Dynamic magnetic information storage or retrieval – Head – Core
Reexamination Certificate
2000-09-11
2003-02-25
Evans, Jefferson (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Core
C360S123090
Reexamination Certificate
active
06525905
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thin-film magnetic head having at least an inductive-type magnetic transducer for writing and to a method of manufacturing the same.
2. Description of the Related Art
In recent years, improvements in the performance of a thin-film magnetic head are sought since a surface recording density of a hard disk device has been improved. A composite thin-film magnetic head having a structure, in which a recording head having an inductive-type magnetic transducer for writing and a reproducing head having a magnetoresistive (hereinafter referred to as MR) element for reading are stacked, is widely used as the thin-film magnetic head.
A factor that determines the performance of the recording head is accuracy in processing a throat height (TH). The throat height is a length (height) of a portion (magnetic pole portion) between an air bearing surface and an edge of an insulating layer which electrically isolates a thin-film coil. The air bearing surface, here, is a surface of the thin-film magnetic head facing a magnetic recording medium, and is also called a track surface. A reduction in the throat height is desired in order to improve the recording head performance. The throat height is controlled by an amount of polishing in processing the air bearing surface.
In order to improve the performance of the thin-film magnetic head, the above recording head and the reproducing head must be formed in a good balance.
A method of manufacturing a composite thin-film magnetic head is described with reference to
FIGS. 42A and 42B
to
FIGS. 48A and 48B
as an example of the thin-film magnetic head of the art related to the present invention.
FIG. 49
is a plan view of the composite thin-film magnetic head of the art related to the present invention.
FIG. 42A
to
48
A each illustrate a manufacturing step taken along the line XLVIIIA—XLVIIIA in
FIG. 49
, while
FIG. 42B
to
48
B each illustrate a manufacturing step taken along the line XLVIIIB—XLVIIIB in FIG.
49
.
First, as shown in FIG.
42
A and
FIG. 42B
, an insulating layer
102
made of, for example, alumina (aluminum oxide: Al
2
O
3
) of about 5 &mgr;m in thickness is formed on a substrate
101
made of, for example, Altic, i.e., aluminum oxide and titanium carbide (Al
2
O
3
with TiC). A bottom shield layer
103
for a reproducing head is formed of, for example, permalloy (NiFe) on the insulating layer
102
.
As shown in
FIGS. 43A and 43B
, a shield gap film
104
is formed on the bottom shield layer
103
by depositing, for example, alumina in thickness of 35 nm to 60 nm. An MR film
105
of tens of nanometers in thickness for making up the MR element for reproduction is formed on the shield gap film
104
, and a desired shape is obtained through photolithography with high precision. Next, a pair of lead terminal layers
106
are formed by a lift-off method on both sides of the MR film
105
. A shield gap film
107
is formed on the shield gap film
104
, the MR film
105
, and the lead terminal layers
106
, so that the MR film
105
and the lead terminal layers
106
are buried between the shield gap films
104
and
107
. Further, as shown in FIG.
43
A and
FIG. 43B
, a top-shield-cum-bottom pole (or a bottom magnetic layer; hereinafter referred to simply as a bottom pole)
108
having a thickness of 2.5 &mgr;m to 3.5 &mgr;m and made of a magnetic material, such as permalloy, used for both reproduction and recording heads, is formed on the shield gap film
107
.
As shown in FIG.
44
A and
FIG. 44B
, a write gap layer
109
made of, for example, an alumina film and having a thickness of 200 nm to 250 nm is formed on the bottom pole
108
. The write gap layer
109
is patterned through photolithography, to thereby form an opening
109
a
for magnetically connecting the bottom pole
108
and a top pole (or a top magnetic layer; hereinafter referred to simply as a top pole)
113
to be formed thereon in a later step. A photoresist film
110
as a first layer of photoresist films of 1.0 &mgr;m to 1.5 &mgr;m in thickness is formed on the write gap layer
109
, and the photoresist film
110
is then processed to a prescribed pattern through high-precision photolithography. The purpose of providing the photoresist film
110
is to improve insulation capability between the bottom pole
108
and a thin-film coil
111
to be formed on the photoresist film
110
in a later step.
As shown in
FIG. 45A
, the thin-film coil
111
for an inductive recording head made of, copper (Cu) and having a thickness of 1.5 &mgr;m to 2.0 &mgr;m is selectively formed on the photoresist film
110
by, for example, electroplating.
Next, as shown in
FIG. 46A
, a photoresist film
112
of, for example, 1.0 &mgr;m to 1.5 &mgr;m in thickness is formed on the thin-film coil
111
, and the photoresist film
112
as a second layer of photoresist films is patterned to a prescribed shape through photolithography with high precision. The photoresist film
112
is subjected to a predetermined heat treatment, so as to planarize the surface and improve insulation capability between the thin-film coil
111
and the top pole
113
which will be formed on the photoresist film
112
in a later step. This kind of photoresist film
112
can achieve surface planarization regardless of the surface irregularity of the underlayer, and can also provide a very gentle slope at the edge (peripheral area) of the photoresist film
112
by performing heat treatment after patterning to gradually change the thickness of the film.
An end (or edge) of the second photoresist film
112
shown on the left hand side in
FIG. 46A
corresponds to the reference position for determining the throat height (TH), i.e. the throat height zero (TH
0
) position. As shown in this figure, a side surface of the photoresist film
112
located on the above edge side can effectively determine an apex angle. The apex angle is an angle &thgr; between the tangent line to an end surface of the photoresist film
112
on the track surface (air bearing surface)
100
side and an upper surface of the top pole
113
to be formed in a later step (or the surface of the substrate
101
).
The apex angle (angle &thgr;) formed by the gentle slope of the second photoresist film
112
can be reduced to about 25 degrees to 35 degrees by setting the distance between the throat height zero (TH
0
) position and the position of the side surface of the outermost periphery portion of the thin-film coil
111
to, for example, 10 &mgr;m. In other words, when the bottom pole
108
, the write gap layer
109
, and the top pole
113
are patterned through photolithography to define the recording track width in a later step, a relatively small apex angle allows such patterning to be performed on planarized regions, so that patterning accuracy can be improved and therefore the narrower track can be realized.
As shown in
FIG. 47A
, a top yoke-cum-top pole
113
of 2.0 &mgr;m to 3.0 &mgr;m in thickness is formed of a magnetic material for the recording head, such as permalloy, on the photoresist film
112
. The top pole
113
has, for example, such a plan shape as shown in
FIG. 49
, which will be described hereinafter. As shown in
FIG. 49
, the top pole
113
has a top pole tip portion
113
a
having a width corresponding to the track width on the track surface (air bearing surface)
100
side. As shown in FIG.
47
A and
FIG. 47B
, the top pole tip portion
113
a
of the top pole
113
faces part of the bottom pole
108
located on the track surface (air bearing surface)
100
side with the write gap layer
109
in between. The top pole
113
has contact with the bottom pole
108
through the opening
109
a
, magnetically coupled thereto.
As shown in
FIG. 48B
, the write gap layer
109
and the bottom pole
108
are partially etched by about 0.3 &mgr;m to 0.4 &mgr;m by ion milling etching using the top pole tip portion
113
a
of the top pole
113
as a mask. By etching as far as the bottom pole
108
to form a trim structure, the effective writing trac
Evans Jefferson
Oliff & Berridge PLC.
TDK Corporation
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