Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
2001-06-14
2003-06-24
Klimowicz, William (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
C360S324200
Reexamination Certificate
active
06583967
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thin-film magnetic head that utilizes a magnetoresistive element for reading the magnetic field intensity of a magnetic recording medium, for example, as a signal, and to a method of manufacturing such a thin-film magnetic head.
2. Description of the Related Art
Performance improvements in thin-film magnetic heads have been sought as recording density of hard disk drives has increased. Such thin-film magnetic heads include composite thin-film magnetic heads that have been widely used. A composite head is made of a layered structure including a write (recording) head having an induction-type electromagnetic transducer for writing and a read (reproducing) head having a magnetoresistive (MR) element for reading that detects a magnetic field through the use of the magnetoresistive effect.
Read heads that exhibit high sensitivity and produce high outputs have been required. In response to such demands, attention has been focused on tunnel magnetoresistive elements (that may be hereinafter called TMR elements) that detect a magnetic field through the use of the tunnel magnetoresistive effect.
The TMR element has a structure in which a lower magnetic layer, a tunnel barrier layer and an upper magnetic layer are stacked on a substrate. Each of the lower magnetic layer and the upper magnetic layer includes a ferromagnetic substance. In general, the magnetic layer closer to the substrate is called the lower magnetic layer and the magnetic layer farther from the substrate is called the upper magnetic layer. Therefore, the terms ‘upper’ and ‘lower’ of the upper and lower magnetic layers do not always correspond to the position in the arrangement of an actual TMR element.
The tunnel barrier layer is a layer made of a thin nonmagnetic insulating film through which electrons are capable of passing while maintaining spins thereof by means of the tunnel effect, that is, through which a tunnel current is allowed to pass. The tunnel magnetoresistive effect is a phenomenon that, when a current is fed to a pair of magnetic layers sandwiching the tunnel barrier layer, a tunnel current passing through the tunnel barrier layer changes, depending on the relative angle between magnetizations of the two magnetic layers. If the relative angle between magnetizations of the magnetic layers is small, the tunneling rate is high. As a result, the resistance to the current passing across the magnetic layers is reduced. If the relative angle between magnetizations of the magnetic layers is large, the tunneling rate is low. The resistance to the current passing across the magnetic layers is therefore increased.
With regard to the structure of a thin-film magnetic head incorporating a TMR element, if the tunnel barrier layer made up of a thin insulating layer is exposed from the medium facing surface that faces toward a recording medium, a short circuit may occur between the two magnetic layers opposed to each other with the tunnel barrier layer in between, during or after lapping of the medium facing surface. Such a structure is therefore not preferred.
To cope with such a problem, the inventors including the inventors of the present application disclose a thin-film magnetic head in U.S. patent application Ser. No. 09/517,580. This head has a structure in which a TMR element retreats from the medium facing surface, and a soft magnetic layer is provided for introducing a signal magnetic flux to the TMR element. The soft magnetic layer extends from the medium facing surface to the point in which the TMR element is located. In the present application this soft magnetic layer is called a front flux guide (FFG) and the thin-film magnetic head having the above-described structure is called an FFG-type TMR head. It is impossible that the TMR element incorporated in the FFG-type TMR head is lapped when the distance between the medium facing surface and the TMR element is controlled by lapping the medium facing surface. Therefore, the FFG-type TMR head has a feature that the medium facing surface of the head is defined by mechanical lapping without creating a short circuit between the two magnetic layers.
Reference is now made to
FIG. 18
to
FIG. 23
to describe an example of method of manufacturing the FFG-type TMR head.
FIG. 18
to
FIG. 23
are cross sections that illustrate steps of the method.
In this method, as shown in
FIG. 18
, a lower electrode layer
102
is formed on a substrate
101
. Next, a lower magnetic layer
103
, a tunnel barrier layer
104
and an upper magnetic layer
105
are stacked on the lower electrode layer
102
one by one. Next, a resist mask
106
used for patterning the TMR element is formed by photolithography on the upper magnetic layer
105
.
Next, the upper magnetic layer
105
, the tunnel barrier layer
104
and the lower magnetic layer
103
are selectively etched through ion milling, for example, using the resist mask
106
. The TMR element
120
made up of the lower magnetic layer
103
, the tunnel barrier layer
104
and the upper magnetic layer
105
that are patterned is thus formed, as shown in FIG.
19
. Next, an insulating layer
107
is formed around the TMR element
120
through liftoff. That is, the insulating layer
107
is formed over the entire surface while the resist mask
106
is left. The resist mask
106
is then removed.
Next, as shown in
FIG. 20
, an FFG layer
109
made of a soft magnetic material is formed on the upper magnetic layer
105
and the insulating layer
107
. Next, a resist mask
110
used for patterning the FFG layer
109
is formed by photolithography on the FFG layer
109
.
Next, as shown in
FIG. 21
, the FFG layer
109
is selectively etched through ion milling, for example, using the resist mask
110
. The FFG layer
109
is thereby patterned. The FFG layer
109
patterned is T-shaped and has a portion extending from the portion above the upper magnetic layer
105
toward the medium facing surface, and two portions extending from the portion above the upper magnetic layer
105
toward both sides in the direction parallel to the medium facing surface. The resist mask
110
is then removed.
Next, as shown in
FIG. 22
, hard magnetic layers
111
for applying a bias magnetic field to the TMR element
120
are formed on outer sides of the two portions of the FFG layer
109
extending toward both sides in the direction parallel to the medium facing surface.
Next, as shown in
FIG. 23
, an upper electrode layer
112
is formed on the FFG layer
109
and the hard magnetic layer
111
. Through the foregoing steps, the TMR element
120
of the FFG-type TMR head and its periphery are formed.
Next, the medium facing surface of the head is defined by lapping. Through this lapping the FFG layer
109
is exposed from the medium facing surface and the distance from the medium facing surface to the TMR element
120
is controlled.
The FFG as described above is not limited to a TMR head but may be applied to an MR head having a structure that is disclosed in Published Unexamined Japanese Patent Application Heisei 5-275769 (1993), that is, a structure in which a sense current used for signal detection is fed to the MR element in the direction perpendicular to the film surface of the MR element. Such a structure is called a current perpendicular to plane (CPP) structure in the present application. The structure of the TMR head is included in the CPP structure.
One type of CPP-structure MR head incorporates a multilayer magnetic film made up of a plurality of magnetic layers stacked with nonmagnetic layers in between, in place of the lower magnetic layer
103
, the tunnel barrier layer
104
and the upper magnetic layer
105
of FIG.
23
. This multilayer magnetic film has a property that the RKKY interaction occurs between the magnetic layers and the directions of magnetization of the magnetic layers are thereby made antiparallel when the material and the thickness of the nonmagnetic layers are suitably chosen. The multilayer magnetic film thus exhibits the giant magnet
Kasahara Noriaki
Shimazawa Koji
Klimowicz William
Oliff & Berridg,e PLC
TDK Corporation
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