JPH035642B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method of manufacturing a magnetic thin film, and particularly to a method of manufacturing a magnetic thin film with a low coercive force by a magnetron sputtering method.

[Prior art]

FIG. 1 shows the structure of a magnetoresistive magnetic head, which is a type of thin film magnetic head, near the medium facing surface.

A magnetoresistive magnetic head generally uses a thin film forming technique such as sputtering on a ceramic substrate 1 to form a lower shield film 2, which is a magnetic film with a thickness of 1 μm or more, and a magnetoresistive film, which is a magnetic film with a film thickness of 500 Å or less. It is formed by laminating a film 3, a conductor film 4, and an upper shield film 5 which is a magnetic film with a thickness of 1 μm or more.

Insulating films 6 and 7 are formed between the lower shield film 2 and the magnetoresistive film 3, and between the magnetoresistive film 3 and the upper shield film 5, respectively, for forming gaps.

The characteristics of such a thin film magnetic head are significantly influenced by the magnetic characteristics of the magnetic films 2, 3, and 5 made of permalloy formed by evaporation in a magnetic field or sputtering method. The coercive force is the quantity that directly represents the magnetic properties of a magnetic thin film, but in order to obtain good head characteristics, the shielding film (magnetic film) 2, 5
The coercive force in the easy axis direction of the magnetoresistive film 3 is at least 1.0 O¨e or less, and the coercive force in the easy axis direction of the magnetoresistive film 3 is at least 1.0 O¨e or less.
Must be kept below 2.5O¨.

When forming a permalloy film by sputtering, argon gas pressure is a factor that affects coercive force, and in order to reduce coercive force, it is desirable to lower the argon gas pressure as much as possible within the capability of the apparatus. This is because the amount of active impurity gas (e.g. oxygen) occluded in the film during sputtering decreases as the argon gas pressure decreases.
This is because deterioration of magnetic properties due to impurity gas is prevented.

By the way, in a normal two-pole sputtering device, 1×
Since the discharge will not continue stably unless the argon gas pressure is 10 ^-2 Torr or higher, the main valve must be mostly closed and the pumping speed must be kept low to prevent the oil diffusion pump from going down. An increase in coercive force due to (active impurity gas such as oxygen) is unavoidable. That is, the coercive force of a film of 1 μm or more is usually 1.0 to 3.0 O¨e, and a film with such a high coercive force cannot be used as a magnetic film for a thin film magnetic head.

To solve this problem, a method is known in which sputtering is performed by applying a bias voltage to the substrate using a two-pole sputtering device and sputtering the substrate surface, but this method tends to result in non-uniform film thickness. In particular, it has a major drawback in that the film thickness tends to become extremely thin around the substrate, so it has not been put into practical use at present.

Removes defects such as 2-pole spatter, 1x
Ion beam sputtering, three-pole sputtering, or four-pole sputtering are known as methods that allow sputtering even under low argon gas pressures of 10 ^-3 Torr or less. Among these, the ion beam sputtering method is a method in which sputtering is performed by irradiating a target with an ion beam.(1) It is possible to form a film in a plasma-free state, so it is possible to keep the substrate surface temperature low during film formation. (2) It is possible to precisely control the film formation conditions, so it has played a major role in elucidating the spatter phenomenon and in analytical equipment. However, because it is difficult to develop a high-current ion source, the film formation rate is slow, and its application to film formation is significantly slower than the plasma sputtering method.

On the other hand, the three-pole or four-pole sputtering method, in which a third electrode for thermionic emission is added as an electron supply source for plasma generation, (1) has a short filament life;
This method is rarely used today because of the problem that (2) impurities from the filament get mixed into the membrane and change the characteristics of the membrane, which impedes the continuous operation of the device.

The magnetron sputtering method deflects high-speed electrons emitted from the target by applying a magnetic field parallel to the target surface, suppressing adverse effects such as substrate heating due to substrate collision, and at the same time actively using it to ionize argon gas. do. Therefore, it is possible to form a film on an organic insulating film such as a photoresist at high speed even under a low argon gas pressure of about 5×10 ^-3 Torr, making it an extremely suitable method for forming a magnetic film for a thin-film magnetic head. However, according to experiments conducted by the inventors, even when sputtering is performed under an argon gas pressure of 1×10 ^-3 Torr, which is the limit for sustaining discharge in the normal magnetron sputtering method, permalloy films with a thickness of 1 μm or more The coercive force varies in the range of 0.3 to 1.2 O¨e, and it has been found difficult to always keep the coercive force below 1.0 O¨e, which is the practical limit for magnetic films for thin film magnetic heads.

[Purpose of the invention]

The purpose of the present invention is to improve the above-mentioned conventional drawbacks by performing magnetron sputtering under an argon gas pressure of 1×10 ^-3 Torr or less.
The object of the present invention is to provide a method for producing a magnetic thin film that can produce a magnetic film having a coercive force of 1.0 oersted or less with good reproducibility.

[Summary of the invention]

In order to achieve the above object, the present invention provides a method for forming a magnetic film by a magnetron sputtering method.
Discharge is started under an argon gas pressure of ×10 ^-3 Torr or more, and then the argon gas pressure is increased to 1 ×
It is characterized by sustaining discharge at 10 ^-4 Torr level at 10 ^-3 Torr or less.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described with reference to FIGS. 2 to 6.

FIG. 2 is a schematic diagram of the magnetron type sputtering apparatus used in this example, and FIG. 2 shows the change over time in the gas pressure inside the bell gear 8 when formed by the magnetron type sputtering device shown in FIG.

To form the magnetic films 2 and 5, first, a cleaned substrate 15 is placed in a predetermined location in a bell gear (vacuum groove) 8, and a diffusion pump 10 is used to heat the substrate 15 to 1×10 ^-5 Torr.
exhaust to. After that, the substrate 15 is placed on the heater 16
The gas is heated to 350℃ by the trap 12, and the residual gas is discharged by the trap 12, and the gas pressure in the bell gear 8 is reduced to 1.
When the temperature reaches ×10 ^-6 Torr, the temperature of the substrate 15 is increased to 300
℃, and the gas pressure inside the bell gear 8 is 1×
Argon gas is introduced from the gas inlet 11 while monitoring the flow meter 18 so that the pressure is 10 -3 Torr or higher (5×10 ^-3 Torr as shown in FIG ^. 3 in this embodiment) (T ₁ ).

Next, in order to clean the surface of the target 14, a shutter 17 is used to prevent the film from adhering to the surface of the substrate 15.
Perform Puri Spatsuta while keeping it closed. Previously, the third
As shown by the broken line a in the figure, even after presputtering, the discharge was continued under the same argon gas pressure.
While applying a magnetic field of 100 O¨e to the surface of the substrate 15 by the coil 13, the shutter 17 was opened and the main sputtering began. In this embodiment, as shown by the solid line b in FIG. 2, before opening the shutter 17,
While maintaining the discharge, operate the needle valve 19 to reduce the argon gas pressure to 1×
The substrate 1 is heated under a pressure of 10 ^-3 Torr or less (2×10 ^-4 Torr in this example as shown in FIG. 3).
The main sputtering was started by opening the shutter 17 while applying a magnetic field of 100 O¨e from the coil 13 to the surface of the sample (T ₂ ), and a permalloy film with a thickness of 1 μm was formed. After the main sputtering (H ₃ ), the substrate 15 is cooled while the inside of the bell gear 8 is evacuated, and the substrate temperature is lowered.
When the temperature dropped to below 50°C, it was taken out of the Belgear 8.

It should be noted that, as in this example, it has been found that once a discharge is caused under argon gas pressure (1×10 ^-3 Torr or more), where discharge is easy to occur, the discharge can be sustained even if the argon gas pressure is subsequently lowered. did.

FIG. 4 shows the relationship between the argon gas pressure in the present sputtering when forming an 81Ni-19Fe permalloy thin film and the easy axis coercive force of the formed thin film. In Fig. 4, a is under conventional argon gas pressure;
b shows the characteristics of the permalloy film formed under argon gas pressure in this example. From FIG. 4, the easy-axis coercive force of the permalloy film formed under argon gas pressure of 1×10 ^-3 Torr or less as in this example is small, and even when considering the property variation width C between substrates, it is always It can be seen that it is less than 1.0O¨e and that the variation width C is small. On the other hand, as before, 1×
The easy axis coercive force of permalloy thin films formed under argon gas pressure of 10 ^-3 Torr or more is large, and the variation width d between substrates is also large, so it is difficult to suppress the coercive force of all films to less than 1.0 O¨e. I understand that there is something.

FIG. 5 shows the relationship between the anisotropic dispersion angle (α90) and argon gas pressure in the permalloy film shown in FIG. In FIG. 5, a shows the anisotropic dispersion angle of the permalloy film formed under the conventional argon gas pressure, and b shows the permalloy film formed under the argon gas pressure of this example.

From FIG. 5, the anisotropic dispersion angle of the permalloy film formed by the method according to this example is smaller than that of the permalloy film formed by the conventional method, and the anisotropic dispersion angle between the substrates is small. Dispersion angle variation width e
It can be seen that the variation width f is smaller than that of the conventional method, and a magnetic film with good magnetic properties can be obtained with good reproducibility.

FIG. 6 shows a device comprising a magnetic gap 6, 7 of 1 μm made of SiO ₂ , a permalloy magnetoresistive film 3 of 0.05 μm thick, an Al conductor film 4 of 0.2 μm thick, and shield films 2, 5 of 1 μm thick. Relationship between the half-width (relative value) of a waveform reproduced from an isolated reversed magnetization state recorded on a magnetic disk using a magnetoresistive thin-film magnetic head and the easy-axis coercive force of the shield films 2 and 5 with a thickness of 1 μm. shows. From Figure 6, there is no significant difference in the half-width of the reproduced waveform when the easy-axis coercive force is less than 1.0 O¨e, but when it is more than 1.0 O¨e, the half-width increases and the shielding film has sufficient function. It can be seen that they are not fully utilized. It has been confirmed that such an increase in half-width is undesirable because it causes a decrease in the head output and therefore a decrease in the S/N ratio when reproducing information recorded at high density.

In the above example, the case was described in which an Fe-Ni alloy (permalloy) film was formed as a shield film made of a high magnetic permeability material, but the same effect can be obtained by forming an Fe-Ni alloy (permalloy) film as a shield film made of a high magnetic permeability material.
-It was confirmed that this phenomenon was also observed in amorphous alloy films such as -Ni-Mo, Fe-Al-Si, Fe-B, Co-Ti, and Co-Fe-B.

Further, although the above embodiments have described a magnetoresistive type thin film magnetic head, it has been confirmed that similar effects can also be observed in an inductive type thin film magnetic head.

In this way, a magnetic thin film formed using a magnetron sputtering device under an argon gas pressure of 1×10 ^-3 Torr or less has a constant coercive force.
Not only is it less than 1.0O¨e, but the dispersion angle is also small.
Furthermore, by using a thin film magnetic head having a magnetic film formed by the same method, even information recorded at high density can be reproduced without reducing the S/N ratio.

〔Effect of the invention〕

As explained above, according to the present invention, 1×
Magnetron sputtering can be performed under argon gas pressure of 10 ^-3 Torr or less, making it possible to manufacture magnetic films with low coercive force with good reproducibility, and improving manufacturing yield.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the structure of a magnetoresistive thin film magnetic head in the vicinity of the medium facing surface, FIG. 2 is a diagram showing a schematic configuration of a magnetron type sputtering device used in the present invention, and FIG. FIG. 4 is a diagram showing the change over time in the gas pressure inside the bell jar in Examples; FIG. The figure shows the relationship between the argon gas pressure in the bell gear and the dispersion angle of the permalloy thin film formed under the argon gas pressure. , is a diagram showing the relationship between the half-width of the reproduced waveform in the head. a: Argon gas pressure in the conventional method, b: Argon gas pressure in the present invention, T ₁ : Argon gas introduction time, T ₂ : Main sputtering start time, T ₃ :
End time of this spatuta.

Claims (1)

[Claims] 1 When forming a magnetic thin film by the magnetron sputtering method, discharge is started under an argon gas pressure of 1 × 10 ^-3 Torr or more, and then the argon gas pressure is reduced to 1 × 10 ^-3 Torr or less, and 10 - A method for producing a magnetic thin film, characterized in that the discharge is sustained on a ⁴ Torr stand.