U.S. patent application number 13/354129 was filed with the patent office on 2013-07-25 for conformal amorphous carbon for spacer and spacer protection applications.
This patent application is currently assigned to APPLIED MATERIALS, INC.. The applicant listed for this patent is Song Hyun Hong, Bok Hoen Kim, Sungjin Kim, Deenesh Padhi, Derek R. Witty. Invention is credited to Song Hyun Hong, Bok Hoen Kim, Sungjin Kim, Deenesh Padhi, Derek R. Witty.
Application Number | 20130189845 13/354129 |
Document ID | / |
Family ID | 48797563 |
Filed Date | 2013-07-25 |
United States Patent
Application |
20130189845 |
Kind Code |
A1 |
Kim; Sungjin ; et
al. |
July 25, 2013 |
CONFORMAL AMORPHOUS CARBON FOR SPACER AND SPACER PROTECTION
APPLICATIONS
Abstract
A method of forming a nitrogen-doped amorphous carbon layer on a
substrate in a processing chamber is provided. The method generally
includes depositing a predetermined thickness of a sacrificial
dielectric layer over a substrate, forming patterned features on
the substrate by removing portions of the sacrificial dielectric
layer to expose an upper surface of the substrate, depositing
conformally a predetermined thickness of a nitrogen-doped amorphous
carbon layer on the patterned features and the exposed upper
surface of the substrate, selectively removing the nitrogen-doped
amorphous carbon layer from an upper surface of the patterned
features and the upper surface of the substrate using an
anisotropic etching process to provide the patterned features
filled within sidewall spacers formed from the nitrogen-doped
amorphous carbon layer, and removing the patterned features from
the substrate.
Inventors: |
Kim; Sungjin; (Palo Alto,
CA) ; Padhi; Deenesh; (Sunnyvale, CA) ; Hong;
Song Hyun; (Fremont, CA) ; Kim; Bok Hoen; (San
Jose, CA) ; Witty; Derek R.; (Fremont, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Kim; Sungjin
Padhi; Deenesh
Hong; Song Hyun
Kim; Bok Hoen
Witty; Derek R. |
Palo Alto
Sunnyvale
Fremont
San Jose
Fremont |
CA
CA
CA
CA
CA |
US
US
US
US
US |
|
|
Assignee: |
APPLIED MATERIALS, INC.
Santa Clara
CA
|
Family ID: |
48797563 |
Appl. No.: |
13/354129 |
Filed: |
January 19, 2012 |
Current U.S.
Class: |
438/696 ;
257/E21.256 |
Current CPC
Class: |
H01L 21/31144 20130101;
H01L 21/31111 20130101; H01L 21/02274 20130101; H01L 21/0337
20130101; H01L 21/0338 20130101; H01L 21/32139 20130101; H01L
21/32137 20130101; H01L 21/0332 20130101; H01L 21/32136 20130101;
H01L 21/02115 20130101; H01L 21/31116 20130101 |
Class at
Publication: |
438/696 ;
257/E21.256 |
International
Class: |
H01L 21/311 20060101
H01L021/311 |
Claims
1. A method of forming an amorphous carbon layer on a substrate in
a processing chamber, comprising: depositing a predetermined
thickness of a sacrificial dielectric layer over a substrate;
forming patterned features on the substrate by removing portions of
the sacrificial dielectric layer to expose an upper surface of the
substrate; depositing conformally a predetermined thickness of an
amorphous carbon layer on the patterned features and the exposed
upper surface of the substrate; selectively removing the amorphous
carbon layer from an upper surface of the patterned features and
the upper surface of the substrate using an anisotropic etching
process to provide the patterned features filled within sidewall
spacers formed from the amorphous carbon layer; and removing the
patterned features from the substrate.
2. The method of claim 1, wherein the amorphous carbon layer is
formed by introducing a hydrocarbon source, a nitrogen-containing
gas, and a plasma initiating gas into the processing chamber.
3. The method of claim 2, wherein the hydrocarbon source comprises
one or more hydrocarbon compounds having the general formula
C.sub.xH.sub.y, wherein x has a range of between 1 and 20, and y
has a range of between 1 and 20.
4. The method of claim 3, wherein one or more hydrocarbon compounds
is selected from the group consisting of acetylene
(C.sub.2H.sub.2), ethylene (C.sub.2H.sub.4), ethane
(C.sub.2H.sub.6), propylene (C.sub.3H.sub.6), propyne
(C.sub.3H.sub.4), propane (C.sub.3H.sub.8), butane
(C.sub.4H.sub.10), butylene (C.sub.4H.sub.8), butadiene
(C.sub.4H.sub.6), phenylacetylene (C.sub.8H.sub.6), and
combinations thereof.
5. The method of claim 1, wherein the amorphous carbon layer is
formed by introducing a nitrogen-containing hydrocarbon source and
a plasma-initiating gas into the processing chamber.
6. The method of claim 5, wherein the nitrogen-containing
hydrocarbon source is described by the formula CxHyNz, where x has
a range of between 1 and 12, y has a range of between 2 and 20, and
z has a range of between 1 and 10.
7. The method of claim 6, wherein the nitrogen-containing
hydrocarbon source comprises one or more nitrogen containing
hydrocarbon compounds selected from the group consisting of
methylamine, dimethylamine, trimethylamine (TMA), triethylamine,
aniline, quinoline, pyridine, acrilonitrile, benzonitrile, and
combinations thereof.
8. The method of claim 1, wherein the amorphous carbon layer is a
nitrogen-doped amorphous carbon having a carbon:nitrogen ratio of
between about 0.1% nitrogen to about 4.0% nitrogen.
9. The method of claim 1, wherein the sacrificial dielectric layer
comprises silicon oxide, silicon nitride, polysilicon, or amorphous
carbon.
10. The method of claim 1, wherein the substrate comprises a
plurality of alternating oxide and nitride materials, one or more
oxide materials or nitride materials, polysilicon or amorphous
silicon materials, oxides alternating with amorphous silicon,
oxides alternating with polysilicon, undoped silicon alternating
with doped silicon, undoped polysilicon alternating with doped
polysilicon, or updoped amorphous silicon alternating with doped
amorphous silicon.
11. A method of forming a device in a processing chamber,
comprising: forming patterned features on an upper surface of a
substrate; depositing conformally a predetermined thickness of a
sacrificial dielectric layer on the patterned features and an
exposed upper surface of the substrate; selectively removing the
sacrificial dielectric layer from an upper surface of the patterned
features and the exposed upper surface of the substrate to provide
the patterned features filled within first sidewall spacers formed
from the sacrificial dielectric layer; forming second sidewall
spacers adjacent to the first sidewall spacers, the second sidewall
spacers being formed from a nitrogen-doped amorphous carbon
material having a carbon:nitrogen ratio of between about 0.1%
nitrogen to about 4.0% nitrogen; and removing the patterned
features filled within the first sidewall spacers.
12. The method of claim 11, wherein the patterned features are
formed from amorphous carbon.
13. The method of claim 11, wherein the sacrificial dielectric
layer comprises silicon dioxide, silicon oxynitride, or silicon
nitride.
14. The method of claim 11, wherein the nitrogen-doped amorphous
carbon material is formed by introducing a nitrogen-containing
hydrocarbon source and a plasma-initiating gas into the processing
chamber.
15. The method of claim 14, wherein the nitrogen-containing
hydrocarbon source is described by the formula CxHyNz, where x has
a range of between 1 and 12, y has a range of between 2 and 20, and
z has a range of between 1 and 10.
16. The method of claim 15, wherein the nitrogen-containing
hydrocarbon source comprises one or more nitrogen containing
hydrocarbon compounds selected from the group consisting of
methylamine, dimethylamine, trimethylamine (TMA), triethylamine,
aniline, quinoline, pyridine, acrilonitrile, benzonitrile, and
combinations thereof.
17. The method of claim 11, wherein the substrate comprises a
plurality of alternating oxide and nitride materials, one or more
oxide materials or nitride materials, polysilicon or amorphous
silicon materials, oxides alternating with amorphous silicon,
oxides alternating with polysilicon, undoped silicon alternating
with doped silicon, undoped polysilicon alternating with doped
polysilicon, or updoped amorphous silicon alternating with doped
amorphous silicon.
18. The method of claim 11, wherein the nitrogen-doped amorphous
carbon material is formed by introducing a hydrocarbon source and a
nitrogen-containing gas into the processing chamber.
19. The method of claim 18, wherein the hydrocarbon source
comprises one or more hydrocarbon compounds having the general
formula C.sub.xH.sub.y, wherein x has a range of between 1 and 20,
and y has a range of between 1 and 20.
20. A method of forming a nitrogen-doped amorphous carbon layer on
a substrate in a processing chamber, comprising: depositing
conformally a nitrogen-doped amorphous carbon layer on patterned
features formed on the substrate, wherein the deposition is
performed; selectively removing the nitrogen-doped amorphous carbon
layer from an upper surface of the patterned features and an upper
surface of the substrate using an anisotropic etching process to
provide patterned features filled within sidewall spacers formed
from the nitrogen-doped amorphous carbon layer; and removing the
patterned features from the substrate.
21. The method of claim 20, wherein the nitrogen-doped amorphous
carbon layer is deposited by introducing into the processing
chamber a nitrogen-containing hydrocarbon source at a flow rate of
about 100 ring/min to about 1,000 mg/min, a nitrogen-containing gas
at a flow rate of 0 sccm to about 2,000 sccm, by applying an RF
power of about 30 W to about 200 W (for a 200 mm substrate), and at
an electrode spacing of about 100 mils to about 800 mils.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] Embodiments of the present invention generally relate to the
fabrication of integrated circuits and particularly to a method for
protecting sidewalls of hard mask spacers during an etching
process.
[0003] 2. Description of the Related Art
[0004] Reducing the size of integrated circuits (ICs) results in
improved performance, increased capacity and/or reduced cost. Each
size reduction requires more sophisticated techniques to form the
ICs. Photolithography is commonly used to pattern ICs on a
substrate. An exemplary feature of an IC is a line of a material
which may be a metal, semiconductor or insulator. Linewidth is the
width of the line and the spacing is the distance between adjacent
lines. Pitch is defined as the distance between a same point on two
neighboring lines. The pitch is equal to the sum of the linewidth
and the spacing. Due to factors such as optics and light or
radiation wavelength, however, photolithography techniques have a
minimum pitch below which a particular photolithographic technique
may not reliably form features. Thus, the minimum pitch of a
photolithographic technique can limit feature size reduction.
[0005] Self-aligned double patterning (SADP) is one method for
extending the capabilities of photolithographic techniques beyond
the minimum pitch. Such a method is illustrated in FIGS. 1A-1F.
With reference to FIG. 1A, patterned core features 102 are formed
from sacrificial structural material above a dielectric layer 114
on a substrate 100 using standard photo-lithography and etching
techniques. The patterned features are often referred to as
placeholders or cores and have linewidths and/or spacings near the
optical resolution of a photolithography system using a
high-resolution photomask. As shown in FIG. 1B, a conformal layer
106 of hard mask material such as silicon oxide is subsequently
deposited over core features 102. Hard mask spacers 108 are then
formed on the sides of core features 102 by preferentially etching
the hard mask material from the horizontal surfaces with an
anisotropic plasma etch to open the hard mask material deposited on
top of the patterned core features 102 as well as remove the hard
mask material deposited at the bottom between the two sidewalls, as
shown in FIG. 1C. The patterned core features 102 may then be
removed, leaving behind hard mask spacers 108 (FIG. 1D). At this
point hard mask spacers 108 may be used as an etch mask for
transferring the pattern to the dielectric layer 114 to form
dielectric ribs 116, as shown in FIG. 1E. The hard mask spacers 108
are subsequently removed (FIG. 1F). Therefore, the density of the
dielectric ribs 116 is twice that of the photo-lithographically
patterned core features 102, and the pitch of the dielectric ribs
116 is half the pitch of the patterned core features 102.
[0006] Currently, hard mask spacers 108 are formed by an atomic
layer deposition (ALD) using an etchable material such as silicon
oxides. These oxides are typically deposited at very low
temperature (e.g., less than 200.degree. C.). As a result, the
material quality is poor, with low density and poor mechanical
strength and degraded chemical resistance to subsequent etching
chemistries. During the etching of the hard mask material, the
spacer sidewalls, e.g., sidewalls 107 (FIG. 1D) are exposed to the
plasma. Due to the poor material quality of typical ALD hard mask
spacers, the sidewalls are damaged and thus causing higher line
edge roughness. This issue becomes serious with shrinking feature
size.
[0007] Therefore, there is a need for a method of protecting the
sidewalls of the hard mask spacers such that the patterning
integrity is greatly improved.
SUMMARY OF THE INVENTION
[0008] Embodiments of the present invention provide a method for
protecting sidewalls of hard mask spacers during an etching
process. In one embodiment, a method of forming a nitrogen-doped
amorphous carbon layer on a substrate in a processing chamber is
provided. The method generally includes depositing a predetermined
thickness of a sacrificial dielectric layer over a substrate,
forming patterned features on the substrate by removing portions of
the sacrificial dielectric layer to expose an upper surface of the
substrate, depositing conformally a predetermined thickness of a
nitrogen-doped amorphous carbon layer on the patterned features and
the exposed upper surface of the substrate, selectively removing
the nitrogen-doped amorphous carbon layer from an upper surface of
the patterned features and the upper surface of the substrate using
an anisotropic etching process to provide the patterned features
filled within sidewall spacers formed from the nitrogen-doped
amorphous carbon layer, and removing the patterned features from
the substrate.
[0009] In another embodiment, a method of forming a device in a
processing chamber is provided. The method generally includes
forming patterned features on an upper surface of a substrate,
depositing conformally a predetermined thickness of a sacrificial
dielectric layer on the patterned features and an exposed upper
surface of the substrate, selectively removing the sacrificial
dielectric layer from an upper surface of the patterned features
and the exposed upper surface of the substrate to provide the
patterned features filled within first sidewall spacers formed from
the sacrificial dielectric layer, forming second sidewall spacers
adjacent to the first sidewall spacers, the second sidewall spacers
being formed from a nitrogen-doped amorphous carbon material having
a carbon:nitrogen ratio of between about 0.1% nitrogen to about
4.0% nitrogen, and removing the patterned features filled within
the first sidewall spacers.
[0010] In yet another embodiment, a method of forming a
nitrogen-doped amorphous carbon layer on a substrate in a
processing chamber is provided. The method generally includes
depositing conformally a nitrogen-doped amorphous carbon layer on
patterned features formed on the substrate, wherein the deposition
is performed, selectively removing the nitrogen-doped amorphous
carbon layer from an upper surface of the patterned features and an
upper surface of the substrate using an anisotropic etching process
to provide patterned features filled within sidewall spacers formed
from the nitrogen-doped amorphous carbon layer, and removing the
patterned features from the substrate.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] So that the manner in which the above recited features of
the present invention can be understood in detail, a more
particular description of the invention, briefly summarized above,
may be had by reference to embodiments, some of which are
illustrated in the appended drawings. It is to be noted, however,
that the appended drawings illustrate only typical embodiments of
this invention and are therefore not to be considered limiting of
its scope, for the invention may admit to other equally effective
embodiments.
[0012] FIGS. 1A-1F illustrate cross-sectional views representing a
conventional double patterning process.
[0013] FIG. 2 is a flowchart depicting steps associated with an
exemplary patterning process according to one embodiment of the
invention.
[0014] FIGS. 3A-3E illustrate cross-sectional views of a structure
formed by the steps set forth in FIG. 2.
[0015] FIG. 4 is a flowchart depicting steps associated with an
exemplary patterning process according to another embodiment of the
invention.
[0016] FIGS. 5A-5H illustrate cross-sectional views of a structure
formed by the steps set forth in FIG. 4.
DETAILED DESCRIPTION
[0017] Embodiments of the present invention relate to an
ultra-conformal strippable spacer process. In various embodiments,
an ultra-conformal carbon-based material, such as amorphous carbon,
is deposited over features of sacrificial structure material
patterned using a high-resolution photomask. The ultra-conformal
carbon-based material serves as a protective layer during an ashing
or etching process, leaving the sacrificial structure material with
an upper surface exposed and sidewalls protected by the
carbon-based spacers. Upon removal of the sacrificial structure
material, the remaining carbon-based spacers may perform as a
hardmask layer for etching the underlying layer or structure. In
one example, the carbon-based material may be an undoped or a
nitrogen-doped amorphous carbon material.
[0018] Embodiments of the present invention may be performed using
any suitable processing chamber such as a plasma enhanced chemical
vapor deposition (PECVD) chamber. The processing chamber may be
incorporated into a substrate processing system. An exemplary
substrate processing system that may be used to practice the
invention is described in commonly assigned U.S. Pat. No. 6,364,954
issued on Apr. 2, 2002, to Salvador et. al. and is herein
incorporated by reference. Examples of suitable systems include the
CENTURA.RTM. systems which may use a DxZ.TM. processing chamber,
PRECISION 5000.RTM. systems, PRODUCER.TM. systems, PRODUCER GT.TM.
and the PRODUCER SE.TM. processing chambers which are commercially
available from Applied Materials, Inc., Santa Clara, Calif. It is
contemplated that other processing system, including those
available from other manufacturers, may be adapted to practice the
embodiments described herein.
Exemplary Fabrication Sequence Employing a-C Protective Layer
[0019] FIG. 2 is a process flowchart depicting steps associated
with an exemplary self-aligned double patterning process according
to one embodiment of the invention. FIGS. 3A-3E illustrate
cross-sectional views of a structure formed by the steps set forth
in FIG. 2. It is contemplated that the self-aligned double
patterning process is chosen for illustration purpose. The concept
of the invention is equally applicable to other processes, single
or dual patterning scheme, such as via/hole shrink process,
self-aligned triple patterning (SATP) process, or self-aligned
quadruple patterning (SAQP) process, etc. that may require the use
of protective spacers with variable line width and spacing or
protective sacrificial layer as needed in various semiconductor
processes such as NAND flash application, DRAM application, or CMOS
application, etc. In addition, the number or sequence of steps
illustrated in FIG. 2 is not intended to limiting as to the scope
of the invention described herein, since one or more steps can be
added, deleted and/or reordered without deviating from the basic
scope of the invention described herein.
[0020] The process 200 starts at box 202 by forming a sacrificial
structural layer 320 on a substrate 300. The sacrificial structural
layer 320 may be a silicon-based material such as silicon oxide,
silicon nitride, or polysilicon. Alternatively, the sacrificial
structural layer 320 may be a carbon-based material such as
amorphous carbons. In cases where a carbon-based sacrificial
structural layer is desired, the sacrificial structural layer 320
may be a combination of amorphous carbon and hydrogen (hydrogenated
amorphous carbon film). One exemplary amorphous carbon film may be
a strippable Advanced Patterning Film.TM. (APF) material
commercially available from Applied Materials, Inc. of Santa Clara,
Calif. It is contemplated that the choice of materials used for the
sacrificial structural layer 320 may vary depending upon the
etching/ashing rate relative to the conformal protective layer to
be formed thereon. While not shown, in certain embodiments where a
carbon-based sacrificial structural layer is used, one or more
anti-reflective coating layers may be deposited on the carbon-based
sacrificial structural layer to control the reflection of light
during a lithographic patterning process. Suitable anti-reflective
coating layer may include silicon dioxide, silicon oxynitride,
silicon nitride, or combinations thereof. One exemplary
anti-reflective coating layer may be a DARC.TM. material
commercially available from Applied Materials, Inc. of Santa Clara,
Calif.
[0021] The substrate 300 may have a substantially planar surface
323 as shown. Alternatively, the substrate 300 may have patterned
structures, a surface having trenches, holes, or vias formed
therein. While the substrate 300 is illustrated as a single body,
the substrate 300 may contain one or more materials used in forming
semiconductor devices such as metal contacts, trench isolations,
gates, bitlines, or any other interconnect features. In one
embodiment, the substrate 300 may include one or more metal layers,
one or more dielectric materials, semiconductor material, and
combinations thereof utilized to fabricate semiconductor devices.
For example, the substrate 300 may include an oxide material, a
nitride material, a polysilicon material, or the like, depending
upon application. In cases where a memory application is desired,
the substrate 300 may include the silicon substrate material, an
oxide material, and a nitride material, with or without polysilicon
sandwiched in between.
[0022] In some embodiments, the substrate 300 may include a
plurality of alternating oxide and nitride materials (i.e.,
oxide-nitride-oxide (ONO)), one or more oxide or nitride materials,
polysilicon or amorphous silicon materials, oxides alternating with
amorphous silicon, oxides alternating with polysilicon, undoped
silicon alternating with doped silicon, undoped polysilicon
alternating with doped polysilicon, or updoped amorphous silicon
alternating with doped amorphous silicon deposited on a surface of
the substrate (not shown). The substrate 300 may be a material or a
layer stack comprising one or more of the following: crystalline
silicon, silicon oxide, silicon oxynitride, silicon nitride,
strained silicon, silicon germanium, tungsten, titanium nitride,
doped or undoped polysilicon, doped or undoped silicon wafers and
patterned or non-patterned wafers, silicon on insulator (SOI),
carbon doped silicon oxides, silicon nitrides, doped silicon,
germanium, gallium arsenide, glass, sapphire, low k dielectrics,
and combinations thereof.
[0023] At box 204, a resist layer 330, such as a photoresist
material, is deposited on the sacrificial structural layer 320 as
shown in FIG. 3A.
[0024] At box 206, patterned features 321 formed from the
sacrificial structural layer 320 are produced on the substrate 300
using standard photo-lithography and etching techniques, as shown
in FIG. 3B. The patterned features may be formed from any suitable
material, for example oxides, such as silicon dioxide, silicon
oxynitride, or nitrides such as silicon nitride. The patterned
features are sometimes referred to as placeholders, mandrels or
cores and have specific linewidths and/or spacings based upon the
photoresist material used. The width of the patterned features 321
may be adjusted by subjecting the resist layer 330 to a trimming
process. After the pattern has been transferred into the
sacrificial structural layer 320, any residual photoresist and hard
mask material (if used) are removed using a suitable photoresist
stripping process.
[0025] At box 208, a carbon-based protective layer 340 is deposited
conformally or substantially conformally on the patterned features
321 and the exposed surfaces of the substrate 300, as shown in FIG.
3C. The thickness of the carbon-based protective layer 340 may be
between about 5 .ANG. and about 200 .ANG.. In one embodiment, the
carbon-based protective layer is an amorphous carbon (a-C) layer.
The amorphous carbon may be undoped or doped with nitrogen. In one
example, the carbon-based protective layer 340 is a nitrogen-doped
amorphous carbon layer. The nitrogen-doped amorphous carbon layer
may be deposited by any suitable deposition techniques such as
plasma enhanced chemical vapor deposition (PECVD) process. In one
embodiment, the nitrogen-doped amorphous carbon layer may be
deposited by flowing, among others, a hydrocarbon source, a
nitrogen-containing gas such as N.sub.2 or NH.sub.3, and a
plasma-initiating gas in a PECVD chamber. In another embodiment,
the nitrogen-doped amorphous carbon layer may be deposited by
flowing, among others, a hydrocarbon source, such as a gas-phase
hydrocarbon or a liquid-phase hydrocarbon that has been entrained
in a carrier gas, a nitrogen-containing hydrocarbon source, and a
plasma-initiating gas into a PECVD chamber. The hydrocarbon source
may be a mixture of one or more hydrocarbon compounds. In some
embodiments, the hydrocarbon source may not be required. Instead, a
nitrogen-containing hydrocarbon source and a plasma-initiating gas
are flowed into the PECVD chamber to form the nitrogen-doped
amorphous carbon protective layer on the patterned features 321 and
the exposed surfaces of the substrate 300.
[0026] The hydrocarbon compounds may be partially or completely
doped derivatives of hydrocarbon compounds, including fluorine-,
oxygen-, hydroxyl group-, and boron-containing derivatives of
hydrocarbon compounds. Hydrocarbon compounds or derivatives thereof
that may be included in the hydrocarbon source may be described by
the formula CxHy, where x has a range of between 1 and 10 and y has
a range of between 2 and 30. Suitable hydrocarbon compounds may
include, but are not limited to, acetylene (C.sub.2H.sub.2), ethane
(C.sub.2H.sub.6), propylene (C.sub.3H.sub.6), propyne
(C.sub.3H.sub.4), propane (C.sub.3H.sub.8), butane
(C.sub.4H.sub.10), butylene (C.sub.4H.sub.8), butyne
(C.sub.4H.sub.6), vinylacetylene, phenylacetylene (C.sub.8H.sub.6),
benzene, styrene, toluene, xylene, ethylbenzene, acetophenone,
methyl benzoate, phenyl acetate, phenol, cresol, furan,
alpha-terpinene, cymene, 1,1,3,3,-tetramethylbutylbenzene,
t-butylether, t-butylethylene, methyl-methacrylate, and
t-butylfurfurylether, compounds having the formula C.sub.3H.sub.2
and C.sub.5H.sub.4, monofluorobenzene, difluorobenzenes,
tetrafluorobenzenes, hexafluorobenzene, and the like. Additional
suitable hydrocarbons may include ethylene, pentene, butadiene,
isoprene, pentadiene, hexadiene, monofluoroethylene,
difluoroethylenes, trifluoroethylene, tetrafluoroethylene,
monochloroethylene, dichloroethylenes, trichloroethylene,
tetrachloroethylene, and the like.
[0027] Nitrogen containing hydrocarbon compounds or derivatives
thereof that may be included in the nitrogen containing hydrocarbon
source can be described by the formula CxHyNz, where x has a range
of between 1 and 12, y has a range of between 2 and 20, and z has a
range of between 1 and 10. Suitable nitrogen containing hydrocarbon
compounds may include one or more of the following compounds
methylamine, dimethylamine, trimethylamine (TMA), triethylamine,
aniline, quinoline, pyridine, acrilonitrile, and benzonitrile.
[0028] In certain embodiments, the nitrogen doped amorphous carbon
deposition process may include the use of a plasma-initiating gas
that is introduced into the PECVD chamber at before and/or same
time as the hydrocarbon compound and a plasma is initiated to begin
deposition. The plasma-initiating gas may be a high ionization
potential gas including, and not limited to, helium gas, hydrogen
gas, nitrogen gas, argon gas and combinations thereof. The
plasma-initiating gas may also be a chemically inert gas, such as
helium gas, nitrogen gas, or argon gas. Suitable ionization
potentials for gases are from about 5 eV (electron potential) to 25
eV. The plasma-initiating gas may be introduced into the PECVD
chamber prior to the nitrogen containing hydrocarbon source and/or
the hydrocarbon source, which allows a stable plasma to be formed
and reduces the chances of arcing. An inert gas used as a diluent
gas or a carrier gas, such as argon, may be introduced with the
plasma-initiating gas, the nitrogen containing hydrocarbon source,
the hydrocarbon source, or combinations thereof. Suitable dilution
gases such as helium (He), hydrogen (H.sub.2), nitrogen (N.sub.2),
ammonia (NH.sub.3), or combinations thereof, among others, may be
added to the gas mixture, if desired. Ar, He, and N.sub.2 are used
to control the density and deposition rate of the amorphous carbon
layer. In some cases, the addition of H.sub.2 and/or NH.sub.3 can
be used to control the hydrogen ratio of the amorphous carbon
layer. Alternatively, dilution gases may not be used during the
deposition.
[0029] In cases where the nitrogen-doped amorphous carbon is
deposited using a hydrocarbon source and a nitrogen-containing gas,
the nitrogen-containing gas may be introduced into the PECVD
chamber at a nitrogen-containing gas to hydrocarbon source ratio of
about 1:100 to about 10:1.
[0030] In various embodiments, the nitrogen doped amorphous carbon
layer may be deposited at a chamber pressure of about 0.5 Torr or
greater, such as from about 0.5 Torr to about 20 Torr, and in one
embodiment, about 2 Torr or greater, for example, from about 2 Torr
to about 12 Torr, and a substrate temperature from about 25.degree.
C. to about 800.degree. C., such as at a temperature from about
200.degree. C. to about 400.degree. C. The electrode spacing
between a showerhead and substrate surface when depositing the
layer may be between 200 mils and 5,000 mils spacing, for example,
about 500 mils spacing. In certain embodiments, where a plasma is
used, the hydrocarbon source, the nitrogen doped amorphous carbon
source, and the plasma-initiating gas are introduced into the PECVD
chamber and a plasma is initiated to begin the deposition.
[0031] Plasma may be generated by applying RF power at a power
density to substrate surface area of from about 0.01 W/cm.sup.2 to
about 5 W/cm.sup.2, such as from about 0.8 W/cm.sup.2 to about 2.3
W/cm.sup.2, for example, about 2 W/cm.sup.2. The power application
may be from about 1 Watt to about 2,000 watts, such as from about
10 W to about 100 W, for a 300 mm substrate. It is noted that the
RF power can be either single frequency or dual frequency. If a
single frequency power is used, the frequency power may be between
about 10 KHz and about 30 MHz. If a dual-frequency RF power is used
to generate the plasma, a mixed RF power may be used. The mixed RF
power may provide a high frequency power in a range from about 10
MHz to about 30 MHz, for example, about 13.56 MHz, as well as a low
frequency power in a range of from about 10 KHz to about 1 MHz, for
example, about 350 KHz. A dual frequency RF power application is
believed to provide independent control of flux and ion energy
since the energy of the ions hitting the film surface influences
the film density. The applied RF power and use of one or more
frequencies may be varied based upon the substrate size and the
equipment used. In certain embodiments, a single frequency RF power
application may be used, and is typically, an application of the
high frequency power as described herein.
[0032] An exemplary deposition process for processing 300 mm
circular substrates may employ, among others, a plasma-initiating
gas, a nitrogen containing hydrocarbon source, and a dilution gas.
The deposition process may include supplying a plasma-initiating
gas, such as helium and/or argon, at a flow rate from about 0 sccm
to about 50,000 sccm, for example, between about 400 sccm to about
8,000 sccm, supplying a nitrogen containing hydrocarbon source, at
a flow rate from about 10 sccm to about 2,000 sccm, for example,
from about 500 sccm to about 1,500 sccm. In case the nitrogen
containing hydrocarbon source is a liquid precursor, then the
nitrogen containing hydrocarbon source flow can be between 15
mg/min and 2,000 mg/min, for example between 100 mg/min and 1,000
mg/min. A dilution gas, such as NH.sub.3, He, Ar, H.sub.2, or
N.sub.2, may be supplied at a flow rate from about 0 sccm to about
5,000 sccm, for example about 500 sccm to about 1,000 sccm. The
deposition process may be performed with a dual frequency RF power
from about 5 W to about 1,600 W, for example between about 10 W and
about 100 W, at a chamber pressure from about 0.5 Torr to about 50
Torr, for example between about 5 torr and about 15 Torr, and a
substrate temperature from about 25.degree. C. to about 650.degree.
C., for example between about 200.degree. C. and about 400.degree.
C. This process range provides a deposition rate for a nitrogen
doped amorphous carbon layer in the range of about 10 .ANG./min to
about 30,000 .ANG./min. One skilled in the art, upon reading the
disclosure herein, can calculate appropriate process parameters in
order to produce a nitrogen doped amorphous carbon film of
different deposition rates. The as-deposited nitrogen-doped
amorphous carbon layer has an adjustable carbon:nitrogen ratio that
ranges from about 0.1% nitrogen to about 4.0% nitrogen, such as
about 1.5% to about 2%. An example of nitrogen doped amorphous
carbon materials deposited by the processes described herein is
provided as follows.
[0033] A nitrogen doped amorphous carbon deposition process may
include providing a flow rate of helium to the processing chamber
at about 200 sccm to 1,500 sccm, for example about 500 sccm,
providing a flow rate of benzonitrile to the processing chamber at
about 100 mg/min to about 1,000 mg/min, and providing a flow rate
of ammonia to the processing chamber at about 0 sccm to about 2,000
sccm, applying a high frequency RF power (13.56 MHz) at about 30 W
to 200 W (for a 200 mm wafer), maintaining a deposition temperature
of about 200.degree. C. to about 550.degree. C., maintaining a
chamber pressure of about 2 Torr to 15 Torr, with a spacing of
about 100 mils to about 800 mils to produce a nitrogen doped
amorphous carbon layer having a thickness of about 10 .ANG. to
about 1,000 .ANG..
[0034] Referring back to FIG. 2, at box 210, after the carbon-based
protective layer 340 has been deposited conformally on the
patterned features 321, the carbon-based protective layer 340 is
anisotropically etched (a vertical etch) to expose an upper surface
of the substrate 300 in areas 311 and expose an upper surface of
patterned features 321, resulting in patterned features 321 (formed
from the sacrificial structural layer 320) protected by
carbon-based sidewall spacers 341, as shown in FIG. 3D.
[0035] At box 212, the patterned features 321 (formed from the
sacrificial structural layer 320) are removed using a conventional
plasma etching process or other suitable wet stripping process,
leaving non-sacrificial carbon-based sidewall spacers 341 as shown
in FIG. 3E. The plasma etching process may be done by introducing a
fluorine-based etching chemistry into a plasma above the substrate.
Due to the improved material quality and coverage, the carbon-based
sidewall spacers 341 are not damaged because they have very good
selectivity to the fluorine-based reactive etching chemistry or the
wet strip-based chemistry. Upon removal of the patterned features
321, the remaining carbon-based sidewall spacers 341 may be used as
a hardmask for etching the underlying layer, layer stack, or
structure. Particularly, the density of the carbon-based sidewall
spacers 341 in accordance with this patterning process is twice
that of the photo-lithographically patterned features 321, the
pitch of carbon-based sidewall spacer 341 is half the pitch of the
patterned features 321.
[0036] FIG. 4 is a flowchart depicting steps associated with an
exemplary patterning process according to another embodiment of the
invention. FIGS. 5A-5H illustrate cross-sectional views of a
structure formed by the steps set forth in FIG. 4. It is noted that
the concept of this embodiment is equally applicable to other
processes, single or dual patterning scheme, such as via/hole
shrink process, back end of line (BEOL) self-aligned double
patterning (SADP) process, or self-aligned quadruple patterning
(SAQP) process, etc. that may require the use of protective spacers
with variable line width and spacing or protective sacrificial
layer as needed in various semiconductor processes such as NAND
flash application, DRAM application, or CMOS application, etc.
[0037] The process 400 starts at box 402 by providing a substrate
500 into a processing chamber, such as a PECVD chamber. The
substrate 500 may be one or more materials used in forming
semiconductor devices including a silicon material, an oxide
material, a polysilicon material, or the like, as discussed above
with respect to substrate 300 shown in FIG. 3A.
[0038] At box 404, a non-sacrificial structural layer 520 is
deposited on the substrate 500 as shown in FIG. 5B. The
non-sacrificial structural layer 520 may be a carbon-based material
such as amorphous carbons. In one example, the non-sacrificial
structural layer 520 is an Advanced Patterning Film.TM. (APF)
material commercially available from Applied Materials, Inc. of
Santa Clara, Calif. While not shown, in certain embodiments where a
carbon-based non-sacrificial structural layer is used, one or more
anti-reflective coating layers may be deposited on the carbon-based
non-sacrificial structural layer to control the reflection of light
during a lithographic patterning process. Suitable anti-reflective
coating layer may include silicon dioxide, silicon oxynitride,
silicon nitride, or combinations thereof. One exemplary
anti-reflective coating layer may be a DARC.TM. material
commercially available from Applied Materials, Inc. of Santa Clara,
Calif.
[0039] At box 406, a bottom anti-reflective coating (BARC) layer
540 is deposited over the non-sacrificial structure layer 520. The
BARC layer 540 may be an organic material such as polyamides and
polysulfones. The BARC layer 540 is believed to reduce reflection
of light during patterning of the subsequent resist layer and is
also helpful for thinner resist layers because the BARC layer 540
increases the total thickness of the multi-layered mask for
improved etch resistance during etch of underlying layer or
structure. In certain embodiments, the BARC layer 540 may further
include a light absorbing layer 530 deposited between the BARC
layer 540 and the non-sacrificial structure layer 520 as shown in
FIG. 5C, to improve photolithography performance. The light
absorbing layer 530 may be a metal layer, such as nitrides. In one
example, the light absorbing layer 530 is titanium nitride.
[0040] At box 408, a resist layer, such as a photoresist material,
is then deposited on the BARC layer 540. The resist layer is then
patterned by a lithographic process producing a patterned resist
layer 550 with a desired etch pattern 551, as shown in FIG. 5D. The
etch pattern 551 is shown to have different pattern width for
exemplary purpose.
[0041] At box 410, the BARC layer 540, the light absorbing layer
530, and the non-sacrificial structure layer 520 are patterned
respectively using conventional photolithography and etching
processes to transfer the desired etch pattern 551 into the
non-sacrificial structure layer 520, leaving patterned
non-sacrificial features 521, as shown in FIG. 5E.
[0042] At box 412, a first conformal layer is deposited conformally
or substantially conformally on the patterned non-sacrificial
features 521 and the exposed surfaces of the substrate 500. The
first conformal layer may comprise a strippable material having an
etching rate different from the patterned sacrificial features 521.
Suitable materials for the first conformal layer may include, for
example, oxides such as silicon dioxide, silicon oxynitride, or
nitride such as silicon nitride. The first conformal layer is then
anisotropically etched to expose an upper surface of the substrate
500 in areas 511 and expose an upper surface of patterned
non-sacrificial features 521, resulting in patterned
non-sacrificial features 521 (formed from the non-sacrificial
structural layer 520) protected by strippable sidewall spacers 561
formed from the first conformal layer, as shown in FIG. 5F.
[0043] At box 414, non-sacrificial carbon-based sidewall spacers
571 are then formed adjacent the patterned non-sacrificial features
521 in a manner similar to the sidewall spacers 561 as shown in
FIG. 5G. The non-sacrificial carbon-based sidewall spacers 571 may
be an amorphous carbon (a-C) undoped or doped with nitrogen formed
by the processes as described above with respect to boxes 208 and
210. In one embodiment, the non-sacrificial carbon-based sidewall
spacers 571 are nitrogen-doped amorphous carbon.
[0044] At box 416, the strippable sidewall spacers 561, located
between the patterned non-sacrificial features 521 and the
non-sacrificial carbon-based sidewall spacers 571, are removed
using a conventional wet stripping process or other suitable
process, leaving patterned non-sacrificial features 521 and
non-sacrificial carbon-based sidewall spacers 571 as shown in FIG.
5H. The remaining patterned non-sacrificial features 521 and
non-sacrificial carbon-based sidewall spacers 571 may then be used
as a hardmask for etching the underlying layer, layer stack, or
structure. Particularly, the density of the resulting hardmask
(i.e., patterned non-sacrificial features 521 and non-sacrificial
carbon-based sidewall spacers 571) in accordance with this
patterning process is triple that of the patterned resist layer
550, the pitch of resulting hardmask (i.e., patterned
non-sacrificial features 521 and non-sacrificial carbon-based
sidewall spacers 571) is half the pitch of the patterned resist
layer 550.
[0045] Carbon-based protective layers or sidewall spacers deposited
in accordance with the present invention have been observed to be
able to provide excellent conformality higher than 95% with an
improved film uniformity of about 1.5%, high film density of about
1.25-1.60 g/cc, and a compressive film stress less than 50 MPa.
Since the sidewalls of hard mask spacers are not damaged during the
ashing or anisotropic plasma etching process, the line edge
roughness is significantly reduced as compared to the conventional
ALD grown spacers using silicon oxide materials. Therefore, the
resulting hard mask spacers can provide superior etch profile and
etch selectivity with little or no microloading.
[0046] While the foregoing is directed to embodiments of the
present invention, other and further embodiments of the invention
may be devised without departing from the basic scope thereof, and
the scope thereof is determined by the claims that follow.
* * * * *