Dynamic magnetic information storage or retrieval – Head – Core
Reexamination Certificate
2000-06-22
2003-02-25
Evans, Jefferson (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Core
C360S317000
Reexamination Certificate
active
06525904
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a thin film magnetic head having at least an inductive magnetic transducer for writing and a method of manufacturing the same.
2. Description of the Related Art
Recently, an improvement in performance of a thin film magnetic head has been sought in accordance with an increase in a surface recording density of a hard disk drive. A composite thin film magnetic head, which has a stacked structure comprising a recording head having an inductive magnetic transducer for writing and a reproducing head having a magnetoresistive (hereinafter referred to as MR) element for reading, is widely used as the thin film magnetic head.
Factors that determine the performance of the recording head include a throat height (TH). The throat height refers to a length (height) of a magnetic pole between an air bearing surface and an edge of an insulating layer for electrically isolating thin film coils for generating a magnetic flux. The air bearing surface refers to a surface of the thin film magnetic head facing a magnetic recording medium and is sometimes called a track surface. A reduction in the throat height is desired for the improvement in the performance of the recording head. The throat height is controlled in accordance with an amount of polishing of the air bearing surface.
An increase in a recording density of the performance of the recording head requires the increase in a track density of the magnetic recording medium. For this purpose, it is necessary to realize the recording head having a narrow track structure. In this structure, a bottom pole and a top pole, which are formed on the bottom and top of a write gap sandwiched between the bottom pole and the top pole, have a narrow width of from a few microns to the submicron order on the air bearing surface. Semiconductor processing technology is used in order to achieve this structure.
An example of a method of manufacturing the composite thin film magnetic head will be now described as an example of a conventional method of manufacturing the thin film magnetic head with reference to
FIGS. 43
to
48
.
In the manufacturing method, first, as shown in
FIG. 43
, an insulating layer
102
made of, for example, alumina (Al
2
O
3
) is deposited with a thickness of about 5 &mgr;m to 10 &mgr;m on a substrate
101
made of, for example, altic (Al
2
O
3
and TiC). Then, a bottom shield layer
103
for the reproducing head is formed on the insulating layer
102
. Then, for example, alumina is sputter deposited with a thickness of 100 nm to 200 nm on the bottom shield layer
103
, whereby a shield gap film
104
is formed. Then, an MR film
105
for constituting the MR element for reproducing is formed with a thickness of a few tens of nanometers on the shield gap film
104
, and the MR film
105
is patterned into a desired shape by high-accuracy photolithography. Then, a lead layer (not shown) for functioning as a lead electrode layer electrically connected to the MR film
105
is formed on both sides of the MR film
105
. Then, a shield gap film
106
is formed on the lead layer, the shield gap film
104
and the MR film
105
, whereby the MR film
105
is buried in the shield gap films
104
and
106
. Then, a top shield-cum-bottom pole (hereinafter referred to as a bottom pole)
107
made of a magnetic material for use in both of the reproducing head and the recording head, e.g., permalloy (NiFe) is formed on the shield gap film
106
.
Then, as shown in
FIG. 44
, a write gap layer
108
made of an insulating film, e.g., an alumina film is formed on the bottom pole
107
, and a photoresist layer
109
is formed into a predetermined pattern on the write gap layer
108
by high-accuracy photolithography. Then, first-layer thin film coils
110
made of, for example, copper (Cu) for an inductive recording head are formed on the photoresist layer
109
by plating, for example. Then, a photoresist layer
111
is formed into a predetermined pattern by high-accuracy photolithography so as to coat the photoresist layer
109
and the coils
110
. Then, heat treatment takes place at a temperature of, for example, 250° C. in order to flatten the coils
110
and provide insulation among the coils
110
. Then, second-layer thin film coils
112
made of, for example, copper are formed on the photoresist layer
111
by plating, for example. Then, a photoresist layer
113
is formed into a predetermined pattern on the photoresist layer
111
and the coils
112
by high-accuracy photolithography. Then, heat treatment takes place at a temperature of, for example, 250° C. in order to flatten the coils
112
and provide insulation among the coils
112
.
Then, as shown in
FIG. 45
, the write gap layer
108
is partially etched at the rear of the coils
110
and
112
(on the right side in
FIG. 45
) in order to form a magnetic path, whereby an opening
108
A is formed. Then, a top yoke-cum-top pole (hereinafter referred to as a top pole)
114
made of a magnetic material for the recording head, e.g., permalloy is selectively formed on the write gap layer
108
and the photoresist layers
109
,
111
and
113
. The top pole
114
is in contact with and magnetically coupled to the bottom pole
107
in the above-mentioned opening
108
A. Then, the write gap layer
108
and the bottom pole
107
are etched by about 0.5 &mgr;m by ion milling using the top pole
114
as a mask. Then, an overcoat layer
115
made of, for example, alumina is formed on the top pole
114
. Finally, a slider is machined, whereby a track surface (air bearing surface)
120
of the recording head and the reproducing head is formed. As a result, the thin film magnetic head is completed.
FIGS. 46
to
48
show the structure of the completed thin film magnetic head.
FIG. 46
shows a cross section of the thin film magnetic head perpendicular to the air bearing surface
120
.
FIG. 47
shows an enlarged view of a cross section of the magnetic pole parallel to the air bearing surface
120
.
FIG. 48
shows a plan view.
FIGS. 43
to
46
correspond to a cross section viewed from the direction of the arrows along the line A-AA of FIG.
48
. The overcoat layer
115
is not shown in
FIGS. 46
to
48
.
To improve the performance of the thin film magnetic head, it is important to precisely 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. 46 and 47
. The apex angle &thgr; refers to an angle between a straight line connecting corners of side surfaces of the photoresist layers
109
,
111
and
113
on the side of the track surface and a top surface of the top pole
114
. The pole width P
2
W defines a write track width on the recording medium. The pole length P
2
L represents the thickness of the magnetic pole. In
FIGS. 46 and 48
, a ‘TH
0
position’ refers to an edge of the photoresist layer
109
that is the insulating layer for electrically isolating the thin film coils
110
and
112
, on the side of the track surface. The TH
0
position indicates a reference position
0
of the throat height TH.
As shown in
FIG. 47
, the structure, in which the respective side walls of parts of the top pole
114
, the write gap layer
108
and the bottom pole
107
are vertically formed in self-alignment, is called a trim structure. The trim structure can prevent the increase in an effective track width resulting from a spread of the magnetic flux generated during writing data on a narrow track. As shown in
FIG. 47
, a lead layer
121
for functioning as the lead electrode layer electrically connected to the MR film
105
is provided on both sides of the MR film
105
. The lead layer
121
is not shown in
FIGS. 43
to
46
.
FIG. 49
shows a plan structure of the top pole
114
. As shown in
FIG. 49
, the top pole
114
has a yoke portion
114
A occupying most of the top pole
114
, and a pole chip portion
114
B having a substantially constant width W
1
as the pole width P
2
W. An outer edge of the yoke portion
114
A forms an angle &agr; with the surface parallel to the a
Evans Jefferson
TDK Corporation
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