Chemistry: electrical and wave energy – Processes and products – Coating – forming or etching by sputtering
Reexamination Certificate
1999-10-28
2001-04-03
Kiliman, Leszek (Department: 1773)
Chemistry: electrical and wave energy
Processes and products
Coating, forming or etching by sputtering
C204S192340, C360S112000, C324S252000, C427S128000, C427S129000, C427S130000, C427S131000, C428S692100, C428S690000, C428S690000, C428S690000, C428S690000, C428S690000, C428S900000
Reexamination Certificate
active
06210543
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a combination MR (magnetoresistive)/inductive thin film magnetic head carried on, for example, a hard disk drive, and particularly to a thin film magnetic head in which materials of an upper core layer and a lower core layer are improved to improve magnetic characteristics, and a manufacturing method thereof.
2. Description of the Related Art
FIG. 15
is an enlarged sectional view showing a conventional thin film magnetic head as viewed from the side thereof opposite to a recording medium.
This thin film magnetic head comprises a reading head h
1
which employs the magnetoresistive effect and a writing inductive head h
2
, which are laminated on the trailing-side end surface of a slider which constitutes, for example, a floating head.
The reading head h
1
comprises a lower shielding layer
1
made of sendust, an Ni—Fe alloy (permalloy) or the like, a lower gap layer
2
made of a non-magnetic material such as Al
2
O
3
(aluminum oxide) or the like and formed on the lower shielding layer
1
, and a magnetoresistive element
3
deposited on the lower gap layer
2
. The magnetoresistive element
3
comprises three layers including a soft adjacent layer (SAL), a non-magnetic layer (SHUNT layer), and a magnetoresistive layer (MR layer) which are laminated in turn. Generally, the magnetoresistive layer comprises an Ni—Fe alloy (permalloy) layer, the non-magnetic layer comprises a tantalum layer, and the soft adjacent layer comprises an Ni—Fe—Nb alloy layer.
On both sides of the magnetoresistive layer
3
are formed hard bias layers serving as longitudinal bias layers. On the hard bias layers are formed main lead layers
5
made of a non-magnetic conductive material having low electric resistance, such as Cu (copper), W (tungsten) or the like. On the main lead layers
5
is further formed an upper gap layer
6
made of a non-magnetic material such as aluminum oxide or the like.
On the upper gap layer
6
is formed a lower core layer
20
by plating permalloy. In the inductive head h
2
, the lower core layer
20
functions as a leading-side core portion which gives a recording magnetic field to a recording medium. In the reading head h
1
, the lower core layer
20
functions as an upper shielding layer, and a gap length G
11
is determined by the gap between the lower shielding layer
1
and the lower core layer
20
.
On the lower core layer
20
are laminated a gap layer (non-magnetic material layer)
8
made of aluminum oxide or the like, and an insulation layer (not shown in the drawing) made of polyimide or a resist material, and a coil layer
9
patterned to a spiral form is provided on the insulation layer. The coil layer
9
is made of a non-magnetic conductive material having low electric resistance, such as Cu (copper) or the like. The coil layer
9
is surrounded by an insulation layer (not shown) made of polyimide or a resist material, and an upper core layer
21
made of a magnetic material such as permalloy is formed on the insulation layer by plating. The upper core layer
21
functions as the trailing-side core portion of the inductive head h
2
which gives a recording magnetic field to the recording medium.
As shown in
FIG. 15
, on the side opposite to the recording medium, the tip
21
a
of the upper core layer
21
is opposed to the upper side of the lower core layer
20
with the gap layer
8
therebetween to form a magnetic gap having a magnetic gap length G
12
which gives a magnetic field to the recording medium. On the upper core layer
21
is provided a protective layer
11
made of aluminum oxide or the like.
In the inductive head h
2
, when a recording current is supplied to the coil layer
9
, a recording magnetic field is applied to the upper core layer
21
and the lower core layer
20
from the coil layer
9
. In the magnetic gap, magnetic signals are recorded on the recording medium such as a hard disk by a leakage magnetic field between the lower core layer
20
and the upper core layer
21
.
FIG. 16
is an enlarged sectional view showing a conventional method of producing the lower core layer
20
.
As shown in
FIG. 16A
, a base layer
22
made of a magnetic material such as permalloy or the like is formed on the upper gap layer
6
by plating. On the base layer
22
is coated a resist solution, followed by exposure to form rectangular resist layers
23
on the base layer
22
. In
FIG. 16B
, magnetic material layers
20
and
24
made of permalloy or the like are formed, by plating, on portions of the base layer
22
where the resist layers
23
are not formed. The magnetic material layer
20
formed between the resist layers
23
is left behind as the lower core layer.
In
FIG. 16C
, the resist layers
23
are removed, and portions of the base layer
22
which are formed below the resist layers
23
are removed by ion milling. In
FIG. 16D
, a protective layer
25
made of a resist material is formed on the portions on the upper gap layer
6
where the resist layers
23
were removed, to cover the magnetic material layer
20
. In
FIG. 16E
, the magnetic material layers
24
and portions of the base layer
22
which are formed directly below the magnetic material layers
24
are removed by wet etching. In
FIG. 16F
, the protective layer
25
is removed to leave only the rectangular lower core layer
20
on the upper gap layer
6
with the base layer
22
therebetween.
The conventional thin film magnetic head shown in
FIG. 15
comprises the lower core layer
20
formed by plating permalloy and thus has the following problems.
(i) Since the lower core layer
20
(the upper shielding layer) is thick and has a substantially rectangular sectional shape, step portions A each having a corner are formed at both side ends of the lower core layer
20
. Therefore, it is difficult to form the gap layer
8
having a uniform thickness on the lower core layer
20
. Particularly, the thickness of the gap layer
8
is extremely small near the corners of the step portions A at both side ends of the lower core layer
20
, and thus an insulation failure easily occurs between the lower core layer
20
and the coil layer
9
.
Also, in order to increase the recording density, it is necessary to thin the gap layer
8
to decrease the gap length G
12
of the magnetic gap. However, when the gap layer is thinned, pin holes easily occur in the gap layer
8
near the step portions A.
(ii) Since the lower core layer
20
(the upper shielding layer) has a rectangular sectional shape, and the step portions A are formed at both side ends thereof, a difference in height is also formed in the surface of the gap layer
8
formed on the step portions A. Therefore, when the area of the lower core layer
20
is smaller than the region of the coil layer
9
, the coil layer
9
is formed on the step portions of the gap layer
8
, thereby making it difficult to form the coil layer
9
and easily causing defects in the coil layer
9
.
(iii) In order to increase the recording density of signals on the recording medium, and increase the magnetic writing frequency, it is necessary to improve the soft magnetic characteristics of the lower core layer
20
and the upper core layer
21
to impart low coercive force and high resistivity thereto. Although the saturation magnetic flux density is preferably as high as possible, particularly when the saturation magnetic flux density of the lower core layer
20
is lower than that of the upper core layer
21
so that magnetization of a leakage magnetic field between the lower core layer
20
and the upper core layer
21
is easily reversed, the density of signal writing on the recording medium can possibly be increased.
In the thin film magnetic head shown in
FIG. 15
, since the lower core layer
20
functions not only as a leading-side core portion for the inductive head h
2
but also as an upper shielding layer for the reading head h
1
, the lower core layer
20
must be provided with both the properties as a core and the properties as a shield.
In order to impr
Alps Electric Co. ,Ltd.
Brinks Hofer Gilson & Lione
Kiliman Leszek
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