Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
2000-07-03
2004-06-01
Arbes, Carl J. (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C029S603140, C029S603150, C029S603180, C360S122000, C360S125330
Reexamination Certificate
active
06742241
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of manufacturing a thin film magnetic head having at least an inductive magnetic transducer.
2. Description of the Related Art
In recent years, improvement in performances of a thin film magnetic head is demanded in association with improvement in surface recording density of a hard disk device. As a thin film magnetic head, a composite thin film magnetic head in which a recording head having an inductive magnetic transducer for writing and a reproduction head having a magneto resistive (hereinbelow, referred to as MR) device for reading are stacked is widely used.
One of factors which determine the performances of the recording head is throat height (TH). The throat height is a length (height) from the air bearing surface to the edge of an insulating layer for electrically isolating a thin film coil for generating a magnetic flux. The air bearing surface is a surface of a thin film magnetic head, which faces a magnetic recording medium and is also called a track surface. In order to improve the performances of the recording head, reduction in throat height is desired. The throat height is controlled by a polishing amount at the time of processing the air bearing surface.
In order to improve the recording density in the performances of the recording head, it is necessary to increase the track density of a magnetic recording medium. For this purpose, it is necessary to realize a recording head of a narrow track structure in which the width on the air bearing surface, of each of a bottom pole and a top pole formed while sandwiching a write gap is reduced to the order of a few microns to submicrons. In order to achieve it, semiconductor processing techniques are used.
Referring to
FIGS. 45
to
47
, as an example of a method of manufacturing a conventional thin film magnetic head, a method of manufacturing a composite thin film magnetic head will be described. Each of
FIGS. 45
to
47
is a cross section orthogonal to the air bearing surface.
According to the manufacturing method, first, as shown in
FIG. 45
, an insulating layer
102
made of, for example, alumina (Al
2
O
3
) is deposited in thickness of about 5 to 10 &mgr;m on a substrate
101
made of, for example, altic (Al
2
O
3
·TiC). Subsequently, a lower shield layer
103
for a reproduction head is formed on the insulating layer
102
. For example, alumina is then deposited in thickness of 100 to 200 nm on the lower shield layer
103
to thereby form a shield gap film
104
. An MR film
105
for constructing an MR device for reproduction is deposited in thickness of tens nm on the shield gap film
104
and is patterned in a desired shape by high-precision photolithography. Then a lead layer (not shown) as a lead electrode layer which is electrically connected to the MR film
105
is formed on both sides of the MR film
105
. After that, a shield gap film
106
is formed on the lead layer, shield gap film
104
, and MR film
105
to bury the MR film
105
between the shield gap films
104
and
106
. An upper shield-cum-bottom pole (hereinbelow, referred to as bottom pole)
107
made of a magnetic material used for both of the reproduction head and the recording head such as Permalloy (NiFe) is formed on the shield gap film
106
.
As shown in
FIG. 46
, on the bottom pole
107
, a write gap layer
108
made of an insulating film such as alumina is formed. Further, a photoresist layer
109
is formed in a predetermined pattern on the write gap layer
108
by high-precision photolithography. On the photoresist layer
109
, a first thin film coil
110
for an inductive recording head made of, for example, copper (Cu) is formed by plating or the like. A photoresist layer
111
is formed in a predetermined pattern by high-precision photolithography so as to cover the photoresist layer
109
and the coil
110
. In order to flatten the coil
110
and insulate turns of the thin film coil
110
from each other, a heat treatment is performed at, for example, 250° C. A second thin film coil
112
made of, for example, copper is formed on the photoresist layer
111
by plating or the like. A photoresist layer
113
is formed in a predetermined pattern by high-precision photolithography on the photoresist layer
111
and the coil
112
. In order to flatten the coil
112
and insulate turns of the thin film coil
112
from each other, a heat treatment is performed at, for example, 250° C.
As shown in
FIG. 47
, in a position rearward of the coils
110
and
112
(right side in FIG.
47
), an opening
108
A is formed by partially etching the write gap layer
108
in order to form a magnetic path. A top yoke-cum-top pole (hereinbelow, called top pole)
114
made of a magnetic material for recording head such as Permalloy is selectively formed on the write gap layer
108
and the photoresist films
109
,
111
and
113
. The top pole
114
is in contact with and magnetically coupled to the bottom pole
107
in the opening
108
A. The top pole
114
is used as a mask and the write gap layer
108
and the bottom pole
107
are etched about 0.5 &mgr;m by ion milling. After that, an overcoat layer
115
made of, for example, alumina is formed on the top pole
114
. Finally, a slider is machined to thereby form a track surface (air bearing surface)
120
of the recording head and the reproduction head. In such a manner, a thin film magnetic head is completed.
FIGS. 48
to
50
show the structure of the thin film magnetic head in a completed state.
FIG. 48
is a cross section of the thin film magnetic head perpendicular to the air bearing surface
120
.
FIG. 49
is an enlarged cross section parallel to the air bearing surface
120
of the pole portion.
FIG. 50
is a plan view. Each of
FIGS. 45
to
48
is a cross section taken along line A-AA of FIG.
50
. In
FIGS. 48
to
50
, the overcoat layer
115
is not shown.
In order to improve the performances of the thin film magnetic head, it is important to form the head with accurate throat height TH, apex angle &thgr;, pole width P
2
W and pole length P
2
L shown in
FIGS. 48 and 49
. The apex angle &thgr; is an angle formed between a straight line connecting corners of side faces on the track face side of the photoresist layers
109
,
111
and
113
and the top face of the top pole
114
. The pole width P
2
W defines the width of a recording track on a recording medium. The pole length P
2
L indicates the length of the pole. In
FIGS. 48 and 50
, “TH
0
position” denotes the edge on the track face side of the photoresist layer
109
as an insulating layer which electrically isolates the thin film coils
110
and
112
, that is, a reference position
0
of the throat height TH.
As shown in
FIG. 49
, a structure in which side walls of the top pole
114
, the write gap layer
108
and a portion of the bottom pole
107
are formed vertically in a self-aligned manner is called a trim structure. According to the trim structure, an increase in the effective track width due to expansion of the magnetic flux which occurs at the time of writing data to a narrow track can be prevented. As shown in
FIG. 49
, a lead layer
121
as a lead electrode layer electrically connected to the MR film
105
is provided on both sides of the MR film
105
. In
FIGS. 45
to
48
and
FIG. 50
, the lead layer
121
is omitted.
FIG. 51
shows the structure in plan view of the top pole
114
. As shown in the diagram, the top pole
114
has a yoke
114
A which occupies a major portion of the top pole
114
and a pole tip
114
B having an almost constant width W
1
as the pole width P
2
W. In the connecting portion between the yoke
114
A and the pole tip
114
B, the outer periphery of the yoke
114
A forms an angle &agr; to a plane parallel to the air bearing surface
120
. In the connecting portion, the outer periphery of the pole tip
114
B forms an angle &bgr; to a plane parallel to the air bearing surface
120
. For example, &agr; is about 45 degrees and &bgr; is about 90 degrees. The width of the pole tip
114
B spec
Arbes Carl J.
Nguyen Tai
TDK Corporation
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