U.S. patent application number 10/128296 was filed with the patent office on 2003-01-09 for interlayer dielectric film.
This patent application is currently assigned to MATASUSHITA ELECTRIC INDUSTRIAL CO., LTD.. Invention is credited to Aoi, Nobuo.
Application Number | 20030008998 10/128296 |
Document ID | / |
Family ID | 18987561 |
Filed Date | 2003-01-09 |
United States Patent
Application |
20030008998 |
Kind Code |
A1 |
Aoi, Nobuo |
January 9, 2003 |
Interlayer dielectric film
Abstract
An interlayer dielectric film is made from an organic/inorganic
hybrid film. The organic/inorganic hybrid film has a main chain in
which a first site of siloxane and a second site of an organic
molecule are alternately bonded to each other.
Inventors: |
Aoi, Nobuo;
(Nishinomiya-shi, JP) |
Correspondence
Address: |
NIXON PEABODY, LLP
8180 GREENSBORO DRIVE
SUITE 800
MCLEAN
VA
22102
US
|
Assignee: |
MATASUSHITA ELECTRIC INDUSTRIAL
CO., LTD.
Osaka
JP
|
Family ID: |
18987561 |
Appl. No.: |
10/128296 |
Filed: |
April 24, 2002 |
Current U.S.
Class: |
528/10 ;
257/E21.261; 257/E21.262; 257/E21.273; 257/E21.576;
257/E21.581 |
Current CPC
Class: |
H01L 21/3124 20130101;
H01L 21/02211 20130101; H01L 21/02126 20130101; H01L 21/3122
20130101; H01L 21/7682 20130101; Y10T 428/12361 20150115; C08G
77/50 20130101; H01L 21/02282 20130101; H01L 21/31695 20130101;
H01L 2221/1047 20130101; Y10T 428/12542 20150115; Y10T 428/31663
20150401 |
Class at
Publication: |
528/10 |
International
Class: |
C08G 077/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 11, 2001 |
JP |
2001-141055 |
Claims
What is claimed is:
1. An interlayer dielectric film comprising an organic/inorganic
hybrid film having a main chain in which a first site of siloxane
and a second site of an organic molecule are alternately bonded to
each other.
2. The interlayer dielectric film of claim 1, wherein pores are
dispersed in said organic/inorganic hybrid film.
3. The interlayer dielectric film of claim 1, wherein said first
site is represented by the following general formula (1): 5wherein
R.sub.1, R.sub.2 and R.sub.3 are an oxygen atom or an organic
group.
4. The interlayer dielectric film of claim 1, wherein said first
site is represented by the following general formula (2): 6wherein
R is an organic group; and R.sub.1 and R.sub.2 are an oxygen atom
or an organic group, which is selected from the group consisting of
an alkyl group, an aryl group and an aryl group
5. The interlayer dielectric film of claim 1, wherein said second
site is polyimide, polyamide, polyimidazole, polyoxazole,
polyphenylene, polyarylene, polyaryl ether, polyalkane or a
fluorinated polymer of any of these polymers.
6. An interlayer dielectric film comprising an organic/inorganic
hybrid film composed of a plurality of first sites of siloxane and
a plurality of second sites of an organic molecule, wherein said
first sites are bonded to said second sites alone and said second
sites are bonded to said first sites alone.
7. The interlayer dielectric film of claim 6, wherein pores are
dispersed in said organic/inorganic hybrid film.
8. The interlayer dielectric film of claim 6, wherein each of said
plurality of first sites is represented by the following general
formula (1): 7wherein R.sub.1, R.sub.2 and R.sub.3 are an oxygen
atom or an organic group.
9. The interlayer dielectric film of claim 6, wherein each of said
plurality of first sites is represented by the following general
formula (2): 8wherein R is an organic group; and R.sub.1 and
R.sub.2 are an oxygen atom or an organic group, which is selected
from the group consisting of an alkyl group, an aryl group and an
aryl group.
10. The interlayer dielectric film of claim 6, wherein each of said
plurality of second sites is polyimide, polyamide, polyimidazole,
polyoxazole, polyphenylene, polyarylene, polyaryl ether, polyalkane
or a fluorinated polymer of any of these polymers.
11. An interlayer dielectric film comprising an organic/inorganic
hybrid film composed of a plurality of first sites of siloxane and
a plurality of second sites of an organic molecule, wherein each of
said plurality of first sites is surrounded with said plurality of
second sites.
12. The interlayer dielectric film of claim 11, wherein pores are
dispersed in said organic/inorganic hybrid film.
13. The interlayer dielectric film of claim 11, wherein each of
said plurality of first sites is represented by the following
general formula (1): 9wherein R.sub.1, R.sub.2 and R.sub.3 are an
oxygen atom or an organic group.
14. The interlayer dielectric film of claim 11, wherein each of
said plurality of first sites is represented by the following
general formula (2): 10wherein R is an organic group; and R.sub.1
and R.sub.2 are an oxygen atom or an organic group, which is
selected from the group consisting of an alkyl group, an aryl group
and an aryl group.
15. The interlayer dielectric film of claim 11, wherein each of
said plurality of second sites is polyimide, polyamide,
polyimidazole, polyoxazole, polyphenylene, polyarylene, polyaryl
ether, polyalkane or a fluorinated polymer of any of these
polymers.
16. An interlayer dielectric film comprising an organic/inorganic
hybrid film composed of a plurality of first sites of siloxane and
a plurality of second sites of an organic molecule, wherein each of
said plurality of second sites is surrounded with said plurality of
first sites.
17. The interlayer dielectric film of claim 16, wherein pores are
dispersed in said organic/inorganic hybrid film.
18. The interlayer dielectric film of claim 16, wherein each of
said plurality of first sites is represented by the following
general formula (1): 11wherein R.sub.1, R.sub.2 and R.sub.3 are an
oxygen atom or an organic group.
19. The interlayer dielectric film of claim 16, wherein each of
said plurality of first sites is represented by the following
general formula (2): 12wherein R is an organic group; and R.sub.1
and R.sub.2 are an oxygen atom or an organic group, which is
selected from the group consisting of an alkyl group, an aryl group
and an aryl group.
20. The interlayer dielectric film of claim 16, wherein each of
said plurality of second sites is polyimide, polyamide,
polyimidazole, polyoxazole, polyphenylene, polyarylene, polyaryl
ether, polyalkane or a fluorinated polymer of any of these
polymers.
21. An interlayer dielectric film comprising a plurality of first
sites of siloxane and a plurality of second sites of an organic
molecule, wherein said plurality of second sites together form an
organic polymer film, and said plurality of first sites are
dispersed in said organic polymer film.
22. The interlayer dielectric film of claim 21, wherein a largest
distance between said plurality of first sites is smaller than a
distance between a pair of copper interconnects disposed with said
organic polymer film sandwiched therebetween.
23. The interlayer dielectric film of claim 21, wherein pores are
dispersed in said organic polymer film.
24. The interlayer dielectric film of claim 21, wherein each of
said plurality of first sites is represented by the following
general formula (1): 13wherein R.sub.1, R.sub.2 and R.sub.3 are an
oxygen atom or an organic group.
25. The interlayer dielectric film of claim 21, wherein each of
said plurality of first sites is represented by the following
general formula (2): 14wherein R is an organic group; and R.sub.1
and R.sub.2 are an oxygen atom or an organic group, which is
selected from the group consisting of an alkyl group, an aryl group
and an aryl group.
26. The interlayer dielectric film of claim 21, wherein each of
said plurality of second sites is polyimide, polyamide,
polyimidazole, polyoxazole, polyphenylene, polyarylene, polyaryl
ether, polyalkane or a fluorinated polymer of any of these
polymers.
27. An interlayer dielectric film comprising a multi-layer film in
which a first layer of siloxane and a second layer of an organic
molecule are alternately stacked on each other.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to an interlayer dielectric
film with a low dielectric constant capable of preventing
diffuision of copper, that is, a material for interconnects.
[0002] In an interlayer dielectric film of a VLSI, reduction of
design rule has led to a problem of increase of parasitic
capacitance between adjacent interconnects, and it is significant
to lower the dielectric constant of the interlayer dielectric film
in order to reduce the parasitic capacitance between
interconnects.
[0003] As a low dielectric interlayer dielectric film, a siloxane
film, such as a methylsilsesquioxane (MSQ) film (with a dielectric
constant of approximately 2.9) and a hydrogenated silsesquioxane
(HSQ) film (with a dielectric constant of approximately 3.0),
including SiO.sub.2 as a principal constituent has been proposed.
FIG. 14 shows the chemical structure of methylsilsesquioxane, that
is, an example of conventional organic siloxane in which an organic
group is bonded to siloxane. In FIG. 14, a methyl group is bonded
to a Si atom included in the main chain of the siloxane.
[0004] Alternatively, an organic polymer film including an aromatic
compound polymer, such as a polyimide derivative, a polyalyl ether
derivative, a polyquinoline derivative or a polyparaxylene
derivative, having a low dielectric constant and high heat
resistance has been proposed as the low dielectric interlayer
dielectric film. Such an organic polymer film has a low dielectric
constant because it includes carbon as a principal constituent, and
hence, the polarizability of molecules included in the film is
lower than that of a conventionally used interlayer dielectric film
including SiO.sub.2 as a principal constituent.
[0005] Therefore, such an organic polymer film is regarded as a
promising low dielectric interlayer dielectric film.
[0006] However, when copper is used as the material for
interconnects, copper ions are diffused by an electric field or
heat into such a low dielectric interlayer dielectric film.
Therefore, the breakdown voltage of the interlayer dielectric film
is disadvantageously lowered when it is used for a long period of
time. When the breakdown voltage of the interlayer dielectric film
is lowered, dielectric failure is caused, which may result in
failure of the operation of the VLSI.
SUMMARY OF THE INVENTION
[0007] In consideration of the aforementioned conventional problem,
an object of the invention is preventing copper used as the
material for interconnects from diffusing into an interlayer
dielectric film so as to prevent the breakdown voltage of the
interlayer dielectric film from lowering over a long period of
use.
[0008] The mechanism of the diffusion of copper into an interlayer
dielectric film has not been completely solved. Probably, copper
atoms included in the interconnect material are ionized to dissolve
in the interlayer dielectric film, so that the copper ions
dissolved in the interlayer dielectric film can drift in the
interlayer dielectric film due to an electric field.
[0009] Also, the interlayer dielectric film attains a low
dielectric constant by reducing the density of the interlayer
dielectric film, for example, by making it porous. The mechanism of
the drift of copper ions in an interlayer dielectric film with low
density is different from that of the drift of copper ions in a
conventional dense interlayer dielectric film. The interaction
between molecules included in the interlayer dielectric film and
copper ions is probably dominant in the interlayer dielectric film
with low density. Specifically, the interaction between molecules
included in a polymer film is smaller in the interlayer dielectric
film with low density than in a dense interlayer dielectric film
(that is, a bulk solid). Therefore, the degeneracy of electron
orbitals between the molecules is solved, so that the molecules
included in the polymer film can behave as if they were individual
molecules also in the interlayer dielectric film. Furthermore,
copper ions drift in the interlayer dielectric film dominantly
through the interaction between the molecules and the copper ions.
Accordingly, drift paths of the copper ions are along the surfaces
of the molecules included in the interlayer dielectric film.
[0010] The present invention was devised on the basis of these
findings and utilizes the interaction between copper ions and
siloxane larger than that between copper ions and an organic
molecule.
[0011] Specifically, the first interlayer dielectric film of the
invention comprises an organic/inorganic hybrid film having a main
chain in which a first site of siloxane and a second site of an
organic molecule are alternately bonded to each other.
[0012] The second interlayer dielectric film of the invention
comprises an organic/inorganic hybrid film composed of a plurality
of first sites of siloxane and a plurality of second sites of an
organic molecule, and the plurality of first sites are bonded to
the plurality of second sites alone and the plurality of second
sites are bonded to the plurality of first sites alone.
[0013] The third interlayer dielectric film of the invention
comprises an organic/inorganic hybrid film composed of a plurality
of first sites of siloxane and a plurality of second sites of an
organic molecule, and each of the plurality of first sites is
surrounded with the plurality of second sites.
[0014] The fourth interlayer dielectric film of the invention
comprises an organic/inorganic hybrid film composed of a plurality
of first sites of siloxane and a plurality of second sites of an
organic molecule, and each of the plurality of second sites is
surrounded with the plurality of first sites.
[0015] In any of the first through fourth interlayer dielectric
films, the potential energy required for, namely, the barrier
height to be cleared by, copper ions drifting in the
organic/inorganic hybrid film from a copper film used as an
interconnect material and moving along the main chain of the
polymer included in the organic/inorganic hybrid film is much
larger than the potential energy required for, namely, the barrier
height to be cleared by, copper ions moving along the main chain of
a polymer included in a conventional interlayer dielectric film.
Therefore, the copper ions are easily trapped by the first sites of
siloxane in the interlayer dielectric film. Accordingly, the copper
ions are minimally diffused into the interlayer dielectric film. As
a result, the breakdown voltage of the interlayer dielectric film
of any of the first through fourth interlayer dielectric films is
minimally lowered even when used for a long period of time.
[0016] In any of the first through fourth interlayer dielectric
films, pores are preferably dispersed in the organic/inorganic
hybrid film.
[0017] Thus, the dielectric constant of the first, second, third or
fourth interlayer dielectric film can be lowered.
[0018] The fifth interlayer dielectric film of the invention
comprises a plurality of first sites of siloxane and a plurality of
second sites of an organic molecule, and the plurality of second
sites together form an organic polymer film and the plurality of
first sites are dispersed in the organic polymer film.
[0019] In the fifth interlayer dielectric film, the first site of
siloxane may or may not be bonded to the second site of an organic
molecule.
[0020] In the fifth interlayer dielectric film, the first sites of
siloxane are dispersed in the organic polymer film made from the
organic molecules. Therefore, copper interconnects disposed with
the interlayer dielectric film sandwiched therebetween are never
electrically connected to each other through the first sites of
siloxane. Accordingly, copper ions drifting from the copper
interconnects into the interlayer dielectric film are easily
trapped by the first sites of siloxane, and hence the copper ions
are minimally diffused into the interlayer dielectric film. As a
result, the breakdown voltage of the fifth interlayer dielectric
film is minimally lowered even when used for a long period of
time.
[0021] In the fifth interlayer dielectric film, a largest distance
between the plurality of first sites is preferably smaller than a
distance between a pair of copper interconnects disposed with the
organic polymer film sandwiched therebetween.
[0022] Thus, the copper interconnects adjacent to each other with
the interlayer dielectric film sandwiched therebetween can be
definitely prevented from being electrically connected through the
first sites of siloxane. Therefore, copper ions drifting from one
of the adjacent copper interconnects into the interlayer dielectric
film minimally pass by the vicinity of the first sites of siloxane
to reach the other copper interconnect. Accordingly, the copper
ions drifting from one copper interconnect can be prevented from
reaching the other copper interconnect, and hence, the copper
interconnects can be prevented from being electrically connected to
each other through the copper ions.
[0023] In the fifth interlayer dielectric film, pores are
preferably dispersed in the organic polymer film.
[0024] Thus, the dielectric constant of the fifth interlayer
dielectric film can be lowered.
[0025] In any of the first through fifth interlayer dielectric
films, the first site is preferably represented by the following
general formula (1): 1
[0026] wherein R.sub.1, R.sub.2 and R.sub.3 are an oxygen atom or
an organic group.
[0027] Thus, the copper ions can be definitely prevented from
passing by the vicinity of the first sites of siloxane to diffuse
into the interlayer dielectric film.
[0028] Alternatively, in any of the first through fifth interlayer
dielectric films, the first site is preferably represented by the
following general formula (2): 2
[0029] wherein R is an organic group; and R.sub.1 and R.sub.2 are
an oxygen atom or an organic group, which is selected from the
group consisting of an alkyl group, an aryl group and an aryl
group.
[0030] Thus, the copper ions can be definitely prevented from
passing by the vicinity of the first sites of siloxane to diffuise
into the interlayer dielectric film.
[0031] In any of the first through fifth interlayer dielectric
films, the second site is preferably polyimide, polyamide,
polyimidazole, polyoxazole, polyphenylene, polyarylene, polyaryl
ether, polyalkane or a fluorinated polymer of any of these
polymers.
[0032] The sixth interlayer dielectric film of the invention
comprises a multi-layer film, in which a first layer of siloxane
and a second layer of an organic molecule are alternately stacked
on each other.
[0033] In the sixth interlayer dielectric film, a lower copper
interconnect and an upper copper interconnect disposed below and on
the interlayer dielectric film are never connected to each other
through the first layer of siloxane or the second layer of the
organic molecule. Therefore, copper ions drifting from the lower or
upper copper interconnect into the interlayer dielectric film are
easily trapped by siloxane included in the first layer.
Accordingly, the copper ions are minimally diffused into the
interlayer dielectric film, and hence, the lower copper
interconnect and the upper copper interconnect can be prevented
from being electrically connected to each other through the copper
ions.
BRIEF DESCRIPTION OF THE DRAWINGS
[0034] FIG. 1 is a diagram for showing the molecular structure of
an organic/inorganic hybrid film corresponding to an interlayer
dielectric film according to Embodiment 1 of the invention;
[0035] FIG. 2 is a conceptual diagram for showing the molecular
structure of the organic/inorganic hybrid film corresponding to the
interlayer dielectric film of Embodiment 1;
[0036] FIG. 3 is a diagram for roughly showing the molecular
structure of a region A of FIG. 2;
[0037] FIG. 4 is a schematic diagram for showing the molecular
structure of the region A of FIG. 2;
[0038] FIG. 5 is a diagram for three-dimensionally showing a bond
between a first site composed of siloxane and a second site
composed of an organic molecule in the organic/inorganic hybrid
film of Embodiment 1;
[0039] FIG. 6 is a diagram for two-dimensionally showing the bond
between the first site composed of siloxane and the second site
composed of the organic molecule in the organic/inorganic hybrid
film of Embodiment 1;
[0040] FIG. 7(a) is a characteristic diagram for showing the
relationship between a coordinate axis corresponding to a distance
from the center of the main chain of a polymer included in the
organic/inorganic hybrid film of Embodiment 1 and the potential
energy required for movement of a copper ion and FIG. 7(b) is a
schematic diagram of the main chain of the polymer of the
organic/inorganic hybrid film of Embodiment 1;
[0041] FIG. 8(a) is a characteristic diagram for showing the
relationship between a coordinate axis corresponding to a distance
from the center of the main chain of a polymer included in a
conventional organic polymer film and the potential energy required
for movement of a copper ion and FIG. 8(b) is a schematic diagram
of the main chain of the polymer of the conventional organic
polymer film;
[0042] FIG. 9(a) is a characteristic diagram for showing the
relationship between a coordinate axis corresponding to a distance
from the center of the main chain of a polymer included in a
conventional ladder type siloxane film and the potential energy
required for movement of a copper ion and FIG. 9(b) is a schematic
diagram of the main chain of the polymer of the conventional ladder
type siloxane film;
[0043] FIG. 10 is a characteristic diagram for showing the height
of a barrier and the drift rate of copper ions in the
organic/inorganic hybrid film of Embodiment 1, the conventional
organic polymer film and the conventional siloxane film;
[0044] FIGS. 11(a), 11(b) and 11(c) are diagrams for showing
chemical reactions occurring in forming the organic/inorganic
hybrid film of Embodiment 1;
[0045] FIG. 12 is a cross-sectional view of an interlayer
dielectric film according to Embodiment 2 of the invention;
[0046] FIG. 13 is a cross-sectional view of an interlayer
dielectric film according to Embodiment 3 of the invention; and
[0047] FIG. 14 is a diagram of general formula representing the
chemical structure of conventional organic siloxane.
DETAILED DESCRIPTION OF THE INVENTION
[0048] Embodiment 1
[0049] An interlayer dielectric film and a method for forming the
same according to Embodiment 1 of the invention will now be
described with reference to the accompanying drawings.
[0050] FIG. 1 shows the molecular structure of an organic/inorganic
hybrid film corresponding to the interlayer dielectric film of
Embodiment 1. In FIG. 1, a indicates a first site composed of
siloxane, b indicates a second site composed of an organic molecule
and c indicates a free volume.
[0051] FIG. 2 is a conceptual diagram for showing the molecular
structure of the organic/inorganic hybrid film corresponding to the
interlayer dielectric film of Embodiment 1.
[0052] FIG. 3 roughly shows the molecular structure of a region A
of FIG. 2, wherein a indicates the first site composed of siloxane,
b indicates the second site composed of the organic molecule and c
indicates the free volume.
[0053] FIG. 4 schematically shows the molecular structure of the
region A of FIG. 2.
[0054] FIG. 5 three-dimensionally shows a bond between the first
site a composed of siloxane and the second site b composed of the
organic molecule in the organic/inorganic hybrid film of Embodiment
1.
[0055] FIG. 6 two-dimensionally shows the bond between the first
site a composed of siloxane and the second site b composed of the
organic molecule in the organic/inorganic hybrid film of Embodiment
1.
[0056] As shown in FIGS. 1, 3, 5 and 6, the organic/inorganic
hybrid film of Embodiment 1 includes a plurality of first site a
each composed of siloxane, a plurality of second sites b each
composed of the organic molecule and a plurality of third sites c
disposed dispersedly.
[0057] As a first characteristic of the organic/inorganic hybrid
film of Embodiment 1, the first sites a each composed of siloxane
and the second sites b each composed of the organic molecule
together forming a main chain are alternately bonded to each other.
As a second characteristic, the first site a is bonded to the
second site b alone and the second site b is bonded to the first
site a alone. As a third characteristic, each of the first sites a
is surrounded with the plural second sites b. As a fourth
characteristic, each of the second sites b is surrounded with the
plural first sites a.
[0058] Although the first sites a and the second sites b are
alternately bonded to each other in FIGS. 1, 3, 5 and 6, the first
sites a and the second sites b may not be bonded to each other. In
other words, the organic/inorganic hybrid film of Embodiment 1 may
have the third or fourth characteristic without having the first
and second characteristics.
[0059] FIG. 7(a) shows the relationship between the coordinate axis
(x-axis) corresponding to a distance from the center of the main
chain of a polymer included in the organic/inorganic hybrid film of
Embodiment 1 and the potential energy required for a copper ion to
move along the main chain. FIG. 7(b) is a schematic diagram of the
main chain of the polymer included in the organic/inorganic hybrid
film of Embodiment 1. As is understood from FIGS. 7(a) and 7(b),
the potential energy required for a copper ion to move from the
vicinity of an oxygen atom (O) of siloxane (i.e., the first site a)
to the vicinity of a carbon atom (C) of the organic molecule (i.e.,
the second site b) is very high and is specifically approximately 3
kcal/mol. In other words, a barrier to be cleared by the copper ion
in moving from the first site a to the second site b is very high.
Therefore, the copper ion drifting in the organic/inorganic hybrid
film is easily trapped by the first site a.
[0060] FIG. 8(a) shows the relationship between the coordinate axis
(x-axis) corresponding to a distance from the center of the main
chain of a polymer included in a conventional organic polymer film
and the potential energy required for a copper ion to move along
the main chain. FIG. 8(b) is a schematic diagram of the main chain
of the polymer included in the organic polymer film. As is
understood from FIGS. 8(a) and 8(b), the potential energy required
for a copper ion to move from the vicinity of one carbon atom (C)
included in the organic polymer to the vicinity of another carbon
atom (C) is low and is specifically approximately 1.3 kcal/mol.
Therefore, the copper ion drifting in the organic polymer film is
minimally trapped.
[0061] FIG. 9(a) shows the relationship between the coordinate axis
(x-axis) corresponding to a distance from the center of the main
chain of a polymer included in a conventional ladder type siloxane
film and the potential energy required for a copper ion to move
along the main chain. FIG. 9(b) is a schematic diagram of the main
chain of the polymer included in the ladder type siloxane film. As
is understood from FIGS. 9(a) and 9(b), the potential energy
required for a copper ion to move from the vicinity of an oxygen
atom (O) of siloxane to the vicinity of silicon (Si) is low and is
specifically approximately 0.5 kcal/mol. Therefore, the copper ion
drifting in the ladder type siloxane film is minimally trapped.
[0062] In FIG. 9(b), when a hydrogen atom bonded to a Si atom is
replaced with an organic group, the film is an organic siloxane
film. Also in the organic siloxane film, the potential energy
required for a copper ion to move from the vicinity of an oxygen
atom (O) of siloxane to the vicinity of silicon (Si) is the same as
that shown in FIG. 9(b). Therefore, the copper ion drifting in the
organic siloxane film is minimally trapped.
[0063] FIG. 10 shows the barrier height and the drift rate of
copper ions in the organic/inorganic hybrid film of Embodiment 1
shown in FIG. 7(b), the conventional organic polymer film shown in
FIG. 8(b) and the conventional siloxane film shown in FIG. 9(b). In
the organic polymer film, the data obtained in the experiment are
varied. As is understood from FIG. 10, the barrier height for
copper ions is large and the drift rate is low in the
organic/inorganic hybrid film of Embodiment 1.
[0064] As is understood from the above description, the potential
energy required for, namely, the barrier height to be cleared by, a
copper ion moving along the main chain of the polymer included in
the organic/inorganic hybrid film of Embodiment 1 is much higher
than the potential energy required for, namely, the barrier height
to be cleared by, a copper ion moving along the main chain of the
organic polymer or the ladder type siloxane. Therefore, the copper
ions are easily trapped and difficult to drift in the
organic/inorganic hybrid film of Embodiment 1. Accordingly, copper
(copper ions) used as the material for interconnects is minimally
diffused into the interlayer dielectric film of Embodiment 1. As a
result, the breakdown voltage of the interlayer dielectric film is
minimally lowered even when used for a long period of time.
[0065] Now, a method for forming the organic/inorganic hybrid film
of Embodiment 1 will be described with reference to FIGS. 11(a)
through 11(c).
[0066] First, 1,6-(bistrichlorosilyl)hexane (a trichlorosilane
derivative; a first silane derivative) shown on the left hand side
of FIG. 11(a) and methyltrichlorosilane (a second silane derivate)
shown on the right hand side of FIG. 11(a) are hydrolyzed in a
ratio of 1:1 in an alcohol solution, so as to obtain two silanols
as shown in FIG. 11(b).
[0067] Next, the two silanols are polymerized through a dehydration
condensation reaction, so as to give a silanol condensate as shown
in FIG. 11(c).
[0068] Then, a solution including the silanol condensate of FIG.
11(c) is applied on a semiconductor substrate by spin coating and
the resultant substrate is annealed. In this manner, the interlayer
dielectric film of the organic/inorganic hybrid film having the
structure as shown in FIG. 1 in which methylsilsesquioxanes in a
cage structure (i.e., the first sites a) are bonded via methylene
of hexane (i.e., the second site b) in a network structure is
formed.
[0069] Although the trichlorosilane derivative is used as the first
silane derivative in the above-described method for forming the
interlayer dielectric film of Embodiment 1, a trialkoxysilane
derivative may be used instead.
[0070] Also, although the silane derivative in which silicon atoms
are crosslinked via hexane including six methylene groups is used
as the second silane derivative, the number of methylene groups is
not specified. Also, an organic molecule other than the methylene
groups, such as phenylene, may be used as the crosslinking
molecule.
[0071] Furthermore, any siloxane represented by the following
general formula (1) may be widely used as the first site a included
in the organic/inorganic hybrid film of Embodiment 1: 3
[0072] wherein R.sub.1, R.sub.2 and R.sub.3 are an oxygen atom or
an organic group.
[0073] Alternatively, any siloxane represented by the following
general formula (2) may be widely used as the first site a included
in the organic/inorganic hybrid film of Embodiment 1: 4
[0074] wherein R is an organic group; and R.sub.1 and R.sub.2 are
an oxygen atom or an organic group, which is selected from the
group consisting of an alkyl group, an aryl group and an aryl
group.
[0075] Moreover, polyimide, polyamide, polyimidazole, polyoxazole,
polyphenylene, polyarylene, polyaryl ether, polyalkane or a
fluorinated polymer of any of these polymers may be widely used as
the second site b included in the organic/inorganic hybrid film of
Embodiment 1.
[0076] Embodiment 2
[0077] An interlayer dielectric film and a method for forming the
same according to Embodiment 2 of the invention will now be
described with reference to the accompanying drawing.
[0078] The interlayer dielectric film of Embodiment 2 includes a
plurality of first sites a each composed of siloxane and a
plurality of second sites b each composed of an organic molecule.
The plural second sites b together form an organic polymer film, in
which the plural first sites a and a plurality of holes c are
dispersed. In this case, the first site a composed of siloxane may
be or may not be bonded to the second site b composed of the
organic molecule.
[0079] FIG. 12 shows the cross-sectional structure of the
interlayer dielectric film of Embodiment 2. As shown in FIG. 12, in
the interlayer dielectric film formed on a semiconductor substrate
10, a plurality of silica fine particles 12 each corresponding to
the first site a and a plurality of holes 13 are dispersed in an
organic polymer film 11 formed from the plural second sites b.
[0080] Since the silica fine particles 12 of siloxane are dispersed
in the organic polymer film 11 of the organic molecules in the
interlayer dielectric film of Embodiment 2, copper interconnects 14
adjacent to each other are never connected through the silica fine
particles 12 of siloxane. Therefore, copper ions drifting in the
organic polymer film 11 from the copper interconnect 14 are trapped
by the first sites a of siloxane and hence are minimally diffused
into the organic polymer film 11. Accordingly, the copper
interconnects 14 adjacent to each other can be prevented from being
electrically connected through the copper ions.
[0081] In this case, the largest distance between the first sites a
of siloxane forming the silica fine particles 12 is preferably
smaller than the distance between the copper interconnects 14
adjacent to each other. Thus, the copper interconnects 14 adjacent
to each other can be definitely prevented from being electrically
connected through the first sites a of siloxane, and therefore,
copper ions drifting in the organic polymer film 11 from one copper
interconnect 14 can never pass by the vicinity of the first sites a
of siloxane to reach the other adjacent copper interconnect 14.
Accordingly, the copper ions drifting from one copper interconnect
14 can be prevented from reaching the other copper interconnect 14,
and hence, the dielectric property of the interlayer dielectric
film is never degraded.
[0082] Now, the method for forming the interlayer dielectric film
of Embodiment 2 will be described.
[0083] Silica fine particles with an average particle size of 10 nm
are dispersed in, for example, a polymer solution of the polyalyl
ether family. Then, the solution in which the silica fine particles
are dispersed is applied on a semiconductor substrate by spin
coating, and the resultant semiconductor substrate is annealed. In
this manner, the interlayer dielectric film as shown in FIG. 12 in
which the plural silica fine particles 12 and the plural holes 13
are dispersed in the organic polymer film 11 formed from the plural
second sites b can be obtained.
[0084] Although the polymer solution of the polyalyl ether family
in which the silica fine particles are dispersed is used for
forming the interlayer dielectric film in Embodiment 2, the
interlayer dielectric film may be formed by using a solution
including a silanol condensate obtained through hydrolysis and
dehydration condensation of 1,6-(bistrichlorosily)hexane (first
silane derivative) and methyltrichlorosilane as in Embodiment
1.
[0085] As the first site a included in the organic/inorganic hybrid
film of Embodiment 2, any siloxane represented by the
above-described general formula (1) or (2) may be widely used. As
the second site b, polyimide, polyamide, polyimidazole,
polyoxazole, polyphenylene, polyarylene, polyaryl ether, polyalkane
or a fluorinated polymer of any of these polymers may be widely
used.
[0086] Embodiment 3
[0087] An interlayer dielectric film according to Embodiment 3 of
the invention will now be described with reference to the
accompanying drawing.
[0088] FIG. 13 shows the cross-sectional structure of the
interlayer dielectric film of Embodiment 3. As shown in FIG. 13, a
lower interlayer dielectric film 21 and an upper interlayer
dielectric film 22 are successively formed on a semiconductor
substrate 20. A lower copper interconnect 23 is buried in the lower
interlayer dielectric film 21, and an upper copper interconnect 24
is buried in the upper interlayer dielectric film 22.
[0089] As shown in FIG. 13, each of the lower and upper interlayer
dielectric films 21 and 22 is made from a multi-layer film composed
of a first layer d of siloxane and a second layer e of an organic
molecule alternately stacked.
[0090] Since the first layer d of siloxane and the second layer e
of the organic molecule are alternately stacked in the interlayer
dielectric film of Embodiment 3, the lower copper interconnect 23
and the upper copper interconnect 24 are never electrically
connected to each other through the first layer d of siloxane and
the second layer e of the organic molecule. Therefore, copper ions
drifting from the lower or upper copper interconnect 23 or 24 into
the upper interlayer dielectric film 22 are trapped by siloxane
included in the first layer d and hence are minimally diffused into
the upper interlayer dielectric film 22. Accordingly, the lower
copper interconnect 23 and the upper copper interconnect 24 can be
prevented from being electrically connected to each other through
the copper ions.
* * * * *