Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
1999-06-09
2001-12-25
Klimowicz, William (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
C360S125330
Reexamination Certificate
active
06333841
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a thin film magnetic head having at least an inductive-type magnetic transducer for writing and a method of manufacturing the same.
2. Description of the Related Art
Performance improvement in thin film magnetic heads has been sought in accordance with an increase in surface recording density of a hard disk device. A composite thin film magnetic head, which is made of a layered structure including a recording head with an inductive-type magnetic transducer for writing and a reproducing head with a magnetoresistive (MR) element for reading, is widely used as a thin film magnetic head. As MR elements there are an anisotropic magnetoresistive (AMR) element that utilizes the AMR effect and a giant magnetoresistive (GMR) element that utilizes the GMR effect. A reproducing head using an AMR element is called an AMR head or simply an MR head. A reproducing head using the GMR element is called a GMR head. The AMR head is used as a reproducing head whose surface recording density is more than 1 gigabit per square inch. The GMR head is used as a reproducing head whose surface recording density is more than 3 gigabit per square inch.
The AMAR head includes an AMR film having an AMR effect. In a GMR head the AMR film is replaced with a GMR film having the GMR effect and the configuration of the GMR head is similar to that of the AMR head. However, the GMR film exhibits a greater change in resistance under a specific external magnetic field compared to the AMR film. Therefore, the reproducing output of the GMR head becomes about three to five times greater than that of the AMR head.
An MR film may be changed in order to improve the performance of a reproducing head. In general, an AMR film is a film made of a magnetic substance which exhibits the MR effect and has a single-layered structure. In contrast, many of the GMR films have a multi-layered structure consisting a plurality of films. There are several types of mechanisms which produce the GMR effect. The layer structure of the GMR film depends on those mechanisms. GMR films include a superlattice GMR film, a granular film, a spin valve film and so on. The spin valve film is most sufficient since the film has a relatively simple structure, exhibits a great change in resistance in a low magnetic field, and is suitable for mass production. The performance of a reproducing head is thus easily improved by changing an AMR film with a GMR film and the like with an excellent magnetoresistive sensitivity.
As a primary factor for determining the performance of a reproducing head, there is a pattern width, especially an MR height. The MR height is the length (height) between the end of an MR element closer to an air bearing surface and the other end. The MR height is originally controlled by an amount of grinding when the air bearing surface is processed. The air bearing surface (ABS) here is a surface of a thin film magnetic head that faces a magnetic recording medium and is also called a track surface.
Performance improvement in a recording head have also been expected in accordance with the performance improvement in a reproducing head. It is required to increase the track density of a magnetic recording medium in order to increase the recording density among the performance of a recording head. In order to achieve this, a recording head with a narrow track structure in which the width of a bottom pole and a top pole sandwiching a write gap on the air bearing surface is required to be reduced to the order of some microns to submicron. Semiconductor process technique is used to achieve the narrow track structure.
Another factor which determines the performance of a recording head is the throat height (TH). The throat height is the length (height) of a portion (magnetic pole portion) which is from the air bearing surface to an edge of an insulating layer which electrically isolates the thin film coil. Reducing the throat height is desired in order to improve the performance of a recording head. The throat height is also controlled by an amount of grinding when the air bearing surface is processed.
In order to improve the performance of a thin film magnetic head, it is important to form the recording head and the reproducing head as described in well balance.
Here, an example of a method of manufacturing a composite thin film magnetic head will be described with reference to
FIGS. 16A
,
16
B to
FIGS. 21A
,
21
B as an example of a method of manufacturing a thin film magnetic head of the related art.
As shown in
FIG. 16
, an insulating layer
102
made of, for example, alumina (aluminum oxide, Al
2
O
3
) is formed to a thickness of about 5 to 10 &mgr;m on a substrate
101
made of, for example, aluminum oxide and titanium carbide (Al
2
O
3
TiC). Further, a bottom shield layer
103
for a reproducing head made of, for example, permalloy (NiFe) is formed on the insulating layer
102
.
Next, as shown in
FIG. 17
, for example, alumina of about 100-200 nm in thickness is deposited on the bottom shield layer
103
to form a shield gap film
104
. Next, an MR film
105
of tens of nanometers in thickness for making up the MR element for reproducing is formed on the shield gap film
104
, and photolithography with high precision is applied to obtain a desired shape. Next, a lead terminal layer
106
for the MR film
105
is formed by lift-off method. Next, a shield gap film
107
is formed on the shield gap film
104
, the MR film
105
and the lead terminal layer
106
, and the MR film
105
and the lead terminal layer
106
are buried in the shield gap films
104
and
107
. Next, a top shield-cum-bottom pole (called bottom pole in the followings)
108
of about 3 &mgr;m in thickness made of, for example, permalloy (NiFe), which is a material used for both of the reproducing head and the recording head, is formed on the shield gap film
107
.
Next, as shown in
FIG. 18
, a write gap layer
109
of about 200 nm in thickness made of an insulating layer such as an alumina film is formed on the bottom pole
108
. Further, an opening
109
a
for connecting the top pole and the bottom pole is formed through patterning the write gap layer
109
by photolithography. Next, a pole tip
110
is formed with magnetic materials made of permalloy (NiFe) and nitride ferrous (FeN) through plating method, while a connecting-portion pattern
110
a
of the top pole and the bottom pole is formed. The bottom pole
108
and a top pole layer
116
which is to be described later are connected by the connecting-portion pattern
110
a
and so that forming a through hole after CMP (Chemical and Mechanical Polishing) procedure, which is to be described later, becomes easier.
Next, as shown in
FIG. 19
, the write gap layer
109
and the bottom pole
108
are etched about 0.3-0.5 &mgr;m by ion milling with the pole tip
110
being a mask. By etching the bottom pole
108
to be a trim structure, widening of effective write track width can be avoided (that is, suppressing spread of magnetic flux in the bottom pole when data is being written). Next, after an insulating layer
111
of about 3 &mgr;m, made of, for example, alumina is formed all over the surface, the whole surface is flattened by CMP.
Next, as shown in
FIG. 20
a first layer of thin film coil
112
for an inductive-type recording head made of, for example, copper (Cu) is selectively formed on the insulating layer
111
by, for example, plating method. Further, a photoresist film
113
is formed in a desired pattern on the insulating layer
111
and the thin film coil
112
by photolithography with high precision. Further, a heat treatment of desired temperature is applied to flatten the photoresist film
113
and to insulate between the turns of the thin film coil
112
. Likewise, a second layer of thin film coil
114
and a photoresist film
115
are formed on the photoresist film
113
, and a heat treatment of desired temperature is applied to flatten the photoresist film
115
and to insulate between the turns of the thin film coils
Klimowicz William
Oliff & Berridg,e PLC
TDK Corporation
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