U.S. patent application number 13/575371 was filed with the patent office on 2012-11-22 for interconnection structure made of redirected carbon nanotubes.
This patent application is currently assigned to COMMISSARIAT A L'ENERGIE ATOMIQUE ET AUX ENERGIES ALTEMATIVES. Invention is credited to Jean Dijon.
Application Number | 20120292103 13/575371 |
Document ID | / |
Family ID | 42667917 |
Filed Date | 2012-11-22 |
United States Patent
Application |
20120292103 |
Kind Code |
A1 |
Dijon; Jean |
November 22, 2012 |
INTERCONNECTION STRUCTURE MADE OF REDIRECTED CARBON NANOTUBES
Abstract
The invention relates to an electronic device including electric
connections extending along at least two different directions, said
connections being essentially formed by means of bundles of carbon
nanotubes (CNT) (8), where at least two CNT bundles comprise a
portion (8a) having its axis directed along a first direction and a
portion (8b) having its axis redirected along a second direction,
the connections between CNT bundles being achieved by overlapping
of the portions (8b) of said at least two bundles to form a
connection line (4).
Inventors: |
Dijon; Jean; (Champagnier,
FR) |
Assignee: |
COMMISSARIAT A L'ENERGIE ATOMIQUE
ET AUX ENERGIES ALTEMATIVES
Paris
FR
|
Family ID: |
42667917 |
Appl. No.: |
13/575371 |
Filed: |
December 17, 2010 |
PCT Filed: |
December 17, 2010 |
PCT NO: |
PCT/FR10/52792 |
371 Date: |
July 26, 2012 |
Current U.S.
Class: |
174/75R ;
29/592.1; 977/932 |
Current CPC
Class: |
Y10T 29/49117 20150115;
H01L 2221/1094 20130101; Y10S 977/842 20130101; H01L 2924/0002
20130101; H01L 21/76877 20130101; Y10T 29/49002 20150115; H01L
21/76841 20130101; H01L 23/53276 20130101; B82Y 40/00 20130101;
H01L 2924/0002 20130101; H01L 2924/00 20130101 |
Class at
Publication: |
174/75.R ;
29/592.1; 977/932 |
International
Class: |
H02G 15/08 20060101
H02G015/08; H05K 13/00 20060101 H05K013/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 11, 2010 |
FR |
1050986 |
Claims
1-13. (canceled)
14. An electronic device comprising electric connections extending
along at least two different directions, said connections being
formed by means of carbon nanotube (CNT) bundles, wherein at least
two CNT bundles each comprise a portion having an axis directed
along a first direction and a portion having an axis redirected
along a second direction, the connections being achieved by
connecting portions of said at least two CNT bundles to form a
connection line.
15. The electronic device of claim 14, wherein the at least two
different directions are substantially perpendicular.
16. The electronic device of claim 14, wherein the first direction
is substantially vertical and the CNT bundle portion having an axis
directed along the first direction forms a via.
17. The electronic device of claim 14, wherein the second direction
is substantially horizontal and the CNT bundle portion having an
axis redirected along the second direction forms a connection
line.
18. The electronic device of claim 17, wherein the connection line
comprises a metal layer.
19. The electronic device of claim 14, wherein the electronic
device further comprises another CNT bundle laterally connected to
at least one of the at least two CNT bundles, at the portion of the
CNT bundle having an axis redirected along the second direction, to
form the connection line.
20. The electronic device of claim 19, wherein the other CNT bundle
is laterally connected to at least two CNT bundles to ensure the
connection between vias.
21. A method of creating electric connections extending along at
least two directions of the electronic device of claim 1, the
method comprising: growing at least two CNT bundles along a first
direction in a cavity of said device; and redirecting a portion of
said at least two CNT bundles along a second direction by flowing a
liquid to form a connection line.
22. The method of claim 21, wherein: growing at least two CNT
bundles along the first direction is carried out within vias; a
portion of the at least two CNT bundles is redirected along the
second direction; and the portions of the at least two CNT bundles
redirected along the second direction are connected by overlapping
to form the connection line.
23. The method of claim 21, comprising depositing at least one
metal layer on the portion of the at least two CNT bundles
redirected along the second direction.
24. The method of claim 21, comprising growing, and optionally
redirecting along the second direction, another CNT bundle to
connect laterally at least one CNT bundle to the portion of the CNT
bundle redirected along the second direction, to form the
connection line.
25. The method of claim 24, comprising depositing a metal layer on
the other CNT bundle.
26. The method of claim 21, comprising depositing TiN on areas
where CNT bundles should not grow.
Description
TECHNICAL FIELD
[0001] The present disclosure relates to an electronic device
comprising electric connections formed by means of carbon nanotubes
(CNT), it also relates to methods for forming such connections.
[0002] This invention especially has applications for thermal,
electric, and mechanical connectors.
BACKGROUND OF THE INVENTION
[0003] The use of carbon nanotubes (CNT) or of CNT bundles to
manufacture through vias or chip interconnects has already been
provided, especially to provide a complement or even an alternative
to the use of copper, indeed, the latter is not adapted when minute
sizes are involved, CNTs further have the necessary properties,
such as a low electric resistance, enabling to provide the best
electric conductivity between the different chip levels.
[0004] A via is a cavity enabling to create a connection between
conductive plates. The electric lines formed on the plates create
the connection between vias. Conductive plates are made of a metal,
such as aluminum, and are separated by an insulating layer having
the cavity forming the via dug therein.
[0005] The miniaturization of electronic devices makes the use of
copper quite problematic since copper causes difficulties due to
electromigration when current densities become too high.
Architectures formed of copper lines and vias thus show their
limits in integrated circuits having a resolution close to 22
nanometers.
[0006] As illustrated in FIGS. 1 and 2, the use of CNTs for
ensuring the connection between conductive tracks has been
provided, by replacing copper or tungsten vias with CNTs (Katagiri
et al., interconnect Technology Conference, 2009, IEEE
international 1-3 Jun. 2009, pp. 44-46; Yokoyama et al. Japanese
Journal of Applied Physics, Vol. 47, No 4, 2008, pp. 1985-1990).
However, this method does not enable to totally do away with
copper, the connection between vias being always ensured by a
copper line. Electromigration-related issues are thus not totally
suppressed.
[0007] Document US 200810042287 describes an electronic device in
which the connections are at least partially ensured by CNT
bundles. The via is covered with a layer of conductive material on
which another CNT bundle can be deposited and directed along the
line direction. However, the vias and the lines are not formed from
the same CNT bundle.
[0008] Document US 2006/0212974 discloses an electronic device
comprising CNT bundles prepared inside of the via, and then
redirected along another direction to connect two conductive layers
of two different levels. There are no connections between vias.
[0009] Document CN 101562148 relates to a method for creating
vertical. CNT connections by deposition of a CNT solution on a
conductive layer. In this device, two conductive layers of
different levels are connected by means of CNT bundles.
[0010] Another technology is based on the same concept of CNT vias,
but comprises using metal blocks to change the orientation of the
CNTs and thus form the horizontal lines (FIG. 3). It is however
difficult to control the deposition of a catalyst and the CNT
growth along two perpendicular directions on two surfaces of a
metal block (FIG. 4). Another disadvantage of this technique is the
repeated crossing of many CNT--metal interfaces to ensure the
conduction.
[0011] Document US 2009/0294966 describes vertical CNT vias
ensuring the electric connection between two conductive layers, but
also horizontal CNT lines providing an electric connection between
vias. This involves two separate bundles directed along two
different directions. The CNT bundles coming from the via do not
enable to form the line.
[0012] These different approaches imply controlling the CNT growth
within smaller and smaller cavities, thus raising the issue of the
CNT bundle density. Indeed, just like the homogeneity of their
properties and of their orientation, the control of the CNT density
is of major importance to provide good electric connections in
nanoelectronics. High CNT densities are thus indispensable.
[0013] Hata and co-workers (Hayamizu et al., Nature nanotechnology,
Vol. 3, 2008, 289-294) have recently revealed an organizing and
densifying effect capable of being obtained by dipping of a film of
scattered. CNTs in an alcohol solution. Indeed, when the CNT film
is dipped into the alcohol bath, perpendicularly to the surface
thereof, and then dried, the CNTs gather and align. Due to the
surface tension of the liquid and to the strong Van der Waals
interactions, the CNTs achieve a structure close to that of
graphite. No disassembly of the CNTs has been observed after
densification. However, Hata only obtains structures formed of CNTs
directed along the same direction, which thus limits possible
applications.
[0014] The present invention comes from the search for technical
solutions especially enabling to do away with the use of metals and
implementing simple manufacturing processes.
SUMMARY OF THE INVENTION
[0015] Thus, the present invention provides a new architecture,
enabling to do away with the use of metals to ensure the connection
between plates or to ensure the change of direction of a CNT
bundle, which is based on the growth and the redirection of carbon
nanotubes (CNTs).
[0016] Generally, the present invention comprises forming the
electric connections, in an electronic device, with bundles of
carbon nanotubes (CNT) directed along a first direction and
contained in cavities called vias. Such CNT bundles are laterally
interconnected by lines, also formed of CNT bundles along a second
direction.
[0017] In the rest of the discussion, terms "via" and "line" are
used to designate the CNT bundles contained in the cavities or vias
and representing the connection lines, respectively.
[0018] Typically, an electronic device according to the present
invention comprises a sequence of structures especially made of a
conductive plate (for example, made of aluminum) covered with an
insulator layer (silica or low-K microelectronics material).
Cavities interconnected by lines are dug into the insulating block
to create interconnects between plates (vias) or between vias
(lines).
[0019] More specifically, the present invention relates to an
electronic device comprising electric connections extending along
at least two different directions. Typically, said connections are
essentially formed by means of bundles of carbon nanotubes (CNT),
where at least two CNT bundles comprise a portion having its axis
directed along a first direction and a portion having its axis
redirected along a second direction. Further, the connection
between CNT bundles is achieved by overlapping of the portions of
said at least two CNT bundles to form a connection line.
[0020] At least two bundles forming the electric connections are
bent, an area of the CNT bundles being directed along the first
direction and another area being directed along a second different
direction.
[0021] it should be noted that the electric connection system of
the present invention enables to form connections in at least two
directions, advantageously vertical and horizontal, but may also be
used to create connections in more than two directions, especially
three, in particular in the case of two different connections in
the horizontal plane.
[0022] According to the present invention, the electric connections
are mainly formed by means of CNT bundles or bunches, that is, a
multitude of aggregated carbon nanotubes having a substantially
parallel growth axis. Term "essentially" indicates that the
electric connections may be only ensured by the CNTs, and thus in
the absence of metal lines or blocks, as used to be the case in
prior art. However, and as will described hereafter, the electric
contact between bundles may be improved by further performing a
metal deposition.
[0023] In practice, such electric connections are created by
implementing the following method: [0024] growth of at least one
CNT bundle along the first direction; [0025] redirection of a
portion of the CNT bundle along the second direction,
advantageously by flowing of a liquid.
[0026] Typically, the method for creating electric connections in
at least two directions within an electronic device according to
the present invention comprises the steps of: [0027] growing at
least two CNT bundles along a first direction in a cavity of said
device; [0028] redirecting a portion of said two CNT bundles along
a second direction, advantageously by flowing of a liquid, to form
the connection line.
[0029] The forming of this device thus comprises the controlled
growth of CNT bundles along a first direction within cavities,
according to techniques tried and tested in prior art, especially
by means of catalysts such as iron.
[0030] Typically, the growth of the CNT bundles is stopped when
said bundles have a height at least greater than that of the via. A
portion of these CNT bundles is then redirected along a second
direction, advantageously by flowing of a liquid.
[0031] The redirection of the CNT bundle may be performed by the
technique described in the Hayamizu et al. document. (Nature
nanotechnology, Vol. 3, 2008, 289-294). In practice, it comprises
immersing the CNTs in an isopropyl alcohol solution and pulling
them parallel to the direction of a groove, the groove being
perpendicular to the meniscus of the liquid. This operation also
enables to densify the CNT bundles.
[0032] According to a privileged embodiment, the portion of the CNT
bundle which has been redirected along the second direction is
substantially perpendicular to the portion of the CNT bundle along
the first direction.
[0033] Typically, the first direction is substantially vertical.
Advantageously, the portion of the CNT bundle along the first
direction forms the via of the electronic device.
[0034] Preferentially, the second direction is substantially
horizontal. Advantageously, the portion of the CNT bundle along the
second direction forms the connection line of the electronic
device.
[0035] In a privileged embodiment, vias and lines are thus
substantially perpendicular.
[0036] To form connections between vias, in particular, the
electronic device according to the present invention preferentially
comprises at least two CNT bundles having their portions along the
second direction, which may be substantially horizontal, forming
the connection line. The line is advantageously formed by
overlapping of the portions of the CNT bundles along the second
direction, that is, by successive superposition of the bundle
ends.
[0037] This embodiment is implemented by the following method:
[0038] growth of a plurality of parallel CNT bundles along the
first direction, advantageously within vias; [0039] redirection of
a portion of the CNT bundles along the second direction; [0040]
connection, advantageously by overlapping, of the portions of the
CNT bundles along the second direction, to form the connection
line.
[0041] The overlapping is actually obtained by flattening of the
upper portion of the CNT bundles, thus only leaving the portion of
the CNT bundle contained in the cavity in the first direction,
preferably substantially vertically. Advantageously, the second
direction, that is, the overlapping direction, is that of a groove
previously dug into the insulating block to contain the connection
line.
[0042] According to a specific embodiment, the device of the
present invention further comprises a metal layer. Advantageously,
it covers at least the portion of the CNT bundles along the second
direction, and more advantageously still the connection line.
[0043] This metal layer may enable: [0044] to uniformize the
surface of the device for an encapsulation or to be used as a
support to form an upper connection level. In this last case, it is
advantageous to deposit a metallic material, for example, aluminum,
capable of promoting the growth of a second CNT level; and/or
[0045] promote the connection between vias.
[0046] This metal layer is deposited by means of any adapted
technique known by those skilled in the art.
[0047] According to another embodiment, the electronic device may
further comprise another CNT bundle laterally connected to at least
one CNT bundle of the device, at the level of its portion in the
second direction, to form the line. This other CNT bundle ensures
the connection with a bundle coming from a via and possibly between
several vias. The connection is achieved after the growth of this
other CNT bundle, either directly along the second direction, or
after its redirection along the second direction, as described
previously.
[0048] Preferentially, the other CNT bundle is laterally connected
to at least two CNT bundles to ensure the connection between
vias.
[0049] According to the selected operating mode, the growths of CNT
bundles forming either the vias, or the connection lines, may be
simultaneous or separate.
[0050] Advantageously, the growth of the other CNT bundle is
performed within a groove and not within a cavity. The other CNT
bundle thus cannot directly come into contact with the conductive
plate, since it is physically separated therefrom by the insulating
block. The redirection of this other CNT bundle along the second
direction may be performed in the groove.
[0051] In this specific embodiment, the lateral connection between
CNT bundles is advantageously achieved by the deposition of a metal
layer. In practice, it is located at the interface of the two types
of CNT bundles: at least one CNT bundle, at the level of its
portion along the second direction, coming from the via(s) and the
other bundle forming the line. This layer is advantageously formed
by means of a so-called contact metal selected from the following
group:
[0052] palladium, copper, gold, or titanium. Thus, the contact
metal ensures the connection between the CNT bundles coming from
the vias and the CNT bundle forming the connection line.
[0053] In the context of the present invention, to locate CNTs in
predetermined growth areas, one may: [0054] either deposit the
growth catalyst over the entire plate, and then remove it (by
etching, polishing . . . ) from the non-predetermined areas; [0055]
or deposit TiN on the non-predetermined areas, then deposit the
catalyst fall wafer, as described in Dijon et al. (Diam. Relat.
Mater., 2009, doi:10.1016/j.diamond.2009.11.017).
[0056] According to a preferred embodiment, the method for creating
electric connections in at least two directions within an
electronic device according to the present invention further
comprises a step of deposition of at least one metal layer on the
portion of the CNT bundles along the second direction.
[0057] It may also comprise a step of growth, and possibly of
redirection along the second direction, of another CNT bundle
intended to laterally connect at least one CNT bundle, at the level
of its portion along the second direction, to form the connection
line. In this specific case, the method may possibly comprise a
step of deposition of a metal layer on the other CNT bundle.
[0058] Further, the method for forming the device according to the
present invention may comprise at least one step of deposition of
TiN on the areas where CNTs should not grow.
[0059] In electronic devices according to the present invention,
the electric current appears to essentially flow through the carbon
nanotubes, thus considerably decreasing electromigration problems.
Further, methods for forming such devices implement relatively
tried and tested techniques.
EMBODIMENTS OF THE INVENTION
[0060] The foregoing and other features and advantages of the
present invention will be discussed in the following non-limiting
description of the following embodiments in connection with the
accompanying drawings.
[0061] FIG. 1 shows a diagram illustrating the integration of
carbon nanotubes (CNT) in prior art ULSI ("Ultra Large Scale
integration") interconnects.
[0062] FIG. 2 is a diagram illustrating prior art, that is, the
growth of carbon nanotubes (CNT) in vias, creating a contact with
the copper cables.
[0063] FIG. 3 is a three-dimensional microscope view of a prior art
line/via interconnection system, implying a metal contact
block.
[0064] FIG. 4 is a diagram of a prior art line/via interconnection
system, implying a metal contact block.
[0065] FIG. 5 is a diagram of the interconnection device according
to the present invention, by overlapping of redirected CNTs coming
from vias (A) or by connection between separate CNTs (B),
respectively. The arrow indicates the current flow and the circles
indicate the interfaces to be crossed.
[0066] FIG. 6 is a diagram of two interconnection devices according
to the invention (A, B), where the contact between CNT bundles is
improved by means of a metal.
[0067] FIG. 7 is a schematic diagram of an embodiment of the
invention according to which the vias and lines are formed
simultaneously. Left-hand views: cross-section views; right-hand
views: top views.
[0068] FIG. 8 is a diagram illustrating a method for forming an
interconnection device according to the present invention by CNT
overlapping; A/ to F/: end views, perpendicular to the groove; G/
and H/: views parallel to the groove direction.
[0069] FIG. 9 is a diagram illustrating a method for forming an
alternative interconnection device according to the present
invention by simultaneous growth of the vias and of the line.
[0070] FIG. 10 is a diagram illustrating a method for forming an
alternative interconnection device according to the present
invention by independent growth of the vias and of the line, and
insertion of a contact metal.
DETAILED DESCRIPTION OF THE INVENTION
[0071] The different embodiments described hereafter relate to an
electronic device requiring both vertical and horizontal
interconnects, thus in two different perpendicular directions. All
these connections are formed by means of carbon nanotuhes (CNT):
[0072] the vertical connections are formed by vertical CNT bundles
which grow within vias, formed in a layer of insulating material;
[0073] the horizontal connections are also ensured by CNTs and form
the connection lines. They may result from the overlapping of the
bundles coning from the vias, said bundles having been redirected
(first embodiment; FIG. 5A) or result from the growth of an
independent bundle in lateral contact with the bundles coming from
the vias, said bundles having been redirected (second embodiment;
FIG. 5B).
[0074] According to a specific embodiment, a metal layer 2, 10 is
also in contact with the CNT bundles, especially on portions 8b of
the CNT bundles (FIG. 6A and FIG. 6B).
[0075] Such a layer may advantageously be formed of [0076] a layer
10, for example, made of Pd or Ti, thus improving the contact of
CNTs; and/or [0077] a layer 2, for example, made of Al, allowing
the growth of a new CNT level, and thus of a new interconnection
level.
[0078] As a variation, it may be a bilayer associating the two
types of layers 10 and 2.
I/ First Embodiment of the Invention
[0079] As already mentioned, this first embodiment by overlapping
of vertical CNT bundles is illustrated in FIGS. 5A and 6A,
respectively.
[0080] More specifically, its forming method is illustrated in FIG.
8. It should be noted that steps A to F are schematically shown in
end views, that is, perpendicular to groove 3, FIGS. 8G and 8H
corresponding to views parallel to the direction of groove 3.
[0081] A/ Forming of the Base Structure:
[0082] An insulating layer 1, made of silica or of a low-K material
of microelectronics is deposited on conductive layer 2. Conductor 2
typically is aluminum.
[0083] B/ Etching of the Groove:
[0084] Within insulator 1, groove 3, which will become future line
4, is formed by conventional lithography methods.
[0085] C/ TiN Deposition:
[0086] A TiN layer 5, having a thickness of approximately 50
nanometers, is deposited in groove 3, if possible by means of a
conformal deposition method. TiN has the function of inhibiting the
growth of carbon nanotubes when catalyst 6, here iron, is deposited
on the TiN.
[0087] D/ Via Opening:
[0088] Vias 7 are opened in groove 3, the etching through insulator
1 stopping on conductor 2.
[0089] E/ Catalyst Deposition:
[0090] The deposition of catalyst 6 is performed at ambient
temperature. It typically is a layer of 1 nanometer of iron,
deposited by evaporation or by ion beam sputtering. The deposition
is performed with a normal incidence, to minimize the side
coverage.
[0091] F/ Selective Nanotube Growth:
[0092] Conventionally, carbon nanotubes (CNT) 8 are grown at
600''C, by means of a C.sub.2H.sub.2+H.sub.2+He mixture (10 sccm,
50 sccm, 50 sccm), after having previously oxidized the iron by
means of an RF air plasma formed at ambient temperature. The plasma
conditions are the following: [0093] P=0.3 Torr; [0094] 70-W power
for 30 minutes.
[0095] This method allows the growth of nanotubes 8 on iron 6,
except if the latter is deposited on TiN 5. In this case, there is
no growth.
[0096] The pressure during the 600'C growth is 1 Torr. The reactive
gases are introduced after the cold plasma and the temperature rise
is performed within 15 minutes with a 0.3-Torr pressure.
[0097] The height of nanotubes 8 is set by the growth time.
[0098] G/ Nanotube Redirection:
[0099] After the growth, the device is immersed in isopropylic
alcohol and pulled perpendicularly to the direction of groove 3:
the meniscus of the liquid is perpendicular to groove 3. The liquid
flowing through the groove tubes flattens tubes 8 coming from vias
7. The tubes are highly densified after this operation. Further,
tubes 8 have two different portions: [0100] a portion 8a, having an
axis parallel to that of vias 7, and [0101] a portion 8b, having an
axis parallel to that of groove 3.
[0102] Nanotube bundles 8, coming from the different vias 7, are
thus flattened in groove 3 and come into contact. It is thus
possible to form a line connection 4 by overlapping of at least two
nanotube bundles coming from different vias 7.
[0103] At the end of this step, an interconnection system such as
illustrated in FIG. 5A is obtained. Line 4 is formed by overlapping
of nanotube bundles 8b coming from vias 7. In this embodiment, the
line resistance R is formed of a series of interface resistances
added to the nanotube resistance.
[0104] However, in a subsequent step (FIG. 8H), it may be
recommended to perform a metal deposition 2, again with aluminum,
at the surface of line 4 to planarize the structure and to be able
to repeat the operation (creation of interconnects) at the next
level (encapsulation). At the end of this step, an interconnection
system such as illustrated in FIG. 6A is obtained.
II/ Second Embodiment of the Invention
[0105] This second embodiment is illustrated in FIGS. 5B, 6B, 7, 9,
and 10,
[0106] FIG. 5B illustrates the fact that the line resistance is
lower than in the first embodiment since there is only one
interface resistance left.
[0107] FIG. 7 is a drawing illustrating the principle of this
second embodiment according to which the substantially
perpendicular interconnects, respectively vias 7 and lines 4, come
from at least two different bundles of nanotubes, advantageously
formed simultaneously. It should be noted that the diagrams of the
left-hand portion show cross-section views while the right-hand
diagrams are top views.
[0108] Further, the embodiment implying the simultaneous growth of
nanotubes 8 and 8' from line 4 and vias 7 is illustrated in FIG. 9,
which is derived from FIG. 8.
[0109] Steps A to C are similar to those of FIG. 8.
[0110] However, before the opening of vias 7, an additional step is
carried out (FIG. 9D'): an opening 9 of TiN 5 is formed in groove
3, to obtain the growth of carbon nanotubes 8' in this area after
deposition of catalyst 6. This corresponds to the arranging of
growth area 9 of the line.
[0111] The next step comprises openings vias 7 after having
protected openings 9 with a resin layer (FIG. 9E').
[0112] After deposition of catalyst 6 (FIG. 9F') and during the
growth step (FIG. 9G'), tubes 8 and 8' grow in vias 7 and in growth
area 9 formed at the line level, respectively. The bundles coming
from CNTs 8 and 8' may be given a different length, by varying the
catalyst thickness and the different plasma conditions in the vias
and on the line.
[0113] After redirection of the two nanotube bundles (8, 8') coming
from vias 7 and from growth area 9, respectively, the obtained
interconnection system corresponds to that illustrated in FIG. 5B.
It can be observed that connection line 4 is formed by means of a
nanotube bundle 8' which does not come from vias 7.
[0114] FIG. 10 derives from FIG. 8, but in an embodiment where the
growth of nanotubes 8 and 8' is performed separately from line 4
and vias 7, and where an interface metal 10 is inserted between the
two nanotube bundles (between the CNTs of vias 8b and the CNTs of
lines 8', respectively).
[0115] The method starts as in steps A to G of FIG. 8.
[0116] However, instead of step H, steps H' to M' of FIG. 10 are
implemented:
[0117] H'/Deposition of a Contact Metal:
[0118] After redirection of nanotubes 8 coming from vias 7 (8a,
8b), contact metal 10, such as palladium, copper, gold, or titanium
is deposited.
[0119] I'/Contact Metal Opening;
[0120] Contact metal 10 is then opened by etching at the end of
groove 3 and all the way to insulator 1. Growth area 9 of the
future nanotubes 8' coming from line 4 is thus formed.
[0121] J'/ Catalyst Deposition:
[0122] The catalyst is deposited by evaporation or sputtering.
[0123] K'/ Contact Metal Planarization:
[0124] The device is planarized by CMP ("Chemical and Mechanical
Polishing") to suppress catalyst deposit 6 on contact metal 10,
while keeping catalyst 6 in growth area 9.
[0125] L'/ Second Nanotube Growth:
[0126] A second growth in the same conditions as at step F of FIG.
8 is performed. The bundle of nanotubes 8' coming from growth area
9 and intended to form line 4 is thus obtained.
[0127] M'/ Line Redirection:
[0128] After the growth, the nanotube bundle is redirected in the
same way as at step G of FIG. 8. A connection line 4 in contact via
metal 10 with nanotubes 8 coming from via 7 is thus obtained.
[0129] At the end of such a process, an interconnection system such
as illustrated in FIG. 6B is obtained.
* * * * *