U.S. patent application number 13/633662 was filed with the patent office on 2013-07-04 for composite transducer apparatus and system for processing a substrate and method of constructing the same.
The applicant listed for this patent is John A. Korbler, Richard Novak. Invention is credited to John A. Korbler, Richard Novak.
Application Number | 20130167881 13/633662 |
Document ID | / |
Family ID | 40626179 |
Filed Date | 2013-07-04 |
United States Patent
Application |
20130167881 |
Kind Code |
A1 |
Korbler; John A. ; et
al. |
July 4, 2013 |
COMPOSITE TRANSDUCER APPARATUS AND SYSTEM FOR PROCESSING A
SUBSTRATE AND METHOD OF CONSTRUCTING THE SAME
Abstract
An apparatus for processing articles with acoustic energy and a
method of constructing a transducer that utilizes a composite of
piezoelectric pillars. In one embodiment, the invention is a method
of constructing a device for generating acoustic energy comprising:
providing a layer of supporting material; positioning a
piezoelectric material atop the layer of adhesive material; cutting
the piezoelectric material into a plurality of pillars so that
spaces exist between adjacent pillars; and filling the spaces with
a resilient material to form a composite assembly.
Inventors: |
Korbler; John A.;
(Mertztown, PA) ; Novak; Richard; (Plymouth,
MN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Korbler; John A.
Novak; Richard |
Mertztown
Plymouth |
PA
MN |
US
US |
|
|
Family ID: |
40626179 |
Appl. No.: |
13/633662 |
Filed: |
October 2, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12266543 |
Nov 6, 2008 |
8279712 |
|
|
13633662 |
|
|
|
|
60985947 |
Nov 6, 2007 |
|
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61034142 |
Mar 5, 2008 |
|
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Current U.S.
Class: |
134/34 ;
29/25.35; 367/155 |
Current CPC
Class: |
B06B 1/0629 20130101;
H01L 41/37 20130101; Y10T 29/42 20150115 |
Class at
Publication: |
134/34 ; 367/155;
29/25.35 |
International
Class: |
B08B 3/12 20060101
B08B003/12; H04R 31/00 20060101 H04R031/00; H04R 17/00 20060101
H04R017/00 |
Claims
1. An apparatus for processing articles with acoustic energy
comprising: a transducer assembly comprising: a transmitting
structure having a concave inner surface and a convex outer
surface; a first transducer having a convex bottom surface bonded
to the concave inner surface of the transmitting structure; a
second transducer having a convex bottom surface bonded to the
concave inner surface of the transmitting structure, the second
active transducer spaced from the first active transducer so that a
non-active acoustic energy area exists on the transmitting
structure between the first and second transducers.
2. The apparatus of claim 1 wherein the first and second transducer
are spaced from one another by at least 45 degrees of the concave
inner surface.
3. The apparatus of claim 1 further comprising: a support for
supporting an article to be processed; a conduit for applying a
fluid to a surface of the article; the transducer assembly
positioned adjacent to and opposing the surface of the article so
when the fluid is applied to the surface of the article by the
conduit, the convex bottom surface of the transmitting structure is
fluidly coupled to the surface of the article; and the transducer
assembly oriented so that the non-active acoustic area of the
transmitting structure faces the surface of the article.
4. The apparatus of claim wherein the support is a rotatable
support.
5. The apparatus of claim 3 wherein the support is a translational
motion support.
6. The apparatus of claim 3 wherein the transducer assembly is
oriented so that acoustic waves generated by the first and second
transducers are propagated at the surface of the article at a
non-normal angle that results in reflected acoustic waves traveling
away from the transducer assembly.
7. The apparatus of claim 1 wherein each of the first and second
transducers are formed by a composite assembly comprising a
plurality of pillars constructed of a piezoelectric material, the
pillars arranged in a spaced-apart manner so that spaces exist
between adjacent pillars; the pillars having a width and a height
extending between a top surface and a bottom surface, wherein the
height of the pillars is greater than the width of the pillars; and
the spaces filled with a resilient material so as to form the
composite assembly.
8. A method of constructing a device for generating acoustic energy
comprising: providing a layer of supporting material; positioning a
piezoelectric material atop the layer of adhesive material; cutting
the piezoelectric material into a plurality of pillars so that
spaces exist between adjacent pillars; and filling the spaces with
a resilient material to form a composite assembly.
9. The method of claim 8 wherein the pillars have a width and a
height, the height being greater than the width.
10. The method of claim 8 wherein the height of the pillars is at
least twice the width of the pillars.
11. The method of claim 8 further comprising: applying an
electrically conductive material to at least a portion of a top
surface of the composite assembly; and applying an electrically
conductive material to at least a portion of a bottom surface of
the composite assembly.
12. The method of claim 8 wherein the supporting material is a wax
or an adhesive.
13. The method of claim 8 further comprising: forming the composite
assembly so that a bottom surface of the composite assembly has a
radius of curvature.
14. The method of claim 13 further comprising: applying an
electrically conductive material to at least a portion of a top
surface of the composite assembly; and applying an electrically
conductive material to at least a portion of the curved bottom
surface of the composite assembly.
15. The method of claim 13 further comprising: bonding a
transmitting material to the electrically conductive material on
the bottom surface of the composite assembly.
16. The method of claim 15 wherein the transmitting material is
sapphire or quartz.
17. The method of claim 15 wherein the transmitting material is a
polymer film.
18. The method of claim 15 wherein the transmitting material has a
convex outer surface.
19. The method of claim 18 wherein the electrically conductive
material applied to the top surface of the composite assembly is
two electrically isolated sections separated by a non-active
area.
20. The method of claim 18 further comprising: treating the outer
surface of the transmitting material to decrease its surface
tension with a fluid.
21. The method of claim 18 wherein the transmitting material forms
an internal cavity in which the composite assembly is located, the
method further comprising: filling the internal cavity with a
dampening material.
22. A method of processing an article comprising: supporting an
article on a support; providing a transducer assembly comprising: a
transmitting structure having a concave inner surface and a convex
outer surface; a first transducer having a convex bottom surface
bonded to the concave inner surface of the transmitting structure;
a second transducer having a convex bottom surface bonded to the
concave inner surface of the transmitting structure, the second
active transducer spaced from the first active transducer so that a
non-active acoustic energy area exists on the transmitting
structure between the first and second transducers; positioning the
transducer assembly adjacent to a surface of the article on the
support and in an orientation wherein the non-active acoustic area
of the transmitting structure faces the surface of the article;
applying fluid to the surface of the article so that the convex
bottom surface of the transmitting structure is fluidly coupled to
the surface of the article; and activating the first and/or second
transducers, thereby generating acoustic energy propagated at the
surface of the article at a non-normal angle that results in
reflected acoustic waves traveling away from the transducer
assembly.
23. The method of claim 22 wherein each of the first and second
transducers are formed by a composite assembly comprising a
plurality of pillars constructed of a piezoelectric material, the
pillars arranged in a spaced-apart manner so that spaces exist
between adjacent pillars; the pillars having a width and a height
extending between a top surface and a bottom surface, wherein the
height of the pillars is greater than the width of the pillars; and
the spaces filled with a resilient material so as to form the
composite assembly.
24. The method of claim 22 wherein the support is capable of
rotation or translation of the article.
Description
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS
[0001] The present patent application is a continuation of U.S.
patent application Ser. No. 12/266,543, filed Nov. 6, 2008, which
in turn claims the benefit of U.S. Provisional Patent Application
Ser. No. 60/985,947, filed Nov. 6, 2007 and U.S. Provisional Patent
Application Ser. No. 61/034,142, filed Mar. 5, 2008, the entireties
of which are hereby incorporated by reference.
FIELD OF THE INVENTION
[0002] The present invention relates generally to an apparatus and
system for generating acoustic energy for the processing of
substrates, such as semiconductor wafers, raw silicon substrates,
flat panel displays, solar panels, photomasks, discs, magnetic
heads or any other item that requires a high level of processing
precision. Specifically, the invention relates to an acoustic
generating apparatus, or a system incorporating the same, that can
provide high levels of particle removal efficiency from substrates
containing delicate devices that minimizes damage to the delicate
devices.
BACKGROUND OF THE INVENTION
[0003] In the field of semiconductor manufacturing, it has been
recognized since the beginning of the industry that removing
particles from semiconductor wafers during the manufacturing
process is a critical requirement to producing quality profitable
wafers. While many different systems and methods have been
developed over the years to remove particles from semiconductor
wafers, many of these systems and methods are undesirable because
they cause damage to the wafers. Thus, the removal of particles
from wafers must be balanced against the amount of damage caused to
the waters by the cleaning method and/or system. It is therefore
desirable for a cleaning method or system to be able to break
particles free from the delicate semiconductor wafer without
resulting in damage to the device structure.
[0004] Existing techniques for freeing the particles from the
surface of a semiconductor wafer utilize a combination of chemical
and mechanical processes. One typical cleaning chemistry used in
the art is standard clean 1 ("SC1"), which is a mixture of ammonium
hydroxide, hydrogen peroxide, and water. SC1 oxidizes and etches
the surface of the wafer. This etching process, known as
undercutting, reduces the physical contact area to which the
particle binds to the surface, thus facilitating removal. However,
a mechanical process is still required to actually remove the
particle from the wafer surface.
[0005] For larger particles and for larger devices, scrubbers have
been used to physically brush the particle off the surface of the
wafer. However, as device sizes shrank in size, scrubbers and other
forms of physical cleaners became inadequate because their physical
contact with the wafers cause catastrophic damage to smaller
devices.
[0006] The application of acoustic energy during wet processing has
gained widespread acceptance to effectuate particle removal,
especially to clean sub-micron particles off wafers (or plates)
undergoing fabrication in the semiconductor process line. The
acoustic energy used in substrate processing is generated via a
source of acoustic energy. Typically, this source of sonic energy
comprises a transducer which is made of piezoelectric material,
such as a ceramic or crystal. In operation, the transducer is
coupled to a source of electrical energy. An electrical energy
signal (i.e. electricity) is supplied to the transducer. The
transducer converts this electrical energy signal into vibrational
mechanical energy (i.e. acoustic energy) which is then transmitted
to the substrates being processed. The transmission of the acoustic
energy from the transducer to the substrates is typically
accomplished by a fluid that acoustically couples the transducer to
the substrate. It is also typical that a material capable of
acoustic energy transmission be positioned between the transducer
itself and the fluid coupling layer to avoid "shorting" of the
electrical contacts on the piezoelectric material. This
transmitting material can take on a wide variety of structural
arrangements, including a thin layer, a rigid plate, a rod-like
probe, a lens, etc. The transmitting material is usually produced
of a material that is inert with respect to the fluid coupling
layer to avoid contamination of the substrate.
[0007] The application of acoustic energy to substrates has proven
to be a very effective way to remove particles and to improve the
efficiency of other process steps, but as with any mechanical
process, damage to the substrates and devices thereon is still
possible. Thus, acoustic cleaning of substrates is faced with the
same damage issues as traditional physical cleaning.
[0008] The acoustic energy generated by existing transducer
assemblies is often energetic enough to cause some of the fragile
structures that make up the electrical circuit to be damaged (i.e.,
removed or partially removed causing the circuit to no longer
(unction). Through long-term study of existing transducer
assemblies and the associated acoustic properties, the current
inventors have determined that a myriad of problems exist both with
the structure of the piezoelectric material and the direction and
orientation of the acoustic waves propagated by existing transducer
assemblies.
SUMMARY OF THE INVENTION
[0009] It is therefore an object of the present invention to
provide a sys em and method of cleaning substrates using sonic
energy.
[0010] Another object of the present invention is to provide a
system and method processing substrates using sonic energy that
reduces damage to devices on the substrates.
[0011] Still another object of the present invention is to provide
a system and method of cleaning substrates using sonic energy that
reduces damage to devices on the substrates while achieving
suitable particle removal efficiency.
[0012] Yet another object of the present invention is to provide a
system and method of processing substrates using sonic energy that
controls cavitation within the processing fluid.
[0013] A yet further object of the present invention is to provide
a system and method for processing substrates that results less
energy loss between the transducer and the substrate to be
processed.
[0014] Another object of the present invention is to provide a
system and method for processing substrates that results in a more
uniform energy distribution on the surface of the substrate.
[0015] This invention is of an acoustic generation device formed
using ceramic piezoelectric material formed into a radial section
and segmented such that it is composed of individual acoustic
generating pillars that can be interconnected to generate an
acoustic wave that efficiently and precisely couples into a fluid
acoustic transmission media applied to either the front and/or the
back of a wafer. The radial nature of the piezoelectric element is
designed so that the acoustic energy is directed into the
acoustical transmission fluid and on to the wafer (or plate)
surface and reflects away from the generating source, suppressing
standing waves which contain nodes of very high energy and very low
energy. The high energy regions can lead to structure damage and
the low energy regions can lead to reduced removal of particles.
Both these conditions are unwanted in the use of these
transducers.
[0016] In one aspect, the invention can be an apparatus for
generating acoustic energy comprising: a plurality of pillars
constructed of a piezoelectric material, the pillars arranged in a
spaced-apart manner so that spaces exist between adjacent pillars;
the pillars having a width and a height extending between a top
surface and a bottom surface, wherein the height of the pillars is
greater than the width of the pillars; and the spaces filled with a
resilient material so as to form a composite assembly.
[0017] In another aspect, the invention is an apparatus for
processing articles with acoustic energy comprising: a transducer
assembly comprising: a transmitting structure having a concave
inner surface and a convex outer surface; a first transducer having
a convex bottom surface bonded to the concave inner surface of the
transmitting structure; a second transducer having a convex bottom
surface bonded to the concave inner surface of the transmitting
structure, the second active transducer spaced from the first
active transducer so that a non-active acoustic energy area exists
on the transmitting structure between the first and second
transducers.
[0018] In yet another aspect, the invention is a method of
constructing a device for generating acoustic energy comprising:
providing a layer of supporting material; positioning a
piezoelectric material atop the layer of adhesive material; cutting
the piezoelectric material into a plurality of pillars so that
spaces exist between adjacent pillars; and filling the spaces with
a resilient material to form a composite assembly.
[0019] In a further aspect, the invention can be a method of
processing an article comprising: supporting an article on a
support; providing a transducer assembly comprising a transmitting
structure having a concave inner surface and a convex outer
surface; a first transducer having a convex bottom surface bonded
to the concave inner surface of the transmitting structure; a
second transducer having a convex bottom surface bonded to the
concave inner surface of the transmitting structure, the second
active transducer spaced from the first active transducer so that a
non-active acoustic energy area exists on the transmitting
structure between the first and second transducers; positioning the
transducer assembly adjacent to a surface of the article on the
support and in an orientation wherein the non-active acoustic area
of the transmitting structure faces the surface of the article;
applying fluid to the surface of the article so that the convex
bottom surface of the transmitting structure is fluidly coupled to
the surface of the article; and activating the first and/or second
transducers, thereby generating acoustic are propagated at the
surface of the article at a non-normal angle that results in
reflected acoustic waves travelling away from the transducer
assembly.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 is a schematic of a prior art transducer.
[0021] FIG. 2 is a schematic illustrating an acoustic wave
generated by the prior art transducer of FIG. 1 having nodes and
=Modes.
[0022] FIG. 3A is a top view of an array of piezoelectric pillars
supported on a wax base and used to create a transducer according
to one embodiment of the present invention.
[0023] FIG. 3B is a side view of the array of piezoelectric pillars
of FIG. 3A,
[0024] FIG. 3C is a perspective view of the array of piezoelectric
pillars of FIG. 3A.
[0025] FIG. 3D is a side view of the array of piezoelectric pillars
of FIG. 3A with the spaces between pillars filled with a resilient
material, according to one embodiment of the present invention.
[0026] FIG. 3E is a side view of a composite assembly comprising
the piezoelectric pillars with the spaces between pillars filled
with a resilient material as shown in FIG. 3D, wherein the wax base
has been removed, according to one embodiment of the present
invention.
[0027] FIG. 3F is a side view of a transducer incorporating the
composite assembly of FIG. 3E according to one embodiment of the
present invention, wherein a transmitting material is bonded to the
bottom electrode.
[0028] FIG. 4A is a schematic representation of the transducer of
FIG. 3F wherein the electrodes are energized so that the individual
pillars are generating acoustic energy waves, according to one
embodiment of the present invention.
[0029] FIG. 4B is a schematic representation of the transducer of
FIG. 3F wherein the electrodes are energized so that the individual
acoustic energy waves of the pillars effectively combine to form a
plane wave profile, according to one embodiment of the present
invention.
[0030] FIG. 5 is a side view of a composite transducer according to
one embodiment of the present invention wherein an impedance
matching layer has been added.
[0031] FIG. 6 is a cross-sectional side view of a curved composite
transducer according to one embodiment of the present
invention.
[0032] FIG. 7 is a perspective view of an acoustic processing
system according to one embodiment of the present invention.
[0033] FIG. 8 is a cross-sectional view of the transducer assembly
of the acoustic processing system of FIG. 7 along perspective
VIII-VIII.
[0034] FIG. 9 is a diagram of the transducer assembly of FIG. 8
showing one set of preferred dimensions.
[0035] FIG. 10 is a perspective view of an acoustic processing
system according to a second embodiment of the present invention
wherein a small composite transducer assembly is moved across the
surface of a wafer by a support rod.
[0036] FIG. 11 is a perspective view of an acoustic processing
system according to a third embodiment of the present invention
wherein a composite transducer assembly extends across the entire
diameter of a wafer.
[0037] FIG. 12 is a perspective view of the acoustic processing
system of FIG. 11 processing a rectangular panel.
[0038] FIG. 13 is an illustration of different shapes in which a
curved composite transducer according to the present invention can
be constructed.
[0039] FIG. 14 is a graph comparing acoustic levels generated at
various distances along a wafer for a transducer assembly according
to the present invention and three prior art transducer
configurations.
DETAILED DESCRIPTION OF THE DRAWINGS
[0040] Referring to FIG. 1, a typical prior art transducer 1 used
in existing acoustic processing systems is illustrated. While the
exact shape and orientation of the prior art transducer 1 used in
the industry varies, all known prior art transducers 1 are large
flat plate structures. It has been discovered that these prior art
transducers 1 have an issue in that when they are driven with
electrodes 2, 3 on opposite sides the plate and the piezoelectric
material 4 is set into oscillation by its inherent piezoelectric
effect, the resulting oscillations tend to be multi-nodal depending
on the exact shape of the flat plate structure. As can be seen in
FIG. 2, this in effect launches a complicated acoustic wave 5. This
acoustic wave 5 has a non uniform energy pattern.
[0041] In addition, if the transducer 1 is positioned so that its
major surfaces are parallel to a substrate to be processed (i.e.,
the acoustic wave 5 propagates in a direction perpendicular to the
surface of the substrate), the acoustic wave 5 reflects off the
surface of the wafer and returns toward the transducer 1. This
creates a standing wave. In fact, the standing wave problem has
been discovered to exist even in transducer arrangements where the
acoustic energy wave is transmitted parallel to the surface of the
wafer but has a radial component that is normal to the wafer.
[0042] A standing wave consists of nodes and antinodes and
therefore in terms of energy, subjects the wafer to localized areas
of high and low energy points. The wave returning to the transducer
1 dissipates heat into the transducer 1 and consequently requires
some form of cooling, either liquid and/or gas. Without cooling,
some of the components associated with the construction can be
quickly degraded. The impedance of a typical ceramic or crystal
piezoelectric material also changes as a function of temperature.
If the temperature changes from the temperature at which it was
matched to the power supply (fixed match to 50 ohm load) the
piezoelectric material dissipates additional energy in the material
as heat. This further heats the transducer 1 causing still more
changes in impedance. Left unchecked, this will lead to failure of
the transducer 1.
[0043] Referring now to FIGS. 3A-3F, a composite transducer 100 and
its construction at according to one embodiment of the present
invention will be described. To begin, a typical flat stock piece
of a piezoelectric material is provided (not shown). The
piezoelectric material can be a ceramic, crystal or any other
material capable of converting electrical energy to mechanical
energy. The flat stock piece of piezoelectric material is then
placed on a wax base 10 or other supporting material, such as an
adhesive. In some embodiment, the supporting material may be an
electrode (discussed later). The supporting material can be any
material or structure capable of performing the supporting function
described below.
[0044] Referring now to FIGS. 3A-3C exclusively, once the flat
stock piezoelectric material is placed on the wax base 10, the
piezoelectric material is cut into pieces in both x and y planes,
thereby forming an array of pillars 20 of the piezoelectric
material. During the cutting process the saw preferably cuts only
through the flat stock piezoelectric material, and not the wax base
10. The wax base 10 holds the pillars 20 in place in their spaced
apart and generally upright orientation. A plurality of
intersecting channels are formed between the pillars 20 thereby
providing spaces 30 between adjacent pillars 20. While the pillars
20 are in an equally spaced-apart array configuration in the
illustrated embodiment, other configurations and geometric patterns
can be achieved. Moreover, if desired, the pillars 20 can take on
other geometric shapes, including cylindrical, radial segment, etc.
In order to avoid clutter, only a few of the pillars 20 and spaces
30 are numerically identified in the drawings.
[0045] Each of the pillars 20 has a height H defined by the
distance between its bottom surface 21 and its top surface 22. Each
of the pillars also has a width W. It is preferable that the height
H of the pillars 20 be greater than the width W. It is even more
preferred that the height H be twice the width W or greater. It is
also (preferred that pillar width W and the width of spaces 30 be
approximately equal, or at the very least of the same magnitude. In
other embodiments, it may be preferred that the width of the spaces
30 be smaller than the width W of the pillars 20.
[0046] Moreover, from a functionality standpoint, it is also
preferred that the width W of the pillars 20 and the width of the
spaces 30 be less than a wavelength of the acoustic energy waves to
be generated by the composite transducer 100. For the example, for
a pillar 20 operating at a 1 MHz frequency, the preferred
dimensions are that the height H of the pillar 20 be approximately
1.6 mm, the width W of the pillar 20 be approximately 0.8 mm or
less, and the width of the surrounding spaces 30 be less than or
equal to 0.8 mm in the active areas. In other embodiments which are
described later, it may be desirable to have not acoustically
active areas. There are various means to create active and
non-active acoustical generating areas described later.
[0047] Referring now to FIG. 3D, once the pillars 20 are created,
the spaces 30 are backfilled with a curable filler 40. In one
embodiment, the curable filler is preferably a resilient material
40. Other examples of curable fillers include elastomers and
epoxies. Once the filler 40 cures, the wax base 10 is removed,
thereby resulting in a composite assembly 50 formed by the pillars
20 of piezoelectric elements separated by the filler 40. The
composite assembly is shown in FIG. 3E.
[0048] Referring now to FIG. 3E, the composite assembly 50
comprises a bottom surface 51 and a top surface 52. As will be
described in detail below, the composite assembly 50 can be formed
or later shaped so as have curvature.
[0049] Referring now to FIG. 3F, once the composite assembly 50 is
in the desired shape (which is flat in the illustrated embodiment),
an electrically conductive material is applied to the bottom and
top surfaces 51, 52 of the composite assembly 50, thereby forming
electrodes 61, 62. As a result, a transducer 100 according to one
embodiment of the present invention is formed. The electrically
conductive material used to form the electrodes 61, 62 can be a
metal, such as silver, an electrically, conductive epoxy, or any
material that can conduct an electric current to excite the
piezoelectric pillars 20.
[0050] As will be described in greater detail below, in certain
situations it may be desirable to only energize a certain one or
subsets of the piezoelectric pillars 20. Thus, while the electrodes
61, 62 are shown as being applied to entirety of the bottom and top
surfaces 51, 52 of the composite assembly 50, in other embodiments
the electrodes 61, 62 may cover only selected areas that are
electrically isolated from one another (as shown in the embodiment
of FIG. 6).
[0051] When the transducer 100 is to be used in conjunction with
the wet processing of articles, it may be desirable to shield the
transducer 100 (and its electrodes) from the processing liquid so
as to avoid shorting and/or contamination of the processing fluid.
This can be achieved by bonding a transmitting structure 70
(generically illustrated) to the transducer 100. As illustrated in
FIG. 3F, the transmitting structure 70 is bonded directly to the
transducer 100. The transmitting structure 70 can be constructed of
a wide variety of materials, shapes and dimensions. Depending on
the intended function, the transmitting structure can be a rigid
structure or a thin film or foil. Suitable materials for the
transmitting structure 70 include polymers, quartz, sapphire, boron
nitride vitreous carbide, stainless steel, or any other material
that can effectively transmit acoustic energy to facilitate the
intended processing.
[0052] In one embodiment, it may be preferred that the transmitting
structure 70 be a polymer film. Suitable polymers include materials
like Halar (ECTFE), Polyvinylidene Fluoride (PVDF), Polysulfone or
other polymers. The thickness of the polymer film can preferably
range from 0.1 mil to 18 mil, and more preferably range from 1 mil
to 5 mil. These polymer films may be treated chemically or
otherwise manufactured to improve the surface characteristics of
the material to provide a low surface tension toward the processing
fluid.
[0053] Referring now to FIG. 4A, a schematic representation of the
transducer 100 energized so as to generate acoustic energy.
Electricity is supplied to the electrodes 61, 62 by wires that are
operably connected to a source of electricity. The electricity is
converted by each of the piezoelectric pillars 20 into independent
acoustic waves 80. As can be seen, the pillars 20 act as
independent pistons, each generating its own independent acoustic
wave 80 in a direction that is substantially parallel to its height
H.
[0054] However, as can be seen in FIG. 4B, the summary effect of
the acoustic waves 80 is the launching of a plane wave that is free
of nodes of anti-nodes. As the pillars 20 extend in their axial
direction (i.e., vertically along their height H) by the
piezoelectric effect, the pillars 20 contract by Poisson's ratio in
the lateral direct horizontally along their width W), when the
pillars 20 contract in their axial direction by the piezoelectric
effect, the pillars 20 expand by Poisson's ratio in the lateral
direct. However since the spaces 30 are filled with a resilient
material, any waves generated in the lateral direction are greatly
dampened or suppressed. This in effect launches the plane wave from
the surface of the transducer 100.
[0055] As mentioned above, the pillars 20 can be energized
independently or grouped in subsets to create acoustically active
areas and acoustically inactive areas. Pillars 20 that have no
opposing electrodes or do not have their electrodes energized, do
not have the piezoelectric effect and do not launch an acoustic
wave. Thus the extent of the acoustically active area can be
tailored to the precise situation desired. In addition, if areas of
the transducer 100 (or assembly in which the device is to be used)
are not required to be acoustically active, these sections can have
the piezoelectric pillars 20 removed from the composite and filled
with a resilient material or left as avoid.
[0056] Referring now to FIG. 5, an embodiment of the transducer 100
is illustrated wherein a matching layer 75 is added between the
transmitting structure 70 and the electrode. The matching layer 75
(or layers) are preferably chosen to act as impedance matching
layers to reduce energy loss during transmission of acoustic energy
to the processing fluid. In other words, the matching layer (75) is
designed acoustically so that the acoustic wave is efficiently
coupled into the transmission fluid and not reflected at the
interface. As an example, a 1/4 wave epoxy matching layer
(Approximately 0.029'') and a very thin polymer (Halar film) which
is acoustical transparent can be used as the matching layer 75 and
the transmitting structure 70 respectively. In design variations,
as the external polymer film thickness is increased and is seen as
part of the acoustical layers; then the polymer film is included as
a matching layer and all layer thickness and properties are
adjusted to efficiently transfer the acoustical energy from the
piezoelectric pillars 20 to the processing fluid
[0057] Referring now to FIG. 6, a transducer 100 having a radius of
curvature is illustrated according to one embodiment of the present
invention. In certain processing applications of articles, it may
be desirable for the transducer 100 to take a curved shape to
effectuate acoustic energy control and fluid coupling to the
article.
[0058] The curved transducer 100 of FIG. 6 can be formed by either
forming the composite assembly 50 to have a radius of curvature
during the steps discussed above or manipulating the composite
assembly 50 subsequent to being formed in a flat shape. The
electrodes 61, 62 and the transmitting structure 70 (and any
matching layers) can be bonded to the composite assembly 50 before
or after the curvature is formed. In FIG. 6, these materials were
bonded prior to forming the curvature. As an alternate order of
construction, the composite assembly 50 alone can be formed in a
curved form and then the electrodes 61, 62 and transmitting
structure 70 (and impedance matching layers if any) can be bonded
in later steps. The transmitter structure 70 is typically included
after the curvature forming process and in the next steps of
assembly.
[0059] The transmitting structure 70 comprises a convex outer
surface 71 and a concave inner surface 72. The transducer 100 is
bonded to the concave inner surface 71. As can be seen, the top
electrodes 62 are applied as two isolated regions on the top
surface of the composite assembly 50. Thus, when the transducer is
energized by applying an electrical signal to the electrodes 61,
62, only those pillars 20 covered by the electrodes 62 will
generate acoustic energy, thereby resulting in two separate
acoustically active regions A, B. Because the central region of the
composite assembly 50 does not receive an electric signal as a
result of there being no electrode 62 in that region, the pillars
20 in that region do not generate acoustic energy, thereby
resulting in an acoustically inactive area C. The acoustically
active regions A, B are circumferentially separated by the
acoustically inactive area C.
[0060] The pattern of the electrodes 61, 62 to create the active
piezoelectric pillars 20 can be varied to change the acoustical
energy pattern to any desired configuration. Reduced electrode
pattern area can also reduce the effective acoustical strength in a
given area. In addition, areas of the composite assembly 50 where
no acoustical energy is required may be made inactive by not only
omitting electrodes in that area, but also may have electrodes that
do not receive power, or these areas can have the composite
assembly 50 removed and/or left as void or replaced with a
resilient material. In alternate embodiments, the piezoelectric
pillars 20 can be grouped, and each group would have its own
electrode(s) 61, 62 and power/control wire. This would allow each
group of pillars 20 to be controlled independently by an outside
controller. This allows for each group of pillars to have its own
power level, operating frequency, on/off cycle time. In other
embodiments, the outer electrode can be divided into multiple
regions. Each electrode would have its own power/control wire. This
is an alternate method to control the active region(s) of the
device.
[0061] Referring now to FIG. 7, a megasonic system 1000 for
processing a fiat article 400 is illustrated. The megasonic system
1000 comprises a rotary support (not visible) upon which the
article is supported in a generally horizontal orientation and
rotated. The megasonic system 1000 also comprises a transducer
assembly 200 that is positioned adjacent to and opposing an upper
surface 401 of the article 400. The transducer assembly 200 is
supported in a cantilevered fashion by the support mechanism,
generically illustrated at block 210. If desired, the support
mechanism can be capable of translational and/or pivotal movement.
The transducer assembly 200 is supported sufficiently close to the
surface 401 of the article so that when the dispenser 300 applies a
liquid to the surface of the wafer, a liquid film of the liquid
couples the transducer assembly 200 to the surface 401 so that
acoustic energy generated by the transducer assembly 200 can be
transmitted to the article 400. The general concept of such
single-article acoustic-assisted processing systems are known in
the art and disclosed in such patents at U.S. Pat. No. 6,684,891,
to Mario Bran, the entirety of which is incorporated by
reference.
[0062] The transducer assembly 200 is supported substantially
parallel to the surface 401 of the article 400. While the
transducer assembly 200 is illustrated as an elongated rod-like
probe, the invention is not so limited. It is to be understood that
the transducer assembly can take on a wide variety of shapes,
orientations, and structural arrangements.
[0063] Referring now to FIG. 8, a cross-sectional view of the
transducer assembly 200 is illustrated. The transducer assembly 200
incorporates the curved transducer described in FIG. 6 above except
that a impedance matching layer 75 has been incorporated and the
transmitting structure 70 is in the shape of a tubular element. In
this embodiment, the transmitting structure 70 is a protective
polymer film extended over a supporting structure 90 that plays no
role acoustically in the device, but supplies rigidity and
structural integrity. In an alternative embodiment, the
transmitting structure 70 can be constructed of a material and/or
thickness that is sufficiently rigid to provide the necessary
structural integrity for supporting. For example, the transmitting
structure 70 can be constructed of quartz, sapphire, fused silica,
or other materials that are inert to the chemicals and/or liquid
used in the processes.
[0064] The transmitting structure 70 is the form of a cylindrical
tube and comprises an outer surface 71 and inner surface 72. Of
course, the transmitting structure 70 can take other curved
embodiments, such as a lens, a curved plate, a par-cylindrical
trough, etc.
[0065] Electrical wires 63, 64 are operably connected to the
electrodes 61, 62 and routed through the transducer assembly 200 to
the outside where they are connected to a source of an electrical
signal. The source of electricity provides an electrical signal
that drives the piezoelectric pillars 20 located in the active
areas A, B of the composite transducer 100 to generate waves 80 of
acoustic energy. Preferably, the wave 80 of acoustic energy have a
frequency that is in the megasonic range, and more preferably
between 500 KHz and 5 MHz.
[0066] The composite transducer 100 is bonded to the inner surface
71 of the transmitting structure 70 at the bottom circumferential
portion so that the waves 80 of acoustic energy generated by the
acoustically active sections A, B of the composite transducer 100
are transmitted into the layer of liquid 310 on the article surface
401. Through a combination of the rotational orientation of the
transducer assembly 200 and the circumferential spacing between the
acoustically active sections A, B of the piezoelectric pillars 20,
the plane waves 80 of acoustic energy are transmitted through the
liquid layer 310 to the surface 401 of the article 400 at an angle
so that the waves 80 do not reflect back into the transducer
assembly 200. Instead, the waves 80 reflect off the article 400 and
angle harmlessly away from the transducer assembly 200.
[0067] In other words, by having only those pillars 20 on the two
upper edges electrically active, acoustic waves launched from these
pillars 20 do not reflect back to the transducer 100, thereby
suppressing standing waves. The pillars 20 that would generate a
standing wave (those in acoustically inactive region C) are not
electrically connected with electrodes.
[0068] The transmitting structure 70 forms an internal cavity 95,
may be left as a void tilled with air or another gas, or optionally
may be filled with a dampening material which dampens acoustic
energy that may be applied to the backside of the transducer 100
inside of this construction. The presence of a dampening material
suppresses any undesirable acoustical energy. The transmitting
structure 70 is sealed such that the liquid 310 cannot breach the
cavity 95 and the material inside of the cavity 95 cannot get
outside to contaminate the liquid 310 and potentially the article,
which may be a semiconductor wafer or solar panel having delicate
structures.
[0069] It may also be desirable to have the outer surface of the
transmitting structure 70 treated or altered to have a low surface
tension toward the transmission liquid 310 so at least partial
wetting occurs. Air pockets, bubbles or voids will cause
reflections of acoustical energy back to the transducer.
[0070] Referring to FIGS. 7 and 8 concurrently, a method of
cleaning a semiconductor wafer 400 using the system 1000 will be
described. First, a semiconductor wafer 400 is positioned on the
rotatable support where it is supported in a generally horizontal
orientation. The wafer 400 is then rotated, as indicated by the
arrow. A liquid medium 310 is then dispensed via the dispenser 300
onto the top surface 401 of the wafer 400. The liquid can be any
chemical, solution or the like used in processing wafers, such as
DI water, SC1, SC2 ozonated DI water, etc.
[0071] The transducer assembly 200 is positioned adjacent the
surface 401 of the wafer so that a small gap exists between the
bottom of the transmitting structure 70 and the surface 401 of the
wafer 400. The transducer assembly is just larger than a radius of
the wafer 400. For example, for a 300 mm silicon wafers, the
transducer assembly 200 would be rod like 240 mm long rod with 150
mm of active acoustical length.
[0072] As the wafer 400 rotates, the liquid 310 supplied to the
surface 401 forms a layer of liquid 310 that fluidly couples the
transducer assembly 200 to the wafer 400. Electricity is then
supplied via the wires, 63, 64 to excite the pillars 20 in the
active regions A, B, thereby generating acoustic energy waves 80 at
the desired frequency and power level. The waves 80 of acoustic
energy are then transmitted outward through the transducer assembly
200 in an angled manner and enter the liquid layer 310, eventually
contacting the wafer surface 401. Rotating the wafer 400 on the
chuck beneath the transducer assembly 200 provides complete
acoustic coverage of the surface 401. The acoustic energy waves 80
dislodge particles from the wafer surface 401, thereby effectuating
cleaning.
[0073] As shown in FIG. 9, the acoustically active areas A, B are
separated by an acoustically inactive area C of at least 45 degrees
or more. This ensures that the waves 80 do not reflect back into
the transducer assembly 200. Of course, the size of the inactive
area C will be dictated by the curvature of the structure and other
characteristics. Furthermore, while the inner and outer surfaces
71, 72 of the transmitting structure 70 are shown as curved
surfaces, it is possible that the angled wave application technique
of the present invention can be accomplished by using planar
surfaces that are angled to one another. Thus, the terms curved,
convex, and concave are intended to cover embodiments wherein
planar surface are angularly oriented with respect to one another
to achieve the same effect.
[0074] Referring now to FIG. 10, a second embodiment of a system
2000 according to the present invention is illustrated. In this
embodiment, the composite transducer assembly 200 is a short
segment of the transducer assembly of the first system 1000. This
short segment transducer 200 is attached to a support arm 90 that
traverses the rotating chuck in a radial manner. The radial scan
can be programmed to account for the area of the wafer increasing
as the transducer moves toward the outer edge. The acoustical
transmission media 310 would be dispensed onto the water surface
401 as set forth above to achieve the fluid coupling. The
acoustical device 200 would be rod like 24 mm long with 20 mm of
active acoustical length.
[0075] Referring now to FIGS. 11-12, a third embodiment of a system
3000 according to the present invention is illustrated processing
articles of different shape. In this embodiment, the composite
transducer 200 is a full diameter (or width) of the object 400 to
be treated. The transducer 200 could be held in place and the
object (wafer, plate etc.) could be linearly scanned beneath the
transducer 200. The acoustical transmission media would be
dispensed onto the wafer/plate surface.
[0076] In each instance the desired goal is to suppress structure
damage from the acoustic energy applied to the surface, yet having
sufficient energy to remove particles. Using composite
piezoelectric material, it is also possible to make a transducer
that is made up of many segments (extending the composite pattern)
so that the length can be any dimension in principal. Furthermore,
the general shape is not required to be a round rod, alternative
variations in the shape of the device can enhance the
characteristics of the device, as shown in FIG. 13.
[0077] The foregoing description of the preferred embodiment of the
invention has been presented for the purpose of illustration and
description. It is not intended to be exhaustive or to limit the
invention to the precise form disclosed. Many modifications and
variations are possible in light of the above teaching. It is
intended that the scope of the invention be limited not by this
detailed description, but rather by the claims appended hereto.
* * * * *