Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
2000-06-13
2003-08-26
Chang, Richard (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C029S603070, C029S603150, C029S603230, C360S112000, C360S125330
Reexamination Certificate
active
06609291
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thin film magnetic head and a method of manufacturing the same, and more particularly to technique of improving a performance of an inductive type thin film writing magnetic head of a composite type thin film magnetic head constructed by stacking the inductive type thin film writing magnetic head and a magnetoresistive type reading magnetic head one on the other.
2. Description of the Related Art
Recently a surface recording density of a hard disc device has been improved, and it has been required to develop a thin film magnetic head having an improved performance accordingly. In order to improve a performance of a reading magnetic head, a reproducing head utilizing a magnetoresistive effect has been widely used. As the reproducing magnetic head utilizing the magnetoresistive effect, an AMR reproducing element utilizing a conventional anisotropic magnetoresistive (AMR) effect has been widely used. There has been further developed a GMR reproducing element utilizing a giant magnetoresistive (GMR) effect having a resistance change ratio higher than the normal anisotropic magnetoresistive effect by several times. In the present specification, these AMR and GMR reproducing elements are termed as a magnetoresistive reproducing element or MR reproducing element.
By using the AMR reproducing element, a very high surface recording density of several gigabits per a unit square inch has been realized, and a surface recording density can be further increased by using the GMR element. By increasing a surface recording density in this manner, it is possible to realize a hard disc device which has a very large storage capacity of more than 10 gigabytes and is still small in size.
A height of a magnetoresistive reproducing element is one of factors which determine a performance of a reproducing head including a magnetoresistive reproducing element. This height is generally called MR Height, here denoted by MRH. The MR height MRH is a distance measured from an air bearing surface on which one edge of the magnetoresistive reproducing element is exposed to the other edge of the element remote from the air bearing surface. During a manufacturing process of the magnetic head, a desired MR height MRH can be obtained by controlling an amount of polishing the air bearing surface.
At the same time, a performance of a recording head has been also required to be improved. In order to increase a surface recording density, it is necessary to make a track density on a magnetic record medium as high as possible. For this purpose, a width of a pole portion at the air bearing surface has to be reduced to a value within a range from several micron meters to several sub-micron meters. In order to satisfy such a requirement, the semiconductor manufacturing process has been adopted for manufacturing the thin film magnetic head. One of factors determining a performance of an inductive type thin film writing magnetic film is a throat height TH. This throat height TH is a distance of a pole portion measured from the air bearing surface to an edge of an insulating layer which serves to separate electrically a thin film coil from the air bearing surface. It has been required to shorten this distance as small as possible. Also this throat height TH is determined by an amount of polishing the air bearing surface.
FIGS. 1
a
,
1
b
-
9
a
,
9
b
are cross sectional views showing successive steps of a known method of manufacturing a conventional typical thin film magnetic head, said cross sectional views being cut along a plane perpendicular to the air bearing surface and cut along a plane parallel with the air bearing surface.
FIGS. 10-12
are a cross sectional view illustrating a completed thin film magnetic head cut along a plane perpendicular to the air bearing surface, a cross sectional view of the pole portion cut along a plane parallel with the air bearing surface, and a plan view depicting the pole portion. This magnetic head belongs to a composite type thin film magnetic head which is constructed by stacking an inductive type thin film writing magnetic head and a magnetoresistive type thin film reading magnetic head one on the other.
At first, as illustrated in
FIGS. 1
a
and
1
b
, on a substrate
1
made of a hard non-magnetic material such as aluminum-titan-carbon (AlTiC), is deposited an insulating layer
2
made of alumina (Al
2
O
3
) and having a thickness of about 5-10 &mgr;m. Then, as depicted in
FIGS. 2
a
and
2
b
, a bottom shield layer
3
constituting a magnetic shield for the MR reproducing magnetic head is formed to have a thickness of about 3 &mgr;m on the insulating layer.
Then, after depositing by sputtering a shield gap layer
4
made of an alumina with a thickness of 100-150 nm as shown in
FIGS. 3
a
and
3
b
, a magnetoresistive layer
5
having a thickness of several tens nano meters and being made of a material having the magnetoresistive effect, and the magnetoresistive layer is shaped into a desired pattern by a highly precise mask alignment.
Next, as represented in
FIGS. 4
a
and
4
b
, a shield gap layer
6
is formed such that the electromagnetic layer
5
is embedded within the shield gap layers
4
,
6
.
Then a magnetic layer
7
made of a permalloy and having a thickness of 3 &mgr;m is formed as shown in
FIGS. 5
a
and
5
b
. This magnetic layer
7
serves not only as an upper shield layer for magnetically shielding the MR reproducing element together with the above mentioned bottom shield layer
3
, but also as a bottom magnetic layer of the inductive type writing thin film magnetic head to be manufactured later. Here, for the sake of explanation, the magnetic layer
7
is called a first magnetic layer, because this magnetic layer constitutes one of magnetic layers forming the thin film writing magnetic head.
Next, after forming, on the first magnetic layer
7
, a write gap layer
8
made of a nonmagnetic material such as alumina to have a thickness of about 200 nm, a second magnetic layer
8
made of a magnetic material having a high saturated magnetic flux density such as a permalloy (Ni: 50 wt %, Fe: 50 wt %) and iron nitride (FeN) and the second magnetic layer is shaped into a desired pattern by means of a precise mask alignment.
This second magnetic layer
24
having a desired pattern is called a pole chip and a track width is determined by a width of the pole chip.
During this process, a dummy pattern
9
′ for connecting the bottom pole (first magnetic layer) to an upper pole (third magnetic layer) to be formed later is formed. Then a through hole can be easily formed after mechanical polishing or chemical-mechanical polishing (CMP).
In order to prevent an increase of an effective track width, that is, in order to prevent a spread of a magnetic flux at the lower pole during a writing operation, the gap layer
8
and bottom pole (first magnetic layer) near the pole chip
9
are removed by an ion beam etching such as an ion milling. This condition is illustrated in
FIG. 5
, and this structure is called a trim structure. It should be noted that this portion constitutes the pole portion of the first magnetic layer.
Next, as illustrated in
FIGS. 6
a
and
6
b
, an insulating layer
10
such as an alumina layer is formed to have a thickness of about 3 &mgr;m, and then an assembly is flattened by, for instance CMP.
After that, an electrically insulating photo-resist layer
11
is formed in accordance with a given pattern by a highly precise mask alignment, and then a first layer of a thin film coil
12
made of, for instance copper is formed on the photo-resist layer
11
.
Next, as depicted in
FIGS. 7
a
and
7
b
, an insulating photo-resist layer
13
is formed on the thin film coil
12
by a highly precise mask alignment, a surface is flattened by baking at a temperature of, for instance 250-300° C.
Furthermore, as shown in
FIGS. 8
a
and
8
b
, on the thus flattened surface of the photo-resist layer
13
, a second layer thin film coil
14
is formed. Then, a photo-resist laye
Fukuda Kazumasa
Iijima Atsushi
Sasaki Yoshitaka
Chang Richard
TDK Corporation
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