U.S. patent application number 15/644857 was filed with the patent office on 2017-10-26 for angled lift jetting.
The applicant listed for this patent is ORBOTECH LTD.. Invention is credited to Zvi Kotler, Michael Zenou.
Application Number | 20170306495 15/644857 |
Document ID | / |
Family ID | 56416516 |
Filed Date | 2017-10-26 |
United States Patent
Application |
20170306495 |
Kind Code |
A1 |
Kotler; Zvi ; et
al. |
October 26, 2017 |
ANGLED LIFT JETTING
Abstract
An apparatus for material deposition on an acceptor surface
includes a transparent donor substrate having opposing first and
second surfaces, such that at least a part of the second surface is
not parallel to the acceptor surface, and including a donor film on
the second surface. The apparatus additionally includes an optical
assembly, which is configured to direct a beam of radiation to pass
through the first surface of the donor substrate and impinge on the
donor film at a location on the part of the second surface that is
not parallel to the acceptor surface, so as to induce ejection of
droplets of molten material from the donor film onto the acceptor
surface.
Inventors: |
Kotler; Zvi; (Tel Aviv,
IL) ; Zenou; Michael; (Hashmonaim, IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ORBOTECH LTD. |
Yavne |
|
IL |
|
|
Family ID: |
56416516 |
Appl. No.: |
15/644857 |
Filed: |
July 10, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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PCT/IL2016/050007 |
Jan 5, 2016 |
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15644857 |
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62105761 |
Jan 21, 2015 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B23K 2103/00 20180801;
H01L 51/0013 20130101; B23K 26/0648 20130101; C23C 14/225 20130101;
B23K 26/342 20151001; C23C 14/28 20130101; C23C 14/048 20130101;
B23K 2103/42 20180801 |
International
Class: |
C23C 18/14 20060101
C23C018/14 |
Claims
1. Apparatus for material deposition on an acceptor surface,
comprising: a transparent donor substrate having opposing first and
second surfaces, such that at least a part of the second surface is
not parallel to the acceptor surface, and comprising a donor film
on the second surface; and an optical assembly, which is configured
to direct a beam of radiation to pass through the first surface of
the donor substrate and impinge on the donor film at a location on
the part of the second surface that is not parallel to the acceptor
surface, so as to induce ejection of droplets of molten material
from the donor film onto the acceptor surface.
2. The apparatus according to claim 1, wherein the second surface
comprises a periodic structure.
3. The apparatus according to claim 1, wherein the second surface
comprises a multi-faceted structure.
4. The apparatus according to claim 3, wherein the second surface
comprises first and second facets oriented at opposing angles and
coated with different respective donor films.
5. The apparatus according to claim 3, wherein the second surface
comprises first and second facets and wherein only the first facet
is coated with the donor film.
6. Apparatus for material deposition, comprising: a transparent
donor substrate having opposing first and second surfaces, such
that at least a part of the second surface is non-planar, and
comprising a donor film on the non-planar part of the second
surface; and an optical assembly, which is configured to direct a
beam of radiation to pass through the first surface of the donor
substrate and impinge on the donor film at a location on the
non-planar part of the second surface, so as to induce ejection of
droplets of molten material from the donor film onto an acceptor
surface.
7. The apparatus according to claim 6, wherein the second surface
comprises a periodic structure.
8. The apparatus according to claim 6, wherein the second surface
comprises a curved structure.
9. The apparatus according to claim 6, wherein the second surface
comprises a multi-faceted structure.
10. The apparatus according to claim 9, wherein the second surface
comprises first and second facets oriented at opposing angles and
coated with different respective donor films.
11. The apparatus according to claim 9, wherein the second surface
comprises first and second facets and wherein only the first facet
is coated with the donor film.
12. A method for material deposition, comprising: providing a
transparent donor substrate having opposing first and second
surfaces and having first and second facets oriented at opposing
angles on the second surface, and comprising a donor film on the
first and second facets; positioning the donor substrate in
proximity to an acceptor substrate, with the second surface facing
toward the acceptor substrate; and directing a beam of radiation to
pass through the first surface of the donor substrate and impinge
on the donor film at a location selected responsively to the first
and second facets of the second surface, so as to induce ejection
of droplets of molten material from the donor film on the first and
second facets onto the acceptor substrate.
13. The method according to claim 12, wherein the ejection of
droplets of molten material from the donor film on the first and
second facets is performed simultaneously.
14. The method according to claim 12, wherein the ejection of
droplets of molten material from the donor film on the first and
second facets is performed sequentially.
15. A method for material deposition, comprising: providing a
transparent donor substrate, which has opposing first and second
surfaces and has a donor film on the second surface; positioning
the donor substrate in proximity to an acceptor surface of an
acceptor substrate, with the second surface facing toward the
acceptor substrate and oriented at an oblique angle relative to the
acceptor surface; and directing a beam of radiation to pass through
the first surface of the donor substrate and impinge on the donor
film while the second surface is oriented at the oblique angle so
as to induce ejection of droplets of molten material from the donor
film onto the acceptor surface.
16. The method according to claim 15, wherein positioning the donor
substrate comprises identifying a three-dimensional (3D) shape of a
topographical feature on the acceptor surface, and orienting the
donor substrate responsively to the 3D shape.
17. The method according to claim 15, wherein the second surface
comprises a curved structure.
18. The method according to claim 15, wherein the second surface of
the donor substrate comprises a multi-faceted structure.
19. The method according to claim 18, wherein the multi-faceted
structure comprises first and second facets oriented at opposing
angles and coated with the donor film.
20. The method according to claim 19, and comprising ejecting the
droplets from the donor film of the first and second facets, onto
the 3D shape, simultaneously.
21. The method according to claim 19, and comprising ejecting the
droplets from the donor film of the first and second facets, onto
the 3D shape, sequentially.
22. The method according to claim 15, wherein the second surface of
the donor substrate comprises a periodic structure.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of International
Patent Application PCT/IL2016/050007, entitled "Angled LIFT
jetting," filed Jan. 5, 2016, which claims the benefit of U.S.
provisional application 62/105,761, entitled "Angled LIFT jetting,"
filed Jan. 21, 2015. The respective disclosures of the
aforementioned applications are incorporated herein by
reference.
FIELD OF THE INVENTION
[0002] The present invention relates generally to laser direct
writing, and particularly to methods and systems for Laser Induced
Forward Transfer jetting.
BACKGROUND OF THE INVENTION
[0003] Laser-Induced Forward Transfer (LIFT) is a technology for
direct printing of various materials such as metals and polymers.
LIFT provides high printing quality however advanced electronic
devices comprise three-dimensional (3D) patterns that are hard to
coat uniformly. Examples of prior art techniques are provided
below.
[0004] U.S. Pat. No. 6,792,326, to Duignan, whose disclosure is
incorporated herein by reference, describes a material delivery
system for miniature structure fabrication which has a substrate, a
material carrier having a deposition layer, and a laser beam
directed towards the material carrier element. The system operates
in either an additive mode of operation, or a subtractive mode of
operation so that a workpiece does not have to be removed from a
tool when change of modes of operation takes place.
[0005] U.S. Pat. No. 6,805,918, to Auyeung, et al., whose
disclosure is incorporated herein by reference, describes a method
for laser transfer and deposition of a rheological fluid wherein
laser energy strikes a target substrate comprising a rheological
fluid, causing a portion of the rheological fluid to evaporate and
propel non-evaporated rheological fluid onto a receiving
substrate.
[0006] U.S. Pat. No. 7,277,770, to Huang, whose disclosure is
incorporated herein by reference, describes a direct write process
and apparatus for fabricating a desired circuit component onto a
substrate surface of a microelectronic device according to a
computer-aided design (CAD).
[0007] U.S. Patent application publication 2005/0095367, to
Babiarz, et al., whose disclosure is incorporated herein by
reference, describes a method of noncontact dispensing a viscous
material onto a surface of a substrate, which uses a jetting valve
having a nozzle directing the viscous material flow in a jetting
direction nonperpendicular to the surface of the substrate. The
nonperpendicular jetting direction results in the droplet producing
a reduced wetted area on the substrate.
[0008] Documents incorporated by reference in the present patent
application are to be considered an integral part of the
application except that, to the extent that any terms are defined
in these incorporated documents in a manner that conflicts with
definitions made explicitly or implicitly in the present
specification, only the definitions in the present specification
should be considered.
SUMMARY OF THE INVENTION
[0009] An embodiment of the present invention that is described
herein provides an apparatus for material deposition on an acceptor
surface including a transparent donor substrate having opposing
first and second surfaces, such that at least a part of the second
surface is not parallel to the acceptor surface, and including a
donor film on the second surface. The apparatus additionally
includes an optical assembly, which is configured to direct a beam
of radiation to pass through the first surface of the donor
substrate and impinge on the donor film at a location on the part
of the second surface that is not parallel to the acceptor surface,
so as to induce ejection of droplets of molten material from the
donor film onto the acceptor surface.
[0010] In some embodiments, the second surface includes a periodic
structure. In other embodiments, the second surface includes a
multi-faceted structure. In yet other embodiments, the second
surface includes first and second facets oriented at opposing
angles and coated with different respective donor films. In
alternative embodiments, the second surface includes first and
second facets wherein only the first facet is coated with the donor
film. In an embodiment, the second surface includes a curved
structure.
[0011] There is additionally provided, in accordance with an
embodiment of the present invention, an apparatus for material
deposition including a transparent donor substrate having opposing
first and second surfaces, such that at least a part of the second
surface is non-planar, and including a donor film on the non-planar
part of the second surface. The apparatus additionally includes an
optical assembly, which is configured to direct a beam of radiation
to pass through the first surface of the donor substrate and
impinge on the donor film at a location on the non-planar part of
the second surface, so as to induce ejection of droplets of molten
material from the donor film onto an acceptor surface.
[0012] There is additionally provided, in accordance with an
embodiment of the present invention, a method for material
deposition including providing a transparent donor substrate having
opposing first and second surfaces and having first and second
facets oriented at opposing angles on the second surface, and
including a donor film on the first and second facets. The donor
substrate is positioned in proximity to an acceptor substrate, with
the second surface facing toward the acceptor substrate. A beam of
radiation is directed to pass through the first surface of the
donor substrate and impinge on the donor film at a location
selected responsively to the first and second facets of the second
surface, so as to induce ejection of droplets of molten material
from the donor film on the first and second facets onto the
acceptor substrate.
[0013] There is further provided, in accordance with an embodiment
of the present invention, a method for material deposition
including providing a transparent donor substrate, which has
opposing first and second surfaces and has a donor film on the
second surface. The donor substrate is positioned in proximity to
an acceptor surface of an acceptor substrate, with the second
surface facing toward the acceptor substrate and oriented at an
oblique angle, i.e., at a non-normal angle, relative to the
acceptor surface. A beam of radiation is directed to pass through
the first surface of the donor substrate and impinge on the donor
film while the second surface is oriented at the oblique angle so
as to induce ejection of droplets of molten material from the donor
film onto the acceptor surface.
[0014] The present invention will be more fully understood from the
following detailed description of the embodiments thereof, taken
together with the drawings in which:
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a schematic, pictorial illustration of a system
for direct writing on a substrate, in accordance with an embodiment
of the present invention;
[0016] FIG. 2 is a schematic side view showing details of the
system of FIG. 1, in accordance with an embodiment of the present
invention;
[0017] FIGS. 3-6 are schematic, sectional views showing details of
non-planar Laser-Induced Forward Transfer (LIFT) donors, in
accordance with embodiments of the present invention; and
[0018] FIG. 7 is a schematic sectional view showing details of a
non-planar LIFT donor, which is not parallel to an acceptor
substrate, in accordance with embodiments of the present
invention.
DETAILED DESCRIPTION OF EMBODIMENTS
Overview
[0019] Embodiments of the present invention that are described
hereinbelow provide methods and apparatus that enhance the
capabilities and usability of Laser-Induced Forward Transfer (LIFT)
techniques. The enhancements offered by these embodiments are
useful for printing on electronic circuits comprising various types
of substrates, and particularly for printing on three-dimensional
(3D) structures. The disclosed techniques are by no means limited
to these specific application contexts, however, and aspects of the
embodiments described herein may also be applied, mutatis mutandis,
to LIFT-based printing on substrates other than electronic circuit
substrates. The enhancements include printing of both metallic and
non-metallic materials.
[0020] In a typical LIFT-based system, a small distance between a
donor surface and an acceptor substrate yields high printing
quality on the substrate. However, printing on 3D structures on the
substrate poses two challenges: a possible large distance between
the donor surface and the lower surfaces of the acceptor, (yielding
low printing quality on the acceptor) and a possible poor coating
("step coverage") of vertical sidewalls of the 3D structures of the
substrate.
[0021] Embodiments of the present invention that are described
hereinbelow overcome some of these limitations by providing
different, novel types of donor structures and orientations, and
corresponding methods of operation of LIFT systems. In some
embodiments, a transparent donor substrate has opposing first and
second surfaces, such that at least a part of the second surface is
not parallel to an acceptor surface and comprises a donor film
thereon. An optical assembly is configured to direct a beam of
radiation to pass through the first surface of the donor substrate
so as to impinge on the donor film at a location on the part of the
second surface that is not parallel to the acceptor surface. The
impingement induces ejection of droplets of molten material, such
as metals and polymers, from the donor film onto the acceptor
surface.
[0022] In other embodiments, the second surface comprises a
multi-faceted, periodic structure, wherein at least some of the
facets are coated with donor films. The multi-faceted structure
comprises first substantially similar facets and second
substantially similar facets, and the first and second facets are
oriented at opposing angles and are coated with different
respective donor films. In yet other embodiments, the second
surface of the donor comprises first substantially similar facets
and second substantially similar facets, which are not parallel to
a horizontal surface of the substrate, as well as third
substantially similar facets, which are parallel to the horizontal
surface of the substrate but which are not coated with donor films.
The third facets may be used for in-situ inspection of the LIFT
process through the donor.
[0023] In alternative embodiments, the second surface comprises a
curved structure.
[0024] In another embodiment, a transparent donor substrate has
opposing first and second surfaces, such that at least a part of
the second surface is non-planar and has a donor film on the
non-planar part of the second surface. An optical assembly directs
a beam of radiation to pass through the first surface of the donor
substrate and impinge on the donor film at a location on the
non-planar part of the second surface, so as to induce ejection of
droplets of molten material from the donor film onto an acceptor
surface.
System Description
[0025] FIG. 1 is a schematic, pictorial illustration of a system
for direct writing on a substrate 24, in accordance with an
embodiment of the present invention. This system and its components
are shown here solely to illustrate the sort of environment in
which the techniques described herein may be implemented. Such
techniques may similarly be carried out using suitable equipment of
other types and in other configurations.
[0026] The system of FIG. 1 is built around a print and direct
write apparatus 10, which operates on substrate 24 of an electronic
circuit 12, such as a Flat panel Display (FPD) or a printed circuit
board (PCB), which is held on a mounting surface 14. In generic
LIFT processes substrate is also termed a receiver or an acceptor.
The terms "Flat panel Display", "FPD", "printed circuit board", and
"PCB" are used herein to refer generally to any sort of a
dielectric or a metal or a semiconductor substrate on which
conductive materials such as metals, or non-conductive materials
such as dielectrics and polymers are deposited, regardless of the
type of substrate material and the process used for deposition.
Apparatus 10 may be used to deposit new layers such as printing of
metal circuitry on various substrates or in any other electronic
devices.
[0027] Apparatus 10 comprises an optical assembly 16, containing a
laser and optics for Laser-Induced Forward Transfer (LIFT). Optical
assembly 16 and its operations are described with reference to FIG.
2 below. In some embodiments, direct printing applications, such as
are performed by apparatus 10, for example as patterning or layer
deposition on a PCB or FPD or any other applicable device, may
comprise other diagnostics capabilities that may be in-situ (i.e.,
monitoring and inspecting during the printing process), integrated
(i.e., monitoring and inspecting selected devices immediately after
completion of the LIFT process), or offline, by a stand-alone
diagnostics system.
[0028] A positioning assembly 20, in the form of a bridge,
positions optical assembly 16 over pertinent sites on substrate 24
in question, by linear motion along the axes of apparatus 10. In
other embodiments, positioning assembly 20 may be in other forms,
such as a moving stage along one (X) axis, two (X, Y) axes, or
three (X, Y, Z) axes below circuit 12 and static assembly 16. A
control unit 27 controls the operation of the optical and
positioning assemblies, and carries out additional functions such
as temperature control, so as to carry out the required inspection,
printing, patterning and/or other manufacturing and repair
operations, as described below.
[0029] Typically, control unit 27 communicates with an operator
terminal 23, comprising a general-purpose computer including a
processor 34 and a display 36, along with a user interface and
software.
[0030] FIG. 2 is a schematic side view showing details of apparatus
10, and particularly of optical assembly 16, in accordance with an
embodiment of the present invention. A laser 13 emits pulsed
radiation, which is focused by optics 15. The laser may comprise,
for example, a pulsed Nd:YAG laser with frequency-doubled output,
and the pulse amplitude of the laser may be controlled conveniently
by control unit 27. (Control unit 27 may also be configured, albeit
possibly by non-trivial means, to control the pulse duration.)
Optics 15 are similarly controllable in order to adjust the
location and size of the focal spot formed by the laser beam.
[0031] In some embodiments an additional laser (not shown) or any
other illumination source (e.g., LED or lamp), with different beam
characteristics, may be used. The additional laser may operate in
another wavelength and with another optics setup, and may be used,
for example, for surface inspection.
[0032] Optical assembly 16 is shown in FIG. 2 in the LIFT
configuration. Optics 15 focus the beam from laser 13 onto a donor
19, which comprises a donor substrate 17 with one or more donor
films 18 deposited on substrate 17. Typically, substrate 17
comprises a transparent optical material, such as glass or a
plastic sheet, or other types of transparent substrates, such as
silicon wafers or flexible plastic foils. The beam from laser 13 is
aligned (by positioning assembly 20) with a selected site on
substrate 24 of circuit 12, and donor 19 is positioned above the
site at a desired gap width D from the substrate. Typically, this
gap width is at least 0.1 mm, and the inventors have found that gap
widths of 0.2 mm or even 0.5 mm or greater can be used, subject to
proper selection of the laser beam parameters.
[0033] Optics 15 focus the laser beam through the outer surface of
substrate 17 onto film 18, thereby causing droplets of molten
material to be ejected from the film, across the gap and onto the
surface of substrate 24 (e.g. into an opening in a structured layer
25).
[0034] FIG. 3 is a schematic, sectional view showing details of a
non-planar LIFT donor 22A, in accordance with an embodiment of the
present invention. Donor 22A is transparent to a laser beam 28 and
comprises two surfaces, a planar first (upper) surface 23A,
typically perpendicular to laser beam 28 and parallel to substrate
24, and a second (lower) surface 21A, which faces substrate 24. In
an embodiment, the lower surface of donor 22A is non-planar and
comprises two or more facets, which are not parallel to substrate
24. In the example of FIG. 3, the lower surface of donor 22A
comprises substantially similar facets 32, and substantially
similar facets 26. Facets 32 are typically parallel to laser 28,
and facets 26 have a slope (gradient) and are coated with one or
more films of materials 26M to form a single layer or a
multilayered stack of respective materials. In the disclosure and
in the claims, a facet is assumed to have a surface which is flat
and plane.
[0035] During a LIFT process, laser beam 28 provides pulsed
radiation on donor 22A. The radiation passes through surface 23A
and impinges on the donor film of a selected facet 26. Since the
selected facet is not parallel to an acceptor surface 33A of
substrate 24, herein assumed to be parallel to a base surface 35A
of the substrate, ejection of droplets 30 of molten material from
the donor film occurs at an angle 29 to acceptor surface 33A of
substrate 24. Acceptor surface 33A of substrate 24 is also referred
to herein as top surface 33A of the substrate. Typically, the
ejection of droplets 30 is orthogonal to facet 26, and is indicated
by an arrow 31. Thus, while laser beam 28 is perpendicular to
substrate 24, the slope of facet 26 causes the angled ejection
illustrated, so as to deposit droplets 30 on a sidewall of a
structure 25A on substrate 24. As is illustrated in the figure,
structure 25A has surfaces, such as the sidewall, which are not
parallel to acceptor surface 33A, i.e., to base surface 35A. In the
description hereinbelow, other structures 25B, 25C, 25D, 25E are
mounted on substrate 24. The other structures have the same
property as structure 25A described here, i.e., they have surfaces
which are not parallel to the base surface of substrate 24.
[0036] In the example of FIG. 3, the angle of droplet ejection from
coated facets is set primarily by the design of donor 22A.
[0037] In typical LIFT processes, a small distance between donor
22A and substrate 24 (as well as structure 25A) yields high
printing quality on substrate 24 and structure 25A. In addition,
the multi-faceted structure provides easy jetting in predefined
desired directions perpendicular to each of the facets, and thus
enables high coating uniformity of sidewalls of a 3D structure.
[0038] In some embodiments, the lower surface of donor 22A
comprises a periodic structure (as shown in FIG. 3). In other
embodiments, the structure of the lower surface of donor 22A may
have a non-periodic structure with different slopes of facets along
the lower surface of donor 22A. I.e., the structure may be
different from the center of donor 22A to the edge of the donor.
For example the slope angle of facets at the edge of donor 22A may
be steeper than the angle of the facets at the center.
[0039] In an alternative embodiment, the lower surface of donor 22A
may comprise more than two facets as will be described with respect
to FIG. 5.
[0040] FIG. 4 is a schematic, sectional view showing details of a
non-planar LIFT donor 22B, in accordance with an embodiment of the
present invention. Donor 22B is transparent to laser beam 28 (not
shown in FIG. 4). An upper surface 23B of donor 22B is parallel to
top surface 33A of substrate 24. A lower surface 21B of donor 22B
is non-planar and comprises a multi-faceted structure, such as
substantially similar facets 40 and substantially similar facets
42, which are not parallel to acceptor surface 33A of substrate 24.
Each facet thus has a different slope with respect to the acceptor
surface of substrate 24. In an embodiment, the facets are oriented
at opposing, not necessarily equal, angles (e.g., +45.degree.
and)-30.degree. with respect to beam 28. Both facets may be coated
with different respective donor films such as material 26M, as
described with respect to FIG. 3, and another material.
[0041] Such dual material structures may be manufactured by various
techniques, such lithography, direct evaporation (in the case of
metal coating), or by placing bi-angled (e.g., pyramidal)
structures with different materials coated on each facet. (In some
embodiments some of the facets may be left uncoated.) During LIFT
operation the two materials may be ejected substantially
simultaneously, for example by using two or more beams in parallel.
Alternatively or additionally, a high repetition rate laser may be
scanned to effectively achieve simultaneous jetting. The
simultaneous ejection may be used to form a mixed material (e.g., a
compound) on substrate 24. Further alternatively or additionally,
the two materials may be printed consecutively to form mixed
material structures.
[0042] Since facets 40 and 42 are not parallel to the surface of
substrate 24, the ejection of droplets 30 of molten material from
the donor film occurs at an angle to the surface of substrate 24,
(i.e., angle 29 in FIG. 3). In an embodiment both facets 40 and 42
are coated with films formed by similar or by different materials.
In an alternative embodiment, only one facet (e.g., facet 40) is
coated with a film. The ejection of droplets 30 from facet is
indicated by an arrow 41, and droplets 30 eject, typically at an
orthogonal angle to surface 40, so as to coat the left sidewall of
a structure 25B. An arrow 43 illustrates ejection of droplets 30
from facet 42, typically at an orthogonal ejection angle to facet
42, so as to coat the right sidewalls of structure 25B. Both
ejections also coat the top surfaces of substrate 24 and structures
25B, which are parallel to the upper surface of donor 22B.
[0043] In some embodiments, the ejections of droplets 30 are
performed simultaneously, and in the case of different materials on
each facet, the ejections of droplets 30 may form a mixed film
(e.g., a compound or an alloy) of the respective materials on
substrate 24. In other embodiments, the ejection of droplets 30
from facet 40 is performed before or after the ejection of droplets
30 from facet 42. In the case of different materials on facets 40
and 42, the sequential ejections of droplets 30 may form a
multilayered structure or a mixed material structure in the same
layer on substrate 24.
[0044] The ejecting angles of the droplets are defined by the
slopes of facets 40 and 42 respectively. In some embodiments, the
coated materials on facets 40 and 42 are similar, so as to print
the same material across structures 25B and substrate 24. In other
embodiments, the coated materials may be different, so as to print
mixed or multilayered materials on structures 25B and substrate
24.
[0045] FIG. 5 is a schematic, sectional view showing details of a
non-planar LIFT donor 22C, in accordance with an embodiment of the
present invention. Donor 22C is transparent to laser beam 28 (not
shown in FIG. 5). In some embodiments, donor 22C may be configured
to be transparent to another laser or another illumination source,
such as an LED or a lamp, that may be used for LIFT process
inspection, as is described hereinbelow.
[0046] An upper surface 23C of donor 22C is parallel to top surface
33A of substrate 24. A lower surface 21C of donor 22C comprises
substantially similar facets 50 and substantially similar facets
52, which are not parallel to surfaces 33A and 35A of substrate 24,
and substantially similar facets 54, which are parallel to surface
33A.
[0047] Facets 50 and 52 may be coated with the same materials or
with different materials on each facet, as described with reference
to FIG. 4. In some embodiments, facets 54 are not coated and may be
used for in-situ inspection during a LIFT process so as to monitor
the quality of the LIFT printing process. Alternatively or
additionally, the uncoated facets may be used for additional
inspection applications such as registration and/or alignment. The
inspection via the uncoated facets may use the same laser as is
used for ejection or an additional laser (not shown in FIG. 5) or
any other suitable illumination source (e.g., a LED or a lamp) as
is described above.
[0048] In other embodiments, facets 54 may be coated with material
to be ejected, typically perpendicularly to substrate 24 in an
ejection illustrated by arrow 55. The ejections from facets 50 and
52 (illustrated by arrows 51 and 53, respectively), are typically
perpendicular to facets 50 and 52 respectively. Arrows 51
illustrate that droplets 30 from facets 50 coat the left sidewalls
and the top surfaces of structures 25C. Arrows 55 illustrate that
droplets 30 coat the top surfaces of structures 25C. Arrows 53
illustrate that droplets 30 coat the right surfaces of structures
25C. The ejection angles of facets 50 and 52 are set primarily by
the respective slopes of the facets.
[0049] FIG. 6 is a schematic, sectional view showing details of a
non-planar LIFT donor 22D, in accordance with an embodiment of the
present invention. Donor 22D is transparent to laser beam 28. An
upper surface 23D of donor 22C is parallel to top surface 33A of
substrate 24. A lower surface 21D of donor 22D comprises one or
more curved structures 71 which are coated by a donor film on top
of a flat lower surface 77 of donor 22D. Each curved structure 71
has a thickness h and a width L. Structures 71 are also referred to
herein as elements 71. By way of example, four curved elements 71
are shown in FIG. 6, and are assumed to be sections of respective
spheres with equal radii of curvature 73.
[0050] However, it will be understood that elements 71 may comprise
substantially any curved surface, and so, for example, may comprise
sections of a cylinder, or sections of another curved entity such
as an ellipsoid. Furthermore, elements 71 may be arranged in a
periodic manner on surface 21D, or may be arranged to be
non-periodic.
[0051] Typically, the width L of each element 71 is substantially
larger than the thickness h of the same element, so as to avoid
distortion of the spot of beam 28 when it impinges on element 71.
In an embodiment, thickness h is about 100 .mu.m or less, for a gap
79 between donor 22D and surface 33A in a range of 200 .mu.m to 300
.mu.m or more. Such values of the thickness and the gap ensure that
the printing conditions between donor 22D and substrate 24 are
substantially uniform.
[0052] The curvature of element 71 and the location of beam 28
where it impinges on the element define an ejection angle
.theta..sub.e of droplet 30 from the element, the droplet typically
being ejected orthogonally to the region of impingement. Thus, an
operator may control the position of beam 28 on the curved donor so
as to achieve a required ejection angle of a given droplet 30 for a
desired position on the substrate. In general, by controlling the
positions of beam 28, donor 22D, and/or substrate 24, the operator
may select the ejection angle of droplets 30 to be any angle within
a continuous range, and may thus change the landing angle and the
landing position of each droplet 30 on surface 33A and on
structures 25D. In an embodiment, the continuous range of ejection
angles lies between +30.degree. and -30.degree. measured with
respect to beam 28.
[0053] For example, when beam 28 impinges on the center of element
71 (herein assumed to be parallel to surface 33A), droplet 30 is
typically ejected orthogonally to surface 33A, as is illustrated by
arrow 72. In this case the droplet coats surface 33A or the top
surface of 25D. When beam 28 impinges on the right side of element
71, ejection of droplets 30 from the donor film occurs at an angle,
as is illustrated by arrow 74. In this case, the droplets land at a
non-normal angle (such as angle 29 described in FIG. 3) to acceptor
surface 33A, or on a left sidewall of structure 25D. Similarly,
when beam 28 impinges on the left side of element 71, ejection of a
droplet 30 from the donor film occurs at an opposite angle to that
when the beam impinges on the right side of the element, as is
illustrated by arrow 76. In this case, the droplet lands at an
opposite angle (compared to the example represented by arrow 74) to
acceptor surface 33A, or on a right sidewall of structure 25D.
[0054] In close packing of elements 71, width L is dictated by a
maximal allowed ejection angle and thickness h of element 71. If
.theta..sub.m is the maximal ejection angle, then the width of
element 71 (for the element a section of a sphere) is given by the
following equation:
L = 2 Sin ( .theta. m ) 1 - Cos ( .theta. m ) h ##EQU00001##
[0055] Thus for example, setting the thickness h to 100 .mu.m and
assuming a maximal ejection angle of 30.degree., the curved surface
width L is about 750 .mu.m, which is substantially larger than a
typical spot size. Similar considerations apply for other compact
curved structure cases.
[0056] FIG. 7 is a schematic sectional view showing details of a
non-planar LIFT donor 22E, which is not parallel to surfaces 33A
and 35A of substrate 24, in accordance with embodiments of the
present invention. Donor 22E is tilted at a tilt angle 66, measured
between a plane upper surface 23E of donor 22E, and a horizontal
line parallel to surfaces 33A and 35A of substrate 24. Surface 23E
acts as a defining plane surface of donor 22E, and tilt angle 66 is
between surface 23E and a line parallel to surfaces 33A, 35A of
substrate 24.
[0057] Donor 22E is transparent to laser beam 28 and comprises a
lower surface 21E which is coated by donor films and which faces
substrate 24 at an oblique angle. Structures 25E are located on
substrate 24 and typically have a three-dimensional (3D) structure
as shown in FIG. 7.
[0058] In an embodiment, a user 11 of apparatus 10 (FIG. 1)
identifies a topographic feature on the 3D structure of structures
25E and positions donor 22E so that the lower surface of the donor
is aimed towards a surface of the 3D structure at an angle that is
oblique, i.e., non-normal, to the surface. Once donor 22E and
substrate 24 are positioned, the user directs beam 28 to impinge on
donor 22E so as to eject material from the donor films, typically
orthogonal to the lower surface of donor 22E, onto the 3D
structure. For example, if angle 66 equals 10.degree. and droplets
30 are ejected orthogonally to the lower surface of donor 22E, the
droplets will be ejected at 100.degree. with respect to the
horizontal line parallel to substrate 24, and will land on the top
surface of structures 25E at an angle of 80.degree.
(90.degree.-10.degree.) measured relative to surface 33A of
substrate 24.
[0059] In some embodiments, surface 21E of donor 22E comprises
multiple facets, such as facets 62 and 64, which are typically
coated by donor films. In other embodiments, surface 21E is planar
(i.e., does not comprise facets), and is coated with a donor
film.
[0060] During a LIFT process, laser beam 28 emits pulsed radiation
onto donor 22E. The radiation passes through surface 23E and
impinges on the donor films on the lower surface of donor 22E, so
as to induce ejections of droplets of molten material from the
donor film, onto the acceptor surfaces, comprising portions of
surface 33A of substrate 24 and upper surfaces of structure 25E in
the example of FIG. 7.
[0061] In a first case of a planar (non-faceted) surface 21E of
donor 22E, the ejection angle from the donor film is constant
across the donor, and thus, beam 28 ejects droplets towards
structure 25E at an angle 90.degree.+angle 66. As a result,
droplets 66 land on the top surfaces of substrate 24 and structures
25E at a non-orthogonal angle. As described in the above example,
angle 66 equals 10.degree. and thus the ejection angle from donor
22E is 100.degree. and the landing angle on the top surface of
structures 25E is 80.degree.. In the case of the droplets landing
on a sidewall of structure 25E, which is orthogonal to the surface
of substrate 24, the landing angle will typically be 10.degree.
with respect to the surface of the sidewall.
[0062] In a second case (shown in FIG. 7) the lower surface of
donor 22E comprises substantially similar facets 62 and
substantially similar facets 64. In this embodiment during the LIFT
process, beam 28 passes through surface 23E and impinges on the
donor film of facet 62 resulting in ejection (represented by arrow
68) of droplets 30 towards the right sidewalls and the horizontal
top surfaces of structures 25E. In this case, the ejecting and
landing angles depend on angle 66 and the slope angle of facet 62
with respect to surface 21E.
[0063] For example, if angle 66 equals 10.degree., the angle of
facet 62 is 60.degree. with respect to the lower surface of donor
22E, and the ejection is orthogonal to the surface of facet 62,
then the angle of ejection from facet 62 (arrow 68) equals
10.degree.+60.degree.+90.degree., which equals 160.degree. with
respect to the lower surface of donor 22E. The landing angle of
droplets 30 on the top surface of structures 25E will be 20.degree.
(90.degree.-70.degree.), and the landing angle on the left
orthogonal sidewalls of structures 25E will be 70.degree..
[0064] Similarly, beam 28 passes through the upper surface of donor
22E and impinges on the donor film of facet 64 resulting in
ejection of droplets 30 (represented by arrow 70) towards the right
sidewalls and the horizontal surfaces of structures 25E.
[0065] In both embodiments a non-zero tilt angle 66 provides
specific locations on donor 22E that are closer to substrate 24
compared to a parallel donor-to-acceptor configuration. Smaller
distance between the donor and the acceptor typically results high
printing quality in a LIFT process.
[0066] In FIG. 7, the left side of donor 22E is lower than the
right side due to tilt angle 66, and together with facets 62 and
64, may provide short distances between the films on donor 22E and
structures 25E (so as to provide higher printing quality of
droplets 30 on structures 25E at these short distances) compared to
prior art systems. The tilted embodiment provides high printing
performance in cases of non-uniform height across structures 25E,
as shown in FIG. 7, where the right side of structure 25E is higher
than the left side of the structure.
[0067] As is illustrated in FIG. 7, the combination of a non-zero
tilt angle 66 and a multi-faceted structure on the lower surface of
donor 22E provides a flexibility to adapt the LIFT process with
respect to specific topographies of structures 25E. For example, in
FIG. 7 the highest 3D structure is in the right side of structures
25E and thus the donor 22E is tilted down to the left. In an
opposite case where the 3D structures are higher on the left side
of structures 25E, donor 22E may be tilted down to the right, which
means that tilt angle 66 is opposite to the angle shown in FIG. 7.
For example, instead of 10.degree., angle 66 will be -10.degree.
(or 170.degree.). A combination of adaptable tilt angle and
multi-faceted structure of the donor provides flexibility that can
be used to achieve small distances between surface 21E of donor 22E
and structures 25E, and thus, to provide high printing quality for
any type of 3D features of structures 25E.
[0068] It will be appreciated that the embodiments described above
are cited by way of example, and that the present invention is not
limited to what has been particularly shown and described
hereinabove. Rather, the scope of the present invention includes
both combinations and sub-combinations of the various features
described hereinabove, as well as variations and modifications
thereof which would occur to persons skilled in the art upon
reading the foregoing description and which are not disclosed in
the prior art.
* * * * *