CN113562687B

CN113562687B - Manufacturing method of low-frequency MEMS (micro-electromechanical systems) magneto-resistive sensor modulated by magneto-resistive motion

Info

Publication number: CN113562687B
Application number: CN202110837583.3A
Authority: CN
Inventors: 邹旭东; 刘振溪; 陈嘉民; 李志天; 杨伍昊; 熊兴崟; 汪政
Original assignee: Aerospace Information Research Institute of CAS
Current assignee: Aerospace Information Research Institute of CAS
Priority date: 2021-07-23
Filing date: 2021-07-23
Publication date: 2024-04-09
Anticipated expiration: 2041-07-23
Also published as: CN113562687A

Abstract

The invention relates to a manufacturing method of a low-frequency MEMS (micro-electromechanical system) magnetic resistance sensor modulated by magnetic resistance movement, belongs to the field of magnetic field detection, and solves the technical problem of detection precision reduction caused by asynchronous movement of magnetic flux collectors on two sides of an existing MEMS magnetic resistance sensor. The manufacturing method of the sensor comprises the following steps: forming a T-shaped insulating layer A on a substrate; forming a magnetoresistive sensor MTJ at a top end of a longitudinal portion of the T-shaped insulating layer a; forming magnetic flux concentrators on the substrate, wherein the magnetic flux concentrators are symmetrically arranged on two sides of the MTJ; covering an insulating layer B on the MTJ and the insulating layer A, and covering an insulating layer C on the magnetic flux concentrator; forming a piezoelectric layer on a longitudinal portion of the insulating layer B; etching the insulating layer B to expose electrode windows of the MTJ and the piezoelectric layer; forming an electrode layer on the electrode window, the piezoelectric layer and the insulating layer B; and etching the substrate to form the piezoelectric cantilever beam. The problem that the movement of the magnetic flux collector is asynchronous is avoided through cantilever beam vibration, the magnetic field detection resolution is improved, and the magnetic flux collector can be widely applied to detection of low-frequency weak magnetic fields.

Description

Manufacturing method of low-frequency MEMS (micro-electromechanical systems) magneto-resistive sensor modulated by magneto-resistive motion

Technical Field

The invention relates to the field of magnetic field detection, in particular to a low-frequency MEMS (micro-electromechanical systems) magnetic resistance sensor modulated by magnetic resistance movement and a manufacturing method thereof.

Background

The magneto-resistive sensor is widely applied to the fields of industrial sensing, data storage, biomedicine and the like due to small volume, low power consumption and high sensitivity, but is affected by 1/f noise when measuring a low-frequency weak magnetic field, so that the detection resolution of the low-frequency weak magnetic field is severely limited. To reduce the influence of 1/f noise and improve resolution, a micro-electromechanical system (Micro electromechanical systems, MEMS) technology is used to drive the magnetic flux concentrator to move, and the low-frequency weak magnetic field of the detection area of the magnetoresistive sensor is modulated to a high-frequency area (more than 10 kHz) so that the detection resolution is three orders of magnitude higher than the low frequency.

The existing MEMS magnetic resistance sensor utilizes the motion of an MEMS resonator to drive a magnetic flux collector to move, carries out high-frequency modulation on the magnetic flux density in the middle of the magnetic flux collector, detects a high-frequency magnetic field through the fixedly placed magnetic resistance sensor, and is matched with a corresponding interface circuit to read magnetic field signals. Such as the variable gap and torsional modulation proposed by the army laboratories in the united states, the vertical motion modulation proposed by the national defense science and technology university and the cantilever Liang Diaozhi proposed by the international nano-laboratories in ibralia. The modulation modes are all to realize high-frequency modulation of the low-frequency magnetic field by changing the motion form of the magnetic flux concentrator, so that 1/f noise is suppressed to improve the detection resolution of the low-frequency magnetic field. In the existing MEMS magneto-resistance sensors, the magnetic flux collectors move, the magneto-resistance sensors are fixedly arranged, and the biggest problem is that the movement synchronization of the magnetic flux collectors at two sides is difficult to keep. For example, a MEMS magnetoresistive sensor designed by the army laboratory in the united states with comb-driven magnetic flux concentrators, as shown in fig. 1, has two magnetic flux concentrators driven laterally by the comb on opposite sides of a fixed magnetoresistive sensor, and the modulated ac magnetic field is a signal having the same frequency as the frequency of the resonators only when the two resonators resonate synchronously. Once out of synchronization, the modulated magnetic field will be a very spectrally rich signal that cannot be read out of the correct magnetic field signal by the interface circuit and signal site. Not only the 1/f noise cannot be suppressed but also the noise is increased. In addition, the common process of the structure is complex, and the consistency requirement on the process tolerance is high.

Disclosure of Invention

In view of the above analysis, the embodiment of the invention aims to provide a low-frequency MEMS magnetoresistive sensor modulated by magnetoresistive motion and a manufacturing method thereof, which are used for solving the technical problem that the detection precision is reduced due to noise increase caused by asynchronous motion of magnetic flux concentrators on two sides of the conventional MEMS magnetoresistive sensor.

In one aspect, embodiments of the present invention provide a low frequency MEMS magnetoresistive sensor with magnetoresistive motion modulation, the MEMS magnetoresistive sensor comprising: a magnetoresistive sensor MTJ, a magnetic flux concentrator, a piezoelectric cantilever, a first substrate;

the piezoelectric cantilever beam is arranged in the through hole, one end of the piezoelectric cantilever beam is suspended in the air, and the other end of the piezoelectric cantilever beam is fixedly connected with the first substrate;

the magnetic resistance sensor MTJ is arranged above the suspension end of the piezoelectric cantilever beam, and the piezoelectric cantilever beam drives the magnetic resistance sensor MTJ to do periodic simple harmonic vibration along the axial direction of the through hole;

the magnetic flux concentrators are disposed on the first substrate and symmetrically disposed on both sides of the magnetoresistive sensor MTJ.

Further, the piezoelectric cantilever beam is of a laminated structure and comprises a second substrate, a first insulating layer and a piezoelectric layer which are sequentially arranged from bottom to top, the magnetic resistance sensor MTJ is buried in the first insulating layer at the suspension end of the piezoelectric cantilever beam, an electrode window is leaked, the piezoelectric layer is positioned at a position on the first insulating layer where the magnetic resistance sensor MTJ is not buried, and the piezoelectric layer and the magnetic resistance sensor MTJ are separated by a certain distance.

Further, the first substrate is an SOI base and sequentially comprises an Si layer, an oxygen burying layer and an Si layer from bottom to top, the second substrate is formed by removing the Si layer and the oxygen burying layer at the bottom layer of the first substrate, and the Si layer in the first substrate and the Si layer in the second substrate are of an integrated structure.

Further, a second insulating layer is further arranged at the joint of the first substrate and the cantilever beam, the second insulating layer and the first insulating layer are of an integrated structure, the first insulating layer and the second insulating layer form a T-shaped structure, and an electrode window of the piezoelectric layer is arranged on the second insulating layer.

Further, the MEMS magnetoresistive sensor further comprises an electrode layer, wherein the electrode layer comprises an MTJ signal detection output electrode and a piezoelectric driving electrode; the MTJ signal detection output electrode comprises an MTJ signal detection electrode, an MTJ signal transmission line and an MTJ signal interface electrode which are sequentially connected, wherein the MTJ signal detection electrode is positioned in an MTJ electrode window of the magnetic resistance sensor and is electrically connected with the magnetic resistance sensor through an electrode interface of the magnetic resistance sensor MTJ; the MTJ signal transmission line is positioned in a region on the first insulating layer, where the piezoelectric layer is not arranged, and the MTJ signal interface electrode is arranged on the second insulating layer;

The piezoelectric driving electrode comprises a driving electrode, a detecting electrode, a piezoelectric driving interface electrode and a grounding electrode, wherein the driving electrode and the detecting electrode are connected with the piezoelectric driving interface electrode, the driving electrode and the detecting electrode are positioned on the piezoelectric layer, and the piezoelectric driving interface electrode is positioned on the second insulating layer; the grounding electrode is arranged in the electrode window of the piezoelectric layer on the second insulating layer and is directly connected with the first substrate.

Further, the piezoelectric layer is made of zinc oxide and has a thickness of 500-1000nm.

Further, the magnetic flux concentrator is formed by a high magnetic permeability material plated on the first substrate, and has a thickness of 0.5-10 μm; the two magnetic flux concentrators are symmetrically arranged by taking the magnetic resistance sensor MTJ as a center, and the distance between the two magnetic flux concentrators is larger than the width of the cantilever beam; the magnetic flux concentrator is also provided with a third insulating layer.

Further, the magnetic flux concentrator is horn-shaped, the narrow end of the horn shape is close to the magnetic resistance sensor MTJ, and the wide end of the horn shape is far away from the magnetic resistance sensor MTJ; the distance between the narrow end and the wide end is 0.5-3mm.

Further, the materials of the first insulating layer, the second insulating layer and the third insulating layer are SiO2, and the thickness is 200-500nm.

Further, the magnetoresistive sensor MTJ has a stacked structure, and sequentially from bottom to top: tantalum metal layer, ruthenium metal layer, nickel-iron alloy layer, ruthenium metal layer, cobalt-iron-boron material layer, magnesium oxide layer, cobalt-iron-boron material layer, ruthenium metal layer, cobalt-iron alloy layer, iridium-manganese alloy layer, tantalum metal layer, ruthenium metal layer.

On the other hand, the invention also provides a manufacturing method of the low-frequency MEMS magneto-resistance sensor modulated by magneto-resistance motion, which comprises the following steps:

forming a T-shaped insulating layer A on a substrate;

forming a magnetoresistive sensor MTJ at a top end of a longitudinal portion of the T-shaped insulating layer a;

forming magnetic flux concentrators on the substrate, wherein the magnetic flux concentrators are symmetrically arranged on two sides of the magnetic resistance sensor MTJ;

covering an insulating layer B on the magnetic resistance sensor MTJ and the insulating layer A, wherein the insulating layer B is also T-shaped; covering an insulating layer C on the magnetic flux collector;

forming a piezoelectric layer on a longitudinal portion of the insulating layer B, the piezoelectric layer being located at a position on the longitudinal portion of the insulating layer B not covered with the magnetoresistive sensor MTJ;

etching the insulating layer B to expose electrode windows of the magnetoresistive sensor MTJ and the piezoelectric layer;

forming an electrode layer on the electrode window, the piezoelectric layer and the insulating layer B;

and etching the substrate to suspend the substrate where the longitudinal part of the insulating layer A is positioned, so as to form a piezoelectric cantilever beam, and enabling the piezoelectric cantilever beam to perform periodic simple harmonic vibration along the normal direction of the substrate.

Further, the MTJ is a stacked structure, and the MTJ stacked structure sequentially includes, from bottom to top: a bottom electrode, a free layer, a barrier layer, a pinning layer, and a top electrode; the bottom electrode and the top electrode comprise a tantalum metal layer and a ruthenium metal layer which are sequentially arranged from bottom to top, the free layer comprises a nickel-iron alloy layer, a ruthenium metal layer and a cobalt-iron-boron material layer which are sequentially arranged from bottom to top, and the barrier layer is a magnesium oxide layer; the pinning layer comprises a cobalt iron boron material layer, a ruthenium metal layer, a cobalt iron alloy layer and an iridium manganese alloy layer which are sequentially arranged from bottom to top.

Further, the forming a magnetoresistive sensor MTJ includes:

s11, forming an MTJ (magnetic tunnel junction) layer film structure on the insulating layer A by adopting a magnetron sputtering method;

s12, patterning the film structure of each layer of the MTJ to form an MTJ outline;

and S13, etching the film structure of each layer of the MTJ from top to bottom by adopting an ion beam etching method until the bottom electrode is exposed.

Further, the insulating layer A is made by a thermal oxidation method, the insulating layer B and the insulating layer C are made by a plasma chemical vapor deposition (PECVD) method, the insulating layer A, B, C is made of SiO2, and the thickness is 100-250nm.

Further, forming the piezoelectric layer on the longitudinal portion of the insulating layer B includes:

s51, coating a layer of photoresist on the insulating layer B;

s52, exposing and developing the photoresist by using a mask plate to form a pattern;

s53, depositing a piezoelectric material on the photoresist pattern by adopting a magnetron sputtering process;

s54, dissolving and stripping the photoresist to form a piezoelectric layer.

The piezoelectric material is ZnO, the thickness is 500-1000nm, and the width of the piezoelectric layer is smaller than that of the insulating layer B.

Further, the forming an electrode layer on the electrode window, the piezoelectric layer and the insulating layer B includes:

s71, coating a layer of photoresist on the electrode window, the piezoelectric layer and the insulating layer B;

S72, exposing and developing the photoresist by using a mask plate to form an electrode pattern;

s73, sequentially depositing a first metal layer and a second metal layer on an electrode pattern formed by photoresist by adopting a magnetron sputtering method;

s74, dissolving and stripping the photoresist to form an electrode layer;

the first metal layer is chromium Cr, and the second metal layer is gold Au or platinum Pt.

Further, the electrode layer comprises an MTJ signal detection output electrode and a piezoelectric driving electrode; the MTJ signal detection output electrode comprises an MTJ signal detection electrode, an MTJ signal transmission line and an MTJ signal interface electrode which are sequentially connected, and the MTJ signal detection electrode is positioned in an electrode window of the magnetic resistance sensor MTJ and is electrically connected with the magnetic resistance sensor MTJ; the MTJ signal transmission line is positioned in a region on the longitudinal part of the insulating layer B, where the piezoelectric layer is not arranged, and the MTJ signal interface electrode is arranged on the transverse region of the insulating layer B;

the piezoelectric driving electrode comprises a driving electrode, a detecting electrode, a piezoelectric driving interface electrode and a grounding electrode, wherein the driving electrode and the detecting electrode are connected with the piezoelectric driving interface electrode, the driving electrode and the detecting electrode are positioned on the piezoelectric layer, and the piezoelectric driving interface electrode is positioned on the transverse area of the insulating layer B; the grounding electrode is arranged in an electrode window of the piezoelectric layer and is directly connected with the substrate; the electrode window of the piezoelectric layer is located at the transverse portion of the insulating layer B.

Further, the substrate is an SOI substrate and comprises a Si layer, a buried oxide layer and a Si layer from bottom to top in sequence;

the etching substrate is used for suspending the substrate where the longitudinal part of the T-shaped insulating layer A is located, so that a piezoelectric cantilever beam is formed, and the method comprises the following steps:

s81, coating photoresist on the front surface of the prepared substrate with each layer of structure;

s82, exposing and developing the photoresist by using a mask plate to form an etching pattern;

s83, etching the Si layer on the front surface by using the photoresist as a mask and adopting a deep reactive ion etching method;

s84, coating photoresist on the back surface of the substrate, and exposing and developing the photoresist by using a mask plate to form an etching pattern;

and S85, using the photoresist as a mask, etching the Si layer on the back by adopting a deep reactive ion etching method, and etching the buried oxide layer by adopting a reactive ion etching method, so that the substrate on which the longitudinal part of the insulating layer A is positioned is suspended, and forming the piezoelectric cantilever.

Further, the magnetic flux collector is made of high-permeability material, and the thickness of the magnetic flux collector is 0.5-10 mu m.

Further, the forming the magnetic flux concentrator on the substrate includes:

s31, coating a layer of photoresist on the substrate;

s32, exposing and developing the photoresist by using a mask plate to form a pattern;

s33, depositing a high-permeability material on the photoresist pattern by adopting a magnetron sputtering process;

S34, dissolving and stripping the photoresist to form a magnetic flux collector;

the magnetic flux collector is in a horn shape, the narrow end of the horn-shaped magnetic flux collector is close to the magnetic resistance sensor MTJ, and the wide end of the horn-shaped magnetic flux collector is far away from the magnetic resistance sensor MTJ; the distance between the narrow end and the wide end is 0.5-3mm; the high permeability material is preferably nickel-iron alloy.

Compared with the prior art, the invention has at least one of the following beneficial effects:

1. compared with the situation that the existing magnetic flux collector moves and the magnetic resistance sensor is fixed, the magnetic resistance sensor MTJ is driven to move through the piezoelectric cantilever beam, the problem of asynchronous movement is avoided, and the direct current magnetic field can be well modulated to a high-frequency area to inhibit 1/f noise, so that the magnetic field detection resolution can be greatly improved.

2. In the application, the magnetic flux collector is fixed, so that the size of the magnetic flux collector is as large as possible within the allowable range of the device, the maximum magnetic field amplification factor is obtained as much as possible, and the magnetic field detection resolution is improved.

3. The sensor designed by the application has the advantages that only one cantilever beam moves, so that the process is simple, and the requirement on the consistency of process tolerance is low.

4. The manufacturing process of the MTJ and the manufacturing process of the cantilever resonator are integrated, so that the manufacturing steps are simplified, and the manufacturing success rate is improved.

In the invention, the technical schemes can be mutually combined to realize more preferable combination schemes. Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and drawings.

Drawings

The drawings are only for purposes of illustrating particular embodiments and are not to be construed as limiting the invention, like reference numerals being used to refer to like parts throughout the several views.

FIG. 1 is a schematic diagram of a conventional MEMS magnetoresistive sensor.

FIG. 2 is a schematic diagram of the overall structure of a MEMS magnetoresistive sensor in one embodiment of the application.

FIG. 3 is a front view of a piezoelectric cantilever;

FIG. 4 is a schematic diagram of a piezoelectric cantilever with the uppermost electrode removed to expose a magnetoresistive sensor;

FIG. 5 is a schematic cross-sectional view of a piezoelectric cantilever along the A-A' axis;

FIG. 6 is a schematic diagram of the variation waveform of the piezoelectric cantilever displacement and the modulated magnetic field;

FIG. 7 is a mask plate used in the fabrication of MEMS magnetoresistive sensors;

FIG. 8 is a flow chart of a method of fabricating a MEMS magnetoresistive sensor;

FIG. 9 is a schematic diagram of an MTJ stack structure;

FIG. 10 is a schematic diagram of a flux concentrator fabrication process;

FIG. 11 is a schematic diagram of a flux concentrator prepared using a magnetron sputter stripping process;

FIG. 12 is a schematic illustration of a process for etching to form a cantilever;

FIG. 13 is a schematic diagram of the direction of the magnetic field of the two anneals;

reference numerals:

10-magnetoresistive sensor MTJ; 20-flux concentrator; 30-a piezoelectric cantilever; 40-a first substrate; 50 a second insulating layer; 301-a second substrate; 302-a first insulating layer; 303-a piezoelectric layer;

611-MTJ signal detection electrodes; 612-MTJ signal transmission line; 613-MTJ signal interface electrode; 621-driving electrodes; 622 detection electrodes; 623 piezoelectric drive interface electrodes; 624 ground electrode.

Detailed Description

Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form a part hereof, and together with the description serve to explain the principles of the invention, and are not intended to limit the scope of the invention.

Example 1

In one embodiment of the present invention, a low frequency MEMS magnetoresistive sensor is disclosed that is magnetoresistive motion modulated, as shown in fig. 2, the MEMS magnetoresistive sensor comprising: a magnetoresistive sensor MTJ10, a magnetic flux concentrator 20, a piezoelectric cantilever 30, a first substrate 40; the first substrate 40 is provided with a through hole which is matched with the size of the piezoelectric cantilever beam 30, the piezoelectric cantilever beam 30 is arranged in the through hole, one end of the piezoelectric cantilever beam is suspended, and the other end of the piezoelectric cantilever beam is fixedly connected with the first substrate 40;

The magnetic resistance sensor MTJ10 is placed above the suspended end of the piezoelectric cantilever 30, and the piezoelectric cantilever 30 drives the magnetic resistance sensor MTJ to make periodic simple harmonic vibration along the axial direction of the through hole.

The flux concentrator 20 is disposed on the first substrate 40 and symmetrically placed on both sides of the magnetoresistive sensor MTJ 10.

In order to prevent the piezoelectric layer in the cantilever from being broken down and oxidized by the magnetoresistive sensor MTJ, a first insulating layer 302 is disposed in the piezoelectric cantilever 30, preferably, the piezoelectric cantilever 30 has a laminated structure, and referring to fig. 3-5, fig. 3 is a front view of the piezoelectric cantilever, fig. 4 is a schematic view of the structure of the piezoelectric cantilever with the uppermost electrode removed and exposing the magnetoresistive sensor, and fig. 5 is a schematic view of a cross section of the piezoelectric cantilever along the A-A' axis; the laminated structure includes a second substrate 301, a first insulating layer 302, and a piezoelectric layer 303 sequentially disposed from bottom to top, where the magnetoresistive sensor MTJ10 is embedded in the first insulating layer at the suspended end of the piezoelectric cantilever 30 and leaks out of the electrode window, the piezoelectric layer 303 is located at a position on the first insulating layer 302 where the magnetoresistive sensor MTJ10 is not embedded, and the piezoelectric layer 303 and the magnetoresistive sensor MTJ10 are spaced by a certain distance, and the specific distance may be set to 20um, so as to avoid affecting the magnetoresistive sensor MTJ and prevent electrical interference caused by too close proximity of the detection electrode of the MTJ and the electrode of the piezoelectric layer.

Preferably, the first substrate is an SOI substrate, and comprises a Si layer, an oxygen-buried layer and a Si layer in sequence from bottom to top, the second substrate is formed by removing the Si layer and the oxygen-buried layer on the bottom layer of the first substrate, and the Si layer in the first substrate and the Si layer in the second substrate are in an integrated structure; i.e. the whole MEMS magnetoresistive sensor is completed on an SOI substrate;

the parameters of the SOI are selected from 300um of SOI substrate Si layer, 0.5um of buried oxide layer, 10um of upper Si layer, crystal orientation <100>, P type doping, double-sided polishing, 0.001-0.005ohm cm of Si layer resistivity and 0.01-0.05ohm cm of substrate resistivity.

The second insulating layer 50 is further disposed on the first substrate 40 at the connection position with the cantilever beam 30, the second insulating layer 50 and the first insulating layer 302 are in an integrated structure, the first insulating layer 302 and the second insulating layer 50 form a T shape, the first insulating layer 302 is a longitudinal portion of the T shape, and the second insulating layer 50 is a transverse portion of the T shape. And an electrode window of the piezoelectric layer is arranged on the second insulating layer.

Preferably, the first insulating layer and the second insulating layer are made of SiO2, and the thickness is 200-500nm.

Preferably, the piezoelectric layer material is zinc oxide, and the thickness is 500-1000nm.

In order to realize signal detection output of the magnetic resistance sensor MTJ and driving of the piezoelectric layer, the MEMS magnetic resistance sensor is also provided with an electrode layer, wherein the electrode layer comprises an MTJ signal detection output electrode and a piezoelectric driving electrode; the MTJ signal detecting output electrode includes an MTJ signal detecting electrode 611, an MTJ signal transmission line 612, and an MTJ signal interface electrode 613 that are sequentially connected, where the MTJ signal detecting electrode 611 is located in an electrode window of the magnetoresistive sensor MTJ10 and is electrically connected to the magnetoresistive sensor MTJ; the MTJ signal transmission line 612 is located on the second insulating layer 302 in a region where the piezoelectric layer 303 is not located, and the MTJ signal interface electrode 613 is located on the second insulating layer 50;

The MTJ signal interface electrode 613 includes positive and negative current interface electrodes, positive and negative voltage interface electrodes. The power supply is input into the magnetoresistive sensor MTJ10 in the form of a current signal through the positive and negative current interface electrodes and the MTJ signal transmission line 612, and the voltage signal measured by the magnetoresistive sensor MTJ10 is transmitted to the positive and negative voltage interface electrodes through the MTJ signal detection electrode 611 and the MTJ signal transmission line 612, and the measured voltage signal is output to the external signal processing circuit through the positive and negative voltage interface electrodes.

The piezoelectric driving electrode includes a driving electrode 621, a detecting electrode 622, a piezoelectric driving interface electrode 623, and a ground electrode 624, the driving electrode 621 and the detecting electrode 622 are connected to the piezoelectric driving interface electrode 623, the driving electrode 621 and the detecting electrode 622 are located on the piezoelectric layer 303, and the piezoelectric driving interface electrode 623 is located on the second insulating layer 50; the ground electrode 624 is provided in the piezoelectric layer electrode interface on the second insulating layer 50, directly communicating with the upper Si layer (device layer) of the first substrate SOI, as an electrical ground.

The piezoelectric driving interface electrode 623 includes a driving interface electrode D connected to the driving electrode 621 and a detecting interface electrode S connected to the detecting electrode 622. The driving signal is transmitted to the driving electrode 621 through the driving interface electrode D, the driving electrode 621 further transmits the driving signal to the piezoelectric layer 302, and under the action of the driving signal, the piezoelectric layer makes simple harmonic vibration, so that the whole cantilever beam is driven to vibrate, and the cantilever beam drives the magneto-resistance sensor to vibrate. The detection electrode 622 detects the vibration signal of the piezoelectric layer, and transmits the vibration signal to the detection interface electrode S, through which the vibration signal is fed back to the external signal processing circuit.

Specifically, each electrode and each signal transmission line are made of a metal material, and the metal material can be platinum Pt or gold Au, because the metal material is very stable in chemical property and hardly reacts with conventional chemicals. It is particularly noted that chromium (Cr) needs to be sputtered as an adhesion layer prior to sputtering the conductive material, otherwise the sputtered gold or platinum may come off during lift-off.

Thus, the preferred electrode material in this embodiment is 30nm/200nm Cr/Au or Cr/Pt.

Preferably, the magnetoresistive sensor MTJ has a stacked structure, and sequentially from bottom to top: tantalum metal layer, ruthenium metal layer, nickel-iron alloy layer, ruthenium metal layer, cobalt-iron-boron material layer, magnesium oxide layer, cobalt-iron-boron material layer, ruthenium metal layer, cobalt-iron alloy layer, iridium-manganese alloy layer, tantalum metal layer, ruthenium metal layer. The thickness of each layer of the magnetic resistance sensor is as follows from bottom to top in sequence: ta (5 nm)/Ru (10 nm)/NiFe (70 nm)/Ru (0.9 nm)/CoFeB (3 nm)/MgO (1.6 nm)/Co FeB (3 nm)/Ru (0.9 nm)/CoFe (5 nm)/IrMn (10 nm)/Ta (5 nm)/Ru (30 nm).

Preferably, the magnetic flux concentrator is formed by a high magnetic permeability material plated on the first substrate, and has a thickness of 0.5um to 10um; the high permeability material may be permalloy or nickel-iron alloy;

The two magnetic flux concentrators are symmetrically arranged by taking the magnetic resistance sensor MTJ as a center, and the distance between the two magnetic flux concentrators is larger than the width of the cantilever beam;

preferably, the magnetic flux concentrator is horn-shaped, the narrow end of the horn shape is close to the magnetic resistance sensor MTJ, and the wide end of the horn shape is far away from the magnetic resistance sensor MTJ; the distance between the narrow end and the wide end is 0.5-3mm.

In order to prevent the flux concentrator from being oxidized, it is preferable that a third insulating layer is further provided on the flux concentrator.

Specifically, the third insulating layer is SiO and has a thickness of 200-500nm.

The basic working principle of the MEMS magneto-resistance sensor is that a magnetic field to be detected is converged and amplified by a magnetic flux converging device, a magneto-resistance sensor (MTJ) positioned at the tail end of a piezoelectric cantilever beam moves along with the piezoelectric cantilever beam in a high-frequency period, and the magnetic field intensity at the gap between the two magnetic flux converging devices is uneven, so that the magneto-resistance sensor (MTJ) detects a periodically-changed alternating magnetic field, and then outputs corresponding alternating voltage through a corresponding interface electrode.

Compared with the situation that the magnetic flux collector moves and the magnetic resistance sensor is fixed, the MEMS magnetic resistance sensor of the invention has no problem that the two sides of the magnetic flux collector need to move synchronously as the magnetic resistance sensor moves. On the other hand, since the larger the area of the flux concentrator is, the larger the magnification of the magnetic field is, once the flux concentrator is fixed, the size thereof can be as large as possible within the allowable range of the layout, thereby obtaining the maximum magnification of the magnetic field as much as possible. For a moving magnetic flux concentrator, since the modulation frequency is in a high-frequency region, the resonance frequency and the mass are inversely proportional to each other:

Wherein f _r K, m are the resonant frequency of the resonator, the stiffness coefficient of the beam supporting the resonator, the mass of the resonator, respectively. To bring the frequency to a certain range (e.g. greater than 10kHz), the size of the flux concentrator cannot be arbitrarily large, and the corresponding magnification of the magnetic field will be limited and often small.

When the sensor is used for measuring an external direct current magnetic field B ₀ In the initial rest state, the magnetic field detected by the magneto-resistive sensor is B, assuming that the magnetic field of the magnetic flux concentrator at the center of the gap has a magnification of G ₀ G. When the piezoelectric cantilever resonator with length L oscillates at frequency f and amplitude x as high frequency, the oscillation angle of the tip is θ, and θ=4x/3L according to the geometrical relationship, when the cantilever Liang Zhengxian oscillates, namely

θ＝θ ₀ sin(2πft) (2)

Wherein θ is ₀ Is the maximum oscillation angle. Since the magneto-resistive sensor is located at the end of the piezoelectric cantilever, the magnetic field detected by the magneto-resistive sensor can be expressed as

Bringing (2) into (3), the detected magnetic field can be expressed as follows:

it can be separated into a direct current component and an alternating current component

As is clear from (6), the dc magnetic field will be modulated into a high frequency ac magnetic field, and its frequency is twice the resonant frequency of the resonator, as shown in fig. 3. The modulation efficiency (η) is generally defined as the ratio of the alternating current component to the direct current component, so the modulation efficiency of the sensor is

As is clear from (7), the larger the vibration displacement (angle) of the piezoelectric resonator is, the higher the modulation efficiency is.

Example 2

In another embodiment of the present invention, a method for manufacturing a low-frequency MEMS magnetoresistive sensor modulated by magnetoresistive motion is provided, wherein a mask plate used in a manufacturing process is shown in fig. 7, and a specific manufacturing method is shown in fig. 8, and the method includes the following steps:

s1, forming a T-shaped insulating layer A on a substrate;

specifically, step S1 specifically includes the following:

s11, selecting a substrate;

the substrate is a carrier for all subsequent processing processes, and has direct influence on the subsequent processes and the device performance. Therefore, the selection of an appropriate substrate is a necessary condition to ensure successful fabrication and high performance devices. According to the structural characteristics and the preparation process of the device and the requirements of the subsequent coating quality, the factors to be considered in the selection of the substrate material are as follows: (1) The two surfaces of the substrate are smooth, compact and not fragile, and have proper hardness, so that large deformation and warping are prevented, and the later stage of experiment is facilitated; (2) The substrate is ensured to be capable of being etched to obtain a cantilever beam with a determined thickness; (3) The substrate material has no magnetism, so that magnetic field interference on a sample in the later period is avoided; (4) The substrate should have stable chemical properties to avoid chemical reaction with the contacted elements during growth and photolithography; (5) The substrate has good thermal property and avoids deformation in the post annealing process; (6) The substrate should have good conductivity properties to participate in conduction as a bottom electrode of the entire device. In view of the above, the substrate used in the present application is an SOI monocrystalline silicon wafer, the base Si layer thickness is 300 μm, the buried oxide layer is 0.5um, the top Si layer (device layer) is 10um, the crystal orientation is <100>, P-doping, double-sided polishing, the top Si layer resistivity is 0.001-0.005ohm cm, and the base Si layer resistivity is 0.01-0.05ohm cm.

S12, forming a T-shaped insulating layer A on the substrate;

preferably, the material of the insulating layer a is SiO2.

To sputter high quality MTJ magnetic films, it is often necessary to grow an SiO2 insulating layer prior to fabricating the MTJ film. The lattice constant of SiO2 is similar to that of the MTJ film, so that the adhesion of the film on the substrate can be enhanced, and the film is prevented from falling off in the cleaning or photoetching process. Meanwhile, siO2 has good chemical stability and electrical insulation, and is commonly used as a shielding layer for ion implantation, a masking layer for diffusion, a gate oxide layer, a sacrificial layer and an isolation layer in integrated circuits.

Specifically, the SiO2 insulating layer may be prepared by the following method: thermal decomposition deposition, sputtering, vacuum evaporation, anodic oxidation, chemical vapor deposition, and thermal oxidation.

Since the best quality of SiO2 is produced by the thermal oxidation process, in a preferred embodiment, the SiO2 insulating layer is produced by the thermal oxidation process.

Specifically, siO2 with the thickness of 100-250nm can be grown by adopting an oxidation furnace thermal oxidation method as the insulating layer A. The insulating layer A can well isolate the MTJ from the piezoelectric cantilever beam, and prevents the measurement signal of the MTJ from being influenced by the electrical signal of the piezoelectric cantilever beam.

S2, forming a magnetic resistance sensor (MTJ) at the top end of the longitudinal part of the T-shaped insulating layer A;

Specifically, step S2 includes the following steps:

s21, forming an MTJ (magnetic tunnel junction) layer film structure on the insulating layer A by adopting a magnetron sputtering method;

specifically, the magnetoresistive sensor MTJ is a stacked structure, as shown in fig. 9, where the stacked structure of the MTJ sequentially includes, from bottom to top: a bottom electrode, a free layer, a barrier layer, a pinning layer, and a top electrode; the bottom electrode and the top electrode comprise a tantalum metal layer and a ruthenium metal layer which are sequentially arranged from bottom to top, the free layer comprises a nickel-iron alloy layer, a ruthenium metal layer and a cobalt-iron-boron material layer which are sequentially arranged from bottom to top, and the barrier layer comprises a magnesium oxide layer; the pinning layer comprises a cobalt iron boron material layer, a ruthenium metal layer, a cobalt iron alloy layer and an iridium manganese alloy layer which are sequentially arranged from bottom to top.

The growth preparation method of the film mainly comprises evaporation, magnetron sputtering, ion plating, chemical Vapor Deposition (CVD), liquid phase epitaxy and chemical solution coating. Compared with other film plating methods, the magnetron sputtering has the following advantages: (1) The deposition speed of the film is high, and the temperature requirement on the substrate is low; (2) The nucleation density of the film is high in the initial stage of sputtering, and an extremely thin continuous film with the thickness below 10nm can be prepared; (3) The thickness of the film can be precisely controlled by adjusting the sputtering time length; (4) The adhesion force between the sputtering film and the substrate is more than ten times that between the sputtering film and the substrate; (5) The coating range is wide, almost all materials which can be made into target materials can be sputtered into films, and the materials comprise various metals, semiconductors, ferromagnetic materials, oxides, ceramics and the like, and the coating is particularly suitable for deposition coating of materials with high melting point and low vapor pressure; (6) The method can carry out mixed sputtering on various materials, and deposit compound films with different components by utilizing a multi-target co-sputtering mode or introducing active gas into a sputtering cavity; (7) The repeatability of the sputtering process is strong, and the deposition rate and the roughness of the film can be controlled by controlling the pressure and the sputtering power in the sputtering cavity; and (8) the industrial mass production can be realized. Based on the above advantages, the MTJ stack structure is preferably prepared by a magnetron sputtering method.

Specifically, the magnetron sputtering instrument adopts a vacuum magnetron sputtering instrument with 4 chambers and 12 target positions produced by Aifa, thereby ensuring continuous coating of different targets. Before coating, the sputtering rates of different targets are calibrated, then the required sputtering time is calculated according to the expected film thickness, and finally the continuous sputtering of the multilayer films can be completed by programming corresponding programs, wherein the sputtering rate and the sputtering time of each layer of film are shown in the table 1, and the sputtering time of the 145 nm-thick MTJ multilayer film is about 50 minutes.

TABLE 1

S22, patterning the film structure of each layer of the MTJ to form an MTJ outline;

because the structural materials of the layers of the MTJ are mainly metal and have rich components, the ion beam etching method is selected as a general etching mode without selectivity. Meanwhile, the ion beam etching method has no selectivity, so that the ion beam etching equipment with the terminal detection function is preferable, and the etching depth can be monitored in real time.

Specifically, the method of forming the MTJ profile includes:

s221, coating a layer of photoresist on each layer of film structure of the MTJ;

s222, exposing and developing the photoresist by using a mask plate to form an etching pattern;

specifically, the Mask used is Mask1 in fig. 7;

And S223, taking the photoresist as a mask, and performing ion beam etching on the film structure of each layer of the MTJ to form the outline of the MTJ.

Preferably, the etching device is an ion beam etching device with a terminal detection function, for example, an IBE150 ion beam etching machine can be used.

S23, etching the film structure of each layer of the MTJ from top to bottom by adopting an ion beam etching method until the bottom electrode is exposed.

The step is the same as the step S22, except that Mask2 is used, and the etching thickness needs to be monitored in real time in the etching process, and the etching is stopped when the bottom electrode is exposed.

S3, forming magnetic flux concentrators on the substrate, wherein the magnetic flux concentrators are symmetrically arranged on two sides of the magnetic resistance sensor MTJ;

the method for preparing the magnetic flux concentrator is generally divided into electroplating and sputtering stripping, and is limited by the lack of mature electroplating equipment, so that the magnetic sputtering stripping process is adopted in the embodiment. The disadvantage of using magnetron sputtering is the slow coating speed, thin film, but good quality. Stripping is a pattern transfer process simpler than etching and its basic principle is to use photoresist as a sacrificial layer, and when a thin film is deposited on the lithographic pattern, acetone is used to dissolve the photoresist, so that no photoresist is covered to leave a thin film, thereby achieving the same effect as etching. In particular, referring to fig. 10, a method of forming a flux concentrator includes the steps of,

S31, coating a layer of photoresist on the substrate;

s32, exposing and developing the photoresist by using a Mask plate Mask3 to form a pattern;

preferably, the high magnetic permeability material is nickel-iron alloy or permalloy;

s34, dissolving and stripping the photoresist to form a magnetic flux collector.

Specifically, acetone may be used to dissolve the photoresist, and the method used in the present application may be the same as that used in the present step when the photoresist is dissolved; after the photoresist is dissolved, the high magnetic permeability material covered on the photoresist is stripped from the substrate, so that the high magnetic permeability material directly plated on the substrate is reserved to form a magnetic flux concentrator with a certain shape, and the magnetic flux concentrator is obtained through a magnetron sputtering stripping process as shown in fig. 11.

In order to achieve a better magnetic field amplifying effect, preferably, the magnetic flux concentrator is arranged in a horn shape, the narrow end of the horn-shaped magnetic flux concentrator is close to the magnetic resistance sensor MTJ, and the wide end of the horn-shaped magnetic flux concentrator is far away from the magnetic resistance sensor MTJ; the distance between the narrow end and the wide end is 0.5-3mm.

S4, covering an insulating layer B on the magnetic resistance sensor MTJ and the insulating layer A, wherein the insulating layer B is also T-shaped; covering an insulating layer C on the magnetic flux collector;

In order to prevent the MTJ and the magnetic flux concentrator from being oxidized and damaged in the subsequent process, an insulating layer needs to be prepared thereon, and the thin film can protect the MTJ and the magnetic flux concentrator and isolate the magnetically sensitive portion from the MEMS resonator portion, so that the signal transmission of the MTJ and the signal transmission of the MEMS piezoelectric resonator do not affect each other.

Since the MTJ and flux concentrator are not capable of withstanding high temperatures, the silicon dioxide herein can no longer be prepared by the thermal oxidation process used in preparing insulating layer a, but by a low temperature Plasma Enhanced Chemical Vapor Deposition (PECVD) process.

Preferably, the material of the insulating layer B, C is SiO2;

preferably, the thickness of the insulating layer B, C is 150-250nm.

S5, forming a piezoelectric layer on the longitudinal part of the insulating layer B, wherein the piezoelectric layer is positioned at a position on the longitudinal part of the insulating layer B where the magnetic resistance sensor MTJ is not embedded;

the method for preparing the piezoelectric layer is similar to the method for preparing the magnetic flux concentrator, and also adopts a magnetron sputtering stripping process, and the specific method is as follows:

s51, coating a layer of photoresist on the insulating layer B;

s52, exposing and developing the photoresist by using a Mask5 to form a pattern;

preferably, the piezoelectric material is ZnO;

s54, dissolving and stripping the photoresist to form a piezoelectric layer.

The thickness of the finally formed piezoelectric layer is 200-1000nm, and the width of the piezoelectric layer is smaller than that of the insulating layer B, so that the two sides of the insulating layer B can accommodate signal transmission lines in the MTJ signal detection output electrode.

S6, etching the insulating layer B to expose electrode windows of the magnetic resistance sensor MTJ and the piezoelectric layer;

since it is necessary to test the MTJ extraction electrode line and expose the upper Si layer (device layer) of the SOI as the bottom electrode, it is necessary to etch SiO2 for windowing for sputtering the metal electrode.

The reactive ion etching (Reaction Ion Etch, RIE) has physical bombardment and chemical reaction, has the advantages of good anisotropism and selectivity, and is particularly suitable for etching SiO2 films on different media. The insulating layer B is etched by a reactive ion etching method.

Specifically, CHF3 is used as an etching gas of SiO2, a Mask plate used in etching is Mask4, and finally, the SiO2 layer at the position corresponding to the magnetoresistive sensor MTJ on the insulating layer B is etched to form an electrode window outside the MTJ; the SiO2 layer is etched away at the position corresponding to the grounding electrode of the piezoelectric layer on the transverse area of the insulating layer B, so as to form a grounding electrode window of the piezoelectric layer.

S7, forming an electrode layer on the electrode window, the piezoelectric layer and the insulating layer B;

in order to ensure the quality of the electrode, a magnetron sputtering method with the best compactness and adhesion is preferable.

Commonly used electrode materials are gold (Au) and platinum (Pt) because of their very stable chemical nature and little reaction with conventional chemicals. It is particularly noted that chromium (Cr) needs to be sputtered as an adhesion layer prior to sputtering the conductive material, otherwise the sputtered gold or platinum may come off during lift-off.

Thus, the preferred electrode material in this embodiment is 30nm/200nm Cr/Au or Cr/Pt. In general, no other electrode is prepared by a lift-off process without etching, so the electrode layer of this embodiment is also prepared by lift-off.

The preparation method comprises the following steps:

s72, exposing and developing the photoresist by using a Mask plate Mask6 to form an electrode layer pattern;

s73, sequentially depositing a Cr layer with the thickness of 30nm and an Au layer with the thickness of 200nm on an electrode layer pattern formed by photoresist by adopting a magnetron sputtering method;

and S74, dissolving and stripping the photoresist to form an electrode layer.

Specifically, the electrode layer finally formed comprises an MTJ signal detection output electrode and a piezoelectric driving electrode; the MTJ signal detection output electrode comprises an MTJ signal detection electrode, an MTJ signal transmission line and an MTJ signal interface electrode which are sequentially connected, wherein the MTJ signal detection electrode is plated in an electrode window of the magnetic resistance sensor MTJ and is electrically connected with the magnetic resistance sensor MTJ; the MTJ signal transmission line is plated on the area without the piezoelectric layer on the longitudinal part of the insulating layer B, and the MTJ signal interface electrode is arranged on the transverse area of the insulating layer B;

the piezoelectric driving electrode comprises a driving electrode, a detecting electrode, a piezoelectric driving interface electrode and a grounding electrode, wherein the driving electrode and the detecting electrode are connected with the piezoelectric driving interface electrode, the driving electrode and the detecting electrode are plated on the piezoelectric layer, and the piezoelectric driving interface electrode is positioned above the transverse area of the insulating layer B; the grounding electrode is arranged in an electrode window of the piezoelectric layer and is directly connected with the substrate; the electrode window of the piezoelectric layer is located at the transverse portion of the insulating layer B.

And S8, etching the substrate to suspend the substrate where the longitudinal part of the insulating layer A is located, and forming a piezoelectric cantilever beam, so that the piezoelectric cantilever beam can perform periodic simple harmonic vibration along the normal direction of the substrate.

For MEMS-MTJ integrated magnetic sensor, the basic principle is to modulate the space magnetic field by using the vibration of the piezoelectric cantilever beam, so the piezoelectric beam must be suspended and can vibrate freely. In order to obtain the suspended piezoelectric cantilever, a two-step deep reactive ion etching (Deep Reaction Ion Etch, DRIE) is adopted to etch the Si layer (i.e. the device layer) on the upper part of the SOI and the silicon substrate on the bottom, and then the buried oxide layer is removed by reactive ion etching. In addition to having the advantage of reactive ions, deep reactive ion etching also has a better aspect ratio than reactive ion etching. The current gas for deep reactive ion etching of silicon is mainly SF6 and C4F8, firstly SF6 is used for etching the area to be etched, then C4F8 is used for protecting the side wall and the bottom, and then SF6 is used for etching, so that the process is repeated circularly until the etching requirement is met.

Specifically, referring to fig. 12, the specific steps for forming the piezoelectric cantilever beam are as follows:

(1) The original SOI wafer after the previous process is cleaned, as shown in the figure (a), and the existing structure of the surface is omitted.

(2) Front side spin coating AZ1500 photoresist (Bao Jiao) because the photoresist to Si selectivity is about 1:70, so that the photoresist with the thickness of 1.5um is completely enough for 10um Si etching, and the Mask7 is adopted to expose and develop the photoresist to form a photoetching pattern, as shown in a figure (b);

(3) Etching the Si layer on the front surface by using a deep reactive ion etching machine which is created in the North China, as shown in a figure (c);

(4) Removing the photoresist on the front surface, and cleaning the wafer, as shown in the figure (d);

(5) The front spin-coating photoresist AZ1500 is used for protection, and meanwhile, the surface is flat so as to facilitate the adhesion of the lining, as shown in the figure (e);

(6) Spin-coating back photoresist AZ4903, exposing and developing the photoresist by using a Mask8 to obtain an etching pattern, as shown in a figure (f);

since the photoresist on the back needs to act as a mask for etching 200nm SiO2,300um Si and 500nm SiO2, such a thin film as AZ1500 cannot be used any more, thick films as AZ4903, AZ4620 must be used, the thickness of the film AZ4903 used in this embodiment is 9um, the etching requirement is satisfied,

(7) In order to prevent the etched slag from falling into a chamber of an etching machine in back etching, a common silicon wafer with the same size is stuck on the front surface of an original wafer by using heat-conducting silicone grease, as shown in a figure (g);

(8) Since a dense SiO2 layer is formed on the back during the first thermal oxidation step, 200nm SiO2 needs to be etched by DRIE before Si is etched, as shown in the figure (h);

(9) After SiO2 etching is finished, etching 300um of Si by DRIE, as shown in a figure (i);

(10) Then etching the buried oxide layer by adopting a reactive ion etching method to completely release the piezoelectric cantilever beam, as shown in a figure (j);

(11) Etching is completed, and the lining is removed, as shown in a figure (k);

(12) The removal of the residual photoresist is completed to the piezoelectric cantilever Liang Keshi, and the 4-inch wafer is broken into square chips with the size of 2cm x 2cm according to the pre-designed breaking grooves, so that subsequent annealing and packaging tests are facilitated, as shown in the figure (l).

After the device processing is completed, a two-step annealing process is adopted for the device to obtain high magnetic resistance and linear resistance response. The magnetic field direction in the two anneals is shown in FIG. 13, the first annealing is performed at 350 ℃ and 1T for 1 hour to induce the magnetic anisotropy of the free layer, the second annealing is performed at 300 ℃ for 1 hour, and the magnetic field of 1T is applied after rotating 90 degrees along the easy axis direction of the pinned layer. After the second anneal, the MTJ is capable of providing a linear magnetoresistive response due to the orthogonal easy axes of the free and pinned layers, which, when the annealing step is completed, marks the completion of the MEMS magnetoresistive sensor fabrication.

After the substrate is etched, a gap with a certain width is formed between the piezoelectric cantilever beam and the substrate, the cantilever beam can be regarded as being positioned in a through hole on the substrate, namely, the through hole in the device corresponds to the through hole, and the through hole can accommodate the cantilever beam and can enable the piezoelectric cantilever beam to perform periodic simple harmonic vibration along the normal direction of the substrate.

The insulating layer A and the insulating layer B formed in the manufacturing method are T-shaped, the longitudinal part of the insulating layer A and the insulating layer B after being overlapped is the first insulating layer in the finally formed device, and the transverse part of the insulating layer A and the insulating layer B after being overlapped is the second insulating layer in the finally formed device. The insulating layer C formed in the preparation method is the third insulating layer in the device.

The resulting MEMS magnetoresistive sensor is illustrated in fig. 2-5.

The present invention is not limited to the above-mentioned embodiments, and any changes or substitutions that can be easily understood by those skilled in the art within the technical scope of the present invention are intended to be included in the scope of the present invention.

Claims

1. A method of fabricating a magneto-resistive motion modulated low frequency MEMS magneto-resistive sensor, the method comprising the steps of:

forming a T-shaped insulating layer A on a substrate;

etching the substrate to suspend the substrate where the longitudinal part of the insulating layer A is positioned to form a piezoelectric cantilever beam, so that the piezoelectric cantilever beam can perform periodic simple harmonic vibration along the normal direction of the substrate; the piezoelectric cantilever beam is of a laminated structure and comprises a second substrate, a first insulating layer and a piezoelectric layer which are sequentially arranged from bottom to top, the magnetic resistance sensor MTJ is buried in the first insulating layer at the suspension end of the piezoelectric cantilever beam, an electrode window is leaked, the piezoelectric layer is located at a position on the first insulating layer where the magnetic resistance sensor MTJ is not buried, and the piezoelectric layer and the magnetic resistance sensor MTJ are separated by a certain distance.

2. The method for manufacturing a low-frequency MEMS magnetoresistive sensor according to claim 1, wherein the MTJ is a stacked structure comprising, in order from bottom to top: a bottom electrode, a free layer, a barrier layer, a pinning layer, and a top electrode; the bottom electrode and the top electrode comprise a tantalum metal layer and a ruthenium metal layer which are sequentially arranged from bottom to top, the free layer comprises a nickel-iron alloy layer, a ruthenium metal layer and a cobalt-iron-boron material layer which are sequentially arranged from bottom to top, and the barrier layer is a magnesium oxide layer; the pinning layer comprises a cobalt iron boron material layer, a ruthenium metal layer, a cobalt iron alloy layer and an iridium manganese alloy layer which are sequentially arranged from bottom to top.

3. The method of fabricating a low frequency MEMS magnetoresistive sensor according to claim 2, wherein forming the magnetoresistive sensor MTJ comprises:

4. The method of claim 1, wherein the insulating layer a is formed by thermal oxidation, the insulating layer B and the insulating layer C are formed by plasma chemical vapor deposition (PECVD), the insulating layers A, B, C are all SiO2, and the thicknesses thereof are all 100-250nm.

5. The method of manufacturing a low frequency MEMS magnetoresistive sensor according to claim 1 wherein forming a piezoelectric layer on a longitudinal portion of the insulating layer B comprises:

s51, coating a layer of photoresist on the insulating layer B;

s54, dissolving and stripping the photoresist to form a piezoelectric layer;

6. The method of manufacturing a low frequency MEMS magnetoresistive sensor according to claim 5 wherein forming an electrode layer over the electrode window, piezoelectric layer and insulating layer B comprises:

s74, dissolving and stripping the photoresist to form an electrode layer;

7. The method of manufacturing a low frequency MEMS magnetoresistive sensor according to claim 6 wherein the electrode layer comprises an MTJ signal sense output electrode, a piezoelectric drive electrode; the MTJ signal detection output electrode comprises an MTJ signal detection electrode, an MTJ signal transmission line and an MTJ signal interface electrode which are sequentially connected, and the MTJ signal detection electrode is positioned in an electrode window of the magnetic resistance sensor MTJ and is electrically connected with the magnetic resistance sensor MTJ; the MTJ signal transmission line is positioned in a region on the longitudinal part of the insulating layer B, where the piezoelectric layer is not arranged, and the MTJ signal interface electrode is arranged on the transverse region of the insulating layer B;

8. The method for manufacturing the low-frequency MEMS magnetoresistive sensor according to claim 1, wherein the substrate is an SOI substrate and comprises a Si layer, a buried oxide layer and a Si layer in sequence from bottom to top;

9. The method of manufacturing a low frequency MEMS magnetoresistive sensor according to claim 1 wherein the flux concentrator is made of a high permeability material having a thickness of 0.5-10 μm.

10. The method of fabricating a low frequency MEMS magnetoresistive sensor according to claim 1 wherein forming a flux concentrator on a substrate comprises:

s31, coating a layer of photoresist on the substrate;

the magnetic flux collector is in a horn shape, the narrow end of the horn-shaped magnetic flux collector is close to the magnetic resistance sensor MTJ, and the wide end of the horn-shaped magnetic flux collector is far away from the magnetic resistance sensor MTJ; the distance between the narrow end and the wide end is 0.5-3mm; the high magnetic permeability material is nickel-iron alloy.