Dynamic magnetic information storage or retrieval – Head – Core
Reexamination Certificate
2001-09-14
2004-05-04
Heinz, A. J. (Department: 2653)
Dynamic magnetic information storage or retrieval
Head
Core
Reexamination Certificate
active
06731460
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a thin film magnetic head having at least an inductive magnetic transducer for writing, a method of manufacturing the same and a method of forming a magnetic layer pattern in other technical fields.
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 heads.
To increase a recording density of the performance of the recording head, it is necessary to increase 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 a top pole and a bottom pole, which are formed on and under a write gap therebetween, respectively, have a narrow width of from a few microns to the submicron order on an air bearing surface, and semiconductor fabrication technology is used in order to achieve the recording head having the above-mentioned structure.
The description is now given with reference to
FIGS. 39
to
44
with regard to a method of manufacturing a composite thin film magnetic head as an example of a method of manufacturing a thin film magnetic head of the related art.
In the manufacturing method, first of all, as shown in
FIG. 39
, 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 10.0 &mgr;m on a substrate
101
made of for example, altic (A
2
O
3
—TiC). Then, a bottom shield layer
103
for a reproducing head is formed on the insulating layer
102
. Then, an alumina layer, for example, is deposited with a thickness of 100 nm to 200 nm on the bottom shield layer
103
by means of sputtering, and thus a shield gap film
104
is formed. Then, an MR film
105
for constituting an MR element for reproducing is formed into a desired pattern with a thickness of a few tens of nanometers on the shield gap film
104
by means of 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 reproducing and recording heads, e.g., a nickel-iron alloy (NiFe, hereinafter referred to as “Permalloy trade name)”), is formed on the shield gap film
106
.
Next, as shown in
FIG. 40
, a write gap layer
108
made of an insulating material, e.g., alumina, is formed on the bottom pole
107
. Then, a photoresist film
109
is formed into a predetermined pattern on the write gap layer
108
by means of 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 means of electroplating. Then, a photoresist is formed into a predetermined pattern by means of high-accuracy photolithography so as to coat the photoresist film
109
and the thin film coil
110
, and thereafter the photoresist is subjected to heat treatment at a temperature of 250 degrees, for example. By this heat treatment, a photoresist film
111
for providing insulation between windings of the thin film coil
110
is formed.
Next, as shown in
FIG. 41
, a part of the write gap layer
108
, which is located rearward with respect to the thin film coil
110
(on the right side in FIG.
41
), is partly etched 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 top yoke-cum-top pole (hereinafter referred to as “a top pole”)
112
made of a magnetic material for the recording head, e.g., Permalloy, is formed by means of electroplating so as to coat an exposed surface of the bottom pole
107
, the photoresist film
111
and the write gap layer
108
. For example, the top pole
112
has a planar shape shown in
FIG. 44
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, the respective parts of the write gap layer
108
and the bottom pole
107
, which are located in a peripheral region around the pole chip portion
112
B, are selectively etched and removed by about 0.5 &mgr;m by means of ion milling using the pole chip portion
112
B of the top pole
112
as a mask (see FIG.
43
). Then, an overcoat layer
118
made of, for example, alumina is formed so as to coat 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 through the steps of machining and polishing, and thus a thin film magnetic head is completed.
FIGS. 42
to
44
show a structure of the completed thin film magnetic head.
FIG. 42
shows a cross section of the thin film magnetic head in a direction perpendicular to the air bearing surface
120
.
FIG. 43
shows an enlarged view of a cross section of a pole portion
500
in a direction parallel to the air bearing surface
120
.
FIG. 44
shows a planar structure of the thin film magnetic head.
FIG. 41
corresponds to a cross section viewed in the direction of the arrows along the line XXXXI—XXXXI of FIG.
44
.
FIGS. 42
to
44
do not show the overcoat layer
113
and so forth.
FIG. 44
shows the thin film coil
110
and the photoresist film
111
whose outermost ends alone are shown.
In
FIGS. 42 and 44
, “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 an insulating layer (the photoresist film
111
) for electrically isolating the thin film coil
110
from the other conductive portions, more specifically, an edge closest to the air bearing surface
120
, that is, a throat height zero position (a TH
0
position), and the position of the air bearing surface
120
. An optimization of the throat height (TH is desired for an 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 an edge of the MR film
105
, more specifically, an edge furthest from the air bearing surface
120
, that is, an MR height zero position (an MRH
0
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. 42
, as well as 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. 43
, a structure in which the respective parts of 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 allows preventing an increase in an effective track width resulting from a spread of a magnetic flux generated during the writing of data on a narrow track. “P2W” indicates a width of a portion (hereinafter referred to as “a pole portion
500
”)
Heinz A. J.
Oliff & Berridg,e PLC
TDK Corporation
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