Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
2001-06-13
2004-02-03
Ometz, David L. (Department: 2653)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
C360S125330
Reexamination Certificate
active
06687096
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 electromagnetic transducer and 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 areal 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 write (recording) head having an induction-type electromagnetic transducer for writing and a read (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 write head. To achieve this, it is required to implement a write head of a narrow track structure wherein the width of top and bottom poles sandwiching the write gap layer on a side of the air bearing surface is reduced down to microns or the order of submicron. Semiconductor process techniques are utilized to implement such a structure.
Reference is now made to
FIG. 34A
to FIG.
37
A and
FIG. 34B
to
FIG. 37B
to describe an example of a method of manufacturing a composite thin-film magnetic head as an example of a method of manufacturing a thin-film magnetic head of related-art.
FIG. 34A
to
FIG. 37A
are cross sections each orthogonal to an air bearing surface of the thin-film magnetic head.
FIG. 34B
to
FIG. 37B
are cross sections of pole portions of the head each parallel to the air bearing surface.
In the manufacturing method, as shown in FIG.
34
A and
FIG. 34B
, an insulating layer
202
made of alumina (Al
2
O
3
), for example, having a thickness of about 5 to 10 &mgr;m is deposited on a substrate
201
made of aluminum oxide and titanium carbide (Al
2
O
3
—TiC), for example. On the insulating layer
202
a bottom shield layer
203
made of a magnetic material is formed for making a read head.
Next, on the bottom shield layer
203
, alumina, for example, is deposited to a thickness of 100 to 200 nm through sputtering to form a bottom shield gap film
204
as an insulating layer. On the bottom shield gap film
204
an MR element
205
for reading having a thickness of tens of nanometers is formed. Next, a pair of electrode layers
206
are formed on the bottom shield gap film
204
. The electrode layers
206
are electrically connected to the MR element
205
.
Next, a top shield gap film
207
is formed as an insulating layer on the bottom shield gap film
204
and the MR element
205
. The MR element
205
is embedded in the shield gap films
204
and
207
.
Next, on the top shield gap film
207
, a top-shield-layer-cum-bottom-pole-layer (called a bottom pole layer in the following description)
208
having a thickness of about 3 &mgr;m is formed. The bottom pole layer
208
is made of a magnetic material and used for both a write head and a read head.
Next, as shown in FIG.
35
A and
FIG. 35B
, on the bottom pole layer
208
, a write gap layer
209
made of an insulating film such as an alumina film whose thickness is 0.2 &mgr;m is formed. Next, a portion of the write gap layer
209
is etched to form a contact hole
209
a
to make a magnetic path. On the write gap layer
209
in the pole portion, a top pole tip
210
made of a magnetic material and having a thickness of 0.5 to 1.0 &mgr;m is formed for the write head. At the same time, a magnetic layer
219
made of a magnetic material is formed for making the magnetic path in the contact hole
209
a
for making the magnetic path.
Next, as shown in FIG.
36
A and
FIG. 36B
, the write gap layer
209
and the bottom pole layer
208
are etched through ion milling, using the top pole tip
210
as a mask. As shown in
FIG. 36B
, the structure is called a trim structure wherein the sidewalls of the top pole (the top pole tip
210
), the write gap layer
209
, and part of the bottom pole layer
208
are formed vertically in a self-aligned manner.
Next, an insulating layer
211
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
211
is then polished to the surfaces of the top pole tip
210
and the magnetic layer
219
and flattened.
Next, on the flattened insulating layer
211
, a first layer
212
of a thin-film coil is made of copper (Cu), for example, for the induction-type write head. Next, a photoresist layer
213
is formed into a specific shape on the insulating layer
211
and the first layer
212
. Heat treatment is then performed at a specific temperature to flatten the surface of the photoresist layer
213
. On the photoresist layer
213
, a second layer
214
of the thin-film coil is then formed. Next, a photoresist layer
215
is formed into a specific shape on the photoresist layer
213
and the second layer
214
. Heat treatment is then performed at a specific temperature to flatten the surface of the photoresist layer
215
.
Next, as shown in FIG.
37
A and
FIG. 37B
, a top pole layer
216
is formed for the write head on the top pole tip
210
, the photoresist layers
213
and
215
, and the magnetic layer
219
. The top pole layer
216
is made of a magnetic material such as Permalloy. Next, an overcoat layer
217
of alumina, for example, is formed to cover the top pole layer
216
. Finally, machine processing of the slider including the foregoing layers is performed to form the air bearing surface
218
of the thin-film magnetic head including the write head and the read head. The thin-film magnetic head is thus completed.
FIG. 38
is a top view of the thin-film magnetic head shown in FIG.
37
A and FIG.
37
B. The overcoat layer
217
and the other insulating layers and insulating films are omitted in FIG.
38
.
In
FIG. 37A
, ‘TH’ indicates the throat height and ‘MR-H’ indicates the MR height. The throat height is the length (height) of portions of magnetic pole layers facing each other with the write gap layer in between, between the air-bearing-surface-side end and the other end. The MR height is the length (height) between the air-bearing-surface-side end of the MR element and the other end. In
FIG. 37B
, ‘P
2
W’ indicates the pole width, that is, the write track width. In addition to the throat height, the MR height and so on, the apex angle as indicated with &thgr; in
FIG. 37A
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 coil covered with the photoresist layers
213
and
215
. The apex angle is the angle formed between the top surface of the insulating layer
211
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 track width P
2
W as shown in FIG.
37
A and FIG.
37
B.
To achieve high areal recording density, that is, to fabricate a write 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 smaller. It is therefore required to process the top pole into the submicron order through semiconductor process techniques.
A problem is that it is difficult to form the top pole layer having 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
Oyama Nobuya
Sasaki Yoshitaka
Blouin Mark
Oliff & Berridg,e PLC
Ometz David L.
TDK Corporation
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