 is a square hole and extends along the length direction of the coupled resonator 2. The square hole extending along the length direction can provide a larger stress release area, further making it easier to release stress, effectively dispersing the stress along the length direction, and further reducing the stress concentration phenomenon.

[0048] See also Figures 1 to 5 In one embodiment, the number of coupled resonators 2 is multiple, and the multiple coupled resonators 2 are arranged at intervals. Multiple coupled resonators 2 can amplify the changes in the input signal through the mutual coupling effect, and even very small magnetic field changes can be effectively detected, and each coupled resonator 2 can be optimized for different frequency ranges, so that the MEMS magnetic field sensor can respond more sensitively to magnetic field changes within a wide frequency band, and different coupled resonators 2 can cover different magnetic field strength intervals, so that the MEMS magnetic field sensor can maintain a linear response within a wider magnetic field range. When one of the coupled resonators 2 fails, the other coupled resonators 2 can continue to work to ensure the normal operation of the system. In this embodiment, the number of coupled resonators 2 can be one to nine, which can ensure that the size of the MEMS magnetic field sensor does not increase too much.

[0049] See also Figures 1 to 5 In one embodiment, the coupling resonator 2 is rectangular, the aspect ratio of the coupling resonator 2 is in the range of 5 to 10, and the length of the coupling resonator 2 is ≤1200 μm. The aspect ratio is between 5 and 10, which can optimize the frequency response characteristics of the coupling resonator 2. A longer coupling resonator 2 can provide a lower resonance frequency, while a wider coupling resonator 2 helps to improve the separation of modes and reduce interference between modes; the length of the coupling resonator 2 is set to ≤1200 μm, so that the coupling resonator 2 can cover a larger frequency range without increasing the structural size of the MEMS magnetic field sensor too much.

[0050] In one embodiment, the ratio of the length of the stress release hole 23 to the length of the coupled resonator 2 is in the range of 0.8 to 0.9, the ratio of the width of the stress release hole 23 to the width of the coupled resonator 2 is in the range of 0.05 to 0.15, and the width of the stress release hole 23 is ≥2μm. The ratio of the length of the stress release hole 23 to the length of the coupled resonator 2 is between 0.8 and 0.9, which can effectively cover most of the stress in the length direction of the coupled resonator 2 and ensure that the stress is uniformly released along the length direction. The ratio of the width of the stress release hole 23 to the width of the coupled resonator 2 is between 0.05 and 0.15, which can provide sufficient width to release the lateral stress without excessively weakening the structural strength of the resonator. The width of the stress release hole 23 is ≥2μm, which can ensure high-precision processing and reduce manufacturing errors.

[0051] For example, the length of the coupling resonator 2 is set to L, the width of the coupling resonator 2 is set to W, and the length of the stress release hole 23 is set to L. h , the length of the stress release hole 23 is set to W h , then:

[0052] 0.8L≤L h ≤0.9L

[0053] 0.05W≤W h ≤0.15W

[0054] W h ≥2μm

[0055] Through the above formula, the sizes of the coupling resonator 2 and the stress release hole 23 can be calculated according to different usage requirements.

[0056] In one embodiment, the thickness of the suspension plate 12 ranges from 500nm to 20μm, the thickness of the piezoelectric film layer 221 ranges from 500nm to 2μm, the thickness of the magnetostrictive film layer 222 ranges from 500nm to 2μm, and the ratio of the thickness of the piezoelectric film layer 221 to the thickness of the magnetostrictive film layer 222 ranges from 0.8 to 1.2. The thickness of the suspension plate 12 is set between 500nm and 20μm, which can ensure both high mechanical strength and high sensitivity of the MEMS magnetic field sensor; the thickness of the piezoelectric film layer 221 is set between 500nm and 2μm, which can ensure good piezoelectric performance and efficient power conversion, and such a thickness range can ensure high processing accuracy; the thickness ratio of the piezoelectric film layer 221 to the magnetostrictive film layer 222 is set between 0.8 and 1.2, which can ensure good matching between the two and avoid stress unevenness and performance degradation caused by excessive thickness difference.

[0057] In one embodiment, the material of the piezoelectric film layer 221 is AlN, AlSc x N or lead zirconate titanate, wherein the range of x is 0.40 to 0.45. AlN (aluminum nitride) is used to make the piezoelectric film layer 221. AlN has a high sound velocity and is suitable for use in a high frequency range. x The piezoelectric film layer 221 is made of AlN (scandium aluminum nitride), which is equivalent to doping scandium in AlN, which can significantly increase the piezoelectric coefficient of AlN, thereby improving the sensitivity of the MEMS magnetic field sensor. When the doping ratio x is in the range of 0.40 to 0.45, within this range, AlSc xThe piezoelectric coefficient of N reaches the optimum, which can further significantly improve the sensitivity of the MEMS magnetic field sensor 100; the piezoelectric film layer 221 is made of lead zirconate titanate, and the sound velocity of lead zirconate titanate is low, which is suitable for use in the low frequency range.

[0058] According to another aspect of the present invention, see Figure 6 , Figure 6 The present invention further provides a method for manufacturing a MEMS magnetic field sensor. The method for manufacturing a MEMS magnetic field sensor is applied to the above-mentioned MEMS magnetic field sensor. The method for manufacturing a MEMS magnetic field sensor comprises the following steps:

[0059] S1, forming a coupled resonator 2 on a substrate 1;

[0060] The coupled resonator 2 is formed on the substrate 1 through processes such as deposition, photolithography and etching.

[0061] S2, making a mask on the coupled resonator 2 by photolithography patterning, and etching a pattern on the coupled resonator 2 by a front dry method to form a stress release hole 23;

[0062] A layer of photoresist is uniformly coated on the surface of the coupled resonator 2, wherein commonly used photoresists include positive photoresists and negative photoresists. Then, the MEMS magnetic field sensor coated with the photoresist is pre-baked on a hot plate to remove the solvent in the photoresist and improve the adhesion of the photoresist. The MEMS magnetic field sensor is placed in a photolithography machine, and the photoresist is exposed using a mask plate, on which a pattern of stress release holes 23 is included. The exposed MEMS magnetic field sensor is post-baked again to fix the pattern of the photoresist. The MEMS magnetic field sensor is immersed in a developer to remove the unexposed or exposed parts to form a desired pattern. Then, the MEMS magnetic field sensor is placed in an etching device and etched according to set parameters until the desired stress release holes 23 are formed. In this way, the stress release holes 23 formed by processing change the stress distribution, provide free deformation space, inhibit crack propagation, and smooth the stress gradient, thereby effectively releasing residual stress and ensuring the coupling manufacturing yield of the MEMS magnetic field sensor.

[0063] S3 , a mask is made on the back side of the substrate 1 by photolithography patterning, and a cavity 11 is formed on the substrate 1 by a back side deep dry method, and a suspended plate 12 is formed on the coupled resonator 2 .

[0064] First, the back side of the substrate 1 is ground to a desired thickness, a layer of photoresist is uniformly coated on the back side of the substrate 1, and the MEMS magnetic field sensor coated with the photoresist is pre-baked on a hot plate to remove the solvent in the photoresist and improve the adhesion of the photoresist. The MEMS magnetic field sensor is placed in a photolithography machine, and the photoresist is exposed using a mask. The exposed MEMS magnetic field sensor is post-baked again to fix the pattern of the photoresist, and the sample is immersed in a developer to remove the unexposed or exposed parts to form the desired pattern. The MEMS magnetic field sensor is placed in an etching device and etched according to the set parameters until the desired depth of the cavity 11 is formed. Usually, multiple etching steps are required, and the etching depth is checked after each etching to ensure that the design requirements are met. Then, the MEMS magnetic field sensor is cleaned with deionized water and isopropyl alcohol and other solvents to remove the residual degumming solution and impurities, and a layer of sacrificial layer material, such as silicon dioxide, is deposited on the coupled resonator 2. The required pattern is formed on the sacrificial layer by photolithography and etching technology, and the sacrificial layer material is removed by wet etching or dry etching to form a suspension plate 12; the suspension plate 12 can move freely and produce a mechanical response to changes in the external magnetic field. When the magnetic field changes, the coupled resonator 2 will deform, thereby driving the suspension plate 12 to vibrate or displace. The cavity 11 enables the suspension plate 12 or the coupled resonator 2 to vibrate or displace freely without the constraint of the substrate 1. This degree of freedom increases the mechanical response to changes in the external magnetic field, thereby improving the sensitivity of the sensor.

[0065] In this embodiment, stress release holes 23 are formed on the coupled resonator 2. After stress is applied, the stress release holes 23 introduce local discontinuity geometry in the stress concentration area, which redistributes the stress. The stress originally concentrated in a certain area is dispersed into the surrounding materials, thereby reducing the local maximum stress value and reducing the stress concentration phenomenon. Free boundaries are formed around the stress release holes 23. These boundaries allow the material to deform freely when subjected to stress, rather than being constrained in a fixed area, so that elastic deformation can occur more easily. Then, it is ensured that the stress release holes 23 are connected to the cavity 11, which provides more free deformation space and stress release path, so that residual stress can be effectively released, and the residual stress of the MEMS magnetic field sensor is easier to release, thereby greatly improving the coupling manufacturing yield of the MEMS magnetic field sensor.

[0066] See also Figure 7 , Figure 7 This is a flow chart of a second embodiment of a method for manufacturing a MEMS magnetic field sensor provided by the present invention. In one embodiment, the step of depositing a coupled resonator 2 on a substrate 1 includes:

[0067] S11, depositing a bottom electrode layer 212 on the substrate 1;

[0068] Select a suitable substrate 1 material, generally silicon, glass or sapphire is used, and then use a standard cleaning process to remove pollutants and organic matter on the surface of the substrate 1; then a buffer layer can be coated on the substrate 1, the buffer layer can reduce the stress between the substrate 1 and the subsequent deposited layer and improve the adhesion, or the buffer layer is not coated on the substrate 1, which can also meet the subsequent use; then select materials to deposit the bottom electrode layer 212 on the substrate 1, the materials include gold, platinum and aluminum.

[0069] S12, depositing a piezoelectric thin film layer 221 on the bottom electrode layer 212, and making a mask on the bottom electrode layer 212 by photolithography patterning, and then patterning the piezoelectric thin film layer 221 by wet etching or dry etching process;

[0070] A piezoelectric film layer 221 is deposited on the substrate 1 using selected materials. Common materials include aluminum nitride, scandium aluminum nitride or lead zirconate titanate, etc. A layer of photoresist is then uniformly coated on the surface of the piezoelectric film layer 221. The sample is placed in a photolithography machine and the photoresist is exposed using a mask. The exposed sample is post-baked again to fix the pattern of the photoresist. The sample is immersed in a developer to remove the unexposed or exposed parts to form a desired pattern. The sample is placed in an etching device and is etched according to the set parameters until the desired pattern of the piezoelectric film layer 221 is formed.

[0071] S13, patterning the bottom electrode layer 212 by wet etching or dry etching process on the bottom electrode layer 212;

[0072] A layer of photoresist is uniformly coated on the surface of the bottom electrode layer 212, the sample is placed in a photolithography machine, the photoresist is exposed using a mask, the exposed sample is post-baked again to fix the pattern of the photoresist, the sample is immersed in a developer, the unexposed or exposed parts are removed to form the desired pattern, the sample is placed in an etching device, and etching is performed according to the set parameters until the desired bottom electrode pattern is formed.

[0073] S14, making a mask on the piezoelectric film layer 221 by photolithography patterning, and depositing a magnetostrictive film layer 222 on the piezoelectric film layer 221, and then patterning the magnetostrictive film layer 222 by a lift-off process;

[0074] A layer of photoresist is uniformly coated on the surface of the piezoelectric film layer 221, and the sample coated with the photoresist is pre-baked on a hot plate to remove the solvent in the photoresist and improve the adhesion of the photoresist. The sample is placed in a photolithography machine and exposed using a mask plate. The mask plate contains the pattern of the magnetostrictive film layer 222. The exposed sample is post-baked again to fix the pattern of the photoresist. The sample is immersed in a developer to remove the unexposed or exposed parts to form a desired pattern. Then, the magnetostrictive film layer 222 is deposited on the piezoelectric film layer 221. Common magnetostrictive materials include nickel-iron alloy and terbium-dysprosium-iron alloy. First, a layer of metal is deposited on the photoresist pattern to enhance the stripping effect of the photoresist. The sample is immersed in a stripping solution to remove the photoresist and the magnetostrictive film layer 222 thereon, thereby completing the deposition of the magnetostrictive film layer 222.

[0075] S15 , a mask is made on the magnetostrictive thin film layer 222 by photolithography patterning, and a top electrode layer 211 is deposited on the magnetostrictive thin film layer 222 , and then the top electrode layer 211 is patterned by a lift-off process.

[0076] A layer of photoresist is uniformly coated on the surface of the magnetostrictive film layer 222, and the sample coated with the photoresist is pre-baked on a hot plate to remove the solvent in the photoresist and improve the adhesion of the photoresist. The sample is placed in a photolithography machine and the photoresist is exposed using a mask. The mask contains the pattern of the top electrode layer 211. The exposed sample is post-baked again to fix the pattern of the photoresist. The sample is immersed in a developer to remove the unexposed or exposed part to form a desired pattern. Then, the top electrode layer 211 is deposited on the magnetostrictive film layer 222, and then a layer of metal is deposited on the photoresist pattern to enhance the stripping effect of the photoresist. The sample is immersed in a stripping solution to remove the photoresist and the top electrode layer 211 thereon, leaving the desired pattern. In this way, the deposition of the top electrode layer 211 is completed, and the entire coupled resonator 2 is processed.

[0077] In this embodiment, the use of photolithography for patterning can achieve very high resolution and accuracy, which is essential for manufacturing a coupled resonator 2 of microscopic size. This helps to improve the performance and consistency of the device, and allows the use of different materials to form various layers, such as the bottom electrode layer 212, the piezoelectric film layer 221, the magnetostrictive film layer 222, and the top electrode layer 211, which means that the most suitable material combination can be selected according to specific application requirements, thereby optimizing the overall performance of the device. Whether it is wet etching or dry etching, these processes can provide better control and repeatability to ensure that consistent results can be obtained in each production process, which is very important for large-scale production and quality control. The use of a lift-off process to pattern the magnetostrictive film layer 222 and the top electrode layer 211 can effectively reduce surface damage or residues that may be caused by direct etching, thereby reducing the device defect rate and improving the yield rate.

[0078] The above description is only an exemplary embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the technical concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A MEMS magnetic field sensor, characterized in that: include: A substrate, wherein the substrate is formed with a cavity and forms a suspension plate; A coupled resonator, the coupled resonator comprising an electrode assembly and a magnetoelectric composite film; the electrode assembly comprising a bottom electrode layer, the bottom electrode layer being adhered to the substrate, anchor beams being provided at both ends of the suspension plate, the anchor beams being connected to the bottom electrode layer so that the suspension plate is suspended over the cavity; the magnetoelectric composite film being adhered to the bottom electrode layer; the coupled resonator being formed with a stress release hole, the stress release hole being connected to the cavity.

2. The MEMS magnetic field sensor according to claim 1, characterized in that: The electrode assembly also includes a top electrode layer. The magnetoelectric composite film includes a piezoelectric film layer and a magnetostrictive film layer laminated in sequence. The piezoelectric film layer is laminated to the bottom electrode layer, and the top electrode layer is laminated to the magnetostrictive film layer.

3. The MEMS magnetic field sensor according to claim 1, characterized in that: The electrode assembly also includes a top electrode layer, the magnetoelectric composite film includes a piezoelectric film layer and a magnetostrictive film layer, the piezoelectric film layer is attached to the bottom electrode layer, and the two sides of the top electrode layer are attached to the piezoelectric film layer and the magnetostrictive film layer respectively.

4. The MEMS magnetic field sensor according to claim 1, wherein: The number of the stress release holes is two, and the two stress release holes are arranged at intervals along the width direction of the coupled resonator.

5. The MEMS magnetic field sensor according to any one of claims 1 to 4, characterized in that: The stress release hole is a square hole and extends along the length direction of the coupling resonator.

6. The MEMS magnetic field sensor according to any one of claims 1 to 4, characterized in that: There are multiple coupling resonators, and the multiple coupling resonators are arranged at intervals.

7. The MEMS magnetic field sensor according to claim 2 or 3, characterized in that: The thickness of the suspension plate ranges from 500nm to 20μm, the thickness of the piezoelectric film layer ranges from 500nm to 2μm, the thickness of the magnetostrictive film layer ranges from 500nm to 2μm, and the ratio of the thickness of the piezoelectric film layer to the thickness of the magnetostrictive film layer ranges from 0.8 to 1.

2.

8. The MEMS magnetic field sensor according to claim 2 or 3, characterized in that: The material of the piezoelectric film layer is AlN or AlSc x N, or lead zirconate titanate, wherein x ranges from 0.40 to 0.

45.

9. A method for manufacturing a MEMS magnetic field sensor, wherein the method for manufacturing a MEMS magnetic field sensor is applied to the MEMS magnetic field sensor according to any one of claims 1 to 8, characterized in that: The method for manufacturing the MEMS magnetic field sensor comprises the following steps: Depositing a coupled resonator on a substrate; A mask is fabricated on the coupled resonator by photolithography patterning, and a pattern is etched on the coupled resonator by a front dry method to form a stress release hole; A mask is fabricated on the back side of the substrate by photolithography patterning, a cavity is formed on the substrate by a back side deep dry method, and a suspended plate is formed on the coupled resonator.

10. The method for manufacturing a MEMS magnetic field sensor according to claim 9, characterized in that: The step of depositing a coupled resonator on a substrate comprises: Processing and forming a bottom electrode layer on the substrate; Depositing a piezoelectric thin film layer on the bottom electrode layer, making a mask on the bottom electrode layer by photolithography, and then patterning the piezoelectric thin film layer by wet etching or dry etching process; Patterning the bottom electrode layer by wet etching or dry etching process; A mask is made on the piezoelectric film layer by photolithography patterning, and a magnetostrictive film layer is deposited on the piezoelectric film layer, and then the magnetostrictive film layer is patterned by a lift-off process; A mask is made on the magnetostrictive film layer by photolithography and patterning, and a top electrode layer is deposited on the magnetostrictive film layer, and then the top electrode layer is patterned by a lift-off process.

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