U.S. patent application number 17/075179 was filed with the patent office on 2021-02-04 for ultrasound transducer arrangement and assembly, coaxial wire assembly, ultrasound probe and ultrasonic imaging system.
The applicant listed for this patent is KONINKLIJKE PHILIPS N.V.. Invention is credited to Ronald DEKKER, Vincent Andrianus HENNEKEN, Marcus Cornelis LOUWERSE, Marc Godfriedus Marie NOTTEN, Antonia Cornelia Jeannet VAN RENS, Johannes Wilhelmus WEEKAMP.
Application Number | 20210031234 17/075179 |
Document ID | / |
Family ID | 1000005162322 |
Filed Date | 2021-02-04 |
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United States Patent
Application |
20210031234 |
Kind Code |
A1 |
HENNEKEN; Vincent Andrianus ;
et al. |
February 4, 2021 |
ULTRASOUND TRANSDUCER ARRANGEMENT AND ASSEMBLY, COAXIAL WIRE
ASSEMBLY, ULTRASOUND PROBE AND ULTRASONIC IMAGING SYSTEM
Abstract
An ultrasound transducer arrangement (100) is disclosed
comprising a plurality of substrate islands (110, 120, 130)
spatially separated and electrically interconnected by a flexible
polymer assembly (150) including electrically conductive tracks
providing said electrical interconnections, said plurality
including a first substrate island (110) comprising a plurality of
ultrasound transducer cells (112) and a second substrate island
(120) comprising an array of external contacts for connecting the
ultrasound sensor arrangement to a flexible tubular body including
a coaxial wire assembly (200) comprising a plurality of coaxial
wires (220) each having a conductive core (228) covered by an
electrically insulating sleeve (226); and an electrically
insulating body (210) having a first main surface (211), a second
main surface (213) and a plurality of through holes (212) each
extending from the first main surface to the second main surface
and coated with an electrically conductive member, wherein each
coaxial wire comprises an exposed terminal core portion mounted in
one of said though holes from the first main surface, and wherein
each through hole is sealed by a solder bump (214) on the second
main surface such that the ultrasound transducer arrangement can be
directly mounted on the flexible tubular body without the need for
a PCB.
Inventors: |
HENNEKEN; Vincent Andrianus;
(EINDHOVEN, NL) ; LOUWERSE; Marcus Cornelis;
(EINDHOVEN, NL) ; WEEKAMP; Johannes Wilhelmus;
(EINDHOVEN, NL) ; DEKKER; Ronald; (EINDHOVEN,
NL) ; NOTTEN; Marc Godfriedus Marie; (EINDHOVEN,
NL) ; VAN RENS; Antonia Cornelia Jeannet; (EINDHOVEN,
NL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KONINKLIJKE PHILIPS N.V. |
Eindhoven |
|
NL |
|
|
Family ID: |
1000005162322 |
Appl. No.: |
17/075179 |
Filed: |
October 20, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15326055 |
Jan 13, 2017 |
10828673 |
|
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PCT/EP2015/064365 |
Jun 25, 2015 |
|
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17075179 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B06B 1/0622 20130101;
H01R 12/515 20130101; A61B 8/12 20130101; B06B 1/0292 20130101;
A61B 8/4494 20130101; H01R 4/023 20130101; A61B 8/445 20130101 |
International
Class: |
B06B 1/02 20060101
B06B001/02; B06B 1/06 20060101 B06B001/06; A61B 8/12 20060101
A61B008/12; A61B 8/00 20060101 A61B008/00; H01R 4/02 20060101
H01R004/02; H01R 12/51 20060101 H01R012/51 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 17, 2014 |
EP |
14177454.7 |
Claims
1. A transducer arrangement for an invasive diagnostic device,
comprising: a flexible polymer assembly comprising electrically
conductive tracks; a plurality of transducer elements on a
transducer substrate island; and one or more support substrate
islands comprising application specific integrated circuits and
capacitors, wherein the transducer substrate island and the one or
more support substrate islands are attached to the flexible polymer
assembly.
2. The transducer arrangement of claim 1, wherein the capacitors
comprise decoupling capacitors.
3. The transducer arrangement of claim 1, wherein the capacitors
comprise trench capacitors formed within a plurality of trenches
extending into the one or more support substrate islands in a
substantially perpendicular direction with respect to a surface of
a corresponding one of the one or more support substrate
islands.
4. The transducer arrangement of claim 3, wherein each of the
trench capacitors comprises a plurality of electrically connected
trenches filled with a dielectric material and an electrically
conductive material.
5. The transducer arrangement of claim 4, wherein a first electrode
of a capacitor of the capacitors comprises the support substrate
island on which the capacitor is located and a second electrode
comprises the electrically conductive material comprised within the
trenches.
6. The transducer arrangement of claim 3, wherein a depth of the
trench is in a range of 50-60% of a thickness of the support
substrate island on which a corresponding capacitor of the
capacitors is located.
7. The transducer arrangement of claim 1, wherein each of at least
two support substrate islands comprises a decoupling capacitor.
8. The transducer arrangement of claim 1, wherein the transducer
elements comprise capacitive micromachined ultrasound transducer
elements.
9. The transducer arrangement of claim 1, wherein the transducer
elements comprise lead zirconate titanate.
10. The transducer arrangement of claim 1, wherein the transducer
elements comprise polyvinylidenefluoride.
11. An ultrasound device comprising: a catheter; and a transducer
arrangement comprising: a flexible polymer assembly comprising
electrically conductive tracks; a plurality of transducer elements
on a transducer substrate island; and one or more support substrate
islands comprising application specific integrated circuits and
capacitors, wherein the transducer substrate island and the one or
more support substrate islands are attached to the flexible polymer
assembly.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 15/326,055, filed Jan. 13, 2017, which is the U.S. National
Phase application under 35 U.S.C. .sctn. 371 of International
Application No. PCT/EP2015/064365, filed on Jun. 25, 2015, which
claims the benefit of EP Application Serial No. 14177454.7 filed
Jul. 17, 2014. These applications are hereby incorporated by
reference herein.
FIELD OF THE INVENTION
[0002] The present invention relates to an ultrasound transducer
arrangement comprising a plurality of substrate islands spatially
separated and electrically interconnected by a flexible polymer
assembly.
[0003] The present invention further relates to an ultrasound
transducer assembly including such an ultrasound transducer
arrangement.
[0004] The present invention yet further relates to a coaxial wire
assembly for mating with the ultrasound transducer assembly.
[0005] The present invention still further relates to an ultrasound
probe including such an ultrasound transducer assembly and coaxial
wire assembly.
[0006] The present invention even still further relates to an
ultrasound imaging system including such an ultrasound probe.
BACKGROUND OF THE INVENTION
[0007] IC dies including ultrasound sensing capabilities, e.g.
ultrasonic transducer chips, are increasingly used as a sensing tip
of an ultrasound probe such as an ultrasound catheter. The
ultrasound sensing capabilities may for instance be provided by a
plurality of transducer elements in a main surface of the
ultrasonic transducer chip, e.g. to provide a forward looking or
sideward looking ultrasound probe. Popular technologies to
implement the transducer elements include piezoelectric transducer
elements formed of materials such as lead zirconate titanate (PZT)
or polyvinylidenefluoride (PVDF) and capacitive micro-machined
ultrasonic transducer (CMUT) elements. An ultrasonic transducer
chip based on such CMUT elements is sometimes referred to as a CMUT
device.
[0008] CMUT devices are becoming increasingly popular because CMUT
devices can offer excellent bandwidth and acoustic impedance
characteristics, which makes them the preferable over e.g.
piezoelectric transducers. Vibration of the CMUT membrane can be
triggered by applying pressure (for example using ultrasound) or
can be induced electrically. Electrical connection to the CMUT
device, often by means of an integrated circuit (IC) such as an
application specific integrated circuit (ASIC) facilitates both
transmission and reception modes of the device. In reception mode,
changes in the membrane position cause changes in electrical
capacitance, which can be registered electronically. In
transmission mode, applying an electrical signal causes vibration
of the membrane. A pressure causes a deflection of the membrane
that is electronically sensed as a change of capacitance. A
pressure reading can then be derived.
[0009] Miniaturization is a particular challenge when developing
ultrasound probes. In particular, where such probes are to be used
for advanced diagnostic purposes, e.g. cardiac investigations and
surgery, such probes must be as small as possible to allow the
probe to enter the body part of interest. At the same time, the
ultrasound probe should be rigid, e.g. when used as the tip of a
catheter to allow the probe to be guided into the body part of
interest in a controlled manner. These requirements are difficult
to reconcile with the desire to include significant signal
processing capability at the probe.
[0010] Specifically, it may be desirable to include active
components, e.g. application specific integrated circuits (ASICs)
at the probe tip to provide the ultrasound transducer cells with
control signals and to process the response signals, as well as
passive components such as decoupling capacitors that for instance
protect the various circuits from fluctuations in the supply
voltage, e.g. supply bounce, which can be caused by the power
consumption behaviour some of the components, in particular the
ASICs.
[0011] US 2010/0280388 A1 discloses a CMUT array mounted on a
flexible member together with support electronics. This subassembly
can be rolled into a tube (cylinder) to form a CMUT based
ultrasonic scanner, wherein ultrasound transducers are distributed
over the side surface of said cylinder. However, it is not
straightforward to achieve a sufficiently compact ultrasonic
scanner in this manner. Specifically, in order to mount the
subassembly onto a catheter lumen, the subassembly is typically
connected to a printed circuit board (PCB) carrying further support
electronics such as discrete components, e.g. decoupling
capacitors, that cannot be readily formed in the subassembly
manufacturing process, e.g. because these components are
manufactured in a different technology. The PCB is connected to a
number of coaxial wires inside the lumen, the number typically
matching the number of channels of the ultrasonic scanner. Such a
PCB gives the desired rigidity to the ultrasonic scanner. However,
the minimum dimensions of the PCB and discrete components typically
preclude sufficient miniaturization to facilitate use of such
probes in dimensionally challenging environments, e.g. cardiac
environments. Yet another disadvantage of the array shown is US
2010/0280388 A1 is its limited field of view in the forward looking
direction.
SUMMARY OF THE INVENTION
[0012] The present invention seeks to provide an ultrasound
transducer assembly that obviates the need for a separate PCB.
[0013] The present invention seeks to provide a coaxial wire
assembly that can be connected to such an ultrasound transducer
assembly in a straightforward manner.
[0014] The present invention further seeks to provide an ultrasound
probe including such an ultrasound transducer assembly and coaxial
wire assembly connected to each other.
[0015] The present invention yet further seeks to provide an
ultrasonic imaging system including such an ultrasound probe.
[0016] According to an aspect, there is provided a foldable
ultrasound transducer arrangement comprising a plurality of
substrate islands spatially separated and electrically
interconnected by a flexible polymer assembly including
electrically conductive tracks providing said electrical
interconnections, said plurality including a first substrate island
comprising a plurality of ultrasound transducer cells and a second
substrate island comprising an array of external contacts for
connecting the ultrasound sensor arrangement to a flexible tubular
body; and a rigid support structure having a first planar portion
comprising a first surface, a second planar portion opposite the
first portion having a second surface and a third planar portion
having a third surface extending between the first surface and the
second surface, wherein the foldable ultrasound transducer
arrangement is arranged to be folded onto the support structure
such that the first substrate island is mounted on the first
surface and the second island is mounted on the second surface.
[0017] The present invention is based on the insight that some
embodiments of a flexible transducer arrangement may be provided
that can be folded onto a pre-shaped rigid carrier (structure) such
that the transducer arrangement can be directly connected to a set
of coaxial wires without requirement of an interconnecting PCB.
Consequently, a particularly compact transducer assembly may be
produced that can be used in an ultrasound probe for a flexible
tubular body such as a catheter. In addition the first substrate
island comprising a plurality of ultrasound transducer cells may
provide a high density ultrasound array capable of acquiring high
resolution ultrasound images in a forward looking direction away
from the first surface of the rigid support structure.
[0018] Advantageously, the ultrasound transducer assembly further
comprises at least one further substrate island comprising a
plurality of external contacts for receiving active and/or passive
components. This further obviates the need for a separate PCB as
the further substrate islands can act as mounting pads for such
active components, e.g. ASICs, and/or passive components, e.g.
decoupling capacitors.
[0019] In an embodiment, at least one of the first substrate
island, the second substrate island and the at least one further
substrate island comprises a plurality of trenches defining a
decoupling capacitor, each trench being filled by a conductive
material separated from the substrate material by an electrically
insulating material. Such an embedded vertical or trench capacitor
may have a large plate area due to the three-dimensional nature of
such a capacitor and may therefore function as a decoupling
capacitor, thus obviating the need for discrete capacitors. This
further reduces the overall size of the ultrasound transducer
arrangement as discrete decoupling capacitors are typically
relatively large and in some application domains are too large to
facilitate sufficient miniaturization of the ultrasound transducer
arrangement.
[0020] The ultrasound transducer arrangement may comprise a
plurality of said decoupling capacitors, each decoupling capacitor
being located on a different substrate island. This has the further
advantage that the respective decoupling capacitors are truly
electrically insulated from each other, such that different
decoupling capacitors may be operated at different potentials, i.e.
the substrates may be operated at different potentials. This
increases the operational flexibility and robustness of the
ultrasound transducer arrangement.
[0021] In an alternative embodiment, the flexible polymer assembly
is a strip-shaped assembly and the first substrate island and the
second substrate island are at opposite ends of the strip-shaped
assembly, the ultrasound transducer arrangement further comprising
a plurality of support islands in between the first substrate
island and the second substrate island, the respective substrate
and support islands being interconnected by the flexible polymer
assembly.
[0022] This allows for the formation of a compact rigid ultrasound
transducer assembly in which the need for a separate PCB or
pre-shaped rigid carrier can be avoided.
[0023] The ultrasound transducer arrangement may further comprise
at least one further substrate island comprising a plurality of
external contacts for receiving active and/or passive components,
said at least one further substrate island being mounted on the
third planar portion. Due to the planar nature of the second
surface in between the first surface and the third surface, such
components can be added to the ultrasound transducer arrangement
whilst retaining a compact arrangement. The ultrasound transducer
may include active and/or passive components mounted on the at
least one further substrate island.
[0024] The rigid support structure may be a metal support
structure. This provides a particularly rigid support structure
than can be manufactured at low cost.
[0025] The first substrate island may be separated from the first
surface by a backing member in order to insulate the ultrasound
transducer cells from scattered ultrasound waves from undesirable
directions.
[0026] According to another aspect, there is provided an ultrasound
transducer assembly comprising a backing member; and the ultrasound
transducer arrangement according to the alternative embodiment,
wherein the first substrate island is mounted on a first surface of
the backing member and said strip-shaped assembly is folded to
define a plurality of meandering folds mounted on a second surface
of the backing member opposite said first surface, wherein the
folds are dimensioned such that neighbouring support islands are
adhered together within a single fold, and wherein the second
substrate island is exposed at a distal end of the folded
strip-shaped assembly relative to the backing member. This provides
a compact and rigid ultrasound transducer assembly without
requiring a separate rigid support structure.
[0027] According to yet another aspect, there is provided a coaxial
wire assembly comprising a plurality of coaxial wires each having a
conductive core covered by an electrically insulating sleeve; and a
electrically insulating body having a first main surface, a second
main surface and a plurality of through holes each extending from
the first main surface to the second main surface, each of said
holes being coated with an electrically conductive member; wherein
each coaxial wire comprises an exposed terminal core portion
mounted in one of said though holes from the first main surface,
and wherein each through hole is sealed by a solder bump on the
second main surface.
[0028] By securing the coaxial wires in a connection pad, which may
for instance act as a ball grid array, a connection between the
coaxial wires and the item to be connected thereto, e.g. the second
substrate island of the ultrasound transducer arrangement, can be
made in a simple and straightforward manner. To this end, the
coaxial wire assembly may further comprise a flexible tubular body
such as a catheter lumen housing said coaxial wires, wherein the
electrically insulating body is mounted on an end portion of the
flexible tubular body. However, it should be understood that such a
coaxial wire assembly is not limited to connecting with the coaxial
wire assembly of the present invention; such a coaxial wire
assembly may be connected to any item that requires connection to a
plurality of coaxial wires. Specifically, the coaxial wire assembly
may be connected to an edge portion of a carrier such as a PCB to
facilitate a straightforward connection between the coaxial wire
assembly and the carrier.
[0029] According to a further aspect, there is provided an
ultrasound probe comprising one or more embodiments of the above
ultrasound transducer assembly and the coaxial wire assembly,
wherein each of the external contacts of the second substrate
island is conductively coupled to one of the solder bumps. This
yields a particularly compact and rigid ultrasound probe that can
be reliably used in small spaces such as cardiac volumes.
[0030] According to a yet further aspect, there is provided an
ultrasonic imaging system including such an ultrasound probe. Such
an imaging system can be reliably used to produce images of small
spaces of interest, such as cardiac volumes.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] Embodiments of the invention are described in more detail
and by way of non-limiting examples with reference to the
accompanying drawings, wherein:
[0032] FIG. 1 schematically depicts an aspect of a coaxial wire
assembly according to an embodiment;
[0033] FIG. 2 schematically depicts another aspect of a coaxial
wire assembly according to an embodiment;
[0034] FIG. 3 schematically depicts a coaxial wire assembly
according to an embodiment mounted onto an edge of a printed
circuit board;
[0035] FIG. 4 schematically depicts an ultrasound transducer
arrangement according to an embodiment;
[0036] FIG. 5 schematically depicts a rigid carrier onto which the
ultrasound transducer arrangement of FIG. 4 can be mounted;
[0037] FIG. 6 schematically depicts an ultrasound transducer
assembly according to an embodiment;
[0038] FIG. 7 schematically depicts an aspect of an ultrasound
probe tip including an ultrasound transducer arrangement according
to another embodiment;
[0039] FIG. 8 schematically depicts the ultrasound probe tip of
FIG. 7 with the ultrasound transducer arrangement in a folded
arrangement;
[0040] FIG. 9 schematically depicts an example embodiment of a
method of manufacturing an ultrasound transducer arrangement;
[0041] FIG. 10 schematically depicts a method of integrating trench
capacitors into an ultrasound transducer arrangement according to
an embodiment; and
[0042] FIG. 11 schematically depicts ultrasonic imaging system
according to an example embodiment.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0043] It should be understood that the Figures are merely
schematic and are not drawn to scale. It should also be understood
that the same reference numerals are used throughout the Figures to
indicate the same or similar parts.
[0044] Embodiments of the present invention are directed to the
provision of a compact and rigid ultrasound probe tip where the
rigidity of the tip can be provided without the need for a printed
circuit board (PCB). To this end, a plug and socket type
arrangement has been devised in which an ultrasound transducer
assembly and a coaxial wire assembly are directly mated to connect
the ultrasound transducer assembly to a flexible lumen such as a
flexible catheter, in contrast to prior art arrangements in which
the ultrasound transducer assembly is typically mounted to a PCB
onto which the coaxial wires are soldered. As previously explained,
these prior art arrangements cannot achieve the desired
miniaturization of the ultrasound probe tip due to the size
constraints of the PCB.
[0045] FIGS. 1 and 2 schematically provide respective perspective
views of a coaxial wire assembly 200 according to an embodiment.
The coaxial wire assembly 200 comprises a plurality of coaxial
wires 220 each having a conductive core 228 covered by an
electrically insulating sleeve 226. The electrically insulating
sleeve 226 typically separates the electrically conductive core 228
from an electrically conductive outer sheath 224, which is
electrically insulated by an outer sleeve 222. As such coaxial
wires 220 are well known per se, this will not be explained in
further detail. It is however noted for the avoidance of doubt that
any suitable type of coaxial wire may be used in the coaxial wire
assembly 200.
[0046] The coaxial wire assembly further comprises an electrically
insulating body 210 having a first main surface 211, a second main
surface 213 and a plurality of through holes 212 each extending
from the first main surface 211 to the second main surface 213.
Each of said through holes 212 is coated with an electrically
conductive member, e.g. a metal or metal alloy layer which may be
applied to the inner surface of the through holes 212 in any
suitable manner, e.g. by any suitable plating technique. The
through holes 212 may be formed in the electrically insulating body
210 in any suitable manner, for instance using a suitable etch
recipe. The electrically insulating body 210 may be made of any
suitable material, such as for instance undoped silicon or any
other electrically insulating material through which the through
holes 212 may be formed in a suitable manner, e.g. any electrically
insulating material that can be etched to form the through holes
212. Each coaxial wire 220 comprises an exposed terminal core
portion where the electrically insulating sleeve 226 has been
stripped back to expose the terminal core portion. Each exposed
terminal core portion is mounted in one of the though holes 212
such that the terminal core portion enters the through hole 212
from the first main surface 211. Each terminal core portion is
secured in its through hole 212 such that the terminal core portion
is electrically coupled to the electrically conductive member
inside the through hole 212. For instance, the terminal core
portion may be secured in the through hole 212 using a solder. Each
through hole 212 may be further sealed by a solder bump (not shown)
on the second main surface 213, which solder bumps may define a
ball grid array on the second main surface 213. The solder bump may
form part of the solder securing the terminal core portion inside
the through hole 212. Alternatively, the electrically conductive
member formed inside each through hole 212 may be shaped such that
the electrically conductive members protrude from the second main
surface 213, which protrusions may instead define an array of
contacts on the second main surface 213. In an embodiment, the
coaxial wires 220 form part of a flexible lumen such as a catheter,
wherein the coaxial wires 220 are typically housed within a
flexible tubular body as is well known per se. In this embodiment,
the array of contacts, e.g. a ball grid array, may be used to
directly connect the flexible lumen to an ultrasound transducer
assembly, i.e. without the need to connect the coaxial wires 220 to
a PCB, as will be explained in more detail later.
[0047] However, it should be understood that the coaxial wire
assembly 200 is not limited to such a use. The coaxial wire
assembly 200 may be used as a coaxial wire connection to any
further assembly that requires a plurality of coaxial wires to be
connected thereto. In particular, the coaxial wire assembly 200 may
be advantageously used in devices in which the coaxial wires 220
are to be connected in relatively close vicinity to each other,
where the required close vicinity makes it difficult to reliably
establish the desired interconnections on an individual basis. For
instance, the coaxial wire assembly 200 according to embodiments
can facilitate a connection matrix of coaxial wires 220 having a
pitch of 200 microns or less.
[0048] FIG. 3 schematically depicts an example in which the coaxial
wire assembly 200 is mounted to a PCB 300 carrying one or more
discrete components 310. Here, the coaxial wire assembly 200 is
electrically coupled, e.g. soldered or glued using drops of a
conductive glue between opposing contacts, to an edge portion of
the PCB 300. Such an edge arrangement is particularly compact and
may be achieved because the coaxial wire assembly 200 may have an
overall height of about 1 mm or less, which is well within the
thickness of most PCBs. More generally, the form factor of the
coaxial wire assembly 200 makes it particular suitable for
connection to an edge portion of a further assembly, where the edge
portion connects two opposing major surfaces of the further
assembly.
[0049] In a specific embodiment, the coaxial wire assembly 200 may
form part of a flexible lumen, e.g. a catheter, and may be used to
form a compact rigid probe tip with an ultrasound transducer
arrangement, where the ultrasound transducer arrangement is
designed to comprise a substrate island comprising an array of
external contacts for connecting the ultrasound sensor arrangement
to the catheter via the coaxial wire assembly 200 without the need
for an intermediary rigid carrier such as a PCB in between the
ultrasound transducer arrangement and the coaxial wire assembly
200.
[0050] FIG. 4 schematically depicts an ultrasound transducer
arrangement 100 according to such an embodiment. The ultrasound
transducer arrangement 100 typically comprises an ultrasonic
transducer substrate island or chip 110 having a major surface
comprising an ultrasound transducer area, which typically comprises
a plurality of transducer elements, such as CMUT or PZT elements.
In a preferred embodiment, the major surface comprises an
ultrasound transducer area formed by a plurality of CMUT
elements.
[0051] The major surface further comprises a plurality of contacts,
which may provide points of contact to the transducer elements in
any suitable manner as is well-known per se. Any suitable
embodiment of such a transducer substrate island or chip 110 may be
chosen; it should be understood that embodiments of the present
invention are not limited to a particular embodiment of such a
transducer chip. For instance, the transducer chip 110 may be
realized in any suitable semiconductor technology, e.g. CMOS,
BiCMOS, bipolar technology and so on, using any suitable
semiconductor substrate material, e.g. silicon,
silicon-on-insulator, SiGe, GaAs and so on. Moreover, it should be
understood that the transducer substrate island or chip 110 is
shown as a circular chip by way of non-limiting example only; the
transducer substrate island or chip 110 may take any suitable shape
or form.
[0052] The ultrasonic transducer assembly further comprises a
contact substrate island or chip 120 spatially separated from the
transducer substrate island or chip 110 by a flexible polymer
assembly 150 including, e.g., embedding, conductive tracks between
the transducer substrate island or chip 110 and the contact
substrate island or chip 120. The contact chip 120 typically
comprises a plurality of external contacts 420 for engaging with
the coaxial wire assembly 200 as will be explained in more detail
later. Any suitable embodiment of such a contact substrate island
or chip 120 may be chosen; it should be understood that embodiments
of the present invention are not limited to a particular embodiment
of such a contact chip. For instance, the contact chip 120 may be
realized in any suitable semiconductor technology, e.g. CMOS,
BiCMOS, bipolar technology and so on, using any suitable
semiconductor substrate material, e.g. silicon,
silicon-on-insulator, SiGe, GaAs and so on.
[0053] The external contacts may be realized in any suitable
electrically conductive material, such as any material that is
commonly used for the formation of such contacts, e.g. any suitable
metal or metal alloy. In an embodiment, the external contacts 420
carry a solder bump for establishing the electrical connection with
the coaxial wire assembly 200.
[0054] The flexible polymer assembly 150 may for instance be formed
of an electrically insulating flexible polymer such as polyimide,
wherein the conductive tracks may be formed by depositing a metal
layer such as a copper layer over the electrically insulating
flexible polymer and patterning the metal layer to form the
conductive tracks. In an embodiment, the flexible interconnect 150
may be a Flex foil or a copper-coated polyimide such as a
Pyralux.RTM. foil as marketed by the Du Pont company.
[0055] In the embodiment shown in FIG. 4, the ultrasonic transducer
substrate island or chip 110 and the contact substrate island or
chip 120 may be discretely manufactured chips, e.g. chips
manufactured in different manufacturing processes using different
technologies, which chips are interconnected to each other by the
flexible polymer assembly 150 after singulation. This has the
advantage of increased flexibility in the designs of the ultrasonic
transducer chips 110 and the contact chips 120, but comes at the
cost of a more involved assembly process of the ultrasonic producer
assembly, as it can be cumbersome to connect the flexible
interconnect 150 to the respective chips 110, 120. Therefore, in an
alternative embodiment, which will be explained in more detail
later with the aid of FIG. 9, the ultrasonic transducer substrate
island or chip 110, the contact substrate island or chip 120 and
the flexible polymer assembly 150 may be produced in a single
(integrated) production process.
[0056] The ultrasound transducer arrangement 100 may further
comprise one or more mounting substrate islands or chips 130, which
may be realized in the same technology as the ultrasonic transducer
substrate island or chip 110 and/or the contact substrate island or
chip 120, i.e. in a single integrated production process, or in a
distinct technology as previously explained. The one or more
mounting substrate islands or chips 130 are electrically connected
to the ultrasonic transducer substrate island or chip 110 and/or
the contact substrate island or chip 120 through the conductive
tracks in the flexible polymer assembly 150. The one or more
mounting substrate islands or chips 130 comprise contacts on an
exposed surface onto which active components 132, e.g. transducer
controllers and/or signal processing components such as ICs, e.g.
application-specific ICs (ASICs), or passive components 134, e.g.
decoupling capacitors or the like, may be mounted in any suitable
manner, e.g. soldered, thermo compression bonded, and so on. This
has the advantage that discrete components may be added to the
ultrasound transducer arrangement 100 without having to manufacture
these components in the same technology as for instance the
ultrasonic transducer substrate island or chip 110. This increases
the design flexibility of the ultrasound transducer arrangement
100. The at least one mounting substrate island or chip 130 in
essence serves as a replacement mounting platform for such discrete
components, thereby facilitating the omission of a PCB from an
ultrasound transducer assembly including the ultrasound transducer
arrangement 100.
[0057] It should however be understood that embodiments the present
invention are not limited to such discrete components being mounted
on dedicated substrate islands 130; it is equally feasible that the
ultrasonic transducer substrate island or chip 110 and/or the
contact substrate island or chip 120 contain such external contacts
for mounting such discrete components in addition to or instead of
on the mounting substrate islands or chips 130.
[0058] In the absence of such a PCB, additional measures are
required to ensure that the ultrasound transducer assembly achieves
the desired stiffness when used as a probe tip of e.g. an invasive
diagnostic device such as a catheter. In a first embodiment, the
ultrasound transducer arrangement 100 may be mounted on a
pre-shaped rigid support structure 400, an example embodiment of
which is schematically depicted in FIG. 5 to form an ultrasound
transducer assembly 600 as schematically depicted in FIG. 6. The
rigid support structure 400 may have a first planar portion 410
comprising a first surface for supporting the ultrasonic transducer
substrate island or chip 110, a second planar portion 420 opposite
the first portion 410 having a second surface for supporting the
contact substrate island or chip 120 and a third planar portion 430
having a third surface extending between the first surface and the
second surface for supporting the one or more mounting substrate
islands or chips 130, which one or more mounting substrate islands
or chips 130 may carry active components 132 and/or passive
components 134 as previously explained. The third planar portion
may be aligned with an overall length of a probe (while being
perpendicular to the first and second surfaces), wherein such an
assembly can be used. In an embodiment, both main surfaces of the
third planar portion 430 may be used to support mounting substrate
islands or chips 130.
[0059] The ultrasound transducer arrangement 100 may be mounted on
the rigid support 400 by folding the flexible polymer assembly 150
such that the relevant substrate islands are mounted on the
aforementioned planar surfaces. To this end, the flexible polymer
assembly 150 may be shaped, e.g. patterned, to contain multiple
flaps each carrying one or more of the substrate islands, which
flaps are folded over the appropriate planar surface of the rigid
support structure 400 to form the rigid ultrasound transducer
assembly 600. The ultrasound transducer arrangement 100 may be
secured on the rigid support structure 400 in any suitable manner,
e.g. using a suitable adhesive, which will be known per se to the
person skilled in the art.
[0060] The rigid support structure 400 may be made of any suitable
rigid material, such as a rigid (bio)polymer, a metal, metal alloy,
e.g. stainless steel, and so on. In an embodiment, the rigid
support structure 400 is made of a rigid material that is cleared
for internal use in a patient, e.g. titanium or stainless steel.
The rigid support structure 400 may take any suitable shape. In an
embodiment, the first surface of the first planar portion 410 is
substantially parallel with the second surface of the second planar
portion 420, wherein the first surface and second surface face
opposite directions.
[0061] This for instance may be used to provide an ultrasound
transducer assembly 600 having a forward looking ultrasound
transducer array and a contact substrate island or chip 120 being
arranged to connect to a coaxial wire assembly 100 mounted on a tip
of a flexible tubular member, e.g. a lumen or catheter. Upon
connection of such a ultrasound transducer assembly 600 to such a
coaxial wire assembly 100, a particularly compact probe tip can be
achieved, e.g. having the overall length from transducer chip 110
to contact chip 120 of less than 10 mm, or even less than 8 mm,
with a high degree of rigidity, thus providing an ultrasound probe
tip that is particularly suitable for investigations and procedures
involving small body volumes, e.g. cardiac investigations and
procedures. The advantage of such a probe comprising the forward
looking ultrasound array located at its tip's front surface may be
compact size and a capability of high resolution ultrasound imaging
due to the possibility in varying the transducer density within
ultrasonic transducer substrate island 110.
[0062] Optionally, in the ultrasound transducer assembly 600 used
for the probe tip, the ultrasonic transducer chip 110 may be
separated from the first surface of the first planar portion 410 by
a backing member 610. In this embodiment, at least a part of the
flexible polymer assembly 150 may extend along an outer side of the
backing member 610, such that the transducer chip 110 and the
contact ship 120 are electrically interconnected. The backing
member 610 typically comprises a resin such as an epoxy resin in
which ultrasound scattering and/or absorbing bodies are included.
For instance, the ultrasound scattering bodies and/or ultrasound
absorbing bodies may be dispersed in the resin. Such bodies
suppress or even prevent scattered and/or reflected ultrasound
waves from reaching the ultrasonic transducer elements of the
ultrasonic transducer chip 110. This may improve the resolution of
the ultrasound image generated by the ultrasonic transducer chip
110, as predominantly or only ultrasound waves generated and
reflected in the intended direction (e.g. forward generated and
reflected ultrasound waves in the case of a forward-looking
ultrasound probe including the ultrasonic transducer chip 100) are
detected by the ultrasonic transducer elements of the ultrasonic
transducer chip 100. In other words, the suppression or prevention
of ultrasound waves from other directions reaching the ultrasonic
transducer chip 110 by the backing member 610 reduces or even
avoids interference from such stray ultrasound waves with the
ultrasound waves from the direction of interest.
[0063] Any suitable ultrasound scattering materials may be used to
form the ultrasound scattering bodies in the backing member 610.
For instance, a non-limiting example of such an ultrasound
scattering body is a hollow glass sphere although other suitable
ultrasound scattering bodies will be immediately apparent to the
skilled person. Similarly, any suitable solid materials may be used
to form the ultrasound absorbing bodies. It is well-known per se
that heavy materials, e.g. materials based on heavy metals, are
ideally suited for such a purpose. A non-limiting example of such a
material is tungsten. For instance, the ultrasound absorbing bodies
may comprise tungsten, such as in the form of tungsten oxide.
Again, it will be immediately apparent to the skilled person that
many suitable alternatives to tungsten are readily available, and
such suitable alternatives are equally feasible to be used in the
backing member 610.
[0064] FIG. 7 schematically depicts an alternative embodiment of an
ultrasound transducer arrangement 100 that can be folded into a
rigid ultrasound transducer assembly 600 having a plurality of
meandering folds as schematically shown in FIG. 8. In this
embodiment, the flexible polymer assembly 150 is shaped as an
elongated strip, wherein the ultrasound transducer arrangement 100
in addition to the ultrasonic transducer substrate island or chip
110 and the contact substrate island or chip 120 further comprises
a plurality of support substrate islands or chips 140
interconnected by the flexible polymer assembly 150 as previously
explained.
[0065] The support substrate islands or chips 140 are spaced apart
such that exposed major surfaces of neighbouring support substrate
islands or chips 140 may be contacting each other when the flexible
polymer assembly 150 is folded into a plurality of meandering loops
or folds, with the neighbouring support substrate islands or chips
140 occupying a single fold or loop as shown in FIG. 8. The
neighbouring support substrate islands or chips 140 may be secured
to each other in any suitable manner, e.g. using a suitable
adhesive. The support substrate islands or chips 140 act as rigid
support members of the ultrasound transducer assembly 600 that help
to give the ultrasound transducer assembly 600 its desired
rigidity.
[0066] In an embodiment, at least some of the support substrate
islands or chips 140 may perform the role of the previously
described mounting substrate islands or chips 130. In other words,
at least some of the support substrate islands or chips 140 may
comprise contacts on an exposed surface onto which active
components 132, e.g. transducer controllers and/or signal
processing components such as ICs, e.g. application-specific ICs
(ASICs), or passive components 134, e.g. decoupling capacitors or
the like, may be mounted in any suitable manner, e.g. soldered,
thermo compression bonded, and so on.
[0067] In an embodiment, the ultrasound transducer substrate island
or chip 110 is spatially separated from a further substrate island,
e.g. one of the support substrate islands or chips 140, by a
backing member 610, which may be a backing member as previously
explained. The ultrasound transducer substrate island or chip 110
and the further substrate island may be affixed to the backing
member 610 in any suitable manner, e.g. using an adhesive.
[0068] The ultrasound transducer substrate island or chip 110 may
be located at a proximal end and the contact substrate island or
chip 120 may be located at a distal end of the strip-shaped
flexible polymer assembly 150 relative to the backing member 610.
As shown in FIG. 8, the contact substrate island or chip 120 may be
connected to a coaxial wire assembly 200 comprising a plurality of
coaxial wires 220 as previously discussed.
[0069] In FIG. 9, a non-limiting example of a method in accordance
with an embodiment of the present invention is schematically
depicted in which an ultrasound transducer arrangement 100 is
formed. In a first step, depicted in FIG. 9(a), a wafer 900 is
provided in which a plurality of ultrasonic transducer substrate
islands or chips 110 having a plurality of ultrasonic transducer
elements 112 and a plurality of first contacts 114 have been formed
in one or more arrays 920 and in which contact substrate islands or
chips 120 including a plurality of second contacts 122 are formed
in one or more arrays 930 (two arrays 920, 930 are shown by way of
non-limiting example). The arrays 920 of the ultrasonic transducer
substrate islands or chips 110 are separated from a neighbouring
array 930 of the contact substrate islands or chips 120 by a
sacrificial region 910 of the wafer 900. Individual substrate
islands or chips within each of the arrays 920, 930 are separated
by a further sacrificial wafer region 912, e.g. a scribe line or
the like as will be explained in more detail later.
[0070] The wafer 900 may be any suitable wafer, such as a silicon
wafer, a silicon-on-insulator wafer or a wafer of other suitable
semiconductor materials. In an embodiment, the wafer 900 may
comprise an etch stop layer (not shown), such as an oxide layer.
Its purpose will be explained in more detail later. The first
contacts 114 of each ultrasonic transducer substrate island or chip
110 are to be connected to the second contacts 122 of an opposing
contact substrate island or chip 120 by a flexible polymer assembly
150 extending across the sacrificial region 910. Such a flexible
contact extension can be seen as a microscopic version of a flat
cable, which use is well-known at the printed circuit board (PCB)
level.
[0071] The method proceeds as shown in FIG. 9(b) with the provision
of a layer of a flexible and electrically insulating material 150
on the front side of the wafer 900, which is subsequently patterned
by photolithography to expose the first and second contacts 114,
122 underneath the layer 200. Any suitable material may be used for
the layer 200. The flexible and electrically insulating material
may be chosen from the group consisting of parylene, polyimide,
polyimide resins, polycarbonate, fluorocarbon, polysulphon,
epoxide, phenol, melamine, polyester, and silicone resins or their
co-polymers. Polyimide and parylene are particularly suitable when
the IC is to be integrated into an invasive medical device as these
materials have been cleared for use in invasive medical
devices.
[0072] The thickness of the layer of a flexible and electrically
insulating material 150 preferably is selected in the range from
1-20 .mu.m and more preferably in the range of 1-10 .mu.m to ensure
that the resultant has sufficient flexibility. If the layer 150
becomes too thick, its flexibility will be reduced. However, if the
layer 150 becomes too thin, it may be damaged too easily.
[0073] In a subsequent step, shown in FIG. 9(c), a conductive
material is deposited on the layer of the flexible and electrically
insulating material 150 and subsequently patterned to provide
respective conductive tracks 152 in conductive contact with the
exposed first and second contacts 114, 122 underneath the layer
150. Any suitable electrically conductive material, such as Al, Cu
or other suitable metals and metal alloys may be used.
[0074] In an optional step shown in FIG. 9(d), the conductive
tracks 152 are subsequently covered with a second layer of a
flexible and electrically insulating material 150', which
preferably is the same material as used for layer 150, although
this is not essential. In other words, the materials used for
layers 150 and 150' respectively may be individually selected from
the previously described group of suitable compounds.
[0075] In a preferred embodiment, layers 150 and 150' are made of
the same material, e.g. polyimide or parylene, and have the same
thickness, e.g. approximately 5 .mu.m. By using the same thickness
for both layers 150 and 150', the conductive track(s) 152 are
situated at the so called neutral line of stress of the flexible
contact extension of the contacts 114, 122. If present, the second
layer 150' of a flexible and electrically insulating material may
be covered with a thin protective layer (not shown) from subsequent
wafer processing steps. Any suitable material, such as a metal,
e.g. Al may be used. The use of a material that can serve both to
protect the layer 150' during the subsequent processing steps as
well as a hard-etch mask for the subsequent patterning of the
second layer of a flexible and electrically insulating material
150' is preferred as it reduces the wafer processing complexity.
For this reason, metals such as Al are preferred.
[0076] As shown in FIG. 9(e), the method proceeds by applying and
patterning a resist layer 902 on the backside of the wafer 900.
Alternatively the resist layer 902 may be replaced by a patterned
hard mask. The patterned resist layer 902, which may be any
suitable material including a similar or the same material used for
the previously mentioned thin protective layer over the second
layer 150', protects (covers) the areas of the arrays 920, 930 in
the wafer 500.
[0077] In a final step, shown in FIG. 9(f), the exposed parts of
the back-side of the wafer 900, i.e. the parts not covered by the
patterned resist 902 are exposed to an etch recipe, preferably an
anisotropic etch recipe such as the Bosch process, for instance in
case of the wafer 900 being a silicon wafer, with the exposed parts
being etched to a depth corresponding to the intended final
thickness of the substrate islands or chips 110, 120 to be formed
from the wafer 900, to release (singulate) the arrays 920, 930,
with each array 920 connected to an array 530 by the flexible
interconnect 200. It is noted that the Bosch process, which
typically comprises consecutive etching and passivation steps, is
well-known per se, and will therefore not be explained in further
detail for reasons of brevity only. Other suitable etch recipes of
course may also be contemplated. The patterned resist 902 is
subsequently stripped from the backside of the wafer 900.
[0078] Although not specifically shown, a further singulation step
may be employed to singulate the ultrasound transducer arrangements
100, e.g. by dicing the sacrificial regions 912. Alternatively, the
etch step shown in step (f) may include the removal of the
sacrificial regions 912 such that the ultrasound transducer
arrangements 100 are individualized in a single step process.
[0079] At this point, it is noted that the wafer 900 may of course
include further substrate islands, e.g. mounting substrate islands
130 and/or dummy substrate islands 140, which, were necessary, may
be connected to the ultrasonic transducer substrate islands or
chips 110 and/or the contact substrate islands or chips 120 as
explained above for the electrical connection between the contacts
114, 122. These further substrate islands have not been shown for
reasons of clarity only.
[0080] It is further noted that the contact substrate islands or
chips 120 further comprise a plurality of external contacts for
connecting the contact substrate islands or chips 120 to coaxial
wire assemblies 200 as previously explained. Again, these external
contacts may be formed in any suitable manner and have not been
shown for reasons of clarity only. In an embodiment, solder bumps
may be formed on these external contacts. The solder bumps may be
formed on the external contacts at any suitable point in the
aforementioned manufacturing process, for instance before or after
the singulation of the arrays 520, 530. The solder bumps may be
formed on the contacts in any suitable manner, for instance by
using a laser process as available from the PacTech Company, Nauen,
Germany.
[0081] As previously mentioned, the ultrasound transducer
arrangement 100 may include passive components 134 such as one or
more capacitors, e.g. decoupling capacitors. Such decoupling
capacitors are typically necessary if the ultrasound transducer
arrangement 100 comprises components that produce switching
transients that are large enough to compromise the integrity of the
power supply. An example of such a component is a signal processing
IC such as an ASIC. This problem is particularly prevalent at a
miniature probe tip where the power supply lines tend to have a
relatively high and undefined impedance. In such a scenario,
decoupling capacitors are used to decouple various components from
the power supply lines such that these components are shielded from
fluctuations in the power supply. Such decoupling capacitors have
capacitances typically ranging from 1 to 100 nF. Furthermore,
discrete capacitors may be included to establish an AC connection
between different circuit parts operating at different DC
potentials, e.g. in the case of a CMUT transducer array and an
ASIC. Such a capacitor must be electrically floating, i.e. must be
dielectrically insulated from the substrate and ground.
[0082] The size of such discrete capacitors is such that
integration in a miniaturized ultrasound probe tip is prohibited as
such capacitors are simply too big. In an embodiment, this problem
is addressed by the integration of trench capacitors in at least
some of the substrate islands 110, 120, 130, such that the need for
the inclusion of discrete capacitors in the ultrasound transducer
arrangement 100 is obviated.
[0083] Advantageously, the ultrasound transducer arrangement 100
comprises a plurality of substrate islands at least including a
first substrate island 110 comprising a plurality of ultrasound
transducer cells 112 and a second substrate island 120 comprising
an array of external contacts for connecting the ultrasound sensor
arrangement to a flexible tubular body, with the plurality of
substrate islands optionally further comprising at least one
mounting substrate island 130 for mounting one or more active
and/or passive components thereon as previously explained. In an
embodiment, at least two of these substrate islands each comprise
such a trench capacitor, which has the advantage that the
respective trench capacitors are truly electrically isolated from
each other due to the fact that they are located in different
substrates, such that these different substrates can be operated at
different potentials. Moreover, the inclusion of the trench
capacitors obviates the need for discrete capacitors to be included
in the ultrasound transducer arrangement 100, thereby further
aiding the miniaturization of the ultrasound transducer arrangement
100 and an ultrasound probe tip formed from such an
arrangement.
[0084] In the context of the present application, a trench
capacitor is a capacitor formed by a plurality of trenches
extending more or less perpendicularly from a major surface of the
substrate into the substrate. The trenches may have any suitable
shape, e.g. outline, e.g. the trenches may be square, rectangular,
circular trenches and so on. The substrate typically is a
conducting or semiconducting substrate and acts as the first plate
of the trench capacitor. The trenches are typically lined with an
electrical insulator, e.g. a dielectric material, and filled with a
further conductive or semiconductive material acting as the second
plate of the trench capacitor, wherein the electrical insulator
separates the first plate from the second plate. Due to the fact
that the plates of the trench capacitor extend in all three
dimensions and are formed by multiple trenches, a capacitor is
obtained that have a large plate area in a compact substrate
volume, thereby achieving a compact high capacity capacitor.
[0085] FIG. 10 schematically depicts an example embodiment of a
method of manufacturing such a trench capacitor. It should be
understood that alternative manufacturing methods are readily
available and will be known to the skilled person. Such alternative
manufacturing methods may also be contemplated.
[0086] The method begins in step (a) with the provision of a
conductive substrate 1000, which may be a part of a wafer 900 and
may be converted into one of the aforementioned substrate islands
110, 120, 130 as previously explained, for instance with the aid of
FIG. 9. The conductive substrate 1000 for instance may be a highly
conductive silicon substrate, such as an n-type substrate, e.g. an
As-doped substrate although p-type substrates may also be used.
Also, substrate materials other than silicon may be contemplated as
previously explained. A suitable etch-mask 1002 is formed on the
substrate 100 for instance by growing a thermal oxide on the
substrate 1000, which thermal oxide is opened to create openings
1004 where the trenches of the trench capacitor are to be formed.
The etch-mask 1002 may be formed to any suitable thickness, e.g.
about 1 .mu.m.
[0087] Next, as shown in step (b), the trenches 1006 are etched
using a suitable etch recipe, e.g. using Deep Reactive Ion Etching
in case of a silicon substrate 1000. The trenches 1006 may be
etched to a depth of about 50-60% of the final thickness of the
substrate island to be formed. For instance, for a substrate island
having a final thickness of about 50 .mu.m, the trenches 1006 may
be etched to a depth of about 30 .mu.m The trenches 1006 may have
any suitable width, such as a width of about 1-2 .mu.m.
[0088] After etching of the pores 1006, a capacitor dielectric 1008
is deposited in step (c). Any suitable dielectric material may be
used for this purpose. A particularly suitable material is silicon
nitride, which for instance may be deposited using LPCVD. However,
other dielectric materials such as silicon oxide, aluminium oxide
or combinations of these materials may also be used, and other
deposition techniques, e.g. ALD, may also be contemplated. The
capacitor dielectric 1008 may be formed to any suitable thickness,
e.g. several tens of nm, e.g. 20 nm.
[0089] In step (d), the trenches 1006 lined with the capacitor
dielectric 1008 are filled with a conductive material 1010 to form
the second plate of the trench capacitor. In an embodiment, the
trenches 1006 may be filled by depositing a layer of in-situ doped
poly-silicon although other conductive materials may also be used.
After patterning the conductive material 1010, e.g. using a
suitable etch recipe in step (e), a further dielectric layer 1012
is formed over the patterned conductive material 1010 in step (f)
to electrically isolate the conductive material 1010 from
subsequent metallization steps. The manufacturing of the trench
capacitor is completed by the etching of contact windows 1014, 1016
in step (g) and the deposition and patterning of a metal
interconnect layer such as an aluminium interconnect layer in step
(h) to form metal contacts 1020 and 1022 to the first plate and
second plate of the trench capacitor respectively. As such
finalization steps are well-known per se they are not explained in
further detail for the sake of brevity only.
[0090] As will be clear to the skilled person, the substrate 1000
may be subsequently subjected to further processing steps, e.g. to
form an array of transducer elements thereon. For instance, a
passivation layer or layer stack may be formed on the trench
capacitor after which an array of ultrasonic transducer elements,
e.g. CMUT elements may be formed on the passivation layer (stack)
as is well known per se. Other further processing steps, e.g. the
formation of other elements on such a substrate, will be apparent
to the skilled person. It should further be understood that each
substrate island may comprise a plurality of such trench
capacitors.
[0091] Referring to FIG. 11, an example embodiment of an ultrasonic
diagnostic imaging system with an array transducer probe according
to an embodiment of the present invention is shown in block diagram
form. In FIG. 11 a CMUT transducer array 110 on an ultrasound
transducer chip 100 (not shown in FIG. 11) is provided in an
ultrasound probe 10 for transmitting ultrasonic waves and receiving
echo information. The transducer array 110 may alternatively
comprise piezoelectric transducer elements formed of materials such
as lead zirconate titanate (PZT) or polyvinylidenefluoride (PVDF).
The transducer array 110 may be a one- or a two-dimensional array
of transducer elements capable of scanning in a 2D plane or in
three dimensions for 3D imaging.
[0092] The transducer array 110 is coupled to a microbeam former 12
in the probe 10 which controls transmission and reception of
signals by the CMUT array cells or piezoelectric elements.
Microbeam formers are capable of at least partial beam forming of
the signals received by groups or "patches" of transducer elements
for instance as described in U.S. Pat. No. 5,997,479 (Savord et
al.), U.S. Pat. No. 6,013,032 (Savord), and U.S. Pat. No. 6,623,432
(Powers et al.).
[0093] The microbeam former 12 is coupled by the probe cable, e.g.
coaxial wire 410, to a transmit/receive (T/R) switch 16 which
switches between transmission and reception and protects the main
beam former 20 from high energy transmit signals when a microbeam
former is not present or used and the transducer array 110 is
operated directly by the main system beam former 20. The
transmission of ultrasonic beams from the transducer array 110
under control of the microbeam former 12 is directed by a
transducer controller 18 coupled to the microbeam former by the T/R
switch 16 and the main system beam former 20, which receives input
from the user's operation of the user interface or control panel
38. One of the functions controlled by the transducer controller 18
is the direction in which beams are steered and focused. Beams may
be steered straight ahead from (orthogonal to) the transducer array
110, or at different angles for a wider field of view. The
transducer controller 18 may be coupled to control a DC bias
control 45 for the CMUT array. For instance, the DC bias control 45
sets DC bias voltage(s) that are applied to the CMUT cells 150 of a
CMUT array 110.
[0094] The partially beam-formed signals produced by the microbeam
former 12 are forwarded to the main beam former 20 where partially
beam-formed signals from individual patches of transducer elements
are combined into a fully beam-formed signal. For example, the main
beam former 20 may have 128 channels, each of which receives a
partially beam-formed signal from a patch of dozens or hundreds of
CMUT transducer cells 112 (see FIG. 1-3) or piezoelectric elements.
In this way the signals received by thousands of transducer
elements of a transducer array 110 can contribute efficiently to a
single beam-formed signal.
[0095] The beam-formed signals are coupled to a signal processor
22. The signal processor 22 can process the received echo signals
in various ways, such as bandpass filtering, decimation, I and Q
component separation, and harmonic signal separation which acts to
separate linear and nonlinear signals so as to enable the
identification of nonlinear (higher harmonics of the fundamental
frequency) echo signals returned from tissue and microbubbles.
[0096] The signal processor 22 optionally may perform additional
signal enhancement such as speckle reduction, signal compounding,
and noise elimination. The bandpass filter in the signal processor
22 may be a tracking filter, with its passband sliding from a
higher frequency band to a lower frequency band as echo signals are
received from increasing depths, thereby rejecting the noise at
higher frequencies from greater depths where these frequencies are
devoid of anatomical information.
[0097] The processed signals are coupled to a B-mode processor 26
and optionally to a Doppler processor 28. The B-mode processor 26
employs detection of an amplitude of the received ultrasound signal
for the imaging of structures in the body such as the tissue of
organs and vessels in the body. B-mode images of structure of the
body may be formed in either the harmonic image mode or the
fundamental image mode or a combination of both for instance as
described in U.S. Pat. No. 6,283,919 (Roundhill et al.) and U.S.
Pat. No. 6,458,083 (Jago et al.)
[0098] The Doppler processor 28, if present, processes temporally
distinct signals from tissue movement and blood flow for the
detection of the motion of substances, such as the flow of blood
cells in the image field. The Doppler processor typically includes
a wall filter with parameters which may be set to pass and/or
reject echoes returned from selected types of materials in the
body. For instance, the wall filter can be set to have a passband
characteristic which passes signal of relatively low amplitude from
higher velocity materials while rejecting relatively strong signals
from lower or zero velocity material.
[0099] This passband characteristic will pass signals from flowing
blood while rejecting signals from nearby stationary or slowing
moving objects such as the wall of the heart. An inverse
characteristic would pass signals from moving tissue of the heart
while rejecting blood flow signals for what is referred to as
tissue Doppler imaging, detecting and depicting the motion of
tissue. The Doppler processor receives and processes a sequence of
temporally discrete echo signals from different points in an image
field, the sequence of echoes from a particular point referred to
as an ensemble. An ensemble of echoes received in rapid succession
over a relatively short interval can be used to estimate the
Doppler shift frequency of flowing blood, with the correspondence
of the Doppler frequency to velocity indicating the blood flow
velocity. An ensemble of echoes received over a longer period of
time is used to estimate the velocity of slower flowing blood or
slowly moving tissue.
[0100] The structural and motion signals produced by the B-mode
(and Doppler) processor(s) are coupled to a scan converter 32 and a
multiplanar reformatter 44. The scan converter 32 arranges the echo
signals in the spatial relationship from which they were received
in a desired image format. For instance, the scan converter may
arrange the echo signal into a two dimensional (2D) sector-shaped
format, or a pyramidal three dimensional (3D) image.
[0101] The scan converter can overlay a B-mode structural image
with colors corresponding to motion at points in the image field
with their Doppler-estimated velocities to produce a color Doppler
image which depicts the motion of tissue and blood flow in the
image field. The multiplanar reformatter 44 will convert echoes
which are received from points in a common plane in a volumetric
region of the body into an ultrasonic image of that plane, for
instance as described in U.S. Pat. No. 6,443,896 (Detmer). A volume
renderer 42 converts the echo signals of a 3D data set into a
projected 3D image as viewed from a given reference point as
described in U.S. Pat. No. 6,530,885 (Entrekin et al.) The 2D or 3D
images are coupled from the scan converter 32, multiplanar
reformatter 44, and volume renderer 42 to an image processor 30 for
further enhancement, buffering and temporary storage for display on
an image display 40. In addition to being used for imaging, the
blood flow values produced by the Doppler processor 28 and tissue
structure information produced by the B-mode processor 26 are
coupled to a quantification processor 34. The quantification
processor produces measures of different flow conditions such as
the volume rate of blood flow as well as structural measurements
such as the sizes of organs and gestational age. The quantification
processor may receive input from the user control panel 38, such as
the point in the anatomy of an image where a measurement is to be
made.
[0102] Output data from the quantification processor is coupled to
a graphics processor 36 for the reproduction of measurement
graphics and values with the image on the display 40. The graphics
processor 36 can also generate graphic overlays for display with
the ultrasound images. These graphic overlays can contain standard
identifying information such as patient name, date and time of the
image, imaging parameters, and the like. For these purposes the
graphics processor receives input from the user interface 38, such
as patient name.
[0103] The user interface is also coupled to the transmit
controller 18 to control the generation of ultrasound signals from
the transducer array 110 and hence the images produced by the
transducer array and the ultrasound system. The user interface is
also coupled to the multiplanar reformatter 44 for selection and
control of the planes of multiple multiplanar reformatted (MPR)
images which may be used to perform quantified measures in the
image field of the MPR images.
[0104] As will be understood by the skilled person, the above
embodiment of an ultrasonic diagnostic imaging system is intended
to give a non-limiting example of such an ultrasonic diagnostic
imaging system. The skilled person will immediately realize that
several variations in the architecture of the ultrasonic diagnostic
imaging system are feasible without departing from the teachings of
the present invention. For instance, as also indicated in the above
embodiment, the microbeam former 12 and/or the Doppler processor 28
may be omitted, the ultrasound probe 10 may not have 3D imaging
capabilities and so on. Other variations will be apparent to the
skilled person.
[0105] It should be noted that the above-mentioned embodiments
illustrate rather than limit the invention, and that those skilled
in the art will be able to design many alternative embodiments
without departing from the scope of the appended claims. In the
claims, any reference signs placed between parentheses shall not be
construed as limiting the claim. The word "comprising" does not
exclude the presence of elements or steps other than those listed
in a claim. The word "a" or "an" preceding an element does not
exclude the presence of a plurality of such elements. The invention
can be implemented by means of hardware comprising several distinct
elements. In the device claim enumerating several means, several of
these means can be embodied by one and the same item of hardware.
The mere fact that certain measures are recited in mutually
different dependent claims does not indicate that a combination of
these measures cannot be used to advantage.
* * * * *