Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
2000-11-30
2004-11-02
Renner, Craig A. (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
Reexamination Certificate
active
06813121
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to the field of magnetic transducers (heads) and more particularly to materials and structures used to form conductive leads in the heads.
BACKGROUND OF THE INVENTION
A typical prior art head and disk system is illustrated in FIG.
1
. In operation the head
10
is supported by the 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 (leads)
14
which are attached to or embedded in the suspension
13
. Typically there are two electrical contact pads (not shown) each for the read and write heads
12
,
23
. Wires or leads
14
are connected to these pads and routed in the suspension
13
to the arm electronics (not shown). The disk
16
is attached to a spindle
18
that is driven by a spindle motor
24
to rotate the disk
16
. The disk
16
comprises a substrate
26
on which a plurality of thin films
21
are deposited. The thin films
21
include ferromagnetic material in which the write head
23
records the magnetic transitions in which information is encoded.
There are several types of read heads
12
including Giant Magnetoresistive (GMR) and tunnel junction. It is important for the two leads (not shown) that provide the electrical connection to the sensor element (not shown) in a magnetoresistive head
12
to be of low resistance, to be consistently manufacturable and to be resistant to formation of shorts during the manufacturing process. Typically leads (not shown) have been made from copper, tungsten, tantalum or gold, but the requirements of heads like spin valves make these traditional simple leads inadequate. To meet the new requirements, leads with a multilayer structure have been proposed. For example, U.S. Pat. No. 5,438,470 to Ravipati, et al., suggest using a thin layer of tantalum under a layer of gold for the leads. Ravipati '470 also teaches that lower resistance leads are obtained by placing the leads in contact with the hard bias layer as well the magnetoresistive sensor. U.S. Pat. No. 5,491,600 to Chen, at al., describes leads with two refractory metal layers sandwiching a highly conductive metal layer. One embodiment is alternating layers of tantalum and gold. In the particular type of head described in Chen '600, the leads from the spin valve sensor layer stack are formed on material used for the hard bias, e.g., CoPtCr. The CoPtCr layer in turn has a Cr underlayer.
U.S. Pat. No. 5,883,764 to Pinarbasi similarly describes a multilayer lead structure, for example, 3.5 nm Ta, 3.5 nm Cr and 75 nm Ta. The hard bias layer is again CoPtCr.
The substrate on which hard bias layers are formed in some head designs is NiO or alumina. Rhodium has been used as a lead material for these heads. Other designs use PtMn as the substrate for the hard bias layer on which the leads must be formed. However, the resistance of rhodium leads is unacceptably increased when the hard bias and lead stack are formed on a PtMn substrate.
SUMMARY OF THE INVENTION
A head according to the invention includes multilayered electrically conductive leads from the magnetic sensor which include a thin tantalum seed layer followed by a thin chromium seed layer which is followed by a thicker rhodium layer. The dual seed layer of the invention significantly improves the conductivity of the rhodium. The Ta/Cr/Rh leads can be used with hard bias structures formed on a PtMn layer without having increased resistance.
REFERENCES:
patent: 5438470 (1995-08-01), Ravipati et al.
patent: 5491600 (1996-02-01), Chen et al.
patent: 5742459 (1998-04-01), Shen et al.
patent: 5883764 (1999-03-01), Pinarbasi
patent: 5936810 (1999-08-01), Nakamoto et al.
patent: 5991125 (1999-11-01), Iwasaki et al.
patent: 6086727 (2000-07-01), Pinarbasi
patent: 6128167 (2000-10-01), Saito et al.
patent: 0 552890A2 (1993-07-01), None
patent: 05-258246 (1993-10-01), None
Hitachi Global Storage Technologies - Netherlands B.V.
Knight G. Marlin
Renner Craig A.
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