Dynamic magnetic information storage or retrieval – Head – Core
Reexamination Certificate
2001-01-24
2003-11-18
Heinz, A. J. (Department: 2653)
Dynamic magnetic information storage or retrieval
Head
Core
Reexamination Certificate
active
06650502
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thin-film magnetic head wherein a coil layer is formed between core layers. More particularly, the present invention relates to a thin-film magnetic head and a method of manufacturing the head, which enables an upper core layer to be satisfactorily formed, is adaptable for a narrower track width, and can improve an overwrite characteristic and suppress the occurrence of write fringing.
2. Description of the Related Art
FIG. 30
is a vertical sectional view showing the structure of a conventional a thin-film magnetic head.
The thin-film magnetic head of
FIG. 30
is an inductive head for recording, which is disposed at a trailing-side end surface of a slider of a floating magnetic head, the slider floating in an opposed relation to a recording medium, e.g., a disk of a hard disk drive.
Numeral
1
denotes a lower core layer formed of a magnetic material such as an NiFe alloy. A gap layer
2
of a nonmagnetic material, such as Al
2
O
3
(alumina) or SiO
2
, is formed on the lower core layer
1
. An insulating layer
9
of a resist material or any other suitable organic material is formed on the gap layer
2
.
On the insulating layer
9
, a coil layer
4
is spirally formed using a conductive material having low electrical resistance, such as Cu. Note that the coil layer
4
is formed to surround a base end portion
6
b
of an upper core layer
6
(described later), but only a part of the coil layer
4
appears in FIG.
30
.
The coil layer
4
is covered by an insulating layer
5
of, e.g., an organic material, and the upper core layer
6
is formed on the insulating layer
5
by plating a magnetic material such as Permalloy. A fore end portion
6
a
of the upper core layer
6
is joined to the lower core layer
1
through the gap layer
2
on the side facing a recording medium, whereby a magnetic gap with a gap length GI is formed. The base end portion
6
b
of the upper core layer
6
is magnetically connected to the lower core layer
1
through a hole formed in the gap layer
2
.
The fore end portion
6
a
of the upper core layer
6
is formed such that its size in the direction of track width (X-direction as indicated in
FIG. 30
) is equal to a track width Tw. A recent trend toward a higher recording density requires the track width Tw to be reduced to a smaller value.
In such an inductive head for writing, when a recording current is applied to the coil layer
4
, a recording magnetic field is induced in the lower core layer
1
and the upper core layer
6
. Then, a magnetic signal is recorded on a recording medium, such as a disk of a hard disk drive, with a fringing magnetic field through a magnetic gap area between the lower core layer
1
and the fore end portion
6
a
of the upper core layer
6
.
The upper core layer
6
of the thin-film magnetic head described above is formed by the so-called frame plating method.
FIG. 31
shows one of successive steps for forming the upper core layer
6
.
As shown in
FIG. 31
, after forming the coil layer
4
and covering the coil layer
4
by the insulating layer
5
, an undercoat layer
7
of a magnetic material, e.g., an NiFe alloy, is formed over an area extending from an exposed portion of the gap layer
2
near a fore end of the head to the insulating layer
5
.
Then, after forming a resist layer
8
on the undercoat layer
7
, a pattern corresponding to the shape of the upper core layer
6
is formed on the resist layer
8
by exposure and development, and a layer of a magnetic material (i.e., the upper core layer
6
) is formed by plating on the undercoat layer
7
that is exposed through the formed pattern. After the plating, by removing the resist layer
8
remained, the upper core layer
6
is completed as shown in FIG.
30
.
However, the conventional thin-film magnetic head has accompanied the following problems in forming the upper core layer
6
from the structural point of view.
As shown in
FIG. 31
, since the insulating layer
9
, the coil layer
4
and the insulating layer
5
are formed on the lower core layer
1
one above another, the layered films are heaped from the surface of the lower core layer
1
with a thickness H3. Therefore, the resist layer
8
has a very large film thickness H1 in an area of the lower core layer
1
on which the coil layer
4
, etc. are not formed, i.e., in a part of the resist layer
8
which is formed on the lower core layer
1
near its fore end. On the contrary, the resist layer
8
formed on the insulating layer
5
has a small film thickness H2.
For that reason, it is hard to precisely adjust the depth of a focus in the steps of exposure and development for patterning the resist layer
8
, thus resulting in a difficulty in forming the pattern of the upper core layer
6
in a predetermined shape on the resist layer
8
and hence deterioration of pattern accuracy.
In particular, as described above, the fore end portion
6
a
of the upper core layer
6
is formed to have a width equal to the track width Tw. To realize a higher recording density in future, the track width Tw must be realized at a smaller value.
Further, as described above, the film thickness H1 of a portion of the resist layer
8
, in which the fore end portion
6
a
of the upper core layer
6
is to be formed, is very large. The large depth of a focus is therefore required in the steps of exposure and development to form a pattern in the portion of the resist layer
8
having the film thickness Hi. However, the large depth of a focus deteriorates resolution, and the fore end portion
6
a
of the upper core layer
6
is formed with a width larger than the track width Tw of a predetermined size.
Moreover, because of a heap defined by the insulating layers
5
,
9
and the coil layer
4
which are formed on the lower core layer
1
, the film thickness H1 of the resist layer
8
is not uniform and an adverse effect such as diffused reflection is more likely to occur during exposure and development. It is hence impossible to form the upper core layer
6
into a predetermined shape. Particularly, it is impossible to form the fore end portion
6
a
of the upper core layer
6
so as to have a width equal to the track width Tw of a predetermined size.
To overcome the above-mentioned problems, there is proposed, for example, a method of forming the insulating layers
5
,
9
and the coil layer
4
at a position shifted in the height direction (Y-direction as indicated in the drawings), and increasing a length T1 of the area of the lower core layer
1
near its fore end on which the coil layer
4
, etc. are not formed. Thus, the method is intended to form the fore end portion
6
a
of the upper core layer
6
to have a width, which is equal to the predetermined track width Tw, by reducing the film thickness of the resist layer
8
formed on the area of the length T1 to a value smaller than in the case shown in FIG.
31
.
Even with the above-mentioned method, however, it is unavoidable that the film thickness of the resist layer
8
is not uniform. Accordingly, a difficulty still remains in forming the upper core layer
6
into a predetermined shape due to such an adverse effect as diffused reflection occurred during exposure and development.
Further, when the coil layer
4
, etc. are formed at a position shifted in the height direction (Y-direction as indicated in the drawings), the fore end portion
6
a
of the upper core layer
6
can be formed to have a larger length. However, since the fore end portion
6
a
of the upper core layer
6
is in the elongate form of the track width Tw, magnetic saturation is more likely to occur in the fore end portion
6
a
, and deterioration of the OW characteristic is caused.
The term “overwrite” means an operation of writing data over data previously written in the same position. The OW characteristic is evaluated by the steps of recording data at low frequency, overwriting the recorded data with new data at high frequency, and measuring how much a remaining output of a recording signal at the low
Oki Naruaki
Yazawa Hisayuki
Alps Electric Co. ,Ltd.
Blouin Mark
Brinks Hofer Gilsor & Lione
Heinz A. J.
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