Dynamic magnetic information storage or retrieval – Head – Core
Reexamination Certificate
2001-01-04
2004-05-04
Heinz, A. J. (Department: 2653)
Dynamic magnetic information storage or retrieval
Head
Core
Reexamination Certificate
active
06731457
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thin-film magnetic head having a coil layer provided between core layers. In particular, the present invention relates to a thin-film magnetic head suitable for narrower track widths and to a method for making the thin-film magnetic head in which the front end of the upper core layer can be precisely formed so as to have a track width Tw.
2. Description of the Related Art
FIG. 24
is a longitudinal cross-sectional view showing a structure of a conventional thin-film magnetic head. This thin-film magnetic head is an inductive write head and is mounted at the trailing end of a slider of a floating magnetic head which opposes recording media such as hard disks.
The thin-film magnetic head has a lower core layer
1
composed of a magnetic material such as a NiFe alloy. A gap layer
3
composed of a nonmagnetic material, such as alumina (Al
2
O
3
) or SiO
2
, is formed on the lower core layer
1
. Furthermore, an insulating layer
7
composed of an organic material such as a resist material is formed on the gap layer
3
.
A spiral coil layer
4
composed of a conductive material having low electrical resistance such as copper is formed on the insulating layer
7
. The coil layer
4
is provided so as to surround a base end
6
b
of an upper core layer
6
, although only part of the coil layer
4
is depicted in FIG.
24
. The coil layer
4
is covered with a coil-insulating layer
5
composed of an organic material or the like. The upper core layer
6
is formed on the coil-insulating layer
5
by plating a magnetic material such as Permalloy. A front end
6
a
of the upper core layer
6
is jointed to the lower core layer
1
with the gap layer
3
provided therebetween at a face opposing a recording medium to define a magnetic gap having a gap length Gl. The base end
6
b
of the upper core layer
6
is magnetically coupled with the lower core layer
1
via a hole formed in the gap layer
3
.
The width of the front end
6
a
of the upper core layer
6
in the track width direction (X direction in the drawing) defines a track width Tw. Trends toward recent high-density recording require the formation of a smaller track width Tw.
In the inductive write head, a recording current applied to the coil layer
4
induces a recording magnetic field to the lower core layer
1
and the upper core layer
6
. A leakage magnetic field from the magnetic gap portion between the lower core layer
1
and the front end
6
a
of the upper core layer
6
is recorded on a recording medium such as a hard disk as a magnetic signal.
The upper core layer
6
of the thin-film magnetic head is formed by a frame plating process.
FIG. 25
shows a step for forming the upper core layer
6
. The gap layer
3
is formed on the lower core layer
1
, and the insulating layer
7
is formed on the gap layer
3
with a predetermined gap depth T1 in the height direction (Y direction in the drawing) from the face opposing a recording medium. Next, the coil layer
4
is formed on the insulating layer
7
. After the coil layer
4
is covered by the coil-insulating layer
5
, a plating underlayer
9
composed of a magnetic material such as a NiFe alloy is formed over the exposed front portion of the gap layer
3
and the coil-insulating layer
5
.
A resist layer
8
is formed on the plating underlayer
9
and is exposed and developed to form a pattern of the upper core layer
6
on the resist layer
8
. A magnetic layer is formed by plating on the exposed plating underlayer
9
and the remaining resist layer
8
is removed. The upper core layer
6
shown in
FIG. 24
is thereby completed.
In the above conventional thin-film magnetic head, the formation of the upper core layer
6
has the following problems.
As shown in
FIG. 25
, a protrusion having a height H3 from the surface of the gap layer
3
is formed by depositing the insulating layer
7
, the coil layer
4
, and the coil-insulating layer
5
on the lower core layer
1
. When the resist layer
8
is coated on the plating underlayer
9
, the thickness H1 of the resist layer
8
is significantly large on the front portion of the lower core layer
1
. Moreover, the thickness of the resist layer
8
is not uniform.
Thus, focusing in the exposure and develop step of the resist layer
8
is difficult, and thus, a precise pattern of the upper core layer
6
cannot be formed in the resist layer
8
. Accordingly, the uneven thickness causes a decrease in precision of the patterning.
The front end
6
a
of the upper core layer
6
is defined by the track width Tw as described above. To satisfy future trends towards high-density recording, the track width Tw must be smaller. Since the thickness H1 of the resist layer
8
is significantly large at a portion to form the front end
6
a
of the upper core layer
6
, a large focal depth is required in the exposure and develop step to form a pattern in the resist layer
8
having the thickness H1. Such a large focal depth requires light having a shorter wavelength in the exposure and develop step. The light having the shorter wavelength causes a decrease in resolution and the width of the front end
6
a
of the resulting upper core layer
6
is inevitably larger than the track width Tw.
Since the thickness of the resist layer
8
is not uniform due to the protrusion formed by the coil-insulating layer
5
, the insulating layer
7
, and the coil layer
4
on the lower core layer
1
, irregular reflection readily occurs in the exposure and develop step. Thus, the pattern formed in the resist layer
8
is distorted. As a result, the front end
6
a
of the upper core layer
6
cannot have the track width Tw.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a thin-film magnetic head which has a front end, defined by the track width Tw, of an upper core layer and can be used for narrower tracks.
It is another object of the present invention to provide a method for making the same.
An aspect of the present invention relates to a thin-film magnetic head comprising a lower core layer; a lower magnetic pole layer formed independently of or integrally with the lower core layer; a nonmagnetic gap layer extending from a face opposing a recording medium on the lower magnetic pole layer; an upper core layer in contact with the upper face of the gap layer; and a coil layer lying behind the lower magnetic pole layer in the height direction, the coil layer being covered with a coil-insulating layer and inducing a recording magnetic field in the lower core layer and the upper core layer; wherein the upper core layer in contact with the gap layer has a track width Tw at an exposed face opposing a recording medium, and the upper core layer extends on the coil-insulating layer.
This configuration reduces the protrusion of the surface for forming the upper core layer compared to conventional configurations, and precisely forms the front end with the track width Tw of the upper core layer within a predetermined range. Since the lower magnetic pole layer is formed on the lower core layer, the coil layer is formed on the lower core layer which is indented from the surface of the lower magnetic pole layer. The upper core layer is formed over the lower magnetic pole layer and the coil-insulating layer covering the coil layer. Thus, the protrusion of the coil-insulating layer is determined based on the surface of the gap layer formed on the lower magnetic pole layer.
In contrast, a lower magnetic pole layer is not formed on a lower core layer in conventional configurations. Thus, the protrusion of the coil-insulating layer is determined based on the gap layer formed on the lower core layer.
Accordingly, the protrusion of the coil-insulating layer in the present invention can be reduced by a the thickness of the lower magnetic pole layer formed at least on the lower core layer. As a result, the thickness of a resist layer used in the formation of the upper core layer can be reduced in the vicinity of the front end having a track width Tw. Moreo
Arai Takashi
Morita Sumihito
Oki Naruaki
Alps Electric Co. ,Ltd.
Heinz A. J.
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