JPS6035729B2 - Thin film magnetic head manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a thin film magnetic head using a magnetoresistive element, and provides a novel manufacturing method that provides good characteristics and contributes to improved manufacturing yield.

Conventionally, a thin film magnetic head using a ferromagnetic thin film having a magnetoresistive effect has a Ni-F film on a substrate 1, as shown in FIG.
After a ferromagnetic thin film is produced using e-alloy or Ni-Co alloy as a base material by vacuum evaporation, sputtering, electrodeposition, etc., it is formed into a predetermined pattern using photolithography and etching techniques. A magnetoresistive element 2 is formed.

Thereafter, conductor layers 3 are formed on both ends of the magnetoresistive element 2. The magnetic head then uses a predetermined pressure. However, in the end, the recording medium 4 and the magnetoresistive element 2 are processed at a position where they are in close proximity to each other. The magnetization Ms in the magnetoresistive element 2 is rotated by the signal magnetic field Hs from the recording medium 4 and tilted by an angle of 8 with respect to the current i. This state causes a change in resistivity Δp in the longitudinal direction of the magnetoresistive element 2, and the relationship between the two is Δp of cos20. Thereby, the magnetic information recorded on the recording medium 4 is detected as an electric signal. The most important thing here is the magnetoresistive effect element 2.
is the orientation of magnetization Ms at .

Normally, orientation is achieved by producing induced magnetic anisotropy in the longitudinal direction (in-track direction) by evaporation in a magnetic field, but in the process of etching into a predetermined shape, conventionally Irregular irregularities of several mm are likely to occur at the ends, which causes disturbances in the magnetic domain structure near the ends of the element. Particularly with chemical etching, it is nearly impossible to remove irregularities at the edges. That is, in the chemical etching method, the speed at which the chemical reaction proceeds from the surface of the ferromagnetic thin film 5 and the speed at which it proceeds from the side surface are different as shown in FIG. If there is unevenness in gender,
The speed at which it advances from the sides may be greater, resulting in unevenness at the edges. On the other hand, sputter etching has recently come to be used as a dry etching method. This is a method of etching by colliding atoms in a plasma state with the sample surface and knocking out atoms or molecules from the sample surface.Essentially, etching proceeds perpendicularly from the surface, resulting in unevenness at the edge of the sample. becomes less. However, etching a thin film with a unique magnetic domain structure, such as a ferromagnetic thin film, requires careful manufacturing methods and has not generally been used. If the orientation of the magnetization NL is disordered in this way, Barkhausen noise is likely to occur when used as a magnetic head, and when a multi-element structure is used, the characteristics between the elements will vary.

As mentioned above, in order to operate with good linearity,
As is clear from the difference between the resistivity change Δp and a, the angle between the magnetization Ms and the current i is set to 450 by some means.
It is necessary to set it at or near it.

One method is to change the bias magnetic field HB to the signal magnetic field Hs.
There is a method of applying force in the same direction. In such a case, the horizontal structure of the magnetic domains of the magnetoresistive element itself is disordered, and since there is a magnetic domain structure between each element, the bias point is different for each element, and the equivalent optimal bias point between elements varies. Put it away. In the present invention, by interrupting plasma generation at least once during sputter etching,
This solves the problems mentioned above.

One embodiment of the present invention will be described below with reference to the drawings.
First, as shown in FIG. 4, a ferromagnetic thin film 5 was formed on a substrate 1, and then a photoresist layer 6 in a predetermined pattern was formed thereon.

Here, the material of the ferromagnetic thin film 5 is 78% Ni-2
The compositions ranging from 2% Fe to 86% Ni-14% Fe were investigated. The substrate 1 was placed on a target in a sputtering apparatus, and the distance between the target and the counter electrode was set to 4.5 cm, and then the inside of the tank was evacuated to a degree of vacuum of approximately 10-6 tons.

Then, after introducing 3×10 orr of Ar gas into the tank, adjust the main exhaust valve to reduce the pressure in the tank to about 5×10 orr.
I made it 3Ton.

Then, a high frequency voltage of approximately 13.8 MHZ (
1600~1800V) is applied, and the effective power is 180~1
Plasma was generated at 90W. Normally, when the ferromagnetic thin film 5 is continuously etched in this state, the etching rate ratio between the ferromagnetic thin film 5 and the photoresist layer 6 cannot be maintained, as shown in FIG. It will be largely removed.

Therefore, unevenness occurs at the end of the ferromagnetic thin film 5, similar to the chemical etching method. Experiments conducted by the inventors have revealed that such problems can be solved very effectively by intermittently generating plasma for etching.

It is thought that the main reason why good results are obtained when sputter etching is performed by intermittently generating plasma is the cooling effect of the substrate 1. When sputter etching is performed by repeatedly generating plasma for 1 minute and stopping for 1 minute, the ratio of etching rates between the ferromagnetic thin film 5 and the photoresist layer 6 is approximately 1. It was found that the increase was about 5 to 2 times.

That is, the peripheral portion of the photoresist layer 6 is more difficult to remove than the ferromagnetic thin film 5, and the unevenness at the end portion is reduced. When a ferromagnetic thin film with a thickness of about 1500 A was sputter-etched under these conditions, the etching was completed in 6 to 7 minutes in total for plasma generation. When the plasma stop time is increased, the etching rate ratio between the photoresist layer 6 and the ferromagnetic thin film 5 is further improved, but when the stop time is longer than 10 minutes, the effect of the improvement becomes almost constant. Even when sputter etching is performed intermittently in this manner, the etching rate ratio Q between the photoresist layer and the ferromagnetic thin film is usually 4 to 5.

Therefore, in order to etch a ferromagnetic thin film with a thickness of approximately 1500A, a resist layer of at least 6000 to 7500A is sufficient, but in reality, the peripheral portions of the photoresist layer may sag. Since it is effectively thinner and etching is faster in the central portion as shown in FIG. 5, the residual resist thickness in the central portion must be taken into consideration as shown in FIG. 6. It has been found that when the residual resist thickness tR at the central portion is approximately 0.5 m or more, the magnetic domain structure of the ferromagnetic thin film 5 is not damaged.
Moreover, if it becomes thinner than 0.51 m, peeling of the photoresist layer becomes extremely slow. That is, about 1
In the case of a 500A thick ferromagnetic thin film, a resist thickness of approximately one diagonal or more is required. However, if the photoresist layer is too thick, it will be difficult to form fine patterns.
Even when etching a ferromagnetic thin film with a thickness of about 1500 Δ, the maximum thickness of the photoresist layer is about 2.5 m. If the thickness of the ferromagnetic thin film is t (French m) and the resist thickness is T (mm), then 2.5T and (Qt+0.5/t
) is important.

The resist thickness T mentioned here is the resist thickness after post-baking.

Normally, resists commercially available under the names "KMR" and "Az-1350L" are used with post-bake temperatures of 140°C or lower, but in the case of sputter etching, resists with a temperature of 150°C or less are used.
By post-baking at ~16,000 C for 1 to 2 hours, the etching rate of the resist layer could be made slower. In addition, after post-baking, place the substrate 1 in the sputtering equipment, and before starting evacuation to a vacuum, place the substrate 1 in the
It is effective to increase the etching rate of the ferromagnetic thin film 5 by placing it in a drying oven with a temperature of 00 CO or more and leaving it in a dry atmosphere to remove molecules such as ○ on the substrate 1, especially on the ferromagnetic thin film 5. I found out something. Actually 1000
~ Put it in a drying oven at 120o0 for at least 5 minutes, take it out, and start evacuation to a vacuum for at most 10 minutes.
By keeping the etching rate within minutes, the etching rate of the ferromagnetic thin film can be kept almost constant, and a manufacturing process with good reproducibility and smooth steps can be established. This process of putting the substrate in a drying oven is not necessary if you put the substrate etc. into the sputtering equipment immediately after post-bake, but it is usually not necessary to leave it after post-bake for microscopic observation or from the perspective of the process flow. In the worst case, the 1-mark window may be exposed to the surrounding atmosphere. Even in such a case, good sputter etching can be achieved by passing through the above process. Since the manufacturing method of the present invention is concerned with forming the shape of the ferromagnetic thin film that becomes the magnetoresistive element, it does not matter what the processes before and after it are, and structurally, It can be applied not only to etching directly produced ferromagnetic thin films but also to etching ferromagnetic thin films formed on multiple layers. In the above embodiment, Ar gas was used to generate plasma, but it goes without saying that other inert gases may be used. Furthermore, CF
4. Using active gas such as CC14, CC12F2,
The method of the present invention can also be applied to etching by physical sputtering and a chemical reaction by generated active groups. As described above, the present invention can increase the etching rate ratio between the ferromagnetic thin film and the resist layer by interrupting plasma generation at least once during sputter etching, thereby increasing the magnetoresistive effect. It is possible to eliminate irregular irregularities on the edges of the ferromagnetic thin film that becomes the element.

Furthermore, since thermal deterioration of the ferromagnetic thin film and damage caused by sputtered atoms do not occur, the direction of magnetization Ms can be stably maintained. Therefore, a magnetic head without Barkhausen noise and with less variation in characteristics between each element can be realized.

[Brief explanation of the drawing]

Figure 1 is a perspective view for explaining the basic configuration and operation of a thin-film magnetic head using a magnetoresistive element;
The figure is a plan view showing the state of etching of a ferromagnetic thin film by the conventional method, FIG. 3 is a cross-sectional view showing the state of etching at the edge of a pattern by chemical etching, and FIG. 4 is a resist and ferromagnetic thin film by the manufacturing method of the present invention. 5 is a sectional view showing the etching state of the ferromagnetic thin film when sputter etching is performed continuously, and FIG. 6 is a sectional view showing the etching state of the ferromagnetic thin film by the manufacturing method of the present invention. FIG. 3 is a cross-sectional view showing the state of residual resist. 1...Substrate, 5...Ferromagnetic thin film, 6.
...Resist layer. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] 1. A step of forming a ferromagnetic thin film having a magnetoresistive effect on a substrate, further forming a resist layer with a predetermined pattern on the substrate, and then performing post-baking; The ferromagnetic thin film is covered with the resist layer by setting the substrate in a sputtering device, evacuation to a vacuum state, introducing a predetermined gas, and interrupting plasma generation by applying a high-frequency electric field at least once. 1. A method for manufacturing a thin film magnetic head, comprising the step of sputter etching the missing portions. 2. The method for manufacturing a thin film magnetic head according to claim 1, wherein the gas introduced into the sputtering device is argon. 3. Spatter etching is performed by repeating one or more times without a cycle of generating plasma and stopping for 1 to 10 minutes.
1. Method for manufacturing a thin film magnetic head as described in Section 1. 4 The thickness of the photoresist layer after post-baking is 2.5μ
2. The method of manufacturing a thin film magnetic head according to claim 1, wherein the residual thickness of the photoresist layer at the central portion thereof is at least 0.5 μm. 5. The method of manufacturing a thin film magnetic head according to claim 1, wherein the post-baking is carried out at a temperature of 150 to 160° C. for one hour or more.