Dynamic magnetic information storage or retrieval – Head – Core
Reexamination Certificate
2000-09-15
2003-11-11
Klimowicz, William (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Core
Reexamination Certificate
active
06646828
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 magnetic transducer for writing and a method of manufacturing the same.
2. Description of the Related Art
In recent years, improvement in performance of a thin film magnetic head is demanded in association with improvement 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 magnetic transducer for writing and a reproducing head having a magnetoresistive (hereinbelow, referred to as MR) device for reading are stacked is widely used. MR devices include an anisotropic magnetoresistive (hereinbelow, described as AMR) device using the AMR effect and a GMR (giant magnetoresistive) device using the GMR effect. 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 having a surface recording density which is higher than 1 Gbit/inch
2
. The GMR head is used as a reproducing head whose surface recording density is higher than 3 Gbits/inch
2
.
The AMR film is a film made of a magnetic substance producing the MR effect and has a single layer structure. On the other hand, many of GMR films have a multi-layer structure in which a plurality of films are combined. There are some kinds of mechanisms of producing the GMR effect. The layer structure of the GMR film varies according to the mechanism. As GMR films, a super lattice GMR film, a spin valve film, a granular film, and the like have been proposed. The spin valve film is promising as a GMR film having a relatively simple construction and exhibiting a large resistance change with a weak magnetic field, which is intended for mass production.
A factor of determining the performance of the reproducing head is processing accuracy of a pattern width, especially, an MR height. The MR height is the length (height) from the end on the air bearing surface (ABS) side of the MR device to the end on the opposite side, and is inherently controlled by a polishing amount at the time of processing the air bearing surface. 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.
On the other hand, in association with the improvement in performance of a reproducing head, improvement in performance of a recording head is also demanded. In order to increase the recording density in the performance of the recording head, it is necessary to raise the track density in a magnetic recording medium. For this purpose, it is necessary to realize a recording head of a narrow track structure in which the track 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.
Another factor of determining the performance of the recording head is processing accuracy of the throat height (TH). The throat height is the length (height) of a portion (magnetic pole portion) extending from the air bearing surface to the edge of an insulating layer which electrically isolates a thin film coil. In order to improve the performance of the recording head, reduction in the throat height is desired. The throat height is also controlled by a polishing amount at the time of processing the air bearing surface.
In order to improve the performance of a thin film magnetic head, it is important to form the recording head and a reproducing head as described above with a good balance.
Referring now to
FIGS. 30A and 30B
to
FIGS. 35A and 35B
, a method of manufacturing a composite thin film magnetic head as an example of a conventional thin film magnetic head will be described.
FIG. 36
is a plan view of a conventional composite thin film magnetic head.
FIGS. 30A
to
35
A are cross sections each taken along cut line XXXVA—XXXVA of FIG.
36
.
FIGS. 30B
to
35
B are process cross sections each taken along cut line XXXVB—XXXVB of FIG.
36
.
First, as shown in
FIGS. 30A and 30B
, an insulating layer
102
made of, for example, alumina (aluminium oxide, Al
2
O
3
) is formed 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 bottom shield layer
103
for a reproducing head made of permalloy (NiFe) or the like is formed on the insulating layer
102
.
As shown in
FIGS. 31A and 31B
, for example, alumina is then formed in thickness of 100 nm 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 reproduction is deposited in thickness of tens nm on the shield gap film
104
and is formed in a desired shape by high-precision photolithography. Then a pair of lead terminal layers
106
are formed on both ends of the MR film
105
by a lift-off method. A shield gap film
107
is formed on the shield gap film
104
, MR film
105
, and lead terminal layers
106
and the MR film
105
and the lead terminal layers
106
are buried between the shield gap films
104
and
107
. A top shield-cum-bottom pole (hereinbelow, simply described as bottom pole)
108
having a thickness of 3 &mgr;m made of a magnetic material such as NiFe used for both the reproducing head and the recording head is formed on the shield gap film
107
.
As shown in
FIGS. 32A and 32B
, on the bottom pole
108
, a write gap layer
109
having a thickness of 200 nm as an insulating film which is, for example, an alumina film is formed. Further, the write gap layer
109
is patterned by photolithography and an opening
109
A for connecting the bottom pole
108
and a top pole (
116
) which will be formed later on the write gap layer is formed. Subsequently, a pole tip
110
is formed by using a magnetic material such as NiFe or iron nitride (FeN) by plating and a poles coupling portion
110
A for magnetically connecting the top pole and the bottom pole
108
is formed. By preliminarily forming the poles coupling portion
110
A, the bottom pole
108
and the top pole can be easily magnetically connected to each other without forming an opening (through hole) for connecting both of the poles after forming an insulating layer
111
and planarizing the surface of the insulating layer
111
by a CMP (Chemical and Mechanical Polishing) process.
As shown in
FIGS. 33A and 33B
, the pole tip
110
is used as a mask and etching of about: 0.3 to 0.5 &mgr;m is performed by ion milling to remove a part of the surfaces of the write gap layer
109
and the bottom pole
108
. Etching is performed to the bottom pole
108
and a trim structure is obtained, thereby preventing the effective write track width from being expanded (that is, the expansion of a magnetic flux in the bottom pole
108
is suppress at the time of writing data). Subsequently, the insulating layer
111
made of, for example, alumina having a thickness of about 3 &mgr;m is formed on the whole surface of the substrate and the whole surface of the insulating layer
111
is planarized by CMP.
As shown in
FIGS. 34A and 34B
, a thin film coil
112
as the first layer for an inductive recording head made of, for example, copper (Cu) is selectively formed on the insulating layer
111
by plating or the like. Subsequently, a photoresist film
113
is formed in a predetermined pattern by high-precision photolithography on the insulating layer
111
and the thin film coil
112
. Then, heat treatment is performed at a predetermined temperature for planarizing the photoresist film
113
and insulating t urns of the thin film coil
112
. Further, under conditions similar to those of the first thin film coil
112
, a thin film coil
114
as the second layer is formed on the photoresist film
113
. A photoresist film
115
is formed on the second thin film coil
114
and heat treatment is performed at a predetermined temper
Klimowicz William
Oliff & Berridg,e PLC
TDK Corporation
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