Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
2000-11-10
2003-12-16
Vo, Peter (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C029S603110, C029S603130, C029S603150, C029S603160, C029S603170, C029S605000, C360S121000, C360S123090, C360S125330, C451S005000, C451S041000
Reexamination Certificate
active
06662433
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is a divisional of application Ser. No. 09/337,425, filed on Jun. 21, 1999, which relates to a thin film magnetic head in which a recording head (inductive magnetic head) and a reproducing head (magnetoresistive head) are combined, and more particularly, to a thin film magnetic head in which the tip and the vicinity thereof of an upper core layer can be formed in a predetermined shape, enabling the track to be narrowed, and to a method of fabricating the same.
2. Description of the Related Art
FIG. 11
is a longitudinal sectional view of a conventional thin film magnetic head.
The thin film magnetic head is provided on the trailing end of a slider of a floating type magnetic head which faces a recording medium such as a hard disk, and is a combined thin film magnetic head in which a magnetoresistive head for reproducing, using magnetoresistance, and an inductive magnetic head for recording, are laminated.
A lower shielding layer
1
is composed of a magnetic material such as an NiFe alloy (permalloy), and a magnetoresistive element layer
2
is formed on the lower shielding layer
1
with a first gap layer (not shown in the drawing) therebetween. An upper shielding layer
3
, which is composed of a magnetic material such as an NiFe alloy, is formed on the magnetoresistive element layer
2
. As described above, the thin film magnetic head shown in
FIG. 11
is a combined thin film magnetic head in which a magnetoresistive head and an inductive magnetic head are laminated, and the upper shielding layer
3
also functions as a lower core layer of the inductive magnetic head. Hereinafter, the layer represented by numeral
3
is referred to as a lower core layer.
A gap layer
4
(second gap layer) composed of a nonmagnetic material such as aluminum oxide (Al
2
O
3
) or silicon dioxide (SiO
2
) is formed on the lower core layer
3
. An insulating layer
5
(first insulating layer) composed of a resist or other organic material is formed on the gap layer
4
.
A coil layer
6
, composed of a conductive material having low electrical resistance, such as Cu, is spirally formed on the insulating layer
5
. Although the coil layer
6
is formed so as to go around a base
8
b
of an upper core layer
8
, which will be described later, only a portion of the coil layer
6
is shown in FIG.
11
.
The coil layer
6
is covered by an insulating layer
7
(second insulating layer) composed of an organic material or the like, and the upper core layer
8
is formed on the insulating layer
7
by plating a magnetic material such as a permalloy. The tip
8
a
of the upper core layer
8
is joined to the lower core layer
3
with the gap layer
4
therebetween at the section facing a recording medium to form a magnetic gap having a gap length Gl. The base
8
b
of the upper core layer
8
is magnetically connected to the lower core layer
3
through a hole made in the gap layer
4
.
In the inductive magnetic head for writing, when a recording current is applied to the coil layer
6
, a recording magnetic field is induced in the lower core layer
3
and the upper core layer
8
, and a magnetic signal is recorded onto a recording medium such as a hard disk by means of a leakage magnetic field from the magnetic gap between the lower core layer
3
and the tip
8
a
of the upper core layer
8
.
In the thin film magnetic head shown in
FIG. 11
, the coil layer
6
has a double-layered structure. The double-layered structure is employed for the purposes of enhancing writing efficiency by shortening the magnetic path formed over the lower core layer
3
and the upper core layer
8
, and reducing inductance.
FIG. 12
is a longitudinal sectional view which shows a step of fabricating the upper core layer
8
of the thin film magnetic head shown in FIG.
11
.
The upper core layer
8
of the thin film magnetic head shown in
FIG. 11
is formed by frame plating. As shown in
FIG. 12
, after the coil layer
6
is formed and is covered by the insulating layer
7
, an underlying layer
9
composed of a magnetic material such as an NiFe alloy is formed from on the gap layer
4
, which is exposed around the tip, to on the insulating layer
7
.
Next, after a resist layer
10
is formed on the underlying layer
9
, a pattern of the upper core layer
8
is formed on the resist layer
10
by exposure and development, and a magnetic material layer (upper core layer
8
) is formed by plating on the section in which the resist
10
is removed and the underlying layer
9
is exposed. When the remaining resist layer
10
is removed, the upper core layer
8
is completed. In the final step, by removing the thin film laminate on the left side of the line A—A (shown by dotted lines in the drawing), the thin film magnetic head having the shape shown in
FIG. 11
can be obtained.
However, in the structure of the conventional thin film magnetic head as shown in
FIG. 11
, when the upper core layer
8
is formed by frame plating, narrowing of the track cannot be realized.
As shown in
FIG. 11
, by forming the coil layer
6
having a double-layered structure, the total thickness of the insulating layers
5
and
7
which cover the coil layer
6
is increased, and in such a state, as shown in
FIG. 12
, when the resist layer
10
is formed from on the gap layer
4
around the tip in which the insulating layers
5
and
7
are not formed to on the insulating layer
7
, the thickness tl of the resist layer
10
formed on the gap layer
4
is significantly increased. On the gap layer
4
, as shown in
FIG. 11
, the tip
8
a
of the upper core layer
8
is formed. The tip
8
a
is narrowly shaped as shown in the plan view of
FIG. 13
, and the width of the tip
8
a
determines a track width Tw. In particular, as recording density is increased, the track width Tw must be further decreased, and the pattern of the resist layer
10
must be formed with particular precision when the tip
8
a
and its vicinity of the upper core layer
8
are formed.
However, as shown in
FIG. 12
, since the thickness tl of the resist layer
10
on the gap layer
4
, in which the tip
8
a
of the upper core layer
8
is to be formed, is significantly increased, when the wavelength of a light source for exposure is decreased and the depth of focus is increased, resolution (resolving power) is degraded and the track width Tw having a predetermined size cannot be obtained; it is thus not possible to meet the need for narrowing of a gap. In order to improve resolution, a smaller depth of focus is better.
Another reason for not being able to realize narrowing of the track is that since the thickness tl of the resist layer
10
formed on the gap layer
4
differs greatly from that of the resist layer
10
formed on the insulating layer
7
, irregular reflection may occur during exposure and development because of differences in focus.
FIG. 14
is a longitudinal sectional view of another conventional thin film magnetic head.
In
FIG. 14
, a lower shielding layer
11
is partially formed only around the tip, and a magnetoresistive element layer
12
is formed on the lower shielding layer
11
. A lower core layer
13
(upper shielding layer) is formed from on the magnetoresistive element layer
12
and to in the rear of the lower shielding layer
11
. A coil layer
14
is formed on the lower core layer
13
, and an upper core layer
15
is formed so as to face the lower core layer
13
at the tip and to extend over an insulating layer
17
formed on the coil layer
14
.
In the conventional example, the lower shielding layer
11
is partially formed only around the tip, and in the rear of the lower shielding layer
11
, the lower core layer
13
is lowered to the same level as that of the lower shielding layer
11
through an inclined plane
13
a
. As shown in
FIG. 14
, the coil layer
14
is formed from on the inclined plane
13
a
to on the lower core layer
13
lying in the rear of the inclined plane
13
a
. Therefore, the insulating layer
17
is formed on the coil layer
14
, being swollen
Alps Electric Co. ,Ltd.
Brinks Hofer Gilson & Lione
Kim Paul
Vo Peter
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