U.S. patent application number 17/487459 was filed with the patent office on 2022-01-13 for dram capacitor module.
This patent application is currently assigned to Micromaterials LLC. The applicant listed for this patent is Micromaterials LLC. Invention is credited to Regina Freed, Ho-yung David Hwang, Lequn Liu, Uday Mitra, Sanjay Natarajan.
Application Number | 20220013624 17/487459 |
Document ID | / |
Family ID | 1000005869489 |
Filed Date | 2022-01-13 |
United States Patent
Application |
20220013624 |
Kind Code |
A1 |
Mitra; Uday ; et
al. |
January 13, 2022 |
DRAM Capacitor Module
Abstract
Methods of forming and processing semiconductor devices are
described. Certain embodiments relate to the formation of
self-aligned DRAM capacitors. More particularly, certain
embodiments relate to the formation of self-aligned DRAM capacitors
utilizing the formation of self-aligned growth pillars. The pillars
lead to greater capacitor heights, increase critical dimension
uniformity, and self-aligned bottom and top contacts.
Inventors: |
Mitra; Uday; (Cupertino,
CA) ; Freed; Regina; (Los Altos, CA) ; Hwang;
Ho-yung David; (Cupertino, CA) ; Natarajan;
Sanjay; (Portland, OR) ; Liu; Lequn; (San
Jose, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Micromaterials LLC |
Wilmington |
DE |
US |
|
|
Assignee: |
Micromaterials LLC
Wilmington
DE
|
Family ID: |
1000005869489 |
Appl. No.: |
17/487459 |
Filed: |
September 28, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
16826597 |
Mar 23, 2020 |
11164938 |
|
|
17487459 |
|
|
|
|
62823977 |
Mar 26, 2019 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 28/91 20130101;
H01L 27/10852 20130101; H01L 27/10808 20130101 |
International
Class: |
H01L 49/02 20060101
H01L049/02; H01L 27/108 20060101 H01L027/108 |
Claims
1. A DRAM capacitor comprising: a capacitor bottom contact and a
first dielectric material on a substrate; a second dielectric
material on the first dielectric material; a fourth dielectric
material on the second dielectric material; a capacitor memory
channel formed through the fourth dielectric material, the second
dielectric material, and the first dielectric material; and a
capacitor formed in the capacitor memory channel, wherein the
capacitor is self-aligned with the capacitor bottom contact.
2. The DRAM capacitor of claim 1, wherein the capacitor comprises a
first conductive material, a third dielectric material on the first
conductive material, and a second conductive material on the third
dielectric material.
3. The DRAM capacitor of claim 1, wherein the capacitor has a top
and a bottom, and a critical dimension of the top is substantially
the same as a critical dimension of the bottom.
4. The DRAM capacitor of claim 1, wherein the first dielectric
material and the second dielectric material independently comprise
one or more of silicon oxide and silicon nitride.
5. The DRAM capacitor of claim 1, wherein the capacitor bottom
contact comprises one or more of a metal, a metal silicide,
poly-silicon, and EPI-silicon.
6. The DRAM capacitor of claim 2, wherein the first conductive
material comprises one or more of metal mode titanium (MMTi), metal
silicide, and highly doped poly-silicon.
7. The DRAM capacitor of claim 2, wherein the third dielectric
material comprises a high-.kappa. dielectric selected from one or
more of aluminum oxide, hafnium oxide, and aluminum hafnium oxide
(AlHfOx).
8. The DRAM capacitor of claim 2, wherein the second conductive
material comprises one or more of poly-silicon, metal, and metal
silicide.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a Divisional application of U.S.
application Ser. No. 16/826,597, filed on Mar. 23, 2020, which
claims priority to U.S. Provisional Application No. 62/823,977,
filed Mar. 26, 2019, the entire disclosures of which are hereby
incorporated by reference herein.
TECHNICAL FIELD
[0002] Embodiments of the present invention pertain to the field of
semiconductor device manufacturing and methods for device
patterning. In particular, embodiments pertain to the self-aligned
DRAM devices and their manufacturing methods.
BACKGROUND
[0003] Electronic devices, such as personal computers,
workstations, computer servers, mainframes and other computer
related equipment such as printers, scanners and hard disk drives
use memory devices that provide substantial data storage
capability, while incurring low power consumption. There are two
major types of random-access memory cells, dynamic and static,
which are well-suited for use in electronic devices. Dynamic
random-access memories (DRAMs) can be programmed to store a voltage
which represents one of two binary values, but require periodic
reprogramming or "refreshing" to maintain this voltage for more
than very short periods of time. Static random-access memories
(SRAM) are so named because they do not require periodic
refreshing.
[0004] DRAM memory circuits are manufactured by replicating
millions of identical circuit elements, known as DRAM cells, on a
single semiconductor wafer. Each DRAM cell is an addressable
location that can store one bit (binary digit) of data. In its most
common form, a DRAM cell consists of two circuit components: a
field effect transistor (FET) and a capacitor.
[0005] The manufacturing of a DRAM cell includes the fabrication of
a transistor, a capacitor, and three contacts: one each to the bit
line, the word line, and the reference voltage. The output voltage
of a DRAM cell is proportional to the capacitance value of the
storage capacitor of the DRAM cell and, therefore, the storage
capacitor must have a satisfactory capacitance value to have stable
operation of the cell as the applied voltage is scaled. The storage
capacitor can be implemented in a trench-type or a stack-type. The
trench-type capacitor is formed by forming a trench in a
semiconductor substrate without increasing the surface area of the
semiconductor-substrate surface; however, the trench formation
becomes difficult as the feature size decreases. There is
continuous pressure to decrease the size of individual cells and to
increase memory cell density to allow more memory to be squeezed
onto a single memory chip, especially for densities greater than
256 Megabits. Limitations on cell size reduction include the
passage of both active and passive word lines through the cell, the
size of the cell capacitor, and the compatibility of array devices
with nonarray devices.
[0006] DRAM cells and circuits may be produced using semiconductor
lithography. Modern trends in DRAM production include scaling DRAMs
to ever smaller lithography sizes. As sizes are reduced, it becomes
more difficult to maintain reliability and performance as
lithography error rates increase. Thus, there is a need for DRAMs
that are scalable while maintaining reliability and
performance.
SUMMARY
[0007] One or more embodiments of the disclosure are directed to
electronic devices and to methods of manufacturing the electronic
devices. In one embodiment, a method of manufacturing a DRAM
capacitor comprises: selectively etching a capacitor bottom contact
from a substrate comprising the capacitor bottom contact and a
first dielectric material to form a recess; forming pillars in the
recess on the capacitor bottom contact; depositing a second
dielectric material on the first dielectric material; selectively
removing the pillars to form capacitor memory holes; conformally
depositing a first conductive material in the capacitor memory
hole; conformally depositing a third dielectric material on the
first conductive material; and depositing a second conductive
material on the third dielectric material to form the DRAM
capacitor, wherein the capacitor bottom contact is self-aligned
with the first conductive material.
[0008] In one embodiment, a DRAM capacitor comprises: a capacitor
bottom contact and a first dielectric material on a substrate; a
second dielectric material on the first dielectric material; a
fourth dielectric material on the second dielectric material; a
capacitor memory channel formed through the fourth dielectric
material and the second dielectric material; and a capacitor formed
in the memory channel, wherein the capacitor is self-aligned with
the capacitor bottom contact.
[0009] In one an embodiment, a method of manufacturing a DRAM
capacitor comprises: providing a substrate having a capacitor
bottom contact and a first dielectric material; selectively etching
the capacitor bottom contact to form a first recess; depositing a
conformal liner in the first recess; selectively depositing a first
seed layer in the first recess on the capacitor bottom contact;
forming first pillars from the first seed layer; depositing a
second dielectric material on the first dielectric material to form
an overburden of the second dielectric material; removing the
overburden of the second dielectric material such that a top
surface of the second dielectric material is substantially coplanar
with a top surface of the first pillars; selectively etching the
first pillars to form a second recess; selectively depositing a
second seed layer in the second recess on the first pillars;
forming second pillars from the second seed layer; depositing a
fourth dielectric material on the second dielectric material to
form an overburden of the third dielectric material; removing the
overburden of the fourth dielectric material such that a top
surface of the fourth dielectric material is substantially coplanar
with a top surface of the second pillars; selectively removing the
first pillars and the second pillars to form capacitor memory
holes; removing the conformal liner; and forming a capacitor in the
capacitor memory holes by conformally depositing a first conductive
material in the capacitor memory holes, conformally depositing a
third dielectric material on the first conductive material, and
depositing a second conductive material on the third dielectric
material to form the DRAM capacitor, wherein the capacitor is
self-aligned with capacitor bottom contact.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] So that the manner in which the above recited features of
the present disclosure can be understood in detail, a more
particular description of the disclosure, briefly summarized above,
may be had by reference to embodiments, some of which are
illustrated in the appended drawings. It is to be noted, however,
that the appended drawings illustrate only typical embodiments of
this disclosure and are therefore not to be considered limiting of
its scope, for the disclosure may admit to other equally effective
embodiments. The embodiments as described herein are illustrated by
way of example and not limitation in the figures of the
accompanying drawings in which like references indicate similar
elements.
[0011] FIG. 1 illustrates a circuit diagram of a DRAM cell block in
accordance with the prior art;
[0012] FIG. 2 illustrates a cross-section view of an electronic
device according to one or more embodiments of the disclosure;
[0013] FIG. 3 illustrates a cross-section view of an electronic
device according to one or more embodiments of the disclosure;
[0014] FIG. 4 illustrates a cross-section view of an electronic
device according to one or more embodiments of the disclosure;
[0015] FIG. 5 illustrates a cross-section view of an electronic
device according to one or more embodiments of the disclosure;
[0016] FIG. 6 illustrates a cross-section view of an electronic
device according to one or more embodiments of the disclosure;
[0017] FIG. 7 illustrates a cross-section view of an electronic
device according to one or more embodiments of the disclosure;
[0018] FIG. 8 illustrates a cross-section view of an electronic
device according to one or more embodiments of the disclosure;
[0019] FIG. 9 illustrates a cross-section view of an electronic
device according to one or more embodiments of the disclosure;
[0020] FIG. 10A illustrates a cross-section view of an electronic
device according to one or more embodiments of the disclosure;
[0021] FIG. 10B illustrates a cross-section view of an electronic
device according to one or more embodiments of the disclosure;
[0022] FIG. 10C illustrates a cross-section view of an electronic
device according to one or more embodiments of the disclosure;
[0023] FIG. 10D illustrates a cross-section view of an electronic
device according to one or more embodiments of the disclosure;
[0024] FIG. 10E illustrates a cross-section view of an electronic
device according to one or more embodiments of the disclosure;
[0025] FIG. 11 illustrates a cross-section view of an electronic
device according to one or more embodiments of the disclosure;
[0026] FIG. 12 illustrates a cross-section view of an electronic
device according to one or more embodiments of the disclosure;
[0027] FIG. 13 illustrates a cross-section view of an electronic
device according to one or more embodiments of the disclosure;
[0028] FIG. 14 illustrates a cross-section view of an electronic
device according to one or more embodiments of the disclosure;
[0029] FIG. 15 illustrates a cross-section view of an electronic
device according to one or more embodiments of the disclosure;
[0030] FIG. 16 illustrates a cross-section view of an electronic
device according to one or more embodiments of the disclosure;
[0031] FIG. 17 illustrates a cross-section view of an electronic
device according to one or more embodiments of the disclosure;
[0032] FIG. 18 illustrates a cross-section view of an electronic
device according to one or more embodiments of the disclosure;
[0033] FIG. 19A illustrates a cross-section view of an electronic
device according to one or more embodiments of the disclosure;
[0034] FIG. 19B illustrates a cross-section view of an electronic
device according to one or more embodiments of the disclosure;
[0035] FIG. 20 illustrates a cross-section view of an electronic
device according to one or more embodiments of the disclosure;
and
[0036] FIG. 21 illustrates a cross-section view of an electronic
device according to one or more embodiments of the disclosure.
DETAILED DESCRIPTION
[0037] Before describing several exemplary embodiments of the
disclosure, it is to be understood that the disclosure is not
limited to the details of construction or process steps set forth
in the following description. The disclosure is capable of other
embodiments and of being practiced or being carried out in various
ways.
[0038] A "substrate" as used herein, refers to any substrate or
material surface formed on a substrate upon which film processing
is performed during a fabrication process. For example, a substrate
surface on which processing can be performed include materials such
as silicon, silicon oxide, strained silicon, silicon on insulator
(SOI), carbon doped silicon oxides, amorphous silicon, doped
silicon, germanium, gallium arsenide, glass, sapphire, and any
other materials such as metals, metal nitrides, metal alloys, and
other conductive materials, depending on the application.
Substrates include, without limitation, semiconductor wafers.
Substrates may be exposed to a pretreatment process to polish,
etch, reduce, oxidize, hydroxylate, anneal and/or bake the
substrate surface. In addition to film processing directly on the
surface of the substrate itself, in the present disclosure, any of
the film processing steps disclosed may also be performed on an
under-layer formed on the substrate as disclosed in more detail
below, and the term "substrate surface" is intended to include such
under-layer as the context indicates. Thus for example, where a
film/layer or partial film/layer has been deposited onto a
substrate surface, the exposed surface of the newly deposited
film/layer becomes the substrate surface.
[0039] As used in this specification and the appended claims, the
terms "precursor", "reactant", "reactive gas" and the like are used
interchangeably to refer to any gaseous species that can react with
the substrate surface.
[0040] As used herein, the term "dynamic random access memory" or
"DRAM" refers to a memory cell that stores a datum bit by storing a
packet of charge (i.e., a binary one), or no charge (i.e., a binary
zero) on a capacitor. The charge is gated onto the capacitor via an
access transistor, and sensed by turning on the same transistor and
looking at the voltage perturbation created by dumping the charge
packet on the interconnect line on the transistor output. Thus, a
single DRAM cell is made of one transistor and one capacitor. The
DRAM device, as illustrated in FIG. 1, is formed of an array of
DRAM cells. The rows on access transistors are linked by word lines
52a, 52b, and the transistor inputs/outputs are linked by bit lines
54a, 54b, and 54c. Historically, DRAM capacitors have evolved from
planar polysilicon-oxide-substrate plate capacitors to 3-D
structures which have diverged into "stack" capacitors with both
plates above the substrate, and "trench" capacitors using an etched
cavity in the substrate as the common plate.
[0041] In one or more embodiments, memory devices, DRAM capacitors
in particular, are provided where the capacitor is advantageously
self-aligned with the capacitor bottom contact, resulting in a
uniform critical dimension, better bottom contact, and increased
height of the capacitor.
[0042] Example embodiments are described herein with reference to
cross-sectional illustrations that are schematic illustrations of
example embodiments (and intermediate structures). As such,
variations from the shapes of the illustrations as a result, for
example, of manufacturing techniques and/or tolerances, are to be
expected. Thus, example embodiments should not be construed as
limited to the particular shapes of regions illustrated herein but
may be to include deviations in shapes that result, for example,
from manufacturing.
[0043] FIGS. 2 through 21 are cross-sectional views illustrating a
memory device 100, a DRAM capacitor for example, according to one
or more embodiments. With reference to FIGS. 2 and 3, in one or
more embodiments, a capacitor bottom contact 104 is selectively
etched from a substrate comprising the capacitor bottom contact 104
and a first dielectric material 102 to form a recess 106.
[0044] As used herein, the term "dielectric material" refers to a
layer of material that is an electrical insulator that can be
polarized in an electric field. In one or more embodiments, the
dielectric layer comprises one or more of oxides, carbon doped
oxides, silicon oxide (SiO), porous silicon dioxide (SiO.sub.2),
silicon oxide (SiO), silicon nitride (SiN), silicon oxide/silicon
nitride, carbides, oxycarbides, nitrides, oxynitrides,
oxycarbonitrides, polymers, phosphosilicate glass, fluorosilicate
(SiOF) glass, or organosilicate glass (SiOCH).
[0045] In one or more embodiments, the first dielectric material
can be any suitable material known to the skilled artisan. In one
or more embodiments, the first dielectric material 102 comprises
silicon oxide or silicon nitride.
[0046] In one or more embodiments, the capacitor bottom contact 104
can be any suitable material known to the skilled artisan. In one
or more embodiments, the capacitor bottom contact 104 comprises one
or more of a metal, a metal silicide, poly-silicon, or EPI-silicon.
In one or more embodiments, the capacitor bottom contact 104 is
doped by either N type dopants or P type dopants in order to reduce
contact resistance. In one or more embodiments, the metal of the
capacitor bottom contact 104 is selected from one or more of copper
(Cu), cobalt (Co), tungsten (W), titanium (Ti), molybdenum (Mo),
nickel (Ni), ruthenium (Ru), silver (Ag), gold (Au), iridium (Ir),
tantalum (Ta), or platinum (Pt).
[0047] In one or more embodiments, as illustrated in FIG. 4, a
conformal liner 108 is optionally deposited on the first dielectric
material 102 and the recessed capacitor bottom contact 104. In one
or more embodiments, the optional liner 108 can be conformal liner
108. In one or more embodiments, the conformal liner 108 is
selected from a conductive liner or a dielectric liner. In one or
more embodiments, the conformal liner 108 can be any suitable metal
liner material known to the skilled artisan. In one or more
embodiments, the conformal liner 108 comprises a metal nitride
film. In some embodiments, the conformal liner 108 comprises one or
more of tungsten nitride, tantalum nitride, or titanium
nitride.
[0048] As used herein, a layer or a liner which is "substantially
conformal" refers to a layer where the thickness is about the same
throughout (e.g., on the dielectric material 102, on the sidewalls
of the recess 106, and on the recessed capacitor bottom contact
104). A layer which is substantially conformal varies in thickness
by less than or equal to about 5%, 2%, 1% or 0.5%.
[0049] Referring to FIG. 5, the conformal liner 108 is removed from
the top surface of the dielectric material 102. In other
embodiments, the conformal liner 108 is not present. Referring to
FIGS. 6 and 7, pillars 112 are formed in the recess 106 on the
capacitor bottom contact 104.
[0050] In one or more embodiments, selective pillar growth
technique is used to grow pillars 112 on the capacitor bottom
contact 104. Pillars 112 are formed on the capacitor bottom contact
104. FIG. 7 illustrates pillars 112 being grown on an optional
liner 108. Referring to FIG. 6, in one or more embodiments,
self-aligned selective growth pillars 112 are formed using a seed
gapfill layer 110, optionally on the liner 108, on the recessed
conductive lines of the capacitor bottom contact 104.
[0051] As used herein, the term "self-aligned growth pillars"
refers to columns or towers of a metal (e.g. tungsten) that are
used to form self-aligned capacitor memory holes. The self-aligned
growth pillars have a height H.sub.1 of about 5 angstroms (.ANG.)
to about 10 microns (.mu.m) that extends above the top surface 105
of the electronic device 100. The width W.sub.1 of the self-aligned
growth pillars is in a range of about 0.5 nm to about 2000 nm.
[0052] As shown in FIG. 7, the pillars 112 extend substantially
orthogonally from the top surface 105 of the electronic device 100.
As shown in FIG. 7, the pillars 112 extend along the same direction
as the conductive lines of the capacitor bottom contact 104, and
are separated by gaps 107.
[0053] With reference to FIG. 6, in one or more embodiments, a seed
gapfill layer 110 is deposited on the capacitor bottom contact 104.
In one embodiment, the seed gapfill layer 110 is a self-aligned
selective growth seed film. In one or more embodiments, the seed
gapfill layer 110 is deposited on capacitor bottom contact 104 on
the top surface of the recessed conductive lines. In one or more
embodiments, the seed gapfill layer 110 is a tungsten (W) layer, or
other seed gapfill layer to provide selective growth pillars 112.
In some embodiments, the seed gapfill layer 110 is a metal film or
a metal containing film. Suitable metal films include, but are not
limited to, films including one or more of cobalt (Co), molybdenum
(Mo), tungsten (W), tantalum (Ta), titanium (Ti), ruthenium (Ru),
rhodium (Rh), copper (Cu), iron (Fe), manganese (Mn), vanadium (V),
niobium (Nb), hafnium (Hf), zirconium (Zr), yttrium (Y), aluminum
(Al), tin (Sn), chromium (Cr), lanthanum (La), or any combination
thereof. In some embodiments, the seed gapfill layer 110 is a
tungsten (W) seed gapfill layer.
[0054] In one or more embodiments, the seed gapfill layer 110 is
deposited using one or more deposition techniques, such as but not
limited to ALD, CVD, PVD, MBE, MOCVD, spin-on or other deposition
techniques known to one of ordinary skill in the art of
microelectronic device manufacturing.
[0055] In one or more embodiments, portions of the seed gapfill
layer 110 above the capacitor bottom contact 104 are expanded for
example, by oxidation, nitridation, or other process to grow
pillars 112. In one embodiment, the seed gap fill layer 112 is
oxidized by exposure to an oxidizing agent or oxidizing conditions
to transform the metal or metal containing seed gapfill layer 110
to metal oxide pillars 112. In one or more embodiments, pillars 112
include an oxide of one or more metals listed above. In more
specific embodiment, pillars 112 include tungsten oxide (e.g., WO,
WO.sub.3 and other tungsten oxide).
[0056] The oxidizing agent can be any suitable oxidizing agent
including, but not limited to, O.sub.2, O.sub.3, N.sub.2O,
H.sub.2O, H.sub.2O.sub.2, CO, CO.sub.2, NH.sub.3, N.sub.2/Ar,
N.sub.2/He, N.sub.2/Ar/He or any combination thereof. In some
embodiments, the oxidizing conditions comprise a thermal oxidation,
plasma enhanced oxidation, remote plasma oxidation, microwave and
radio-frequency oxidation (e.g., inductively coupled plasma (ICP),
capacitively coupled plasma (CCP)).
[0057] In one or more embodiments, the pillars 112 are formed by
oxidation of the seed gapfill layer 110 at any suitable temperature
depending on, for example, the composition of the seed gapfill
layer 110 and the oxidizing agent. In some embodiments, the
oxidation occurs at a temperature in an approximate range of about
25.degree. C. to about 800.degree. C. In some embodiments, the
oxidation occurs at a temperature greater than or equal to about
150.degree. C.
[0058] In one or more embodiments, deposition or formation of a
material may be performed by any suitable technique known to the
skilled artisan including, but not limited to, atomic layer
deposition (ALD), chemical vapor deposition (CVD), physical vapor
deposition (PVD), and the like. Referring to FIG. 8, a second
dielectric material 114 is deposited on the first dielectric
material 102 and on the top surface 113 of the pillars 112. In one
or more embodiments, the second dielectric material 114 can be any
suitable material known to the skilled artisan. In one or more
embodiments, the second dielectric material 114 comprises silicon
oxide or silicon nitride. In one or more embodiments, the second
dielectric material 114 is the same material as the first
dielectric material 102.
[0059] As illustrated in FIG. 8, in one or more embodiments, an
overburden 116 of the second dielectric material 114 is formed.
Referring to FIG. 9, the overburden 116 may be removed by any
suitable technique known to one of skill in the art including, but
not limited to, chemical mechanical planarization (CMP), dry
etching, or wet etching. In one or more embodiments, when the
overburden 116 of the second dielectric material 114 is removed,
the second dielectric material 114 is substantially coplanar with
the top surface 113 of the pillars 112.
[0060] Referring to FIG. 10A, in one or more embodiments, the
pillars 112 are selectively removed to form capacitor memory holes
118. In one or more embodiments, the capacitor memory holes 118 are
self-aligned with the capacitor bottom contact 104. In one or more
embodiments, the self-aligned capacitor memory holes 118 have a
minimum width that is equal to the width of the self-aligned growth
pillars 112.
[0061] As shown in FIG. 10A, the pillars 112 are removed
selectively to the capacitor bottom contact 104. In one or more
embodiments, if the optional conformal liner 108 is a
non-conductive liner (e.g. a dielectric liner), it is also removed.
In one embodiment, the pillars 112 and liner 108 are removed
selectively to the capacitor bottom contact 104. As shown in FIG.
10A, self-aligned capacitor memory holes 118 are formed in the
second dielectric material 114 and the first dielectric material
102. As illustrated in FIG. 10A, each self-aligned capacitor memory
holes 118 has a bottom that is a top surface of the capacitor
bottom contact 104 and opposing sidewalls that include a sidewall
portion of first dielectric material 102 and second dielectric
material 114. Generally, the aspect ratio of the self-aligned
capacitor memory holes 118 refers to the ratio of the depth of the
self-aligned capacitor memory holes 118 to the width of the
self-aligned capacitor memory holes 118. In one embodiment, the
aspect ratio of each self-aligned capacitor memory hole 118 is in
an approximate range from about 1:1 to about 200:1. In one or more
embodiments, the critical dimensions of the self-aligned capacitor
memory holes 118 is substantially uniform along the depth of the
self-aligned capacitor memory holes 118. As used herein, the term
"substantially uniform" means that the critical dimension at the
top of the self-aligned capacitor memory holes 118 is within .+-.5%
of the critical dimension at the bottom of the self-aligned
capacitor memory holes 118. In one or more embodiments, the
critical dimension variation from the top of the self-aligned
capacitor memory holes 118 to the bottom of the self-aligned
capacitor memory holes 118 is within 5%.
[0062] In one embodiment, the pillars 112 are selectively removed
using one or more of the dry and wet etching techniques known to
one of ordinary skill in the art of electronic device
manufacturing. In one embodiment, the pillars 112 are selectively
wet etched by e.g., 5 wt. % of ammonium hydroxide (NH.sub.4OH)
aqueous solution at the temperature of about 80 degrees C. In one
embodiment, hydrogen peroxide (H.sub.2O.sub.2) is added to the 5
wt. % NH.sub.4OH aqueous solution to increase the etching rate of
the pillars 112. In one embodiment, the pillars 112 are selectively
wet etched using hydrofluoric acid (HF) and nitric acid (HNO.sub.3)
in a ratio of 1:1. In one embodiment, the pillars 112 are
selectively wet etched using HF and HNO.sub.3 in a ratio of 3:7
respectively. In one embodiment, the pillars 112 are selectively
wet etched using HF and HNO.sub.3 in a ratio of 4:1, respectively.
In one embodiment, the pillars 112 are selectively wet etched using
HF and HNO.sub.3 in a ratio of 30%:70%, respectively. In one
embodiment, the pillars 112 including tungsten, titanium or both
titanium and tungsten are selectively wet etched using NH.sub.4OH
and H.sub.2O.sub.2 in a ratio of 1:2, respectively. In one
embodiment, the pillars 112 are selectively wet etched using 305
grams of potassium ferricyanide (K.sub.3Fe(CN).sub.6), 44.5 grams
of sodium hydroxide (NaOH) and 1000 ml of water (H.sub.2O). In one
embodiment, the pillars 112 are selectively wet etched using
diluted or concentrated one or more of the chemistries including
hydrochloric acid (HCl), HNO.sub.3, sulfuric acid
(H.sub.2SO.sub.4), HF, and H.sub.2O.sub.2. In one embodiment, the
pillars 112 are selectively wet etched using HF, HNO.sub.3 and
acetic acid (AcOH) in a ratio of 4:4:3, respectively. In one
embodiment, the pillars 112 are selectively dry etched using a
bromotrifluoromethane (CBrF3) reactive ion etching (RIE) technique.
In one embodiment, the pillars 112 are selectively dry etched using
chlorine, fluorine, bromine or any combination thereof based
chemistries. In one embodiment, the pillars 112 are selectively wet
etched using hot or warm Aqua Regia mixture including HCl and
HNO.sub.3 in a ratio of 3:1, respectively. In one embodiment, the
pillars 112 are selectively etched using alkali with oxidizers
(potassium nitrate (KNOB) and lead dioxide (PbO.sub.2)). In one
embodiment, the liner 108 is selectively removed using one or more
of the dry and wet etching techniques known to one of ordinary
skill in the art of electronic device manufacturing.
[0063] Referring to FIG. 10B, a first conductive material 120 is
conformally deposited in the capacitor memory holes 118. The first
conductive material 120 may be deposited by any deposition method
known to one of skill in the art, including, but not limited to,
ALD, CVD, or PVD. The first conductive material 120 may be any
suitable material known to the skilled artisan. In one or more
embodiments, the first conductive material 120 comprises one or
more of metal mode titanium (MMTi), metal silicide, or highly doped
poly-silicon.
[0064] As illustrated in FIG. 10B, in one or more embodiments, a
layer 122 of the first conductive material 120 is formed on the top
surface 121 of the second dielectric material 114. Referring to
FIG. 10C, the layer 122 of the first conductive material 120 formed
on the top surface 121 of the second dielectric material 114 may be
removed by any suitable technique known to one of skill in the art
including, but not limited to, chemical mechanical planarization
(CMP). In one or more embodiments, when the layer 122 of the first
conductive material 120 formed on the top surface 121 of the second
dielectric material 114 is removed, the first conductive material
120 is substantially coplanar with the top surface 121 of the
second dielectric material 114.
[0065] Referring to FIG. 10D, a third dielectric material 124 is
conformally deposited in the capacitor memory holes 118 on the
first conductive material 120. The third dielectric material 124
may be deposited by any deposition method known to one of skill in
the art, including, but not limited to, ALD, CVD, or PVD. The third
dielectric material 124 may be any suitable material known to the
skilled artisan. In one or more embodiments, the third dielectric
material 124 comprises a high-.kappa. dielectric. In one or more
embodiments, the third dielectric material 124 comprises a
high-.kappa. dielectric selected from one or more of aluminum
oxide, hafnium oxide, or aluminum hafnium oxide (AlHfOx).
[0066] Referring to FIG. 10E, in one or more embodiments a second
conductive material 126 is deposited on the third dielectric
material 124 to form a DRAM capacitor. The second conductive
material 126 may be deposited by any deposition method known to one
of skill in the art, including, but not limited to, ALD, CVD, or
PVD. The second conductive material 126 may be any suitable
material known to the skilled artisan. In one or more embodiments,
the second conductive material 126 comprises one or more of
poly-silicon, metal, or metal silicide. In one or more embodiments,
the poly-silicon may be doped by N-type or P-type dopants. In one
or more embodiments, the capacitor bottom contact 104 is
self-aligned with the first conductive material 120.
[0067] FIGS. 11-21 describe alternative embodiments of the
disclosure. FIG. 11 is the same as FIG. 9 and is merely duplicated
for convenience. Referring to FIG. 11, the overburden 116 of the
second dielectric material 114 has been removed, such that the
second dielectric material 114 is substantially coplanar with the
top surface 113 of the pillars 112.
[0068] With reference to FIG. 12, in one or more embodiments, prior
to forming the capacitor memory holes 118, the pillars 112 are
selectively etched to form a second recess 128. Referring to FIGS.
13 and 14, second pillars 132 are grown in the second recess 128 on
the pillars 112.
[0069] Second pillars 132 are formed on the pillars 112. Referring
to FIG. 13, in one or more embodiments, self-aligned selective
growth pillars 132 are formed using a seed gapfill layer 130 on
pillars 112. In one or more embodiments, an optional liner may be
deposited in the recess 128 and seed gapfill layer 130 is then
deposited on the optional liner to grow the second pillars 132.
[0070] In one or more embodiments, the self-aligned growth second
pillars 132 have a height H.sub.2 of about 5 angstroms (.ANG.) to
about 10 microns (.mu.m) that extends above the top surface 133 of
the second dielectric material 114. In one or more embodiments, the
height H.sub.2 of the self-aligned growth second pillars 132 is
substantially the same as the height H.sub.2 of the self-aligned
growth pillars 112. In other embodiments, the height H.sub.2 of the
self-aligned growth second pillars 132 is greater than the height
H.sub.2 of the self-aligned growth pillars 112. The width W.sub.2
of the self-aligned growth second pillars 132 is in a range of
about 0.5 nm to about 2000 nm. In one or more embodiments, the
width W.sub.2 of the self-aligned growth second pillars 132 is
substantially the same as the width W.sub.1 of the self-aligned
growth pillars 112.
[0071] As shown in FIG. 14, the second pillars 132 extend
substantially orthogonally from the top surface 133 of the second
dielectric material 114. As shown in FIG. 14, the second pillars
132 extend along the same direction as the conductive lines of the
capacitor bottom contact 104, and are separated by gaps 135.
[0072] With reference to FIG. 13, in one or more embodiments, a
second seed gapfill layer 130 is deposited on the pillars 112. In
one embodiment, the second seed gapfill layer 130 is a self-aligned
selective growth seed film. In one or more embodiments, the second
seed gapfill layer 130 is deposited on pillars 112 on capacitor
bottom contact 104 on the top surface of the recessed conductive
lines. In one or more embodiments, optional conformal liner 108 is
present on the capacitor bottom contact 104. In one or more
embodiments, the second seed gapfill layer 130 is a tungsten (W)
layer, or other seed gapfill layer to provide selective growth
second pillars 132. In some embodiments, the second seed gapfill
layer 130 is a metal film or a metal containing film. Suitable
metal films include, but are not limited to, films including one or
more of cobalt (Co), molybdenum (Mo), tungsten (W), tantalum (Ta),
titanium (Ti), ruthenium (Ru), rhodium (Rh), copper (Cu), iron
(Fe), manganese (Mn), vanadium (V), niobium (Nb), hafnium (Hf),
zirconium (Zr), yttrium (Y), aluminum (Al), tin (Sn), chromium
(Cr), lanthanum (La), or any combination thereof. In some
embodiments, the second seed gapfill layer 130 is a tungsten (W)
seed gapfill layer.
[0073] In one or more embodiments, the second seed gapfill layer
130 is deposited using one or more deposition techniques, such as
but not limited to ALD, CVD, PVD, MBE, MOCVD, spin-on or other
deposition techniques known to one of ordinary skill in the art of
microelectronic device manufacturing.
[0074] In one or more embodiments, portions of the second seed
gapfill layer 130 above the pillars 112 are expanded for example,
by oxidation, nitridation, or other process to grow second pillars
132. In one embodiment, the second seed gap fill layer 130 is
oxidized by exposure to an oxidizing agent or oxidizing conditions
to transform the metal or metal containing second seed gapfill
layer 130 to metal oxide second pillars 132. In one or more
embodiments, second pillars 132 include an oxide of one or more
metals listed above. In more specific embodiment, second pillars
132 include tungsten oxide (e.g., WO, WO.sub.3 and other tungsten
oxide). In one or more embodiments, second pillars 132 comprise the
same material as pillars 112. In one or more embodiments, second
pillars 132 comprise a material different from pillars 112.
[0075] The oxidizing agent can be any suitable oxidizing agent
including, but not limited to, O.sub.2, O.sub.3, N.sub.2O,
H.sub.2O, H.sub.2O.sub.2, CO, CO.sub.2, NH.sub.3, N.sub.2/Ar,
N.sub.2/He, N.sub.2/Ar/He or any combination thereof. In some
embodiments, the oxidizing conditions comprise a thermal oxidation,
plasma enhanced oxidation, remote plasma oxidation, microwave and
radio-frequency oxidation (e.g., inductively coupled plasma (ICP),
capacitively coupled plasma (CCP)).
[0076] In one or more embodiments, the second pillars 132 are
formed by oxidation of the second seed gapfill layer 130 at any
suitable temperature depending on, for example, the composition of
the second seed gapfill layer 130 and the oxidizing agent. In some
embodiments, the oxidation occurs at a temperature in an
approximate range of about 25.degree. C. to about 800.degree. C. In
some embodiments, the oxidation occurs at a temperature greater
than or equal to about 150.degree. C.
[0077] With reference to FIG. 15, a fourth dielectric material 134
is deposited on the second dielectric material 114. In one or more
embodiments, the fourth dielectric material 134 can be any suitable
material known to the skilled artisan. In one or more embodiments,
the fourth dielectric material 134 comprises silicon oxide or
silicon nitride. In one or more embodiments, the fourth dielectric
material 134 is the same material as the second dielectric material
114. In one or more embodiments, the fourth dielectric material 134
is the same material as the first dielectric material 102.
[0078] As illustrated in FIG. 15, in one or more embodiments, an
overburden 136 of the fourth dielectric material 134 may be formed.
Referring to FIG. 16, the overburden 136 may be removed by any
suitable technique known to one of skill in the art including, but
not limited to, chemical mechanical planarization (CMP), dry
etching, or wet etching. In one or more embodiments, when the
overburden 136 of the fourth dielectric material 134 is removed,
the fourth dielectric material 134 is substantially coplanar with
the top surface 135 of the second pillars 132.
[0079] While FIGS. 11-16 illustrate two layers of stacked pillars
and dielectric layers, the skilled artisan recognizes that the
structures and methods described in FIGS. 11-16 may be repeated
multiple times to produce more than two stacks of pillars and
dielectric layers. In some embodiments, there are three stacks of
pillars and dielectric layers. In some embodiments, there are four
stacks of pillars and dielectric layers. In some embodiments there
are five or more stacks of pillars and dielectric layers.
Additional stacks of pillars and dielectric layers will increase
the height/depth of the capacitor that may be formed. The method of
one or more embodiments advantageously leads to a capacitor
self-aligned with the capacitor bottom contact, resulting in a
uniform critical dimension and increased height of the capacitor.
As used herein, the term "substantially uniform" means that the
critical dimension at the top of the self-aligned capacitor memory
holes (or capacitor memory channel(s)) is within .+-.5% of the
critical dimension at the bottom of the self-aligned capacitor
memory holes (or capacitor memory channel(s)). In one or more
embodiments, the critical dimension variation from the top of the
self-aligned capacitor memory holes to the bottom of the
self-aligned capacitor memory holes is within 5%.
[0080] Referring to FIG. 17, in one or more embodiments, the second
pillars 132 and pillars 112 are selectively removed to form
capacitor memory holes 138. In one or more embodiments, the
capacitor memory holes 138 are self-aligned with the capacitor
bottom contact 104. In one or more embodiments, the self-aligned
capacitor memory holes 138 have a minimum width that is equal to
the width of the self-aligned growth pillars 132 and the
self-aligned growth pillars 112.
[0081] As shown in FIG. 17, the second pillars 132 and pillars 112
are removed selectively to the capacitor bottom contact 104. In one
or more embodiments, if the optional conformal liner 108 is a
non-conductive liner (e.g. dielectric liner), it is also removed.
In one or more embodiments, trimming of the second dielectric
material 114 and the fourth dielectric material 134 may be
necessary to ensure that the side walls of the capacitor memory
holes 138 are substantially uniform. In one embodiment, the second
pillars 132, pillars 112 and liner 108 are removed selectively to
the capacitor bottom contact 104. As shown in FIG. 17, self-aligned
capacitor memory holes 138 are formed in the fourth dielectric
material 134, second dielectric material 114, and the first
dielectric material 102. As illustrated in FIG. 17, each
self-aligned capacitor memory hole 118 has a bottom that is a top
surface of the capacitor bottom contact 104 and opposing sidewalls
that include a sidewall portion of first dielectric material 102,
second dielectric material 114, and fourth dielectric material 134.
Generally, the aspect ratio of the self-aligned capacitor memory
holes 138 refers to the ratio of the depth of the self-aligned
capacitor memory holes 138 to the width of the self-aligned
capacitor memory holes 138. In one embodiment, the aspect ratio of
each self-aligned capacitor memory hole 138 is in an approximate
range from about 1:1 to about 200:1, or from about 10:1 to about
200:1, or from about 200:1 to about 100:1. In one or more
embodiments, the critical dimension of the self-aligned capacitor
memory holes 138 is substantially uniform along the depth of the
self-aligned capacitor memory holes 138. As used herein, the term
"substantially uniform" means that the critical dimension at the
top of the self-aligned capacitor memory hole 138 is within .+-.5%
of the critical dimension at the bottom of the self-aligned
capacitor memory holes 138. In one or more embodiments, the
critical dimension variation from the top of the self-aligned
capacitor memory holes 138 to the bottom of the self-aligned
capacitor memory holes 138 is within 5%.
[0082] In one embodiment, the second pillars 132 and pillars 112
are selectively removed using one or more of the dry and wet
etching techniques known to one of ordinary skill in the art of
electronic device manufacturing. In one embodiment, the second
pillars 132 and pillars 112 are selectively wet etched by e.g., 5
wt. % of ammonium hydroxide (NH.sub.4OH) aqueous solution at the
temperature of about 80 degrees C. In one embodiment, hydrogen
peroxide (H.sub.2O.sub.2) is added to the 5 wt. % NH.sub.4OH
aqueous solution to increase the etching rate of the second pillars
132 and pillars 112. In one embodiment, the second pillars 132 and
pillars 112 are selectively wet etched using hydrofluoric acid (HF)
and nitric acid (HNO.sub.3) in a ratio of 1:1. In one embodiment,
the second pillars 132 and pillars 112 are selectively wet etched
using HF and HNO.sub.3 in a ratio of 3:7 respectively. In one
embodiment, the second pillars 132 and pillars 112 are selectively
wet etched using HF and HNO.sub.3 in a ratio of 4:1, respectively.
In one embodiment, the second pillars 132 and pillars 112 are
selectively wet etched using HF and HNO.sub.3 in a ratio of
30%:70%, respectively. In one embodiment, the second pillars 132
and pillars 112 including tungsten, titanium or both titanium and
tungsten are selectively wet etched using NH.sub.4OH and
H.sub.2O.sub.2 in a ratio of 1:2, respectively. In one embodiment,
the second pillars 132 and pillars 112 are selectively wet etched
using 305 grams of potassium ferricyanide (K.sub.3Fe(CN).sub.6),
44.5 grams of sodium hydroxide (NaOH) and 1000 ml of water
(H.sub.2O). In one embodiment, the second pillars 132 and pillars
112 are selectively wet etched using diluted or concentrated one or
more of the chemistries including hydrochloric acid (HCl),
HNO.sub.3, sulfuric acid (H.sub.2SO.sub.4), HF, and H.sub.2O.sub.2.
In one embodiment, the second pillars 132 and pillars 112 are
selectively wet etched using HF, HNO.sub.3 and acetic acid (AcOH)
in a ratio of 4:4:3, respectively. In one embodiment, the second
pillars 132 and pillars 112 are selectively dry etched using a
bromotrifluoromethane (CBrF3) reactive ion etching (RIE) technique.
In one embodiment, the second pillars 132 and pillars 112 are
selectively dry etched using chlorine, fluorine, bromine or any
combination thereof based chemistries. In one embodiment, the
second pillars 132 and pillars 112 are selectively wet etched using
hot or warm Aqua Regia mixture including HCl and HNO.sub.3 in a
ratio of 3:1, respectively. In one embodiment, the second pillars
132 and pillars 112 are selectively etched using alkali with
oxidizers (potassium nitrate (KNOB) and lead dioxide (PbO.sub.2)).
In one embodiment, the liner 108 is selectively removed using one
or more of the dry and wet etching techniques known to one of
ordinary skill in the art of electronic device manufacturing.
[0083] Referring to FIG. 18, a first conductive material 140 is
continuously and conformally deposited in the capacitor memory
holes 138 and on the top surface 141 of the fourth dielectric
material. The first conductive material 140 may be deposited by any
deposition method known to one of skill in the art, including, but
not limited to, ALD, CVD, or PVD. The first conductive material 140
may be any suitable material known to the skilled artisan. In one
or more embodiments, the first conductive material 140 comprises
one or more of metal mode titanium (MMTi), metal silicide, or
highly doped poly-silicon.
[0084] As illustrated in FIG. 18, in one or more embodiments, an
overburden 142 of the first conductive material 140 is formed on
the top surface 141 of the fourth dielectric material 134.
Referring to FIG. 19A, the overburden 142 of the first conductive
material 140 formed on the top surface 141 of the fourth dielectric
material 134 may be removed by any suitable technique known to one
of skill in the art including, but not limited to, chemical
mechanical planarization (CMP), dry etching, or wet etching. In one
or more embodiments, when the overburden 142 of the first
conductive material 140 formed on the top surface 141 of the fourth
dielectric material 134 is completely removed, the first conductive
material 140 is substantially coplanar with the top surface 141 of
the fourth dielectric material 134. Without intending to be by
bound by theory, it is believed that, with the complete removal of
the overburden 142, each capacitor memory hole 138 will be formed
into one memory capacitor.
[0085] Referring to FIG. 19B, in one or more embodiments, the
overburden 142 of the first conductive material 140 formed on the
top surface 141 of the fourth dielectric material 134 is partially
removed to partially separate the first conductive material 140.
Without intending to be bound by theory, it is believed that, in
this circumstance, the total capacitor for one memory cell will be
made by more than one adjacent capacitor memory hole 138.
[0086] Referring to FIG. 20, a third dielectric material 144 is
conformally deposited in the capacitor memory holes 138 on the
first conductive material 140. The third dielectric material 144
may be deposited by any deposition method known to one of skill in
the art, including, but not limited to, ALD, CVD, or PVD. The third
dielectric material 144 may be any suitable material known to the
skilled artisan. In one or more embodiments, the third dielectric
material 144 comprises a high-.kappa. dielectric. In one or more
embodiments, the third dielectric material 144 comprises a
high-.kappa. dielectric selected from one or more of aluminum
oxide, hafnium oxide, or aluminum hafnium oxide (AlHfOx).
[0087] Referring to FIG. 21, in one or more embodiments a second
conductive material 146 is deposited on the third dielectric
material 144 to form a DRAM capacitor. The second conductive
material 146 may be deposited by any deposition method known to one
of skill in the art, including, but not limited to, ALD, CVD, or
PVD. The second conductive material 126 may be any suitable
material known to the skilled artisan. In one or more embodiments,
the second conductive material 146 comprises one or more of
poly-silicon, highly doped poly-silicon, metal, or metal silicide.
In one or more embodiments, the capacitor bottom contact 104 is
self-aligned with the first conductive material 140.
[0088] Referring to FIG. 21, one or more embodiments provide a DRAM
capacitor comprising: a capacitor bottom contact 104 and a first
dielectric material 102 on a substrate. A second dielectric
material 114 is on the first dielectric material 102. A fourth
dielectric material 134 is on the second dielectric material 114. A
capacitor memory channel 138 is formed through the fourth
dielectric material 134, the second dielectric material 114, and
the first dielectric material 102. A capacitor 150 is formed in the
capacitor memory channel 138. The capacitor 150 is self-aligned
with the capacitor bottom contact 104. In one or more embodiments,
the capacitor 150 comprises a first conductive material 140, a
third dielectric material 144 on the first conductive material 140,
and a second conductive material 146 on the third dielectric
material 144. In one or more embodiments, the capacitor 150 has a
top and a bottom, and a critical dimension of the top is
substantially the same as a critical dimension of the bottom.
[0089] Processes may generally be stored in the memory of the
system controller 990 as a software routine that, when executed by
the processor, causes the process chamber to perform processes of
the present disclosure. The software routine may also be stored
and/or executed by a second processor (not shown) that is remotely
located from the hardware being controlled by the processor. Some
or all of the method of the present disclosure may also be
performed in hardware. As such, the process may be implemented in
software and executed using a computer system, in hardware as,
e.g., an application specific integrated circuit or other type of
hardware implementation, or as a combination of software and
hardware. The software routine, when executed by the processor,
transforms the general purpose computer into a specific purpose
computer (controller) that controls the chamber operation such that
the processes are performed.
[0090] Spatially relative terms, such as "beneath," "below,"
"lower," "above," "upper" and the like, may be used herein for ease
of description to describe one element or feature's relationship to
another element(s) or feature(s) as illustrated in the figures. It
will be understood that the spatially relative terms are intended
to encompass different orientations of the device in use or
operation in addition to the orientation depicted in the figures.
For example, if the device in the figures is turned over, elements
described as "below" or "beneath" other elements or features would
then be oriented "above" the other elements or features. Thus, the
exemplary term "below" may encompass both an orientation of above
and below. The device may be otherwise oriented (rotated 90 degrees
or at other orientations) and the spatially relative descriptors
used herein interpreted accordingly.
[0091] The use of the terms "a" and "an" and "the" and similar
referents in the context of describing the materials and methods
discussed herein (especially in the context of the following
claims) are to be construed to cover both the singular and the
plural, unless otherwise indicated herein or clearly contradicted
by context. Recitation of ranges of values herein are merely
intended to serve as a shorthand method of referring individually
to each separate value falling within the range, unless otherwise
indicated herein, and each separate value is incorporated into the
specification as if it were individually recited herein. All
methods described herein can be performed in any suitable order
unless otherwise indicated herein or otherwise clearly contradicted
by context. The use of any and all examples, or exemplary language
(e.g., "such as") provided herein, is intended merely to better
illuminate the materials and methods and does not pose a limitation
on the scope unless otherwise claimed. No language in the
specification should be construed as indicating any non-claimed
element as essential to the practice of the disclosed materials and
methods.
[0092] Reference throughout this specification to "one embodiment,"
"certain embodiments," "one or more embodiments" or "an embodiment"
means that a particular feature, structure, material, or
characteristic described in connection with the embodiment is
included in at least one embodiment of the disclosure. Thus, the
appearances of the phrases such as "in one or more embodiments,"
"in certain embodiments," "in one embodiment" or "in an embodiment"
in various places throughout this specification are not necessarily
referring to the same embodiment of the disclosure. Furthermore,
the particular features, structures, materials, or characteristics
may be combined in any suitable manner in one or more
embodiments.
[0093] Although the disclosure herein has been described with
reference to particular embodiments, it is to be understood that
these embodiments are merely illustrative of the principles and
applications of the present disclosure. It will be apparent to
those skilled in the art that various modifications and variations
can be made to the method and apparatus of the present disclosure
without departing from the spirit and scope of the disclosure.
Thus, it is intended that the present disclosure include
modifications and variations that are within the scope of the
appended claims and their equivalents.
* * * * *