Dynamic magnetic information storage or retrieval – Head – Coil
Reexamination Certificate
1998-09-08
2001-03-20
Miller, Brian E. (Department: 2754)
Dynamic magnetic information storage or retrieval
Head
Coil
C360S125330
Reexamination Certificate
active
06204997
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thin-film magnetic head having at least an induction magnetic transducer for writing and a method of manufacturing the thin-film magnetic head.
2. Description of the Related Art
Performance improvements in thin-film magnetic heads have been sought with an increase in surface recording density of a hard disk drive. A composite thin-film magnetic head has been widely used which 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 anisotropic 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 and AMR head or simply MR head. A reproducing head using a GMR element is called an 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 gigabit per square inch.
An AMR head includes an AMR film having the AMR effect. In a GMR head the AMR film is replaced with a GMR film having the GMR effect and 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.
An MR film may be changed 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 the 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 mechanism. GMR films include a superlattice GMR film, a granular film, a spin valve film and so on. The spin valve film is the most efficient since the film has a relatively simple structure, exhibits a great change in resistance in a low magnetic field, and is suitable for mass production. The performance of a reproducing head is thus easily improved by replacing an AMR film with a GMR film and the like with an excellent magnetoresistive sensitivity.
Besides selection of a material as described above, the pattern width such as the MR height, in particular, determines the performance of a reproducing head. The MR height is the length (height) between the end of an MR element closer to the air bearing surface and the other end. The MR height is controlled by an amount of lapping when the air bearing surface is processed. The air bearing surface is the surface of a thin-film magnetic head that faces a magnetic recording medium and may be called track surface as well.
Performance improvements in a recording head have been expected, too, with performance improvements in a reproducing head. It is required to increase the track density of a magnetic recording medium in order to increase the recording density among the performances of a recording head. In order to achieve this, a recording head of a narrow track structure is required to be implemented, wherein the width on the air bearing surface between a bottom pole and a top pole sandwiching a write gap is reduced to the order of some microns to submicron. Semiconductor process techniques are employed to achieve the narrow track structure.
Another factor determining the recording head performance is the throat height (TH). The throat height is the length (height) of the pole portion between the air bearing surface and the edge of the insulating layer electrically isolating the thin-film coil for generating magnetic flux. 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.
Furthermore, a reduction in length of the portion of the bottom and top poles sandwiching the thin-film coil (called magnetic path length in the following description) is proposed in order to improve the recording head performance.
As thus described, it is important to fabricate a recording head and reproducing head appropriately balanced so as to improve performances of a thin-film magnetic head.
Referring to the accompanying drawings, the configuration of the thin-film coil that determines the magnetic path length and a method of fabricating the coil will now be described.
FIG. 1
to
FIG. 8
illustrate main parts of a method of manufacturing a composite thin-film magnetic head having an MR element as an example of a typical thin-film magnetic head of related art.
FIG. 1
to
FIG. 8
are cross sections of the main parts of intermediate products taken along the plane orthogonal to the air bearing surface. The example shown is a composite thin-film magnetic head made of an induction-type thin-film magnetic head for recording stacked on a magnetoresistive effect type composite thin-film magnetic head for reproduction.
As shown in
FIG. 1
, 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. On the insulating layer
102
a bottom shield layer
103
of 3 to 4 &mgr;m in thickness is formed which makes up a magnetic shield layer for protecting an MR element (an MR film
105
described below) of a reproducing head from an external magnetic field. Next, on the bottom shield layer
103
alumina of 100 to 200 nm in thickness, for example, is deposited through sputtering to form a shield gap film
104
. On the shield gap film
104
the MR film
105
of tens of nanometers in thickness for making up the MR element of the reproducing head is formed and a desired shape is obtained through high-precision photolithography. Next, a shield gap film
106
is formed on the shield gap film
104
and the MR film
105
is buried in the shield gap films
104
and
106
. Next, on the shield gap film
106
a magnetic layer
107
of Permalloy (NiFe) of 3 to 4 &mgr;m in thickness is formed. The magnetic layer
107
not only functions as a top shield layer for magnetically shielding the GMR element of the reproducing head together with the bottom shield layer
103
described above but also functions as a bottom pole of the recording head. For convenience of description, the magnetic layer
107
is simply called bottom pole
107
in the following description, attention being focused on the fact that the magnetic layer
107
is one of the magnetic layers forming the recording head.
Next, as shown in
FIG. 2
, on the bottom pole
107
, a recording gap layer
109
made of a nonmagnetic material such as alumina having a thickness of about 200 nm is formed. A photoresist
110
for determining the reference position of the throat height is formed on the recording gap layer
109
except the part to make up the pole. A thin seed layer
111
made of copper (Cu), for example, of the order of 100 nm in thickness is formed through sputtering over the whole surface. The seed layer
111
is to be a seed of forming a thin-film coil by electroplating. Next, a thick photoresist
112
of 3 to 4 &mgr;m in thickness is formed on the seed layer
111
. A helical opening
113
that reaches the seed layer
111
is formed in the photoresist
112
by photolithography. The depth of the opening
113
is equal to the thickness of the photoresist
112
and the width is about 2 &mgr;m. The width of the helical photoresist pattern formed by the opening
113
is about 2 &mgr;m as well.
Next, as shown in
FIG. 3
, copper electroplating is performed with copper sulfate to form a coil element
114
making up a first layer of the thin-film coil in the opening
113
of the photoresist
112
. The thickness
Miller Brian E.
Oliff & Berridg,e PLC
TDK Corporation
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