JP7709036B2 - Metal component fixing method - Google Patents

Description

The present invention relates to a method for fixing metal members.

For example, when manufacturing an MI sensor, there is a process for fixing a magnetic wire onto a substrate. In such a case, Patent Document 1 discloses a technique for forming guide posts at predetermined positions on the substrate in order to position the magnetic wire on the substrate. The document describes that photolithography is used to form the guide posts, and that the magnetic wire is arranged on the substrate along the formed guide posts.

JP 2019-35743 A

However, the inventors have found that when a resin is formed to cover the magnetic wires and then the magnetic wires are fixed on a substrate, the following problems arise.
That is, after arranging the magnetic wire on the substrate, when attempting to fix the magnetic wire to the substrate with a fixing resin formed by photolithography, resin residue may remain. That is, when attempting to form a fixing resin at a predetermined position by exposing, heating, and developing a negative photosensitive resist, an event occurred in which resist residue remained in places other than the predetermined positions (i.e., places not exposed to light).

The present invention was made in consideration of these problems, and aims to provide a method for fixing metal members that can suppress the generation of resin residue.

One aspect of the present invention is a method for fixing a metal member to a substrate by using a fixing resin to fix a plurality of mutually separated locations of the metal member, the method comprising the steps of:
placing the metal member at a predetermined position on the substrate;
A negative photosensitive resist diluted with a dilution solvent is applied onto the substrate so as to cover at least a portion of the metal member;
a part of the photosensitive resist is exposed to light, heated, and developed to form the fixed resin at a predetermined position so as to cover a plurality of mutually separated portions of the metal member , and to expose the metal member other than the plurality of portions from the fixed resin ;
The photosensitive resist is made of SU-8,
The diluent solvent is PGMEA.
The present invention relates to a method for fixing a metal member.

In the metal member fixing method, SU-8 is used as the photosensitive resist and PGMEA is used as the dilution solvent. This makes it possible to suppress the generation of resin residue when the fixing resin is formed.

As described above, the present invention provides a method for fixing metal members that can suppress the generation of resin residue.

FIG. 1A is a plan view of a substrate provided with a guide pattern, and FIG. 1B is a cross-sectional view taken along line Ib-Ib in FIG. FIG. 2A is a plan view of a state in which a magnetic sensitive body is placed on a substrate in the first embodiment, and FIG. 2B is a cross-sectional view taken along line IIb-IIb in FIG. FIG. 3A is a plan view showing a state in which a photosensitive resist is applied, and FIG. 3B is a cross-sectional view taken along line IIIb-IIIb in FIG. 5A to 5C are cross-sectional explanatory views showing an exposure step in the first embodiment. FIG. 1A is a plan view of a state in which a magnetic sensitive body is fixed onto a substrate with a fixing resin, and FIG. 1B is a cross-sectional view taken along line Vb-Vb in FIG. FIG. 2 is a plan view of the MI element according to the first embodiment. 1A is a planar photograph of sample 1 in Experimental Example 1; FIG. 1B is a planar photograph of another sample 1 in Experimental Example 1; 1 is a plan view of Sample 2 in Experimental Example 1. 13 is a table showing the experimental results in Experimental Example 2.

The metal member may be an amorphous wire. In this case, the generation of resin residue can be suppressed when the amorphous wire is fixed onto the substrate.

The metal member can also be the magnetic sensitive body of a magneto-impedance sensor element (hereinafter also referred to as an MI element, as appropriate). In this case, a high-quality magneto-impedance sensor element can be easily manufactured.

(Embodiment 1)
An embodiment of a metal member fixing method will be described with reference to FIGS.
The metal member fixing method of this embodiment is a metal member fixing method in which a metal member 3 is fixed onto a substrate 2 with a fixing resin 4 by using photolithography, as shown in FIGS.

That is, in this embodiment of the metal member fixing method, the metal member 3 is placed at a predetermined position on the substrate 2 (see Figs. 1 and 2). Then, a negative photosensitive resist 40 diluted with a dilution solvent is applied onto the substrate 2 so as to cover at least a portion of the metal member 3 (see Fig. 3). Then, a portion of the photosensitive resist 40 is exposed to light, heated, and developed to form a fixing resin 4 at the predetermined position (see Figs. 4 and 5).

The photosensitive resist 40 is made of SU-8, and the dilution solvent is made of PGMEA.
SU-8 is a negative photoresist whose main component is epoxy resin and contains cyclopentanone as a solvent.
PGMEA is an abbreviation for propylene glycol monomethyl ether acetate, and is generally used as a developer for SU-8.

In this embodiment, the metal member 3 is an amorphous wire. The metal member 3 is a magnetic sensitive body of the MI element. In this embodiment, the metal member 3 will be described as a magnetic sensitive body 3.
The metal member fixing method of this embodiment is carried out in a part of the steps of the manufacturing method of the MI element.

As shown in FIG. 6, the MI element 1 has a magnetic sensor 3 and a detection coil 11 wound around it. The magnetic sensor 3 and detection coil 11 are arranged on the surface of the substrate 2. A part 111 of the detection coil 11 is formed by a conductor pattern formed on the surface of the substrate 2. In addition, the lead-out wiring 121 connected to the detection coil 11 and the lead-out wiring 122 connected to the magnetic sensor 3 are also patterned on the surface of the substrate 2. The other part 112 of the detection coil 11 is formed on the outer periphery of the magnetic sensor 3 via an insulating layer (not shown) after the magnetic sensor 3 is arranged.

An example of a method for manufacturing the MI element 1 will be described below.
A conductor pattern is formed as appropriate on the surface of a substrate 2 made of a non-magnetic material such as alumina or semiconductor silicon. Then, a magnetic sensitive body 3 is placed at a predetermined position on the surface of the substrate 2. In order to position the magnetic sensitive body 3, a guide pattern 5 is formed in advance on the substrate 2, as shown in Fig. 1. This guide pattern 5 can be formed, for example, by forming an insulating material such as resin so as to protrude on the substrate 2.

In this embodiment, as shown in FIG. 2, the linear magnetic sensitive body 3 is arranged in a state in which it is sandwiched between the guide patterns 5 arranged close to each other.
3, a photosensitive resist 40 is applied onto the substrate 2. At this time, the photosensitive resist 40 is applied over substantially the entire substrate 2 so as to cover the magnetosensitive body 3. The photosensitive resist 40 is made of SU-8, which is a negative photoresist. The photosensitive resist 40 is applied onto the substrate 2 in a state diluted with a dilution solvent. PGMEA is used as the dilution solvent.

The photosensitive resist 40, SU-8, is a liquid resist in which epoxy resin is dissolved in a solvent made of cyclopentanone. The photosensitive resist 40 is then diluted with a dilution solvent made of PGMEA to adjust the viscosity to an appropriate level. For example, the mixture ratio of SU-8 to PGMEA can be set to about 1:1 to 1:5. The photosensitive resist 40 with adjusted viscosity is then applied to the substrate 2.

The substrate 2 coated with the photosensitive resist 40 is pre-baked. At this time, the dilution solvent evaporates. Then, as shown in FIG. 4, a photomask 61 is placed on the substrate 2, and the photosensitive resist 40 at a predetermined position is exposed to ultraviolet light. Next, the photosensitive resist 40 is heated. In other words, a post-exposure bake (PEB) is performed. This causes the chain polymers of SU-8 in the exposed photosensitive resist 40 to crosslink.

The photosensitive resist 40 is then developed with a developer. This dissolves and removes the unexposed portions of the photosensitive resist 40. As a result, as shown in FIG. 5, the fixing resin 4 is formed at the desired position. The magnetic sensor 3 is then fixed onto the substrate 2 by this fixing resin 4. The developer used in this development process is made of PGMEA.

After the magnetic sensor 3 is fixed to the substrate 2, the MI element 1 is obtained by etching a part of the magnetic sensor 3, forming an insulating layer, electrically connecting the magnetic sensor 3 to the lead-out wiring (see reference numeral 122 in FIG. 6), and forming a conductor pattern of a part of the detection coil 11 (see reference numeral 112 in FIG. 6).

Next, the effects of this embodiment will be described.
In the metal member fixing method of this embodiment, SU-8 is used as the photosensitive resist 40, and PGMEA is used as the dilution solvent, thereby making it possible to suppress the generation of resin residue when the fixing resin 4 is formed by photolithography.

The inventors of the present application discovered that when cyclopentanone is used as a diluting solvent for the photosensitive resist 40, SU-8, is applied to the substrate 2, resin residue may be generated (see Experimental Example 1, FIG. 7, described later). Cyclopentanone is contained in SU-8 as a solvent. Therefore, the inventors adopted the method of using cyclopentanone as a diluting solvent to adjust the viscosity of SU-8.

However, as described above, when the fixing resin 4 was formed to fix the magnetosensitive element 3 on the substrate 2, resin residue was sometimes left behind. The cause of this is thought to be that some of the SU-8 may have undergone a cross-linking reaction even in the unexposed areas. Possible causes of the cross-linking reaction include ultraviolet light, heat, and acid. When the SU-8 was developed without exposure to light, the same resin residue as above was found, so ultraviolet light is thought to be not the cause. Also, since the cross-linking reaction is promoted by heat after some kind of trigger is given, it is unlikely that heat is the main cause. Therefore, the remaining likely cause is acid.

In other words, the hypothesis is that acid adheres to the surface of the magnetosensitive body 3 before it is placed on the substrate 2. In an experiment to support this hypothesis, the photosensitive resist 40 was exposed to light, heated, and developed without the magnetosensitive body 3 being placed thereon, and no residue was left behind. Therefore, this hypothesis is plausible. It is also possible that, for example, acidic chemicals may adhere to the surface of the magnetosensitive body 3 during the processing step of the magnetosensitive body 3. When this acid comes into contact with the photosensitive resist 40, a cross-linking reaction may progress, even if only slightly, and as a result, even the unexposed parts may remain as residue after development.

One possible solution would be to thoroughly clean the magnetosensitive element 3 before placing it on the substrate 2, so that no acid remains on its surface. However, it is difficult to completely remove the acid, and considering productivity, this is not realistic.

The inventors of the present application therefore considered changing the dilution solvent used during application from cyclopentanone to PGMEA, taking into consideration the possibility that a crosslinking reaction of the photosensitive resist 40 may have occurred before exposure. As mentioned above, PGMEA is used as a developer for SU-8. The inventors reasoned that the PGMEA used as this developer might have the effect of inhibiting a small crosslinking reaction of SU-8 caused by a small amount of acid.

In this regard, when PGMEA was actually used as the dilution solvent as described above, it was confirmed that no resin residue remained after development (see Experimental Example 1, FIG. 8, described later).
In this manner, by using PGMEA as the dilution solvent for the photosensitive resist 40, the generation of resin residues can be suppressed.

Generally, a chemical solution that does not affect the crosslinking reaction is used as a dilution solution for photosensitive resist, but as described above, the inventors of the present application solved the above problem by using PGMEA, which has the effect of suppressing the crosslinking reaction of SU-8, as a dilution solvent.

As described above, this embodiment provides a method for fixing metal members that can suppress the generation of resin residue.

(Reference form)
In this embodiment, 4-hydroxy-4-methyl-2-pentanone or ethyl lactate is used as a dilution solvent for SU-8 instead of PGMEA.
4-hydroxy-4-methyl-2-pentanone and ethyl lactate are generally used as developers for SU-8, and therefore, by using these as dilution solvents for SU-8, it is expected that the effect of suppressing the generation of resin residues can be achieved, similarly to the first embodiment.
The rest is the same as in the first embodiment.

(Experimental Example 1)
This example is an example in which the effect of suppressing the generation of resin residue by the metal member fixing method shown in the first embodiment was confirmed, as shown in Figs.
That is, the appearance of the MI element obtained when cyclopentanone was used as the dilution solvent for the photosensitive resist 40 and when PGMEA was used were compared.

The MI element obtained when the dilution solvent was cyclopentanone was designated as sample 1. The MI element obtained when the dilution solvent was PGMEA was designated as sample 2. The method of producing sample 2 was the same as that of embodiment 1. Sample 1 was also produced in the same manner as embodiment 1, except that cyclopentanone was used as the dilution solvent for SU-8, which is a photosensitive resist. In both samples 1 and 2, the mixture ratio of SU-8 to the dilution solvent was 1:5. Note that multiple samples 1 and 2 were produced.

7(a) and (b) show the appearance of the obtained sample 1 in which the residue was particularly noticeable, and FIG. 8 shows the appearance of the obtained sample 2.
7A and 7B, resin residue was found in some samples of Sample 1. In Sample 1, the residue appears to be spreading especially from the magnetosensitive element.
On the other hand, as shown in FIG. 8, in Sample 2, no particular resin residue was observed.

The results of this example confirmed that the generation of resin residues can be suppressed by using PGMEA as a dilution solvent for the photosensitive resist 40.

(Experimental Example 2)
As shown in FIG. 9, this example is an example in which it was confirmed that there was no trade-off caused by using PGMEA as a dilution solvent for SU-8.

That is, the chemical resistance of the fixed resin 4 formed by the method shown in embodiment 1 was confirmed. As described above, PGMEA is generally used as a developer for SU-8, and is thought to have the effect of suppressing crosslinking of SU-8. Therefore, the tradeoff when using PGMEA as a dilution solvent for SU-8 is that the chemical resistance of the fixed resin after development is a concern. Therefore, in this example, a test was conducted to confirm that there was no problem with the chemical resistance of the fixed resin.

Here, the resistance to chemicals that may come into contact with the fixing resin 4 during the manufacturing process of the MI element was confirmed.
The steps after forming the fixing resin 4 include, for example, a step of etching a part of the magnetosensitive body 3, and a step of forming a connection pattern that connects both ends of the magnetosensitive body 3 to the conductor pattern on the substrate 2. In each step, an etching solution, a resist stripping solution, etc. are used. In the former step, these chemicals may come into contact with the fixing resin 4, and in the latter step, these chemicals may come into indirect contact with the fixing resin 4.

Specifically, in the former process, hydrogen peroxide is used as the etching solution, Clean Strip HP-2 (a product name manufactured by Tokyo Ohka Kogyo Co., Ltd.) is used as the resist stripper, and ethanol is used as a rinse after stripping. In the latter process, sulfuric acid is used as the etching solution, PGMEA is used as the resist developer, and acetone is used as the resist stripper.

Therefore, the resistance of the fixing resin to each of these chemicals, namely PGMEA, ethanol, sulfuric acid, hydrogen peroxide, acetone, and Clean Strip HP-2, was evaluated through testing.

Specifically, SU-8 diluted with PGMEA was applied onto a substrate, and then exposed to light, PEB, and developed to form a resin pattern (test pattern) equivalent to the fixed resin 4 shown in embodiment 1. However, since this test pattern was for testing chemical resistance, it was formed on the substrate without any magnetic sensitive material or the like.

The test patterns thus formed were then immersed in each of the chemicals for a specified period of time, after which their appearance was observed. The results are shown in Figure 9. The test conditions were as shown in Table 1 below. These test conditions were set based on the conditions expected in the actual manufacturing process of MI elements. Table 1 also shows the evaluation results. The evaluation was based on whether swelling, peeling, dissolution, etc. occurred in the test patterns after the test. In Table 1 and Figure 9, "OK" indicates that no problems such as swelling, peeling, or dissolution occurred.

As shown in FIG. 9 and Table 1, none of the samples showed any swelling, peeling, dissolution, or the like, and it was confirmed that the samples had sufficient resistance to all of the chemicals.
In fact, even after the MI element was manufactured by the method shown in embodiment 1 (i.e., after the sample 2 in experimental example 1 was produced), no swelling, peeling, dissolution, etc. of the fixing resin 4 occurred, and no defects such as the magnetic sensitive body 3 coming off occurred.

The present invention is not limited to the above-described embodiment, and can be applied to various embodiments without departing from the spirit of the present invention.

1 magneto-impedance sensor element 2 substrate 3 metal member (magnetic sensitive body)
4 Fixing resin

Claims (4)

A method for fixing a metal member, comprising the steps of: fixing a metal member to a substrate at a plurality of mutually separated locations with a fixing resin, the method comprising the steps of:
placing the metal member at a predetermined position on the substrate;
A negative photosensitive resist diluted with a dilution solvent is applied onto the substrate so as to cover at least a portion of the metal member;
a part of the photosensitive resist is exposed to light, heated, and developed to form the fixed resin at a predetermined position so as to cover a plurality of mutually separated portions of the metal member , and to expose the metal member other than the plurality of portions from the fixed resin ;
The photosensitive resist is made of SU-8,
The diluent solvent is PGMEA.
Method for fixing metal parts. The metal member fixing method according to claim 1, wherein the metal member is an amorphous wire. The metal member fixing method according to claim 2, wherein the metal member is a magnetic sensitive body of a magneto-impedance sensor element. 3. The method for fixing a metal member according to claim 1, wherein the photosensitive resist is applied onto the substrate so as to cover the entire metal member.