U.S. patent application number 17/115181 was filed with the patent office on 2021-04-22 for method and system for the localized deposit of metal on a surface.
The applicant listed for this patent is Illinois Tool Works Inc. Invention is credited to Zhigang Xiao.
Application Number | 20210115558 17/115181 |
Document ID | / |
Family ID | 1000005305903 |
Filed Date | 2021-04-22 |
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United States Patent
Application |
20210115558 |
Kind Code |
A1 |
Xiao; Zhigang |
April 22, 2021 |
METHOD AND SYSTEM FOR THE LOCALIZED DEPOSIT OF METAL ON A
SURFACE
Abstract
The present disclosure is directed to a method and system for
the localized deposition of a metal layer on a surface. The method
involves introducing at least two gaseous reactants to a substrate
surface that is locally heated by a laser. The surface is heated to
a temperature at which the gaseous reactants undergo a reaction
that results in metal crystal growth on the substrate surface. The
reaction is maintained for a desired period of time and under
desired conditions to produce a localized deposit of a metal layer
on the heated zone of the substrate. In some embodiments, the gas
outlets and the laser may be moved in a controlled manner so that a
metal layer may be deposited in a desired pattern on the substrate
surface.
Inventors: |
Xiao; Zhigang; (Washington
Township, OH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Illinois Tool Works Inc |
Glenview |
IL |
US |
|
|
Family ID: |
1000005305903 |
Appl. No.: |
17/115181 |
Filed: |
December 8, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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15018148 |
Feb 8, 2016 |
10865477 |
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17115181 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C23C 16/14 20130101;
C23C 16/455 20130101; C23C 16/45514 20130101; H01L 21/28562
20130101; C23C 16/047 20130101 |
International
Class: |
C23C 16/455 20060101
C23C016/455; C23C 16/14 20060101 C23C016/14; C23C 16/04 20060101
C23C016/04; H01L 21/285 20060101 H01L021/285 |
Claims
1. A method for the localized deposition of a metal layer
comprising: (a) introducing a first gaseous reactant, the first
gaseous reactant comprising a metal-containing precursor, and a
second gaseous reactant to a surface of a substrate, wherein the
first and second gaseous reactants are introduced to the surface of
the substrate through one or more gas outlets; and (b) directing a
laser against a location on the substrate surface that is adjacent
to the one or more gas outlets, thereby heating a zone of the
surface to a temperature at which the first and second gaseous
reactants react, such that a metal layer is deposited on the heated
zone of the substrate surface.
2. The method of claim 1, further comprising: (c) moving the one or
more gas outlets and the laser in a controlled manner so as to
deposit the metal layer in a desired pattern on the substrate
surface.
3. The method of claim 2, wherein the substrate comprises a pattern
and the one or more gas outlets and the laser follow the
pattern.
4. The method of claim 1, wherein the one or more gas outlets are
configured to introduce a mixture of the first and second gaseous
reactants substantially evenly across the heated zone of the
surface.
5. The method of claim 1, wherein the first and second gaseous
reactants are introduced through a single outlet, the diameter of
the outlet being less than the diameter of the heated zone.
6. The method of claim 5, wherein the outlet has a diameter that is
between about 50% and about 95% of the diameter of the heated
zone.
7. The method of claim 1, in which the first gaseous reactant and
the second gaseous reactant are introduced through separate gas
outlets.
8. The method of claim 1, wherein the heated zone has a diameter
that is less than 10 mm.
9. The method of claim 1, wherein the heated zone has a diameter
that is less than 5 mm.
10. The method of claim 1, wherein the one or more gas outlets are
positioned between about 3 mm and about 20 mm above the substrate
surface.
11. The method of claim 10, wherein the one or more gas outlets are
positioned between about 5 mm and about 10 mm above the substrate
surface.
12. The method of claim 1, wherein the metal of the
metal-containing precursor is a transition metal.
13. The method of claim 1, wherein the metal-containing precursor
has the formula MX.sub.n, in which: M is a transition metal, X is a
halogen, and n is an integer selected from the group consisting of
5 and 6; and the second gaseous reactant is H.sub.2.
14. The method of claim 13, in which the transition metal is
selected from the group consisting of tungsten (W), molybdenum
(Mo), tantalum (Ta), titanium (Ti), rhenium (Re), niobium (Nb),
nickel (Ni), and hafnium (Hf); and the halogen is selected from the
group consisting of fluorine, chlorine, and bromine.
15. The method of claim 13, in which the metal-containing precursor
is selected from the group consisting of tungsten hexafluoride and
tungsten hexachloride.
16. The method of claim 1, wherein the deposited metal layer is
monocrystalline.
17. The method of claim 16, wherein the deposited metal layer is
monocrystalline tungsten.
18. The method of claim 1, in which the substrate is a silicon
wafer.
19. A system for the localized deposition of a metal layer
according to the method of claim 1, comprising: (a) a substrate,
the substrate having a surface; (b) one or more gas outlets, the
one or more gas outlets being in communication with at least a
first gaseous reactant and a second gaseous reactant, and the one
or more gas outlets being positioned adjacent to a portion of the
substrate surface; and (c) a laser, the laser being configured to
direct its output against the portion of the substrate surface in
order to heat a zone of the substrate surface to a desired
temperature.
20. The system of claim 19, wherein both the one or more gas
outlets and the laser are configured to travel along the substrate
surface in a controlled manner.
Description
BACKGROUND OF THE INVENTION
[0001] The present disclosure is directed toward methods and
systems for the printing of a substrate with a metal surface
layer.
[0002] The use of chemical vapor deposition processes for the
coating of a substrate with a metal is known in the art. In a
conventional chemical vapor deposition process, a substrate is
heated and the reactants are introduced across that substrate,
resulting in the deposition of a metal layer across the entirety of
the substrate. If less than the entirety of a substrate is to be
coated, complex patterning or overlaying procedures are
required.
[0003] The present disclosure provides improved methods and systems
for the deposit of a metal surface layer. By restricting the
reactants to a relatively small space and performing the reaction
on a limited portion of the substrate, the methods and systems
described herein provide for a localized deposit of a metal surface
coating on a controlled portion of a substrate, as opposed to the
less constrained conventional deposition process. The methods and
systems of the present disclosure also do not require any
additional patterning or overlaying steps to obtain a metal layer
having a specific configuration. Moreover, by introducing the
reactants locally to the portion of the substrate on which the
metal is deposited, the methods and systems described herein
provide for a significant reduction in the amount of reactants
needed to prepare a metal surface layer.
SUMMARY OF THE INVENTION
[0004] Embodiments of the present disclosure are directed to a
method for the localized deposition of a metal layer on a surface.
The method involves introducing at least two reactants, each of the
reactants in a gaseous state, to a surface of a substrate. One of
the gaseous reactants comprises a metal-containing precursor
compound. Another of the gaseous reactants comprises a compound
that is capable of reacting with the metal-containing precursor to
produce metal crystal growth on a heated surface. These first and
second gaseous reactants are introduced to the substrate surface
through one or more gas outlets, which are located near the
substrate surface. As the first and second gaseous reactants are
introduced to the substrate surface, a laser is directed against a
location on the substrate surface that is adjacent to the one or
more gas outlets. The laser is configured and positioned to heat a
zone of the substrate surface to a temperature at which the first
and second gaseous reactants undergo a reaction that results in
metal crystal growth on the heated zone of the substrate surface.
The reaction is maintained for a desired period of time (and under
desired conditions) to produce a localized deposit of a metal layer
on the heated zone.
[0005] In some embodiments, each of (a) the one or more gas outlets
and (b) the laser may be moved in a controlled manner so that a
metal layer may be deposited in a desired pattern on the substrate
surface. The area of the heated zone on the substrate surface may
be altered by changing one or more of the laser variables (e.g.
beam size, power, positioning, etc.). Accordingly, in some
embodiments the metal layer may be patterned such that one section
of a continuous deposit might cover a greater portion of the
surface, i.e. have a larger width, and another section of the
deposit might cover a lesser portion of the surface, i.e. have a
smaller width. Similarly, the thickness of the metal layer may be
altered by changing one of more of the reaction conditions (e.g.
temperature, reactant flowrate, reaction time, etc.). Accordingly,
in some embodiments the metal layer may be patterned such that one
section of a continuous deposit might have a greater thickness and
another section of the deposit might have a lesser thickness. In
some embodiments, a consistent continuous deposit may be obtained
by controlling the movement of the gas outlets and laser such that
the reaction conditions remain substantially consistent across
different sections of the deposit.
[0006] In some embodiments, the presently disclosed method may be
directed toward the controlled deposit of a transition metal, such
as tungsten, to a substrate surface by reacting a halogenated
metal-containing precursor gas, such as tungsten hexafluoride or
tungsten hexachloride, with hydrogen gas at conditions which
produce a localized deposit of the transition metal, e.g. tungsten,
on a heated zone of the surface. Further, by selecting a proper
substrate material and properly controlling the reaction
conditions, the metal may be caused to form as a single crystal. If
desired, the single crystal material, e.g. monocrystalline
tungsten, can then be separated from the substrate using
conventional methods.
[0007] Embodiments of the present disclosure are also directed to a
system for the localized deposition of a metal on a substrate. The
system includes one or more gas outlets that are positioned
adjacent to a portion of a substrate surface. The one or more gas
outlets are in fluid communication with a source of a first gaseous
reactant and a source of a second gaseous reactant. The system also
includes at least one laser. The laser is positioned to direct its
output against a portion of the substrate surface that is adjacent
to the one or more gas outlets. The laser is configured to heat a
zone of the surface to a desired temperature range. In some
embodiments, both (a) the one or more gas outlets and (b) the laser
are configured to travel along the substrate surface in a
controlled manner, such that the system may provide for the
continuous (or interrupted) deposit of a metal layer in a desired
pattern on the substrate surface.
[0008] The presently disclosed method and system may find
particular application in a variety of contexts. For example,
embodiments of the presently disclosed method and system may be
useful for the manufacture of a variety of electronic components on
a surface, such as on the surface of a silicon wafer. Embodiments
of the presently disclosed method and system may also be useful for
the growth of monocrystalline metal structures, such as
monocrystalline tungsten which is used in space travel. And
embodiments of the presently disclosed method and system may be
used for the localized deposit of metal layers in a precise pattern
on a variety of substrates.
[0009] Additional features and advantages will be set forth in the
detailed description which follows, and in part will be readily
apparent to those skilled in the art from that description or
recognized by practicing the embodiments as described herein,
including the detailed description which follows, the claims, as
well as the appended drawings.
[0010] It is to be understood that both the foregoing general
description and the following detailed description are merely
exemplary, and are intended to provide an overview or framework to
understanding the nature and character of the claims. The
accompanying drawings are included to provide a further
understanding, and are incorporated in and constitute a part of
this specification. The drawings illustrate one or more
embodiment(s), and together with the description serve to explain
principles and operation of the various embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] A clear conception of the advantages and features of one or
more embodiments will become more readily apparent by reference to
the exemplary, and therefore non-limiting, embodiments illustrated
in the drawings:
[0012] FIG. 1 is an illustration of a system for printing a metal
layer on a substrate according to an embodiment of the present
disclosure.
[0013] FIG. 2 is an illustration of a system for printing a metal
layer on a substrate according to an embodiment of the present
disclosure, which includes the preparation of the metal-containing
precursor gas.
[0014] FIG. 3 is an illustration of a system for printing a metal
layer on a substrate according to an embodiment of the present
disclosure in which the reaction gases are introduced through
separate gas outlets.
DETAILED DESCRIPTION OF THE INVENTION
[0015] Reference will now be made in detail to certain
embodiment(s), examples of which are illustrated in the
accompanying drawings. Whenever possible, the same reference
numerals will be used throughout the drawings to refer to the same
or like parts. Embodiments of the present disclosure are directed
to a system and process for the localized deposit of a metal layer
on substrate.
Systems
[0016] An embodiment of the system 10 of the present disclosure is
illustrated in FIG. 1. The system shown in FIG. 1 comprises a
vacuum chamber 11. The vacuum chamber 11 is configured to maintain
a vacuum within the chamber. A mechanical vacuum pump is generally
sufficient for most applications. In some applications, however, a
high vacuum state may be desirable. A substrate 20, on which a
metal layer is to be printed, is positioned within the vacuum
chamber 11. As such, the vacuum chamber 11 may contain a substrate
holder. If it is desirable that more than one substrate 20 is to be
coated within the vacuum chamber 11, the vacuum chamber may
comprise a plurality of substrate holders.
[0017] The system also comprises one or more gas lines 12 for
conveying at least a first gaseous reactant and a second gaseous
reactant to one or more gas outlets 13. The one or more gas lines
12 may comprise pipes, tubes, or the like, which are generally
understood to be useful in the conveyance of gases. In the
embodiments illustrated in the Figures, the first and second
gaseous reactants are shown as being conveyed to the one or more
gas outlets 13 in separate gas lines 12. Although the separate gas
lines 12 are shown as being unconnected from one another, it may
often be desirable that the separate gas lines are linked. For
instance, the separate gas lines 12 may be connected in a
side-by-side relationship, twisted together, in a concentric
relationship (i.e. one gas line may be contained within another),
etc. In other (non-illustrated) embodiments, a mixture of the first
and second gaseous reactants may be conveyed to one or more gas
outlets 13 through a single gas line 12.
[0018] Each of the one or more gas lines 12 is in fluid
communication with at least one source of a gaseous reactant 16.
For instance, where separate gas lines 12 are used to convey the
first and second gaseous reactants, a first gas line may be
operably connected to a source of the first gaseous reactant 16 and
a second gas line may be operably connected to a source of the
second gaseous reactant. Where a single gas line 12 is used to
convey a mixture of the first and second gaseous reactants, the gas
line 12 may be operably connected to both a source 16 of the first
gaseous reactant and a source of the second gaseous reactant. The
source 16 of each gaseous reactant may comprise a storage tank or
gas canister.
[0019] In some embodiments, the source 16 of one or more of the
gaseous reactants may comprise a system 30 for preparing the
gaseous reactant. For instance, the embodiment illustrated in FIG.
2 comprises a system 30 for preparing tungsten hexachloride, which
is then conveyed to the gas outlet 13 and employed as the
metal-containing precursor in the deposition process. The system 30
comprises a chamber containing tungsten metal chips 31 and a source
of chlorine gas 32. When operational, the system is configured such
that the chlorine gas flows from the source 32 through the chamber
containing tungsten metal chips 31 at an elevated temperature. As
the chlorine gas contacts the tungsten chips at this elevated
temperature, a reaction occurs and tungsten hexachloride gas is
produced. Each of the one or more gas lines 12 may also be in fluid
communication to a source of additional gaseous components, such as
a carrier gas.
[0020] In order to control the flowrates of each of the first and
second gaseous reactants, the system 10 also desirably comprises
one or more flowmeters 17. For example, each gas source 16 may
comprise a flowmeter 17 that is configured to provide for a
controlled flow of the gas at a desired rate.
[0021] In some embodiments, one or more of gas lines 12 may also
comprise a heating or cooling element 14. In some embodiments it
may be necessary to maintain a gaseous reactant, such as the
metal-containing precursor, at an elevated temperature prior to its
reaction with the second gaseous reactant. Or it may simply be
desirable to pre-heat one or more of the gas streams, such as in
order to increase the speed with which the metal-producing reaction
occurs. Alternatively, in some embodiments it may be desirable to
cool one or more of the gas streams in order to prevent the first
and second gaseous reactants from reacting within either a gas
lines 12 or a gas outlet 13. Any conventional heating or cooling
element 14 may be used to control the temperature of the gases
flowing through the one or more gas lines 12. In the embodiment
shown in FIG. 2, for example, the gas line 12 for the first gaseous
reactant is shown surrounded by heating coils.
[0022] The one or more gas lines 12 comprise one or more gas
outlets 13, the one or more gas outlets being configured to
introduce the gaseous reactants into the vacuum chamber 11 and,
more particularly, against the surface of the substrate 20.
Accordingly, the one or more gas outlets 13 may comprise
conventional elements for introducing gas from a gas line 12 into a
chamber 11, and in particular against a substrate 20. For example,
each of the one or more gas outlets 13 may comprise a nozzle, a
manifold, or the like. For the same reasons described above with
respect to the gas lines 12, embodiments of the one or more gas
outlets 13 may also be outfitted with a heating or cooling
unit.
[0023] In some embodiments, the first and second gaseous reactants
may be introduced to the surface of the substrate 20 through a
single gas outlet 13, such as is shown in the embodiments
illustrated in FIGS. 1 and 2. In order to provide a substantially
consistent contact of the gaseous reaction mixture across a desired
zone of the substrate 20 surface, the first and second gaseous
reactants may be mixed just prior to reaching the gas outlet 13.
Additionally, the gas outlet 13 may have a diameter that is similar
to the diameter of the desired zone.
[0024] In other embodiments, the first and second gaseous reactants
may be introduced through separate gas outlets 13, as is shown for
example in the embodiment illustrated in FIG. 3. In order to
provide a substantially consistent contact of the gaseous reaction
mixture across a desired zone of the substrate 20 surface, the gas
outlets 13 may be positioned to spray the gases at carefully
controlled flowrates, at controlled angles relative to one another,
and the like. For example, where the gas lines 12 are concentric,
the outlet 13 of the outer gas line may be angled inward and the
outlet of the inner gas line may be angled outward. The desired
relative flowrates of the first and second gaseous reactants may
also be taken into account in selecting the sizes and configuration
of the separate gas outlets. In some embodiments, the separate gas
outlets 13 for the first and second gaseous reactants may be
alternated in order to produce a substantially consistent ratio of
reactants across the desired reaction zone. For example, each
separate gas outlet 13 may comprise a manifold, and the individual
spouts of the separate manifolds may alternate with one another in
order to provide for a consistent mixture of the gaseous reactants
across the desired zone of the substrate 20. In some embodiments,
the diameter of the combination of gas outlet 13 manifolds or
nozzles may also be similar to the diameter of the desired
zone.
[0025] When the system 10 is in use, the one or more gas outlets 13
are desirably located close to the surface of the substrate 20. For
example, the one or more gas outlets 13 may be configured to be
positioned less than 20 mm from the surface of the substrate 20,
alternatively less than 15 mm from the surface, alternatively less
than 12 mm from the surface, alternatively less than 10 mm from the
surface. In some embodiments, the one or more gas outlets 13 may be
moveable toward and away from the substrate surface 20 in order to
obtain a desired working distance from the surface of the substrate
20. In other embodiments, the one or more gas outlets 13 may be
fixed at a particular distance above the substrate 20 surface.
[0026] The system also comprises at least one laser 15. The laser
15 is positioned to direct its output against a location on the
substrate surface 20 that is adjacent to the one or more gas
outlets 13. As such, the laser 15 is configured to heat an area of
a desired size, or zone 21, on the surface of the substrate 20. The
laser 15 may be selected from any of the known laser types, such as
those that are conventionally used in selective laser sintering
(SLS) printing technologies. The type of laser, as well as the
power of the laser, may be selected depending on the desired
temperature to which the zone 21 on the substrate surface 20 is
heated. It should be understood that the reference to a laser 15 or
the laser in the present disclosure encompasses the use of one or
more than one laser. In some embodiments, the laser 15 may be
attached to the one or more gas lines 12 or gas outlets 13 such
that the combination of the gas outlets and the laser may together
be moved along the surface of a substrate 20 in a controlled and
coordinated manner.
[0027] Each of the one or more gas outlets 13 and the laser 15 may
be configured to travel along the surface of the substrate 20 in a
controlled manner. By moving the one or more gas outlets 13 and the
laser 15 along the substrate surface 20 during operation, one may
deposit a metal layer in a desired pattern on the substrate
surface. For instance, the one or more gas outlets 13 and the laser
15 may be configured to provide a coordinated movement along the
substrate surface 20, such that the relationship between the one or
more gas outlets 13 and the heated zone 21 of the substrate surface
remains substantially the same throughout the movement. A
coordinated movement of this sort may provide for the deposit of a
consistent metal layer in a desired pattern. The movement of the
one or more gas outlets 13 and the laser 15 may be computer
controlled, such as in order to provide a precisely patterned metal
layer. It is also contemplated that the one or more gas outlets 13
and the laser 15 may remain stationary during use and the substrate
20 may be controllably moved in a desired pattern in order to
produce a patterned metal layer.
[0028] In some embodiments, the surface of the substrate 20 may
comprise a pattern and the one or more gas outlets 13 and laser 15
may be configured to follow that pattern. For example, a
photoresist, such as SU-8, may be used to provide a pattern on the
surface of the substrate 20 using methods that are generally
understood in the art. Other techniques for patterning and/or
masking substrates, such as those that employ various types of
polymers, treatments, etc., are generally known in the art. It is
contemplated that any of these techniques could be applied in
cooperation with the method and system disclosed herein without
departing from the scope of the present disclosure.
[0029] The system 10 may also comprise one or more gas outlet
scrubber units 18. In some applications, the reaction of the
metal-containing precursor and the second gaseous reactant may
produce a byproduct that is potentially dangerous to equipment,
humans, the environment, etc. Accordingly, it may be desirable to
filter the reaction gas and/or to contact the reaction gas with a
neutralizing agent as it exits the vacuum chamber 11. For instance,
where the reaction is between a halogenated metal precursor (e.g.
WF.sub.6 or WCl.sub.6) and hydrogen gas, the reaction produces an
acidic byproduct such as HF or HCl. The acidic byproduct can be
neutralized by contacting the gas with an alkali compound as it
exits the vacuum chamber. The embodiments illustrated in FIGS. 1-3,
for example, each include a scrubber unit 18 in which the gases
exiting the vacuum chamber 11 are contacted with an alkali
compound. The alkali compound may be in a solid, liquid, or gas
state. In some embodiments, it may be desirable to flow the outlet
gas through an alkali liquid bath and/or to flow the gas through a
packed bed of alkali salts.
[0030] Although the foregoing embodiments are described in terms of
supplying first and second gaseous reactants, it should be
understood that the above-described systems 10 may be configured to
supply any number of gaseous reactants to the substrate surface 20.
For instance, any number of additional gas lines 12, gas outlets
13, and the like may be employed in the system 10 without departing
from the scope of the present disclosure.
Methods
[0031] Embodiments of the present disclosure are directed to
methods for the localized deposition of a metal layer on a
substrate. The method comprises introducing a first gaseous
reactant and a second gaseous reactant to the surface of a
substrate and, at the same time, directing laser energy against a
location on the substrate surface in order to heat a zone of the
surface such that a metal reaction product is deposited on the
heated zone of the surface.
[0032] The first gaseous reactant comprises a metal-containing
precursor gas. The metal-containing precursor gas may be any
metal-containing compound that may be conveyed in the gas phase to
the surface of the substrate and which may be reacted with a second
gaseous reactant to produce metal crystal growth. In some
embodiments, it may be possible to use a metal-containing precursor
compound that is both gaseous and stable at relatively low
temperatures, such as room temperature, so that first gaseous
reactant may be conveyed to the substrate surface without the need
for pre-heating. In other embodiments, the metal-containing
precursor compound will need to be prepared and conveyed under
elevated temperatures. The first gaseous reactant may also comprise
one or more additional gaseous components, such as a carrier gas,
one or more additional reactants, or the like.
[0033] In some embodiments, the metal layer being deposited may be
a transition metal and the metal-containing precursor gas may
therefore be a gaseous compound that contains a transition metal.
For instance, in some embodiments, the metal-containing precursor
gas may comprise tungsten, titanium, tantalum, niobium, chromium,
molybdenum, iron, nickel, zirconium, rhenium, hafnium, or the like.
In other embodiments, the metal layer being deposited may comprise
a basic or semi-metal. Accordingly, in some embodiments the metal
or semi-metal containing precursor gas may comprise aluminum, tin,
boron, silicon, germanium, arsenic, or the like.
[0034] The second gaseous reactant comprises a compound that is
capable of reacting with the metal-containing precursor gas to
produce metal crystal growth. In some embodiments, for example, the
second gaseous reactant may comprise hydrogen gas. At elevated
temperature the hydrogen gas may react with the metal-containing
precursor compound to produce a free metal, which may deposit on a
heated surface. The second gaseous reactant may also comprise one
or more additional gaseous components, such as a carrier gas, one
or more additional reactants, or the like.
[0035] In some embodiments, for example, the first gaseous reactant
comprises a metal-containing precursor compound having the formula
MX.sub.n, in which M is a transition metal; X is selected from the
group consisting of fluorine (F) and chlorine (Cl), bromine (Br);
and n is an integer selected from the group consisting of three,
four, five, and six. For example, in some embodiments, the
metal-containing precursor may be tungsten hexafluoride (WF.sub.6)
or tungsten hexachloride (WCl.sub.6). In other embodiments, the
metal-containing precursor may be molybdenum pentachloride
(MoCl.sub.5), tantalum pentachloride (TaCl.sub.5), or titanium
pentachloride (TiCl.sub.5). Each of these compounds are capable of
reacting with hydrogen (H.sub.2) to form a free metal and an acidic
byproduct. For example, the reaction of tungsten hexafluoride and
hydrogen proceeds according to the following:
WF.sub.6+3 H.sub.2.fwdarw.W+6 HF.
Similarly, the reaction of titanium pentachloride generally
proceeds according to the following:
2 TiCl.sub.5+5 H.sub.2.fwdarw.2 Ti+10 HCl.
[0036] Each of the first and second gaseous reactants are
introduced to a portion of a substrate surface that is heated using
laser energy, i.e. a heated zone of the substrate surface. For
example, a laser may be directed to a position on the substrate
surface such that the laser energy contacts the substrate surface
at a desired location. The laser parameters may be controlled so
that the heat produced by the laser energy expands outwardly from
the point of contact to produce a heated zone on the substrate
surface having a desired size and/or configuration. The heat
produced by the laser energy may also cause the first and second
gaseous reactants to react, producing a metal, such as a free
metal, that is deposited on the heated zone of the substrate
surface to form a metal layer.
[0037] Each of the first and second gaseous reactants may be
introduced to the surface of a substrate 20 through one or more gas
outlets 13. In some embodiments, such as the embodiment illustrated
in FIGS. 1 and 2, the first and second gaseous reactants may be
mixed prior to being introduced to the surface of the substrate 20.
One benefit of this approach is that mixing of the first and second
gaseous reactants may be easily performed prior to the reactants
reaching the substrate surface, in to obtain a consistent mixture
of reactants at the heated reaction zone. This may provide for the
deposit of a more consistent metal layer, i.e. one having a
consistent thickness, a smooth surface, or desirably both. In other
embodiments, such as the embodiment illustrated in FIG. 3, the
first and second gaseous reactants may be supplied via separate gas
outlets 13, such that they come into contact with one another for
the first time in the vicinity of the substrate surface 20. One
benefit of this approach is that it tends to prevent the first and
second gaseous reactants from undergoing unwanted reaction in the
gas lines 12 and/or gas outlets 13, which can lead to clogging and
destruction of the process equipment.
[0038] To prepare a more consistent metal deposit, it may be
desirable to introduce a mixture of the first and second gaseous
reactants substantially evenly across the heated zone 21 of the
substrate surface 20. For instance, in some embodiments, the one or
more gas outlets may be configured to introduce the mixture of
gases across substantially the entirety of the heated zone 21. This
could be accomplished, for example, by using either a single gas
outlet 13 having a gas flow area that is similar to the area of the
heated zone 21 or a plurality of gas outlets which, taken together,
have a gas flow area that is similar to the area of the heated
zone. For example, the diameter of the gas outlet or outlets 13 may
make up between about 80% and about 110% of the diameter of the
heated zone, alternatively between about 70% and about 100%,
alternatively between about 50% and about 99%, alternatively
between about 50% and about 95%, alternatively between about 60%
and about 99%, alternatively between about 70% and about 95%,
alternatively between about 75% and about 99%, alternatively
between about 80% and about 95%. In order to prevent unnecessary
loss of reactants due to gas flow around the heated zone 21, it may
generally be desirable to have a gas flow area of the gas outlet or
outlets 13 that is less than the area of the heated zone. It is
also believed that by ensuring that the gas flow area of the gas
outlet or outlets 13 is less than the area of the heated zone 21,
one may prepare a metal layer having a smoother surface than
embodiments in which the gas flow area of the gas outlet or outlets
is greater than the area of the heated zone 21. That said, it may
still be desirable in some embodiments to utilize one or more gas
outlets 13 in which the gas flow area is greater than the area of
the heated zone 21.
[0039] In other embodiments, at least one of the one or more gas
outlets 13 may include a nozzle, such as a nozzle that is
specifically configured to introduce the reactants substantially
evenly across the entirety of the heated zone 21. Careful control
over the flowrates of the first and second gaseous reactants may
also be used to provide for a substantially even mixture of gaseous
reactants across the heated zone 21.
[0040] The distance between the one or more gas outlets 13 and the
heated zone 21 of the substrate surface 20 may also be carefully
controlled in order to provide for an efficient and controllable
metal deposition. In general, it is desirable for the distance
between the one or more gas outlets 13 and the heated zone 21 of
the substrate surface 20 to be kept at a minimum in order to ensure
that the first and second gaseous reactants make adequate contact
with the heated surface, as opposed to simply flowing around the
heated zone. In some instances, however, too close of a
relationship between the gas outlets 13 and the heated zone 21 may
result in a heating of the gas outlets 13 to a temperature at which
metallic reactions products are deposited on the gas outlets,
thereby clogging the gas outlets 13 and potentially destroying the
process equipment. Accordingly the distance between the gas outlets
13 and the heated zone 21 should be maintained within a desirable
working range. For example, in some embodiments the one or more gas
outlets 13 may be between about 3 mm and about 20 mm above the
substrate surface, alternatively between about 3 mm and about 10
mm, alternatively between about 5 mm and about 20 mm, alternatively
between about 5 mm and about 10 mm.
[0041] In some embodiments, it may be desirable to pre-heat one or
more of the gaseous reactants prior to introducing the gaseous
reactants to the surface of the substrate 20. By increasing the
temperature of the gaseous reactants prior to their contact with
the heated zone 21 of the substrate surface 20, for example, one
may ensure that the gaseous reactants are adequately heated to the
desired reaction temperature that is necessary to cause a metal
deposit and that the reaction and deposition of the metal occur
quickly.
[0042] Since care should be taken to avoid having the gas lines 12
and/or the gas outlets 13 reach a temperature at which the reaction
of the first and second gaseous reactants would result in the
formation of a metal layer on the process equipment, in some
embodiments it may be desirable to cool one or more of the gas
lines 12 and/or the gas outlets 13. For instance, reflected heat
from the heated zone 21 of the substrate surface 20 may result in a
heating of the one or more gas outlets 13 to a temperature at which
the metallic reaction product would form on the gas outlets 13. In
such instances, it may be necessary for the one or more gas outlets
13 to comprise a cooling system or insulation. Because the gaseous
reactants need a heated surface in order for a substantial deposit
to occur, in some embodiments, the gaseous reactants may be
preheated to a temperature at which reaction may occur and yet the
surfaces of the process equipment, e.g. the gas lines 12 and/or gas
outlets 13, may be cooled in order to prevent the metal reaction
production from depositing on those surfaces.
[0043] The temperature to which the heated zone 21 of the substrate
surface 20 must be brought in order to induce the formation of a
desirable metal layer will depend on the specific reactants, as
well as the other process parameters. In some embodiments, the zone
21 of the substrate surface 20 is heated to at least a temperature
that is sufficient to cause the first and second gaseous reactants
to react. For example, where tungsten hexafluoride is used as the
metal-containing precursor and hydrogen is used as the second
gaseous reactant, the reaction will occur at temperatures above
about 300.degree. C. Accordingly, in some embodiments, the zone 21
of the substrate surface 20 may be heated to a temperature of at
least 300.degree. C. Or, for example, where tungsten hexachloride
is used as the metal-containing precursor and hydrogen is used as
the second gaseous reactant, the reaction will occur at
temperatures above about 500.degree. C. Accordingly, in some
embodiments, the substrate surface may be heated to a temperature
of at least about 500.degree. C. In some embodiments, such as where
the gaseous reactants may already be preheated to a desired
reaction temperature, the heated zone of the substrate may be
brought to a temperature below the reaction temperature of the
first and second gaseous reactants.
[0044] The exact temperature to which the surface is heated may be
selected so as to provide a desired combination of metal growth
rate and quality of the metal layer. As the temperature is
increased, for example, the metal growth rate is increased, but the
smoothness of the metal layer may decrease. Additionally, if the
substrate surface 20 is heated above a certain upper bound
temperature, the metal layer will not form at all. Accordingly, for
example, where tungsten hexafluoride and hydrogen are reacted so as
to deposit tungsten using the presently disclosed method, the
temperature may generally be selected to be between about
300.degree. C. and about 900.degree. C., alternatively between
about 400.degree. C. and about 800.degree. C. Or, for example,
where tungsten hexachloride and hydrogen are reacted so as to
deposit tungsten using the presently disclosed method, the
temperature may generally be selected to be between about
500.degree. C. and about 900.degree. C., alternatively between
about 600.degree. C. and 800.degree. C. However, it should be
understood that the temperature to which the surface is heated may
vary greatly depending on what metal is being deposited and what
reaction is being used to deposit that metal. The above temperature
ranges are provided as non-limiting examples.
[0045] In some instances, one or more of the reactants may have to
be maintained at an elevated temperature prior to being introduced
to the surface of the substrate 20. For example, in the embodiment
illustrated in FIG. 2, a tungsten hexachloride gas, which is not
stable at room temperature, is prepared immediately before its use
in the deposition process. As such, the tungsten hexachloride gas
is maintained at an elevated temperature as it is conveyed to the
gas outlet 13. Specifically, as illustrated in FIG. 2, the tungsten
hexachloride gas may be prepared by contacting tungsten metal chips
with chlorine gas at an elevated temperature, such as above
600.degree. C. Accordingly, in order to prevent the tungsten
hexachloride gas from breaking down prior to being introduced to
the surface of the substrate 20, the first gaseous reactant is
heated as it conveyed to the gas outlet 13. Because the metal
formed in the reaction will only deposit to a significant extent on
a heated surface, the tungsten hexachloride gas and the hydrogen
may be premixed at a temperature at which a reaction occurs so long
as the equipment surfaces that the mixture comes into contact with
prior to being introduced to the substrate surface are cool enough
to avoid unwanted metal deposition. Alternatively, the tungsten
hexachloride gas and the hydrogen may be introduced to the surface
of the substrate through separate gas lines.
[0046] In some embodiments, the reaction between the first and
second gaseous reactants may need to be performed under vacuum.
Generally, a vacuum between about 25 Torr and about 0.001 Torr
should be sufficient. In some embodiments, such as where the method
is being used to prepare a single crystal metal, higher vacuum
levels, such as those between about 5 Torr and about 0.001 Torr,
may be necessary.
[0047] Additionally, in some embodiments, an acidic byproduct is
produced by the reaction of the first and second gaseous reactants.
For example, where a fluorinated metal compound is reduced by a
reaction with hydrogen, the reaction produces a hydrofluoric acid
byproduct. Similarly, where a chlorinated metal compound is reacted
with hydrogen, the reaction products a hydrochloric acid byproduct.
These acid gases are corrosive to process equipment and dangerous
for workers and the environment. Accordingly, it may be desirable
to contact the gases exiting the reaction chamber 11 with an
alkaline element in order to neutralize the acidic byproducts. For
instance, the gases exiting the reaction chamber may be directed
through an alkali-containing liquid solution, such as an aqueous
solution of NaOH or KOH. Alternatively (or in addition), the gases
exiting the reaction chamber may be directed across solid alkali
components.
[0048] The size of the heated zone 21 of the substrate surface 20,
and hence the area of the surface on which the metal layer is
formed, is determined by the size and power of the laser beam as
well as the conductivity of the substrate. Accordingly, embodiments
of the present disclosure provide a method by which one may prepare
a metal layer in a controlled fashion over a very small portion of
a surface. For example, in some embodiments, the laser may be
controlled to provide a heated zone 21 having a diameter that is
less than 10 mm, alternatively less than 8 mm, alternatively less
than 6 mm, alternatively less than 5 mm, alternatively less than 4
mm, alternatively less than 3 mm, alternatively less than 2 mm,
alternatively less than 1 mm.
[0049] For substrates that are highly conductive, one may wish to
contact a smaller area of the substrate with the laser energy in
order to limit the size of the heated zone 21 on which the metal
will deposit. It also may be desirable to adjust the reaction
parameters in order to increase the speed of the reaction and metal
deposition, in order to limit undesired expansion of the heated
zone, and the resulting metal layer. Additionally, if needed,
insulation, such as coatings on the substrate surface or the use of
other cooling elements, may be used to limit the effects of high
substrate conductivity.
[0050] The thickness of the metal layer may be precisely controlled
through control over the relevant reaction parameters, such as the
temperature of the heated zone, the flowrate of the first and
second gaseous reactants, and the length of time that the
deposition is performed on the heated zone. For example, in some
embodiments, the deposition may be performed to prepare a metal (or
semi-metal) layer having a thickness in the nanometer scale (e.g.
between about 1 nm and about 100 nm, alternatively between about 1
nm and about 50 nm, alternatively between about 1 nm and about 10
nm). In other embodiments, the deposition may be performed to
prepare a metal (or semi-metal) layer having a thickness in the
millimeter scale (e.g. between about 1 mm and about 100 mm,
alternatively between about 1 mm and about 50 mm, alternatively
between about 1 mm and about 10 mm). In some embodiments, the
deposition may be performed to prepare a metal (or semi-metal)
layer having a thickness between about 1 nanometer (nm) and about 5
millimeters (mm), alternatively between about 1 nm and about 3 mm,
alternatively between about 1 nm and about 1 mm, alternatively
between about 10 nm and about 5 mm, alternatively between about 10
nm and about 3 mm, alternatively between about 10 nm and about 1
mm.
[0051] Because the size and thickness of metal deposits may be
precisely controlled using the presently disclosed method,
embodiments of the presently disclosed method may be used as a
mechanism for three-dimensional printing. For example, by
repositioning the laser 15 one may change the location of the
heated zone 21 on the surface of the substrate 20. The gas outlets
13 may also be repositioned, desirably in coordination with the
repositioning of the heated zone 21, so that the first and second
gaseous reactants remain in contact with the heated zone 21. In
some embodiments, for instance, each of the laser 15 and the gas
outlets 13 are moved in a controlled manner during operation so as
to deposit the metal layer in a desired pattern on the substrate
surface 20. It is also contemplated that the laser 15 and the gas
outlets 13 may remain stationary and that the substrate 20 may be
moved in a controlled manner during operation. In some embodiments,
the surface of the substrate 20 may comprise a pattern, such as may
be formed by a photoresist or polymer coating, which may assist in
the controlled patterning of the metal deposit.
[0052] Embodiments of the presently disclosed method may be used,
for example, for the printing of one or more electronic components
on a substrate. For example, the method may be used for the
printing of electronic components, such as gates, semiconductors,
and the like on a silicon wafer. Accordingly, in some embodiments
the substrate may be silicon, such as a silicon wafer. In other
embodiments, the substrate may be metallic. Additionally, in some
embodiments, the method may be utilized to prepare multiple layers
of a single material or multiple layers of different materials on a
substrate surface.
[0053] Embodiments of the presently disclosed method may also be
used, for example, for the preparation of metals having any number
of desired characteristics. In some embodiments, embodiments of the
presently disclosed method may be performed to produce a
monocrystalline metal. For example, one may select a substrate that
has a similar crystal structure to the metal layer being formed.
This may influence the metal crystal that forms as a result of the
reaction between the first and second gaseous reactants to grow as
a single crystal on the substrate surface. For example, by
performing a carefully controlled deposition of tungsten on a
monocrystalline molybdenum substrate (molybdenum having a similar
crystal structure to tungsten), one may prepare a monocrystalline
tungsten.
[0054] Embodiments of the presently disclosed method may also be
used for the deposit of ceramic materials onto a substrate. For
example, embodiments of the presently disclosed method may be
configured to deposit SiO.sub.2, Al.sub.2O.sub.3, or SnO.sub.2.
Embodiments of the presently disclosed method may also be used for
the deposit of semiconductor materials onto a substrate. For
example, embodiments of the presently disclosed method may be
configured to deposit silicon, germanium, tin, silicon carbide,
boron nitride, aluminum nitride, gallium nitride, zinc oxide,
titanium dioxide, tin dioxide, nickel oxide, or the like.
Similarly, embodiments of the presently disclosed method may also
be configured to deposit semiconductor alloys, such as
silicon-germanium alloy, silicon-tin alloys, and the like.
[0055] In some embodiments, the substrate may be removed after the
metal layer is deposited, yielding a pure metal having a desired
shape and/or desirable properties. The substrate may be removed
using chemical processing, as would generally be understood by a
person of ordinary skill in the art.
[0056] It can be seen that the described embodiments provide a
unique and novel method and system that has a number of advantages
over those in the art. While there is shown and described herein
certain specific structures embodying the invention, it will be
manifest to those skilled in the art that various modifications and
rearrangements of the parts may be made without departing from the
spirit and scope of the underlying inventive concept and that the
same is not limited to the particular forms herein shown and
described except insofar as indicated by the scope of the appended
claims.
* * * * *