Vertical giant magnetoresistance sensor using a recessed shield

Details Vertical giant magnetoresistance sensor using a recessed shield Vertical giant magnetoresistance sensor using a recessed shield

1999-11-09

2002-09-24

Ometz, David L. (Department: 2651)

Dynamic magnetic information storage or retrieval

Head

Magnetoresistive reproducing head

C360S322000

Reexamination Certificate

active

06456465

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to magnetic recording technology, and more particularly to a giant magnetoresistive read head which is capable of being used at high magnetic recording densities.
BACKGROUND OF THE INVENTION
Magnetoresistive (“MR”) heads are currently used in read heads or for reading in a composite head.
FIG. 1A
is a diagram of a conventional MR head
10
. The MR head
10
includes a first shield
14
formed on a substrate
12
. The MR head
10
also includes a first gap
16
separating a MR sensor
30
from the first shield
14
. The MR head
10
also includes a pair of hard bias layers
18
a
and
18
b
. The hard bias layers
18
a
and
18
b
magnetically bias layers in the MR element
30
. The MR head
10
also includes lead layers
19
a
and
19
b
, which conduct current to and from the MR element
30
. A second gap
20
separates the MR sensor
30
from a second shield
22
. When brought in proximity to a recording media (not shown), the MR head
10
reads data based on a change in the resistance of the MR sensor
30
due to the field of the recording media.
FIG. 1B
depicts another view of the conventional MR head
10
. For clarity, only a portion of the conventional MR head
10
is depicted. Also shown is the surface of the recording media
40
. Thus, the air-bearing surface (ABS) is shown. Depicted in
FIGS. 1B
are the first shield
14
, the second shield
22
, the MR sensor
30
and the leads
19
a
and
19
b
. Also shown is the height of the MR sensor
30
, also known as the stripe height (h).
Giant magnetoresistance (“GMR”) has been found to provide a higher signal for a given magnetic field. Thus, GMR is increasingly used as a mechanism for conventional higher density MR sensors
30
. One MR sensor
30
which utilizes GMR to sense the magnetization stored in recording media is a conventional spin valve.
FIG. 2A
depicts one conventional GMR sensor
30
′, a conventional spin valve. The conventional GMR sensor
30
′ typically includes a seed layer
31
, an antiferromagnetic (“AFM”) layer
32
, a pinned layer
34
, a spacer layer
36
, a free layer
38
, and a capping layer
39
. The seed layer is used to ensure that the material used for the AFM layer
32
has the appropriate crystal structure and is antiferromagnetic in nature. The spacer layer
36
is a nonmagnetic metal, such as copper. The pinned layer
34
and the free layer
38
are magnetic layers, such as CoFe. The magnetization of the pinned layer
34
is pinned in place due to an exchange coupling between the AFM layer
32
and the pinned layer
34
. The magnetization of the free layer
38
is free to rotate in response to the magnetic field of the recording media
40
. However, note that other conventional GMR sensors, such as conventional dual spin valves, conventional synthetic spin valves, are also used.
Conventional GMR sensors
30
′ are used in one of two configurations, current-in-plane (“CIP”) or current-perpendicular-to-plane (“CPP”). For most commercial devices, however, the CIP configuration is used.
FIG. 3
depicts the CIP configuration. Only portions of the conventional GMR sensor
30
′ as it is used in the conventional MR head
10
, is depicted. Also depicted is the recording media
40
. The height (h), width (w) and thickness (t) of the conventional GMR sensor
30
′ is also shown. In the CIP configuration, current is driven parallel to the planes of the conventional GMR sensor
30
′. Thus, the arrow
44
depicts the direction of current. The down track direction
42
is the direction in which the head is traveling. Thus, the track width of the recording media
40
lies along the direction in which current flows. The width of the conventional GMR sensor
30
′ is set by and typically lower than the track width of the recording media
40
. Note that in the CPP configuration, not shown, current is driven perpendicular to the planes of the conventional GMR sensor
30
′. Thus, current would be parallel or antiparallel to the down track direction
42
of FIG.
3
.
Use of a the GMR sensor
30
′ in another configuration is described in U.S. Pat. No. 5,8589,753 by Ohtsuka et al. (Ohtsuka). Ohtsuka discloses the use of pairs of spin valves in which current is driven perpendicular to the surface of the recording media. In one spin valve, current is driven towards the recording media, while in the other spin valve current is driven away from the recording media. In order to drive the current, Ohtsuka couples the spin valves to the shields.
Although the conventional MR head
10
is capable of reading the recording media
40
, the current trend in magnetic recording is toward higher densities. For example, it is currently desired to read recording media having a track density of thirty-five kilo-tracks-per-inch (“kTPI”). At these densities, the width (w) of the conventional GMR sensor
30
′ is desired to be less than 0.5 &mgr;m, which is less than the width of the conventional GMR sensor
30
′ in current generation devices. At higher densities, the width of the conventional GMR sensor
30
′ will be less, for example on the order of 0.2-0.3 &mgr;m. At the same time, it is desirable to have a particular resistance for the sensor, typically on the order of twenty-five to forty-five Ohms. The resistance of the sensor is proportional to the length of the sensor along which the current travels and inversely proportional to the cross-sectional area through which the current passes. In the CIP configuration, depicted in
FIG. 3
, the resistance is proportional to the track width (w) and inversely proportional to the thickness (t) and stripe height (h). Furthermore, the thickness of the conventional GMR sensor
30
′ cannot be radically changed. Consequently, the thickness of the conventional GMR sensor
30
′ cannot be used as a mechanism for altering the resistance of the conventional GMR sensor
30
′. As the track width and, therefore, the width of the conventional GMR sensor
30
′ decrease, the stripe height must decrease to maintain approximately the same resistance. Current generation stripe heights may be on the order of 0.5 &mgr;m, approximately half of the width of current generation versions of the conventional GMR sensor
30
′. However, as discussed above, the width of the GMR sensor
30
′ is desired to be below 0.5 &mgr;m. For a sensor width of approximately 0.2-0.3 &mgr;m, the stripe height would be reduced to on the order of 0.1 &mgr;m in order to maintain the same resistance. Significantly shorter stripe heights may be difficult to fabricate because the conventional GMR sensor
30
′ is typically lapped to set the stripe height. Lapping can vary by approximately 0.2 to 0.3 &mgr;m. When the stripe height is desired to be less than or approximately the same as the variation induced by lapping, it may not be possible to fabricate conventional GMR sensors
30
′ using conventional techniques. Furthermore, even if a conventional GMR sensor
30
′ having such a small stripe height can be fabricated, heating may drastically shorten the life of the GMR sensor
30
′. Consequently, the conventional GMR sensor
30
′ in the conventional MR head
10
may be unsuitable for higher track densities.
Furthermore, as the stripe height of the conventional GMR sensor
30
′ is decreased, the conventional GMR sensor
30
′ becomes more subject to destruction due to electrostatic discharge (“ESD”). Reducing the stripe height of the conventional GMR sensor
30
′ renders the GMR sensor
30
′ less able to dissipate a charge through the leads
19
a
and
19
b
(shown in FIG.
1
B). Consequently, when the conventional GMR sensor
30
′ gains an electrostatic charge, the charge is more liable to jump through one of the gaps
16
or
20
(shown in
FIG. 1A
) to one of the shields
14
or
22
, respectively. Generally, such a discharge destroys the conventional GMR sensor
30
′. Consequently, as the stripe height of the conven

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