U.S. patent application number 12/986531 was filed with the patent office on 2011-05-05 for sicoh dielectric material with improved toughness and improved si-c bonding, semiconductor device containing the same, and method to make the same.
This patent application is currently assigned to INTERNATIONAL BUSINESS MACHINES CORPORATION. Invention is credited to Daniel C. Edelstein, Stephen M. Gates, Alfred Grill, Michael Lane, Robert D. Miller, Deborah A. Neumayer, Son Van Nguyen.
Application Number | 20110101489 12/986531 |
Document ID | / |
Family ID | 36021759 |
Filed Date | 2011-05-05 |
United States Patent
Application |
20110101489 |
Kind Code |
A1 |
Edelstein; Daniel C. ; et
al. |
May 5, 2011 |
SiCOH DIELECTRIC MATERIAL WITH IMPROVED TOUGHNESS AND IMPROVED Si-C
BONDING, SEMICONDUCTOR DEVICE CONTAINING THE SAME, AND METHOD TO
MAKE THE SAME
Abstract
A low-k dielectric material with increased cohesive strength for
use in electronic structures including interconnect and sensing
structures is provided that includes atoms of Si, C, O, and H in
which a fraction of the C atoms are bonded as Si--CH.sub.3
functional groups, and another fraction of the C atoms are bonded
as Si--R--Si, wherein R is phenyl, --[CH.sub.2].sub.n-- where n is
greater than or equal to 1, HC.dbd.CH, C.dbd.CH.sub.2, C.ident.C or
a [S].sub.n linkage, where n is a defined above.
Inventors: |
Edelstein; Daniel C.; (White
Plains, NY) ; Gates; Stephen M.; (Ossining, NY)
; Grill; Alfred; (White Plains, NY) ; Lane;
Michael; (Glade Spring, VA) ; Miller; Robert D.;
(San Jose, CA) ; Neumayer; Deborah A.; (Danbury,
CT) ; Nguyen; Son Van; (Yorktown Heights,
NY) |
Assignee: |
INTERNATIONAL BUSINESS MACHINES
CORPORATION
Armonk
NY
|
Family ID: |
36021759 |
Appl. No.: |
12/986531 |
Filed: |
January 7, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11040778 |
Jan 21, 2005 |
7892648 |
|
|
12986531 |
|
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Current U.S.
Class: |
257/506 ;
257/E23.142 |
Current CPC
Class: |
Y10T 428/31663 20150401;
H01L 31/103 20130101 |
Class at
Publication: |
257/506 ;
257/E23.142 |
International
Class: |
H01L 23/522 20060101
H01L023/522 |
Claims
1. An interconnect structure located on a substrate comprising at
least one dielectric material comprising at least atoms of Si, C,
O, H, and having a covalently bonded tri-dimensional network
structure in which a fraction of the C atoms are bonded as
Si--CH.sub.3 functional groups, and another fraction of the C atoms
are bonded as Si--R--Si, wherein R is phenyl, --[CH.sub.2].sub.n--
where n is greater than or equal to 1, HC.dbd.CH, C.dbd.CH.sub.2,
C.ident.C or a [S].sub.n linkage, where n is a defined above.
2. The interconnect structure of claim 1 wherein said dielectric
material further comprises at least one of F, N, or Ge.
3. The interconnect structure of claim 1 wherein the fraction of
the total carbon atoms in the material that is bonded as Si--R--Si
is between 0.01 and 0.99.
4. The interconnect structure of claim 1 wherein said material is
porous or dense has a cohesive strength greater than about 6
J/m.sup.2 and a dielectric constant less than about 3.2.
5. The interconnect structure of claim 1 wherein said material is
porous or dense and has a cohesive strength greater than about 3
J/m.sup.2 and a dielectric constant less than about 2.5.
6. The interconnect structure of claim 1 wherein said material is
dense or porous and has a cohesive strength greater than about 3
J/m.sup.2 at a water pressure of 1570 Pa at 25.degree. C. and a
dielectric constant less than about 3.2.
7. The interconnect structure of claim 1 wherein said material is
dense or porous and has a cohesive strength greater than about 2.1
J/m.sup.2 at a water pressure of 1570 Pa at 25.degree. C. and a
dielectric constant less than about 2.5.
8. The interconnect structure of claim 1 wherein the material has a
cohesive strength that lies in the shaded region of FIG. 2A or
2B.
9. An electronic structure containing at least two metallic
conductor elements and an insulator dielectric wherein said
dielectric is comprised of at least atoms Si, C, O, H and having a
covalently bonded tri-dimensional network structure in which a
fraction of the C atoms are bonded as Si--CH.sub.3 functional
groups, and another fraction of the C atoms are bonded as
Si--R--Si, wherein R is phenyl, --[CH.sub.2].sub.n-- where n is
greater than or equal to 1, HC.dbd.CH, C.dbd.CH.sub.2, C.ident.C or
a [S].sub.n linkage, where n is a defined above.
10. The electronic structure of claim 9 wherein the at least two
metal conductor elements are patterned in a shape required for a
function of a passive or active circuit element.
11. The electronic structure of claim 10 wherein said passive or
active circuit element comprises one of an inductor, a resistor, a
capacitor, or a resonator.
12. An electronic sensing structure surrounded by a layer of
insulator dielectric wherein said dielectric is comprised of at
least atoms of Si, C, O, H and having a covalently bonded
tri-dimensional network structure in which a fraction of the C
atoms are bonded as Si--CH.sub.3 functional groups, and another
fraction of the C atoms are bonded as Si--R--Si, wherein R is
phenyl, --[CH.sub.2].sub.n-- where n is greater than or equal to 1,
HC.dbd.CH, C.dbd.CH.sub.2, C.ident.C or a [S].sub.n linkage, where
n is a defined above.
Description
RELATED APPLICATIONS
[0001] This application is a divisional of U.S. application Ser.
No. 11/040,778 filed Jan. 21, 2005. The present application is
related to co-assigned U.S. Pat. Nos. 6,147,009, 6,312,793,
6,437,443, 6,441,491, 6,541,398, 6,479,110, and 6,497,963, the
contents of which are incorporated herein by reference. The present
application is also related to co-pending and co-assigned U.S.
patent application Ser. Nos. 10/174,749, filed Jun. 19, 2002, now
U.S. Pat. No. 6,768,200, U.S. patent application Ser. No.
10/340,000, filed Jan. 23, 2003, now U.S. Pat. No. 6,770,573 and
U.S. patent application Ser. No. 10/390,801, filed Mar. 18, 2003,
the entire contents of each of the aforementioned U.S. patent
applications are also incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention generally relates to a class of
dielectric materials comprising Si, C, O and H atoms (SiCOH) that
have a low dielectric constant (k), and methods for fabricating
films of these materials and electronic devices containing such
films. Such materials are also called C doped oxide (CDO) or
organosilicate glass (OSG). The material of the present invention
exhibits improved cohesive strength (or equivalently, improved
fracture toughness or reduced brittleness), and increased
resistance to water degradation of properties such as
stress-corrosion cracking, Cu ingress, and other critical
properties. The present invention includes methods to make the
inventive material, and relates to the use of said dielectric
material as an intralevel or interlevel dielectric film, a
dielectric cap or a hard mask/polish stop in back end of the line
(BEOL) interconnect structures on ultra-large scale integrated
(ULSI) circuits and related electronic structures. The present
invention also relates to the use of the inventive dielectric
material in an electronic device containing at least two conductors
or an electronic sensing structure.
BACKGROUND OF THE INVENTION
[0003] The continuous shrinking in dimensions of electronic devices
utilized in ULSI circuits in recent years has resulted in
increasing the resistance of the BEOL metallization as well as
increasing the capacitance of the intralayer and interlayer
dielectric. This combined effect increases signal delays in ULSI
electronic devices. In order to improve the switching performance
of future ULSI circuits, low dielectric constant (k) insulators and
particularly those with k significantly lower than silicon oxide
are needed to reduce the capacitances.
[0004] Most of the fabrication steps of
very-large-scale-integration ("VLSI") and ULSI chips are carried
out by plasma enhanced chemical or physical vapor deposition
techniques. The ability to fabricate a low k material by a plasma
enhanced chemical vapor deposition (PECVD) technique using
previously installed and available processing equipment will thus
simplify its integration in the manufacturing process, reduce
manufacturing cost, and create less hazardous waste. U.S. Pat. Nos.
6,147,009 and 6,497,963 assigned to the common assignee of the
present invention, which are incorporated herein by reference in
their entirety, describe a low dielectric constant material
consisting of elements of Si, C, O and H atoms having a dielectric
constant not more than 3.6 and which exhibits very low crack
propagation velocities.
[0005] U.S. Pat. Nos. 6,312,793, 6,441,491 and 6,479,110 B2,
assigned to the common assignee of the present invention and
incorporated herein by reference in their entirety, describe a
multiphase low k dielectric material that consists of a matrix
composed of elements of Si, C, O and H atoms, a phase composed
mainly of C and H and having a dielectric constant of not more than
3.2.
[0006] Ultra low k dielectric materials having a dielectric
constant of less than 2.7 (and preferably less than 2.3) are also
known in the art. Key problems with prior art ultra low k SiCOH
films include, for example: (a) they are brittle (i.e., low
cohesive strength, low elongation to break, low fracture
toughness); (b) liquid water and water vapor reduce the cohesive
strength of the material even further. A plot of the cohesive
strength, CS vs. pressure of water, P.sub.H2O or % humidity, which
is referred as a "CS humidity plot", has a characteristic slope for
each k value and material; (c) they tend to possess a tensile
stress in combination with low fracture toughness, and hence can
tend to crack when in contact with water when the film is above
some critical thickness; (d) they can absorb water and other
process chemicals when porous, which in turn can lead to enhanced
Cu electrochemical corrosion under electric fields, and ingress
into the porous dielectric leading to electrical leakage and high
conductivity between conductors; and (e) when C is bound as
Si--CH.sub.3 groups, prior art SiCOH dielectrics readily react with
resist strip plasmas, CMP processes, and other integration
processes, causing the SiCOH dielectric to be "damaged" resulting
in a more hydrophilic surface layer.
[0007] For example, the silicate and organosilicate glasses tend to
fall on a universal curve of cohesive strength vs. dielectric
constant as shown in FIG. 1. This figure includes conventional
oxides (point A), conventional SiCOH dielectrics (point B),
conventional k=2.6 SiCOH dielectrics (point C), and conventional
CVD ultra low k dielectrics with k about 2.2 (point D). The fact
that both quantities are predominantly determined by the volume
density of Si--O bonds explains the proportional variation between
them. It also suggests that OSG materials with ultra low dielectric
constants (e.g., k<2.4) are fundamentally limited to having
cohesive strengths about 3 J/m.sup.2 or less in a totally dry
environment. Cohesive strength is further reduced as the humidity
increases.
[0008] Another problem with prior art SiCOH films is that their
strength tends to be degraded by H.sub.2O. The effects of H.sub.2O
degradation on prior art SiCOH films can be measured using a
4-point bend technique as described, for example, in M. W. Lane, X.
H. Liu, T. M. Shaw, "Environmental Effects on Cracking and
Delamination of Dielectric Films", IEEE Transactions on Device and
Materials Reliability, 4, 2004, pp. 142-147. FIG. 2A is taken from
this reference, and is a plot illustrating the effects that
H.sub.2O has on the strength of a typical SiCOH film having a
dielectric constant, k of about 2.9. The data are measured by the
4-point bend technique in a chamber in which the pressure of water
(P.sub.H2O) is controlled and changed. Specifically, FIG. 2A shows
the cohesive strength plotted vs. natural log (ln) of the H.sub.2O
pressure in the controlled chamber. The slope of this plot is
approximately -1 in the units used. Increasing the pressure of
H.sub.2O decreases the cohesive strength. The region above the line
in FIG. 2A, which is shaded, represents an area of cohesive
strength that is difficult to achieve with prior art SiCOH
dielectrics.
[0009] FIG. 2B is also taken from the M. W. Lane reference cited
above, and is similar to FIG. 2A. Specifically, FIG. 2B is a plot
of the cohesive strength of another SiCOH film measured using the
same procedure as FIG. 2A. The prior art SiCOH film has a
dielectric constant of 2.6 and the slope of this plot is about
-0.66 in the units used. The region above the line in FIG. 2B,
which is shaded, represents an area of cohesive strength that is
difficult to achieve with prior art SiCOH dielectrics.
[0010] It is known that Si--C bonds are less polar than Si--O
bonds. Further, it is known that organic polymer dielectrics have a
fracture toughness higher than organosilicate glasses and are not
prone to stress corrosion cracking (as are the Si--O based
dielectrics). This suggests that the addition of more organic
polymer content and more Si--C bonds to SiCOH dielectrics can
decrease the effects of water degradation described above and
increase the nonlinear energy dissipation mechanisms such as
plasticity. Addition of more organic polymer content to SiCOH will
lead to a dielectric with increased fracture toughness and
decreased environmental sensitivity.
[0011] It is known in other fields that mechanical properties of
some materials, for example, organic elastomers, can be improved by
certain crosslinking reactions involving added chemical species to
induce and form crosslinked chemical bonds. This can increase the
elastic modulus, glass transition temperature, and cohesive
strength of the material, as well as, in some cases, the resistance
to oxidation, resistance to water uptake, and related degradations.
These crosslinked bonds can be folded, such that under tensile
stress they can support some amount of elongation of the molecular
backbone without breaking, effectively increasing the fracture
toughness of the material. One most famous example is the
"vulcanization" of natural and synthetic rubber by the addition of
sulfur or peroxide and curing, as invented by Charles Goodyear and
independently by Thomas Hancock. When sulfur or peroxide are added
to gum rubber, often with an aniline or other accelerator agent,
and then the material is cured under heat and pressure, the sulfur
forms folded or slanted polymer crosslinks between the polymer
strands, binding them together elastically. The result is a greatly
strengthened material with increased cohesive strength, and high
resistance to moisture and other chemistries. Vulcanization has
essentially enabled the ubiquitous use of rubber in many worldwide
applications and industries.
[0012] In view of the above drawbacks with prior art low and ultra
low k SiCOH dielectrics, there exists a need for developing a class
of SiCOH dielectrics, both porous and dense, having a dielectric
constant value of about 3.2 or less with a significantly increased
cohesive strength vs. k curve that lies above the universal curve
defined in FIG. 1 For the particular case in FIG. 1, the fracture
toughness and the cohesive strength are equivalent. There further
exists a need for developing a class of SiCOH dielectrics, both
porous and dense, with specific forms of C bonding, possibly
including Si--S, S--S and S--CH bonding, with greater organic
character, increased resistance to water, particularly within the
shaded regions of FIGS. 2A and 2B, and favorable mechanical
properties that allow for such films to be used in new applications
in ULSI devices.
SUMMARY OF THE INVENTION
[0013] One object of the present invention is to provide a low or
ultra low k dielectric constant material comprising atoms of Si, C,
O and H (hereinafter "SiCOH") having a dielectric constant of not
more than 3.2, and having increased cohesive strength of not less
than about 6 J/m.sup.2, and preferably not less than about 7
J/m.sup.2, as measured by channel cracking or a sandwiched 4 point
bend fracture mechanics test.
[0014] It is yet another object of the present invention to provide
a SiCOH dielectric having a covalently bonded tri-dimensional
network structure, which includes C bonded as Si--CH.sub.3 and also
C bonded as Si--R--Si, wherein R is phenyl (i.e.,
--C.sub.6H.sub.4--), --[CH.sub.2].sub.n-- where n is greater than
or equal to 1, HC.dbd.CH (i.e., a double bond), C.dbd.CH.sub.2,
C.ident.C (i.e., a triple bond), or a [S].sub.n linkage, where n is
as defined above. In one preferred embodiment, the SiCOH dielectric
includes Si-[CH.sub.2].sub.n--Si wherein n is 1 or 3.
[0015] It is yet another object of the present invention to provide
a SiCOH dielectric material in which the fraction of C atoms bonded
as Si--CH.sub.2--Si (as detected by solid state NMR and by FTIR) is
larger than in prior art SiCOH dielectrics.
[0016] It is another object of the present invention to provide a
SiCOH dielectric material having a dielectric constant of not more
than 3.2, which has a plot of CS vs. % humidity that shows a weak
dependence on humidity. That is, at a given dielectric constant,
the SiCOH dielectric materials of this invention have a smaller
slope than the plots shown in FIGS. 2A and 2B, and the cohesive
strength at a specific value of P.sub.H2O therefore lies above the
line in FIG. 2A or 2B, in the shaded regions. By "weak dependence"
it is meant that the inventive SiCOH dielectrics have a lower slope
in the plot than prior art materials. Within the invention, this is
achieved by decreasing the number of reactive sites (Si--O--Si).
The slope of the CS vs ln P.sub.H2O curves is determined by the
density of reactive Si--O--Si sites. While decreasing the number of
Si--O--Si sites decreases the sensitivity to moisture, it also
decreases the cohesive strength which depends linearly on the
Si--O--Si bond density. However, the dielectric material of this
invention overcomes this initial drop in cohesive strength (due to
decreased Si--O--Si bond density), by incorporating Si--C type
bonding, as described above, which may or may not exhibit nonlinear
deformation behavior that further increases the mechanical strength
of the material. The net result is a dielectric with cohesive
strength in a dry ambient that is at least equal, but preferably,
greater than an Si--O based dielectric with the same dielectric
constant, and the inventive dielectric material has significantly
reduced environmental sensitivity.
[0017] It is another object of the present invention to provide a
SiCOH dielectric material having a dielectric constant of not more
than 3.2, which is very stable towards H.sub.2O vapor (humidity)
exposure, including a resistance to crack formation in water.
[0018] It is still another object of the present invention to
provide an electronic structure incorporating the inventive SiCOH
material as an intralevel and or interlevel dielectric in a BEOL
wiring structure.
[0019] It is another object of the present invention to provide
PECVD methods for depositing and appropriate methods for curing the
inventive SiCOH dielectric material.
[0020] It is another object of the present invention to provide
further electronic structures (such as circuit boards or passive
analogue devices) in which the inventive SiCOH dielectric material
is used.
[0021] In broad terms, the present invention provides a dielectric
material comprised of Si, C, O, and H in which a fraction of the C
atoms are bonded as Si--CH.sub.3 functional groups, and another
fraction of the C atoms are bonded as Si--R--Si, wherein R is
phenyl (i.e., C.sub.6H.sub.4), --[CH.sub.2].sub.n-- where n is
greater than or equal to 1, HC.dbd.CH (i.e., a double bond),
C.dbd.CH.sub.2, C.ident.C (i.e., a triple bond) or a [S].sub.n
linkage, where n is a defined above. In accordance with the present
invention, the fraction of the total carbon atoms in the material
that is bonded as Si--R--Si is typically between 0.01 and 0.99, as
determined by solid state NMR. In one preferred embodiment, the
SiCOH dielectric includes Si--[CH.sub.2].sub.n--Si wherein n is 1
or 3.
[0022] In a first embodiment of the present invention, a stable
ultra low k SiCOH dielectric material is provided that has a
dielectric constant of 3.0, a tensile stress of 30 MPa or less, an
elastic modulus greater than 15 GPa, a cohesive strength
significantly greater than 6 J/m.sup.2, such as from about 6 to
about 12 J/m.sup.2, a crack development velocity in water of not
more than 1.times.10.sup.-10 m/sec for a film thickness of 3
microns, and a fraction of the C atoms are bonded in the functional
group Si--CH.sub.2--Si, wherein said methylene, CH.sub.2 carbon
fraction is from about 0.05 to about 0.5, as measured by C solid
state NMR.
[0023] In a second embodiment of the present invention, a stable
ultra low k SiCOH dielectric material is provided that has a
dielectric constant of less than about 2.5, a tensile stress less
than about 40 MPa, an elastic modulus greater than about 5 GPa, a
cohesive strength greater than about 3 to about 6 J/m.sup.2, a
crack development velocity in water of not more than
1.times.10.sup.-10 m/sec for a film thickness of 3 microns, and a
fraction of the C atoms are bonded in the functional group
Si--CH.sub.2--Si wherein the carbon fraction is from about to 0.05
to about 0.5, as measured by C solid state NMR.
[0024] In alternative embodiments of the present invention, there
is carbon bonded as Si--CH.sub.3 and also carbon bonded as
Si--R--Si, where R can be different organic groups.
[0025] In all embodiments of the inventive material, improved C--Si
bonding is a feature of the materials compared to the Si--CH.sub.3
bonding characteristic of prior art SiCOH and pSiCOH
dielectrics.
[0026] In alternative embodiments of the present invention, there
may be C--S, Si--S, and optionally S--S bonding.
[0027] In addition to the aforementioned properties, the inventive
dielectric materials of the present invention are hydrophobic with
a water contact angle of greater than 70.degree., more preferably
greater than 80.degree., and exhibit a cohesive strength in shaded
regions of FIGS. 2A and 2B. The equation for the line shown in FIG.
2A is .gamma.(J/m.sup.2)=-1.094 J/m.sup.2*X+10.97 J/m.sup.2 where X
is ln of P.sub.H2O with P being in Pa. The equation for the line
shown in FIG. 2B is .gamma.(J/m.sup.2)=-0.662 J/m.sup.2*X+6.759
J/m.sup.2 where X is ln of P.sub.H2O with P being in Pa.
[0028] The present invention also relates to electronic structures,
in which the SiCOH dielectric material of the present invention may
be used as the interlevel or intralevel dielectric, a capping
layer, and/or as a hard mask/polish-stop layer in electronic
structures.
[0029] Specifically, the electronic structures of the present
invention includes a pre-processed semiconducting substrate that
has a first region of metal embedded in a first layer of insulating
material, a first region of conductor embedded in a second layer of
insulating material, the second layer of insulating material being
in intimate contact with the first layer of insulating material,
the first region of conductor being in electrical communication
with the first region of metal, and a second region of conductor
being in electrical communication with the first region of
conductor and being embedded in a third layer of insulating
material, the third layer of insulating material being in intimate
contact with the second layer of insulating material.
[0030] In the above structure, each of the insulating layers can
comprise the inventive low or ultra low k SiCOH dielectric material
with improved C bonding of the present invention.
[0031] The electronic structure may further include a dielectric
cap layer situated in-between the first layer of insulating
material and the second layer of insulating material, and may
further include a dielectric cap layer situated in-between the
second layer of insulating material and the third layer of
insulating material. The electronic structure may further include a
first dielectric cap layer between the second layer of insulating
material and the third layer of insulating material, and a second
dielectric cap layer on top of the third layer of insulating
material.
[0032] In some embodiments, the dielectric cap itself can comprise
the inventive low or ultra low k SiCOH dielectric material.
[0033] The electronic structure may further include a diffusion
barrier layer of a dielectric material deposited on at least one of
the second and third layer of insulating material. The electronic
structure may further include a dielectric layer on top of the
second layer of insulating material for use as a RIE hard
mask/polish-stop layer and a dielectric diffusion barrier layer on
top of the dielectric RIE hard mask/polish-stop layer. The
electronic structure may further include a first dielectric RIE
hard mask/polish-stop layer on top of the second layer of
insulating material, a first dielectric RIE diffusion barrier layer
on top of the first dielectric polish-stop layer a second
dielectric RIE hard mask/polish-stop layer on top of the third
layer of insulating material, and a second dielectric diffusion
barrier layer on top of the second dielectric polish-stop layer.
The dielectric RIE hard mask/polish-stop layer may be comprised of
the inventive SiCOH dielectric material as well.
[0034] The present invention also relates to various methods of
fabricating the inventive SiCOH material.
[0035] The present invention also relates to the use of the
inventive SiCOH dielectric film in other electronic structures
including a structure including at least two conductors and an
optoelectronic sensing structure, for use in detection of
light.
BRIEF DESCRIPTION OF THE DRAWINGS
[0036] FIG. 1 is a universal curve of cohesive strength vs.
dielectric constant showing prior art dielectrics.
[0037] FIGS. 2A-2B show the cohesive strength plotted vs. natural
log (ln) of the H.sub.2O pressure in a controlled chamber for prior
art SiCOH dielectrics.
[0038] FIG. 3 is a universal curve of cohesive strength vs.
dielectric constant including prior art dielectrics as shown in
FIG. 1 as well as the inventive SiCOH dielectric material.
[0039] FIG. 4A is an illustration showing preferred first
precursors that can be used in the present invention in forming the
SiCOH dielectric material, while FIG. 4B is an illustration showing
additional CVD carbosilane precursors that can be used.
[0040] FIG. 5 is the solid state NMR (nuclear magnetic resonance)
spectra for the .sup.13C nuclei for the inventive SiCOH film A
(Curve 31), for a prior art SiCOH film B (Curve 35), and for
another prior art SiCOH film C (Curve 37).
[0041] FIG. 6 is an enlarged, cross-sectional view of an electronic
device of the present invention that includes the inventive SiCOH
dielectric film as both the intralevel dielectric layer and the
interlevel dielectric layer.
[0042] FIG. 7 is an enlarged, cross-sectional view of the
electronic structure of FIG. 6 having an additional diffusion
barrier dielectric cap layer deposited on top of the inventive
SiCOH dielectric film.
[0043] FIG. 8 is an enlarged, cross-sectional view of the
electronic structure of FIG. 7 having an additional RIE hard
mask/polish-stop dielectric cap layer and a dielectric cap
diffusion barrier layer deposited on top of the polish-stop
layer.
[0044] FIG. 9 is an enlarged, cross-sectional view of the
electronic structure of FIG. 8 having additional RIE hard
mask/polish-stop dielectric layers deposited on top of the SiCOH
dielectric film of the present invention.
[0045] FIG. 10 is a pictorial representation (through a cross
sectional view) illustrating an electronic structure including at
least two conductors and the inventive SiCOH dielectric
material.
[0046] FIGS. 11A-11B are pictorial representations (through cross
sectional views) illustrating electronic structures including a
sensing element and the inventive SiCOH dielectric material.
DETAILED DESCRIPTION OF THE INVENTION
[0047] As stated above, the present invention provides dielectric
materials (porous or dense, i.e., non-porous) that comprise a
matrix of a hydrogenated oxidized silicon carbon material (SiCOH)
comprising elements of Si, C, O and H in a covalently bonded
tri-dimensional network and have a dielectric constant of about 3.2
or less. The term "tri-dimensional network" is used throughout the
present application to denote a SiCOH dielectric material which
includes silicon, carbon, oxygen and hydrogen that are
interconnected and interrelated in the x, y, and z directions.
[0048] The present invention provides SiCOH dielectrics that have a
covalently bonded tri-dimensional network structure which includes
C bonded as Si--CH.sub.3 and also C bonded as Si--R--Si, wherein R
is phenyl (i.e., C.sub.6H.sub.4), --[CH.sub.2].sub.n-- where n is
greater than or equal to 1, HC.dbd.CH (i.e., a double bond),
C.dbd.CH.sub.2, C.ident.C (i.e., a triple bond) or a [S].sub.n
linkage, where n is a defined above. In some embodiments of the
present invention, the inventive dielectric material has a fraction
of the total carbon atoms that is bonded as Si--R--Si between 0.01
and 0.99, as determined by solid state NMR. In one preferred
embodiment, the SiCOH dielectric includes Si--[CH.sub.2].sub.2--Si
wherein n is 1 or 3. In the preferred embodiment, the total
fraction of carbon atoms ion the material that is bonded as
Si--CH.sub.2--Si is between 0.05 and 0.5, as measured by solid
state NMR.
[0049] The SiCOH dielectric material of the present invention
comprises between about 5 and about 40, more preferably from about
10 to about 20, atomic percent of Si; between about 5 and about 50,
more preferably from about 15 to about 40, atomic percent of C;
between 0 and about 50, more preferably from about 10 to about 30,
atomic percent of 0; and between about 10 and about 55, more
preferably from about 20 to about 45, atomic percent of H.
[0050] In some embodiments, the SiCOH dielectric material of the
present invention may further comprise F and/or N. In yet another
embodiment of the present invention, the SiCOH dielectric material
may optionally have the Si atoms partially substituted by Ge atoms.
The amount of these optional elements that may be present in the
inventive dielectric material of the present invention is dependent
on the amount of precursor that contains the optional elements that
is used during deposition.
[0051] The SiCOH dielectric material of the present invention
optionally contains molecular scale voids (i.e., nanometer-sized
pores) between about 0.3 to about 10 nanometers in diameter, and
most preferably between about 0.4 and about 5 nanometers in
diameter, which further reduce the dielectric constant of the SiCOH
dielectric material. The nanometer-sized pores occupy a volume
between about 0.5% and about 50% of a volume of the material. When
these voids are present, the material is known as porous SiCOH or
"pSiCOH".
[0052] FIG. 3 shows a universal curve of cohesive strength vs.
dielectric constant including prior art dielectrics as shown in
FIG. 1 as well as the inventive SiCOH dielectric material. The plot
in FIG. 3 shows that the inventive SiCOH dielectric has a higher
cohesive strength than prior art dielectrics at equivalent values
of k. In FIGS. 1 and 3, the k is reported as the relative
dielectric constant.
[0053] In a first embodiment of the present invention, a stable
ultra low k SiCOH dielectric material is provided that has a
dielectric constant of 3.0, a tensile stress of 30 MPa or less, an
elastic modulus greater than 15 GPa, cohesive strength greater than
about 6 J/m.sup.2, a crack development velocity in water of not
more than 1.times.10.sup.-10 msec for a film thickness of 3
microns, and a fraction of the C atoms are bonded in the functional
group Si--CH.sub.2--Si, wherein said methylene, CH.sub.2 carbon
fraction is about 0.1 is provided. Within the invention and as
stated above, this fraction may be between about 0.05 to about 0.5,
as measured by C solid state NMR.
[0054] In a second embodiment of the present invention, a stable
ultra low k SiCOH dielectric material is provided that has a
dielectric constant of less than 2.5, a tensile stress of from
about 30 to about 40 MPa or less, an elastic modulus greater than 5
GPa, a cohesive strength greater than about 4 J/m.sup.2, a crack
development velocity in water of not more than 1.times.10.sup.-10
msec for a film thickness of 3 microns, and a fraction of the C
atoms are bonded in the functional group Si--CH.sub.2--Si wherein
the methylene carbon fraction is from about 0.05 to about 0.5, as
measured by C solid state NMR.
[0055] In some embodiments of the present invention, there is
carbon bonded as Si--CH.sub.3 and also carbon bonded as Si--R--Si,
where R can be different organic groups 4.
[0056] In some embodiments of the present invention, the inventive
dielectric material is characterized has (i) being dense or porous
and having a cohesive strength in a dry ambient, i.e., the complete
absence of water, greater than about 3 J/m.sup.2 and a dielectric
constant less than about 2.5, (ii) being dense or porous and having
a cohesive strength greater than about 3 J/m.sup.2 at a water
pressure of 1570 Pa at 25.degree. C. and a dielectric constant less
than about 3.2 (50% relative humidity), or (iii) being dense or
porous and having a cohesive strength greater than about 2.1
J/m.sup.2 at a water pressure of 1570 Pa at 25.degree. C. and a
dielectric constant less than about 2.5.
[0057] The inventive SiCOH dielectric of the present invention has
more carbon bonded in organic groups bridging between two Si atoms
compared to the Si--CH.sub.3 bonding characteristic of prior art
SiCOH and pSiCOH dielectrics.
[0058] In some other embodiments of the present invention, there
may be C--S, Si--S, and optionally S--S bonding in the inventive
SiCOH dielectric.
[0059] In addition to the aforementioned properties, the SiCOH
dielectric materials of the present invention are hydrophobic with
a water contact angle of greater than 70.degree., more preferably
greater than 80.degree. and exhibit a cohesive strength in shaded
regions of FIGS. 2A and 2B.
[0060] The inventive SiCOH dielectric materials are typically
deposited using plasma enhanced chemical vapor deposition (PECVD).
In addition to PECVD, the present invention also contemplates that
the SiCOH dielectric materials can be formed utilizing chemical
vapor deposition (CVD), high-density plasma (HDP), pulsed PECVD,
spin-on application, or other related methods.
[0061] In the deposition process, the inventive SiCOH dielectric
material is formed by providing at least a first carbosilane or
alkoxycarbosilane precursor (liquid, gas or vapor) comprising atoms
of Si, C, O, and H, and an inert carrier such as He or Ar, into a
reactor, preferably the reactor is a PECVD reactor, and then
depositing a film derived from said first precursor onto a suitable
substrate utilizing conditions that are effective in forming the
SiCOH dielectric material of the present invention. The present
invention yet further provides for optionally an oxidizing agent
such as O.sub.2, N.sub.2O, CO.sub.2 or a combination thereof to the
gas mixture, thereby stabilizing the reactants in the reactor and
improving the properties and uniformity of the dielectric film
deposited on the substrate. The first precursor may include sulfur
or S derivatives thereof as well.
[0062] Within the present invention, the first precursor comprises
at least one of the following compounds: 1,3-disilacyclobutane,
1,3-disilapropane, 1,5-disilapentane, 1,4-bis-trihydrosilyl
benzene, or the methoxy and ethoxy substituted derivatives of these
compounds.
[0063] Illustrative examples of some preferred compounds used in
forming the inventive SiCOH dielectric include:
1,1,3,3,-tetrahydrido-1,3-disilacyclobutane;
1,1,3,3-tetramethoxy(ethoxy)-1,3 disilacyclobutane;
1,3-dimethyl-1,3-dimethoxy-1,3 disilacyclobutane;
1,3-disilacyclobutane;
1,3-dimethyl-1,3-dihydrido-1,3-disilylcyclobutane;
1,1,3,3,tetramethyl-1,3-disilacyclobutane;
1,1,3,3,5,5-hexamethoxy-1,3,5-trisilane;
1,1,3,3,5,5-hexahydrido-1,3,5-trisilane;
1,1,3,3,5,5-hexamethyl-1,3,5-trisilane;
1,1,1,3,3,3-hexamethoxy(ethoxy)-1,3-disilapropane;
1,1,3,3-tetramethoxy-1-methyl-1,3-disilabutane;
1,1,3,3-tetramethoxy-1,3-disilapropane;
1,1,1,3,3,3-hexahydrido-1,3-disilapropane;
3-(1,1-dimethoxy-1-silaethyl)-1,4,4-trimethoxy-1-methyl-1,4-disilpentane;
methoxymethane
2-(dimethoxysilamethyl)-1,1,4-trimethoxy-1,4-disilabutane;
methoxymethane
1,1,4-trimethoxy-1,4-disila-2-(trimethoxysilylmethyl)butane;
dimethoxymethane, methoxymethane;
1,1,1,5,5,5-hexamethoxy-1,5-disilapentane;
1,1,5,5-tetramethoxy-1,5-disilahexane;
1,1,5,5-tetramethoxy-1,5-disilapentane;
1,1,1,4,4,4-hexamethoxy(ethoxy)-1,4-disilylbutane,
1,1,1,4,4,4,-hexahydrido-1,4-disilabutane;
1,1,4,4-tetramethoxy(ethoxy)-1,4-dimethyl-1,4-disilabutane;
1,4-bis-trimethoxy(ethoxy)silyl benzene;
1,4-bis-dimethoxymethylsilyl benzene; and 1,4-bis-trihydrosilyl
benzene. Also the corresponding meta substituted isomers, such as,
1,1,1,4,4,4-hexamethoxy(ethoxy)-1,4-disilabut-2-ene;
1,1,1,4,4,4-hexamethoxy(ethoxy)-1,4-disilabut-2-yne;
1,1,3,3-tetramethoxy(ethoxy)-1,3-disilolane 1,3-disilolane;
1,1,3,3-tetramethyl-1,3-disilolane;
1,1,3,3-tetramethoxy(ethoxy)-1,3-disilane;
1,3-dimethoxy(ethoxy)-1,3-dimethyl-1,3-disilane; 1,3-disilane;
1,3-dimethoxy-1,3-disilane;
1,1-dimethoxy(ethoxy)-3,3-dimethyl-1-propyl-3-silabutane; or
2-silapropane.
[0064] In addition to the above mentioned materials, the present
invention also contemplates sulfur derivatives thereof.
[0065] FIG. 4A shows preferred first precursors that can be used in
the present invention in forming the SiCOH dielectric material.
FIG. 4B is an illustration showing additional CVD carbosilane
precursors that can be used in the present invention in forming the
SiCOH dielectric material. The sulfur derivatives of the compounds
shown in FIGS. 4A and 4B are also contemplated herein.
[0066] Optionally, a second SiCOH precursor may be added to the
reactor, for example, diethoxymethylsilane,
octamethyltetrasiloxane, tetramethyltetrasiloxane, trimethylsilane,
or any other common alkylsilane or alkoxysilane (cyclic or linear)
molecule.
[0067] Optionally, a precursor containing C--S--C or
C--[S].sub.n--C or Si--S--Si, or Si--[S].sub.n--Si bonding may be
added to the reactor.
[0068] In addition to the first precursor, a second precursor (gas,
liquid or vapor) comprising atoms of C, H, and optionally O, F
and/or N can be used. Optionally, a third precursor (gas, liquid or
gas) comprising Ge may also be used.
[0069] The second or third precursor may be a hydrocarbon molecule,
as described in U.S. Pat. Nos. 6,147,009, 6,312,793, 6,441,491,
6,437,443, 6,441,491, 6,541,398, 6,479,110 B2, and 6,497,963, the
contents of which are incorporated herein by reference.
[0070] The method of the present invention may further comprise the
step of providing a parallel plate reactor, which has a conductive
area of a substrate chuck between about 85 cm.sup.2 and about 750
cm.sup.2, and a gap between the substrate and a top electrode
between about 1 cm and about 12 cm. A high frequency RF power is
applied to one of the electrodes at a frequency between about 0.45
MHz and about 200 MHz. Optionally, an additional RF power of lower
frequency than the first RF power can be applied to one of the
electrodes.
[0071] The conditions used for the deposition step may vary
depending on the desired final dielectric constant of the SiCOH
dielectric material of the present invention. Broadly, the
conditions used for providing a stable dielectric material
comprising elements of Si, C, O, H that has a dielectric constant
of about 3.2 or less, a tensile stress of less than 45 MPa, an
elastic modulus from about 2 to about 15 GPa, and a hardness from
about 0.2 to about 2 GPa include: setting the substrate temperature
at between about 100.degree. C. and about 425.degree. C.; setting
the high frequency RF power density at between about 0.1 W/cm.sup.2
and about 2.0 W/cm.sup.2; setting the first liquid precursor flow
rate at between about 10 mg/min and about 5000 mg/min, optionally
setting the second liquid precursor flow rate at between about 10
mg/min to about 5,000 mg/min; optionally setting the third liquid
precursor flow rate at between about 10 mg/min to about 5000
mg/min; optionally setting the inert carrier gases such as Helium
(or/and Argon) flow rate at between about 10 sccm to about 5000
sccm; setting the reactor pressure at a pressure between about 1000
mTorr and about 10,000 mTorr; and setting the high frequency RF
power between about 50 W and about 1000 W. Optionally, an ultra low
frequency power may be added to the plasma between about 20 W and
about 400 W. When the conductive area of the substrate chuck is
changed by a factor of X, the RF power applied to the substrate
chuck is also changed by a factor of X.
[0072] When an oxidizing agent is employed in the present
invention, it is flowed into the PECVD reactor at a flow rate
between about 10 sccm to about 1000 sccm.
[0073] While liquid precursors are used in the above example, it is
known in the art that the organosilicon gas phase precursors (such
as trimethylsilane) can also be used for the deposition.
[0074] The film resulting from the above processes is called herein
the "as deposited film".
[0075] According to the present invention, the fabrication of the
stable SiCOH dielectric materials of the present invention may
require a combination of several steps:
the material is deposited on a substrate in a 1.sup.st step, using
deposition tool parameters in a specific range of values given
below in the process embodiments, forming the as deposited film;
the material is cured or treated using thermal, UV light, electron
beam irradiation, chemical energy, or a combination of more than
one of these, forming the final film having the desired mechanical
and other properties described herein. For example, after
deposition a treatment of the SiCOH film (using both thermal energy
and a second energy source) may be performed to stabilize the film
and obtain improved properties. The second energy source may be
electromagnetic radiation (UV, microwaves, etc.), charged particles
(electron or ion beam) or may be chemical (using atoms of hydrogen,
or other reactive gas, formed in a plasma).
[0076] In a preferred treatment, the substrate (containing the film
deposited according to the above process) is placed in a
ultraviolet (UV) treatment tool, with a controlled environment
(vacuum or ultra pure inert gas with a low O.sub.2 and H.sub.2O
concentration). A pulsed or continuous UV source may be used.
[0077] Within the invention, the UV treatment tool may be connected
to the deposition tool ("clustered"), or may be a separate
tool.
[0078] As is known in the art, the two process steps will be
conducted within the invention in two separate process chambers
that may be clustered on a single process tool, or the two chambers
may be in separate process tools ("declustered"). For porous SiCOH
films, the cure step may involve removal of a sacrificial
hydrocarbon (porogen) component, co-deposited with the dielectric
material. Suitable sacrificial hydrocarbon components that can be
employed in the present invention include, but are not limited to:
the second precursors that are mentioned in U.S. Pat. Nos.
6,147,009, 6,312,793, 6,441,491, 6,437,443, 6,441,491, 6,541,398,
6,479,110 B2, and 6,497,963, the contents of which are incorporated
herein by reference.
[0079] The following are examples illustrating material and
processing embodiments of the present invention.
Example 1
SiCOH Material A
[0080] In this example, an inventive SiCOH dielectric, referred to
as SiCOH film A, which was made in accordance with the present
invention, was characterized by the data in FIG. 5 and in Table 1
below. For comparison, SiCOH films B and C are "typical" prior art
SiCOH films, that have a dielectric constant about 2.7-2.8 are also
shown in FIG. 5 and Table 1.
[0081] Referring to FIG. 5, this figure shows solid-state NMR
(nuclear magnetic resonance) spectra for the .sup.13C nuclei for
the film SiCOH film A. Peak 33 corresponds to .sup.13C for CH.sub.3
methyl groups bonded to Si, and the breadth of peak 33 is due to
CH.sub.3 groups in different magnetic environments. The peak 32 was
assigned to .sup.13C in --CH.sub.2-- species, bridging between two
Si atoms, Si--CH.sub.2--Si. Based on the height of peak 32, the
fraction of the total C in the film that is C present as methylene
bridge groups, --CH.sub.2-- was about 0.1. Since peaks 33 and 32
were overlapping, this was an estimate only. The areas have not
been measured. Also, in FIG. 5 is curve 35 measured from SiCOH film
B and curve 37 measured from SiCOH film C. It was seen that spectra
35 and 37 (NMR spectra) from other SiCOH films, which are "typical"
prior art SiCOH films, contained peak 33 assigned to CH.sub.3
groups. The spectra 35 and 37 do not contain peak 32.
[0082] Table 1 below summarizes the FTIR (Fourier transform
infrared spectroscopy) spectra measured from SiCOH films A, B, and
C. The numbers in the table are integrated areas under the FTIR
peaks, and the last column is the ratio of two FTIR peak areas. The
ratio (CH.sub.2+CH.sub.3)/SiCH.sub.3 was calculated in order to
show the enhanced contribution of CH.sub.2 species to the FTIR peak
area of (CH.sub.2+CH.sub.3) in the inventive SiCOH film A. It was
seen that this ratio was about 0.9 in the inventive SiCOH film A,
and was about 0.6 in a typical SiCOH film such as SiCOH film B or
C. Moreover, the SiCOH film A contained more CH.sub.2 species than
films B or C. From the NMR analysis, these were assigned to
Si--CH.sub.2--Si in the inventive SiCOH film A.
TABLE-US-00001 TABLE 1 Si--CH.sub.3 (CH.sub.2 + CH.sub.3) total
Ratio of Film Peak Area FTIR Peak Area (CH.sub.2 +
CH.sub.3)/Si--CH.sub.3 SiCOH film A 1.67 1.48 0.89 SiCOH film B
2.18 1.35 0.62 SiCOH film C 2.09 1.23 0.59
Example 2
First Process Embodiment
[0083] A 300 mm or 200 mm substrate was placed in a PECVD reactor
on a heated wafer chuck at 350.degree. C. Temperatures between
300.degree.-425.degree. C. may also be used. Any PECVD deposition
reactor may be used within the present invention. Gas and liquid
precursor flows were then stabilized to reach a pressure in the
range from 0.1-10 Torr, and RF radiation was applied to the reactor
showerhead for a time between about 5 to about 500 seconds.
[0084] Specifically and for the growth of the inventive SiCOH
dielectric material A containing enhanced Si--CH.sub.2--Si bridging
methylene carbon (described above), the single SiCOH precursor was
OMCTS (octamethylcyclotetrasiloxane) set at a flow of 2500 mg/m, an
oxygen, O.sub.2 flow of 220 sccm, a helium, He gas flow of 2000
sccm, said flows were stabilized to reach a reactor pressure of 5
Torr. The wafer chuck was set at 350.degree. C., and the high
frequency RF power of 400 W at a frequency of 13.6 MHz was applied
to the showerhead, and the low frequency RF power of 60 W at a
frequency of 13.6 MHz was applied to the substrate. The film
deposition rate was 2025 Angstrom/min.
Example 3
Second Process Embodiment
[0085] A 300 mm or 200 mm substrate was placed in a PECVD reactor
on a heated wafer chuck at 300.degree.-425.degree. C. and
preferably at 350.degree.-400.degree. C. Any PECVD deposition
reactor may be used within the present invention. Gas and liquid
precursor flows were then stabilized to reach a pressure in the
range from 0.1-10 Torr, and RF radiation was applied to the reactor
showerhead for a time between about 5 to 500 seconds.
[0086] Specifically and for the growth of the inventive SiCOH
dielectric containing enhanced Si--CH.sub.2--Si bridging methylene
carbon (described above), the conditions used include:
1,1,1,3,3,3-hexamethoxy-1,3-disilapropane, flow of 2500 mg/m, an
oxygen, O.sub.2 flow of 220 sccm, a helium, He gas flow of 2000
sccm, said flows were stabilized to reach a reactor pressure of 5
Torr. The wafer chuck was set at 350.degree. C., and the high
frequency RF power of 500 W at a frequency of 13.6 MHz was applied
to the showerhead, and the low frequency RF power of 160 W at a
frequency of 13.6 MHz was applied to the substrate. The film
deposition rate was in the range between 10-100
Angstrom/second.
[0087] As is known in the art, each of the above process parameters
may be adjusted within the scope of invention described above. For
example, different RF frequencies including, but not limited to,
0.26, 0.35, 0.45 MHz, may also be used in the present invention.
Also for example, the O.sub.2 flow rate may be zero, and
alternative oxidizers including N.sub.2O, CO, or CO.sub.2 may be
used in place of O.sub.2. Also, in the precursor
1,1,1,3,3,3-hexamethoxy-1,3-disilapropane, the methoxy substituent
groups may be replaced by hydrido, methyl or ethoxy groups. Also,
the precursor 1,3-disilabutane
(H.sub.3Si--CH.sub.2--Si(H.sub.2)--CH.sub.3) may be used in an
alternative embodiment, and the flow of O.sub.2 and other gases
would be adjusted, as is known in the art.
[0088] In still other alternative embodiments, any of the
carbosilane precursors shown in FIGS. 4A and 4B may be used.
Example 4
Third Process Embodiment
[0089] A 300 mm or 200 mm substrate was placed in a PECVD reactor
on a heated wafer chuck at 300.degree.-425.degree. C. and
preferably at 350.degree.-400.degree. C. Any PECVD deposition
reactor may be used within the present invention. Gas and liquid
precursor flows were then stabilized to reach a pressure in the
range from 1-10 Torr, and RF radiation was applied to the reactor
showerhead for a time between about 5 to 500 seconds.
[0090] For the growth of a SiCOH material with k greater than or
equal to 1.8, and having enhanced Si--CH.sub.2--Si bridging
methylene carbon, two precursors were used, specifically
1,3-disilacyclobutane and DEMS (diethoxymethylsilane). Within the
invention, any alkoxysilane precursor may be used in place of DEMS,
including but not limited to: OMCTS, TMCTS, or
dimethyldmethoxysilane. Also, within the invention, the
alkoxysilane precursor (used in place of DEMS) may be an
organosilicon precursor with a built-in porogen, and may optionally
comprise one of vinylmethyldiethoxysilane, vinyltriethoxysilane,
vinyldimethylethoxysilane, cyclohexenylethyltriethoxysilane,
1,1-diethoxy-1-silacyclopent-3-ene, divinyltetramethyldisiloxane,
2-(3,4-epoxycyclohexyl)ethyltriethoxysilane,
2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane,
epoxyhexyltriethoxysilane, hexavinyldisiloxane,
trivinylmethoxysilane, trivinylethoxysilane,
vinylmethylethoxysilane, vinylmethyldiethoxysilane,
vinylmethyldimethoxysilane, vinylpentamethyldisiloxane,
vinyltetramethyldisiloxane, vinyltriethoxysilane, or
vinyltrimethoxysilane.
[0091] As is known in the art, gases such as O.sub.2 may be added,
and He may be replaced by gases such as Ar, CO.sub.2, or another
noble gas.
[0092] The conditions used include a DEMS flow of 2000 mg/m, a
1,3-disilacyclobutane flow of 100 to 1000 mg/m, and a He gas flow
of 1000 sccm, said flows were stabilized to reach a reactor
pressure of 6 Torr. The wafer chuck was set at 350.degree. C., and
the high frequency RF power of 470 W was applied to the showerhead,
and the low frequency RF (LRF) power was 0 W so that no LRF was
applied to the substrate. The film deposition rate was about
2,000-4,000 Angstrom/second.
[0093] As is known in the art, each of the above process parameters
may be adjusted within the scope of invention described above. For
example, different RF frequencies including, but not limited to,
0.26, 0.35, 0.45 MHz, may also be used in the present invention.
Also for example, an oxidizer such as O.sub.2, or alternative
oxidizers including N.sub.2O, CO, or CO.sub.2 may be used.
Specifically, the wafer chuck temperature may be lower, for
example, to 150.degree.-350.degree. C.
[0094] While 1,3-disilacyclobutane is the preferred carbosilane to
provide an enhanced fraction of Si--CH.sub.2--Si bridging methylene
carbon, other carbosilane or alkoxycarbosilane precursors described
above can be used, including but not limited to the precursors
shown in FIGS. 4A and 4B.
[0095] In alternate embodiments, the conditions are adjusted to
produce SiCOH films with dielectric constant from 1.8 up to
2.7.
[0096] In alternate embodiments, other functional groups may be
added as bridging groups between Si and Si, using the selected
carbosilane precursors, with illustrative examples given here. In
order to add the --CH.sub.2--CH.sub.2--CH.sub.2-- functional group
bridging between Si atoms the selected carbosilane precursor may be
selected from 1,3-disilolane,
1,1,3,3-tetramethoxy(ethoxy)-1,3-disilolane or
1,1,3,3-tetramethyl-1,3-disilolane.
[0097] In order to add the phenyl functional group bridging between
Si atoms the selected carbosilane precursor may be selected
1,4-bis-trimethoxy(ethoxy)silyl benzene,
1,4-bis-dimethoxymethylsilyl benzene, 1,4-bis-trihydrosilyl benzene
or related Si containing benzene derivatives.
[0098] In order to add the HC.dbd.CH functional group bridging
between Si atoms, the selected carbosilane precursor may be
selected from 1,1,1,4,4,4-hexamethoxy(ethoxy)-1,4-disilabut-2-ene
or another Si containing ethylene derivative.
[0099] In order to add the C.ident.C (triple bond) functional group
bridging between Si atoms, the selected carbosilane precursor may
be 1,1,1,4,4,4-hexamethoxy-1,4-disilabut-2-yne,
1,1,1,4,4,4-hexaethoxy-1,4-disilabut-2-yne, or another Si
containing acetylene derivative.
[0100] In the above examples, the precursors are described having
methoxy and ethoxy substituent groups, but these may be replaced by
hydrido or methyl groups, and a carbosilane molecule containing a
mixture of methoxy, ethoxy, hydrido and methyl substituent groups
may be used within the invention.
Example 5
Fourth Process Embodiment
[0101] A 300 mm or 200 mm substrate was placed in a PECVD reactor
on a heated wafer chuck at 300.degree.-425.degree. C. and
preferably at 350.degree.-400.degree. C. Any PECVD deposition
reactor may be used within the present invention. Gas and liquid
precursor flows were then stabilized to reach a pressure in the
range from 0.1-10 Torr, and RF radiation was applied to the reactor
showerhead for a time between about 5 to 500 seconds.
[0102] For the growth of a SiCOH material with k greater than or
equal to 1.8, and having enhanced Si--CH.sub.2--Si bridging
methylene carbon, a single alkoxycarbosilane precursor was used.
The linear precursors shown in FIG. 4A are preferred.
[0103] The conditions used include a single precursor flow of 2000
mg/m, and a He gas flow of 1000 sccm, said flows were stabilized to
reach a reactor pressure of 6 Torr. The wafer chuck was set at
350.degree. C., and the high frequency RF power of 470 W was
applied to the showerhead, and the low frequency RF (LRF) power was
0 W so that no LRF is applied to the substrate. The film deposition
rate was about 1,000 to 5,000 Angstrom/second.
[0104] As is known in the art, each of the above process parameters
may be adjusted within the invention. Specifically, the wafer chuck
temperature may be lower, for example 150.degree.-350.degree. C. As
is known in the art, gases such as O.sub.2 may be added, and He may
be replaced by gases such as Ar, CO.sub.2, or another noble
gas.
[0105] In alternate embodiments, the conditions are adjusted to
produce SiCOH films with dielectric constant from 1.8 up to
2.7.
[0106] While linear precursors from FIG. 4A are the preferred
alkoxycarbosilane to provide an enhanced fraction of
Si--CH.sub.2--Si bridging methylene carbon, any alkoxycarbosilane
mentioned above in the detailed description of the present
invention can be used. Other functional groups may be added using
the selected carbosilane precursors, with illustrative examples
given here. In order to add the --CH.sub.2--CH.sub.2--CH.sub.2--
functional group bridging between Si atoms, the selected
carbosilane precursor may be selected from 1,3-disilolane,
1,1,3,3-tetramethoxy(ethoxy)-1,3-disilolane or
1,1,3,3-tetramethyl-1,3-disilolane.
[0107] In order to add the phenyl functional group bridging between
Si atoms, the selected carbosilane precursor may be selected
1,4-bis-trimethoxy(ethoxy)silyl benzene,
[0108] 1,4-bis-dimethoxymethylsilyl benzene, 1,4-bis-trihydrosilyl
benzene or related Si containing benzene derivatives.
[0109] In order to add the HC.dbd.CH functional group bridging
between Si atoms, the selected carbosilane precursor may be
selected from 1,1,1,4,4,4-hexamethoxy(ethoxy)-1,4-disilabut-2-ene
or another Si containing ethylene derivative.
[0110] In order to add the C.ident.C (triple bond) functional group
bridging between Si atoms the selected carbosilane precursor may be
1,1,1,4,4,4-hexamethoxy-1,4-disilabut-2-yne,
1,1,1,4,4,4-hexaethoxy-1,4-disilabut-2-yne, or another Si
containing acetylene derivative.
[0111] In the above examples, the precursors are described having
methoxy and ethoxy substituent groups, but these may be replaced by
hydrido or methyl groups, and a carbosilane molecule containing a
mixture of methoxy, ethoxy, hydrido and methyl substituent groups
may be used within the invention.
Example 6
Fifth Process Embodiment
[0112] A 300 mm or 200 mm substrate was placed in a PECVD reactor
on a heated wafer chuck at 300.degree.-425.degree. C. and
preferably at 350.degree.-400.degree. C. Any PECVD deposition
reactor may be used within the present invention. Gas and liquid
precursor flows were then stabilized to reach a pressure in the
range from 1-10 Torr, and RF radiation was applied to the reactor
showerhead for a time between about 5 to 500 seconds.
[0113] In this example and for the growth of a porous SiCOH
material with k greater than or equal to 1.8, and having enhanced
Si--CH.sub.2--Si bridging methylene carbon or other organic
functions bridging between two Si atoms, a porogen is added
according to methods known in the art. The porogen may be
bicycloheptadiene (BCHD), or other molecules described, for
example, in U.S. Pat. Nos. 6,147,009, 6,312,793, 6,441,491,
6,437,443, 6,441,491, 6,541,398, 6,479,110 B2, and 6,497,963.
[0114] For the SiCOH precursor, the linear alkoxysilane precursors
shown in FIG. 4A are preferred.
[0115] The conditions used include a precursor flow of 100-2000
mg/m, a He gas flow of 10-500 sccm, and a porogen flow of about
50-2000 mg/m, said flows were stabilized to reach a reactor
pressure of 7 Torr. The wafer chuck was set at 225.degree. C., and
the high frequency RF power of 300 W was applied to the showerhead,
and the low frequency RF (LRF) power was 0 W so that no LRF was
applied to the substrate. The film deposition rate was about 1,000
to 5,000 Angstrom/second.
[0116] As is known in the art, each of the above process parameters
may be adjusted within the invention. For example, the wafer chuck
temperature may be between 150.degree.-350.degree. C.
[0117] While the preferred linear alkoxycarbosilanes of FIG. 4A are
useful, any alkoxycarbosilane as mentioned above may be used within
the invention. Also within the invention, two SiCOH precursors may
be used, for example DEMS and a carbosilane or alkoxycarbosilane
described above. As is known in the art, gases such as O.sub.2,
N.sub.2O, or another oxidizer may be added, and He may be replaced
by gases such as Ar, CO.sub.2, or another noble gas. Again, other
functional groups, as described in the above examples, can be used
to form a bridging group between two Si atoms.
[0118] The electronic devices which can include the inventive SiCOH
dielectric are shown in FIGS. 6-9. It should be noted that the
devices shown in FIGS. 6-9 are merely illustrative examples of the
present invention, while an infinite number of other devices may
also be formed by the present invention novel methods.
[0119] In FIG. 6, an electronic device 30 built on a silicon
substrate 32 is shown. On top of the silicon substrate 32, an
insulating material layer 34 is first formed with a first region of
metal 36 embedded therein. After a CMP process is conducted on the
first region of metal 36, a SiCOH dielectric film 38 of the present
invention is deposited on top of the first layer of insulating
material 34 and the first region of metal 36. The first layer of
insulating material 34 may be suitably formed of silicon oxide,
silicon nitride, doped varieties of these materials, or any other
suitable insulating materials. The SiCOH dielectric film 38 is then
patterned in a photolithography process followed by etching and a
conductor layer 40 is deposited thereon. After a CMP process on the
first conductor layer 40 is carried out, a second layer of the
inventive SiCOH film 44 is deposited by a plasma enhanced chemical
vapor deposition process overlying the first SiCOH dielectric film
38 and the first conductor layer 40. The conductor layer 40 may be
deposited of a metallic material or a nonmetallic conductive
material. For instance, a metallic material of aluminum or copper,
or a nonmetallic material of nitride or polysilicon. The first
conductor 40 is in electrical communication with the first region
of metal 36.
[0120] A second region of conductor 50 is then formed after a
photolithographic process on the SiCOH dielectric film 44 is
conducted followed by etching and then a deposition process for the
second conductor material. The second region of conductor 50 may
also be deposited of either a metallic material or a nonmetallic
material, similar to that used in depositing the first conductor
layer 40. The second region of conductor 50 is in electrical
communication with the first region of conductor 40 and is embedded
in the second layer of the SiCOH dielectric film 44. The second
layer of the SiCOH dielectric film is in intimate contact with the
first layer of SiCOH dielectric material 38. In this example, the
first layer of the SiCOH dielectric film 38 is an intralevel
dielectric material, while the second layer of the SiCOH dielectric
film 44 is both an intralevel and an interlevel dielectric. Based
on the low dielectric constant of the inventive SiCOH dielectric
films, superior insulating property can be achieved by the first
insulating layer 38 and the second insulating layer 44.
[0121] FIG. 7 shows a present invention electronic device 60
similar to that of electronic device 30 shown in FIG. 6, but with
an additional dielectric cap layer 62 deposited between the first
insulating material layer 38 and the second insulating material
layer 44. The dielectric cap layer 62 can be suitably formed of a
material such as silicon oxide, silicon nitride, silicon
oxynitride, silicon carbide, silicon carbo-nitride (SiCN), silicon
carbo-oxide (SiCO), and their hydrogenated compounds. The
additional dielectric cap layer 62 functions as a diffusion barrier
layer for preventing diffusion of the first conductor layer 40 into
the second insulating material layer 44 or into the lower layers,
especially into layers 34 and 32.
[0122] Another alternate embodiment of the present invention
electronic device 70 is shown in FIG. 8. In the electronic device
70, two additional dielectric cap layers 72 and 74 which act as a
RIE mask and CMP (chemical mechanical polishing) polish stop layer
are used. The first dielectric cap layer 72 is deposited on top of
the first ultra low k insulating material layer 38 and used as a
RIE mask and CMP stop, so the first conductor layer 40 and layer 72
are approximately co-planar after CMP. The function of the second
dielectric layer 74 is similar to layer 72, however layer 74 is
utilized in planarizing the second conductor layer 50. The polish
stop layer 74 can be deposited of a suitable dielectric material
such as silicon oxide, silicon nitride, silicon oxynitride, silicon
carbide, silicon carbo-oxide (SiCO), and their hydrogenated
compounds. A preferred polish stop layer composition is SiCH or
SiCOH for layers 72 or 74. A second dielectric layer can be added
on top of the second SiCOH dielectric film 44 for the same
purposes.
[0123] Still another alternate embodiment of the present invention
electronic device 80 is shown in FIG. 9. In this alternate
embodiment, an additional layer 82 of dielectric material is
deposited and thus dividing the second insulating material layer 44
into two separate layers 84 and 86. The intralevel and interlevel
dielectric layer 44 formed of the inventive ultra low k material is
therefore divided into an interlayer dielectric layer 84 and an
intralevel dielectric layer 86 at the boundary between via 92 and
interconnect 94. An additional diffusion barrier layer 96 is
further deposited on top of the upper dielectric layer 74. The
additional benefit provided by this alternate embodiment electronic
structure 80 is that dielectric layer 82 acts as an RIE etch stop
providing superior interconnect depth control. Thus, the
composition of layer 82 is selected to provide etch selectivity
with respect to layer 86.
[0124] Still other alternate embodiments may include an electronic
structure which has layers of insulating material as intralevel or
interlevel dielectrics in a wiring structure that includes a
pre-processed semiconducting substrate which has a first region of
metal embedded in a first layer of insulating material, a first
region of conductor embedded in a second layer of the insulating
material wherein the second layer of insulating material is in
intimate contact with the first layer of insulating material, and
the first region of conductor is in electrical communication with
the first region of metal, a second region of conductor in
electrical communication with the first region of conductor and is
embedded in a third layer of insulating material, wherein the third
layer of insulating material is in intimate contact with the second
layer of insulating material, a first dielectric cap layer between
the second layer of insulating material and the third layer of
insulating material and a second dielectric cap layer on top of the
third layer of insulating material, wherein the first and the
second dielectric cap layers are formed of a material that includes
atoms of Si, C, O and H, or preferably a SiCOH dielectric film of
the present invention.
[0125] Still other alternate embodiments of the present invention
include an electronic structure which has layers of insulating
material as intralevel or interlevel dielectrics in a wiring
structure that includes a pre-processed semiconducting substrate
that has a first region of metal embedded in a first layer of
insulating material, a first region of conductor embedded in a
second layer of insulating material which is in intimate contact
with the first layer of insulating material, the first region of
conductor is in electrical communication with the first region of
metal, a second region of conductor that is in electrical
communication with the first region of conductor and is embedded in
a third layer of insulating material, the third layer of insulating
material is in intimate contact with the second layer of insulating
material, and a diffusion barrier layer formed of the dielectric
film of the present invention deposited on at least one of the
second and third layers of insulating material.
[0126] Still other alternate embodiments include an electronic
structure which has layers of insulating material as intralevel or
interlevel dielectrics in a wiring structure that includes a
pre-processed semiconducting substrate that has a first region of
metal embedded in a first layer of insulating material, a first
region of conductor embedded in a second layer of insulating
material which is in intimate contact with the first layer of
insulating material, the first region of conductor is in electrical
communication with the first region of metal, a second region of
conductor in electrical communication with the first region of
conductor and is embedded in a third layer of insulating material,
the third layer of insulating material is in intimate contact with
the second layer of insulating material, a reactive ion etching
(RIE) hard mask/polish stop layer on top of the second layer of
insulating material, and a diffusion barrier layer on top of the
RIE hard mask/polish stop layer, wherein the RIE hard mask/polish
stop layer and the diffusion barrier layer are formed of the SiCOH
dielectric film of the present invention.
[0127] Still other alternate embodiments include an electronic
structure which has layers of insulating materials as intralevel or
interlevel dielectrics in a wiring structure that includes a
pre-processed semiconducting substrate that has a first region of
metal embedded in a first layer of insulating material, a first
region of conductor embedded in a second layer of insulating
material which is in intimate contact with the first layer of
insulating material, the first region of conductor is in electrical
communication with the first region of metal, a second region of
conductor in electrical communication with the first region of
conductor and is embedded in a third layer of insulating material,
the third layer of insulating material is in intimate contact with
the second layer of insulating material, a first RIE hard mask,
polish stop layer on top of the second layer of insulating
material, a first diffusion barrier layer on top of the first RIE
hard mask/polish stop layer, a second RIE hard mask/polish stop
layer on top of the third layer of insulating material, and a
second diffusion barrier layer on top of the second RIE hard
mask/polish stop layer, wherein the RIE hard mask/polish stop
layers and the diffusion barrier layers are formed of the SiCOH
dielectric film of the present invention.
[0128] Still other alternate embodiments of the present invention
includes an electronic structure that has layers of insulating
material as intralevel or interlevel dielectrics in a wiring
structure similar to that described immediately above but further
includes a dielectric cap layer which is formed of the SiCOH
dielectric material of the present invention situated between an
interlevel dielectric layer and an intralevel dielectric layer.
[0129] In some embodiments as shown, for example in FIG. 10, an
electronic structure containing at least two metallic conductor
elements (labeled as reference numerals 97 and 101) and a SiCOH
dielectric material (labeled as reference numeral 98). Optionally,
metal contacts 95 and 102 are used to make electrical contact to
conductors 97 and 101. The inventive SiCOH dielectric 98 provides
electrical isolation and low capacitance between the two
conductors. The electronic structure is made using a conventional
technique that is well known to those skilled in the art such as
described, for example, in U.S. Pat. No. 6,737,727, the entire
content of which is incorporated herein by reference.
[0130] The at least two metal conductor elements are patterned in a
shape required for a function of a passive or active circuit
element including, for example, an inductor, a resistor, a
capacitor, or a resonator.
[0131] Additionally, the inventive SiCOH can be used in an
electronic sensing structure wherein the optoelectronic sensing
element (detector) shown in FIG. 11A or 11B is surrounded by a
layer of the inventive SiCOH dielectric material. The electronic
structure is made using a conventional technique that is well known
to those skilled in the art. Referring to FIG. 11A, a p-i-n diode
structure is shown which can be a high speed Si based photodetector
for IR signals. The n+ substrate is 110, and atop this is an
intrinsic semiconductor region 112, and within region 112 p+
regions 114 are formed, completing the p-i-n layer sequence. Layer
116 is a dielectric (such as SiO.sub.2) used to isolate the metal
contacts 118 from the substrate. Contacts 118 provide electrical
connection to the p+ regions. The entire structure is covered by
the inventive SiCOH dielectric material, 120. This material is
transparent in the IR region, and serves as a passivation
layer.
[0132] A second optical sensing structure is shown in FIG. 11B,
this is a simple p-n junction photodiode, which can be a high speed
IR light detector. Referring to FIG. 11B, the metal contact to
substrate is 122, and atop this is an n-type semiconductor region
124, and within this region p+ regions 126 are formed, completing
the p-n junction structure. Layer 128 is a dielectric (such as
SiO.sub.2) used to isolate the metal contacts 130 from the
substrate. Contacts 130 provide electrical connection to the p+
regions. The entire structure is covered by the inventive SiCOH
dielectric material, 132. This material is transparent in the IR
region, and serves as a passivation layer.
[0133] While the present invention has been described in an
illustrative manner, it should be understood that the terminology
used is intended to be in a nature of words of description rather
than of limitation. Furthermore, while the present invention has
been described in terms of a preferred and several alternate
embodiments, it is to be appreciated that those skilled in the art
will readily apply these teachings to other possible variations of
the invention.
* * * * *