Dynamic magnetic information storage or retrieval – Head – Core
Reexamination Certificate
2000-11-09
2003-12-02
Tupper, Robert S. (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Core
Reexamination Certificate
active
06657815
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a thin film magnetic head comprising at least an inductive 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. As a thin film magnetic head, a composite thin film magnetic head has been widely used. A composite thin film magnetic head has a layered structure which includes a recording head with an inductive magnetic transducer for writing and a reproducing head with a magnetoresistive device (referred to as MR device in the followings) for reading-out. There are a few types of MR devices: one is an AMR device that utilizes an anisotropic magnetoresistive effect (referred to as AMR effect in the followings) and the other is a GMR device that utilizes a giant magnetoresistive effect (referred to as GMR effect in the followings). A reproducing head using the AMR device is called an AMR head or simply an MR head. A reproducing head using the GMR device is called a GMR head. The AMR head is used as a reproducing head whose surface recording density is more than 1 gigabit per square inch. The GMR head is used as a reproducing head whose surface recording density is more than 3 gigabits per square inch.
The AMR head includes an AMR film having the AMR effect. The GMR head has the similar configuration to the AMR head except that the AMR film is replaced with a GMR film having the GMR effect. However, compared to the AMR film, the GMR film exhibits a greater change in resistance under a specific external magnetic field. Accordingly, the reproducing output of the GMR head becomes about three to five times greater than that of the AMR head.
In order to improve the performance of a reproducing head, the MR film may be changed from an AMR film to a GMR film or the like which is made of a material with more excellent magnetoresistive sensitivity. The pattern width of the MR film, specifically the MR height, may be adjusted appropriate. The MR height is the length (height) between the edge of an MR element closer to an air bearing surface and the other edge, and is determined by an amount of polishing the air bearing surface. The air bearing surface (ABS) is a surface of a thin film magnetic head facing 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. The main factor which determines the performance of a recording head is a throat height (TH). The throat height is a length (height) of a portion of a magnetic pole from the air bearing surface to an edge of an insulating layer which electrically isolates a thin film coil for generating a magnetic flux. It is necessary to reduce the throat height in order to improve the performance of the recording head. The throat height is also controlled by an amount of polishing the air bearing surface.
It is necessary to increase the track density of a magnetic recording medium in order to increase the recording density among the performance of a recording head. In order to achieve this, it is necessary to realize a recording head with a narrow track structure in which the width of a bottom pole and a top pole sandwiching a write gap on the air bearing surface is reduced to the order of some microns to submicron. Semiconductor processing technology is used to achieve the narrow track structure.
Now, an example of a method of manufacturing the composite thin film magnetic head will be described as an example of a method of manufacturing the thin film magnetic head of the related art with reference to
FIG. 30
to FIG.
35
.
In the manufacturing method, as shown in
FIG. 30
, an insulating layer
102
about 5 to 10 &mgr;m thick made of alumina (aluminum oxide, Al
2
O
3
), for example, is deposited on a substrate
101
made of altic (Al
2
O
3
and TiC), for example. Then, a bottom shield layer
103
for a reproducing head is formed on the insulating layer
102
. Next, for example, alumina about 100 to 200 nm thick is deposited on the bottom shield layer
103
, whereby a shield gap film
104
is formed. Next, an MR film
105
of a few tens of nanometers in thickness for making up the MR element for reproducing is formed on the shield gap film
104
, and is patterned to a desired shape by photolithography with high precision. Next, a lead layer (not shown in figure) as a lead electrode layer which is 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
, and the MR film
105
is buried in the shield gap films
104
and
106
. Next, a top shield-cum-bottom pole (referred to as a bottom pole in the followings)
107
made of permalloy (NiFe), for example, which is a magnetic material used for both the reproducing head and the recording head, is formed on the shield gap film
106
.
Next, as shown in
FIG. 31
, a write gap layer
108
made of an insulating film such as an alumina film is formed on the bottom pole
107
, and a photoresist film
109
is formed in a predetermined pattern on the write gap layer
108
by photolithography with high precision. Then, a first layer of a thin film coil
110
for an inductive recording head made of copper (Cu), for example, is formed on the photoresist film
109
by plating, for example. Next, a photoresist film
111
is formed in a predetermined pattern so as to cover the photoresist film
109
and the coil
110
by photolithography with high precision. A heat treatment at 250° C., for example, is applied in order to flatten the photoresist film
111
and to isolate between the turns of the coil
110
. Then, a second layer of a thin film coil
112
made of copper, for example, is formed on the photoresist film
111
by plating, for example. Next, a photoresist film
113
is formed in a predetermined pattern on the photoresist film
111
and the coil
112
by photolithography with high precision, and a heat treatment at 250° C., for example, is applied in order to flatten the photoresist film
113
and to isolate between the turns of the coil
112
.
Next, as shown in
FIG. 32
, an opening
108
a for forming a magnetic path is formed in a rear position (right-hand side in
FIG. 32
) of the coils
110
and
112
by partially etching the write gap layer
108
. Then, a top yoke-cum-top pole (referred to as a top pole in the followings)
114
made of a magnetic material for a recording head such as permalloy is selectively formed on the write gap layer
108
, the photoresist films
109
,
111
and
113
. The top pole
114
is in contact with the bottom pole
107
in the above-mentioned opening
108
a
and is magnetically coupled to each other. Next, after etching the write gap layer
108
and the bottom pole
107
about 0.5 &mgr;m thick by ion milling using the top pole
114
as a mask, an overcoat layer
115
made of alumina, for example, is formed on the top pole
114
. A thin film magnetic head is completed after performing machine processing on the slider to form a track surface of a recording head and a reproducing head, that is, an air bearing surface
120
.
FIG. 33
to
FIG. 35
show a completed structure of a thin film magnetic head.
FIG. 33
shows a cross section of the thin film magnetic head vertical to the air bearing surface
120
, while
FIG. 34
shows an enlarged cross section of the magnetic pole portion parallel to the air bearing surface
120
, and
FIG. 35
shows a plan view.
FIG.32
corresponds to a cross-sectional view taken along the line XXX II—XXX II of FIG.
35
. In
FIG. 33
to
FIG. 35
, the overcoat layer
115
is omitted.
In order to improve the performance of a 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 F
Oliff & Berridg,e PLC
TDK Corporation
Tupper Robert S.
LandOfFree
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