Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
2000-05-09
2002-08-13
Cao, Allen (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
Reexamination Certificate
active
06433971
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thin film magnetic head comprising a magnetoresistive element exhibiting magnetoresistance, and a substrate comprising a monitor element used in a step before the thin film magnetic head is manufactured. Particularly, the present invention relates to a thin film magnetic head which can decrease the occurrence of smearing in order to comply with the demand for gap narrowing accompanying an increase in recording density in future, and a substrate for forming the thin film magnetic head thereon.
2. Description of the Related Art
FIG. 5
is a partial plan view of a substrate on which a conventional thin film magnetic head is formed, and
FIG. 6
is a sectional view taken along line VI—VI in FIG.
5
. In
FIG. 5
, an upper gap layer
11
and an upper shielding layer
12
are not shown.
As shown in
FIG. 6
, a lower shielding layer
3
made of a magnetic material such as a NiFe alloy or the like is formed on a substrate
1
comprising, for example, Al
2
O
3
—TiC (alumina-titanium carbide), and a lower gap layer
4
made of an insulating material such as Al
2
O
3
or the like is further formed on the lower shielding layer
3
.
Referring to
FIG. 6
, a plurality of magnetoresistive elements
13
and a monitor element
5
are formed in a line in the ABS direction (the X direction shown in the drawing) on the lower gap layer
4
.
Furthermore, a multilayer film
7
comprising, for example, an antiferromagnetic layer, a pinned magnetic layer, a nonmagnetic conductive layer, and a spin-valve film (a GMR element) comprising a free magnetic layer is formed at the center of each of the magnetoresistive elements
13
. The spin-valve film serves as an element which utilizes magnetoresistance so that the electric resistance changes with a change in a leakage magnetic field from a recording medium to detect a recording signal. As shown in
FIG. 6
, electrode layers
8
made of a nonmagnetic metal material such as Cr (chromium) or the like are formed on both sides of the multilayer film
7
.
The monitor element
5
also has the same structure as the magnetoresistive elements
13
. Namely, a multilayer film
9
exhibiting magnetoresistance is formed at the center of the monitor element
5
, and electrode layers
10
made of Cr (chromium) or the like are formed on both sides of the multilayer film
9
. The magnetoresistive elements
13
and the monitor element
5
are simultaneously formed in a pattern on the lower gap layer
4
.
As shown in
FIG. 5
, a pair of the electrode layers
8
constituting each of the magnetoresistive element
13
, and a pair of the electrode layers
10
constituting the monitor element
5
are formed symmetrically on both sides of the multilayer films
7
and
9
, respectively. The electrode layers
8
and
10
are exposed from the ABS.
As shown in
FIG. 5
, in the electrode layers
8
or
10
formed on both sides of each of the multilayer film
7
or
9
exposed from the ABS, the width dimension from one of the electrodes layers
8
or
10
to the other is T
1
. For example, the width dimension T
1
is conventionally 80 &mgr;m or more.
As shown in
FIG. 6
, an upper gap layer
11
made of an insulating material such as Al
2
O
3
or the like is formed on the magnetoresistive elements
13
and the monitor element
5
, and an upper shielding layer
12
made of a NiFe alloy (permalloy) or the like is further formed on the upper gap layer
11
.
The length dimension from the lower gap layer
4
to the upper gap layer
11
is defined as a magnetic gap G
1
.
The monitor element
5
serves as a processing monitor provided for setting the DC resistance (DCR) of each of the plurality of magnetoresistive elements
13
, which are formed in the same line as the monitor element
5
, to a predetermined value. After the monitor element
5
plays the role as the processing monitor, the monitor element is removed.
In order to set the DC resistance (DCR) of each of the magnetoresistive elements
13
to the predetermined value, the ABS-side surfaces (refer to
FIG. 5
) of the magnetoresistive elements
13
and the monitor element
5
are ground (height controlling) while measuring the DC resistance between the electrode layers
10
constituting the monitor element
5
. Once a predetermined DC resistance value is obtained, grinding of the ABS side is finished.
Since the plurality of magnetoresistive elements
13
have the same structure and are formed in a line parallel to the ABS, as described above, when the DC resistance of the monitor element
5
reaches a predetermined value by grinding, the DC resistance value of each of the magnetoresistive elements
13
also reaches the predetermined value.
However, the gap is narrowed accompanying an increase in the recording density, and thus in grinding the ABS-side surfaces of the magnetoresistive elements
13
and the monitor element
5
while measuring the DC resistance between the electrode layers
10
constituting the monitor element
5
, smearing occurs between the shielding layers
3
and
12
and the electrode layers
10
of the monitor element
5
, which are exposed from the ABS, to cause a problem in which the electrode layers
10
are electrically connected to the shielding layers
3
and
12
. Therefore, the DC resistance (DCR) between the electrode layers
10
of the monitor element
5
cannot be precisely measured, and thus the length dimension of the magnetoresistive elements
13
in the height direction (the Y direction shown in the drawing) cannot be set to a value with which the predetermined resistance value is obtained.
The smearing also occurs between the electrode layers
8
of each of the magnetoresistive elements
13
and the shielding layers
3
and
12
.
Since the portion of the substrate where the magnetoresistive elements
13
are formed is used for products as thin film magnetic heads after the DC resistance of each of the magnetoresistive elements
13
is set to the predetermined value, the work of removing smearing between the electrode layers
8
and the shielding layers
3
and
12
in each magnetoresistive element
3
must be carried out before products of thin film magnetic heads are manufactured.
However, with an excessively narrow gap, it is very difficult to appropriately remove smearing which occurs in narrow magnetic gap G
1
, thereby causing the problem of deteriorating the yield of thin film magnetic heads.
Particularly, a conventional element has a structure in which each of the electrode layer pairs
8
and
10
exposed from the ABS have a large width dimension T
1
, and thus smearing readily occurs in the electrode layers
8
and
10
in controlling the height as the gap is increasingly narrowed.
SUMMARY OF THE INVENTION
The present invention has been achieved for solving the above problems, and it is an object of the present invention to provide a thin film magnetic head in which the shape of electrode layers is improved for decreasing smearing between the electrode layers and shielding layers in controlling the height, thereby making adaptable to gap narrowing, and provide a substrate for forming the magnetic head thereon.
The present invention provides a thin film magnetic head comprising a lower shielding layer, a magnetoresistive element formed on the lower shielding layer with a lower gap layer provided therebetween and comprising a multilayer film exhibiting magnetoresistance, a pair of bias layers formed on both sides of the multilayer film, for applying a bias magnetic field to the multilayer film, and a pair of electrode layers formed on the bias layers to conduct to the multilayer film, and an upper shielding layer formed on the magnetoresistive element with an upper gap layer provided therebetween, wherein each of the electrode layers and the bias layers comprises a front end region with a predetermined length dimension from the ABS in the height direction, and a back end region formed in the height direction to extend from the boundary with the front end region in the track width direction.
In the above
Sato Kiyoshi
Sugai Katsuya
Alps Electric Co. ,Ltd.
Brinks Hofer Gilson & Lione
Cao Allen
LandOfFree
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