Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
1999-07-08
2004-06-29
Letscher, George J. (Department: 2653)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
Reexamination Certificate
active
06757142
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a magnetoresistive effect (MR) element used as a magnetic sensor, a thin-film magnetic head with the MR element and a manufacturing method of the MR element. The present invention particularly relates to a MR element of a thin-film magnetic head for hard disk drive units, and to a manufacturing method of the MR element.
DESCRIPTION OF THE RELATED ART
Recently, thin-film magnetic heads based on spin valve effect of giant magnetoresistive characteristics (GMR) are proposed as magnetic heads with high sensitivity and high output in order to satisfy the requirement for ever increasing data storage densities in today's magnetic storage systems such as hard disk drive units.
The spin valve effect thin-film structure includes first and second thin-film layers of a ferromagnetic material separated by a thin-film layer of non-magnetic material, and an adjacent layer of anti-ferromagnetic material is formed in physical contact with the second ferromagnetic layer to provide exchange bias magnetic field by exchange coupling at the interface of the layers. The magnetization direction in the second ferromagnetic layer is constrained or maintained by the exchange coupling, hereinafter the second layer is called “pinned layer”. On the other hand the magnetization direction of the first ferromagnetic layer is free to rotate in response to an externally applied magnetic field, hereinafter the first layer is called “free layer”. The direction of the magnetization in the free layer changes between parallel and anti-parallel against the direction of the magnetization in the pinned layer, and hence the magneto-resistance greatly changes and giant magneto-resistance characteristics are obtained.
Japanese Patent Unexamined Publication No. 04-358310 discloses a spin valve MR sensor which consists of sequentially stacked layers of a bottom layer, a free layer, a non-magnetic layer, a pinned layer and an anti-ferromagnetic layer on a substrate. In this spin valve MR sensor, all the layers except for the bottom and free layers are partly removed to form a magnetic sensing region corresponding to a track width region in case the sensor is used in a magnetic head. In other words, the free layer that will operate as a magnetic sensor exceeds both ends of the magnetic sensing region or the track width region. Therefore, when this spin valve MR sensor is used in the magnetic head, the magnetic sensor will be overlapped on the neighboring tracks and hence this head structure is not effective in more high dense data sensing.
Japanese Patent Unexamined Publication No. 08-221719 discloses a spin valve MR sensor in which a free layer exists only within the track width region. This type of spin valve MR sensor is fabricated by sequentially stacking on a substrate, a lower shield layer, a shield gap layer of an insulation material and a spin valve multi-layered structure which is constituted by a free layer, a non-magnetic metal layer, a pinned layer and an anti-ferromagnetic layer sequentially stacked from the bottom. Then, a specifically patterned resist layer is formed as a mask on the spin valve multi-layered structure by photo-lithographic technique, and ion milling process is implemented to form a specific shaped magnetic sensor of the spin valve multi-layered structure. Namely, the both end portions of the spin valve multi-layered structure, which exceed the magnetic sensing region, are removed away. After this process, magnetic domain control layers and lead conductor layers are formed.
However, according to this Japanese Patent Unexamined Publication No. 08-221719, over-milling onto the spin valve multi-layered structure is necessary at the ion milling process of this structure in order that incomplete milled part of the structure does not exist in any area of the wafer. Namely, the milling process is to be done extending into the shield gap layer exceeding the spin valve multi-layered structure.
As a result of such ion milling, the released particles of the shield gap layer of insulation material such as Al
2
O
3
are re-deposited on the interface area between the spin valve multi-layered structure, and the magnetic domain control layers and lead conductors to form high electrical resistive residual layers. This results in not only higher electrical resistance of the spin valve MR sensor, but also wider spread of the dispersion in electrical resistance values of such sensors. Furthermore, the over-milling may cause definite degradation of electrical insulation characteristic between the lower shield layer and the spin valve multi-layered structure due to the thinned shield gap layer.
In addition, according to this Japanese Patent Unexamined Publication No. 08-221719, the electrical contact between the spin valve multi-layered structure, and the magnetic domain control layers and the lead conductor layers is only by the cross sectional side interfaces of the patterned spin valve multi-layered structure. More thinly spin valve multi-layered structure and lower height of the stripe from ABS (Air Bearing Surface) or lower MR height result in definite decrease of the electrical contact area and increase of the contact resistance. This increase of the contact resistance may cause shorter life of the sensor due to self-heating and/or electro-migration of the MR sensor. It is possible to enlarge the contact area by making the shape of the cross sectional side interfaces in a greatly tapered shape. However, such shape may invite increase in Barkhousen noise and also increase of the output signal fluctuations.
The above-mentioned problems may be caused not only in such spin valve MR element, but also in an usual anisotropic MR element.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a MR element, a thin-film magnetic head with the MR element and a manufacturing method of the MR element, whereby electric resistance at the interface between a spin valve multi-layered structure or other MR multi-layered structure and a magnetic domain control layer and a lead conductor layer becomes low and its dispersion can exist in a narrow range.
Another object of the present invention is to provide a MR element, a thin-film magnetic head with the MR element and a manufacturing method of the MR element, whereby electrical contact area at the interface between a spin valve multi-layered structure or other MR multi-layered structure and a magnetic domain control layer and a lead conductor layer becomes more larger.
According to the present invention, a MR element, with a magnetic sensing region and outside regions thereof which locate outside the magnetic sensing region along a track width direction, includes a multi-layered structure with an anti-ferromagnetic thin-film layer, a first ferromagnetic thin-film layer constituted by a single layer of ferromagnetic material or by multi layers of ferromagnetic material, a non-magnetic metal thin-film layer and a second ferromagnetic thin-film layer constituted by a single layer of ferromagnetic material or by multi layers of ferromagnetic material which are sequentially formed on a substrate. The all layers in the multi-layered structure exist in the magnetic sensing region, and at least the anti-ferromagnetic thin-film layer with its initial thickness exists in the outside regions.
In this multi-layered structure, the second ferromagnetic thin-film layer (free layer) is formed in the opposite (upper) side of the substrate, and at least the anti-ferromagnetic thin-film layer with the initial thickness exists in the outside regions of the magnetic sensing region, and hence even when over milling process is implemented to pattern the free layer, an insulation layer under the anti-ferromagnetic thin-film layer is not attacked. Therefore, insulation material particles do not re-deposit on the cross sectional interface area of the spin valve multi-layered structure, the magnetic domain control layers and lead conductor layers, and the interface electrical resistance can become low and its dispe
Arent Fox Kintner & Plotkin & Kahn, PLLC
Letscher George J.
LandOfFree
Magnetoresistive effect element with a magnetic sensing... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Magnetoresistive effect element with a magnetic sensing..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Magnetoresistive effect element with a magnetic sensing... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3336735