Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
2001-02-20
2004-02-10
Vo, Peter (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C029S603060, C029S603130, C029S603180, C029S603160, C360S324200, C360S324000
Reexamination Certificate
active
06687977
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to magnetic disk drives, more particularly to magnetoresistive (MR) read heads, and most particularly to methods and structures for current-perpendicular-to-plane operation of submicron MR heads.
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 magnetic read/write head
30
including a read element
32
and a write element
34
. The edges of the read element
32
and write element
34
also define an air bearing surface, ABS, which faces the surface of the magnetic disk
16
.
Read element
32
includes a first shield
36
, a second shield
38
, and a read sensor
40
located between the first shield
36
and the second shield
38
. One type of such as anisotropic magnetoresistive (AMR), spin valve, and giant magneto-resistive (GMR). The particular read sensor
40
shown is a multilayer GMR, formed of successive layer pairs
42
of various materials. Such an MR device typically can be formed by depositing the layer pairs
42
one upon the next to form a multilayer wafer (not shown). The material of each layer and the ordering of layers are appropriately selected to achieve a desired read performance. Multiple portions of the wafer are then removed to provide multiple read sensors
40
.
The operation of the read element
32
can be better understood with reference to the perspective view of read element
34
in
FIG. 1D. A
sense current I is caused to flow through the read sensor. While here the sense current is shown injected through the shields, other configurations have the read sensor electrically isolated from the shields, with additional leads injecting the sense current I. As the sense current passes through, the read sensor exhibits a resistive response, which results in a particular output voltage. The higher the output voltage, the greater the precision and sensitivity of the read sensor in sensing magnetic fields from the magnetic medium
16
.
The output voltage is affected by various characteristics of the read element
32
. For example, the greater the component of the sense current I that flows across the read sensor layers, the greater the output voltage. This component of the sense current I is called the current-perpendicular-to-plane component, CPP. On the other hand, the component of the sense current I that flows along the read sensor layers
42
is the current-in-plane, CIP, which results in lower output voltage. In the configuration of
FIG. 1D
, the first and.second shields
36
,
38
are conductive and are in electrical contact with the read sensor
40
. Here, the sense current I of the read sensor
40
flows, for example, from the first shield
36
to the second shield
38
through the read sensor
40
. As the sense current I flows through the read sensor
40
, the current flows substantially perpendicularly to the orientation of the layers
42
of the read sensor
40
. Thus, substantially all of the sense current I is CPP. Other read sensors may be designed to operate with varying CPP and CIP components of the sense current. However, it is desirable to maximize the CPP component to maximize the output voltage of the read sensor. The design and manufacture of magnetoresistive heads, such as read sensor
40
, are well known to those skilled in the art.
Write element
34
is typically an inductive write element and includes a first yoke element
44
and the second shield
38
, which forms a second yoke element, defining a write gap
46
therebetween. The first yoke element
44
and second yoke element
38
are configured and arranged relative to each other such that the write gap
46
has a particular throat height, TH. Also included in write element
34
, is a conductive coil
48
that is positioned within a dielectric medium
50
. As is well known to those skilled in the art, these elements operate to magnetically write data on a magnetic medium such as a magnetic disk
16
.
Although current MR read sensors such as read sensor
40
have been used in the past, their performance is limited. In particular, their output voltage is limited by various factors such as cross-sectional area that is normal to the sense current vector (i.e., decreasing output voltage with increasing area), and the device length that is parallel to the sense current vector (i.e., decreasing output voltage with decreasing length). With demand for increasingly smaller read/write heads, the shield-to-shield height H between the read element first and second shields
38
,
44
is increasingly smaller, thus leaving increasingly less space to accommodate the read sensor
46
. Thus, in a read sensor such as shown in
FIG. 1D
, decreasing height H results in decreasing device length, thereby reducing the sensor output voltage. Furthermore, even without limitations on device length, GMR multilayer properties have been found to degrade as the number of multilayers (i.e., layer pairs) increases. In particular, degradation has occurred above 20-30 multilayers.
In addition to the limitations of currently available materials, edges E (shown in
FIG. 1D
) of each layer in a multilayer device can be damaged in the fabrication process. For example, during a cutting operation to remove a single read sensor from a wafer, materials from individual layers may be smeared along the layer edges. Thus, the sense current I traveling perpendicular to the layers may be shunted at the edges, thereby reducing the effectiveness of the sense current I to drive the MR read sensor.
Also, the fabrication of read sensors is becoming increasingly more complex and expensive as increasingly smaller MR read/write devices are sought by users. Particularly, designs are being driven to submicron geometry scales. Such geometries are typically formed by direct photolithographic techniques which are more time and cost consuming. In addition to the challenges of the device size itself fabrication tolerances are accordingly becoming increasingly smaller.
Thus, what is desired is an MR head, and method for making the same, that has increased performance, while limiting cost and complexity, even at increasingly smaller MR head sizes.
SUMMARY OF THE INVENTION
The present invention provides an MR head and method for making the same that provides higher performance and fabrication with less cost and complexity. This is accomplished by providing a CPP MR read sensor that is formed in a groove between two conductors by a method that can be performed with submicron precision, and that results in the sense current passing twice through the MR thickness. Thus, twice as many layers of MR material are used without increasing the shield-to-shield height H. Further, the method for making the MR head uses thin film processes, deposition, and etching to define the submicron geometries.
According to an embodiment of the present invention, a magnetoresistive device includes a metal layer that is formed over a substrate. The metal layer is provi
Barr Ronald A.
Knapp Kenneth E.
Kallman Nathan N.
Kim Paul
Western Digital (Fremont) Inc.
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