Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
2001-09-24
2004-11-09
Ometz, David L. (Department: 2653)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
Reexamination Certificate
active
06816345
ABSTRACT:
BACKGROUND
The present invention relates to devices, such as magnetoresistive (MR) sensors or electronic circuits, having submicron features that are manufactured with a mask that is undercut, with the undercut allowing the mask and overlying materials to be lifted off.
FIG. 1
shows a prior art step in the formation of a conventional MR sensor for a hard disk drive. Over a wafer substrate
20
a magnetic shield layer
22
has been formed, either directly on the substrate or on an intermediate layer, not shown. Atop the shield layer
22
a first read gap layer
24
of dielectric materials has been formed, and atop the read gap layer
24
a plurality of MR sensor layers
26
has been formed. A bi-layer mask
25
has been formed of layers
27
and
28
, and after photolithographic patterning, layer
27
has been chemically removed relative to layer
28
, forming undercut edges
30
and
33
. A directional removal step such as ion beam etching (IBE) has been performed to create edges
35
and
36
of the sensor layers
26
, the IBE also removing part of the read gap layer
24
.
In
FIG. 2
a bias layer
40
has been sputter deposited, followed by an electrically conductive lead layer
44
. The electrically conductive bias layer
40
and lead layer
44
abut the edges
35
and
36
of the sensor layers
26
to stabilize magnetic domains of the sensor layers and provide electric current to the sensor layers. The bias layer
40
and lead layer
44
are also deposited atop mask layer
25
, but due to undercuts
30
and
33
, a chemical etch can be applied that dissolves mask layer
27
allows the mask and the layers
40
and
44
atop the mask to be lifted off.
FIG. 3
shows a cross-sectional view of the sensor layers
26
, bias layer
40
and lead layer
44
after the mask has been lifted off. This cross-sectional view of the sensor layers is essentially that which will be seen from a media such as a disk, after the wafer
20
has been diced and the die or head containing the sensor layers
26
has been positioned adjacent the media in a drive system. An active width or track width TW
0
of the sensor layers
26
between lead layers
44
may be in a range between one-half micron and one micron, corresponding to a resolution at which the sensor layers can read magnetic tracks in the media.
FIG. 4
is a top view of the sensor layers
26
, bias layer
40
and lead layer
44
of FIG.
3
. The wafer and thin film layers will, as mentioned above, be diced along the dashed line
3
—
3
that indicates the cross-sectional view of FIG.
3
. The sensor layers
26
shown in
FIG. 4
have been trimmed along back edges
50
and
52
distal to the dashed line
3
—
3
by conventional masking and IBE such as ion milling, not shown. The leads
44
are typically so much thicker than the sensor layers
26
that the ion milling of the back edges
50
and
52
of the sensor layers
26
does not cut through the leads. The leads have a lead height LH
0
, measured from the dashed line
3
—
3
that will be the approximate location of the media-facing surface, of about 50-100 microns.
After forming the back edges
50
and
52
, another read gap layer, not shown, is formed over the sensor layers
26
and lead layer
44
shown in
FIG. 3. A
magnetic shield layer that may optionally serve as a write pole layer, not shown, is then formed. After optional formation of a write transducer, not shown, the wafer
20
upon which perhaps a thousand of these sensors has been formed is diced into rows of sensors, one of the rows diced along the dashed line
3
—
3
. The structure shown in
FIG. 4
is symmetrical about line
3
—
3
, so that a pair of sensors may be formed upon cutting along that line
3
—
3
, each of the sensors having a media-facing surface adjacent to line
3
—
3
. After further processing, including creation of a protective coating on the media-facing surface, the row is divided into individual heads for interaction with a media.
In an effort to increase storage density, the track width TW
0
of the sensor layers
26
may be reduced below that current commercially available range of 0.5 micron to 1.0 micron. As the track width TW
0
is reduced, however, the undercut used in the lift off process may become a larger fraction of the mask width, so that the lower mask layer
27
can no longer support the upper layer
28
. Moreover, reducing the width of mask
25
below 0.5 micron approaches the limits of conventional photolithography.
SUMMARY
In accordance with the present invention, methods are disclosed for reducing feature sizes of devices such as electromagnetic sensors. A track width of such a sensor may be defined by a mask having an upper layer with a reduced width and a lower layer with a further reduced width. Instead of or in addition to being supported by the lower layer in the area defining the sensor, the upper layer is supported by the lower layer in areas that do not define the sensor width. In some embodiments the upper layer forms a bridge mask, supported at its ends by the lower layer, and the lower layer is completely removed over an area that will become a sensor. Also advantageous is a mask having more than two layers, with a bottom layer completely removed over the sensor area, and a middle layer undercut relative to a top layer.
REFERENCES:
patent: 5147740 (1992-09-01), Robinson
patent: 5847904 (1998-12-01), Bharthulwar
patent: 6108176 (2000-08-01), Yokoyama
patent: 6156665 (2000-12-01), Hamm et al.
patent: 6218056 (2001-04-01), Pinarbasi et al.
patent: 6228276 (2001-05-01), Ju et al.
patent: 6229678 (2001-05-01), Xue et al.
patent: 6235342 (2001-05-01), Xue et al.
patent: 6433971 (2002-08-01), Sato et al.
patent: 6515837 (2003-02-01), Hamakawa et al.
patent: 6570743 (2003-05-01), Garfunkel et al.
patent: 6583970 (2003-06-01), Sakata
patent: 5-189727 (1993-07-01), None
patent: 7-29122 (1995-01-01), None
patent: 7-272221 (1995-10-01), None
Barr Ronald A.
Cagan Myron R.
Knapp Kenneth E.
Thomas Mark D.
Lauer Mark
Ometz David L.
Silicon Edge Law Group LLP
Western Digital (Fremont) Inc.
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