Chemistry: electrical and wave energy – Processes and products – Coating – forming or etching by sputtering
Reexamination Certificate
2001-06-20
2003-05-27
VerSteeg, Steven H. (Department: 1753)
Chemistry: electrical and wave energy
Processes and products
Coating, forming or etching by sputtering
C204S192120, C204S192150, C204S298110, C204S298130
Reexamination Certificate
active
06569294
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a target assembly and its method of use in depositing a layer of material having relatively thin and relatively thick portions adjacent to each other, with a very narrow transition region therebetween. More particularly, the present invention relates to an apparatus and method useful in forming a protective overcoat on a magnetic recording/information storage/read-out disk, wherein the thickness of the overcoat layer in an annularly-shaped inner landing, or CSS, zone of the disk is greater than the thickness of the overcoat layer in an outer, data zone of the disk. The present invention also relates to the formation of coatings, such as optical, anti-friction, wear or corrosion-resistant coatings, which require variation of the properties thereof in a radial direction.
BACKGROUND OF THE INVENTION
Magnetic recording media typically require an overcoat for wear and corrosion protection, inasmuch as contact start/stop (CSS) failures in hard disk drives can result in unrecoverable data loss. As a consequence, good tribological performance is one of the most stringent requirements for hard disk drives. Various overcoat materials have been developed for use in the manufacture of hard disk drives, including carbon (C), silicon (Si), and zirconium (Zr)-based materials. Of these, carbon-based overcoats have become widely utilized as a standard protective material in the hard disk industry. Various types of carbon-based overcoats, with and without various dopants, such as hydrogen (H), nitrogen (N), fluorine (F), and N
x
H
y
, and various deposition methods, such as ion beam deposition, chemical vapor deposition (CVD), cathode sputtering, etc. have been studied for use as protective overcoat materials.
When used in disk-type media employed in CSS type operation, the overcoat typically protects the magnetic thin-film layer at its inner diameter landing zone from damage when the data transducer head contacts the disk during a start-stop cycle, whereas, in the outer diameter data zone of the disk, the overcoat functions to protect the disk from environmental factors, such as oxidation or humidity, that can lead to corrosion and/or degradation of film properties. The tribological performance of disk-type media in CSS operation is highly dependent upon the thickness of the protective overcoat, e.g., of carbon or carbon-based material. In general, thicker carbon-based overcoats exhibit better tribological performance than thinner overcoats. However, an increase in the thickness of the overcoat results in a concomitant increase in the spacing, or flying height, of the magnetic head or other type data transducer, over the surface of the magnetic medium, which, inter alia, limits the recording density and degrades performance parameters such as, for example, signal-to-noise ratio (SNR).
In view of the above, and since the most tribologically critical portion of the surface area of disk-shaped magnetic recording media is the CSS (i.e., head landing) zone and the most critical portion for recording performance is the data zone, which zones have different overcoat layer thickness requirements, multi-zone protective overcoats have been proposed. One such zone design or concept utilizes a relatively thick protective overcoat (e.g., carbon-based) on the CSS zone to provide more robust tribological performance and a relatively thin carbon-based overcoat on the data zone to ensure a smaller spacing loss (e.g., SNR loss) between the transducer head and the magnetic media in order to achieve better performance.
FIG. 1
shows, in cross-sectional schematic view, a magnetic recording disk
10
composed of a base or substrate
12
and incorporating a multi-zone protective overcoat
14
as described above. Disk
10
also includes an under-layer
16
formed directly on the substrate and a magnetic thin film layer
18
formed on the under-layer. Disk
10
further comprises an inner diameter CSS (or landing) zone
20
, where, as described above, the transducer head contacts the disk surface during a start-stop cycle. An outer, data zone
22
extends from the outer edge
20
a
of the landing zone to the outer diameter
24
of substrate
12
. According to the multi-zone concept, protective overcoat
14
which extends between the annular inner diameter region
20
b
of the CSS zone to the outer edge
22
a
of the data zone, has a greater thickness in the CSS zone
20
than in the data zone
22
. Typically, the thickness of the overcoat
14
in the CSS zone
20
is 2-3 times the thickness of the overcoat
14
in the data zone
22
.
For magnetic media, the substrate
12
may comprise aluminum (Al), textured if desired and plated with a selected alloy, e.g., nickel-phosphorus (NiP), to achieve a requisite surface hardness. Alternatively, substrate
12
may comprise glass, ceramic, or glass-ceramic composite materials, similarly textured if desired. Conventionally-sized substrates for use in typical magnetic hard disk drives have outer diameters
24
of 130 mm (5.25 in.), 95 mm (3.5 in.), and 65 mm (2.5 in.), with corresponding inner diameters
26
of 40 mm (1.57 in.), 25 mm (0.98 in.), and 20 or 25 mm (0.79 or 0.98 in.).
Under-layer
16
is preferably comprised of sputtered chromium (Cr) or a Cr-based alloy, and the magnetic film layer
18
typically comprises a cobalt (Co)-based alloy, including binary, ternary, quaternary, and five-membered alloys. The protective overcoat
14
is comprised of a material imparting good tribological, i.e., wear-resistant, protective properties to the medium
10
and is typically composed of carbon (C), zirconium oxide (ZrO
2
), silicon (Si), silicon carbide (SiC), or silicon oxide (SiO
2
).
Referring now to
FIG. 2
, shown therein, in perspective view, is a magnetic recording disk
30
having a CSS (landing) zone
36
and a data zone
40
. More specifically,
FIG. 2
illustrates an annularly-shaped magnetic recording disk
30
of the type having a protective overcoat thereon as shown in FIG.
1
. Annularly-shaped disk
30
includes an inner diameter
32
and an outer diameter
34
. Adjacent to the inner diameter
32
is an annularly-shaped, inner diameter CSS (landing) zone
36
. When the disk
30
is operated in conjunction with a magnetic transducer head (not shown), the CSS zone
36
is the region where the head makes contact with the disk during start-stop cycles or other intermittent occurrences. In
FIG. 2
, the edge of the CSS zone
36
is indicated by line
38
, which is the boundary between the landing zone
36
and a data zone
40
, where magnetic information is stored in the magnetic recording layer of the disk.
As best illustrated in
FIG. 1
, the thickness transition of the protective overcoat
14
between the thinner and thicker data and CSS zones
22
and
20
, respectively, is gradual. In practice, however, such gradual transition of protective overcoat thickness is not particularly useful or satisfactory because full advantage cannot be taken of the relatively thick protective overcoat over the CSS zone
20
providing robust tribological performance and the thinner protective overcoat providing better data recording performance within the relatively wide transition region which includes a significant portion of the width of the data zone
22
.
Accordingly, there exists a need for improved means and methodology for forming, as by sputtering techniques, single- and dual-sided magnetic information storage and read-out disks, which means and methodology, provide rapid, simple, and reliable formation of multi-zone protective overcoat layers thereon with abrupt (i.e., narrow) transition zones between thinner and thicker portions respectively formed on data and CSS zones of the disks.
The present invention addresses and solves the problems attendant upon the manufacture of high recording density magnetic media with multi-zone protective overcoats having highly delineated thickness variation between data recording and CSS (landing) zones, while maintaining full compatibility with all aspects of conventional automated dis
Hwang Kuo-Hsing
Khazanov Alexander Boris
McLeod Paul Stephen
Rou Shanghsien
Shih Chung-Yuang
McDermott & Will & Emery
Seagate Technology LLC
VerSteeg Steven H.
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