Resist removal from patterned recording media

Details Resist removal from patterned recording media Resist removal from patterned recording media

2002-01-17

2004-06-22

Barreca, Nicole (Department: 1756)

Radiation imagery chemistry: process, composition, or product th

Imaging affecting physical property of radiation sensitive...

Making electrical device

C430S256000, C430S311000, C430S317000, C430S329000

Reexamination Certificate

active

06753130

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to methods for safe, reliable, and efficient removal of patterned photoresist layers utilized in forming features and patterns in the surfaces of magnetic and/or magneto-optical (MO) recording media. The invention has particular utility in the formation of servo patterns, data tracks, identification numbers or symbols, etc., in high areal density hard disk magnetic data/information storage and retrieval media.
BACKGROUND OF THE INVENTION
Formation of patterned media has been considered and extensively studied as an approach for the development of high areal density magnetic data storage media, e.g., hard disks. A variety of patterning techniques for forming patterned magnetic media have been proposed and developed, including, inter alia, a number of processes widely employed in the fabrication of semiconductor integrated circuit (IC) devices, such as e-beam lithography, photolithography, sputter etching, reactive ion etching (RIE), ion beam etching (ion milling), electrolytic techniques, chemical-mechanical-polishing (CMP), etc. However, each of these processes is tedious and requires complex and expensive equipment, which requirement presents a significant cost disadvantage when utilized in large-scale manufacture of magnetic recording/data storage media, e.g., hard disks.
Of the above-enumerated approaches for patterning of magnetic media, patterning by ion irradiation, e.g., ion beam etching, milling, and implantation has shown great promise in achieving high areal density without incurring any substantial change in surface topography of the media. Pattern generation utilizing ion irradiation techniques is typically performed with the aid of stencil masks. While it has been demonstrated that ion irradiation through stencil masks can produce stable magnetic lines having widths less than about 50 nm, the technical difficulties involved in making stencil masks with sub-0.1 &mgr;m features over a large area, e.g., a 3″×3″ square or 3″ diameter disk, and the relatively short lifetime of the stencil masks, render this approach unfeasible from a commercial standpoint.
As utilized herein, the term or expression “patterned magnetic media” is taken as including thin film, high areal density, longitudinal or perpendicular magnetic media which are patterned to include at least one of a servo pattern, a data track pattern, and an identification number or symbol, as well as magnetic media comprising a large plurality of discrete magnetic nano-structures, e.g., columns or pillars of magnetic material.
Thin film magnetic media including discrete track and servo patterns are disclosed in, for example, U.S. Pat. No. 6,139,936, the entire disclosure of which is incorporated herein by reference. As disclosed therein, a method for increasing the areal density of thin film magnetic media in, e.g., hard disk form, involves patterning the surface of a thin film disk to form discrete data tracks. Such “discrete track media” typically include surface geometry data which are utilized by the hard disk drive servo mechanism, allowing specific recording tracks to be identified, and providing feedback for improving the accuracy of read/write head tracking.
Such discrete track media, however, suffer from several disadvantages, largely due to the fabrication methodology and resultant pattern structure. Specifically, the surface patterns of such discrete track media have generally been formed using standard lithographic techniques to remove material from the magnetic recording layer or by creating recessed zones or regions in the substrate prior to deposition of the magnetic thin film layer(s) thereon. In the former case, the magnetic recording material is etched, or ion milled, through a resist mask to leave a system or pattern of recesses which are devoid of magnetic material. In the latter case, the magnetic thin film layer(s) subsequently applied to the etched or ion milled substrate surface, is (are) spaced far enough away from the recording head such that the flux from the head does not sufficiently “write” the magnetic medium. Servo track information can be conveyed by the difference in magnetic flux at the boundary between the elevated and depressed regions.
Referring now to
FIG. 1
, shown therein, in simplified, schematic cross-sectional view, is a portion of a dual-sided, thin-film magnetic disk medium
1
of the type contemplated by the present invention, comprising a rigid, non-magnetic substrate
10
, typically comprised of an aluminum (Al) alloy, e.g., Al-Mg. Alternative materials for use as substrate
10
include glass, ceramics, glass-ceramics composites and laminates, polymers, and other non-magnetic metals and alloys. Al-based substrate
10
is provided, in sequence, at both major surfaces, with a polished and/or textured amorphous Ni-P underlayer
12
, a polycrystalline seed layer
14
, typically a Cr-based layer deposited by sputtering, a magnetic layer
16
comprised of a ferromagnetic material, e.g., an oxide or a Co-based alloy, a protective overcoat layer
18
, typically of a diamond-like carbon (DLC) material, and a lubricant topcoat layer
20
, e.g., of a fluorine-containing polymer.
Adverting to
FIG. 2
, shown therein, in simplified, schematic plan view, is a magnetic recording disk
30
having a data zone
34
including a plurality of discrete servo tracks, and a contact start/stop (CSS) zone
32
. A discrete servo pattern
40
is formed on or within the data zone
34
, and includes a number of data track zones
38
separated by servo tracking zones
36
. The data storage function of disk
30
is confined to the data track zones
38
, while servo tracking zones
36
provide information to the disk drive which allows a read/write head to maintain alignment on the individual, tightly-spaced discrete data tracks.
Although only a relatively few of the servo tracking zones are shown in
FIG. 2
for illustrative simplicity, it should be recognized that the discrete track patterns of the media contemplated herein may include several hundreds of servo zones to improve head tracking during each rotation of the disk. In addition, the servo tracking zones need not be straight radial zones as shown in the figure, but may instead , comprise arcs, intermittent zones, or irregularly-shaped zones separating individual data tracks.
Referring now to
FIG. 3
, shown therein in simplified, schematic perspective view, is an enlarged portion of a discrete servo track pattern
40
formed on or within the recording media thin film layer structure
41
(corresponding to layers
12
-
20
of FIG.
1
), which in turn is disposed on the surface of substrate
42
for a discrete track medium (corresponding to substrate
10
of FIG.
1
). The various elements or features of pattern
40
are generally defined by a difference in height between recessed zones or regions
44
and raised zones or regions
46
. As illustrated, pattern
40
includes a pair of discrete track zones
38
separated by a servo tracking zone
36
.
Servo tracking zone
36
generally includes track identification (ID) bars
50
and tracking position bars
52
. ID bars
50
provide the identification for each of the discrete tracks
48
of the discrete track pattern
40
. Tracking bars
52
provide the disk drive with feedback of the accuracy with which the read/write head is tracking a particular discrete track
48
. Typically, tracking bars
52
extend to approximately the middle of the path defined by each track
48
and are staggered, so that each discrete track
48
includes at least one tracking bar
52
extending from the middle of the track path toward the axis of the disk, and one tracking bar
52
which extends radially outward from the middle of the track path.
A recently developed, low cost technique which can be utilized for forming a pattern in a substrate surface, e.g., a discrete track pattern
40
in the surface of a magnetic recording medium, is disclosed in U.S. Pat. No. 5,772,905, the disclosure of which is incorporated herein by reference. In e

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