U.S. patent application number 17/168335 was filed with the patent office on 2022-08-11 for system and method for mitigating trace triggering of channels in x-ray detector.
The applicant listed for this patent is GE PRECISION HEALTHCARE LLC. Invention is credited to Biju Jacob, Brian David Yanoff.
Application Number | 20220249040 17/168335 |
Document ID | / |
Family ID | 1000006489667 |
Filed Date | 2022-08-11 |
United States Patent
Application |
20220249040 |
Kind Code |
A1 |
Yanoff; Brian David ; et
al. |
August 11, 2022 |
SYSTEM AND METHOD FOR MITIGATING TRACE TRIGGERING OF CHANNELS IN
X-RAY DETECTOR
Abstract
An X-ray detector is provided. The X-ray detector includes
multiple detector sub-modules. Each detector sub-module includes a
semiconductor layer and multiple detector elements. A first
detector element of the multiple detector elements includes a first
electrode disposed on a first doped implant and a second detector
element of the multiple detector elements includes a second
electrode disposed on a second doped implant. The first and second
detector elements are disposed on the semiconductor layer adjacent
to each other with a gap therebetween. Each detector sub-module
also includes wiring traces extending from one or more detector
elements of the multiple detector elements to readout circuitry.
The wiring traces are routed within the gap between the first and
second electrodes. The first doped implant extends underneath a
portion of the wiring traces is configured to shield the wiring
traces from electrical activity occurring underneath due to
absorption of an X-ray.
Inventors: |
Yanoff; Brian David;
(Schenectady, NY) ; Jacob; Biju; (Niskayuna,
NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GE PRECISION HEALTHCARE LLC |
Wauwatosa |
WI |
US |
|
|
Family ID: |
1000006489667 |
Appl. No.: |
17/168335 |
Filed: |
February 5, 2021 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01T 1/244 20130101;
A61B 6/4241 20130101; G01T 1/241 20130101; G01T 1/247 20130101 |
International
Class: |
A61B 6/00 20060101
A61B006/00; G01T 1/24 20060101 G01T001/24 |
Claims
1. An X-ray detector, comprising: a plurality of detector
sub-modules, wherein each detector sub-module comprises: a
semiconductor layer; a plurality of detector elements, wherein a
first detector element of the plurality of detector elements
comprises a first electrode disposed on a first doped implant and a
second detector element of the plurality of detector elements
comprises a second electrode disposed on a second doped implant,
the first and second detector elements being disposed on the
semiconductor layer adjacent to each other with a gap therebetween;
and wiring traces extending from one or more detector elements of
the plurality of detector elements to readout circuitry, wherein
the wiring traces are routed within the gap between the first and
second electrodes; wherein the first doped implant extends
underneath a portion of the wiring traces and is configured to
shield the wiring traces from electrical activity occurring
underneath due to absorption of an X-ray.
2. The X-ray detector of claim 1, wherein the X-ray detector
comprises a photon-counting X-ray detector.
3. The X-ray detector of claim 1, wherein each detector sub-module
comprises an edge-on detector sub-module.
4. The X-ray detector of claim 1, wherein a subset of detector
elements of the plurality of detector elements are located at a
side edge of a respective edge of the detector sub-module.
5. The X-ray detector of claim 1, wherein each detector sub-module
comprises an electrical insulator layer disposed on the
semiconductor layer and extending between the first electrode and
the second electrode, the wiring traces being disposed on the
electrical insulation layer.
6. The X-ray detector of claim 5, wherein the first doped implant
extends underneath the electrical insulation layer.
7. The X-ray detector of claim 1, wherein the first doped implant
comprises a first portion disposed underneath the first electrode
and a second portion extending underneath the portion of the wiring
traces, wherein the second portion of the first doped implant
comprises a series of spaced protrusions extending from the first
portion toward the second doped implant.
8. The X-ray detector of claim 1, wherein the second doped implant
extends underneath the portion of the wiring traces and is
configured to shield the wiring traces from electrical activity
occurring underneath due to absorption of the X-ray.
9.-20. (canceled)
Description
BACKGROUND
[0001] The subject matter disclosed herein relates to X-ray
detectors and, more particularly, to mitigating undesired signals
originating from the interconnecting wire traces in an X-ray
detector.
[0002] Non-invasive imaging technologies allow images of the
internal structures or features of a subject (patient, manufactured
good, baggage, package, or passenger) to be obtained without
physical contact.
[0003] For example, in X-ray-based imaging technologies, X-ray
radiation penetrates a subject of interest, such as a human
patient, and a portion of the radiation impacts a detector where
the intensity data is collected. In digital X-ray systems, a
detector produces signals representative of the amount or intensity
of radiation impacting discrete pixel regions of a detector
surface. The signals may then be processed to generate an image
that may be displayed for review.
[0004] In one such X-ray based technique, known as computed
tomography (CT), a scanner may project fan-shaped or cone-shaped
X-ray beams from an X-ray source at numerous view angle positions
about an object being imaged, such as a patient. The X-ray beams
are attenuated as they traverse the object and are detected by a
set of detector elements which produce signals representing the
intensity or number of incident X-rays reaching the detector. The
signals are processed to produce data representing the line
integrals of the linear attenuation coefficients of the object
along the X-ray paths. These signals are typically called
"projection data" or just "projections". By using reconstruction
techniques, such as filtered backprojection, images may be
generated that represent a cross sectional slice or three
dimensional volume of a region of interest of the patient or imaged
object. In a medical context, pathologies or other structures of
interest may then be located or identified from the reconstructed
images or rendered volume.
[0005] There is a general need for improved X-ray detector designs,
and for improved image quality and/or reduced radiation doses.
BRIEF DESCRIPTION
[0006] A summary of certain embodiments disclosed herein is set
forth below. It should be understood that these aspects are
presented merely to provide the reader with a brief summary of
these certain embodiments and that these aspects are not intended
to limit the scope of this disclosure. Indeed, this disclosure may
encompass a variety of aspects that may not be set forth below.
[0007] In an embodiment, an X-ray detector is provided. The X-ray
detector includes multiple detector sub-modules. Each detector
sub-module includes a semiconductor layer and multiple detector
elements. A first detector element of the multiple detector
elements includes a first electrode disposed on a first doped
implant and a second detector element of the multiple detector
elements includes a second electrode disposed on a second doped
implant. The first and second detector elements are disposed on the
semiconductor layer adjacent to each other with a gap therebetween.
Each detector sub-module also includes wiring traces extending from
one or more detector elements of the multiple detector elements to
readout circuitry. The wiring traces are routed within the gap
between the first and second electrodes. The first doped implant
extends underneath a portion of the wiring traces and is configured
to shield the wiring traces from electrical activity occurring
underneath due to absorption of an X-ray.
[0008] In another embodiment, an X-ray detector is provided. The
X-ray detector includes multiple detector sub-modules. Each
detector sub-module includes a semiconductor layer and multiple
detector elements disposed on the semiconductor layer. Each
detector sub-module also includes wiring traces extending from the
multiple detector elements to readout circuitry. Each detector
element is coupled to a respective wiring trace. The wiring traces
are routed within a gap between adjacent detector elements of the
plurality of detector elements. The X-ray detector also includes
processing circuitry configured to perform coincidence detection to
determine which detector element of the multiple detector elements
is associated with a location of an X-ray hit when the X-ray
coincidently hits one of the detectors elements and one or more of
the wiring traces coupled to respective detector elements of the
multiple detector elements.
[0009] In a further embodiment, a method for reducing electrical
coupling of wiring traces to an underlying semiconductor layer for
an X-ray detector is provided. The method includes subjecting the
X-ray detector to a first exposure of X-rays prior to imaging an
object utilizing the X-ray detector. Each detector sub-module
includes a semiconductor layer and multiple detector elements. A
first detector element of the multiple detector includes a first
electrode and a second detector element of the multiple detector
elements includes a second electrode. The first and second
electrodes being disposed on the semiconductor layer adjacent to
each other with a gap therebetween. Each detector sub-module also
includes wiring traces extending from one or more detector elements
of the multiple detector elements to readout circuitry. The wiring
traces are routed within the gap between the first and second
electrodes. The first exposure of X-rays creates an accumulated
charge near a surface of the semiconductor layer underneath the
wiring traces. The method also includes utilizing the X-ray
detector during a second exposure of X-rays when imaging the object
while electrical coupling between the wiring traces and a portion
of the semiconductor layer underlying the wiring traces is reduced
due to the first exposure of X-rays, wherein the electrical
coupling is reduced due to the accumulated charge repelling charges
of a same polarity induced by the second exposure of X-rays
underneath the wiring traces.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] These and other features, aspects, and advantages of the
present subject matter will become better understood when the
following detailed description is read with reference to the
accompanying drawings in which like characters represent like parts
throughout the drawings, wherein:
[0011] FIG. 1 is a block diagram representation of a CT system, in
accordance with aspects of the present disclosure;
[0012] FIG. 2 is a schematic diagram illustrating an example of
modular X-ray detector sub-modules arranged side-by-side and
stacked one after the other, in accordance with aspects of the
present disclosure;
[0013] FIG. 3 is a cross-sectional view through a portion of an
X-ray detector sub-module, in accordance with aspects of the
present disclosure;
[0014] FIG. 4 is a schematic diagram illustrating a portion of an
X-ray detector sub-module (with a single p-type implant extension
under wiring traces), in accordance with aspects of the present
disclosure;
[0015] FIG. 5 is a schematic diagram illustrating a portion of an
X-ray detector sub-module (with multiple p-type implant extensions
under wiring traces), in accordance with aspects of the present
disclosure;
[0016] FIG. 6 is a schematic diagram illustrating a portion of an X
detector sub-module (with an undulating p-type implant extension
under wiring traces); in accordance with aspects of the present
disclosure;
[0017] FIG. 7 is a cross-sectional view through a portion of an
X-ray detector sub-module (e.g., having a thicker electrical
insulation layer between electrodes), in accordance with aspects of
the present disclosure;
[0018] FIG. 8 is a cross-sectional view through a portion of an
X-ray detector sub-module (e.g., having wiring traces routed over
electrodes in an x-direction), in accordance with aspects of the
present disclosure;
[0019] FIG. 9 is a cross-sectional view through a portion of an
X-ray detector sub-module (e.g., having wiring traces routed over
electrodes in a y-direction), in accordance with aspects of the
present disclosure;
[0020] FIG. 10 is a schematic diagram of a portion of an X-ray
detector sub-module (e.g., having wiring traces routed over
electrodes in the y-direction), in accordance with aspects of the
present disclosure;
[0021] FIG. 11 is a schematic diagram of a portion of an X-ray
detector submodule (e.g., having wiring traces routed over
electrodes), in accordance with aspects of the present
disclosure;
[0022] FIG. 12 is a schematic diagram of a portion of an X-ray
detector submodule (e.g., having a position change for edge
electrodes), in accordance with aspects of the present
disclosure;
[0023] FIG. 13 is a schematic diagram of a portion of an X-ray
detector submodule (e.g., having a size change for edge
electrodes), in accordance with aspects of the present
disclosure;
[0024] FIG. 14 is a schematic diagram of a portion of an X-ray
detector submodule (e.g., having a shape change for edge
electrodes), in accordance with aspects of the present
disclosure;
[0025] FIG. 15 is a cross-sectional view through a portion of an
X-ray detector sub-module (e.g., having a metal shield for wiring
traces), in accordance with aspects of the present disclosure;
[0026] FIG. 16 is a flow diagram of a method for reducing
electrical coupling of wiring traces to an underlying semiconductor
layer for an X-ray detector, in accordance with aspects of the
present disclosure;
[0027] FIG. 17 is a schematic diagram illustrating a portion of an
X-ray detector sub-module (e.g., having trace extensions), in
accordance with aspects of the disclosure; and
[0028] FIG. 18 is a schematic diagram illustrating a portion of an
X-ray detector sub-module (e.g., utilizing coincidence detection),
in accordance with aspects of the disclosure.
DETAILED DESCRIPTION
[0029] One or more specific embodiments will be described below. In
an effort to provide a concise description of these embodiments,
not all features of an actual implementation are described in the
specification. It should be appreciated that in the development of
any such actual implementation, as in any engineering or design
project, numerous implementation-specific decisions must be made to
achieve the developers' specific goals, such as compliance with
system-related and business-related constraints, which may vary
from one implementation to another. Moreover, it should be
appreciated that such a development effort might be complex and
time consuming, but would nevertheless be a routine undertaking of
design, fabrication, and manufacture for those of ordinary skill
having the benefit of this disclosure.
[0030] When introducing elements of various embodiments of the
present subject matter, the articles "a," "an," "the," and "said"
are intended to mean that there are one or more of the elements.
The terms "comprising," "including," and "having" are intended to
be inclusive and mean that there may be additional elements other
than the listed elements. Furthermore, any numerical examples in
the following discussion are intended to be non-limiting, and thus
additional numerical values, ranges, and percentages are within the
scope of the disclosed embodiments.
[0031] While the following discussion is generally provided in the
context of medical imaging, it should be appreciated that the
present techniques are not limited to such medical contexts.
Indeed, the provision of examples and explanations in such a
medical context is only to facilitate explanation by providing
instances of real-world implementations and applications. However,
the present approaches may also be utilized in other contexts, such
as the non-destructive inspection of manufactured parts or goods
(i.e., quality control or quality review applications), and/or the
non-invasive inspection of packages, boxes, luggage, and so forth
(i.e., security or screening applications). In general, the present
approaches may be desirable in any imaging or screening context in
which a photon-counting detector is utilized.
[0032] Energy-resolved, photon-counting detectors can provide
spectral information that is not available with conventional
energy-integrating detectors. One type of energy-discriminating,
photon-counting detection technology employs silicon strips as a
direct-conversion sensor material. Use of silicon as the
direct-conversion material may provide a higher count rate
capability than may be obtained with other direct-conversion
materials, such as CZT or CdTe. In certain embodiments, the
detector may be arranged edge-on to increase absorption efficiency
by enabling an absorption depth to be chosen to any length and the
detector can still be fully depleted without going to very high
voltages. However, the arrangement of detector elements on detector
sub-modules or sensors (in particular those detector elements along
an edge of the detector sub-module or sensor) may result in wiring
traces being routed along paths distant from the detector element
(e.g., pixel). X-rays absorbed in the detector sub-module or sensor
beneath the routing may induce signals on the traces (hereafter
referred to as trace triggering) resulting in a non-local crosstalk
effects (i.e., signals attributed to the wrong detector
element).
[0033] The present approaches address these effects by mitigating
trace triggering of channels (e.g., readout channels) and, thus,
mitigating or eliminating crosstalk effects. These techniques
improve the performance of silicon-based photon-counting detectors,
such as computed tomography detectors or other suitable types of
radiographic X-ray detectors.
[0034] With the preceding discussion in mind, FIG. 1 illustrates an
embodiment of an imaging system 10 for acquiring and processing
image data in accordance with aspects of the trace triggering
mitigating approaches discussed herein. Although the following
embodiments are discussed in terms of the computed tomography (CT)
imaging system, the embodiments may also be utilized with other
imaging systems (e.g., X-ray, PET, CT/PET, SPECT, nuclear CT,
etc.). In the illustrated embodiment, system 10 is a computed
tomography (CT) system designed to acquire X-ray projection data,
to reconstruct the projection data into a tomographic image, and to
process the image data for display and analysis. The CT imaging
system 10 includes one or more X-ray sources 12, such as one or
more X-ray tubes or solid-state emission structures which allow
X-ray generation at one or more locations and/or one or more energy
spectra during an imaging session.
[0035] In certain implementations, the source 12 may be positioned
proximate to a collimator 22 used to define the size and shape of
the one or more X-ray beams 20 that pass into a region in which a
subject 24 (e.g., a patient) or object of interest is positioned.
The subject 24 attenuates at least a portion of the X-rays.
Resulting attenuated X-rays 26 impact a detector array 28 formed by
a plurality of detector elements (e.g., pixels). As discussed
herein, the detector 28 may be a photon-counting detector,
including an energy-discriminating photon-counting detector, whose
outputs convey information about the number and energy of photons
that impact the detector at measured positions and over a time
interval corresponding to a scan or imaging session. In certain
such embodiments, the energy-discriminating, photon-counting
detector may be a direct-conversion type detector (i.e., not
employing a scintillator intermediary), such as a detector based on
silicon strips. In certain embodiments, the detector array 28 may
be formed by a plurality of detector sub-modules or sensors (each
having a plurality of detector elements). In certain embodiments,
the detector array 28 and the detector sub-modules may be an
edge-on detector and edge-on detector sub-modules configured for
edge illumination from the X-rays (i.e., the X-rays enter through
the edge of the detector sub-modules). In particular, the detector
array 28 may be structured similar to the detectors disclosed in
U.S. Publication No. 2019/0383955 filed Feb. 19, 2019 and titled
"X-ray Detector System Design", which is incorporated herein in its
entirety for all purposes.
[0036] Each detector element produces an electrical signal that
represents the intensity of the incident X-ray photons (e.g., the
energy and number of incident photons) at the position of the
detector element when the beam strikes the detector 28. Electrical
signals are acquired and processed to generate one or more scan
datasets.
[0037] A system controller 30 commands operation of the imaging
system 10 to execute examination and/or calibration protocols and
to process the acquired data. With respect to the X-ray source 12,
the system controller 30 furnishes power, focal spot location,
control signals and so forth, for the X-ray examination sequences.
The detector 28 is coupled to the system controller 30, which
commands acquisition of the signals generated by the detector 28.
In addition, the system controller 30, via a motor controller 36,
may control operation of a linear positioning subsystem 32 and/or a
rotational subsystem 34 used to move components of the imaging
system 10 and/or the subject 24. The system controller 30 may
include signal processing circuitry and associated memory
circuitry. In such embodiments, the memory circuitry may store
programs, routines, and/or encoded algorithms executed by the
system controller 30 to operate the imaging system 10, including
the X-ray source 12, and to process the data acquired by the
detector 28 in accordance with the steps and processes discussed
herein. In one embodiment, the system controller 30 may be
implemented as all or part of a processor-based system such as a
general purpose or application-specific computer system.
[0038] The source 12 may be controlled by an X-ray controller 38
contained within the system controller 30. The X-ray controller 38
may be configured to provide power and timing signals to the source
12. In addition, in some embodiments the X-ray controller 38 may be
configured to selectively activate the source 12 such that tubes or
emitters at different locations within the system 10 may be
operated in synchrony with one another or independent of one
another.
[0039] The system controller 30 may include a data acquisition
system (DAS) 40. The DAS 40 receives data collected by readout
electronics of the detector 28, such as sampled analog signals from
the detector 28. The DAS 40 may then convert the data to digital
signals for subsequent processing by a processor-based system, such
as a computer 42. In other embodiments, the detector 28 may convert
the sampled analog signals to digital signals prior to transmission
to the data acquisition system 40. The computer may include
processing circuitry 44 (e.g., image processing circuitry). The
computer 42 may include or communicate with one or more
non-transitory memory devices 46 that can store data processed by
the computer 42, data to be processed by the computer 42, or
instructions to be executed by a processor (e.g., processing
circuitry 44) of the computer 42. For example, the processing
circuitry 44 of the computer 42 may execute one or more sets of
instructions stored on the memory 46, which may be a memory of the
computer 42, a memory of the processor, firmware, or a similar
instantiation.
[0040] The computer 42 may also be adapted to control features
enabled by the system controller 30 (i.e., scanning operations and
data acquisition), such as in response to commands and scanning
parameters provided by an operator via an operator workstation 48.
The system 10 may also include a display 50 coupled to the operator
workstation 48 that allows the operator to view relevant system
data, imaging parameters, raw imaging data, reconstructed data, and
so forth. Additionally, the system 10 may include a printer 52
coupled to the operator workstation 48 and configured to print any
desired measurement results. The display 50 and the printer 52 may
also be connected to the computer 42 directly or via the operator
workstation 48. Further, the operator workstation 48 may include or
be coupled to a picture archiving and communications system (PACS)
54. PACS 54 may be coupled to a remote system 56, radiology
department information system (RIS), hospital information system
(HIS) or to an internal or external network, so that others at
different locations can gain access to the image data.
[0041] FIG. 2 is a schematic diagram illustrating an example of a
modular X-ray detector sub-module 58 (e.g., detector sensors)
arranged side-by-side and stacked one after the other. The detector
sub-modules 58 may be edge-on detector sub-modules. As depicted,
X-rays enter through an edge 59 of the detector sub-module 58. A
guard ring may extend along the edges 59 of the detector sub-module
58 to protect the detector sub-module 58 from electrical breakdown
and isolate the detector area from excessive leakage current. In
certain embodiments, the detector sub-modules 58 may be planar
modules. The X-ray detector sub-modules 58 may be stacked one after
the other to form larger detector modules that may be assembled
together side-by side to build up an overall X-ray detector. The
detector sub-modules 58 may generally be arranged side-by-side,
e.g., in a slightly curved overall configuration, in a direction
substantially perpendicular to the z-direction. In certain
embodiments, the detector sub-modules 58 may be stacked one after
the other in the z-direction.
[0042] As depicted, each detector sub-module 58 includes a
plurality of detector elements 60 (e.g., pixels). The detector
elements 60 may be elongated electrodes (e.g., metal electrodes)
with the length extension directed towards a focal point of an
X-ray system. Depending on the detector topology, the detector
element 60 may correspond to a pixel. In certain embodiments, the
detector sub-module 58 may be a depth-segmented detector sub-module
having a number of detector strips 62 with each strip 62 having a
number of depth segments 65. As depicted, each strip 62 has a first
segment 64, a second segment 66, and a third segment 68 associated
with a different depth (relative to the focal point) along a
detection line. As depicted, at least portions of each segment 64,
66, 68 are co-linearly arranged. The number of segments 65 may vary
(e.g., 1 to 3 or more). For such a depth-segmented detector
sub-module 58, each depth segment 65 may be regarded as an
individual detector element (if each depth segment is associated
with its own individual charge collecting electrode). In certain
embodiments, circuitry may treat the depth segments 65 of a single
strip 62 logically as a single detector element.
[0043] The shape of the detector sub-module 58 may vary. In certain
embodiments, the detector sub-module 58 may have a parallelogram
shape, a trapezoidal shape, a triangular shape, or another shape.
In certain embodiments, one or more edges 59 of the detector
sub-module 58 may be slanted. The shapes of the detector elements
60 may vary. In certain embodiments, the detector elements 60
arranged along a slanted side edge 69 of the detector sub-module 58
may include tapered edge segments (e.g., trapezoidal or triangular
segments and/or truncated trapezoidal or triangular segments with
rounded corners). In certain embodiments, a segment 65 of a strip
62 that is closest to a slanted side edge of a detector sub-module
58 may be orientated so that it extends into an area of an adjacent
strip 62. In certain embodiments, the segments 65 may also be
slanted.
[0044] FIG. 3 is a cross-sectional view through a portion of the
X-ray detector sub-module 70. The X-ray detector sub-module 70
includes a semiconductor layer 72. The semiconductor layer 72 is
made of silicon. In certain embodiments, the semiconductor layer 72
may be made of gallium arsenide, cadmium zinc telluride, or another
semiconductor material. Detector elements or segments 74, 76 (e.g.,
metal electrodes) are disposed on the semiconductor layer 72. The
electrodes may be made of aluminum. In particular, the electrodes
74, 76 are disposed on doped implants 78, 80 (e.g., p-type or
n-type silicon implants depending on whether the silicon of the
semiconductor layer is n-type or p-type) that are disposed on the
semiconductor layer 72. The detector elements 74, 76 may be
respective segments for different strips of segments disposed
adjacent to each other. The detector elements 74, 76 and the doped
implants 78, 80 are disposed on the semiconductor layer 72 spaced
apart so that a gap 82 is formed between them. The X-ray detector
sub-module 70 includes an electrical insulator layer 84 extending
between--the adjacent electrodes 74, 76. The electrical insulator
layer 84 may be silicon dioxide, silicon nitride, polyimide,
spin-on glass, or another insulating material. One or more wiring
traces 86 (e.g., metal traces) are routed within the gap 84 between
the electrodes 74, 76. As depicted, the wiring traces 86 are
disposed on the electrical insulator layer 84. As depicted, the
wiring traces 86 are disposed in an evenly spaced manner across the
gap 84. In certain embodiments, the wiring traces 86 may be routed
as close as possible to the edges of the electrodes 74, 76. The
wiring traces 86 may be coupled to the electrodes 74, 76 or
different electrodes. The wiring traces 86 are routed along the gap
82 (and possibly other gaps) to readout circuitry. As depicted, a
passivation layer 88 is disposed over these components of the X-ray
detector sub-module 70. The passivation layer 88 may be made of
silicon oxide, silicon nitride or another insulator.
[0045] As depicted, the doped implant 78 includes a main or base
portion 90 and an extension 92 that extends beyond a normal
perimeter 94 (indicated by a dashed line). The extension 92 extends
underneath both the wiring traces 86 and the electrical insulation
layer 84 in a direction from the doped implant 78 to the doped
implant 80. In certain embodiments, the normal perimeter 94 also
represents the outer perimeter of the doped implant 78 at a
different location of the doped implant 78. The extension 92 of the
doped implant 78 acts as a shield for the wiring traces 86 against
charges or electrical activity (e.g., due to the absorption of
X-rays) in the bulk silicon volume (the semiconductor layer 72).
The extension 92 of the doped implant 78 reduces or minimizes the
coupling (e.g., electrical coupling) between the semiconductor
layer 72 and the wiring traces 86. The extension 92 of the doped
implant 78 underneath the wiring traces 86 is depicted in FIG. 4 as
well. Only a portion of the wiring traces 86 are shown in FIG. 4.
The doped implant 78 may extend underneath the wiring traces 86
along the entire longitudinal length of the implant 78 or only
along a portion of the longitudinal length of the doped implant
78.
[0046] In certain embodiments, as depicted in FIG. 5, both doped
implants 78, 80 may include extensions 92 that extend within the
gap 82 underneath the wiring traces 86. As depicted in FIG. 5, the
wiring traces 86 are disposed as close as possible to the edges of
the main portion 90 of the doped implants 78, 80 and, thus, the
electrodes (as opposed to being evenly spaced across the gap 82).
Only a portion of the wiring traces 86 are shown in FIG. 5.
[0047] In certain embodiments, as depicted in FIG. 6, the extension
92 of the doped implant 78 extending underneath the wiring traces
86 has an undulating shape. In particular, the extension includes
multiple spaced apart protrusions 96 extending across the gap 82
from the doped implant 78 towards the doped implant 80. The
undulating shape of the extension 92 minimizes the capacitance
added to the wiring traces 86 due to the extension 92 being
underneath the wiring traces 86. Only a portion of the wiring
traces 86 are shown in FIG. 5.
[0048] Alternative techniques may be utilized to reduce coupling
(e.g., electrical coupling) between the wiring traces and the
underlying semiconductor layer (e.g., bulk silicon). FIG. 7 is a
cross-sectional view through a portion of the X-ray detector
sub-module 98. The X-ray detector sub-module 98 is similar to the
X-ray detector sub-module 70 in FIG. 3 except the doped implant 78
does not extend underneath the wiring traces 86. Instead, the
electrical insulation layer 84 is thicker. The electrical
insulation layer 84 (e.g., as shown in FIG. 3) is typically
approximately 200 nanometers (nm) thick. A thickness 100 of the
electrical insulation layer 84 in FIG. 7 may be approximately 2 to
3 times thicker than the electrical insulation layer 84 in FIG. 3.
Thus, the thickness 100 of the electrical insulation layer 84 in
FIG. 7 may range between approximately 400 to 600 nm. The
electrical insulation 84 in FIG. 7 may include a single layer or
multiple layers as indicated by dashed line 102. The increased
thickness of the electrical insulation layer 84 reduces or
minimizes the coupling (e.g., electrical coupling) between the
semiconductor layer 72 and the wiring traces 86.
[0049] A further technique to reduce coupling between the wiring
traces and the underling semiconductor layer may include altering
the material utilized for the electrical insulation layer located
within the gaps between the pixels. In particular, a material for
the electrical insulation layer may be chosen that minimizes
electrical coupling even more than silicon dioxide. For example,
polyimide may be utilized as the material for the electrical
insulation layer.
[0050] As noted above, the arrangement of detector elements on
detector sub-modules or sensors (in particular those detector
elements along an edge of the detector sub-module or sensor) may
result in wiring traces being routed along paths not adjacent to
the detector element (e.g., pixel). X-rays absorbed in the detector
sub-module or sensor beneath the routing may induce signals on the
traces resulting in non-local crosstalk effects (i.e., signals
attributed to the wrong detector element). In certain embodiments,
to facilitate rerouting of the wiring traces additional layers may
be utilized. FIG. 8 is a cross-sectional view through a portion of
the X-ray detector sub-module 104. In this embodiment, the
electrodes 74, 76 are adjacent to each other (in the x-direction)
but part of different strips (e.g., segmented strips) that run from
toward a top portion to a bottom portion of the X-ray detector
sub-module 104 (in other words, the electrodes 74, 76 are
horizontally adjacent or aligned). The X-ray detector sub-module
104 is similar to the X-ray detector sub-module 70 in FIG. 3 except
the doped implant 78 does not extend into the gap 84. Instead, the
wiring traces 86 are routed over the electrodes 74, 76. An
electrical insulation layer 88 (e.g., made of silicon nitride or
another material) is disposed over the detector electrodes 74, 76
and the wiring traces 86 are disposed over the insulation layer 88.
Rerouting of the wire traces 86 minimizes these non-local
cross-talk effects.
[0051] FIG. 9 is a cross-sectional view through a portion of the
X-ray detector sub-module 156. In this embodiment, the electrodes
74, 76 are adjacent to each other (in the y-direction) as part of
the same strip (e.g., segmented strip) running from a top portion
to a bottom portion of the X-ray detector sub-module 156 (in other
words, the electrodes 74, 76 are vertically adjacent or aligned).
The X-ray detector sub-module 156 is similar to the X-ray detector
sub-module 104 in FIG. 8. The wiring trace 86 is coupled (e.g.,
electrically coupled) to the electrode 78 thru via 158 through the
insulation layer 88. The wiring trace 86 extends over the adjacent
electrode 80 (in the y-direction) between the insulation layers 88,
106. Along its path over the various electrodes, the wiring trace
86 may be coupled to a bond pad 160 (e.g., metal bond pad) thru
vias 162 through both of the insulation layers 88, 106. FIG. 10
provides a view of wiring traces 86 routed over vertically adjacent
detector elements or segments 164 (e.g., electrodes) of a strip 166
for a portion of the detector sub-module 168.
[0052] FIG. 11 is a schematic diagram of a portion of an X-ray
detector submodule 108 (e.g., having wiring traces 86 routed over
electrodes). As depicted, the detector sub-module 108 has a slanted
edge or side 110 that forms an obtuse angle relative to another
edge or side 112 of the detector sub-module 108. In certain
embodiments, the detector sub-module has a slanted edge or side 110
that forms an acute angle relative to another edge or side 112. The
detector sub-module 108 includes a first strip of segments or
electrodes (e.g., detector elements) 114 and a second strip of
segments or electrodes 116. The first strip of segments 114
includes electrodes 118, 120 forming a first detection line
(indicated by dashed lines 122) and the second strip of segments
includes electrodes 124, 126 forming a second detection line
(indicated by dashed lines 128). The electrodes 118, 120 are
slanted. The electrodes 120, 126 are located adjacent to a guard
ring 130 along the edge 110 of the detector sub-module 108. To
avoid having to route the wiring traces 86 between the gaps of the
detector elements, the wiring traces 86 are routed more directly
over the electrodes 118, 120, 124, 126 (as depicted in FIGS. 8-10)
toward and along the edges 110, 112 of the detector sub-module 108
(away from a top portion 131 of the detector sub-module 108).
Routing the wiring traces 86 over the detector elements adjacent
the slanted edge 110 maintains their detection efficiency since the
shape or size of the detector elements are not altered.
[0053] In certain embodiments, the wiring traces may be routed
along the edges of the detector sub-module within a gap between the
detector elements disposed along the edge and the guard ring. As
depicted in FIG. 12, for the detector sub-module 132, one or more
electrodes 120 disposed along the slanted edge 110 may have a
position 134 further away from the edge 110 (compared to position
136 indicated by the dashed outline) to form a gap 138 between the
electrodes 120 and the guard ring 130 for the wiring traces 86 to
be routed along. In certain embodiments, as depicted in FIG. 13,
for the detector sub-module 140, the size of the electrode 120 may
be altered from a first size 142 (indicated by the dashed outline)
to a second size 144 to create the gap 138 for the wiring traces 86
to be routed along. In other embodiments, as depicted in FIG. 14,
for the detector sub-module 146, the shape of the electrode 120 may
be altered from a first shape 148 (indicated by the dashed outline)
to a second shape 150 to create the gap 138 for the wiring traces
86 to be routed along.
[0054] FIG. 15 provide an alternative way to shield the wiring
traces. FIG. 15 is a cross-sectional view through a portion of the
X-ray detector sub-module 152. The X-ray detector sub-module 152 is
similar to the X-ray detector sub-module 70 in FIG. 3 except the
doped implant 78 does not extend into the gap 84. Instead, a metal
shielding layer 154 (e.g., made of aluminum or another metal) may
be disposed between insulating layer 84 and insulating layer 88 in
the gap 82 between detector elements 78 and 80. The wiring traces
86 may then be routed over the metal shielding layer 154 (with the
insulation layer 88 underneath) within the gap 82. The insulation
layers 88, 106 and the metal shielding layer 154 provide a
dedicated layer for the routing of the wiring traces 86.
[0055] As noted above, electrical coupling between the wiring
traces and the underlying semiconductor layer (bulk silicon) may be
reduced via restructuring of the detector sub-module. Other
techniques may be utilized to reduce the electrical coupling
between the wiring traces and the semiconductor layer. FIG. 16 is a
flow diagram of a method 170 for reducing electrical coupling of
wiring traces to an underlying semiconductor layer for an X-ray
detector (e.g., edge-on detector as described above). The method
170 includes subjecting the X-ray detector to a first exposure of
X-rays prior to imaging an object or subject utilizing the X-ray
detector (block 172). In other words, the subject or object is not
being exposed to X-rays during the first exposure. This first
exposure reduces or minimizes the electrical coupling between the
wiring traces and the semiconductor layer (e.g., bulk silicon)
underneath the wiring traces by producing an accumulation of slowly
moving charge (e.g. positive charge) near the semiconductor layer
(e.g., silicon) surface, under the traces. X-ray-induced charges of
the same polarity (e.g. positive charge) are then slightly repelled
by the accumulated positive charge, and steered away from the
traces, reducing the coupling of the charges to the traces. The
method 170 also includes utilizing the X-ray detector during a
second exposure of X-rays when imaging the object or subject while
electrical coupling between the wiring traces and a portion of the
semiconductor layer underlying the wiring traces remains reduced
due to the first exposure of X-rays (block 174). The second
exposure occurs within a time period when the electrical coupling
is still reduced or minimized due to the first exposure.
[0056] To ensure the counting of X-rays, trace extensions may be
added to certain spaces on the detector sub-module. FIG. 17 is a
schematic diagram illustrating a portion of an X-ray detector
sub-module 176 (e.g., having trace extensions). As noted above,
each depth segment may be regarded as an individual detector
element (if each depth segment is associated with its own
individual charge collecting electrode). In certain embodiments,
circuitry may treat the depth segments of a single strip logically
as a single detector element. As depicted, the detector sub-module
176 (e.g., edge-on detector sub-module) includes a depth-segmented
detector sub-module having a number of detector strips 178 (e.g.,
detector strips 180, 182, 184) with each strip 178 having a number
of depth segments 186. As depicted, each strip 178 has a first
segment 188, a second segment 190, and a third segment 192
associated with a different depth (relative to the focal point)
along a detection line. As depicted, at least portions of each
segment 188, 190, 192 are co-linearly arranged. The number of
segments 186 may vary (e.g., 1 to 3 or more). Each segment 186 has
a respective wiring trace 194 that is routed toward readout
circuitry (e.g., and associated with a readout channel). As
depicted, the wiring trace 194 extends from a bottom portion 195 of
the segment 186. To ensure X-rays that hit within the spaces or
gaps 196 between the segments 188 (e.g., top segments) are counted
(i.e., to increase sensitivity within these gaps 196), a respective
trace extension 198 (e.g., metal trace extension) is coupled to the
respective wiring trace 194 coupled to each segment 188. The trace
extension 198 extends within the gap 196 in a direction from the
bottom portion 195 of the segment 186 toward a top portion 200 of
the segment 186.
[0057] FIG. 18 is a schematic diagram illustrating a portion of an
X-ray detector sub-module 202 utilizing coincidence detection to
ensure the accurate counting of X-rays and determination of X-ray
hit location. As depicted, the detector sub-module 202 (e.g.,
edge-on detector sub-module) includes a depth-segmented detector
sub-module having a number of detector strips 204 (e.g., detector
strips 206, 208) with each strip 204 having a number of depth
segments 210. As noted above, each depth segment may be regarded as
an individual detector element (if each depth segment is associated
with its own individual charge collecting electrode). In certain
embodiments, circuitry may treat the depth segments of a single
strip logically as a single detector element. As depicted, each
strip 204 has a first segment 212, a second segment 214, and a
third segment 216 associated with a different depth (relative to
the focal point) along a detection line. As depicted, at least
portions of each segment 212, 214, 216 are co-linearly arranged.
The number of segments 210 may vary (e.g., 1 to 3 or more). Each
segment 210 has a respective wiring trace 218 that is routed toward
readout circuitry (and associated with a readout channel).
[0058] Processing circuitry as part of the X-ray detector or the
X-ray system utilizes coincidence detection to determine which
segment 210 (or segments) within the same strip 204 is triggered by
an X-ray hit. As depicted in FIG. 18, a cloud of electrons
(depicted by an X within a circle) caused by an X-ray hit 220
represents the X-ray hit 220. Two separate X-ray hits 220 are shown
(X-ray hits 222, 224). Assuming trace triggers (by X-ray hits 220)
are coincident with charge sharing triggers on the associated pixel
(i.e., the X-ray hit 220 hits and triggers both the segment 210 and
its respective wiring trace 218 at the same time), coincident
detection may be utilized by the processing circuitry to determine
where the X-ray hits occurred and what pixels they should be
associated with. In addition, the processing circuitry can
determine a depth of the X-ray hit 220 along the strip 204 of
segments 210. Further, the processing circuitry can associate a
single segment 210 with the X-ray hit 220 to avoid double counting
(i.e., incorrectly contributing the X-ray hit 220 to a segment 210
due to its respective wiring trace 218 being hit at a location
remote form the segment 210). In particular, coincidence detection
by the processing circuitry is the logical deduction that the
particular combination of coincidently hit channels is consistent
with the hit having occurred adjacent to a specific electrode
(e.g., segment or detector element).
[0059] For example, if the X-ray hit 222 triggered both segment 212
and 214 simultaneously (e.g., due to triggering the wiring trace
218 for the segment 212 at a location remote from the segment 212),
the processing circuitry determines that the event (X-ray hit 222)
belongs to the segment 214. If the X-ray hit 224 triggered segments
212, 214, 216 (with segments 212 and 214 triggered due to the
triggering of the respective wiring traces 218 for the segments
212, 214 at a location remote from both segments 212, 214), the
processing circuitry determines that the event (X-ray hit 224)
belongs to the segment 216. In other words, the processing
circuitry is configured during coincidence detection (when assuming
trace triggers (by X-ray hits 220) are coincident with charge
sharing triggers on the associated pixel) to assign the X-ray hit
220 to the segment 210 that is adjacent to the most triggered
traces of those segments 210 within the strip 204 triggered by the
X-ray hit 220. In certain embodiments, the processing circuitry is
configured to estimate an energy (i.e., total amplitude of a peak)
of the X-ray hit 220 based on a linear combination (e.g., sum) of
pulse heights for each readout channel associated with segments 210
and wiring traces 218 triggered by the X-ray hit 220. For example,
estimating the energy for the X-ray hit 222 may be a linear
combination of the pulse heights for the readout channels
associated with both segment 214 and the wiring trace 218 for the
segment 210. It should be noted that the X-ray hit 220 may hit
multiple segments 210 at the same time.
[0060] It should be noted that one or more embodiments for
mitigating trace triggering in channels disclosed above may be
combined.
[0061] Technical effects of the disclosed subject matter include
providing systems and methods for mitigating trace triggering of
channels (e.g., readout channels) and, thus, mitigating or
eliminating crosstalk effects. In certain embodiments, electrical
coupling between wiring traces and the underlying semiconductor
volume (e.g., bulk silicon) may be reduced. In certain embodiments,
the wiring traces may be rerouted. In further embodiments,
dedicated layers may be provided for rerouting the wiring traces.
In even further embodiments, coincidence detection may be utilized
to correctly attribute an X-ray hit to the proper pixel. Overall,
these embodiments may reduce false triggering events. These
techniques improve the performance of silicon-based photon-counting
detectors, such as computed tomography detectors or other suitable
types of radiographic X-ray detectors.
[0062] The techniques presented and claimed herein are referenced
and applied to material objects and concrete examples of a
practical nature that demonstrably improve the present technical
field and, as such, are not abstract, intangible or purely
theoretical. Further, if any claims appended to the end of this
specification contain one or more elements designated as "means for
[perform]ing [a function] . . . " or "step for [perform]ing [a
function] . . . ", it is intended that such elements are to be
interpreted under 35 U.S.C. 112(f). However, for any claims
containing elements designated in any other manner, it is intended
that such elements are not to be interpreted under 35 U.S.C.
112(f).
[0063] This written description uses examples to disclose the
present subject matter, including the best mode, and also to enable
any person skilled in the art to practice the subject matter,
including making and using any devices or systems and performing
any incorporated methods. The patentable scope of the subject
matter is defined by the claims, and may include other examples
that occur to those skilled in the art. Such other examples are
intended to be within the scope of the claims if they have
structural elements that do not differ from the literal language of
the claims, or if they include equivalent structural elements with
insubstantial differences from the literal languages of the
claims.
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