JPH07287816A - Magnetoresistive thin film head - Google Patents

Abstract

PURPOSE:To form electrodes of low resistance and to reduce the deterioration of an MR element or disconnection at the time of forming electrodes by ion milling, by using Au as the upper electrode layer which constitutes the electrodes. CONSTITUTION:A NiFe film as an MR element 1 is formed on a Al2O3-TiC substrate 3 to specified thickness by sputtering. A resist 6 is applied and patterned. Then the resist 6 is removed with an org. solvent or the like, on which a Ta film is formed by sputtering and an Au film is formed by the same procedure. Then a resist 7 is applied and patterned into a shape of an electrode by photolithography. Then Au and Ta not covered with the resist 7 is etched by ion milling method. Ion milling is stopped on the interface between the lower electrode layer 4 and the element 1. Then the resist 7 is removed by using an org. solvent or a resist removing soln. to obtain a magnetoresistive thin film head.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetoresistive thin film head for stably reproducing a magnetic signal recorded on a magnetic recording medium.

[0002]

2. Description of the Related Art FIG. 4 is a sectional view of a conventional magnetoresistive thin film head. However, in FIG. 4, the longitudinal bias layer for the purpose of controlling the magnetic domain and the lateral bias layer used for the linear detection of the magnetic field by the magnetoresistive effect element (hereinafter referred to as MR element) 1 have the gist of the present invention. Not drawn for clarity. As shown in FIG. 4, a magnetoresistive thin film head is generally provided by laminating a pair of electrodes 2 on both ends of an MR element 1 arranged on a substrate 3, and passing a detection current through the MR element 1 to form the MR element. The resistance change of 1 is detected.

Conventionally, low resistance materials such as Au and Cu have been generally used as materials for electrodes so that MR devices can detect them with high output. Further, in order to improve the adhesion with the MR element, an electrode having a multilayer structure in which Cr or Ti is sandwiched between the MR element and Au or Cu is also common.

Further, Japanese Patent Laid-Open No. 2-68706 discloses the case where W is used as the material of the electrode for the purpose of ensuring the stability of signal detection. In addition, an electrode structure in which Ti or Ta is laminated in order to improve the porosity and adhesion of W is also disclosed.

Further, Japanese Patent Laid-Open No. 4-149812 discloses a structure in which Nb is used as a material of an electrode because it is a low resistance material having good corrosion resistance and adhesion.

[0006]

In the above prior art, in the structure using Au or Cu for the electrode material or the structure in which Cr or Ti is laminated on Au or Cu, Au, C is used.
Since u, Cr, and Ti have low thermal reaction temperatures, thermal diffusion occurs with the MR element under high temperature conditions. Therefore, in the heating process in the manufacturing process of the magnetoresistive thin film head, M
This causes deterioration or destruction of the R element.

When W or a stack of W and Ta is used as the electrode material, since the thermal reaction temperature is higher than the temperature applied during the manufacturing process, thermal diffusion with the MR element can be prevented, but the electrode by ion milling is used. There is a high possibility that the MR element will be deteriorated or broken during formation, and the reliability of the MR element will be reduced. This is due to the fact that the film thickness distribution of the electrode and the sputtering rate of W or Ta used in the electrode material (the rate of sputtering in a unit time) are small. The electrode is etched by ion milling to form an electrode shape.
At that time, the MR element arranged under the electrode as much as possible must be etched and the ion milling must be completed. However, it must be taken into consideration that the MR element is etched to some extent by ion milling because the film thickness distribution is always generated. However, when W or Ta is used as the electrode material as in the conventional example, the sputtering rate of both materials is small, so the sputtering time also varies greatly due to the variation of the film thickness, and the thick portion of the electrode is thin. Compared with the above, the etching of the electrodes ends earlier, and more MR elements are etched accordingly.
The larger the variation in the film thickness, the more remarkable this effect is, and in the worst case, the MR element is disconnected.

Even when Nb is used as the electrode material, since the sputtering rate is small, the possibility of deterioration or disconnection of the MR element increases at the time of forming the electrode by ion milling, and the reliability of the MR element increases. Goes down.

[0009]

According to the present invention, in order to solve the above-mentioned problems, the electrode material has high adhesion to the upper electrode layer made of Au having a low resistance and a very high sputter rate. A two-layer structure of a lower electrode layer made of Ta having a high thermal reaction temperature was adopted, and a lower electrode layer was arranged between the upper electrode layer and the MR element.

In the present invention, the film thickness of the lower electrode layer is 10 nm in order to have low resistance and prevent thermal diffusion of the upper electrode layer material.
The thickness of the upper electrode layer is set to 50 μm or less and the film thickness of the upper electrode layer is set to 0.1 μm or more and 0.4 μm or less in order to achieve low resistance and stable reliability during processing.

[0011]

By sandwiching Ta, which has a high thermal reaction temperature of 350 ° C., between the MR element and Au, during the heating step in the manufacturing process of the magnetoresistive thin film head (heating temperature of about 200 ° C.)
In addition to preventing Au from thermally diffusing into the MR element,
It also plays the role of increasing the adhesion to the element. Ta film thickness is 1
By setting the thickness to 0 nm or more, heat diffusion of Au into the MR element can be prevented. However, since Ta is a high-resistance material, it is desirable that the film thickness of Ta be 50 nm or less in order to make it easier to pass a current through the MR element.

Since Au has a sputtering rate that is about three times as large as W, variation in ion milling time due to variation in film thickness is reduced to approximately 1/3 that of W.
As a result, the possibility of deterioration or disconnection of the MR element is reduced. By setting the Au film thickness to 0.4 μm or less, deterioration and disconnection of the MR element are significantly reduced. Also A
By setting the film thickness of u to 0.1 μm or more, it is possible to prevent disconnection due to heat generation that occurs during energization. With the structure as described above, the manufacturing accuracy is not so much required, and the reliability of the MR element at the time of manufacturing is improved.

[0013]

【Example】

(Embodiment 1) FIG. 1 is a sectional view showing a first embodiment of the magnetoresistive thin film head of the present invention. An MR element 1 having a magnetoresistive effect on a substrate 3 selected from a non-magnetic and insulating material
Is configured. A pair of electrodes 2 are arranged on both ends of the MR element 1. The electrode 2 has a two-layer structure of a lower electrode layer 4 made of Ta and an upper electrode layer 5 made of Au thereon.

FIG. 2 is a view showing the manufacturing process of the first embodiment. First material is deposited by sputtering to a thickness of 40nm of NiFe as the MR element 1 on the Al ₂ 0 ₃ substrate -TiC 3. After coating the resist 6 with a thickness of 3 μm, patterning is performed by photolithography and ion milling to obtain the state of FIG.

After stripping the resist 6 using an organic solvent or a resist stripping solution, Ta is sputter-deposited to a thickness of 30 nm, and Au is sputter-deposited to a thickness of 0.2 μm. 7 is coated to a thickness of 3 μm, and the resist 7 is patterned into an electrode shape by photolithography to obtain the state of FIG.

Next, by performing ion milling, Au not covered with the resist 7 as shown in FIG.
And Ta are etched. At this time, the lower electrode layer 4 and the MR
It is most desirable to stop the ion milling at the boundary with the element 1. The resist 7 is also etched in the same manner as Au or Ta, but the film thickness of the resist 7 is 10 times or more thicker than the film thickness of the upper electrode layer 5 or the lower electrode layer 4, so that the resist 7 is not lost by etching. Absent. After that, the resist 7 is stripped using an organic solvent or a resist stripping solution, and the manufacturing process of the first embodiment is completed.

In the first embodiment, Au is used for the upper electrode layer 5. Au has a very high sputter rate of 0.108 μm / min in an Ar atmosphere of 500 eV. This value is about three times the sputter rate under the same W condition. Therefore, the ion milling of the upper electrode layer 5 (material Au) having a film thickness of 0.2 μm in the first embodiment is completed in about 110 seconds, which is about three times as large as that of the upper electrode layer 5 using W. early. Here, if the variation in the film thickness of the upper electrode layer 5 composed of Au is 0.2 μm ± 10% (0.18 μm to 0.22).
μm), the upper electrode layer 5 is formed by ion milling.
The time taken to completely etch the film varies from 99 seconds to 121 seconds depending on the film thickness. On the other hand, when the upper electrode layer 5 using W is formed with an equivalent film thickness variation (0.18 μm to 0.22 μm), the time when the upper electrode layer 5 finishes etching is 297 seconds to 363 seconds. Not only does the ion milling time take longer, but the time variations also increase. As a result, the etching end time of the lower electrode layer 4 disposed below the upper electrode layer 5 varies, and finally, in a place where the thickness of the upper electrode layer 5 is thin, the MR element 1 is etched in large quantities by ion milling. Will be.

The upper electrode layer 5 made of Au has a thickness of 0.
6 μm ± 10%, 0.4 μm ± 10%, 0.2 μm ± 1
The magnetoresistive effect thin film head having a structure of 0%, which is the structure described in the first embodiment, was formed on each of three square substrates each having a side of 2 inches, 1320 pieces each, and the breakage of the element 1 was examined. The experimental results are shown in Table 1.

[0019]

[Table 1]

As shown in Table 1, the film thickness of the upper electrode layer 5 is 0.
The wire breakage did not occur at 4 μm or 0.2 μm, but about 40% of the wire breakage occurred at 0.6 μm.
From this result, the film thickness of the upper electrode layer 5 made of Au is 0.
It can be seen that disconnection of the MR element can be prevented by setting the thickness to 4 μm or less. However, if the film thickness of the upper electrode 5 is made too thin, the resistance becomes large and heat is generated during energization, which causes the electrode itself to be disconnected. Generally 0.1
If the thickness is less than μm, disconnection may occur, which is not preferable. Therefore, the thickness of the upper electrode layer 5 is 0.1 μm to 0.4 μm.
Is desirable.

As another material used for the upper electrode layer 5, A
Although Ag is mentioned as a material having a lower specific resistance and a higher sputtering rate than u, it is not preferable to use Ag as the upper electrode layer 5 because Ag has poor corrosion resistance. Therefore, Au is most suitable as the material of the upper electrode layer 5 because it has a low specific resistance, a large sputtering rate, and excellent corrosion resistance.

The Ta used for the lower electrode layer 4 serves to improve the adhesion between the upper electrode layer 5 and the MR element 1, and the Au used for the upper electrode layer 5 in the MR element 1 during the heating step during manufacturing is used for the MR element 1. It has the role of preventing diffusion into the NiFe used.
Originally, Ta is not suitable as an electrode because it is a material having a large specific resistance, but in the first embodiment, since it is a very thin film having a film thickness of 30 nm, it can be sufficiently used as an electrode.
The film thickness of Ta is preferably 50 nm or less in order to obtain a resistance that can be used as an electrode. In addition, the upper electrode layer 5
In order to prevent Au, which is the material of (1), from thermally diffusing into NiFe of the MR element 1, the film thickness of Ta must be at least 10 nm or more. For the above reasons, the Ta film thickness allowable range is 1
It is 0 nm to 50 nm.

In the present invention, ion milling is used to form the electrodes. However, ion milling can be processed with higher precision than wet etching, and the etching solution corrodes the MR element, degrading the performance of the MR element. This is because there is no risk of causing

(Embodiment 2) A second embodiment of the present invention is shown in FIG.
Shown in. In FIG. 3, a pair of vertical bias layers 8 and lateral bias layers 9 are vertically stacked with the elongated MR element 1 having a magnetoresistive effect interposed therebetween. The longitudinal bias layer 8 serves to generate a magnetic field in the longitudinal direction of the MR element 1 to make the MR element 1 into a single magnetic domain and reduce noise, and is made of an antiferromagnetic material. In the second embodiment, FeMn is used as the antiferromagnetic material forming the longitudinal bias layer 8.
Was used and the film thickness was 40 nm. On the other hand, the lateral bias layer 9 serves to make the resistance change of the MR element 1 linear with respect to the external magnetic field, and generates a magnetic field in the width direction of the MR element 1. In the second embodiment, a soft film bias method having a structure in which Ta and NiFeRh are laminated is used as the lateral bias layer 9. However, in the present invention, any type of lateral bias method can be applied.

In the second embodiment, the upper electrode layer 4 and the lower electrode layer 5 and the vertical bias layer 8 are simultaneously formed by ion milling. However, as in the first embodiment, the MR element 1 disposed below the vertical bias layer 8 should not be etched by ion milling. Since the vertical bias layer has to be additionally ion-milled, the control of the time required for ion milling is somewhat difficult as compared with the first embodiment, but the thickness of the vertical bias layer is 40 nm, which is extremely small. Therefore, there was no particular problem.

[0026]

According to the present invention, by using Au for the upper electrode layer forming the electrode, a low resistance electrode can be formed, and deterioration or disconnection of the MR element at the time of forming the electrode by ion milling. Can be reduced.

By setting the film thickness of the upper electrode layer to 0.1 μm or more, low resistance can be realized, and disconnection of the electrode due to heat generation during energization can be prevented. On the other hand, 0.4 μm
By the following, the breakage of the MR element at the time of forming the electrode by ion milling can be significantly reduced.

Further, according to the present invention, by using Ta for the lower electrode layer constituting the electrode, it is possible to prevent Au of the upper electrode layer material from diffusing into the MR element due to heating during the manufacturing process. can do.

By setting the thickness of the lower electrode layer to 10 nm or more, it is possible to completely prevent Au of the upper electrode material from diffusing into the MR element. On the other hand, since the lower electrode layer also has a role of allowing the current from the upper electrode layer to flow to the MR element, it is preferable to make the film thickness of Ta, which is a high resistance material, as thin as possible. For this reason, the film thickness of Ta is 50 nm. The following is preferable.

According to the present invention, a two-layer structure of an upper electrode layer made of Au and a lower electrode layer made of Ta is formed, and the lower electrode layer is formed between the upper electrode layer and the MR element. The deterioration of the MR element during the manufacturing process can be prevented, and as a result, it is possible to manufacture a highly reliable magnetoresistive thin film head.

[Brief description of drawings]

FIG. 1 is a sectional view of a first embodiment of a magnetoresistive effect thin film head of the present invention.

FIG. 2 is a manufacturing process diagram of a first embodiment of the magnetoresistive thin film head of the present invention.

FIG. 3 is a sectional view of a second embodiment of the magnetoresistive effect thin film head of the present invention.

FIG. 4 is a sectional view of a conventional magnetoresistive thin film head.

[Explanation of symbols]

 1 MR element 2 electrode 3 substrate 4 lower electrode layer 5 upper electrode layer 6 resist 7 resist 8 longitudinal bias layer 9 lateral bias layer

Claims (2)

[Claims] 1. A magnetoresistive effect thin film head comprising a magnetoresistive effect element and a pair of electrodes formed on both ends of the magnetoresistive effect element, wherein the electrode is made of Ta. A magnetoresistive thin-film head, characterized in that an electrode layer and an upper electrode layer made of Au are sequentially laminated. 2. The film thickness of the lower electrode layer is 10 nm or more and 50 or more.
nm or less and the film thickness of the upper electrode layer is 0.1 μm
2. The magnetoresistive effect thin film head according to claim 1, wherein the thickness is 0.4 μm or more.