U.S. patent application number 11/191941 was filed with the patent office on 2006-09-21 for carbon nanotube device and manufacturing method of the same.
This patent application is currently assigned to Fujitsu Limited. Invention is credited to Akio Kawabata, Daiyu Kondo, Mizuhisa Nihei, Shintaro Sato.
Application Number | 20060212974 11/191941 |
Document ID | / |
Family ID | 37011905 |
Filed Date | 2006-09-21 |
United States Patent
Application |
20060212974 |
Kind Code |
A1 |
Kawabata; Akio ; et
al. |
September 21, 2006 |
Carbon nanotube device and manufacturing method of the same
Abstract
After forming an opening, a resist film is formed on the entire
surface and a resist pattern is formed by patterning the resist
film. The shape of the resist pattern is such that it covers one
side of the bottom of the opening. As a result, a Si substrate is
exposed only in one part of the opening. Then, using the resist
pattern as a mask, a catalytic layer is formed on the bottom of the
opening. Then, the resist pattern is removed. Carbon nanotubes are
grown on the catalytic layer. At this time, since the catalytic
layer is formed on only one side of the bottom of the opening, the
Van der Waals force biased towards that side works horizontally on
the growing carbon nanotubes. Therefore, the carbon nanotubes are
attracted towards the nearest side of the SiO.sub.2 film and grow
biased towards that side.
Inventors: |
Kawabata; Akio; (Kawasaki,
JP) ; Nihei; Mizuhisa; (Kawasaki, JP) ; Kondo;
Daiyu; (Kawasaki, JP) ; Sato; Shintaro;
(Kawasaki, JP) |
Correspondence
Address: |
ARMSTRONG, KRATZ, QUINTOS, HANSON & BROOKS, LLP
1725 K STREET, NW
SUITE 1000
WASHINGTON
DC
20006
US
|
Assignee: |
Fujitsu Limited
Kawasaki
JP
|
Family ID: |
37011905 |
Appl. No.: |
11/191941 |
Filed: |
July 29, 2005 |
Current U.S.
Class: |
423/447.3 ;
257/E21.582; 257/E21.586; 977/742 |
Current CPC
Class: |
H01L 21/76879 20130101;
H01L 21/76838 20130101; H01L 21/76876 20130101; H01L 2221/1094
20130101; D01F 9/12 20130101; B82Y 30/00 20130101 |
Class at
Publication: |
977/742 ;
423/447.3 |
International
Class: |
D01F 9/12 20060101
D01F009/12; D01C 5/00 20060101 D01C005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 18, 2005 |
JP |
2005-080519 |
Claims
1. A carbon nanotube device, comprising: a catalytic layer; a body
situated around said catalytic layer; and a carbon nanotube grown
along said body from said catalytic layer, said carbon nanotube
being curved at a corner of said body.
2. The carbon nanotube device according to claim 1, wherein said
body is an insulating film.
3. The carbon nanotube device according to claim 2, wherein said
insulating film is a silicon oxide film or a silicon nitride
film.
4. The carbon nanotube device according to claim 2, wherein said
insulating film is a low dielectric constant film.
5. The carbon nanotube device according to claim 4, wherein said
low dielectric constant film is one kind of films selected from the
group consisting of a porous silicon-based film, a
fluorocarbon-based film, and a resin-based film.
6. The carbon nanotube device according to claim 2, wherein an
opening is formed in said insulating film, and said catalytic layer
is formed on only one side in said opening when seen in plane
view.
7. The carbon nanotube device according to claim 1, wherein said
catalytic layer contains at least one kind of metal elements
selected from the group consisting of cobalt (Co), iron (Fe) and
nickel (Ni).
8. The carbon nanotube device according to claim 1, wherein said
catalytic layer contains fine particles of a catalytic metal.
9. The carbon nanotube device according to claim 1, wherein said
carbon nanotube functions as a component of wiring.
10. The carbon nanotube device according to claim 1, wherein said
carbon nanotube functions as a part of a coil.
11. The carbon nanotube device according to claim 1, wherein said
carbon nanotube is connected to a lead frame.
12. A manufacturing method of a carbon nanotube device, comprising
the steps of: forming a catalytic layer and a body extending to a
position above said catalytic layer around said catalytic layer;
and growing a carbon nanotube from said catalytic layer along said
body while being bent by the effect of the Van der Waals force from
said body.
13. The manufacturing method of the carbon nanotube device
according to claim 12, wherein the step of forming said catalytic
layer and said body comprise the steps of: forming an insulating
film as said body on or above a substrate; forming an opening in
said insulating film; and forming said catalytic layer on the
bottom of said opening.
14. The manufacturing method of the carbon nanotube device
according to claim 13, wherein said catalytic layer is formed on
only one side in said opening in plane view, in the step of forming
said catalytic layer on the bottom of said opening.
15. The manufacturing method of the carbon nanotube device
according to claim 12, wherein the step of forming said catalytic
layer and said body comprise the steps of: forming said catalytic
layer on or above a substrate; forming an insulating film covering
said catalytic layer as said body; and forming an opening reaching
down to said catalytic layer in said insulating film.
16. The manufacturing method of the carbon nanotube device
according to claim 15, wherein said catalytic layer is exposed in a
part of said opening, in the step of forming said opening.
17. The manufacturing method of the carbon nanotube device
according to claim 13, wherein a silicon oxide film or a silicon
nitride film is formed as said insulating film.
18. The manufacturing method of the carbon nanotube device
according to claim 13, wherein a low dielectric constant film is
formed as said insulating film.
19. The manufacturing method of the carbon nanotube device
according to claim 18, wherein one kind of films selected from the
group consisting of a porous silicon-based film, a
fluorocarbon-based film and a resin-based film as said low
dielectric constant film.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from the prior Japanese Patent Application No.
2005-080519, filed on Mar. 18, 2005, the entire contents of which
are incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a carbon nanotube device
suitable for integrated circuits and the like and a manufacturing
method of the same.
[0004] 2. Description of the Related Art
[0005] In recent years, many researches have been directed to
application of a carbon nanotube to semiconductor devices. As a
method of obtaining a carbon nanotube, a catalytic layer is
arranged in a hole formed in an insulating film, and the carbon
nanotubes are grown vertically from the catalytic layer as shown in
FIG. 11A, FIG. 11B, FIG. 12A and FIG. 12B.
[0006] In addition to the above method, there is a method of
growing a carbon nanotube in a horizontal direction. This method
will be explained. FIG. 13 is a view showing a method of growing
the carbon nanotube horizontally. A laminate of a titanium (Ti)
film 102 and a cobalt (Co) film 103 is formed at two spots on a
silicon (Si) substrate 101 in advance. An electric field is applied
between these two spots to grow a carbon nanotube 104. As a result,
as shown in FIG. 13, the carbon nanotubes 104 running along the
direction of the electric field applied thereto are formed.
[0007] However, there is a limitation in shape of the carbon
nanotube formed according to these methods only. Furthermore, under
a circumstance where no electric field is applied, it is impossible
to connect between two spots existing apart from each other
horizontally by the carbon nanotubes.
[0008] Related arts are disclosed in Japanese Patent Application
Laid-open No. 2004-181620 (Patent Document 1), and Japanese Patent
Application Laid-open No. 2004-174637 (Patent Document 2).
SUMMARY OF THE INVENTION
[0009] The present invention is made in view of the aforementioned
problems, and its object is to provide a carbon nanotube device
having a high degree of freedom in the shape of the carbon nanotube
and a manufacturing method of the same.
[0010] As a result of earnest studies to solve the above-described
problems, the present inventors have arrived at several aspects of
the present invention as shown below.
[0011] A carbon nanotube device according to the present invention
includes a catalytic layer, a body positioned around the catalytic
layer, and a carbon nanotube grown along the body from the
catalytic layer. The carbon nanotube is curved at a corner of the
body.
[0012] In a manufacturing method of the carbon nanotube according
to the present invention, after a catalytic layer and a body
extending to a position above the catalytic layer around the
catalytic layer are formed, a carbon nanotube is grown from the
catalytic layer along the body while being bent by the effect of
the Van der Waals force from the body.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1A to FIG. 1C are sectional views showing a
manufacturing method of a carbon nanotube device according to a
first embodiment of the present invention in process order;
[0014] FIG. 2A is an SEM photograph showing carbon nanotubes grown
from an opening;
[0015] FIG. 2B is a schematic view showing the contents of the SEM
photograph shown in FIG. 2A;
[0016] FIG. 3A is an SEM photograph showing carbon nanotubes grown
from a plurality of openings;
[0017] FIG. 3B is a schematic view showing the contents of the SEM
photograph shown in FIG. 3A;
[0018] FIG. 4A to FIG. 4C are sectional views showing a
manufacturing method of a carbon nanotube device according to a
second embodiment of the present invention in process order;
[0019] FIG. 5A is an SEM photograph showing carbon nanotubes grown
from a T-shaped groove in plane view;
[0020] FIG. 5B is a schematic view showing the contents of the SEM
photograph shown in FIG. 5A FIG. 6A is an SEM photograph enlargedly
showing a bent portion on the right side of FIG. 5A;
[0021] FIG. 6B is a schematic view showing the contents of the SEM
photograph shown in FIG. 6A;
[0022] FIG. 7A and FIG. 7B are sectional views showing a
manufacturing method of a carbon nanotube device according to a
third embodiment of the present invention in process order;
[0023] FIG. 8A is an SEM photograph showing carbon nanotubes grown
from an opening;
[0024] FIG. 8B is a schematic view showing the contents of the SEM
photograph shown in FIG. 8A;
[0025] FIG. 9A is an SEM photograph showing carbon nanotubes grown
from a plurality of openings;
[0026] FIG. 9B is a schematic view showing the contents of the SEM
photograph shown in FIG. 9A;
[0027] FIG. 10 is a sectional view showing a carbon nanotube device
according to a fourth embodiment of the present invention;
[0028] FIG. 11A is an SEM photograph of carbon nanotubes formed by
a conventional method seen from above;
[0029] FIG. 11B is a schematic view showing the contents of the SEM
photograph shown in FIG. 11A;
[0030] FIG. 12A is an SEM photograph of carbon nanotubes formed by
a conventional method seen from side;
[0031] FIG. 12B is a schematic view showing the contents of the SEM
photograph shown in FIG. 12A;
[0032] FIG. 13 is a view showing a conventional method with which
carbon nanotubes are grown horizontally.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0033] Hereinafter, embodiments of the present invention will be
concretely explained with reference to attached drawings. However,
for convenience' sake, the structure of a carbon nanotube device
will be explained when the manufacturing method of the same is
explained.
[0034] First Embodiment
[0035] Firstly, a first embodiment of the present invention will be
explained. FIG. 1A to FIG. 1C are sectional views showing a
manufacturing method of a carbon nanotube device according to the
first embodiment of the present invention in process order.
[0036] In the first embodiment, as shown in FIG. 1A, a SiO.sub.2
film 12 is first formed on a silicon (Si) substrate 11. The
SiO.sub.2 film 12 is, for instance, about 350 nm in thickness.
Next, a cylindrical opening 13 is formed in the SiO.sub.2 film 12
by patterning with a resist pattern (not shown). The opening 13 is,
for instance, about 2 .mu.m in diameter.
[0037] Then, a resist film is formed on the entire surface, and a
resist pattern 16 is formed by patterning the resist film, as shown
in FIG. 1B. The resist pattern 16 has a shape covering the bottom
of the opening 13 on only one side. As a result, the Si substrate
11 is exposed only from a part of the opening 13. In the present
embodiment, especially when the resist pattern 16 is formed, a part
of a side surface of the SiO.sub.2 film 12 is exposed without being
covered by the resist pattern 16.
[0038] Then, as shown also in FIG. 1B, using the resist pattern 16
as a mask, a catalytic layer 14 is formed on the bottom of the
opening 13. A cobalt (Co) film of, for instance, about 1 nm in
thickness., is formed as the catalytic layer 14. At this time, the
catalytic layer 14 is not formed over the entire bottom of the
opening 13 but only on the exposed part of the Si substrate 11.
[0039] Next, as shown in FIG. 1C, the resist pattern 16 is removed.
Then, carbon nanotubes 15 are grown on the catalytic layer 14. At
this time, since the catalytic layer 14 is formed biased towards
one side in the opening 13, the Van der Waals force biased towards
that side works horizontally on the carbon nanotubes 15 in the
growing process. Therefore, as shown in FIG. 1C, the carbon
nanotubes 15 are attracted towards the nearest side surface of the
SiO.sub.2 film 12 and grows biased towards that side. After they
grow higher than the surface of the SiO.sub.2 film 12, the Van der
Waals force nearly ceases to have effect. However, the inclination
is succeeded as is. During further growth, the carbon nanotubes 15
are largely affected by their own weight, so that their shape are
significantly curved.
[0040] The SEM photographs of the carbon nanotubes actually taken
by the present inventors are shown in FIG. 2A and FIG. 3A. FIG. 2A
is an SEM photograph showing carbon nanotube s grown from an
opening, and FIG. 2B is a schematic view showing the contents of
the SEM photograph shown in FIG. 2A. FIG. 3A is an SEM photograph
showing carbon nanotubes grown from a plurality of openings, and
FIG. 3B is a schematic view showing the contents of the SEM
photograph shown in FIG. 3A.
[0041] After the carbon nanotubes 15 are formed as described above,
required elements, wiring layers, insulating layers and the like
are formed to complete a carbon nanotube device.
[0042] According to the first embodiment, the carbon nanotubes 15
can be substantially grown in a direction parallel to the surface
of the Si substrate 11 even without application of an electric
field. In addition, since the carbon nanotubes 15 take a curved
shape, the carbon nanotubes can be used extensively. For instance,
a coil can be formed by connecting a plurality of curved carbon
nanotubes 15 to each other.
[0043] Second Embodiment
[0044] Next, a second embodiment of the present invention will be
explained next. FIG. 4A to FIG. 4C are sectional views showing a
manufacturing method of a carbon nanotube device according to the
second embodiment of the present invention in process order.
[0045] First, in the second embodiment, as shown in FIG. 4A, a
catalytic layer 24 is selectively formed on a Si substrate 21. As
the catalytic layer 24, for instance, a cobalt (Co) film having a
thickness of about 1 nm is formed.
[0046] Next, a SiO.sub.2 film 22 is formed over the entire surface
thereof. Then, a groove 23 is formed in the SiO.sub.2 film 22 by
patterning using a resist pattern (not shown). The thickness of the
SiO.sub.2 film 22 is, for instance, about 350 nm. When forming the
groove 23, as shown in FIG. 4B, both of the Si substrate 21 and the
catalytic layer 24 are to be exposed from the groove 23.
[0047] Thereafter, as shown in FIG. 4C, carbon nanotubes 25 are
grown on the catalytic layer 24. At this time, since the catalytic
layer 24 is not formed evenly on the entire bottom portion of the
groove 23, but formed biased towards one side in the present
embodiment, the Van der Waals force biased towards that side works
horizontally on the carbon nanotubes 25 in the growing process.
Accordingly, as shown in FIG. 4C, the carbon nanotubes 25 are
attracted to a nearest side surface of the SiO.sub.2 film 22 and
grow biasedly. After they grow higher than the surface of the
SiO.sub.2 film 22, the Van der Waals force scarcely works, but the
inclination is succeeded as it is. When they further grow, a large
own weight works on the carbon nanotubes 25, so that the shape of
the carbon nanotubes 25 are largely curved.
[0048] SEM photographs of the carbon nanotubes actually taken by
the present inventors are shown in FIG. 5A and FIG. 6A. FIG. 5A is
an SEM photograph showing carbon nanotubes grown from a T-shaped
groove in plane view, and FIG. 5B is a schematic view showing the
contents of the SEM photograph shown in FIG. 5A. FIG. 6A is an SEM
photograph enlargedly shown a bent portion on the right side of
FIG. 5A, and FIG. 6B is a schematic view showing the contents of
the SEM photograph shown in FIG. 6A. Note that in FIG. 5A and FIG.
5B, parts of the carbon nanotubes on the left are missing. They
were dropped out when handling before taking the SEM photographs,
which does not deny the effect of the present invention.
[0049] Thus, it is possible to obtain the same effect as that of
the first embodiment according to the second embodiment.
[0050] Third Embodiment
[0051] Next, a third embodiment of the present invention will be
explained next. FIG. 7A to FIG. 7B are sectional views showing a
manufacturing method of a carbon nanotube device according to the
third embodiment of the present invention in process order.
[0052] In the third embodiment, first, as shown in FIG. 7A, a
copper (Cu) film 32 and a tantalum (Ta) film 33 are formed in
sequence on a Si substrate 31 by, for instance, a sputtering
method. The Cu film 32 and the Ta film 33 are about 150 nm and
about 5 nm in thickness, respectively. Then, a SiO.sub.2 film 34 is
formed over the entire surface. The SiO.sub.2 film 34 is, for
instance, about 350 nm in thickness. Next, a cylindrical opening 38
is formed on the SiO.sub.2 film 34 by patterning with a resist
pattern (not shown). The opening 38 is, for instance, about 2 .mu.m
in diameter.
[0053] Then, similarly to the first embodiment, a resist film is
formed on the entire surface, and a resist pattern (not shown) is
formed by patterning the resist film so that the Ta film 33 is
exposed only from a part of the opening 38. When this resist
pattern is formed, a part of a side surface of the SiO.sub.2 film
34 is to be exposed without being covered by the resist pattern in
this embodiment. Then, using the resist pattern as a mask, a
titanium (Ti) film 35 and a cobalt (Co) film 36 are formed in
sequence on the bottom of the opening 38. At this time, the Ti film
35 and the Co film 36 are not formed over the entire bottom of the
opening 38 but only on a part where the Ta film 33 is exposed. Both
the Ti film 35 and the Co film 36 are about 1 nm in thickness.
After forming the Ti film 35 and the Co film 36, the resist pattern
is removed.
[0054] Then, as shown in FIG. 7B, carbon nanotubes 37 are grown on
the Co film 36, which is a catalytic layer. At this time, since the
Co film 36 is formed biased towards one side within the opening 38
in the present embodiment, the Van der Waals force biased towards
that side works horizontally on the carbon nanotubes 37 which is in
the process of growing. Accordingly, as shown in FIG. 7B, the
carbon nanotubes 37 are attracted to the nearest side surface of
the SiO.sub.2 film 34 and grow biased to that side. Thus, the shape
of the carbon nanotubes 37 is largely curved similarly to the first
and second embodiments.
[0055] SEM photographs of the carbon nanotubes actually taken by
the present inventors are shown in FIG. 8A and FIG. 9A. FIG. 8A is
an SEM photograph showing carbon nanotubes grown from an opening,
and FIG. 8B is a schematic view showing the contents of the SEM
photograph shown in FIG. 8A. FIG. 9A is an SEM photograph showing
carbon nanotubes grown from a plurality of openings, and FIG. 9B is
a schematic view showing the contents of the SEM photograph shown
in FIG. 9A.
[0056] It is possible to obtain the same effect as that of the
first embodiment according to the third embodiment. In the third
embodiment, by adjusting the thickness of the Ti film 35 and the Co
film 36, the growing conditions of the carbon nanotubes 37 can be
controlled.
[0057] Fourth Embodiment
[0058] Next, a fourth embodiment of the present invention will be
explained. FIG. 10 is a sectional view showing a carbon nanotube
device according to the fourth embodiment of the present
invention.
[0059] In the fourth embodiment, a catalytic layer 55 is formed on
wiring 51 buried in an insulating film 52. An insulating layer 54
is formed on the wiring 51 and the insulating film 52, and an
opening reaching down to the catalytic layer 55 is formed in the
insulating film 54. The catalytic layer 55 is not formed on the
entire bottom of the opening, but is located biased towards one
side. Wiring 57 is formed on the insulating film 54. The catalytic
layer 55 and the wiring 57 are connected by carbon nanotubes 56. An
insulating film 58 covering the wiring 57 and the like is
formed.
[0060] In the fourth embodiment like this, the carbon nanotubes 56
grown from the catalytic layer 55 to the wiring 57 function as a
part of wiring. Since the resistance of the carbon nanotubes 56 is
remarkably low compared with Cu and Al wiring, it is possible to
realize a device with a low power consumption.
[0061] It should be noted that these embodiments are on an
assumption that curved carbon nanotubes are used inside an
integrated circuit chip, it is also possible to use curved carbon
nanotubes as wiring to connect an electrode of an integrated
circuit chip and a lead frame. In addition, curved carbon nanotubes
can be applied to an electron source, a connector, a heating device
and the like.
[0062] As a catalytic layer, an iron (Fe) film or a nickel (Ni)
film may be used as well as the Co film. An alloy film of these
metals can also be used. Further, a body in which metal fine
particles containing Co, Fe and/or Ni are carried by alumina,
silica, magnesia or zeolite can be used.
[0063] Additionally, a body exerting the Van der Waals force on
carbon nanotubes is not limited to an insulating film. As an
insulating film, a silicon nitride film can also be used other than
the above-described silicon oxide film. Furthermore, silicon-based
porous low dielectric constant film, fluorocarbon-based low
dielectric constant film and resin-based low dielectric constant
film can also be used.
[0064] Note that it is disclosed in Patent Document 1 that a carbon
nanotube can be bent by adjusting the thickness of a catalytic
layer, constituent elements and the like. However, this is an
impracticable method, because much trial and error is required to
obtain an appropriate degree of curvature. On the other hand, in
the present invention, it is possible to change the direction of
the bending and the curvature of a carbon nanotube by changing at
least either the thickness (height) of the silicon oxide film or
the distance between the catalytic layer and the side surface of
the opening. Therefore, it is easy to adjust the degree of
curvature.
[0065] A carbon nanotube having a curved shape can be obtained
according to the present invention. Therefore, the freedom of shape
is improved and the range of application can be widened.
Additionally, it is possible to grow a carbon nanotube in an
arbitrary direction without applying an electric field.
[0066] The present embodiments are to be considered in all respects
as illustrative and no restrictive, and all changes which come
within the meaning and range of equivalency of the claims are
therefore intended to be embraced therein. The invention may be
embodied in other specific forms without departing from the spirit
or essential characteristics thereof.
* * * * *