U.S. patent application number 15/630095 was filed with the patent office on 2017-11-23 for apparatus and method for programmable spatially selective nanoscale surface functionalization.
The applicant listed for this patent is Plasmotica, LLC. Invention is credited to Waqas Khalid, Faisal Saleh, Nedal Saleh.
Application Number | 20170338080 15/630095 |
Document ID | / |
Family ID | 60326623 |
Filed Date | 2017-11-23 |
United States Patent
Application |
20170338080 |
Kind Code |
A1 |
Saleh; Nedal ; et
al. |
November 23, 2017 |
APPARATUS AND METHOD FOR PROGRAMMABLE SPATIALLY SELECTIVE NANOSCALE
SURFACE FUNCTIONALIZATION
Abstract
A spatially selective surface functionalization device
configured to generate a pattern of micro plasmas and functionalize
a substrate surface may include: a pattern management system, a
patterning head, and a gas delivery system, wherein the gas
delivery system provides a primed gas mixture for forming a plasma
between the patterning head and a target substrate below the
patterning head. A patterning head may generate a distribution of
micro plasmas from individual directed beams of electrons with
spatial separation. A pattern management system may store and
manipulate information about a pattern of surface functionalization
and generate instructions for regulating a distribution of micro
plasmas that functionalize a substrate surface.
Inventors: |
Saleh; Nedal; (Woodbridge,
CT) ; Khalid; Waqas; (Woodbridge, CT) ; Saleh;
Faisal; (Woodbridge, CT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Plasmotica, LLC |
Woodbridge |
CT |
US |
|
|
Family ID: |
60326623 |
Appl. No.: |
15/630095 |
Filed: |
June 22, 2017 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
15600470 |
May 19, 2017 |
|
|
|
15630095 |
|
|
|
|
62338955 |
May 19, 2016 |
|
|
|
62338996 |
May 19, 2016 |
|
|
|
62339002 |
May 19, 2016 |
|
|
|
62339008 |
May 19, 2016 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B01F 13/0064 20130101;
B01J 19/0093 20130101; C12Q 1/6837 20130101; H01J 37/32366
20130101; H01J 2237/327 20130101; B01L 3/502753 20130101; B01L
2400/0688 20130101; H01J 37/3233 20130101; B01L 2300/0654 20130101;
H01J 37/32733 20130101; B01L 2200/06 20130101; B01L 2300/0645
20130101; H01J 37/3244 20130101; B01L 3/5027 20130101; B01L
3/502715 20130101; B01L 2300/0681 20130101; B01J 2219/00781
20130101; B01L 2300/1827 20130101; H01J 37/3299 20130101; H01J
2237/334 20130101; B01J 2219/00869 20130101; B01L 3/5023 20130101;
G01N 1/38 20130101 |
International
Class: |
H01J 37/32 20060101
H01J037/32 |
Claims
1. A device for spatially selective surface functionalization,
comprising: a pattern management system; a patterning head; and a
gas delivery system; wherein the patterning head is configured to
generate a first distribution of micro plasmas against a top
surface of a substrate according to a pattern stored in the pattern
management system, wherein the first distribution of micro plasmas
is formed in a gas mixture at least partially provided by the gas
delivery system, the first distribution of micro plasmas
corresponding to a first portion of the pattern.
2. The device of claim 1, further comprising an instruction
generator of the pattern management system connected to the
patterning head and to the position regulation system by a
communication bus, wherein the instruction generator is configured
to generate at least a first instruction and a second instruction,
and wherein the patterning head is configured to generate the first
distribution of micro plasmas at a first position on the top
surface of the substrate according to the first instruction, and a
second distribution of micro plasmas at a second position on the
top surface of the substrate according to the second instruction,
wherein the second distribution of micro plasmas corresponds to a
second portion of the pattern, the second portion being different
from the first portion, and wherein the first position is different
from the second position.
3. The device of claim 1, wherein at least one of the first or
second distribution of micro plasmas is formed from an array of
electron emission structures of the electron source.
4. The device of claim 3, wherein at least a first electron
emission structure at a first location of the array and at least a
second electron emission structure at a second location of the
array are configured to be activated independently according to at
least one instruction.
5. The device of claim 2, wherein the electron emission structures
comprise pyroelectric electron (PE) emission structures.
6. The device of claim 2, wherein the electron emission structures
comprise thermionic electron emission structures.
7. The device of claim 2, wherein the electron emission structures
comprise field emission (FE) electron emission structures.
8. The device of claim 4, further comprising an electron emission
structure activation element configured to receive at least one
instruction and to activate or deactivate electron emission
structures at locations in the array according to the at least one
instruction.
9. The device of claim 2, further comprising a pattern buffer
configured to store at least a portion of the pattern, the
instruction generator being configured to generate the instructions
based on the stored portion of the pattern.
10. The device of claim 5, further comprising an accelerating
structure and a membrane of the electron source, wherein the
accelerating structure is configured to direct a beam of electrons
from the at least one electron emission structure at a location of
the array toward the membrane, and wherein the membrane is
configured to allow passage of the directed beam of electrons
through the membrane into a working volume between the patterning
head and the top surface of the substrate.
11. The device of claim 9, further comprising a voltage regulator
configured to apply a positive voltage to the accelerating
structure.
12. The device of claim 10, wherein the membrane is reinforced to
withstand a pressure differential across the membrane between the
first membrane face and the second membrane face.
13. The device of claim 1, wherein the gas system comprises at
least one orifice separate from the patterning head.
14. The device of claim 1, wherein the gas system comprises at
least one orifice configured to supply an atomized liquid to a
working volume between the patterning head and a substrate.
15. The device of claim 7, further comprising a vacuum source
configured to form a pressure differential across the membrane,
wherein the working volume contains the gas mixture at a first
pressure and an interior of the electron has a second pressure
smaller than the first pressure.
16. The device of claim 3, wherein the plurality of electron
emission structures include are conductive structures selected from
the group consisting of nano rods, nanowires, carbon nanotubes,
fullerene-like structures, tunneling cold field emitter cathodes,
and pyroelectric material cathodes.
17. The device of claim 15, wherein the plurality of electron
emission structures includes conductive materials selected from the
group consisting of silicon, silicon carbide, and carbon.
18. The device of claim 3, wherein the electron emission structure
includes a diode structure.
19. The device of claim 1, wherein the electron emission structure
includes a triode structure.
20. A method of modifying a surface with a plasma, the method
comprising: energizing a first set of individually addressable
electron emission structures in an electron source, the electron
source having a membrane with a first surface and a second surface;
creating a blend of gases in a working volume adjacent to the
second surface of the membrane, the second surface being on an
outer surface of the electron source; accelerating electrons from
the first set of individually addressable electron emission
structures towards the membrane; forming a first set of micro
plasmas where the accelerated electrons from the first set of
individually addressable electron emission structures intersects
the blend of gases; and adjusting a distance between a substrate
and the second surface such that the first set of micro plasmas
intersects a top surface of the substrate at a first location.
21. The method of claim 19, further comprising energizing a second
set of individually addressable electron emission structures to
form a second set of micro plasmas that intersect the top surface
of the substrate at a second location, wherein the first set of
micro plasmas has a first distribution of intersection points with
the top surface, the second set of micro plasmas has a second
distribution of intersection points with the sop surface points,
and the second distribution is different from the first
distribution.
22. The method claim 20, wherein, upon forming the second set of
micro plasmas, functionalization of the top surface at the first
distribution of intersection points with the top surface remains
unchanged within an overlap area of the top surface, the first
distribution of intersection points having a first perimeter on the
top surface, the second distribution of intersection points having
a second perimeter on the top surface, and the overlap area falling
within the first perimeter and the second perimeter.
23. The method of claim 19 further comprising modifying a set of
functional groups on the top surface of the substrate at the first
distribution of intersection points or the second distribution of
intersection points, and wherein the top surface outside the first
and second distributions of intersection points does not undergo
modifying a set of functional groups.
24. The method of claim 20, further comprising modifying the first
distribution of intersection points into the second distribution of
intersection points while first set of micro plasmas intersects the
top surface of the substrate, upon displacement of the substrate
beneath the electron source.
25. A method of making a plasma device having an electron source,
comprising: forming, in the electron source, an array of
individually addressable electron emission structures on an chip;
placing, in the electron source, an electron accelerating structure
between the chip and a target substrate; interconnecting the array
of individually addressable electron emission structures with a
power supply and the electron accelerating structure; placing, in a
wall of the electron source, a membrane configured to pass a
directed beam of electrons; positioning a nozzle of a gas delivery
system to deliver a flow of gas into a working volume between the
electron source and the target substrate; and connecting a
controller element to the power supply configured to regulate an
electrical potential between the array of individually addressable
electron emission structures and the electron accelerating
structure.
26. A arrangement of materials for generating spatially confined
plasma beams, wherein the arrangement comprises of, an array of
individually addressable nanostructures on a substrate, an
accelerating structure placed adjacent to the nanostructures, an
electrical connection between the nanostructures, a power supply,
and the accelerating structure, a membrane adjacent to the
accelerating structure, wherein the membrane has a first face and a
second face, at least one nozzle near the second face of the
membrane, wherein the nozzle allows for introducing gases forming a
primed atmosphere near surface of the second face of the membrane,
wherein when a potential difference is applied between the
accelerating structure and the nanostructure array at least one
directional electron beam is generated, wherein the directional
electron beam penetrates through the membrane entering from the
first face of the membrane and leaving through the second face of
the membrane, wherein when the directional electron beam strikes
the primed atmosphere on the surface of the second face of the
membrane a plasma beam is formed.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present patent filing is a continuation of U.S. patent
application Ser. No. 15/600,470, titled APPARATUS AND METHOD FOR
PROGRAMMABLE SPATIALLY SELECTIVE NANOSCALE SURFACE
FUNCTIONALIZATION, filed 19 May 2017, which claims the benefit of
U.S. Provisional Patent Application 62/338,955, titled APPARATUS
AND METHOD FOR PROGRAMMABLE SPATIALLY SELECTIVE NANOSCALE SURFACE
FUNCTIONALIZATION, filed 19 May 2016; U.S. Provisional Patent
Application 62/338,996, titled PUMP-FREE MICROFLUIDIC ANALYTICAL
CHIP, filed 19 May 2016; U.S. Provisional Patent Application
62/339,002, titled PUMP-FREE MICROFLUIDIC ANALYTICAL SYSTEMS, filed
19 May 2016; and U.S. Provisional Patent Application 62/339,008,
titled STAND ALONE PUMP-FREE MICROFLUIDIC ANALYTICAL CHIP DEVICE,
filed 19 May 2016. The content of each of these earlier filed
patent applications is hereby incorporated by reference in its
entirety.
FIELD OF THE INVENTION
[0002] The invention relates generally to methods and apparatus for
performing modification of surfaces of materials. Modification of
surfaces may include modifying form and structure of surfaces and
modifying the chemical composition of surfaces. Surface
modification may be performed using a plasma.
BACKGROUND OF THE INVENTION
[0003] The present disclosure relates to a device for forming a
plasma to modify surface chemistry or functionalization of a
material after exposure of the material to the plasma. Surface
chemistry modification may include modifying the hydrophobicity of
a surface, modifying a dimension of the surface, modifying an
electrochemical characteristic of a material, modifying an optical
characteristic of a material, or modifying a dimension of modified
area of a surface.
SUMMARY OF THE INVENTION
[0004] The invention addressing these and other drawbacks relates
to methods, apparatuses, and/or systems for prioritizing retrieval
and/or processing of data over retrieval and/or processing of other
data.
[0005] Aspects of the present disclosure relate to a device for
spatially selective surface functionalization, comprising a pattern
management system, a patterning head, and a gas delivery system,
wherein the patterning head is configured to generate a first
distribution of micro plasmas against a top surface of a substrate
in a gas mixture at least partially provided by the gas delivery
system. The distribution of micro plasmas may be according to a
pattern stored in the pattern management system, according to a
first portion of the pattern.
[0006] Aspects of the present disclosure relate to a method for
modifying a surface with a plasma. The method includes operations
of energizing a first set of individually addressable electron
emission structures in an electron source, the electron source
having a membrane with a first surface and a second surface; and
creating a blend of gases in a working volume adjacent to the
second surface of the membrane on an outer surface of the electron
source. The method also includes operations of accelerating
electrons from the first set of individually addressable electron
emission structures towards the membrane, forming a first set of
micro plasmas where the accelerated electrons from the first set of
individually addressable electron emission structures intersects
the blend of gases, and adjusting a distance between a substrate
and the second surface such that the first set of micro plasmas
intersects a top surface of the substrate at a first location.
[0007] Aspects of the present disclosure relate to a method of
making a plasma device having an electron source that comprises
operations of forming, in the electron source, an array of
individually addressable electron emission structures on an chip,
placing, in the electron source, an electron accelerating structure
between the chip and a target substrate, and interconnecting the
array of individually addressable electron emission structures with
a power supply and the electron accelerating structure. The method
also includes operations of placing, in a wall of the electron
source, a membrane configured to pass a directed beam of electrons,
positioning a nozzle of a gas delivery system to deliver a flow of
gas into a working volume between the electron source and the
target substrate, and connecting a controller element to the power
supply configured to regulate an electrical potential between the
array of individually addressable electron emission structures and
the electron accelerating structure.
[0008] These and other features of the present invention, as well
as the methods of operation and functions of the related elements
of structure and the combination of parts and economies of
manufacture, will become more apparent upon consideration of the
following description and the appended claims with reference to the
accompanying drawings, all of which form a part of this
specification, wherein like reference numerals designate
corresponding parts in the various figures. It is to be expressly
understood, however, that the drawings are for the purpose of
illustration and description only and are not intended as a
definition of the limits of the invention. As used in the
specification and in the claims, the singular form of "a", "an",
and "the" include plural referents unless the context clearly
dictates otherwise. In addition, as used in the specification and
the claims, the term "or" means "and/or" unless the context clearly
dictates otherwise. Further, the terms "on", "over", "above",
"below", "beneath", and "under" may generally be used to indicate
the position of portions of embodiments described herein along an
axis through the portions, without an absolute reference to a
particular direction. Thus, one portion may be "on" or "above" or
"below" or "under" another, even when the portions are rotated with
respect to an external frame of reference.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The invention is illustrated by way of example, and not by
way of limitation, in the figures of the accompanying drawing and
in which like reference numerals refer to similar elements.
[0010] FIG. 1 depicts a cross-sectional diagram of an embodiment of
a nanoscale surface functionalization device;
[0011] FIG. 2 depicts a cross-sectional view of an embodiment of
apparatus for generating micro plasmas using electron emission
structures;
[0012] FIG. 3 depicts a cross-sectional view of an embodiment of a
chip having electron emission structures;
[0013] FIG. 4 depicts a cross-sectional analysis of an embodiment
of an apparatus having electron emission structures;
[0014] FIG. 5A depicts a cross-sectional view of an embodiment of a
substrate patterned by an electron-emission patterning head by a
maskless patterning method;
[0015] FIGS. 5B-5E depict patterns of micro-plasmas generated by a
electron-emission patterning head to form the embodiment of FIG.
5A;
[0016] FIG. 6 depicts a flow diagram of an implementation of a
method of generating a patterned array of micro-plasmas;
[0017] FIG. 7 depicts a flow diagram of an implementation of a
method for modifying surface functionalization of a material;
[0018] FIG. 8 depicts a plasma device having an array of emission
structures of an electron source substrate; and
[0019] FIG. 9 depicts an embodiment of a plasma device having a
plurality of pyroelectric emission structures.
[0020] Methods, embodiments, implementations, and apparatus
described herein are merely representative of the invention claimed
herein. Accordingly, other methods, embodiments, implementations,
and apparatus may also fall within the scope of the present
disclosure after being envisioned by a person of ordinary skill in
the art.
DETAILED DESCRIPTION OF THE INVENTION
[0021] Surface modification during a manufacturing processes can
impart new properties to materials. One method of surface
modification includes using a plasma to modify a chemical structure
of the surface. Surface modification using plasma tools can provide
a rapid, low cost method of changing the characteristics of a
material surface while retaining characteristics of the bulk of the
material. For example, a glass or plastic substrate material may
have desirable bulk characteristics such as optical transparency,
structural rigidity, or flexibility, but the surface of the
substrate material may not have a desired physical or chemical
property such as hydrophobicity, or an ability to interact with
components of a solution applied to the substrate material.
Plasma-based surface modification may alter the characteristics of
a surface of the substrate material by breaking chemical bonds at
the material surface. Broken chemical bonds at a material surface
may react with one or more plasma species. Thus, the chemical
structure of the surface may be modified and the surface may be
functionalized. After functionalization, a surface of a material
may have a different characteristic (such as a degree of
hydrophobicity hydrophilicity) than before functionalization.
Further, a functionalized surface may be able to bind to chemical
compounds or biomaterials used for chemical testing, in vitro
diagnostics, or point of care diagnostics.
[0022] In an exemplary embodiment, a substrate material may include
a top layer of poly-methyl-methacrylate (PMMA). PMMA may be
modified or functionalized by exposure of the PMMA surface to
plasma containing oxygen atoms. The plasma may break surface
molecular bonds, and oxygen atoms from the plasma may react with
the PMMA substrate material without degrading the bulk of the PMMA
substrate material. Thus, a number of carbon-oxygen bonds,
including both C--O single bonds and C.dbd.O double bonds, may be
greater on functionalized PMMA surface after plasma exposure than
on the original PMMA surface prior to plasma exposure. New
functional groups, such as the C--O single bonds and the C.dbd.O
double bonds described above, may be involved in further
functionalization steps to bind other compounds to a substrate
material surface for analytical testing purposes or to receive
chemical treatment to make materials more biocompatible. Surface
modification or surface functionalization may be relevant to
developing or manufacturing analytical testing devices, diagnostic
probes, or medical devices.
[0023] Among the diagnostic probes and analytical devices that may
be developed using plasma processing are microfluidic devices that
direct the flow of small volumes of fluid through channels toward
locations in the microfluidic device that are configured to perform
chemical, electrical, or optical tests on the fluid. Microfluidic
device manufacturing may be include one or more masking steps.
Masking may be performed on a substrate surface for patterning
purposes. Masking and functionalization may be performed on a
substrate to induce interaction between the substrate surface
(e.g., the unmasked portion) and a fluid analyte on the surface.
Masking may be performed to modify a behavior characteristic of a
fluid analyte (e.g., evaporation reduction by modifying surface
tension of the fluid). Masking processes associated with
traditional methods of surface functionalization may be performed
to protect masked portions of a substrate material from
surface-modifying processes while exposed portions of the substrate
material surface may undergo functionalization. While masking of a
surface may be advisable during manufacturing of a microfluidic
device, processing conditions for removing a mask material may harm
a previously-functionalized area of a surface. For example, a
surface may be masked by applying a layer of photoresist to the
material surface, followed by an exposure process and a developing
process, wherein a pattern is formed in the photoresist layer.
Plasma may be applied to the substrate to functionalize the exposed
portion of the substrate, while the masked portion of the substrate
is protected by the photoresist/However, removal of the photoresist
layer, typically performed by applying a solvent (such as acetone
or alcohol) to the photoresist may reduce a degree of
functionalization of the exposed portion of the substrate. In some
embodiments, compounds used to remove photoresist may also remove
the functionalization of the material surface. Further, compounds
that may remove photoresist or other masking materials may be
incompatible with biological materials applied to a surface, or
with biological substrate materials. Organic materials or polymeric
materials may also be adversely affected upon exposure to
mask-removing chemistries.
[0024] Traditional plasma-based surface modification methods may
involve high temperatures in plasmas and on surfaces of the
substrate, may involve large currents, or may have high ion impact
energies or particle velocities. In some embodiments, biomaterials
such as tissues, membranes, or enzymes, may not retain desirable
characteristics upon exposure to conditions associated with
traditional plasmas, including high electron energy, high current,
or high temperatures.
[0025] Substrate masking may also involve additional cost and
manufacturing complexity to perform. For example, masking may
involve additional steps in order to clean substrates, apply mask
materials, pattern mask materials, and remove mask materials after
a chemical or plasma surface modification is performed. Increased
cost may result from at least one of additional time, additional
materials, additional manufacturing equipment associated with
masking, or additional cleaning steps during manufacturing.
Further, additional handling and storage steps for substrates may
increase facilities cost and provide opportunities for substrates
to be damaged during a manufacturing process, lowering overall
yield of the devices being manufactured.
[0026] In an embodiment of the present disclosure, instead of
masking a substrate surface for patterning purposes, one may
generate a plasma that has spatial resolution determined by the
spatial characteristics of the electron beams. In a non-limiting
embodiment, a plurality of directional electron beams with spatial
separation may make a pattern of micro plasmas corresponding to the
pattern of the directional electron beams, retaining at least some
of the spatial separation of the pattern. According to an
embodiment, the pattern of micro plasmas may be modified during
operation of a plasma device by regulating a pattern of electron
beams that form the micro plasmas. During a surface
functionalization process, a pattern of electron beams/micro
plasmas may be regulated to bypass areas of the substrate surface
that may have already been functionalized by a plasma device or
some other process. Patterning a substrate using an array of micro
plasmas generated by a patterning head may lead to increased
throughput processed devices because the plasma-processing volume
(the working volume) has a larger cross-sectional area against a
surface of a substrate than single electron-beam processing
equipment.
[0027] It may be desirable to reduce cost of manufacturing objects
with modified surfaces or functionalized surfaces by directly
making patterns of surface functionalization on a substrate, using
a plasma device with spatial separation between electron beams (or,
between micro plasmas). A distribution of micro plasmas may involve
gaps between individual micro plasmas, or between groups of micro
plasmas. Gaps in a distribution or pattern of micro plasmas may
correspond to positions, between the micro plasmas, where a surface
may have undergone previous functionalization. Gaps in the
distribution of micro plasmas may preserve previous surface
functionalization during a subsequent surface functionalization
process. A distribution of micro plasmas may undergo changes
according to a position of the patterning head over a substrate
being functionalized. The pattern may undergo changes according to
a number of surface functionalization steps that may already have
been performed in an area of a substrate surface.
[0028] Embodiments of an apparatus to perform spatially-selective
nanoscale surface functionalization may include: an electron source
having a grid or an array of beam sources, a gas supply system to
regulate a chemical composition of a working volume where a plasma
can form, and a movement system to regulate a position and
alignment of a substrate with regard to the patterning head of a
plasma device. Some embodiments of the apparatus may also include a
gas delivery system wherein a gas or liquid, or combinations
thereof, may be added to a working volume in order to modify the
gas composition (and, therefore, a type of surface
functionalization.
[0029] Spatial resolution of micro plasmas may decrease the number
of manufacturing steps involved in generating surface-modified or
surface-functionalized devices, increasing device manufacturing
throughput. Spatial resolution of micro plasmas may enable plasma
modification and functionalization at pressures above the range of
previously available plasma modification devices (e.g., at or
around atmospheric, or 1 bar of pressure. For example, during a
manufacturing process, a plasma-based surface modification device
may pattern a substrate by positioning a patterning head of the
plasma device in proximity to a substrate and performing
plasma-based service modification at atmospheric pressure, or at
pressures ranging from about 0.5 to 2 atmosphere (atm), without
damage to the substrate during a modification process. The ability
to operate a patterning head of a plasma device at approximately
atmospheric pressure may greatly reduce manufacturing time because
a substrate may be modified without placing the substrate in a
pressure chamber having reduced or elevated pressures, reducing the
need for chamber palm down or chamber purging times.
[0030] In some embodiments, a patterning device may be operated
with an adjustable gas mixture and or plasma composition, at
approximately atmospheric pressure, by directing a flow of gas or a
flow of atomized or evaporated liquid, into a working volume
between a portion of the patterning device where the plasma is
generated and an area of a substrate where service modification is
being performed. By adjusting the chemical composition of the
gaseous mixture before plasma generation and during plasma
generation, the chemistry of a substrate surface may be regulated
to generate predetermined distributions of surface
functionalization according to the chemical composition of the
plasma.
[0031] A patterning head having spatial control of the plasma above
a surface during a modification process may involve generating a
plurality of micro-plasmas arranged in an array between the
patterning head and the surface of the substrate. The micro-plasmas
may remain discrete, or may merge to form larger plasmas. The
working volume between a patterning head and a substrate being
modified during a manufacturing process may contain a plurality of
volumes, each of which may contain an individually adjustable
micro-plasma. Thus, each volume may have a micro plasma that is
turned off or turned on independent of other volumes with other
micro-plasmas (e.g., the micro plasmas, or the array loci at which
micro plasmas may be generated, may be individually addressable).
Thus, spatial control of the plasma in the working volume may
afford greater manufacturing flexibility during modification of the
process to functionalized only a desired and controllable portion
of a substrate while leaving other options of the substrate
unmodified by the present plasma modification process.
[0032] A patterning head may include an electron source that
generates directional beams of electrons. An electron source may
include one or more emission structures that generate electrons
that can form directed beams. Emission structures may include
thermionic emission structures, field-emission (FE) structures, or
pyroelectric (PE) structures. Thermionic emission structures may
generate beams of electrons after the structures are heated in the
present of a strong external electrical field that can accelerated
the emitted electrons from the thermionic emission structures
toward a substrate surface outside a patterning head. Field
emission structures may involve electron emission in the presence
of a strong electrical field (stronger than for thermionic emission
structures), but at lower temperatures for the emission structures
(as compared to thermionic emission structures). Pyroelectric (PE)
structures may generate electron beams following rapid thermal
cycling of PE structures with large thermal gradients, in the
presence of an accelerating voltage that is significantly smaller
than the accelerating voltage for either thermionic emission or FE
emission.
[0033] Electron emission structures may occur singly, or in
clusters, at a location in an electron source. In an embodiment,
electron emission structures may occur in arrays, where each locus
of the array, whether populated by a single electron emission
structure or by a cluster of electron emission structures, may be
individually addressable (e.g., each locus may be regulated
independent of each other locus of the array). Thermionic electron
emission structures may consume more energy to generate an electron
beam than do FE or PE electron emission structures because of the
elevated operational temperatures. FE electron emission may use an
intermediate amount of energy, resulting from the strong electrical
fields applied within the patterning head, to trigger electron beam
formation. PE electron emission may use less energy than either
thermionic electron emission or FE electron emission because
electrons collect on emission structures and may be accelerated
with lower voltages than for thermionic emission or FE emission. FE
and PE nanostructures may be more compatible with organic
materials, polymeric materials, or biomaterials than traditional
methods of producing plasma to modify a surface.
[0034] Electron sources with field emission nanostructures tend to
operate at much lower temperatures than either thermionic or DBD
plasma sources, to the extent that the process is dubbed "cold
emission". Electron emission structures, as disclosed herein, may
generate directional electron beams without use of magnetic lenses
to focus and direct the beam of electrons onto a substrate. A
patterning head without magnetic lenses may be considerably smaller
a plasma device that uses magnetic lenses to focus a beam. By
omitting magnetic lenses from a structure containing an electron
source, the manufacturing cost of the plasma device may be
considerably reduced. Individually addressable electron emission
structures may result in formation of micro plasmas in a working
volume outside of a patterning head of a plasma device when a
directed electron beams strikes a primed atmosphere. Directed beams
of electrons may be accelerated by an electron accelerating
structure into the primed atmosphere with an energy associated with
the potential difference between the electron emission structure
and the electron accelerating structure. Directed beams of
electrons may be focused by optional beam control apertures that
expand or compress a distribution of the directed beams around a
center point of a path between the electron source and the
substrate
[0035] FIG. 1 depicts a cross-sectional diagram of an embodiment of
a spatially selective surface functionalization device, or a plasma
device, 100. While the embodiment described herein may be
representative of other embodiments, not all features of the plasma
device 100 may be present in each other embodiment of the present
disclosure that is described herein. Conversely, other embodiments
of a plasma device may have additional elements that are not
described in the embodiment of FIG. 1, but may still contain
aspects of the present disclosure sufficient to fall within the
scope of said disclosure.
[0036] Plasma device 100 may contain a movement system (or stage)
102, on which a substrate 104 may be situated for surface
functionalization, located below a patterning head 106. During
operation of plasma device 100, patterning head 106 may generate
plasma 108 in a working volume 110 between a window 112 of the
patterning head 106 (through which a directed beam of electrons 114
may pass to trigger plasma formation) and the substrate 104. During
operation of plasma device 100, the patterning head 106 may be
situated a working distance 115 above a top surface of substrate
104. Working distance may range from about 10-micron to a 1
millimeter, according to embodiments of the present disclosure. In
some embodiments, a working distance may increase or decrease
during surface functionalization of the substrate according to a
plasma density within the working volume, according to the size of
the pattern being formed on the substrate, or according to a
composition of the plasma during surface functionalization.
[0037] The patterning head 106 of plasma device 100 may include an
aligner 116 configured to adjust pitch (parallelism between
patterning head and substrate) and orientation (provides rotational
control of the substrate beneath the patterning head) of the
patterning head 106 with regard to the movement system 102 and a
substrate 104 located thereon. Movement system 102 may be
configured to adjust a lateral position of the patterning head 106
and any substrate thereon with regard to the patterning head 106.
Movement system 104 may be configured to move continuously, or to
move incrementally, below the patterning head 106. Incremental
movement of the substrate below the patterning head may be
beneficial for functionalizing discrete blocks of substrate
material on a top surface of the substrate, where the blocks or
regions of the top surface do not contain structures that extend
continuously between adjoining blocks. Continuous movement of the
movement system, and the substrate material, below the patterning
head may be beneficial for functionalizing, on a top surface of the
substrate, patterns that have continuous extensions across borders
of adjoining blocks or regions of a substrate top surface.
According to some embodiments, functionalizing a substrate material
top surface may involve a process of gradual modification of a
distribution of micro plasmas in the working volume between the
patterning head and the substrate. According to some embodiments,
functionalizing a substrate material top surface may involve
forming a first distribution of micro plasmas within a working
volume, extinguishing the micro plasmas, adjusting a position of
the patterning head over the substrate, and re-ignition of a
distribution of micro plasmas at a second position of the
patterning head at a second position above the substrate.
[0038] Micro plasmas may be formed in working volume 110 between
the patterning head 106 and the substrate 104 by a directed beam of
electrons 114 emitted by an electron source 118 located in a cavity
120 of an electron source housing 122. A membrane 124 may be
located between electron source 118 and the working volume 110. An
electron accelerating structure (or, accelerating structure) 126
may be located in a plane below a bottom surface of the electron
source 118. Having the electron source 118 positioned "above" the
electron accelerating structure 126 may allow the electrons
generated by the electron source 118 to be accelerated by a
positive voltage on the electron accelerating structure 126 such
that the electrons achieve a desired electron energy (measured in
electron volts, or eV) as the electrons pass through the membrane
124 and the window 112 before striking atoms and molecules in the
working volume to trigger plasma formation.
[0039] According to embodiments, electron source 118 may have a
plurality of individually addressable electron emission structures
located therein, each capable of generating a beam of electrons
that may be accelerated toward the membrane 124 and window 112 into
working volume 110.
[0040] Electron accelerating structure 126, electron source 118,
aligner 116, and movement system 102 may receive electrical power
from a power supply 128 over electrical connections 130. Electron
accelerating structure 126 may receive an electrical voltage
configured to attract electrons from electron source 118 out of
electron source 118 and toward working volume 110 and substrate
104. According to some embodiments, an electron accelerating
structure may operate with an electrical voltage less than an
electrical voltage ranging from about 1 kV to about 50 kV, such
that electrons exiting an electron source may have an electron
energy ranging from about 1 keV to about 50 keV. An electron
accelerating structure may have a coating of thin films to prevent
discharging between the electron accelerating structure and
components of the plasma device, including the electron source and
electron emission structures located therein. An electron
accelerating structure may be made of one or more metals, or layers
of metals, or alloys of multiple metals, such as copper, aluminum,
tungsten, titanium, or platinum.
[0041] A plasma device may have a control element 132 (or a pattern
management system) configured to handle information regarding the
relative positions of movement system 102, substrate 104, and
aligner 116, as well as regulating information about the pattern
being functionalized on a top surface of the substrate and the
formation of the plasma, or micro plasmas, in the working volume
110 during surface modification and/or functionalization. Control
element 132 may include a communication bus 134, a pattern
repository 136, a pattern buffer 138, a emission structure
activation element 140, and an instruction generator 142. Control
element 132, or the subcomponents of control element 123, including
emission structure activation element 140, may be programmable to
convert a pattern, or a portion of a pattern, into a dynamically
updated pattern of electron beams and micro plasmas during
patterning head operation. Communication bus 134 may interconnect
pattern repository 136, pattern buffer 138, emission structure
activation element 140, and instruction generator 142 to each other
and to aligner 116, electron source 118, and to movement system 102
in order to facilitate regulation of substrate position, alignment,
or orientation, and to regulate formation, adjustment, or
extinguishing of plasmas or micro plasmas below patterning head 106
in working volume 110.
[0042] Pattern repository 136 may be configured to receive, over a
data connection or input/output port, information regarding a
pattern to be formed during a surface functionalization process on
a top surface of substrate 104. The pattern may include information
regarding the boundaries and shapes of areas or regions on a
substrate top surface, the type of functionalization that is
intended for each area or region on the substrate top surface, and
the processing conditions (including plasma composition, electron
energy, plasma density, working distance, exposure time, and micro
plasma pattern regulation parameters) that can produce a region of
surface functionalization on the substrate top surface.
[0043] Pattern buffer 138 may include a storage medium such as DRAM
(dynamic random access memory), a hard disk drive, a solid state
drive, or some other form of volatile or non-volatile storage
medium where information regarding a portion of one or more
patterns stored in the pattern repository 136 may be transferred
and manipulated in order to perform a surface functionalization
process. Information regarding the portion of one or more patterns
in a pattern repository may be transferred from a pattern
repository to a pattern buffer for manipulation and communication
to an instruction generator 142. Further, information regarding the
completion status of surface functionalization of a substrate, or a
portion thereof, may be stored in a pattern buffer and communicated
back to the pattern repository in order to facilitate transfer from
the pattern repository to the pattern buffer of another portion of
one or more patterns.
[0044] Instruction generator 142 may be connected to pattern buffer
138 over communication bus 134 in order to receive a portion of the
information regarding a portion of one or more patterns stored in
the pattern buffer. Instruction generator 142 may be programmable,
configured to analyze the information and to generate, based on the
information regarding the pattern, and on previous, present, or
upcoming processing conditions for surface functionalization, on
the material of the substrate 104, on the progress in
functionalizing a surface of the substrate with the pattern, and on
a position of the substrate with regard to the patterning head 106,
instructions for performing current or upcoming surface
functionalization steps. According to an embodiment, the
instructions may include instructions on a rate of motion of the
substrate below the patterning head, instructions on modifying a
working distance between the patterning head and the substrate,
instructions about modifying a composition of the gas mixture in
the working volume, instructions about retaining a distribution of
micro plasmas within the working volume, or about modifying a
distribution of micro plasmas, instructions about modifying an
accelerating structure voltage to modify electron energy within the
working distance, or instructions about a type of motion of the
substrate with respect to the patterning head (i.e., continuous or
step-wise motion of the substrate, and instructions regarding
modifying a degree of focus (or, of a degree to which a
distribution pattern of micro plasmas is compressed before the
pattern impinges on the top surface of the substrate.
[0045] A distribution of micro plasmas generated by the patterning
device may be modified by instructions from the instruction
generator 142 to a nanostructure activation element 140 for
regulation of the pattern of electron emission structures that emit
electron beams in an array of electron emission structures of an
electron source. An instruction to a emission structure activation
element may include further instructions regarding the activation
or deactivation of individual electron emission structures (or,
loci having clusters of emission structure structures): when an
instruction is performed by the emission structure activation
element, some emission structures may become activated, some may
become deactivated, some may remain activated, and some may remain
deactivated, according to the pattern of functionalization being
performed at the time of the instruction performance, and according
to a position of the substrate below the patterning head.
[0046] Patterning head 106 may further include one or more nozzles
(or micro nozzles, or orifices) 144, connected to one or more
reservoirs 146 with a flow regulator 148, configured to supply a
fluid mixture to the working volume 110 between patterning head 106
and substrate 104. According to an embodiment, a supply of fluid (a
gas or a liquid) to the working volume during surface modification
may adjust the chemical composition of the substrate top surface
during the surface modification process. According to an
embodiment, a fluid mixture may include one or more gaseous
species, or may include a volatilized (or aerosolized) liquid that,
upon evaporation, provides a gaseous component for the gas mixture.
Chemical species that may be used for surface functionalization
include compounds for increasing a concentration of surface oxygen
on a substrate surface, compounds for increasing a concentration of
a halogen on a substrate surface, and compounds for increasing a
concentration of nitrogen on a substrate surface. Chemical species
that functionalize a surface may be radicals or nonradicals.
Chemical species that may promote functionalization of a surface
with halogen atoms, including chlorine or bromine, may include
atomic chlorine or atomic bromine, or non-radical species such as:
hypochlorous acid (HOCl), nitryl chloride (NO.sub.2Cl),
chloramines, chlorine gas (Cl.sub.2), bromine chloride (BrCl),
chlorine dioxide (ClO.sub.2), hypobromous acid (HOBr), or bromine
gas (Br.sub.2). Chemical species related to addition of oxygen to a
substrate surface may include radicals or non-radical species, such
as: superoxide (O.sub.2..sup.-), hydroxyl radicals (HO.),
hydroperoxyl radical (HO.sub.2.), carbonate (CO.sub.3..sup.-),
peroxyl radicals (RO.sub.2.), where R is a carbon or other atom,
and alkolxyl radicals (RO.), where R is a carbon or other atom, as
well as nonradical species such as hydrogen peroxide, hypobromous
acid (HOBr), hypochlorous acid (HOCl), ozone (O.sub.3), organic
peroxides (ROOH), where R.dbd.C, poroxynitrite (ONOO.sup.-), or
peroxynitrous acid (ONOOH). Chemical species related to addition of
nitrogen to a substrate surface may include species such as nitric
oxide NO., nitrogen dioxide NO.sub.2., nitrate radical (NO.sub.3.),
nitrous acid (HNO.sub.2), dinitrogen tetroxide (N.sub.2O.sub.4),
dinitrogen trioxide (N.sub.2O.sub.3), peroxynitrite (ONOO.sup.-),
peroxynitrous acid (ONOOH), or nitryl chloride (NO.sub.2Cl).
[0047] Nozzles 144 may have a pressure that is greater than the
pressure of ambient atmosphere in the working volume. In some
embodiments, nozzles may have a pressure that is lower than the
pressure of ambient atmosphere. Nozzle pressures below ambient
pressure may allow evacuation or flushing of the working volume,
removing spent or reacted gases and byproducts from the working
while some nozzles with pressures above ambient pressure supply new
fluids (e.g., gases or aerosolized liquids) for surface
functionalization. By adjusting the pressures of the nozzles,
plasma in the working volume may be reshaped, or resized, in order
to adjust the pattern of surface functionalization during substrate
processing. Nozzles may be arranged along opposite sides of the
patterning head, in some embodiments. In an embodiment, nozzles may
be arranged around a perimeter of the patterning head. Nozzle
pressures may be regulated independently, or in groups, according
to some embodiments of the present disclosure. Regulating nozzles
in groups may reduce a number of fluid handling components (e.g.,
flow regulators, reservoirs, supply lines, etc. . . . ).
[0048] FIG. 2 depicts a cross-sectional view of an embodiment of a
patterning head 200 having field emission structures. The
cross-sectional view includes a depiction of a path traveled by
directed beams of electrons 202 outward from a chip 203 of the
electron source 204. Chip 203 includes at least one field emission
structures 206, the at least one field emission structure being
oriented downward toward an electron accelerating structure 208, a
membrane 210, and a working volume 210. The directed beams of
electrons 202 may intersect a primed gas mixture 216 in working
volume 210, composed at least partially by a gas 214 emitted by one
or more nozzles 212 oriented toward working volume 210. Plasma 218
may be formed by the intersection of directed beams of electrons
202 with primed mixture 216 in working volume 210.
[0049] Electron source 204 may be a sealed structure with the field
emission structures at an electrical potential less than the
electrical potential of an electron accelerating structure 208.
Electron source 204 may, upon application of a positive electrical
potential to the electron acceleration structure 208, and upon
application of a negative electrical potential to field emission
structures, cause directed electrons to travel toward a substrate
for plasma formation. Upon passage of directed electrons through
the membrane 210 and into the working volume, one or more micro
plasmas may be formed in a working volume. The working volume may
be a controlled region that can undergo spatial adjustment (as by,
for example, modifying a working distance between a substrate and
the patterning head), by regulating the gas temperature, by
regulating the gas composition, or by adjusting a flow rate of the
primed mixture in the working volume.
[0050] In some embodiments, an electron mask (not shown) may be
positioned in the path of the directed electron beams in order to
absorb some of the electrons while passing other of the electrons,
forming a patterned plasma in the working volume. One advantage to
using individually controllable field emission structures of an
electron source is the ability to dynamically reconfigure a
distribution or pattern of micro plasmas within the working volume
without removing or replacing a physical electron mask of the
patterning head.
[0051] According to some embodiments, the chip 203 may be a
substrate material with an interleaved conductive network that
makes contact with the FE nanostructures of the electron source.
The chip substrate material may be made of one or more of silicon,
silicon dioxide, quartz, or some other combination of
semiconducting and dielectric materials that provide insulation
between elements of the interleaved conductive network that
provides a conductive path between the field emission structure and
the power source of the patterning device.
[0052] Field emission structures 206 may include silicon nanowires,
silicon carbide nanowires, carbon fiber nanowires, carbon
nanotubes, or some other conductive material. Field emission
structures may be deposited onto conductive pad areas of the chip.
In some embodiments, field emission structures may be grown in situ
on conductive pad areas of the chip. According to an embodiment,
field emission structures may be formed by seeded growth,
self-organized assembly, or adhesion of emission structures to a
conductive pad of the electron source. Field emission structures
may have distal ends extending toward the electron accelerating
structure of an electron source. Upon exposure of the field
emission structures to an attracting (positive) voltage at the
electron accelerating source, individual field emission structures,
or loci of field emission structures in an array of conductive pad
areas of the chip, may, when at a negative potential individually
(or, as a group when a plurality of field emission structures are
located at a single locus of the array) emit electrons. In an
embodiment, a voltage applied to at least one locus in an array of
field emission structures, or to at least one field emission
structure, may be between about -1 kV and about -10 kV in order to
promote formation of a beam of directed electrons during surface
functionalization and/or surface modification processes. Electron
emission from the field emission structures may be modified
dynamically by instructions supplied by the instruction generator
to the field emission structure activation element of the control
element of a patterning device.
[0053] Electron accelerating structure 208 may be a mesh or a ring
structure held at a positive voltage with respect to the field
emission structures 206 of the electron source 202. An electron
accelerating structure may be located within the electron source
202 in proximity to the field emission structures such that the
electrical field strength at the field emission structures is
sufficient to allow electrons to escape from the field emission
structures without elevated temperature (as would be the case with
thermionic emission electron sources) or significantly large
voltage differentials (as would be the case with a DBD electron
sources). According to an embodiment, an electron accelerating
structure may be made of a metal, such as tungsten, copper,
aluminum, titanium, platinum, or another metal suitable for shaping
into a mesh or ring structure within the electron source. In some
embodiments, the metal may be corrosion resistant to withstand
impacts of directed electron beams and to avoid oxidation/reduction
reactions of the metal with any gas present within the patterning
head. Electron accelerating structure 208 may be used to extract
electrons from the electron source, accelerate electrons toward the
substrate, focus electrons into a smaller area than the area of the
array of FE nanostructures, or scan the directed beams of electrons
across a region of a membrane or across the working volume during
operation of the plasma device.
[0054] Membrane 210 may include a first membrane face 210A and a
second membrane face 210B, with the first membrane face closer to
the FE nanostructures and the second membrane face closer to the
substrate. In an embodiment, first membrane face may be a
conducting layer and second membrane face may be a non-conducting
layer. In an embodiment, first membrane face 210A may be made of a
conducting material, or alloys of conducting metals, such as
copper, aluminum, tungsten, titanium, or platinum. In an
embodiment, second membrane face 210B may be made of a
non-conducting material such as silicon dioxide or silicon nitride
or another insulting material. The combination of the emission
structures 206 and electrodes 210A and 210B may be considered a
triode arrangement. According to an embodiment, one of the membrane
faces may be formed by deposition, either by sputtering, chemical
vapor deposition, epitaxial growth, or electrochemical deposition,
of one of the materials a membrane face on a thicker layer of
material of the other membrane face. For example, a metallic layer
may be formed by sputtering or electroplating of a metal such as
tungsten, on a thicker layer of silicon nitride, to form a
tungsten/silicon nitride membrane. Other combinations of conducting
and non-conducting membrane combinations may be readily apparent to
practitioners of the art using common deposition and film-growth
techniques.
[0055] Electrons can penetrate through a thin membrane if their
kinetic energy is much larger than the energy lost in the membrane
material by collisional scattering. Typically, these membrane are
made of conductive manufacturable material including, but not
limited to, metals such as Ti, Cu, W, or conductive organic
materials such as carbon, graphene, fullerene-like materials, or
carbon nanotubes. A combination of electron energy ranges and
membrane ranges are generally 5,000V to 20,000V and 1 nm to 100 nm,
respectively. In some manifestations, a thin dielectric material is
added to assist in the fabrication of the conductive membrane and
act as backing to the membrane, the thickness of the dielectric
satisfies the condition for small relative loss of the electron
beam energy in the dielectric, typically this dielectric is SiN or
similar material and is less than 300 nm thick.
[0056] As described previously, directed electron beams 202 emitted
from field emission structures 206 may be directed downward into a
working volume 210 to generate a plasma comprising ionized gaseous
species. Composition of the plasma may be modified by modifying,
during surface modification, a chemical composition of the primed
gas mixture in the working volume 210. One benefit of a lower
voltage electron source such as a sealed electron source having a
chip with field emission structures may be that the primed gas
mixture may be a static, or stationary, gas mixture. The plasma, or
micro plasmas, formed in the working volume may be formed with
little or no arcing or pressure fluctuations because of the lower
electron energies for field emission electron sources, as compared
to other electron sources such as thermionic emission electron
sources. Further, because plasmas may be formed with static gas
mixtures present in the working volume, with gas flow rates ranging
from about 1 ml/min to about 100 ml/min.
[0057] FIG. 8 depicts a plasma device 800 having an electron
emission structure array 806 in an electron source substrate 804.
In some embodiments, the electron source substrate may be a chip
comprising semiconductor materials with nanostructures located
thereon as depicted in FIG. 3, below. Electron emission structure
array 806 may include diode structures configured to generate
electron beams 802. Electron source substrate 804 and electron
emission structure array 806, as well as electron accelerating
structure 808, may be located within a sealed enclosure 801,
configured to operate at a first pressure in the sealed enclosure
that is lower than an external pressure outside the sealed
enclosure. Electron accelerating structure 808 may be a conductive
material such as a mesh or thick conductive membrane. Some
embodiments of electron accelerating structures may include
materials that are simple to manufacture into mesh or ring-like
structures, including titanium, copper, tungsten, graphene, etc. .
. . . Electron accelerating structure 808 may extract electrons
from nanostructures in the electron emission structure array 806 by
holding, during operation of the plasma device, a positive voltage,
while the nanostructure of the electron emission structure array
806 may hold a negative voltage. Electron accelerating structure
may also serve to accelerate extracted or emitted electrons from
the nanostructures along a path toward sealing membrane 811 and
working volume 810 (outside the sealed enclosure 801).
[0058] Electron accelerating structure 808 may be kept at a
potential that is less negative than the substrate 804 and the
electron emission structure 802 combined. As a non-limiting
example, the substrate 804 can be held at potential between about
-1 kV and about -10 kiloVolt (kV) with electron accelerating
structure 808 grounded (0 V). The final electron energy of
electrons in electron beams 802, as they exit sealed enclosure 801,
may be a function of the total potential difference between the
electron accelerating structure 808 and electron source substrate
804.
[0059] The distance between the electron source substrate 804 and
the electron accelerating structure 808 may be significantly
smaller than a lateral measurement (length, width) of the electron
source substrate 804. A ratio of about 5:1 (lateral measurement to
separating distance) may be desirable in order to maintain a
uniform electric field and to promote formation of parallel beams
of electrons upon electron emission from nanostructures of electron
source substrate 804. The ratio may be as much as 10:1, while still
maintaining uniform electric fields in the plasma device. Ratios
smaller than about 5:1 may lead to significant electric field
distortions. As with patterning head 200, sealed enclosure 801 may
have an interior pressure smaller than the exterior pressure. A
sealing membrane 811 or, in some embodiments, a hard aperture (not
shown) capable of active differential pumping, may be used. A hard
aperture may further serve to confine the electron beams 802 in a
lateral dimension. Working volume 810, nozzles 812, gases 814, and
primed mixture 816, the plasma formation 818 are similar to the
description of corresponding elements of FIG. 2, wherein the
numerals are incremented by 600.
[0060] FIG. 9 depicts an embodiment of a plasma device 900 having a
plurality of pyroelectric (PE) electron emission structures
(pyroelectric crystals) 904 located within sealed enclosure 901.
Pyroelectric electron emission structures 904 may be situated at a
distal end of individually addressable thermal elements 906, the
distal end being closer to the electron accelerating structure 908
than to a wall of the sealed enclosure 901. Pyroelectric electron
emission structures may be made of materials including, but not
limited to, lithium niobate (LiNbO.sub.3), lithium tantalate
(LiTaO.sub.3), or barium titanate (BaTiO.sub.3).
[0061] Individually addressable thermal elements 906 may be
configured to undergo large amplitude, high gradient thermal
changes to generate, within the pyroelectric nanostructures, a
residual electrical charge on individual pyroelectric
nanostructures. Individually addressable thermal elements 906 may
include one or more micro heating elements and one or more micro
cooling elements, configured to rapidly modulate a temperature of
the individually addressable thermal elements, and the pyroelectric
nanostructures located thereon, to induce electron accumulation on
the PE electron emission structures. A number of micro heating
element sand micro cooling elements in an individually addressable
thermal element may be determined according to the chemical
structure of the PE electron emission structures located thereon,
and the individual electron accumulation characteristics of the PE
electron emission structure material.
[0062] Electrical charges accumulated on PE electron emission
structures may be induced to leave the PE electron emission
structures and travel through the sealed enclosure in directed
electron beams. An electron accelerating structure 904 may trigger
departure of electrons from PE electron emission structures, and
may accelerate the electrons toward a substrate in order to cause
plasma formation above a substrate surface. PE electron emission
structures may be held at a negative voltage of between about -2 kV
and about -10 kV, and an electron accelerating structure may be
held at a positive voltage of about +10 kV, in order to promote
electron beam formation and to regulate electron energy in the
plasma formed in working volume 910. Pyroelectric emission may
occur at pressures within the sealed enclosure 901 of about 1 Torr,
although other pressures may be employed according to voltage
configurations of the plasma device and the identity of the gas
within the sealed enclosure. Pyroelectric emission may occur with
voltages that are significantly lower than thermionic emission or
DBD electron sources, reducing a cost of manufacturing of materials
using a plasma device as disclosed herein.
[0063] Individually addressable thermal elements, and pyroelectric
electron emission structures 904 located thereon, may be arranged
in an array having a plurality of loci, each locus being
individually addressable to trigger electron emission from one
locus independent of electron emission status at a second locus
within the array. Elements of FIG. 9 not mentioned above resemble
the corresponding elements of FIG. 2, having identifying numbers
incremented by 700.
[0064] FIG. 3 depicts a cross-sectional view of an embodiment of a
chip 300 of an electron source. Chip 300 comprises a substrate 302
having a plurality of electrical connections (not shown) extending
through the substrate 302 and connecting to a nanostructure
activation element in a controller element (or, a pattern
management system) of a plasma device as described previously.
Electrical connections may include a plurality of contacts 306 or
pads having a contact top surface 308 that is exposed. Spatial
selectivity of the patterning device may relate to the pitch
between contacts 306 of an electron source, and to the ability of a
nanostructure activation element to, upon receiving an instruction
from an instruction generator of a controller element (see FIG. 2,
above), modify the activation status of individual FE
nanostructures (or, of FE nanostructures at a single locus in an
array of contacts having FE nanostructures on the top surfaces of
the contacts.
[0065] According to some embodiments, a remainder of a contact (the
portion other than the contact top surface) may be surrounded by
substrate material or other materials of the chip. The substrate
302 may have a substrate top surface 308 that is covered by layers
of material 312 and 314 that insulate the contacts 306 and
electrical connections from the electrical field of an electron
accelerating structure of the electron source. In an embodiment, a
contact top surface may be approximately coplanar with a substrate
top surface. According to an embodiment, a contact top surface may
be recessed below a substrate top surface. In an embodiment, a
contact top surface may extend above a substrate top surface.
[0066] Contact top surface 308 may be covered by one or more
electron emission structures 316 from which a directed beam of
electrons may be drawn by an electron accelerating structure of an
electron source. Electron emission structures 316 may include nano
rods, nanowires, carbon nanotubes, fullerene-like structures,
tunneling cold field emitter cathodes, or diode structures.
Electron emission structures may be made from materials that
include silicon, silicon carbide, carbon nanotubes, fullerenes, or
pyroelectric materials. The electron emission structure array in
chip 300 may have a low impedance in order to facilitate electron
emission from the chip toward the electron accelerating structure.
Impedance may be low enough that thermal loading is reduced and
thermal damage to a chip or nanostructures thereon is reduced. In
some embodiments, the activation voltage for field emission from
electron emission structures may be less than or equal to about 1
keV. Electron emission structures as described herein may reduce
power consumption of a patterning head, as described above, to
wattages below about 5 Watts. In some embodiments, power
consumption may be reduced to below 1 Watt of power.
[0067] Electron emission structures 316 may be located below a chip
top surface 318 within chip openings 320. A working distance
between chip top surface 318 and a substrate surface during surface
functionalization may range from 0 mm to about 1 mm, or more, while
plasma modifies or functionalizes a substrate surface.
[0068] FIG. 4 depicts a cross-sectional analysis of an embodiment
of plasma device 400. Plasma device 400 is shown, separated from a
substrate 402 by a working distance 404, during a surface
functionalization process. A plasma 406 may be formed in a working
volume 408 upon ignition of the plasma by a directed beam of
electrons 410 in a gas delivered to the working volume 408 by a gas
supply nozzle 412. Directed beam of electrons 410 may be emitted by
an electron emission structure 416, upon formation of a large
positive electrical voltage by an electron accelerating structure
414, in proximity to electron emission structure 416. Directed beam
of electrons 410 may be drawn from the electron emission structure
416 by the electron accelerating structure 414, through a control
ring (or control mesh) 418 and through a membrane and/or window
418.
[0069] A dimension of the plasma 406 may be regulated by beam
defining aperture 420, configured to electromagnetically compress
or expand the directed beam of electrons 410 during passage through
membrane and/or window 418 and formation of plasma 406. In some
embodiments, a dimension of the plasma may be increased by the beam
defining aperture to expose a larger dimension of substrate to
plasma during surface functionalization. In an embodiment, a
dimension of a plasma may be reduced in order to generate smaller
features and to restrict plasma-induced damage, or the likelihood
thereof, upon sequential surface functionalization steps on a
substrate top surface.
[0070] Plasma device 400 may have an electron scanning element 422
configured to steer directed beam of electrons 410 across a top
surface of substrate 402 during surface functionalization. By
regulating the strength of an electromagnetic field of beam
defining aperture 420, a position of substrate 402, and a magnitude
of electromagnetic fields of electron scanning element, an electron
beam (or beams, according to a number of electron emission
structures in plasma device 400), may scribe plasma across a top
surface of substrate 402 with spatial separation from
already-functionalized regions of the top surface of substrate 402.
According to a pitch between electron emission structures of the
plasma device, and according to the magnitude of the beam
definition field, inter alia, an array of directed electron beams
may be "compressed" into a distribution of directed electron beams
having a separation between adjacent directed electron beams
measured in units of micrometers or nanometers. A pitch between
individual loci for electron emission structures may range from
about 10 nm to about 1 mm, and a pitch between loci in an array of
nanostructure clusters on a surface of an electron source substrate
may range from about 100 nm to about 1000 micrometers. A pitch of
directed electron beams may range from about 250 nanometers (nm) to
about 1 millimeter (mm) according to an embodiment. According to an
embodiment, a second beam defining aperture (not shown) may be used
to contain a plasma (or, a plurality of micro plasmas) formed in a
working volume 408 between plasma device 400 and a substrate
402.
[0071] An electron emission structure 416 (or, an array of electron
emission structures) may be formed on a low impedance substrate 424
of plasma device 400. In some embodiments, low impedance substrate
may be a chip such as chip 203 of FIG. 3, described above. Low
impedance substrate 424 may be located within an electron source
housing 426. An electrical connection 430 may be connected to low
impedance substrate 424, and consequently to the electron emission
structure 416 (or, the array of electron emission structures)
thereon as a source of electrons for the electron beam.
[0072] Electron source housing 426 may be under vacuum in an
embodiment, Electron source housing 426 may be at a pressure less
than ambient atmospheric pressure. Electron source housing 426 may
have a gaseous composition that is different from the gaseous
composition of ambient atmosphere outside of plasma device 400.
Electron source housing 426 may have a gaseous composition that is
different from the gaseous composition of the working volume
between the patterning head and a substrate. A pressure of within
plasma device 400 may be reduced below the ambient outer pressure
by withdrawal of gas from an interior of plasma device 400 through
a vacuum port 428.
[0073] FIG. 5A depicts a top-down view of part of a pattern of
functionalization of a microfluidic device 500. Microfluidic device
500 may have a top surface 502 divided into a first region 504 and
a second region 506. First region 504 and second region 506 may
have a same perimeter shape and a same-sized area within the
perimeters thereof, and adjoin each other along one side. First
region 504 and second region have different functionalization
patterns located within the region perimeters. Description of the
process of functionalizing the regions 504 and 506 may be
illustrative of the performance of micro plasma functionalization
in general on substrates. First region 504 and second region 506
contain a first set of areas 508, having a first type of
functionalization, and a second set of areas 510, having a second
type of functionalization thereon. First region and second region
506 may be functionalized with the first and second sets of areas
without a masking process being performed to protect part of the
top surface 502 from double processing or destruction of a
previously-functionalized area during a current functionalization
step. Top surface 502 may also contain an area 502 that has a third
type of functionalization that differs from both the first type and
second type of functionalization found in the first and second sets
of areas. In an embodiment, the third type of functionalization may
be an original type of surface functionalization present on a top
surface of a substrate prior to any surface functionalization by
spatially selective plasma processing.
[0074] FIGS. 5B-5E depict patterns 520, 530, 540, and 550 of
spatially-selective surface functionalization that may be performed
in order to generate a surface functionalization pattern depicted
in microfluidic device 500, described previously. For purposes of
convenience in describing surface functionalization, the patterns
depicted herein share a common pattern perimeter 526. However, in
many embodiments, a pattern perimeter may have different dimensions
during a process of performing surface functionalization, according
to a dimension of a pattern portion, and according to an ability of
the patterning head to modify a shape and dimension of a
distribution of electron beams and/or micro plasmas during surface
functionalization. FIG. 5B depicts first pattern 520, having an
activated portion 524 and a deactivated portion 522 within a
pattern perimeter 526. Activated portion 524 includes two activated
spaces within pattern perimeter 526. FIG. 7C depicts second pattern
530, having within pattern perimeter 526, deactivated space 532 and
activated space 534. Deactivated portion 534 includes a single
activated space. FIG. 5D depicts, within pattern perimeter 526,
activated portion 544 and deactivated portion 542, and FIG. 5E
depicts, within pattern perimeter 526, activated portion 554 and
deactivated portion 552. Activated portion 554 includes two
activated spaces.
[0075] In a representative, but non-limiting embodiment of a method
of forming the surface functionalization pattern depicted in
microfluidic device 500, the patterns depicted in FIGS. 5B-5E may
be applied in any order. In an embodiment, functionalization
patterns may be formed on a substrate top surface sequentially in a
single region (such as region 504), before moving patterning head
above second region 506 for a second set of surface
functionalization steps [e.g., patterns 520 and 540 may be applied
during functionalization of first region 504, prior to
functionalization of second region 506 using patterns 530 and 550].
In an embodiment, functionalization patterns may be formed in
different regions according to functionalization types, wherein,
e.g. first set of areas 508 may be functionalized before any areas
of second set of areas are functionalized on top surface 502 [e.g.,
patterns 520 and 530 may be applied to the first and second
regions, completing functionalization of first set of areas 508,
before patterns 540 and 550 are applied to the first and second
regions, completing functionalization of the second set of areas
510]. Because micro plasmas formed by the patterning head may be
regulated to remain separate within the working volume between a
patterning head and a substrate top surface, spatial separation of
functionalized areas and micro plasmas may allow maskless plasma
functionalization of top surface without harm to previously
functionalized areas. Determination of an order of micro plasma
patterning of a substrate top surface may relate to a desired speed
of functionalization of a top surface, a complexity of a
functionalization pattern, a resolution of a micro plasma produced
in the working volume, and other factors associated with compatible
chemistry in the plasma, consumption of reactive species by the
plasma during surface functionalization, accuracy of positioning
the patterning head with respect to features on the substrate top
surface, and a speed of refreshing or purging a working volume when
changing from one type of functionalization chemistry to a
different type of surface functionalization chemistry.
[0076] FIG. 6 depicts a flow diagram of an implementation of a
method 600 of generating a patterned array of micro-plasmas. In a
first operation 602, at least one directional electron beam may be
formed by applying a potential difference between an accelerating
structure and an array of electron emission structures of an
electron source. A number of electron beams formed upon application
of the potential difference to the accelerating structure and the
array of emission structures may be a function of a number of
individual emission structures, or loci of the array of emission
structures, in the electron source. A number and pattern of
emission structures, or loci, may be adjusted during operation of a
patterning head by an instruction received from a control element
of a plasma device, where the control element stores a pattern of
surface functionalization, processes the pattern, sends information
regarding the pattern to an instruction generator to determine an
order of operations to form the pattern on a substrate surface, and
regulates the distribution (or pattern) of micro plasmas that form
a pattern by activating or deactivating individual emission
structures, or loci of an array of emission structures, in the
patterning device.
[0077] In an optional operation 604, the directed electron beam may
be directed through a membrane having a first membrane face and a
second membrane face toward a substrate. A membrane may be
configured to permit creation of a pressure differential between an
interior of a sealed enclosure and the exterior of the sealed
enclosure. A membrane may be selectively permeable to gases, or may
have a pinhole located therein to allow some gas to enter the
interior portion of a sealed enclosure while the interior portion
is being pumped to a reduced pressure. An interior portion of a
sealed enclosure may have a pressure as low as 10.sup.-9 Torr while
an exterior portion (outside the sealed enclosure) may have a
pressure of about 760 Torr. The velocity, or energy, of the
directed electron beam, may be regulated by adjusting the potential
difference between emission structures and the electron
accelerating structure of the electron source. By regulating the
electron beam energy, a plasma device may regulate plasma density,
the species that are formed in the micro plasmas in the plasma, and
(optionally) the impact velocity of the ionized species against the
substrate surface during surface functionalization.
[0078] In an optional operation 606, the working volume between the
patterning device and the substrate may be primed with a gas
mixture supplied via nozzles of the patterning head to adjust the
chemistry of the plasma during surface functionalization. The
chemistry may be adjusted according to a type of functionalization
desired in a particular part of the surface functionalization
process. In an operation 608, at least one micro plasma is ignited
by directing the at least one directional electron beam
[0079] FIG. 7 depicts a flow diagram of an implementation of a
method 700 for making a spatially selective surface
functionalization device, or plasma device. In an operation 702, an
array of individually addressable electron emission structures, or
loci in an array of clusters of electron emission structures, may
be formed on an electron source substrate. Electron emission
structures may be thermionic emission structures, field emission
(FE) nanostructures or pyroelectric (PE) nanostructures located on
conductive pads of an electron source substrate, the conductive
pads being connected to a power supply and configured to apply a
negative voltage to the emission structures during operation of a
plasma device.
[0080] In an operation 704, an electron accelerating structure may
be formed in a patterning head in close proximity to an electron
source substrate. A ratio of a lateral dimension of the electron
accelerating structure and a distance between the electron
accelerating structure and an electron source substrate may range
from between about 5:1 to about 10:1, although other, larger
ratios, may be possible.
[0081] In an operation 706, electron emission structures of the
electron source substrate, and the electron accelerating structure,
may be interconnected at a power supply configured to generate an
electrical potential between the electron source substrate and the
electron accelerating structure. In an embodiment, an electron
source substrate may be held at a voltage between about -1 kV and
about -10 kV, while an electron accelerating structure may be held
at a positive voltage ranging between about +1 kV and about +10
kV.
[0082] In an operation 708, a membrane may be located in a wall of
a sealed enclosure to allow passage of directed beams of electrons
from the nanostructures of the electron source substrate to the
working volume outside the sealed enclosure. A membrane may be a
single film membrane, or may have bilayers configured to allow
passage of electrons out of the sealed enclosure.
[0083] In an operation 710, a gas delivery system nozzle may be
positioned to deliver a flow of gas into a working volume of a
plasma device. The working volume may be located between the
membrane and the surface of a target substrate being functionalized
by the plasma device. A working volume may have a gas flow delivery
rate configured to refresh plasma reactant species during surface
functionalization. A gas delivery system may include gaseous
species and liquid species that may be aerosolized or evaporated by
a carrier gas in order to prime a gas mixture in the working
volume. In an operation 712, a controller element may be connected
to the plasma device to regulate activation and deactivation of the
nanostructures during surface functionalization.
[0084] In various embodiments, the chip includes a substrate formed
from one or more of silicon, silicon dioxide, quartz, or silicon,
preferably silicon. The individually addressable electron emission
structures of the emission structure array may be a combination of
one or more of the following: nano rods, nanowires made of a
conductive or semiconductor material (such conductive or
semiconductor materials including, but not limited to silicon,
silicon carbide, and carbon), as well as carbon nanotubes and
fullerene-like structures, tunneling cold field emitter cathodes,
and pyroelectric material cathodes. Individually addressable
nanostructures may be grown directly on a substrate material, or
may be deposited onto a substrate material, or regions of a
substrate material that are electrically connected to a power
supply for the electron source of the patterning head.
[0085] In some embodiments, the techniques described herein may be
used to form an analytical chip like that described in a U.S.
patent application titled SELF-FLOWING MICROFLUIDIC ANALYTICAL CHIP
filed on the same day as this patent filing, the contents of which
are incorporated by reference. In some embodiments, the analytical
chip may be analyzed with a pump-free microfluidic analytical
system described in a U.S. patent application titled STAND ALONE
MICROFLUIDIC ANALYTICAL CHIP DEVICE, filed on the same day as the
present patent filing, the contents of which are incorporated by
reference.
* * * * *