Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
2000-02-23
2003-05-06
Tugbang, A. Dexter (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C029S603090, C029S603100, C029S603140, C029S603150, C029S603230, C451S008000, C451S005000, C360S125330, C360S317000
Reexamination Certificate
active
06557241
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of Invention
This invention relates to a method for manufacturing a combination type thin film magnetic head having a writing inductive type thin film magnetic conversion element and a reading magnetoresistive effective type thin film magnetic conversion element which are, insulated magnetically and electrically, stacked on a substrate. Thin invention also relates to a wafer to be used in manufacturing the same thin film magnetic head.
RELATED ART STATEMENT
Recently, with the development of surface recording densities in hard disk devices, thin film magnetic heads are required to have excellent characteristics. For developing the performances of the reading thin film magnetic heads, magnetoresistive effective type thin film magnetic conversion elements are widely available. Although the magnetoresistive effective type thin film magnetic conversion elements using a normal anisotropic magnetoresistive (AMR) effect has been generally employed, the ones using a giant magnetoresistive (GMR), each element having a several times as large resistance variation as the AMR element, have been developed. In this specification, each of these AMR elements and GMR elements, etc., is generically called as a “magnetoresistive effective type thin film magnetic head” (often abbreviated to an “MR element” hereinafter) 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 drive having a large capacity of more than 10 G bites. The height of the MR element (often called as an “MR Height” hereinafter) is a factor to determine the performance of the reading thin film magnetic head. The MR height is the distance of the MR element from an air bearing surface (often called as an “ABS” hereinafter) to its edge, and in a practical manufacturing process of the thin film magnetic head, the desired MR height can be obtained by controlling the polishing amount of the end of the head in forming the ABS.
In addition, the performances of the writing thin film magnetic heads are required to be developed. The development of the surface recording density requires an enhancement of a track density in a magnetic recording medium. Thus, the width of the write gap in the 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 (often called as a “TH” hereinafter) is a factor to determine the performance of the writing thin film magnetic head. The throat height is the distance of the magnetic pole portion to the ABS from the edge of the insulating film to electrically separate the thin film coil, and is desired to be as short as possible.
FIGS. 1-12
shows successive manufacturing steps of a conventionally normal thin film magnetic head and the same magnetic head. The thin film magnetic head is a combination type thin film magnetic head which has a writing inductive type thin film magnetic head and a reading thin film magnetic head with the MR element.
First of all, as shown in
FIG. 1
, an insulating layer
112
made of alumina (Al
2
O
3
) is formed in a thickness of about 5-10 &mgr;m on a substrate
111
made of alumina-titanium-carbon (AlTiC), for example. Then, as shown in
FIG. 2
, a bottom shield gap layer
113
is formed for protecting the reading MR reproducing element against an external magnetic field, and thereafter, as shown in
FIG. 3
, an insulating layer
114
is formed, of alumina, in a thickness of 100-150 nm by sputtering.
Subsequently, as shown in
FIG. 3
, a magnetoresistive layer
115
to constitute the MR reproducing element is formed, of a material having a magnetoresistive effect, in a thickness of several ten nm on the insulating layer
114
, and thereafter, is processed in a desired formation through mask-alignment. Next, as shown in
FIG. 4
, an insulating layer
116
similar to the insulating film
114
is formed, and as shown in
FIG. 5
, a magnetic layer
117
is formed, of permalloy, in a thickness of 3-4 &mgr;m on the insulating layer
116
. The magnetic layer
117
serves as a top shield magnetic layer to magnetically shield the MR reproducing element with the bottom shield magnetic layer
113
, and also as a bottom magnetic layer for the writing thin film magnetic head. Herein, for convenience, the magnetic layer
117
is called as a “first magnetic layer” because it serves as one magnetic layer in the writing magnetic head.
Subsequently, a gap layer
118
is formed, of a non-magnetic material, e.g., alumina, in a thickness of 150-300 nm, on the first magnetic layer
117
. Then, on the gap layer is formed, in a desired pattern through precise mask-alignment, an insulative photoresist
119
, on which a first layer-thin film coil
120
is formed, of Cu, for example, on the photoresist.
Next, as shown in
FIG. 7
, an insulative photoresist layer
121
is formed on the first layer-thin film coil
120
through precise mask-alignment, and thereafter, is baked at a temperature of 250° C., for example to flatten its top surface. Moreover, as shown in
FIG. 8
, a second layer-thin film coil
122
is formed on the flattened top surface of the photoresist layer
121
, and a photoresist layer
123
is formed on the second layer-thin film coil
122
through precise mask-alignment. Thereafter, the photoresist
123
is baked at a temperature of 250° C., for example, to flatten its top surface. As mentioned above, the photoresist layers
119
,
121
,
123
are formed through the precise mask-alignment because the edges of the photoresist are the standard positions to define the Throat Height (TH) and the MR Height.
Subsequently, a second magnetic layer
124
is selectively formed, of permalloy, for example, on the gap layer
118
and the photoresist layers
119
,
121
,
123
alongside a given pattern. The second magnetic layer
124
is contacted with the first magnetic layer
117
in the remote side from the magnetoresistive layer
115
, and the thin film coils
120
and
122
pass through the close magnetic circuit composed of the first and the second magnetic layers
117
and
124
. The second magnetic layer
124
has the magnetic pole portion having a given shape and a given size to define a track width. Moreover, an overcoat layer
125
is formed, of alumina, on the exposed surfaces of the second magnetic layer
124
and the gap layer
118
. Practically, a conductive pattern including the leads and pods to electrically connect the thin film coils
120
,
122
and the MR reproducing element is formed, but not shown in the figures.
In the practical manufacture of the combination type thin film magnetic head, the above substrate
111
is composed of a wafer. Then, many thin film magnetic head units are formed on the wafer, arranged in matrix thereon, and the wafer is cut out in plural bars, each bar having the thin film magnetic head units in a row. The ends of the bar are polished to form the air bearing surfaces of the plural thin film magnetic heads at the same time, and then, the bar is cut out to obtain the combination type thin film magnetic head, respectively. That is, by polishing the side surface
126
in the side of the magnetoresistive layer
115
of the assembly shown in
FIG. 10
, an air bearing surface
127
is formed, opposing to a magnetic recording medium. During the formation of the air bearing surface, the magnetoresistive layer
115
is polished to obtain the MR reproducing element
128
, and at the same time, the Throat Height TH and the MR Height are defined.
Because in the polish of the air bearing surface, the polish of the Throat Height and the MR Height can not monitored, the change of the resistance of the magnetoresistive layer
115
with the decrease of its height is monitored as the change of the current, for example by a resistance-measuring circuit connected to a conductive pattern (not shown in the figures
TDK Corporation
Tugbang A. Dexter
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