Compositions: coating or plastic – Materials or ingredients – Vehicles or solvents
Reexamination Certificate
2002-05-09
2004-08-24
Pianalto, Bernard (Department: 1762)
Compositions: coating or plastic
Materials or ingredients
Vehicles or solvents
C106S285000
Reexamination Certificate
active
06780233
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to improved spin-on resist and/or thermoplastic material compositions with improved wettabiliiy and adhesion to substrate materials, particularly when utilized with substrate materials utilized in the manufacture of servo-patterned, thin film, hard disk magnetic and/or magneto-optical (MO) recording media, and to an improved method of manufacturing such media.
BACKGROUND OF THE INVENTION
Spin coating of wafer-shaped substrates or workpieces is a widely utilized process in the manufacture of semiconductor integrated circuit (“IC”) devices for applying thin, uniform thickness layers of a coating material, e.g., a photoresist, to the wafer surfaces as part of photolithographic patterning of the IC component devices, interconnections, etc., and is increasingly employed as part of the manufacturing process of disk-shaped magnetic and/or magneto-optical (“MO”) recording media, such as hard disks, for patterning the surfaces of such media, as for example, in the formation of servo patterns therein by means of imprint lithographic techniques.
A typical horizontally oriented spin coating apparatus according to the conventional art is schematically illustrated in the cross-sectional view of
FIG. 1
, wherein reference numeral
1
designates a disk-shaped rotatable table or vacuum chuck, supported by a rotatable shaft
2
perpendicular to the plane of table
1
, the latter being connected to motor
3
for rotation about a central axis. Wafer W is fixed to the surface of table or vacuum chuck
1
by means of suction ports (not shown in the drawing for simplicity).
Reference numeral
4
indicates a process bowl or cup surrounding rotatable table or vacuum chuck
1
, the bottom of which includes at least one exhaust port
5
for removal of superfluous (i.e., excess) resist (or other coating material) which is scattered about during the spin coating process due to centrifugal force; reference numeral
6
indicates a plate or flange for regulating the air currents flowing in the process bowl or cup
4
in order to enhance coating thickness uniformity; and reference numeral
7
indicates an exhaust port for connection to an exhaust source; reference numeral
8
designates a coating material dispensing nozzle, operatively connected via feed tube or conduit
9
to a source S of a coating material, e.g., a photoresist.
In operation of the above-described spin coating apparatus, the coating material, e.g., a photoresist, is dispensed from nozzle
8
of source S onto the surface of wafer W as the wafer is spun by means of rotatable chuck
1
. The spinning of the wafer distributes the photoresist over the surface of the wafer and exerts a shearing force that separates excess photoresist from the wafer and evaporates solvent therefrom, thereby providing a thin, smooth, uniform thickness layer of photoresist on the surface of the wafer.
As indicated above, thermal imprint lithography has been recently studied and developed as a low cost alternative technique for fine dimension pattern/feature formation in the surface of a substrate or workpiece, e.g., servo pattern formation in hard disk magnetic and/or magneto-optical (MO) recording media. See, for example, U.S. Pat. Nos. 4,731,155; 5,772,905; 5,817,242; 6,117,344; 6,165,911; 6,168,845 B1; 6,190,929 B1; and 6,228,294 B1, the disclosures of which are incorporated herein by reference. A typical thermal imprint lithographic process for forming nano-dimensioned patterns/features, such as servo patterns in the surface of a thin film magnetic and/or MO recording medium or in the surface of a substrate therefor, is illustrated with reference to the schematic, cross-sectional views of FIGS.
2
(A)-
2
(D).
Referring to FIG.
2
(A), shown therein is a mold
10
(also termed a “stamper/imprinter”) including a main body
12
having upper and lower opposed surfaces, with a molding (i.e., stamping/imprinting) layer
14
formed on the lower opposed surface. As illustrated, molding layer
14
includes a patterned plurality of features
16
having a desired shape or surface contour, e.g., a servo pattern. A workpiece comprised of a substrate
18
carrying a thin film layer
20
on an upper surface thereof is positioned below, and in facing relation to the molding layer
14
. The expression “workpiece” or substrate
18
, when utilized herein in the context of manufacture of servo-patterned thin film, hard disk magnetic recording media, refers to a bare non-magnetic substrate for the medium, i.e., without any layers formed thereon, or with one or more layers constituting the medium formed thereon. Thin film layer
20
, comprised of a resist or thermoplastic polymeric material, e.g., a poly(methylmethacrylate) (hereinafter “PMMA”), is typically formed on the substrate/workpiece surface by a spin coating process such as described supra.
Adverting to FIG.
2
(B), shown therein is a compressive molding step, wherein mold
10
is pressed into the thin film layer
20
in the direction shown by arrow
22
, so as to form depressed, i.e., compressed, regions
24
. In the illustrated embodiment, features
16
of the molding layer
14
, e.g., servo pattern features, are not pressed all of the way into the thin film layer
20
and thus do not contact the surface of the underlying substrate
18
. However, the top surface portions
24
a
of thin film
20
may contact depressed surface portions
16
a
of molding layer
14
. As a consequence, the top surface portions
24
a
substantially conform to the shape of the depressed surface portions
16
a
, for example, flat. When contact between the depressed surface portions
16
a
of molding layer
14
and thin film layer
20
occurs, further movement of the molding layer
14
into the thin film layer
20
stops, due to the sudden increase in contact area, leading to a decrease in compressive pressure when the compressive force is constant.
FIG.
2
(C) shows the cross-sectional surface contour of the thin film layer
20
following removal of mold
10
. The molded, or imprinted, thin film layer
20
includes a plurality of recesses formed at compressed regions
24
which generally conform to the shape or surface contour of features
16
of the molding layer
14
. Referring to FIG.
2
(D), in a next step, the surface-molded workpiece is subjected to processing to remove the compressed portions
24
of thin film
20
to selectively expose portions
28
of the underlying substrate
18
separated by raised features
26
. Selective removal of the compressed portions
24
, as well as subsequent selective removal of part of the thickness of substrate
18
(or one or more layers thereon) at the exposed portions
28
thereof, may be accomplished by any appropriate process, e.g., reactive ion etching (RIE) or wet chemical etching.
The above-described imprint lithographic processing is capable of providing submicron-dimensioned features, as by utilizing a mold
10
provided with patterned features
16
, e.g., servo pattern features, comprising pillars, holes, trenches, etc., by means of e-beam lithography, RIE, or other appropriate patterning method. Typical depths of features
16
range from about 5 to about 500 nm, depending upon the desired lateral dimension. The material of the molding layer
14
is typically selected to be hard relative to the thin film layer
20
, the latter typically comprising a resist or thermoplastic material which is softened when heated. Thus, suitable materials for use as the molding layer
14
include metals, dielectrics, semiconductors, ceramics, and composite materials. Suitable materials for use as thin film layer
20
include resists and thermoplastic polymers, e.g., PMMA, which can be heated to above their glass temperature, T
g
, such that the material exhibits low viscosity and enhanced flow.
As indicated above, formation of patterned thin film magnetic and MO recording media, e.g., servo-patterned media, by certain pattern replication methods, particularly replication by means of thermal imprint lithography, involve spin coating a layer of a resist or thermopl
Leigh Joseph
Liu Jianwei
McDermott Will & Emery LLP
Pianalto Bernard
Seagate Technology LLC
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