Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Making named article
Reexamination Certificate
2000-03-23
2001-07-03
McPherson, John A. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Making named article
C430S315000, C430S319000, C430S396000, C029S603070
Reexamination Certificate
active
06255040
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.
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 device. A composite thin film magnetic head is widely used as the thin film magnetic head. The composite thin film magnetic head has a laminated 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.
MR elements include an AMR element utilizing an anisotropic magnetoresistive (AMR) effect and a GMR element utilizing a giant magnetoresistive (GMR) effect. The reproducing head using the AMR element is called an AMR head or simply an MR head, and the reproducing head using the GMR element is called a GMR head. The AMR head is used as the reproducing head whose surface recording density exceeds 1 gigabit per square inch, and the GMR head is used as the reproducing head whose surface recording density exceeds 3 gigabits per square inch.
The improvement in the performance of the recording head is also sought in accordance with such an improvement in the performance of the reproducing head. Factors for determining the performance of the recording head include a throat height (TH). This throat height means a length (height) of a magnetic pole portion from an air bearing surface to an edge of an insulating layer for electrically isolating thin film coils for generating a magnetic flux. The air bearing surface means the surface of the thin film magnetic head facing a magnetic recording medium and is sometimes called a track surface.
A reduction in the above-mentioned throat height is desired for the improvement in the performance of the recording head. This throat height is also controlled in accordance with an amount of polishing the air bearing surface.
An increase in a recording density of the performance of the recording head requires the increase in a track density of the magnetic recording medium. For this purpose, it is necessary to realize the recording head having a narrow track structure. In this structure, a bottom pole and a top pole, which are formed on the bottom and top of a write gap sandwiched between the bottom pole and the top pole, have a narrow width of from a few microns to the submicron order on the air bearing surface. Semiconductor processing technology is used in order to achieve this structure.
One example of a method of manufacturing the composite thin film magnetic head will be now described as one example of a conventional method of manufacturing the thin film magnetic head with reference to
FIGS. 36
to
38
.
FIGS. 36
to
38
show a cross section of the thin film magnetic head perpendicular to the air bearing surface.
In this manufacturing method, first, as shown in
FIG. 36
, an insulating layer
102
made of alumina (Al
2
O
3
), for example, is deposited with a thickness of about 5 &mgr;m to 10 &mgr;m on a substrate
101
made of altic (Al
2
O
3
and TiC), for example. Then, a lower shield layer
103
for the reproducing head is formed on the insulating layer
102
. Then, alumina, for example, is sputter deposited with a thickness of 100 nm to 200 nm on the lower shield layer
103
, whereby a shield gap film
104
is formed. Then, an MR film
105
for constituting the 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, a lead layer (not shown) for functioning as a lead electrode layer electrically connected to the MR film
105
is formed on both sides of the MR film
105
. Then, a shield gap film
106
is formed on the lead layer, the shield gap film
104
and the MR film
105
, whereby the MR film
105
is buried in the shield gap films
104
and
106
. Then, an upper shield-cum-bottom pole (hereinafter referred to as a bottom pole)
107
made of a magnetic material for use in both of the reproducing head and the recording head, e.g., permalloy (NiFe) is formed on the shield gap film
106
.
Then, as shown in
FIG. 37
, a write gap layer
108
made of an insulating film, e.g., an alumina film is formed on the bottom pole
107
, and a photoresist layer
109
is formed into a predetermined pattern on the write gap layer
108
by the high-accuracy photolithography. Then, first-layer thin film coils
110
made of copper (Cu), for example, for an inductive recording head are formed on the photoresist layer
109
by plating method, for example. Then, a photoresist layer
111
is formed into a predetermined pattern by the high-accuracy photolithography so that the photoresist layer
109
and the coils
110
may be coated with the photoresist layer
111
. Then, heat treatment takes place at a temperature of 250° C., for example, in order to flatten the coils
110
and provide insulation among the coils
110
. Then, second-layer thin film coils
112
made of copper, for example, are formed on the photoresist layer
111
by the plating, for example. Then, a photoresist layer
113
is formed into a predetermined pattern on the photoresist layer
111
and the coils
112
by the high-accuracy photolithography. Then, the heat treatment takes place at a temperature of 250° C., for example, in order to flatten the coils
112
and provide insulation among the coils
112
.
Then, as shown in
FIG. 38
, the write gap layer
108
is partially etched at the rear of the coils
110
and
112
(on the right side in
FIG. 38
) in order to form a magnetic path, whereby an opening
108
a
is formed. Then, an upper yoke-cum-top pole (hereinafter referred to as a top pole)
114
made of the magnetic material for the recording head, e.g., permalloy is selectively formed on the write gap layer
108
and the photoresist layers
109
,
111
and
113
. The top pole
114
is in contact with and magnetically coupled to the bottom pole
107
in the above-mentioned opening
108
a
. Then, the top pole
114
is used as a mask to etch the write gap layer
108
and the bottom pole
107
by about 0.5 &mgr;m by means of ion milling. Then, an overcoat layer
115
made of alumina, for example, is formed on the top pole
114
. Finally, a slider is machined, whereby a track surface (air bearing surface)
120
of the recording head and the reproducing head is formed. As a result, the 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 perpendicular to the air bearing surface
120
.
FIG. 40
shows an enlarged cross section parallel to the air bearing surface
120
in the magnetic pole portion.
FIG. 41
shows a plan view.
FIGS. 36
to
39
correspond to a cross section taken along line A-A′ of FIG.
41
. The overcoat layer
115
is not shown in
FIGS. 39
to
41
.
For the improvement in the performance of the thin film magnetic head, it is important to precisely form the throat height TH, an apex angle &thgr;, a pole width P
2
W and a pole length P
2
L shown in
FIGS. 39 and 40
. The apex angle &thgr; means the angle between a straight line connecting corners of side surfaces of the photoresist layers
109
,
111
and
113
close to the track surface and an upper surface of the top pole
114
. The pole width P
2
W defines a write track width on the recording medium. The pole length P
2
L represents the thickness of the magnetic pole. In
FIGS. 39 and 40
, a ‘TH
0
position’ means the edge of the photoresist layer
109
that is the insulating layer for electrically isolating the thin film coils
110
and
112
, close to the track surface. The TH
0
position represents a reference position
0
of the throat height TH.
As shown in
FIG. 40
, the structure, in which the respective side walls of parts of the top p
McPherson John A.
Oliff & Berridge PLC.
TDK Corporation
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