Dynamic magnetic information storage or retrieval – Head – Core
Reexamination Certificate
2000-03-28
2002-04-09
Renner, Craig A. (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Core
C360S119050, C360S317000
Reexamination Certificate
active
06369984
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thin film magnetic head and a method of producing the same. Particularly, the present invention relates to techniques preferably used for a thin film magnetic head having a track width of 1 &mgr;m or less, and for a method of producing the same.
2. Description of the Related Art
FIG. 33
is a perspective view showing a magnetic head
150
comprising a conventional combination type thin film magnetic head provided on a slider, and
FIG. 34
is a sectional view showing a principal portion of the magnetic head
150
shown in FIG.
33
.
The floating magnetic head
150
mainly comprises a slider
151
, and a combination type thin film magnetic head
157
provided on the slider
151
, as shown in FIG.
33
. Reference numeral
155
denotes the leading side on the upstream side of the slider
151
in the movement direction of a magnetic recording medium, and reference numeral
156
denotes the trailing side on the downstream side in the movement direction. In the slider
151
, rails
151
a
and
151
b
are formed on the medium-facing surface
152
opposed to the magnetic recording medium to form air grooves
151
c
between the respective rails.
The combination type thin film magnetic head
157
is provided on the end surface
151
d
on the trailing side
156
of the slider
151
.
FIG. 35
is a perspective view showing the principal portion of the combination type thin film magnetic head
157
.
The combination type thin film magnetic head
157
comprises a MR magnetic head h
1
comprising a magnetoresistive element, and a thin film magnetic head h
2
serving as a write head, both of which are laminated on the end surface
151
d
of the slider
151
, as shown in
FIG. 34 and 35
.
The MR magnetic head h
1
comprises a lower shielding layer
163
made of a magnetic alloy and formed on the end surface
151
d
of the slider
151
, a lower gap layer
164
laminated on the lower shielding layer
163
, a magnetoresistive element
165
partially exposed from the medium-facing surface
152
, an upper gap layer
166
formed to cover the magnetoresistive element
165
and the lower gap layer
164
, and an upper shielding layer
167
formed to cover the upper gap layer
166
.
The upper shielding layer
167
also serves as a lower core layer of the thin film magnetic head h
2
.
The MR magnetic head h
1
is used as a read head in which a small leakage magnetic field from the magnetic recording medium is applied to the magnetoresistive element
165
to cause a change in resistance of the magnetoresistive element
165
so that a change in voltage based on the change in resistance is read out as a reproduction signal of the magnetic recording medium.
The thin film magnetic head h
2
comprises a lower core layer (the upper shielding layer)
167
, a gap layer
174
laminated on the lower core layer
167
, a coil
176
formed on the back region Y side of the gap layer
174
, an upper insulating layer
177
formed to cover the coil
176
, and an upper core layer
178
formed to be joined to the gap layer
174
in a pole tip region X and to the lower core layer
167
in the back region Y.
The coil
176
is patterned to have a spiral planar shape. The base end
178
b
of the upper core layer
178
is magnetically connected to the lower core layer
167
in the central portion of the coil
176
.
Furthermore, a protecting layer
179
made of alumina or the like is laminated on the upper core layer
178
.
The lower core layer
167
, the gap layer
174
, and the upper core layer
178
are extended from the back region Y to the pole tip region X of the combination type thin film magnetic head
157
, and exposed from the medium-facing surface
152
. In the medium-facing surface
152
, the upper core layer
178
and the lower core layer
167
are opposed to each other with the gap layer
174
held therebetween to form a magnetic gap.
As shown in
FIG. 34
, the pole tip region X means the region where the upper core layer
178
and the lower core layer
167
are opposed to each other with only the gap layer
174
held therebetween, and the back region Y means the region excluding the pole tip region X.
The thin film magnetic head h
2
is used as a write head in which the supply of a recording current to the coil
176
causes a magnetic flux in the upper core layer
178
and the lower core layer
167
due to the recording current, and the magnetic flux leaks to the outside from the magnetic gap to produce a leakage magnetic field, thereby recording a recording signal by magnetization of the magnetic recording medium due to the leakage magnetic field.
In producing the thin film magnetic head h
2
, the lower core layer
167
, the gap layer
174
, and the upper core layer
178
are previously laminated in turn and patterned. The upper core layer
178
is processed by a flame plating method and ion milling, and the exposure width of the upper core layer
178
exposed from the medium-facing surface
152
is defined by the resist width in the flame plating method, and plating and etching processes. The magnetic recording track width is defined by the exposure width of the upper core layer
178
exposed from the medium-facing surface
152
.
The magnetic recording track width (the exposure width of the upper core layer
178
exposed from the medium-facing surface on the pole tip side) of the thin film magnetic head h
2
is set to a small value to decrease the track width of the magnetic recording medium, thereby increasing the recording density of the magnetic recording medium.
However, the conventional thin film magnetic head h
2
has a step formed by the coil layer
176
and the upper insulating layer
177
, thereby increasing the thickness of the resist film which constitutes the upper core layer
178
. Therefore, even if each of these layers is precisely formed by flame plating, and the pole tip is processed with the present highest processing precision, the limit of resolution in exposure for forming a resist pattern causes difficulties in decreasing the magnetic recording track width to 1 &mgr;m or less, thereby causing a problem in that the recording density of the magnetic recording medium cannot be improved.
In some cases, in order to improve the recording density, a magnetic layer made of a material having a high saturation flux density is laminated on each of the lower core layer
167
and the upper core layer
178
to form a two-layer structure, and in order to set a magnetic recording gap depth Gd, a gap layer
174
and a portion
178
A of the upper core layer
178
are laminated on the lower core layer
167
, and a liftoff resist
81
is formed on the portion
178
A of the upper core layer
178
, as shown in FIG.
36
. Then, an end surface
178
a
is formed in the portion
178
A of the upper core layer
178
by ion milling, as shown in
FIG. 37
, and an insulating layer
83
is then formed by sputtering or the like, as shown in FIG.
38
.
FIG. 39
shows a state in which the liftoff resist
81
is removed, and an upper core layer
178
B is further formed.
FIG. 39
is an enlarged sectional view of portion A shown in
FIG. 34
, as viewed from the back of the drawing.
In some cases, in the pole tip region X, the back region side end of the portion
178
A of the upper core layer
178
which holds the gap layer
174
between the upper core layer
178
and the lower core layer
167
, i.e., the end surface
178
a
which defines the depth of the magnetic gap from the medium-facing surface, gap depth Gd, is not parallel to the medium-facing surface
152
, as shown in FIG.
38
. In this case, the leakage magnetic field is increased in the vicinity of the end surface
178
a
, thereby causing the probability of deteriorating the writing ability of the thin film magnetic head, and a position of the end surface
178
a
where the gap depth Gd is defined is indefinite because the end surface
178
a
is not parallel to the medium-facing surface
152
, as shown in FIG.
38
. This causes deterioration or variations in overwrite performance of
Alps Electric Co. ,Ltd.
Brinks Hofer Gilson & Lione
Renner Craig A.
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