Stock material or miscellaneous articles – Composite – Of inorganic material
Reexamination Certificate
2001-01-24
2002-11-05
Resan, Stevan A. (Department: 1773)
Stock material or miscellaneous articles
Composite
Of inorganic material
C360S327220
Reexamination Certificate
active
06475649
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method of making a magnetic resistance element, which is employed in a magnetic head of a magnetic disc drive unit, etc.
The magnetic resistance element is capable of detecting a magnetic field by the magnetic resistance effect, and it is employed in the magnetic head of the magnetic disc drive unit, which is capable of reading high density data from a magnetic disc. These days, the disc drive units are made smaller in size but they have large capacity of memory, further high power magnetic heads are required, so the magnetic resistance elements, in which magnetic domains are controlled by ferromagnetic layers, draw engineers' attention.
The magnetic resistance element, in which the magnetic domains are controlled by the ferromagnetic layers, is shown in FIG.
6
. An insulating layer
10
is made of an insulator, e.g., alumina, silicon oxide. A first magnetizable layer
12
is formed on the insulating layer
10
; a non-magnetizable layer
14
is formed on the first magnetizable layer
12
; and a second magnetizable layer
16
is formed on the non-magnetizable layer
14
. One of the first and the second magnetizable layers
12
and
16
is a magnetic resistance layer (MR layer), and the other is a bias layer (SAL layer). The SAl layer applies a bias magnetic field to the MR layer so as to detect magnetic data with high sensivity. The non-magnetizable layer
14
is provided between the first and the second magnetizable layers
12
and
16
as a shielding layer. A Ni—Fe layer is employed as the MR layer; an alloy layer, which is made of two or more selected from a group of Ni, Fe, Cr, Rh, Co, etc., is employed as the SAL layer; and a layer made of Ta, Ti or Cr is employed as the non-magnetizable layer.
Planar shapes of the first magnetizable layer
12
, the non-magnetizable layer
14
and the second magnetizable layer
16
are rectangular shapes; their side faces are formed into slope faces on which terminals
18
are formed; and they constitute a main part of the magnetic resistance element. The terminals
18
are formed on the slope faces of the main part. Since the terminals
18
are formed on the slope faces, the contact area between the terminals
18
and the first and the second magnetizable layers
12
and
16
can be broader, so that the resistance of the magnetic resistance element can be reduced.
A conventional method of making the magnetic resistance element is shown in
FIGS. 7A-7C
. In
FIG. 7A
, the insulating layer
10
, the first magnetizable layer
12
, the non-magnetizable layer
14
and the second magnetizable layer
16
are formed on a substrate, e.g., a ceramic member. The layers can be formed, in said order, by sputtering.
As shown in
FIG. 6
, in the case of the magnetic resistance element of the magnetic head, etc., the terminals
18
are formed on the side slope faces. Thus, a resist layer
20
, which is formed into a prescribed shape, is formed on an upper face of the second magnetizable layer
16
, which is the uppermost layer as a mask, then the layers are etched, with the mask of the resist layer
20
, by ion milling, as shown in FIG.
7
A. In
FIG. 7B
, the slope faces, on which the terminals
18
(FIG. C) are formed, are formed in the first magnetizable layer
12
, the non-magnetizable layer
14
and the second magnetizable layer
16
by ion milling. A sectional shape of the resist layer
20
has undercut sections, namely a wider section
20
a
is supported by a supporting section
20
b
, which is narrower than the wider section
20
a
. When ions are radiated by ion milling, the slope faces for the terminals
18
are formed by partially shading the ion radiation by the wider section
20
a
; the terminals
18
can be formed on each slope face.
To form the slope faces in the first magnetizable layer
12
, the non-magnetizable layer
14
and the second magnetizable layer
16
by ion milling, they are gradually etched from the second magnetizable layer
16
toward the lower layers. In an are alocated outside of the slope faces on which the terminals
18
are formed, the insulating layer
10
is exposed, so the surface of the insulating layer
10
is slightly overetched, by ion milling, so as to leave no layers on the insulating layer
10
. In
FIG. 7B
, a symbol “L” stands for depth of overetching the insulating layer
10
.
In the conventional method, to correctly etch the first magnetizable layer
12
, the non-magnetizable layer
14
and the second magnetizable layer
16
by ion milling, the etching is stopped on the basis of the operator's visual observation or on the basis of the time required time to completely remove the first magnetizable layer
12
, which has been previously known. Therefore, overetching of the insulating layer
10
cannot be avoided so as to completely remove the first magnetizable layer
12
from the surface of the insulating layer
10
.
If the insulating layer
10
is overetched after the slope faces are formed in the first magnetizable layer
12
, the non-magnetizable layer
14
and the second magnetizable layer
16
, the insulating materials of the insulating layer
10
are scattered and stick onto the slope faces, on which the terminals
18
are formed. In
FIG. 7C
, the insulating materials
10
a
of the insulating layer
10
stick on the slope faces, and the terminals
18
are formed thereon.
If the terminals
18
are formed on the slope faces on which the materials
10
a
have stuck, the magnetic resistance element has the following disadvantages: the resistance between the terminals
18
and the main part is unstable; and therefore the resistance of the magnetic resistance element must be greater.
Further, the first and the second magnetizable layers are heated while forming on the insulating layer
10
, atoms of the first magnetizable layer
12
are spread in the insulating layer
10
, so that magnetic characteristic of the magnetic resistance element must be worse. In the case that the first magnetizable layer
12
is the SAL layer, if the atoms of the first magnetizable layer
12
are spread in the insulating layer
10
, the magnetic characteristic of the first magnetizable layer
12
is changed, and a prescribed bias magnetic field cannot be applied.
SUMMARY OF THE INVENTION
The present invention is intended to solve the above described disadvantages of the conventional magnetic resistance elements, and an object of the present invention is to provide a method of making a magnetic resistance element, which includes the MR layer, the bias layer and the non-magnetizable layer and which has a stable magnetic characteristic and high reliability.
To achive the object, the present invention has the following steps.
Namely, the method comprises the steps of: forming a first magnetizable layer, a non-magnetizable layer and a second magnetizable layer, in this order, on an insulating layer; providing a,resist layer for forming a main part of the magnetic resistance element on the second magnetizable layer; etching side faces of the first magnetizable layer, the non-magnetizable layer and the second magnetizable layer to form into slope faces by ion milling from the second magnetizable layer side; forming terminals on the slope faces; and removing the resist layer, wherein a part of the first megnetizable layer which is located outside of the slope faces is left on the insulating layer when the side faces of the first magnetizable layer, the non-magnetizable layer and the second magnetizable layer are etched by ion milling. With this method, scattering and sticking the materials of the insulating layer onto the slope faces while the etching step can be prevented, so the highly reliable magnetic resistant element can be provided.
In the method, the thickness of the first magnetizable layer may be detected by an end sensor while the first magnetizable layer, the non-magnetizable layer and the second magnetizable layer may be etched by ion milling, so that the first magnetizable layer having a prescribed thickness can be left on the insulating layer. With
Ito Takashi
Mikami Masaaki
Okada Mitsumasa
Orimoto Takamitsu
Bernatz Kevin M.
Fujitsu Limited
Greer Burns & Crain Ltd
Resan Stevan A.
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