Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
1999-12-07
2002-02-05
Renner, Craig A. (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
Reexamination Certificate
active
06344951
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a substrate comprising magnetoresistive elements exhibiting a magnetoresistive effect, and a monitor element which is formed in the same structure as the magnetoresistive elements, for measuring the direct-current resistance value of the magnetoresistive element, wherein the structure of gap layers formed on and below the monitor element is improved to prevent a short circuit of the monitor element in measurement of direct-current resistance. The present invention also relates to a method of manufacturing the substrate, and a method of processing the substrate.
2. Description of the Related Art
FIG. 34
is a partial sectional view of a conventional substrate comprising magnetoresistive elements as viewed from the ABS side.
As shown in
FIG. 34
, a base insulating layer
13
made of Al
2
O
3
is formed on a substrate
1
made of, for example, Al
2
O
3
—TiC (alumina-titanium carbide). A lower shielding layer
12
made of a magnetic material such as an NiFe alloy or the like is formed on the base insulating layer
13
, and a lower gap layer
3
made of an insulating material such as Al
2
O
3
or the like is formed on the lower shielding layer
12
.
Referring to
FIG. 34
, a plurality of magnetoresistive elements
4
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
3
(the drawing does not show an inductive head).
In
FIG. 34
, a multilayer film
6
comprising a spin valve film (a GMR element), for example, composed of an antiferromagnetic layer, a pinned magnetic layer, a nonmagnetic conductive layer, and a free magnetic layer is formed at the center of each of the magnetoresistive elements
4
. The pin valve film serves as an element using the giant magnetoresistive effect so that electric resistance changes with changes in a leakage magnetic field from a recording medium to detect recording signals. As shown in
FIG. 34
, electrode layers
7
made of a nonmagnetic metal material such as chromium (Cr) or the like are formed on both sides of the multilayer film
6
.
The monitor element
5
is also formed in the same structure as the magnetoresistive elements
4
. Namely, a multilayer film
8
exhibiting the magnetoresistive effect is formed at the center of the monitor element
5
, and electrode layers
9
made of chromium (Cr) are formed on both sides of the multilayer film
8
. The magnetoresistive elements
4
and the monitor element
5
are simultaneously formed on the lower gap layer
3
by pattering.
As shown in
FIG. 34
, an upper gap layer
10
made of an insulating material such as Al
2
O
3
is formed on the magnetoresistive elements
4
and the monitor element
5
, and an upper shielding layer
11
made of a NiFe alloy (permalloy) is further formed on the upper gap layer
10
.
The monitor element
5
functions as a so-called processing monitor provided for setting a predetermined value of direct-current resistance (DCR) of the plurality of magnetoresistive elements
4
formed in alignment with the monitor element
5
. After the monitor element
5
plays the role of the processing monitor, it is removed.
In order to set the direct-current resistance of the magnetoresistive elements
4
to the predetermined value, the ABS side (in the X direction shown in the drawing) of the magnetoresistive elements
4
and the monitor element
5
is ground (height setting), while measuring the direct-current resistance between the electrode layers
9
which constitute the monitor element
5
. Then, when a predetermined direct-current valve is obtained, grinding of the ABS side is finished.
As described above, since the plurality of magnetoresistive elements
4
and the monitor element
5
have the same structure and are formed in a line parallel to the ABS side, the magnetoresistive elements
4
and the monitor element
5
have the same dimension in the height direction (the Y direction shown in FIG.
34
). Therefore, the plurality of magnetoresistive elements
4
and the monitor element
5
can be set to the same direct-current resistance value by grinding the ABS side.
Namely, when the direct-current resistance of the monitor element
5
reaches a predetermined value by grinding, the direct-current resistance of the magnetoresistive elements also reaches the predetermined value.
However, in grinding the ABS side of the magnetoresistive elements
4
and the monitor element
5
while measuring the direct-current resistance between the electrode layers
9
which constitute the monitor element
5
, the shielding layers
11
and
12
and the-electrode layers
9
, which are exposed from the ABS side, cause smearing (sags) to cause electrical contact between the electrode layers
7
and the shielding layers
11
and
12
, thereby short-circuiting the electrode layers
7
and the shielding layers
11
and
12
.
For example, where sags
12
a occur in the lower shielding layer
12
formed below the monitor element
5
, as shown in
FIG. 35
, electrical connection occurs between the sags
12
a and the electrode layers
9
. As a result, the direct-current resistance (DCR) between the electrode layer
9
of the monitor element
5
cannot be precisely measured, and thus the dimensions of the magnetoresistive elements
4
in the height direction (the Y direction shown in
FIG. 35
) cannot be set to a value with which the direct-current resistances are a predetermined value.
Particularly, it is confirmed that the above problem significantly occurs when the gap length G
1
determined by the thickness of the lower gap layer
3
, and the gap length G
2
determined by the thickness of the upper gap layer
10
are 700 angstroms or less.
In grinding the ABS side, sags
12
a
occur not only between the electrode layers
9
of the monitor element
5
and the shielding layers
11
and
12
, but also in the electrode layers
7
of the magnetoresistive elements
4
, and in the lower shielding layer
12
formed below the magnetoresistive elements
4
, for example, as shown in
FIG. 35
, causing electrical connection between the electrode layers
7
of the magnetoresistive elements
4
and the shielding layer
12
. However, after grinding is finished, the ABS side of the magnetoresistive elements
4
is lapped to remove the sags of the electrode layers
7
and the shielding layers
11
and
12
, thereby maintaining an electrical insulation state between the electrode layers
7
of the magnetoresistive elements
4
and the shielding layers
11
and
12
in a magnetic head product.
SUMMARY OF THE INVENTION
The present invention has been achieved for solving the above problem, and an object of the present invention is to provide a substrate comprising magnetoresistive elements, which is capable of preventing a short circuit between electrode layers of a monitor element and shielding layers, and precisely measuring direct-current resistance during height setting processing, a method of manufacturing the substrate, and a method of processing the substrate.
The present invention provides a substrate comprising a lower shielding layer formed on the substrate, a lower gap layer formed on the lower shielding layer, a plurality of magnetoresistive elements each comprising a multilayer film exhibiting the magnetoresistive effect and electrode layers conducting to the multilayer film, and a processing monitor element having substantially the same structure as the magnetoresistive elements, these elements being arranged in a line on the lower gap layer, wherein besides the lower gap layer, an insulating layer is formed between the monitor element and the lower shielding layer to be exposed from the ABS side so that the distance between the monitor element and the lower shield layer exposed from the ABS side is larger than the distance between the magnetoresistive elements and the lower shield layer exposed from the ABS side.
In the present invention, the total thickness of the lower gap layer and the insulating-layer is preferably 700 angstroms or more.
A typ
Sato Kiyoshi
Sugai Katsuya
Alps Electric Co. ,Ltd.
Brinks Hofer Gilson & Lione
Renner Craig A.
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