U.S. patent application number 13/760845 was filed with the patent office on 2014-08-07 for methods of dry stripping boron-carbon films.
The applicant listed for this patent is Irfan JAMIL, Bok Hoen KIM, Kwangduk Douglas LEE, Sudha RATHI, Ramprakash SANKARAKRISHNAN, Martin Jay SEAMONS. Invention is credited to Irfan JAMIL, Bok Hoen KIM, Kwangduk Douglas LEE, Sudha RATHI, Ramprakash SANKARAKRISHNAN, Martin Jay SEAMONS.
Application Number | 20140216498 13/760845 |
Document ID | / |
Family ID | 51258232 |
Filed Date | 2014-08-07 |
United States Patent
Application |
20140216498 |
Kind Code |
A1 |
LEE; Kwangduk Douglas ; et
al. |
August 7, 2014 |
METHODS OF DRY STRIPPING BORON-CARBON FILMS
Abstract
Embodiments of the invention generally relate to methods of dry
stripping boron-carbon films. In one embodiment, alternating
plasmas of hydrogen and oxygen are used to remove a boron-carbon
film. In another embodiment, co-flowed oxygen and hydrogen plasma
is used to remove a boron-carbon containing film. A nitrous oxide
plasma may be used in addition to or as an alternative to either of
the above oxygen plasmas. In another embodiment, a plasma generated
from water vapor is used to remove a boron-carbon film. The
boron-carbon removal processes may also include an optional polymer
removal process prior to removal of the boron-carbon films. The
polymer removal process includes exposing the boron-carbon film to
NF.sub.3 to remove from the surface of the boron-carbon film any
carbon-based polymers generated during a substrate etching
process.
Inventors: |
LEE; Kwangduk Douglas;
(Redwood City, CA) ; RATHI; Sudha; (San Jose,
CA) ; SANKARAKRISHNAN; Ramprakash; (San Jose, CA)
; SEAMONS; Martin Jay; (San Jose, CA) ; JAMIL;
Irfan; (San Jose, CA) ; KIM; Bok Hoen; (San
Jose, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
LEE; Kwangduk Douglas
RATHI; Sudha
SANKARAKRISHNAN; Ramprakash
SEAMONS; Martin Jay
JAMIL; Irfan
KIM; Bok Hoen |
Redwood City
San Jose
San Jose
San Jose
San Jose
San Jose |
CA
CA
CA
CA
CA
CA |
US
US
US
US
US
US |
|
|
Family ID: |
51258232 |
Appl. No.: |
13/760845 |
Filed: |
February 6, 2013 |
Current U.S.
Class: |
134/1.1 |
Current CPC
Class: |
G03F 7/427 20130101;
H01L 21/02041 20130101; B08B 7/0035 20130101; H01L 21/31116
20130101; H01J 37/32853 20130101 |
Class at
Publication: |
134/1.1 |
International
Class: |
B08B 7/00 20060101
B08B007/00 |
Claims
1. A method for stripping a film from a substrate, comprising:
positioning a substrate having a film thereon in a chamber, the
film comprising boron and carbon; exposing the film to a water
vapor plasma at a pressure above 50 Torr to generate one or more
volatile compounds from the boron and carbon; and exhausting the
one or more volatile compounds from the chamber.
2. The method of claim 1, wherein an atomic ratio of boron to
carbon in the film is within a range of about 1:1 to about 3:1.
3. The method of claim 1, wherein the water vapor plasma is formed
from a precursor gas comprising water vapor and a carrier gas, and
a flow rate of the precursor gas is at least about 7 sLm.
4. The method of claim 2, wherein the plasma is maintained at a
power input of at least 2,000 watts and spacing less than 200
mils.
5. The method of claim 4, wherein the water vapor plasma comprises
excess hydrogen.
6. A method of removing a boron-carbon film, comprising: exposing
the boron-carbon film to a water vapor plasma containing excess
hydrogen in a processing chamber; maintaining a pressure in the
processing chamber above 50 Torr; reacting oxygen in the water
vapor plasma with carbon in the boron-carbon film to form volatile
carbon species; reacting hydrogen in the water vapor plasma with
boron in the boron-carbon film to form volatile boron species; and
removing the volatile carbon species and the volatile boron species
from the processing chamber.
7. The method of claim 6, wherein the water vapor plasma is formed
from a precursor gas comprising the excess hydrogen, and the
precursor gas is provided to the processing chamber at a flow rate
of at least 7 sLm.
8. The method of claim 7, wherein the water vapor plasma is formed
by applying at least 2,000 watts of power to the precursor gas.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims benefit of U.S. provisional patent
application Ser. No. 61/485,534, filed May 12, 2011, which is
herein incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] Embodiments of the invention generally relate to methods of
dry stripping boron-carbon films.
[0004] 2. Description of the Related Art
[0005] Boron-carbon films, such as boron-doped carbon, have
demonstrated superior patterning performance as compared to
amorphous carbon when being used as an etching hardmask. However,
boron-carbon films are not easily stripped, since boron-carbon
films cannot be ashed using an oxygen plasma. Boron carbon films
can be dry stripped using fluorine or chlorine along with oxygen;
however, fluorine and chlorine are corrosive to dielectric
materials such as silicon oxide, silicon nitride, and silicon
oxynitride commonly found on semiconductor substrates. A wet etch
solution containing sulfuric acid and hydrogen peroxide can also
remove the boron-carbon films; however, the wet etch solution can
damage exposed metal surfaces or embedded metals also commonly
found on semiconductor substrates.
[0006] Therefore, there is a need for an improved method of
removing boron-carbon films from substrates.
SUMMARY OF THE INVENTION
[0007] Embodiments of the invention generally relate to methods of
dry stripping boron-carbon films using oxygen-containing oxidizing
agents in combination with hydrogen-containing reducing agents. In
one embodiment, alternating plasmas of hydrogen and oxygen are used
to remove a boron-carbon film. In another embodiment, co-flowed
oxygen and hydrogen plasma is used to remove a boron-carbon
containing film. A nitrous oxide plasma may be used in addition to
or as an alternative to either of the above oxygen plasmas. In
another embodiment, a plasma generated from water vapor is used to
remove a boron-carbon film. The boron-carbon removal processes may
also include an optional polymer removal process prior to removal
of the boron-carbon films. The polymer removal process includes
exposing the boron-carbon film to a plasma formed from an
oxygen-containing gas, a fluorine-containing gas, or a combination
thereof to remove from the surface of the boron-carbon film any
carbon-based polymers generated during a substrate etching
process.
[0008] In one embodiment, a method for stripping a film from a
substrate comprises positioning a substrate having a film thereon
in a chamber, wherein the film includes at least one of boron or
carbon. The film is then exposed to oxygen ions or radicals and
hydrogen ions or radicals to generate one or more volatile
compounds, and the one or more volatile compounds are exhausted
from the chamber.
[0009] In another embodiment, a method for stripping a boron-carbon
film from a substrate positioned in a chamber comprises exposing a
substrate comprising boron and carbon to a plasma containing oxygen
radicals or ions and hydrogen radicals or ions. The hydrogen
radicals or ions are reacted with the boron to form a volatile
boron species, and the oxygen radicals or ions are reacted with the
carbon to form a volatile carbon species. The volatile boron
species and the volatile carbon species are then removed from the
chamber.
[0010] In another embodiment, a method for stripping a film from a
substrate positioned in a chamber comprises exposing a substrate to
a plasma formed from a compound comprising H.sub.xO.sub.y, where x
and y are integers or non-integers greater than 1. The film is then
contacted with the plasma to form one or more volatile species, and
the volatile species are removed from the chamber.
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] FIG. 1 is a flow diagram illustrating a method of removing a
boron-carbon film using alternating hydrogen and oxygen plasmas
according to one embodiment of the invention.
[0013] FIG. 2 is a flow diagram illustrating a method of removing a
boron-carbon film using a plasma containing both oxygen and
hydrogen according to one embodiment of the invention.
[0014] FIGS. 3A and 3B illustrate the effect of chamber pressure
and RF power on etch rate when using a plasma containing oxygen and
hydrogen.
[0015] FIG. 4 is a flow diagram illustrating a method of removing a
boron-carbon film using plasma generated from hydrogen and nitrous
oxide according to one embodiment of the invention.
[0016] FIG. 5 is a flow diagram illustrating a method of removing a
boron-carbon film using plasma generated from water vapor according
to one embodiment of the invention.
[0017] FIG. 6 illustrates the etching selectivity of water vapor
plasma.
[0018] To facilitate understanding, identical reference numerals
have been used, where possible, to designate identical elements
that are common to the figures. It is contemplated that elements
and features of one embodiment may be beneficially incorporated in
other embodiments without further recitation.
DETAILED DESCRIPTION
[0019] Embodiments of the invention generally relate to methods of
dry stripping boron-carbon films using oxygen-containing oxidizing
agents in combination with hydrogen-containing reducing agents. In
one embodiment, alternating plasmas of hydrogen and oxygen are used
to remove a boron-carbon film. In another embodiment, co-flowed
oxygen and hydrogen plasma is used to remove a boron-carbon
containing film. A nitrous oxide plasma may be used in addition to
or as an alternative to either of the above oxygen plasmas. In
another embodiment, a plasma generated from water vapor is used to
remove a boron-carbon film. The boron-carbon removal processes may
also include an optional polymer removal process prior to removal
of the boron-carbon films. The polymer removal process includes
exposing the boron-carbon film to a plasma formed from an
oxygen-containing gas, a fluorine-containing gas, or a combination
thereof to remove from the surface of the boron-carbon film any
carbon-based polymers generated during a substrate etching
process.
[0020] Embodiments of the invention may be practiced in the
Producer.RTM. SE or Producer.RTM. GT chambers available from
Applied Materials, Inc., of Santa Clara, Calif. It is contemplated
that other chambers, including those produced by other
manufacturers, may benefit from embodiments described herein.
[0021] FIG. 1 is a flow diagram 100 illustrating a method of
removing a boron-carbon film using alternating hydrogen and oxygen
plasmas according to one embodiment of the invention. Flow diagram
100 begins at operation 102, in which a substrate having a
boron-carbon film thereon, such as a boron-carbon hardmask, is
positioned on a substrate support within a stripping chamber. The
substrate and the boron-carbon film thereon are heated to a
temperature less than about 750.degree. C., such as about
200.degree. C. to about 400.degree. C. The boron-carbon film may be
a boron-doped carbon, or a hydrogenated boron carbide having an
atomic ratio of boron to carbide of about 2:1 or less. The
substrate is generally a silicon-containing substrate, such as a
300 millimeter silicon wafer, and may have one or more dielectric
or conductive metal layers disposed thereon. For example, the
substrate may have a silicon dioxide layer disposed thereon, over
which the boron-carbon layer is disposed to act as an etching
hardmask during a previously performed etching of the silicon
dioxide layer. It is contemplated that substrates other than
silicon-containing substrates may be used.
[0022] After positioning the substrate on a support, carbon-based
polymers located on the boron-carbon film are optionally removed in
a polymer removal operation 104. The carbon-based polymers are
generated on the upper surface of the boron-carbon layer during a
previously performed etching process in which the boron-carbon
layer acts as an etching hardmask. During the etching, the
substrate and the boron-carbon layer thereon are exposed to an
etchant, such as C.sub.4F.sub.8, to etch a desired pattern into the
substrate. Due to polymerization of carbon and fluorine, the
etching process produces a carbon-based polymer, which may also
include silicon and/or oxygen. The carbon-based polymer is
generally removed prior to the stripping process to remove higher
molecular weight molecules to allow for more efficient stripping of
the boron-carbon film.
[0023] The carbon-based polymer is removed from the surface of the
boron-carbon film by exposing the carbon-based polymer to a plasma
formed from a fluorine-containing gas, an oxygen-containing gas, or
a combination thereof. For example, the carbon-based polymer may be
removed using a plasma formed from oxygen gas and NF.sub.3 having a
ratio of about 100:1. Generally, the amount of fluorine desired in
the plasma increases with the amount of silicon present in the
carbon-based polymer. Since oxygen-containing plasmas are capable
of removing the carbon-based polymer, especially when the
carbon-based polymer contains relatively low amounts of silicon,
operation 104 can be omitted due to the exposure of the substrate
to an oxygen-containing plasma in operation 106 (discussed
below).
[0024] During the polymer removal process, a remotely generated
plasma using oxygen gas and NF.sub.3 gas is provided to the
stripping chamber at a flow rate of about 1 SCCM to about 15,000
SCCM per 300 millimeter substrate, for example, about 100 SCCM to
about 5,000 SCCM. The ratio of oxygen to NF.sub.3 is about 100:1 to
about 1000:1. The pressure within the stripping chamber is
maintained at a pressure within a range from about 1 millitorr to
about 760 Torr, such as about 4 millitorr to about 10 Torr, while
the substrate is maintained at a temperature less than 750.degree.
C. The oxygen and the NF.sub.3 react with the carbon-based polymer
to form a volatile compound which is then exhausted from the
stripping chamber. Under such conditions, the carbon-based polymer
is removed at a rate of about 2,000 angstroms per minute to about
10,000 angstroms per minute. It is contemplated that the
carbon-based polymer may be over-etched to ensure removal from the
surface of the substrate.
[0025] After removal of the carbon-based polymer layer from the
boron-carbon layer, the boron-carbon layer is stripped from the
surface of the substrate in operation 106. Operation 106 includes
two sub-operations, 106A and 106B. In sub-operation 106A, the
boron-carbon layer is exposed to an ionized oxygen-containing
compound, such as oxygen plasma, and then subsequently, in
sub-operation 106B, the substrate is exposed to an ionized
hydrogen-containing compound, such as hydrogen plasma. In
sub-operation 106A, the oxygen ions react with the carbon of the
boron-carbon film to form a volatile compound (e.g., CO.sub.2)
which is exhausted from the chamber. After about 10 seconds to
about 50 seconds of exposure to the ionized oxygen, the
boron-carbon film forms a relatively higher concentration of boron
near the surface of the film due to the removal of carbon. The
removal rate of the boron-carbon film begins to decrease due to the
reduction of available carbon on the surface of the film. At this
point, the flow rate of the oxygen-containing compound to the
stripping chamber is halted, and the remaining oxygen-containing
compound is exhausted from the stripping chamber.
[0026] In sub-operation 106B, the boron-carbon layer is exposed to
a hydrogen-containing compound plasma which reacts with the boron
in the boron-carbon layer to form a volatile compound (e.g.,
B.sub.2H.sub.6) which is then exhausted from the chamber. The
boron-carbon layer is exposed to the hydrogen plasma for about 10
seconds to about 50 seconds, until the boron-carbon film has a
relatively higher concentration of carbon near the surface of the
boron-carbon film. After a predetermined time, the flow of hydrogen
gas is halted, and sub-operation 106A is then repeated. Operation
106, which includes sub-operations 106A and 106B, may be repeated a
desired amount of times in order to sufficiently remove the
boron-carbon film from the substrate surface.
[0027] Each of the hydrogen-containing compound and the
oxygen-containing compound are provided to the stripping chamber at
flow rate of about 5 SCCM to about 15,000 SCCM per 300 millimeter
substrate. For example, the hydrogen gas and the oxygen gas may be
provided to the stripping chamber at a flow rate of about 500 SCCM
to about 10,000 SCCM and about 250 SCCM to about 5000 SCCM,
respectively. The hydrogen-containing compound and the
oxygen-containing compound are ionized using an RF generator
operating at 13.56 MHz which applies about 100 watts to about 3,000
watts of power, for example, about 1,000 watts to about 3,000
watts. The pressure within the stripping chamber is maintained at a
pressure within a range from about 1 millitorr to about 760 Torr,
such as about 50 millitorr to about 10 Torr, or about 5 Torr to
about 100 Torr.
[0028] It is to be noted that since the oxygen-containing compound
reacts with carbon, and the hydrogen-containing compound reacts
with boron, the exposure times of each compound can be tailored
based on the atomic composition of the boron-carbon film to effect
a desired removal rate. For example, if the boron concentration in
the boron-carbon film is about twice the concentration of the
carbon in the film, then the hydrogen exposure time may be greater
than the oxygen exposure time, such as about two times greater
(assuming both plasmas have about the same etch rate).
[0029] Flow diagram 100 illustrates one embodiment for removing a
boron-carbon film; however, other embodiments are also
contemplated. In one embodiment, operations 102, 104, and 106 are
all performed in the same chamber. In another embodiment, it is
contemplated that operation 104 may occur in a separate chamber,
such as an etching chamber, and may occur before positioning the
substrate in a stripping chamber. In another embodiment, it is
contemplated that the plasma of operation 104 can be a capacitively
coupled or inductively coupled in addition to or as an alternative
to a remotely generated. For example, it is contemplated that a
capacitively coupled plasma may be generated from a
fluorine-containing gas and an oxygen-containing gas.
Alternatively, a capacitively coupled plasma may be generated from
water vapor and an inert gas. In such an embodiment, water vapor
may be introduced to the chamber at a flow rate between about 10
SCCM and 10,000 SCCM, such as about 4,000 SCCM. The inert gas may
be provided to the chamber at a flow rate of about 3,000 SCCM.
[0030] In another embodiment, it is contemplated that other
fluorine-containing gases can be used in operation 104. For
example, it is contemplated that CF.sub.4, C.sub.3F.sub.6,
CHF.sub.3, CH.sub.2F.sub.2, and CH.sub.3F may be utilized. In
another embodiment, it is contemplated that the NF.sub.3 plasma of
operation 104 or the oxygen-containing or hydrogen-containing
plasmas of operation 106 can be generated in situ via inductive
coupling or may be remotely generated. In yet another embodiment,
it is contemplated that the oxygen-containing compound and
hydrogen-containing compound of operation 106 may be carried to the
stripping chamber using a carrier gas, such as argon, helium or
nitrogen. The carrier gases may be provided to the stripping
chamber containing a 300 millimeter substrate at a flow rate of
about 5 SCCM to about 15,000 SCCM. In another embodiment, it is
contemplated that the chamber may be flushed between sub-operations
106A and 106B using a carrier gas to avoid reaction between the
hydrogen and the oxygen. In yet another embodiment, it is
contemplated that sub-operation 106B may be performed prior to
sub-operation 106A.
[0031] In another embodiment, it is contemplated that any compound
which provides oxygen, such as O.sub.2, N.sub.2O, CO.sub.2, NO, or
NO.sub.2, may be used in operation 106. Additionally, it is also
contemplated that other hydrogen-containing compounds may be used
in addition to or as alternatives to hydrogen gas in operation 106.
For example, it is contemplated that ammonia may be used in
addition to or as an alternative to hydrogen gas.
[0032] In one example, a boron-carbon film having a thickness of
about 2000 angstroms is exposed to 1500 SCCM of hydrogen plasma for
30 seconds at a chamber pressure of 7 Torr and substrate
temperature of 400.degree. C. The boron-carbon film is then exposed
to 1500 SCCM of oxygen plasma for 30 seconds at a chamber pressure
of 7 Torr and substrate temperature of 400.degree. C. The
boron-carbon film is further exposed to alternating hydrogen and
oxygen plasmas until the film is removed. The boron-carbon film was
removed in about 20 minutes.
[0033] FIG. 2 is a flow diagram 200 illustrating a method of
removing a boron-carbon film using a plasma containing both oxygen
and hydrogen according to one embodiment of the invention. Flow
diagram 200 includes operations 102, 104, and 206. Operations 102
and 104 are similar to operations 102 and 104 described with
reference to flow diagram 100. After positioning a substrate on a
support in operation 102, and removing the carbon-based polymer in
operation 104, the substrate and the boron-carbon film thereon are
exposed to a plasma or ionized gas formed from a
hydrogen-containing compound, such as diatomic hydrogen, and an
oxygen-containing compound, such as diatomic oxygen, in operation
206. Thus, while operation 106 of flow diagram 100 exposes the
boron-carbon film to a cycle alternating hydrogen-containing and
oxygen-containing plasmas, operation 206 exposes the boron-carbon
film to simultaneous hydrogen-containing and oxygen-containing
plasmas.
[0034] In operation 206, the hydrogen-containing compound and
oxygen-containing compound are provided to the stripping chamber at
flow rate of about 5 SCCM to about 15,000 SCCM per 300 millimeter
substrate to remove a boron-carbon layer from the surface of the
substrate. For example, the hydrogen-containing compound and the
oxygen-containing compound may be provided at a flow rate of about
200 SCCM to about 4,000 SCCM. The hydrogen-containing compound and
the oxygen-containing compound are ionized using an RF generator
operating at 13.56 MHz and applying about 100 watts to about 3,000
watts of power, such as about 1,500 watts to about 2,000 watts of
power. The substrate is maintained at a temperature less than
750.degree. C., such as at about 400.degree. C. The pressure within
the stripping chamber is generally maintained at a pressure less
than about 20 Torr, such as about 7 Torr to about 19 Torr. By
maintaining the chamber pressure at less than about 20 Torr, the
probability of oxygen plasma and hydrogen plasma undesirably and
dangerously reacting within the stripping chamber is greatly
reduced.
[0035] The hydrogen-containing plasma and the oxygen-containing
plasma within the chamber contact the boron-carbon film and react
to form volatile compounds which are then exhausted from the
chamber. Since the oxygen generally forms a volatile compound with
the carbon in the boron-carbon film, and the hydrogen forms a
volatile compound with the boron, it is contemplated that the
relative ratio of oxygen to hydrogen (and/or flow rates of oxygen
and hydrogen) can be adjusted depending on the composition of the
boron-carbon film to effect the desired removal rate. Table 1
illustrates the change in removal rate of a boron-carbon film from
the surface of a 300 millimeter substrate using varied process
parameters.
TABLE-US-00001 TABLE 1 H.sub.2 O.sub.2 Etch P Power Flow rate Flow
rate rate (Torr) (watts) T (.degree. C.) (SCCM) (SCCM) (.ANG./min)
Example 1 19 1500 400 1000 500 140 Example 2 19 1900 400 1000 500
155 Example 3 19 1900 400 1500 750 152 Example 4 19 1900 400 700
350 151 Example 5 19 1900 400 400 200 141 Example 6 19 1900 400
1250 250 116 Example 7 19 1900 400 750 750 102 Example 8 19 1900
400 250 1250 119 Example 9 19 1900 400 300 300 104 Example 10 19
1900 400 200 400 101 Example 11 19 1500 400 400 200 149 Example 12
19 1500 400 500 1000 88 Example 13 9 1500 400 1000 500 107
[0036] With respect to increased oxygen or hydrogen flow rates,
excess oxygen or hydrogen in the plasma generally has little effect
on etching rate. The rate of etching is limited by the amount of
boron or carbon present on the surface of the boron-carbon film
with which the oxygen or hydrogen can form a volatile compound, and
generally is not significantly increased with the inclusion of
excess process gas. However, it should be noted that the etching
rate can be increased through the inclusion of additional process
gas when the process gas is the limiting reactant (e.g., excess
reactant sites are present on the surface of the boron-carbon
film).
[0037] Flow diagram 200 illustrates one embodiment of stripping a
boron-carbon film; however, other embodiments are also
contemplated. In another embodiment, it is contemplated that the
oxygen-containing compound and hydrogen-containing compound in
operation 206 may be introduced to the stripping chamber using a
carrier gas, such as argon, helium, or nitrogen, having a flow rate
less than 15,000 SCCM per 300 millimeter substrate. The inclusion
of carrier gas to the processing volume may decrease the rate at
which the boron-carbon film is etched, but may also increase plasma
uniformity and stability.
[0038] FIGS. 3A and 3B illustrate the effect of chamber pressure
and RF power on etch rate when using a plasma containing oxygen and
hydrogen. In FIG. 3A, a boron-carbon film at 400.degree. C. was
removed from a substrate using a plasma formed from 2,000 SCCM of
hydrogen gas and 1,000 SCCM of oxygen gas at 1,000 watts of RF
power. As the pressure within the chamber is increased, the etching
rate of the boron-carbon film is correspondingly increased. Thus,
in all methods described herein, etch rate of the boron-carbon film
may be controlled by adjusting the pressure within the chamber. In
FIG. 3B, a boron-carbon film at 400.degree. C. was removed using
plasma formed from 2,000 SCCM of hydrogen gas and 1,000 SCCM of
oxygen gas. The chamber pressure was maintained at 9 Torr. As the
RF power applied to the plasma is increased, the etching rate of
the boron-carbon film is correspondingly increased.
[0039] FIG. 4 is a flow diagram illustrating a method of removing a
boron-carbon film using plasma generated from hydrogen and nitrous
oxide according to one embodiment of the invention. Flow diagram
400 includes operations 102, 104, and 406. Operations 102 and 104
are similar to operations 102 and 104 described with reference to
flow diagram 100. After positioning a substrate on a support in
operation 102, and removing the carbon-based polymer in operation
104, the substrate and the boron-carbon film thereon are exposed to
a plasma formed from hydrogen and nitrous oxide in operation 406.
Thus, while flow diagram 200 uses oxygen as an oxidizing agent to
remove carbon from the boron-carbon film, flow diagram 400 uses
nitrous oxide as an oxidizing agent. The use of nitrous oxide as an
oxidizing agent allows the pressure within the chamber to be
increased, thus increasing etch rate, while reducing the
probability of undesired reactions occurring within the processing
environment as is likely when using oxygen as an oxidizing
agent.
[0040] In operation 406, hydrogen gas and nitrous oxide gas are
provided to the stripping chamber at flow rate of about 5 SCCM to
about 15,000 SCCM for a 300 millimeter substrate to remove a
boron-carbon layer from the surface of the substrate. For example,
the hydrogen gas and the nitrous oxide gas may each be provided at
a flow rate of about 200 SCCM to about 4,000 SCCM. The hydrogen gas
and the nitrous oxide gas are ionized using an RF generator
operating at 13.56 MHz and applying about 100 watts to about 3,000
watts of power, such as about 1,500 watts to about 2,000 watts of
power. The substrate is maintained at a heater temperature less
than 750.degree. C., such as at about 400.degree. C. The pressure
within the stripping chamber is maintained at less than 760 Torr,
such as about 40 Torr to about 60 Torr. The nitrous oxide plasma
and the hydrogen plasma react with the boron-carbon film to form
volatile compounds which are then exhausted from the chamber.
[0041] Table 2 illustrates some exemplary process recipes for
removing a boron-carbon film from the surface of a 300 millimeter
substrate using a plasma formed from hydrogen and nitrous
oxide.
TABLE-US-00002 TABLE 2 H.sub.2 N.sub.2O Etch P Power Flow rate Flow
rate rate (Torr) (watts) T (.degree. C.) (SCCM) (SCCM) (.ANG./min)
Example 14 49 1500 400 1500 750 104 Example 15 49 1500 400 1000 500
121 Example 16 49 1500 400 500 250 143 Example 17 49 1500 400 250
125 129 Example 18 60 2000 400 1500 1000 190 Example 19 60 2000 400
1125 750 215 Example 20 60 2000 400 750 500 239 Example 21 60 2000
400 375 250 244 Example 22 60 2000 400 225 150 241
[0042] As illustrated in Table 2, the use of nitrous oxide as an
oxidizing agent generally yields a greater etching rate than when
using oxygen as an oxidizing agent. This is due partly to the
higher chamber pressures which can be utilized when using nitrous
oxide. In another embodiment, it is contemplated that the oxidizing
gas may be a mixture of nitrous oxide and oxygen, in which case,
the pressure in the chamber may be permitted to exceed 20 Torr.
Furthermore, although flow diagram 400 is described with reference
to co-flowing nitrous oxide and hydrogen gas, it is contemplated
that the nitrous oxide and hydrogen gas be independently provided
to the chamber in a cyclical manner. In yet another embodiment, it
is contemplated that carbon dioxide may be used in addition to or
as an alternative to nitrous oxide.
[0043] FIG. 5 is a flow diagram 500 illustrating a method of
removing a boron-carbon film using plasma generated from water
vapor according to one embodiment of the invention. Flow diagram
500 includes operations 102, 104, and 506. Operations 102 and 104
are similar to operations 102 and 104 described with reference to
flow diagram 100. After positioning a substrate on a support in
operation 102, and removing the carbon-based polymer in operation
104, the substrate and the boron-carbon film thereon are exposed to
a plasma formed from water vapor in operation 506.
[0044] In operation 506, water vapor is produced by a water vapor
generator (WVG) and is provided to a stripping chamber where the
water vapor is ignited into a plasma to etch a boron-carbon film
from the surface of a substrate. The water vapor is introduced to
the stripping chamber at a flow rate of about 5 SCCM to about
15,000 SCCM per 300 millimeter substrate. The substrate is
maintained at a temperature less than about 750.degree. C., such as
about 300.degree. C. to about 500.degree. C., for example about
400.degree. C., while the pressure in the chamber is maintained at
less than about 760 Torr, such as about 10 Torr to about 760 Torr,
such as about 10 Torr to about 100 Torr, for example about 65 Torr.
RF power within a range of about 10 watts to 3,000 watts, for
example about 2,700 watts, is applied to the water vapor to
generate a plasma containing oxygen, hydrogen, and hydroxyl ions or
radicals, which react with the boron-carbon film to form volatile
compounds which are exhausted from the chamber.
[0045] Flow diagram 500 illustrates one embodiment for stripping a
boron-carbon film; however, additional embodiments are also
contemplated. For example, it is contemplated that the water vapor
may be generated via in situ steam generation. In another
embodiment, it is contemplated that non-stoichiometric combinations
of oxygen and hydrogen (e.g., H.sub.xO.sub.y, where x and y may be
integers or non-integers both greater than zero) may be input to or
generated by the WVG. In such an embodiment, some hydrogen peroxide
may be generated by the water vapor generator. In another
embodiment, it is contemplated that oxygen gas, helium gas,
nitrogen gas, argon gas, nitrous oxide gas, and or/hydrogen gas may
be provided to the stripping chamber in addition to water vapor. In
such an embodiment, the addition of hydrogen has been found to
increase the removal rate of the boron-carbon film, especially in
boron-carbon films containing a higher concentration of boron as
compared to carbon. The addition of other carrier gases, such as
helium, has been observed to lower the rate of removal of the
boron-carbon film, while simultaneously improving etch uniformity.
In another embodiment, it is contemplated that the water vapor may
be used to strip a carbon film, such as amorphous carbon,
containing substantially no boron. Alternatively, it is
contemplated that the water vapor may be used to strip a boron
film, such as amorphous boron, containing substantially no
carbon.
[0046] In another embodiment, it is contemplated that a
fluorine-containing gas or a chlorine-containing gas may be ionized
in operation 506 in combination with the water vapor to increase
the etching rate of the boron-carbon film. In such an embodiment,
operation 104 may be omitted. The fluorine-containing gas or the
chlorine-containing gas is generally provided to the chamber at a
flow rate between about 10 SCCM and 50 SCCM. In order to avoid
undesirably etching dielectric materials present on the substrate,
the flow rate of the fluorine-containing gas or the
chlorine-containing gas is tapered, reduced, or eliminated when
approaching the end of operation 506. It is believed that reduction
in flow rate near the end of operation 106 does not undesirably
etch exposed dielectric materials due to the mechanism in which the
fluorine-containing gas or the chlorine-containing gas assists in
removal of the boron-carbon layer.
[0047] Generally, dielectric material on the substrate is exposed
in vias or trenches formed into the substrate during a previous
etching process, while boron-carbon material is exposed on the
upper surface of the substrate. Thus, the fluorine-containing gas
or the chlorine-containing gas which enters the chamber and is
ignited into a plasma generally contacts and reacts with the
boron-carbon layer prior to contacting the dielectric material in
the vias or trenches. However, as the boron-carbon film is removed,
the probability of the fluorine-containing gas or the
chlorine-containing gas contacting and undesirably removing the
dielectric material is increased. Therefore, the flow rate of the
fluorine-containing gas or the chlorine-containing gas is reduced
as the thickness of the boron-containing layer decreases in order
to reduce the probability of etching the dielectric material.
[0048] In another embodiment, when generating a capacitively
coupled water vapor plasma, the spacing between the substrate and a
face place located within the chamber may be within a range of
about 20 mils to about 600 mils, for example about 170 mils.
Reduced spacing between the substrate is beneficial when processing
substrates in larger volumes (for example, when processing large
area substrates) under higher pressures (for example, greater than
about 7 Torr). When processing substrates at pressures greater than
about 7 Torr, the reduced spacing facilitates plasma
sustainability. In one example, when processing a substrate at
about 30 Torr, the spacing between the substrate and the face plate
may be about 300 mils. At 40 Torr, the spacing between the
substrate and the face plate may be within a range of about 240
mils to about 270 mils. At a pressure of about 50 Torr, the spacing
between the substrate and the face plate may be less than 200 mils.
At a pressure above 50 Torr, for example about 65 Torr, the spacing
may be about 170 mils. Performing a stripping operation as
described herein above a pressure of 50 Torr results in
[0049] Table 3 illustrates a change in etch rate of a boron-carbon
film in response to a change in process gas flow rate. Each of
Examples 23-30 in Table 3 includes at least 500 SCCM of helium gas
as a carrier gas to increase etch uniformity, and may contain
additional carrier gas, as noted in Table 3.
TABLE-US-00003 TABLE 3 Power H.sub.2O Flow He Flow Carrier Etch
rate P (Torr) (watts) T (.degree. C.) rate (SCCM) rate (SCCM) gas
(SCCM) (.ANG./min) Example 23 50 1900 400 1000 250 0 679 Example 24
50 1900 400 1000 400 0 613 Example 25 50 1900 400 1000 250 150
H.sub.2 720 Example 26 50 1900 400 1000 250 350 H.sub.2 630 Example
27 50 1900 400 1000 250 150 Ar 617 Example 28 50 1900 400 1000 250
350 Ar 527 Example 29 50 1900 400 1000 250 750 Ar 389 Example 30 50
1900 400 1000 500 0 546
[0050] As shown in Table 3, Example 29, which contains the highest
total flow rate of carrier gas (250 SCCM of helium and 750 SCCM of
argon) has the lowest etch rate.
[0051] Table 4 includes some examples of boron-carbon film
stripping recipes at higher severity. High severity conditions
include pressures above 50 Torr, high gas flow rates of at least 7
sLm, and higher power input of at least about 2000 watts. Such high
severity conditions can maintain a water vapor plasma, optionally
with excess hydrogen, at a spacing less than 200 mils.
TABLE-US-00004 TABLE 4 H.sub.2O Flow He Flow Hydrogen Power Spacing
rate rate Flow Rate P (Torr) (watts) (mils) T (.degree. C.) (mgm)
(SCCM) (mgm) Example 31 65 2700 170 400 5400 2400 0 Example 32 65
2700 170 400 5400 2400 30 Example 33 65 2700 170 400 5400 2400
600
As noted above, it is thought that adding hydrogen in excess of the
stoichiometric proportions of water may accelerate reactions with
boron and accelerate the overall rate of removal of boron-carbon
films. The exact amount of excess hydrogen that is most beneficial
depends on the amount of boron in the carbon film.
[0052] FIG. 6 illustrates the etching selectivity of water vapor
plasma. Plasma A includes 1,000 SCCM of water vapor and 500 SCCM of
helium generated into a plasma using 1900 watts of RF power. The
stripping chamber is maintained at 50 Torr, and the substrate is
maintained at 400.degree. C. Plasma A etched the boron-carbon film
at a rate of about 570 angstroms per minute, and did not etch
silicon oxide, silicon nitride, or amorphous silicon.
[0053] Plasma B includes 1,000 SCCM of water vapor, 250 SCCM of
helium, and 150 SCCM of hydrogen generated into a plasma using 1900
watts of RF power. The stripping chamber is maintained at 50 Torr,
and the substrate is maintained at 400.degree. C. Plasma B etched
the boron-carbon film at a rate of about 770 angstroms per minute,
and did not etch silicon oxide, silicon nitride, or amorphous
silicon.
[0054] Benefits of the methods described herein include stripping
boron-carbon films without damaging dielectric materials or
underlying metal layers located on a substrate. The stripping
methods allow for etching rate, as well as etching uniformity to be
controlled by varying plasma composition.
[0055] 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.
* * * * *