KR20060129868A - Compact micro magnetic field detecting sensor using magneto impedance effects and method for making the same - Google Patents

Abstract

A compact micro magnetic field detecting sensor using an AC magneto-resistance effect and a method for manufacturing the same are provided to simplify a complicated manufacturing process and minimize a level of difficulty of the process, thereby reducing a production cost. A hard-ferrite magnet is made of a hard ferrite, and moves an operation point of a magnetic-field detecting sensor to a portion having excellent linearity by using a magnetizer. A magnetic core is made of a soft ferrite formed one side of the hard-ferrite magnet, and impedance of the magnetic core is changed according to an external micro magnetic field.

Description

Compact Micro Magnetic Field Detecting Sensor Using Magneto Impedance Effects and Method for Making the Same}

1 is a process chart showing a manufacturing process of the AC magnetic resistance sensor according to the present invention,

2a to 2c is a process perspective view showing a manufacturing process of the AC magnetoresistive sensor according to the present invention, respectively;

3A to 3D are cross-sectional views illustrating a manufacturing process of an AC magnetoresistive sensor according to the present invention, respectively;

4A to 4C are graphs showing characteristics of AC magnetoresistive sensors,

5A to 5C are characteristic graphs of an AC magnetoresistive sensor whose operating point is moved in the characteristic graph of FIGS. 4A to 4C after magnetizing the hard magnetic substrate, respectively;

6A and 6B are perspective views of a single AC magnetoresistive effect sensor element manufactured using the manufacturing process, respectively,

7A and 7B are respectively a perspective view of a three-axis magnetic sensor showing three AC magnetoresistive effect sensor elements integrated with a signal processing IC on a main substrate, and 3 diced after molding is made in the structure of FIG. 7A. A perspective view of an axis magnetic sensor.

The present invention relates to a micro-miniature magnetic field detection sensor using an alternating magneto-resistive effect and a method for manufacturing the same. In particular, the manufacturing process of the sensor is extremely simplified and the process difficulty is minimized, thereby facilitating mass production, thereby achieving cost competitiveness. The present invention relates to an ultra-small magnetic field detection sensor using an alternating magneto-resistive effect that can be processed in units, and a manufacturing method thereof.

Sensors that measure micro or earth magnetic fields are currently classified into three methods, that is, a method using a flux gate, a DC magnetoresistance effect, and an AC magnetoresistance (MI) effect.

The flux gate method has been proposed in Japanese Patent Laid-Open Nos. 9-43322 and 11-118892, and the sensor of the flux gate method detects a change in an external magnetic field and an excitation coil that can apply a magnetic field to a magnetic core. It consists of two-axis secondary coil (pick-up coil). The main shape of the core is mainly circular, and the flux gate sensor used for vehicles or ships is manufactured by using a magnetic material of bulk type, and recently, the miniaturization is made by applying a PCB technology. However, the flux gate sensor using the multilayer PCB technology has a disadvantage that the process is complicated and requires a high level of PCB technology.

In addition, the DC magnetoresistive sensor can be mass-produced using a semiconductor manufacturing process and the unit price is low. However, the sensitivity of the DC magnetoresistive sensor is lower than that of the flux gate sensor.

In addition, the AC magnetoresistance sensor mainly detects a magnetic field using a magnetic impedance effect exhibited by a change in an external magnetic field in a soft magnetic material having a high permeability such as an amorphous ribbon, a wire and a thin film. 0086630, 2001-0096553.

AC magnetoresistive sensor is similar to flux gate sensor and has little influence on temperature, so it is suitable for use as a micro magnetic sensor.However, since the pick-up coil, bias coil and feedback coil must be formed in the sensor's output detection method, the manufacturing process is complicated and There is a problem that production is difficult and the unit price rises.

Therefore, there is an urgent need for a sensor, a manufacturing technology, and a process that can use a semiconductor manufacturing process and a simple process to easily mass-produce and secure cost competitiveness.

On the other hand, No. 10-2003-87929 assigned to the applicant has proposed a micro-magnetic field sensor combining a linear core made of a soft magnetic material and a permanent magnet for moving the operating point of the linear core.

In the above application, in order to increase sensitivity to an external magnetic field, it is basically based on heat treatment in the width direction of the ribbon at 350 ° C. at 1 kOe. However, when the heat treatment method is used, the magnetization direction has a large anti-magnetic effect of soft magnetic material. Since it is a difficult axis, the heat treatment magnetic field must be considerably large, such as 1 kOe, and the linearity section is short, so that the measuring range of the sensor is about ± 3 Oe. Therefore, the sensor obtained according to the heat treatment method cannot measure a wide range of magnetic fields.

Moreover, in the above-mentioned application, there is no proposal for mass production of magnetic sensors.

All currently known micro-magnetic sensors have a problem of low competitiveness in mass production and high unit cost as described above.

The inventors of the present invention generally have a large magnetic field and a coercive force, so once magnetized, the magnet has a constant magnetic field, such as a permanent magnet, and gives a magnetic field offset to the sensor, thereby enabling movement of the operating point of the sensor. Compared to the method of moving the operating point by using the coil, the power consumption is lowered, and the soft magnetic material for the sensor has a small residual magnetic field. It was recognized that it would not affect.

Accordingly, the present invention has been made in view of the above-described problems of the prior art, the object of which is to produce a hard magnetic material and a soft magnetic material to each of a large substrate, and then bonded, the process of the sensor element can be processed on a wafer level, The present invention provides an ultra-small magnetic field detection sensor using an alternating magneto-resistive effect having a cost-competitiveness, and a method of manufacturing the same, which greatly simplify the manufacturing process of the sensor and minimize process difficulty.

Another object of the present invention is to provide an ultra-small magnetic field detection sensor using an AC magnetoresistive effect of which the structure of each sensor is extremely simple.

Another object of the present invention is to provide a multi-axis magnetic sensor by combining a plurality of single-axis micro-magnetic field sensor.

In order to achieve the above object, the present invention is made of a hard magnetic material, a hard magnetic magnet for moving the operation point of the magnetic field detection sensor by the magnetized to excellent linearity, and a soft magnetic material patterned on one surface of the hard magnetic magnet It provides a magnetic field detection sensor using the alternating magneto-resistive effect, characterized in that consisting of a magnetic core that changes the impedance according to the external magnetic field.

The micro-magnetic field sensor is bonded to a soft magnetic substrate subjected to heat treatment for imparting magnetic anisotropy to the hard magnetic substrate, to form a plurality of magnetic core by patterning the soft magnetic material in a plurality of magnetic core patterns on a wafer level basis, A magnet is formed by magnetizing a magnetic material to form a magnetic material for moving the operating point of the magnetic core, and dicing and separating the magnetic material.

In the present invention, the manufacturing process of the micro-magnetic field sensor is extremely simplified and the process difficulty is minimized to produce the mass production and cost competitiveness by using a semiconductor process.

(Example)

Hereinafter, with reference to the accompanying drawings showing a preferred embodiment of the present invention described above in more detail.

First, the manufacturing process of the AC magnetoresistive sensor according to the present invention will be described with reference to FIGS. 1 to 3D. In the present invention, a plurality of AC magnetoresistive sensor chips can be obtained by performing batch processing on a wafer level basis using a substrate formed in the form of a large rectangular or circular wafer.

Referring to FIGS. 1, 2A and 3A, the AC magnetoresistive sensor according to the present invention has a rectangular or circular wafer shape as shown in the figure, and a hard magnetic material such as ferrite, NdFe, AlNiCo, or SmCo is 10 nm to 500 μm. A thin hard magnetic material sheet formed to a thickness of about a thickness, a hard hard magnetic material sheet in which nylon or epoxy resin is mixed with the hard magnetic powder, or a hard magnetic material using a flexible hard magnetic sheet using a polymer binder such as polyurethane or silicone resin A substrate on which the hard magnetic thin film is deposited on the substrate 1 or the silicon wafer is prepared.

Thereafter, a soft magnetic material selected from the group consisting of Co, Fe-based amorphous, permalloy, supermalloy and invar in a ribbon shape having a thickness of 15 μm to 500 μm on the hard magnetic substrate 1 was approximately 30 Oe. About 200 Oe, the heat treatment temperature is bonded to the soft magnetic substrate 3 obtained by heat treatment for about 1 to 3 hours between 180 ℃ 400 ℃ (S1).

Since the heat treatment direction of the present invention is a biaxial axis for magnetization, the magnetic field may be about 1/10 of the prior art, and the linearity section is also long as shown in FIGS. 4A to 4C, and the measurement range of the sensor is about ± 20 Oe, thereby providing a wide range of magnetic fields. Can be measured.

The adhesive that can be used to bond the hard magnetic substrate 1 and the heat-treated soft magnetic substrate 3 may be, for example, a heat-resistant adhesive such as homica, heat-resistant epoxy or heat-resistant double-sided tape. In the present invention, Homica was used.

After adhering the magnetic substrates 1 and 3, the adhesive is cured (S2).

Subsequently, in the case of using a soft magnetic material such as ribbon-shaped Co or Fe-based amorphous, permalloy, supermalloy and invar as the soft magnetic substrate 3, the bonding strength of the bonding wire is reduced during wire bonding in the subsequent package process. There is a problem in that reliability and mass productivity are lowered.

Therefore, the conductive metal thin film that can increase the adhesive strength of the bonding wire, such as Al, Ni, Ag, Au, or Cu on the soft magnetic material to increase the adhesive strength of the bonding wire during wire bonding in order to solve the lack of adhesion force (5) ) Is used to deposit (Fig. 3b). In order to increase the adhesion of the bonding wires, the deposited conductive metal thin film 5 needs to be removed by leaving only the positions to be bonded during the final wire bonding, and the others are etched and removed. Proceed.

In order to form the bonding pads 5a and 5b by patterning the conductive metal thin film 5, first, a PR (photoresist) is formed on a soft magnetic material on which the conductive metal thin film 5 is deposited (a thickness of about 1 μm to 10 μm). It is applied to or adhered to the photosensitive film of a predetermined thickness (about 10㎛ ~ 50㎛) (S3).

Subsequently, in the case of applying the PR, after applying at room temperature, it is prebaked at a constant temperature (about 100 ° C. to 150 ° C.) (S4), and in the case of the photosensitive film, at a constant temperature (about 50 ° C. to 150 ° C. for adhesion). ℃) by pressing under a certain load (about 2kg ~ 10 kg) to bond (S3). The coated PR or adhered photosensitive film is exposed by covering the transparent film on which the pattern is printed in the form of bonding pads 5a and 5b for wire bonding and exposing to UV (Ultra violet) (S5).

Thereafter, the exposed magnetic substrates 1 and 3 are placed in a developer to leave the PR or the photosensitive film of the bonding pad portion, and the rest is removed (S6). Subsequently, the PR-coated magnetic material is completely hardened (post bake) at a predetermined temperature (about 100 ° C. to 150 ° C.) (S7), and in the case of the photosensitive film, a complete hardening step is not necessary.

The magnetic substrates 1 and 3, which have been completely cured, are placed in an appropriate etchant to etch the conductive metal thin film 5 in the form of bonding pads to form the bonding pads 5a and 5b (S8). In this case, since only the conductive metal thin film 5 deposited on the soft magnetic material is etched and the soft magnetic substrate 3 should not be etched, an appropriate etchant should be used.

For example, when Al is used as the conductive metal thin film 5, an etching solution of H ₃ PO ₄ : HNO ₃ : H ₃ COOH: H ₂ O = 80: 5: 5: 10 is used. After the etching of the bonding pads is completed, the magnetic substrates 1 and 3 are completely removed by removing the PR or the photosensitive film by etching in the removal liquid to remove the PR or the photosensitive film (S9). When such a process is completed, it will be in the form shown in FIG. 2B and FIG. 3C.

In the present invention, instead of forming the bonding pads 5a and 5b by patterning the conductive metal thin film 5, it is also possible to increase the surface roughness of the magnetic material to increase the adhesive strength of the bonding wire.

In order to increase the surface roughness of the soft magnetic substrate ₃ , micro-etching is performed by a physical method of etching the surface of the substrate 3 with plasma such as Ar + ions and a chemical method of etching with CuCl ₂ or FeCl ₃ . Can be used. In this way, when the surface roughness of the soft magnetic material is increased at a fine perspective, the above steps for forming the bonding pads 5a and 5b are omitted.

After the etching of the bonding pads 5a and 5b is completed, the soft magnetic substrate 3 may have a magnetic core pattern 3a having a plurality of meanders, bars or rings (FIG. 2C). 3D) is performed as follows based on the process (S10-S16) of FIG. 1 to pattern.

First, a PR (photoresist) is applied to a predetermined thickness (about 1 μm to 10 μm) or a photosensitive film of a predetermined thickness (about 10 μm to 50 μm) is adhered onto the soft magnetic substrate 3 (S10).

Subsequently, when the PR is applied, it is prebaked at a constant temperature (about 100 ° C. to 150 ° C.) after application at room temperature (S11), and in the case of a photosensitive film, a constant temperature (about 50 ° C. to 150 ° C. at the time of adhesion is applied. ) Is pressed under constant load (approximately 2kg ~ 10 kg) and no semi-hardening process is required. The coated PR or adhered photosensitive film is exposed by covering the transparent film on which the pattern is printed and exposed to UV (Ultra violet) (S12).

Thereafter, the exposed soft magnetic substrate 3 is placed in a developer, leaving a PR or a photosensitive film of a portion for patterning (S13). Subsequently, the soft magnetic substrate 3 coated with PR patterned with an etching mask is post-baked at a predetermined temperature (about 100 ° C. to 150 ° C.) (S14), and in the case of the photosensitive film, a complete curing process is not necessary. .

When the soft magnetic substrate 3, which is completely cured, is placed in an appropriate etching solution and etched, the soft magnetic substrate 3 is patterned into a plurality of magnetic core patterns 3a as shown in FIGS. 2C and 3D (S15). In this case, when the soft magnetic substrate 3 is made of Co-based amorphous, CuCl ₂ is used, and when it is made of Fe-based amorphous, FeCl ₃ is used.

In the illustrated embodiment, the magnetic core pattern 3a of the soft magnetic substrate 3 has a meander shape, but is not limited thereto. A bar or ring shape may also be used. After the etching is completed, the soft magnetic material is completely removed to remove the PR or the photoresist film after patterning in a removal solution (remover) to remove the PR or the photoresist film (S16).

As described above, a plurality of AC magnetoresistive sensor elements are fabricated at a time in a batch processing step of a wafer level.

Each sensor element thus obtained has a form similar to or similar to that of FIGS. 4A to 4C. The linear part of the graph, which has excellent linearity, is used as the output of the sensor. For this purpose, it is necessary to move the operating point of each sensor to the excellent linearity.

In order to move the operating point of the sensor, a process of magnetizing by applying a magnetic field to the hard magnetic substrate 1 used as the substrate is required. The magnetizer uses a magnetic field generator that can generate an electromagnet or similar high magnetic field, and the applied magnetic field and magnetic field application time vary depending on the degree of magnetization, but it is generally about 10 seconds to 10 minutes from 1 kOe to 10 kOe. The magnetization process is performed at the time of, and when the magnetization is completed, the magnetic field that has been magnetized is temporarily blocked to finish the magnetization process (S17). If the magnetic field used to perform magnetization is gradually reduced, the magnetization effect disappears because the magnetized magnetic field is demagnetized.

Hard magnetic materials generally have a high residual magnetic field and coercive force, so once magnetized, they have a constant magnetic field like permanent magnets, giving a magnetic field offset to the sensor, enabling the movement of the operating point of the sensor. This has the advantage of lowering power consumption compared to the method of moving the operating point. However, the soft magnetic material for the sensor has a small residual magnetic field, so even if the magnetization process proceeds, there is no residual magnetic field after the process.

The magnetization size can be varied according to the characteristics of the magnetic body as shown in Figs. 5a to 5c, so that the sensor having any characteristic can move the operating point to the excellent linearity.

As the magnetization process is finished, the sensor element manufacturing process is completed at the wafer level, so the process is extremely simple and the process difficulty is low compared to the conventional manufacturing process, and thus the sensor manufacturing can be easily performed. In addition, if the mass production is made in this way it can be a large cost reduction effect. For example, even using 6-inch wafers, about 10,000 can be manufactured at a time, and more sensor elements can be obtained when the size of the processable wafer is further increased.

In addition, the final shape of the micro-magnetic field detection sensor element using the alternating magnetoresistive effect produced using the manufacturing method of the present invention has the form as shown in Figure 6a and 6b according to the use and size. The hard magnetic substrate 1 having all the processing steps finished is then diced individually along the dicing line 7 and separated into a plurality of sensor elements 10 and 11 (S18).

In this case, for example, the sensor element 10 for detecting the micro magnetic field in the X-axis and Y-axis directions is a Myander-shaped magnetic core pattern in which a zigzag pattern is formed along the longitudinal direction of the bar-shaped hard magnetic material 1a. (3a), and the sensor element 11 for detecting the micro magnetic field in the Z-axis direction perpendicular to the X- and Y-axis sensor elements is perpendicular to the longitudinal direction of the bar-shaped hard magnetic material 1a. It is preferable to have the Myander type magnetic core pattern 3b in which the zigzag pattern was formed along the direction.

As described above, when an external magnetic field is applied in the longitudinal direction of the core while a high frequency constant current is applied between both ends of the magnetic core patterns 3a and 3b, the permeability of the core is increased to increase the eddy current and thus the thickness of the skin. Decreasing the resistance increases the impedance. Thus, the output voltage across both terminals increases. Since the output voltage increases in proportion to the external magnetic field, the intensity of the external magnetic field can be measured.

The individual sensor elements of the present invention can be variously applied according to the required use.

In the case of packaging with a multi-axis magnetic sensor as shown in FIG. 7A, a signal processing IC includes one to three sensor elements 10a, 10b and 11 formed on a main board 15 formed of a printed circuit board (PCB) and formed in a wafer form. After mounting on the main board 15 together with (13) (S19), each of the bonding pads 5a, 5b of the sensor elements 10a, 10b, 11 and the input terminal of the signal processing IC 13 are interconnected. Wire bonding to perform (S20). In this case, the X-axis and Y-axis sensor elements 10a and 10b are disposed parallel to the plane of the main substrate 15, and the plane of the Z-axis sensor element 11 is perpendicular to the plane of the main substrate 15. Place it upright to set it.

After the wire bonding process, the wire bonding portion is packaged with silicon or epoxy (S21), and separately separated along the dicing line of the main substrate 15. As shown in FIG. ) Is obtained (S22).

 The finished product of FIG. 7B may be manufactured as a single-axis magnetic sensor with one sensor element, a two-axis magnetic sensor with two, or a three-axis magnetic sensor with three depending on the application.

According to the present invention, the sensitivity and temperature which were most problematic in the conventional flux gate sensor, the DC magnetoresistance sensor and the AC magnetoresistance sensor by simplifying the complicated manufacturing process of the micromagnetic field detection sensor using the AC magnetoresistance effect and minimizing the process difficulty. The micro magnetic field detection sensor having excellent characteristics can be processed on a wafer level basis so that the manufacturing cost can be reduced due to mass production and the characteristics of each individual device can be uniformly obtained according to batch production.

In the above, the present invention has been illustrated and described with reference to specific preferred embodiments, but the present invention is not limited to the above-described embodiments and is not limited to the spirit of the present invention. Various changes and modifications can be made by those who have

Claims (2)

A hard magnetic magnet made of a hard magnetic material and used to move the operating point of the magnetic field detection sensor to an excellent linearity part by magnetization; The magnetic field detection sensor using an alternating magneto-resistive effect, comprising: a magnetic core made of a soft magnetic material patterned on one surface of the hard magnetic magnet and composed of a magnetic core whose impedance changes according to an external micro magnetic field. A soft magnetic substrate subjected to heat treatment to impart magnetic anisotropy to the hard magnetic substrate is bonded, and the soft magnetic material is patterned into a plurality of magnetic core patterns on a wafer level to form a plurality of magnetic cores, and the hard magnetic material is magnetized to magnetize the magnetic core. Forming a magnetic body for moving the operating point of the method of manufacturing a micro-magnetic field detection sensor using the AC magnetic resistance effect, characterized in that obtained by the process of dicing and separating.

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