Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
2001-01-22
2003-12-30
Ometz, David L. (Department: 2653)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
C360S234500
Reexamination Certificate
active
06671134
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thin film magnetic head comprising at least one of an inductive type thin film magnetic head for writing and a magnetoresistive type thin film magnetic head for reading, and also relates to a method of manufacturing such a thin film magnetic head. Particularly, the present invention relates to a combination type thin film magnetic head comprising an inductive type thin film magnetic head for writing and a magnetoresistive type thin film magnetic head for reading which are supported by a substrate in a stacked manner.
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. There has been proposed and actually used a combination type thin film magnetic head including an inductive type thin film magnetic head for writing and a magnetoresistive type magnetic head for reading, said magnetic heads being supported by a substrate in a stacked fashion. As the reading magnetic head utilizing the magnetoresistive effect, there has been generally used a reading magnetic head utilizing an anisotropic magnetoresistive (AMR) effect, but there has been also developed a magnetic head 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 elements are termed as a magnetoresistive type thin film magnetic head or simply MR reproducing element.
By using the AMR 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 (MR Height) of a magnetoresistive reproducing element is one of factors which determine a performance of a reproducing head including a magnetoresistive reproducing element. This MR height 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 is 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 accordance with the improvement of the reproducing head. 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 magnetic film for writing is a throat height (TH). This throat height 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 is determined by an amount of polishing the air bearing surface.
In order to improve the performance of the combination type thin film magnetic head including a stack of an inductive type thin film magnetic head for writing and a magnetoresistive type thin film magnetic head for reading, it is important that the inductive type thin film magnetic head for writing and magnetoresistive type thin film magnetic head for reading are formed with a good balance.
FIGS. 1-6
show successive steps of manufacturing a known typical thin film magnetic head, in which A represents a cross sectional view cut along a plane perpendicular to the air bearing surface and B denotes a cross sectional view cut along a plane parallel with the air bearing surface.
FIG. 7
is a plan view illustrating a whole structure of the known thin film magnetic head. This magnetic head belongs to a combination 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
FIG. 1
, on a substrate
1
made of, for instance 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. A first magnetic layer
3
serving as a magnetic shield for protecting the MR element of the reading head from an external magnetic field is formed with a thickness of 3 &mgr;m Then, after depositing by sputtering an insulating layer
4
serving as a shield gap layer made of an alumina with a thickness of 100-150 nm as shown in
FIG. 2
, a magnetoresistive layer
5
having a thickness not larger than 10 nm 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, an insulating layer
6
serving as a second shield gap layer is formed to embed the magnetoresistive layer
5
within the shield gap layer consisting of the insulating layers
4
and
6
.
Next, as shown in
FIG. 3
, a second magnetic layer
7
made of a permalloy and having a thickness of 3 &mgr;m is formed. This second magnetic layer
7
serves not only as the other shield layer for magnetically shielding the MR reproducing element together with the above mentioned first magnetic layer
3
, but also as one of poles of the inductive type writing thin film magnetic head to be manufactured later.
Next, after forming, on the second 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 magnetic layer made of a magnetic material having a high saturation magnetic flux density such as permalloy (Ni 50 wt %: Fe 50 wt %) and iron nitride (FeN), and this magnetic layer is shaped into a given pattern by a highly precise mask alignment to form a pole chip
9
. A width W of the pole chip
9
defines a track width. Therefore, in order to attain the high surface recording density, it is necessary to narrow the width W of the pole chip
9
as small as possible. During the formation of the pole chip
9
, a dummy pattern
9
′ for connecting the second magnetic layer
7
with a third magnetic layer constituting the other pole is formed. This dummy pattern makes the formation of a through hole easy after mechanical polishing or chemical-mechanical polishing (CMP).
Then, 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 second magnetic layer
7
constituting the other pole are removed by an ion beam etching such as an ion milling, while the pole chip
9
is utilized as a mask. The thus formed structure is called a trim structure, and the trim structure constitutes a pole portion of the second magnetic layer.
Furthermore, as depicted in
FIG. 4
, after forming a depression in a surface of the second insulating layer
7
, an insulating layer
10
made of an alumina is formed to have a thickness of about 3 &mgr;m. Then, a first layer thin film coil
11
made of, for instance a copper is formed on the insulating layer
10
as shown in
FIG. 5
, and assembly is flattened by CMP. Then, after forming an electrically insulating photoresist layer
12
, a surface of the photoresist layer is flattened by baking at a temperature of, for instance 250-300° C.
Next, on the flat surface of the photoresist layer
Oliff & Berridg,e PLC
Ometz David L.
TDK Corporation
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