U.S. patent application number 13/966453 was filed with the patent office on 2014-11-20 for delicate dry clean.
This patent application is currently assigned to Applied Materials, Inc.. The applicant listed for this patent is Applied Materials, Inc.. Invention is credited to Sean S. Kang, Chia-Ling Kao, Srinivas D. Nemani, Lina Zhu.
Application Number | 20140342532 13/966453 |
Document ID | / |
Family ID | 51896096 |
Filed Date | 2014-11-20 |
United States Patent
Application |
20140342532 |
Kind Code |
A1 |
Zhu; Lina ; et al. |
November 20, 2014 |
DELICATE DRY CLEAN
Abstract
A method of selectively removing fluorocarbon layers from
overlying low-k dielectric material is described. These protective
plasma treatments (PPT) are delicate alternatives to traditional
post-etch treatments (PET). The method includes sequential exposure
to (1) a local plasma formed from a silicon-fluorine precursor
followed by (2) an exposure to plasma effluents formed in a remote
plasma from a fluorine-containing precursor. The remote plasma etch
(2) has been found to be highly selective of the residual material
following the local plasma silicon-fluorine exposure. The
sequential process (1)-(2) avoids exposing the low-k dielectric
material to oxygen which would undesirably increase its dielectric
constant.
Inventors: |
Zhu; Lina; (San Jose,
CA) ; Kang; Sean S.; (San Ramon, CA) ; Nemani;
Srinivas D.; (Sunnyvale, CA) ; Kao; Chia-Ling;
(San Jose, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Applied Materials, Inc. |
Santa Clara |
CA |
US |
|
|
Assignee: |
Applied Materials, Inc.
Santa Clara
CA
|
Family ID: |
51896096 |
Appl. No.: |
13/966453 |
Filed: |
August 14, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61823995 |
May 16, 2013 |
|
|
|
Current U.S.
Class: |
438/476 |
Current CPC
Class: |
H01L 21/02063 20130101;
H01L 21/31116 20130101; H01L 21/3105 20130101 |
Class at
Publication: |
438/476 |
International
Class: |
H01L 21/3105 20060101
H01L021/3105; H01L 21/311 20060101 H01L021/311 |
Claims
1. A method of removing a fluorocarbon layer from a low-k
dielectric layer on a patterned substrate, the method comprising
two sequential steps: (i) treating the patterned substrate with a
local plasma formed from a silicon-and-fluorine-containing
precursor, wherein the operation of treating the patterned
substrate removes the fluorocarbon layer from patterned substrate
and forms a fluorinated silicon oxide layer on the low-k dielectric
layer and the local plasma is formed by applying a local plasma
power; (ii) flowing a fluorine-containing precursor into a remote
plasma region fluidly coupled to a substrate processing region
while forming a remote plasma in the remote plasma region to
produce plasma effluents, wherein forming the remote plasma in the
remote plasma region to produce the plasma effluents comprises
striking an RF plasma having an RF plasma power to the plasma
region; and etching the fluorinated silicon oxide layer by flowing
the plasma effluents into the substrate processing region.
2. The method of claim 1 wherein the
silicon-and-fluorine-containing precursor comprises silicon
tetrafluoride.
3. The method of claim 1 wherein the substrate processing region is
devoid of oxygen during sequential step (i).
4. The method of claim 1 wherein the substrate processing region is
devoid of nitrogen during sequential step (i).
5. The method of claim 1 wherein the local plasma power is between
about 10 watts and about 500 watts to the substrate processing
region.
6. The method of claim 1 wherein forming a remote plasma in the
remote plasma region to produce plasma effluents comprises applying
RF power between about 1 watts and about 5000 watts to the remote
plasma region.
7. The method of claim 1 wherein the local plasma is formed by
applying a DC bias power such that the local plasma power comprises
both an AC portion and a DC portion.
8. The method of claim 1 wherein the DC bias power comprises
applying a DC bias voltage greater than 200 volts to accelerate
inert gas ions toward the patterned substrate.
9. The method of claim 1 wherein the plasma effluents enter the
substrate processing region through through-holes in a showerhead
which separates the remote plasma region from the substrate
processing region.
10. The method of claim 1 wherein the remote plasma region is
devoid of hydrogen during sequential step (ii).
11. The method of claim 1 wherein the fluorine-containing precursor
comprises nitrogen trifluoride.
12. The method of claim 1 wherein step (ii) further comprises
flowing a hydrogen-containing precursor into the remote plasma
region.
13. The method of claim 12 wherein the hydrogen-containing
precursor comprises ammonia (NH.sub.3).
14. The method of claim 12 wherein step (ii) further comprises
forming solid residue etch by-product on the surface of the
patterned substrate.
15. The method of claim 14 further comprising a step (iii) which
comprises after raising a temperature of the patterned substrate
step above 90.degree. C. to sublimate the solid residue, wherein
step (iii) occurs after step (ii).
16. The method of claim 12 wherein forming a remote plasma in the
remote plasma region to produce plasma effluents comprises applying
RF power between about 10 watts and about 300 watts to the remote
plasma region.
17. The method of claim 1 wherein a pressure within the substrate
processing region is between about 0.01 Torr and about 50 Torr
during sequential step (ii).
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Prov. Pat. App.
No. 61/823,995 filed May 16, 2013, and titled "DELICATE DRY CLEAN"
by Zhu et al., which is hereby incorporated herein in its entirety
by reference for all purposes.
STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSORED
RESEARCH AND DEVELOPMENT
[0002] NOT APPLICABLE
REFERENCE TO A "SEQUENCE LISTING," A TABLE, OR A COMPUTER PROGRAM
LISTING APPENDIX SUBMITTED ON A COMPACT DISK
[0003] NOT APPLICABLE
BACKGROUND OF THE INVENTION
[0004] Integrated circuit fabrication methods have reached a point
where many hundreds of millions of transistors are routinely formed
on a single chip. Each new generation of fabrication techniques and
equipment are allowing commercial scale fabrication of ever smaller
and faster transistors, but also increase the difficulty to make
even smaller, faster circuit elements. The shrinking dimensions of
circuit elements, now well below the 50 nm threshold, has caused
chip designers to look for new low-resistivity conductive materials
and new low-dielectric constant (i.e., low-k) insulating materials
to improve (or simply maintain) the electrical performance of the
integrated circuit.
[0005] Parasitic capacitance becomes a significant impediment to
transistor switching rate as the number of transistors per area is
increased. Capacitance exists between all adjacent electrically
isolated conductors within an integrated circuit and may limit the
switching rate regardless of whether the conducting portions are at
the "front end" or the "back end" of the manufacturing process
flow.
[0006] Thus, there is a need for new techniques and materials to
form low-k material between adjacent conductors. One class of
materials used to provide low-k separation between conductors is
oxidized organo-silane films, such as the Black Diamond films
commercially available from Applied Materials, Inc. of Santa Clara,
Calif. These films have lower dielectric constants (e.g., about 3.5
or less) than conventional spacer materials like silicon oxides and
nitrides. Unfortunately, some new processes involve exposing low-k
films to environments which can increase the effective dielectric
constant and limit device performance.
[0007] Thus there is a need for new processes which maintain a
lower effective dielectric constant following exposure of a low-k
film to these environments.
BRIEF SUMMARY OF THE INVENTION
[0008] A method of selectively removing fluorocarbon layers from
overlying low-k dielectric material is described. These protective
plasma treatments (PPT) are delicate alternatives to traditional
post-etch treatments (PET). The method includes sequential exposure
to (1) a local plasma formed from a silicon-fluorine precursor
followed by (2) an exposure to plasma effluents formed in a remote
plasma from a fluorine-containing precursor. The remote plasma etch
(2) has been found to be highly selective of the residual material
following the local plasma silicon-fluorine exposure. The
sequential process (1)-(2) avoids exposing the low-k dielectric
material to oxygen which would undesirably increase its dielectric
constant.
[0009] Embodiments of the invention include methods of removing a
fluorocarbon layer from a low-k dielectric layer on a patterned
substrate, the method comprising two sequential steps: (i) treating
the patterned substrate with a local plasma formed from a
silicon-and-fluorine-containing precursor, wherein the operation of
treating the patterned substrate removes the fluorocarbon layer
from patterned substrate and forms a fluorinated silicon oxide
layer on the low-k dielectric layer and the local plasma is formed
by applying a local plasma power, and (ii) flowing a
fluorine-containing precursor into a remote plasma region fluidly
coupled to a substrate processing region while forming a remote
plasma in the remote plasma region to produce plasma effluents. The
methods include forming the remote plasma in the remote plasma
region to produce the plasma effluents comprises striking an RF
plasma having an RF plasma power to the plasma region and etching
the fluorinated silicon oxide layer by flowing the plasma effluents
into the substrate processing region.
[0010] Additional embodiments and features are set forth in part in
the description that follows, and in part will become apparent to
those skilled in the art upon examination of the specification or
may be learned by the practice of the disclosed embodiments. The
features and advantages of the disclosed embodiments may be
realized and attained by means of the instrumentalities,
combinations, and methods described in the specification.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] A further understanding of the nature and advantages of the
disclosed embodiments may be realized by reference to the remaining
portions of the specification and the drawings.
[0012] FIG. 1 is a flow chart of a protective plasma treatment
according to disclosed embodiments.
[0013] FIG. 2A-2C show cross-sectional views of a device at various
stages during a protective plasma treatment according to disclosed
embodiments.
[0014] FIG. 3A shows a schematic cross-sectional view of a
substrate processing chamber according to disclosed
embodiments.
[0015] FIG. 3B shows a schematic cross-sectional view of a portion
of a substrate processing chamber according to disclosed
embodiments.
[0016] FIG. 3C shows a bottom plan view of a showerhead according
to disclosed embodiments.
[0017] FIG. 4 shows a top plan view of an exemplary substrate
processing system according to disclosed embodiments.
[0018] In the appended figures, similar components and/or features
may have the same reference label. Further, various components of
the same type may be distinguished by following the reference label
by a dash and a second label that distinguishes among the similar
components. If only the first reference label is used in the
specification, the description is applicable to any one of the
similar components having the same first reference label
irrespective of the second reference label.
DETAILED DESCRIPTION OF THE INVENTION
[0019] A method of selectively removing fluorocarbon layers from
overlying low-k dielectric material is described. These protective
plasma treatments (PPT) are delicate alternatives to traditional
post-etch treatments (PET). The method includes sequential exposure
to (1) a local plasma formed from a silicon-fluorine precursor
followed by (2) an exposure to plasma effluents formed in a remote
plasma from a fluorine-containing precursor. The remote plasma etch
(2) has been found to be highly selective of the residual material
following the local plasma silicon-fluorine exposure. The
sequential process (1)-(2) avoids exposing the low-k dielectric
material to oxygen which would undesirably increase its dielectric
constant.
[0020] The inventors have found new ways to selectively remove
dielectric etch remnants without harming underlying low-k and ultra
low-k (ULK) dielectric material. A two-step sequence includes (i) a
local plasma treatment step which transforms/replaces etch-remnant
fluorocarbon material into/with fluorinated silicon oxide. A
delicate remote fluorine-based etch has been determined to be
highly selective of the transformed/replaced fluorinated silicon
oxide layer. Thus, a subsequent (ii) etch step involves remote
excitation of a fluorine-containing precursor and transferal of the
plasma effluents into a substrate processing region housing the
substrate. The plasma effluents react with the exposed fluorinated
silicon oxide and preferentially remove the transformed/replaced
layer from the patterned substrate without increasing the
dielectric constant of the underlying low-k material in
embodiments. Traditional post-etch treatments (PET) which have been
used previously to remove fluorocarbons have relied on "ashing"
(i.e. exposure to oxygen) which raises the surface dielectric
constant of the underlying low-k dielectric.
[0021] In order to better understand and appreciate the invention,
reference is now made to FIG. 1 which is a flow chart of an
exemplary protective plasma treatment according to disclosed
embodiments. Reference will concurrently be made to FIGS. 2A-2C
which shows cross-sectional views of an exemplary device at various
stages during protective plasma treatments. Prior to the first
operation, a structure is formed in a patterned substrate. The
structure includes a titanium nitride mask (TiN mask) 220 over an
ultra-low-k (ULK) dielectric 210. The ULK dielectric 210 is etched
in regions which are left uncovered by TiN mask 220. The etch
process leaves fluorocarbon 230 residue behind prior to the start
of the removal processes described herein. The structure formed
possesses an exposed roughly conformal layer of leftover
fluorocarbon 230 on TiN mask 220 and ULK dielectric 210. The etch
process described removes fluorocarbon 230 without damaging
(raising the dielectric constant of) ULK dielectric 210.
[0022] The patterned substrate is then delivered into a substrate
processing region. Silicon tetrafluoride is then flowed into the
substrate processing region housing the patterned substrate
(operation 110). The silicon tetrafluoride is excited in a local
capacitively-coupled plasma within the substrate processing region
and the patterned substrate is treated with the local plasma. A DC
voltage may be applied in addition to a radio-frequency AC primary
excitation to form the local plasma. The substrate processing
region may generally include a silicon-and-fluorine-containing
precursor as well as other inert species, such as argon and helium,
which may prove beneficial to stability, uniformity and
strikability of the plasma. The substrate processing region may be
devoid of reactive species containing nitrogen or oxygen, in
disclosed embodiments, in order to suppress a detrimental potential
rise in dielectric constant of ULK dielectric 210 during the
treatment step (operation 110). The inventors have determined that
oxygen from the ULK is sufficient to supply the oxygen to the
fluorinated silicon oxide in disclosed embodiments. The treatment
step using silicon tetrafluoride is the first step in a two step
sequence (the second step includes operations 120-140 described
below). The treatment operation 110 alters or replaces fluorocarbon
layer 230 while forming a fluorinated silicon oxide layer 232 in
place of fluorocarbon layer 230. The inventors have found that
fluorinated silicon oxide layer 232 is much easier to delicately
remove than fluorocarbon layer 230.
[0023] A flow of nitrogen trifluoride is then introduced into a
plasma region separate from the substrate processing region
(operation 120) where the nitrogen trifluoride is excited in a
remote plasma struck within the separate plasma region. The
separate plasma region may be referred to as a remote plasma region
herein and may be within a distinct module from the processing
chamber or a compartment within the processing chamber separated
from the substrate processing region by a permeable barrier. In
general, a fluorine-containing precursor may be flowed into the
remote plasma region and the fluorine-containing precursor
comprises at least one precursor selected from the group consisting
of atomic fluorine, diatomic fluorine, bromine trifluoride,
chlorine trifluoride, nitrogen trifluoride, hydrogen fluoride,
fluorinated hydrocarbons, sulfur hexafluoride, carbon tetrafluoride
and xenon difluoride. In embodiments which do not form solid
residue, broad substrate temperature ranges are possible. The
temperature of the substrate during operations 120-130 may be
between 0.degree. C. and 200.degree. C. or between 10.degree. C.
and 150.degree. C. in disclosed embodiments.
[0024] The plasma effluents formed in the remote plasma region are
then flowed into the substrate processing region (operation 130)
and the patterned substrate is selectively etched (operation 140).
The plasma effluents may enter the substrate processing region
through through-holes in a showerhead which separates the remote
plasma region from the substrate processing region. Fluorinated
silicon oxide layer 232 is removed during operation 140 of the etch
step. The etch step ideally is stopped once the etch step removes
fluorinated silicon oxide layer 232. However, a slight over-etch is
canonical as a result of nonuniformities and other real-world
considerations. The underlying ULK dielectric 210 is exposed to the
plasma effluents for a finite period of time predominantly during
the over-etch. The etch chemistries disclosed herein have been
carefully selected to avoid compromising ULK dielectric 210. A
compromised ULK dielectric 210 would raise the near surface
dielectric constant and therefore would throttle back peak clock
frequencies. The reactive chemical species are removed from the
substrate processing region and then the substrate is removed from
the processing region.
[0025] The remote plasma region may have hydrogen-containing
precursors present (flowed into the remote plasma region
concurrently) or may be devoid of hydrogen during the etching step
of the compound etch (operations 120-140) in disclosed embodiments.
A presence of hydrogen (e.g. in the form of ammonia) during the
etching step may change the mechanism involved in the etch as
discussed in the exemplary equipment section. Regardless of whether
hydrogen is present, the temperature of the substrate may be
between about -20.degree. C. and about 200.degree. C. during both
the treatment step and the etching step. In embodiments of the
invention, a hydrogen-containing precursor is provided along with
the fluorine-containing precursor into the remote plasma region and
the temperature is relatively low (e.g. below 90.degree. C.). Under
such circumstances, solid residue may form on fluorinated silicon
oxide layer 230 possibly according to hypothetical chemical
mechanisms described in the exemplary equipment section. Any solid
residue etch by-products which remain on the surface may then be
removed by sublimation. The temperature of the patterned substrate
throughout the sequence of operations 120-130 may be below one of
90.degree. C., 80.degree. C., 70.degree. C., 60.degree. C.,
50.degree. C., 40.degree. C. or 35.degree. C., in disclosed
embodiments. The substrate may then be heated after the etch step
in order to sublimate any surface-resident solid by-products by
raising the temperature of the patterned substrate above one of
90.degree. C., 100.degree. C., 120.degree. C. or 140.degree. C., in
disclosed embodiments. The duration of the sublimation may be above
one of 45 seconds, 60 seconds, 75 seconds, 90 seconds or 120
seconds, in disclosed embodiments. Sublimation may be carried out
in the same substrate processing region used for the etching
operation, in which case the patterned substrate is finally removed
from the substrate processing region after following
sublimation.
[0026] Generally speaking, the silicon tetrafluoride used in the
exemplary process of FIG. 1 may be any
silicon-and-fluorine-containing precursor, such as Si.sub.2F.sub.6,
SiH.sub.2F.sub.2 and the like. The silicon-and-fluorine-containing
precursor may be a partially fluorinated silane, disilane, higher
order silane or may be a fully fluorinated silane, disilane, higher
order silane, in embodiments of the invention. The
silicon-and-fluorine-containing precursor may be accompanied by one
or more of neon, helium, argon and xenon. The local plasma may
consist only of the silicon-and-fluorine-containing precursor and
inert gases.
[0027] The method includes applying energy in the form of a plasma
to the silicon-and-fluorine-containing precursor (e.g. silicon
tetrafluoride) while in the substrate processing region to generate
the plasma effluents used to treat the substrate (operation 110).
The plasma may be generated using known techniques (e.g., radio
frequency excitations, capacitively-coupled power, inductively
coupled power, and the like). In an embodiment, the energy is
applied using a capacitively-coupled plasma unit. The local plasma
power may be between about 10 watts and about 500 watts, between
about 20 watts and about 400 watts, between about 30 watts and
about 300 watts, or between about 50 watts and about 200 watts in
embodiments of the invention.
[0028] A DC accelerating voltage may and may not be applied, in
embodiments, to assist the local plasma treatment of the patterned
substrate in operation 110. When used, the local plasma may be
formed by applying a DC bias power such that the local plasma power
comprises both an AC portion and a DC portion. The DC bias power
supplies a DC accelerating voltage which may be greater than 200
volts, greater than 300 volts, greater than 400 volts, greater than
500 volts, greater than 600 volts, or greater than 700 volts in
embodiments of the invention. In order to more fully preserve the
integrity of ULK dielectric 210, the DC voltage may be less than
2000 volts, less than 1500 volts, less than 1300 volts or less than
1100 volts. The pressure in the substrate processing region may be
between about 0.5 mTorr and about 50 mTorr, between about 2 mTorr
and about 200 mTorr or between about 5 mTorr and about 100 mTorr in
disclosed embodiments.
[0029] The method also includes applying energy to the
fluorine-containing precursor while in the remote plasma region to
generate the plasma effluents (operation 120). As would be
appreciated by one of ordinary skill in the art, the plasma may
include a number of charged and neutral species including radicals
and ions. The plasma may be generated using known techniques (e.g.,
radio frequency excitations, capacitively-coupled power,
inductively coupled power, and the like). In an embodiment, the
energy is applied using a capacitively-coupled plasma unit. The
remote plasma source power may be between about 300 watts and about
5000 watts, between about 500 watts and about 3000 watts, between
about 750 watts and about 2000 watts, or between about 900 watts
and about 1500 watts in embodiments of the invention. The etch rate
has been observed by the inventors to generally increase as RF
power is raised from about 300 watts to about 1000 watts, after
which the etch rate plateaus. Operating at about 1000 watts or
above produces a process which is substantially insensitive to
fluctuations in plasma power. Exceeding 1000 watts significantly
(e.g. above 1500 watts) does not harm the process, but sacrifices
energy efficiency. As with all complementary ranges provided
herein, upper limits may be combined with any suitable lower limits
to obtain additional disclosed embodiments. The pressure in the
remote plasma region may be such that the pressure in the substrate
processing region ends up between about 0.01 Torr and about 50 Torr
or between about 0.1 Torr and about 5 Torr in disclosed
embodiments.
[0030] In some circumstances, a fluorine-containing precursor is
combined with a hydrogen-containing precursor in the remote plasma
region when the plasma is formed. For relatively low substrate
temperatures, the reaction results in the formation of solid
residue by-product which is sublimated away following the etching
step. Lower plasma powers may be used for this reaction since the
plasma effluents are more stable. The RF power applied to form the
remote plasma may be between about 1 watt and about 5000 watts,
between about 1 watt and about 1000 watts, between about 5 watts
and about 600 watts, between about 10 watts and about 300 watts or
between about 20 watts and about 100 watts in disclosed
embodiments.
[0031] Especially when a fluorine-containing precursor is used
without a hydrogen-containing precursor, an ion suppressor may be
used to filter ions from the plasma effluents during passage from
the remote plasma region to the substrate processing region. It
should be noted that complete elimination of ionically charged
species in the reaction region surrounding the substrate is not
always the desired goal. In many instances, ionic species are
required to reach the substrate in order to perform the etch and/or
deposition process. In these instances, the ion suppressor helps
control the concentration of ionic species in the reaction region.
However, in disclosed embodiments, essentially no ionic species
penetrate to the substrate surface. Using the plasma effluents, a
high etch rate selectivity of silicon relative to silicon oxide,
silicon nitride and many alternative materials may be achieved.
[0032] The RF frequency applied for either the local or remote
plasmas described herein may be low RF frequencies less than about
200 kHz, high RF frequencies between about 10 MHz and about 15 MHz,
or microwave frequencies greater than or about 1 GHz in disclosed
embodiments.
[0033] The two-step etches presented herein are used to clean a
patterned substrate after a pattern transfer step. The disclosed
two-step etch techniques have been developed for use with narrow
trenches and gaps, which are uniquely benefited by maintaining
low-k on ULK dielectric separators used in miniaturized integrated
circuits. Trench or gap widths may be less than or about 70 nm,
less than or about 60 nm, less than or about 50 nm, less than or
about 40 nm, less than or about 30 nm, less than or about 25 nm,
less than or about 20 nm or less than or about 15 nm in embodiments
of the invention.
[0034] The flow of either the silicon-and-fluorine-containing
precursor and, separately, the fluorine-containing precursor may
further include one or more relatively inert gases such as He,
N.sub.2, Ar. The inert gas can be used to improve plasma stability,
process uniformity and the like. Argon is helpful, as an additive,
to promote the formation of a (stable) plasma. Process uniformity
is generally increased when helium is included. These additives are
present in embodiments throughout this specification.
[0035] In disclosed embodiments, the fluorine-containing gas (e.g.
NF.sub.3) is supplied at a flow rate of between about 5 sccm
(standard cubic centimeters per minute) and 400 sccm, He at a flow
rate of between about 0 slm (standard liters per minute) and 3 slm,
and N.sub.2 at a flow rate of between about 0 slm and 3 slm. One of
ordinary skill in the art would recognize that other gases and/or
flows may be used depending on a number of factors including
processing chamber configuration, substrate size, geometry and
layout of features being etched, and the like.
[0036] Additional process parameters are disclosed in the course of
describing an exemplary processing chamber and system.
Exemplary Processing System
[0037] FIG. 3A shows a cross-sectional view of an exemplary
substrate processing chamber 1001 with partitioned plasma
generation regions within the processing chamber. During film
etching, e.g., titanium nitride, tantalum nitride, tungsten,
silicon, polysilicon, silicon oxide, silicon nitride, silicon
oxynitride, silicon oxycarbide, etc., a process gas may be flowed
into chamber plasma region 1015 through a gas inlet assembly 1005.
A remote plasma system (RPS) 1002 may optionally be included in the
system, and may process a first gas which then travels through gas
inlet assembly 1005. The inlet assembly 1005 may include two or
more distinct gas supply channels where the second channel (not
shown) may bypass the RPS 1002, if included. Accordingly, in
disclosed embodiments the precursor gases may be delivered to the
processing chamber in an unexcited state. In another example, the
first channel provided through the RPS may be used for the process
gas and the second channel bypassing the RPS may be used for a
treatment gas in disclosed embodiments. The process gas may be
excited within the RPS 1002 prior to entering the chamber plasma
region 1015. Accordingly, the fluorine-containing precursor as
discussed above, for example, may pass through RPS 1002 or bypass
the RPS unit in disclosed embodiments. Various other examples
encompassed by this arrangement will be similarly understood.
[0038] A cooling plate 1003, faceplate 1017, ion suppressor 1023,
showerhead 1025, and a substrate support 1065 (also known as a
pedestal), having a substrate 1055 disposed thereon, are shown and
may each be included according to disclosed embodiments. The
pedestal 1065 may have a heat exchange channel through which a heat
exchange fluid flows to control the temperature of the substrate.
This configuration may allow the substrate 1055 temperature to be
cooled or heated to maintain relatively low temperatures, such as
between about -20.degree. C. to about 200.degree. C., or
therebetween. The heat exchange fluid may comprise ethylene glycol
and/or water. The wafer support platter of the pedestal 1065, which
may comprise aluminum, ceramic, or a combination thereof, may also
be resistively heated in order to achieve relatively high
temperatures, such as from up to or about 100.degree. C. to above
or about 1100.degree. C., using an embedded resistive heater
element. The heating element may be formed within the pedestal as
one or more loops, and an outer portion of the heater element may
run adjacent to a perimeter of the support platter, while an inner
portion runs on the path of a concentric circle having a smaller
radius. The wiring to the heater element may pass through the stem
of the pedestal 1065, which may be further configured to
rotate.
[0039] The faceplate 1017 may be pyramidal, conical, or of another
similar structure with a narrow top portion expanding to a wide
bottom portion. The faceplate 1017 may additionally be flat as
shown and include a plurality of through-channels used to
distribute process gases. Plasma generating gases and/or plasma
excited species, depending on use of the RPS 1002, may pass through
a plurality of holes, shown in FIG. 3B, in faceplate 1017 for a
more uniform delivery into the chamber plasma region 1015.
[0040] Exemplary configurations may include having the gas inlet
assembly 1005 open into a gas supply region 1058 partitioned from
the chamber plasma region 1015 by faceplate 1017 so that the
gases/species flow through the holes in the faceplate 1017 into the
chamber plasma region 1015. Structural and operational features may
be selected to prevent significant backflow of plasma from the
chamber plasma region 1015 back into the supply region 1058, gas
inlet assembly 1005, and fluid supply system 1010. The structural
features may include the selection of dimensions and
cross-sectional geometries of the apertures in faceplate 1017 to
deactivate back-streaming plasma. The operational features may
include maintaining a pressure difference between the gas supply
region 1058 and chamber plasma region 1015 that maintains a
unidirectional flow of plasma through the showerhead 1025. The
faceplate 1017, or a conductive top portion of the chamber, and
showerhead 1025 are shown with an insulating ring 1020 located
between the features, which allows an AC potential to be applied to
the faceplate 1017 relative to showerhead 1025 and/or ion
suppressor 1023. The insulating ring 1020 may be positioned between
the faceplate 1017 and the showerhead 1025 and/or ion suppressor
1023 enabling a capacitively coupled plasma (CCP) to be formed in
the first plasma region. A baffle (not shown) may additionally be
located in the chamber plasma region 1015, or otherwise coupled
with gas inlet assembly 1005, to affect the flow of fluid into the
region through gas inlet assembly 1005.
[0041] The ion suppressor 1023 may comprise a plate or other
geometry that defines a plurality of apertures throughout the
structure that are configured to suppress the migration of
ionically-charged species out of chamber plasma region 1015 while
allowing uncharged neutral or radical species to pass through the
ion suppressor 1023 into an activated gas delivery region between
the suppressor and the showerhead. In disclosed embodiments, the
ion suppressor 1023 may comprise a perforated plate with a variety
of aperture configurations. These uncharged species may include
highly reactive species that are transported with less reactive
carrier gas through the apertures. As noted above, the migration of
ionic species through the holes may be reduced, and in some
instances completely suppressed. Controlling the amount of ionic
species passing through the ion suppressor 1023 may provide
increased control over the gas mixture brought into contact with
the underlying wafer substrate, which in turn may increase control
of the deposition and/or etch characteristics of the gas mixture.
For example, adjustments in the ion concentration of the gas
mixture can significantly alter its etch selectivity, e.g.,
SiOFx:SiOCH etch ratios, etc.
[0042] The plurality of holes in the ion suppressor 1023 may be
configured to control the passage of the activated gas, i.e., the
ionic, radical, and/or neutral species, through the ion suppressor
1023. For example, the aspect ratio of the holes, or the hole
diameter to length, and/or the geometry of the holes may be
controlled so that the flow of ionically-charged species in the
activated gas passing through the ion suppressor 1023 is reduced.
The holes in the ion suppressor 1023 may include a tapered portion
that faces chamber plasma region 1015, and a cylindrical portion
that faces the showerhead 1025. The cylindrical portion may be
shaped and dimensioned to control the flow of ionic species passing
to the showerhead 1025. An adjustable electrical bias may also be
applied to the ion suppressor 1023 as an additional means to
control the flow of ionic species through the suppressor.
[0043] The ion suppression element 1023 may function to reduce or
eliminate the amount of ionically charged species traveling from
the plasma generation region to the substrate. Uncharged neutral
and radical species may still pass through the openings in the ion
suppressor to react with the substrate. It should be noted that the
complete elimination of ionically charged species in the reaction
region surrounding the substrate is not always the desired goal. In
many instances, ionic species are required to reach the substrate
in order to perform the etch and/or deposition process. In these
instances, the ion suppressor may help to control the concentration
of ionic species in the reaction region at a level that assists the
process.
[0044] Showerhead 1025 in combination with ion suppressor 1023 may
allow a plasma present in chamber plasma region 1015 to avoid
directly exciting gases in substrate processing region 1033, while
still allowing excited species to travel from chamber plasma region
1015 into substrate processing region 1033. In this way, the
chamber may be configured to prevent the plasma from contacting a
substrate 1055 being etched. This may advantageously protect a
variety of intricate structures and films patterned on the
substrate, which may be damaged, dislocated, or otherwise warped if
directly contacted by a generated plasma. Additionally, when plasma
is allowed to contact the substrate or approach the substrate
level, the rate at which silicon oxide or silicon nitride etch may
increase.
[0045] The processing system may further include a power supply
1040 electrically coupled with the processing chamber to provide
electric power to the faceplate 1017, ion suppressor 1023,
showerhead 1025, and/or pedestal 1065 to generate a plasma in the
chamber plasma region 1015 or processing region 1033. The power
supply may be configured to deliver an adjustable amount of power
to the chamber depending on the process performed. Such a
configuration may allow for a tunable plasma to be used in the
processes being performed. Unlike a remote plasma unit, which is
often presented with on or off functionality, a tunable plasma may
be configured to deliver a specific amount of power to chamber
plasma region 1015. This in turn may allow development of
particular plasma characteristics such that precursors may be
dissociated in specific ways to enhance the etching profiles
produced by these precursors.
[0046] A plasma may be ignited either in chamber plasma region 1015
above showerhead 1025 or substrate processing region 1033 below
showerhead 1025. A plasma may be present in chamber plasma region
1015 to produce the radical-fluorine precursors from an inflow of
the fluorine-containing precursor. An AC voltage typically in the
radio frequency (RF) range may be applied between the conductive
top portion of the processing chamber, such as faceplate 1017, and
showerhead 1025 and/or ion suppressor 1023 to ignite a plasma in
chamber plasma region 1015 during deposition. An RF power supply
may generate a high RF frequency of 13.56 MHz but may also generate
other frequencies alone or in combination with the 13.56 MHz
frequency.
[0047] Plasma power can be of a variety of frequencies or a
combination of multiple frequencies. In the exemplary processing
system the plasma may be provided by RF power delivered to
faceplate 1017 relative to ion suppressor 1023 and/or showerhead
1025. The RF power may be between about 10 watts and about 5000
watts, between about 100 watts and about 2000 watts, between about
200 watts and about 1500 watts, or between about 200 watts and
about 1000 watts in disclosed embodiments. The RF frequency applied
in the exemplary processing system may be low RF frequencies less
than about 200 kHz, high RF frequencies between about 10 MHz and
about 15 MHz, or microwave frequencies greater than or about 1 GHz
in disclosed embodiments. The plasma power may be
capacitively-coupled (CCP) or inductively-coupled (ICP) into the
remote plasma region.
[0048] Chamber plasma region 1015 (top plasma in figure) may be
left at low or no power when a bottom plasma in the substrate
processing region 1033 is turned on to, for example, cure a film or
clean the interior surfaces bordering substrate processing region
1033. A plasma in substrate processing region 1033 may be ignited
by applying an AC voltage between showerhead 1025 and the pedestal
1065 or bottom of the chamber. A treatment gas (such as argon) may
be introduced into substrate processing region 1033 while the
plasma is present to facilitate treatment of the patterned
substrate. The showerhead 1025 may also be biased at a positive DC
voltage relative to the pedestal 1065 or bottom of the chamber in
order to accelerate positively charged ions toward patterned
substrate 1055. In disclosed embodiments, the local plasma in
substrate processing region 1033 may be struck by applying AC power
via an inductively-coupled source while applying DC power by
capacitively coupled means. As indicated previously, the local
plasma power may be between about 10 watts and about 500 watts,
between about 20 watts and about 400 watts, between about 30 watts
and about 300 watts, or between about 50 watts and about 200 watts
in embodiments of the invention.
[0049] A fluid, such as a precursor, for example a
fluorine-containing precursor, may be flowed into the processing
region 1033 by embodiments of the showerhead described herein.
Excited species derived from the process gas in chamber plasma
region 1015 may travel through apertures in the ion suppressor
1023, and/or showerhead 1025 and react with an additional precursor
flowing into the processing region 1033 from a separate portion of
the showerhead. Alternatively, if all precursor species are being
excited in chamber plasma region 1015, no additional precursors may
be flowed through the separate portion of the showerhead. Little or
no plasma may be present in the processing region 1033 during the
compound two-step etch. Excited derivatives of the precursors may
combine in the region above the substrate and, on occasion, on the
substrate to etch structures or remove species on the substrate in
disclosed applications.
[0050] Exciting the fluids in the chamber plasma region 1015
directly, or exciting the fluids in the RPS units 1002, may provide
several benefits. The concentration of the excited species derived
from the fluids may be increased within the processing region 1033
due to the plasma in the chamber plasma region 1015. This increase
may result from the location of the plasma in the chamber plasma
region 1015. The processing region 1033 may be located closer to
the chamber plasma region 1015 than the remote plasma system (RPS)
1002, leaving less time for the excited species to leave excited
states through collisions with other gas molecules, walls of the
chamber, and surfaces of the showerhead.
[0051] The uniformity of the concentration of the excited species
derived from the process gas may also be increased within the
processing region 1033. This may result from the shape of the
chamber plasma region 1015, which may be more similar to the shape
of the processing region 1033. Excited species created in the RPS
1002 may travel greater distances in order to pass through
apertures near the edges of the showerhead 1025 relative to species
that pass through apertures near the center of the showerhead 1025.
The greater distance may result in a reduced excitation of the
excited species and, for example, may result in a slower growth
rate near the edge of a substrate. Exciting the fluids in the
chamber plasma region 1015 may mitigate this variation for the
fluid flowed through RPS 1002, or alternatively bypassed around the
RPS unit.
[0052] The processing gases may be excited in chamber plasma region
1015 and may be passed through the showerhead 1025 to the
processing region 1033 in the excited state. While a plasma may be
generated in the processing region 1033, a plasma may alternatively
not be generated in the processing region. In one example, the only
excitation of the processing gas or precursors may be from exciting
the processing gases in chamber plasma region 1015 to react with
one another in the processing region 1033. As previously discussed,
this may be to protect the structures patterned on the substrate
1055.
[0053] In addition to the fluid precursors, there may be other
gases introduced at varied times for varied purposes, including
carrier gases to aid delivery. A treatment gas may be introduced to
remove unwanted species from the chamber walls, the substrate, the
deposited film and/or the film during deposition. A treatment gas
may be excited in a plasma and then used to reduce or remove
residual content inside the chamber. In other disclosed embodiments
the treatment gas may be used without a plasma. When the treatment
gas includes water vapor, the delivery may be achieved using a mass
flow meter (MFM), an injection valve, or by commercially available
water vapor generators. The treatment gas may be introduced to the
processing region 1033, either through the RPS unit or bypassing
the RPS unit, and may further be excited in the first plasma
region.
[0054] FIG. 3B shows a detailed view of the features affecting the
processing gas distribution through faceplate 1017. As shown in
FIG. 3A and FIG. 3B, faceplate 1017, cooling plate 1003, and gas
inlet assembly 1005 intersect to define a gas supply region 1058
into which process gases may be delivered from gas inlet 1005. The
gases may fill the gas supply region 1058 and flow to chamber
plasma region 1015 through apertures 1059 in faceplate 1017. The
apertures 1059 may be configured to direct flow in a substantially
unidirectional manner such that process gases may flow into
processing region 1033, but may be partially or fully prevented
from backflow into the gas supply region 1058 after traversing the
faceplate 1017.
[0055] The gas distribution assemblies such as showerhead 1025 for
use in the processing chamber section 1001 may be referred to as
dual channel showerheads (DCSH) and are additionally detailed in
the embodiments described in FIG. 3A as well as FIG. 3C herein. The
dual channel showerhead may provide for etching processes that
allow for separation of etchants outside of the processing region
1033 to provide limited interaction with chamber components and
each other prior to being delivered into the processing region.
[0056] The showerhead 1025 may comprise an upper plate 1014 and a
lower plate 1016. The plates may be coupled with one another to
define a volume 1018 between the plates. The coupling of the plates
may be so as to provide first fluid channels 1019 through the upper
and lower plates, and second fluid channels 1021 through the lower
plate 1016. The formed channels may be configured to provide fluid
access from the volume 1018 through the lower plate 1016 via second
fluid channels 1021 alone, and the first fluid channels 1019 may be
fluidly isolated from the volume 1018 between the plates and the
second fluid channels 1021. The volume 1018 may be fluidly
accessible through a side of the gas distribution assembly 1025.
Although the exemplary system of FIGS. 3A-3C includes a
dual-channel showerhead, it is understood that alternative
distribution assemblies may be utilized that maintain first and
second precursors fluidly isolated prior to the processing region
1033. For example, a perforated plate and tubes underneath the
plate may be utilized, although other configurations may operate
with reduced efficiency or not provide as uniform processing as the
dual-channel showerhead as described.
[0057] In the embodiment shown, showerhead 1025 may distribute via
first fluid channels 1019 process gases which contain plasma
effluents upon excitation by a plasma in chamber plasma region
1015. In embodiments, the process gas introduced into the RPS 1002
and/or chamber plasma region 1015 may contain fluorine, e.g.,
CF.sub.4, NF.sub.3 or XeF.sub.2. The process gas may also include a
carrier gas such as helium, argon, nitrogen (N.sub.2), etc. Plasma
effluents may include ionized or neutral derivatives of the process
gas and may also be referred to herein as a radical-fluorine
precursor referring to the atomic constituent of the process gas
introduced.
[0058] FIG. 3C is a bottom view of a showerhead 1025 for use with a
processing chamber according to disclosed embodiments. Showerhead
1025 corresponds with the showerhead shown in FIG. 3A.
Through-holes 1031, which show a view of first fluid channels 1019,
may have a plurality of shapes and configurations in order to
control and affect the flow of precursors through the showerhead
1025. Small holes 1027, which show a view of second fluid channels
1021, may be distributed substantially evenly over the surface of
the showerhead, even amongst the through-holes 1031, which may help
to provide more even mixing of the precursors as they exit the
showerhead than other configurations.
[0059] An additional dual channel showerhead, as well as this
processing system and chamber, are more fully described in patent
application Ser. No. 13/251,714 filed on Oct. 3, 2011, which is
hereby incorporated by reference for all purposes to the extent not
inconsistent with the claimed features and description herein.
[0060] The chamber plasma region 1015 or a region in an RPS may be
referred to as a remote plasma region. In embodiments, the radical
precursor, e.g., a radical-fluorine precursor, is created in the
remote plasma region and travels into the substrate processing
region where it may or may not combine with additional precursors.
Plasma power may essentially be applied only to the remote plasma
region in disclosed embodiments.
[0061] Plasma effluents include a variety of molecules, molecular
fragments and ionized species. In disclosed embodiments, both
ammonia and nitrogen trifluoride are delivered to chamber plasma
region 1015 to perform a Siconi.TM. etch during the second step
(operations 120-140). Currently entertained theoretical mechanisms
of Siconi.TM. etching may or may not be entirely correct but plasma
effluents are thought to include NH.sub.4F and NH.sub.4F.HF which
react readily with low temperature substrates described herein.
Plasma effluents may react with a silicon oxide surface to form
(NH.sub.4).sub.2SiF.sub.6, NH.sub.3 and H.sub.2O products. The
NH.sub.3 and H.sub.2O are vapors under the processing conditions
described herein and may be removed from substrate processing
region 1033 by a vacuum pump. A thin continuous or discontinuous
layer of (NH.sub.4).sub.2SiF.sub.6 solid by-products is left behind
on the substrate surface.
[0062] Following exposure to plasma effluents and the associated
accumulation of solid by-products, the substrate may be heated to
remove the by-products. In embodiments, the lower plate 1016 is
heatable by incorporating a heating element within lower plate
1016. The substrate may be heated by reducing the distance between
the substrate and the heated lower plate. Lower plate 1020 may be
heated to between about 100.degree. C. and 150.degree. C., between
about 110.degree. C. and 140.degree. C. or between about
120.degree. C. and 130.degree. C. in disclosed embodiments. By
reducing the separation between the substrate and the heated gas
delivery plate, the substrate may be heated to above about
75.degree. C., above about 90.degree. C., above about 100.degree.
C. or between about 115.degree. C. and about 150.degree. C. in
disclosed embodiments. The heat radiated from lower plate 1016 to
the substrate should be made sufficient to dissociate or sublimate
solid (NH.sub.4).sub.2SiF.sub.6 on the substrate into volatile
SiF.sub.4, NH.sub.3 and HF products which may be pumped away from
substrate processing region 1033. Other methods of imparting heat
to the substrate may also be used.
[0063] Nitrogen trifluoride (or another fluorine-containing
precursor) may be flowed into chamber plasma region 1015 at rates
between about 5 sccm and about 500 sccm, between about 10 sccm and
about 150 sccm, or between about 25 sccm and about 125 sccm in
disclosed embodiments. When a hydrogen-containing precursor is
used, ammonia (or hydrogen-containing precursors in general) may be
flowed into chamber plasma region 1015 at rates between about 5
sccm and about 800 sccm, between about 20 sccm and about 300 sccm,
or between about 50 sccm and about 250 sccm in disclosed
embodiments.
[0064] Combined flow rates of precursors into the chamber may
account for 0.05% to about 20% by volume of the overall gas
mixture; the remainder being carrier gases. The fluorine-containing
precursor may be flowed into the remote plasma region, but the
plasma effluents may have the same volumetric flow ratio in
embodiments. In the case of the fluorine-containing precursor, a
purge or carrier gas may be first initiated into the remote plasma
region before the fluorine-containing gas to stabilize the pressure
within the remote plasma region. Substrate processing region 1033
can be maintained at a variety of pressures during the flow of
precursors, any carrier gases, and plasma effluents into substrate
processing region 1033. The pressure may be maintained between
about 0.1 mTorr and about 100 Torr, between about 1 Torr and about
20 Torr or between about 1 Torr and about 5 Torr in disclosed
embodiments.
[0065] Embodiments of the deposition systems may be incorporated
into larger fabrication systems for producing integrated circuit
chips. FIG. 4 shows one such processing system 1101 of deposition,
etching, baking, and curing chambers according to disclosed
embodiments. In the figure, a pair of front opening unified pods
(load lock chambers 1102) supply substrates of a variety of sizes
that are received by robotic arms 1104 and placed into a low
pressure holding area 1106 before being placed into one of the
substrate processing chambers 1108a-f. A second robotic arm 1110
may be used to transport the substrate wafers from the holding area
1106 to the substrate processing chambers 1108a-f and back. Each
substrate processing chamber 1108a-f, can be outfitted to perform a
number of substrate processing operations including the dry etch
processes described herein in addition to cyclical layer deposition
(CLD), atomic layer deposition (ALD), chemical vapor deposition
(CVD), physical vapor deposition (PVD), etch, pre-clean, degas,
orientation, and other substrate processes.
[0066] The substrate processing chambers 1108a-f may include one or
more system components for depositing, annealing, curing and/or
etching a dielectric film on the substrate wafer. In one
configuration, two pairs of the processing chamber, e.g., 1108c-d
and 1108e-f, may be used to deposit dielectric material on the
substrate, and the third pair of processing chambers, e.g.,
1108a-b, may be used to etch the deposited dielectric. In another
configuration, all three pairs of chambers, e.g., 1108a-f, may be
configured to etch a dielectric film on the substrate. Any one or
more of the processes described may be carried out in chamber(s)
separated from the fabrication system shown in disclosed
embodiments.
[0067] In the preceding description, for the purposes of
explanation, numerous details have been set forth in order to
provide an understanding of various embodiments of the present
invention. It will be apparent to one skilled in the art, however,
that certain embodiments may be practiced without some of these
details, or with additional details.
[0068] As used herein "substrate" may be a support substrate with
or without layers formed thereon. The patterned substrate may be an
insulator or a semiconductor of a variety of doping concentrations
and profiles and may, for example, be a semiconductor substrate of
the type used in the manufacture of integrated circuits. Exposed
"silicon" of the patterned substrate is predominantly Si but may
include minority concentrations of other elemental constituents
such as nitrogen, oxygen, hydrogen, carbon and the like. Exposed
"silicon" may consist only of silicon. Exposed "titanium nitride"
of the patterned substrate is predominantly Ti.sub.xN.sub.y but may
include minority concentrations of other elemental constituents
such as nitrogen, oxygen, hydrogen, carbon and the like. "Exposed
titanium nitride" may consist only of titanium and nitrogen.
Exposed "silicon oxide" of the patterned substrate is predominantly
SiO.sub.2 but may include minority concentrations of other
elemental constituents such as nitrogen, hydrogen, carbon and the
like. In some embodiments, silicon oxide films etched using the
methods disclosed herein consist of silicon and oxygen.
[0069] The term "precursor" is used to refer to any process gas
which takes part in a reaction to either remove material from or
deposit material onto a surface. "Plasma effluents" describe gas
exiting from the chamber plasma region and entering the substrate
processing region. Plasma effluents are in an "excited state"
wherein at least some of the gas molecules are in
vibrationally-excited, dissociated and/or ionized states. A
"radical precursor" is used to describe plasma effluents (a gas in
an excited state which is exiting a plasma) which participate in a
reaction to either remove material from or deposit material on a
surface. "Radical-fluorine" are radical precursors which contain
fluorine but may contain other elemental constituents. The phrase
"inert gas" refers to any gas which does not form chemical bonds
when etching or being incorporated into a film. Exemplary inert
gases include noble gases but may include other gases so long as no
chemical bonds are formed when (typically) trace amounts are
trapped in a film.
[0070] The terms "gap" and "trench" are used throughout with no
implication that the etched geometry has a large horizontal aspect
ratio. Viewed from above the surface, trenches may appear circular,
oval, polygonal, rectangular, or a variety of other shapes. A
trench may be in the shape of a moat around an island of material.
The term "via" is used to refer to a low aspect ratio trench (as
viewed from above) which may or may not be filled with metal to
form a vertical electrical connection. As used herein, a conformal
etch process refers to a generally uniform removal of material on a
surface in the same shape as the surface, i.e., the surface of the
etched layer and the pre-etch surface are generally parallel. A
person having ordinary skill in the art will recognize that the
etched interface likely cannot be 100% conformal and thus the term
"generally" allows for acceptable tolerances.
[0071] Having disclosed several embodiments, it will be recognized
by those of skill in the art that various modifications,
alternative constructions, and equivalents may be used without
departing from the spirit of the disclosed embodiments.
Additionally, a number of well known processes and elements have
not been described in order to avoid unnecessarily obscuring the
present invention. Accordingly, the above description should not be
taken as limiting the scope of the invention.
[0072] Where a range of values is provided, it is understood that
each intervening value, to the tenth of the unit of the lower limit
unless the context clearly dictates otherwise, between the upper
and lower limits of that range is also specifically disclosed. Each
smaller range between any stated value or intervening value in a
stated range and any other stated or intervening value in that
stated range is encompassed. The upper and lower limits of these
smaller ranges may independently be included or excluded in the
range, and each range where either, neither or both limits are
included in the smaller ranges is also encompassed within the
invention, subject to any specifically excluded limit in the stated
range. Where the stated range includes one or both of the limits,
ranges excluding either or both of those included limits are also
included.
[0073] As used herein and in the appended claims, the singular
forms "a", "an", and "the" include plural referents unless the
context clearly dictates otherwise. Thus, for example, reference to
"a process" includes a plurality of such processes and reference to
"the dielectric material" includes reference to one or more
dielectric materials and equivalents thereof known to those skilled
in the art, and so forth.
[0074] Also, the words "comprise," "comprising," "include,"
"including," and "includes" when used in this specification and in
the following claims are intended to specify the presence of stated
features, integers, components, or steps, but they do not preclude
the presence or addition of one or more other features, integers,
components, steps, acts, or groups.
* * * * *