Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
2002-03-16
2004-04-20
Chen, Tianjie (Department: 3652)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
Reexamination Certificate
active
06724581
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to high moment iron nitride Fe—N based magnetic head layers or thin films that are resistant to hard axis annealing and more particularly to ferromagnetic shield and/or pole piece layers or thin films wherein loss of magnetic anisotropy upon annealing in the presence of a field directed along the hard axis of these layers or films is minimized.
2. Description of the Related Art
The heart of a computer is an assembly that is referred to as a magnetic disk drive. The magnetic disk drive includes a rotating magnetic disk, a slider that has read and write heads, a suspension arm above the rotating disk and an actuator that swings the suspension arm to place the read and write heads over selected circular tracks on the rotating disk. The suspension arm biases the slider into contact with the surface of the disk when the disk is not rotating but, when the disk rotates, air is swirled by the rotating disk adjacent an air bearing surface (ABS) of the slider causing the slider to ride on an air bearing a slight distance from the surface of the rotating disk. When the slider rides on the air bearing the write and read heads are employed for writing magnetic impressions to and reading magnetic impressions from the rotating disk. The read and write heads are connected to processing circuitry that operates according to a computer program to implement the writing and reading functions.
The write head includes a coil layer embedded in first, second and third insulation layers (insulation stack), the insulation stack being sandwiched between first and second pole piece layers. A gap is formed between the first and second pole piece layers by a nonmagnetic gap layer at an air bearing surface (ABS) of the write head. The pole piece layers are connected at a back gap. Current conducted to the coil layer induces a magnetic field into the pole pieces that fringes across the gap between the pole pieces at the ABS. The fringe field writes information in the form of magnetic impressions in circular tracks on the rotating disk.
An exemplary high performance read head employs a spin valve sensor for sensing magnetic signal fields from the rotating magnetic disk. The spin valve sensor is located between nonmagnetic nonconductive first and second read gap layers and the first and second read gap layers are located between ferromagnetic first and second shield layers. The second shield layer may also serve as the first pole piece layer for the write head or may be a separate layer that is separated from the first pole piece layer by a nonmagnetic separation layer. In the latter case the read write head is referred to as a piggyback head. When the second shield and first pole piece are a common layer the magnetic head is referred to as a merged head. The sensor includes a nonmagnetic electrically conductive first spacer layer sandwiched between a ferromagnetic pinned layer and a ferromagnetic free layer. An antiferromagnetic pinning layer interfaces the pinned layer for pinning the magnetic moment of the pinned layer 90° to an air bearing surface (ABS) which is an exposed surface of the sensor that faces the rotating disk. First and second leads are connected to the spin valve sensor for conducting a sense current therethrough. A magnetic moment of the free layer is free to rotate upwardly and downwardly with respect to the ABS from a quiescent or zero bias point position in response to positive and negative magnetic signal fields from the rotating magnetic disk. The quiescent position of the magnetic moment of the free layer, which is preferably parallel to the ABS, is when the sense current is conducted through the sensor without magnetic field signals from the rotating magnetic disk. If the quiescent position of the magnetic moment is not parallel to the ABS the positive and negative responses of the free layer will not be equal which results in read signal asymmetry which is discussed in more detail hereinbelow.
A typical sequence of steps in the fabrication of the above read write head is to form the first shield layer (S
1
) by sputter deposition on a slider substrate wafer, sputter deposit the read gap layer on the first shield layer, sputter deposit the sensor, which includes the free, pinned and pinning layers, on the first read gap layer, sputter deposit hard bias and lead layers connected to the sensor, sputter deposit the second read gap layer on the sensor and the hard bias and lead layers, plate a second shield/first pole piece layer (S
2
/P
1
) on the second read gap layer if the head is a merged head, sputter deposit the write gap layer on the second shield/first pole piece layer in the pole tip region, form a first insulation layer (I
1
) on the second shield/first pole piece layer (S
2
/P
1
) in a yoke region by photopatterning a first layer of photoresist followed by hardbaking the photoresist at a temperature of 232° C. for 400 minutes, plate the write coil layer on the first insulation layer, form the second insulation layer (I
2
) on the coil layer by photopatterning a photoresist layer in the yoke region and hardbaking it at 232° C. for 400 minutes, frame plate a second pole piece layer (P
2
) on the write gap layer and the second insulation layer (I
2
), and connect it to the second shield/first pole piece layer (S
2
/P
1
) in a back gap region, anneal a second pole piece layer (P
2
) at 232° C. for 400 minutes, plate copper straps and studs, deposit and lap alumina overcoat, plate gold electrical connection pads, and perform a GMR reset anneal at 220° for 5 minutes. A subset of the steps which are critical in determining the magnetic properties of the shield and pole layers is shown in the following Chart A along with magnetic fields employed in each step.
CHART A
Magnetic Field Orientation
in Annealing Steps
Process Step
GMR Wafer Process
S1 Deposition and Anneal
Longitudinal (easy axis)
Sensor Deposition
Sensor Anneal: 220° C., 5 min
Transverse (hard axis)
S2/P1 Plating (80/20 NiFe)
11 Insulation Hardbake: 232° C., 400 min
Transverse (hard axis)
12 Insulation Hardbake: 232° C., 400 min
Transverse (hard axis)
P2 Plating (45/55 NiFe)
P2 Anneal: 232° C., 400 min
Transverse (hard axis)
GMR Reset: 220° C., 5 min
Transverse (hard axis)
During formation of the various ferromagnetic layers of the read write head, each ferromagnetic layer is formed with a magnetic easy axis which is oriented parallel to the ABS by sputter depositing or plating the ferromagnetic layer in the presence of a magnetic field that is oriented parallel to the ABS. Each of these layers also has a hard axis which is 90° to the easy axis and has a magnetic anisotropy (H
K
) which is the amount of applied field required to rotate a magnetic moment of the ferromagnetic layer from the easy axis to the hard axis, which rotation magnetically saturates the ferromagnetic layer. It is desirable that the ferromagnetic layers have a high magnetic anisotropy for improving their performance in the magnetic read write head. After fabrication the easy axis of each of the first shield layer (S
1
), the second shield/first pole piece layer (S
2
/P
1
) and the second pole piece layer (P
2
) is oriented parallel to the ABS. It is important that subsequent processing steps not alter the easy axis orientation of the first shield layer (S
1
) and the second shield/first pole piece layer (S
2
/P
1
) so that a bias point of the sensor is not changed by nonparallel magnetic fields from these ferromagnetic layers. Further, it is important that the easy axis of each of the second shield/first pole piece layer (S
2
/P
1
) and the second pole piece layer (P
2
) be parallel to the ABS so that a write field current from the write coil rotates the magnetic moments of these free layers from the parallel position to effectively write a write signal into a track on the rotating magnetic disk.
As shown in the second column of Chart A, various field orientations are employed during various annealing steps shown in the first column of Chart A. After sputter depositing
Chen Tianjie
International Business Machines - Corporation
Johnston Ervin F.
LandOfFree
High moment iron nitride based magnetic head layers... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with High moment iron nitride based magnetic head layers..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and High moment iron nitride based magnetic head layers... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3244619