JPS63196874A - Magnetoresistance effect sensor and manufacture thereof - Google Patents

Abstract

PURPOSE:To manufacture a magnetoresistance effect (MR) sensor at a low cost with a better yield in a simple process, by arranging a process of forming a magnetic thin film on the surface of a substrate and a process of making the substrate thinner with the removal of the back thereof. CONSTITUTION:As indicated in Fig. A, a ferromagnetic alloy thin film of Ni-Fe, Ni-Co or the like is formed by evaporation on the top surface of a substrate 1 as illustrated in Fig. B and worked into a shape of an MR element 2 by etching or the like. Then, as indicated in Fig. C, a protective film 3 is formed on the element 2 by vacuum thin film formation art from Sio, organic resin or glass. Moreover, as indicated in Fig. D, the back portion of the substrate 1 is removed at the MR element area thereof 1. In such a simple process, an MR sensor can be manufactured at a low cost.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a magnetoresistive sensor formed by forming a magnetic thin film as a magnetoresistive element on one surface of a substrate, and a method for manufacturing the same. .

[Prior art] This type of magnetoresistive sensor (hereinafter referred to as MR sensor)
detects changes in the applied magnetic field based on resistance changes of a magnetoresistive element (hereinafter referred to as MR element) made of a ferromagnetic alloy PJ film such as Ni-Fe or N1-Go. Therefore, in this MR sensor, it is only necessary to magnetize the object to be detected, and the structure is simpler and more durable than a photo sensor that requires a consumable light source such as an LED.

According to the conventional structure of this type of MR sensor, the MR sensor is
After the element is formed, lead wires for extracting output signals are connected to the electrodes of the MR element by soldering or by pressure contacting a flexible printed circuit board with a pattern of the lead wires, and the MR element including this connection part is then connected. Cover and heat
An insulating protective film is formed to protect the MR element from moisture, acids, bases, and the like. The MR sensor detects a magnetic field by facing the object to be detected, with the surface on which the MR element is formed as a detection surface.

[Problems to be Solved by the Invention] Incidentally, in a magnetic sensor such as an FG (frequency signal generation) sensor or a magnetic encoder, an object to be detected having a magnetic recording pattern is detected using the above-mentioned MR sensor as the object to be detected. In some cases, in order to obtain a satisfactory output as a sensor by taking advantage of the MR element's characteristic of being able to accurately detect minute magnetic field changes compared to a Hall element, the MR element, which is the detection object, is It is necessary to approach the recording pattern at a sufficiently narrow distance.

As described above, in the conventional MR sensor, detection is performed with the surface on which the MR element is provided facing the object to be detected, with the surface on which the MR element is provided as the detection surface.

However, in the conventional structure of the MR element as described above, it is inevitable that the connection portion between the electrode of the MR element and the lead wire by soldering or the like will swell to some extent on the detection surface of the sensor.

As a result, a problem arises in that the presence of this raised portion places a limit on the distance at which the MR sensor can be brought closer to the object to be detected. In addition, in order to ensure the above-mentioned close spacing, the sensing part of the MR element must be provided at a certain distance from the interfering connection part.This limits the degree of freedom in designing the pattern of the MR element, and accordingly Miniaturization of the object to be detected q and cost reduction are limited. Furthermore, in order to ensure the above-mentioned close spacing, the protective film of the MR element cannot be thickened, which reduces the reliability of the MR sensor.
There were various problems.

[Means for Solving the Problems] In order to solve these problems, according to the present invention, a magnetoresistive element is formed by forming a ferromagnetic thin film as a magnetoresistive element on one surface of a substrate. In the effect sensor, a structure is adopted in which at least the back surface of the magnetoresistive element forming area of the magnetoresistive element forming surface of the substrate is used as a detection surface facing the object to be detected.

Further, according to the method for manufacturing a magnetoresistive element according to the present invention, there is provided a step of forming a magnetic thin film as a magnetoresistive element on one surface of a substrate, and after the step, at least a magnetoresistive element formation region of the substrate. A configuration is adopted that includes a step of thinning the substrate by removing a portion of the substrate on the back side of the surface on which the magnetoresistive element is formed.

[Function] According to the structure of the magnetoresistive effect sensor according to the present invention, magnetic field detection is performed using the back surface of the magnetoresistive element forming surface of the substrate as a detection surface, and the electrode for signal extraction of the magnetoresistive element and the lead wire are connected. Since the connecting portion is on the element side and not on the detection surface side, it is possible to avoid the above-mentioned problem caused by the swelling of the connecting portion.

Further, according to the manufacturing method of the present invention, the magnetoresistive sensor of the present invention can be manufactured at low cost and with a high yield through simple steps.

[Embodiments] Hereinafter, details of embodiments of the present invention will be described with reference to the attached drawings.

111 FIGS. 1A to 1D show MR according to the first embodiment of the present invention.
This is to explain the structure and manufacturing process of the main body of the detection part of the sensor.

First, the structure of the MR sensor will be described with reference to FIG. 1(D), which schematically shows a cross section of a completed product of the detection section of the MR sensor.

As shown in FIG. 1(D), the MR sensor has a structure in which an MR element 2 as a thin film is provided on the upper surface of a substrate 1 in the figure, and a protective film 3 is further provided thereon.

The substrate 1 is made of a material suitable for use in an MR sensor and which can be processed by grinding, polishing, etching, etc., such as alkali-free glass.

The MR element 2 is formed as a thin film of a ferromagnetic alloy, such as Ni-Fe or Ni-Co, into a zigzag shape.Although not shown, the MR element 2 is used to extract a detection output signal. An electrode is formed, and a lead wire for leading out to the outside is connected to this electrode by soldering or pressure contact with a printed circuit board.

The protective film 3 protects the MR element 2 from heat, moisture, acids, bases, etc., and is made of, for example, SiO or organic resin.

Here, in the MR sensor of this embodiment, as a structure related to the present invention, the back surface of the MR element forming surface of the substrate 1 is used as the detection surface 4 facing the object to be detected (not shown), and sufficient detection output is obtained even through the substrate 1. In order to perform magnetic field detection that provides
At least the thickness t2 of the region where the MR element 2 is formed is made sufficiently small. That is, according to the MR sensor of this embodiment, magnetic field detection is performed using the back surface of the MR element forming surface of the substrate 1 as the detection surface 4.

According to the structure of such an MR sensor, the connection portion between the signal extraction electrode of the MR element 2 and the lead wire is connected to the MR element 2.
side and not on the detection surface 4 side, it is possible to avoid the problem caused by the swell of the connection part as in the prior art described above. In other words, there are no restrictions on the distance between the MR element and the object to be detected due to protrusions and restrictions on the pattern design of the MR element, and the MR element can be brought sufficiently close to the object to be detected to accurately detect minute changes in the magnetic field. This freedom allows for miniaturization of the MR sensor and thereby cost reduction. Further, there is no restriction on the thickness of the protection 193, and the protection 193 can be made sufficiently thick, and the reliability of the MR sensor can be improved by ensuring that the thickness can protect the MR element 2. Formation of the protective film 3 also becomes easier. Further, the connection between the electrode and the lead wire by soldering or the like is also facilitated because there is no restriction on swelling.

Next, the manufacturing process of the MR sensor of this example will be explained.

First, as shown in FIG. 1(A), a substrate l whose thickness 11 is sufficiently larger than the finished thickness t2 of FIG. 1(D) is formed from, for example, alkali-free glass as described above.

Next, as shown in FIG. 1(B), an MR
Element 2 is formed. First of all, Ni-Fe, Ni-C
After forming a ferromagnetic alloy S film such as ferromagnetic alloy S film by vapor deposition or the like, this thin film is processed into the shape of the MR element by etching or the like.

Next, a lead wire (not shown) is connected to a signal extraction electrode (not shown) of the MR element 2 by soldering or the like.

Next, as shown in FIG. 1C, a protective film 3 is formed on the MR element 2 using a vacuum thin film forming technique, coating, welding, etc. from SiO1 organic resin or glass.

Next, as shown by the dotted line in FIG. 1(D), at least the backside portion of the MR element forming surface of the substrate l is removed in the MR element forming area, and the thickness of the substrate l is reduced from tl to t2.
Make it thinner. This removal may be performed by a single process such as grinding such as lap grinding or surface grinding, polishing, and wet or dry etching, or may be performed by a combination of these processes.

Note that by removing the back side portion of the substrate l,
Processing stress and protection! It is also conceivable that warpage occurs in the substrate 1 due to a change in stress balance with the substrate 13. This warping can be prevented by selecting an appropriate material for the protection s3, or by selecting a suitable material for the protection s3.
This should be suppressed by laminating 1i3 or thickening the film.

Further, the initial thickness 11 of the substrate 1 is set to a certain level or more so as not to cause any trouble during the process up to the formation of the protective film 3.

The MR sensor of this embodiment can be manufactured at low cost through simple steps such as those described above.

By the way, in the step of finally removing the backside portion of the substrate 1 in the above-mentioned process, in order to accurately determine the finished thickness t2 of the substrate 1, it is necessary to accurately grasp the removal speed of the same step by grinding, polishing, etching, etc. In addition, it is necessary to accurately determine the end point of the process.

A conceivable method for this purpose is to detect and accurately determine the end point of the process in the following manner using the processes shown in FIGS. 2(A) to 2(E).

That is, first, as shown in FIGS. 2(A) to 2(C),
After forming the MR element 2 and the protective film 3 on the substrate 1 through the same steps as shown in FIGS. 1(A) to 1(C), a groove 5 shown in FIG. Protection $3
It is formed by machining from the side to the substrate 1 to a depth corresponding to the finished thickness t2. At this time, the depth of the groove 5 relative to the substrate l (=t2) is accurately determined using the upper surface of the substrate l in the figure as a reference plane. Note that it goes without saying that the groove 5 should be formed in a portion that does not interfere with the operation of the MR element.

Then, as shown in FIG. 2(E), the back side portion of the substrate 1 is removed by grinding, polishing, etching, etc. At this time, the opening 1III5 becomes the surface 1a of the substrate 1, that is, the detection surface 4. The end point of the process can be detected by detecting that it appears on the lower surface in the figure, and the process can be completed with the point where the groove 5 appears as the end point.

In this way, the end point of the process can be detected, the finished thickness t2 of the substrate l can be determined accurately, and an MR sensor with uniform characteristics can be manufactured.

In addition, in the same way, the removal speed of the substrate 1 by grinding, polishing, etching, etc. can be determined in advance by using the groove, and by this, the removal speed can be accurately grasped and the substrate 1 removed.
The thickness due to removal can be controlled by the removal processing time, and the removal process can be carried out efficiently.

Example 1 of "L Practical Example" Next, FIGS. 3(A) to 3(D) illustrate a method of manufacturing an MR sensor according to a second embodiment of the present invention.

In this example, first, as shown in FIG. 3(A), as substrates for manufacturing an MR sensor, a first layer substrate 7 and a second layer substrate 7 are
A substrate 6 having a laminated structure in which layered substrates 8 are laminated in the thickness direction of the entire substrate is used. The substrate 6 is formed by separately forming a first layer substrate 7 and a second layer substrate 8, and then forming a first layer substrate 7 and a second layer substrate 8 on the second layer substrate 8.
The first layer substrate 7 may be formed by bonding the layer substrate 7, or the first layer substrate 7 may be formed on the second layer substrate 8 by a physical method using vacuum thin film formation technology, or by a chemical method using chemical vapor deposition or polymerization reaction. Form and create by. Further, the thickness of the first layer substrate 7 is the final finished thickness t2 of the substrate mentioned above, and the thickness of the second layer substrate 7 is
The material of the layer substrate 8 is selected so that the first layer substrate 7 can be kept flat during the following MR element formation and protective film formation, and the thickness is t.
It is assumed that l' is sufficiently larger than t2.

Next, as shown in FIGS. 3(B) and 3(C), an MR element 2 is formed on the substrate 6 in exactly the same manner as in the steps of FIGS. 1(B) and 1(C) of the first embodiment, Further, a protective film 3 is formed thereon.

Next, as shown in FIG. 3CD), the second layer substrate 8 is removed to complete the MR sensor. If the substrate 6 is made by bonding the first layer substrate 7 and the second layer substrate 8, this removal is performed by dissolving the adhesive. In the case where the substrate 7 is formed, the first layer substrate 7 and the MR element 3 are removed by melting the second layer substrate 8, etc.
Also, a method that does not apply stress to the protective film 4 is used.

According to the manufacturing process of this embodiment, the removal of the back side portion of the substrate 6 in the last step, that is, the removal of the second layer substrate 8, is the same as the removal of the back side portion of the substrate l in the first embodiment. Compared to other methods, this method does not apply stress, does not cause damage, and can be performed easily and efficiently.

Note that the first substrate 6 is not limited to two layers, but may have a laminated structure of three or more layers, and the last layer left as a substrate is not limited to one layer, but has a detectable thickness t2 as described above. It doesn't matter how many layers you have as long as it can be done.

[Effects of the Invention] As is clear from the above description, the present invention provides a magnetoresistive sensor configured by forming a ferromagnetic thin film as a magnetoresistive element on one surface of a substrate. Since we have adopted a structure in which at least the back side of the magnetoresistive element formation area of the substrate's magnetoresistive element formation surface is used as the detection surface, the magnetoresistive element can be brought closer to the object to be detected for detection, making it more sensitive and subtle. It is possible to detect changes in magnetic field. Further, the degree of freedom in pattern design of the magnetoresistive element is increased, and the size of the magnetoresistive sensor can be reduced, thereby reducing costs. Furthermore, excellent effects such as improved sensor reliability can be obtained.

Further, according to the method for manufacturing a magnetoresistive sensor according to the present invention, a step of forming a magnetic thin film as a magnetoresistive element on one surface of a substrate, and a step of forming a magnetic thin film as a magnetoresistive element on at least the magnetoresistive element forming region of the substrate after the step. By adopting a configuration that includes a step of thinning the substrate by removing the back side portion of the magnetoresistive element forming surface of the substrate, the excellent magnetoresistive sensor of the present invention as described above can be manufactured at a low cost through a simple process. Can be manufactured.

[Brief explanation of the drawing]

1A to 1D are explanatory diagrams of the manufacturing process and structure of the magnetoresistive sensor according to the first embodiment of the present invention, and FIG.
A) to (E) are explanatory diagrams of the manufacturing process to explain the end point detection method of the process of removing the back side of the substrate, and FIGS. 3(A) to (D) are diagrams of the manufacturing process according to the second embodiment of the present invention. It is an explanatory diagram. 1.6... Substrate 2... MR element 3... Protective film 4... Detection surface 5... Groove for process end point detection 7... First layer substrate 8... Second Layer board MR-2
＞Sugeshi Saekei 4th episode 1st figure MR> Yoshie 4th episode 2nd figure directed by Chirizo Nio

Claims (1)

[Scope of Claims] 1) A magnetoresistive sensor configured by forming a ferromagnetic thin film as a magnetoresistive element on one surface of a substrate, wherein at least the magnetoresistive element on the surface of the substrate on which the magnetoresistive element is formed is A magnetoresistive effect sensor characterized in that the back surface of an area where an effect element is formed is a detection surface facing a detected object. 2) A step of forming a magnetic thin film as a magnetoresistive element on one surface of the substrate, and after this step, forming a back side portion of the magnetoresistive element forming surface of the substrate in at least the magnetoresistive element forming region of the substrate. A method for manufacturing a magnetoresistive sensor, comprising the step of thinning the substrate by removing it. 3) The magnetoresistive effect according to claim 2, wherein the removal of the back side portion of the substrate after the magnetoresistive element is formed is performed by grinding, polishing, etching, or a combination thereof. How to manufacture the sensor. 4) A substrate with a laminated structure in which a plurality of layers are laminated in the thickness direction is used as the substrate, and the back side portion of the substrate after the magnetoresistive element is formed is removed by removing the back side layer among the plurality of layers. A method for manufacturing a magnetoresistive sensor according to claim 2, characterized in that the method comprises: