Method and system for providing a self-aligned electrical...

Details Method and system for providing a self-aligned electrical... Method and system for providing a self-aligned electrical...

2001-11-21

2004-01-27

Klimowicz, William (Department: 2652)

Dynamic magnetic information storage or retrieval

Head

Magnetoresistive reproducing head

Reexamination Certificate

active

06683763

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to magnetic systems, and more particularly to an improved method and structure for providing electrical contact to a TMR element.
BACKGROUND OF THE INVENTION
Tunneling magnetoresistive (TMR) elements are of increasing interest for a variety of applications.
FIG. 1
depicts a conventional method
10
for providing a conventional TMR element.
FIGS. 2A through 2D
depict the conventional TMR element
30
during formation. Referring to FIGS.
1
and
2
A-
2
D, the layers for the conventional TMR element
30
are formed, via step
12
. Step
12
includes forming ferromagnetic layers separated by a nonmagnetic insulating layer. One of the ferromagnetic layers is a pinned layer, having its magnetization pinned in placed, typically using an antiferromagnetic layer. The other ferromagnetic layer is a free layer, having its magnetization free to move in response to an external field. A capping layer, for example Ta is also typically provided. A PMGI layer is formed on the TMR layer, via step
14
. A layer of photoresist is formed on the PMGI layer and patterned, via step
16
. Typically, the resist is patterned by photolithography. The PMGI is then undercut, via step
18
. Step
18
is performed by selectively dissolving a portion of the PMGI under the resist.
FIG. 2A
depicts the conventional TMR element
30
after step
18
has been performed. Ferromagnetic layers
32
and
36
of the TMR element
30
are separated by a thin insulating layer
34
. An antiferromagnetic layer
31
is also depicted. Thus, the conventional TMR element
30
is a conventional bottom pinned TMR element. A capping layer
37
is also typically present. The insulating layer
34
is thin enough to allow charge carriers to tunnel through the insulating layer
34
. Based upon the difference between the magnetizations of the ferromagnetic layers
32
and
36
the resistance of the conventional TMR element
30
changes. Also shown are the photoresist
40
and the PMGI
38
. The PMGI
38
has been undercut below the edge of the photoresist
40
. Thus, bi-layer structure is formed by the PMGI
38
and the photoresist
40
.
The conventional TMR element
30
is then defined, via step
20
. Typically, step
20
is accomplished using a reactive ion etch or by ion milling.
FIG. 2B
depicts the conventional TMR element
30
after step
20
has been performed. Because of the bi-layer structure formed by the undercut PMGI
38
and the resist
40
, the conventional TMR element
30
has the desired shape and size. A dielectric film is then deposited to partially encapsulate the conventional TMR element
30
, via step
22
.
FIG. 2C
depicts the conventional TMR element
30
after step
22
has been preformed. The dielectric film having portions
42
A,
42
B and
42
C has been deposited. Because of the presence of the PMGI
38
and the photoresist
40
, the dielectric film
42
A and
42
B covers only the side portions of the conventional TMR element
10
. Also shown is dielectric film
42
C that covers the photoresist
40
. The photoresist
40
, PMGI
38
and dielectric film
42
C are then removed, via step
24
.
FIG. 2D
depicts the conventional TMR element
30
after removal of the PMGI
38
and the photoresist
40
. Because the top of the conventional TMR element
30
is now exposed, electrical contact can then be made to the conventional TMR element
30
.
Although the conventional method
10
functions, one of ordinary skill in the art will readily recognize that the method
10
may not adequately function for smaller sizes of the conventional TMR element
30
. As the size of the conventional TMR element
30
decreases, for example below 0.5 microns, undercutting the PMGI
38
in step
18
becomes problematic. In particular, the PMGI
38
may wash away entirely instead of being selectively dissolved. Because the PMGI
38
is completely removed instead of being undercut, the conventional TMR element
30
cannot be defined.
Accordingly, what is needed is a structure and method for providing a smaller TMR element as well as for providing electrical contact to such a smaller TMR element. The present invention addresses such a need.
SUMMARY OF THE INVENTION
The present invention provides a method and structure for providing a tunneling magnetoresistive (TMR) element. The method and structure comprise providing a TMR layer that includes a first magnetic layer, a second magnetic layer and a first insulating layer disposed between the first magnetic layer and the second magnetic layer. The method and structure also comprise providing a first material and a protective layer. The first material allows electrical contact to be made to the tunneling magnetoresistive layer and is disposed above the tunneling magnetoresistive layer. The first material is capable of being undercut by a plasma etch without exposing a portion of the tunneling magnetoresistive layer under the remaining portion of the first material. The second protective layer covers a portion of the tunneling magnetoresistive sensor and a portion of the first material. In one aspect, the method and structure also include providing a second material disposed between the tunneling magnetoresistive layer and the first material. The second material allows electrical contact to be made to the tunneling magnetoresistive layer through the first material and the second material. The second material is both resistant to removal by the plasma etch and provides protection for the TMR element.
According to the structure and method disclosed herein, the present invention provides a TMR element that can be made smaller and to which electrical contact can be made.


REFERENCES:
patent: 6330136 (2001-12-01), Wang et al.
patent: 6353318 (2002-03-01), Sin et al.

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