U.S. patent application number 12/987688 was filed with the patent office on 2011-05-05 for method for depositing an amorphous carbon film with improved density and step coverage.
Invention is credited to Ganesh Balasubramanian, Chiu Chan, Hyoung-Chan Ha, Karthik Janakiraman, Bok Hoen Kim, Hichem M'Saad, Deenesh Padhi, Sohyun Park, Sudha Rathi, Martin Jay Seamons, Visweswaren Sivaramakrishnan, Derek R. Witty.
Application Number | 20110104400 12/987688 |
Document ID | / |
Family ID | 38846433 |
Filed Date | 2011-05-05 |
United States Patent
Application |
20110104400 |
Kind Code |
A1 |
Padhi; Deenesh ; et
al. |
May 5, 2011 |
METHOD FOR DEPOSITING AN AMORPHOUS CARBON FILM WITH IMPROVED
DENSITY AND STEP COVERAGE
Abstract
A method for depositing an amorphous carbon layer on a substrate
includes the steps of positioning a substrate in a chamber,
introducing a hydrocarbon source into the processing chamber,
introducing a heavy noble gas into the processing chamber, and
generating a plasma in the processing chamber. The heavy noble gas
is selected from the group consisting of argon, krypton, xenon, and
combinations thereof and the molar flow rate of the noble gas is
greater than the molar flow rate of the hydrocarbon source. A
post-deposition termination step may be included, wherein the flow
of the hydrocarbon source and the noble gas is stopped and a plasma
is maintained in the chamber for a period of time to remove
particles therefrom.
Inventors: |
Padhi; Deenesh; (Sunnyvale,
CA) ; Ha; Hyoung-Chan; (San Jose, CA) ; Rathi;
Sudha; (San Jose, CA) ; Witty; Derek R.;
(Fremont, CA) ; Chan; Chiu; (Foster City, CA)
; Park; Sohyun; (Santa Clara, CA) ;
Balasubramanian; Ganesh; (Sunnyvale, CA) ;
Janakiraman; Karthik; (San Jose, CA) ; Seamons;
Martin Jay; (San Jose, CA) ; Sivaramakrishnan;
Visweswaren; (Cupertino, CA) ; Kim; Bok Hoen;
(San Jose, CA) ; M'Saad; Hichem; (Santa Clara,
CA) |
Family ID: |
38846433 |
Appl. No.: |
12/987688 |
Filed: |
January 10, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11427324 |
Jun 28, 2006 |
7867578 |
|
|
12987688 |
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Current U.S.
Class: |
427/569 |
Current CPC
Class: |
H01L 21/31144 20130101;
C23C 16/5096 20130101; C23C 16/045 20130101; C23C 16/26 20130101;
C23C 16/56 20130101; H01L 21/02274 20130101; H01L 21/3146 20130101;
H01L 21/02115 20130101 |
Class at
Publication: |
427/569 |
International
Class: |
C23C 26/00 20060101
C23C026/00; H05H 1/24 20060101 H05H001/24 |
Claims
1. A method of forming an amorphous carbon layer on a substrate,
comprising: positioning a substrate in a substrate processing
chamber; introducing a hydrocarbon source into the processing
chamber; introducing a diluent gas selected from the group
consisting of argon, krypton, xenon, and combinations thereof, into
the processing chamber, wherein the molar flow rate of the diluent
gas is greater than the molar flow rate of the hydrocarbon source;
introducing a plasma-initiating gas into the processing chamber,
wherein the plasma-initiating gas is a different gas than the
diluent gas; generating a plasma in the processing chamber; and
forming an amorphous carbon layer on the substrate.
2. The method of claim 1, wherein the molar flow rate of the
diluent gas is from 2 to 40 times greater than the molar flow rate
of the hydrocarbon source.
3. The method of claim 1, wherein the molar flow rate of the
diluent gas is from 10 to 14 times greater than the molar flow rate
of the hydrocarbon source.
4. The method of claim 1, further comprises flowing hydrogen gas
into the processing chamber.
5. The method of claim 4, wherein the ratio of the molar flow rate
of the diluent gas to the molar flow rate of the hydrogen gas is
from 2:1 to 4:1.
6. The method of claim 1, wherein the hydrocarbon source is
selected from the group consisting of aliphatic hydrocarbons,
alicyclic hydrocarbons, aromatic hydrocarbons, and combinations
thereof.
7. The method of claim 1, wherein the flow rate of the diluent gas
is 4000 sccm or higher and the flow rate of the hydrocarbon gas is
1800 sccm or less.
8. The method of claim 1, wherein the amorphous carbon layer is
formed to have a density from 1.2 g/cc to 1.8 g/cc and an
absorption coefficient in the visible spectrum that is less than
0.10.
9. A method of forming an amorphous carbon layer on a substrate,
comprising: positioning a substrate in a substrate processing
chamber; introducing a hydrocarbon source into the processing
chamber; introducing a diluent gas at least as massive as argon
into the processing chamber, wherein the molar flow rate of the
diluent gas is from 2 to 40 times the molar flow rate of the
hydrocarbon source; introducing a plasma-initiating gas into the
processing chamber, wherein the plasma-initiating gas is a
different gas than the diluent gas; generating a plasma in the
processing chamber; and forming an amorphous carbon layer on the
substrate.
10. The method of claim 9, wherein the diluent gas is argon, the
plasma-initiating gas is helium, and the hydrocarbon source is
selected from the group consisting of aliphatic hydrocarbons,
alicyclic hydrocarbons, aromatic hydrocarbons, and combinations
thereof.
11. The method of claim 9, wherein the molar flow rate of the
diluent gas is from 10 to 14 times greater than the molar flow rate
of the hydrocarbon source.
12. The method of claim 9, further comprises flowing hydrogen gas
into the processing chamber, wherein the ratio of the molar flow
rate of the diluent gas to the molar flow rate of the hydrogen gas
is from 2:1 to 4:1.
13. The method of claim 9, wherein the flow rate of the diluent gas
is 4000 sccm or higher and the flow rate of the hydrocarbon gas is
1800 sccm or less.
14. The method of claim 9, wherein the amorphous carbon layer is
formed to have a density from 1.2 g/cc to 1.8 g/cc and an
absorption coefficient in the visible spectrum that is less than
0.10.
15. The method of claim 9, further comprising maintaining a
pressure from 2 Torr to 8 Torr in the processing chamber after
initiating plasma therein.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of co-pending U.S. patent
application Ser. No. 11/427,324, filed Jun. 28, 2006, which is
herein incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] Embodiments of the present invention generally relate to the
fabrication of integrated circuits and particularly to the
deposition of an amorphous carbon layer on a semiconductor
substrate.
[0004] 2. Description of the Related Art
[0005] Integrated circuits have evolved into complex devices that
can include millions of transistors, capacitors and resistors on a
single chip. The evolution of chip design continually requires
faster circuitry and greater circuit density. The demand for faster
circuits with greater circuit densities imposes corresponding
demands on the materials used to fabricate such integrated
circuits. In particular, as the dimensions of integrated circuit
components are reduced to sub-micron dimensions, it has been
necessary to use not only low resistivity conductive materials such
as copper to improve the electrical performance of devices, but
also low dielectric constant insulating materials, often referred
to as low-k materials. Low-k materials generally have a dielectric
constant of less than 4.0.
[0006] Producing devices having low-k materials with little or no
surface defects or feature deformation is problematic. Low-k
dielectric materials are often porous and susceptible to being
scratched or damaged during subsequent process steps, thus
increasing the likelihood of defects being formed on the substrate
surface. Low-k materials are often brittle and may deform under
conventional polishing processes, such as chemical mechanical
polishing (CMP). One solution to limiting or reducing surface
defects and deformation of low-k materials is the deposition of a
hardmask over the exposed low-k materials prior to patterning and
etching. The hardmask prevents damage and deformation of the
delicate low-k materials. In addition, a hardmask layer may act as
an etch mask in conjunction with conventional lithographic
techniques to prevent the removal of a low-k material during
etch.
[0007] Typically, the hardmask is an intermediate oxide layer,
e.g., silicon dioxide or silicon nitride. However, some device
structures already include silicon dioxide and/or silicon nitride
layers, for example, damascene structures. Such device structures,
therefore, cannot be patterned using a silicon dioxide or silicon
nitride hardmask as an etch mask, since there will be little or no
etch selectivity between the hardmask and the material thereunder,
i.e., removal of the hardmask will result in unacceptable damage to
underlying layers. To act as an etch mask for oxide layers, such as
silicon dioxide or silicon nitride, a material must have good etch
selectivity relative to those oxide layers. Amorphous hydrogenated
carbon is a material used as a hardmask for silicon dioxide or
silicon nitride materials.
[0008] Amorphous hydrogenated carbon, also referred to as amorphous
carbon and denoted a-C:H, is essentially a carbon material with no
long-range crystalline order which may contain a substantial
hydrogen content, for example on the order of about 10 to 45 atomic
%. a-C:H is used as hardmask material in semiconductor applications
because of its chemical inertness, optical transparency, and good
mechanical properties. While a-C:H films can be deposited via
various techniques, plasma enhanced chemical vapor deposition
(PECVD) is widely used due to cost efficiency and film property
tunability. In a typical PECVD process, a hydrocarbon source, such
as a gas-phase hydrocarbon or vapors of a liquid-phase hydrocarbon
that have been entrained in a carrier gas, is introduced into a
PECVD chamber. A plasma-initiated gas, typically helium, is also
introduced into the chamber. Plasma is then initiated in the
chamber to create excited CH-- radicals. The excited CH-radicals
are chemically bound to the surface of a substrate positioned in
the chamber, forming the desired a-C:H film thereon.
[0009] FIGS. 1A-1E illustrate schematic cross-sectional views of a
substrate 100 at different stages of an integrated circuit
fabrication sequence incorporating an a-C:H layer as a hardmask. A
substrate structure 150 denotes the substrate 100 together with
other material layers formed on the substrate 100. FIG. 1A
illustrates a cross-sectional view of a substrate structure 150
having a material layer 102 that has been conventionally formed
thereon. The material layer 102 may be a low-k material and/or an
oxide, e.g., SiO.sub.2.
[0010] mom FIG. 1B depicts an amorphous carbon layer 104 deposited
on the substrate structure 150 of FIG. 1A. The amorphous carbon
layer 104 is formed on the substrate structure 150 by conventional
means, such as via PECVD. The thickness of amorphous carbon layer
104 is variable depending on the specific stage of processing.
Typically, amorphous carbon layer 104 has a thickness in the range
of about 500 .ANG. to about 10000 .ANG.. Depending on the etch
chemistry of the energy sensitive resist material 108 used in the
fabrication sequence, an optional capping layer (not shown) may be
formed on amorphous carbon layer 104 prior to the formation of
energy sensitive resist material 108. The optional capping layer
functions as a mask for the amorphous carbon layer 104 when the
pattern is transferred therein and protects amorphous carbon layer
104 from energy sensitive resist material 108.
[0011] As depicted in FIG. 1B, energy sensitive resist material 108
is formed on amorphous carbon layer 104. The layer of energy
sensitive resist material 108 can be spin-coated on the substrate
to a thickness within the range of about 2000 .ANG. to about 6000
.ANG.. Most energy sensitive resist materials are sensitive to
ultraviolet (UV) radiation having a wavelength less than about 450
nm, and for some applications having wavelengths of 245 nm or 193
nm.
[0012] A pattern is introduced into the layer of energy sensitive
resist material 108 by exposing energy sensitive resist material
108 to UV radiation 130 through a patterning device, such as a mask
110, and subsequently developing energy sensitive resist material
108 in an appropriate developer. After energy sensitive resist
material 108 has been developed, the desired pattern, consisting of
apertures 140, is present in energy sensitive resist material 108,
as shown in FIG. 1C.
[0013] Thereafter, referring to FIG. 1D, the pattern defined in
energy sensitive resist material 108 is transferred through
amorphous carbon layer 104 using the energy sensitive resist
material 108 as a mask. An appropriate chemical etchant is used
that selectively etches amorphous carbon layer 104 over the energy
sensitive resist material 108 and the material layer 102, extending
apertures 140 to the surface of material layer 102. Appropriate
chemical etchants include ozone, oxygen or ammonia plasmas.
[0014] Referring to FIG. 1E, the pattern is then transferred
through material layer 102 using the amorphous carbon layer 104 as
a hardmask. In this process step, an etchant is used that
selectively removes material layer 102 over amorphous carbon layer
104, such as a dry etch, i.e. a non-reactive plasma etch. After the
material layer 102 is patterned, the amorphous carbon layer 104 can
optionally be stripped from the substrate 100. In a specific
example of a fabrication sequence, the pattern defined in the a-C:H
hardmask is incorporated into the structure of the integrated
circuit, such as a damascene structure. Damascene structures are
typically used to form metal interconnects on integrated
circuits.
[0015] Device manufacturers using a-C:H hardmask layers demand two
critical requirements to be met: (1) very high selectivity of the
hardmask during the dry etching of underlying materials and (2)
high optical transparency in the visible spectrum for lithographic
registration accuracy. The term "dry etching" generally refers to
etching processes wherein a material is not dissolved by immersion
in a chemical solution and includes methods such as reactive ion
etching, sputter etching, and vapor phase etching. Further, for
applications in which a hardmask layer is deposited on a substrate
having topographic features, an additional requirement for an a-C:H
hardmask is that the hardmask layer conformally covers all surfaces
of said topographic features.
[0016] Referring back to FIGS. 1A-E, to ensure that amorphous
carbon layer 104 adequately protects material layer 102 during dry
etching, it is important that amorphous carbon layer 104 possesses
a relatively high etch selectivity, or removal rate ratio, with
respect to material layer 102. Generally, an etch selectivity
during the dry etch process of at least about 10:1 or more is
desirable between amorphous carbon layer 104 and material layer
102, i.e., material layer 102 is etched ten times faster than
amorphous carbon layer 104. In this way, the hardmask layer formed
by amorphous carbon layer 104 protects regions of material layer
102 that are not to be etched or damaged while apertures 140 are
formed therein via a dry etch process.
[0017] In addition, a hardmask that is highly transparent to
optical radiation, i.e., light wavelengths between about 400 nm and
about 700 nm, is desirable in some applications, such as the
lithographic processing step shown in FIG. 1B. Transparency to a
particular wavelength of light allows for more accurate
lithographic registration, which in turn allows for very precise
alignment of mask 110 with specific locations on substrate 100. The
transparency of a material to a given frequency of light is
generally quantified as the absorption coefficient of a material,
which is also referred to as the extinction coefficient. For
example, for an a-C:H layer that is approximately 6000 .ANG. to
7000 .ANG. thick, the a-C:H layer should have an absorption
coefficient of 0.12 or less at the frequency of light used for the
lithographic registration, for example 630 nm, otherwise mask 110
may not be aligned accurately. Producing a layer with an absorption
coefficient of 0.12 or less may be accomplished by modulating
deposition parameters, such as substrate temperature or plasma ion
energy.
[0018] However, there is typically a trade-off between creating an
a-C:H film that possesses high transparency and one with high etch
selectivity. An amorphous carbon layer with better etch selectivity
will generally have worse transparency. For example, when
deposition temperature is used as the modulating factor, a-C:H
films deposited at relatively high temperatures, i.e.
>500.degree. C., typically possess good etch selectivity but low
transparency. Lowering the deposition temperature, especially below
400.degree. C., improves the transparency of the a-C:H film but
results in a higher etching rate for the film and, hence, less etch
selectivity.
[0019] As noted above, in some applications, a hardmask layer may
be deposited on a substrate with an underlying topography, for
example an alignment key used to align the patterning process. In
these applications, an a-C:H layer that is highly conformal to the
underlying topography is also desirable. FIG. 2 illustrates a
schematic cross-sectional view of a substrate 200 with a feature
201 and a non-conformal amorphous carbon layer 202 formed thereon.
Because non-conformal amorphous carbon layer 202 does not
completely cover the sidewalls 204 of feature 201, subsequent
etching processes may result in unwanted erosion of sidewalls 204.
The lack of complete coverage of sidewalls 204 by non-conformal
amorphous carbon layer 202 may also lead to photoresist poisoning
of the material under non-conformal carbon layer 202, which is
known to damage electronic devices. Conformality of a layer is
typically quantified by a ratio of the average thickness of a layer
deposited on the sidewalls of a feature to the average thickness of
the same deposited layer on the field, or upper surface, of the
substrate.
[0020] Further, it is important that the formation of a hardmask
layer does not deleteriously affect a semiconductor substrate in
other ways. For example, if, during the formation of a hardmask, a
large numbers of particles that can contaminate the substrate are
generated, or the devices formed on the substrate are excessively
heated, the resulting problems can easily outweigh any
benefits.
[0021] Therefore, there is a need for a method of depositing a
material layer useful for integrated circuit fabrication which has
good etch selectivity with oxides, has high optical transparency in
the visible spectrum, can be conformally deposited on substrates
having topographic features, and can be produced at relatively low
temperatures without generating large numbers of particles.
SUMMARY OF THE INVENTION
[0022] Embodiments of the present invention provide a method for
depositing an amorphous carbon layer on a substrate. The method,
according to a first embodiment, comprises positioning a substrate
in a chamber, introducing a hydrocarbon source into the processing
chamber, introducing a heavy noble gas the processing chamber, and
generating a plasma in the processing chamber. The heavy noble gas
is selected from the group consisting of argon, krypton, xenon, and
combinations thereof and the molar flow rate of the noble gas is
greater than the molar flow rate of the hydrocarbon source. A
post-deposition termination step may be included, wherein the flow
of the hydrocarbon source and the noble gas is stopped and a plasma
is maintained in the chamber for a period of time to remove
particles therefrom. Hydrogen may also be introduced into the
chamber during the post-deposition termination step.
[0023] A method, according to a second embodiment, comprises
positioning a substrate in a chamber, introducing a hydrocarbon
source into the processing chamber, introducing a diluent gas of
the hydrocarbon source into the processing chamber, and generating
a plasma in the processing chamber. The molar flow rate of the
diluent gas into the processing chamber is between about 2 times
and about 40 times the molar flow rate of the hydrocarbon source. A
post-deposition termination step similar to that of the first
embodiment may also be included in this method.
[0024] The method, according to a third embodiment, comprises
positioning a substrate in a chamber, introducing a hydrocarbon
source into the processing chamber, introducing a diluent gas of
the hydrocarbon source into the processing chamber, generating a
plasma in the processing chamber, and maintaining a pressure of
about 2 Torr to 8 Torr in the processing chamber after initiating
plasma therein. The amorphous carbon layer may have a density of
between about 1.2 g/cc and about 1.8 g/cc and the absorption
coefficient of the amorphous carbon layer may be less than about
0.10 in the visible spectrum.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] 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.
[0026] FIGS. 1A-1E (Prior Art) illustrate schematic cross-sectional
views of a substrate at different stages of an integrated circuit
fabrication sequence incorporating an amorphous carbon layer as a
hardmask.
[0027] FIG. 2 (Prior Art) illustrates a schematic cross-sectional
view of a substrate with a feature and a non-conformal amorphous
carbon layer formed thereon.
[0028] FIG. 3 is a graph plotting the relationship between film
density and etch selectivity of amorphous carbon films.
[0029] FIG. 3A is a schematic representation of a substrate
processing system that can be used to perform amorphous carbon
layer deposition according to embodiments of the invention.
[0030] FIG. 4 is a graph demonstrating the effect of an argon
diluent gas on amorphous carbon film density.
[0031] FIG. 5 illustrates the effect of diluent gas type on
resultant film density.
[0032] FIG. 6 illustrates the effect of lower hydrocarbon flow rate
on film density.
[0033] FIG. 7 illustrates the effect of chamber pressure on film
density.
[0034] FIG. 8 illustrates the deposition rate improvement by
introducing a heavy noble gas as a high flow rate diluent while
depositing an amorphous carbon film.
[0035] FIG. 9 illustrates a schematic cross-sectional view of a
substrate with a feature and an amorphous carbon layer formed
thereon.
[0036] For clarity, identical reference numerals have been used,
where applicable, to designate identical elements that are common
between figures.
DETAILED DESCRIPTION
[0037] The inventors have learned that there is a strong
correlation between a-C:H film density and etch selectivity
regardless of the hydrocarbon source used to deposit the a-C:H
film. FIG. 3 is a graph plotting the relationship between film
density and etch selectivity of multiple samples of four different
a-C:H films 301A-D deposited on different substrates. Etch
selectivity is the factor by which an underlying material is etched
compared to a given a-C:H film, i.e., an etch selectivity of 10
indicates that an underlying material is removed ten times faster
than the a-C:H film. Each of films 301A-D were formed from
different precursors and processing conditions. The data reveal a
substantially linear correlation between the density and etch
selectivity of each film regardless of the precursor. These results
demonstrate that it is possible to achieve a desired etch
selectivity for an a-C:H film by increasing the film density, even
though the processing temperatures and precursors are substantially
different. Hence, densification of a-C:H films may be one method of
improving etch selectivity.
[0038] Aspects of the invention contemplate the use of a relatively
large flow rate of argon or other heavy noble gas, such as krypton
or xenon, as a diluent gas during a-C:H film deposition to increase
the resultant film density (and therefore etch selectivity), the
deposition rate of the film, and the conformality of the film to
features on the surface of the substrate. The application of a
heavy noble gas as a large flow rate diluent gas also improves the
efficiency of hydrocarbon precursor utilization during the
deposition process, minimizing unwanted deposition on interior
surfaces of the deposition chamber. Helium has been used as the
primary non-reactive component of the working gas in a PECVD
chamber for a-C:H film deposition since it is easily ionized and is
therefore advantageous for initiating plasma in a chamber with low
risk of arcing. Although argon is sometimes used as a carrier gas
for introducing a liquid-phase precursor into a PECVD processing
chamber, argon has not been used in very high quantities as
contemplated by aspects of the invention and, hence, does not
provide the benefits thereof when used as a carrier gas.
Exemplary Apparatus
[0039] FIG. 3A is a schematic representation of a substrate
processing system, system 1000, that can be used to perform
amorphous carbon layer deposition according to embodiments of the
present invention. Examples of suitable systems include the
CENTURA.RTM. systems which may use a DxZ.TM. processing chamber,
PRECISION 5000.RTM. systems, PRODUCER.TM. systems, and the PRODUCER
SE.TM. processing chambers which are commercially available from
Applied Materials, Inc., Santa Clara, Calif.
[0040] System 1000 includes a process chamber 1025, a gas panel
1030, a control unit 1010, and other hardware components such as
power supplies and vacuum pumps. Details of one embodiment of the
system used in the present invention are described in a commonly
assigned U.S. patent "High Temperature Chemical Vapor Deposition
Chamber", U.S. Pat. No. 6,364,954, issued on Apr. 2, 2002, which is
hereby incorporated by reference herein.
[0041] The process chamber 1025 generally comprises a substrate
support pedestal 1050, which is used to support a substrate such as
a semiconductor substrate 1090. This substrate support pedestal
1050 moves in a vertical direction inside the process chamber 1025
using a displacement mechanism (not shown) coupled to shaft 1060.
Depending on the process, the semiconductor substrate 1090 can be
heated to a desired temperature prior to processing. The substrate
support pedestal 1050 is heated by an embedded heater element 1070.
For example, the substrate support pedestal 1050 may be resistively
heated by applying an electric current from a power supply 1006 to
the heater element 1070. The semiconductor substrate 1090 is, in
turn, heated by the pedestal 1050. A temperature sensor 1072, such
as a thermocouple, is also embedded in the substrate support
pedestal 1050 to monitor the temperature of the substrate support
pedestal 1050. The measured temperature is used in a feedback loop
to control the power supply 1006 for the heater element 1070. The
substrate temperature can be maintained or controlled at a
temperature that is selected for the particular process
application.
[0042] A vacuum pump 1002 is used to evacuate the process chamber
1025 and to maintain the proper gas flows and pressure inside the
process chamber 1025. A showerhead 1020, through which process
gases are introduced into process chamber 1025, is located above
the substrate support pedestal 1050 and is adapted to provide a
uniform distribution of process gases into process chamber 1025.
The showerhead 1020 is connected to a gas panel 1030, which
controls and supplies the various process gases used in different
steps of the process sequence. Process gases may include a
hydrocarbon source and a plasma-initiating gas and are described in
more detail below in conjunction with a description of an exemplary
argon-diluted deposition process.
[0043] The gas panel 1030 may also be used to control and supply
various vaporized liquid precursors. While not shown, liquid
precursors from a liquid precursor supply may be vaporized, for
example, by a liquid injection vaporizer, and delivered to process
chamber 1025 in the presence of a carrier gas. The carrier gas is
typically an inert gas, such as nitrogen, or a noble gas, such as
argon or helium. Alternatively, the liquid precursor may be
vaporized from an ampoule by a thermal and/or vacuum enhanced
vaporization process.
[0044] The showerhead 1020 and substrate support pedestal 1050 may
also form a pair of spaced electrodes. When an electric field is
generated between these electrodes, the process gases introduced
into chamber 1025 are ignited into a plasma 1092. Typically, the
electric field is generated by connecting the substrate support
pedestal 1050 to a source of single-frequency or dual-frequency
radio frequency (RF) power (not shown) through a matching network
(not shown). Alternatively, the RF power source and matching
network may be coupled to the showerhead 1020, or coupled to both
the showerhead 1020 and the substrate support pedestal 1050.
[0045] PECVD techniques promote excitation and/or disassociation of
the reactant gases by the application of the electric field to the
reaction zone near the substrate surface, creating a plasma of
reactive species. The reactivity of the species in the plasma
reduces the energy required for a chemical reaction to take place,
in effect lowering the required temperature for such PECVD
processes.
[0046] Proper control and regulation of the gas and liquid flows
through the gas panel 1030 is performed by mass flow controllers
(not shown) and a control unit 1010 such as a computer. The
showerhead 1020 allows process gases from the gas panel 1030 to be
uniformly distributed and introduced into the process chamber 1025.
Illustratively, the control unit 1010 comprises a central
processing unit (CPU) 1012, support circuitry 1014, and memories
containing associated control software 1016. This control unit 1010
is responsible for automated control of the numerous steps required
for substrate processing, such as substrate transport, gas flow
control, liquid flow control, temperature control, chamber
evacuation, and so on. When the process gas mixture exits the
showerhead 1020, plasma enhanced thermal decomposition of the
hydrocarbon compound occurs at the surface 1091 of the
semiconductor substrate 1090, resulting in the deposition of an
amorphous carbon layer on the semiconductor substrate 1090.
Deposition Process
[0047] Aspects of the invention contemplate the deposition of an
a-C:H layer by a process that includes introducing a hydrocarbon
source, a plasma-initiating gas, and a diluent gas into a
processing chamber, such as process chamber 1025 described above in
conjunction with FIG. 3A. The hydrocarbon source is a mixture of
one or more hydrocarbon compounds. The hydrocarbon source may
include a gas-phase hydrocarbon compound, preferably
C.sub.3H.sub.6, and/or a gas mixture including vapors of a
liquid-phase hydrocarbon compound and a carrier gas. The
plasma-initiating gas is preferably helium, because it is easily
ionized, however other gases, such as argon, may also be used. The
diluent gas is an easily ionized, relatively massive, and
chemically inert gas. Preferred diluent gases include argon,
krypton, and xenon. Gases less massive than argon are not preferred
due to their inability to achieve the beneficial improvements in
film density, throughput, and conformality described below in
conjunction with FIGS. 4-9.
[0048] Additionally, amorphous carbon layers formed using partially
or completely doped derivatives of hydrocarbon compounds may also
benefit from the inventive method. Derivatives include nitrogen-,
fluorine-, oxygen-, hydroxyl group-, and boron-containing
derivatives of hydrocarbon compounds as well as fluorinated
derivatives thereof. The hydrocarbon compounds may contain nitrogen
or be deposited with a nitrogen-containing gas, such as ammonia, or
the hydrocarbon compounds may have substituents such as fluorine
and oxygen. Any of these processes may benefit from the density,
deposition rate and conformality improvements demonstrated for
undoped a-C:H films deposited with the inventive method. A more
detailed description of doped derivatives of hydrocarbon compounds
and combinations thereof that may be used in processes benefiting
from aspects of the invention may be found in commonly assigned
United States Pub. No. 2005/0287771 entitled "Liquid Precursors for
the CVD deposition of Amorphous Carbon Films," filed on Feb. 24,
2005, which is hereby incorporated by reference in its entirety to
the extent not inconsistent with the claimed invention.
[0049] Generally, hydrocarbon compounds or derivatives thereof that
may be included in the hydrocarbon source may be described by the
formula C.sub.AH.sub.BO.sub.CF.sub.D, where A has a range of
between 1 and 24, B has a range of between 0 and 50, C has a range
of 0 to 10, D has a range of 0 to 50, and the sum of B and D is at
least 2. Specific examples of suitable hydrocarbon compounds
include saturated or unsaturated aliphatic, saturated or
unsaturated alicyclic hydrocarbons, and aromatic hydrocarbons.
[0050] Aliphatic hydrocarbons include, for example, alkanes such as
methane, ethane, propane, butane, pentane, hexane, heptane, octane,
nonane, decane, and the like; alkenes such as ethylene, propylene,
butylene, pentene, and the like; dienes such as butadiene,
isoprene, pentadiene, hexadiene and the like; alkynes such as
acetylene, vinylacetylene and the like. Alicyclic hydrocarbons
include, for example, cyclopropane, cyclobutane, cyclopentane,
cyclopentadiene, toluene, and the like. Aromatic hydrocarbons
include, for example, benzene, styrene, toluene, xylene, pyridine,
ethylbenzene, acetophenone, methyl benzoate, phenyl acetate,
phenol, cresol, furan, and the like. Additionally, alpha-terpinene,
cymene, 1,1,3,3,-tetramethylbutylbenzene, t-butylether,
t-butylethylene, methyl-methacrylate, and t-butylfurfurylether may
be selected.
[0051] Examples of suitable derivatives of hydrocarbon compounds
are fluorinated alkanes, halogenated alkanes, and halogenated
aromatic compounds. Fluorinated alkanes include, for example,
monofluoromethane, difluoromethane, trifluoromethane,
tetrafluoromethane, monofluoroethane, tetrafluoroethanes,
pentafluoroethane, hexafluoroethane, monofluoropropanes,
trifluoropropanes, pentafluoropropanes, perfluoropropane,
monofluorobutanes, trifluorobutanes, tetrafluorobutanes,
octafluorobutanes, difluorobutanes, monofluoropentanes,
pentafluoropentanes, tetrafluorohexanes, tetrafluoroheptanes,
hexafluoroheptanes, difluorooctanes, pentafluorooctanes,
difluorotetrafluorooctanes, monofluorononanes, hexafluorononanes,
difluorodecanes, pentafluorodecanes, and the like. Halogenated
alkenes include monofluoroethylene, difluoroethylenes,
trifluoroethylene, tetrafluoroethylene, monochloroethylene,
dichloroethylenes, trichloroethylene, tetrachloroethylene, and the
like. Halogenated aromatic compounds include monofluorobenzene,
difluorobenzenes, tetrafluorobenzenes, hexafluorobenzene and the
like.
[0052] The a-C:H deposition process with argon dilution is a PECVD
process. The a-C:H layer may be deposited from the processing gas
by maintaining a substrate temperature between about 100.degree. C.
and about 450.degree. C. and preferably between about 300.degree.
C. and about 450.degree. C. in order to minimize the coefficient of
absorption of the resultant film. The process further includes
maintaining a chamber pressure between about 2 Torr and about 8
Torr. The hydrocarbon source, a plasma-initiating gas, and a
diluent gas are introduced into the chamber and plasma is initiated
to begin deposition. Preferably, the plasma-initiating gas is
helium or another easily ionized gas and is introduced into the
chamber before the hydrocarbon source and the diluent gas, which
allows a stable plasma to be formed and reduces the chances of
arcing. A preferred hydrocarbon source is C.sub.3H.sub.6, although,
as described above, other hydrocarbon compounds may be used
depending on the desired film, including one or more vaporized
liquid-phase hydrocarbon compounds entrained in a carrier gas. The
diluent gas may be any noble gas at least as massive as argon,
however argon is preferred for reasons of economy. Plasma is
generated by applying RF power at a power density to substrate
surface area of between about 0.7 W/cm.sup.2 and about 3 W/cm.sup.2
and preferably about 1.1 to 2.3 W/cm.sup.2. Electrode spacing,
i.e., the distance between the substrate and the showerhead, is
between about 200 mils and about 1000 mils.
[0053] A dual-frequency RF system may be used to generate plasma.
The dual frequency 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 high frequency plasma
controls plasma density and the low frequency plasma controls
kinetic energy of the ions hitting the wafer surface. A
dual-frequency source of mixed RF power provides a high frequency
power in a range between about 10 MHz and about 30 MHz, for
example, about 13.56 MHz, as well as a low frequency power in a
range of between about 10 KHz and about 1 MHz, for example, about
350 KHz. When a dual frequency RF system is used to deposit an
a-C:H film, the ratio of the second RF power to the total mixed
frequency power is preferably less than about 0.6 to 1.0 (0.6:1).
The applied RF power and use of one or more frequencies may be
varied based upon the substrate size and the equipment used.
[0054] In order to maximize the benefits of the argon-dilution
deposition method, it is important that a large quantity of diluent
is introduced into the PECVD chamber relative to the quantity of
hydrocarbon compounds. However, it is equally important that
diluent is not introduced into the chamber at a flow rate that is
too high. Higher density a-C:H layers may be formed with increasing
diluent flow rates, producing even higher etch selectivity for the
a-C:H film, but higher density also leads to higher film stress.
Very high film stress in the a-C:H film causes serious problems
such as poor adhesion of the a-C:H film to substrate surfaces
and/or cracking of the a-C:H film. Therefore, the addition of argon
or other diluent beyond a certain molar ratio relative to the
hydrocarbon compound will deleteriously affect the properties of
the film. Hence, there is a process window, wherein the ratio of
molar flow rate of argon diluent to the molar flow rate of
hydrocarbon compound into the PECVD chamber is preferably
maintained between about 2:1 and about 40:1, depending on the
desired properties of the deposited film. For the deposition of
some a-C:H films, the most desirable range of this ratio is between
about 10:1 and about 14:1.
[0055] An exemplary deposition process for processing 300 mm
circular substrates employs helium as the plasma-initiating gas,
C.sub.3H.sub.6 as the hydrocarbon source, and argon as the diluent
gas. The flow rate of helium is between about 200 sccm and about
5000 sccm, the flow rate of C.sub.3H.sub.6 is between about 300
sccm and 600 sccm, and the flow rate of argon is between about 4000
sccm and about 10000 sccm. Single frequency RF power is between
about 800 W and about 1600 W. Intensive parameters for this
process, i.e., chamber pressure, substrate temperature, etc., are
as described above. These process parameters provide a deposition
rate for an a-C:H layer in the range of about 2000 .ANG./min to
about 6000 .ANG./min, with a density in the range of about 1.2 g/cc
and about 1.8 g/cc, and an absorption coefficient of about 0.10 for
633 nm radiation. One skilled in the art, upon reading the
disclosure herein, can calculate appropriate process parameters in
order to produce an a-C:H film of different density, absorption
coefficient, or deposition rate than those discussed herein.
[0056] Table 1 summarizes a comparison of two a-C:H films deposited
on two respective 300 mm circular substrates. Film 1 was deposited
using a conventional, helium-based deposition process that is
currently considered the standard process for the semiconductor
industry. Film 2 was deposited using one aspect of the
invention.
TABLE-US-00001 TABLE 1 Comparison of Two Deposition Recipes and
Resultant Films Parameters Film 1 Film 2 Substrate Temp. (C.) 550
300 Chamber Pressure (Torr) 7 5 C.sub.3H.sub.6 Flow (sccm) 1800 600
He Flow (sccm) 700 400 Argon Flow (sccm) 0 8000 Dep. Rate
(.ANG./min) 2200 4550 Absorption Coefficient @ 633 nm 0.40 0.09
Film Density (g/cc) 1.40 1.42 Conformality (%) 5 20-30
[0057] Referring to Table 1, Film 2 was deposited at a
substantially lower temperature than Film 1 and with flow rate of
hydrocarbon compound 1/3 that of Film 1. Despite the lower
hydrocarbon flow rate, Film 2 was nonetheless deposited at more
than twice the rate of Film 1. Further, the properties of Film 2
are superior to those of Film 1, namely, greatly improved
conformality and a very low absorption coefficient. Hence, using
the inventive method described herein, amorphous carbon layers may
be formed on a substrate surface at a higher deposition rate and
having superior film properties to conventional a-C:H layers.
Film Density Enhancement
[0058] According to an embodiment of the invention, one important
benefit of this method is the ability to increase the density, and
therefore dry etch selectivity, of a-C:H films. FIG. 4 is a graph
demonstrating the effect of an argon diluent gas on a-C:H film
density. Film density for three 300 mm semiconductor substrates
401-403 is illustrated. Processing conditions for all three
substrates, including chamber pressure, radio frequency (RF) plasma
power, hydrocarbon precursor, and hydrocarbon flow rate, were
identical except for the flow rate of argon into the processing
chamber during the deposition process. Argon flow rate during
deposition on substrate 401 was 7200 standard cubic centimeters per
minute (sccm) and was increased to 8000 sccm and 8500 sccm for
substrates 402 and 403, respectively. Relative to substrate 401,
film density for substrates 402, 403 is increased proportionate to
the higher argon flow rates applied during the processing thereof.
This indicates that the density of an amorphous carbon film can be
increased by the addition of a relatively large flow rate of argon
diluent without altering other process variables, such as
hydrocarbon precursor flow rate or RF plasma power.
[0059] It is important to note that aspects of the inventive method
contemplate the use of substantially higher flow rates of argon
than are necessary for the initiation of plasma in a PECVD chamber
or to act as a carrier gas for a liquid-phase precursor chemical.
For example, a typical flow rate of argon into a 300 mm PECVD
chamber, when used as a carrier gas for a liquid-phase precursor,
is on the order of about 2000 sccm or less. The flow rate of helium
into such a chamber is generally even less. In contrast, the
desired flow rate of argon as a diluent gas for increasing the
density of an amorphous carbon film is much higher, i.e., greater
than about 7000 sccm.
[0060] Argon ions, which are approximately ten times as massive as
helium ions, are much more effective at bombarding the surface of a
substrate during film growth. The more intense bombardment of argon
ions during deposition is likely to create many more dangling bonds
and chemically active sites where CH-- radicals in the plasma can
stick to thereby form a denser film. Lighter ions, such as helium
ions, are unable to produce similar results due to the lack of
momentum associated with their lower mass. FIG. 5 illustrates the
effect of diluent gas type on resultant film density. Film density
on two substrates 501, 502 is shown. For the deposition of
substrate 501, argon was used as the diluent gas. For the
deposition of substrate 502, helium was used. Except for diluent
gas type, all other process conditions were kept constant. As
illustrated in FIG. 5, the a-C:H density is substantially higher
for substrate 501 than substrate 502.
[0061] It has also been determined that other factors may
beneficially increase deposited film density for a-C:H films to
thereby increase the dry etch selectivity. These factors include
dilution of the hydrocarbon source with a relatively high ratio of
diluent gas (not only argon), decreasing the flow rate of the
hydrocarbon source, and reducing the processing pressure.
[0062] The increased use of diluent gases and/or the reduction of
the hydrocarbon source flow rate decreases the deposition rate of
the a-C:H film and thereby allows ion bombardment from CVD plasma
to be more effective in compacting the growing film. This has been
found to be true for a number of diluent gases, including helium
and hydrogen, although these two gases do not have the additional
densification capability of argon and heavier noble gases, as
described above in conjunction with FIG. 4. The effect of lower
hydrocarbon flow rate on film density is illustrated in FIG. 6,
wherein a different flow rate of C.sub.3H.sub.6 is used for the
deposition of an a-C:H film on three different substrates 601-603,
respectively. Film density is shown to decrease with increasing
C.sub.3H.sub.6 flow rate due to higher deposition rate and the
corresponding lack of compaction of the film during deposition.
Hence, the film on substrate 603 has the lowest density and the
highest C.sub.3H.sub.6 flow rate during deposition.
[0063] In addition to the ratio of diluent gas to hydrocarbon
source, chamber pressure also has a substantial effect on the film
density. Because the ion energy in a plasma is directly
proportional to the sheath voltage, and the sheath voltage across a
substrate increases with decreasing pressure, film density can be
expected to increase with decreasing pressure. This is illustrated
in FIG. 7, wherein a different process pressure is used for the
deposition of an a-C:H film on three different substrates 701-703,
respectively. Film density is shown to decrease with increasing
process pressure, due to the more energetic ions found in a lower
pressure plasma.
Deposition Rate Improvement
[0064] Another advantage of the inventive method is a significant
improvement on deposition rate of a-C:H films. Ordinarily, a
trade-off exists between film density and deposition rate; with a
standard, i.e., helium-based, deposition process, deposition
parameters may be tuned to produce a higher density a-C:H film, but
only by reducing throughput significantly. For example, as
described above in conjunction with FIG. 6, a higher density a-C:H
film is deposited when the flow rate of hydrocarbon precursor is
reduced, but deposition rate is also correspondingly reduced. So
although the resultant film may have a desired density, such a
deposition process may not be commercially viable due to the
restrictively long process time required to deposit such a film on
a substrate.
[0065] The inventive method allows for both a high density film and
a relatively high deposition rate of such a film. Compared to a
standard a helium-based PECVD process, the deposition rate of a-C:H
films is greatly increased when argon is used as a diluent gas in
large quantities. As described above in conjunction with FIG. 6,
the dilution of the hydrocarbon source results in a higher density
film and a lower deposition rate. Besides increasing film density,
the addition of argon raises the deposition rate significantly.
[0066] FIG. 8 illustrates the deposition rate improvement afforded
by the introduction of a heavy noble gas, e.g., argon, as a high
flow rate diluent during the process of depositing an a-C:H film.
The deposition rates of three diluent gases are compared on three
different substrates 801-803, respectively, wherein the diluent gas
flow rate was held constant at 8000 sccm for all three substrates.
Argon dilution was used for the deposition of substrate 801, helium
for substrate 802, and hydrogen for substrate 803. All other
process conditions were identical for all three substrates. Argon
dilution produces a more than three-fold increase in the deposition
rate compared to He or H.sub.2 dilution. As described above in
conjunction with FIGS. 4 and 5, the easily ionized--but much more
massive--argon atoms are able to create more reactive sites on the
surface of an a-C:H film by breaking the C-H bonds thereon,
increasing the probability of incoming radicals sticking to the
film surface. In addition, the large flow rate of an easily ionized
gas, e.g., argon, may give rise to higher plasma density and
therefore, more --CH.sub.x radical creation in the gas phase.
Together, the more reactive plasma and more reactive film surface
associated with argon dilution lead to the beneficial combination
of high deposition rate and high film density.
[0067] Furthermore, the combination of more --CH.sub.x radicals
present in the plasma and more reactive sites on the surface of the
film due to argon dilution also explains the substantial
improvement in chemistry utilization observed with the
argon-diluted process. Rather than depositing on all interior
surfaces of the PECVD chamber as unwanted hydrocarbon residue, the
majority of hydrocarbon material is efficiently deposited on the
substrate surface in the argon-dilution process. This preferential
deposition onto the substrate translates into a major productivity
gain. The chamber clean time for the argon-diluted process is much
shorter compared to a helium- or hydrogen-diluted process due to
the reduced residue build-up in the PECVD chamber. Shorter clean
time increases throughput of the PECVD chamber since less time is
dedicated to cleaning the chamber between the processing of
substrates. Further, particle contamination of substrates resulting
from hydrocarbon residue flaking off interior surfaces of the PECVD
chamber is also greatly reduced by the improvement in chemistry
utilization of the argon-diluted process; less residue build-up
inside the PECVD chamber equates to less particle contamination of
substrates processed therein.
Conformality Improvement
[0068] Another major advantage of the inventive method is the
enhancement of conformality over other a-C:H deposition processes,
as illustrated in FIG. 9. FIG. 9 illustrates a schematic
cross-sectional view of a substrate 900 with a feature 901 and an
amorphous carbon layer 902 formed thereon. Amorphous carbon layer
902 illustrates the typical appearance of a film deposited using
the inventive method. Qualitatively, amorphous carbon layer 902 is
highly conformal and completely covers sidewalls 904 and floor 903
of feature 901. Quantitatively, amorphous carbon layer 902 may have
a conformality on the order of about 20-30%, wherein conformality
is defined as the ratio of the average thickness S of amorphous
carbon layer 902 deposited on the sidewalls 904 to the average
thickness T of amorphous carbon layer 902 on upper surface 905 of
substrate 900. Referring back to FIG. 2, non-conformal amorphous
carbon layer 202, which illustrates the general appearance of a
film deposited with a hydrogen- or helium-diluted process,
typically has a conformality of about 5%. A comparison of the
deposition profiles of non-conformal amorphous carbon layer 202 in
FIG. 2 and amorphous carbon layer 902 in FIG. 9 suggests that the
trajectory of argon atoms is not as directional as hydrogen or
helium ions. It may also be possible that the gas phase species
present in the plasma are different with argon dilution compared to
other diluents. These factors, in conjunction with the higher
sticking probability of --CH.sub.x radicals on the substrate
surface with an argon dilution process result in the improvement in
conformality depicted in FIG. 9.
Lower Temperature Process
[0069] Another advantage of an argon-diluted process is that a
lower temperature process may be used to produce an a-C:H layer
with the desired density and transparency. Ordinarily, higher
substrate temperature during deposition is the process parameter
used to encourage the formation of a higher density film. Because
the argon-diluted process already increases density for the reasons
described above, substrate temperature may be reduced during
deposition, for example to as low as about 300.degree. C., and
still produce a film of the desired density, i.e., from about 1.2
g/cc to about 1.8 g/cc. Hence, the argon-dilution process may
produce a relatively high density film with an absorption
coefficient as low as about 0.09. Further, lower processing
temperatures are generally desirable for all substrates since this
lowers the thermal budget of the process, protecting devices formed
thereon from dopant migration
Post-Deposition Termination Process for Particle Reduction
[0070] During PECVD deposition of a-C:H films, nano-particles are
generated in the bulk plasma due to gas phase polymerization of
--CH.sub.x species. These particles naturally gain negative charge
in the plasma and, thus, remain suspended in the plasma during
deposition. However, when RF power is turned off and plasma is
extinguished in the chamber, these particles tend to fall on the
substrate surface due to gravity and viscous drag forces during
pump-down. It is very important to ensure that these particles are
flushed out of the chamber before the pump-down step. This can be
accomplished by maintaining plasma in the chamber for a period of
time after the film deposition has ended, i.e., after the flow of
the hydrocarbon source has been stopped. The time for this
termination step varies depending on the duration of the deposition
process, since deposition time determines the size and number of
particles generated during the deposition process. Longer
deposition processes generally produce more and larger particles in
the bulk plasma. The optimal duration of the post-deposition
termination step is between about 5 seconds and about 20 seconds.
It is also preferred that the plasma-maintaining gas is a light
gas, such as helium or hydrogen, to minimize generation of
particles by sputtering the showerhead. RF power is preferably
reduced during the post-deposition termination step to a minimum
level required to safely maintain a stable plasma and avoid arcing.
A more energetic plasma is undesirable due to the deleterious
effect it may have on the substrate, such as etching of the
substrate surface, or sputtering of the shower head.
[0071] In addition, it has been found that H.sub.2 doping of the
plasma during the bulk deposition step and/or the post-deposition
termination step further improves particle performance. Since a
hydrogen atom may act as a terminating bond, it can passivate the
gas phase species present in the plasma and prevent them from
bonding with each other and growing into the unwanted
nano-particles. Additionally, H.sup.+ ions may reduce the size of
extant nano-particles by chemically reacting with them and causing
subsequent fragmentation. In so doing, the particles detected on
substrates after a-C:H film deposition have been reduced by more
than half for thinner a-C:H films, e.g, 7000 .ANG.. For thicker
a-C:H films, e.g., about 1 .mu.m, the number of detected particles
has been reduced by an order of magnitude with hydrogen doping. In
a preferred aspect of the post-deposition termination step, the
ratio of the molar flow rate of plasma-initiating gas to the molar
flow rate of hydrogen gas is between about 1:1 and about 3:1.
Higher flow rates of hydrogen during this process step are
undesirable because higher concentrations of hydrogen in the
chamber can adversely affect the deposited film. In the bulk
deposition process, a preferred ratio of the molar flow rate of the
diluent gas to the molar flow rate of the hydrogen gas is between
about 2:1 and 4:1. Higher concentrations of hydrogen result in more
aggressive particle reduction, but also may degrade the
conformality of the a:C-H film.
[0072] In one example, a post-deposition termination step is used
to reduce the number of particles contaminating the surface of 300
mm substrates when a 7000 .ANG. thick a-C:H film is deposited
thereon. After the deposition process, the flow of the hydrocarbon
source, in this example 600 sccm of C.sub.3H.sub.6, is stopped. RF
power is not terminated, however, and is instead reduced to the
level required to maintain a stable plasma in the chamber. In this
example, the RF power is reduced from about 1200 W to about 200-500
W. H.sub.2 is introduced into the chamber in addition to the
continued flow of plasma initiating gas, which in this example is
helium. The flow rate of the hydrogen gas is about 1000-2000 sccm
and the flow rate of helium is about 4000-6000 sccm. On average,
the number of particles >0.12 .mu.m that have been detected on
the surface of a 300 mm substrate using the above post-deposition
termination process is less than 15. In contrast, the number of
particles >0.12 .mu.m that have been detected on substrates when
no post-deposition termination step is used is generally more than
about 30.
[0073] 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.
* * * * *