Dynamic magnetic information storage or retrieval – Head – Core
Reexamination Certificate
1999-10-13
2001-08-21
Evans, Jefferson (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Core
C360S125330, C360S317000
Reexamination Certificate
active
06278580
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an inductive type thin film magnetic head and a method for manufacturing the same, particularly a composite type thin film magnetic head comprising a writing inductive type thin film magnetic head and a reading magnetoresistive effective type thin film magnetic head which are stacked and supported by a substrate and a method for manufacturing the composite type thin film magnetic head.
2. Related Art Statement
Recently, with the development of surface recording density in hard disk devices, composite type thin film magnetic heads are required to have excellent characteristics.
Then, a composite type thin film magnetic head comprising an inductive type thin film magnetic head for writing and a magnetoresistive effective type thin film magnetic head for reading which are stacked on a substrate is suggested and practically used. Although as the reading magnetoresistive element, a magnetoresistive effective type thin film magnetic head using a normal anisotropic magnetoresistive (AMR) effect has been generally employed, magnetoresistive effective type thin film magnetic heads using a giant magnetoresistive (GMR), each head having a several times as large resistance variation as the AMR element, are developed. Moreover, magnetoresistive effective type tin film magnetic heads using a tunneling junction magnetoresistive (TMR) effect are developed.
In this specification, each of these AMR elements, GMR elements and TMR elements is generically called as a “magnetoresistive effective type thin film magnetic head” or a “MR reproducing element” in brief.
The use of the AMR element enables a surface recording density of several giga bits/inch
2
to be realized, and the use of the GMR element enables the surface recording density to be more enhanced. Such a high surface recording density can realize a hard disk having a large capacity of more than 10G bites.
A height of a magnetoresistive reproducing element (MRH: MR Height) is a factor to determine a performance of a reproducing head composed of such a magnetoresistive reproducing element. The MR height is a distance between an air bearing surface and the end of the magnetoresistive reproducing element exposing to the air bearing surface. In a manufacturing process of a thin film magnetic head, a desired MR height is obtained by controlling the polishing amount of its air bearing surface when polishing the air bearing surface.
On the other hand, with the characteristics of the reproducing head being enhanced, the characteristics of the writing head is required to be developed. The development of the surface recording density requires an enhancement of a track density in a magnetic recording medium. Thus, a width of a write gap in an air bearing surface has to be narrowed to a submicron order from a several micron order, and for realizing it, a semiconductor processing technique is employed.
A throat height is a factor to determine a performance of a writing thin film magnetic head. The throat height is a distance to an edge of an insulating layer to electrically separate a thin film from its air bearing surface, which is desired to be as short as possible. The narrowing of the throat height is determined by a polishing amount from the air bearing surface.
Thus, for enhancing the performance of the composite type thin film magnetic head composed of the stacked writing inductive type thin film magnetic head and reading magnetoresistive effective type thin film magnetic head, it is important to balance the writing inductive type thin film magnetic head with the reading magnetoresistive effective type thin film magnetic head.
FIGS. 1-8
shows successive manufacturing steps of a conventional normal composite type thin film magnetic head. In each figures, reference “A” depicts a cross sectional view, taken on a surface perpendicular to an air bearing surface, and reference “B” depicts a cross sectional view, taken on a surface parallel to the air bearing surface.
First of all, as shown in
FIG. 1
, an insulating layer
2
made of alumina (Al
2
O
3
) is formed in a thickness of about 5-10 &mgr;m on a substrate
1
made of alumina-titanium-carbon (AlTiC), for example, on which a bottom shielding layer
3
constituting one magnetic shield layer to protect a MR reproducing element from an external magnetic field is formed, of permalloy, in a thickness of 2-3 &mgr;m. Then, as shown in
FIG. 2
, a bottom shield gap layer
4
is sputter-formed, of alumina, in a thickness of about 100-150 &mgr;m, and thereafter a magnetoresistive layer
5
constituting the MR reproducing element is formed, of a material having a magnetoresistive effect, in a thickness of several ten nm, and processed into a desired shape with a precise mask alignment. Subsequently, conductive layers
6
a
and
6
b
to connect the magnetoresistive element to an external circuit are formed. A top shield gap layer
7
is formed, of alumina, on a thickness of 100-150 nm, and thereafter, a top pole
8
is formed, of permalloy in a thickness of 3 &mgr;m. The top pole
8
functions as a top shield to magnetically shield the MR reproducing element as well as the above bottom shield layer
3
, but does as a bottom pole of the writing thin film magnetic head importantly, so it is called as a “bottom pole” hereinafter.
Next, as shown in
FIG. 3
, on the bottom pole
8
is formed, of a non magnetic material, for example, alumina, a write gap layer
9
having a thickness of about 200 nm, on which a magnetic layer is formed of a high saturated magnetic flux density such as permalloy (Ni: 50 wt %, Fe: 50 wt %) or iron nitride (FeN). Then, a top pole
10
is formed into a desired shape through a precise mask alignment. The width W of the pole chip
10
defines the track width. Thus, high surface recording density requires to narrow the width W of the pole chip
10
. In this case, a connecting member
11
to magnetically connect the bottom pole
8
and a top pole to be formed later is formed at the same time, which can make easy open a through hole after mechanical polishing or chemical mechanical polishing (CMP).
Then, as shown in
FIG. 4
, for preventing the broadening of the effective writing track width, that is, for preventing the broadening of the magnetic flux of one pole in writing data, the write gap layer
9
and the bottom pole are etched by ion beam etching such as ion milling to form a trim structure. Thereafter, an insulating layer
12
is formed, of alumina, in a thickness of 3 &mgr;m, and is flattened by CMP so as to have the same level surface as the pole chip
10
.
Thereafter, as shown in
FIG. 5
, a first thin film coil
13
is formed, of Cu, for example, so as to be supported in insulated separation by an insulating layer
14
, the surface of which is flattened. Then, a second thin film coil
15
is formed on the surface of the insulating layer
14
so as to be supported in insulated separation by an insulating layer
16
.
The thus obtained assembly is fired at 250° C., for example, to flatten the surface of the insulating layer
16
to support the second thin film coil
15
. Thereafter, as shown in
FIG. 6
, a top pole
17
made of permalloy is selectively formed alongside a desired pattern, in a thickness of 3 &mgr;m, on the pole chip
10
and the insulating layers
14
,
16
, and an overcoat layer
18
is formed, of alumina, on the surface over the thus obtained assembly.
Finally, the sides of the assembly are polished to form an air bearing surface (ABS)
19
opposing to a magnetic recording medium. In the forming process of the air bearing surface
19
, the magnetoresistive layer
5
is polished, too and thereby, a MR reproducing element
20
is obtained. In this way, the above throat height TH and MR height MRH are determined.
In a real thin film magnetic head, pads to electrically connect the thin film coils
13
,
15
and the MR reproducing element
20
are formed, but omitted in the figures.
FIG. 7
is a plan view, as shown in
FIG. 4
, showing the state in which the pole chip
10
and the conne
Evans Jefferson
Oliff & Berridg,e PLC
TDK Corporation
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