CN111537921B - Cantilever beam type MEMS magnetic sensor and preparation method thereof - Google Patents
Cantilever beam type MEMS magnetic sensor and preparation method thereof Download PDFInfo
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- CN111537921B CN111537921B CN202010323013.8A CN202010323013A CN111537921B CN 111537921 B CN111537921 B CN 111537921B CN 202010323013 A CN202010323013 A CN 202010323013A CN 111537921 B CN111537921 B CN 111537921B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/02—Measuring direction or magnitude of magnetic fields or magnetic flux
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B81—MICROSTRUCTURAL TECHNOLOGY
- B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
- B81B7/00—Microstructural systems; Auxiliary parts of microstructural devices or systems
- B81B7/02—Microstructural systems; Auxiliary parts of microstructural devices or systems containing distinct electrical or optical devices of particular relevance for their function, e.g. microelectro-mechanical systems [MEMS]
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B81—MICROSTRUCTURAL TECHNOLOGY
- B81C—PROCESSES OR APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OR TREATMENT OF MICROSTRUCTURAL DEVICES OR SYSTEMS
- B81C1/00—Manufacture or treatment of devices or systems in or on a substrate
- B81C1/00015—Manufacture or treatment of devices or systems in or on a substrate for manufacturing microsystems
- B81C1/00134—Manufacture or treatment of devices or systems in or on a substrate for manufacturing microsystems comprising flexible or deformable structures
- B81C1/0015—Cantilevers
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/0052—Manufacturing aspects; Manufacturing of single devices, i.e. of semiconductor magnetic sensor chips
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B81—MICROSTRUCTURAL TECHNOLOGY
- B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
- B81B2201/00—Specific applications of microelectromechanical systems
- B81B2201/02—Sensors
- B81B2201/0257—Microphones or microspeakers
Abstract
A cantilever beam type MEMS magnetic sensor and a preparation method thereof comprise a cantilever beam, a surface acoustic wave device, a magnetostrictive film and a magnetic quality block; the surface acoustic wave device is arranged above the cantilever beam, and the magnetic mass block is positioned at the free end of the cantilever beam; the magnetostrictive film is positioned above the surface acoustic wave device; the surface acoustic wave device comprises a piezoelectric film and an interdigital electrode; the piezoelectric film is arranged on the upper surface of the cantilever beam, and the interdigital electrodes are arranged on the piezoelectric film. The invention provides a cantilever beam type MEMS magnetic sensor. Different from the traditional surface acoustic wave magnetic sensor, the cantilever beam with the magnetic mass block is introduced, the structure not only improves the sensitivity through the magnetic torque effect, but also adopts the MEMS process, and the prepared sensor has small volume and is beneficial to high integration.
Description
Technical Field
The invention belongs to the technical field of sensors, and particularly relates to a cantilever beam type MEMS magnetic sensor and a preparation method thereof.
Background
Magnetic sensors are used in a variety of applications, such as the automotive industry, biomagnetic signal detection, smart homes, and the like. However, the existing magnetic sensor has certain challenges in realizing wireless passive detection. In recent years, magnetic sensors based on acoustic waves have attracted considerable attention, in particular surface acoustic wave magnetic sensors. Since the propagation velocity of an acoustic wave is much smaller than that of an electromagnetic wave, a magnetic signal is easily acquired and processed on its propagation path. More importantly, the device based on the surface acoustic wave can realize wireless passive detection, so that an effective way is provided for the magnetic sensor to realize the wireless passive detection.
The surface acoustic wave magnetic sensor is characterized in that a material sensitive to a magnetic field is placed on a sound wave propagation path, and the magnetic field detection purpose is achieved by utilizing the characteristic that a surface acoustic wave signal is easy to extract and detect. The traditional surface acoustic wave magnetic sensor structure adopts a single-port or delay line device, and the structure mainly depends on the change of magnetostrictive materials under a magnetic field to cause the Young modulus of piezoelectric layer materials to change. However, the magnetostrictive film has a relatively small size extension or shortening under an external magnetic field, so that the perturbation capability on sound waves is limited, which on one hand results in low sensitivity of the device, and on the other hand increases the difficulty in extracting the weak perturbation signal, resulting in limited capability of detecting a weak magnetic field.
The advent of MEMS (Micro-Electro-Mechanical systems) technology has made it possible to miniaturize sensors and achieve higher integration. By means of MEMS technology, the surface acoustic wave structure is integrated on a silicon substrate, and a bulk silicon process of MEMS is utilized to prepare the surface acoustic wave magnetic sensor different from the traditional structure, and the structure has great potential for improving the sensitivity of the sensor.
Disclosure of Invention
The invention aims to provide a cantilever beam type MEMS magnetic sensor and a preparation method thereof, so as to solve the problems.
In order to achieve the purpose, the invention adopts the following technical scheme:
a cantilever beam type MEMS magnetic sensor comprises a cantilever beam, a surface acoustic wave device, a magnetostrictive film and a magnetic quality block; the surface acoustic wave device is arranged above the cantilever beam, and the magnetic mass block is positioned at the free end of the cantilever beam; the magnetostrictive film is positioned above the surface acoustic wave device;
the surface acoustic wave device comprises a piezoelectric film and an interdigital electrode; the piezoelectric film is arranged on the upper surface of the cantilever beam, and the interdigital electrodes are arranged on the piezoelectric film.
Furthermore, the cantilever beam is a silicon-based cantilever beam.
Furthermore, the surface acoustic wave device is a single-port or delay line structure; a reflective layer is disposed in the single port or delay line structure.
Further, the piezoelectric material is LiNbO3、LiTaO3AlN and ZnO film.
Further, the interdigital electrode material comprises an adhesion layer and an electrode material; the adhesion layer is Ta or Cr; the electrode material is one of Al, Cu, Pt and Au conductive films.
Further, the magnetic quality block is one of Ni, Fe and CoFeB magnetic films.
Further, a preparation method of the cantilever beam type MEMS magnetic sensor comprises the following steps:
1) washing the silicon substrate with a mixed solution of ethanol, acetone, concentrated sulfuric acid and hydrogen peroxide for three times respectively, ultrasonically washing the silicon substrate with deionized water for three times in the middle of each washing, washing for 30 seconds each time, and drying for later use;
2) depositing a piezoelectric film on a silicon substrate, spin-coating photoresist on the piezoelectric film, and exposing to define the pattern of the magnetic mass block;
3) depositing a magnetic mass block, and then peeling in acetone to obtain a pattern of the magnetic mass block;
4) spin-coating photoresist, exposing to obtain an interdigital electrode pattern, depositing an adhesion layer and an electrode material, and obtaining an interdigital electrode through a stripping process;
5) spin-coating photoresist, aligning exposure to obtain a magnetostrictive film pattern, depositing a film, and obtaining the magnetostrictive film through a stripping process;
6) spin-coating photoresist on the back of the device, and exposing to obtain a cantilever beam pattern; and etching the silicon substrate by a wet method or a dry method, and finally removing the photoresist by acetone to obtain the cantilever beam type MEMS magnetic sensor.
Compared with the prior art, the invention has the following technical effects:
the invention provides a cantilever beam type MEMS magnetic sensor. Different from the traditional surface acoustic wave magnetic sensor, the cantilever beam with the magnetic mass block is introduced, the structure not only improves the sensitivity through the magnetic torque effect, but also adopts the MEMS process, and the prepared sensor has small volume and is beneficial to high integration.
The invention uses silicon substrate to accord with semiconductor technology, and has low cost and easy mass production.
Drawings
Fig. 1 is a structure of a cantilever-beam MEMS magnetic sensor of the present invention.
Fig. 2 is a process for manufacturing the cantilever-beam-type MEMS magnetic sensor of the present invention.
Detailed Description
The invention is further described below with reference to the accompanying drawings:
referring to fig. 1 to 2, a cantilever MEMS magnetic sensor includes a silicon-based cantilever 1, a surface acoustic wave device 4, a magnetostrictive film 5, and a magnetic mass 6. The surface acoustic wave device 4 is arranged above the silicon-based cantilever beam 1; the surface acoustic wave device 4 consists of a piezoelectric film 2 and interdigital electrodes 3; the magnetic mass 6 is located at the free end of the silicon-based cantilever 1.
The cantilever beam is composed of a silicon substrate. The silicon substrate is in accordance with the semiconductor technology, has low cost and is easy for mass production.
The surface acoustic wave device is composed of a piezoelectric film and interdigital electrodes.
The surface acoustic wave device is a single port or delay line structure. In this embodiment, a delay line structure is selected.
The piezoelectric material is one of thin films of LiNbO3, LiTaO3, AlN, ZnO and the like. In the embodiment, the piezoelectric material is ZnO, and the thickness is 5-6 microns.
The number and the size of the interdigital electrodes in the delay line structure are determined according to actual needs, and the smaller the size is, the higher the frequency is, and the greater the process difficulty is. The width of the interdigital electrode is set to 25 μm in this embodiment, and 15 pairs are taken as pairs.
A reflective layer is disposed in the delay line structure. The material of the reflecting layer is the same as that of the interdigital electrode, and the logarithm is 10.
The interdigital electrode material comprises an adhesion layer and an electrode material. The adhesion layer in this example was Ta with a thickness of 5nm, the electrode material was Cu with a thickness of 150 nm.
The magnetic mass block is one of Ni, Fe, CoFeB and other films. In this example, Ni is used, and the thickness is 200 nm.
The magnetostrictive film is one of CoFeB, FeGaB, and the like.
According to the cantilever beam type MEMS magnetic sensor, the magnetic material is deposited on the cantilever beam, so that the cantilever beam can be bent based on a torque effect in a magnetic field, and further the frequency offset of a surface acoustic wave device on the cantilever beam is caused. The frequency shift of the surface acoustic wave is due to the young's modulus effect, and when the strain of the cantilever beam is transferred to the piezoelectric layer of the surface acoustic wave structure, the young's modulus of the piezoelectric layer and the electrode size are changed, so that the center frequency shift is caused. The sensitivity of the magnetic sensor is influenced by the bonding force between the piezoelectric layer and the cantilever beam, and if the bonding force is too weak, the film of the piezoelectric layer is easy to crack or fall off in multiple bending. Therefore, the substrate is sufficiently pretreated before the piezoelectric thin film is deposited to ensure strong bonding force of the piezoelectric thin film. In addition, the thickness of the cantilever beam is also a critical factor affecting the sensitivity, but this requires a compromise between the process conditions and the stress distribution on the cantilever beam.
The invention discloses a preparation process of a cantilever beam type MEMS magnetic sensor, which is characterized by comprising the following steps: the steps are as follows,
1) the silicon substrate is respectively washed three times by mixed solution of ethanol, acetone, concentrated sulfuric acid and hydrogen peroxide, the silicon substrate is ultrasonically washed three times by deionized water every time, the washing time is 30 seconds every time, and then the silicon substrate is dried for standby.
2) And depositing a piezoelectric film on the silicon substrate by magnetron sputtering, then spin-coating photoresist on the piezoelectric film, and exposing to define the pattern of the magnetic mass block.
3) And depositing a magnetic mass block, and then peeling in acetone to obtain a magnetic mass block pattern.
4) Spin-coating photoresist, and exposing to obtain interdigital electrode pattern. Depositing an adhesion layer and an electrode material, and obtaining the interdigital electrode through a stripping process.
5) Spin-coating photoresist, and aligning exposure to obtain a magnetostrictive film pattern. Depositing a film, and obtaining the magnetostrictive film through a stripping process.
6) And spin-coating photoresist on the back of the device, and exposing to obtain a cantilever beam pattern. And etching the silicon substrate by a wet method, and finally removing the photoresist by acetone to obtain the cantilever beam type MEMS magnetic sensor.
Claims (2)
1. A cantilever beam type MEMS magnetic sensor is characterized by comprising a cantilever beam, a surface acoustic wave device, a magnetostrictive film and a magnetic quality block; the surface acoustic wave device is arranged above the cantilever beam, and the magnetic mass block is positioned at the free end of the cantilever beam; the magnetostrictive film is positioned above the surface acoustic wave device;
the surface acoustic wave device comprises a piezoelectric film and an interdigital electrode; the piezoelectric film is arranged on the upper surface of the cantilever beam, and the plurality of interdigital electrodes are arranged on the piezoelectric film;
the surface acoustic wave device is a single port or delay line structure; a reflecting layer is arranged in the single-port or delay line structure;
the magnetic mass block is one of Ni, Fe and CoFeB magnetic films;
the cantilever beam is a silicon-based cantilever beam;
the piezoelectric material being LiNbO3、LiTaO3One of AlN and ZnO films;
the interdigital electrode material comprises an adhesion layer and an electrode material; the adhesion layer is Ta or Cr; the electrode material is one of Al, Cu, Pt and Au conductive films.
2. A method for manufacturing an izod MEMS magnetic sensor, based on the method of claim 1, comprising the steps of:
1) washing the silicon substrate with a mixed solution of ethanol, acetone, concentrated sulfuric acid and hydrogen peroxide for three times respectively, ultrasonically washing the silicon substrate with deionized water for three times in the middle of each washing, washing for 30 seconds each time, and drying for later use;
2) depositing a piezoelectric film on a silicon substrate, spin-coating photoresist on the piezoelectric film, and exposing to define the pattern of the magnetic mass block;
3) depositing a magnetic mass block, and then peeling in acetone to obtain a pattern of the magnetic mass block;
4) spin-coating photoresist, exposing to obtain an interdigital electrode pattern, depositing an adhesion layer and an electrode material, and obtaining an interdigital electrode through a stripping process;
5) spin-coating photoresist, aligning exposure to obtain a magnetostrictive film pattern, depositing a film, and obtaining the magnetostrictive film through a stripping process;
6) spin-coating photoresist on the back of the device, and exposing to obtain a cantilever beam pattern; and etching the silicon substrate by a wet method or a dry method, and finally removing the photoresist by acetone to obtain the cantilever beam type MEMS magnetic sensor.
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| CN113567898B (en) * | 2021-07-23 | 2023-08-08 | 中国科学院空天信息创新研究院 | Low-frequency MEMS (micro-electromechanical systems) magneto-resistance sensor with magneto-resistance motion modulation |
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