Active solid-state devices (e.g. – transistors – solid-state diode – Field effect device – Having insulated electrode
Reexamination Certificate
2002-07-09
2004-03-30
Nelms, David (Department: 2818)
Active solid-state devices (e.g., transistors, solid-state diode
Field effect device
Having insulated electrode
C257S296000, C257S300000, C257S421000, C438S003000, C438S240000
Reexamination Certificate
active
06713801
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to magnetic system, and more particularly to a method and system for providing magnetic tunneling junctions having improved reliability.
BACKGROUND OF THE INVENTION
Because of their high magnetoresistanse ratio, spin dependent tunneling sensors, otherwise known as magnetic tunneling junctions (MTJs), are currently of interest for use in a variety of devices, including magnetic memories such as magnetic random access memories (MRAM).
FIG. 1
depicts a portion of a conventional magnetic memory, a conventional MRAM
1
. The conventional MRAM
1
includes MTJs
10
. Each MTJ
10
includes at least a conventional pinned layer
20
, a conventional barrier layer
30
and a conventional free layer
40
. The conventional barrier layer
30
is typically an insulator that serves as a tunneling barrier between the conventional pinned layer
20
and the conventional fire layer
40
. The conventional pinned layer
20
and the conventional free layer
40
are ferromagnetic. The magnetization of the conventional pinned layer
20
is pinned in a particular direction, generally by an antiferromagnetic layer (not shown). The magnetization of the conventional free layer
40
is free to rotate in response to an external field. The conventional MRAM
1
includes a conventional bit line
60
and a conventional bottom lead
50
. Current through the MTJ
10
is carried by the conventional bit line
60
and the conventional bottom lead
50
.
FIG. 2
is a more detailed diagram of a conventional MTJ
10
and the bottom lead
50
. The conventional MTJ
10
includes a conventional seed layer
12
and a conventional antiferromagnetic layer
14
. The conventional MTJ
10
shown utilizes a conventional synthetic pinned layer
20
. The conventional synthetic pinned layer
20
includes conventional ferromagnetic layers
22
and
26
separated by a nonmagnetic spacer layer
24
. The conventional ferromagnetic layers
22
and
26
are antiferromagnetically coupled. The conventional barrier layer
30
is typically Al
2
O
3
. In addition, the MTJ
10
typically includes a conventional capping layer
16
. The conventional bit line
60
is generally coupled to the conventional capping layer
16
. The conventional bottom lead
50
, which typically carries a current during reading and writing, is generally composed of Cu or Al. As a result, the conventional bottom lead
50
has a high electrical conductivity, allowing for current to be carried by the conventional bottom lead with little loss.
Although the conventional MRAM
1
and conventional MTJ
10
function, one of ordinary skill in the art will readily recognize that the conventional MTJ
10
may be subject to failure. In particular, conventional barrier layer
30
can be nonuniform. The conventional barrier layer
30
is also typically very thin to allow tunneling of current carriers between the conventional pinned layer
20
and the conventional free layer
40
. Because of this nonuniformity, the conventional tunneling barrier
30
is subject to pinholes and other defects which decrease the reliability of the conventional tunneling barrier
30
. For example, the current through the conventional tunneling barrier
30
may vary and/or the conventional tunneling barrier
30
may be subject to breakdown. The reliability of the conventional tunneling barrier
30
and, therefore, the reliability of the conventional MTJ
10
are adversely affected.
Accordingly, what is needed is a system and method for providing a more reliable MTJ. The present invention addresses such a need.
SUMMARY OF THE INVENTION
The present invention provides a method and system for providing a tunneling junction. The method and system comprise providing a free layer, a pinned layer, and a barrier between the free layer and the pinned layer. The free layer and the pinned layer are ferromagnetic. The barrier layer is an insulator. The magnetic tunneling junction is coupled to an &agr;-Ta lead.
According to the system and method disclosed herein, the present invention provides a magnetic tunneling junction having improved reliability.
REFERENCES:
patent: 5764567 (1998-06-01), Parkin
patent: 5801984 (1998-09-01), Parkin
patent: 5841692 (1998-11-01), Gallagher et al.
patent: 5898549 (1999-04-01), Gill
patent: 5920446 (1999-07-01), Gill
patent: 6219212 (2001-04-01), Gill et al.
patent: 6518588 (2003-02-01), Parkin et al.
patent: 6574079 (2003-06-01), Sun et al.
patent: 2002/0067580 (2002-06-01), Li et al.
patent: 2002/0097534 (2002-07-01), Sun et al.
Hiner Hugh C.
Shi Xizeng
Sin Kyusik
Huynh Andy
Nelms David
Sawyer Law Group LLP
Western Digital (Fremont) Inc.
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