Dynamic magnetic information storage or retrieval – Head – Core
Reexamination Certificate
1998-11-16
2001-12-11
Ometz, David L. (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Core
C029S603140
Reexamination Certificate
active
06330127
ABSTRACT:
BACK GROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thin-film magnetic head having at least an inductive-type magnetic transducer for writing and a method of manufacturing the same.
2. Description of the Related Art
Improvements in the performance of a thin-film magnetic head are sought since a surface recording density of a hard disk device has been improved. A composite thin-film magnetic head having a structure in which, a recording head having a inductive-type magnetic transducer for writing and a reproducing head having a magneto resistive (referred as MR) element for reading are stacked is broadly used as the thin-film magnetic head. The MR element includes an device using an effect of anisotropic magneto resistive (referred as AMR) and another device using an effect of giant magneto resistive (referred as GMR). The reproducing head using the AMR element is called an AMR head or simply MR head, and the reproducing head using the GMR element is called a GMR head. The AMR head is used as a reproducing head whose surface recording density is over 1 gigabit per square inch, and the GMR head is used as the reproducing head whose surface recording density is over 3 gigabit per square inch.
The AMR head has an AMR film having the AMR effect. The GMR head has a structure identical to the AMR head except that a GMR film having the GMR effect is used instead of the AMR film. However, when the same external magnetic field is applied, the GMR film exhibits greater change in resistance than the AMR film. As a result, the GMR head can increase the reproduction output three to five times the AMR head.
A method is disclosed in which the AMR film being used as the MR film is exchanged with a material with better reactive magnetic resist such as GMR film, and a method in which a pattern width of the MR film, especially the MR height is used as the methods of improving the performance of the reproducing head. The MR height is a length (height) from an edge of air bearing side to an edge of the other side, and it is controlled by an etching amount of the air bearing surface. The air bearing surface, here, is facing a magnetic recording medium and called a track surface as well.
On the other hand, performance improvements in a recording head have been called while performances in a reproducing head has improved. A factor which determines the performance of the recording head is a throat height (TH). The throat height is a length (height) of a pole between the air bearing surface and an edge of an insulator which electrically isolates a thin-film coil for generating magnetic flux. A reduction of the throat height is needed in order to improve the recording head performance. The throat height is controlled by an etching amount when the air bearing surface is processed.
To improve a recording density among the performance of the recording head, a track density of magnetic recording medium is required to be increased. In order to achieve this, a recording head with a narrow track structure in which a width of the top and bottom pole on the air bearing surface, which are formed on top and bottom sandwiching a write gap, is reduced from some microns to sub-microns. Semiconductor process techniques are employed to achieve the narrow track structure.
A method of manufacturing the composite thin-film magnetic head as an example of a method of manufacturing the thin-film magnetic head of the related art will be described by referring to FIG.
39
through FIG.
44
.
As shown in
FIG. 39
, an insulating film
102
made of alumina (Al
2
O
3
), for example, of about 5 to 10 &mgr;m in thickness is deposited on a substrate
101
made of aluminum oxide and titanium carbide (Al
2
O
3
—TiC), for example. A bottom shield layer
103
for a reproducing head is formed on the insulating film
102
. A shield gap film
104
is formed on the bottom shield layer
103
by depositing alumina 100 to 200 nm in thickness through sputtering. An MR film
105
of tens of nanometers in thickness for making up the MR element for reproduction is formed on the shield gap film
104
, and a desired shape is obtained by patterning through photolithography with high precision. Next, after forming a lead layer (not shown) on both sides of the MR film
105
as an extraction electrode layer which is electrically connected to the MR film
105
, a shield gap film
106
is formed on the lead layer, the shield gap film
104
and the MR film
105
, and then the MR film
105
is buried in the shield gap film
104
and
106
. Further, a top shield serving as a bottom pole (referred as bottom pole in the following description)
107
made of magnetic materials such as permalloy (NiFe) used for both reproduction and recording head is formed on the shield gap layer
106
.
As shown in
FIG. 40
, an insulating film such as a write gap layer
108
made of alumina film is formed, for example, on the bottom pole
107
, and a photoresist layer
109
in a desired pattern is formed on the write gap layer
108
through photolithography with high precision. Next, a thin-film magnetic coil
110
as a first layer for an inductive recording head made of, for example, copper (Cu) is formed on the photoresist layer
109
by, for example, plating method. A photoresist layer
111
in a desired pattern is formed covering the photoresist layer
109
and the coil
110
through photolithography with high precision. Next, a heat treatment at 250° C., for example, is applied to have the coil
110
flattened and have turns of the coil
110
insulated from each other. Further, a thin-film coil
112
as a second layer made of, for example, copper is formed by plating method. A photoresist layer
113
in a desired pattern is formed on the photoresist film
111
and the coil
112
through photolithography with high precision, and a heat treatment at 250° C. is applied to have the coil
112
flattened and have turns of the coil
112
insulate from each other.
As shown in
FIG. 41
, an opening
108
a
is formed by partially etching the write gap layer
108
in a position behind the coil
110
and
112
(right-hand side in
FIG. 41
) in order to form a magnetic path. Further, a top yolk-cum-top pole (referred as a top pole in the following description)
114
made of magnetic materials for recording head such as permalloy is selectively formed on the write gap layer
108
, the photoresist layers
109
,
111
and
113
. The top pole
114
has a contact with the bottom pole
107
in the opening
108
a
being magnetically coupled. Next, after the write gap layer
108
and the bottom pole
107
are etched about 0.5 &mgr;m by ion milling etching using the top pole
114
as a mask, an overcoat layer
115
made of such as alumina is formed. The thin-film magnetic head is completed after a track surface (air bearing surface)
120
of the recording head and reproducing head are formed by applying machine grinding with a slider.
FIGS.
42
,
43
, and
44
illustrate a completed configuration of the thin-film magnetic head. Here,
FIG. 42
shows a sectional view of the thin-film magnetic head orthogonal to the air bearing surface
120
, and
FIG. 43
is an enlarged cross-sectional view of parallel to the air bearing surface
120
and
FIG. 44
is a plan view.
FIGS. 39
to
42
show a cross section taken along the line A-A′ in FIG.
44
. An illustration of the overcoat layer
115
is omitted in
FIGS. 42
to
44
.
It is important to form the throat height (TH), an apex angle (&thgr;), a pole width (P
2
W) and a pole length P
2
L shown in
FIGS. 42 and 43
precisely in order to improve the performance of the thin-film magnetic head. The apex angle &thgr; is an angle between the corner of the track surface of the photoresist layer
109
,
111
and
113
, and a straight line connecting the surface of the top pole
114
. The pole width P
2
W provides a width of a recording track in a recording medium. The pole length P
2
L represents the thickness of the pole. Further, in
FIGS. 42 and 44
, ‘TH
0
position’ represents a reference position
0
of the t
Oliff & Berridge PLC.
Ometz David L.
TDK Corporation
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