Dynamic magnetic information storage or retrieval – Head – Core
Reexamination Certificate
2001-06-18
2004-01-13
Miller, Brian E. (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Core
Reexamination Certificate
active
06678117
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to the field of magnetic transducers (heads) having inductive write heads and more particularly to the structure of a pole piece and a method for forming a pole piece tip for the write head.
BACKGROUND OF THE INVENTION
A typical prior art head and disk system is illustrated in FIG.
1
. In operation the magnetic transducer
10
is supported by a suspension
13
as it flies above the disk
16
. The magnetic transducer, usually called a “head,” is composed of elements that perform the task of writing magnetic transitions (the write head
23
) and reading the magnetic transitions (the read head
12
). The electrical signals to and from the read and write heads
12
,
23
travel along conductive paths
14
which are attached to or embedded in the suspension
13
. Typically there are two electrical contact pads each for the read and write heads
12
,
23
. Wires or leads are connected to these pads (not shown) and routed in the suspension
13
to the arm electronics (not shown). The disk
16
is attached to spindle
22
that is driven by the spindle motor
24
to rotate the disk. The disk
16
comprises a substrate
26
on which a plurality of thin films
21
are deposited. The thin films include ferromagnetic material that is used to record the magnetic transitions in which information is encoded.
The write head
23
portion of the transducer
10
includes two pole pieces (P
1
and P
2
) and a coil (not shown). To decrease the side writing and, therefore, to reduce the track width the pole pieces are shaped into narrow tips at the gap (not shown). To be effective the P
1
tip should be the same size as the P
2
pole tip and should extend up from the larger body of P
1
pole piece about 1 to 1.5 times the gap thickness. In one prior art method P
1
is deposited first and initially has a broad, flat tip that is subsequently ion milled using the P
2
tip as a mask to form the P
1
tip. Since the top surface of P
2
is also exposed to milling during this process, the P
2
layer must initially be thicker than the final desired thickness. For the same reason it is necessary to protect all regions of the wafer that would be harmed by the milling.
Variations of this process are described in U.S. Pat. No. 6,119,331 to Chen, et al.; U.S. Pat. No. 5,452,164 to Cole, et al.; and U.S. Pat. No. 5,438,747 to Krounbi, et al. Chen '331 describes the use of a notching layer that is deposited by plating on top of the initial P
1
layer which is also plated. The ion milling can then proceed until only the notching layer outside of the desired tip area is removed or it can proceed to also mill away some of the initial P
1
layer. The notching layer, therefore, contributes the P
1
tip in this design and must be ferromagnetic.
One problem with all of the prior art ion milling methods is that it is difficult to determine the precise point at which milling should stop. In current practice the end point must be determined by experimentation with the particular equipment and materials being used.
SUMMARY OF THE INVENTION
Applicant discloses a magnetic transducer with a bilayer pole piece in which a first layer of material forms the body of the pole piece and a second layer forms the pole tip after milling. The described embodiment of the invention is in a head with a bilayer P
1
comprising a body and a tip. The process of making the head proceeds conventionally through plating of the P
1
layer which in applicant's head is the layer which forms the body of P
1
. The process of the invention deposits a P
1
protection layer and then uses a photo lift-off technique to form a void in the P
1
protection layer where the gap and the P
1
and P
2
tips will be formed, i.e., the zero throat region. An additional ferromagnetic layer that will be called the “P
1
tip layer” is vacuum deposited on the P
1
protection layer and the void area to a thickness equal to the final desired pole tip height. The gap layer is deposited and the P
2
tip is formed as in the prior art. Ion milling is then performed as in the prior art with the exceptions: 1) that the P
1
protection layer protects areas of the wafer which should not be milled; and 2) instead of milling a notch in the planar surface of P
1
, only the excess of the P
1
tip layer is required to be milled. A disk drive using the magnetic transducer of the invention is also described. The Applicant also discloses a method to improve the determination of the optimum stopping point for the ion milling using the optically observable process of the gap layer and P
1
tip layer being milled off of the P
1
protection layer forming a gradually disappearing halo.
REFERENCES:
patent: 5438747 (1995-08-01), Krounbi et al.
patent: 5452164 (1995-09-01), Cole et al.
patent: 5652687 (1997-07-01), Chen et al.
patent: 5793578 (1998-08-01), Heim et al.
patent: 5798897 (1998-08-01), Chang et al.
patent: 5805391 (1998-09-01), Chang et al.
patent: 5901431 (1999-05-01), Santini
patent: 6119331 (2000-09-01), Chang et al.
patent: 6199267 (2001-03-01), Koshikawa et al.
patent: 6317290 (2001-11-01), Wang et al.
patent: 6339524 (2002-01-01), Furusawa et al.
patent: 6466403 (2002-10-01), Sato et al.
patent: 6469874 (2002-10-01), Han et al.
patent: 6477005 (2002-11-01), Sasaki
patent: 6483664 (2002-11-01), Kamijima
patent: 6483665 (2002-11-01), Sasaki
patent: 6490125 (2002-12-01), Barr
patent: 6490126 (2002-12-01), Sasaki
patent: 6504676 (2003-01-01), Hiner et al.
patent: 6507448 (2003-01-01), Nishida et al.
Hitachi Global Storage Technologies - Netherlands B.V.
Knight G. Marlin
Miller Brian E.
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