Process to form a flux concentration stitched write head

Details Process to form a flux concentration stitched write head Process to form a flux concentration stitched write head

2000-09-11

2003-07-22

Huff, Mark F. (Department: 1756)

Radiation imagery chemistry: process, composition, or product th

Imaging affecting physical property of radiation sensitive...

Making electrical device

C430S312000, C430S313000, C430S314000, C430S319000, C430S322000, C430S323000

Reexamination Certificate

active

06596468

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to the general field of magnetic disk systems with particular reference to forming step P
1
.
BACKGROUND OF THE INVENTION
Read-write heads for magnetic disk systems have undergone substantial development during the last few years. In particular, older systems in which a single device was used for both reading and writing, have given way to configurations in which the two functions are performed by different structures that have been integrated into a single unit. In
FIG. 1
we show a schematic representation of a write head of a type currently under development in our laboratories. The magnetic field that ‘writes’ a bit at the surface of recording medium
18
(generally referred to as the air bearing surface or ABS) is generated by a flat coil, whose windings, such as
16
, can be seen in the figure. The magnetic flux generated by the flat coil is largely confined to the pole pieces. These comprise the upper pole pieces
12
and
13
(known as P
2
and P
3
respectively), which are connected on the right side of the figure to lower pole piece
11
, known as P
1
. On the left side of the figure, P
1
and P
2
are seen to be separated by a layer of non-magnetic material
15
so that most of the magnetic flux generated by the flat coil passes across gap
19
where fringing fields extending out for a short distance are still powerful enough to magnetize a small portion of recoding medium
18
It can be seen that where P
1
and P
2
face each other their cross-sectional areas have been reduced so as to further concentrate the magnetic flux at
19
. In the case of P
1
this has been achieved by the introduction of an area of non-magnetic material
111
, generally referred to as step P
1
. In
FIG. 2
we illustrate the prior art process that has been used till now to form step P
1
. Given substrate
22
on which layer
21
(P
1
) rests, a trench
25
was formed in P
1
and then overfilled with non-magnetic material
23
. Excess material
23
was then removed by means of chemical-mechanical polishing (CMP) so that the trench ended up being just filled as
111
, thereby forming step P
1
as shown in FIG.
3
.
In the interests of product reproducibility, it is important that the thickness of step P
1
be closely controlled and that the entire surface of layer
21
be uniformly planar. lf it is not, any unevenness in the topology will be transmitted to subsequent layers, including the lower portions of P
2
. Furthermore, as write heads continue to shrink, so will the thickness of step P
1
, making control ever more difficult.
While being an extremely useful tool for planarizing surfaces that are made up of several different materials, CMP is subject to problems of dishing at heterogeneous interfaces and, additionally, it is usually necessary to over-polish in order to achieve full planarization. The extent of this over-polish is difficult to control, making the final thickness of 111 likewise difficult to control.
The present invention is directed towards solving the problem of how to form step P
1
with tight control of thickness and no loss of planarity to the upper surface of P
1
A routine search of the prior art was performed. The following references of interest were found: In U.S. Pat. No. 5,805,391, Chang et al. show a stitched head process by IBM while in U.S. Pat. No. 5,282,308, Chen et al. (also IBM) disclose a stitched head planarization process. In U.S. Pat. No. 5,325,254, Cooperrider shows a thin film inductive transducer having improved yoke and pole tip structure.
SUMMARY OF THE INVENTION
It has been an object of the present invention to provide a process for filling a trench without disturbing the surrounding surface.
Another object of the invention has been to provide a process for forming step P
1
in a read head.
A further object has been that said process provide better process tolerance than CMP.
These objects have been achieved by using a liftoff mask for both the trench formation and the filling processes. As a result of this approach, the area surrounding the trench is not disturbed, the trench depth is not reduced, and the original overall planarity, prior to etching and filling, is maintained.


REFERENCES:
patent: 5282308 (1994-02-01), Chen et al.
patent: 5325254 (1994-06-01), Cooperrider
patent: 5617277 (1997-04-01), Chen et al.
patent: 5805391 (1998-09-01), Chang et al.
patent: 6303260 (2001-10-01), Hurditch et al.
patent: 6320725 (2001-11-01), Payne et al.

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