U.S. patent application number 12/585756 was filed with the patent office on 2010-03-25 for method for manufacturing a stamper.
Invention is credited to Yoshiyuki Kamata, Takuya Shimada, Shinobu Sugimura.
Application Number | 20100072069 12/585756 |
Document ID | / |
Family ID | 42036516 |
Filed Date | 2010-03-25 |
United States Patent
Application |
20100072069 |
Kind Code |
A1 |
Shimada; Takuya ; et
al. |
March 25, 2010 |
Method for manufacturing a stamper
Abstract
A method for manufacturing an imprint stamper includes the steps
of forming a first electroformed layer on a concavo-convex pattern
of an original disk with the pattern, peeling off the first
electroformed layer to provide a first stamper, forming a second
electroformed layer on a concavo-convex pattern of the first
stamper, peeling off the second electroformed layer to provide a
second stamper, forming a third electroformed layer on a
concavo-convex pattern of the second stamper, and peeling off the
third electroformed layer to provide a third stamper. In addition,
a conductive film is formed at least on one of a bottom of the
concave portion and a top surface of the convex portion of the
concavo-convex pattern at least in one of the first stamper and the
second stamper.
Inventors: |
Shimada; Takuya;
(Kanagawa-ken, JP) ; Sugimura; Shinobu;
(Kanagawa-ken, JP) ; Kamata; Yoshiyuki; (Tokyo,
JP) |
Correspondence
Address: |
NIXON & VANDERHYE, PC
901 NORTH GLEBE ROAD, 11TH FLOOR
ARLINGTON
VA
22203
US
|
Family ID: |
42036516 |
Appl. No.: |
12/585756 |
Filed: |
September 24, 2009 |
Current U.S.
Class: |
205/70 |
Current CPC
Class: |
C25D 5/02 20130101; C25D
1/10 20130101 |
Class at
Publication: |
205/70 |
International
Class: |
C25D 1/10 20060101
C25D001/10 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 25, 2008 |
JP |
2008-245967 |
Claims
1. A method for manufacturing a stamper, comprising the steps of:
forming a first electroformed layer on a concavo-convex pattern of
an original disk; peeling off the first electroformed layer to
provide a first stamper; forming a second electroformed layer on a
concavo-convex pattern of the first stamper; peeling off the second
electroformed layer to provide a second stamper; forming a third
electroformed layer on a concavo-convex pattern of the second
stamper; and peeling off the third electroformed layer to provide a
third stamper, wherein a conductive film is formed on at least one
of a bottom of a concave portion and a top surface of a convex
portion of the concavo-convex pattern in at least one of the first
stamper and the second stamper.
2. The method according to claim 1, wherein the conductive film is
formed so as to make the conductive film on the top surface of the
convex portion thicker than that on the bottom surface of the
concave portion.
3. The method according to claim 1, wherein the conductive film is
formed on the concavo-convex pattern by a sputtering method.
4. The method according to claim 1, wherein the conductive film is
formed on a stamper having the concavo-convex pattern with a track
pitch ranging from 10 nm to 100 nm and a sidewall slope ranging
from 60.degree. to 100.degree..
5. The method according to claim 1, wherein the conductive film
includes nickel.
6. The method according to claim 2, wherein the conductive film
includes nickel.
7. The method according to claim 3, wherein the conductive film
includes nickel.
8. The method according to claim 4, wherein the conductive film
includes nickel.
9. A method for manufacturing a stamper comprising the steps of: a
first step comprising: forming a conductive film on a
concavo-convex pattern of an original disk; forming an
electroformed layer on the conductive film; and peeling off the
conductive film and the electroformed layer from the original disk
so as to provide a father stamper; a second step comprising:
forming a releasing layer on a concavo-convex pattern of the father
stamper; forming an electroformed layer on the releasing layer; and
peeling off the electroformed layer from the father stamper so as
to provide a mother stamper; and a third step comprising: forming a
conductive film on at least one of a bottom surface of a concave
portion and a top surface of a convex portion of the concavo-convex
pattern in at least the mother stamper; forming a releasing layer
on the conductive film, which is followed by forming a
electroformed layer thereon; and peeling off the electroformed
layer so as to provide a son stamper.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is based upon and claims the benefit of
priority from the prior Japanese Patent Application No.
2008-245967, filed on Sep. 25, 2008, the entire contents of which
are incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to a method for manufacturing
a stamper as a metal mold used for a technique for manufacturing
recording media, the technique being injection molding or
imprinting for transferring a recording pattern onto a large amount
of recording media.
DESCRIPTION OF THE BACKGROUND
[0003] A recent increase in recording capacity for information
recording apparatuses is due to the improvement of the recording
density of recording media. There is known, e.g., a discrete track
recording (DTR) magnetic medium as such a recording medium, the DTR
medium being provided with two or more data-recording tracks
concentrically formed thereon, the tracks forming a pattern
composed of magnetic and nonmagnetic portions.
[0004] Methods for manufacturing such a magnetic recording medium
include a nanoimprint method, the method employing a nickel (Ni)
stamper as a metal mold. JP-A 2008-12705 (KOKAI) discloses the
nanoimprint method.
[0005] Actually, a stamper for manufacturing DTR magnetic recording
media has a concavo-convex pattern with a track pitch of 100 nm or
less, thus requiring a microfabrication technique capable of
forming the pattern.
[0006] However, as the track pitch of the concavo-convex pattern
thus becomes narrow for high-density recording, a thinner resist
layer is more advantageous for an EB drawing. That is, a
performance of the EB drawing is enhanced when employing a thinner
resist layer. This rate controlling of the EB drawing results in
the thinner resist layer, reducing a difference in height between
concave and convex portions on an original disk thus manufactured.
According to a stamper with a thin concavo-convex pattern,
manufactured using the above-mentioned original disk, an
insufficient transfer often takes place while imprinting, giving
rise to a defective concavo-convex pattern of the medium
manufactured using the stamper. Moreover, a reduced difference in
height between concave and convex portions on the medium imprinted
reduces a degree of separation between magnetic signals on adjacent
tracks of the recording medium, causing difficulty in high-density
recording.
SUMMARY OF THE INVENTION
[0007] According to a first aspect of the invention, a method for
manufacturing a stamper includes the steps of forming a first
electroformed layer on a concavo-convex pattern of an original disk
with the pattern, peeling off the first electroformed layer to
provide a first stamper, forming a second electroformed layer on a
concavo-convex pattern of the first stamper, peeling off the second
electroformed layer to provide a second stamper, forming a third
electroformed layer on a concavo-convex pattern of the second
stamper, and peeling off the third electroformed layer to provide a
third stamper. In addition, a conductive film is formed at least on
one of a bottom of a concave portion and a top surface of a convex
portion of the concavo-convex pattern at least in one of the first
stamper and the second stamper.
[0008] According to a second aspect of the invention, a method for
manufacturing a stamper includes the following 3 steps. A first
step includes forming a conductive film on a concavo-convex pattern
of an original disk with the pattern, forming an electroformed
layer on the conductive film, and peeling off the conductive film
and the electroformed layer from the original disk to provide a
father stamper. A second step includes forming a releasing layer on
a concavo-convex pattern of the father stamper, forming an
electroformed layer on the releasing layer, and subsequently
peeling off the electroformed layer from the father stamper to
provide a mother stamper. A third step includes forming a
conductive film at least on one of a bottom surface of a concave
portion and a top surface of a convex portion of the concavo-convex
pattern at least in the mother stamper, forming a releasing layer
on the conductive film, which is followed by forming an
electroformed layer on the releasing layer, and subsequently
peeling off the electroformed layer to provide a son stamper.
BRIEF DESCRIPTION OF DRAWINGS
[0009] The accompanying drawings, which are incorporated in and
constitute a part of this specification, illustrate embodiments of
the invention and together with the description, serve to explain
the principles of the invention.
[0010] FIGS. 1A to 1H are sectional views schematically showing
steps of manufacturing a stamper according to an embodiment of the
present invention.
[0011] FIGS. 2A to 2D are sectional views schematically showing
steps of manufacturing a stamper according to the embodiment.
DETAILED DESCRIPTION OF THE EMBODIMENTS OF THE INVENTION
[0012] An embodiment of the present invention is explained below
with reference to drawings.
Embodiment
[0013] FIGS. 1A to 1H are sectional views schematically showing
steps for manufacturing a stamper according to an embodiment of the
invention. The stamper is manufactured as will be described below,
using a coating applicator, a drawing apparatus, a development
apparatus, a deposition system and an electroforming apparatus.
[0014] As shown in FIG. 1A, a glass substrate or a Si substrate is
coated with a photoresistive resin (referred to as a "resist") by
spin coating using a coating applicator, thus forming a resist
layer 12.
[0015] Next, as shown in FIG. 1B, a latent image is formed by
irradiating the resist layer 12 with an electron beam (EB) using an
EB drawing apparatus. Furthermore, the resist layer 12 with the
latent image thereon is developed to form a concavo-convex pattern
using a development apparatus. A substrate thus manufactured
through a series of these steps is called an original disk 10.
[0016] Next, as shown in FIG. 1C, a conducting film 13 is formed on
the concavo-convex pattern of the original disk 10, and an
electroformed layer 14 is further formed on the conducting film 13
using an electroforming apparatus. Then, a double layer formed of
the conducting film 13 and the electroformed layer 14 is peeled off
from the original disk 10 to provide a father stamper 15 as a first
stamper shown in FIG. 1E.
[0017] Next, as shown in FIG. 1F, an oxide film 16 is formed as a
releasing layer on a concavo-convex pattern of the father stamper
15 by anodic oxidation coating or oxygen plasma ashing. Then, as
shown in FIG. 1G, an electroformed layer 17 is formed on the oxide
film 16, the oxide film 16 and electroformed layer 17 being peeled
off from the father stamper 15 to provide a mother stamper 18 as a
second stamper.
[0018] According to the invention, the mother stamper 18 is
subjected to a treatment. The treatment allows it to enhance the
difference in height between the concave and convex portions
thereof, i.e., the difference in height between bottoms of the
concave portions and top surfaces of the convex portions. As shown
in FIG. 2A, the treatment provides a conductive film 19 to the
bottoms of the concave portions and the top surfaces of the convex
portions of the mother stamper 18. The conductive film 19 is formed
on the concavo-convex pattern of the mother stamper 18.
Specifically, the mother stamper 18 has a concavo-convex pitch,
i.e., a predetermined track pitch L.sub.t=100 nm and a sidewall
slope of the concavo-convex pattern D.sub.t=90.degree., as shown in
FIG. 2A. The conductive film 19 was deposited by DC sputtering
under a sputtering pressure of 1.0 Pa, at a discharge power of 100
W and for a deposition time of 225 sec. The sputtering under these
conditions provided a 10-nm thick film and a 20-nm thick film to
bottoms 18a of the concave portions and top surfaces 18b of the
convex portions, respectively, thus enabling to make the conductive
film on the top surfaces thicker than that on the bottoms. As a
result, it was achieved that the difference in height between the
concave and convex portions was enhanced by 10 nm, compared with
that before the treatment.
[0019] In the treatment, the conductive film 19 may be deposited on
sidewalls of the concavo-convex portions. Furthermore, it is
preferable that the mother stamper 18 is subjected to the treatment
just after peeling off the mother stamper 18 from the father
stamper 15. This is because a surface of the mother stamper 18
oxidizes progressively with time, obstructing a stable formation of
the conductive film 19 on the surface.
[0020] Next, a releasing layer 20 is formed on the surface of the
conductive layer 19 by oxygen RIE (Reactive Ion Etching), etc., as
shown in FIG. 2B. The mother stamper with the releasing layer 20
thereon is immersed in a nickel-sulfamate bath to electroform an
electroformed layer 21. After that, the electroformed layer 21 is
peeled off from the mother stamper to duplicate a son stamper 22 as
a third stamper shown in FIG. 2D. In addition, a
concavo-convex-patterned surface of the son stamper 22 is spin
coated with a protective film, and then dried. The son stamper 22
is subjected to a rear surface grind as needed and punching to
obtain a final stamper for transferring a final recording pattern
onto massive amounts of magnetic recording media.
[0021] Here, a material consisting primarily of Ni is employed for
the conductive film 19 and the releasing layer, as Ni has a high
mechanical strength, resistance to corrosion and wear, and high
adhesion to the electroformed Ni. In addition, Ni or a Ni-based
metal containing Co, S, B, or P is employed for the electroformed
layer 21.
[0022] In a specific example shown in FIG. 2A, the track pitch
L.sub.t and the slope D.sub.t of the track sidewall of the
concavo-convex pattern of the mother stamper 18 was set to 100 nm
and 90.degree., respectively. However, these numerals are specified
just as one example. That is, the track pitch L.sub.t may range
from 10 to 100 nm, and the slope of the track sidewall D.sub.t may
range from 60 to 100.degree.. Here, the reason for setting the
lowest track pitch to 10 nm is that even forming the conductive
film 19 on the surface of the mother stamper 18 may not allow it to
easily give a difference in height between the concave and convex
portions when the track pitch is under 10 nm. Here, the reason for
setting the slope D.sub.t of track sidewall to a range from 60 to
100.degree. is that it becomes impossible to acquire a sufficient
area for the magnetic portion of the medium when D.sub.t is under
60.degree., whereas it becomes difficult to peel off the releasing
layer 20 from the mother stamper 18 when D.sub.t is larger than
100.degree.. As mentioned above, the thicknesses of the conductive
film formed on the mother stamper 18 are set to 10 nm and 20 nm at
the bottom and the top surface, respectively. Meanwhile, these
thicknesses are specified just as an example. It is possible to
make the conductive film on the top surface thicker than that on
the bottoms by selecting sputtering conditions such as a sputtering
pressure, a discharge power, a sputtering time, etc.
[0023] As described above, the mother stamper 18 was obtained such
that the conductive film was provided to the bottoms and top
surfaces of the concavo-convex pattern to enhance the difference in
height between the convex and concave portions. The son stamper 22
duplicated using such a mother stamper 18 is also made to have an
enhanced difference in height between the convex and concave
portions. Hence, the son stamper 22 allows it to eliminate
insufficient transfers of the pattern while subsequent imprinting
and to surely form the concavo-convex pattern of the resist mask on
the medium. A difference in height between the convex and concave
portions of the imprinted medium itself may also be enhanced to
heighten a degree of separation between magnetic signals on
adjacent tracks of the recording medium. Such a medium enables
higher recording density. The mother stamper 18 has its surface of
the concavo-convex pattern coated with the conductive layer,
standing long use without wear, even if the mother stamper 18 is
used repeatedly for duplicating the son stamper 18.
[0024] The present invention is not limited to the above-described
embodiment, but may be variously modified for the practice of the
invention unless the scope of the invention is altered. For
example, it was described above that the mother stamper 18 was
subjected to the treatment, so that the difference in height
between the concave and convex portions of the concavo-convex
pattern was enhanced. As a modified embodiment, the mother stamper
18 and the father stamper 15 may be subjected to the treatments for
enhancing the differences in height between the concave and convex
portions of the respective concavo-convex patterns. In this case,
it is important that the respective treatments provide the
conductive film to the bottoms of the concave portions and the top
surfaces of the convex portions of the respective concavo-convex
patterns. It was described throughout that the conductive film was
formed on the bottoms of the concave portions and the top surfaces
of the convex portions of the concavo-convex pattern. However, what
is important is to form the conductive film at least on the top
surfaces of the convex portions of the concavo-convex pattern.
Moreover, although the above-described shapes or numerals of the
embodiment are different partially from those of the practical
examples, the shapes or numerals may be altered with reference to
publicly known techniques.
[0025] Additional advantages and modifications will readily occur
to those skilled in the art. Therefore, the invention in its
broader aspects is not limited to the specific details and
representative embodiment shown and described herein. Accordingly,
various modifications may be made without departing from the spirit
or scope of the inventive concept as defined by the claims and
their equivalents.
* * * * *