JPS61248213A - Thin film magnetic head - Google Patents

Abstract

PURPOSE:To improve the magnetic characteristics of a lower yoke and upper yoke by forming the yokes via an SiO2 film formed by a coating stage on a substrate. CONSTITUTION:The upper yoke 11 consists of a high-permeability magnetic film such as 'Permalloy(R)' and acts as the magnetic path to conduct the magnetic field generated by a magnetic recording medium 13 to an MR element 7. The MR element 7 consists of a vapor-deposited 'Permally(R)' film and the conductor 5 consists of a film of Al, Cu or Al-Cu alloy, etc. The conductor 5, the MR element 7 and the upper yoke 11 are formed via the insulating layers 4, 6, 9 and the lower yoke 3 consists of a high-permeability magnetic film of 'Sendust(R)' or 'Permalloy(R)' and is formed via the coating type SiO2 film 2 on a nonmagnetidc substrate 1 having the coefft. of thermal expansion approximate to the coefft. of thermal expansion of the lower yoke 3. The ruggedness on the surface of the substrate 1 is flattened by the coating type SiO2 film 2. The coating type SiO2 film has the excellent film quality as a substrate so that the high-permeability magnetic film of the lower yoke 3 has the good magnetic characteristics.

Description

[Detailed Description of the Invention] Technical Field> The present invention detects changes in a signal magnetic field applied in the direction of the hard axis of magnetization of a ferromagnetic thin film having uniaxial magnetic anisotropy as changes in electrical resistance in the direction of the easy axis of magnetization. Magnetoresistive element (hereinafter referred to as
The present invention relates to a thin film magnetic head (hereinafter referred to as a thin film MR head) that is equipped with an MR element (hereinafter referred to as a thin film MR element) and detects a signal recorded on a magnetic recording medium.

<Prior Art> Conventionally, thin film MR heads are known to have many advantages over wire-wound magnetic heads.

In this thin-film MR head, the magnetization direction inside the MR element changes by receiving a signal magnetic field written on a magnetic recording medium such as a magnetic tape, and the M
The change in internal resistance of the R element is extracted as an external output. Therefore, the thin film MR head is a magnetic flux responsive head and can reproduce a signal magnetic field without depending on the transport speed of the magnetic recording medium. Since this thin film MR head can easily be highly integrated and multi-elemented using semiconductor microfabrication technology, it is seen as a promising magnetic head for reproduction in fixed head type PCM recorders that perform high-density recording.

Originally, an MR element has a sensitivity characteristic that shows a square change in response to an external magnetic field. Therefore, when configuring an MR element as a read head, the element shape should be made into a stripe shape and linear response characteristics. In order to obtain this, it is necessary to provide a configuration for applying a predetermined bias magnetic field. Known methods for applying this bias magnetic field include a method of inducing a bias magnetic field by flowing a direct current through a conductor, and a method of applying a bias magnetic field using a high coercive force thin film such as a Co-P layer. (Refer to Japanese Patent Application No. 55-126255, 4th Japanese Society of Applied Magnetics Academic Lecture Abstracts (1980) 5PA-4r Multitrack Thin Film MR Head). In actual use, in a thin film MR head, an MR element is formed on the conductor or high coercive force thin film with an insulating layer interposed therebetween.

On the other hand, compared to a thin film MR head composed of a single MR element,
A normal yoke type MR head (hereinafter referred to as YMR head) has a structure as shown in Figure 3, in which a magnetic flux introduction path (hereinafter referred to as yoke) is arranged to separate the MR element from the tip of the head and guide the magnetic flux generated in the magnetic recording medium to the MR element. It is known that a thin-film magnetic head called MR head is more effective in improving the resolution of signals and the durability of MR elements. (8th
Japanese Society of Applied Magnetics Academic Lecture Abstracts (1984) 14 pages
(Refer to "Reproduction characteristics of B-11r York type MR head")
.

FIG. 3 shows a cross-sectional structure of a conventional YMR hefed magnetic recording medium in a direction perpendicular to the track width direction.

The upper yoke 11 is usually made of a permalloy (Ni-Fe alloy) film with a film thickness of about 0.5 to 1.0 μm, and serves as a magnetic path for guiding the magnetic field generated by the magnetic recording medium 13 to the MR element 7. . The MR element 7 is made of a permalloy (Ni--Fe alloy) vapor-deposited film, and has a film thickness of 200 to 500 μm, and a track width of about 50 to 200 μm since it has a multi-track configuration. Further, in order to apply a bias magnetic field, a conductor 5 made of a film of Al, Cu, AN-Cu alloy, or the like is provided. Since the recording wavelength actually used is about 0.5 μm, the head gap portion 12 has a diameter of 0.2 μm.
It is set to about 0.3 μm.

The above-described conductor 5, MR element 7, and upper yoke 11 are formed via the insulating layer 4.6.9. The lower yoke 3 is made of a high permeability magnetic film, such as Sendust (Fe-Al
l-3i alloy) membrane or permalloy (Ni-Fe alloy)
A film is used and is formed on a nonmagnetic substrate 1 such as crystallized glass by electron beam evaporation, sputtering, or the like.

The lower yoke 3 made of the above-mentioned high permeability magnetic film needs to have a film thickness of about several μm for the operation of the YMR head. Therefore, in order to obtain good characteristics of this magnetic film, the thermal expansion coefficient of the substrate 1 should be adjusted to this value. Needless to say, it is necessary to match the thermal expansion coefficient of the high permeability magnetic film.

Furthermore, in order to obtain good magnetic properties, it is necessary that the surface roughness of the substrate 1 is small. However, the surface roughness of commonly available crystallized glass is about 50 to 200, and when a high permeability magnetic film is formed on this crystallized glass, the crystal orientation of the magnetic film changes, resulting in a desired surface roughness. magnetic properties cannot be obtained. In addition, the surface roughness of the high permeability magnetic film formed on this crystallized glass substrate is the same as that of the substrate, and the surface roughness of the magnetic film is 5%, reflecting the surface roughness of the substrate.
It will be about 0 to 200 people. As a result, in the head gap portion 12, the machining accuracy of the gap length decreases due to the unevenness of the surface of the lower yoke 3, and the upper yoke 11
This results in changes in the characteristics of the magnetic film forming the magnetic film. Furthermore, since the bank yoke portion 10 is coupled to the lower yoke 3 in a state where crystallinity is uneven, the magnetic behavior becomes discontinuous and good magnetic properties cannot be obtained.

Therefore, in the above-mentioned YMR head, noise peculiar to ferromagnetic materials and distortion of the signal waveform have a large effect on the S/N ratio of the reproduced waveform.

<Object of the Invention> The present invention has been made in view of the above problems, and provides a thin film magnetic head in which the magnetic properties of the lower yoke and the upper yoke are good even when the surface roughness of the substrate is large. The purpose is to provide.

<Structure of the Invention> The present invention provides a thin film in which a yoke in contact with a magnetic recording medium is formed above or below a head gap portion, and a magnetoresistive effect element is internally connected to the yoke, which is magnetically coupled using this yoke as a magnetic path. The magnetic head is characterized in that the yoke is formed through a 5102 film formed on a substrate through a coating process.

<Example> An embodiment of the present invention will be described below.

FIG. 1 shows the cross-sectional structure of the YMR head of this embodiment in a direction perpendicular to the track width direction of the magnetic recording medium, and FIG. 2 shows the planar structure of this YMR head.

FIG. 1 shows the structure of the YMR head shown in FIG. 2 taken along the line AA'.

The upper yoke 11 is made of a high permeability magnetic film such as permalloy (Ni-Fe alloy) with a thickness of about 0.5 to 1.0 μm, and the upper yoke 11 transfers the magnetic field generated by the magnetic recording medium 13 to the MR element. It becomes a magnetic path to lead to 7. MR element 7
is made of a permalloy (Ni-Fe alloy) vapor-deposited film, the thickness of which is 200 to 50,000 mm, and the track width is set to about 50 to 200 μm since it has a multi-trunk configuration.

The conductor 5 for applying a bias magnetic field to the MR element 7 is
It is made of a film of Al5Cu or A#-Cu alloy. Since the minimum recording wavelength actually used is about 0.5 μm, the head gap portion 12 is set to about 0.2 to 0.3 μm. The above-described conductor 5, MR element 7, and upper yoke 11 are formed via the insulating layer 4.6.9. The lower yoke 3 is made of a high permeability magnetic film such as Sendust (Fe-Aj!-3i alloy) or Permalloy (Ni-Fe alloy). The lower yoke 3 is formed on a substrate 1 made of a non-magnetic material such as crystallized glass having a coefficient of thermal expansion similar to that of the lower yoke 3, with a coated 5i02 film 2 interposed therebetween.

The coating type 5i02 film 2 is obtained by applying a solution of a silicon compound or the like in an organic solvent or the like onto the substrate 1 using a spinner and baking it. The thickness of this coated 5t02 film 2 can be controlled by the rotation speed of the spin code and the concentration of silicon compound in the solvent.
Similar to the case where an organic material such as IQ is used, the unevenness on the surface of the substrate 1 is flattened. The surface roughness of the Si02 film 2 when this coating type 5i02 film 2 is formed on the substrate 1 is as follows:
While the surface roughness of the substrate 1 is about 50 to 200, it is about 10.

On this coating type 5i02 film 2, a lower yoke 3 made of a high permeability magnetic film is formed by electron beam evaporation, sputtering, or the like. In this case, the unevenness on the surface of the substrate 1 is flattened by the coating type 5i02 film 2, and the coating type 5t0
Since the second film has excellent film quality (film density, film composition, etc.) as a base, the high permeability magnetic film forming the lower yoke 3 obtained by the above method has good magnetic properties.

After an insulating layer 4 of SiO2, Si3N4, Al2O3, etc. is formed on the lower yoke 3 by P-CVD or RF sputtering, a conductor 5 for applying a bypass magnetic field is formed by resistance heating, electron beam evaporation, or RF. It is formed by sputtering. The conductor 5 has A 12 as described above.
% Cu −, A I Cu alloy, etc. films are used,
The Cu film is made of nitric acid (HNOa) + ammonium peroxide ((N
Ha ) 2 S20e ) + water (H20) as an etching solution, Aj2 film and Al-Cu alloy film were etched with potassium hydroxide (KOH) + ammonium persulfate ((NH3)23
20B) + water (H20) or phosphoric acid (Ha PO4)
Deca-nitric acid (HNO3) Deca-acetic acid (CH3C00H) Raw water (H
If an etching solution called 2O) is used, each can be processed into the desired dimensions. On this conductor 5, P-CV
5t02.5t3N by D method or RF sputtering method
4. An insulating layer 6 made of Af203 or the like is formed.

Furthermore, ・M made of permalloy (Ni-Fe alloy)
The lead layer 8 consisting of the R element 7 and Af etc. is heated by a resistance heating method.
After being formed by electron beam evaporation or the like, the insulating layer of the head gap portion 12 is etched. The insulating layer of this head gap portion 12 is etched using a parallel plate dry etching device (RIE), and is etched using CHFa (Freon 23), C
F4 (Freon 14), CF4+02, CF4+
Etching can be performed using H2 as an introduced gas. M
The R element 7 has a film thickness of 200 to 500 mm and is etched by chemical etching or sputter etching.
Processed into stripes of ~100 μm.

P-CVD method or R
An insulating layer 9 is formed by F sputtering, and the insulating layer of the back yoke portion 10 is etched by a parallel plate dry etching device. Finally, a high permeability magnetic film such as permalloy (Ni--Fe alloy) is formed as the upper yoke 11 by sputtering or the like.

The table below shows the magnetic properties of the high permeability magnetic films of the thin film magnetic heads in the conventional example and the present example. Hc is the coercive force in the direction of the axis of easy magnetization, Hch is the coercive force in the direction of the axis of hard magnetization, and Hk is the anisotropic magnetic field.

As is clear from this table, in the conventional example, the magnetic properties of permalloy (Ni-Fe alloy) films formed by direct sputtering or vapor deposition on crystallized glass (PEG) substrates with surface roughness of 50 to 200. Compared to the characteristics
In this example, a coated Si02 film was formed on a similar substrate, and a permalloy film (permalloy) was formed on the coated Si02 film by sputtering or vapor deposition.
It can be seen that the magnetic properties of the Ni--Fe alloy film are improved. That is, permalloy sputtered film (thickness 1 μm)
), the coercive force Hc in the direction of the axis of easy magnetization is 2.1o.
e to 1.2oe. In addition, even in a permalloy vapor-deposited film with a thickness of 300, which is easily affected by surface roughness, the coercive force Hc in the direction of the axis of easy magnetization ranges from 4 to 5 oe to 2.5 oe. The QOE is small. This is a coating type 5i
This is thought to be because the unevenness on the substrate surface was flattened by the 02 film, and also because the quality of the film was improved as an underlying layer.

Furthermore, when forming the upper yoke 11 made of permalloy (Ni-Fe alloy) film, the bed gap portion 1
2 and the influence of the surface irregularities of the back yoke portion 10 will be considered. That is, in this example, the coating type 5i02 film 2
Since the lower yoke 3 is formed above, the lower yoke 3
The surface roughness of is ~10 Å or less. Furthermore, the surface roughness of the bed gap portion 12 after the insulating layer 9 is formed is also ~10 Å or less. Therefore, since the surface roughness of the head gap part 12 and the back yoke part 10 is small, when the upper yoke 11 is made of a high permeability magnetic film such as permalloy (N i -F e alloy), good magnetic properties can be achieved. A film having the following properties is obtained.

Furthermore, since the unevenness of the head gap portion 12 is small, gap loss can also be reduced.

<Effects of the Invention> As detailed above, according to the present invention, a coated SiO2 film is formed on a substrate to reduce the surface roughness.
The lower and upper yokes can be formed of a high permeability magnetic film that has good magnetic properties that are not affected by the unevenness of the substrate surface and the film quality.
A thin film MR head having a /N ratio is obtained.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an embodiment of the present invention, FIG. 2 is a plan view of the embodiment of the present invention, and FIG. 3 is a cross-sectional view of a conventional example. 1...Substrate 2...Coated SiO2 film 3...Lower yoke

Claims (1)

[Claims] (1) In a thin-film magnetic head in which a yoke that contacts the magnetic recording medium is formed above or below the head gap, and a magnetoresistive element that is magnetically coupled using this yoke as a magnetic path is installed, A thin film magnetic head characterized in that the yoke is formed through a SiO_2 film formed through a coating process.