U.S. patent application number 12/002030 was filed with the patent office on 2008-04-24 for isothermal imprint embossing system.
Invention is credited to Christopher H. Bajorek, Bruce M. Harper, Toshiyuki Max Saito.
Application Number | 20080093760 12/002030 |
Document ID | / |
Family ID | 34750180 |
Filed Date | 2008-04-24 |
United States Patent
Application |
20080093760 |
Kind Code |
A1 |
Harper; Bruce M. ; et
al. |
April 24, 2008 |
Isothermal imprint embossing system
Abstract
Isothermal imprint embossing system. In one embodiment, the
system includes a heater to pre-heat a disk substrate to an
embossing temperature, a die assembly with an embossing foil to
imprint the embossable film disposed on the disk substrate, and a
heat tunnel disposed between the heater and the die assembly to
maintain the embossing temperature.
Inventors: |
Harper; Bruce M.; (San Jose,
CA) ; Saito; Toshiyuki Max; (Saratoga, CA) ;
Bajorek; Christopher H.; (Los Gatos, CA) |
Correspondence
Address: |
WESTERN DIGITAL TECHNOLOGIES, INC.;ATTN: RENEE M. QUICK
20511 LAKE FOREST DR.
E-118H
LAKE FOREST
CA
92630
US
|
Family ID: |
34750180 |
Appl. No.: |
12/002030 |
Filed: |
December 14, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10761486 |
Jan 20, 2004 |
7329114 |
|
|
12002030 |
Dec 14, 2007 |
|
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Current U.S.
Class: |
264/40.1 ;
264/293; 264/322 |
Current CPC
Class: |
Y10S 425/81 20130101;
B29C 59/026 20130101; B29C 59/02 20130101; B29L 2017/005 20130101;
Y10S 425/808 20130101; B29B 13/023 20130101 |
Class at
Publication: |
264/040.1 ;
264/293; 264/322 |
International
Class: |
B29C 51/08 20060101
B29C051/08 |
Claims
1. A method, comprising: pre-heating an embossable film disposed
above a substrate to approximately an embossing temperature; and
transporting the substrate through a heat tunnel to a die assembly
to imprint an embossable film, the heat tunnel to maintain the
embossing temperature.
2. The method of claim 1, further comprising centering the
substrate relative to an embossing foil within the die
assembly.
3. The method of claim 1, wherein pre-heating further comprises
placing the substrate in an oven disposed adjacent to the die
assembly.
4. The method of claim 1, wherein transporting further comprises
picking up the substrate with a vacuum chuck coupled to a robotic
arm disposed near the die assembly.
5. The method of claim 1, wherein transporting further comprises
sliding the substrate through the heat tunnel with a servo
slide.
6. The method of claim 5, further comprising centering the
substrate relative to an embossing foil within the die
assembly.
7. The method of claim 5, wherein transporting further comprises
gripping the substrate with flexure joints.
8. The method of claim 2, wherein centering further comprises
heating a ball bushing disposed within the die assembly to hold a
precise alignment between the embossing foil and the substrate.
9. The method of claim 2, further comprising pressing the embossing
foil into the embossable film of the substrate.
10. The method of claim 9, further comprising inspecting an
embossed pattern on the embossable film.
11. The method of claim 9, wherein inspecting further comprises
placing the substrate under a microscope to inspect an embossed
pattern on the embossable film.
12. The method of claim 9, further comprising cooling the
substrate.
Description
REFERENCE TO RELATED APPLICATION
[0001] This application is a divisional of Ser. No. 10/761,486
filed Jan. 20, 2004.
TECHNICAL FIELD
[0002] Embodiments of this invention relate to the field of disk
drives and, more specifically, to disks used in disk drive
systems.
BACKGROUND
[0003] A disk drive system includes one or more magnetic recording
disks and control mechanisms for storing data within approximately
circular tracks on the disk. A disk is composed of a substrate and
one or more layers deposited on the substrate (e.g., aluminum). A
trend in the design of disk drive systems is to increase the
recording density of the magnetic recording disk used in the
system. One method for increasing recording density is to pattern
the surface of the disk with discrete tracks, referred to as
discrete track recording (DTR). A DTR pattern may be formed by
nano-imprint lithography (NIL) techniques, in which a rigid,
pre-embossed forming tool (a.k.a., stamper, embosser, etc.), having
an inverse pattern to be imprinted, is pressed into an embossable
film (i.e., polymer) disposed above a disk substrate to form an
initial pattern of compressed areas. This initial pattern
ultimately forms a pattern of raised and recessed areas. After
stamping the embossable film, an etching process is used to
transfer the pattern through the embossable film by removing the
residual film in the compressed areas. After the imprint
lithography process, another etching process may be used to form
the pattern in a layer (e.g., substrate, nickel-phosphorous, soft
magnetic layer, etc.) residing underneath the embossable film.
[0004] One prior DTR structure forms a pattern of concentric raised
areas and recessed areas under a magnetic recording layer. The
raised areas (also known as hills, lands, elevations, etc.) are
used for storing data and the recessed areas (also known as
troughs, valleys, grooves, etc.) provide inter-track isolation to
reduce noise. The raised areas have a width less than the width of
the recording head such that portions of the head extend over the
recessed areas during operation. The recessed areas have a depth
relative to fly height of a recording head and raised areas. The
recessed areas are sufficiently distanced from the head to inhibit
storage of data by the head in the magnetic layer directly below
the recessed areas. The raised areas are sufficiently close to the
head to enable the writing of data in the magnetic layer directly
on the raised areas. Therefore, when data are written to the
recoding medium, the raised areas correspond to the data tracks.
The recessed areas isolate the raised areas (e.g., the data tracks)
from one another, resulting in data tracks that are defined both
physically and magnetically.
[0005] A DTR disk may not be viable if the imprinting surface is
not concentrically aligned with the disk substrate. An imprinted
track that has excessive offset from a centerline of the disk may
not operate properly when read by a disk drive head. This
requirement may be particularly important when data tracks are
generated on both sides of the disk. As such, the imprinting of an
embossable film above a disk substrate requires an alignment step,
in which a centerline of the disk is aligned with a centerline of
the imprinting surface, before the embossable film is actually
imprinted.
[0006] Current alignment methods typically require the use of high
precision actuators or robotics. For example, high precision
actuators would first determine a centerline for the disk substrate
and align it with a centerline of the imprinting surface through a
high resolution X-Y translation procedure. FIG. 1 illustrates a
conventional X-Y translation stage that includes flexures for
gripping a disk. Flexures are widely used in precision machines
because they may provide frictionless, particle-free and low
maintenance operation, while providing high precision. However,
flexure based systems have limited ranges of motion and may not be
adequate to center a disk relative to the imprinting surface of a
stamper. The translation stage allows heat to dissipate from the
surface of the disk that may result in inconsistent imprint
patterns. Moreover, the use of such high precision actuators and
robotics are expensive, with high maintenance costs, inconsistent
accuracy and reliability, slow cycle times, and mechanical
breakdown. The high precision actuators and robotics are bulky
pieces of machinery, requiring large amounts of floor space.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] The present invention is illustrated by way of example, and
not limitation, in the figures of the accompanying drawings in
which:
[0008] FIG. 1 illustrates a conventional X-Y translation stage that
includes flexures for gripping a substrate.
[0009] FIG. 2 illustrates one embodiment an imprinting system.
[0010] FIG. 3 illustrates an alternative embodiment of an
imprinting system.
[0011] FIG. 4 illustrates another embodiment of an imprinting
system.
[0012] FIG. 4A illustrates an enlarged view of a heater assembly
that is part of the imprinting system of FIG. 4.
[0013] FIGS. 5A-5B show alternate views of a disk substrate
transporting device that is part an imprinting system.
[0014] FIG. 6 illustrates one embodiment of a die assembly of an
imprinting system.
[0015] FIG. 7 illustrates another embodiment of a die assembly of
an imprinting system.
[0016] FIG. 7A illustrates a cross-sectional view of the die
assembly shown in FIG. 7.
[0017] FIG. 7B illustrates an enlarged view of the cross-sectional
view of the die assembly shown in FIG. 7A.
[0018] FIG. 8 illustrates an enlarged view of one embodiment of a
disk transporting device.
[0019] FIGS. 9A-9C illustrate one embodiment of a disk transporting
device in various positions.
[0020] FIG. 10 illustrates an enlarged view of a portion of a disk
transporting device with a disk substrate clamped onto a support
tray.
[0021] FIG. 11 illustrates an alternative embodiment of clamping or
gripping structure that may be embedded within a support tray.
[0022] FIG. 12 illustrates one embodiment of a gripper embedded
within a support tray for a clamping disk substrate.
[0023] FIG. 13A is a flow chart illustrating one embodiment of a
method of imprinting an embossable film disposed above a disk
substrate with an imprinting system.
[0024] FIG. 13B is a flow chart illustrating an alternative
embodiment of a method of imprinting an embossable film disposed
above a disk substrate with an imprinting system.
[0025] FIG. 13C is a flow chart illustrating an alternative
embodiment of a method of imprinting an embossable film disposed
above a disk substrate with an imprinting system.
[0026] FIG. 14A is a cross sectional view illustrating one
embodiment of an embossable film disposed above a disk
substrate.
[0027] FIG. 14B is a cross sectional view illustrating one
embodiment of the imprinting of an embossable film by an imprinting
stamper.
[0028] FIG. 15A is a flow chart illustrating one embodiment of a
method of imprinting an embossable film.
[0029] FIG. 15B is a flow chart illustrating an alternative
embodiment of a method of imprinting an embossable film.
[0030] FIG. 15C is a flow chart illustrating another embodiment of
a method of imprinting an embossable film.
DETAILED DESCRIPTION
[0031] In the following description, numerous specific details are
set forth such as examples of specific materials or components in
order to provide a thorough understanding of the present invention.
It will be apparent, however, to one skilled in the art that these
specific details need not be employed to practice the invention. In
other instances, well known components or methods have not been
described in detail in order to avoid unnecessarily obscuring the
present invention.
[0032] The terms "above," "below," and "between" as used herein
refer to a relative position of one layer or component with respect
to other layers or components. As such, a first layer or component
disposed above or below another layer or component may be directly
in contact with the first layer or component or may have one or
more intervening layers or components. Moreover, one layer or
component disposed next to or adjacent another layer or component
may be directly in contact with the first layer or component or may
have one or more intervening layers or components.
[0033] It should be noted that the apparatus and methods discussed
herein may be used with various types of substrates (e.g., disk
substrates and wafer substrates). In one embodiment, the apparatus
and methods discussed herein may be used for the imprinting of
embossable materials for the production of magnetic recording
disks. The magnetic recording disk may be, for example, a DTR
longitudinal magnetic recording disk having, for example, a
nickel-phosphorous (NiP) plated substrate as a base structure.
Alternatively, the magnetic recording disk may be a DTR
perpendicular magnetic recording disk having a soft magnetic film
disposed above a substrate for the base structure. In an
alternative embodiment, the apparatus and methods discussed herein
may be used for the imprinting of embossable materials for the
production of other types of digital recording disks, for examples,
optical recording disks such as a compact disc (CD) and a
digital-versatile-disk (DVD). In yet other embodiments, the
apparatus and methods discussed herein may be used in other
applications, for examples, the production of semiconductor wafers,
display panels (e.g., liquid crystal display panels), etc.
[0034] Apparatus and methods for the imprinting an embossable film
disposed above a substrate are described. By way of example only,
embodiments of an imprint embossing system are described with
respect to a disk substrate. However, it may be appreciated by one
of skill in the art that embodiments of an imprint embossing system
may be easily adapted for substrates that vary in shape and size
(e.g., square, rectangular), for the production of different types
of substrates discussed above. Embodiments of an imprinting system
described herein may be used for imprinting embossable films with
nano-imprint lithography techniques. Alternatively, other scale
imprint lithography techniques may be used, such as micro-imprint
lithography. FIG. 2 illustrates one embodiment of an imprinting
system 200 that includes imprint or die assembly 210, heater
assembly 230, heat tunnel 240, disk substrate cooling station 250,
and disk cassette 260 mounted to table 201. Assembly 200 also
includes a disk substrate transporting device 220 disposed next to
table 201. In one embodiment, transporting device 220 may be a
vacuum chuck coupled to a robotic arm that extends over table 201.
Imprint assembly 210 includes upper die assembly 212 and lower die
assembly 214 that may include one or more embossing foils (a.k.a.,
stamper) that press into an embossable film disposed above a disk
substrate to transfer a pattern into the embossable film. Heater
230 having heating element 232 may be used to pre-heat the
embossable film on the disk substrate to a desired embossing
temperature. Heating element 232 may also extend along a length of
top and bottom portions 242, 244 that form heat tunnel 240. In one
embodiment, heater 230 and heating element 232 may have separate
heating sources. In an alternative embodiment, heater 230 and
heating element 232 may share the same heating source. In one
embodiment, heating element 232 may be heat coils utilizing
inductive heating to maintain the temperature of the embossable
film. In alternative embodiments, heat element 232 may be another
type of element, for example, an infrared (IR) heat source. In one
embodiment, a heat tunnel connects heater 230 with die assembly 210
in order to maintain the desired embossing temperature during
transport of the disk substrate from heater 230 to die assembly
210.
[0035] In one method for imprinting the embossable film on disk
substrates, transporting device 220 picks up a disk substrate from
cassette 260 using vacuum chuck 224. Vacuum chucks for handling
disk substrates are known in the art; accordingly, a detailed
description is not provided herein. In alternative embodiments,
other pick and place devices known in the art may be used to remove
a disk substrate from cassette 260. A disk substrate may be
pre-heated to bring up the temperature of the embossable film on
the disk substrate to an optimum embossing level. To do so, in one
embodiment, vacuum chuck 224 places a disk substrate within heater
230. In one embodiment, the embossable film on the disk substrate
may be heated to a temperature in the range of approximately 20 to
350 degrees C. After the embossable film on the disk substrate is
heated to a desired embossing temperature, the vacuum chuck 224
moves the disk substrate through heat tunnel 240 towards die
assembly 210. The disk substrate is then centered relative to the
top and/or bottom embossing foils and then pressed against the
embossable film of the disk substrate to form an embossing pattern
(e.g., DTR pattern). After the embossable film is imprinted, vacuum
chuck 224 transports the disk substrate to cooling tray 250 before
returning it to cassette 260.
[0036] The use of heat tunnel 240 minimizes thermal dissipation of
the heated embossable film of the disk substrate. Thermal
dissipation may lead to inconsistencies in the embossable film and
subsequent inconsistencies in the embossed pattern. As discussed
above, heat tunnel 240 maintains the approximate embossing
temperature of the heated embossable film until the disk substrate
is placed in the die assembly. Although the embossing foils in die
assembly 210 may be heated, a heated embossable film may result in
a quicker and more efficient imprint. Moreover, by positioning
heater assembly 280 relatively close to die assembly 210, thermal
distortion of the embossable film is minimized.
[0037] FIG. 3 illustrates another embodiment of an imprinting
system 300 having a heater 330 disposed near die assembly 310 that
does not include a heat tunnel as shown above with respect to FIG.
2. The close proximity of heater 330 to die assembly 310 may not
require a heat tunnel to maintain the temperature of the embossable
film/disk substrate that is sufficiently close to the desired
embossing temperature. Vacuum chuck 324, coupled to robotic arm 322
of transporting device 320, moves a disk substrate around
imprinting system 300. For example, in one embodiment, a disk
substrate may be transported from cassette 360 to heater 330 to be
pre-heated to a temperature below, substantially at, or above the
desired embossing temperature. The preheated embossable film/disk
substrate is positioned in close proximity (e.g., nest area of
lower die assembly 314) to the die assembly 310. Alternatively, the
embossable film/disk substrate may be preheated to a temperature
below that of (e.g., close to) the embossing temperature and then
heated to the embossing temperature during or after its positioning
close to die assembly 310. Alternatively, embossable film/disk
substrate may be preheated to the die assembly's
temperature/embossing temperature and imprinted after its close
positioning to die assembly 310. Die assembly 310 may include one
or more embossing foils for imprinting the embossable film disposed
above a disk substrate transported from cassette 360. An embossing
foil is then pressed into the embossable film at the embossing
temperature. The embossing foil is then separated from embossable
film after imprinting. Then, the disk substrate may be transported
to die assembly 310 to be embossed followed by a period at cooling
station 350.
[0038] Heater 330 of FIG. 3 is illustrated in a partially
see-through view to show some of its internal components. A heat
lamp 334 is disposed near a top portion of heater 330 to serve as
the heat source. An ejecting tray 332 is disposed below heat lamp
334 to receive a disk substrate. Ejecting tray 332 slides out from
heater 330 to receive a disk substrate from vacuum chuck 324 and
slides back in under heat lamp 334. Tray 332, in one embodiment,
may also have a spinning mechanism that spins a disk substrate
while heating the embossable film. Cooling station 350 includes a
receiving tray 352 for a disk substrate to rest on after being
imprinted in die assembly 310.
[0039] FIG. 4 illustrates an alternative embodiment of an
imprinting system 400 that includes imprint or die assembly 410,
disk substrate transport device in the form of an infeed/outfeed
assembly 420, visual assembly 470, and heater assembly 480 mounted
to table 401. Assembly 400 also includes a robotic arm assembly 440
positioned next to table 401. Imprint assembly 410 includes upper
die assembly 402 and lower die assembly 404. The upper and lower
die assemblies are disposed above press baseplate 406. Draw bars
408 and 409 couple the upper and lower die assemblies 402, 404 and
extend through table 401. Imprint assembly 410 also includes
embossing die foils coupled to adjustable die holders (not shown).
The die holders are fixed to a high precision, rolling element
bushing die set. The die set is controlled by a stout framework,
which accommodates a large diameter, low-pressure, high forced
sealed bladder (not shown, but disposed below table 401). Upon
application of gas (e.g., air) pressure to the bladder, it expands
against a thrust plate, which causes draw bars 408, 409 to pull
down on overhead yolk or cross beam 419. Cross beam 419 moves a top
plate of the die set down to compress the dies together. In one
embodiment, infeed/outfeed assembly 420 may be a servo slide having
a tray portion 430 that receives a disk substrate from robotic arm
assembly 440 and slides the disk substrate through heater 480 and
into die assembly 410.
[0040] In one method for imprinting the embossable film disposed on
disk substrates, robotic arm assembly 440 transports a disk
substrate from cassette 460 and places it on a disk holder plate
430 of infeed/outfeed assembly 420. Robotic arm assembly 440
includes link arm 442 coupled to one end of upper arm 444 to allow
for full rotational movement around table 401. Assembly 400 has the
ability to impart thermal qualities to the handling of disk
substrates. The embossable film disposed above a disk substrate may
be pre-heated to bring up the temperature of the embossable film on
the disk substrate to an optimum embossing level. Disk holder plate
430 may be positioned within heater assembly 480 to heat the
embossable film to an optimum embossing temperature. In one
embodiment, the embossable film disposed above a disk substrate may
be heated to a temperature in the range of approximately 20 to 350
degrees C.
[0041] After the embossable film is heated, disk infeed/outfeed
assembly 420 continues to move the disk substrate between top die
402 and bottom die 404 of die assembly 410. The disk substrate is
then centered relative to the top and bottom embossing foils which
are pressed into the embossable film to form an embossing pattern
(e.g., DTR pattern). After the embossable film is embossed,
infeed/outfeed assembly 420 may retract the disk substrate back
into heater assembly 480 for inspection with visual assembly
470.
[0042] In one embodiment, an inspection step may be used to ensure
that the embossed pattern is centered on the disk substrate. The
visual assembly 470 inspects target track features on the imprinted
embossable film to determine if its features are concentric with a
center hole. This inspection routine may be done on a real-time or
sampling basis. The use of heater assembly 480 provides the
advantage of pre-heating the embossable film disposed on the disk
substrate to an embossing temperature. Although the embossing foils
in die assembly 410 may be heated, a heated embossable film/disk
substrate may result in quicker and more efficient imprint.
Moreover, thermal distortion of the disk substrate is minimized by
positioning heater assembly 480 relatively close to die assembly
410.
[0043] FIG. 4A illustrates an enlarged view of die assembly 410,
visual assembly 470, and heater assembly 480 of assembly 400. In
one embodiment, heater assembly 480 includes a stand 486 that
positions a heater box portion 481 at a height level with die
assembly 410 and between top die 402 and bottom die 404. Box
portion 481 includes an opening 484 to receive disk holder tray
430, and well as an opening 482 near a top surface to allow a line
of sight for microscope 472 of visual assembly 470. In one
embodiment, opening 482 may be covered with transparent glass.
Bracket 474 allows microscope 472 to be positioned above box
portion 481.
[0044] FIGS. 5A and 5B illustrate an overall assembly of an
embodiment for imprinting an embossable film disposed above a disk
substrate. Assembly 500 includes imprint assembly 510,
infeed/outfeed assembly 520, robotic arm assembly 540, and visual
assembly 570. Imprint assembly 510 and infeed/outfeed assembly 520,
and visual assembly 570 are mounted to table 501. Robotic arm
assembly 540 is positioned next to table 501. In one method for
imprinting the embossable film disposed on disk substrates, robotic
arm assembly 540 takes a disk substrate to be imprinted from
cassette 560 and transports it to the infeed/outfeed assembly 520.
Robotic arm assembly 540 includes link arm 542 coupled to one end
of upper arm 544, and end effector 546 coupled to an opposite end
of upper arm 544. Palm extension 548 is coupled to end effector
546, capable of holding a disk substrate on each side.
Infeed/outfeed assembly 520 includes a disk holder plate 530
supported on a pair of cantilevered flexures 526, 528, which in
turn, are mounted on a precision X-Y servo slide (i.e., first
slider 522 and second slider 524). In a retracted position the
infeed/outfeed assembly 520 receives a disk substrate and securely
maintains its position in a disk holder plate 530. In one
embodiment, the disk substrate is clamped on his edges by 3
radially disposed fingers, which are linked together and supported
by a series of flexure joints (discussed in greater detail below).
A single thrusting actuator repeatedly captures a disk substrate in
the exact same position. Cantilevered flexures 526, 528 allow disk
holder plate 530 to be urged up or down within imprint assembly
510. In addition to transporting disk holder plate 530 into and out
of the imprint assembly 510, the infeed/outfeed assembly 520 can be
commanded to position a disk substrate at the center of the
imprinting foil dies precisely. This positional information may be
obtained by inspection feedback from the visual assembly 570.
[0045] Imprint assembly 510 includes upper die assembly 502 and
lower die assembly 504. The upper and lower die assemblies are
disposed above press baseplate 506. Draw bars 508 and 509 couple
the upper and lower die assemblies 502, 504 and extend through
table 501. Imprint assembly 510 also includes embossing die foils
coupled to adjustable die holders (not shown). The die holders are
fixed to a high precision, rolling element bushing die set. The die
set is controlled by a stout framework, which accommodates a large
diameter, low-pressure, high forced sealed bladder (not shown, but
disposed below table 501). Upon application of gas pressure to the
bladder, it expands against a thrust plate, which causes draw bars
508, 509 to pull down on overhead yolk or cross beam 519. Cross
beam 519 moves a top plate of the die set down to compress the dies
together. The disk substrate may then be inspected by visual
assembly 570 for proper alignment. The visual assembly 570 inspects
target track features on the embossable film to determine if track
features are concentric with a center hole of the disk substrate. A
computer/controller or may command the final position of the servo
slide to correspond with the exact center of the imprinting dies or
foils when placing the disk substrate. This inspection routine may
be done on a real-time or sampling basis.
[0046] Infeed/outfeed assembly 520 includes a first slider 522, a
second slider 524 disposed above and perpendicular to first slider
522, flex supports 526, 528 extending from second slider 524, and
holder plate 530 disposed near and end portion of flex supports
526, 528. In one embodiment, first and second sliders 522, 524 form
a X-Y servo slide mechanism. Holder plate 530 is configured to
receive a disk substrate (e.g., disk substrates 550,551). In one
embodiment, palm extension 548 may hold to disk substrates at one
time. Visual unit 570 may be positioned between imprint assembly
510 and infeed/outfeed assembly 520. Bracket 574 is mounted to
table 521, with microscope 572 coupled to a top portion of bracket
574.
[0047] FIG. 5A illustrates one end of palm extension 548
positioning disk substrate 551 in holder plate 530. FIG. 5B
illustrates holder plate 530 positioned between upper die assembly
502 and lower die assembly 504 of imprint assembly 510. Second
slider 524 slides along rails on first slider 522 to advance holder
plate 530 towards imprint assembly 510. The palm extension 548
returns to cassette 560 to retrieve additional disk substrates.
Alternatively, robotic arm 540 may also be used to retrieve a disk
substrate after it has been imprinted with imprint assembly 510.
Visual assembly 570 may be used to check for proper alignment of
the imprinting foils on the disk substrate. The proper alignment
for a disk substrate may be achieved by the X-Y servo mechanism of
infeed/outfeed assembly 520. In one embodiment, a vision assembly
inspects a disk substrate after an embossing procedure to check for
proper alignment with respect to a disk substrate center. The disk
substrate is retracted from the imprint assembly and positioned to
a known reference point directly below a microscope or an optical
device (e.g., camera). The pattern printed on the disk is then
examined. If it is found that the imprinted pattern is offset,
instructions may be forwarded to the infeed/outfeed assembly to
shift the holder plate to the proper position via the X-Y servo
slide. This permits future disk substrates to be aligned properly
with the embossing foils.
[0048] FIG. 6 illustrates one embodiment of a die assembly 600. In
one embodiment, die assembly 600 may be the same as the die
assemblies discussed above with respect to FIGS. 2, 3, and 4. An
upper portion of imprint assembly 600 includes top cross beam 620,
upper die assembly 602, lower die assembly 604, and press baseplate
606. Upper die assembly 602 and lower die assembly 600 are coupled
by posts 610, 611, 612, and 613. The base portion of each post has
a bushing (e.g., bushings 614, 615, 616, and 617). Upper die
assembly 602 also includes upper holder 640 for mounting an upper
imprinting foil 650. Lower die assembly 604 includes lower holder
642 for mounting a lower imprinting foil (not shown). Lower holder
642 is disposed above lower holder base 646, floater plate 647, and
baseplate 648. Upper and lower die assemblies 602, 604 are disposed
above press base plate 606.
[0049] A lower portion of imprint assembly 600 includes gas
actuators 660 disposed between first bottom baseplate 607 and
second bottom baseplate 667. Lower cross beam 622 is disposed below
second bottom baseplate 667. Spring rods 631, 632, 633, and 634
allow first bottom baseplate 607 and second bottom baseplate 667 to
compress gas actuator 660. In one embodiment, as gas actuator 660
expands, second bottom baseplate 667 moves downward and away from
first bottom baseplate 607, with springs 661, 662, 663, and 664.
This expansion causes top cross beam 620 to lower and force upper
holder 640 and lower holder 642 together. The gap between press
baseplate 606 and first bottom baseplate 607 would be where the
upper lower portions of input assembly 600 would be mounted, for
example, to table as illustrated in FIG. 2A.
[0050] FIG. 7 illustrates one embodiment of an enlarged view of the
top portion of imprint assembly 600. Top support 603 of top die
assembly 602 is substantially similar in size and shape with lower
support 605 of lower die assembly 604. Posts 610, 611, 612, and 613
are disposed near the corners of the rectangular shaped top and
lower supports. Each of the posts have a cylindrical shape having
an outer diameter that is slightly less than an inner diameter of
each of the bushings (e.g., 614, 615, 616, and 617) to allow upper
die assembly 602 to move down towards lower die assembly 604. Upper
holder 640 is coupled near a central portion of top support 603. As
discussed above, lower holder 642 is disposed above base 646, float
plate 647, and baseplate 648. A number of pressure nozzles (e.g.,
670, 671) secure float plate 647 to baseplate 648. Screws mounted
on each of the pressure nozzles allow for adjustments of the flow
plate 647 with respect to the baseplate 648 to align lower holder
642 with upper holder 640 properly. This may be necessary when
adjustments are made to align lower embossing foil 651 with upper
imprinting foil (not shown). As such, imprint assembly 600 allows
for movement of top die assembly 602 towards lower die assembly 604
with the four posts mounted near the corners of top and lower
supports. Lower holder 642 may be moved or adjusted laterally to
align itself with upper holder 640 properly.
[0051] FIGS. 7A-7B illustrate cross-sectional views of one
embodiment of upper die assembly 602 and lower die assembly 604. A
bottom embossing foil 651 is disposed above a press pad 680 of
lower die assembly 604. In one embodiment, press pad 680 may
include be one or more elastomeric layers 681, 682 that allow for a
uniform press of embossing foil 651 against the embossable film of
disk substrate 650. A central rod 684 extends through a center
portion of lower die assembly 604 and is coupled to spring 685.
Central rod 684 has a tip portion 686 that is a tapered mandrel and
exposed above press pad 680 and embossing foil 651. Tip portion 686
is tapered to fit inside the inner diameter (ID) of bottom foil 651
as well as disk substrate 650. A linear ball bushing 688 surrounds
the elongated portion of central rod 684, and an outer sleeve 690
surrounds linear ball bushing 618. A ring portion 692 is disposed
between outer sleeve 690 and tapered portion 686 of central rod
684. Ring portion 692 is also in contact with an ID of embossing
foil 651. A portion of the inner diameter of bottom foil 614
extends downward and is disposed between lower mandrel 612 and
outer sleeve 620.
[0052] In one embodiment, linear ball bushing 688 holds a precise
alignment between central rod 684 and outer sleeve 690 to center
embossing-foil 651 with a centerline of central rod 684. Ball
bushing 688 has a higher coefficient of thermal expansion compared
to outer sleeve 620. As such, when the temperature of lower die
assembly 604 is raised, ball bushing 688 expands radially to hold a
firm contact with outer sleeve 690 and to hold the centering
alignment of bottom foil 651 with the inner diameter of outer
sleeve 690. This allows for a concentricity to be established and
maintained between bottom foil 651 and disk substrate 650. Ball
bushing 688 also maintains a contact with the inner diameter of
bottom foil 651 through binding compressive force, which holds
bottom foil 651 in place when disk substrate 650 is stripped off
after imprinting. As illustrated in FIG. 7B, spring 685 lifts outer
sleeve 690, which in turn lifts a portion of bottom foil 651 near
the inner diameter. In effect, lifting outer sleeve 690 creates a
dome-like shape for bottom foil 651 to strip disk substrate 650
cleanly off the surface of bottom foil 651.
[0053] FIG. 8 illustrates an enlarged view of a disk transporting
device in the form of infeed/outfeed assembly 700 without the
slider portions. A holder plate 704 is disposed on frame 702. A
disk substrate 750 is secured to holder plate 704 with center
finger 706, first side finger 708, and second side finger 710
radially disposed around disk substrate 750. In one embodiment, the
fingers may be linked together and supported by a series of flexure
joints. A pair of cantilevered flexures 712, 714, support frame 702
and are also coupled to baseplate 726. Flexures 712, 714 allow
holder plate 704 to move up and down when placed within the imprint
assembly (e.g., imprint assemblies 410, 510 described above with
respect to FIGS. 4, 4A, 5A, and 5B). Holder plate 704 may also be
supported by fixed supports 716, 718. These supports are rigid to
provide stiffness and support the weight of frame 702. Top lifts
720, 722 couple fixed supports 716, 718 to base plate 726. One side
of frame 702 also includes a bracket 722 that has an opening to
receive a thrusting actuator to rotate the flexure joints of center
finger 706, first side finger 708, and second side finger 710. As
described in greater detail below, the thrusting actuator allows
for a disk substrate to be captured repeatedly in the exact same
position.
[0054] FIGS. 9A-9C illustrate infeed/outfeed assembly 700 in
various slide positions including a load position as shown in FIG.
9A, an imprinting position as shown in FIG. 9B, and an inspection
position as shown in FIG. 9C. Analogous to the assembly described
above respect to FIGS. 4, 4A, 5A, and 5B, holder plate 704 is
disposed on frame 702. A pair of cantilevered flexures 712, 714
support holder plate 704. A baseplate 726 is mounted on a X-Y servo
slide that includes first slider 740 and second slider 730. Rails
732, 734 allow holder plate 704 to move along the Y-axis, and rails
742, 744 allow holder plate 704 to move along the X-axis. In one
embodiment, first and second sliders 730, 740 are part of a high
precision X-Y servo slide. In the load position illustrated in FIG.
9A, second slider 730 is positioned near one end of first slider
740 to retract holder plate 704. This position is similar to the
position of infeed/outfeed assembly 520 illustrated in FIG. 5B,
which allows a robotic arm assembly to place a disk substrate onto
holder plate 704. In the load position illustrated in FIG. 9B,
second slider 730 is positioned near an opposite end of first
slider 740 to advance holder plate 704 into the imprint assembly.
This position is similar to the position of infeed/outfeed assembly
520 illustrated in FIG. 5A, which shows the holder plate pressed
between the upper and lower die assemblies. In the inspection
position of FIG. 9C, second slider 730 is slightly retracted along
the X-axis to position itself directly under a microscope of the
vision assembly (e.g., microscope 572 of vision assembly 570
illustrated in FIG. 5A). Based on the results of the inspection,
base plate 726 may be moved along the rails 732, 734 of second
slider 730 (i.e., the Y-axis) to center the disk substrate with
respect to the embossing foils of the imprinting assembly.
[0055] FIG. 10 illustrates an enlarged view of a portion of
infeed/outfeed assembly 800 in one embodiment showing a disk
substrate clamped onto a support plate. Holder plate 804 is
disposed on frame 802. Flexures 812, 814 and fixed supports 816,
818 are coupled to frame 802. Central finger 806, first side finger
808, and second side finger 810 are embedded within holder plate
804. Each finger has extensions 830, 832, and 834 that make contact
with and clamp disk substrate 850. In one embodiment, the fingers
are linked together and supported by flexure joints 840, 842. As
such, a single thrusting actuator causes all the extensions (e.g.,
830, 832, 834) to clamp disk substrate 850 at the same time and in
the exact same position repeatedly. The thrusting actuator enters
through bracket 822 and applies force first towards central finger
806. This in turn applies a force to first finger 808 and second
finger 810. A single thrusting actuator provides the advantage of
being able to capture a disk in the exact same position each
time.
[0056] FIG. 11 illustrates an alternative embodiment of clamping or
gripping structure 900 that may be embedded within a plate holder.
Gripper 900 does not require a thrusting actuator but has an outer
ring that includes a series of joints 920, 922, and 944 that
connect fingers 912, 914, and 916. Each of the fingers has
extensions 912, 914, and 916 that are configured to make contact
with an outer diameter of a disk substrate. Each of the joints are
flexible to allow the fingers to expand outward or pivot to receive
a disk and then compress to make contact with the disk. FIG. 12
illustrates one embodiment of gripper 900 embedded within holder
plate 904 and clamping disk substrate 950. Joints 920, 922, and 944
have expanded outward to receive disk substrate 950. Extensions
912, 914, and 916 of fingers 906, 908, and 910 respectively make
contact with an outer diameter 952 of disk substrate 950.
[0057] FIGS. 13A, 13B, and 13C illustrate embodiments of a method
of imprinting an embossable film disposed above a substrate. An
embossable film disposed above a substrate (e.g., a disk substrate)
is pre-heated, for example, to an embossing temperature, step 1005.
The embossable substrate may be pre-heated in an oven (e.g., oven
330) designed to receive the substrate. In one embodiment, the
substrate is then transported through a heat tunnel (e.g., heat
tunnel 240) to a die assembly, step 1010. Once placed in the die
assembly, the substrate is centered or aligned relative to an
embossing foil (e.g., embossing foil 651) disposed within the die
assembly, step 1015, followed by imprinting, step 1020. The imprint
pattern on the embossable film of the substrate may then be
inspected, step 1025, and then cooled, step 1030.
[0058] In an alternative embodiment illustrated in FIG. 13B, a
substrate (e.g., a disk substrate) may be picked up with a pick and
place device such as a vacuum chuck (e.g., 224) from a holding
source, such as a cassette tray (e.g., 260), step 1040. The vacuum
chuck transports the substrate to a pre-heater (e.g., 230) to raise
the temperature of the embossable film to an embossing temperature,
step 1045. The substrate is then removed from the heater and
transported to a die assembly (e.g., 210), step 1050, and centered
relative to an embossing foil disposed within the die assembly,
step 1055. The embossable film of the substrate is imprinted with
the pattern on the embossing foil, step 1060 and cooled, step
1065.
[0059] In an alternative embodiment illustrated in FIG. 13C, a
substrate (e.g., a disk substrate) is placed on a servo slide tray
(e.g., 430) that is part of the imprinting system, step 1070. The
servo slide is used to position the substrate in a heater (e.g.,
480), and raise the temperature of the embossable film to an
embossing temperature, step 1075. The substrate is then removed
from the heater and inserted into a die assembly (e.g., 410) for
imprinting, step 1080, and centered relative to an embossing foil,
step 1085. The embossable film of the substrate is then imprinted
with the embossing pattern, step 1090, followed by an inspection of
the imprinted pattern, step 1095. The substrate may then be cooled,
step 1099.
[0060] As previously mentioned, the apparatus and methods discussed
above may be used for the imprinting of an embossable film disposed
above a base structure of a disk. Referring to FIG. 14A, the base
structure 1110 of a disk may be composed of a substrate 1115 and a
plated NiP layer 1120. Substrate 1115 may be manufactured from, for
examples, a glass or metal/metal alloy material. Glass substrates
that may be used include, for example, a silica containing glass
such as borosilicate glass and aluminosilicate glass. Metal alloy
substrates that may be used include, for example,
aluminum-magnesium (AlMg) substrates. In an alternative embodiment,
other substrate materials including polymers and ceramics may be
used.
[0061] NiP layer 1120 may be formed by electroplating, electroless
plating, or by other methods known in the art. Plating disk
substrate 1115 with a rigid or metallic material such as NiP
provides mechanical support to disk substrate 1115 for e.g.,
subsequent polishing, and/or imprinting processes. NiP layer 1120
may be polished, planarized, and/or textured. NiP layer 1120 may be
polished, for example, by a uniform etch or other polishing
techniques known in the art. NiP layer 1120 may also be textured
with a pattern, by various methods such as mechanical texturing
using fixed or free abrasive particles (e.g., diamond).
Alternatively, other types of texturing methods, such as laser
texturing, may be used. Plating of disk substrate 1115 may not be
necessary, however, if disk substrate 1115 is composed of a
sufficiently rigid or hard material such as glass. Accordingly,
substrate 1115, itself, may be polished, planarized, and/or
textured using methods described above.
[0062] In an alternative embodiment, base structure 1110 may be
composed of a substrate 1115 having other layers disposed thereon,
for examples, a soft magnetic film. Layer 1120 may represent a soft
magnetic film or a soft magnetic film disposed over a NiP layer. A
soft magnetic film may be used to achieve the proper magnetic
properties associated with perpendicular magnetic recording. The
soft magnetic film may be a layer of iron-cobalt-nickel (FeCoNi)
material. Other materials that may be used for the soft magnetic
film include cobalt-iron (CoFe) nickel-iron (NiFe), and alloys
thereof. Soft magnetic films and materials that may be used for
manufacturing a soft magnetic film are well known in the art of
magnetic recording disks; accordingly, a detailed discussion is not
provided. The soft magnetic film may be polished and/or textured.
The soft magnetic film may be textured with a pattern, by various
methods such as mechanical texturing using fixed or free abrasive
particles (e.g., diamond). Alternatively, other types of texturing
methods, such as laser texturing, may be used to texture the soft
magnetic film. In yet another embodiment, a thin NiP layer may be
disposed on top of the soft magnetic film and polished and/or
textured. In yet another embodiment, the soft magnetic film may be
composed of one or more soft magnetic underlayers and one or more
Ru interlayers disposed between soft magnetic underlayers.
[0063] Embossable film 1130 is disposed on the base structure 1110
in order to form an imprintable (i.e., embossable) film. Various
embossable materials may be used to form the embossable film 1130.
In one embodiment, for example, poly(methyl methacrylate) (PMMA) or
a co-polymer-poly(methyl methacrylate methacrylic acid copolymer)
(P(MMA-MAA) may be used for embossable film 1130. Alternatively,
other embossable materials may be used for example, PMMA and a
thermo-set polymer such as MR-I 9000 available from Micro Resists
Technology of Germany. Alternatively, embossable film 1130 may be
composed of multiple embossable films. The embossable materials may
be spin coated on base structure 1110 to produce the embossable
film 1130. Other coating methods such as dip coating, dip-spin
coating, spray coating, sputtering and vacuum deposition (e.g.,
CVD) may be used.
[0064] FIGS. 14A, 14B, 15A, 15B and 15C illustrate alternative
embodiments of a method of imprinting an embossable film such as an
embossable film disposed above a base structure. In one embodiment,
the base structure may be a substrate or a disk substrate.
Embossable film 1130 is disposed over base structure 1115, step
1210. In one embodiment, embossable film 1130/base structure 1115
and stamper 1190 are heated at or above the "glass transition
temperature" (Tg) of embossable film 1130, step 1230. The glass
transition temperature is a term of art that refers to the
temperature where a polymer material becomes viscoelastic above
this temperature (which is different for each polymer).
[0065] Stamper 1190 is then pressed into the embossable film 1130,
step 1235. In one embodiment, stamper 1190 is separated from
embossable film 1130, step 1240, and then cooled after separation,
step 1243. An imprinted pattern of trenches areas (a.k.a., recessed
areas, grooves, valleys, etc.) and plateaus (a.k.a., raised areas)
is thereby formed in the embossable film 1130 (as illustrated in
FIG. 14B). The separation of stamper 1190 from embossable film 1130
before cooling may facilitate the separation process and result in
less damage to the imprinted pattern in embossable film 1130.
[0066] In an alternative embodiment illustrated in FIG. 15B, the
system may be cooled to a temperature above room temperature, step
1260, prior to the separation of stamper 1190 from embossable film
1130, step 1270. For example, where the embossable film 1130 is
heated above its transition temperature, the coupled stamper
1190/embossable film 1130 may be cooled to a lower temperature down
to approximately the glass transition temperature of the embossable
film 1130 prior to separation. Alternatively, for another example,
the coupled stamper 1190/embossable film 1130 may be cooled to a
temperature in the range of approximately at the transition
temperature of the embossable film 1130 to just above room
temperature. In yet another embodiment, the coupled stamper
1190/embossable film 1130 may be cooled to room temperature and
then separated.
[0067] FIG. 15C illustrates an alternative embodiment of imprinting
an embossable film including preheating the embossable film prior
to imprinting. In this embodiment, embossable film 1130 and stamper
1190 may be separately heated. In step 1212, after disposing
embossable film 1130 over the base structure, this structure may be
preheated to the embossing temperature prior its introduction into
die assembly 230 by, for example, heater 230 of FIG. 2. In step
1214, the preheated embossable film 1130/base structure 1115 is
positioned in close proximity (e.g., nest area of lower die
assembly 214) to the stamper 1190. Alternatively, the embossable
film 1130/base structure 1115 may be preheated to a temperature
below that of (e.g., close to) the embossing temperature and then
heated to the embossing temperature during or after its positioning
in the nest area of lower die assembly 214. Alternatively, the
embossable film 1130/base structure 1115 may be preheated to the
stamper's temperature/embossing temperature and imprinted after its
close positioning to stamper 1190. Stamper 1190 is then pressed
into the embossable film 1130 at the embossing temperature, step
1230. The stamper 1190 is then separated from embossable film 1130
after imprinting, step 1240. In one embodiment, the embossable film
1130/base structure 1115 may be removed from close proximity to
stamper 1190, step 1241, and then cooled to a temperature below the
glass transition temperature of embossable film 1130. The stamper
1190 is then separated from embossable film 1130 after imprinting.
In one embodiment, the embossable film 1130/base structure 1115 may
be removed from close proximity to stamper 1190 and then cooled to
a temperature below the glass transition temperature of embossable
film 1130, step 1243.
[0068] An imprinted pattern of trenches areas (a.k.a., recessed
areas, grooves, valleys, etc.) and plateaus (a.k.a., raised areas)
is thereby formed in the embossable film 1230 (as illustrated in
FIG. 14B). Following the imprinting of a pattern into embossable
film 1130, a subtractive or an additive process may be used to form
the desired DTR pattern in the disk. In a subtractive process, for
example, one or more layers disposed above the substrate 1115 may
be removed (e.g., through imprint lithography and etching) to
expose a desired pattern on layer 1120 (e.g., a NiP or soft
magnetic layer). Alternatively, the DTR pattern may be formed in
substrate 1115. In an additive process where layer 1120 is, for
example, a NiP layer, a material compatible or identical to
material forming the initial NiP layer is added or plated to form
the raised areas 1110 of the discrete track recording pattern.
[0069] In one embodiment, the imprinting of an embossable film 1130
may be performed at approximately room temperature using an
embossable material that does not have a glass transition
temperature (Tg), for examples, thermosetting (e.g., epoxies,
phenolics, polysiloxanes, ormosils, silica-gel) and radiation
curable (e.g., UV curable, electron-beam curable) polymers.
Silica-gel may be obtained from industry manufacturers, for
example, SOL-GEL available from General Electric Corp., of
Waterford N.Y. In another embodiment, a thermo plastic material,
for example, a polymer such as Ultem available from General
Electric Corp., of Waterford N.Y. may be used for the embossable
film. In such an embodiment, for example, the use of a disk heater
(e.g., heater assembly 230) may not be necessary since an elevated
temperature of a substrate need not be maintained during transport
to stamper 1190.
[0070] As previously noted, the apparatus and methods discussed
herein may be used with various types of base structures (e.g.,
optical disk substrates and wafer substrates, panel substrates)
having embossable films. For example, the imprinting system
discussed herein may be used in the production of optical recording
disks, semiconductor wafers, liquid crystal display panels, etc. In
one embodiment, the apparatus and methods discussed herein may be
used with various types of base structures (e.g., wafer and panel
oxide/substrates) having an embossable layer disposed thereon. In
an alternative embodiment, for example, the imprinting apparatus
and methods discussed herein may be used to fabricate semiconductor
devices such as, for example, a transistor. In such a fabrication,
an embossable layer may be disposed above a base structure of, for
example, an oxide (e.g., SiO.sub.2) layer on top of a silicon wafer
substrate. A stamper may be generated with a patterned structure
for active areas of the transistor. The stamper is imprinted into
the embossable layer with the embossed pattern transferred into the
oxide layer using etching techniques (e.g., reactive ion etching).
Subsequent semiconductor wafer fabrication techniques well known in
the art are used to produce the transistor.
[0071] In an alternative embodiment, for example, the imprinting
apparatus and methods discussed herein may be used to fabricate
pixel arrays for flat panel displays. In such a fabrication, an
embossable layer may be disposed above a base structure of, for
example, an indium tin oxide (ITO) layer on top of a substrate. The
stamper is generated with a patterned layer being an inverse of the
pixel array pattern. The stamper is imprinted into the embossable
layer with the embossed pattern transferred into the ITO using
etching techniques to pattern the ITO layer. As a result, each
pixel of the array is separated by an absence of ITO material
(removed by the etching) on the otherwise continuous ITO anode.
Subsequent fabrication techniques well known in the art are used to
produce the pixel array.
[0072] In yet another embodiment, as another example, the
imprinting apparatus and methods discussed herein may be used to
fabricate lasers. In such a fabrication, embossable material areas
patterned by the stamper are used as a mask to define laser
cavities for light emitting materials. Subsequent fabrication
techniques well known in the art are used to produce the laser. In
yet other embodiments, the apparatus and methods discussed herein
may be used in other applications, for example, the production of
multiple layer electronic packaging, the production of optical
communication devices, and contact/transfer printing.
[0073] In the foregoing specification, the invention has been
described with reference to specific exemplary embodiments thereof.
It will, however, be evident that various modifications and changes
may be made thereto without departing from the broader spirit and
scope of the invention as set forth in the appended claims. For
example, although certain figures and methods herein are discussed
with respect to single-sided imprinting, they may be used for
double-sided imprinting as well. The specification and figures are,
accordingly, to be regarded in an illustrative rather than a
restrictive sense.
* * * * *