Chemistry: electrical and wave energy – Processes and products – Coating – forming or etching by sputtering
Reexamination Certificate
2002-08-14
2003-07-15
Ryan, Patrick (Department: 1745)
Chemistry: electrical and wave energy
Processes and products
Coating, forming or etching by sputtering
C204S192110, C204S192150, C029S603070, C029S603140
Reexamination Certificate
active
06592725
ABSTRACT:
FIELD OF THE INVENTION
The field of invention relates to giant magnetoresistance (GMR) head technology generally; and more specifically, to techniques that may be used to forming high read sensitivity heads via seed layer processing.
BACKGROUND
Hardware systems often include memory storage devices having media on which data can be written to and read from. A direct access storage device (DASD or disk drive) incorporating rotating magnetic disks are commonly used for storing data in a magnetic form. Magnetic heads, when writing data, record concentric, radially spaced information tracks on the rotating disks.
Magnetic heads also typically include read sensors that read data from the tracks on the disk surfaces. In high capacity disk drives, magnetoresistive (MR) read sensors, the defining structure of MR heads, can read stored data at higher linear densities than thin film heads. An MR head detects the magnetic field(s) through the change in resistance of its MR sensor. The resistance of the MR sensor changes as a function of the strength of magnetic fields that emanates from the rotating disk.
One type of MR sensor, referred to as a giant magnetoresistance (GMR) sensor, takes advantage of the GMR effect. In the GMR sensor, the resistance of the GMR sensor varies with the strength of magnetic fields from the rotating disk and as a function of the spin dependent transmission of conducting electrons between ferromagnetic layers separated by a nonmagnetic layer (commonly referred to as a spacer layer) and the accompanying spin dependent scattering within the ferromagnetic layers that takes place at the interface of the magnetic and nonmagnetic layers.
GMR sensors using two layers of ferromagnetic material separated by a layer of GMR promoting nonmagnetic material (the spacer layer) are generally referred to as spin valve (SV) sensors. In an SV sensor, one of the ferromagnetic layers, referred to as the pinned layer, has its magnetization “pinned” via the influence of exchange coupling to an antiferromagnetic layer. Due to the relatively high unidirectional anisotropy field (H
UA
) associated with the pinned layer, the magnetization of the pinned layer typically does not rotate with respect to the magnetic flux lines that emanate/terminate from/to the rotating disk. The magnetization of the other ferromagnetic layer (commonly referred to as a ferromagnetic free layer), however, is free to rotate with respect to the magnetic flux lines that emanate/terminate from/to the rotating disk.
FIG. 1
shows a prior art SV sensor
100
comprising a seed layer
102
formed upon a gap layer
101
. The seed layer
102
helps form properly microstructures of the layers formed thereon. Over seed layer
102
is a ferromagnetic free layer
103
. An antiferromagnetic (AFM) layer
105
is used to pin the magnetization of the pinned layer
104
. Pinned layer
104
is separated from ferromagnetic free layer
103
by the nonmagnetic, GMR promoting, spacer layer
119
. Note that the ferromagnetic free layer
103
may have a multilayered structure with two or more ferromagnetic layers.
FIG. 2
shows another prior art SV sensor
200
where the pinned layer is implemented as a structure
220
having two ferromagnetic films
221
,
222
(also referred to as AP
2
and AP
1
layers, respectively) separated by a nonmagnetic film
223
(such as ruthenium Ru) that provides antiparallel (AP) exchange coupling of the two ferromagnetic films
221
,
222
. The spin valve sensor such as that
200
shown in
FIG. 2
is referred to as a synthetic spin valve sensor in light of its synthetic structure based on the antiparallel exchange-coupling relationship between films
221
,
222
.
FIG. 2
shows a synthetic spin valve sensor
200
comprising a seed layer
202
formed upon a gap layer
201
. The seed layer
202
helps form properly microstructures of the layers formed thereon. Over the seed layer
202
is a ferromagnetic free layer
203
. An antiferromagnetic (AFM) layer
205
are used to pin the magnetization of the AP
2
layer
221
. An AP
1
layer
222
is separated from the ferromagnetic free layer
203
by a spacer layer
204
. Note that ferromagnetic free layer
203
may have a multilayered structure with two or more ferromagnetic layers.
Problems with forming the sensors
100
,
200
shown in
FIGS. 1 and 2
include forming the seed layer
102
,
202
with a microstructure that suitably influences the microstructure of the AFM layer
105
,
205
as well as the other layers. Since the microstructure of the AFM layer
105
,
205
(in light of its material composition) as well as the microstructure of the other layers affect the GMR properties of the spin valve sensor, the quality of the read sensitivity of the spin valve sensor
100
,
200
depends upon the techniques used to form the seed layer
102
,
202
.
SUMMARY OF INVENTION
A method is described comprising forming an insulating polycrystalline seed layer in a first chamber by reactively pulsed DC magnetron sputtering, then forming an insulating amorphous-like seed layer in a second chamber by reactively pulsed DC magnetron sputtering, then forming a conducting seed layer and a ferromagnetic free layer in a third chamber by ion beam sputtering, and then forming the remainder of a spin valve sensor through the antiferromagnetic layer in a fourth chamber by DC magnetron sputtering.
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Lin Tsann
Mauri Daniele
Blakely & Sokoloff, Taylor & Zafman
Cantelmo Gregg
International Business Machines - Corporation
Ryan Patrick
LandOfFree
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