A magnetic cantilever beam sensor, a method of manufacturing the same and a microscopic imaging system

Abstract

The application discloses a magnetic cantilever beam sensor, a manufacturing method thereof and a microscopic imaging system. The magnetic cantilever beam sensor comprises a glass substrate, a silicon-based cantilever beam, a magnet, an air suction unit and a silicon-based cover. The glass substrate is provided with a first chamber and a second chamber in communication. The second chamber is located at the bottom of the first chamber. The fixed end of the silicon-based cantilever beam is fixedly connected to the bottom of the first chamber of the glass substrate. The magnet is fixedly connected to the free end of the silicon-based cantilever beam. The sum of the height of the magnet and the thickness of the silicon-based cantilever beam is less than the depth of the first chamber. The air suction unit is arranged in the second chamber. The silicon-based cover is fixedly connected to the opening end of the glass substrate above the first chamber. A sensing window is formed in the silicon-based cover and located above the magnet. The application can have higher detection sensitivity on the basis of a high-vacuum environment.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sensors, in particular to a magnetic cantilever sensor, a manufacturing method thereof and a microscopic imaging system. BACKGROUND

[0002] Magnetic Resonant Imaging (MRI) is a common and mature technology applied in the biomedical field, which can non-invasively image the internal structure of the human body and has the characteristics of safety, speed and accuracy in clinical diagnosis. When the MRI system is based on the working principle of coil induction detection technology, its spatial resolution can only achieve the level of tens of microns. After combining the MRI system with Atomic Force Microscope (AFM), the spatial resolution can achieve nanometer level, and the Magnetic Resonant Force Microscope (MRFM) is born. By using a super-sensitive magnetic micro-cantilever sensor, free radicals or electron spin density can be detected at the nanoscale. So far, this technology has been widely applied in the fields of biology, materials, clinical medicine, etc.

[0003] The cantilever sensor utilizes the principle of mechanical resonance for sensing. In order to reduce air damping, improve the quality factor and improve the detection sensitivity, the working conditions generally need to be maintained in a high vacuum state. However, the existing cantilever sensor is difficult to simultaneously ensure high vacuum state and high detection sensitivity.

[0004] The disclosure of the above background art content is only used to assist in understanding the concept and technical solutions of the present application, and it does not necessarily belong to the prior art of the present patent application. In the absence of explicit evidence that the above content has been disclosed on the filing date of the present patent application, the above background art should not be used to evaluate the novelty and inventiveness of the present application. SUMMARY

[0005] To solve the above technical problems, the present application provides a magnetic cantilever sensor, a manufacturing method thereof and a microscopic imaging system, which can have higher detection sensitivity on the basis of having a high vacuum environment.

[0006] In order to achieve the above purpose, the present application adopts the following technical solutions:

[0007] In a first aspect, the present application discloses a magnetic cantilever beam sensor, comprising a glass substrate, a silicon-based cantilever beam, a magnet, an air suction unit and a silicon-based cover, wherein the glass substrate is provided with a first chamber and a second chamber in communication, the second chamber is located at the bottom of the first chamber, the fixed end of the silicon-based cantilever beam is fixedly connected to the bottom of the first chamber of the glass substrate, the magnet is fixedly connected to the free end of the silicon-based cantilever beam, the sum of the height of the magnet and the thickness of the silicon-based cantilever beam is less than the depth of the first chamber, the air suction unit is placed in the second chamber, the silicon-based cover is fixedly connected to the opening end of the glass substrate above the first chamber, and a sensing window is formed on the silicon-based cover and located above the magnet.

[0008] Preferably, the silicon-based cover is made of an SOI wafer comprising a substrate layer, an oxide layer and a device layer, and the sensing window is a silicon thin film window formed by removing the substrate layer and the oxide layer at the position of the silicon-based cover above the magnet.

[0009] Preferably, the thickness of the substrate layer of the SOI wafer for making the silicon-based cover is 200-300 μm, the thickness of the oxide layer is 1-2 μm, and the thickness of the device layer is 1-2 μm.

[0010] Preferably, the thickness of the silicon-based cover at the sensing window is 1-2 μm.

[0011] Preferably, the length of the silicon-based cantilever beam is 100-1000 μm, the width is 5-50 μm, and the thickness is 0.1-10 μm.

[0012] Preferably, the magnet is a spherical structure with a diameter of 10-20 μm, and the gap between the top end of the magnet and the silicon-based cover is 0.1-1 μm.

[0013] Preferably, the depth of the first chamber is 10.2-31 μm, and the depth of the second chamber is 150-200 μm.

[0014] In a second aspect, the present application discloses a method for manufacturing the magnetic cantilever beam sensor of the first aspect, comprising the following steps:

[0015] S1: using a deep silicon etching process to process a silicon-based cantilever beam in the device layer of an SOI wafer;

[0016] S2: sequentially forming a first chamber and a second chamber on a glass substrate by wet etching, and placing the air suction unit in the second chamber;

[0017] S3: Deep silicon etching is performed on the substrate layer of another SOI wafer at the sensing window position, and then wet etching is performed on the oxide layer of the SOI wafer at the sensing window position, so as to form the silicon-based cover body with the sensing window;

[0018] S4: The silicon-based cantilever is bonded to the bottom of the first cavity of the glass substrate by an anodic bonding process;

[0019] S5: The substrate layer and the oxide layer of the SOI wafer in step S1 are removed, the silicon-based cantilever is released in a liquid by a supercritical drying process, the magnet is fixedly connected to the free end of the silicon-based cantilever, and the magnet is magnetized;

[0020] S6: The silicon-based cover body is fixedly connected to the opening end of the glass substrate above the first cavity by an anodic bonding process.

[0021] Preferably, after the silicon-based cantilever is processed in the device layer of the SOI wafer in step S1, the method further comprises: performing wet etching on the oxide layer of the SOI wafer and deep silicon etching on the substrate layer of the SOI wafer, wherein the etching depth of the substrate layer of the SOI wafer is 20-30 μm, and then a 100-300 nm stop layer is deposited on the substrate layer; and before the step of releasing the silicon-based cantilever in step S5, the method further comprises: removing the stop layer of the SOI wafer in step S1.

[0022] In a third aspect, the present application discloses a microscopic imaging system, comprising a radio frequency coil, a magnetic field modulation coil, an optical fiber interferometer, a lock-in amplifier and the magnetic cantilever sensor of the first aspect, wherein the sample to be measured is placed at the corresponding position of the sensing window, the radio frequency coil is used to apply a radio frequency signal to the sample to be measured, the magnetic field modulation coil is used to excite the resonance of the silicon-based cantilever based on the magnetic force generated between the sample to be measured and the magnet, and the optical fiber interferometer and the lock-in amplifier are used to measure the vibration of the silicon-based cantilever.

[0023] Compared with the prior art, the application has the beneficial effect that the magnetic cantilever beam sensor based on silicon-glass anode combination and the manufacturing method thereof provided by the preferred embodiment of the application have two packaging chambers designed on the glass substrate, the micro cantilever beam sensor is placed in the upper chamber for detection, the depth of the upper chamber matches the height of the magnet, so that the magnet is close to the packaged silicon-based cover, the getter unit is placed in the lower chamber for absorbing the gas generated in the anode combination process, such as O2 and H2; and the observation window is opened on the silicon-based cover to further expand the sensing range and sensing accuracy of the magnet, so that the packaged magnetic cantilever beam has higher detection sensitivity on the basis of high vacuum environment, and the spatial resolution of the magnetic resonance force microscopic imaging system based on the magnetic cantilever beam sensor can be greatly improved. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is a structural schematic diagram of the magnetic cantilever beam sensor disclosed by the preferred embodiment of the application;

[0025] Figures 2a to 2j is a flow chart of the manufacturing method of the magnetic cantilever beam sensor disclosed by the preferred embodiment of the application;

[0026] Figure 3 is a schematic diagram of the external magnetic field gradient measuring device based on the cantilever beam resonance frequency fluctuation disclosed by the preferred embodiment of the application;

[0027] Figure 4 is a schematic diagram of the magnetic resonance force microscopic imaging system of the magnetic cantilever beam sensor based on vacuum packaging in the atmospheric environment disclosed by the preferred embodiment of the application. DETAILED DESCRIPTION

[0028] The embodiments of the application are described in detail below. It should be emphasized that the following description is only exemplary and is not intended to limit the scope of the application and its applications.

[0029] It should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element. In addition, the connection can be for fixing or for circuit / signal communication.

[0030] It should be understood that the terms "length", "width", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like, indicate directions or positions based on the directions or positions shown in the drawings, and are used only for the purpose of facilitating the description of the embodiments of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0031] In addition, the terms "first", "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined as "first", "second" can explicitly or implicitly include one or more of the features. In the description of the embodiments of the present application, the meaning of "a plurality of" is two or more, unless otherwise specifically limited.

[0032] As shown in Figure 1 The preferred embodiment of the present application discloses a magnetic cantilever beam sensor 100, comprising a glass substrate 10, a silicon-based cantilever beam 20, a magnetic ball 30, an air suction unit 40 and a silicon-based cover 50, the glass substrate 10 is provided with a first chamber 11 and a second chamber 12 in communication, the second chamber 12 is located at the bottom of the first chamber 11, the fixed end of the silicon-based cantilever beam 20 is fixedly connected to the bottom of the first chamber 11 of the glass substrate 10, the magnetic ball 30 is fixedly connected to the free end of the silicon-based cantilever beam 20, the sum of the diameter of the magnetic ball 30 and the thickness of the silicon-based cantilever beam 20 is less than the depth of the first chamber 11, the air suction unit 40 is placed in the second chamber 12, the silicon-based cover 50 is fixedly connected to the opening end of the glass substrate 10 above the first chamber 11, and a sensing window 54 is opened on the silicon-based cover 50, and the sensing window 54 is located above the magnetic ball 30.

[0033] The silicon-based cover 50 is made of an SOI wafer (SOI: silicon on insulator) including a substrate layer 51, an oxide layer 52 and a device layer 53, and the sensing window 54 is a silicon thin film window formed by removing the substrate layer 51 and the oxide layer 52 at the position of the silicon-based cover 50 above the magnetic ball 30, that is, there is only one layer of silicon thin film (device layer 53) at the sensing window 54. Among them, the thickness of the substrate layer 51 is 200-300 μm, the thickness of the oxide layer 52 is 1-2 μm, and the thickness of the device layer 53 is 1-2 μm, so the thickness of the silicon-based cover 50 at the sensing window is 1-2 μm. The length of the silicon-based cantilever beam 20 is 100-1000 μm, the width is 5-50 μm, and the thickness is 0.1-10 μm.

[0034] The diameter of the magnetic ball 30 is 10~20μm, and the gap between the top of the magnetic ball 30 and the silicon-based cap 50 is 0.1~1μm.

[0035] The depth of the first chamber 11 is 10.2~31μm, and the depth of the second chamber 12 is 150~200μm.

[0036] In this embodiment, the sensing window 54 is a circular window; in other embodiments, it can also be a square window or a window of any other shape. In a more preferred embodiment, the magnetic ball 30 is located at the center of the sensing window 54.

[0037] In this embodiment, a silicon-based cantilever beam 20 is fixedly connected to the bottom of the first chamber 11. In other embodiments, multiple silicon-based cantilever beams 20 can also be fixedly connected in parallel to the bottom of the first chamber 11 to increase the sensing range and improve the sensing accuracy.

[0038] Specifically, Figure 1 The diagram shows a vacuum-encapsulated magnetic cantilever beam sensor with an embedded silicon thin-film sensing window based on silicon-glass anodic bonding. The silicon-based cantilever beam 20 is bonded to a glass substrate 10 with a chamber structure via an anodic bonding process. A magnetic ball 30 is fixed to the tip of the silicon-based cantilever beam 20 using an adhesive to sense external magnetic forces. The glass substrate 10 and the silicon thin film (i.e., the silicon cap 50) are bonded together using a silicon-glass anodic bonding process, and then vacuum-encapsulated in a high-vacuum environment.

[0039] In existing technologies, the anodic bonding process struggles to guarantee the required vacuum level within the cavity, while other processes suffer from a large gap between the silicon-based cap and the magnetic sphere. In a preferred embodiment of this invention, while using anodic bonding, the glass substrate is designed with two separate chambers. The depth of the upper chamber is controlled to ensure the magnetic sphere is as close as possible to the upper encapsulation layer (the gap between the top of the magnetic sphere and the silicon-based cap is 0.1~1μm). A getter is placed in the lower chamber to address the issue of gas generation during anodic bonding affecting the vacuum level. This allows the magnetic cantilever beam sensor to achieve higher detection sensitivity within a high vacuum environment.

[0040] like Figures 2a to 2j As shown, a preferred embodiment of the present invention discloses a method for fabricating the above-mentioned magnetic cantilever beam sensor 100, the specific micro-nano fabrication process of which is as follows:

[0041] S1: A silicon-based cantilever beam is fabricated in the device layer of an SOI wafer using a deep silicon etching process;

[0042] like Figure 2aAs shown, the cantilever beam structure is processed by the device layer 23 of the SOI wafer, the thickness of the device layer 23 is 5-10 μm;

[0043] As shown in Figure 2b , the cantilever beam structure is processed by the device layer of the SOI wafer using the deep silicon etching process (DEIR: deep reactive iron etching), considering the reserved space required by the cavity (first chamber 11) of the glass substrate in the anodic bonding process, further wet etching the oxide layer (SiO2 layer) 22 and deep silicon etching the substrate layer (handle layer) 21, wherein the etching depth of the substrate layer 21 is approximately 20-30 μm;

[0044] As shown in Figure 2c , a 100-300 nm thick aluminum layer 24 is deposited on the substrate layer 21 as a stop layer for deep silicon etching of the substrate layer 21.

[0045] S2: sequentially forming the first chamber and the second chamber on the glass substrate by wet etching, and placing the getter unit in the second chamber;

[0046] As shown in Figure 2d , a cavity (first chamber 11) with a depth of about 10.2-31 μm is processed on the glass substrate 10 (200-300 μm thick) by wet etching, to provide a certain space for the resonant motion of the cantilever beam;

[0047] As shown in Figure 2e , a cavity (second chamber 12) with a depth of about 150-200 μm is further processed by wet etching, to be able to reserve a certain space for the getter, so that the getter (getter unit 40) can absorb the gas in the cavity (first chamber 11 and second chamber 12) to create a vacuum environment.

[0048] S3: deep silicon etching the substrate layer at the sensing window position of another SOI wafer, and then further wet etching the oxide layer at the sensing window position of the SOI wafer to form a silicon-based cover with a sensing window;

[0049] As shown in Figure 2f , the SOI wafer used to make the sensing window 54 has a device layer 53 with a thickness of 1-2 μm, an oxide layer 52 with a thickness of 1-2 μm, and a substrate layer 53 with a thickness of 200-300 μm;

[0050] As shown in Figure 2g , the substrate layer (handle layer) 53 of the SOI wafer is deep silicon etched and the oxide layer (SiO2 layer) 52 is wet etched to form the sensing window 54.

[0051] S4: bonding the silicon-based cantilever on the bottom of the first chamber of the glass substrate by an anodic bonding process;

[0052] As Figure 2h , the cantilever structure is bonded on the glass substrate 10 by an anodic bonding process.

[0053] S5: removing the substrate layer and the oxide layer of the SOI wafer in step S1, releasing the silicon-based cantilever in a liquid by a supercritical drying process, fixing and connecting a magnetic ball to the free end of the silicon-based cantilever, and magnetizing the magnetic ball;

[0054] As Figure 2i , the substrate layer 21, the oxide layer 22, and the aluminum layer 24 are removed by etching, the cantilever structure is released in a liquid (isopropyl alcohol) by a supercritical drying process, a small magnetic ball is attached to the glass needle tip by electrostatic force, the small magnetic ball is precisely attached to the tip of the cantilever structure by colloidal adhesion, and the small magnetic ball is magnetized.

[0055] S6: fixing and connecting the silicon-based cover to the opening end of the glass substrate above the first chamber by an anodic bonding process.

[0056] As Figure 2j , the sensing window 54 and the frame position of the glass substrate 10 are positionally aligned, and the anodic bonding is finally performed to obtain a vacuum-encapsulated magnetic cantilever sensor with a built-in silicon thin film sensing window.

[0057] As Figure 3 shown, the vacuum-encapsulated magnetic cantilever sensor based on silicon-glass anodic bonding constructed by the preferred embodiment of the present application is used for measuring external magnetic field gradient and magnetic resonance force.

[0058] In order to evaluate the sensitivity of the vacuum-encapsulated magnetic cantilever sensor 100 to external magnetic field gradient and magnetic resonance force, an actuator (such as a PZT actuator 210) is placed at the bottom of the vacuum-encapsulated device and supported by a support platform 220. A function generator 230 is directly connected to the PZT driver 210 by wires to apply a driving signal to the PZT driver 210 for mechanical resonance excitation. A laser Doppler vibration detector 240 is focused by a lens 250 to detect the vibration of the vacuum-encapsulated magnetic cantilever sensor 100, and a fast Fourier transform (FFT) analyzer 260 converts the vibration signal measured by the laser Doppler vibration detector 240 into a frequency domain signal.

[0059] First, the resonance frequency f 0 of the magnetic cantilever sensor 100 can be expressed by the formula:

[0060] (1)

[0061] wherein, m W0 is the effective weight of the magnetic cantilever beam, k 0 is the intrinsic spring constant of the magnetic cantilever beam. When an external magnet is close to the magnetic cantilever beam, due to the gradient magnetic field of the external magnet in the vertical direction, the magnetic force between the external magnet and the magnetic sphere will be generated F z which can be expressed as:

[0062] (2)

[0063] wherein, M z M is the magnetic moment of the magnetic sphere, H z Gz is the magnetic field gradient of the external magnet. Under the action of the magnetic force F z , the effective spring constant value of the magnetic cantilever beam sensor 100 becomes k eff which can be expressed as:

[0064] (3)

[0065] wherein, F z Gz is the gradient of the magnetic force. Therefore, by combining equations (1) and (3), the resonance frequency change Δ f of the magnetic cantilever beam can be expressed as:

[0066] (4)

[0067] wherein, f eff W0 is the effective resonance frequency of the magnetic cantilever beam sensor 100 (Δ f ≪ f 0). Through the equation, it can be seen that the magnetic force gradient generated by the external magnet has a certain proportional relationship with the resonance frequency change value of the magnetic cantilever beam; by moving the external magnet in the horizontal direction, different magnetic field gradients are generated at the position of the magnetic sphere; under the action of each magnetic field gradient, the effective resonance frequency value of the magnetic cantilever beam sensor 100 is measured.

[0068] The magnetic resonance force microscopy system is sensed by using a micro cantilever sensor, so the system needs to be integrated in a sealed cavity and kept in a vacuum state to meet the working conditions of the cantilever sensor. However, during observation in the prior art, some biological samples to be tested are difficult to maintain activity in a high vacuum environment, especially living samples such as cells, so the type of sample needs to be limited. It is worth noting that for the working conditions of the cantilever sensor, an independent vacuum micro chamber is constructed to separate the observation platform on which the sample is placed from the vacuum environment, so that more types of samples can be measured by using the magnetic resonance force microscopy system. The vacuum packaging of the magnetic cantilever can be realized by using the method of metal thermal bonding, but the method of metal thermal bonding makes the gap between the silicon-based cover and the small magnetic ball larger, so that the detection range of the magnetic cantilever is greatly limited.

[0069] In the preferred embodiment of the present application, a circular observation window 54 is opened on the SOI wafer, so that the packaging thickness of the sensing part is greatly reduced, only about 1 μm. The size of the observation window 54 is reasonably controlled to ensure the packaging strength of the silicon film. The magnetic cantilever is suspended at the bottom of the first chamber 11, and the depth of the first chamber 11 is reasonably designed in the embodiment of the present application, so that the magnetic ball on the cantilever is as close as possible to the upper packaging silicon film (in the specific embodiment, the distance from the magnetic ball 30 to the silicon film is 0.1-1 μm). Therefore, the sample to be tested can be sensed by the magnetic cantilever sensor 100 in a larger range, and the packaged magnetic cantilever can realize higher detection sensitivity, greatly improving the spatial resolution of the magnetic resonance force microscopy system. Since gas such as O2 and H2 will be released during anodic bonding, in order to ensure the vacuum degree in the chamber, a getter is added at the bottom of the second chamber 12 to absorb residual gas to meet the working conditions of the magnetic cantilever sensor.

[0070] The vacuum packaged magnetic cantilever sensor 100 provided by the preferred embodiment of the present application can further detect the internal free radical concentration such as cells in an atmospheric environment. For example, the magnetic cantilever sensor 100 can be used to detect the internal free radical concentration of a cell in an atmospheric environment, and the internal free radical concentration of the cell can be calculated by using the magnetic cantilever sensor 100. Figure 4The magnetic resonance force microscopy system based on the vacuum-encapsulated magnetic cantilever sensor constructed in the atmospheric environment includes a radio frequency coil 310, a magnetic field modulation coil 320, a vacuum-encapsulated magnetic cantilever sensor 100, an optical fiber interferometer 330, a lock-in amplifier 340 and the like, wherein a free radical sample 360 is arranged on a displacement scanning table 350. First, the radio frequency (RF: radio frequency) coil 310 applies a radio frequency signal to the free radical sample 360 to excite the electron spin resonance (ESR: electro spin resonance) in the resonance slice of the free radical; at the same time, the vacuum-encapsulated magnetic cantilever sensor 100 can provide a high gradient magnetic field for the free radical sample 360. When the radio frequency magnetic field applied by the radio frequency coil 310 meets the electron spin magnetic resonance condition of the free radical sample 360, the magnetic force generated between the free radical sample 360 and the magnetic ball 30 can be excited by modulating the radio frequency signal of the magnetic field modulation coil 320 to excite the resonance of the magnetic cantilever structure. Here, the ESR condition requires that the Larmor precession frequency of the spin v 0= H 0 / 2π (wherein H 0 is the static magnetic field applied by the small magnetic ball, Y is the gyromagnetic ratio) matches the oscillation frequency applied by the radio frequency coil 310. Finally, the vibration of the magnetic cantilever can be measured by the optical fiber interferometer 330 (for example, a laser Doppler interferometer) + lock-in amplifier 340 to analyze the size of the generated magnetic resonance force F z = A ( k / Q ) (wherein A is the amplitude of the magnetic cantilever, k is the spring constant of the magnetic cantilever, Q is the quality factor), and the free radical concentration of the detected target (free radical sample 360) can be further obtained.

[0071] In the preferred embodiment of the present application, a circular observation window is opened on the SOI wafer to reduce the thickness of the packaging layer. Two sub-chambers are designed to accommodate the silicon-based cantilever and the getter, respectively. Based on the design of the magnetic ball size, the sub-chamber depth and the design of the packaged silicon film, the magnetic cantilever has higher detection sensitivity on the basis of high vacuum environment, greatly improving the spatial resolution of the magnetic resonance force microscopy system.

[0072] The background section of the present application can contain background information about the problems or environment of the present application, rather than the prior art described by others. Therefore, the content contained in the background section is not the admission of the prior art by the applicant.

[0073] The above description is further to the present application in conjunction with specific / preferred embodiments, and cannot be deemed as limiting the specific implementation of the present application to these descriptions. For those skilled in the art to which the present application belongs, without departing from the concept of the present application, they can make several substitutions or variations to the described embodiments, and these substitutions or variations shall be deemed as falling within the protection scope of the present application. In the description of the present application, the description of the terms "an embodiment", "some embodiments", "a preferred embodiment", "an example", "a specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are contained in at least one embodiment or example of the present application. In the present application, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. Furthermore, the skilled in the art can combine and combine the different embodiments or examples described in the present application and the features of the different embodiments or examples without contradiction. Although the embodiments of the present application and their advantages have been described in detail, it should be understood that various changes, substitutions and modifications can be made herein without departing from the scope defined by the appended claims.

Claims

1. A magnetic cantilever beam sensor, characterized by The application relates to a glass substrate, a silicon-based cantilever beam, a magnet, an air absorption unit and a silicon-based cover body, wherein the glass substrate is provided with a first cavity and a second cavity in communication, the second cavity is located at the bottom of the first cavity, the fixed end of the silicon-based cantilever beam is fixedly connected to the bottom of the first cavity of the glass substrate, the magnet is fixedly connected to the free end of the silicon-based cantilever beam, the sum of the height of the magnet and the thickness of the silicon-based cantilever beam is smaller than the depth of the first cavity, and the gap between the top end of the magnet and the silicon-based cover body is 0.1-1 mu m, so that the sample to be tested can be sensed by the magnetic cantilever beam sensor in a larger range, and the detection sensitivity of the magnetic cantilever beam is improved; the air absorption unit is arranged in the second cavity to absorb the gas generated in the anode combination process, the silicon-based cover body is fixedly connected to the opening end of the glass substrate above the first cavity, and a sensing window is formed in the silicon-based cover body and located above the magnet. The silicon-based cover body is made of an SOI wafer comprising a substrate layer, an oxide layer and a device layer, and the sensing window is a silicon film window formed by removing the substrate layer and the oxide layer at the position of the silicon-based cover body above the magnet.

2. The magnetic cantilever beam sensor according to claim 1, characterized in that The thickness of the substrate layer of the SOI wafer used to make the silicon-based cover body is 200-300 mu m, the thickness of the oxide layer is 1-2 mu m, and the thickness of the device layer is 1-2 mu m.

3. The magnetic cantilever beam sensor of claim 1, wherein, The thickness of the silicon-based cover body at the sensing window is 1-2 mu m.

4. The magnetic cantilever beam sensor of claim 1, wherein, The length of the silicon-based cantilever beam is 100-1000 mu m, the width is 5-50 mu m, and the thickness is 0.1-10 mu m.

5. The magnetic cantilever beam sensor of claim 1, wherein, The magnet is a spherical structure with a diameter of 10-20 mu m.

6. The magnetic cantilever beam sensor of claim 1, wherein, The depth of the first cavity is 10.2-31 mu m, and the depth of the second cavity is 150-200 mu m.

7. A method of fabricating the magnetic cantilever beam sensor of any one of claims 1 to 6, characterized in that, The application comprises the following steps: S1: using a deep silicon etching process to process a silicon-based cantilever beam in the device layer of an SOI wafer; S2: using wet etching to process a first cavity and a second cavity in sequence on a glass substrate, and placing the air absorption unit in the second cavity; S3: using deep silicon etching to process the substrate layer at the position of the sensing window of another SOI wafer, and then using wet etching to process the oxide layer at the position of the sensing window of the SOI wafer, so as to form the silicon-based cover body with the sensing window; S4: using an anode combination process to bond the silicon-based cantilever beam to the bottom of the first cavity of the glass substrate; S5: removing the substrate layer and the oxide layer of the SOI wafer in step S1, releasing the silicon-based cantilever beam in a liquid by using a supercritical drying process, fixing the magnet to the free end of the silicon-based cantilever beam, and magnetizing the magnet; S6: fixing the silicon-based cover body to the opening end of the glass substrate above the first cavity by using an anode combination process.

8. The method of claim 7, wherein, The step S1 of processing the silicon-based cantilever in the device layer of the SOI wafer further comprises: wet etching the oxide layer of the SOI wafer, deep silicon etching the substrate layer of the SOI wafer, wherein the etching depth of the substrate layer of the SOI wafer is 20-30 μm, and then depositing a 100-300 nm stop layer on the substrate layer; and the step S5 further comprises: removing the stop layer of the SOI wafer in the step S1 before releasing the silicon-based cantilever.

9. A microscopy system, characterized in that, The magnetic cantilever sensor of any one of claims 1 to 6, wherein the radio frequency coil is configured to apply a radio frequency signal to the sample, the magnetic field modulation coil is configured to excite a resonance of the silicon-based cantilever based on a magnetic force generated between the sample and the magnet, and the fiber optic interferometer and the lock-in amplifier are configured to measure a vibration of the silicon-based cantilever.

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