Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
2001-02-12
2003-09-23
Tugbang, A. Dexter (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C029S603110, C029S603130, C029S603150, C029S603160, C029S605000, C029S606000, C300S013000, C300S013000, C451S005000, C451S041000
Reexamination Certificate
active
06622371
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The 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
Recently, an improvement in performance of a thin film magnetic head has been sought in accordance with an increase in a surface recording density of a hard disk drive. A composite thin film magnetic head, which has a stacked structure comprising a recording head having an inductive magnetic transducer for writing and a reproducing head having a magnetoresistive (hereinafter referred to as MR) element for reading, is widely used as the thin film magnetic head.
The increase of the recording density of the performance of the recording head requires the increase of a track density on a magnetic recording medium. For this purpose, it is necessary to realize a recording head having a narrow track structure in which the on-air-bearing-surface widths of a top pole and a bottom pole, which are formed on and under a write gap, respectively, with the write gap in between, are as narrow as a few microns to the submicron order. Semiconductor processing technology is used in order to achieve this recording head.
A method of manufacturing a composite thin film magnetic head will be now described with reference to
FIGS. 36
to
41
, as an example of a conventional method of manufacturing a thin film magnetic head.
In the method of manufacturing, first, as shown in
FIG. 36
, an insulating layer
102
made of, for example, aluminum oxide (Al
2
O
3
, hereinafter referred to as “alumina”) is deposited with a thickness of about 5.0 &mgr;m to about 10.0 &mgr;m on a substrate
101
made of, for example, altic (Al
2
O
3
—TiC). Then, a bottom shield layer
103
for a reproducing head is formed on the insulating layer
102
. Then, for example, an alumina layer is deposited by sputtering with a thickness of 100 nm to 200 nm on the bottom shield layer
103
, and thus a shield gap film
104
is formed. Then, an MR film
105
for forming an MR element for reproducing is formed with a thickness of a few tens of nanometers on the shield gap film
104
, and the MR film
105
is patterned into a desired shape by high-accuracy photolithography. Then, lead layers (not shown) for functioning as lead electrode layers to be 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
, and thus the MR film
105
is sandwiched in between the shield gap films
104
and
106
. Then, a top shield-cum-bottom pole (hereinafter referred to as a bottom pole)
107
made of a magnetic material for use in both the reproducing and recording heads, e.g., a nickel-iron alloy (NiFe, hereinafter referred to as “Permalloy (a trade name)”) is formed on the shield gap film
106
.
Then, as shown in
FIG. 37
, a write gap layer
108
made of an insulating material, e.g., alumina is formed on the bottom pole
107
, and a photoresist film
109
is formed into a predetermined pattern on the write gap layer
108
by high-accuracy photolithography. Then, a thin film coil
110
made of, for example, copper (Cu) for an inductive recording head is formed on the photoresist film
109
by plating, for example. Then, a photoresist film
111
is formed into a predetermined pattern by high-accuracy photolithography so as to coat the photoresist film
109
and the thin film coil
110
. Then, the photoresist film
111
is subjected to heat treatment at a temperature of, for example, 250° C. in order to provide insulation among windings of the thin film coil
110
.
Then, as shown in
FIG. 38
, the write gap layer
108
is partially etched at a more rearward position than the thin film coil
110
(on the right side in
FIG. 38
) in order to form a magnetic path, whereby an opening
108
a
is formed and thus a part of the bottom pole
107
is exposed. Then, a magnetic material having high saturation magnetic flux density, e.g., Permalloy is formed into a film by electroplating so as to coat an exposed surface of the bottom pole
107
, the photoresist film
111
and the write gap layer
108
. Then, the plated film made of Permalloy is selectively etched by ion milling using a mask (not shown) made of a photoresist film having a predetermined planar shape, and thus a top yoke-cum-top pole (hereinafter referred to as a top pole)
112
is formed. For example, the top pole
112
has a planar shape shown in
FIG. 41
to be described later and includes a yoke portion
112
a
and a pole chip portion
112
b
. The top pole
112
is in contact with and magnetically coupled to the bottom pole
107
in the opening
108
a
. Then, both the write gap layer
108
and the bottom pole
107
are selectively etched by about 0.5 &mgr;m by ion milling using a part (the pole chip portion
112
b
) of the top pole
112
as a mask (see FIG.
40
), and thereafter an overcoat layer
113
made of, for example, alumina is formed on the top pole
112
. Finally, a track surface of the recording head and the reproducing head, i.e., an air bearing surface
120
is formed by machining and polishing, and, as a result, a thin film magnetic head is completed.
FIGS. 39
to
41
show the structure of the completed thin film magnetic head.
FIG. 39
shows a cross section of the thin film magnetic head in a direction perpendicular to the air bearing surface
120
.
FIG. 40
shows an enlarged view of a cross section of a pole portion in a direction parallel to the air bearing surface
120
.
FIG. 41
shows a planar structure of the thin film magnetic head.
FIG. 38
corresponds to a cross section viewed from the direction of the arrows along the line XXXVIII—XXXVIII of FIG.
41
. The overcoat layer
113
and so on are not shown in
FIGS. 39
to
41
. In
FIG. 41
, the thin film coil
110
and the photoresist film
111
are shown, but their outermost ends alone are shown.
In
FIGS. 39 and 41
, “TH” indicates a throat height, and “MRH” indicates an MR height. The “throat height (TH)” refers to one of factors that determine the performance of the recording head, and refers to a length between the position of an edge of the insulating layer (the photoresist film
111
) for electrically isolating the thin film coil
110
from the other conductive portions, which is closest to the air bearing surface
120
, i.e., a throat height zero position (a THO position) and the position of the air bearing surface
120
. The optimization of the throat height (TH) is desired for the improvement in the performance of the recording head. The throat height (TH) is controlled by the amount of polishing of the air bearing surface
120
. The “MR height (MRH)” refers to a length between the position of a farthest edge of the MR film
105
from the air bearing surface
120
, i.e., an MR height zero position (an MRH0 position) and the position of the air bearing surface
120
. The MR height (MRH) is also controlled by the amount of polishing of the air bearing surface
120
.
Factors that determine the performance of the thin film magnetic head include an apex angle (&thgr;) shown in
FIG. 39
, in addition to the throat height (TH), the MR height (MRH) and so on. The apex angle &thgr; refers to an average degree of inclination of an inclined surface of the photoresist film
111
close to the air bearing surface
120
.
As shown in
FIG. 40
, a structure in which the respective parts of both the write gap layer
108
and the bottom pole
107
are etched in self-alignment with the pole chip portion
112
b
of the top pole
112
is called a trim structure. The trim structure can prevent the increase in an effective track width resulting from a spread of a magnetic flux generated during writing data on a narrow track. In
FIG. 40
, “P
2
W” indicates a width of a portion (hereinafter referred to as “a pole portion
500
”) having the trim structure, namely, a pole width (hereinafter sometimes referred to as “a track width”). In
FIG. 40
, “P
2
L” indicates a thickn
Kim Paul D.
Oliff & Berridg,e PLC
TDK Corporation
Tugbang A. Dexter
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