Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
1998-10-14
2001-12-11
Ometz, David L. (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
Reexamination Certificate
active
06330136
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to magnetic disk drives, more particularly to magnetoresistive (MR) read heads, and most particularly to spin-dependent tunneling (SDT) read sensors and methods of making the same.
Magnetic disk drives are used to store and retrieve data for digital electronic apparatuses such as computers. In
FIGS. 1A and 1B
, a magnetic disk drive
10
of the prior art includes a sealed enclosure
12
, a disk drive motor
14
, a magnetic disk
16
, supported for rotation by a drive spindle S
1
of motor
14
, an actuator
18
and an arm
20
attached to an actuator spindle S
2
of actuator
18
. A suspension
22
is coupled at one end to the arm
20
, and at its other end to a read/write head or transducer
24
. The transducer
24
typically includes an inductive write element with a sensor read element (shown in FIG.
1
C). As the motor
14
rotates the magnetic disk
16
, as indicated by the arrow R, an air bearing is formed under the transducer
24
causing it to lift slightly off of the surface of the magnetic disk
16
, or, as it is termed in the art, to “fly” above the magnetic disk
16
. Various magnetic “tracks” of information can be read from the magnetic disk
16
as the actuator
18
causes the transducer
24
to pivot in a short arc as indicated by the arrows P. The design and manufacture of magnetic disk drives is well known to those skilled in the art.
FIG. 1C
depicts a cross-sectional view of a magnetic read/write head
24
including a read element
32
and a write element
34
, which is typically an inductive write element. Exposed edges of the read element
32
and the write element
34
define an air-bearing surface ABS, along a plane
35
, which faces the surface of the magnetic disk
16
.
Read element
32
includes a first shield SH
1
, an intermediate layer
39
which serves as a second shield SH
2
, and a read sensor
40
located between the first shield SH
1
and the second shield SH
2
. Read elements commonly make use of a phenomenon termed the magnetoresistive effect (MRE), where the electrical resistance R of the read sensor
40
changes with exposure to an external magnetic field, such as magnetic fringing flux from magnetic disk
16
. The incremental electrical resistance &Dgr;R is detected by using a sense current that is passed through the read sensor
40
to measure the voltage across the read sensor
40
. The precision and sensitivity of the read sensor in sensing the magnetic fringing flux increases as the ratio of &Dgr;R/R increases. Also, larger resistances result in larger voltages measured across the read sensor
40
which, in turn, results in greater effectiveness of the read sensor. Thus, it is desirable to maximize both the output voltage and &Dgr;R/R.
Types of magnetoresistive effects utilized in the read sensor
40
include the anisotropic magnetoresistive (AMR) effect and the giant magnetoresistive (GMR) effect. A particular type of effect is the spin-dependent tunneling (SDT) effect, which can be used in an SDT sensor. A schematic of such an SDT sensor is illustrated by the read sensor
40
in FIG.
1
D. As is shown, the SDT read sensor
40
can include a tri-layer, sometimes referred to as a tri-layer tunnel junction, having a first ferromagnetic (FM) layer FM
1
and a second ferromagnetic layer FM
2
, which are separated by an insulating layer INS. These layers are oriented substantially parallel to the shields SH
1
and SH
2
. Thus, when the sense current I is injected to the SDT read sensor
40
between the shields SH
1
and SH
2
, the current can travel substantially perpendicular to the layers FM
1
, FM
2
, and INS. In other words, the SDT read sensor can operate in current perpendicular to plane (CPP) mode. Write element
34
includes an intermediate layer
39
that functions as a first pole (P
1
), and a second pole (P
2
) disposed above the first pole P
1
. P
1
and P
2
are physically and electrically attached to one another by a backgap portion (not shown) distal to the ABS. A write gap
46
is formed of an electrically insulating material between P
1
and P
2
proximate to the ABS. Also included in write element
34
in the space defined between P
1
and P
2
are conductive coils
48
disposed within an insulation layer
50
.
In the SDT read sensor
40
, the ferromagnetic layers FM
1
and FM
2
can act as electrodes between which the sense current I passes through the insulating layer INS, which is sometimes referred to as the tunnel barrier. The relative directions of the magnetizations M
1
and M
2
of the ferromagnetic layers FM
1
and FM
2
, respectively, can be influenced by external magnetic fields, thereby changing the resistance of the SDT read sensor
40
, which can be detected with the sense current I. More specifically, when the magnetization of one of the ferromagnetic layers is anti-parallel to that of the other ferromagnetic layer the SDT effect results in a higher resistance across the SDT read sensor, with a lower resistance being experienced when M
1
and M
2
are parallel to each other. Typically, SDT read sensors exhibit &Dgr;R/R of up to 18-30% and output voltages higher than 10 mV, which is higher than that produced with many other types of MR read sensors. Thus, while advances in magnetic disk and drive technology are resulting in magnetic media that have increasingly higher area density, corresponding increasing read sensor performance needs can be met by the higher &Dgr;R/R and higher output voltages of SDT read sensors.
The SDT read sensor
40
can be formed by successive deposition over a first lead (here the first shield SH
1
) of different materials to form the first FM layer FM
1
, the insulating layer INS, and the second FM layer FM
2
. Because the SDT read sensor is operated in CPP mode, the &Dgr;R/R is particularly sensitive to the interfaces between the layers of the SDT read sensor (interlayer interfaces). To provide interlayer interfaces with minimal pin holes and impurities, and therefore higher &Dgr;R/R, FM
1
, FM
2
, and INS can be successively deposited in a one-pump-down process.
The sensor layers
42
are then etched using typical processes to form the FM
1
, FM
2
, and INS, over which a second lead, here the second shield SH
2
, is deposited. Such etching is needed to provide suitable read sensor dimension control to meet increasingly high magnetic media area densities. Unfortunately, if the etching is performed after all three materials have been deposited in a one-pump-down process, material which has been etched away from one of the three layers can redeposit on the exposed remaining portions of the other layers (along the sidewalls
41
). This can often result in the redeposition of portions of the first and/or second ferromagnetic layers such that an undesirable electrical path, or short circuit, is formed between FM
1
and FM
2
along the sidewalls
41
. With such a short circuit path, the SDT sensor
40
may not effectively produce the spin-dependent tunneling phenomenon, and therefore exhibits reduced sensor effectiveness. Theoretically, short circuits could be minimized through the use of complex, expensive, and/or time-consuming processes to limit such redeposition, however, this would not be cost-effective for commercial production of SDT read sensors.
Later in the fabrication process, the layers of the SDT sensor
40
are lapped substantially perpendicularly to the sensor layers
42
to form the air bearing surface ABS. Unfortunately, during this process, material from a facing (or front) surface (or edge) of one of the various layers can be smeared over the other layers. If the material from FM
1
and/or FM
2
is smeared between the two layers, such material can also form an undesirable short circuit path between them. Further, as the read sensor
40
thickness H becomes increasingly smaller, to accommodate higher area densities, FM
1
and FM
2
may become closer together, thereby increasing the likelihood of smearing between them. As can be understood by those skilled in the art, the problems of edge redeposition and s
Crue, Jr. Billy W.
Lai Chih-Huang
Min Tai
Shi Zhupei
Wang Lien-Chang
Carr & Ferrell LLP
Ferrell John S.
Hayden Robert D.
Ometz David L.
Read-Rite Corporation
LandOfFree
Magnetic read sensor with SDT tri-layer and method for... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Magnetic read sensor with SDT tri-layer and method for..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Magnetic read sensor with SDT tri-layer and method for... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2582596