U.S. patent application number 14/719546 was filed with the patent office on 2015-11-19 for methods and apparatus for processing substrates using an ion shield.
The applicant listed for this patent is APPLIED MATERIALS, INC.. Invention is credited to LARA HAWRYLCHAK, BERNARD L. HWANG, CANFENG LAI, WEI LIU, JOHANES SWENBERG, JEFFREY TOBIN.
Application Number | 20150332941 14/719546 |
Document ID | / |
Family ID | 50432994 |
Filed Date | 2015-11-19 |
United States Patent
Application |
20150332941 |
Kind Code |
A1 |
TOBIN; JEFFREY ; et
al. |
November 19, 2015 |
METHODS AND APPARATUS FOR PROCESSING SUBSTRATES USING AN ION
SHIELD
Abstract
Methods and apparatus for processing a substrate are provided.
In some embodiments, a method of processing a substrate having a
first layer may include disposing a substrate atop a substrate
support in a lower processing volume of a process chamber beneath
an ion shield having a bias power applied thereto, the ion shield
comprising a substantially flat member supported parallel to the
substrate support, and a plurality of apertures formed through the
flat member, wherein the ratio of the aperture diameter to the
thickness flat member ranges from about 10:1-1:10; flowing a
process gas into an upper processing volume above the ion shield;
forming a plasma from the process gas within the upper processing
volume; treating the first layer with neutral radicals that pass
through the ion shield; and heating the substrate to a temperature
of up to about 550 degrees Celsius while treating the first
layer.
Inventors: |
TOBIN; JEFFREY; (Mountain
View, CA) ; HWANG; BERNARD L.; (Santa Clara, CA)
; LAI; CANFENG; (Fremont, CA) ; HAWRYLCHAK;
LARA; (San Jose, CA) ; LIU; WEI; (San Jose,
CA) ; SWENBERG; JOHANES; (Los Gatos, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
APPLIED MATERIALS, INC. |
Santa Clara |
CA |
US |
|
|
Family ID: |
50432994 |
Appl. No.: |
14/719546 |
Filed: |
May 22, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
14044090 |
Oct 2, 2013 |
9048190 |
|
|
14719546 |
|
|
|
|
61711495 |
Oct 9, 2012 |
|
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Current U.S.
Class: |
156/345.48 |
Current CPC
Class: |
H01L 21/31116 20130101;
H01J 37/32422 20130101; H01L 21/0217 20130101; H01L 21/67103
20130101; H01J 37/32082 20130101; H01L 21/67115 20130101; H01L
21/6831 20130101; H01L 21/3065 20130101; H01J 37/32357 20130101;
H01L 21/67069 20130101; H01J 37/32091 20130101 |
International
Class: |
H01L 21/67 20060101
H01L021/67; H01J 37/32 20060101 H01J037/32 |
Claims
1. A substrate processing apparatus, comprising: a chamber body
defining a processing volume having an upper processing volume and
a lower processing volume; a substrate support disposed within the
lower processing volume; an ion shield disposed in the processing
volume and dividing the processing volume into the upper processing
volume and the lower processing volume, the ion shield comprising a
substantially flat member supported parallel to the substrate
support, and having a plurality of apertures formed through the
substantially flat member, wherein the ratio of the diameter of the
apertures to the thickness of the substantially flat member has a
range of about 10:1 to about 1:10; a biasing power source coupled
to the ion shield; a shield support disposed within the processing
volume configured to support the ion shield above the substrate
support in a substantially parallel orientation with respect to the
substrate; a heat source to provide heat energy to a substrate when
disposed on the substrate support; and an RF power source for
forming a plasma within the upper processing volume.
2. The apparatus of claim 1, wherein the upper processing volume is
fluidly coupled to the lower processing volume substantially only
through the ion shield.
3. The apparatus of claim 1, wherein the biasing power source is
configured to supply about 10 to about 2000 V DC or about 10 to
about 2000 W of RF power to bias the ion shield.
4. The apparatus of claim 1, further comprising a
nitrogen-containing gas source coupled to the process chamber to
provide a nitrogen-containing gas to the upper processing
volume.
5. The apparatus of claim 4, wherein the nitrogen-containing gas is
ammonia (NH.sub.3).
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of co-pending U.S. patent
application Ser. No. 14/044,090, filed Oct. 2, 2013, which claims
benefit of United States provisional patent application Ser. No.
61/711,495, filed Oct. 9, 2012, which are herein incorporated by
reference in their entirety.
FIELD
[0002] Embodiments of the present invention generally relate to
semiconductor processing equipment.
BACKGROUND
[0003] The inventors have observed that nitridation of 3D device
structures cannot be easily performed using typical plasma ion
exposure due to the non-conformal nature of the plasma sheath,
which prevents conformal doping of the top surface of a film and
the device sidewall. Instead, the inventors believe that 3D
conformal nitridation requires radical or neutral species driven
reactions. One method of nitridizing a hafnium oxide based 3D
high-k gate stack is through the use of an inductively coupled
plasma generated using ammonia and, optionally, an inert gas,
and/or nitrogen gas (N.sub.2). However, the inventors have observed
that this process also leads to the formation of a number of
reactive hydrogen species, including both hydrogen radicals and
hydrogen ions. These reactive hydrogen species can potentially
penetrate the nitridized film and negatively interact with the gate
stack materials. Additionally, the inventors have observed that
this process also leads to the formation of a number of inert gas
and/or nitrogen ions, which also undesirably contribute to the
non-conformal processing results. The inventors propose that
reducing or eliminating the reactive hydrogen species prior to
their penetration and interaction with the gate stack materials can
prevent device failure, and reducing or eliminating the inert gas
and/or ions prior to their interaction with the substrate can
enhance conformal processing results.
[0004] As such, the inventors have provided improved methods and
apparatus for nitridizing materials, such as those in 3D device
structures.
SUMMARY
[0005] Methods and apparatus for processing a substrate are
provided herein. In some embodiments, such processing includes
nitridizing a substrate. In some embodiments, a method of
processing a substrate having a first layer disposed thereon, for
example that is part of a 3D device disposed on or being fabricated
on the substrate, may include disposing a substrate atop a
substrate support disposed in a lower processing volume of a
process chamber beneath an ion shield having a bias power applied
thereto, wherein the ion shield comprises a substantially flat
member supported parallel to the substrate support, and a plurality
of apertures formed through the flat member, and wherein the ratio
of the diameter of the apertures to the thickness of the flat
member has a range of about 10:1 to about 1:10; flowing a process
gas into an upper processing volume above the ion shield; forming a
plasma from the process gas within the upper processing volume;
treating the first layer with neutral radicals that pass through
the ion shield; and heating the substrate to a temperature of up to
about 550 degrees Celsius while treating the first layer.
[0006] In some embodiments, a substrate processing apparatus may
include a chamber body defining a processing volume having an upper
processing volume and a lower processing volume; a substrate
support disposed within the lower processing volume; an ion shield
disposed in the processing volume and dividing the processing
volume into the upper processing volume and the lower processing
volume, the ion shield comprising a substantially flat member
supported parallel to the substrate support, and having a plurality
of apertures formed through the substantially flat member, wherein
the ratio of the diameter of the apertures to the thickness of the
substantially flat member has a range of about 10:1 to about 1:10;
a biasing power source coupled to the ion shield; a shield support
disposed within the processing volume configured to support the ion
shield above the substrate support in a substantially parallel
orientation with respect to the substrate; a heat source to provide
heat energy to a substrate when disposed on the substrate support;
and an RF power source for forming a plasma within the upper
processing volume.
[0007] Other and further embodiments of the present invention are
described below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] Embodiments of the present invention, briefly summarized
above and discussed in greater detail below, can be understood by
reference to the illustrative embodiments of the invention depicted
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.
[0009] FIG. 1 depicts a flow chart for a method of processing a
substrate in accordance with some embodiments of the present
invention.
[0010] FIGS. 2A-2B depict a schematic view of a substrate
processing chamber in accordance with some embodiments of the
present invention.
[0011] FIG. 3 depicts a partial perspective view of an ion shield
in accordance with some embodiments of the present invention.
[0012] FIGS. 4A-4C depict stages of fabrication of a nitridized
layer atop a substrate in accordance with some embodiments of the
present invention.
[0013] To facilitate understanding, identical reference numerals
have been used, where possible, to designate identical elements
that are common to the figures. The figures are not drawn to scale
and may be simplified for clarity. It is contemplated that elements
and features of one embodiment may be beneficially incorporated in
other embodiments without further recitation.
DETAILED DESCRIPTION
[0014] Embodiments of the present invention provide improved
methods and apparatus for processing a substrate. Embodiments of
the present invention may advantageously allow for the conformal
nitridation of 3D structures, such as high-k materials used in 3D
structures, by reducing the impact of reactive species, such as
hydrogen radicals and hydrogen ions, as well as other ions,
resulting from an inductively coupled plasma formed from an ammonia
source. The methods and apparatus may also be used to nitridize
other materials in other applications including those not having 3D
structures.
[0015] FIGS. 2A and 2B depict particular embodiments of a process
chamber 200 for processing substrates in accordance with some
embodiments of the present invention. The process chamber 200 is
depicted for illustrative purposes and should not be used to limit
the scope of the invention. In the depicted embodiment, the process
chamber 200 has a substantially flat dielectric ceiling 212.
However, other modifications of the process chamber 200 may have
other types of ceilings, for example, a dome-shaped ceiling.
[0016] The process chamber 200 depicted in FIGS. 2A and 2B
generally comprises a substrate support 202 and a slit valve 224
within a chamber body 204. The slit valve 224 allows the ingress
and egress of a substrate 206 to and from the substrate support
202. The substrate support 202 has an upper surface to support the
substrate 206 such that a first layer 230 of the substrate 206 is
positioned for processing. In some embodiments, the process chamber
200 further comprises a heat source 240 to heat the substrate 206
to a desired temperature. The heat source 240 may be any type of
heat source suitable to provide control over the substrate
temperature, for example a resistive heater coupled to the
substrate support 202 or heat lamps (not shown) disposed in a
position to provide heat energy to the surface of the substrate 206
either directly or through some other component. For example, in
some embodiments, the heat source 240 is the resistive heater
disposed within an electrostatic chuck, which advantageously
enhances temperature control of the substrate due to enhanced
thermal contact between the substrate and the electrostatic chuck
due to the clamping force provided by the electrostatic chuck.
[0017] The chamber body 204 defines a processing volume 208 divided
into an upper processing volume 234 and a lower processing volume
236 by an ion shield 210 disposed within the processing volume 208.
The upper processing volume 234 is disposed above the ion shield
210 and the lower processing volume 236 is disposed below the ion
shield 210. The upper processing volume 234 and the lower
processing volume 236 are fluidly coupled by openings in the ion
shield 210.
[0018] A process gas source 222 is coupled to the process chamber
200 to supply a process gas to the upper processing volume 234. In
some embodiments, the process gas is a nitrogen containing gas, for
example ammonia (NH.sub.3), alone or in combination with an inert
gas, such as argon (Ar) or the like, which is suitable for a
nitridation process. In some embodiments, the process gas is an
oxygen containing gas, such as oxygen (O.sub.2), suitable for an
oxidation process. In some embodiments, the process gas is a
halogen containing gas, such as chlorine (Cl.sub.2), fluorine
(F.sub.2), bromine (Br.sub.2), nitrogen trifluoride (NF.sub.3),
trifluoromethane (CHF.sub.3), hydrogen chloride (HCl), hydrogen
bromide (HBr), or the like, suitable for an etch process.
[0019] A plasma can be formed in the upper processing volume 234
from the process gas by applying RF power from a plasma power
source 216. The plasma power source 216 can be coupled to an
electrode disposed in or near the ceiling 212 of the process
chamber suitable to couple RF power to the process gases disposed
in the process chamber. For example, the plasma power source 216
and the electrode can be configured to form a capacitively coupled
plasma, and inductively coupled plasma, or the like.
[0020] The plasma may form reactive species, such as in a
nitridation process where the plasma can form hydrogen radicals and
hydrogen ions, as well as nitrogen and/or inert gas ions, in
addition to the other components of the plasma. These reactive
hydrogen species can potentially penetrate the nitridized film and
negatively interact with the substrate or materials disposed on the
substrate. In addition, inert or nitrogen gas ions can also
negatively impact conformal reactions or processing of
three-dimensional structures on the substrate. The ion shield 210
advantageously controls the spatial distribution of the reactive
and neutral species in the process chamber 200 during nitridation,
or other, processes. Specifically, the ion shield 210 substantially
prevents the reactive hydrogen species and other ions from reaching
the substrate 206 in the lower process volume 236. Moreover, the
ion shield 210 allows species with high surface recombination
rates, such as hydrogen radicals, to recombine preferentially on
the surface of the ion shield 210, leaving a higher relative
concentration of desirable species (for example,
nitrogen-containing species in a nitridation process) to reach the
surface of the substrate 206.
[0021] In some embodiments, the ion shield 210 is coupled to a bias
power source 220 which advantageously allows for the selective
biasing of the ion shield 210 to enhance ion screening (e.g.,
reduction of charged radicals and ions) during the nitridation
process. The bias power source can be a DC power source or an RF
power source. For example, a negative voltage applied to the ion
shield 210 can enhance the screening of positive ions by attracting
the positive ions to the surface of the ion shield 210. The ion
shield 210 is made of a conductive material such as aluminum,
anodized aluminum, aluminum oxide, or quartz. In some embodiments,
the ion shield 210 is electrically isolated from the chamber body
204 and the substrate support 202. In some embodiments, the ion
shield 210 is grounded, for example by electrically coupling to the
chamber body 204 and/or the substrate support 202. The choice of
material used for the ion shield 210 can be selected to contribute
to the control of the recombination rate at the surface of the ion
shield 210. For example, hydrogen radicals recombine more readily
on an aluminum surface than on a quartz surface.
[0022] The ion shield 210 is supported above the substrate support
202 by a support element. In some embodiments, the height at which
the ion shield 210 is supported may vary in order to control the
process within the process chamber 200. For example, in an etch
process, a faster etch rate may be obtained by locating the ion
shield 210 closer to the substrate support 202 and, therefore, the
substrate 206. Alternatively, a lower, but more controlled, etch
rate may be obtained by locating the ion shield 210 farther from
substrate support 202. In some embodiments, the height of the ion
shield 210 may range from about 0.5 inches (3.81 cm) to about 5.5
inches (10.16 cm) in a process chamber 200 having a distance of
about 6 inches (15.24 cm) between the substrate 206 and the ceiling
212. In some embodiments, the ion shield 210 is supported above the
substrate support 202 at distance of about 2 to about 4 inches
above the substrate 206 in a process chamber having a substrate to
ceiling distance of about 6 inches. Other support heights may be
used in chambers having other configurations.
[0023] The ion shield 210 is supported using any suitable structure
in a manner that maintains the ion shield 210 in a substantially
parallel orientation with respect to the substrate 206 or the
substrate support 202. In some embodiments, the shield support
element 238 is a ledge 242, as depicted in FIG. 2A, attached to the
chamber wall 204 (or to a process cavity liner disposed along the
chamber wall) and supporting the ion shield 210 above the substrate
support 202. In some embodiments as shown in FIG. 2B, the shield
support element 238 is a stand 244 coupled to a bottom of the
process chamber 200 and located around an outer perimeter of the
substrate support 202, or a stand 244 having a lift mechanism 246
(e.g., an actuator, a motor, combinations thereof, or the like) to
raise and lower the ion shield 210, or any other suitable structure
within the process chamber 200.
[0024] For example, in some embodiments, a lift mechanism 246 may
be coupled to the ion shield 210 to control the position of the ion
shield 210 with respect to the substrate support 202, for example
over a range extending above and below the slit valve 224. The lift
mechanism 246 can support the ion shield 210 (e.g., the lift
mechanism can be the support element) or the lift mechanism 246 can
move the ion shield 210 from resting on the support element to a
position disposed above the support element (such as the ledge 242
shown in FIG. 2A). The lift mechanism 246 can raise the ion shield
210 from a first position above the substrate 206, but below the
slit valve 224, to a second position above the slit valve 224 to
allow the substrate 226 to enter and exit the processing chamber
200 from the slit valve 224. In some embodiments, the lift
mechanism 246 is generally located around an outer perimeter of the
substrate support 202. An upper end of the lift mechanism 246 may
be press fit into a corresponding hole formed in the ion shield
210. Alternatively, the upper end of the lift mechanism 246 may be
threaded into the ion shield 210 or into a bracket secured to an
underside of the ion shield 210. Other fastening methods not
inconsistent with processing conditions may also be used to secure
the lift mechanism 246 to the ion shield 210.
[0025] In some embodiments, the support element for the ion shield
210 is made of conductive material. In some embodiments, the
support element is anodized. In some embodiments, the support
element is not conductive but is connected to a ground path. In
some embodiments, the ion shield 210 may be part of an
easily-replaceable process kit for ease of use, maintenance,
replacement, and the like. It is contemplated that the ion shield
210 may be configured to be easily retrofitted in existing process
chambers.
[0026] FIG. 3 depicts a perspective view of one specific embodiment
of the ion shield 210. In some embodiments, the ion shield 210
comprises one or more substantially flat members 214 supported
parallel to the substrate support 202 and a plurality of apertures
218 formed through the one or more flat members 214. In some
embodiments, multiple flat members 214 having apertures 218 are
stacked together in order to manipulate the quantity of ions that
pass from a plasma formed in an upper processing volume 234 of the
process chamber 200 to a lower processing volume 236 located
between the ion shield 210 and the substrate 206. In some
embodiments, the flat member 214, could comprise a plate, a screen
a mesh, or a combination thereof.
[0027] The plurality of apertures 218 may vary in size, spacing and
geometric arrangement across the surface of the substantially flat
member 214. The plurality of apertures 218 control the quantity of
ions that pass from a plasma formed in the upper processing volume
234 of the process chamber 200 to the lower processing volume 236
located between the ion shield 210 and the substrate 206. As such,
the size and quantity of the apertures 218 affects the ion density
in the lower processing volume 236. For example, the ion density
may be substantially lowered, such that processing is predominantly
provided by neutral radical species of the plasma.
[0028] The size of the apertures 218 generally range from about
0.03 inches (0.07 cm) to about 3 inches (7.62 cm), or from about
0.125 inches to about 1 inch. The apertures 218 may be arranged to
define an open area in the surface of the substantially flat member
214 of from about 2 percent to about 90 percent. In one embodiment,
the one or more apertures 218 includes a plurality of approximately
half-inch (1.25 cm) diameter holes arranged in a square grid
pattern defining an open area of about 30 percent. It is
contemplated that the holes may be arranged in other geometric or
random patterns utilizing other size holes or holes of various
sizes.
[0029] In some embodiments, the size, shape and/or patterning of
the holes may vary depending upon the desired ion density in the
lower processing volume 236. For example, in some embodiments, a
similar hole size may be provided in a geometric pattern having
regions of relatively higher and lower numbers of holes to control
the concentration of radicals in regions corresponding to the
geometric pattern without altering the overall composition of the
species reaching the substrate.
[0030] In some embodiments, the size, shape and patterning of the
holes may vary depending upon the desired ion density in the lower
processing volume 236. For example, more holes of small diameter
may be used to increase the radical to ion density ratio in the
lower processing volume 236. In other situations, a number of
larger holes may be interspersed with small holes to increase the
ion to radical density ratio in the lower processing volume 236.
Alternatively, the larger holes may be positioned in specific areas
of the substantially flat member 214 to contour the ion
distribution in the lower processing volume 236.
[0031] In combination with the size of the apertures 218, the
thickness of the one or more substantially flat members 214 may be
selected to control the length of each aperture 218. The aspect
ratio (i.e. the ratio of the diameter of the apertures 218 to the
thickness of the one or more substantially flat members 214) of the
ion shield 210 controls the ion density within the lower processing
region 236. In some embodiments, the aspect ratio ranges from about
10:1 to about 1:10. In some embodiments, the aspect ratio ranges
from about 2:1 to about 1:2.
[0032] FIG. 1 depicts one exemplary method 100 of processing a
substrate using the processing chamber 200 described above. In some
embodiments, at least some portions of the method 100 may be
performed in a substrate processing chamber, for example, such as
the processing chamber 200 described above with respect to FIGS. 2A
and 2B (although other suitable process chambers may alternatively
be used). Suitable process chambers that may be adapted in
accordance with the teachings disclosed herein include, for
example, a Decoupled Plasma Nitridation (DPN) reactor, or a
toroidal source plasma immersion ion implantation reactor, such as
the CONFORMA.TM. chamber, each of which are available from Applied
Materials, Inc. of Santa Clara, Calif.
[0033] The method 100 is also described herein with respect to
FIGS. 4A-4C, which depicts the stages of fabrication of a
nitridized layer atop a substrate in accordance with some
embodiments of the present invention. The stages of fabrication of
a nitridized layer are depicted for illustrative purposes and do
not limit the scope of the invention. For example, in some
embodiments, the method 100 may be used to oxidize or etch a
substrate 206.
[0034] The method 100 begins at 102, where a substrate 206 is
disposed atop a substrate support 202 in a processing volume 208 of
a process chamber 200 and beneath an ion shield 210 disposed over
the substrate support 202.
[0035] The substrate 206 may have various dimensions, such as 200
mm, 300 mm, or other diameter wafers, as well as rectangular or
square panels. The substrate 206 may comprise a material such as
crystalline silicon (e.g., Si<100> or Si<111>), silicon
oxide, strained silicon, silicon germanium, doped or undoped
polysilicon, doped or undoped silicon wafers, patterned or
non-patterned wafers, silicon on insulator (SOI), carbon doped
silicon oxides, silicon nitride, doped silicon, germanium, gallium
arsenide, glass, sapphire, or the like.
[0036] The substrate 206 includes a first layer 230 to be
processed. The first layer 230 may be defined by a base material of
the substrate 206 (e.g., silicon) or by one or more layers disposed
atop the base material. For example, the substrate 206 may include
one or more completely or partially fabricated semiconductor
devices 400, as depicted in FIG. 4A. The semiconductor device 400
may be completely or partially formed upon the substrate 206 and
includes the first layer 230 to be processed, for example
nitridized. The semiconductor device (when completed) may be, for
example, a field effect transistor (FET), dynamic random access
memory (DRAM), a flash memory device, or a 3D device, such as a 3D
logic device, or other 3D devices requiring 3D conformal
processing, such as nitridation, oxidation, or etch, or the
like.
[0037] The first layer 230 may be, for example, utilized as a gate
dielectric layer of a transistor device, a tunnel oxide layer in a
flash memory device, a spacer layer atop a gate structure, an
inter-poly dielectric (IPD) layer of a flash memory device, or the
like. The first layer 230 may have any thickness suitable in
accordance with the particular application for which the first
layer 230 may be utilized.
[0038] The first layer 230 may comprise an oxide layer, such as
silicon oxide (SiO.sub.2), a metal oxide, hafnium oxide
(HfO.sub.2), hafnium silicate (HfSiO.sub.x), or any suitable oxide
layer used in a semiconductor device and requiring nitridation. For
example, in some embodiments, the oxide layer may be a native oxide
layer, or formed by any suitable oxidation process including the
oxidation process discussed below. The first layer 230 need not be
limited to an oxide layer, and other suitable layers may benefit
from the inventive methods disclosed herein. For example, other
suitable embodiments of the first layer 230 may include other
silicon-containing layers such as SiC, or metal nitride layers, or
the like. The first layer 230 can also be a stack of layers, such
as a first sub-layer of SiO.sub.2 and a second sub-layer of
HfO.sub.2 or a first sub-layer of SiO.sub.2 and a second sub-layer
of HfSiO.sub.x, or the like.
[0039] The first layer 230 may be fabricated in one or more process
chambers coupled to a cluster tool that also has the process
chamber 200 coupled thereto. One example of a suitable cluster tool
is a Gate Stack CENTURA.RTM., available from Applied Materials,
Inc., of Santa Clara, Calif.
[0040] Next, at 104, a process gas is flowed from a process gas
source 222 into the upper processing volume 234 above the ion
shield 210. In some embodiments, the process gas is a nitrogen
containing process gas, such as ammonia (NH.sub.3). The use of
ammonia (NH.sub.3) to form a plasma advantageously generates a
thicker film atop the substrate 206 than a plasma formed using pure
nitrogen. The nitrogen-containing process gas is provided at a flow
rate of about 50 to about 1000 sccm, or from about 100 to about 500
sccm. In some embodiments, an inert gas, such as argon or helium,
is also provided into the process chamber along with the
nitrogen-containing process gas. Diluting ammonia in an argon
ambiance advantageously enhances the dissociation of ammonia and,
thus, increases the nitridation rate. The ammonium/argon process
gas is provided at a total flow rate of about 100 to about 2000
sccm, or about 200 to about 1000 sccm. The ammonia may be about 1%
to about 99%, or about 2.5 to about 25%, of the process gas. In
some embodiments, the process gas is an oxygen containing gas, such
as oxygen (O.sub.2), ozone (O.sub.3), or water (H.sub.2O) vapor,
suitable for an oxidation process or a halogen containing gas, such
as chlorine (Cl.sub.2), fluorine (F.sub.2), bromine (Br.sub.2),
nitrogen trifluoride (NF.sub.3), trifluoromethane (CHF.sub.3),
hydrogen chloride (HCl), hydrogen bromide (HBr), or the like,
suitable for an etch process.
[0041] Next, at 106 a plasma is formed in the process chamber 200
from the nitrogen-containing process gas by applying RF power from
a plasma power source (such as plasma power source 216) coupled to
the process chamber 200. The plasma is formed in the upper
processing volume 234 of the process chamber 200. In some
embodiments, RF power (continuous wave or effective pulsed power)
is provided in a range of about 50 to about 3000 watts, or in some
embodiments about 200 to about 1000 watts. RF power may be pulsed
at a duty cycle of about 2 to about 50%. The pressure in the
process chamber may range from about 2 mTorr to about 200 mTorr, or
in some embodiments, about 10 to about 60 mTorr.
[0042] Optionally, at 108, a bias power of about 10 to about 2000
volts DC power, or about 10 to about 2000 watts RF power, may be
applied by a bias power source 220 to the ion shield 210. Applying
a bias power to the ion shield 210 advantageously applies a voltage
to the ion shield 210 to enhance ion screening.
[0043] Next, at 110, which is depicted in FIG. 4B, the first layer
230 is treated using the neutral radicals 402 that pass through the
ion shield 210 to the lower processing volume 236. The neutral
radicals 402 that pass through the ion shield 210 are
advantageously the dominant species, with little or no ions
present. The inventors have discovered that a high ion
concentration in the plasma results in a more vertical path for the
ions attracted to the substrate, which leads to poor conformality
in applications where top surfaces and sidewall surfaces need to be
processed, such as in 3D devices, trenches, vias, or the like.
Thus, the inventors have discovered that a reduced ion
concentration in the plasma improves conformality in applications
where top surfaces and sidewall surfaces need to be processed, such
as in 3D devices, trenches, vias, or the like.
[0044] The inventors have further discovered that providing thermal
energy, for example by heating the substrate, enhances such radical
driven conformal processing results. For example, in a nitridation
process, as depicted in FIG. 4C, the neutral radicals 402 result in
a conformally nitridized first layer 404 atop the substrate 206.
Alternatively, the substrate 206 can be conformally oxidized using
neutral radicals that pass through the ion shield 210 by providing
an oxygen-containing process gas. In some embodiments, the
substrate 206 can be conformally etched using neutral radicals that
pass through the ion shield 210 by providing an etchant
species.
[0045] In some embodiments, the substrate 206 is heated while
treating the first layer 230 using the neutral radicals 402 that
pass through the ion shield 210. For example, the substrate 206 may
be heated from about room temperature (about 30 degrees Celsius) to
about 550 degrees Celsius, for example from about 350 to about 450
degrees Celsius. The pressure inside the process chamber 200 during
nitridation is generally controlled at about 2 mTorr to about 200
mTorr, or in some embodiments, about 10 to about 60 mTorr. Although
illustratively discussed above as treating the first layer 230 or
forming a conformally nitridized first layer 404, the inventive
methods disclosed herein can be used to advantageously conformally
process substrates having three dimensional structures formed in
one or many layers.
[0046] Thus, methods of nitridizing materials on substrates and
apparatus for performing same have been disclosed herein. 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.
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