Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
2001-07-03
2003-10-14
Arbes, Carl J. (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C029S603130, C029S603240, C360S319000
Reexamination Certificate
active
06631550
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to a composite thin-film magnetic head comprising a recording head and a reproducing head and a method of manufacturing such a thin-film magnetic head, and to a thin-film magnetic head sub-structure used for producing such a thin-film magnetic head and a method of manufacturing such a thin-film magnetic head sub-structure.
2. Description of Related Art
Performance improvements in thin-film magnetic heads have been sought as surface recording density of hard disk drives has increased. Composite thin-film magnetic heads have been widely used. A composite head is made of a layered structure including a recording head having an induction magnetic transducer for writing and a reproducing head having a magnetoresistive (MR) element for reading. MR elements include an an isotropic magnetoresistive (AMR) element that utilizes the AMR effect and a giant magnetoresistive (GMR) element that utilizes the GMR effect. A reproducing head using an AMR element is called an AMR head or simply an MR head. A reproducing head using a GMR element is called a GMR head. An AMR head is used as a reproducing head whose surface recording density is more than 1 gigabit per square inch. A GMR head is used as a reproducing head whose surface recording density is more than 3 gigabits per square inch.
An AMR head comprises an AMR film having the AMR effect. In place of the AMR film a GMR head comprises a GMR film having the GMR effect. The configuration of the GMR head is similar to that of the AMR head. However, the GMR film exhibits a greater change in resistance under a specific external magnetic field compared to the AMR film. As a result, the reproducing output of the GMR head is about three to five times as great as that of the AMR head.
The MR film may be replaced in order to improve the performance of a reproducing head. In general, an AMR film is made of a magnetic substance that exhibits the MR effect and has a single-layer structure. In contrast, many of GMR films have a multilayer structure consisting of a plurality of films. There are several types of mechanisms of producing the GMR effect. The layer structure of a GMR film depends on the type of mechanism. GMR films include a superlattice GMR film, a granular film, a spin valve film and so on. The spin valve film is most efficient since the film has a relatively simple structure, exhibits a great change in resistance in a low magnetic field, and suitable for mass production. The performance of the reproducing head is thus easily improved by replacing the AMR film with a GMR film and the like with an excellent magnetoresistive sensitivity.
Besides selection of a structure as described above, a pattern width such as an MR height, in particular, determines the performance of a reproducing head. The MR height is the length (height) between the end of the MR element closer to the air bearing surface (medium facing surface) and the other end. The MR height is basically controlled by an amount of lapping when the air bearing surface is processed.
Performance improvements in a recording head are also required as the performance of a reproducing head is improved. It is required to increase the track density on a magnetic recording medium in order to increase recording density among the performance characteristics of a recording head. To achieve this, it is required to implement a recording head of a narrow track structure by performing submicron processing on a magnetic layer making up a top pole through the use of semiconductor process techniques. It is also required to use a magnetic material having higher saturation flux density.
Another factor determining the recording head performance is a throat height. The throat height is the length (height) of a portion (called a pole portion in the invention) between the air bearing surface and the end of the insulating layer electrically isolating the thin-film coil. A reduction in throat height is desired in order to improve the recording head performance. The throat height is controlled as well by an amount of lapping when the air bearing surface is processed.
As thus described, it is important to fabricate well-balanced recording and reproducing heads to improve the performance of a thin-film magnetic head.
Reference is now made to
FIG. 15A
to
FIG. 23A
,
FIG. 15B
to
FIG. 23B
, and
FIG. 24
to
FIG. 27
to describe an example of a manufacturing method of a composite thin-film magnetic head as an example of a manufacturing method of a related-art thin-film magnetic head.
FIG. 15A
to
FIG. 23A
are cross sections each orthogonal to the air bearing surface.
FIG. 15B
to
FIG. 23B
are cross sections each parallel to the air bearing surface of the pole portion.
According to the manufacturing method, as shown in FIG.
15
A and
FIG. 15B
, an insulating layer
102
made of alumina (Al
2
O
3
), for example, of about 5 to 10 &mgr;m in thickness is deposited on a substrate
101
made of aluminum oxide and titanium carbide (Al
2
O
3
—TiC), for example.
Next, as shown in FIG.
16
A and
FIG. 16B
, on the insulating layer
102
a bottom shield layer
103
made of a magnetic material is formed for a reproducing head.
Next, as shown in FIG.
17
A and
FIG. 17B
, on the bottom shield layer
103
alumina or aluminum nitride, for example, of 100 to 200 nm in thickness is deposited through sputtering to form a bottom shield gap film
104
as an insulating layer. On the bottom shield gap film
104
an MR film of tens of nanometers in thickness is formed for making an MR element
105
for reproduction. Next, with a photoresist pattern as a mask, the MR film is etched through ion milling, for example, to form the MR element
105
. The MR element
105
may be either a GMR element or an AMR element.
Next, as shown in FIG.
18
A and
FIG. 18B
, a top shield gap film
106
is formed as an insulating layer on the bottom shield gap film
104
and the MR element
105
. The MR element
105
is embedded in the shield gap films
104
and
106
.
Next, as shown in FIG.
19
A and
FIG. 19B
, on the top shield gap film
106
a top shield layer-cum-bottom pole layer (called top shield layer in the following description)
107
is formed. The top shield layer
107
is made of a magnetic material and used for both a reproducing head and a recording head.
Next, a recording gap layer
108
made of an insulating film such as an alumina film is formed on the top shield layer
107
. Next, the recording gap layer
108
is partially etched in a backward portion (the right side of
FIG. 19A
) to form a contact hole for making a magnetic path. Next, a top pole tip
109
for the recording head is formed on the pole portion of the recording gap layer
108
. The top pole layer
109
is made of a magnetic material such as Permalloy (NiFe) or FeN as a high saturation flux density material. At the same time, a magnetic layer
119
made of a magnetic material is formed for making the magnetic path in the contact hole for making the magnetic path.
Next, the recording gap layer
108
and the top shield layer (bottom pole layer)
107
are etched through ion milling, using the top pole tip
109
as a mask. As shown in
FIG. 19B
, the structure is called a trim structure wherein the sidewalls of the top pole (the top pole tip
109
), the recording gap layer
108
, and part of the top shield layer (bottom pole layer)
107
are formed vertically in a self-aligned manner. The trim structure suppresses an increase in the effective track width due to expansion of the magnetic flux generated during writing in a narrow track.
Next, as shown in FIG.
20
A and
FIG. 20B
, an insulating layer
110
of alumina, for example, having a thickness of about 3 &mgr;m is formed over the entire surface. The insulating layer
110
is polished to the surfaces of the pole tip
109
and the magnetic layer
119
and flattened. The polishing method may be mechanical polishing or chemical mechanical polishing (CMP). The surfaces of the pole tip
109
and the magnetic layer
119
are thereby exposed.
On
Arbes Carl J.
Nguyen Tai
TDK Corporation
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