Etching a substrate: processes – Forming or treating article containing magnetically...
Reexamination Certificate
1998-07-30
2001-10-02
Markoff, Alexander (Department: 1746)
Etching a substrate: processes
Forming or treating article containing magnetically...
C216S072000, C360S313000, C360S125330, C029S603180
Reexamination Certificate
active
06296776
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of manufacturing a thin film magnetic head, and more particularly to a method of manufacturing a combination type thin film magnetic head constructed by stacking an inductive type writing thin film magnetic head and a magnetoresistive type reading thin film magnetic head on a substrate in an electrically insulating and magnetically isolated 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. In general, as a reading magnetoresistive element, an element utilizing anisotropic magnetoresistive (AMR) effect has been used so far, but there has been further developed a GMR reproducing element utilizing a giant magnetoresistive (GMR) effect having a resistance change ratio higher than that of the normal anisotropic magnetoresistive effect by several times. In the present specification, elements exhibiting a magnetoresistive effect such as 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/inch
2
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. A height (MR Height: MRH) of a magnetoresistive reproducing element is one of factors which determine a performance of a reproducing head including a magnetoresistive reproducing element. 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 ABS. During a manufacturing process of the magnetic head, a desired MR height can be obtained by controlling an amount of polishing the ABS.
The performance of the recording magnetic head is also required to be improved in accordance with the improvement of the performance of the reproducing magnetic 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 write gap at the air bearing surface has to be reduced to a value within a range from several microns to several sub-microns. 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 the performance of the inductive type thin film writing magnetic head 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 a thin film coil from the air bearing surface. It has been required to shorten this distance as small as possible.
FIGS. 1-12
show successive steps for manufacturing a conventional standard thin film magnetic head and a plan view illustrating a completed thin film magnetic head. It should be noted that the thin film magnetic head is of a combination type in which an inductive type thin film magnetic head for writing and a reproducing thin film magnetic head including a MR element are stacked on a substrate.
First of all, as shown in
FIG. 1
, an insulating layer
112
consisting of alumina is deposited on a substance
111
made of, for instance AlTiC and having a thickness of about 5-10 &mgr;m. Next, as shown in
FIG. 2
, after forming a bottom shield magnetic layer
113
which protects the MR reproduction element of the reproducing head from the influence of an external magnetic field, an alumina insulating layer
114
of thickness 100-150 nm is deposited by sputtering as shown in FIG.
3
.
As illustrated in
FIG. 3
, a magnetoresistive layer
115
made of a material having the magnetoresistive effect and constituting the MR reproduction element is formed on the insulating layer with a thickness of several tens nano meters and is then shaped into a given pattern by the highly precise mask alignment. Then, as shown in the
FIG. 4
, an alumina insulating layer
116
similar to the alumina insulating layer
114
is formed, and a magnetic layer
117
made of a permalloy is formed with a film thickness of 3-4 &mgr;m as shown in FIG.
5
. This magnetic layer
117
has not only the function of the upper shield layer which magnetically shields the MR reproduction element together with the above described bottom shield layer
113
, but also has the function of one of poles of the writing thin film magnetic head. Here, the magnetic layer
117
is called a first magnetic layer by taking into account the latter function.
Then, as shown in
FIG. 6
, after forming a write gap layer
118
made of a non-magnetic material such as alumina and having a thickness of about 150-300 nm on the first magnetic layer
117
, an electrically insulating photoresist layer
119
is formed on the gap layer, and then a first layer thin film coil
120
made of, for instance copper is formed on the photoresist layer.
Continuously, as shown in
FIG. 7
, after forming an electrically insulating photoresist layer
121
on the thin film coil
120
by the highly precise mask alignment, the photoresist layer is sintered at a temperature of, for example 250° C. In addition, as shown in
FIG. 8
, a second layer thin film coil
122
is formed on the thus flattened surface of the photoresist layer
121
, and after forming a photoresist layer
123
on the second layer thin film coil
122
with the highly precise mask alignment, the photoresist layer is flattened by performing the sintering process at a temperature of, for example 250° C. As described above, the reason why the photoresist layers
119
,
121
, and
123
are formed by the highly precise mask alignment process, is that the throat height (TH) and MR height (MRH) are defined on the basis of a position of the edges of the photoresist layers on a side of the pole portion.
Next, as shown in
FIG. 9
, a second magnetic layer
124
made of, for example a permalloy and having a thickness of 3-4 &mgr;m is selectively formed on the gap layer
118
and photoresist layers
119
,
121
and
123
in accordance with a desired pattern.
This second magnetic layer
1124
is coupled with the first magnetic layer
117
at a rear position remote from the magnetoresistive layer
115
such that the thin film coils
120
,
122
pass through a closed magnetic circuit composed of the first and second magnetic layers. The second magnetic layer
124
includes a pole portion which has desired configuration and size defining a track width. Furthermore, an overcoat layer
125
made of alumina is deposited on the exposed surfaces of the second magnetic layer
124
and gap layer
118
. In an actual thin film magnetic head, electric conductors and contact pads for performing the electrical connection to the thin film coils
120
,
122
and MR reproduction element are formed, but they are not shown in the drawings.
In an actual manufacturing process of the combination type thin film magnetic head, the above mentioned substrate
111
is formed by a wafer, and after forming a number of thin film magnetic head units in the wafer in matrix, the wafer is divided into a plurality of bars in which a plurality of thin film magnetic head units are aligned, a side surface of a bar is polished to obtain simultaneously air bearing surfaces of said plurality of thin film magnetic heads, and finally the bar is divided into respective thin film magnetic head. That is to say, as shown in
FIG. 10
, a side wall
126
at which the magnetoresistive layer
115
is formed is polished to form the air bearing surface
127
which is to be opposed to a magnetic record medium. During the formation of the air bearing surface
127
, the magnetoresistive lay
Markoff Alexander
Oliff & Berridg,e PLC
Olsen Allan
TDK Corporation
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