Dynamic magnetic information storage or retrieval – Head – Core
Reexamination Certificate
1999-11-09
2002-06-04
Tupper, Robert S. (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Core
Reexamination Certificate
active
06400527
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thin film magnetic head and to a production process thereof. More particularly it relates to a thin film magnetic head having an upper core with a narrow track width on an inductive head surface facing to a magnetic recording medium, and to a production process thereof.
2. Description of the Related Art
FIGS. 16A and 16B
are diagrams each illustrating a conventional thin film magnetic head, in which
FIG. 16A
is a cross sectional side view of its substantial part, and
FIG. 16B
is a top view of its upper core layer.
FIGS. 17A through 17E
are cross sectional side views showing various steps involved in producing a conventional thin film magnetic head.
FIGS. 18A and 18B
are illustrations of a production process of the conventional thin film magnetic head, in which
FIG. 18A
is a schematic diagram illustrating a reflection behavior of light exposure at sloping regions in a photolithography step, and
FIG. 18B
is a top view showing an upper core layer obtained by photolithography.
FIGS. 19A and 19B
are cross sectional side views of a substantial part of a thin film magnetic head described in U.S. Pat. No. 25,621,596.
An inductive write head for writing magnetic signals on a magnetic recording medium such as a hard disk is laminated on a magnetoresistive read head (MR read head) for reading magnetic signals with the aid of the magnetoresistive effect, at a trailing edge of a slider of a floating type magnetic head facing a magnetic recording medium, and the resultant laminate is used as a composite thin film magnetic head.
In the thin film magnetic head shown in
FIG. 16A
, a lower core layer
51
of an inductive write head is composed of an Fe—Ni alloy (e.g., permalloy) or another highly magnetically permeable material, and serves also as an upper shield layer of an MR read head having an magnetoresistive read element (MR read element)
20
. A gap layer
52
of Al
2
O
3
or another nonmagnetic material and is formed to a thickness of Gl on the lower core layer
51
.
A first insulation layer
53
of a resist material or another organic resinous material is formed on the gap layer
52
and slopes upward with respect to the top of the gap layer
52
. The first insulation layer
53
has a first forward end or apex
53
a
and a first sloping region
53
b
extending upward from the first apex
53
a
, in which the first apex
53
a
establishes a zero throat height which, in turn, defines a gap depth Gd. A coil layer
54
is composed of Cu or another low-resistance conductive material, and is formed helical in plane on top of the first insulation layer
53
.
A second insulation layer
55
of a resist material or another organic resinous material is formed on the first insulation layer
53
so as to cover the coil layer
54
, and on the second insulation layer
55
is laminated a third insulation layer
56
. The second and third insulation layers
55
and
56
have a second sloped apex
55
a
and its second sloping region
55
b
, and a third sloped apex
56
a
and its third sloping region
56
b
, respectively. An inclined plane K
1
is constituted by the first, second and third sloping regions
53
b
,
55
b
and
56
b
which are formed nearly flush with one another. The inclined plane K
1
is set to have a predetermined angle (apex angle) &thgr;
1
with respect to the gap layer
52
.
An upper core layer
57
of an Fe—Ni alloy (e.g., permalloy) or another magnetic material is formed above the first, second, and third insulation layers
53
,
55
and
56
, and the gap layer
52
. The upper core layer
57
is provided with a narrow tip region
57
a
, a connecting portion
57
b
, a body portion
57
c
, and a back end region (not shown); in which the tip region
57
a
is connected via the gap layer
52
to the lower core layer
51
on a surface facing a magnetic recording medium; the connecting portion
57
b
is connected to the tip region
57
a
in a nearly identical width and is formed on the inclined plane K
1
; the body portion
57
c
extends wider from the connecting portion
57
b
, and covers part of the coil layer
54
; and the back end region is magnetically connected via a hole to the lower core layer
51
and is wrapped with the coil layer
54
therearound, which hole is formed in the gap layer
52
and the first insulation layer
53
at a position which is nearly the center of the coil layer
54
(FIG.
16
B). A connecting region between the connecting portion
57
b
and the body portion
57
c
on the inclined plane K
1
is called a pole straight Ps.
A magnetic gap G has a gap length Gl and a gap depth Gd, and the gap length Gl is determined by a distance between the lower core layer
51
and the tip region
57
a
connected via the gap layer
52
, i.e., the thickness of the gap layer
52
. The gap depth Gd is determined by a depth of the tip region
57
a
, that is, a distance between an air bearing surface (ABS) A which is for facing the magnetic recording medium, the left end shown in the figure, and the first apex
53
a
(zero throat height Z). In a composite thin magnetic head, the lower core layer
51
also serves as an upper shield layer of an MR head, and has a width larger than that of the tip region
57
a
of the upper core layer
57
. A track width Tw is therefore determined by the width of the tip region
57
a.
In the inductive write head configured as above, a recording current is applied to the coil layer
54
and a recording magnetic field is induced to the lower and upper core layers
51
and
57
, and magnetic signals are recorded on a magnetic recording medium through a leakage magnetic field, in the air bearing surface (ABS) A, from the magnetic gap G between the lower core layer
51
and the tip region
57
a
of the upper core layer
57
.
Next, a production process of the above conventional thin film magnetic head will be described. Initially, the gap layer
52
having a thickness (gap length) of Gl is formed from Al
2
O
3
or another nonmagnetic material on the lower core layer
51
of an Fe—Ni alloy or another magnetic material. The first insulation layer
53
is then formed by lithography using a resist material or another organic resinous material. Subsequently, the resist material slopes, due to its comparatively high viscosity, through heat applied in a heating step for curing the resist material, and thus the first sloping region
53
b
extending from the first apex
53
a
is formed (FIG.
17
A).
Next, the coil layer
54
helical in plane is formed on the first insulation layer
53
, by plating with, for example, Cu (FIG.
17
B). The second insulation layer
55
having the second sloping region
55
b
provided at the second apex
55
a
is formed on the first insulation layer
53
, by photolithography using a resist material or another organic resinous material (FIG.
17
C).
On the second insulation layer
55
, the third insulation layer
56
having the third sloping region
56
b
extending upward from the third apex
56
a
is formed, by photolithography using a resist material or another organic resinous material (FIG.
17
D). In the formation of the second and third insulation layers
55
and
56
, the first, second and third sloping regions
53
b
,
55
b
and
56
b
are arranged nearly flush with one another to form the inclined plane K
1
having the apex angle &thgr;
1
.
The upper core layer
57
is then formed by frame plating. Initially, a thin film of a primary coat
58
a
of the same material with the upper core layer
57
, i.e., an Fe—Ni alloy or another magnetic material, is formed on the second and third insulation layers
55
and
56
, by sputtering or another vacuum film formation technique. A resist material is then coated onto the primary coat
58
a
to form a photoresist layer
58
b
(FIG.
17
E). The upper core layer
57
is then patterned by exposing the photoresist layer
58
b
with light from above in the direction indicated by arrows (FIG.
17
E), and a film of an Fe—Ni alloy or another magnetic material is plated on areas where the primar
Gochou Hideki
Kobayashi Kiyoshi
Oki Naruaki
Alps Electric Co. ,Ltd.
Brinks Hofer Gilson & Lione
Tupper Robert S.
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