Dynamic magnetic information storage or retrieval – Head – Core
Reexamination Certificate
2000-04-06
2002-12-03
Renner, Craig A. (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Core
Reexamination Certificate
active
06490127
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 for writing.
2. Description of the Related Art
In recent years, an improvement in performance of a thin film magnetic head is demanded in accordance with an increase in surface recording density of a hard disk drive. As a thin film magnetic head, a composite thin film magnetic head in which a recording head having an inductive-type magnetic transducer for writing and a reproducing head having a magnetoresistive (hereinbelow, referred to as MR) element for reading are stacked is widely used.
In order to improve the recording density in the performances of the recording head, it is necessary to increase 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 this, semiconductor processing techniques are used.
Referring to
FIGS. 31 and 36
, 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.
According to the manufacturing method, first, as shown in
FIG. 31
, an insulating layer
102
made of, for example, aluminium oxide (Al
2
O
3
; hereinbelow, simply called “alumina”) is deposited in a thickness of about 5.0 to 10.0 &mgr;m on a substrate
101
made of altic (Al
2
O
3
.TiC) or the like. Subsequently, a bottom shield layer
103
for a reproducing head is formed on the insulating layer
102
. For example, alumina layer is then sputter-deposited in a thickness of 100 to 200 nm on the bottom shield layer
103
to form a shield gap film
104
. An MR film
105
for constructing an MR device for reproducing is deposited in a thickness of tens nm on the shield gap film
104
and is patterned in a desired shape by high-precision photolithography. Then lead layers (not shown) as lead electrode layers, which are electrically connected to the MR film
105
, are formed on both sides of the MR film
105
. After that, a shield gap film
106
is formed on the lead layers, the shield gap film
104
, and the MR film
105
, and the MR film
105
is buried in the shield gap films
104
and
106
. A top shield-cum-bottom pole (hereinbelow, referred to as a bottom pole)
107
made of a magnetic material such as nickel iron alloy (NiFe; hereinbelow, also simply called “Permalloy (trade name)”) used for both of the reproducing head and the recording head is formed on the shield gap film
106
.
As shown in
FIG. 32
, on the bottom pole
107
, a write gap layer
108
made of an insulating material such as alumina is formed. Further, a photoresist film
109
is formed in a predetermined pattern on the write gap layer
108
by high-precision photolithography. On the photoresist film
109
, a thin film coil
110
for an inductive-type recording head made of, for example, copper (Cu) is formed by plating or the like. A photoresist film
111
is formed in a predetermined pattern by high-precision photolithography so as to cover the photoresist film
109
and the thin film coil
110
. In order to insulate the winding portions of the thin film coil
110
from each other, a heat treatment is conducted at, for example, 250 degrees on the photoresist film
111
.
As shown in
FIG. 33
, in a position rearward of the thin film coil
110
(the right side in FIG.
33
), an opening
108
a
is formed by partially etching the write gap layer
108
in order to form a magnetic path, thereby exposing part of the bottom pole
107
. A top yoke-cum-top pole (hereinbelow, called top pole)
112
made of a magnetic material having high saturated magnetic flux density such as Permalloy is selectively formed so as to cover the exposed face of the bottom pole
107
, the photoresist film
111
and the write gap layer
108
.
As a method of forming the top pole
112
, for example, as disclosed in Japanese Unexamined Patent Application No. Hei 7-262519, a frame plating is used. When the top pole
112
is formed by using the frame plating, first, on the whole coil portion (hereinbelow, called an “apex portion”) projected like a mountain covered with the photoresist film
111
, a thin electrode film made of, for example, Permalloy is deposited by sputtering or the like. A photoresist is then applied on the electrode film, thereby forming the photoresist film. The photoresist film is patterned by a photolithography to form a frame (outer frame) for a plating. Then the electrode film formed before is used as a seed layer and a plating film made of Permalloy is grown by plating, thereby forming the top pole
112
.
The top pole
112
has, for example, a shape in plane as shown in
FIG. 36
which will be described hereinlater and includes a yoke part
112
a
and a pole tip part
112
b
. The top pole
112
is in contact with and magnetically coupled to the bottom pole
107
in the opening
108
a
. Subsequently, by using part (pole tip part
112
b
) of the top pole
112
as a mask, both the write gap layer
108
and bottom pole
107
are selectively etched about 0.5 &mgr;m by ion milling (refer to
FIG. 35
) and, after that, an overcoat layer
113
made of, for example, alumina is formed on the top pole
112
. Finally, by machining and polishing, the track surface, that is, an air bearing surface
120
of the recording head and reproducing head is formed, thereby completing a thin film magnetic head.
FIGS. 34
to
36
show the structure of the thin film magnetic head in a completed state.
FIG. 34
is a cross section of the thin film magnetic head in the direction perpendicular to the air bearing surface
120
.
FIG. 35
is an enlarged cross section in the direction parallel to the air bearing surface
120
of the pole part.
FIG. 36
is a plan view of the structure.
FIG. 33
is a cross section taken along line XXXIII—XXXIII of FIG.
36
. In
FIGS. 34
to
36
, the overcoat layer
113
and the like are omitted. In
FIG. 36
, with respect to the thin film coil
110
and the photoresist film
111
, only their outlines are shown.
In
FIGS. 34 and 36
, “TH” denotes the throat height and “MRH” indicates the MR height. The “throat height (TH)” is one of factors which determine the performance of the recording head and is length from the position of the edge on the side closest to the air bearing surface
120
of the insulating layer (photoresist film
111
) for electrically isolating the thin film coil
110
from the other conductive portions, that is, from the throat height zero position (THO) to the air bearing surface
120
. In order to improve the performance of the recording head, it is necessary to optimize the throat height (TH). The throat height (TH) is controlled by a polishing amount at the time of forming the air bearing surface
120
. The “MR height (MRH)” denotes length from the position of the edge on the side furthest from the air bearing surface
120
of the MR film
105
, that is, the MR height zero position (MRH
0
) to the position of the air bearing surface
120
. The MR height (MRH) is also controlled by the polishing amount at the time of forming the air bearing surface
120
.
Besides the throat height (TH) and the MR height (MRH), another factor which determines the performance of the thin film magnetic head is an apex angle (&thgr;) shown in FIG.
34
. The apex angle &thgr; is an average inclination angle of an inclined face close to the air bearing surface
120
of the photoresist film
111
.
As shown in
FIG. 35
, a structure such that part of the write gap layer
108
and part of the bottom pole
107
are etched in a self aligned manner to the pole tip part
112
b
of the top pole
112
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 wr
Oliff & Berridg,e PLC
Renner Craig A.
TDK Corporation
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