CN118393407A - Magneto-resistive element and preparation method thereof - Google Patents

Abstract

The invention belongs to the technical field of magnetic sensors, and discloses a magneto-resistance element and a preparation method thereof. The magnetoresistive element includes a soft magnetic layer; the preparation method of the magnetic resistance element comprises the following steps: sequentially depositing a seed layer and an insulating layer above the substrate; forming a containing groove with a seed layer at the bottom and an insulating layer at the periphery above the seed layer by photoetching; soft magnetic materials are filled in the accommodating groove through electroplating, and the soft magnetic layer is obtained. According to the invention, the surrounding materials of the accommodating groove are replaced by the insulating layer, so that photoresist is prevented from directly acting on the soft magnetic material, and the forming structure of the soft magnetic layer is limited by the insulating layer, so that the consistency and the service performance of the manufactured magnetic resistance element are improved. The preparation method also has the beneficial effects of low preparation difficulty and easy industrial realization.

Description

A magnetoresistive element and a method for manufacturing the same

Technical Field

The present invention relates to the technical field of magnetic sensors, and in particular to a magnetoresistive element and a preparation method thereof.

Background technique

Magnetoresistive sensor is a sensor that can detect the direction, strength and position of magnetic field and has been widely used in many fields.

In the preparation process of magnetoresistive sensors, soft magnets are often required to be used as flux concentrators to enhance the magnetic field strength acting on the magnetoresistive sensing unit, thereby improving the resolution of magnetoresistive sensors; or as flux guides to change the direction of magnetic flux and realize three-dimensional magnetic field sensing on the same chip; or as magnetic shields to eliminate the influence of environmental magnetic fields.

When soft magnets are used as flux concentrators or flux guides, the magnets are generally required to be thicker and are usually prepared by electrochemical plating.

During the integrated molding process of the soft magnet and the magnetoresistive sensor, the filling area is surrounded by photoresist, and its overall shape is easily affected by the photoresist, resulting in defects such as edge imbalance, which affects the magnetic flux guiding function of the soft magnet and leads to poor performance and consistency of the chip.

The above contents are only used to assist in understanding the technical solution of the present invention and do not constitute an admission that the above contents are prior art.

Summary of the invention

The object of the present invention is to provide a magnetoresistive element and a method for preparing the same, so as to improve the problem that the overall shape defect of the soft magnetic layer in the existing magnetoresistive element leads to poor chip performance and consistency.

To achieve the above object, a first aspect of the present invention provides a method for preparing a magnetoresistive element, wherein the magnetoresistive element includes a soft magnetic layer; the preparation method comprises:

Depositing a seed layer and an insulating layer sequentially on the substrate;

Forming a receiving groove with a seed layer at the bottom and an insulating layer around it on the seed layer by photolithography and etching;

The soft magnetic layer is obtained by filling the containing groove with soft magnetic material through electroplating.

According to some embodiments of the present invention, the step of forming a receiving groove having a seed layer at the bottom and an insulating layer around the seed layer by photolithography and etching includes:

Depositing photoresist in a partial area above the insulating layer by photolithography;

Remove the area of the insulating layer where the photoresist is not deposited by etching to expose a receiving groove with a seed layer at the bottom and an insulating layer around it;

The photoresist on the insulating layer is removed.

According to some embodiments of the present invention, the step of filling the receiving groove with a soft magnetic material by electroplating to obtain the soft magnetic layer includes:

Filling the containing groove with soft magnetic material by electroplating to obtain the soft magnetic layer;

The upper surface of the soft magnetic layer is made flat by chemical mechanical polishing.

According to some embodiments of the present invention, after the soft magnetic material is filled in the receiving groove by electroplating to obtain the soft magnetic layer, the method further includes: removing the insulating layer above the seed layer.

According to some embodiments of the present invention, the seed layer is made of copper or titanium;

The insulating layer is silicon dioxide or silicon nitride; the thickness of the soft magnetic layer is 5-20 μm; the thickness of the insulating layer is 5-20 μm.

According to some embodiments of the present invention, the magnetoresistive element further comprises a plurality of magnetic tunnel junctions, wherein the magnetic tunnel junctions are located close to the edge of the soft magnetic layer;

The soft magnetic layer is used to deflect a first magnetic field perpendicular to a plane of the substrate into a second magnetic field parallel to a plane of the substrate and acting on the magnetic tunnel junction.

According to some embodiments of the present invention, sequentially depositing a seed layer and an insulating layer on the substrate includes:

Depositing and taping on the substrate in sequence to obtain multiple magnetic tunnel junctions;

Depositing a second insulating layer on the substrate so that the second insulating layer covers the plurality of magnetic tunnel junctions;

A seed layer and an insulating layer are sequentially deposited on the second insulating layer.

According to some embodiments of the present invention, after the soft magnetic material is filled in the receiving groove by electroplating to obtain the soft magnetic layer, the method further includes:

depositing a third insulating layer above the soft magnetic layer;

Depositing and taping on the third insulating layer to obtain a plurality of magnetic tunnel junctions;

Wherein, the magnetic tunnel junction is close to the edge of the soft magnetic layer.

According to some embodiments of the present invention, the magnetic tunnel junction includes a free layer, a tunneling layer, a reference layer and a pinned layer;

By performing high temperature magnetic field annealing under the first magnetic field, the reference layer can have a fixed magnetization direction parallel to the plane of the substrate.

According to some embodiments of the present invention, the magnetic tunnel junction is sensitive to the first magnetic field.

To achieve the above object, the second aspect of the present invention further provides a magnetoresistive element, which is manufactured using the above method.

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

The present invention provides a magnetoresistive element and a method for preparing the same; the magnetoresistive element includes a soft magnetic layer, and the method for preparing the magnetoresistive element includes: depositing a seed layer and an insulating layer in sequence on top of a substrate; forming a receiving groove with a seed layer at the bottom and an insulating layer around the seed layer by photolithography; and filling the receiving groove with a soft magnetic material by electroplating to obtain a soft magnetic layer. The present invention replaces the surrounding material of the receiving groove with an insulating layer to avoid direct action of the photoresist on the soft magnetic material, and at the same time limits the molding structure of the soft magnetic layer by the insulating layer, thereby improving the consistency and performance of the magnetoresistive element obtained. The preparation method also has the beneficial effects of low preparation difficulty and easy industrialization.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of the structure of a conventional magnetoresistive sensing unit before electroplating a soft magnetic layer (a) and a schematic diagram of the structure of the electroplated soft magnetic layer;

FIG2 is a schematic diagram of structural changes of a substrate during the preparation of a magnetoresistive element according to an embodiment of the present invention;

FIG3 is a schematic diagram of the structure of a magnetoresistive element according to an embodiment of the present invention;

FIG4 is a schematic structural diagram of a magnetoresistive element in another embodiment of the present invention;

FIG. 5 is a schematic diagram of a method for preparing a magnetoresistive element according to an embodiment of the present invention.

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

Detailed ways

It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention.

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

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

In addition, the descriptions of "first", "second", etc. in the present invention are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

Magnetoresistive sensor is a sensor that can detect the direction, strength and position of magnetic field and has been widely used in many fields.

In the preparation process of magnetoresistive sensors, soft magnets are often required to be used as flux concentrators to enhance the magnetic field strength acting on the magnetoresistive sensing unit, thereby improving the resolution of magnetoresistive sensors; or as flux guides to change the direction of magnetic flux and realize three-dimensional magnetic field sensing on the same chip; or as magnetic shields to eliminate the influence of environmental magnetic fields.

When soft magnets are used as flux concentrators or flux guides, the magnets are generally required to be thicker and are usually prepared by electrochemical plating.

During the integrated molding process of the soft magnet and the magnetoresistive sensor, the filling area is surrounded by photoresist, and its overall shape is easily affected by the photoresist, resulting in defects such as unbalanced edges and crooked side walls, which affects the magnetic flux guiding function of the soft magnet and leads to poor performance and consistency of the chip.

FIG1 is a schematic diagram of the structure of a conventional magnetoresistive sensing unit before electroplating a soft magnetic layer (a) and a schematic diagram of the structure of the electroplated soft magnetic layer (b). Before electroplating the soft magnetic layer, the cavity containing the soft magnetic layer is surrounded by photoresist. After etching, that is, before the electroplating step, the edge corners of the cavity for containing the soft magnetic layer in the magnetoresistive sensing unit are prone to residual glue that is difficult to remove due to the photoresist, which causes defects such as uneven edges and corners of the electroplated soft magnetic layer. This defect is not easy to solve through post-processing in the preparation process, which leads to its effect of being used for flux guidance being limited, affecting the performance of the chip.

Therefore, an embodiment of the present invention provides a method for preparing a magnetoresistive element, which is used to improve the problem that the overall shape defects of the soft magnetic layer in the existing magnetoresistive element lead to poor chip performance and consistency.

As shown in FIG. 5 , the method for preparing the magnetoresistive element according to the embodiment of the present invention includes the following steps.

Step S100: depositing a seed layer and an insulating layer in sequence on a substrate.

It should be understood that the seed layer and the insulating layer are parallel to the substrate plane, and the insulating layer is located above the seed layer. A magnetic sensing element may or may not be included between the seed layer and the substrate, and the magnetic sensing element may be an AMR, GMR, TMR or other electronic element that realizes magnetic field measurement based on the magnetoresistance effect.

After depositing the seed layer, the schematic diagram of the structure of the substrate is shown in FIG2 (1); after depositing the insulating layer, the schematic diagram of the structure of the substrate is shown in FIG2 (2).

Step S200: forming a receiving groove with a seed layer at the bottom and an insulating layer around it on the seed layer by photolithography and etching;

It should be understood that the photolithography step is used to deposit photoresist on a portion of the insulating layer; the etching step is used to etch away the region of the insulating layer where the photoresist is not deposited, thereby exposing a receiving groove with a seed layer at the bottom and an insulating layer around it. This step may also include removing the insulating glue on the insulating layer.

After the photolithography step, the schematic diagram of the structure of the substrate is shown in FIG2 (3); after the etching step, the schematic diagram of the structure of the substrate is shown in FIG2 (4); after the photoresist removal step, the schematic diagram of the structure of the substrate is shown in FIG2 (5).

The top view of the receiving groove can be a rectangle, square, ring or other shape, which is not specifically limited here.

Step S300: filling the receiving groove with soft magnetic material by electroplating to obtain a soft magnetic layer.

It should be understood that the soft magnetic layer is a soft magnetic material, and the soft magnetic material is filled into the receiving groove by electroplating. The filling height of the soft magnetic layer can be higher than the top of the insulating layer, and is cut to be flush with the top surface of the insulating layer in subsequent chemical mechanical polishing and other steps. This step may also include: etching the insulating layer around the soft magnetic layer.

After the electroplating step, the schematic diagram of the structure of the substrate is shown in FIG2 (6); after the flattening step, the schematic diagram of the structure of the substrate is shown in FIG2 (7).

The edge position of the soft magnetic layer in the magnetoresistive element manufactured by the embodiment of the present invention is not prone to defects, meets the design requirements, and improves the consistency of the magnetoresistive element.

Therefore, the embodiment of the present invention replaces the surrounding material of the receiving groove with an insulating layer to prevent the photoresist from directly acting on the soft magnetic material, and limits the molding structure of the soft magnetic layer through the insulating layer, thereby improving the consistency and performance of the prepared magnetoresistive element. The preparation method also has the beneficial effects of low preparation difficulty and easy industrialization.

In one embodiment of the present invention, the method for preparing the magnetoresistive element comprises the following steps:

Step S111: depositing a seed layer on a substrate;

Specifically, the seed layer is made of metal materials such as copper and titanium, preferably copper.

Step S112: depositing an insulating layer on the seed layer;

Specifically, the insulating layer is made of insulating materials such as silicon dioxide and silicon nitride, preferably silicon nitride.

Step S211: depositing photoresist on a partial area above the insulating layer by photolithography.

Specifically, by coating photoresist on the insulating layer, placing a photomask, developing and exposing, etc., some areas above the insulating layer are deposited with photoresist, while some areas are not deposited with photoresist.

Step S212: removing the area of the insulating layer where the photoresist is not deposited by etching, thereby exposing a receiving groove with a seed layer at the bottom and an insulating layer around it.

Step S213: removing the photoresist on the insulating layer.

Step S311: Fill the receiving groove with soft magnetic material by electroplating to obtain a soft magnetic layer.

The soft magnetic material of the embodiment of the present invention is made of nickel iron, and its thickness is 5-20 μm; the height of the receiving groove is not higher than the thickness of the soft magnetic layer.

Step S312: Make the upper surface of the soft magnetic layer flat by chemical mechanical polishing.

Step S411: depositing a third insulating layer on the soft magnetic layer;

The third insulating layer is located above the soft magnetic layer, and an upper surface of the third insulating layer is parallel to a plane where the substrate is located.

Step S412: obtain a plurality of magnetic tunnel junctions by deposition and wafer taping on the third insulating layer.

The magnetic tunnel junction is located above the soft magnetic layer and close to its edge. The magnetic tunnel junction at least includes a free layer, a tunnel layer, a reference layer and a pinning layer.

Preferably, this step further includes depositing a third insulating layer in the gaps between the magnetic tunnel junctions.

Step S510: placing the substrate in a first magnetic field parallel to the plane of the substrate for high temperature magnetic field annealing to obtain a magnetoresistive element.

The reference layer of the magnetic tunnel junction can have a fixed magnetization direction under the action of the soft magnetic layer, and the magnetization direction is a magnetization direction parallel to the plane of the substrate. The magnetization direction is specifically related to the placement of the soft magnetic layer and the magnetic tunnel junction.

Since the magnetoresistive element obtained in this step is close to the edge of the soft magnetic layer, the soft magnetic layer can sensitively sense the second magnetic field parallel to the plane of the substrate and deflected by the first magnetic field. Therefore, the magnetoresistive element can be sensitive to the first magnetic field.

The structural schematic diagram of the magnetoresistive element obtained in step S510 may be shown in FIG. 3 .

According to FIG. 3 , the magnetoresistive element includes a substrate 10 , a seed layer 20 , a soft magnetic layer 40 , a third insulating layer 70 and a tunnel junction 50 arranged in sequence from bottom to top. The soft magnetic layer 40 and the insulating layer 30 are at the same height.

In another embodiment of the present invention, the method for preparing the magnetoresistive element comprises the following steps:

Step S121: depositing a pinned layer, a reference layer, a tunneling layer and a free layer on a substrate in sequence, and obtaining a plurality of magnetic tunnel junctions through tape-out;

Step S122: depositing a second insulating layer above the plurality of magnetic tunnel junctions so that the second insulating layer covers the plurality of magnetic tunnel junctions;

It should be understood that the second insulating layer is located above the plurality of magnetic tunnel junctions, and the top surface of the second insulating layer is parallel to the plane of the substrate.

Step S123: depositing a seed layer on the second insulating layer.

Specifically, the seed layer is made of metal materials such as copper and titanium, preferably copper.

Step S124: depositing an insulating layer on the seed layer;

Specifically, the insulating layer is made of insulating materials such as silicon dioxide and silicon nitride, preferably silicon nitride.

Step S221: depositing photoresist on a partial area above the insulating layer by photolithography.

In this embodiment, the area above the insulating layer that is not covered by the photoresist deposition should be close to the location of the magnetic tunnel junction.

Step S222: removing the area of the insulating layer where the photoresist is not deposited by etching, thereby exposing a receiving groove with a seed layer at the bottom and an insulating layer around it.

The etching is a dry etching, preferably RIE (Reactive ion Etching) or ICPCVD (Inductively Coupled Plasma Chemical Vapor Deposition).

Step S223: removing the photoresist on the insulating layer.

Step S321: Fill the soft magnetic material into the receiving groove by electroplating to obtain a soft magnetic layer.

The soft magnetic material is a soft magnetic material, such as nickel iron; its thickness is preferably 5-20 μm.

Step S322: performing chemical mechanical polishing on the substrate to make the upper surface of the soft magnetic layer on the substrate flat.

Step S520: placing the substrate obtained in the above steps in a first magnetic field parallel to the plane of the substrate for high temperature magnetic field annealing to obtain a magnetoresistive element.

Through this step, the reference layer of the magnetic tunnel junction can have a fixed magnetization direction, and the magnetization direction is a magnetization direction parallel to the plane of the substrate. At the same time, the magnetoresistive element can be sensitive to the first magnetic field.

The structural schematic diagram of the magnetoresistive element obtained after step S520 may be shown in FIG. 4 .

According to Figure 4, the magnetoresistive element includes a substrate 10, a magnetic tunnel junction 50, a third insulating layer 60, a seed layer 20, and a soft magnetic layer 40 arranged in sequence from bottom to top. The soft magnetic layer 40 is at the same height as the insulating layer 30 and is located between the two insulating layers 30. After the tunnel junction 50 is formed, the third insulating layer 60 continues to fill the gaps between the tunnel junctions 50 and makes the top surface of the third insulating layer 60 higher than the top surface of each tunnel junction 50.

An embodiment of the present invention further provides a magnetoresistive element, which is manufactured by the above-mentioned manufacturing method.

As shown in FIGS. 3-4 , the magnetoresistive element according to the embodiment of the present invention includes a substrate 10 , a soft magnetic layer 40 and at least one magnetic tunnel junction 50 . The soft magnetic layer 40 may be located above or below the magnetic tunnel junction 50 .

3, when the soft magnetic layer 40 is located below the magnetic tunnel junction 50, the soft magnetic layer 40 and the magnetic tunnel junction 50 are separated by a second insulating layer 70. The signal output of the tunnel junction can be directly led out or realized by etching the second insulating layer.

4 , when the soft magnetic layer 40 is located above the magnetic tunnel junction 50, the soft magnetic layer 40 and the magnetic tunnel junction 50 are separated by the third insulating layer 60 and the seed layer 20. The signal output of the magnetic tunnel junction 50 can be achieved by etching the third insulating layer 60, the seed layer and the insulating layer 30.

It should be understood that the above is only an example and does not constitute any limitation on the technical solution of the present invention. In specific applications, technicians in this field can make settings as needed, and the present invention does not limit this.

It should be noted that the workflow described above is merely illustrative and does not limit the scope of protection of the present invention. In practical applications, technicians in this field can select part or all of them according to actual needs to achieve the purpose of the present embodiment, and no limitation is made here.

Claims (10)

1. A method of manufacturing a magneto-resistive element, wherein the magneto-resistive element comprises a soft magnetic layer;

the preparation method comprises the following steps:

sequentially depositing a seed layer and an insulating layer above the substrate;

Forming a containing groove with a seed layer at the bottom and an insulating layer at the periphery above the seed layer by photoetching;

and filling soft magnetic materials in the accommodating groove through electroplating to obtain the soft magnetic layer.

2. The method according to claim 1, wherein,

The method for forming the accommodating groove with the seed layer at the bottom and the insulating layer at the periphery above the seed layer through photoetching and etching comprises the following steps:

depositing photoresist on a partial region above the insulating layer by photolithography;

Removing the region of the insulating layer, where the photoresist is not deposited, by etching to expose a containing groove with a seed layer at the bottom and an insulating layer around the containing groove;

and removing the photoresist on the insulating layer.

3. The method according to claim 2, wherein,

Filling soft magnetic materials in the accommodating groove through electroplating to obtain the soft magnetic layer, wherein the soft magnetic layer comprises the following components:

filling soft magnetic materials into the accommodating groove through electroplating to obtain the soft magnetic layer;

and flattening the upper surface of the soft magnetic layer by a chemical mechanical polishing mode.

4. A process according to any one of claim 1 to3, wherein,

The seed layer is made of copper or titanium;

The insulating layer is silicon dioxide or silicon nitride;

the thickness of the soft magnetic layer is 5-20 mu m;

the thickness of the insulating layer is 5-20 mu m.

5. The method according to claim 1, wherein,

The magnetoresistive element further includes a plurality of magnetic tunnel junctions positioned proximate an edge of the soft magnetic layer;

the soft magnetic layer is configured to deflect a first magnetic field perpendicular to a plane of the substrate into a second magnetic field parallel to the plane of the substrate that acts on the magnetic tunnel junction.

6. The method of claim 5, wherein the step of determining the position of the probe is performed,

The seed layer and the insulating layer are sequentially deposited above the substrate, and the method comprises the following steps:

Sequentially depositing and flowing a sheet on a substrate, and forming a plurality of magnetic tunnel junctions;

Depositing a second insulating layer on the substrate such that the second insulating layer covers the plurality of magnetic tunnel junctions;

and depositing a seed layer and an insulating layer above the second insulating layer in sequence.

7. The method of claim 5, wherein the step of determining the position of the probe is performed,

After the soft magnetic material is filled in the accommodating groove through electroplating to obtain the soft magnetic layer, the method further comprises the following steps:

depositing a third insulating layer over the soft magnetic layer;

a plurality of magnetic tunnel junctions deposited over the third insulating layer;

Wherein the magnetic tunnel junction is near an edge of the soft magnetic layer.

8. The method of claim 5, wherein the step of determining the position of the probe is performed,

The magnetic tunnel junction includes a free layer, a tunneling layer, a reference layer, and a pinned layer;

the reference layer can have a fixed magnetization direction parallel to the plane of the substrate by high temperature magnetic field annealing under the first magnetic field.

9. The method of claim 8, wherein the magnetic tunnel junction is capable of being sensitive to the first magnetic field.

10. A magneto-resistive element, characterized in that the magneto-resistive element is manufactured by the method according to any one of claims 1-8.