WO2023122921A1

WO2023122921A1 - Image sensors with small and thin integrated circuit chips

Info

Publication number: WO2023122921A1
Application number: PCT/CN2021/141836
Authority: WO
Inventors: Peiyan CAO; Yurun LIU
Original assignee: Shenzhen Xpectvision Technology Co., Ltd.
Priority date: 2021-12-28
Filing date: 2021-12-28
Publication date: 2023-07-06
Also published as: TW202326128A; TWI822463B

Abstract

A system comprising: an image sensor comprising M radiation detectors (radiation detectors (i), i=1, …, M), M being a positive integer. For each value of i, the radiation detector (i) comprises (A) a radiation absorption layer (i) which comprises multiple sensing elements, and (B) an electronics layer (i) configured to process electrical signals generated in the radiation absorption layer (i). The radiation absorption layers (i), i=1, …, M and the electronics layers (i), i=1, …, M together form a stack. For each value of i, the electronics layer (i) comprises Ni integrated circuit chips, Ni being a positive integer. A best-fit plane passes through all sensing elements of a radiation absorption layer of the radiation absorption layers (i), i=1, …, M. For each value of i, in terms of area, total footprints on the best-fit plane of the Ni integrated circuit chips of the radiation detector (i) are at most 10%, at most 20%, at most 30%, at most 40%, at most 50%, or at most 60% of total footprints on the best-fit plane of all sensing elements of the radiation detector (i).

Description

IMAGE SENSORS WITH SMALL AND THIN INTEGRATED CIRCUIT CHIPS

Background

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

Summary

Disclosed herein is a system comprising: an image sensor comprising M radiation detectors (radiation detectors (i) , i=1, …, M) , M being a positive integer. For each value of i, the radiation detector (i) comprises (A) a radiation absorption layer (i) which comprises multiple sensing elements, and (B) an electronics layer (i) configured to process electrical signals generated in the radiation absorption layer (i) . The radiation absorption layers (i) , i=1, …, M and the electronics layers (i) , i=1, …, M together form a stack. For each value of i, the electronics layer (i) comprises Ni integrated circuit chips, Ni being a positive integer. A best-fit plane passes through all sensing elements of a radiation absorption layer of the radiation absorption layers (i) , i=1, …, M. For each value of i, in terms of area, total footprints on the best-fit plane of the Ni integrated circuit chips of the radiation detector (i) are at most 10%, at most 20%, at most 30%, at most 40%, at most 50%, or at most 60%of total footprints on the best-fit plane of all sensing elements of the radiation detector (i) .

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

In an aspect, for each value of i, each integrated circuit chip of the Ni integrated circuit chips of the radiation detector (i) comprises an application-specific integrated circuit (ASIC) .

In an aspect, M=1.

In an aspect, all Ni, i=1, …, M are the same.

In an aspect, for each value of i, in terms of area, a footprint on the best-fit plane of each integrated circuit chip of the Ni integrated circuit chips of the radiation detector (i) is at most 10%, at most 20%, at most 30%, at most 40%, at most 50%, or at most 60%of total footprints on the best-fit plane of all sensing elements of the radiation detector (i) served by said each integrated circuit chip.

In an aspect, the radiation absorption layers (i) , i=1, …, M and the electronics layers (i) , i=1, …, M are arranged in an alternating manner in the stack.

In an aspect, M>2, and for M-1 radiation detectors of the M radiation detectors at one end of the stack, there is no overlapping among the footprints on the best-fit plane of all the integrated circuit chips of the M-1 radiation detectors.

In an aspect, the radiation absorption layer of the remaining radiation detector of the M radiation detectors is positioned between (A) the electronics layer of the remaining radiation detector and (B) the M-1 radiation detectors.

In an aspect, a reference direction for the image sensor is perpendicular to the best-fit plane, and for each value of i, a thickness in the reference direction of the electronics layer (i) divided by a thickness in the reference direction of the radiation absorption layer (i) is at most 1/1000.

In an aspect, a reference direction for the image sensor is perpendicular to the best-fit plane, and for each value of i, a thickness in the reference direction of the electronics layer (i) is in a range of 10 microns to 100 microns.

In an aspect, for each value of i, the radiation detector (i) further comprises an input/output (I/O) area (i) , a footprint on the best-fit plane of the image sensor has a shape of a rectangle and has 4 sides, and for each value of i, a same side of said 4 sides overlaps a footprint on the best-fit plane of the I/O area (i) the most.

In an aspect, the system further comprises a radiation source. The radiation source is configured to send radiation toward the image sensor, a straight line intersecting the radiation source and the image sensor is parallel to the best-fit plane, and every straight line segment having a first end point on the radiation source and a second end point on any sensing element of the image sensor does not intersect any I/O area of the I/O areas (i) , i=1, …, M.

In an aspect, the radiation sent by the radiation source comprises X-rays.

In an aspect, for each value of i, the radiation detector (i) further comprises an input/output (I/O) area (i) , the stack comprises multiple flat faces, and all the I/O areas (i) , i=1, …, M are on a same flat face of the multiple flat faces of the stack.

In an aspect, the multiple flat faces comprise 6 faces of a cuboid.

Brief Description of Figures

Fig. 1 schematically shows a radiation detector, according to an embodiment.

Fig. 2 schematically shows a simplified cross-sectional view of the radiation detector, according to an embodiment.

Fig. 3 schematically shows a detailed cross-sectional view of the radiation detector, according to an embodiment.

Fig. 4 schematically shows a detailed cross-sectional view of the radiation detector, according to an alternative embodiment.

Fig. 5 schematically shows a top view of another radiation detector, according to an embodiment.

Fig. 6 schematically shows a perspective view of an image sensor, according to an embodiment.

Fig. 7 schematically shows a top view of a radiation detector of the image sensor, according to an embodiment.

Fig. 8 schematically shows a top view of another radiation detector of the image sensor, according to an embodiment.

Fig. 9 schematically shows a perspective view of an imaging system, according to an embodiment.

Detailed Description

RADIATION DETECTOR

Fig. 1 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 Fig. 1) , a honeycomb array, a hexagonal array, or any other suitable array. The array of pixels 150 in the example of Fig. 1 has 4 rows and 7 columns; 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 from a radiation source (not shown) incident thereon and may be configured to measure a characteristic (e.g., the energy of the particles, the wavelength, and the frequency) of the radiation. A radiation may include particles such as photons and subatomic particles. Each pixel 150 may be configured to count numbers of particles of radiation incident thereon whose energy falls in a plurality of bins of energy, within a period of time. All the pixels 150 may be configured to count the numbers of particles of radiation incident thereon within a plurality of bins of energy within the same period of time. When the incident particles of radiation have similar energy, the pixels 150 may be simply configured to count numbers of particles of radiation incident thereon within a period of time, without measuring the energy of the individual particles of radiation.

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

The radiation detector 100 described here may have applications such as in an X-ray telescope, X-ray mammography, industrial X-ray defect detection, X-ray microscopy or microradiography, X-ray casting inspection, X-ray non-destructive testing, X-ray weld inspection, X-ray digital subtraction angiography, etc. It may be suitable to use this radiation detector 100 in place of a photographic plate, a photographic film, a PSP plate, an X-ray image intensifier, a scintillator, or another semiconductor X-ray detector.

Fig. 2 schematically shows a simplified cross-sectional view of the radiation detector 100 of Fig. 1 along a line 2-2, according to an embodiment. Specifically, the radiation detector 100 may include a radiation absorption layer 110 and an electronics layer 120 (which may include one or more ASICs or application-specific integrated circuits) for processing or analyzing electrical signals which incident radiation generates in the radiation absorption layer 110. The radiation detector 100 may or may not include a scintillator (not shown) . The radiation absorption 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 mass attenuation coefficient for the radiation of interest.

Fig. 3 schematically shows a detailed cross-sectional view of the radiation detector 100 of Fig. 1 along the line 2-2, as an example. Specifically, the radiation absorption layer 110 may include one or more diodes (e.g., p-i-n or p-n) formed by a first doped region 111, one or more discrete regions 114 of a 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 one another 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 Fig. 3, each of the discrete regions 114 of the second doped region 113 forms a diode with the first doped region 111 and the optional intrinsic region 112. Namely, in the example in Fig. 3, the radiation absorption layer 110 has a plurality of diodes (more specifically, 7 diodes corresponding to 7 pixels 150 of one row in the array of Fig. 1, of which only 2 pixels 150 are labeled in Fig. 3 for simplicity) . The plurality of diodes may have an electrical contact 119A as a shared (common) electrode. The first doped region 111 may also have discrete portions.

The electronics layer 120 may include an electronic system 121 suitable for processing or interpreting signals generated by the radiation incident on the radiation absorption layer 110. The electronic system 121 may include an analog circuitry such as a filter network, amplifiers, integrators, and comparators, or a digital circuitry such as a microprocessor, and memory. The electronic system 121 may include one or more ADCs (analog to digital converters) . The electronic system 121 may include components shared by the pixels 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 among all the pixels 150. The electronic system 121 may be electrically connected to the pixels 150 by vias 131. Space among the vias may be filled with a filler material 130, which may increase the mechanical stability of the connection of the electronics layer 120 to the radiation absorption layer 110. Other bonding techniques are possible to connect the electronic system 121 to the pixels 150 without using the vias 131.

When radiation from the radiation source (not shown) hits the radiation absorption layer 110 including diodes, particles of the radiation may be absorbed and generate one or more charge carriers (e.g., electrons, holes) by a number of mechanisms. The charge carriers may drift to the electrodes of one of the diodes under an electric field. The electric field may be an external electric field. The electrical contact 119B may include discrete portions each of which is in electrical contact with the discrete regions 114. The term “electrical contact” may be used interchangeably with the word “electrode. ” In an embodiment, the charge carriers may drift in directions such that the charge carriers generated by a single particle of the radiation are not substantially shared by two different discrete regions 114 ( “not substantially shared” here means less than 2%, less than 0.5%, less than 0.1%, or less than 0.01%of these charge carriers flow to a different one of the discrete regions 114 than the rest of the charge carriers) . Charge carriers generated by a particle of the radiation incident around the footprint of one of these discrete regions 114 are not substantially shared with another of these discrete regions 114. A pixel 150 associated with a discrete region 114 may be an area 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) charge carriers generated by a particle of the radiation incident therein flow to the discrete region 114. Namely, less than 2%, less than 1%, less than 0.1%, or less than 0.01%of these charge carriers flow beyond the pixel 150.

Fig. 4 schematically shows a detailed cross-sectional view of the radiation detector 100 of Fig. 1 along the line 2-2, according to an alternative embodiment. More specifically, the radiation absorption layer 110 may include a resistor of a semiconductor material such as silicon, germanium, GaAs, CdTe, CdZnTe, or a combination thereof, but does not include a diode. The semiconductor material may have a high mass attenuation coefficient for the radiation of interest. In an embodiment, the electronics layer 120 of Fig. 4 is similar to the electronics layer 120 of Fig. 3 in terms of structure and function.

When the radiation hits the radiation absorption layer 110 including the resistor but not diodes, it may be absorbed and generate one or more charge carriers by a number of mechanisms. A particle of the radiation may generate 10 to 100, 000 charge carriers. The charge carriers may drift to the

electrical contacts

119A and 119B under an electric field. The electric field may be an external electric field. The electrical contact 119B may include discrete portions. In an embodiment, the charge carriers may drift in directions such that the charge carriers generated by a single particle of the radiation are not substantially shared by two different discrete portions of the electrical contact 119B ( “not substantially shared” here means less than 2%, less than 0.5%, less than 0.1%, or less than 0.01%of these charge carriers flow to a different one of the discrete portions than the rest of the charge carriers) . Charge carriers generated by a particle of the radiation incident around the footprint of one of these discrete portions of the electrical contact 119B are not substantially shared with another of these discrete portions of the electrical contact 119B. A pixel 150 associated with a 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) charge carriers generated by a particle of the radiation incident therein flow to the discrete portion of the electrical contact 119B. Namely, less than 2%, less than 0.5%, less than 0.1%, or less than 0.01%of these charge carriers flow beyond the pixel associated with the one discrete portion of the electrical contact 119B.

RADIATION DETECTOR WITH INPUT/OUTPUT (I/O) AREA

Fig. 5 schematically shows a top view of a radiation detector 102, according to an embodiment. In an embodiment, the radiation detector 102 may be similar to the radiation detector 100 except that the radiation detector 102 may include an input/output (I/O) area 512 on its perimeter as shown. For example, like the radiation detector 100 of Fig. 1 –Fig. 4, the radiation detector 102 may include a radiation absorption layer 110 and an electronics layer 120. In an embodiment, transmission lines (not shown) may electrically connect components (e.g., ASIC chips) of the electronics layer 120 of the radiation detector 102 to the I/O area 512.

IMAGE SENSOR

Fig. 6 schematically shows a perspective view of an image sensor 600, according to an embodiment. In an embodiment, the image sensor 600 may include one or more radiation detectors 102 of Fig. 5. For example, the image sensor 600 may include 3 radiation detectors 102.1, 102.2, and 102.3 as shown.

In an embodiment, each radiation detector 102 of the image sensor 600 may include a radiation absorption layer 110 and an electronics layer 120. Specifically, the radiation detector 102.1 may include a radiation absorption layer 110.1 and an electronics layer 120.1. The radiation detector 102.2 may include a radiation absorption layer 110.2 and an electronics layer 120.2. The radiation detector 102.3 may include a radiation absorption layer 110.3 and an electronics layer 120.3.

In an embodiment, the radiation detectors 102.1, 102.2, and 102.3 may be arranged such that the 3 radiation absorption layers 110.1, 110.2, and 110.3 and the 3 electronics layers 120.1, 120.2, and 120.3 together form a stack of 6 layers as shown in Fig. 6.

In an embodiment, the 3 radiation absorption layers 110.1, 110.2, and 110.3 and the 3 electronics layers 120.1, 120.2, and 120.3 may be arranged in an alternating manner in the stack as shown in Fig. 6. “Alternating manner” means the layers are arranged in the order of a radiation absorption layer 110, then an electronics layer 120, then a radiation absorption layer 110, then an electronics layer 120, and so on.

To help with description, a best-fit plane 605 is identified that passes through all the sensing elements 150 of one of the 3 radiation absorption layers 110 (e.g., the radiation absorption layer 110.1) of the image sensor 600.

ALL ASIC CHIPS VS. ALL SENSING ELEMENTS IN EACH RADIATION DETECTOR 102

Fig. 7 schematically shows a top view of the radiation detector 102.1 of the image sensor 600 of Fig. 6, according to an embodiment. In an embodiment, the radiation detector 102.1 may include one or more ASIC (application-specific integrated circuit) chips 125 in the electronics layer 120.1 (Fig. 6) . For example, the radiation detector 102.1 may include 4 ASIC chips 125.1a, 125.1b, 125.1c, and 125.1d as shown in Fig. 7.

In an embodiment, with reference to Fig. 6 –Fig. 7, the remaining radiation detectors 102.2 and 102.3 of the image sensor 600 may be similar to the radiation detector 102.1 in terms of the number of ASIC chips 125. In other words, all the radiation detectors 102.1, 102.2, and 102.3 of the image sensor 600 may have the same number of ASIC chips 125 (e.g., 4 ASIC chips) . In general, the numbers of ASIC chips 125 in the radiation detectors 102.1, 102.2, and 102.3 of the image sensor 600 may or may not be the same.

In an embodiment, for each radiation detector 102 of the image sensor 600, in terms of area, the total footprints (i.e., projection) on the best-fit plane 605 of all the ASIC chips 125 of said each radiation detector 102 may be at most 10%, at most 20%, at most 30%, at most 40%, at most 50%, or at most 60%of the total footprints on the best-fit plane 605 of all the sensing elements 150 of said each radiation detector 102.

For example, for the radiation detector 102.1, the feature specified above means that, in terms of area, the total footprints (i.e., projection) on the best-fit plane 605 of all the ASIC chips 125.1a, 125.1b, 125.1c, and 125.1d of the radiation detector 102.1 are at most 10%, at most 20%, at most 30%, at most 40%, at most 50%, or at most 60%of the total footprints on the best-fit plane 605 of all the 28 sensing elements 150 of the radiation detector 102.1.

EACH ASIC CHIP VS. ALL SENSING ELEMENTS SERVED BY SAID EACH ASIC CHIP

In an embodiment, regarding the radiation detector 102.1, the ASIC chip 125.1a may serve (i.e., process and analyze electrical signals generated in) the 2×4 array of 8 sensing elements 150 at the top left corner of the radiation detector 102.1. The ASIC chip 125.1b may serve the 2×3 array of 6 sensing elements 150 at the top right corner of the radiation detector 102.1. The ASIC chip 125.1c may serve the 2×4 array of 8 sensing elements 150 at the bottom left corner of the radiation detector 102.1. The ASIC chip 125.1d may serve the 2×3 array of 6 sensing elements 150 at the bottom right corner of the radiation detector 102.1.

In an embodiment, the remaining radiation detectors 102.2 and 102.3 of the image sensor 600 may be similar to the radiation detector 102.1 in that each ASIC chip 125 of these 3 radiation detectors 102 serves a group of sensing elements 150.

In an embodiment, for each ASIC chip 125 of the image sensor 600, in terms of area, the footprint on the best-fit plane 605 of said each ASIC chip 125 may be at most 10%, at most 20%, at most 30%, at most 40%, at most 50%, or at most 60%of the total footprints on the best-fit plane 605 of all the sensing elements 150 served by said each ASIC chip 125.

For an example, for the ASIC chip 125.1a of the radiation detector 102.1, the feature specified above means that, in terms of area, the footprint on the best-fit plane 605 of the ASIC chip 125.1a may be at most 10%, at most 20%, at most 30%, at most 40%, at most 50%, or at most 60%of the total footprints on the best-fit plane 605 of all the 8 sensing elements 150 (at the top left corner of the radiation detector 102.1) served by the ASIC chip 125.1a.

For another example, for the ASIC chip 125.1b of the radiation detector 102.1, the feature specified above means that, in terms of area, the footprint on the best-fit plane 605 of the ASIC chip 125.1b may be at most 10%, at most 20%, at most 30%, at most 40%, at most 50%, or at most 60%of the total footprints on the best-fit plane 605 of all the 6 sensing elements 150 (at the top right corner of the radiation detector 102.1) served by the ASIC chip 125.1b.

OFFSET ASIC CHIPS

Fig. 8 schematically shows a top view of the radiation detector 102.2 of the image sensor 600 of Fig. 6, according to an embodiment. In an embodiment, the radiation detector 102.2 may include one or more ASIC chips 125 in the electronics layer 120.2 (Fig. 6) . For example, the radiation detector 102.2 may include 4 ASIC chips 125.2a, 125.2b, 125.2c, and 125.2d as shown in Fig. 8. Note that the 4 ASIC chips 125.1a, 125.1b, 125.1c, and 125.1d of the radiation detector 102.1 (Fig. 7) are also shown in Fig. 8 for comparison.

With reference to Fig. 6 –Fig. 8, in general, the image sensor 600 may have M radiation detectors 102 (M is a positive integer) . In an embodiment, with M being an integer greater than 2, for the (M-1) radiation detectors 102 of the M radiation detectors 102 at one end of the stack, there may be no overlapping among the footprints on the best-fit plane 605 of all the ASIC chips 125 of the (M-1) radiation detectors 102.

For example, in the embodiments described above, with M=3, the feature specified above means that there may be no overlapping among the footprints on the best-fit plane 605 of all the 8 ASIC chips 125.1a, 125.1b, 125.1c, 125.1d, 125.2a, 125.2b, 125.2c, and 125.2d of the radiation detectors 102.1 and 102.2 as shown in Fig. 8.

RELATIVE THICKNESSES OF LAYERS

With reference back to Fig. 6, a reference direction 610 for the image sensor 600 may be defined to be perpendicular to the best-fit plane 605. In an embodiment, for each radiation detector 102 of the image sensor 600, the thickness in the reference direction 610 of the electronics layer 120 of said each radiation detector 102 divided by the thickness in the reference direction 610 of the radiation absorption layer 110 of said each radiation detector 102 may be at most 1/1000.

For example, for the radiation detector 102.1, the feature specified above means that the thickness 120.1t in the reference direction 610 of the electronics layer 120.1 divided by the thickness 110.1t in the reference direction 610 of the radiation absorption layer 110.1 may be at most 1/1000.

For another example, for the radiation detector 102.2, the feature specified above means that the thickness 120.2t in the reference direction 610 of the electronics layer 120.2 divided by the thickness 110.2t in the reference direction 610 of the radiation absorption layer 110.2 may be at most 1/1000.

ABSOLUTE THICKNESSES OF LAYERS

With reference to Fig. 6, in an embodiment, for each radiation detector 102 of the image sensor 600, the thickness in the reference direction 610 of the electronics layer 120 of said each radiation detector 102 may be in the range of 10 microns to 100 microns.

For an example, for the radiation detector 102.1, the feature specified above means that the thickness 120.1t in the reference direction 610 of the electronics layer 120.1 may be in the range of 10 microns to 100 microns.

For another example, for the radiation detector 102.2, the feature specified above means that the thickness 120.2t in the reference direction 610 of the electronics layer 120.2 may be in the range of 10 microns to 100 microns.

ALL I/O AREAS ON SAME SIDE OF IMAGE SENSOR

In an embodiment, with reference to Fig. 6, the stack of the 3 radiation absorption layers 110.1, 110.2, and 110.3 and the 3 electronics layers 120.1, 120.2, and 120.3 may have the shape of a cuboid (rectangular prism) as shown. In an embodiment, the I/O areas 512.1, 512.2, and 512.3 of the radiation detectors 102.1, 102.2, and 102.3 respectively may be on the same face (the right face) of the cuboid as shown.

This feature specified above means that the footprint on the best-fit plane 605 of the stack has the shape of a rectangle and therefore has 4 sides; and for each radiation detector 102 of the image sensor 600, the same side (the right side) of said 4 sides overlaps the footprint on the best-fit plane 605 of the I/O area 512 of said each radiation detector 102 the most.

For an example, for the radiation detector 102.1, the feature specified above means that the right side of the 4 sides of the footprint on the best-fit plane 605 of the stack (or just “right side” for short) overlaps the footprint on the best-fit plane 605 of the I/O area 512.1 the most.

Note that the front side and back side of the 4 sides of the footprint on the best-fit plane 605 of the stack also overlap the footprint on the best-fit plane 605 of the I/O area 512.1, but the right side overlaps it the most (because most of the right side is part of the footprint on the best-fit plane 605 of the I/O area 512.1) .

For another example, for the radiation detector 102.2, the feature specified above means that the right side of the 4 sides of the footprint on the best-fit plane 605 of the stack overlaps the footprint on the best-fit plane 605 of the I/O area 512.2 the most.

IMAGING SYSTEM

Fig. 9 schematically shows a perspective view of 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. In an embodiment, an object 920 may be positioned between the radiation source 910 and the image sensor 600.

In an embodiment, the radiation source 910 may send a radiation beam 912 toward the object 920 and toward the image sensor 600. The radiation beam 912 may include X-rays. In an embodiment, the image sensor 600 may capture an image of the object 920 by using radiation of the radiation beam 912 from the radiation source 910 that has transmitted through the object 920.

In an embodiment, the radiation source 910 and the image sensor 600 may be arranged such that a straight line intersecting both the radiation source 910 and the image sensor 600 is parallel to the best-fit plane 605.

In an embodiment, every straight line segment having a first end point on the radiation source 910 and a second end point on any sensing element 150 of the image sensor 600 does not intersect any I/O area of the I/O areas 512.1, 512.2, and 512.3 (as shown) .

While 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 purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.

Claims

A system, comprising:

an image sensor comprising M radiation detectors (radiation detectors (i) , i=1, …, M) , M being a positive integer,

wherein for each value of i, the radiation detector (i) comprises (A) a radiation absorption layer (i) which comprises multiple sensing elements, and (B) an electronics layer (i) configured to process electrical signals generated in the radiation absorption layer (i) ,

wherein the radiation absorption layers (i) , i=1, …, M and the electronics layers (i) , i=1, …, M together form a stack,

wherein for each value of i, the electronics layer (i) comprises Ni integrated circuit chips, Ni being a positive integer,

wherein a best-fit plane passes through all sensing elements of a radiation absorption layer of the radiation absorption layers (i) , i=1, …, M, and

wherein for each value of i, in terms of area, total footprints on the best-fit plane of the Ni integrated circuit chips of the radiation detector (i) are at most 10%, at most 20%, at most 30%, at most 40%, at most 50%, or at most 60%of total footprints on the best-fit plane of all sensing elements of the radiation detector (i) .
The system of claim 1, wherein the stack comprises 2×M layers.
The system of claim 1, wherein for each value of i, each integrated circuit chip of the Ni integrated circuit chips of the radiation detector (i) comprises an application-specific integrated circuit (ASIC) .
The system of claim 1, wherein M=1.
The system of claim 1, wherein all Ni, i=1, …, M are the same.
The system of claim 1, wherein for each value of i, in terms of area, a footprint on the best-fit plane of each integrated circuit chip of the Ni integrated circuit chips of the radiation detector (i) is at most 10%, at most 20%, at most 30%, at most 40%, at most 50%, or at most 60%of total footprints on the best-fit plane of all sensing elements of the radiation detector (i) served by said each integrated circuit chip.
The system of claim 1, wherein the radiation absorption layers (i) , i=1, …, M and the electronics layers (i) , i=1, …, M are arranged in an alternating manner in the stack.
The system of claim 1,

wherein M>2, and

wherein for M-1 radiation detectors of the M radiation detectors at one end of the stack, there is no overlapping among the footprints on the best-fit plane of all the integrated circuit chips of the M-1 radiation detectors.
The system of claim 8, wherein the radiation absorption layer of the remaining radiation detector of the M radiation detectors is positioned between (A) the electronics layer of the remaining radiation detector and (B) the M-1 radiation detectors.
The system of claim 1,

wherein a reference direction for the image sensor is perpendicular to the best-fit plane, and

wherein for each value of i, a thickness in the reference direction of the electronics layer (i) divided by a thickness in the reference direction of the radiation absorption layer (i) is at most 1/1000.
The system of claim 1,

wherein a reference direction for the image sensor is perpendicular to the best-fit plane, and

wherein for each value of i, a thickness in the reference direction of the electronics layer (i) is in a range of 10 microns to 100 microns.
The system of claim 1,

wherein for each value of i, the radiation detector (i) further comprises an input/output (I/O) area (i) ,

wherein a footprint on the best-fit plane of the image sensor has a shape of a rectangle and has 4 sides, and

wherein for each value of i, a same side of said 4 sides overlaps a footprint on the best-fit plane of the I/O area (i) the most.
The system of claim 12, further comprising a radiation source,

wherein the radiation source is configured to send radiation toward the image sensor,

wherein a straight line intersecting the radiation source and the image sensor is parallel to the best-fit plane, and

wherein every straight line segment having a first end point on the radiation source and a second end point on any sensing element of the image sensor does not intersect any I/O area of the I/O areas (i) , i=1, …, M.
The system of claim 13, wherein the radiation sent by the radiation source comprises X-rays.
The system of claim 1,

wherein for each value of i, the radiation detector (i) further comprises an input/output (I/O) area (i) ,

wherein the stack comprises multiple flat faces, and

wherein all the I/O areas (i) , i=1, …, M are on a same flat face of the multiple flat faces of the stack.
The system of claim 15, wherein the multiple flat faces comprise 6 faces of a cuboid.