Thin-film magnetic head and production method thereof

Details Thin-film magnetic head and production method thereof Thin-film magnetic head and production method thereof

1999-01-26

2001-10-23

Cao, Allen (Department: 2754)

Dynamic magnetic information storage or retrieval

Head

Magnetoresistive reproducing head

Reexamination Certificate

active

06307722

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thin-film magnetic head for use for example as a floating type magnetic head in a hard disk device, which is designed to detect, by means of the magnetoresistance effect, a leakage magnetic flux coming from a recording medium, and more particularly to a thin-film magnetic head having a plurality of layers, which can be formed easily, and exhibiting improved performance in terms of detecting a magnetic field, and furthermore to a production method thereof.
2. Description of the Prior Art
FIGS. 12A
to
12
D are schematic diagrams illustrating a production method of a conventional thin-film magnetic head based on the magneto-resistance effect.
FIG. 13
is an enlarged sectional view illustrating a part (the portion denoted by reference symbol XIII in
FIG. 12D
) of a thin-film magnetic head obtained after completion of the production process.
In a conventional method of producing a thin-film magnetic head, as shown in
FIG. 12A
, a three-layer film
2
is deposited, by means of for example a sputtering technique, on a non-magnetic material layer (lower gap layer)
1
such as Al
2
O
3
formed on a lower shielding layer. As shown in an enlarged fashion in
FIG. 13
, the bottom layer of the three-layer film
2
serves as a transverse bias layer
2
a
for generating a transverse bias field. The transverse bias layer
2
a
is a soft magnetic layer (SAL) made of a soft magnetic material such as an Fe—Ni—Nb (iron-nickel-niobium) alloy. The layer disposed on the transverse bias layer
2
a
is a non-magnetic layer (shunt layer)
2
b
made of for example Ta (tantalum). The top layer is a magnetoresistance effect layer (MR layer)
2
c
. The magnetoresistance effect layer
2
c
is made of for example a Ni—Fe alloy.
A resist material is coated on the three-layer film
2
shown in
FIG. 12A
, and then subjected to an exposing and developing process using a deep-UV technique or the like thereby forming a resist layer
3
having a shape such as that shown in FIG.
12
B. As shown in
FIG. 12B
, the resist layer
3
has undercuts
3
a
,
3
a
formed at its lower positions on both sides. The track width (TW) of the thin-film magnetic head is determined by the dimension of the resist layer
3
.
The three-layer film
2
, except regions on which the resist layer
3
is formed, is then removed using an etching technique such as an ion milling technique, as shown in FIG.
12
C. In this etching process, both sides of the three-layer film
2
are removed, and slanted planes (i) are produced. A longitudinal bias layer (hard bias layer)
4
and an electrode layer
5
are then sputtered using the resist layer
3
as a mask so that these layers are formed only in the regions in which the three-layer film
2
is not formed. In the regions near the contacting interface between the three-layer
2
and the longitudinal layer
4
and the electrode layer
5
, the thickness of the longitudinal layer
4
and the electrode layer
5
changes in such a manner as shown in
FIG. 13
due to the undercuts
3
a
,
3
a
formed on the sides of the resist layer
3
,
After the resist layer
3
is removed, an upper gap of a non-magnetic material such as Al
2
O
3
is formed on the resultant multi-layer structure shown in
FIG. 12D
, and furthermore an upper shielding layer is formed thereon.
In this thin-film magnetic head, the longitudinal bias layer
4
is a so-called hard bias layer or a hard magnetic layer made of for example Co—Pt (cobalt-platinum) alloy. The magnetoresistance effect layer
2
c
is magnetized in the X-direction into a single magnetic domain by a magnetic field maintained in the longitudinal bias layer
4
. If a detection current is supplied to the magnetoresistance effect layer
2
c
from the electrode layer
5
via the longitudinal bias layer
4
, a magnetic field is induced in the magnetoresistance effect layer
2
c
by the current, and thus the transverse bias layer
2
a
experiences a magnetic field in the Y-direction originating from the magnetoresistance effect layer
2
c
. As a result, the transverse bias layer
2
a
or the soft magnetic layer, is magnetized in the Y-direction. The transverse bias field in the Y-direction in this transverse bias layer
2
a
is applied to the magnetoresistance effect layer
2
c
, and thus the uniform magnetization performed by the longitudinal bias field and the transverse bias field ensure the linearity of the detection output relative to the change in the leakage magnetic field in the Y-direction applied from a recording medium.
FIG. 14
is a front view of a conventional thin-film magnetic head of the spin valve type. The magnetic recording medium such as a hard disk moves in the Z-direction relative to this thin-film magnetic head, while the leakage magnetic field (external magnetic field) from the magnetic recording medium occurs in the Y-direction. The thin-film magnetic head shown in
FIG. 14
includes a non-magnetic material layer (lower gap layer)
1
formed of a non-magnetic material such as Al
2
O
3
(aluminum oxide), and a spin valve layer (SV) formed on the non-magnetic material layer, wherein the spin valve layer consists of
6
layers including a lower non-magnetic layer
20
such as a Ta (tantalum), free magnetic layer
21
, non-magnetic conductive layer
22
, fixed magnetic layer (pinned magnetic layer)
23
, antiferromagnetic layer
24
, and upper non-magnetic layer
25
such as Ta.
The lower non-magnetic layer
20
ensures that the free magnetic layer
21
formed on the lower non-magnetic layer
20
can have a uniform crystal orientations, and can have a low specific resistance. The free magnetic layer
21
and the fixed magnetic layer
23
are made of a Ni—Fe (nickel-iron) alloy. The antiferromagnetic layer
24
is a bias layer for making the magnetization of the fixed magnetic layer
23
uniformly occur in the Y-direction. That is, anisotropic exchange coupling occurs at the interface between the antiferromagnetic layer
6
and the fixed magnetic layer
23
, and as a result the fixed magnetic layer
23
is magnetized in the Y-direction (in the upward direction perpendicular to the drawing plane of
FIG. 14
) into a single magnetic domain. The antiferromagnetic layer
24
is made of an alloy such as Fe—Mn (iron-manganese), Ni—Mn (nickel-manganese), or Pt—Mn (platinum-manganese).
A longitudinal bias layer
4
such as a Co—Pt (cobalt-platinum) alloy is formed on both sides of the spin valve layer SV having the 6-layer structure described above in such a manner that the longitudinal bias layer is in contact at the contacting interface (V) with all six layers constituting the spin valve layer SV. On the longitudinal bias layer
4
, there is further disposed a layer made of a material having a small specific resistance, such as Cu (copper), Ta, or Cr (chromium).
In this thin-film magnetic head of the spin valve type, the longitudinal bias layer
4
is permanently magnetized in the X-direction, and the free magnetic layer
21
is magnetized in the X-direction by a magnetic field from the permanently magnetized longitudinal bias layer
4
. The fixed magnetic layer
23
is magnetized in the Y-direction (the upward direction perpendicular to the drawing plane) by the antiferromagnetic layer
24
. A steady-state current flows from the electrode layer
5
to the longitudinal bias layer
4
and further into the spin valve layer SV having the six-layer structure in the X-direction. If a magnetic field in the Y-direction is applied from a magnetic recording medium, the magnetization direction of the free magnetic layer
21
is inverted by this external magnetic field from the X-direction to the Y-direction. The electric resistance of the spin valve layer SV changes depending on the relationship between the magnetization direction of the free magnetic layer
21
and the magnetization direction of the fixed magnetic layer
23
. Therefore, it is possible to detect the leakage magnetic field from the magnetic recording medium by detecting the voltage drop associated with the stead

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