Etching a substrate: processes – Forming or treating article containing magnetically...
Reexamination Certificate
2001-03-21
2004-03-30
Mills, Gregory (Department: 1763)
Etching a substrate: processes
Forming or treating article containing magnetically...
C029S603070, C029S603120, C029S603130, C029S603150, C029S603160
Reexamination Certificate
active
06712984
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of manufacturing a thin film magnetic head having at least an inductive magnetic transducer for writing.
2. Description of the Related Art
In recent years, an improvement in performance of a thin film magnetic head is demanded in association with an increase in surface recording density of a hard disk drive. As a thin film magnetic head, a composite thin film magnetic head of a structure in which a recording head having an inductive magnetic transducer for writing and a reproducing head having a magnetoresistive (hereinbelow, referred to as MR) element for reading are stacked is widely used.
In order to improve the recording density in the performances of a recording head, it is necessary to increase track density of a magnetic recording medium. For this purpose, it is necessary to realize a recording head of a narrow track structure in which the width on the air bearing surface of each of a bottom pole and a top pole formed sandwiching a write gap is reduced to the order of a few microns to submicrons. In order to achieve this, semiconductor processing techniques are used.
Referring to
FIGS. 37
to
42
, as an example of a method of manufacturing a conventional thin film magnetic head, a method of manufacturing a composite thin film magnetic head will be described.
According to the manufacturing method, first, as shown in
FIG. 37
, an insulating layer
102
made of, for example, aluminium oxide (Al
2
O
3
, hereinafter referred to as “alumina”) is deposited in thickness of about 5 to 10.0 &mgr;m on a substrate
101
made of altic (Al
2
O
3
.TiC) or the like. Subsequently, a bottom shield layer
103
for a reproducing head is formed on the insulating layer
102
. For example, alumina is then deposited by sputtering in thickness of 100 to 200 nm on the bottom shield layer
103
to form a shield gap film
104
. An MR film
105
for constructing an MR device for reproduction is deposited in thickness of tens nm on the shield gap film
104
and is patterned in a desired shape by high-precision photolithography. Then lead layers (not shown) as lead electrode layers which are electrically connected to the MR film
105
are formed on both sides of the MR film
105
. After that, a shield gap film
106
is formed on the lead layers, the shield gap film
104
, and the MR film
105
, so that the MR film
105
is buried in the shield gap films
104
and
106
. An top shield-cum-bottom pole (hereinafter referred to as a bottom pole)
107
made of a magnetic material such as a nickel iron alloy (NiFe, hereinafter also simply referred to as Permalloy (trademark)) used for both of the reproducing head and the recording head is formed on the shield gap film
106
.
As shown in
FIG. 38
, on the bottom pole
107
, a write gap layer
108
made of an insulating material such as alumina is formed. Further, a photoresist film
109
is formed in a predetermined pattern on the write gap film
108
by high-precision photolithography. On the photoresist film
109
, a thin film coil
110
for an inductive recording head made of copper (Cu) or the like is formed by, for example, plating. A photoresist film
111
is formed in a predetermined pattern by high-precision photolithography so as to cover the photoresist film
109
and the thin film coil
110
. In order to insulate turns of the thin film coil
110
from each other, a heat treatment is performed at, for example, 250° C. on the photoresist film
111
.
As shown in
FIG. 39
, in a position rearward of the thin film coil
110
(right side in FIG.
39
), to form a magnetic path, an opening
108
a
is formed by partially etching a part of the write gap layer
108
to expose a part of the bottom pole
107
. A magnetic material having high saturated flux density, for example, Permalloy is selectively formed so as to cover the exposed face of the bottom pole
107
, the photoresist film
111
, and the write gap layer
108
by electrolyte plating. A photoresist film is formed on this plating film made of Permalloy and, after that, the photoresist film is subjected to a selective exposure process (photolithography process), thereby forming a photoresist film pattern (not shown) having a predetermined plane shape. By using the photoresist film pattern as a mask, the plating film is selectively etched by ion milling, thereby forming a top yoke-cum-top magnetic pole (hereinbelow, called top pole)
112
. The top pole
112
has a plane shape as shown in
FIG. 42
which will be described hereinlater, and includes a yoke portion
112
a
and a pole tip portion
112
b
. The top pole
112
is in contact with and magnetically coupled to the bottom pole
107
via the opening
108
a
. By using a part (pole tip portion
112
b
) of the top pole
112
as a mask, both the write gap layer
108
and the bottom pole
107
are selectively etched about 0.5 &mgr;m by ion million (refer to FIG.
41
). After that, an overcoat layer
113
made of, for example, alumina is formed on the top pole
112
. Finally, a track surface, namely, an air bearing surface
120
of the recording head and the reproducing head is formed by a mechanical process and a polishing process. In such a manner, a thin film magnetic head is completed.
FIGS. 40
to
42
show the structure of the thin film magnetic head in a completed state.
FIG. 40
is a cross section of the thin film magnetic head perpendicular to the air bearing surface
120
.
FIG. 41
is an enlarged cross section parallel to the air bearing surface
120
of the pole portion.
FIG. 42
is a plan view of the structure.
FIG. 39
is a cross section taken along line XXXIX—XXXIX of FIG.
42
. In
FIGS. 40
to
42
, the overcoat layer
113
and the like are not shown. In
FIG. 42
, with respect to the thin film coil
110
and the photoresist film
111
, only the outlines are shown.
FIGS. 40 and 42
, “TH” denotes throat height. “MRH” denotes an MR height. The “throat height (TH)” is one of factors determining the performances of the recording head and is a length from a position of the end on the side closest to the air bearing surface
120
, of the insulating layer (photoresist film
111
) for electrically isolating the thin film coil
110
from the other conductive portion, that is, the throat height zero position (TH
0
position) to the position of the air bearing surface
120
. In order to improve the performances of the recording head, it is necessary to optimize the throat height TH. The throat height (TH) is controlled according to a polishing amount at the time of processing the air bearing surface
120
. An “MR height (MRH)” denotes a length from the position of the end on the side furthest from the air bearing surface
120
, of the MR film
105
, that is, the MR height zero position (MRH
0
position) to the position of the air bearing surface
120
. The MR height (MRH) is also controlled by the polishing amount at the time of processing the air bearing surface
120
.
Factors determining the performances of the thin film magnetic head include not only the throat height (TH) and the MR height (MRH) but also an apex angle &thgr; shown in FIG.
40
. The apex angle &thgr; is an average inclination angle of an inclined face on the side close to the air bearing surface
120
of the photoresist film
111
.
As shown in
FIG. 41
, a structure in which a part of the write gap layer
108
and a part of the bottom pole
107
are etched in a self-aligned manner with respect to the pole tip portion
112
b
of the top pole
112
is called a trim structure. According to the trim structure, an increase in effective track width due to expansion of the magnetic flux generated at the time of writing data to a narrow track can be prevented. “P
2
W” shown in
FIG. 41
denotes a width of the portion having the trim structure (hereinbelow, simply called “pole tip portion
500
”), that is, a pole width (hereinbelow, also called “track width”). The process dimension of the pole width P
2
W depends on the width of the portion corresponding to the pole tip portion
500
,
Culbert Roberts
Mills Gregory
Oliff & Berridg,e PLC
TDK Corporation
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