Chemistry: electrical and wave energy – Processes and products – Coating – forming or etching by sputtering
Reexamination Certificate
2002-07-15
2004-09-21
Versteeg, Steven (Department: 1753)
Chemistry: electrical and wave energy
Processes and products
Coating, forming or etching by sputtering
C204S192120, C216S012000, C216S052000, C216S058000, C216S067000, C216S083000, C427S402000
Reexamination Certificate
active
06793778
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to the field of magnetic transducers (heads) used with moving magnetic media and more particularly to methods for fabricating pads on slider surfaces including the air bearing surface of the transducers that confront the moving media in data storage systems.
BACKGROUND OF THE INVENTION
A typical prior art head and disk system
10
is illustrated in FIG.
1
. In operation the magnetic transducer
20
is supported by the suspension
13
as it flies above the disk
16
. The magnetic transducer, usually called a “head” or “slider” 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 pairs of electrical contact pads (not shown); one pair 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. The read head
12
reads magnetic transitions as the disk rotates under the air-bearing surface (ABS) of the head
20
. In the typical process of fabricating thin film magnetic transducers, a large number of transducers are formed simultaneously on a wafer. After the basic structures are formed the wafer may be sliced into quadrants or rows which are further processed by lapping and formation of the pad structures by prior art lithographic etching techniques. Ultimately the rows are sliced into individual transducers.
The ABS of magnetic transducer
20
illustrated in FIG..
2
is conventionally fabricated with a pattern of rails
27
that extend toward the media from the slider body
28
to determine the aerodynamics and serve as the contact area should the transducer come in contact with the disk either while rotating or when stationary. Landing pads
29
or bumps have been formed on the rails and other areas of the ABS to reduce the stiction that results when the rails contact a stationary surface. Only a few pads have been shown for illustration, but there could be hundreds of microscopic pads on or near the rails. These pads have conventionally been formed by laser heating of spots on the rail surface, but photolithography is also used to form multi-layered pad structures. The invention which will be described below is a process for making the pads using photolithography. The pads can be formed by a photolithographic technique in which a photoresist pattern is formed with voids in the areas for the pads. The pad material(s) is then deposited over the entire surface including the photoresist. When the photoresist is removed the pad material deposited on the photoresist material is removed leaving the pads in the voids in the photoresist. The photoresist is typically removed by application of a liquid solvent accompanied by brushing. One problem with the prior art photolithographic technique is that the pads tend to have a ridge or fence of material around the outer edge due to the deposition of the pad material on the sidewalls of the photoresist surrounding the pad area. This fence material is potentially damaging to the disk and may fracture into debris which can damage the disk and other components in the drive.
U.S. Pat. No. 6,236,543 to Han, et al. titled “Durable Landing Pads for an Air-Bearing Slider” addresses the delamination problem for the pads which tends to accompany the use of very hard materials which typically have higher stress. A solution to this problem is said to include forming pads of tetrahedral amorphous carbon (t-aC), an extremely hard material, and reducing the stress by interleaving at least one layer of a stress-reducing material such as Si, SiC, SiO
2
or Si
3
N
4
. A rotating angled deposition of the t-aC is suggested to round the pad tops, which may be trimmed to smooth corners.
What is needed is a method for making durable slider pads with minimized fence structures.
SUMMARY OF THE INVENTION
A method for fabricating a transducer with landing pads without edge fences will be described herein. The pad shape and location are defined by voids in a photoresist formed on or near the rail surfaces using prior art methods. Preferably the initial layer for the pad structure is deposited as an adhesion or seed layer using a vertical beam angle. The next layer is the pad layer which is preferably deposited at a nonvertical (slanted) angle according to the prior art as dictated by the pad topography. A final masking layer is vertically deposited on the pad layer to provide anisotropic protection during the subsequent ashing step. The vertical deposition processes minimize the buildup of the masking and seed layer materials on the sidewall of the void in the resist. Thus, by vertically depositing the masking layer, the fence structures have a significantly thinner layer of masking and seed layer material than does the planar portion of the structure. The thickness of the masking layer on the surface of the pad layer should be sufficient to protect pad layer during the subsequent ashing by oxygen plasma, but the thickness of the masking material at the sidewalls on the pad layer fences should be thin enough so that the fences are not protected during ashing. The masking layer should be a material that forms a passivating oxide which prevents subsequent penetration of the oxygen plasma. After the layers of material for the pads have been deposited the resist is preferably stripped by a method including mechanical abrasion (e.g. soda blast or by solvent assisted scrubbing). After stripping the photoresist material, the structure is ashed by an oxygen-containing plasma. The ashing process removes the fence structures on the pad layer, since the masking layer provides less protection to the fence structures than is provided to the bulk of the pad layer. Mechanical abrasion provides additional assurance in removal of the fences due to the induced damage to thin masking fragments on the fences. During the ashing it is expected that most of the masking layer will be converted to an oxide which is also structurally discontinuous and not self-supporting. The remaining masking material as well as the oxide material are removed by sputtering etching leaving the pad layer exposed and having no fences.
REFERENCES:
patent: 4555303 (1985-11-01), Legge et al.
patent: 4659650 (1987-04-01), Moritz et al.
patent: 5091288 (1992-02-01), Zappella et al.
patent: 5271802 (1993-12-01), Chang et al.
patent: 5654128 (1997-08-01), Hsu
patent: 5709754 (1998-01-01), Morinville et al.
patent: 6055128 (2000-04-01), Dorius
patent: 6236543 (2001-05-01), Han et al.
patent: 6254792 (2001-07-01), Van Buskirk et al.
patent: 6278582 (2001-08-01), Okawa et al.
patent: 6333835 (2001-12-01), Kang et al.
patent: 2002/0127342 (2002-09-01), Watanuki et al.
patent: 55122873 (1980-09-01), None
Wayne Moreau,Semiconductor Lithography, Principles, Practices and Materials, Plenum Press 1988, ISBN 0-306-42185-2, pp. 567-630.
Gador Detlef
Hwang Cherngye
Row Eun Kyoung
Shi Ning
Hitachi Global Storage Technologies Netherlands N.V.
Knight G. Marlin
Versteeg Steven
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