U.S. patent application number 13/847740 was filed with the patent office on 2013-08-15 for dimensional silica-based porous silicon structures and methods of fabrication.
The applicant listed for this patent is Robert Alan Bellman, Nicholas Francis Borrelli, David Alan Deneka, Shawn Michael O'Malley, Vitor Marino Schneider. Invention is credited to Robert Alan Bellman, Nicholas Francis Borrelli, David Alan Deneka, Shawn Michael O'Malley, Vitor Marino Schneider.
Application Number | 20130209781 13/847740 |
Document ID | / |
Family ID | 45697815 |
Filed Date | 2013-08-15 |
United States Patent
Application |
20130209781 |
Kind Code |
A1 |
Bellman; Robert Alan ; et
al. |
August 15, 2013 |
DIMENSIONAL SILICA-BASED POROUS SILICON STRUCTURES AND METHODS OF
FABRICATION
Abstract
Methods of fabricating dimensional silica-based substrates or
structures comprising a porous silicon layers are contemplated.
According to one embodiment, oxygen is extracted from the atomic
elemental composition of a silica glass substrate by reacting a
metallic gas with the substrate in a heated inert atmosphere to
form a metal-oxygen complex along a surface of the substrate. The
metal-oxygen complex is removed from the surface of the silica
glass substrate to yield a crystalline porous silicon surface
portion and one or more additional layers are formed over the
crystalline porous silicon surface portion of the silica glass
substrate to yield a dimensional silica-based substrate or
structure comprising the porous silicon layer. Embodiments are also
contemplated where the substrate is glass-based, but is not
necessarily a silica-based glass substrate. Additional embodiments
are disclosed and claimed.
Inventors: |
Bellman; Robert Alan;
(Painted Post, NY) ; Borrelli; Nicholas Francis;
(Elmira, NY) ; Deneka; David Alan; (Corning,
NY) ; O'Malley; Shawn Michael; (Horseheads, NY)
; Schneider; Vitor Marino; (Painted Post, NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Bellman; Robert Alan
Borrelli; Nicholas Francis
Deneka; David Alan
O'Malley; Shawn Michael
Schneider; Vitor Marino |
Painted Post
Elmira
Corning
Horseheads
Painted Post |
NY
NY
NY
NY
NY |
US
US
US
US
US |
|
|
Family ID: |
45697815 |
Appl. No.: |
13/847740 |
Filed: |
March 20, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13100593 |
May 4, 2011 |
8415555 |
|
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13847740 |
|
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61376379 |
Aug 24, 2010 |
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Current U.S.
Class: |
428/312.6 ;
438/477; 65/30.1; 65/31 |
Current CPC
Class: |
C03C 23/0095 20130101;
H01L 21/02658 20130101; H01L 21/02002 20130101; H01L 21/02422
20130101; H01L 21/2257 20130101; H01L 21/3221 20130101; H01L
21/0245 20130101; H01L 29/78603 20130101; C03C 23/008 20130101;
Y10T 428/249969 20150401; H01L 21/02513 20130101; H01L 21/02532
20130101 |
Class at
Publication: |
428/312.6 ;
65/30.1; 65/31; 438/477 |
International
Class: |
C03C 23/00 20060101
C03C023/00; H01L 21/322 20060101 H01L021/322 |
Claims
1. A method of fabricating a dimensional silica glass substrate or
structure having a porous silicon surface layer portion of the
method comprising: providing a silica glass substrate; extracting
oxygen from the atomic elemental composition of a surface portion
of the silica glass substrate by reacting a metallic gas with the
surface of the silica glass substrate in a heated inert atmosphere
to form a metal-oxygen complex in the surface portion of the silica
glass substrate, wherein the inert atmosphere is heated to a
reaction temperature sufficient to facilitate the oxygen
extraction; and removing the metal-oxygen complex from the surface
portion of the silica glass substrate to yield a crystalline porous
silicon surface portion in the surface of the silica glass
substrate;
2. A method as claimed in claim 1 further the step of of: utilizing
the porous silicon surface portion of the silica glass substrate as
a seed layer and epitaxially growing or depositing a semiconductor
or crystalline material overlayer on the porous silicon surface
portion of the silica glass substrate.
3. A method as claimed in claim 2 wherein: the overlayer comprises
a monocrystalline silicon layer, a microcrystalline silicon layer,
a polycrystalline silicon layer, or an amorphous silicon layer; and
the method further comprises the step of recrystallizing the
overlayer by annealing the overlayer at a temperature and duration
sufficient to enhance crystallization and increase grain size in
the overlayer.
4. A method as claimed in claim 1 further comprising utilizing the
porous silicon layer as a seed layer for the epitaxial fabrication
of a silicon-on-insulator structure.
5. A method as claimed in claim 4 further comprising the step of
forming a separation layer configured to inhibit migration of
impurities from the silica glass substrate to remaining portions of
the structure.
6. A method as claimed in claim 1 wherein: the silica glass
substrate comprises N-type or P-type dopants; and the oxygen
extraction and the metal-oxygen complex removal steps are tailored
to leave significant amount of dopants in the crystalline porous
silicon surface portion of the silica glass substrate.
7. A method as claimed in claim 1 further comprising the step of
providing a topical film on the silica glass substrate for
controlling the thickness, porosity or crystalline character of the
resulting crystalline porous silicon surface portion of the silica
glass substrate.
8. A method as claimed in claim 1 wherein the method comprises a
patterning step where one or more inert blocking layers are
provided over the silica glass substrate prior to reacting the
metallic gas with the silica glass substrate.
9. A method as claimed in claim 1 wherein the method comprises a
reducing agent doping step where the silica glass substrate is
pre-treated with a gaseous reducing agent to infiltrate the surface
of the silica glass substrate with the reducing agent and enhance
the reaction of the metallic gas and the silica glass
substrate.
10. A method as claimed in claim 1 wherein the silica glass
substrate is characterized by a thermal strain point and the inert
atmosphere is heated to a reaction temperature below the thermal
strain point of the silica glass substrate.
11. A method as claimed in claim 1 wherein the metallic gas
comprises Mg and a reaction with the silica glass substrate
comprises: 2Mg+SiO.sub.2.fwdarw.2MgO.
12. A method as claimed in claim 1 wherein the metallic gas is
provided in an amount that is sufficient for stoichiometric
reaction conditions.
13. A method as claimed in claim 1 wherein a reaction of the
metallic gas with the silica glass substrate generates reaction
byproducts and the method comprises one or more byproduct removal
steps.
14. A method as claimed in claim 1 wherein the substrate is subject
to microwave or RF exposure while reacting the metallic gas with
the silica glass substrate.
15. A method as claimed in claim 1 wherein the silica glass
substrate is subject to electron beam irradiation prior to reacting
the metallic gas with the silica glass substrate in the heated
inert atmosphere.
16. A method as claimed in claim 1 wherein: the reaction of the
metallic gas with the silica glass substrate additionally forms a
metal-non-oxygen complex along a surface of the silica glass
substrate; and the method further comprises a post-reaction thermal
treatment that is maintained in an inert atmosphere at a
post-reaction temperature exceeding the reaction temperature for a
period of time that is sufficient to evaporate the metal-non-oxygen
complex.
17. A method as claimed in claim 1 wherein the method further
comprises a post-reaction acid etching step for removing the
metal-oxygen complex or amorphous silicon.
18. (canceled)
19. A method as claimed in claim 1 further comprising the step of
densifying the silica based structure by coating the crystalline
porous silicon surface portion of the silica glass substrate with
an additional glass or metal oxide layer and reacting a metallic
gas with the crystalline porous surface portion of the glass
substrate at the reaction temperature to yield a densified oxygen
substrate.
20. (canceled)
21. A method as claimed in claim 1 further comprising the step of
forming one or more additional layers over the crystalline porous
silicon surface portion of the silica glass substrate.
22. A dimensional semiconductor on insulator substrate comprising a
dimensional silica glass substrate, wherein an integral surface
portion of the dimensional silica glass substrate comprises a
porous silicon layer.
Description
CLAIMING BENEFIT OF PRIOR FILED U.S. APPLICATION
[0001] This application claims the benefit of and priority to U.S.
Provisional Application Ser. No. 61/376,379, filed on Aug. 24,
2010. The content of this document and the entire disclosure of
publications, patents, and patent documents mentioned herein are
incorporated by reference.
BACKGROUND
[0002] The present disclosure relates to dimensional silica-based
porous silicon structures and, more particularly, to methods of
fabricating the structures.
BRIEF SUMMARY
[0003] In accordance with one embodiment of the present disclosure,
a method of fabricating a dimensional silica-based structure
comprising a porous silicon layer is provided. According to the
method, oxygen is extracted from the atomic elemental composition
of a silica glass substrate by reacting a metallic gas with the
substrate in a heated inert atmosphere to form a metal-oxygen
complex along a surface of the substrate. The metal-oxygen complex
is removed from the surface of the silica glass substrate to yield
a crystalline porous silicon surface portion and one or more
additional layers are formed over the crystalline porous silicon
surface portion of the silica glass substrate to yield a
dimensional silica-based structure comprising the porous silicon
layer. Embodiments are also contemplated where the substrate is
glass-based, but is not necessarily a silica-based glass substrate.
Additional embodiments are disclosed and claimed.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0004] The following detailed description of specific embodiments
of the present disclosure can be best understood when read in
conjunction with the following drawings, where like structure is
indicated with like reference numerals and in which:
[0005] FIGS. 1-3 illustrate schematically a method of fabricating a
dimensional silica-based porous silicon structure according to one
embodiment of the present disclosure;
[0006] FIG. 4 illustrates a dimensional silica-based porous silicon
structure according to an alternative embodiment of the present
disclosure;
[0007] FIG. 5 illustrates schematically a silicon-on-insulator
structure incorporating a silica-based porous silicon layer
according to the present disclosure; and
[0008] FIG. 6 illustrates schematically a photovoltaic cell
incorporating a silica-based porous silicon layer according to the
present disclosure.
DETAILED DESCRIPTION
[0009] FIGS. 1-3 of the present disclosure describe the fabrication
methodology of the present disclosure with reference to a silica
glass substrate and a Mg-based metallo-thermic reduction process,
although the scope of the present disclosure extends well beyond
specific metallo-thermic reduction processes. More specifically,
according to the illustrated fabrication methodology, a dimensional
silica-based structure comprising a porous silicon layer can be
fabricated by extracting oxygen from the atomic elemental
composition of a silica glass substrate 10. The silica glass
substrate 10 may be a high purity fused silica substrate, an
alkaline earth alumina borosilicate glass, or any type of glass
comprising silica. Oxygen is extracted from the silica glass
substrate 10 by reacting a metallic gas Mg with the silica glass
substrate 10 in a heated inert atmosphere 20 to form a metal-oxygen
complex 30 along a surface of the silica glass substrate 10.
[0010] To facilitate the oxygen extraction, the inert atmosphere 20
is heated to a reaction temperature T, which, in the case of many
silica glass substrates, will be between approximately 650.degree.
C. and approximately 750.degree. C. For example, and not by way of
limitation, for alkaline earth alumina borosilicate glass, a
suitable reaction temperature T will be approximately 675.degree.
C. or slightly less and can be maintained for approximately two
hours. In most cases, the silica glass substrate 10 can be
characterized by a thermal strain point and the inert atmosphere 20
can be heated to a reaction temperature below the thermal strain
point of the silica glass substrate 10. For example, and not by way
of limitation, for glass having a strain point of about 669.degree.
C., the inert atmosphere can be heated to about 660.degree. C.
Reduced reaction temperatures are contemplated for low pressure
reaction chambers.
[0011] The silica glass substrate 10 may comprise any type of
silica-based glass including, but not limited to high purity fused
silica, aerogel glasses, alkaline earth alumina borosilicate
glasses, which may include oxides of boron, phosphorous, titanium,
germanium, zirconium, vanadium, etc., and which may or may not be
fabricated to be free of added arsenic, antimony, barium, and
halides. For the purposes of describing and defining the present
invention, it is noted that reference herein to "high purity fused
silica" is intended to encompass the compositions and purity levels
of high purity fused silica commonly recognized in the art. In the
case of high purity fused silica, it is contemplated that the glass
may be presented as a fusion drawn sheet of glass that can be a
re-drawn, flexible glass sheet for silicon or silicon laminate
substrates for roll-to-roll fabrication.
[0012] Although embodiments of the present disclosure are described
with primary reference to silica-based glasses and the use of Mg as
the metallic gas, embodiments are also contemplated where the
substrate is glass-based, but is not necessarily a silica-based
glass substrate. For example, it is contemplated that alternative
glass substrates may be provided using non-silica glass formers
such as the oxides of boron, phosphorous, titanium, germanium,
zirconium, vanadium, and other metallic oxides. Further, it is
contemplated that a variety of suitable reduction gases can be
utilized without departing from the scope of the present
disclosure. For example, and not by way of limitation, it is
contemplated that the metallic reducing gas may comprise Mg, Na,
Rb, or combinations thereof. In a simplified, somewhat ideal case,
where the metallic gas comprises Mg, the corresponding
stoichiometric reaction with the silica glass substrate is as
follows:
2Mg+SiO.sub.2.fwdarw.Si+2MgO.
Analogous reactions would characteristic for similar reducing
gases.
[0013] In non-stoichiometric or more complex cases, reaction
byproducts like Mg.sub.2Si are generated and the reducing step
described above can be followed by the byproduct removal steps
described herein. To avoid byproduct generation and the need for
the byproduct removal step, it is contemplated that the
stoichiometry of the reduction can be tailored such that the
metallic gas is provided in an amount that is not sufficient to
generate the byproduct. However, in many cases, the composition of
the glass will be such that the generation of additional reaction
byproducts is inevitable, in which case these additional byproducts
can be removed by the etching and thermal byproduct removal steps
described herein.
[0014] To enhance reduction, the substrate 10 can be subject to
microwave or RF exposure while reacting the metallic gas with the
silica glass substrate 10. The metallic gas can be derived from any
conventional or yet to be developed source including, for example,
a metal source subject to microwave, plasma or laser sublimation,
an electrical current, or a plasma arc to induce metal gas
formation. In cases where the metallic gas is derived from a metal
source, it is contemplated that the composition of the metal source
can be varied while reacting the metallic gas with the silica glass
substrate to further enhance reduction.
[0015] Additional defects can be formed in the silica glass
substrate by irradiating the surface of the substrate with
electrons. The resulting defects enable a more facile and extensive
extraction of oxygen by the metallo-thermic reducing gas agent and,
as such, can be used to enhance oxygen extraction by subjecting the
glass substrate to electron beam irradiation prior to the
above-described metallo-thermic reduction processes. Contemplated
dosages include, but are not limited to, dosages from approximately
10 kGy to approximately 75 kGy, with acceleration voltages of
approximately 125 KV. Higher dosages and acceleration voltages are
contemplated and deemed likely to be advantageous.
[0016] As is illustrated schematically in FIG. 2, the metal-oxygen
complex 30 that is formed along the surface of the silica glass
substrate 10 is removed from the surface of the silica glass
substrate 10 to yield a crystalline porous silicon surface portion
forming a porous silicon layer 40. Although the various embodiments
of the present disclosure are not limited to a particular removal
process, it is noted that the metal-oxygen complex 30 can be
removed from the surface of the silica glass substrate 10 by
executing a post-reaction acid etching step. For example, and not
by way of limitation, post-reaction acid etching may be executed in
1M HCl solution (molar HCl:H2O:EtOH ratio=0.66:4.72:8.88) for at
least 2 hours. Depending on the porosity of the glass, some
additional MgO may be trapped inside the glass and additional
etching may be needed for longer periods of time with multiple
flushes of the acidic mixture.
[0017] As is illustrated schematically in FIG. 3, one or more
additional layers 50 can be formed over the crystalline porous
silicon surface portion of the silica glass substrate 10 to yield a
dimensional silica-based structure 100 including the porous silicon
layer 40. Typically, the additional layer 50 comprises a
semiconductor or crystalline overlayer and the porous silicon layer
40 is used as a seed layer for the epitaxial growth or deposition
of the overlayer. It is contemplated that the eptixially grown or
deposited layer may, for example be silicon, germanium, or another
semiconductor or crystalline material.
[0018] In cases where the additional layer 50 comprises a
monocrystalline silicon layer, a microcrystalline silicon layer, a
polycrystalline silicon layer, or an amorphous silicon layer, the
method may further comprise the step of recrystallizing the
additional layer 50 by annealing the layer 50 at a temperature and
duration sufficient to enhance crystallization and increase grain
size in the overlayer. It is contemplated that conventional
annealing configurations as well as localized laser or torch
annealing may be suitable. Typically, the porous silicon layer 40
will increase the degree of crystallization of the epitaxially
grown or deposited silicon layer 50. In the case of polycrystalline
silicon growth, the silicon that is epitaxially grown or deposited
onto the porous silicon on glass template may have grain sizes from
about 10 nm up to tens of microns such as>20 um. For the
purposes of describing and defining the present invention, it is
noted that monocrystalline silicon, also sometimes referred to as
single crystal silicon, is a form in which the crystal structure is
homogenous throughout the material. The orientation, lattice
parameter, and electronic properties are constant throughout the
material. Polycrystalline silicon is composed of many smaller
silicon grains of varied crystallographic orientation.
Microcrystalline silicon, sometimes also known as nanocrystalline
silicon, is a form of porous silicon that is similar to amorphous
silicon, in that it has an amorphous phase. However,
microcrystalline silicon has small grains of crystalline silicon
within the amorphous phase. This is in contrast to polycrystalline
silicon which consists solely of crystalline silicon grains,
separated by grain boundaries.
[0019] Referring to the dimensional silica-based structure 100'
illustrated in FIG. 4, it is noted that, in many cases, the
structure 100' will be formed over an underlying silica glass
substrate 70 that is not high purity fused silica, i.e., a silica
glass substrate including dopants, additives, or other impurities.
For example, and not by way of limitation, alumina borosilicate
glass substrates are the subject of widespread use in the industry.
Other contemplated silica glass substrates include additives such
as boron, phosphorous, titanium, germanium, zirconium, vanadium,
etc. In these cases, it will often be desirable to utilize a
separation layer 60 to inhibit the migration of these impurities
from the underlying glass substrate 70 to remaining portions of the
structure 100'. For example, the separation layer 60 may comprise a
silicon nitride dielectric layer.
[0020] Referring to the silicon-on-insulator thin film transistor
structure 200 illustrated schematically in FIG. 5, where a variety
of additional layers are arranged to form a single crystal
silicon-on-insulator structure, the porous silicon layer 40 is used
as a seed layer for the epitaxial fabrication of the
silicon-on-insulator structure including the porous silicon layer
40. It is contemplated that dimensional silica-based structures
according to the present disclosure can also be arranged to form a
photovoltaic cell 300 (see FIG. 6), a thermoelectric cell, and
other similar structures. It is also contemplated that dimensional
silica-based structures according to the present disclosure can be
arranged to form a silicon-based optoelectric device, e.g., a light
emitting device, a waveguide, a photonic crystal, or a solar cell.
In many of the above-noted embodiments, the structure will be
formed over a silica glass substrate including significant amounts
of dopants, additives or other impurities, like an alumina
borosilicate glass substrate. In these and other cases, it is
contemplated that a separation layer similar to that described
above with reference to FIG. 4 will be incorporated in the
structure.
[0021] In addition, it is contemplated that dimensional
silica-based structures according to the present disclosure can be
arranged to form an environmental interface device, which, for the
purposes of describing and defining the present invention, is a
device that is configured to alter, be altered by, or otherwise
interface with an external environmental component such as air,
water, an external body, etc. For example, and not by way of
limitation, the environmental interface device may be a
micro-reactor, filter media, or a gas sensor, in which case the
porous silicon layer in the active structure of the environmental
interface device would comprise a catalytic, zeolite, or other
active layer of the device. Additional environmental interface
devices are contemplated where the porous silicon layer is
configured as a hydrophobic layer, an anti-fingerprint contact
layer, or a chemically resistant or strength-enhanced surface
layer.
[0022] In some embodiments of the present disclosure, the silica
glass substrate is configured to comprise N-type or P-type dopants
and the oxygen extraction and the metal-oxygen complex removal
steps are tailored to leave significant amounts of dopants in the
crystalline porous silicon surface portion of the silica glass
substrate. These dopants, if present in sufficient amounts, can
contribute dopants to the additional layers formed over the
crystalline porous silicon surface portion of the silica glass
substrate. For example, typical dopants include but are not limited
to Al, P, B, and As. Alternatively, it is contemplated that N-type
or P-type dopants can be introduced into the crystalline porous
silicon surface portion of the silica glass substrate by
conventional diffusion or ion implantation techniques.
[0023] In further embodiments of the present disclosure, it is
contemplated that the silica glass substrate can be provided with a
topical film for controlling the thickness, porosity or crystalline
character of the resulting crystalline porous silicon surface
portion of the silica glass substrate. It is contemplated that
these topical films can be silicates, phosphates, or any glass
former including, but not limited to, the oxides of boron,
phosphorous, titanium, germanium, zirconium, vanadium, and other
metallic oxides. For example, and not by way of limitation, a
topical film can be formed on the glass through atomic layer
deposition (ALD), chemical vapor deposition (CVD) and its variants
(such as PECVD, LPCVD, APCVD), molecular beam evaporation (MBE),
sputter deposition, etc. It is also contemplated that the surface
of the silica glass substrate may be provided with grooves, raised
features or other texturing to yield specific optical or combined
opto-electronic properties, such as optical scattering. It is
further contemplated that the starting substrate glass composition
may be tailored to enhance thermal processing capabilities, e.g.,
JADE.TM. glass contains barium and is stable up to 725.degree. C.
In addition, it is contemplated that the glass composition may be
chosen to enhance optical transparency, polarizability, or shock
resistance.
[0024] In still further embodiments of the present disclosure, it
is contemplated that dimensional silica-based structures can be
densified by coating the crystalline porous silicon surface portion
of the silica glass substrate with an additional glass or metal
oxide layer and reacting a metallic gas with the crystalline porous
surface portion of the glass substrate at the reaction temperature
to yield a densified oxygen substrate. This process can be repeated
a plurality of times with relatively thin, e.g., 10 nm to 300 nm,
glass or metal oxide layers, under the various metallo-thermic
reaction conditions described herein.
[0025] One or more inert blocking layers can be provided over the
silica glass substrate, prior to reacting the metallic gas with the
silica glass substrate, to facilitate overlayer patterning. For
example, and not by way of limitation, a graphite blocking layer
could be used in a patterning step. It is also contemplated that
fabrication methods according to the present disclosure could
incorporate a reducing agent doping step where the silica glass
substrate is pre-treated with a gaseous reducing agent to
infiltrate the surface of the silica glass substrate with the
reducing agent and enhance the reaction of the metallic gas and the
silica glass substrate. For example, the silica glass substrate may
be exposed to pressurized hydrogen and an inert carrier gas in a
Parr vessel for quicker and more complete topical reduction.
[0026] Fabrication methods according to the present disclosure
could also incorporate a post-reaction acid etching step for the
removal of amorphous silicon from the porous silicon, e.g., by HF
etching or other conventional or yet-to-be developed acid etching
protocols. It is contemplated that the post-reaction acid etching
step will, in many cases, yield crystalline porous silicon
characterized by X-ray diffraction spectra dominated by a
preferential <111> crystalline orientation.
[0027] Fabrication methods according to the present disclosure
could further incorporate one or more post-reaction thermal
treatment steps. For example, and not by way of limitation,
substrates including porous silicon layers according to the present
disclosure can be treated in an inert atmosphere at a post-reaction
temperature exceeding the reaction temperature. More specifically,
a substrate processed for 2 hours at 675.degree. C. and etched in
1M HCL for 2 hours can be subject to post-reaction thermal
treatment in Ar for 6 hours at 725.degree. C. In most cases, where
the inert atmosphere is heated to a reaction temperature between
approximately 650.degree. C. and approximately 750.degree. C., the
post-reaction temperature will be above 700.degree. C., e.g.,
between 725.degree. C. and 750.degree. C., and will be maintained
for several hours. In the case of high purity fused silica, the
post-reaction treatment is typically maintained for approximately 6
hours for complete removal of Mg.sub.2Si. For alkaline earth
alumina borosilicate glasses, which may be fabricated to be free of
added arsenic, antimony, barium, and halides, post-reaction
treatment is typically maintained for more than approximately 18
hours and can be executed intermittently at intermediate 6 hour
treatment steps. In cases where the reaction of the metallic gas
with the silica glass substrate additionally forms a
metal-non-oxygen complex along a surface of the silica glass
substrate, the post reaction thermal treatment can be maintained
for a period of time that is sufficient to evaporate the
metal-non-oxygen complex as well.
[0028] For the purposes of describing and defining the present
invention, it is noted that a "dimensional" substrate or a
"dimensional" structure is one where the dimensions of the
substrate or structure have a predefined utilitarian shape and
size, i.e., a shape and size designed for a particular utility.
Dimensional substrates and structures may be fully functional
structures, intermediate structures, partially functional
structures, precursor substrates or structures, or seed substrates
or structures for the formation of intermediate, partially or fully
functional structures. Dimensional substrates and structures can,
for example, be distinguished from powders, grains, or other types
of coarse or fine particulate matter of undefined, pseudo-random,
or otherwise indeterminate shape. Dimensional substrates and
structures can also be distinguished from nanostructures or
nanoparticles. Examples of dimensional substrates and structures
include, but are not limited to seed substrates or sheet layers for
structure growth, thin film transistors, photovoltaic cells,
thermoelectric cells, light emitting devices, waveguides, photonic
crystals, solar cells, and other similar structures. In addition,
it is noted that porous silicon is a form of the chemical element
silicon having a distribution of nanoscale sized voids in its
microstructure, rendering a relatively large surface to volume
ratio, in some cases greater than 500 m.sup.2/g. It is also noted
that recitations herein of "at least one" component, element, etc.,
should not be used to create an inference that the alternative use
of the articles "a" or "an" should be limited to a single
component, element, etc.
[0029] It is noted that terms like "preferably," "commonly," and
"typically," when utilized herein, are not utilized to limit the
scope of the claimed invention or to imply that certain features
are critical, essential, or even important to the structure or
function of the claimed invention. Rather, these terms are merely
intended to identify particular aspects of an embodiment of the
present disclosure or to emphasize alternative or additional
features that may or may not be utilized in a particular embodiment
of the present disclosure.
[0030] For the purposes of describing and defining the present
invention it is noted that the term "approximately" is utilized
herein to represent the inherent degree of uncertainty that may be
attributed to any quantitative comparison, value, measurement, or
other representation. The term "substantially" is also utilized to
represent the degree by which a quantitative representation may
vary from a stated reference without resulting in a change in the
basic function of the subject matter at issue.
[0031] Having described the subject matter of the present
disclosure in detail and by reference to specific embodiments
thereof, it is noted that the various details disclosed herein
should not be taken to imply that these details relate to elements
that are essential components of the various embodiments described
herein, even in cases where a particular element is illustrated in
each of the drawings that accompany the present description.
Rather, the claims appended hereto should be taken as the sole
representation of the breadth of the present disclosure and the
corresponding scope of the various inventions described herein.
Further, it will be apparent that modifications and variations are
possible without departing from the scope of the invention defined
in the appended claims. More specifically, although some aspects of
the present disclosure are identified herein as preferred or
particularly advantageous, it is contemplated that the present
disclosure is not necessarily limited to these aspects.
* * * * *