Dynamic magnetic information storage or retrieval – Head – Core
Reexamination Certificate
2000-06-23
2002-09-17
Evans, Jefferson (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Core
C360S317000
Reexamination Certificate
active
06452743
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 to a method of manufacturing such a thin-film magnetic head.
2. Description of the Related Art
Performance improvements in thin-film magnetic heads have been sought as surface recording density of hard disk drives has increased. Such thin-film magnetic heads include composite thin-film magnetic heads that have been widely used. A composite head 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 recording density among the performance characteristics of a recording head. To achieve this, it is required to implement a recording head of a narrow track structure wherein a track width, that is, the width of top and bottom poles sandwiching the recording gap layer on a side of the air bearing surface, is reduced down to microns or the submicron order. Semiconductor process techniques are utilized to implement such a structure.
Reference is now made to
FIG. 19A
to FIG.
22
A and
FIG. 19B
to
FIG. 22B
to describe an example of a method of manufacturing a composite thin-film magnetic head as an example of a related-art method of manufacturing a thin-film magnetic head.
FIG. 19A
to
FIG. 22A
are cross sections each orthogonal to an air bearing surface of the thin-film magnetic head.
FIG. 19B
to
FIG. 22B
are cross sections of a pole portion of the head each parallel to the air bearing surface.
In the manufacturing method, as shown in FIG.
19
A and
FIG. 19B
, an insulating layer
102
made of alumina (Al
2
O
3
), for example, having a thickness of about 5 &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 35 to 60 nm, for example, 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, a pair of electrode layers
106
are formed on the bottom shield gap film
104
. The electrode layers
106
are electrically connected to the MR element
105
.
Next, a top shield gap film
107
having a thickness of about 35 to 60 nm, for example, 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 2.5 to 3.5 &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.
20
A and
FIG. 20B
, a recording gap layer
109
made of an insulating film such as an alumina film whose thickness is 0.2 to 0.25 &mgr;m, for example, is formed on the bottom pole layer
108
. Next, a portion of the recording gap layer
109
is etched to form a contact hole
109
a
to make a magnetic path. Next, a photoresist layer
110
having a thickness of 1.0 to 1.5 &mgr;m, for example, is formed on top of a region of the recording gap layer
109
where a thin-film coil described later is to be formed. On the photoresist layer
110
, the thin-film coil
111
for an induction-type recording head is formed through electrolytic plating, for example. A photoresist layer
112
is then formed to cover the thin-film coil
111
.
Next, as shown in FIG.
21
A and
FIG. 21B
, a top pole layer
113
made of a magnetic material and having a thickness of 2.0 to 3.0 &mgr;m, for example, is formed for the recording head in a region extending from the top of a portion of the recording gap layer
109
located in the pole portion, through the top of the photoresist layer
112
to the contact hole
109
a.
Next, as shown in FIG.
22
A and
FIG. 22B
, a portion of the recording gap layer
109
around the top pole layer
113
is removed and the bottom pole layer
108
is etched by only 0.3 to 0.4 &mgr;m, for example, through ion milling, for example, using the top pole layer
113
as a mask. As shown in
FIG. 22B
, the structure is called a trim structure wherein the sidewalls of the top pole portion (the top pole layer
113
), the recording gap layer
109
, and a part of the bottom pole layer
108
are formed vertically in a self-aligned manner.
Next, an overcoat layer
114
of alumina, for example, is formed to cover the top pole layer
113
. Finally, lapping of the slider is performed to form the air bearing surface
120
of the thin-film magnetic head including the recording head and the reproducing head. The thin-film magnetic head is thus completed.
In
FIG. 22A
, the throat height is indicated with ‘TH’, the zero throat height position with ‘TH
0
’, the MR height with ‘MR-H’, and the apex angle with &thgr;. The throat height is the length (height) of pole portions, that is, portions of magnetic pole layers facing each other with a recording gap layer in between, the length between the air-bearing-surface-side end and the other end. The zero throat height position is the position of an end of a pole portion opposite to the air bearing surface. The MR height is the length (height) between the air-bearing-surface-side end of the MR element
105
and the other end. The apex is a hill-like raised portion of the coil covered with an insulating layer such as the photoresist layer
112
. The apex angle is the angle formed between the top surface of the recording gap layer
109
and the slope of the apex on a side of the pole. In the thin-film magnetic head shown in
FIG. 22A
, zero throat height position TH
0
is the position of an end of the photoresist layer
112
on a side of the air bearing surface
120
.
FIG. 23
is an explanatory view for illustrating the relationship between a top view (an upper view of
FIG. 23
) of the main part of the thin-film magnetic head shown in FIG.
22
A and
FIG. 22B and a
cross-sectional view (a lower view of
FIG. 23
) thereof. The overcoat layer
114
and some of the other insulating layers and insulating films are omitted in FIG.
23
. In
FIG. 23
, ‘P
2
W’ indicates the recording track width.
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, and apex angle &thgr; as shown in
FIG. 22A
, and recording track width P
2
W as shown in FIG.
23
.
To achieve high surface recording density, that is, to fabricate a recording head with a narrow track structure, it has been particularly required that track width P
2
W fall within the submicron order of 1.0 &mgr;m or less. It is therefore required to process the top pole of the submicron order through semiconductor process techniques.
A problem is that it is difficult to form the top pole layer of small dimensions on the apex.
As disclosed in Published Unexamined Japanese Patent Application Hei 7-262519 (1995), for example, frame plating may be used as a method for fabricating the top pole layer. In this case, a thin electrode film made of Permalloy, for example, is formed by sputtering, for example, to fully cover the apex. Next, a photoresist is applied to the top of the electrode film and patterned through a photolithography process to form a frame to be used for plating. The top pole layer is then formed by plating through the use of the electrode film previously formed as a seed layer.
However, there is a difference in height between the apex and the other part, such as 7 to 10 &mgr;m or more. The photoresist whose thickness is 3 to 4 &mgr;m is applied to cover the
Evans Jefferson
Oliff & Berridg,e PLC
TDK Corporation
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