Dynamic magnetic information storage or retrieval – Head – Coil
Reexamination Certificate
2000-01-10
2002-06-04
Davis, David (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Coil
Reexamination Certificate
active
06400525
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thin-film magnetic head having at least an induction-type magnetic transducer and a method of manufacturing the thin-film magnetic head.
2. Description of the Related Art
Performance improvements in thin-film magnetic heads have been sought with an increase in surface recording density of a hard disk drive. A composite thin-film magnetic head has been widely used, which is made of a layered structure including a recording head having an induction-type magnetic transducer for writing and a reproducing head having a magnetoresistive (MR) element for reading.
It is required to increase the track density on a magnetic recording medium in order to increase the recording density as one of the performance characteristics of a recording head. To achieve this, it is required to implement a recording head of a narrow track structure wherein the track width, that is, the width of a bottom pole and a top pole sandwiching the recording gap layer on the air bearing surface (medium facing surface) is reduced to the micron or submicron order. Semiconductor process techniques are employed to achieve the narrow track structure.
Reference is now made to
FIG. 16A
to FIG.
19
A and
FIG. 16B
to FIG.
19
B to describe an example of a method of manufacturing a composite thin-film magnetic head as a related-art method of manufacturing a thin-film magnetic head.
FIG. 16A
to
FIG. 19A
are cross sections each orthogonal to the air bearing surface.
FIG. 16B
to
FIG. 19B
are cross sections of a pole portion each parallel to the air bearing surface.
In the manufacturing method, as shown in FIG.
16
A and
FIG. 16B
, an insulating layer
102
made of alumina (Al
2
O
3
), for example, having a thickness of about 5 to 10 &mgr;m is deposited on a substrate
101
made of aluminum oxide and titanium carbide (Al
2
O
3
—TiC), for example. On the insulating layer
102
a bottom shield layer
103
made of a magnetic material is formed for making a reproducing head.
Next, on the bottom shield layer
103
, alumina, for example, is deposited to a thickness of 100 to 200 nm through sputtering to form a bottom shield gap film
104
as an insulating layer. On the bottom shield gap film
104
an MR element
105
for reproduction having a thickness of tens of nanometers is formed. Next, on the bottom shield gap film
104
, a pair of electrode layers
106
are formed. The electrode layers
106
are electrically connected to the MR element
105
.
Next, a top shield gap film
107
is formed as an insulating layer on the bottom shield gap film
104
and the MR element
105
. The MR element
105
is embedded in the shield gap films
104
and
107
.
Next, on the top shield gap film
107
, a top shield layer-cum-bottom pole layer (called a bottom pole layer in the following description)
108
having a thickness of about 3 &mgr;m is formed. The bottom pole layer
108
is made of a magnetic material and used for both a reproducing head and a recording head.
Next, as shown in FIG.
17
A and
FIG. 17B
, on the bottom pole layer
108
, a recording gap layer
109
made of an insulating film such as an alumina film whose thickness is 0.2 &mgr;m is formed. Next, a portion of the recording gap layer
109
is etched to form a contact hole
109
a
to make a magnetic path. On the recording gap layer
109
in the pole portion, a top pole tip
110
made of a magnetic material and having a thickness of 0.5 to 1.0 &mgr;m is formed for the recording head. At the same time, a magnetic layer
119
made of a magnetic material is formed for making the magnetic path in the contact hole
109
a
for making the magnetic path.
Next, as shown in FIG.
18
A and
FIG. 18B
, the recording gap layer
109
and the bottom pole layer
108
are etched through ion-milling, using the top pole tip
110
as a mask. As shown in
FIG. 18B
, the structure is called a trim structure wherein the sidewalls of the top pole (the top pole tip
110
), the recording gap layer
109
, and part of the bottom pole layer
108
are formed vertically in a self-aligned manner.
Next, an insulating layer
111
made of an alumina film, for example, and having a thickness of about 3 &mgr;m is formed on the entire surface. The insulating layer
111
is then polished to the surfaces of the top pole tip
110
and the magnetic layer
119
and flattened.
Next, on the flattened insulating layer
111
, a thin-film coil
112
of a first layer is made of copper (Cu), for example, for the induction-type recording head. Next, a photoresist layer
113
is formed into a specific pattern on the insulating layer
111
and the coil
112
. Heat treatment is then performed to flatten the surface of the photoresist layer
113
. On the photoresist layer
113
, a thin-film coil
114
of a second layer is formed. Next, a photoresist layer
115
is formed into a specific pattern on the photoresist layer
113
and the coil
114
. Heat treatment is performed to flatten the surface of the photoresist layer
115
.
Next, as shown in FIG.
19
A and
FIG. 19B
, a top pole layer
116
is formed for the recording head on the top pole tip
110
, the photoresist layers
113
and
115
, and the magnetic layer
119
. The top pole layer
116
is made of a magnetic material such as Permalloy. Next, an overcoat layer
117
of alumina, for example, is formed to cover the top pole layer
116
. Finally, machine processing of the slider including the above-described layers is performed to form an air bearing surface
118
of the recording head and the reproducing head. The thin-film magnetic head is thus completed.
FIG. 20
is a top view of the thin-film magnetic head shown in FIG.
19
A and FIG.
19
B. The overcoat layer
117
and other insulating layers and insulating films are omitted in FIG.
20
.
In FIG.
19
A and
FIG. 19B
, ‘TH’ indicates the throat height and ‘MR-H’ indicates the MR height. The throat height is the length (height) of the pole portion, that is, the portion of the two magnetic layers facing each other with the recording gap layer in between, between the air-bearing-surface-side end and the other end. The MR height is the length (height) of the MR element between the air-bearing-surface-side end and the other end. In FIG.
19
A and
FIG. 19B
, ‘P
2
W’ indicates the pole width, that is, the track width of the recording head (hereinafter called the recording track width). In addition to the throat height, the MR height and so on, the apex angle as indicated with &thgr; in FIG.
19
A and
FIG. 19B
is one of the factors that determine the performance of a thin-film magnetic head. The apex is a hill-like raised portion of the coils
112
and
114
covered with the photoresist layers
113
and
115
. The apex angle is the angle formed between the top surface of the insulating layer
111
and the straight line drawn through the edges of the pole-side lateral walls of the apex.
In order to improve the performance of the thin-film magnetic head, it is important to precisely form throat height TH, MR height MR-H, apex angle &thgr;, and recording track width P
2
W as shown in
FIG. 19A
or FIG.
19
B.
To achieve high density recording, a reduction in track width and an increase in reproducing output are required for a recording head of a composite thin-film magnetic head as described above. A reduction in track width is required for a recording head, too. An improvement in high-frequency characteristic is required, too, for a recording head to cope with an increase in frequency of data to be written. To improve the high-frequency characteristic of a recording head, it is known that it is preferred to reduce the yoke length, that is, the length of the magnetic path made of the magnetic layers between the air-bearing-surface-side end and the other end.
One of the methods to reduce the yoke length may be to reduce the coil pitch. For example, the yoke length is required to be 20 to 10 &mgr;m or less in order to implement a thin-film magnetic head that achieves recording density of 30 to 50 gigabits per square inch or more and p
Iijima Atsushi
Sasaki Yoshitaka
Davis David
Oliff & Berridg,e PLC
TDK Corporation
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