TWI864870B - Imaging system and imaging method using imaging system - Google Patents

Abstract

Disclosed herein is a system with an image sensor including: M metal layers (i) and M radiation detectors (i), i=1, …, M. M is an integer greater than 1. The radiation detector (i) includes a radiation absorption layer (i) and IC chips (i, j), j=1, …, Ni. Ni, i=1, …, M are positive integers. The metal layers and the radiation absorption layers together form a stack of layers. There is a best-fit plane of all sensing elements of a radiation detector of the radiation detectors. Each IC chip of the IC chips (i, j), j=1, …, Ni at least partially overlaps the radiation absorption layer (i) in a direction perpendicular to the best-fit plane. There exists a first plane perpendicular to the best-fit plane that intersects all the integrated circuit chips, and does not intersect any radiation absorption layer of the radiation absorption layers.

Description

Imaging system and imaging method using the same

The present invention relates to an imaging system and an imaging method using the imaging system.

A radiation detector is a device that measures a property of radiation. Examples of the property may include the spatial distribution of intensity, phase, and polarization of the radiation. The radiation measured by the radiation detector may be radiation that has passed through an object. The radiation measured by the radiation detector may be electromagnetic radiation, such as infrared light, visible light, ultraviolet light, X-rays, or gamma rays. The radiation may be of other types, such as alpha rays and beta rays. An imaging system may include one or more image sensors, each of which may have one or more radiation detectors.

A system is disclosed herein, the system comprising an image sensor, the image sensor comprising: M metal layers (metal layer (i), i=1, ..., M) and M radiation detectors (radiation detector (i), i=1, ..., M), wherein M is an integer greater than 1. For each i value, the radiation detector (i) comprises a radiation absorption layer (i), and an integrated circuit chip (i, j), j=1, ..., Ni, configured to process an electrical signal generated in the radiation absorption layer (i). Ni, i=1, ..., M is a positive integer. The M metal layers and the radiation absorption layer (i), i=1, ..., M together form a layer stack. There is an optimal fitting plane for all sensing elements of one radiation detector among the M radiation detectors. For each value of i, each integrated circuit chip in the integrated circuit chip (i, j), j=1, ..., Ni at least partially overlaps with the radiation absorption layer (i) in a direction perpendicular to the optimal fitting plane. There is a first plane, which is perpendicular to the optimal fitting plane, intersects with all the integrated circuit chips (i, j), i=1, ..., M, j=1, ..., Ni, and does not intersect with any radiation absorption layer in the radiation absorption layer (i), i=1, ..., M.

In one aspect, the stack comprises 2×M layers.

In one aspect, the M metal layers comprise a metal having an atomic number of at least 26.

In one aspect, the metal is tungsten, platinum or gold.

In one aspect, the M metal layers and the radiation absorbing layers (i), i=1, ..., M are arranged in the stack in an alternating manner.

In one aspect, there is a second plane, which is perpendicular to the best fitting plane, intersects all of the M metal layers, and does not intersect any radiation absorbing layer in the radiation absorbing layer (i), i=1, ..., M.

In one aspect, the first plane is parallel to the second plane, and each point of the radiation absorbing layer (i), i=1, ..., M is located between the first plane and the second plane.

In one aspect, each of the M metal layers has a thickness in the range of 50 microns to 100 microns measured in a direction perpendicular to the best fitting plane.

In one aspect, each of the integrated circuit chips (i, j), i=1, ..., M, j=1, ..., Ni includes an application specific integrated circuit (ASIC).

In one aspect, the M metal layers are configured to block and absorb X-rays.

In one aspect, an I/O (input/output) device electrically connects an external circuit to an electrode on the integrated circuit chip (i, j), i=1, ..., M, j=1, ..., Ni, and the first plane is between (A) the electrode and (B) the radiation absorbing layer (i), i=1, ..., M.

In one aspect, for each value of i, the radiation absorbing layer (i) comprises a plurality of discrete radiation absorbing regions.

On the one hand, Ni,i=1,......,M are all 1.

In one aspect, the radiation absorbing layer (i), i=1, ..., M comprises GaAs, CdTe or CdZnTe.

In one aspect, each of the integrated circuit chips (i, j), i=1, ..., M, j=1, ..., Ni has a thickness in the range of 10 microns to 100 microns measured in a direction perpendicular to the best fitting plane.

In one aspect, for each value of i and each value of j, a portion of the integrated circuit chip (i, j) is sandwiched between the metal layer (i) and the radiation absorbing layer (i).

In one aspect, for each value of i, the metal layer (i) includes Pi gaps, Pi is a positive integer not greater than Ni, and for each value of i, the integrated circuit chip (i, j), j=1, ..., Ni is within the Pi gaps, so that there is a straight line on the best fitting plane, so that any point of the integrated circuit chip (i, j), j=1, ..., Ni traveling in any direction parallel to the straight line will hit the metal layer (i).

On the one hand, for every value of i, Ni>Pi.

In one aspect, for each value of i, Ni=Pi, and for each value of i, the integrated circuit chip (i,j), j=1, ..., Ni is respectively in the Pi gaps.

In one aspect, for each value of i, the thickness of each of the integrated circuit chips (i, j), j=1, ..., Ni of the radiation detector (i) measured in a direction perpendicular to the best fitting plane is less than the thickness of the metal layer (i) measured in a direction perpendicular to the best fitting plane.

In one aspect, for each value of i, each integrated circuit chip (i,j), j=1, ..., Ni of the radiation detector (i) is not in direct physical contact with the radiation absorbing layer of any other radiation detector in the M radiation detectors.

On the one hand, each straight line segment having two end points on two adjacent radiation absorbing layers in the radiation absorbing layer (i), i=1, ..., M intersects with at least one gap of (A) at least one metal layer in the M metal layers or (B) one metal layer in the M metal layers.

On the one hand, each straight line segment on two adjacent radiation absorbing layers in the radiation absorbing layer (i), i=1, ..., M, respectively, intersects with a metal layer in the M metal layers.

In one aspect, the system further includes a radiation source. A straight line parallel to the best fitting plane intersects both the radiation source and the image sensor, and the first plane is not between the radiation source and the radiation absorbing layer (i), i=1, ..., M.

This article also discloses a method of using the above system. The method includes transmitting radiation from the radiation source to an object located between the radiation source and the image sensor; and based on the interaction between the radiation and the object, capturing an image of the object with the image sensor.

Radiation detector

FIG1 schematically shows a radiation detector 100 as an example. The radiation detector 100 may include an array of pixels 150 (also referred to as sensing elements 150). The array may be a rectangular array (as shown in FIG1 ), a honeycomb array, a hexagonal array, or any other suitable array. The array of pixels 150 in the example of FIG1 has 4 columns and 7 rows; however, in general, the array of pixels 150 may have any number of rows and any number of columns.

Each pixel 150 may be configured to detect radiation incident thereon from a radiation source (not shown), and may be configured to measure characteristics of the radiation (e.g., energy, wavelength, and frequency of the particles). The radiation may include radiation particles such as photons (X-rays, gamma rays, etc.) and subatomic particles (alpha particles, beta particles, etc.). Each pixel 150 may be configured to count the number of radiation particles whose energy falls into multiple energy intervals incident thereon over a period of time. All pixels 150 may be configured to count the number of radiation particles incident thereon in multiple energy intervals over the same period of time. When the incident radiation particles have similar energies, the pixel 150 may be configured to count only the number of radiation particles incident thereon over a period of time without measuring the energy of a single radiation particle.

Each pixel 150 may have its own analog-to-digital converter (ADC) configured to digitize an analog signal representing the energy of an incident radiation particle into a digital signal, or to digitize an analog signal representing the total energy of multiple incident radiation particles into a digital signal. The pixels 150 may be configured to operate in parallel. For example, while one pixel 150 is measuring an incident radiation particle, another pixel 150 may be waiting for the arrival of a radiation particle. The pixels 150 may not necessarily be individually addressable.

The radiation detector 100 described herein may have applications such as X-ray telescopes, X-ray mammography, industrial X-ray defect detection, X-ray microscopes or microradiography, X-ray casting inspection, X-ray nondestructive inspection, X-ray weld inspection, X-ray digital subtraction angiography, etc. It may be appropriate to use the radiation detector 100 in place of a photographic plate, photographic film, PSP plate, X-ray image intensifier, scintillator, or other semiconductor X-ray detector.

FIG. 2 schematically illustrates a simplified cross-sectional view of the radiation detector 100 of FIG. 1 along line 2-2 according to an embodiment. Specifically, the radiation detector 100 may include a radiation absorbing layer 110 and an electronic device layer 120 (which may include one or more ASICs or application-specific integrated circuits) for processing and analyzing electrical signals generated in the radiation absorbing layer 110 by incident radiation. The radiation detector 100 may or may not include a scintillator (not shown). The radiation absorbing layer 110 may include a semiconductor material such as silicon, germanium, GaAs, CdTe, CdZnTe, or a combination thereof. The semiconductor material may have a high quality attenuation coefficient for the radiation of interest.

As an example, Fig. 3 schematically shows a detailed cross-sectional view of the radiation detector 100 of Fig. 1 along line 2-2. Specifically, the radiation absorbing layer 110 may include one or more diodes (e.g., p-i-n or p-n) formed by one or more discrete regions 114 of the first doped region 111, the second doped region 113. The second doped region 113 may be separated from the first doped region 111 by an optional intrinsic region 112. The discrete regions 114 may be separated from each other by the first doped region 111 or the intrinsic region 112. The first doped region 111 and the second doped region 113 may have opposite types of doping (e.g., region 111 is p-type and region 113 is n-type, or region 111 is n-type and region 113 is p-type). In the example of FIG3 , each discrete region 114 of the second doped region 113 forms a diode having the first doped region 111 and an optional intrinsic region 112. That is, in the example of FIG3 , the radiation absorbing layer 110 has a plurality of diodes (more specifically, 7 diodes correspond to 7 pixels 150 in one column of the array of FIG1 , and for simplicity, only 2 pixels 150 are marked in FIG3 ). Multiple diodes may have an electrical contact 119A as a common electrode. The first doped region 111 may also have a discrete portion.

The electronic device layer 120 may include an electronic system 121 suitable for processing or interpreting signals generated by radiation incident on the radiation absorbing layer 110. The electronic system 121 may include analog circuits such as filter networks, amplifiers, integrators, and comparators, or digital circuits such as microprocessors and memories. The electronic system 121 may include one or more ADCs (analog-to-digital converters). The electronic system 121 may include components shared by each pixel 150 or components dedicated to a single pixel 150. For example, the electronic system 121 may include an amplifier dedicated to each pixel 150 and a microprocessor shared between all pixels 150. The electronic system 121 may be electrically connected to the pixel 150 through the through hole 131. The spaces between the vias can be filled with a filling material 130, which can increase the mechanical stability of the connection between the electronic device layer 120 and the radiation absorbing layer 110. Other bonding techniques can connect the electronic system 121 to the pixel 150 without using the via 131.

When radiation from a radiation source (not shown) strikes the radiation absorbing layer 110 including the diode, the radiation particles may be absorbed and one or more electric carriers (e.g., electrons, holes) may be generated by a variety of mechanisms. The electric carriers may drift to an electrode of one of the diodes under an electric field. The electric field may be an external electric field. The electrical contacts 119B may include discrete portions, each of which is in electrical contact with the discrete region 114. The term "electrical contact" may be used interchangeably with the term "electrode". In one embodiment, the charge carriers can drift in various directions so that the charge carriers generated by a single radiation particle are substantially not shared by two different discrete regions 114 (here “substantially not…shared” means that less than 2%, less than 0.5%, less than 0.1%, or less than 0.01% of these charge carriers flow to a different discrete region 114 compared to the rest of the charge carriers). The charge carriers generated by the radiation particles incident on the surrounding area of the coverage of one of these discrete regions 114 are substantially not shared with another of these discrete regions 114. A pixel 150 associated with a discrete region 114 may be a region around the discrete region 114 in which substantially all (more than 98%, more than 99.5%, more than 99.9%, or more than 99.99%) of the charge carriers generated by radiation particles incident therein flow toward the discrete region 114. That is, less than 2%, less than 1%, less than 0.1%, or less than 0.01% of these charge carriers flow through the pixel 150.

FIG. 4 schematically illustrates a detailed cross-sectional view of the radiation detector 100 of FIG. 1 along line 2-2 according to an alternative embodiment. More specifically, the radiation absorbing layer 110 may include resistors of semiconductor materials such as silicon, germanium, GaAs, CdTe, CdZnTe, or combinations thereof, but does not include diodes. The semiconductor material may have a high quality attenuation coefficient for the radiation of interest. In one embodiment, the electronic device layer 120 of FIG. 4 is similar in structure and function to the electronic device layer 120 of FIG. 3 .

When radiation strikes the radiation absorbing layer 110, which includes a resistor but does not include a diode, it can be absorbed and generate one or more charge carriers through a variety of mechanisms. The radiation particles can generate 10 to 100,000 charge carriers. The charge carriers can drift to the electrical contacts 119A and 119B under an electric field. The electric field can be an external electric field. The electrical contact 119B can include a discrete portion. In one embodiment, the charge carriers can drift in various directions so that the charge carriers generated by a single radiation particle are substantially not shared by two different discrete portions of the electrical contact 119B (here "substantially not...shared" means that less than 2%, less than 0.5%, less than 0.1%, or less than 0.01% of these charge carriers flow to a different discrete portion compared to the rest of the charge carriers). The charge carriers generated by the radiation particles incident on the surrounding area of the coverage of one of these discrete portions of the electrical contact 119B are substantially not shared with another of these discrete portions of the electrical contact 119B. The pixel 150 associated with the discrete portion of the electrical contact 119B may be an area around the discrete portion in which substantially all (more than 98%, more than 99.5%, more than 99.9% or more than 99.99%) of the charge carriers generated by the radiation particles incident therein flow toward the discrete portion of the electrical contact 119B. That is, less than 2%, less than 0.5%, less than 0.1% or less than 0.01% of these charge carriers flow through a pixel associated with a discrete portion of the electrical contact 119B.

Radiation detector with protruding integrated circuit chip

FIG5 schematically shows a perspective view of a radiation detector 105 according to an embodiment. In an embodiment, the radiation detector 105 may include a radiation absorbing layer 115 and one or more integrated circuit chips 125 (e.g., two integrated circuit chips 125a and 125b as shown in the figure).

In an embodiment, the radiation detector 105 may be similar to the radiation detector 100 of FIGS. 1 to 4 because (A) the radiation absorption layer 115 of the radiation detector 105 is similar in structure and function to the radiation absorption layer 110 of the radiation detector 100, and (B) the integrated circuit chip 125 of the radiation detector 105 is similar in function to the electronic device layer 120 of the radiation detector 100.

Specifically, in an embodiment, the integrated circuit chip 125 of the radiation detector 105 may be configured to process the electrical signal generated in the radiation absorption layer 115. In an embodiment, each integrated circuit chip 125 may include an ASIC (application specific integrated circuit).

Image sensor

FIG6 schematically shows a side view of an image sensor 600 according to an embodiment. In an embodiment, the image sensor 600 may include a plurality of radiation detectors 105 of FIG5 (e.g., three radiation detectors 105.1, 105.2, and 105.3 as shown). The radiation detectors 105.1, 105.2, and 105.3 may include radiation absorbing layers 115.1, 115.2, and 115.3, respectively.

Note that each of radiation detectors 105.1, 105.2, and 105.3 includes 2 integrated circuit chips 125, but only one of the 2 integrated circuit chips 125 is shown in FIG6 because the other integrated circuit chip 125 is hidden from view. For example, radiation detector 105.1 includes 2 integrated circuit chips 125a.1 and 125b.1, but only integrated circuit chip 125a.1 is shown in FIG6 because integrated circuit chip 125b.1 is hidden from view (integrated circuit chip 125b.1 is behind integrated circuit chip 125a.1). However, integrated circuit chip 125b.1 can be seen in FIG7.

Layer stacking

In an embodiment, referring to FIG. 6 , the image sensor 600 may further include a plurality of metal layers 610 corresponding one to one with the radiation detectors 105 (for example, three metal layers 610.1, 610.2, and 610.3 as shown in the figure). In an embodiment, the three metal layers 610.1, 610.2, and 610.3 together with the three radiation absorption layers 115.1, 115.2, and 115.3 form a stack of six layers (as shown in the figure).

In an embodiment, three metal layers 610.1, 610.2 and 610.3 and three radiation absorbing layers 115.1, 115.2 and 115.3 may be arranged in an alternating manner in a stack (as shown in the figure). "Alternating manner" means that the layers in the stack are arranged in the order of metal layer 610, then radiation absorbing layer 115, then metal layer 610, and then radiation absorbing layer 115.

In an embodiment, the metal layer 610 of the image sensor 600 may include metals that can block and absorb X-rays, such as tungsten, platinum, and gold.

The integrated circuit chip is sandwiched in the middle

In an embodiment, referring to FIG. 6 , each integrated circuit chip 125 of the image sensor 600 may include a portion sandwiched between a corresponding metal layer 610 and a corresponding radiation absorption layer 115. For example, a portion of the integrated circuit chip 125a.1 is sandwiched between a corresponding metal layer 610.1 and a corresponding radiation absorption layer 115.1. For another example, a portion of the integrated circuit chip 125b.1 is sandwiched between a corresponding metal layer 610.2 and a corresponding radiation absorption layer 115.2.

Best fitting plane

Referring to FIG. 6 , the best fitting plane 620 (e.g., least square method) of all sensing elements 150 of one of the three radiation absorbing layers 115.1, 115.2, and 115.3 (e.g., radiation absorbing layer 115.1) is specified (as shown). Please note that the best fitting plane 620 is perpendicular to the page; therefore, the best fitting plane 620 can be represented by a straight line as shown in the figure.

Integrated circuit chip overlaps with radiation absorbing layer

In an embodiment, referring to FIG. 6 , for each radiation detector 105 in the image sensor 600, each integrated circuit chip 125 of each radiation detector 105 may at least partially overlap with the radiation absorption layer 115 of each radiation detector 105 in a direction perpendicular to the best fitting plane 620. In other words, a straight line perpendicular to the best fitting plane 620 intersects both the integrated circuit chip 125 and the radiation absorption layer 115.

For example, for radiation detector 105.1, integrated circuit chip 125a.1 overlaps with radiation absorption layer 115.1 in a direction perpendicular to the best fitting plane 620. For another example, for radiation detector 105.2, integrated circuit chip 125a.2 overlaps with radiation absorption layer 115.2 in a direction perpendicular to the best fitting plane 620.

Integrated circuit chip protrusion

In an embodiment, referring to FIG. 6 , there may be at least one plane (e.g., plane 625) that is (A) perpendicular to the best fitting plane 620, (B) intersects all integrated circuit chips 125, and (C) does not intersect any radiation absorbing layer 115. In other words, structurally, all six integrated circuit chips 125 protrude from the radiation absorbing layer 115 in the same direction (e.g., downward as shown in the figure). Note that plane 625 is perpendicular to the page; therefore, plane 625 may be represented by a straight line as shown in the figure.

Input/output connections to highlighted areas

In an embodiment, referring to FIG. 6 , an I/O (input/output) device (not shown) can electrically connect an external circuit to an electrode (not shown) on the integrated circuit chip 125 such that a plane 625 is between (A) the electrode and (B) the radiation absorbing layer 115. In other words, the electrode for the I/O connection resides on a protruding area (not shown) of the integrated circuit chip 125. Specifically, in FIG. 6 , in an embodiment, these protruding areas of the integrated circuit chip 125 can be below the plane 625.

Metal layer protrusion

In an embodiment, referring to FIG. 6 , there may be at least one plane (e.g., plane 630) that is (A) perpendicular to the best fit plane 620, (B) intersects all metal layers 610, and (C) does not intersect any radiation absorbing layer 115. In other words, structurally, all metal layers 610 protrude from the radiation absorbing layer 115 in the same direction (e.g., upward as shown in the figure). Note that plane 630 is perpendicular to the page; therefore, plane 630 may be represented by a straight line as shown in the figure.

The integrated circuit chip and the metal layer protrude in opposite directions

In an embodiment, referring to FIG. 6 , plane 625 may be parallel to plane 630; each point of the radiation absorbing layer 115 may be between plane 625 and plane 630 (as shown in the figure). In other words, six integrated circuit chips 125 and three metal layers 610 protrude from the radiation absorbing layer 115 in two opposite directions. Specifically, the six integrated circuit chips 125 protrude downward, while the three metal layers 610 protrude upward (as shown in the figure).

Metal layer thickness

In an embodiment, referring to FIG. 6 , the thickness of each metal layer 610 measured in a direction perpendicular to the best fitting plane 620 may be in the range of 50 microns to 100 microns. For example, the thickness 640 of the metal layer 610.1 measured in a direction perpendicular to the best fitting plane 620 is in the range of 50 microns to 100 microns.

Integrated circuit chip thickness

In an embodiment, referring to FIG. 6 , the thickness of each integrated circuit chip 125 measured in a direction perpendicular to the best fitting plane 620 may be in the range of 10 microns to 100 microns. For example, the thickness 645 of the integrated circuit chip 125a.1 measured in a direction perpendicular to the best fitting plane 620 is in the range of 10 microns to 100 microns.

In an embodiment, referring to FIG. 6 , each straight line segment having two end points on two adjacent radiation absorbing layers 115 intersects with the metal layer 610. For example, each straight line segment having two end points on two adjacent radiation absorbing layers 115.1 and 115.2 intersects with the metal layer 610.2.

Alternative embodiments of image sensor-gaps in metal layers

FIG. 7 schematically illustrates the image sensor 600 of FIG. 6 as viewed from viewpoint 650 (FIG. 6) according to an alternative embodiment. FIG. 8 schematically illustrates a cross-sectional view of the image sensor 600 of FIG. 7 along line 8-8 according to an embodiment.

In an embodiment, referring to FIGS. 7 and 8 , the image sensor 600 of FIGS. 7 and 8 may be similar to the image sensor 600 of FIG. 6 , except that each metal layer 610 may include one or more gaps 612 corresponding one-to-one to the integrated circuit chip 125 of the corresponding radiation detector 105. For example, the metal layer 610.1 may include two gaps 612a.1 and 612b.1 corresponding to the integrated circuit chips 125a.1 and 125b.1, respectively.

In an embodiment, for each radiation detector 105, the integrated circuit chip 125 of each radiation detector 105 can be respectively located in the gap 612 of the corresponding metal layer 610, so that there is a straight line on the best fitting plane 620 (not shown, but the straight line is horizontal in FIG. 7 and perpendicular to the page in FIG. 8), so that any point of the integrated circuit chip 125 of each radiation detector 105 traveling in any direction parallel to the straight line will hit the corresponding metal layer 610.

For example, for radiation detector 105.1, 2 integrated circuit chips 125a.1 and 125b.1 are respectively within 2 gaps 612a.1 and 612b.1 of corresponding metal layer 610.1. Note that in FIG. 7, traveling horizontally (i.e., west or east) from any point of integrated circuit chips 125a.1 and 125b.1 of radiation detector 105.1 will hit metal layer 610.1.

Generally speaking, the number of gaps 612 of each metal layer 610 may be equal to or less than the number of integrated circuit chips 125 of the corresponding radiation detector 105. The case where the number of gaps 612 of the metal layer 610 is equal to the number of integrated circuit chips 125 of the corresponding radiation detector 105 is described above.

In the case where the number of gaps 612 in the metal layer 610 is less than the number of integrated circuit chips 125 of the corresponding radiation detector 105, at least one of the gaps 612 accommodates a plurality of integrated circuit chips 125. For example, referring to FIGS. 7 and 8, if gaps 612a.1 and 612b.1 are replaced by a larger gap (not shown), the larger gap can accommodate two integrated circuit chips 125a.1 and 125b.1. In other words, two integrated circuit chips 125a.1 and 125b.1 are in the larger gap.

In an embodiment, referring to FIG. 8 , the thickness of each integrated circuit chip 125 of the radiation detector 105 measured in a direction perpendicular to the best fitting plane 620 may be smaller than the thickness of the corresponding metal layer 610 measured in a direction perpendicular to the best fitting plane 620. For example, the thickness 127 of the integrated circuit chip 125a.1 of the radiation detector 105 measured in a direction perpendicular to the best fitting plane 620 is smaller than the thickness 640 of the corresponding metal layer 610.1 measured in a direction perpendicular to the best fitting plane 620.

In an embodiment, referring to FIG. 8 , each integrated circuit chip 125 of the radiation detector 105 is not in direct physical contact with the radiation absorption layer 115 of any other radiation detector 105. For example, the integrated circuit chip 125a.1 of the radiation detector 105.1 is not in direct physical contact with the radiation absorption layer 115.2 or the radiation absorption layer 115.3. For another example, the integrated circuit chip 125a.2 of the radiation detector 105.2 is not in direct physical contact with the radiation absorption layer 115.1 or the radiation absorption layer 115.3.

In an embodiment, referring to FIG. 8 , the structure of the image sensor 600 can make each straight line segment with two end points on two adjacent radiation absorption layers 115 intersect with (A) at least one metal layer 610 or (B) at least one gap 612. For example, each straight line segment with two end points on two adjacent radiation absorption layers 115.1 and 115.2 intersects with (A) metal layer 610.2 or (B) at least one gap 612 of metal layer 610.2.

Imaging system

FIG. 9 schematically illustrates an imaging system 900 according to an embodiment. In an embodiment, the imaging system 900 may include a radiation source 910 and the image sensor 600 of FIG. 6 (or the image sensor 600 of FIG. 7 and FIG. 8 ).

In an embodiment, referring to FIG. 9 , the radiation source 910 and the image sensor 600 may be arranged so that a straight line (not shown) parallel to the best fitting plane 620 intersects both the radiation source 910 and the image sensor 600. This arrangement allows side radiation incidence during imaging using the image sensor 600.

In an embodiment, the radiation source 910 may transmit radiation 912 to an object 920 located between the radiation source 910 and the image sensor 600. In an embodiment, the image sensor 600 may capture an image of the object 920 based on the interaction between the radiation 912 and the object 920.

Interactions between radiation 912 and object 920 may include situations such as: (A) some radiation particles of radiation 912 incident on object 920 are blocked by object 920, (B) some radiation particles of radiation 912 incident on object 920 pass through object 920 without changing their direction, and (C) some radiation particles of radiation 912 incident on object 920 collide with atoms of object 920, thereby changing their direction.

The term "image" in this application is not limited to the spatial distribution of properties of radiation (such as intensity). For example, the term "image" may also include the spatial distribution of the density of a substance or element.

Flowchart outlining the operation of the imaging system

FIG. 10 shows a flowchart 1000 outlining the operation of the imaging system 900 of FIG. 9 according to an embodiment. In step 1010, the operation may include transmitting radiation from a radiation source to an object located between the radiation source and the image sensor. For example, in the above embodiment, referring to FIG. 9, the radiation source 910 transmits radiation 912 to an object 920 located between the radiation source 910 and the image sensor 600.

In step 1020, the operation may include capturing an image of the object with an image sensor based on the interaction between the radiation and the object. For example, in the above-mentioned embodiment, referring to FIG. 9, the image sensor 600 captures an image of the object 920 based on the interaction between the radiation 912 and the object 920.

Discrete regions in the radiation absorbing layer

In an embodiment, referring to FIG. 5 , the radiation absorption layer 115 of the radiation detector 105 used for the image sensor 600 (FIGS. 6 to 9) may be integral (as shown). Alternatively, referring to FIG. 11A (top view) and FIG. 11B (perspective view), the radiation absorption layer 115 of the radiation detector 105 used for the image sensor 600 (FIGS. 6 to 9) may include a plurality of discrete radiation absorption regions (e.g., two discrete radiation absorption regions 115a and 115b as shown). In an embodiment, the radiation detector 105 of FIG. 11A and FIG. 11B may include an integrated circuit chip 125 for processing electrical signals generated in the discrete radiation absorption regions 115a and 115b. Note that the manner in which the integrated circuit chips 125 of FIGS. 11A and 11B protrude from the discrete radiation absorbing regions 115a and 115b is similar to the manner in which the integrated circuit chips 125a and 125b protrude from the radiation absorbing layer 115 of FIG. 5 .

Although various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for illustrative purposes and are not intended to be limiting, and the true scope and spirit are indicated by the attached patent application scope.

2-2, 8-8: Line

100, 105, 105.1, 105.2, 105.3: Radiation detectors

110, 115, 115.1, 115.2, 115.3: Radiation absorption layer

111: First mixed area

112: Intrinsic area

113: Second mixed area

114: Dispersed Area

115a, 115b: Radiation absorption area

119A, 119B: electrical contacts

125, 125a, 125a.1, 125a.2, 125a.3, 125b, 125b.1: integrated circuit chip

120: Electronic device layer

121:Electronic system

127, 640, 645: Thickness

130: Filling material

131:Through hole

150: Pixels/sensing elements

600: Image sensor

610.1, 610.2, 610.3: Metal layer

612a.1, 612b.1: Gap

620: Best fitting plane

625, 630: plane

650: Viewpoint

900: Imaging system

910: Radiation source

912: Fallout

920: Object

1000:Flowchart

1010, 1020: Steps

FIG1 schematically shows a radiation detector according to an embodiment.

FIG2 schematically shows a simplified cross-sectional view of a radiation detector according to an embodiment.

FIG3 schematically shows a detailed cross-sectional view of a radiation detector according to an embodiment.

FIG4 schematically shows a detailed cross-sectional view of a radiation detector according to an alternative embodiment.

FIG5 schematically shows a perspective view of a radiation detector according to an embodiment.

FIG6 schematically shows an image sensor according to an embodiment.

Figures 7 and 8 schematically illustrate image sensors according to alternative embodiments.

FIG9 schematically shows an imaging system according to an embodiment.

FIG10 shows a flow chart outlining the operation of an imaging system according to one embodiment.

Figures 11A and 11B show the radiation detector of Figure 5 according to an alternative embodiment.

105.1, 105.2, 105.3: Radiation detectors

115.1, 115.2, 115.3: Radiation absorption layer

125a.1, 125a.2, 125a.3: Integrated circuit chips

600: Image sensor

610.1, 610.2, 610.3: Metal layer

620: Best fitting plane

625, 630: plane

640, 645: Thickness

650: Viewpoint

Claims (24)

An imaging system, the imaging system includes an image sensor, the image sensor includes: M metal layers (metal layer (i), i=1, ..., M), wherein M is an integer greater than 1; and M radiation detectors (radiation detector (i), i=1, ..., M), wherein, for each i value, the radiation detector (i) includes a radiation absorption layer (i), and an integrated circuit chip (i, j) configured to process an electrical signal generated in the radiation absorption layer (i), j=1, ..., Ni, wherein Ni, i=1, ..., M is a positive integer, wherein the M metal layers and the radiation absorption layer (i), i=1, ..., M together form a stack of layers, wherein there is an optimal fitting plane for all sensing elements of one of the M radiation detectors, wherein, for each i value, each of the integrated circuit chips (i, j), j=1, ..., Ni at least partially overlaps with the radiation absorption layer (i) in a direction perpendicular to the optimal fitting plane, and wherein there is a first plane, which is perpendicular to the optimal fitting plane, intersects with all of the integrated circuit chips (i, j), i=1, ..., M, j=1, ..., Ni, and does not intersect with any of the radiation absorption layers (i), i=1, ..., M. An imaging system as described in claim 1, wherein the stack includes 2×M layers. An imaging system as described in claim 1, wherein the metal material includes tungsten, platinum or gold. An imaging system as claimed in claim 1, wherein the M metal layers and the radiation absorbing layer (i), i=1, ..., M are arranged in the stack in an alternating manner. An imaging system as described in claim 1, wherein there is a second plane, which is perpendicular to the best fitting plane, intersects with all of the M metal layers, and does not intersect with any radiation absorbing layer in the radiation absorbing layer (i), i=1, ..., M. An imaging system as claimed in claim 5, wherein the first plane is parallel to the second plane, and wherein each point of the radiation absorbing layer (i), i=1, ..., M is located between the first plane and the second plane. An imaging system as described in claim 1, wherein the thickness of each of the M metal layers measured in a direction perpendicular to the best fitting plane is in the range of 50 microns to 100 microns. An imaging system as described in claim 1, wherein each of the integrated circuit chips (i, j), i=1, ..., M, j=1, ..., Ni includes an application-specific integrated circuit (ASIC). An imaging system as described in claim 1, wherein the M metal layers are configured to block and absorb X-rays. An imaging system as claimed in claim 1, wherein an I/O (input/output) device electrically connects an external circuit to an electrode on the integrated circuit chip (i, j), i=1, ..., M, j=1, ..., Ni, and wherein the first plane is between (A) the electrode and (B) the radiation absorbing layer (i), i=1, ..., M. An imaging system as described in claim 1, wherein, for each value of i, the radiation absorbing layer (i) includes a plurality of discrete radiation absorbing regions. An imaging system as described in claim 11, wherein Ni, i=1, ..., M are all 1. An imaging system as claimed in claim 1, wherein the radiation absorbing layer (i), i=1, ..., M comprises GaAs, CdTe or CdZnTe. An imaging system as claimed in claim 1, wherein the thickness of each of the integrated circuit chips (i, j), i=1, ..., M, j=1, ..., Ni measured in a direction perpendicular to the best fitting plane is in the range of 10 microns to 100 microns. An imaging system as claimed in claim 1, wherein, for each value of i and each value of j, a portion of the integrated circuit chip (i, j) is sandwiched between the metal layer (i) and the radiation absorbing layer (i). An imaging system as claimed in claim 1, wherein, for each value of i, the metal layer (i) includes Pi gaps, wherein Pi is a positive integer not greater than Ni, and wherein, for each value of i, the integrated circuit chip (i, j), j=1, ..., Ni is within the Pi gaps, so that there exists a straight line on the best fitting plane, so that any direction parallel to the straight line from any point of the integrated circuit chip (i, j), j=1, ..., Ni will hit the metal layer (i). An imaging system as described in claim 16, wherein, for each value of i, Ni>Pi. An imaging system as claimed in claim 16, wherein, for each value of i, Ni=Pi, and wherein, for each value of i, the integrated circuit chip (i,j), j=1, ..., Ni is respectively located in the Pi gaps. An imaging system as claimed in claim 18, wherein, for each value of i, the thickness of each integrated circuit chip (i, j) of the radiation detector (i), j=1, ..., Ni, measured in a direction perpendicular to the best fitting plane, is less than the thickness of the metal layer (i) measured in a direction perpendicular to the best fitting plane. An imaging system as claimed in claim 18, wherein, for each value of i, each integrated circuit chip (i, j) of the radiation detector (i), j=1, ..., Ni, is not in direct physical contact with the radiation absorbing layer of any other radiation detector in the M radiation detectors. An imaging system as described in claim 18, wherein each straight line segment on two adjacent radiation absorbing layers in the radiation absorbing layer (i), i=1, ..., M, respectively, intersects with (A) at least one metal layer in the M metal layers or (B) at least one gap in one metal layer in the M metal layers. An imaging system as described in claim 1, wherein the two end points are respectively on the radiation absorbing layer (i), i=1, ..., M, and each straight line segment on two adjacent radiation absorbing layers intersects with a metal layer among the M metal layers. The imaging system as described in claim 1 further includes a radiation source, wherein a straight line parallel to the best fitting plane intersects both the radiation source and the image sensor, and wherein the first plane is not between the radiation source and the radiation absorbing layer (i), i=1, ..., M. An imaging method using the imaging system as described in claim 23, comprising: transmitting radiation from the radiation source to an object located between the radiation source and the image sensor; and capturing an image of the object with the image sensor based on the interaction between the radiation and the object.

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