Dynamic magnetic information storage or retrieval – Head – Core
Reexamination Certificate
1999-09-30
2002-11-19
Nguyen, Hoa T. (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Core
C360S317000
Reexamination Certificate
active
06483664
ABSTRACT:
BACKGROUND 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
In recent years, performance improvement in thin film magnetic heads has been sought in accordance with an increase in surface recording density of a hard disk drive. A composite thin film magnetic head, which has a layered structure including a recording head having an inductive-type magnetic transducer for writing and a reproducing head having magneto resistive (MR) elements for reading, has been widely used as a thin film magnetic head.
The performance of the reproducing head can be improved in several ways. One way is to form an MR film from a material which has good magnetic resistive sensitivity such as a GMR film instead of an AMR film; another is to adjust a pattern width of the MR film, especially an MR height. The MR height is the length (height) between one end of the MR element closer to an air-bearing surface and the other end thereof. The MR height is originally determined by an amount of grinding when the air-bearing surface is processed. The air-bearing surface as used herein refers to a surface of a thin film magnetic head that faces a magnetic recording medium and is also called a track surface.
Performance improvement in a recording head has also been expected in accordance with the performance improvement in a reproducing head. A factor determining the performance of a recording head is the throat height (TH). The throat height is the length (height) of a portion (magnetic pole portion) spreading from the air-bearing surface to an edge of an insulating layer for electrically isolating a thin film coil for causing magnetic flux. Reducing the throat height is desirable in order to improve the performance of a recording head. The throat height is determined as well by an amount of grinding when the air-bearing surface is processed.
It is required to increase the track density of a magnetic recording medium in order to increase the recording density among the performance of a recording head. This requires a recording head having a narrow track structure in which the width of a bottom pole and a top pole sandwiching a write gap layer on the air-bearing surface is reduced to the order of some microns to submicron. Semiconductor process technique is used to achieve this narrow track structure.
FIGS. 21A and 21B
show a structure of a composite thin film magnetic head as an example of a thin film magnetic head of a related art.
FIG. 21A
shows a cross section perpendicular to the air-bearing surface.
FIG. 21B
shows a cross section parallel to the air-bearing surface of the magnetic pole portion.
The composite thin film magnetic head has an insulating layer
102
made of, for example, alumina (aluminum oxide, Al
2
O
3
) of about 5 to 10 &mgr;m in thickness formed on a substrate
101
made of, for example, aluminum oxide and titanium carbide (Al
2
O
3
.TiC). Further, a bottom shield layer
103
for a reproducing head is formed from a magnetic material on the insulating layer
102
. Alumina or aluminum nitride, for example, is sputtered on the bottom shield layer
103
to form a bottom shield gap film
104
as an insulating layer. An MR element
105
for reproduction is formed on the bottom shield gap film
104
. Furthermore, a pair of first electrode layer
106
which is electrically connected to the MR element
105
is formed on the bottom shield gap film
104
. The first electrode layer
106
is formed by stacking TiW, CoPt, TiW, and Ta, for example.
Also, a pair of second electrode layer
107
is electrically connected to the first electrode layer
106
. The second electrode layer
107
can be formed from copper (Cu), for example. The first electrode layer
106
and the second electrode layer
107
constitute a lead, which is electrically connected to the MR element
105
.
As an insulating layer, an upper shield gap layer
108
is formed on the bottom shield gap layer
104
and the MR element
105
. The MR element
105
is buried in the shield gap layers
104
and
108
. A top shield-cum-bottom pole layer (called bottom pole layer in the following)
109
, made of a magnetic material and used both for a reproducing head and for a recording head is formed on the upper shield gap layer
108
. A write gap layer
110
made of an insulating film such as an alumina film is formed on the bottom pole layer
109
. A photoresist layer
111
which determines throat height is formed on the write gap layer
110
in a predetermined pattern. A first layer of a thin film coil
112
for an inductive-type head for recording is formed on the photoresist layer
111
. Further, a photoresist layer
113
is formed in a predetermined pattern on the photoresist layer
111
and the thin film coil
112
. A heat treatment of the temperature of 200-250° C., for example, is applied for stabilizing the photoresist layer
113
. A second layer of a thin film coil
114
is formed on the photoresist layer
113
. A photoresist layer
115
, which is stabilized by heat treatment, is formed in a predetermined pattern on the photoresist layer
113
and the thin film coil
114
.
The write gap layer
110
is etched partially to form a yoke in the rear (right-hand side in
FIG. 21A
) of the thin film coils
112
and
114
. A top pole layer
116
made of a magnetic material for the recording head, that is, a high saturation flux density material such as permalloy (NiFe) or nitride ferrous (FeN) is formed on the write gap layer
110
, the photoresist layers
111
,
113
, and
115
. The top pole layer
116
has a contact with, and is magnetically coupled to the bottom pole layer
109
in the rear of the thin film coils
112
and
114
. An over coat layer
117
made of alumina, for example, is formed on the top pole layer
116
. Each of the side walls of a part of the top pole layer
116
, the write gap layer
110
and the bottom pole layer
109
is formed vertically and in a self-aligned manner to form a trim structure. This trim structure can prevent widening of effective write track width caused by widening of magnetic flux in writing data in the narrow track.
FIG. 22
shows an example of a shape of the top pole layer
116
. The top pole layer
116
has a magnetic pole portion
116
a
which is placed closer to the air-bearing surface
120
and a yoke area
116
b
which is placed at the position facing the thin film coils
112
and
114
. A part of the yoke area
116
b
at the side of the magnetic pole portion
116
a
is tapered off as it is close to the magnetic pole portion
116
a.
The outer edge of the tapered part is inclined to 45°, for example, against the surface which is parallel to the air-bearing surface
120
. The TH
0
, Throat Height position
0
, in figures indicates a position of the edge of the insulating layer closer to the air bearing surface, which separates thin film coil electrically.
These days, reducing the write track width, or the width of the magnetic pole portion (called pole width in the followings), is required for high surface density writing.
FIG. 23
shows an example of a shape of the top pole layer
116
with narrower pole width than that of FIG.
22
. In this example, the width of the magnetic pole portion
116
a
is 0.8-1.2 &mgr;m. It is possible that the width of the magnetic pole portion
116
a
will be around 0.4 &mgr;m of the submicron order in future.
Conventionally, if the top pole layer
116
is formed like that in
FIG. 22
, the magnetic flux caused from the thin film coils
112
and
114
does not saturate on the way but reaches to the top of the magnetic pole portion.
However, as shown in
FIG. 23
, for example, when the pole width is reduced, the flux saturates in vicinity of the Throat Height
0
position, TH
0
, and the flux does not reach to the top of the magnetic pole portion. As a result, an over write characteristic, that is, a characteristic in over-writing data on a recording media on which something i
Nguyen Hoa T.
Oliff & Berridg,e PLC
TDK Corporation
Watko Julie Anne
LandOfFree
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