Coating apparatus – Immersion or work-confined pool type – With means for moving work through – into or out of pool
Reexamination Certificate
2001-12-19
2004-05-25
Lamb, Brenda A. (Department: 1734)
Coating apparatus
Immersion or work-confined pool type
With means for moving work through, into or out of pool
C118S602000, C118S603000, C118S688000
Reexamination Certificate
active
06740163
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to methods and apparatus for applying a layer of a resist, e.g., a photoresist, to both sides of dual-sided substrates, e.g., disk-shaped substrates. The invention finds particular utility in performing resist coating of substrates as part of manufacturing processing of hard disk magnetic and/or magneto-optical recording media, e.g., for servo patterning, protective layer formation, etc.
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 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
11
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
10
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
10
onto the surface of wafer
11
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.
More specifically, and with reference to
FIG. 2
, the spin coating process as described above comprises 3 distinct process steps or phases, as follows:
1. Resist spin-on—generally the substrate or workpiece, in the form of an annularly-shaped disk, spins at a low spindle speed during this phase, e.g., about 500 rpm, with a resist dispensing nozzle at the end of a movable arm initially positioned facing the inner diameter (“ID”) of the disk. The nozzle/arm assembly dispenses the coating material, e.g., a resist such as a polymethylmethacrylate (“PMMA”) or other photo-sensitive resist, onto the top surface of the disk at a controlled rate and duration. The slow spindle speed ensures that the resist is uniformly distributed from the ID to the outer diameter (“OD”) of the disk, and the flow rate of the resist is adjusted so as to provide a sufficient amount of resist during the spreading process.
2. Resist spin-off—in order to facilitate uniform spreading of the resist, a high spindle speed (e.g.,>1,000 rpm) spin-off step is performed in the next phase to remove superfluous (i.e., excess) resist. Conventional spin coating apparatus, such as illustrated in
FIG. 1
, therefore include a vacuum exhaust system which operates at the backside of the disk to ensure removal of the excess resist without either re-depositing resist material on the top surface of the disk or other critical equipment components located above the disk.
3. Edge bead removal (not shown in FIG.
2
)—subsequent to resist spin-off at high spindle speed, the resist-coated disk is subjected to solvent cleaning at the OD disk edge for edge bead removal and a backside wash in order to ensure that the disk OD does not retain a ring (i.e., edge bead) of accumulated resist at the top edge surface; the backside wash protects against undesired resist contamination of the back side (i.e., bottom) of the disk.
In order to facilitate resist coating of both sides of a disk-shaped substrate or workpiece (i.e., “dual-sided” coating) according to conventional automated manufacturing practices utilizing typical prior art spin coating stations, e.g., as shown in
FIG. 1
, a disk inversion (or “flipping”) station must be provided intermediate separate first and second spin coating stations for sequential coating of the top and bottom disk surfaces. While such an arrangement can be fairly readily implemented, this approach entails several disadvantages, as follows:
1. a certain amount of resist material applied to a first (e.g., top) surface of the disk at a first spin coating station, will inevitably flow to the second surface of the disk, i.e., the bottom or backside surface, which resist flow is problematic at at least the second spin coating station;
2. the area (“equipment footprint”) occupied by the overall spin coating station is increased due to the requirement for first and second spin coating stations;
3. excessive equipment downtime due to malfunctioning, maintenance, etc., of the first and second spin coating stations and intermediate substrate (e.g., disk) flipping station; and
4. increased equipment cost due to the necessity for providing the second spin coating station and the substrate flipping station.
In view of the above-described drawbacks and disadvantages associated with conventional spin coating methodology when utilized for coating both sides of a dual-sided substrate, as in the case of disk-shaped magnetic and MO recording media such as hard disks, dip coating techniques in which a vertically oriented substrate is immersed in and removed from a bath of photoresist solution in an open container, have been considered as a potentially desirable substitute therefor. Specifically, such dip coating process/apparatus can be readily implemented for coating both sides of two-sided substrates, with an attendant reduction in photoresist loss which minimizes photoresist usage. However, conventional dip coating techniques utilizing open dip cup apparatus (described in more detail below) incur several disadvantages and drawbacks, as follows:
1. Increase in viscosity over time—The photoresist solution, composed of a polymeric photoresist material and at least one solvent therefor, is contained in a tank or vessel (“dip cup”) and exposed to the ambient atmosphere, i.e., air. As a consequence of the continuous exposure of the photoresist solution to air, evaporation of the solvent occurs, resulting in an increase in the viscosity of the photoresist solution over time. The increase in viscosity in turn leads to an increase in the thickness of the photoresist coating formed on the substrate surfaces. However, consistent photoresist coating thickness is vital for obtaining acceptable products or results when utilized as part of a manufacturing process, e.g., as a step in the formation of servo-patterned magnetic and MO recording media utilizing imprint lithography of resist-coated substrates. Specifically, a variation, i.e., an increase, in resist layer thickness is problematic in that the latter is a key process variable or parameter in servo pattern formation via imprint lithography utilizing etching or implantation processing for pattern genera
Curtiss Donald Everett
Leigh Joseph
Quan Frank
Lamb Brenda A.
McDermott & Will & Emery
Seagate Technology LLC
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