Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
2002-01-10
2004-11-23
Ometz, David L. (Department: 2653)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
Reexamination Certificate
active
06822837
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thin-film magnetic head that utilizes the magnetoresistive element for reading the magnetic field intensity of a magnetic recording medium, for example, as a signal, and a method of manufacturing such a thin-film magnetic head. The invention also relates to a method of forming a patterned thin film for a thin-film magnetic head that comprises a base body and a thin-film magnetic head element formed on the base body.
2. Description of the Related Art
Increase in recording density has been demanded of magnetic disk drives along with a demand for higher capacity and smaller sizes. Further, performance improvements in thin-film magnetic heads have been demanded. Thin-film magnetic heads in widespread use include composite thin-film magnetic heads. A composite thin-film magnetic 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.
A TMR element normally has a structure in which a lower magnetic layer, a tunnel barrier layer and an upper magnetic layer are stacked. 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 in which, 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 in the medium facing surface that faces 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 respond to such a problem, U.S. patent application Ser. No. 09/517,580, for instance, proposes a thin-film magnetic head having a structure in which a part where the lower magnetic layer, the tunnel barrier layer and the upper magnetic layer overlap (hereinafter called the tunnel joint) retreats from the medium facing surface, and a soft magnetic layer is provided for introducing a signal magnetic flux to the tunnel joint. The soft magnetic layer extends from the medium facing surface to the point in which the tunnel joint 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. FFG may also serve as the lower or upper magnetic layer. In the FFG-type TMR head, when the medium facing surface is lapped to control the distance between the medium facing surface and the TMR element, the TMR element will never be lapped. 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. 25A
to FIG.
31
A and
FIG. 25B
to
FIG. 31B
to describe an example of a method of manufacturing the FFG-type TMR head.
FIG. 25A
to FIG.
31
A and
FIG. 25B
to
FIG. 31B
illustrate the steps of the method.
FIG. 25A
to
FIG. 31A
show the integrated surfaces (on top face), whereas
FIG. 25B
to
FIG. 31B
show the cross sections on the position that corresponds to line
25
B—
25
B in FIG.
25
A.
In this method, as shown in FIG.
25
A and
FIG. 25B
, a lower electrode layer
102
, a lower metallic layer
103
, a lower ferromagnetic layer
104
, a tunnel barrier layer
105
, an upper ferromagnetic layer
106
, a pinning layer
107
and a capping layer
108
are stacked one by one on a substrate that is not illustrated. Here, the pinning layer
107
is provided for fixing the magnetizing direction of the upper ferromagnetic layer
106
in the direction in which the magnetic field is detected. The capping layer
108
is provided for preventing deterioration of properties and oxidization of the surface of the pinning layer
107
. A multi-layer film including the lower ferromagnetic layer
104
, the tunnel barrier layer
105
and the upper ferromagnetic layer
106
is hereinafter called a TMR multi-layer film.
Next, a resist mask
109
used for patterning the TMR multi-layer film is formed by photolithography on the capping layer
108
. After that, the capping layer
108
, the pinning layer
107
, the upper ferromagnetic layer
106
, the tunnel barrier layer
105
and the lower ferromagnetic layer
104
are selectively etched through ion milling, for example, using the resist mask
109
to pattern the TMR multi-layer film as shown in FIG.
26
A and FIG.
26
B. The resist mask
109
is then removed.
Next, as shown in FIG.
27
A and
FIG. 27B
, resist masks
110
are formed by photolithography on the lower metallic layer
103
and the capping layer
108
, to cover regions except where hard magnetic layers are to be formed. Subsequently, the capping layer
108
, the pinning layer
107
, the upper ferromagnetic layer
106
, the tunnel barrier layer
105
and the lower ferromagnetic layer
104
are selectively etched by ion milling, for example, using the resist masks
110
.
Next, as shown in FIG.
28
A and
FIG. 28B
, hard magnetic layers
111
are formed on regions of the lower metallic layer
103
that are not covered with the resist masks
110
. The hard magnetic layers
111
are for applying a bias magnetic field to the tunnel joint. The resist masks
110
are then lifted off.
Next, as shown in FIG.
29
A and
FIG. 29B
, a resist mask
112
is formed on the capping layer
108
by photolithography. This resist mask is for defining the shape of the tunnel joint.
Next, as shown in FIG.
30
A and
FIG. 30B
, at least the capping layer
108
, the pinning layer
107
and the upper ferromagnetic layer
106
are selectively etched using the resist mask
112
, for example through ion milling, to define the shape of the tunnel joint. Here, a position at which the etching is to be stopped is set at a predetermined position between the top surface of the tunnel barrier layer
105
and a position located partway through the lower ferromagnetic layer
104
in its thickness direction. Next, an insulation layer
113
is formed over the surface and the resist mask
112
is then lifted off.
Next, as shown in FIG.
31
A and
FIG. 31B
, an upper electrode layer
114
is formed on the capping layer
108
and on the insulation layer
113
. Thus, a TMR element
Kagami Takeo
Kasahara Noriaki
Ometz David L.
TDK Corporation
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